United States
Environmental Protection
Agency
Robert S Kerr Environmental
Research Laboratory
Ada OK 74820
EPA/600/2-87/035
June 1987
Research and Development
      STIC: A
Standardized System
for Evaluating Ground
Water Pollution
Potential Using
Hydrogeologic
Settings

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                                         EPA/600/2-87/035
                                         May 1987
 DRASTIC:  A  STANDARDIZED  SYSTEM  FOR EVALUATING
     GROUND WATER  POLLUTION  POTENTIAL USING
              HYDROGEOLOGIC SETTINGS
                       by
                  Linda Aller
                 Truman Bennett
                  Jay H. Lehr
                Rebecca J.  Petty
                      and
                  Glen Hackett
         National Water Well Association
              Dublin, Ohio  43017
       Cooperative Agreement CR-810715-01
                Project Officer

                Jerry Thornhill
       Applications and Assistance  Branch
Robert S. Kerr Environmental Research  Laboratory
              Ada, Oklahoma  74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH  LABORATORY
       OFFICE OF RESEARCH AND DEVELOPMENT
      U.S. ENVIRONMENTAL PROTECTION AGENCY
              ADA, OKLAHOMA  74820
                                U.S. Environmental Protection Agency
                                Region 5, Library (PL-12J)

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                                 DISCLAIMER
     The information in this document has been funded wholly or in part
by the United States Environmental Protection Agency under assistance
agreement number CR-810715 to National Water Well Association.   It has
been subjected to the Agency's peer and administrative review,  and it has
been approved for publication as an EPA document.  Mention of trade names
or commercial products does not constitute endorsement or recommendation
for use.
                                      ii

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                                  FOREWORD
     The Environmental Protection Agency was established to coordinate
administration of the major Federal programs designed to protect the quality
of our environment.

     An important part of the Agency's effort involves the search for
information about environmental problems, management techniques and new
technologies through which optimum use of the Nation's land and water
resources can be assured and the threat pollution poses to the welfare of
the American people can be minimized.

     EPA's Office of Research and Development conducts this search through
a nationwide network of research facilities.

     As one of the facilities, the Robert S. Kerr Environmental Research
Laboratory is the Agency's center of expertise for investigation of the
soil and subsurface environment.  Personnel at the Laboratory are responsible
for management of research programs to:  (a) determine the fate, transport
and transformation rates of pollutants in the soil, the unsaturated zone and
the saturated zones of the subsurface environment; (b) define the processes
to be used in characterizing the soil and subsurface environment as a receptor
of pollutants; (c) develop techniques for predicting the effect of pollutants
on grond water, soil and indigenous organisms; and (d) define and demonstrate
the applicability and limitations of using natural processes, indigenous to
the soil and subsurface environment, for the protection of this resource.

     This report contributes to that knowledge which is essential in order
for EPA to establish and enforce pollution control standards which are
reasonable, cost effective and provide adequate environmental protection for
the American public.
                                      Clinton W.  Hall,  Director
                                      Robert S. Kerr Environmental
                                        Research Laboratory
                                    iii

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                                  ABSTRACT

     A methodology is described that will allow the pollution potential of any
hydrogeologic setting to be systematically evaluated anywhere in the United
States.  The system has two major portions:  the designation of mappable units,
termed hydrogeologic settings, and the superposition of a relative rating
system called DRASTIC.

     Hydrogeologic settings form the basis of the system and incorporate the
major hydrogeologic factors which affect and control ground-water movement
including depth to water, net recharge, aquifer media, soil media, topography,
impact of the vadose zone media and hydraulic conductivity of the aquifer.
These factors, which form the acronym DRASTIC, are incorporated into a relative
ranking scheme that uses a combination of weights and ratings to produce a
numerical value called the DRASTIC Index.

     Hydrogeologic settings are combined with DRASTIC Indexes to create units
which can be graphically displayed on a map.  The application of the system to
10 hydrogeologically variable counties resulted in maps with symbols and colors
which illustrate areas of ground-water contamination vulnerability.  The system
optimizes the use of existing data to rank areas with respect to pollution
potential to help direct investigations and resource expenditures and to
pi Loritize protection, monitoring and clean-up efforts.

     This report was submitted in partial fulfillment of Contract No.
Ck-810715-01 by the National Water Well Association under the sponsorship of
the Robert S. Kerr Environmental Research Laboratory, Ada, Oklahoma.  This
report covers a period from October, 1983 to March, 1987, and work was
completed as of April, 1987.
                                        iv

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                                    CONTENTS
Disclaimer	   ii
Foreword	   iii
Abstract	   iv
Figures	   ix
Tables	   xiv
Acknowledgements 	   xvi

Section
   1.  Introduction	      1
         Objectives and scope  	      1
         Project background  	      3
         Classification systems  	      4
         Some existing systems which evaluate ground-water
           pollution potential   	      5
         Organization of the document  	      7
   2.  Development of the System and Overview	     11
         Developing DRASTIC  	     11
         Potential uses	     11
         The  system	     13
         Hydrogeologic settings  	     13
         DRASTIC   	     17
         Pesticide DRASTIC   	     20
         Integration of hydrogeologic settings and  DRASTIC   	     33
   3.  DRASTIC:   A Description of the Factors	     35
         Ground-water contamination and DRASTIC  	     35
         Ground-water contamination and hydrogeologic settings    ...     40
         Assumptions of DRASTIC  	     42
         Depth to water	     44
         Net  recharge	     47
         Aquifer media   	     49
         Soil media	     51
         Topography	     57
         Impact  of the vadose zone  media   	     57
         Hydraulic conductivity of  the aquifer   	     62
         Interaction between parameters  	     62
   4.  How to Use Hydrogeologic Settings and  DRASTIC    	     68
         Where to obtain information on DRASTIC parameters   	     68
         Steps for use of the system   	     70
         How  to  use the range in media ratings   	     75
         How  to  evaluate confined aquifers    	     76
         Single  factor overrides   	     80
         Build-your-own-settings   	  .  	     82
         How  to  interpret a DRASTIC and Pesticide DRASTIC  Index   ...     82

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5.   Application of DRASTIC to Maps	85
      How to perform a DRASTIC evaluation and  produce  a
        DRASTIC map	86
          Drawing the, map manually	86
          Drawing the map by computer	95
          Final map production	100
            Map reduction	100
            National color code	101
            Presentation and field  check 	  104
            Final map and legend	104
      County mapping efforts 	  107
          Cumberland county, Maine  	  107
          Finney county, Kansas  	  112
          Gillespie county, Texas   	  118
          Greenville county, South  Carolina  	  124
          Lake county, Florida	128
          Minidoka county, Idaho 	  135
          New Castle county, Delaware  	  139
          Pierce county, Washington  	  144
          Portage county, Wisconsin  	  150
          Yolo county, California   	  155
6.   Impact - Risk Factors	172
7.   Ground-Water Regions and Hydrogeologic Settings of
      the United States	174
      1.  Western Mountain Ranges   	  184
            lAa East    Mountain Slopes	187
            lAb West    Mountain Slopes	187
            IBa East    Alluvial Mountain Valleys   	  188
            IBb West    Alluvial Mountain Valleys   	  188
            ICa East    Mountain Flanks	189
            1Gb West    Mountain Flanks	189
            ID          Glacial Mountain Valleys    .	190
            lEa East    Wide Alluvial Valleys  (External  Drainage)   .  .  190
            lEb West    Wide Alluvial Valleys  (External  Drainage)   .  .  191
            IF          Coastal Beaches	191
            1G          Swamp/Marsh	192
            1H          Mud Flows	192
      2.  Alluvial Basins	193
            2A          Mountain Slopes	197
            2B          Alluvial Mountain Valleys   	  197
            2C          Alluvial Fans	198
            2D          Alluvial Basins  (Internal  Drainage)   	  198
            2E          Playa Lakes	199
            2F          Swamp/Marsh	199
            2G          Coastal Lowlands   	  200
            2Ha         River Alluvium With Overbank Deposits   ....  200
            2Hb         River Alluvium Without Overbank  Deposits    .  .  201
            21          Mud Flows	201
            2J          Alternating Sandstone  and  Shale  Sequences   .  .  202
            2K          Continental Deposits 	  202
                                    vi

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3.   Columbia Lava Plateau   	     203
      3A          Mountain Slopes	     208
      3B          Alluvial Mountain Valleys 	     208
      3C          Hydraulically Connected Lava Flows  ....     209
      3D          Lava Flows Not Connected Hydraulically  .  .     209
      3E          Alluvial Fans	     210
      3F          Swamp/Marsh	     210
      3G          River Alluvium	     211
4.   Colorado Plateau and Wyoming Basin  	     212
      4A          Resistant Ridges  	     216
      4B          Consolidated Sedimentary Rock 	     216
      4C          River Alluvium	     217
      4D          Alluvium and Dune Sand	     217
      4E          Swamp/Marsh	     218
5.   High Plains   	     219
      5A          Ogallala	     223
      5B          Alluvium	     223
      5C          Sand Dunes	     224
      5D          Playa Lakes	     224
      5E          Braided River Deposits  	     225
      5F          Swamp/Marsh	     225
      5Ga         River Alluvium With Overbank Deposits .  .  .     226
      5Gb         River Alluvium Without Overbank Deposits  .     226
      5H          Alternating Sandstone, Limestone and
                    Shale Sequences 	 .....     227
6.   Non-Glaciated Central   	     228
      6A          Mountain Slopes	     232
      6B          Alluvial Mountain Valleys 	     232
      6C          Mountain Flanks	     233
      6Da         Alternating Sandstone, Limestone and
                    Shale - Thin Soil	     233
      6Db         Alternating Sandstone, Limestone and
                    Shale - Deep Regolith	     234
      6E          Solution Limestone  	     234
      6Fa         River Alluvium With Overbank Deposits .  .  .     235
      6Fb         River Alluvium Without Overbank Deposits  .     235
      6G          Braided River Deposits  	     236
      6H          Triassic Basins	     236
      61          Swamp/Marsh	     237
      6J          Metamorphic/Igneous Domes and Fault
                    Blocks	     237
      6K          Unconsolidated and Semi-consolidated
                    Aquifers	     238
7.   Glaciated Central  	      239
      7Aa         Glacial Till Over Bedded Sedimentary Rock  .     243
      7Ab         Glacial Till Over Outwash	     243
      7Ac         Glacial Till Over Solution Limestone  .  .  .     244
      7Ad         Glacial Till Over Sandstone	     244
      7Ae         Glacial Till Over Shale	     245
      7Ba         Outwash	     245
      7Bb         Outwash Over Bedded Sedimentary Rock  .  .  .     246
                             vii

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       7Bc         Outwash Over Solution Limestone 	    246
       7C          Moraine	    247
       7D          Buried Valley	    247
       7Ea         River Alluvium With Overbank Deposits .  .  .    248
       7Eb         River Alluvium Without Overbank Deposits.  .    248
       7F          Glacial Lake Deposits	    249
       7G          Thin Till Over Bedded Sedimentary Rock.  .  .    249
       7H          Beaches, Beach Ridges and Sand Dunes  .  .  .    250
       71          Swamp/Marsh	    250
 8.  Piedmont and Blue Ridge	    251
       8A          Mountain Slopes	    255
       8B          Alluvial Mountain Valleys 	    255
       8C          Mountain Flanks	    256
       8D          Regolith	    256
       8E          River Alluvium	    257
       8F          Mountain Crests	    257
       8G          Swamp/Marsh	    258
 9.  Northeast and Superior Uplands  	    259
       9A          Mountain Slopes	    263
       9B          Alluvial Mountain Valleys 	    263
       9C          Mountain Flanks	    264
       9Da         Glacial Till Over Crystalline Bedrock .  .  .    264
       9Db         Glacial Till Over Outwash	    265
       9E          Outwash	    265
       9F          Moraine	    266
       9Ga         River Alluvium With Overbank Deposits .  .  .    266
       9Gb         River Alluvium Without Overbank Deposits  .    267
       ,)H          Swamp/Marsh	    267
       >I          Bedrock Uplands	    268
       9J          Glacial Lake/Glacial Marine Deposits  .  .  .    268
       9K          Beaches, Beach Ridges and Sand Dunes  .  .  .    269
10.  Atlantic and Gulf Coastal Plain	    270
      lOAa         Regional Aquifers 	    274
      lOAb         Unconsolidated & Semi-Consolidated
                     Shallow Surficial Aquifer 	    274
      lOBa         River Alluvium With Overbank Deposits .  .  .    275
      lOBb         River Alluvium Without Overbank Deposits  .    275
      IOC          Swamp	    276
11.  Southeast Coastal Plain 	    277
      11A          Solution Limestone and Shallow Surficial
                     Aquifers	    281
      11B          Coastal Deposits  	    281
      11C          Swamp	    282
      11D          Beaches & Bars	    282
12.  Hawaii	    283
      12A          Mountain Slopes	    287
      12B          Alluvial Mountain Valleys   	    287
      12C          Volcanic Uplands  	    288
      12D          Coastal Beaches	    288
                              viii

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        13.  Alaska	    289
               13A         Alluvium	    293
               13B         Glacial and Glaciolacustrine Deposits
                             of the Interior Valleys   	    293
               13C         Coastal Lowland Deposits   	    294
               13D         Bedrock of the Uplands and Mountains  .  .  .    294
Master References  	    296
Appendices
    A.  Processes and Properties Affecting Contaminant
          Fate and Transport	    334
            Density	    335
            Solubility	    335
            Sorption	    336
            Ion exchange	    337
            Oxidation-reduction  	    338
            Biodegradation	    340
            Hydrolysis	    341
            Volatilization 	    342
            Buffering and neutralization 	    342
            Dilution	    343
            Dispersion	    344
            Viscosity	    347
            Mechanical filtration  	    347
    B.  Characteristics of Selected Ground-Water Contaminants  ....    351
          Inorganic metals 	    351
            Cadmium  	 .....    352
            Chromium   	    352
            Copper	    352
            Lead	    353
            Mercury	    353
            Manganese	    353
            Silver	    354
            Zinc	    354
            Iron	    354
          Inorganic non-metals 	   , 355
            Nitrogen	    355
            Phosphorus	    355
            Boron	    356
            Sulfur	    356
            Fluoride	    356
            Chloride	    356
            Arsenic	    357
            Selenium	    357
          Organic compounds  	    357
            Aliphatic compounds  	    361
            Oxygenated hydrocarbons  	    372
            Aromatic compounds 	    373
            Hydrocarbons with specific elements  	    374
                                       ix

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C.  Sources of Ground-Water Contamination   	    379
      Ground-water quality problems that originate on the
         land surface	    380
        Land Disposal	    380
        Stockpiles and mine tailings	    381
        Disposal of sewage and sludge	    384
        Salt spreading	,	    391
        Animal feedlots	    392
        Fertilizers and pesticides  	    393
        Accidental spills 	    398
        Particulate matter from airborne sources  	    400
      Ground-water quality problems that originate in the
         ground above the water table 	    401
        Septic systems, cesspools  and privies 	    401
        Surface impoundments and lagoons  	    404
        Landfills	    406
        Waste disposal in excavations	    409
        Leakage from underground storage tanks  	    410
        Leakage from underground pipelines  	    413
        Artificial recharge 	    414
        Sumps and dry wells	    416
        Graveyards	    417
      Ground-water quality problems that originate in
         the ground water below the water table 	    418
        Waste disposal in wet excavations	    418
        Drainage wells and canals  	    418
        Abandoned and exploration wells 	    419
        Water supply wells	    421
        Waste disposal wells	    422
        Mines	    426
        Salt water intrusion	    428
D.  Cumberland county, Maine  	    456
E.  Finney county, Kansas   	    472
F.  Gillespie county, Texas 	    490
G.  Greenville county, South Carolina 	    505
H.  Lake county, Florida (Surficial Aquifer)  	    520
      (Confined Aquifer)  	    535
I.  Minidoka county, Idaho  	    554
J.  New Castle county, Delaware 	    565
K.  Pierce county, Washington 	    579
L.  Portage county, Wisconsin 	    595
M.  Yolo county, California   	    609

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                                    FIGURES
Number                                                                    Page

  1  Ground-water regions of the  United  States  	   15
  2  Format of hydrogeologic settings   	   16
  3  Graph of ranges and ratings  for depth  to water	   26
  4  Graph of ranges and ratings  for net recharge	   27
  5  Graph of ranges and ratings  for aquifer media  	   28
  6  Graph of ranges and ratings  for soil media	   29
  7  Graph of ranges and ratings  for topography   	   30
  8  Graph of ranges and ratings  for impact of  the vadose  zone  	   31
  9  Graph of ranges and ratings  for hydraulic conductivity   	   32
 10  Travel of contaminant with same density as water  in
       the aquifer	   37
 11  Travel of contaminant that is  denser than water in
       the aquifer	   37
 12  Travel of contaminant that is  less  dense than water
       in the aquifer	   38
 13  Travel of contaminant that is  denser than water and
       sinks in the  aquifer	   38
 14  Travel of contaminant that is  denser than water in the
       aquifer in a  direction opposed  to the ground water
       flow direction	   39
 15  Hydrogeologic impact on a contaminant in an
       unconsolidated aquifer  	   41
 16  Hydrogeologic impact on a contaminant in a
       consolidated  sedimentary aquifer   	   41
 17  Hydrogeologic impact on a contaminant in a
       solutioned aquifer	   43
 18  Hydrogeologic impact on a contaminant in a
       'fractured aquifer	   43
 19  Diagrams showing how to determine the depth
       to water	   46
 20  Soil textural classification chart	   53
 21  Diagrams showing how to determine the impact
       of the vadose zone media	   60
 22  Description and illustration for  setting 7Aa - glacial
       till over bedded  sedimentary rocks   	   71
 23  Description and illustration for  setting 6Da - alternating
       sandstone, limestone and shale  -  thin soil	   71
 24  Hand-drawn map  showing correct delineation and
       labeling of aquifer media    	   89
                                      xi

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25  Hand-drawn map showing correct delineation and
      labeling of depth to water and aquifer media 	    90
26  Hand-drawn map showing correct delineation and
      labeling of all DRASTIC parameters	    91
27  Hand-drawn map showing correctly labeled
      ground-water pollution potential map 	    93
28  Computer-drawn map showing representation of
      aquifer media by symbols 	    97
29  Computer-drawn map showing an unacceptable detailed
      soils map	    98
30  Computer-drawn map showing a final DRASTIC Index
      value map	    99
31  Pollution potential map for a portion of Yolo county,
      California showing hydrogeologic settings  	   102
32  Pollution potential map for a portion of Yolo county,
      California showing the superposition of the national
      color code	   103
33  Sample format of a legend for a ground-water pollution
      potential map	   105
34  Generalized pollution potential map of Cumberland
      county, Maine  	   109
35  Generalized pollution potential map of Finney county,
      Kansas	   114
36  Generalized pollution potential map of Gillespie county,
      Texas	   120
37  Generalized pollution potential map of Greenville county,
      South Carolina	   125
38  Generalized pollution potential map of the surficial
      aquifer, Lake county, Florida  	   130
39  Generalized pollution potential map of the confined
      aquifer, Lake county, Florida  	   131
40  Generalized pollution potential map of Minidoka county,
      Idaho	   136
41  Generalized pollution potential map of New Castle county,
      Delaware	   140
42  Generalized pollution potential map of Pierce county,
      Washington	   146
43  Generalized pollution potential map of Portage county,
      Wisconsin	   151
44  Generalized pollution potential map of Yolo county,
      California	   157
45  Map legend	   177
A-l Schematic of pathlines showing longitudinal and transverse
      dispersion	   345
A-2 Plume configuration based on contaminant input 	   346
B-l Covalent bonding arrangements of carbon atoms  	   360
D-l Index to map sheets, detailed pollution potential
      map", Cumberland county, Maine	   457
E-l Index to map sheets, detailed pollution potential
      map, Finney county, Kansas   	   473
                                     xii

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F-l Index to map sheets, detailed pollution potential
      map, Gillespie county, Texas 	
G-l Index to map sheets, detailed pollution potential
      map, Greenville county, South Carolina 	
H-l Index to map sheets, detailed pollution potential
      map, surficial aquifer, Lake county, Florida  .  .
H-2 Index to map sheets, detailed pollution potential
      map, confined aquifer, Lake county, Florida   .  .
1-1 Index to map sheets, detailed pollution potential
      map, Minidoka county, Idaho  	
J-l Index to map sheets, detailed pollution potential
      map, New Castle county, Delaware 	
K-l Index to map sheets, detailed pollution potential
      map, Pierce county, Washington 	
L-l Index to map sheets, detailed pollution potential
      map, Portage county, Wisconsin 	
M-l Index to map sheets, detailed pollution potential
      map, Yolo county, California 	
491
506
521
536
555
566
580
596
610
                                     xiii

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                                     TABLES
Number                                                                    Page

 1   Sources of hydrogeologic information	    18
 2   Assigned weights for DRASTIC features 	    19
 3   Assigned weights for Pesticide DRASTIC features	    19
 4   Ranges and ratings for depth to water	    21
 5   Ranges and ratings for net recharge	    21
 6   Ranges and ratings for aquifer media  	    22
 7   Ranges and ratings for soil media	    22
 8   Ranges and ratings for topography 	    23
 9   Ranges and ratings for impact of the vadose  zone  media	    24
10   Ranges and ratings for hydraulic conductivity 	  ....    25
11   Potential sources of ground-water contamination and  mode
       of emplacement	    36
12   Range of values of hydraulic conductivity and permeability	    63
13   Conversion factors for permeability and hydraulic
       conductivity units	    69
14   DRASTIC and pesticide DRASTIC charts for setting  7Aa -
       glacial till over bedded sedimentary rocks	    72
15   DRASTIC and pesticide DRASTIC charts for setting  6D1 -
       alternating sandstone, limestone and shale - thin  soil	    73
16   Chart for example setting 7Ac - Glacial till over solution
       limestone showing unconfined conditions 	    79
17   Chart for example setting 7Ac - Glacial till over solution
       limestone showing confined conditions 	    79
18   DRASTIC rating for Maco I	    81
19   DRASTIC rating for Maco II	    81
20   Pencil colors used for DRASTIC mapping exercise  	    87
21   Chart for setting 912 - Bedrock uplands	    94
22   National color code for DRASTIC Index ranges  	   101
23   Hydrogeologic settings mapped in Cumberland  county,  Maine 	   108
24   Hydrogeologic settings mapped in Finney county, Kansas   	   113
25   Hydrogeologic settings mapped in Gillespie county, Texas   	   119
26   Hydrogeologic settings mapped in Greenville  county,  South Carolina  .   124
27   Hydrogeologic settings mapped in Lake county, Florida 	   129
28   Hydrogeologic settings mapped in Minidoka county, Idaho 	   135
29   Hydrogeologic settings mapped in New Castle  county,  Delaware  ....   139
30   Hydrogeologic settings mapped in Pierce county, Washington	144
31   Hydrogeologic settings mapped in Portage county,  Wisconsin	150
32   Hydrogeologic settings mapped in Yolo county, California	156
33   Summary of the principal physical and hydrologic  characteristics
       of the ground-water regions of the United  States  	   175
(continued)

                                      xiv

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                               TABLES (continued)
Number
34   Common ranges for the hydraulic characteristics of ground-water
       regions of the United States	   176
35   Hydrogeologic settings and associated DRASTIC Indexes sorted
       by region	   178
36   Hydrogeologic settings and associated DRASTIC Indexes sorted
       by rating	   179
37   Hydrogeologic settings and associated DRASTIC Indexes sorted
       by setting title	   180
38   Hydrogeologic settings and associated pesticide DRASTIC
       Indexes sorted by regions  	   181
39   Hydrogeologic settings and associated pesticide DRASTIC
       Indexes sorted by rating	•	   182
40   Hydrogeologic settings and associated pesticide DRASTIC
       Indexes sorted by setting title  	   183
B-l  EPA list of 129 priority pollutants and the relative
       frequency of these materials in idustrial waste waters 	   358
B-2  Substances known to occur in ground water, ranges of
       detected concentrations, exceeded standards, examples
       of uses and quantitative estimates of carcinogenic
       potency and noncarcinogenic toxicity 	   362
C-l  Major substances present in coal ore stockpiles and sp
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                                ACKNOWLEDGEMENTS
     This document creates a standardized system which can be used to evaluate
ground-water pollution potential.  At the inception of the project,  the
implications for use of such a system were realized and a technical  advisory
committee was assembled.  Prominent individuals with ground-water expertise
represented federal and state agencies, the Canadian government and  private
consultants.  Throughout the development of the system, the committee provided
guidance and direction.  The document is a result of the synthesis of many
approaches and opinions of individual committee members.  Although each of the
individuals contributed positively and effectively to the process, this report
is a product of the National Water Well Association and is not endorsed
entirely by each of the committee members.  Successful completion of the
project is due to the time and effort which an unusually able advisory
committee was willing to devote to this activity.  To the following  named
persons, grateful acknowledgement of their contribution is made:

       Michael Apgar, Delaware Department of Natural Resources
       William Back, U.S. Geological Survey
       Jim Bachmaier, U.S. EPA, Office of Solid Waste
       Harvey Banks, Consulting Engineer, Inc.
       Truman Bennett, Bennett & Williams Inc.
       Robert E. Bergstrom, Emeritus, Illinois State Geological Survey
       Stephen M. Born, University of Wisconsin-Madison
       Keros Cartwright, Illinois State Geological Survey
       Stuart Cohen, U.S. EPA Hazard Evaluation Division
       Steve Cordle, U.S. EPA Office of Research & Development
       George H. Davis, Editor, Journal of Hydrology
       Stan Davis, University of Arizona
       Norbert Dee, U.S. EPA Office of Ground Water Protection
       Donald A. Duncan, South Carolina Dept. of Health and
          Environmental Control
       Catherine Eiden, U.S. EPA Hazard Evaluation Division
       Grover Emrich, SMC Martin Inc.
       Glen Galen, U.S. EPA, Land Disposl Branch
       Phyllis M. Carman, Consultant, Tennessee
       Jim Gibb, Illinois State Water Survey
       Todd Giddings, Todd Giddings & Associates
       Ralph Heath, U.S. Geological Survey, retired
       Ron Hoffer, U.S. EPA, Office of Ground Water Protection
       George Hughes, Ontario Ministry of the Environment
       Jack Keeley, U.S. EPA, Kerr Research Center
       Jerry Kotas, U.S. EPA, National Pesticide Survey, Offices of Drinking
          Water and Pesticide Programs
       Harry LeGrand, Consultant, North Carolina

                                      xvi

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       Fred Lindsey, U.S. EPA, Waste Management and Economics Division
       Paula Magnuson, Geraghty & Miller Inc.
       Martin Mifflin, Mifflin and Associates, Inc.
       Walter Mulica, IEP Inc.
       John Osgood, Dames and Moore
       Wayne Pettyjohn, Oklahoma State University
       Paul Roberts, Stanford University
       John Robertson, Weston Designers & Consultants
       Dave Severn, U.S. EPA Hazard Evaluation Division
       Frank Trainer, U.S. Geological Survey, retired
       Warren Wood, U.S. Geological Survey

     The basic conceptual foundation for this system is modeled after a waste
disposal site evaluation technique developed by Harry LeGrand.  The geographic
framework for the presented system is developed within ground-water regions as
defined by Ralph C. Heath.  A special note of acknowledgement and gratitude is
made to these two individuals for their inspiration and assistance in
developing this document.

     In addition to the committee members, many individuals assisted in the
demonstration mapping portion of the project.  These individuals provided
guidance in choosing ratings for DRASTIC factors, helped assemble information
about the county, organized and assembled individuals for attendance at the
county presentation on DRASTIC, provided vehicles for field checks, peer
reviewed the pollution potential maps and participated in the field checking of
the county.  Without the varied talents of the following individuals, the
production of the maps would not have been possible.

Cumberland County, Maine
     Woodrow Thompson, Maine Geological Survey
     Andrews L. Tolman, Maine Geological Survey

Finney County Kansas
     Patrick Craig, Southwest Kansas Ground Water Management District #3
     Richard Henkle, Henkle Drilling and Supply Company
     Bruce Reichmuth, Henkle Drilling and Supply Company
     E.J. Richmeier, Soil Conservation Service
     Mark Sexson, Kansas Department of Fish and Game

Gillespie County, Texas
     Curt Black, Student in Hydrogeology, University of Texas
     Taylor Virdell, Sr., Virdell Drilling, Inc.
     Taylor Virdell, Jr., Virdell Drilling, Inc.

Greenville County, South Carolina
     Stan Clark, South Carolina Department of Health and Environmental Control
     Don Duncan, South Carolina Department of Health and Environmental Control
     Harry LeGrand, Consultant, North Carolina
     H. Lee Mitchell, South Carolina Water Resources Commission
                                      xvii

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Lake County, Florida
     Rodney DeHan, Florida Department of Environmental Regulation
     Cindy Humphreys, Florida Department of Environmental Regulation
     David Moore, Southwest Florida Water Management District
     Stoddard Pickett, Florida Department of Environmental Regulation
     Mark Stewart, University of Florida

Minidoka County, Idaho
     Ron Hiddleston, Hiddleston Drilling and Pump
     Gerald F. Lindholm, United States Geological Survey

New Castle County, Delaware
     Michael Apgar, Delaware Department of Natural Resources
     Bernard L. Dworsky, Water Resources Agency for New Castle County
     Robert W. Finkle, Water Resources Agency for New Castle County
     Bruce Kraeuter, Water Resources Agency for New Castle County
     Andrea L. Putscher, Delaware Department of Natural Resources

Pierce County, Washington
     John Barich, U.S. EPA, Region X
     Glen Bruck, U.S. EPA, Region X
     Norm Dion, United States Geological Survey
     Derek Sandison, Tacoma-Pierce County Health Department
     Jack Sceva, U.S. EPA, retired

Portage County, Wisconsin
     Stephen M. Born, University of Wisconsin-Madison
     Ron Hennings, University of Wisconsin-Extension
     Robin Schmidt, Wisconsin Department of Natural Resources

Yolo County, California
     Robert S. Ford, California Water Resources Control Board
     Brenda Grewell, California Water Resources Control Board
     Gene E. Luhdorff, Luhdorff and Scalmanini
     Wayne Taniguchi, Yolo County Environmental Health Department
     Russell Walls, Central Valley Regional Watr Quality Control Board
     Gail Wiggett, Central Valley Regional Water Quality Control Board
     John Woodling, California Department of Water Resources
                                     xviii

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                                   SECTION 1

                                  INTRODUCTION
OBJECTIVES AND SCOPE

     The purpose of this project is to create a methodology  that  will  permit
the ground-water pollution potential of any hydrogeologic  setting to be
systematically evaluated with existing information anywhere  in the United
States.  Pollution potential is a combination of hydrogeologic factors,
anthropogenic influences and sources of contamination in any given area.   This
methodology has been designed to include only the hydrogeologic factors which
influence pollut ion potential.

    This document has been prepared to assist planners,  managers  and
administrators in the task of evaluating the relative vulnerability of areas to
ground-water contamination from various sources of pollution.   Once this
evaluation is complete, it can be used to help direct resources and land-use
activities to the appropriate areas.  The methodology may  also assist  in
helping to prioritize protection, monitoring or clean-up efforts.   This
document will also be useful to industry personnel who desire  to  understand the
relationship between various practices and the ground-vater  pollution  potential
associated with them and to university personnel who teach the fundamentals of
hydrogeology and ground-water contamination.  It has been  assumed that the
reader has only a basic knowledge of hydrogeology and the  processes which
govern ground-water contamination.  However, the greater the hydrogeologic
experience of the user, the more useful the system will  become because the
system can expand to be beneficial at any level of expertise.    This report is
neither designed nor intended to replace on-site inspections,  or specifically
to site any type of facility or practice.   Rather, it is  intended to  provide a
basis for comparative evaluation of areas with respect to  potential for
pollution of ground water.

     The scope of this project includes not only the development of a
standardized system for evaluating pollution potential,  but  also the creation
of a system which can be readily displayed on maps.  For purposes of relative
evaluation, a system has been designed which produces a  numerical rating.  For
purposes of mapping, the United States has been divided  into hydrogeologic
settings. These settings incorporate the many hydrogeologic  factors which  will
influence the vulnerability of that setting to ground-water  pollution. The
settings have been chosen to represent areas larger than 100 acres in  size,
thereby limiting the system to use as a screening tool and not as a site
assessment methodology. The two portions of the system may be used separately
or combined for more in-depth evaluation.  Individuals without specific

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geologic or hydrogeologic expertise  can effectively  use  the numerical rating
portion of the document,  but  may  desire assistance when  producing a  pollution
potential map.  Professional  hydrogeologic  expertise greatly enhances and
facilitates the application of  the methodology  particularly in locating,
evaluating and estimating parameter  values.

     The scope of this project  did not  include  producing pollution potential
maps of the entire United States.  Rather,  a  set  of  demonstration maps were
prepared to 1) demonstrate the  use of  the rating  system  and 2) show  how  the
system could display the  information on a map for ease of use and reference.
Ten widely hydrogeologically  varied  counties  across  the  United States were
selected as part of the testing and  demonstration portion of the project
including:

     1)  Cumberland County, Maine,
     2)  Finney County, Kansas,
     3)  Gillespie County, Texas,
     4)  Greenville County, South Carolina,
     5)  Lake County, Florida,
     6)  Minidoka County, Idaho,
     7)  New Castle County, Delaware,
     8)  Pierce County, Washington,
     9)  Portage County,  Wisconsin,  and
    10)  Yolo County, California.

These counties were chosen to represent both  rural and urban areas and to
exemplify both an abudance and  scarcity of  available hydrogeologic data.

     In the formulation of this document an attempt  was  made to  try  to
assimilate the thought processes  of  knowledgable  professional hydrogeologists
when evaluating the ground-water  pollution  potential of  any area.  From  this
thought process a simple-to-use and  easy-to-understand methodology has been
developed.  It is important to  remember that  this document is intended to be
used as a screening tool  and  is not  intended  to replace  the need  for
professional expertise and field  work  in assessing  the pollution potential  in
specific areas.

     The system has been  designed to use information which is available  through
a variety of sources.  Information on  the parameters including the depth to
water in an area, net recharge, aquifer media,  soil  media, general topography
or slope, vadose zone media and hydraulic conductivity of the aquifer  is
necessary to evaluate the ground-water pollution  potential of any area using
hydrogeologic settings.  Although much of this information is available  in
existing reports, some might  require estimation.   In addition to existing
reports and data, estimates for parameters  can usually be obtained from  experts
employed by the United States Geological Survey,  state geological surveys,  Soil
Conservation Service, colleges  and  universities,  professional hydrogeologic
consultants and other qualified individuals.   In  choosing parameters for which
information is already available  in  some form,  this  system does  not  include
many parameters and types of  information which would be  available  from a more

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detailed site investigation.  Therefore,  it is important to realize  that this
document provides only a general, broad assessment to be used  to evaluate areas
for potential pollution.

     To help illustrate two potential uses of this document, examples have been
included:  1) When a professional hydrogeologist is asked to recommend the most
hydrogeologically acceptable setting for municipal waste disposal in a county
area, he begins by reviewing many types of different information. From the
information, he immediately rejects settings which are obviously unsuitable and
continues to narrow his focus until a number of the most promising areas are
identified.  He will usually then recommend that more detailed  information be
obtained and/or site investigations be made on the most promising areas before
any type of further action is taken.  This is analogous to the  purpose of this
document.  It provides the user with an idea of where to direct resources for
further evaluation.  2) When state or local administrators have limited
resources available to devote to ground-water protection, they  are forced to
focus these resources in certain areas.  The system presented  in this document
helps identify areas which are more or less vulnerable than others to
contamination.  This delineation allows administrators to direct their
resources to those more vulnerable areas most critical to the management
problems thereby making the most of the limited resources which are  available.

PROJECT BACKGROUND

     With the scope of the project in mind it is necessary to understand the
importance of this document.  Ground veter is clearly regarc' >«  to be one of our
nation's most valuable resources.  Americans have long depended on ground water
for many uses, but the primary use has been as a source of drinking  water.
Over 90 percent of the nation's public water supplies obtain their source water
from ground water (Lappenbusch, 1984).  Additionally, 97 percent of  the water
needs for domestic use in rural areas is served by ground-water resources
(Solley et al., 1983).

     National reliance on ground water has increased dramatically over the past
20 years.  In the last 10 years alone, ground-water use has increased almost 30
percent while surface water withdrawals have increased only 15  percent (Solley
et al., 1983).  It is anticipated that the nation's reliance on ground water
will continue to increase as demand for water increases in the  future.

     Concomitant with our reliance on ground water has come the need to protect
our ground-water resources from contamination.  Although contamination due to
man has occurred for centuries, only in the past few years has  the nation
become aware of the dangers of ground-water contamination and of the many ways
in which ground water can become contaminated.  Moreover, in recent  decades,
the diversity of potential pollutants produced and used by man  has increased
dramatically.  Since 1974, the Congress of the United States has been making an
attempt to protect the nation's ground-water resources through  legislation.
The Safe Drinking Water Act (SDWA) (Public Law 93-523) as first passed in
December, 1974 and amended in 1976, 1977,  1979,  1980, 1984 and  1986  mandated
the establishment of drinking water standards to protect the public  health,
established the underground injection control (UIC) program to  protect
underground sources of drinking vrater from subsurface injection of wastes

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 through wells, and established  the  Sole-Source Aquifer  program.   The  Resource
 Conservation and Recovery Act  (RCRA)  (Public  Law  94-580), as  first  passed  in
 October,  1976 and amended in 1978,  1980,  1982, 1984 and  1986,  is  the
 legislation which controls the  management and disposal  of solid and hazardous
 waste  in  such a manner  that ground  water  will not be contaminated.  RCRA also
 mandated  the establishment of an underground  storage tank program which will
 address leak detection, prevention, monitoring and corrective  action.  The
 amended Federal Insecticide, Fungicide and Rodenticide Act  (FIFRA)  (Public Law
 92-516) as first passed in October, 1972  and  amended in  1975,  1978, 1980 and
 1983 allows EPA to prohibit or  mitigate ground-water contamination by
 pesticides by denying registrations, by modifying application  methods and
 through cancellations and suspensions of  pesticide registrations.  FIFRA also
 explicitly requires EPA to monitor  environmental  pollution.  The  Toxic
 Substances Control Act  (TSCA) (Public Law 94-469), signed into law in October,
 1976,  and amended in 1981 has no direct impact on ground-water protection, but
 has the potential to be used as a mechanism in ground-water protection because
 the act provides EPA with the power to regulate the use  and manufacture of
 specific  chemicals, some of which may pose ground water  contamination
 potential.  The Surface Mining  Control and Reclamation Act  (SMCRA)  (Public Law
 95-87) as first passed in August, 1977 and amended in 1978, 1980, 1982 and
 1984,  is  the legislation which  controls environmental impacts  resulting from
 all mining activities.  By establishing standards for these facilities, ground
 water may once again be protected.  Finally the Comprehensive  Emergency
 Response  Compensation and Liability Act (CERCLA)  (Public Law 96-510), also
 known as  "Superfund" was passed in December,  1980 and amended  in  October, 1986.
 This law  provides a mechanism for the clean-up of ground water which has been
 contaminated at abandoned hazardous waste sites.  A more complete discussion of
 these acts and their provisions which relate  to ground water is given by Lehr,
 et al. (1984).  This host of legislative measures has sought to he^p prevent
 the pollution of ground water in the future and to help mitigate  some of the
 problems which have been created in the past.

     Because prevention is the key to helping ensure that future  practices do
not result in ground-water contamination, it is now more important than ever to
use planning and management tools to help recognize the places where certain
activities pose a higher risk.   This document addresses this need by providing
an approach which can be used to help direct resources to protect ground water
 for future generations.

CLASSIFICATION SYSTEMS

     One  of the fundamental needs of any natural science is the development of
an effective system to group similar entities into categories.  Well-
established systems exist in the fields of botany, geology and many other
 sciences  (Joel, 1926).  These systems permit an appropriately trained person to
 gain certain insight about an entity simply by knowing the appropriate category
 in which  it is grouped.

     This systematic and logical way of imposing an artificial system on
natural entities has long been used in the field of geology also.   For example,
 rocks have been classified according to origin and minerals grouped according

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to crystal systems.  However, as a science expands and changes, so must the
types of systems used to describe those characteristics which need to be
studied.  The field of hydrogeology is one area of geology which has only been
overtly recognized since the term was coined by Lucas in 1879 (Davis and
Dewiest, 1966).  Since that time hydrogeology has expanded, from a discipline
devoted to water occurrence and. availability, to include the broad aspect of
water quality and solute chemistry.  Definition of water quality is fundamental
to the protection of the ground-water resource from pollution.

     The idea of an organized way to describe ground-water systems is not new.
Meinzer (1923) prepared a small-scale map of the United States showing general
ground-water provinces.  Thomas (1952) and Heath (1984) prepared similar but
more detailed maps and descriptions which grouped aquifers mainly on their
water bearing characteristics within certain geographic areas.  Blank and
Schroeder (1973) attempted to classify aquifers based on the properties of
rocks which affect ground water.  Of all these systems, geographic ones have
been more widely accepted as ways to describe the quantity of water which is
available in various regions.

SOME EXISTING SYSTEMS WHICH EVALUATE GROUND-WATER POLLUTION POTENTIAL

     Within the last twenty years the need to expand these systems or to create
a new system to address ground-water quality has become evident.  Many
different systems have been developed to address site selection for waste
disposal facilities such as sanitary landfills or liquid waste ponds.  Among
these, the LeGrand System (LeGrand, 1983) and the modified version used by the
U.S. EPA in the Surface Impoundment Assessment (SIA) are probably the most well
known.  The LeGrand system uses numerical weighting to evaluate ground-water
pollution potential from a given waste disposal site.  By evaluating the site
through a series of four stages, a description of the hydrogeology of the site,
the relative aquifer sensitivity combined with the contaminant severity, the
natural pollution potential presented at that site, and the engineering
modifications which might change that potential are all evaluated.

     The LeGrand system presupposes only a limited technical knowledge but
encourages the user to become familiar with the concepts presented in the
manual so that skilled judgements can be made in the subjective portion of the
system.  The similarities between sites are emphasized and the uniqueness of
each site is downplayed.

     The U.S. EPA methodology (U.S. EPA, 1983) uses the basic LeGrand System to
define the hydrogeologic framework, but modifies the system to place emphasis
on establishing a monitoring priority for the facility.  Once the hydrogeologic
characteristics have been rated, a table is used to define the monitoring
priority.  This priority may be adjusted by the rater using prescribed
techniques.  Once again only a limited technical knowledge is presupposed.

     Other systems have been designed to tailor the results to more specific
purposes.  Thornthwaite and Mather (1957) and Fenn et al. (1975) developed
water-balance methods to predict the leachate generation at solid waste
disposal sites.  This approach is based on the premise that by knowing the

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amount of infiltration into the landfill and the design of the cell, the
leachate quantity for the landfill can be determined.  The system is intended
as a tool to be used by engineers in the early design phase of a facility.

     Gibb et al., (1983) devised a rating scheme to establish priorities for
existing waste disposal sites with respect to their threat to human health via
ground water.  By ranking the site through four factors, 1) health risk of the
waste and handling mode, 2) population at risk, 3) proximity to wells or
aquifers, and 4)  susceptibility of aquifers, a number that ranges from 0-100
was used to display the relative risk.  The system was used in a specific
2-county assessment by technically qualified individuals.

     Another rating scheme, developed by the Michigan Department of Natural
Resources (1983), is designed to rank large numbers of sites in terms of risk
of environmental  contamination.  By evaluating the five categories:  1) release
potential, 2) environmental exposure, 3) targets, 4) chemical hazard and 5)
existing exposure, the user obtains a number ranging from 0 to 2000 points
which evaluates the relative hazard of that site with respect to other sites in
Michigan.

     Hutchinson and Hoffman (1983) developed a rating system used by the New
Jersey Geological Survey to prioritize ground-water pollution sites.  By first
evaluating the site geology using eleven separate factors and then evaluating
the waste characteristics using eight criteria, the user generates separate
scores which can then be combined to obtain a total site score.  The scores
range from 0 to 100 with high scores depicting a high degree of hazard.

     Seller and Canter (1980) evaluated seven empirical methods to determine
their usefulness in predicting the ground-water pollution effects of a waste
disposal facility at a particular site.  The methods they reviewed included
rating schemes, a decision tree approach, a matrix and a criteria-listing
method.  They determined that each method took into account the natural
conditions and facility design and construction, but that each method was best
applied  to the specific situation for which it was designed.

     Since the first draft of this document was published in May, 1985 other
rating systems have been developed which attempt to assess ground water
vulnerability.  The U.S. EPA (1986a) developed statutory interpretive guidance
for hazardous waste land treatment,  storage and disposal facilities which
includes a section  for determining ground-water vulnerability at hazardous
waste facilities regulated under  the Resource Conservation and Recovery Act
(RCRA).  By  evaluating three parameters:  1) hydraulic conductivity, 2)
hydraulic gradient  and 3) effective  porosity, the user calculates a time  of
travel (TOT) of a contaminant along  a 100-foot flow  line originating at the
base of  the  hazardous waste management unit.  Sites with a TOT of 100 years or
less are considered vulnerable and typically trigger more detailed site
assessments.

     The United States Air Force  has developed a rating model to establish
priorities for further environmental action at air force bases
(Engineering-Science, 1985).  The model uses information which is typically

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gathered during the record search phase of the Installation Restoration  Program
and includes an evaluation in three main areas:  1) possible receptors of
contamination, 2) the waste characteristics and 3) potential pathways for waste
contaminant migration.  The result is single number which can be adjusted to
account for any efforts to contain the contaminants.

     This brief review of selected existing systems reveals that there are  a
number of methods that can be applied to site specific situations or to
evaluation of the pollution potential of existing sites.  However, a planning
tool is needed for application to broader geographic areas before the
site-specific methods are employed.  The system must:  1) function as a
management tool, 2) be simple and easy-to-use, 3) utilize available information
and 4) be able to be used by individuals with diverse backgrounds and levels of
expertise.  This document contains a system which attempts to meet these needs
and to provide the planning tool necessary before site specific evaluations.

ORGANIZATION OF THE DOCUMENT

     This document contains seven sections and thirteen supporting appendices.
Each section and Appendices A through C contain a reference section.  A
complete list of references can be found immediately following Section 7.
Section 2, Development of the System and Overview, provides a description of
the process used to develop the methodology, including the potential uses of
the system, the fundamental parts of the methodology, the designation of
mappable units and the numerical ranking scheme.  Section 3, DRASTIC:  A
Description of the Factors, explains those factors which most significantly
influence ground-water pollution potential and the assumptions fundamental  to
the methodology.  This section also discusses the relationship between
hydrogeology and the effects of ground-water contamination, and details the use
of the numerical ranking scheme to adequately portray the ground-water
pollution potential.  Section 4, How to Use Hydrogeologic Settings and DRASTIC,
illustrates in greater detail how hydrogeologic settings are combined with the
relative rating scheme to determine the ground-water pollution potential of an
area.   This section also explains how to evaluate the special condition of
confined aquifers, use media ranges and acknowledge the presence of single
factor overrides.   Section 5, Application of DRASTIC to Maps, describes the
stepwise process used to produce a completed DRASTIC map from the initial data
collection to the  printing of affinal map using the National Color Code.   This
section also includes an explanation of how the system was applied in 10
hydrogeologically variable counties.   Section 6, Impact - Risk Factors,
discusses the influence of other parameters that may need to be considered in
addition to the DRASTIC Index when evaluating the ground-water pollution
potential in an area.  Section 7, Hydrogeologic Settings of the United States
by Ground-Water Regions, contains an annotated description, a geographic
location map and an illustration of the major hydrogeologic features of each
ground-water region.  Descriptiqns, illustrations and example charts are  also
included for each hydrogeologic |setting.

     Also included within DRASTIC are Appendices A through M.  Appendix A
discusses the various processes and properties which affect contaminant fate
and transport.  Appendix B reviews the physical and chemical characteristics of

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contaminants and associated reactions in the environment.  Appendix C discusses
the sources of ground-water contamination and related impacts on ground-water
quality.  Appendices D through M contain detailed pollution potential maps
produced using the methodology.  The 10 demonstration maps of counties contain
hydrogeologic setting designations and individual DRASTIC Index computations.
Charts immediately follow each map and include the ranges of the seven DRASTIC
parameters chosen for each area and the system for computing the DRASTIC Index.

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                                   REFERENCES
Blank, Horace R. and Melvin C. Schroeder, 1973.  Geologic classification of
aquifers; Ground Water, vol.  11, no. 2, pp. 3-5.

Davis, S.N. and R.J. DeWiest, 1966.  Hydrogeology; John Wiley & Sons, 463 pp.

Engineering-Science, 1985.  Installation restoration program, phase 1:  records
search Grissom AFB, Indiana, Appendix G: USAF installation restoration program
hazard assessment rating methodology; and Appendix H: site hazard assessment
rating forms; Engineering-Science, Atlanta, Georgia, pp. G-l-11 and H-l-14.

Fenn, Dennis G., Keith J. Hanley and Truett V. DeGeare, 1975.  Use of the water
balance method for predicting leachate generation from solid waste disposal
sites; U.S. EPA Solid Waste Report no. 168, Cincinnati, Ohio, 40 pp.

Gibb, James P., Michael J. Barcelona, Susan C. Schock and Mark W. Hampton,
1983.  Hazardous waste in Ogle and Winnebago Counties:  potential risk via
ground water due to past and present activities; Illinois Dr.*:rtment of Energy
and Natural Resources, Document no. 83/26,  66 pp.

Heath, Ralph C., 1984.  Ground-water regions of the United States; U.S.
Geological Survey, Water Supply Paper 2242, 78 pp.

Hutchinson, Wayne R. and Jeffrey L. Hoffman, 1983.  A ground water pollution
priority system;  New Jersey Geological Survey, Open-file Report no. 83-4,
Trenton, New Jersey, 32 pp.

Joel, A.H., 1926.  Changing viewpoints and  methods in soil classification;
reprinted in soil classification, Charles W. Finkl, Jr., editor (1982),
Hutchinson Ross Publishing Co.,  Stroudsburg, Pennsylvania, pp. 52-59.

Lappenbusch, W.L., 1984.  Health effects of drinking water contaminants;
Proceedings of the Thirty-first Ontario Industrial Waste Conference, Ontario
Ministry of the Environment, Ontario, Canada,  pp. 271-291.

LeGrand, Harry E., 1983.  A standardized system for evaluating waste-disposal
sites; National Water Well Association, Worthington, Ohio, 49 pp.

Lehr, Jay H., David M. Nielsen and John J.  Montgomery, 1984.   U.S. federal
legislation pertaining to ground water protection;  Groundwater Pollution
Microbiology, Gabriel Bitton and Charles P.  Gerba,  editors,  John Wiley &  Sons,
pp. 353-371.

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    Meinzer,  Oscar E.,  1923.   Outline of ground-water hydrology; U.S. Geological
    Survey, Water  Supply  Paper 494,  71 pp.

    Michigan  Department of  Natural Resources,  1983.  Site assessment system  (SAS)
    for the Michigan priority  ranking system under  the Michigan Environmental
    Response  Act;  Michigan  Department of Natural Resources,  91 pp.

    Seller, L.E. and L.W. Canter, 1980.  Summary of selected ground-water quality
    impact assessment methods;  National Center For  Ground Water Research Report no.
    NCGWR 80-3,  Norman, Oklahoma, 142 pp.

    Solley, Wayne  B., Edith B.  Chase and William B. Mann, 1983.  Estimated use of
    water in  the United States in 1980; U.S. Geological  Survey, Circular 1001, 56
    pp.

    Thomas, Harold E.,  1952.   Ground-water regions  of the United States - their
    storage facilities; Interior and Insular Affairs Committee, U.S. House of
    Representatives, 76 pp.

    Thornthwaite,  S.W. and  J.R. Mather, 1957.  Instructions and tables for
    computing potential evapotranspiration and the  water balance; Drexel Institute
    of Technology,  Laboratory  of Climatology,  Publications in Climatology,
    Centerton, New Jersey,  vol. 10, no. 3, 311 pp.

    United States  Environmental Protection Agency,  1983.  Surface impoundment
    assessment national report; U.S. EPA-570/9-84-002, 200 pp.

    United States-!" Environmental Protection Agency,  1986a.  Criteria for identifying
c~~\  areas of  vulnerable hydrogeology under the Resource  Conservation and Recovery
    Act,  U.S. EPA,  Office of Solid Waste and Emergency Response, Washington, D.C.,
    491 pp.
                                        10

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                                    SECTION 2

                      DEVELOPMENT OF THE SYSTEM AND OVERVIEW
DEVELOPING  DRASTIC

     The  focus  of this  project  is  to  create  a  system which can be used to
evaluate  the  ground water  pollution potential  of  any area in the United States.
At  the  inception of the project, the  far-reaching implications of a
standardized  system for evaluating ground-water pollution potential were
realized, and a broadly-based,  highly qualified technical advisory committee
was assembled to assist with  this  effort.  Through the direction and help of
many, and discussion  of opinions and  suggestions, this system has evolved to
represent a compromise  approach.   Further  reference to the role of the
committee will  be made  in  the section discussing  the development of the DRASTIC
Index.  A list  of committee members can be found  in the acknowledgement
section.

     The committee was  charged  with helping  to  develop a system capable of
generalizing  the pollution potential  for any area 100 acres or larger.   Because
pollutants  vary widely  in  their mobility and attenuation characteristics,  it
was necessary to choose a  generic  pollutant  for discussion purposes.   The
concepts of the system  were developed  assuming  the  use of a pollutant  having
the mobility  of water that is introduced at  the surface,  and carried towards
the ground  water by recharge from  precipitation.   The original inception of  a
pollution potential system incorporated  only the  evaluation of unconfined
aquifers.   However, during the  course  of system development,  it  became
desirable to  adapt the  methodology  for use in  confined aquifer situations.   To
accommodate confined conditions, basic  parameter  definitions  must be modified
according to  the discussion in  Section 4,  How  to  Evaluate Confined Aquifers.  A
discussion  of the parameters and the  alterations  is  also  found in Section 3.
Further, the  system does not easily address  the case of  semi-confined  or leaky
aquifer conditions.  Proper evaluation  of  leaky aquifers  requires the user to
select  either confined  or  unconfined  conditions and  modify those conditions
within  the bounds of the system with  consideration  of  hydrogeology and  the
purpose of  the assessment.

POTENTIAL USES

     Upon firm recognition of these assumptions,  the user may  begin to  attempt
to make full use of the system.   The user  must  also  remember  that the
methodology is neither  designed nor intended to replace  on-site  investigations
or to specifically site any type of facility or practice.   DRASTIC does  not
reflect the suitability of a site for waste  disposal  or  land  use  activities.
                                       11

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The suitability of a waste disposal site is based  not  only  on  the  ground water
pollution potential of an area,  but also on other  design criteria.   DRASTIC
provides the user with a measure of relative ground-water vulnerability to
pollution and therefore, may be  one of many criteria used in siting  decisions,
but should not be the sole criteria.   An example of the correct  use  of DRASTIC
would be to use the system as a  screening tool  or  hydrogeologic  zoning map to
ascertain whether such a facility is/may be sited  in an area which is generally
vulnerable to the release of contaminants at the surface.   Thus  the  area around
the facility might be the focus  of a region where  DRASTIC is determined.  High
DRASTIC scores would indicate that the site is  located in a generally sensitive
or vulnerable area.  An additional site specific evaluation would  still be
necessary for determining site suitability for  waste disposal  or land use
activities.  The primary charge  of DRASTIC is to provide assistance  in resource
allocation and prioritization of many types of  ground-water related  activites
as well as to provide a practical educational tool.

     Many other beneficial applications of DRASTIC have also been  recognized.
For example, DRASTIC may be used for preventative  purposes  through the
prioritization of areas where ground-water protection  is critical.   The system
may also be used to identify areas where special attention, or protection
efforts are warranted.  For example,  DRASTIC might be  used  as  part of a
strategy to identify areas where either additional or  less  stringent protection
measures during underground storage tank replacement are advisable.  DRASTIC
coupled with other factors such  as application  methods may  help  delineate areas
where pesticides may pose a greater threat to ground water.

     Another application of DRASTIC includes the prioritization  of areas for
monitoring purposes.  In this situation a denser monitoring system might be
installed in areas where pollution potential is higher and  land  use  suggests a
potential source. The efficient  allocation of resources for clean-up and
restoration efforts after contamination has occured is one  more  possible use of
DRASTIC.  Although DRASTIC cannot be used to identify  areas where  pollution has
occurred, it may be desirable to focus clean-up efforts in  those areas with the
highest pollution potential.  In other situations  DRASTIC might  be better used
to point out special hydrogeologic characteristics which would generally
influence clean-up efforts.  For example, knowledge that the general depth to
water was 50 to 75 feet would rule out the use  of  a suction lift pump in
remediation efforts.

     DRASTIC may be employed in  the evaluation  of  land use  activities with
respect to the development of pollution liability  insurance and  assessment of
the economic impacts of disposal costs in highly vulnerable areas.   The
methodology may be used as a textbook in university courses to teach the
fundamentals of pollution potential and resource protection.   Finally, DRASTIC
may be used to identify data gaps which affect  pollution potential assessment.
For example, justification could be provided for further reconnaissance of the
hydrogeologic parameter which would subsequently form  a better data  base for
future resource assessments or another DRASTIC  analysis.
                                     12

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      As  with any model or classificiation scheme, it is possible to enter
 inaccurate or erroneous data which affect the reliability of the results.  It
 is  also  possible to  extend  the system beyond the intended use of the
 methodology.  For example,  the use of DRASTIC to determine the vulnerability of
 ground water to pollution by an injection well is an inappropriate use of the
 methodology.  By directly injecting the contaminant into the aquifer, the
 opportunity  for the  pollutant to be attenuated by the physical factors included
 in  DRASTIC are removed.  Any use of DRASTIC as the only assessment for siting a
 waste disposal or land use  activity is also an inappropriate use of the system.
 For example,  DRASTIC might  be used as the preliminary screening tool to
 indicate the relative vulnerability of ground water to pollution in an area.
 However,  the methodology would only be one phase of the actual site selection
 process  because it is oftentimes necessary to consider many other factors in
 addition to  ground-water vulnerability when siting a practice or facility.
 Another  inappropriate use of DRASTIC would be to specifically site a municipal
 well  in  a wellfield  located in a fractured bedrock area.  The methodology might
 be  one tool  used to  indicate relative ground-water pollution potential, but
 siting of the actual wells would need to be made based on fracture trace
 analysis and  other considerations.

      In  summary, in  all of  the potential applications,  DRASTIC cannot be used
 to  replace site specific investigations or to preclude the consideration of
 particular factors which may be important at a site by a professional
 hydrogeologist.  While DRASTIC can be a very useful tool, the further the
 application  strays from the assumptions inherent in the methodology, the
 greater the  likelihood of problems with resultant accuracy.

 THE SYSTEM

 The system presented herein has two major portions:  the designation of
 mappable units, termed hydrogeologic settings;  and the application of a scheme
 for relative  ranking of hydrogeologic parameters, called DRASTIC,  which helps
 the user evaluate the relative ground-water pollution potential of any
 hydrogeologic setting.  Although the two parts  of the system are interrelated,
 they  are discussed separately in a logical progression.

 HYDROGEOLOGIC SETTINGS

      This document has been prepared using the  concept  of hydrogeologic
 settings.  A hydrogeologic setting is a composite description of all the major
 geologic and hydrologic factors which affect and  control ground-water movement
 into, through and out of an area.   It is defined  as a mappable unit with common
 hydrogeologic characteristics,  and as a consequence,  common  vulnerability to
 contamination by introduced pollutants.   From these factors  it is  possible to
 make  generalizations about both ground-water availability and ground-water
 pollution potential.

      In order to assist users who  may have a limited  knowledge of  hydrogeology,
 the entire standardized system  for evaluating ground-water pollution potential
has been developed  within the framework of an existing classification system  of
 ground-water regions  of the United  States.   Heath (1984)  divided  the United
                                     13

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States into 15 ground-water regions  based  on  the  features in a ground-water
system which affect the occurrence and  availability of ground water  (Figure 1).
These regions include:

           1.  Western Mountain Ranges
           2.  Alluvial Basins
           3.  Columbia Lava Plateau
           4.  Colorado Plateau and  Wyoming Basin
           5.  High Plains
           6.  Nonglaciated Central  Region
           7.  Glaciated Central Region
           8.  Piedmont and Blue Ridge
           9.  Northeast and Superior Uplands
          10.  Atlantic and Gulf Coastal  Plain
          11.  Southeast Coastal Plain
          12.  Alluvial Valleys
          13.  Hawaiian Islands
          14.  Alaska
          15.  Puerto Rico and  Virgin Islands

Region 12, Alluvial Valleys is  "distributed"  throughout  the United  States.

     For the purposes of the present system,  Region 12  (Alluvial Valleys) has
been reincorporated into each of the other regions and  Region 15 (Puerto Rico
and Virgin Islands) has been omitted.  Since  the  factors which influence
ground-water occurrence and availability  also influence  the pollution  potential
of an area, this regional framework  is  used to  help familiarize  the  user with
the basic hydrogeologic features of  the region.  An annotated description of
each of the regions and the significant hydrogeologic  factors are  included  in
Section 7, Hydrogeologic Settings of the  United States  by  Ground-Water Regions.

     Because pollution potential cannot be determined on a regional  scale,
smaller "hydrogeologic settings" were developed within  each of the regions
described by Heath (1984).  These hydrogeologic settings create  units  which are
mappable and, at the same time, permit  further  delineation of the  factors which
affect pollution potential.

     Each hydrogeologic setting is described  in a written narrative section and
illustrated  in a block diagram.  Figure 2 shows the  format which is used
throughout the document.  The descriptions are  used  to  help orient the user to
typical geologic and hydrologic configurations  which  are found  in  each region
and  to help  focus attention on significant parameters  which are  important in
pollution potential assessment.  The block diagram enables the user to
visualize the described setting by indicating its geology,  geomorphology and
hydrogeology.

     A set of hydrogeologic settings has  been developed for  each region.  The
document is  designed so that once the broad geographic  area is  located the  user
does not have to refer to other hydrogeologic settings in  other  regions.  This
means that similar hydrogeologic settings may appear  more  than  once in the
document, but that they have been tailored to reflect the  typical  hydrogeologic
conditions within each individual region.

                                     14

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                   2 Alluvial Basins
U1
                                                                             Northeast
                                                                             Superior Uplands
                                                               Western Mountain
                                                                          »,      6 Nonglaciated
                                                                           v   _  . .-Central
                                                                          --,        region
                                          Colorado/j^?
  V*  ^A>     ^ (
*  c^-X^
                                                                       6 Nonglaciated
                                                                         Central region
                                       6 Nonglaciated
                                         Central region
                     -r   i \   jf'
                      9 Northeast and
                       ,Superior Uplands
                       ^  1 mi  r
                                                                                                                              1 Glaciated
                                                                                                                                Central
                                                                                                                                region
  6 Nonglaciated
    Central
•    region
                                                                                  0                    500 MILES
                                                                                  I  i  '.  i'  i  1  i ' i  r1
                                                                                  n                    	
                                                                                                       800 KILOMETERS
                              Figure 1.  Ground-water regions of the United States (After Heath, 1984).

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HAWAII

(12C) Volcanic Uplands

This hydrogeologic setting is characterized by moderately rolling
topography, at medium elevations, and rich, dark, soils developed from Che
basaltic bedrock.  The soils are permeable, rainfall is high, and recharge
is high.  Bedrock is composed primarily of alternating extrusive basaltic
lava flows and interlayered weathered zones formed between flows.  Ground
water occurs at moderate to deep depths, and aquifer yield is controlled by
fracture zones, vesicular zones  (both primarily cooling features) and the
inter-flow weathered zones.  Hydraulic conductivity is high.   As with other
settings in Hawaii, heavy pumping stresses often result in salt-water
intrusion.  This is a reflection of the fact that each island is surrounded
by and underlain by salt water, with the fresh water occurring in a
lenticular body that floats on the salt water.  Ground water yield is
therefore limited quite specifically to the amount of water recharged
annually.
                       Figure 2.  Format of hydrogeologic setting.
                                    16

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DRASTIC

     Inherent in each hydrogeologic setting are the physical  characteristics
which affect the ground-water pollution potential.   A wide  range  of  technical
positions was considered regarding the relative importance  of the many physical
characteristics that affect pollution potential.  Factors including  aquifer
chemistry, temperature, transmissivity, tortuosity, gaseous phase transport and
others were evaluated.  The availability of mappable data has also been
considered.  As a result of this evaluation, the most important mappable
factors that control the ground-water pollution potential were determined  to
be:

     D - Depth to Water
     R - (Net) Recharge
     A - Aquifer Media
     S - Soil Media
     T - Topography (Slope)
     I - Impact of the Vadose Zone Media
     C - Conductivity (Hydraulic) of the Aquifer

     These factors have been arranged to form the acronym,  DRASTIC for ease of
reference.  A complete description of the important mechanisms considered
within each factor and a description of the significance of the factor are
included in Section 3, DRASTIC:   A Description of the Factors. While  this list
is not all inclusive, these factors, in combination, were determined to include
the basic requirements needed to assess the general pollution potential of each
hydrogeologic setting.  The DRASTIC factors represent measurable  parameters for
which data are generally available from a variety of sources  witlout detailed
reconnaissance.  Sources of this information are listed in  Table  1.

     A numerical ranking system to assess ground-water pollution  potential in
hydrogeologic settings has been devised using the DRASTIC factors.  The system
contains three significant parts:  weights, ranges  and ratings.   A description
of the technique used for weights and ratings can be found  in Dee et al.,
(1973).

     1)   Weights

          Each DRASTIC factor has been evaluated with respect to  the other to
determine the relative importance of each factor.  Each DRASTIC factor has been
assigned a relative weight ranging from 1 to 5 (Table 2).   The most  significant
factors have weights of 5; the least significant, a weight  of 1.   This exercise
was accomplished by the committee using a Delphi (consensus)  approach. These
weights are a constant and may not be changed.  A second weight has  been
assigned to reflect the agricultural usage of pesticides (Table 3).  These
weights are also constants and cannot be changed.  A description  of  the usage
of this second system can be found in Section 2 under the heading, "Pesticide
DRASTIC".
                                    17

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                         TABLE 1.  SOURCES OF HYOROGEOLOGIC INFORMATION
Source
U S Geological Survey
State Geological Surveys
State Department of Natural/Water Resources
U S Department of Agriculture- Soil Conservation Service
State Department of Environmental Protection
Clean Water Act "208" and other Regional Planning
Authorities
County and Regional Water Supply Agencies and
Companies (private water suppliers)
Private Consulting Firms (hydrogeologic, engineering)
Related Industry Studies (mining, well drilling,
quarrying, etc )
Professional Associations
(Geological Society of America,
National Water Well Association,
American Geophysical Union)
Local Colleges and Universities
(Departments of Geology, Earth Sciences,
Civil Engineering
Other Federal/State Agencies
(Army Corps of Engineers, National Oceanic
and Atmospheric Administration)
Depth to
Water
X
X
X

X
X
-X
X
X
X
X
X
Net Recharge
X
X
X
X
X
X



X
X
X
Aquifer Media
X
X
X

X
X
X
X
X
X
X
X
Soil Media



X








Topography
X


X








Impact of the
Vadose Media
X
X
X

X
X
X
X
X
X
X
X
Hydraulic Conductivity
of the Aquifer
X
X
X

X
X
X
X

X
X

09

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        TABLE 2.  ASSIGNED WEIGHTS FOR
                   DRASTIC FEATURES
                 Feature
  Weight
  Depth to Water

  Net Recharge

  Aquifer Media

  Soil Media

  Topography

  Impact of the Vadose Zone Media

  Hydraulic Conductivity of the Aquifer
  TABLE 3. ASSIGNED WEIGHTS FOR PESTICIDE
            DRASTIC FEATURES
               Feature
Pesticide
 Weight
Depth to Water

Net Recharge

Aquifer Media

Soil Media

Topography

Impact of the Vadose Zone Media

Hydraulic Conductivity of the Aquifer
                         19

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     2)   Ranges

          Each DRASTIC  factor has been divided  into  either  ranges  or
significant media types which have an impact  on pollution potential  (Tables
4-10).  A discussion of the media types is included  in Section 3,  Aquifer
Media, Soil Media and Impact of the Vadose Zone Media.   The ranges and  media
types are graphed to show the linearity and non-linearity of  the factor
(Figures 3-9).

     3)   Ratings

          Each range for each DRASTIC factor  has been evaluated with  respect  to
the others to determine the relative significance of each range with  respect  to
pollution potential.  Based on the graphs, the  range for each DRASTIC factor
has been assigned a rating which varies between 1 and 10 (Tables 4-10). The
factors of D, R, S, T,  and C have been assigned one  value per range.  A and I
have been assigned a "typical" rating and a variable rating.   The  variable
rating allows the user  to choose either a typical value or  to adjust  the value
based on more specific  knowledge.  The ratings  are the same for both  the
DRASTIC' Index and the modified Pesticide DRASTIC Index.

     This system allows the user to determine a numerical value for any
hydrogeologic setting by using an additive model.  The equation for  determining
the DRASTIC Index is:

DRDy + RRRy + ARAw + SRSW + TRTW + IRIW + CRCW   =   Pollution Potential
     Where:

          R = rating
          W = weight

Once a DRASTIC Index has been computed, it is possible to identify areas which
are more likely to be susceptible to ground water contamination relative to one
another.  The higher the DRASTIC Index, the greater the ground-water pollution
potential.  The DRASTIC Index provides only a relative evaluation tool and is
not designed to provide absolute answers.  Therefore, the numbers generated in
the DRASTIC index and in the Pesticide DRASTIC index cannot be equated.

PESTICIDE DRASTIC

     Pesticide DRASTIC is designed to be used where the activity of concern is
the application of pesticides to an area.  It represents a special case of the
DRASTIC Index.  The only way in which Pesticide DRASTIC differs from DRASTIC is
in the assignment of relative weights for the seven DRASTIC factors.  All other
parts of the two indexes are identical; the ranges, ratings and instructions
for use are the same.  If the user is concerned with the ground-water pollution
potential of an area by pesticides, then the weights for Pesticide DRASTIC
should be used.
                                     20

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   TABLE 4. RANGES AND RATINGS FOR DEPTH
          TO WATER
DEPTH TO WATER
(FEET)
Range
0-5
5-15
15-30
30-50
50-75
75-100
100+
Weight. 5
Rating
10
9
7
5
3
2
1
Pesticide Weight: 5
TABLE 5. RANGES AND RATINGS FOR NET RECHARGE
NET RECHARGE
(INCHES)
Range
0-2
2-4
4-7
7-10
10+
Weight 4
Rating
1
3
6
8
9
Pesticide Weight 4
                 21

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TABLE 6.  RANGES AND RATINGS FOR AQUIFER MEDIA
AQUIFER MEDIA
Range Rating
Massive Shale
Metamorphic/lgneous
Weathered Metamorphic/lgneous
Glacial Till
Bedded Sandstone, Limestone and
Shale Sequences
Massive Sandstone
Massive Limestone
Sand and Gravel
Basalt
Karst Limestone
1-3
2-5
3-5
4-6
5-9
4-9
4-9
4-9
2-10
9-10
Weight 3 Pesticide Weight
Typical Rating
2
3
4
5
6
6
6
8
9
10
3
  TABLE 7. RANGES AND RATINGS FOR SOIL MEDIA
SOIL MEDIA
Range Rating
Thin or Absent
Gravel
Sand
Peat
Shrinking and/or Aggregated Clay
Sandy Loam
Loam
Silty Loam
Clay Loam
Muck
Nonshrinking and Nonaggregated Clay
Weight- 2
10
10
9
8
7
6
5
4
3
2
1
Pesticide Weight 5

                    22

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TABLE 8. RANGES AND RATINGS FOR TOPOGRAPHY
TOPOGRAPHY
(PERCENT SLOPE)
Ringe
0-2
2-6
6-12
12-13
18-
Weig'it 1
Ratinq
10
9
5
3
1
Pesticide Weight. 3
                   23

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TABLE 9.  RANGES AND RATINGS FOR IMPACT OF
         THE VADOSE ZONE MEDIA

IMPACT
Range
Confining Layer
Silt/Clay
Shale
Limestone
Sandstone
Bedded Limestone, Sandstone,
Sand and Gravel with
significant Silt and Clay
Metamorphic/lgneous
Sand and Gravel
Basalt
Karst Limestone
OF THE VADOSE ZONE MEDIA
Rating
1
2-6
2-5
2-7
4-8
Shale 4-8
4-8
2-8
6-9
2-10
8-10

Typical Rating
1
3
3
6
6
6
6
4
8
9
10
   Weight 5
Pesticide Weight 4
                    24

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TABLE 10.RANGES AND RATINGS FOR HYDRAULIC
        CONDUCTIVITY

HYDRAULIC CONDUCTIVITY
(GPD/FT?)
Range
1-100
100-300
300-700
700-1000
1000-2000
2000+
Weight 3
Rating
1
2
4
6
8
10
Pesticide Weight: 2
                  25

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    10
D)

I   5
            10     20     30     40     50     60     70     80     90     100
                                        Feet
                  Figure 3. Graph of ranges and ratings for depth to water.
                                            26

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   10
D
Of
     0     1
3456789     10

         Inches
        Figure 4. Graph of ranges and ratings for net recharge.
                                27

-------
    10
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                        in   in
Relative ranges of ease of pollution for the principal
aquifer types.
Ranges are based upon consideration of
a)  route length and tortuosity
b)  potential for consumptive sorption
c)  dispersion
d)  reactivity and
e)  degree of fracturing
The primary factors controlling the rating of each rock are
given below
                                                                     Primary factors affecting rating:
                                                                     © Reactivity (solubility and fracturing)
                                                                     © Fracturing,
                                                                     © Route length  and tortuosity, sorption  dispersion All
                                                                        essentially determined by gram size sorting, and
                                                                        packing,
                                                                     © Route length  and tortuosity as determined by bedding
                                                                        and fracturing
                                                                     © Sorption and dispersion
                                                                     © Fracturing, route length and tortuosity, influenced by
                                                                        mtergranular relationships,
                                                                     © Reactivity (solubility) and fracturing
                                                                     ® Fracturing and sorption
                              Primary Media
                            Figure 5. Graph of ranges and ratings for aquifer media.

                                                           28

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                              Nonshrinking and

                            Nonaggregated Clay



                                         Muck
                                                                                        Rating


                                                         -*N>C*>       ^CnOx^l       OO       *O      O


                                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^1^^^^^^^^^^^^^^^^^^^^^^^^
10

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     CO
     C
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  Clay Loam




  Sitty Loam




      Loam




Sandy Loam
                                                                                                                               (D
                                                                                                                               Q.

                                                                                                                               Q
     3
     (Q
     0)
     (0
     O
                           Shrinking and/or

                           Aggregated Clay



                                      Peat
     a.
     Si'
                                          Sand
                                        Gravel
                                 Thin or Absent

-------
10
           CO
                    CO
CM



<>
                      Percent Slope
  Figure 7. Graph of ranges and ratings for topography.
                         30

-------
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-------
    10
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Of
               O
               O
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                      o
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                       s
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                       6
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                                gpd/ft2
    Figure 9. Graph of ranges and ratings for hydraulic conductivity.
                              32

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     Pesticide DRASTIC was created to address the important processes which
specifically offset the fate and transport of pesticides in the soil.  These
processes, however, may not be as significant when assigning weights to the
other DRASTIC factors for non-agricultural activities.   Thus, by comparing
Tables 2 and 3, it can be seen that for non-agricultural activities, Soil Media
is assigned a weight of 2, while for the modified Pesticide DRASTIC, the Soil
Media is assigned a weight of 5.  Topography, Impact of the Vadose Zone Media
and Hydraulic Conductivity of the Aquifer are also slightly different.   By
making these adjustments, the committee addressed the special conditions which
influence the potential for ground-water contamination  by pesticides.  It is
important to note that the relative relationship between the DRASTIC factors
was not deemed significantly different enough to warrant the development of any
other modified DRASTIC indexes.  The user should be reminded that weights may
not be changed for any of the DRASTIC factors.  These relative weights  form the
basis for the system and any changes will make the system invalid.

INTEGRATION OF HYDROGEOLOGIC SETTINGS AND DRASTIC

     The mappable hydrogeologic units and the DRASTIC Index have been combined
to provide the user with a relative pollution potential for all typical
hydrogeologic settings in the United States.  A "typical" range for each
DRASTIC factor is assigned to each hydrogeologic setting and a DRASTIC  INDEX is
determined for each typical hydrogeologic setting.  These settings are
developed as guides and are not designed to be representative of each and every
area.  The ranges for each factor may be adjusted by the user and the rating
adjusted accordingly when available data indicate different conditions.  These
hydrogeologic settings provide units which are mappable and permit the  drafting
of pollution potential maps.  Thus, the user can uso hydrogeologic settings as
a mappable unit, define the area of interest by modifying the ranges within a
setting to reflect specific conditions within an area,  choose corresponding
ratings and calculate a pollution potential DRASTIC Index or a specialized
index for pesticides.
                                     33

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                                 REFERENCES
Dee, Norbert, Janet Baker, Neil Drobny, Ken Duke, Ira Whitman and Dave
Fahringer, 1973.  An environmental evaluation system for water resource
planning; Water Resources Research, vol. 9, no. 3, pp. 523-535.

Heath, Ralph C., 1984.  Ground-water regions of the United States;  U.S.
Geological Survey, Water Supply Paper 2242, 78 pp.
                                        34

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                                   SECTION  3

                     DRASTIC:  A DESCRIPTION OF THE  FACTORS
GROUND-WATER CONTAMINATION AND DRASTIC

     Ground-water pollution is caused by a variety  of  substances  originating
from many different activities.  In general, man-influenced  contaminants  enter
ground water through three pathways:  1) the placing or  spreading of  liquids or
water soluble products on the land surface, 2) the  burial  of substances  in the
ground above the water table, or 3) the emplacement or injection  of materials
in the ground below the water table (Lehr et al., 1976).   Table 11 lists  the
activities which cause contamination through one or more of  these pathways.   A
description of each of these activities is included in Appendix C, Sources of
Ground-Water Contamination.

     After release at the land surface, the contaminant may  infiltrate downward
through the soil, vadose zone into saturated zone,  thus  finally reaching  the
aquifer. If the volume of contaminant is not great, the  contaminant may be
retained in the soil or vadose zone.  If the contaminant is  not completely
attenuated, it may later be flushed toward the water table by infiltrating
precipitation or additional amounts of contaminant.  Once  within  the  aquifer,
the contaminant may:  1) travel at the velocity of  and in  the direction of
ground water (Figure 10), 2) travel slower than the ground water  (Figure  11),
3) float on the surface of the water table (Figure  12), 4) "sink" through the
aquifer to the bottom (Figure 13) or 5) under some  conditions, may actually
move in a direction against the flow of the ground water (Figure  14).
Generally, the majority of contaminants travel in the  direction of ground-water
flow at a velocity somewhat less than that of the ground water.

     As the contaminant travels through this system, attenuation  of the
contaminant may take place.  Attenuation includes mechanisms which reduce the
velocity of the contaminant through processes such  as  dilution, dispersion,
mechanical filtration, volatilization, biological assimilation and
decomposition, precipitation, sorption, ion exchange,  oxidation-reduction, and
buffering and neutralization (Pye and Kelley, 1984; Fetter,  1980).  The degree
of attenuation which can occur is a function of 1)  the time  that  the
contaminant is in contact with the material through which  it passes,  2) the
grain size and physical and chemical characteristics of the  material  through
which it passes, and 3) the distance which the contaminant has traveled.   In
general, for any given material the longer the time and greater the distance,
the greater the effects of attenuation.  In a similar  manner,  the greater the
surface area of the material through which the contaminant passes, the greater
the potential for sorption of the contaminant and hence for  attenuation.   The


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          TABLE 11. POTENTIAL SOURCES OF GROUND-WATER CONTAMINATION AND MODE OF EMPLACEMENT
                      (AFTER LEHR ET AL, 1976}
w
o>
          On The Land Surface
1. Land disposal of either solid or liquid waste
  materials
2 Stockpiles
3. Disposal of sewage and water-treatment plant
  sludge
4 Salt spreading on roads, airport runways and
  parking lots
5 Animal feed lots
6 Fertilizers and pesticides
7 Accidental spills of hazardous materials
8 Particulate matter from airborne sources
In The Ground Above the Water Table
 1 Leaching tile fields, cesspools and privies
 2 Holding ponds and lagoons
 3 Sanitary landfills
 4 Waste disposal in excavations
 5 Leakage from underground storage tanks
 6. Leakage from underground pipelines
 7 Artificial recharge
 8 Sumps and dry wells
 9 Graveyards
In The Ground Below the Water Table
1 Waste disposal in wet excavations
2. Drainage wells and canals
3. Abandoned/improperly constructed wells
4 Exploratory wells
5 Water supply wells
6 Waste disposal wells
7 Mines
8 Salt water intrusion

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                 Source
  Ground Water Flow
  Direction
Figure 10.   Travel of contaminant with same density as water in the aquifer.
                 Source
                                                          Water Table
  Ground Water Flow
  Direction
Figure 11.  Travel of contaminant that is denser than water in the aquifer.
                                  37

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                  Source
   Ground Water Flow

   Direction
I  I  I   I  J   }//////}//   t
                                                                              '/
  Figure 12.  Travel of contaminant that is less dense than water in the aquifer.
                  Source

                                                           Water Table

                                                          	y	
                -***<>**
                  *      fc.    * *
                   ?/*/  *.;/•
Ground Water Flow   *, »."^ »S? X *,* *if ^

Direction           V*>5 *t rf <>*,' ^ „>/***.»**l!
  Figure 13.  Travel of contaminant that is denser than water and sinks in the aquifer.
                                     38

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                                               Source
             Ground Water Flow
             Direction
                                           ••<	•*=*$ •; ••.•' •••'••" •••'•*•
                                             . %:  '  ,...*.-  "
                                             *•'/#*  V  *'*'*/  »
                                                                          Water Table
Figure 14. Travel of contaminant that is denser than water in the aquifer in a direction opposed to the
           water flow direction.
                                                39

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greater the reactivity of the material through which the  contaminant  passes,
the greater the potential for attenuation.   Any combination  of  these  processes
may be active depending on the hydrogeologic conditions and  the contaminant.
It is therefore necessary to have a general  idea of  these processes and  whether
they are active.  A discussion of the mechanisms which control  contaminant
movement is included in Appendix A, Processes and Properties Affecting
Contaminant Fate and Transport.

     The effectiveness of dilution and attenuation processes is largely
determined by 1) the rate and loading of the applied contaminant,  2)  the
characteristics of the contaminant and 3) the physical characteristics of the
area.  Ultimately, it is these factors which control the  ground-water pollution
potential of any area.  The rate and loading factor  which generally is of site
specific character is discussed briefly in Section 6, IMPACT -  Risk Factors.
The characteristics of the contaminants are  discussed in  more detail  in
Appendix B, Characteristics of Ground-Water  Contaminants. However, it is the
physical properties characterized by the hydrogeologic setting  of  the area  that
determine the extent to which the attenuation mechanisms  may have  the potential
to be active.

     Because it is neither practical nor feasible to obtain  quantitative
evaluations of these intrinsic mechanisms from a regional perspective, it is
necessary to look at the broader physical parameters which incorporate the  many
processes.  Each of the DRASTIC parameters includes  various  mechanisms which
will help to evaluate the vulnerability of ground water to pollution. When
this is coupled with an understanding of the hydrogeology of the area, the
result will be a clearer image of the potential for  pollutant travel  and
attenuation.  The following section provides a discussion of the possible
movement and attenuation of contaminants in  selected hydrogeologic settings.

GROUND-WATER CONTAMINATION AND HYDROGEOLOGIC SETTINGS

     Figure 15 illustrates a typical hydrogeologic setting which provides the
user with a feeling for the hydrologic cycle within  the setting.  This
illustration further serves to depict anticipated flow patterns and reductions
in contaminant concentrations during transport through the setting.   This
particular setting represents an unconsolidated sand, silt and  clay deposit
with a relatively shallow depth to water.  A contaminant  introduced at the
surface is flushed by precipitation through the vadose zone  into the  ground
water.  Once within the ground-water system, a contaminant with an assumed
mobility of water will be transported according to the flow  patterns  present
within the aquifer.  The concentration of the contaminant in the ground  water
will be influenced by dispersion, dilution and other natural attenuation
processes. As the contaminant migrates through the aquifer,  the various
processes of attenuation that occur within this setting will typically cause
reductions in contamination concentrations.

     Similar flow and contaminant transport  processes may be illustrated in
different hydrogeologic settings.  Figure 16 represents a hydrogeologic  setting
composed of bedded sandstones and shales.  A contaminant  introduced at the
surface is flushed by precipitation through  the soil and  toward the sandstone
                                      40

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            Figure 15. Hydrogeologic impact on a contaminant in an unconsolidated aquifer.
Figure 16. Hydrogeologic impact on a contaminant in a consolidated sedimentary aquifer containing a
          restrictive layer.
                                             41

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aquifer.  A contaminant with an assumed mobility of water will migrate  through
the sandstone aquifer in response to the ground-water  flow system.   Upon
reaching a restrictive layer depicted in Figure 16 by  the shale,  the
contaminant will typically travel along that boundary  particularly  when head
differential is upward.  When a breach in the restrictive layer occurs  the
contaminant may migrate into other adjacent formations.   Removal  of the
contaminant as it migrates through the aquifer will be influenced by the
natural attenuation process present within this setting  and the contaminant
characteristics.  Natural attenuation processes which  affect contaminant  fate
and transport may differ significantly between hydrogeologic settings.

     Diverse hydrogeologic conditions such as karst limestone shown in  Figure
17 pose special problems with regard to contaminant transport and attenuation.
Contaminants introduced at the surface and flushed into  the aquifer by
precipitation are transported through the solution channels and cavities  within
the limestone.  The interconnected solution channels allow for rapid dispersal
of the contaminant throughout the limestone aquifer.  Although attenuation
within the aquifer is limited, dilution of the contaminant may be significant.

     A similarly diverse hydrogeologic condition is depicted in Figure  18.
This hydrogeolgic setting represents extensively fractured igneous/metamorphic
bedrock.  Contaminants introduced into this aquifer system are transported
rapidly through the network of interconnected fractures.  Processes affecting
the attenuation of the contaminant within the aquifer  are limited due to  the
non-reactive nature of the bedrock and limited contact between the  contaminant
and the aquifer materials.

     The above examples demonstrate that it is possible  to infer  the pollution
potential of the setting by understanding the hydrogeology.  Inherent
assumptions and generalizations about ground-water flow and contaminant
mobility are incorporated into the numerical score generated by using DRASTIC.
When both the hydrogeologic setting and the DRASTIC Index are used
simultaneously, the user generates a clearer picture of  the true  potential  for
ground-water pollution.

ASSUMPIIONS OF DRASTIC

     DRASTIC and the modified Pesticide DRASTIC have been developed using four
major assumptions:

     1)  the contaminant is introduced at the ground surface;
     2)  the contaminant is flushed into the ground water by
         precipitation;
     3)  the contaminant has the mobility of water; and
     4)  the area evaluated using DRASTIC is 100 acres or larger.

     When deviations from these assumptions occur, there may be special
conditions which would need to be more fully evaluated.   For example, the
methodology assumes that a contaminant will start at the surface, enter the
soil, travel through the vadose zone and enter the aquifer much like water.
However, a contaminant may have unique chemical and physical properties which
                                     42

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Figure 17. Hydrogeologic impact on a contaminant in a solutioned aquifer.
    Figure 18. Hydrogeologic impact on a contaminant in a fractured aquifer.
                                 43

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would restrict movement into ground water.  A contaminant may be denser than
water and exhibit travel characteristics different from water.   Further, a
disposal method which injects contaminants directly into ground water negates
many of the natural attenuation mechanisms assumed in the methodology.   In this
particular case, DRASTIC does not provide an accurate assessment of
ground-water pollution potential.

     In assuming areas of 100 acres or larger, DRASTIC attempts to  evaluate
ground-water pollution potential from a regional perspective rather  than a site
specific focus.  An applicable analogy would be viewing an object with  the
naked eye versus a magnifying glass.  For example, in an area of fractured
rock, ground water generally flows in a regional direction.   However,
ground-water flow at any one site will be directly controlled by fracture
orientation.  In this scenario, exact direction of contaminant  movement is
controlled by a site specific characteristic.  Generally, however,  the
contaminant would still flow in the regional direction.

     In summary, DRASTIC can be a very useful tool when the assumptions of the
methodology are met.  However, the user needs to exercise caution and consider
special conditions when deviations from the assumptions occur.   To  further
assist the user in understanding the criteria upon which DRASTIC was created, a
description of each DRASTIC feature is contained in the following sections.
Processes of contaminant movement are also considered in the description of
each feature.

DEPTH TO WATER                                             ;  *

     Depth to water is important primarily because it determines the depth of
material through which a contaminant must travel before reaching the aquifer,
and it may help to determine the contact time with the surrounding media.   The
depth to water is also important because it provides the maximum opportunity
for oxidation by atmospheric oxygen.  In general, there is a greater chance for
attenuation to occur as the depth to water increases because deeper  water
levels imply longer travel times.  The presence of low permeability  layers
which confine aquifers will also limit the travel of contaminants into  an
aquifer.  Figure 3 shows the relative importance of depth to water.   The ranges
in depth to water as defined in the DRASTIC system have been determined based
on what are considered to be depths where the potential for ground-water
pollution significantly changes.

     Ground water occurs in either unconfined, confined or semi-confined
conditions.  In an unconfined aquifer, the water table represents the uppermost
elevation where the openings in the soil or rock material are filled with
water.  The water table is free to rise and fall under atmospheric  pressure.
Where present, unconfined aquifers are the uppermost aquifer near the ground
surface, and as a result, these aquifers commonly are susceptible to
ground-water pollution.  The water in a confined aquifer is under pressure by
the presence of a confining layer.  By definition, the water level in a well
penetrating a confined aquifer will rise above the base of the  confining layer.
Confined aquifers always underlie unconfined aquifers where unconfined  aquifers
are present.  Confined aquifers have more natural protection from contaminants

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infiltrating from the ground surface and are less vulnerable to pollution.
Semi-confined aquifers refer to aquifers overlain by confining layers which
allow water to move through the layer.  In this case, the aquifer is not truly
confined and the confining bed is termed "leaky".  Semi-confined aquifers
exhibit characteristics ranging from unconfined to confined aquifers.  Rate and
direction of ground-water movement through the confining layer depends on the
ground-water gradients and degree of confinement of the layer.  Leaky confining
layers may allow water to leak into the aquifer under downward gradients.  In
this case, the aquifer is more vulnerable to pollution than a confined aquifer.
Conversely, where ground-water gradients are upward, leakage of water occurs
away from the semi-confined aquifer.  In this situation, the aquifer would  be
less vulnerable to pollution.

     The unconfined or confined condition of the aquifer may have spatial
variation.  For example, the same aquifer may be unconfined in one area and
change to confined conditions in another area.  Varying degrees of confinement
are not uncommon particularly when the aquifer is of large areal extent. All
other variables equal, the pollution potential of the aquifer increases as  the
degree of confinement decreases.

     The methodology can be used to evaluate either confined or unconfined
aquifers.  In an unconfined aquifer, the user chooses depth to water as the
depth from the ground surface to the water table (Figure 19).  The water table
is the expression of the surface below the ground level where all the pore
spaces are filled with water. Above the water table, the pore spaces are
partially filled with water and air. The water table may be present in any  type
of media and may be either permanent or seasonal.  Depth to water does not
include saturated zones which have insufficieit permeability to yield
significant enough quantities of water to be considered an aquifer.  Water
level data is available from a variety of sources including well logs and
published water level maps contained in federal, state and local reports.  A
complete list of sources of potential information is contained in Table 1.

     Because DRASTIC was originally designed for the evaluation of unconfined
aquifers, special definitions must be assumed when evaluating depth to water
for a confined aquifer.  In the methodology, when an aquifer is confined, depth
to water should be redefined as the depth to the top of the aquifer (Figure
19).  This depth also corresponds to the base of the confining layer.  When
evaluating the depth to the top of the aquifer, the user does not refer to
water level maps.  The necessary information may be obtained in geologic
reports containing cross sections or maps of the elevation of the bedrock
surface.  Well logs may also be a source of information.

     Where semi-confined aquifer conditions exist, the user must choose to
evaluate the aquifer as either unconfined or confined.  DRASTIC does not permit
the user to choose a semi-confined aquifer.  The user must make a quantitative
judgement of the degree of leakage with respect to pollution potential.  If an
aquifer is only slightly leaky, the user may evaluate the aquifer as confined
and choose the depth to water as the depth from the ground surface to the top
of the aquifer.  Conversely, if the aquifer is significantly leaky, the user
may wish to evaluate the aquifer as unconfined.  In this case, the user must
find information on water levels in wells penetrating the semi-confined aquifer
for information on depth to water.
                                     45

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*»
o>

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     Key words contained in published reports about ground-water levels may be
of assistance in determining whether the aquifer is confined or  unconfined.
"Piezometric levels" are typically used when referring to water  levels in
confined aquifers.  Piezometric comes from the Greek word for pressure.  This
implies that water in confined aquifers is under pressure and that pressure is
the driving force.  "Water Table" is generally used when referring to
unconfined aquifers.  In water table aquifers, the aquifer is open to the
atmosphere and is not under pressure.  In all cases, the user should gather as
much information as possible about an aquifer in order to make an accurate and
valid selection of the media rating.  Knowledgeable individuals  should be
consulted where necessary.

NET RECHARGE

     The primary source of ground water typically is precipitation which
infiltrates through the surface of the ground and percolates to  the water
table.  Net recharge represents the amount of water per unit area of land which
penetrates the ground surface and reaches the water table.  This recharge water
is thus available to transport a contaminant vertically to the water table and
horizontally within the aquifer.  In addition, the quantity of water available
for dispersion and dilution of the contaminant in the vadose zone and in the
saturated zone is controlled by this parameter.  Recharge water, therefore, is
a principal vehicle for leaching and transporting solid or liquid contaminants
to the water table.  The greater the recharge, the greater the potential for
ground-water pollution.  This general statement is true until the amount of
recharge is great enough to cause dilution of the contaminant, at which point
the ground-water pollution potential ceases to increase and may  actually
decrease.  For purposes of this document, this phenomena has been acknowledged
but the ranges and associated ratings do not reflect the dilution factor.

     As used in the methodology, net recharge is defined as the  total quantity
of water which is applied to the ground surface and infiltrates  to reach the
aquifer.  Net recharge includes the average annual amount of infiltration and
does not take into consideration distribution, intensity or duration of
recharge events.  Net recharge may be expressed in various units;  DRASTIC uses
inches per year.

     Values for net recharge are often calculated for watershed  or specific
study areas, but rarely for a county.  These values typically are found in
published water resource or hydrologic reports and may need to be extrapolated
to obtain representative recharge values for areas situated outside the study
area of the published report.  Where published values for net recharge  are
difficult to obtain, knowledgeable individuals may need to be consulted for
estimates or confirmations of appropriate net recharge values.   Because net
recharge values are less precise and less easily obtained than values for other
ERASTIC parameters, the ranges for net recharge are intentionally broad.   These
broad ranges afford the user "professional leeway" in choosing a range  which is
representative of the amount of recharge for the area.

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     Another potential source of recharge information is a  water atlas which
may contain general maps of average annual precipitation, evaporation and
runoff.  Where net recharge to an area principally occurs from  precipitation,
the user should be able to estimate the net recharge  value  as the amount of
precipitation minus surface runoff, evaporation and transpiration.   When using
this method to determine the value for net recharge,  it is  necessary to ensure
that the selected value is reasonable since net recharge is also influenced by
other factors such as the amount of surface cover, slope and soil permeability.
More accurate estimates of net recharge may be obtained by  using more detailed
water balance equations which account for these factors.

     Net recharge values can be chosen to evaluate either unconfined or
confined aquifers.  A definition of unconfined and confined aquifers can be
found in the section describing aquifer media.  In areas where  the  aquifer is
unconfined, recharge to the aquifer usually occurs more readily and the
pollution potential is generally greater than in areas with confined aquifers.
In unconfined conditions, net recharge values reflect typical water balance
calculations.  Confined aquifers are partially protected from contaminants
introduced at the surface by layers of low permeability media which retard
water movement to the confined aquifer.  In portions  of some confined aquifers,
ground-water gradients are such that movement of water is through the confining
bed from the confined aquifer into the unconfined aquifer.   In  this situation,
there is little opportunity for local contamination of the  confined aquifer and
a low value for net recharge could be chosen.  The principal recharge area  for
the confined aquifer is often many miles away.  However, many confined  aquifers
are not truly confined and are partially recharged by migration of  water
through the confining layers.  The more water that leaks through, the greater
the potential for recharge to carry pollution into the aquifer.  Values  for net
recharge can be chosen to reflect the amount of water which may actually
recharge the aquifer.

     In addition to infiltration from precipitation,  sources of recharge
including irrigation, artificial recharge and wastewater application must be
considered.  These sources of recharge may significantly affect the amount of
water available to carry a pollutant into the aquifer.  For example, irrigation
has been estimated to provide as many as four inches  per year  to net recharge
values.  It is particularly important to account for irrigation water
contribution when using Pesticide DRASTIC.  The user should include all  sources
of recharge when choosing an appropriate net recharge range for DRASTIC.

     Special consideration may need to be given to known recharge-discharge
areas.  Water flows from recharge to discharge areas.  A recharge area  occurs
where there is a downward component of movement to the direction of ground-
water flow; conversely, discharge areas have an upward component of flow near
the surface.  Discharge areas commonly form springs,  rivers or  other surface
water expressions.  Recharge and discharge areas may be influenced by changes
in ground-water gradients.  Changes in ground-water gradient commonly occur
when nearby water wells are pumped.  Where ground-water gradients are strongly
upward, such as in areas with first order magnitude springs, pumpage has little
effect on the recharge-discharge relationship.  In this case,  the user  may  wish
                                     48

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to choose a lower value for net recharge because very little if any water is
moving downward against such strong gradients.   In areas where  gradients  are
not as pronounced, pumpage may affect or reverse ground-water flow.  In
discharge areas where gradients may be easily reversed,  the user may wish not
to reduce net recharge values.  Conversely, in known recharge areas which are
environmentally sensitive, the user may wish to upwardly adjust the recharge
values.

AQUIFER MEDIA

     Aquifer media refers to the consolidated or unconsolidated rock which
serves as an aquifer (such as sand and gravel or limestone).  An aquifer  is
defined as a subsurface rock unit which will yield sufficient quantities  of
water for use.  Water is contained in aquifers  within the pore  spaces of
granular and clastic rock and in the fractures and solution openings of
non-clastic and non-granular rock.  Rocks which yield water from pore spaces
have primary porosity; rocks where the water is held in  fractures and solution
openings which were created after the rock was  formed have secondary porosity.
The flow system within the aquifer is affected  by the aquifer medium.  The
route and path length which a contaminant must  follow are governed by the flow
system within the aquifer.  The path length is an important control (along with
hydraulic conductivity and gradient) in determining the  time available for
attenuation processes such as sorption, reactivity and dispersion to occur.
The aquifer medium also influences the amount of effective surface area of
materials with which the contaminant may come in contact within the aquifer.
The route which a contaminant will take can be  strongly  influenced by
fracturing or by an interconnected series of solution openings  which may
provide pathways for easier flow.  In general,  the larger the grain size  and
the more fractures or openings within the aquifer, the higher the permeability
and the lower the attenuation capacity of the aquifer media.

     For purposes of this document, aquifer media have been designated by
descriptive names.  Each medium is listed in the order of increasing pollution
potential.  A discussion of each medium follows:

     a)  Massive Shale - Thick bedded shales, claystone  or clays which
typically yield only small quantities of water  from fractures and which have a
low pollution potential.  Pollution potential is influenced by  the degree of
fracturing.

     b)  Metamorphic/Igneous Rock - Consolidated bedrock of metamorphic or
igneous origin which contains little or no primary porosity and which yields
water only from fractures within the rock.  Typically well yields are low and
the relative pollution potential is a function  of the degree of fracturing.

     c)  Weathered Metamorphic/Igneous Rock - Unconsolidated material, commonly
termed regolith or saprolite, which is derived  by weathering of the underlying
consolidated bedrock, and which contains primary porosity.   The pollution
potential is largely influenced by the amount of clay material  present; the
higher the clay content, the lower the pollution potential.
                                     49

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     d)  Glacial Till - Unconsolidated to semi-consolidated mixtures of gravel,
sand, silt and clay-size particles which are poorly sorted and stratified.   The
low permeability of the till produces low yields to wells.  Although glacial
tills exhibit low permeabilities, wells completed in tills are typically
shallow and may be more susceptible to contamination.  Fracturing of tills  may
also influence pollution potential.

     e)  Bedded Sandstone, Limestone and Shale - Typically thin-bedded
sequences of sedimentary rocks which contain primary porosity.  The controlling
factor in determining pollution potential is the degree of fracturing.

     f)  Massive Sandstone - Consolidated sandstone bedrock which contains  both
primary and secondary porosity and is typified by thicker deposits than the
Bedded Sandstone Limestone and Shale sequences.  Pollution potential is largely
controlled by both the degree of fracturing and the primary porosity of the
sandstone.

     g)  Massive Limestone - Consolidated limestone or dolomite bedrock which
is characterized by thicker deposits than Bedded Sandstone, Limestone and  Shale
sequences.  Pollution potential is largely affected by the degree of fracturing
and the amount of solution cavities in the limestone.

     h)  Sand and Gravel - Unconsolidated mixtures of sand to gravel-sized
particles which contain varying amounts of fine materials.  Sands and/or
gravels which have only small amounts of fine material are termed "clean."   In
general, the cleaner and more coarse-grained the aquifer, the greater the
pollution potential.

     i)  Basalt - Consolidated extrusive igneous bedrock which contains bedding
planes, fractures and vesicular porosity.  The term is used herein in a generic
sense, even though it is actually a rock type.  Pollution potential is
influenced by the amount of interconnected openings which are present in the
lava flow materials.

     j)  Karst Limestone - Consolidated limestone bedrock which has been
dissolved to the point where large, open, interconnected cavities and fractures
are present.  This is a special case of Massive Limestone.

     A graphic display of the ratings which have been assigned to each media is
contained in Figure 5. This graph also contains a more complete listing of  the
mechanisms which affect the pollution potential of that media.  Because this
DRASTIC parameter is less quantifiable than numerical parameters, the user  will
be instructed to choose a media type and rating based on the above discussion
and available information on the geology of the area (Section 4,  How to Use the
Range in Media Ratings).

     The user may choose to evaluate any aquifer within an area,  however, only
one aquifer may be evaluated at a time.  In a multi-layer system, the user  must
decide which aquifer to choose as the appropriate media.  Information on
aquifers is typically available in published geologic or hydrologic reports,
masters theses, well logs or other exploratory borings.  A complete list of


                                     50

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sources of potential information is contained in Table  1.   Once  the  aquifer  has
been chosen, the aquifer media used for DRASTIC is  selected by identifying the
most significant media of the chosen aquifer.  For  example, if the aquifer is a
limestone, the user would choose either massive or  karst  limestone as  the
aquifer media.  Similarly, if the aquifer is a sand and gravel,  the  user would
choose sand and gravel as the aquifer media.

     DRASTIC provides the user with a range  of ratings  to  choose from  when
evaluating the aquifer media.  This allows the user to  adjust the rating for
the media based on specific information about the aquifer.   If no specific
information is available, or the user is uncertain, a typical rating for each
media is provided.  This typical rating has  been chosen to  depict a  typical
aquifer comprised of the associated aquifer  media.   The user may vary  the
rating based on degree of fracturing or presence of bedding planes in
consolidated aquifers.  For example, a moderately fractured metamorphic/igneous
aquifer would receive a rating of 3.  If however, the aquifer was highly
fractured, the aquifer could be assigned a rating of 5  to  indicate higher
pollution potential.  Conversely, if the metamorphic/igneous aquifer was only
slightly fractured, the yields in the area would be low and the  assigned rating
would be a 2.  In unconsolidated aquifers, the user may vary the rating based
on the sorting and amount of fines within the aquifer.  For example, a typical
sand and gravel would receive a rating of 8.  If the deposits are coarse and
well-washed, the user could assign a rating  of 9.  Conversely, as the  amount of
fines increase and the deposits become more  poorly  sorted,  the assigned rating
can be lowered to 7 or 6.

SOIL MEDIA

     Soil media refers to that uppermost portion of the vadose zone
characterized by significant biological activity.  For  purposes  of this
document, soil is commonly considered the upper weathered  zone of the  earth
which averages a depth of six feet or less from the ground  surface.  Soil has a
significant impact on the amount of recharge which  can  infiltrate into the
ground and hence on the ability of a contaminant to move  vertically  into the
vadose zone.  The presence of fine-textured  materials such as silts  and clays
can decrease relative soil permeabilities and restrict  contaminant migration.
Moreover, where the soil zone is fairly thick, the  attenuation processes of
filtration, biodegradation, sorption and volatilization may be quite
significant.  Thus, for certain land surface practices, such as  agricultural
applications of pesticides, soil may have the primary influence  on pollution
potential.  In general, the pollution potential of  a soil  is largely affected
by the type of clay present, the shrink/swell potential of  that  clay and the
grain size of the soil.  In general, the less the clay  shrinks and swells and
the smaller the grain size, the less the pollution  potential.  The quantity  of
organic material present in the soil may also be an important factor
particularly in the attenuation of pesticides.  Organic matter is typically
contained in the surface layer of the soil and composed of  undecayed plant and
animal tissue, charcoal and various humic compounds. The organic content of
the soil generally decreases with depth from the surface.   Humic compounds are
principally responsible for the adsorption and complexation properties
attributed to organic matter in the soil.  Soil media are  best described by
                                    51

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referring to the basic soil types as classified  by  the Soil  Conservation
Service.  A description of the soil media in order  of  increasing  pollution
potential follows:

     a)  Nonshrinking and Non-aggregated Clay -  Illitic or Kaolinitic  clays
which do not expand and contract  with the addition  of  water  and therefore do
not form vertical secondary permeability which increases the pollution
potential.

     b)  Clay Loam - A soil textural classification which is characterized by
15-55 percent silt, 27-40 percent clay and 20-45 percent sand (Figure  20).
Because of the high amounts of clay and restrictive permeabilities,  it has a
low pollution potential.

     c)  Muck - A soil consisting of fine, dark-colored, well decomposed
organic material that typically contains a higher mineral or ash  content than
peat.  Muck contains the least amount of plant fiber of the  organic  soils, thus
limiting permeability.  The organic matter content  may be a  significant factor
for lowering the pollution potential.

     d)  Silty Loam - A soil textural classification characterized by  50-85
percent silt, 12-27 percent clay and 0-50 percent sand (Figure 20).  The
pollution potential is still low, but higher than a clay loam because  of
typically lower percentages of clay.

     e)  loam - A soil textural classification characterized jy 25-50  percent
silt, 7-27 percent clay and 0-50 percent sand (Figure 20).  The pollution
potential is still low, but higher than a silty  loam because of lower
percentages of clay and silt.

     f)  Sandy Loam - A soil textural classification characterized by  0-50
percent silt, 0-20 percent clay and 15-50 percent sand (Figure 20).  The
pollution potential is greater than a loam due to the higher percentage of
sand.

     g)  Shrinking and/or Aggregated Clay - Characterized by montmorillonitic
clays or smectites which have an expanding lattice  that swell and contract with
alternating wetting and drying.  Dessication cracks may form as the  soil dries.
These cracks may later be shut as the clay swells when hydrated.  Pollutants,
however, may move rapidly through the dessication cracks upon initial  wetting
of the soil.  Although usually of low permeability, this medium can  have a
seemingly high pollution potential based on the  secondary vertical permeability
created by the cracking of the media upon drying.

     h)  Peat - A soil consisting of undecomposed to partially decomposed plant
material that is fresh enough to be identified.   Although peats contain organic
matter which may be significant for contaminant  attenuation, they are
relatively permeable, thus pollution potential is high.

     i)  Sand - A size-based delineation of angular or rounded particles
ranging in size from 1/16 mm to 2 mm.  Sands are typically free of silts and
clays and therefore have a high pollution potential.

                                     52

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                70           jW
                '    /WxyXK^1'' r\r'r
                           • x>  i   i    if i'in
                                 .                   y-AA
                              fl^^
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     j)  Gravel - A particle-based  size  classification typified  by  particles
larger than 2 mm in size.   Gravel  soils  commonly include  a  mixture  of  sand,
silt, clay and gravel particles, with a  preponderance of  large-sized particles.
Permeability is rapid and  pollution potential  is high.

     k)  Thin or Absent -  If a soil layer  is not present  or if the  layer is so
thin as to be considered ineffective for contaminant attenuation, the  pollution
potential is very high. Thin or absent  should generally  be chosen  when the
soil profile is 10 inches  or less  in thickness.

     Figure 6 contains a graphic representation of  the varying impacts which
soil media may have on the ground-water  pollution potential of an area.  Soil
surveys published by the Soil Conservation Service,  United  States Department of
Agriculture, provide the information necessary for  the evaluation of soils in
DRASTIC.  If published soil surveys are  not available for a county, soil
information may often be obtained  from the local Soil and Water  Conservation
District.  The county may  be part  of an  active soil survey  effort and  portions
or all of the county soils information may be  available as  field maps.  If
there is no on-going soil  mapping  project, portions of the  county may  have been
previously evaluated for special projects. Regardless of the status of a
mapping program, local soil scientists may be  able  to provide valuable soil
information.

     Published soil surveys provide information in  three  basic formats:  1)
maps, 2) written descriptions and  3) descriptive charts.  Soil survey  maps are
displayed as either general soil association maps or detailed soil  maps which
delineate individual soil  series.   The general soil association  maps provide an
overview of the major soil associations  which  have  been identified  in  the
county.  These associations represent a  geographically related group of soil
series which are characterized by  surface  soil textures.  The detailed soil
maps are displayed as a series of  fold-out sheets which detail specific soil
series superimposed on aerial photographs.  The soil series characteristics are
described within the main  text of  the soil survey.   A soil  series  is named for
the geographic locality where the  unique characteristics  of the  soil were  first
described.  Soil series descriptions supply information on  the soil drainage,
texture and composition of the various horizons or  layers within the series.
This infomation is expanded into a group of charts  which detail  land capability
usage and other important  characteristics  of each soil series.   Of  particular
interest are the tables which detail the engineering properties  and the
physical and chemical properties  of the  soils.

     The selection of an appropriate soil media in  ERASTIC  requires the user to
consider the characteristics of the soils which influence ground-water
pollution potential.  This is accomplished by  identifying the most  significant
soil textural layer which will influence water movement and contaminant
transport.  The user may take several approaches in this  evaluation, however,
the following approach is recommended until the user becomes familiar  with the
process.
                                     54

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     1)  Look at the general soil association map for the county.

     2)  Read the soil association descriptions in the text to identify major
 soil types.

     3)  Read the individual soil series descriptions for the major soil series
 in each soil association.

     4)  Review the depth and thickness of each soil texture in the soil
 profile by referring to the USDA texture category in the table of  engineering
 properties.

     5)  Evaluate all horizons in the profile of a soil series and choose the
 most significant textural layers that will affect pollution potential  based  on
 consideration of the thickness and texture of the layers.  Compare the chosen
 texture with the surface texture described in the general soil association
 description and map legend to determine what portions, if any, of  the  general
 soil association map may be used in DRASTIC.  The selection of the most
 significant layer can be demonstrated in the following examples.   The  profile
 of a soil series is described as a sequential series of individual layers,
 starting from the ground surface.  In the first example, the Astatula  soil
 series has a profile of only one layer which is 0 to 86 inches of  sand.   The
 user would select sand as the appropriate soil media.  In this case, the
 general soil association map would be usable for DRASTIC because sand  also
 represents the surface texture of this soil series.

     The next example represents a soil series with multiple soil  layers.  The
 Hiwassee soil has a profile of 0 to 7 inches of sandy loam,  7 to 62 inches of
 clay and 62 to 82 inches of sandy clay loam.  In this example, the occurrence
 of 55 inches of clay would represent the most significant layer and would be
 selected as the appropriate soil media.  The use of  the general soils  map or
 series name which denotes the surface texture as sandy loam would  result in  the
 incorrect choice of soil media without consideration of the entire soil
 profile.  When clay is chosen as the significant soil texture, the user  must
 evaluate the shrink-swell potential of each clay layer contained within the
 soil profile.  The relative shrink-swell potential of a clay is important
 because of the possible transport of contaminants in fractures of  shrinking  and
 aggregated clays.  The shrink-swell potential of the soil layers can be
 determined from the physical and chemical property table appearing in  published
 soil surveys.   If the shrink-swell potential is high, assign a DRASTIC  range
 of shrinking and aggregated clay; where the shrink-swell potential is  low,
assign a DRASTIC range of non-shrinking and non-aggregated clay.   If a  soil  has
 a moderate shrink-swell potential in the majority of the profile,  a DRASTIC
range of shrinking and aggregated clay should be assigned.

     The next example illustrates the need to consider additional  factors  in
 the selection of soil media.  The Matapeake soil series has a profile  of 0 to
11 inches of silt loam, 11 to 26 inches of silt loam and silty clay loam,  26 to
 32 inches of very fine sandy loam, and 32 to 50 inches of fine sandy loam.   In
this case, the user must evaluate the relative thicknesses of the  horizons with
 respect to soil texture.  In the event of a difficult decision, the user may
wish to evaluate other information such as organic matter content  or

                                     55

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permeability in making a soil media selection.   In  this example,  the
appropriate soil media selection would  be  the silt  loam;  this media represents
the most significant layer when considering  pollution potential.  The general
soil association map would reflect  this surface  texture and could be used to
help delineate DRASTIC ranges.  Note that  DRASTIC does not permit the
incorporation of a petrocalcic layer (i.e.  fragipan,  durapan or caliche) within
the numerical rating system.   Since the presence of this layer may restrict
vertical fluid movement within the  soil horizon, the  user may wish to
supplement the DRASTIC evaluation with  this  information.

     6)  Where portions or all of the general soil  association map cannot be
used to delineate the soil media for ERASTIC, refer to the detailed soil maps.
In essence, the user must formulate a general soil  map of areas 100 acres or
larger based on the most significant layer from  a pollution potential
standpoint.  The user may find that the easiest  approach is to choose the
correct soil media for each soil series, and separate them into significant
groups on the maps by colors.  Because  the maps  are so detailed,  the user may
experience difficulty in making these generalizations because the process is
time-consuming when evaluating large areas such  as  a  county.

     7)  Where soils are thin or absent, little  protection from pollution is
offered.  In this case, the user may use the DRASTIC  designation  of thin or
absent.  In general, this category  should  be used where the soil  profile is
less than 10 inches thick.  This is particularly true for sands,  however, the
user may wish to consider even less thickness where the soil media is
non-shrinking and non-aggregated clay.   The  decision  of when to use this
category is based on a point where  the  thickness of the soil media does not
significantly contribute to contamination  attenuation.

     Additional information regarding various  soil  characteristics can be found
in other parts of the soil survey should more  specific information be desired.
For example, the tables on engineering  properties of  soil series  frequently
contain information on grain size distribution,  soil  pH and soil  permeability,
liquid limit and plasticity index.   Recent published  soil surveys may also
contain information on soil organic matter content  which may be of particular
interest in evaluating the ground-water pollution  potential in areas where
pesticides are applied.  The current DRASTIC methodology does not permit the
user to incorporate information on organic matter (other than what already
appears in the soil media ranges) into  the numerical  system; however, the user
can use this information to supplement  the IRASTIC  evaluation.

     Although this discussion has centered around the use of soil series and
associated textural layers within the soil,  the  Soil  Conservation Service has
developed a very detailed and descriptive  system for  naming and classifying
soils.  Soil taxonomic classifications  can provide  the user with  additional
information on soil genesis, particle size class,  soil mineralogy and soil
temperature.  A complete discussion of  soil  classification and  taxonomy may be
found in Soil Conservation Service (1960;  1975).
                                     56

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TOPOGRAPHY

     As used here, "topography" refers to the slope and slope variability of
the land surface.  Topography helps control the likelihood that a pollutant
will run off or remain on the surface in one area long enough to infiltrate.
Slopes which provide a greater opportunity for contaminants to infiltrate will
be associated with a higher ground-water pollution potential.  Topography
influences soil development and therefore has an effect on contaminant
attenuation.  Topography is also significant because gradient and direction of
flow often can be inferred for water table conditions from the general slope of
the land.  Typically, steeper slopes signify higher ground-water velocity.

     Figure 7 contains the slope ranges which were chosen as significant
relative to ground-water pollution potential.  These ranges correspond to the
typical ranges identified by the Soil Conservation Service for percent slope.
The ranges are assigned ratings assuming that 0 to 2 percent slope provides the
greatest opportunity for a pollutant to infiltrate because neither the
pollutant nor much precipitation exits the area as runoff.  Conversely, 184-
percent slope affords a high runoff capacity and therefore a lesser probability
of contaminant infiltration and a subsequent lower ground-water pollution
potential.  Steep slopes, however, are more conducive to rapid erosion and
contamination of surface water.

     Percent slopes for topography may be determined from published soil
surveys and U.S. Geological Survey 7 1/2 and 15 minute quadrangle topographic
maps.  Recently published soil surveys have letters on the detailed soil maps
which represent percent slope ranges (i.e. A equals 0 to 2 percent, B equals 2
to 6 percent).  The user may be able to identify soil and topography together
since soil series frequently correspond to topographic breaks.  Percent slope
may also be calculated directly from 7 1/2 and 15 minute topographic maps.
Percent slope is equal to the vertical "rise" divided by the horizontal "run".
The user must measure the change in elevation over a measured distance on the
topographic map.  Distance may be calculated by using a ruler to measure a
length on the map and then by comparing this length to the scale at the bottom
of the map.  The scale for 7 1/2 minute maps is 1 inch equals 2000 feet.
Change in elevation is calculated by counting the number of contour lines
crossed within the measured length, multiplied by the contour interval of the
map.  The user should always check the contour interval for each map;  the
contour interval can vary widely from one map to the next.  Percent slope can
be checked at intervals across the map and the most appropriate slope  range for
an area can then be selected.

IMPACT OF THE VADOSE ZONE MEDIA

     The vadose zone is defined as that zone above the water table which is
unsaturated or discontinuously saturated.   The type of vadose zone media
determines the attenuation characteristics of the material below the typical
soil horizon and above the water table.   Biodegradation, neutralization,
mechanical filtration, chemical reaction,  volatilization and dispersion are all
processes which may occur within the vadose zone.  The amount of biodegradation
and volatilization decreases with depth.   The media also controls the  path
length and routing, thus affecting the time available for attenuation  and the
quantity of material encountered.  The routing is strongly influenced  by any

                                     57

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fracturing present.  The materials at the top of  the vadose zone  also  exert  an
influence on soil development.

     Vadose zone media have been designated by descriptive  names.   Each medium,
listed in order of increasing ground-water pollution potential  is discussed  as
follows:

     a)  Confining layer - This media is chosen when evaluating a confined
aquifer.  A confining layer represents an impermeable layer which restricts  the
movement of water into an aquifer.

     b)  Silt/Clay - A deposit  of silt and clay-sized particles which  serves as
a barrier to retard movement of liquids.  The high clay content provides a low
pollution potential.  Shrinking clays and higher  silt concentrations increase
the pollution potential.

     c)  Metamorphic/Igneous Rock - Consolidated  rock of metamorphic or igneous
origin which contain no significant primary porosity and which  permit  movement
of liquids through fractures.  The relative pollution potential is a function
of the degree of fracturing.

     d)  Shale - A consolidated thick-bedded clay rock which may  be fractured.
Pollution potential is low but  increases with the degree of fracturing.

     e)  Limestone - Consolidated massive limestone or dolomite which  typically
contains fewer bedding planes than Bedded Limestone, Sands D  *e  and Shale
sequences (see "g" below).  Pollution potential is influenced by  the degree  of
fracturing, with a high density of fracturing increasing the chance for
pollutant migration.

     f)  Sandstone - A consolidated sand rock which contains both primary and
secondary porosity and is typified by thicker bedding, as opposed to Bedded
Limestone, Sandstone, Shale sequences.  Pollution potential is  largely
controlled by the degree of fracturing and the primary porosity of the
sandstone.

     g)  Bedded Limestone, Sandstone, Shale - Typically thin-bedded sequences
of sedimentary rocks which contain primary porosity, but where  the controlling
factor in determining pollution potential is the degree of  fracturing.

     h)  Sand and Gravel with Significant Silt and Clay - Unconsolidated
mixtures of sand and gravel which contain an appreciable amount of fine
material.  These deposits have a high concentration of clay, thereby reducing
the permeability of the deposits.  These deposits are commonly referred to as
"dirty" and have a lower pollution potential than "clean" sands and gravels.
In general, finer-grained and "dirtier" sands have a lower  pollution  potential
than coarser-grained "dirtier" gravels.

     i)  Sand and Gravel - Unconsolidated mixtures of sand  to gravel-sized
particles which contain only small amounts of fine materials.  The range in
rating reflects principally a grain size distribution where unsorted  smaller
                                     58

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grained deposits have a lower pollution potential and larger grained,
well-sorted deposits have a higher pollution potential.

     j)  Basalt - Consolidated extrusive igneous bedrock which contains bedding
planes, fractures and vesicular porosity.  This is a special case of
Metamorphic/Igneous.  The term is used herein in a generic sense, even though
it is actually a rock type.  Pollution potential is influenced by the  number
and amount of interconnected openings present in the lava flow materials.
Pollution potential is typically high because there is little chance for
attenuation once a pollutant enters the fracture system.

     k)  Rarst Limestone - Consolidated limestone bedrock which has been
dissolved to the point where large open interconnected cavities and fractures
are present.  This is a special case of Limestone where  pollution potential  is
high based on the amount of open area in the rock.

     A graphic display of the ratings which have been assigned to each vadose
zone medium is contained in Figure 8.  This graph also contains a more complete
listing of the mechanisms which affect the pollution potential of each medium.

     The selection of the vadose zone media depends on whether the aquifer to
be evaluated is unconfined or confined.  A definition of unconfined and
confined aquifers can be found in the discussion on depth to water.  In the
case of an unconfined or semi-confined aquifer that will be evaluated  as
unconfined, the user must select the most significant media which influences
pollution potential.  By definition, the vadose zone will include all  the
unsaturated media below the soil and above the water table (Figure 21).
Information on vadose zone media is typically available  in published geologic
or hydrologic reports, masters theses, well logs or other exploratory  borings.
A complete list of potential sources of information is contained in Table  1.
In a multi-layer system, relative thickness of the media is one parameter  which
influences the selection of the vadose zone media, however pollution potential
must also be considered.  For example, where a limestone aquifer is overlain by
a significant thickness of sand and gravel and the water table is at the top of
the limestone, the vadose zone media would be chosen as sand and gravel.
However, if the sand and gravel were thinner and the water table was deep
within the limestone, limestone might be chosen as the vadose zone media.
Another example would be where a limestone aquifer is overlain by a silt/clay
layer and a sand and  gravel layer of equal or greater thickness.  The
silt/clay layer will be the most significant layer from a ground-water
pollution potential standpoint because it would restrict the movement  of
contaminants into the limestone aquifer.  The user would select silt/clay  as
the most appropriate vadose zone media.  In the special  case where the water
table is very near or at the surface, the vadose zone media may be saturated.
In this situation, the user still must choose a vadose zone media and  assign an
appropriate rating.

     Where an aquifer is confined, the impact of the vadose zone includes  all
media below the soil and above the top of the aquifer (Figure 21).  In many
situations, the vadose zone will not be a true vadose zone, because part of  the
saturated zone may be treated as the vadose zone.  When evaluating a confined
                                     59

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   impact ol vadosezone-.-
„,„—
                        •
                                 — —
                     60

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aquifer, the user must choose "confining layer" as the vadose zone media.
Because the confining layer is the media which most significantly impacts
pollution potential, the user is choosing the true impact of the vadose zone.
Confining layer is used regardless of the other media composition in the area.
For example, where a sandstone aquifer is overlain by a confining shale layer
and a sand and gravel deposit of sufficient thickness, the impact of the vadose
zone media is chosen as "confining layer" even though shale and sand and gravel
would be listed in the table.

     DRASTIC also provides a range of ratings for each media, with the
exception of confining layer.  Confining layer must always be assigned a value
of 1.  When evaluating an unconfined aquifer, the user may adjust the rating
for each media to reflect information gained from published reports, well logs
and knowledgeable individuals.  Ratings are chosen similarly to the ratings for
aquifer media.  The user is referred to the discussion in the aquifer media
section.  Additional assistance in choosing ratings may also be found in the
following discussion.

     In consolidated media, ratings may be chosen to reflect the amount of
secondary porosity by degree of fracturing, bedding ~or solution channels.  A
typical rating is provided for each media.  The typical rating can be used in
an aquifer with a moderate amount of fracturing or where data is not sufficient
to change the media rating.  For example, where a limestone vadose zone is
present, the limestone may be highly solutioned allowing contaminants to
infiltrate the vadose zone rapidly and without any attenuation. The vadose zone
media would be chosen as a karst limestone and assigned a rating of 10.  If
however, less solution channels were present or the channels were not
significantly interconnected, the vadose zone media would still be chosen as
karst limestone, but the rating could be lowered to a 9 or 8 depending on the
amount and interconnection of the channels.  Still using the limestone as an
example, assume the limestone was not karstic but rather a dolomite with few
fractures.   The user would choose a vadose zone media of limestone.  A rating
lower than the typical 6 would then be chosen based on the degree of
fracturing.

     In unconsolidated media, the user is provided with three descriptive media
ranges for unconsolidated deposits.  The user may choose sand and gravel, sand
and gravel deposits with significant silt and clay or silt/clay depending on
the relative proportion of the finer-grained materials.  Ratings for each media
are provided in parenthesis.  Sand and gravel is used where the deposits
consist mostly of sand and gravel with only small amounts of finer-grained
materials (6-9).  Sand and gravel with significant silt and clay is used where
the predominant media is still sand and gravel (usually in lenses) but the
matrix is finer grained deposits (4-8).  Silt/clay is used to delineate
deposits where the predominant material is fine-grained silt or clays, however
small amounts of sand and gravel may still be present in the deposit (2-5).
The three media ranges provide ratings which overlap the entire rating scale.

     The user may choose ratings to reflect grain size, sorting, homogeneity
and amount  of fine material.  For example, a well-sorted sand and gravel that
is well washed may receive a rating of 9 while a sand and gravel with a larger
                                     61

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fine fraction would receive a 7.   Although no specific designation for glacial
till is listed in the vadose zone media chart, glacial tills can be evaluated
using the following discussion.

     Depending on the characteristics of the till,  the user may choose either
silt/clay or sand and gravel with significant silt  and clay as  the appropriate
media and adjust the ratings accordingly.  For example, a sandy till may be
called a sand and gravel with significant silt and  clay and assigned a rating
of 6.  Conversely, a dense, unfractured, clayey till would be called silt/clay
and assigned a rating of 3.

HYDRAULIC CONDUCTIVITY OF THE AQUIFER

     Hydraulic conductivity refers to the ability of the aquifer materials to
transmit water, which in turn, controls the rate at which ground water will
flow under a given hydraulic gradient.  The rate at which the ground water
flows also controls the rate at which a contaminant moves away  from the point
at which it enters the aquifer.  Hydraulic conductivity is controlled by the
amount and interconnection of void spaces within the aquifer which may occur as
a consequence of intergranular porosity, fracturing and bedding planes.   For
purposes of this document, hydraulic conductivity is divided into ranges where
high hydraulic conductivities are associated with higher pollution potential.
Figure 9 shows the relative importance of the ranges.

     Values for hydraulic conductivity are calculated from aquifer pumping
tests.  Information on hydraulic conductivity typically is available in
published hydrogeologic reports or masters theses.   A complete  list of
potential sources of information is contained in Table 1.  If this information
is not available in published reports, values for hydraulic conductivity may be
estimated from Table 12.  Well yields may also provide assistance in estimating
hydraulic conductivity.  The user is advised to contact knowledgeable
individuals such as consultants,  federal, state and local government employees
and drillers in the area which also may be able to  provide or confirm
reasonable estimates of hydraulic conductivity.  The broad ranges for hydraulic
conductivity provided in the DRASTIC charts were designed to provide
flexibility in selecting appropriate values.

INTERACTION BETWEEN PARAMETERS

     From the above discussion and in the application of the DRASTIC Index, it
will be recognized that there is redundance between some of the parameters.
The depth to the water, for example, affects the quantity of material that will
be encountered by a pollutant moving downward toward an aquifer.  The thicker
the vadose zone in a given setting, the greater the effect may  be upon the
degradation, retardation or attenuation of the pollutant.

     However, in considering the impact of the vadose zone, degradation,
retardation and other significant attenuation processes are all varied
according to the nature of the materials present, and their condition within
the vadose zone.  If, for instance, the vadose zone is moderately fractured
granite, the materials within the vadose zone will  have only a  slight impact on
                                     62

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TABLE 12. RANGE OF VALUES OF HYDRAULIC CONDUCTIVITY AND PERMEABILITY
         (FREEZE AND CHERRY,1979)
Rocks Unconsolldated k k k k k
^ deposts ^ (darcy) (cm2) (cm/s) (m/s) (gal/day/ft2)



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•io-5

•106

-10 7


• 10 J'

•109


-10 '°


-10 "

-10 12


-10 '3

-io-14

-10-'-1
.io-1"
•10'

•10


-1

•10 '

-io-2


-103

-10'4


• 10 5


-1Q-6

-107


-10 8

-109

-10-'°
-10-"
-1

•10 '


-10 2

-10 3

•104


-105

•10 6


-TO'7


-10 8

-io-9


•1Q-10

-10 1I

-10 '2
• 10 -13
E
1
•106


-105

-104

•103


-102

•10


-1


-10-'

-102


-103

• 1Q-4


-105
-1Q-6

L1Q-7
                                63

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most pollutants entering the vadose zone.   The protection provided  will  be  a
function of depth and the failure of critical fractures to interconnect.

     If, however, the vadose zone is comprised of  unfractured  glacial  till, it
can be anticipated that consumptive sorption will  be moderately  high;
infiltration will be moderately low; retardation will be significant;  and with
any substantial thickness of till, considerable time will be required  for most
pollutants to penetrate the till.  Thus it can be  seen that the  redundant
consideration of degradation, retardation and attenuation within the context  of
both depth to water and impact of the vadose zone  is useful in the  comparative
evaluation of sites.

     Net recharge determines, on an annual basis,  the quantity of water  from
precipitation that is available for vertical transport, dispersion, and
dilution of a pollutant from a specific point of application.  Net  recharge
exemplifies how some parameters can have both positive and negative effects.
For example, greater recharge typically means more rapid transport  of  a
pollutant and therefore less time for attenuation.  However, in  this situation,
dilution is also greater thereby exerting a positive influence because the
concentration of an introduced contaminant will be lessened.   It is also
evident that a thick unsaturated zone, with a layered sequence of bedded and
fractured shales, sandstones and limestones, can have a profound impact  on  all
three of the same factors (transport, dispersion,  dilution) that are of  primary
importance to net recharge.

     Topography and soil media also influence net  recharge. Topography  has
site-specific influence which determines whether the capacity  for recharge  is
high or low at a given point.  The permeability of the surface soils has &
similar impact.  However, the nature of the surface soil materials  has an
additional impact upon potential pollutant attenuation, consumptive sorption,
route length and direction, and time available for penetration.

     In addition to its direct influence upon recharge, topography  exerts a
significant influence upon soil thickness, drainage characteristics, and
profile development.  These factors, in turn, influence soil media  as  well  as
the previously-mentioned factors.  In addition, topography usually  bears a
predictable relationship to hydraulic gradient, and direction  of probable
pollutant movement under water table conditions, with a consequent  impact on
dispersion and dilution.

     The upper portion of the vadose zone exerts influence on  the type of soils
developed on the surface.  The vulnerability of an aquifer to  a  given  pollution
event varies in response to the nature of the materials in the vadose  zone
including but not limited to:  grain size, sorting, reactivity,  bedding,
fracturing, thickness and sorptive character.  In  general, finer grain-size
materials, i.e. clays and silt, have lower hydraulic conductivity and  greater
capacity for the temporary and long-term attenuation of pollutants.  If
expandable clay minerals are present, the sorptive capacity is further
enhanced.  If a material is even moderately cemented, then grain size  and
sorting may be less significant than the degree of cementation.
                                     64

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     If the material in the vadose zone is reactive to the pollutant,  or
soluble in it, then there may be two different effects.   First,  the pollutant
may be retarded (a positive effect) or second, the solution of the vadose zone
material may actually increase permeability and allow subsequent introduction
of pollutants to pass through more quickly with less retardation (a negative
effect).  In the case of reactive pollutants, the importance of  secondary
by-products must be considered.  It is here that the risks associated  with
gaseous phase transport are most likely to have an impact on ground water.

     The thickness of the vadose zone and the degree of  fracturing and
frequency of bedding planes in the vadose zone all impact upon the tortuosity,
route length, dispersion and consequent travel time that is required for a
pollutant to move through the vadose zone.  This is not  only of  time-delay
importance but also is important as the control of contact time  for reactions
to occur.

     The vadose zone, including the surficial soil, is also of great importance
as the zone where most of the biologic activity occurs.   There are natural
organisms found in this zone that break down many polluting substances into
secondary by-products, both harmless and harmful.  For many chemicals  these
reactions are very poorly understood, if at all, but it  is known that  with
sufficient time the eventual results are generally beneficial.   Among  the best
known of these processes at present are the bacterial fixation of iron and the
bacterial breakdown of non-chlorinated hydrocarbons under natural conditions.
Both of these processes occur in the vadose zone and in  the aerobic portion of
shallow aquifers.

     The hydraulic conductivity, together with gradient  and porosity of  the
aquifer beneath a site influences the rate of movement of an introduced
pollutant away from the point of introduction.  In conjunction with hydraulic
gradient, conductivity also controls the direction of movement.   These are, in
turn, affected with regard to dispersion, by grain size, bedding,  fracturing,
and tortuosity.

     It is evident that all of the DRASTIC parameters are interacting,
dependent variables.  Their selection is based not on available  data
quantitatively developed and rigorously applied, but on  a subjective
understanding of "real world" conditions at a given area-  The value of  the
DRASTIC parameters is in the fact that they are based on information that is
readily available for most portions of the United States, and which can  be
obtained and meaningfully mapped in a minimum of time and at minimum cost.  The
DRASTIC ranking scheme can then be applied by enlightened laymen for
comparative evaluations.

     If the vulnerability of a site, or sites, to ground-water pollution were
to be evaluated with regard to travel time, flux, and concentration associated
with the incidence of a pollutant introduced at the site, the DRASTIC
parameters would be distributed as follows:
                                    65

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     A.  Travel Time
         -  Depth to Water
         -  Soil Media
         -  Impact of the Vadose Zone Media
         -  Net Recharge
         -  Hydraulic Conductivity  of the  Aquifer

     B.  Flux

         -  Aquifer Media
         -  Hydraulic Conductivity  of the  Aquifer  (Existence  of Gradient
            Assumed)

     C.  Concentration

         -  Depth to Water
         -  Net Recharge
         -  Aquifer Media
         -  Soil Media
         -  Topography
         -  Impact of the Vadose Zone Media
         -  Hydraulic Conductivity  of the  Aquifer

It should be noted that although the DRASTIC  parameter  of  hydraulic
conductivity of the aquifer is mapped as a function  of  the ability of a
pollutant to be moved from a point  of incidence, the direction of migration  is
a function of gradient and rate depends on both conductivity  and gradient.
                                     66

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                                   REFERENCES
Fetter, C.W. , 1980.  Applied hydrogeology;  Charles E.  Merrill  Publishing
Company, 448 pp.

Lehr, Jay H., Wayne A. Pettyjohn, Truman W. Bennett,  James R.  Hanson and
Laurence E. Sturtz, 1976.  A manual of laws, regulations  and institutions  for
control of ground water pollution; U.S. EPA-440/9-76-006, 432  pp.

Pye, Veronica I. and Jocelyn Kelley, 1984.   The extent of groundwater
contamination in the United States; Groundwater Contamination,  National Academy
Press, pp. 23-33.

Soil Conservation Service, 1951.   Soil survey manual;  U.S. Department of
Agriculture, 503 pp.

Soil Conservation Service, 1960.   Soil classification: a comprehensive system,
7th approximation; United States  Department of Agriculture, 265 pp.

Soil Conservation Service, 1975.   Soil taxonomy:   A basic system of  soil
classification for making and interpreting  soil surveys;  United States
Department of Agriculture Handbook no. 436, 754 pp.
                                    67

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                                  SECTION 4

                HOW TO USE HYDROGEOLOGIC SETTINGS AND DRASTIC
     The system described in this document presents a simple and
easy-to-use approach to assess the ground-water pollution potential of any
area.  Although the final system appears simplistic, the system actually
includes many complex concepts and relationships.  Before an attempt is
made to make full use of this system, the user needs to develop an
appreciation for the complexity of evaluating ground-water pollution
potential.  It is not necessary to understand every concept in detail, but
the greater the depth of understanding, the more useful the system becomes.
DRASTIC provides mappable results which can be used to provide a quick
reference of relative pollution potential of different areas.  DRASTIC is
designed to be used as a planning, screening or prioritizing tool.  DRASTIC
and associated maps cannot be used in lieu of site specific evaluations
because of local complexities in geologic conditions.

WHERE TO OBTAIN INFORMATION ON DRASTIC PARAMETERS

     Before an area can be evaluated using the DRASTIC system, the basic
information on each factor must be found.  DRASTIC has been designed to use
information which is available from a variety of sources.  Table 1 contains
a listing of possible sources of hydrogeologic information and the types of
information which may be available from each.  The most common source of
information for each parameter is listed below:

     1)   Depth to Water - Well logs or hydrogeologic reports;
     2)   Net Recharge - Water resource reports combined with data on
          precipitation from the National Weather Service;
     3)   Aquifer Media - published geologic and hydrogeologic reports;
     4)   Soil Media - published soil survey reports or local mapping
          projects conducted by the Soil Conservation Service;
     5)   Topography - published U.S. Geological Survey topographic maps
          (various scales);
     6)   Impact of the Vadose Zone Media - published geologic reports;
     7)   Hydraulic Conductivity of the Aquifer - published hydrogeologic
          reports.  (Of all the factors, this information may be the most
          difficult to find.  Because it is related very closely to
          aquifer media, if necessary, hydraulic conductivity may be
          estimated using Table 12).  Conversion factors for permeability
          and hydraulic conductivity are found in Table 13.
                                     68

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TABLE 13. CONVERSION FACTORS FOR PERMEABILITY AND HYDRAULIC CONDUCTIVITY
         UNITS (FREEZE AND CHERRY, 1979)


o>
to





cm2
ft2
darcy
m/s
ft/s
US. gal/day/ft2

cm2
1
9.29 X102
9.87 X 10 9
1.02 X 10 3
3.11 X 10 4
5.42 X 10 10
Permeability, k*
ft2
1 08 X 10 3
1
1.06 X 10 "
1 10X 10 6
335X 10 7
5.83 X 10 13
Hydraulic conductivity, K
darcy
1.01 X 10s
942 X 10'°
1
1.04X 105
3.15 X 104
549X 10 7
m/s
9.80 X 102
9.11 X105
9,66 X 10~6
1
3.05X10 '
4.72 X 10 7
ft/s
3.22 X 103
2.99 X 106
3.17 X 10"5
3.28
1
1.55 X 10 6
US gal/day/ft2
1 85 X 109
1.71 X 101S
1.82 X 101
2 12 X 106
6.46 X 105
1
  *To obtain k in ft2, multiply k in cm2 by 1.08 X 10 3

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It should be noted that the more accurate the data used to compute the
index, the more reliably the pollution potential can be assessed.  There
may be many gaps in the data, of course.  These gaps can be filled with
careful interpolation if such interpolation is reasonable.

STEPS FOR USE OF THE SYSTEM

     In order to use the DRASTIC system, the user must follow a few simple
steps.  The following example illustrates how to use the system.  The exact
same steps are used when applying the modified Pesticide DRASTIC ratings.
A decision-maker wishes to evaluate the pollution potential of two areas in
a county.  The county is located along the glacial boundary such that part
of the county lies in the Glaciated Central Region and the other part lies
in the Non-Glaciated Central Region.  Precipitation in the area averages 42
inches per year.  Area I is typified by 5 to 20 feet of glacial till
deposits which overlie fractured sandstones and shales with hydraulic
conductivities ranging from 100 to 300 gpd/ft2.  xhe terrain is rolling,
and depth to the water in the sandstones averages 30 feet below land
surface.  Typical soils have mixtures of sand, silt and clay with
predominant clay fractions. Area II is typified by alternating sequences of
sandstone, limestone and shale with moderate fracturing and hydraulic
conductivity averaging 300 gpd/ft2-  Relief is low and slopes are
commonly 2 percent.  Depth to water averages 40 feet.  Soil is thin but
significant with soils reflecting equal mixtures of sand, silt and clay.
Average net recharge is 8 Inches per year.

     1)   Identify the Region in which the area is located.  Become
familiar with tho. hydrogeology of the region.  Area I is in the Glaciated
Central Region and Area II is in the Non-Glaciated Central Region.

     2)   Identify which hydrogeologic setting most closely approximates
the conditions of the area.  Area I most closely approximates Setting 7Aa -
Glacial Till Over Bedded Sedimentary Rock; Area II, 6Da - Alternating
Sandstone, Limestone and Shale - Thin Soil.  For ease of reference, these
setting descriptions are included as Figures 22 and 23 and Tables 14 and
15.

     3)   Evaluate available information for each DRASTIC parameter against
the example ranges chosen for each DRASTIC parameter listed in the top
table (Tables 14 and 15).  These ranges represent example values for each
hydrogeologic setting.  In Area I (Table 14), the depth to water averages
30 feet; the example range of 30 to 50 feet would seem appropriate.
Therefore, the associated rating of 5 (Table 4) does not need to be
changed.  No value for net recharge was available; however, precipitation
in the region is 42 inches per year and recharge will typically be
restricted due to the presence of clayey till; the example range of 4 to 7
inches per year seems appropriate.  Therefore, the associated rating of 6
(Table 5) does not need to be changed.  The aquifer media are fractured
sandstones and shales; thin bedded sandstone, limestone and shale sequences
are present, so the example media is appropriate.  Therefore, the
associated rating of 6 (Table 6) does not need to be changed.  Soils have a
                                     70

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               GLACIATED CENTRAL

               (7Aa) Glacial Till Over Bedded Sedimentary Rocks

               This hydrogeologlc getting  Is characterized by low  topography and
               relatively flat-lying, fractured sedimentary rocks  consisting of sandstone,
               shale and limestone which are covered by varying  thicknesses of glacial
               till.  The till Is chiefly  unsorted deposits which  may  be interbedded with
               loess or localized deposits of sand and gravel.  Although ground water
               occurs in both the glacial  deposits and In the Intersecting bedrock
               fractures, the bedrock is the principal aquifer.  The glacial till serves
               as a source of recharge  to  the underlying bedrock.  Although precipitation
               is abundant In most of the  region, recharge is moderate because of the
               glacial till and soils which are typically clay loams.   Depth to water Is
               extremely variable depending in part on the thickness of  the glacial till,
               but tends to average around 30 feet.
 Figure 22. Description and illustration for setting 7Aa—glacial till over bedded sedimentary
             rocks.
               NON-GLACIATED CENTRAL

               (6Da) Alternating SS, IS,  and  SH  - Thin Soil

               This  hydrogeologlc setting is  characterized by low to moderate  topographic
               relief,  relatively thin loamy  soils overlying horizontal or  slightly
               dipping  alternating layers of  fractured consolidated sedimentary  rocks-
               Ground water is obtained primarily from fractures along bedding planes or
               Intersecting vertical fractures.  Precipitation varies widely in  the
               region,  but recharge Is moderate  where precipitation is adequate.  Water
               levels are extremely variable  but on  the average moderately  shallow.  Shale
               or clayey layers often form aquitards, and where sufficient  relief Is
               present, perched ground water  zones of local domestic importance  are often
               developed.
Figure 23.  Description and illustration for setting 6Da—alternating sandstone, limestone and
             shale-thin soil.
                                                71

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TABLE 14.  DRASTIC AND PESTICIDE DRASTIC CHARTS FOR SETTING 7Aa — GLACIAL TILL
         OVER BEDDED SEDIMENTARY ROCKS

Setting 7Aa Glacial Till Over Bedded Sedimentary Rock
Feature
Depth to water
Net recharge
Aquifer media
Soil media
Topography
Impact vadose zone
Hydraulic conductivity
Range
30-50
4-7
Bedded SS. LS, SH sequences
Clay loam
2-6%
Silt/Clay
100-300
General
Weight
5
4
3
2
1
5
3
Rating
5
6
6
3
9
3
2
Drastic Index
Number
25
24
18
6
9
15
6
103
Setting 7Aa Glacial Till Over Bedded Sedimentary Rock
Feature
Depth to water
Net recharge
Aquifer media
Soil media
Topography
Impact vadose zone
Hydraulic conductivity
Range
30-50
4-7
Bedded SS, LS, SH sequences
Clay loam
2-6%
Silt/Clay
100-300
Pesticide
Weight
5
4
3
5
3
4
2
Rating
5
6
6
3
9
3
2
Pesticide Drastic Index
Number
25
24
18
15
27
12
4
125
                                  72

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      TABLE 15.  DRASTIC AND PESTICIDE DRASTIC CHARTS FOR SETTING 6Da —
                ALTERNATING SANDSTONE, LIMESTONE AND SHALE — THIN SOIL

Setting 6Da Alternating Sandstone, Limestone and Shale — Thin Soil
Feature
Depth to water table
Net recharge
Aquifer media
Soil media
Topography
Impact vadose zone
Hydraulic conductivity
Range
15-30
4-7
Thin bedded SS, LS, SH
sequences
Loam
2-6%
Bedded LS, SS. SH
1-100
General
Weight
5
4
3
2
1
5
3
Rating
7
6
6
5
9
6
1
Drastic Index
Number
35
24
18
10
9
30
3
129
Setting  6Da Alternating Sandstone. Limestone and Shale — Thin Soil
Feature
Depth to water table
Net recharge
Aquifer media
Soil media
Topography
Impact vadose zone
Hydraulic conductivity
Range
15-30
4-7
Thin bedded SS, LS, SH
sequences
Loam
2-6%
Bedded LS, SS, SH
1-100
Weight
5
4
3
5
3
4
2
Rating
7
6
6
5
9
6
1
Pesticide Drastic Index
Number
35
24
18
25
27
24
2
155
Pesticide
                                     73

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predominant clay fraction but contain silt and sand; clay loam is the
prevalent soil, so the example soil media would be appropriate.  Therefore,
the associated rating of 3 (Table 7) does not need to be changed.  Terrain
is rolling;  2 to 6 percent slopes are predominant.  The example range is
acceptable.  Therefore, the associated rating of 9 (Table 8) does not need
to be changed.  The vadose zone is comprised of glacial till; silt and clay
is the most significant portion of the glacial till.  The example vadose
zone media is the appropriate media.  Therefore, the associated rating of 3
(Table 9) does not need to be changed.  Hydraulic conductivity values for
the bedrock average 100 to 300 gpd/ft2 as listed on the example chart.
Therefore, the associated rating of 2 (Table 10) does not need to be
changed.  Since all the example ranges in the hydrogeologic setting are
identical to the example values for this setting, no values need to be
modified for this area.  The DRASTIC INDEX has already been computed for
the user by multiplying each rating by the assigned weight to obtain the
value listed in the "number" column.  The sum of the "numbers" is the
DRASTIC Index.  In this instance, the DRASTIC Index of 103 is simply read
from the chart.  It should be noted here that weights are never changed.
These were determined by the committee and are the essence of the system.

     In Area II (Table 15), depth to water averages 40 feet.  The example
range on the chart indicates 15 to 30 feet.  This range differs from the
example values in this setting.  The user should refer to Table 4 to find
the correct range which most closely approximates the area.  In this case
30 to 50 feet would be appropriate.  Note the corresponding rating would
now be 5 instead of 7 and the resultant weight of 5 multiplied by a rating
of 5 is 25 instead of 35.  Net recharge is 8 inches per year.  The range on
the chart differs from the example values in this setting.  Seven to ten
inches per year would be chosen as the appropriate range and the rating of
6 is then changed to an 8 by referring to Table 5.  The aquifer media is
alternating sequences of sandstone, limestone and shale with moderate
fracturing; the media listed on the example chart is accurate and the
associated rating of 6 does not need to be changed.  Soils are typified by
equal mixtures of sand, silt and clay; this is the definition of loam.  The
media on the example chart is adequate and the associated rating of 5 does
not need to be changed.  Topography is low; the range is listed as 2 to 6
percent.  The user may, based on observation, choose 0 to 2 percent, and
change the example rating as before, or may accept the example range of 2
to 6 percent if correct.  For demonstration purposes, the user can refer to
Table 8, choose a 0 to 2 percent range, change the rating from 9 to 10 and
multiply by the weight of 1 to obtain an answer of 10 instead of 9.  The
vadose zone media in the area are fractured limestones, sandstones and
shales; this is the same as the example media for this setting.  Therefore,
the associated rating of 6 does not need to be changed.  Hydraulic
conductivity averages 300 gpd/ft2. the example range indicates 1 to 100
gpd/ft2.  Refer to Table 10 to choose the appropriate range.  In this
case, 100 to 300 gpd/ft2 is chosen, the associated rating of 2 is
substituted and multiplied by 3 to obtain 6.  The DRASTIC Index cannot be
read off the chart because all the ranges were not identical to those
listed in the  example setting.  Calculate the correct DRASTIC Index by
adding the numbers 25+32+18+10+10+30+6-131.  The decision
maker can then compare the two areas relative to one another.


                                     74

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     From the above discussion, it is evident that  the hydrogeologic
settings serve as a guide to the user in evaluating the appropriate range
for each DRASTIC factor.  Each range has an associated rating which can
then be integrated into DRASTIC by combining it with the weighting factor.
The information to evaluate each DRASTIC factor and choose the appropriate
range may not always be expressed in exactly the same terms which are used
in this document.  Section 3, DRASTIC:  A Description of the Factors,
contains a brief description of what is included in each of the media terms
so that the most accurate DRASTIC range can be chosen.  Section 5,
Application of DRASTIC to maps discusses the step-by-step process for
producing detailed DRASTIC maps with associated hydrogeologic settings and
DRASTIC indexes.

HOW TO USE THE RANGE IN MEDIA RATINGS

     Because geologic media are more highly variable than other more easily
quantified DRASTIC factors, the system allows the user to make adjustments
for the variability in aquifer and vadose zone media.  Tables 6 and 9
provide the user with a typical rating and a variable rating which can vary
based on the properties of the media.  If no specific information is
available to provide a rationale for making a change from a typical media,
the typical rating should be used.  The typical ratings for aquifer and
vadose zone media were developed to represent the characteristics of a
typical aquifer or vadose zone associated with a media type.  The variable
range in media ratings provide the user with a mechanism to adjust the
ratings according to information that more accurately characterizes the
nature of the media.  The user may then use this information in conjunction
with the pollution potential to choose a media rating which best represents
the conditions of that media.

     In consolidated rock, ratings may be adjusted to reflect degree of
cementation, amount of primary porosity and presence of secondary porosity
due to bedding planes, fractures, joints or solution openings.  The
relative presence or absence of these factors may significantly affect
contaminant travel, attenuation and dilution within the aquifer.  In
unconsolidated deposits, the ratings may be adjusted to reflect the amount
of fine-grained material and the size, shape and sorting of the entire
deposit.

     The first step in using the system is to choose an aquifer or vadose
zone media.  DRASTIC provides descriptive terms for both consolidated and
unconsolidated media to characterize the aquifer and vadose zone media.
The user must evaluate the geologic and hydrogeologic information about the
area and choose an appropriate media.  A complete discussion of the choices
of media for aquifers and the vadose zone may be found in Section 3,
DRASTIC:  A Description of the Factors under Aquifer Media and Vadose Zone
Media.  Special consideration for aquifer and vadose zone media selection
is necessary in the case of confined aquifers.   The user is referred to
Section 3 and Section 4, How to Evaluate Confined Aquifers for further
information.
                                     75

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     The next step is to evaluate whether the typical rating adequately
characterizes the pollution potential of a contaminant in the media.  For
example, the selection of sandstone as a vadose zone media allows the user
to choose a rating from 4 to 8.  If the sandstone has very little primary
porosity and very few bedding planes which would provide secondary
porosity, the pollution potential would be low and the user would assign a
rating of 4 to the media.  If, however, the sandstone has a relatively high
amount of primary porosity and is extensively fractured, a contaminant
could migrate more rapidly through the media.  The pollution potential
would be higher, thus, the user would select a rating of 8 for this media.

     A second example illustrates the adjustment of the rating to reflect
depositional or formational conditions which affect the movement of a
contaminant in the media.  The rating for basalt may range from 2 to 10 in
both the aquifer and vadose media.  The environment in which the basalt was
formed can significantly affect the interconnection of openings within the
basalt and may also affect the degree of fracturing.  This may be
illustrated by examining the basalts in the Columbia River Plateau.  In
parts of this region, the basalts are dense, impermeable and have few
fractures.  Ground-water movement is restricted to the interflow zones
formed between lava flows.  For this type of basalt, the user would assign
a rating of 2 to the media because the pollution potential is low.
However, in other areas of the plateau, the basalts are comprised of thin
lava flows with extensive fracturing and jointing, permeable interflow
zones, and highly interconnected lava tubes.  Contaminants introduced into
this media would be dispersed rapidly; thus, pollution potential would be
high.  In these basalts, the user would assign a rating of 10.

     Adjustments to unconsolidated media ratings can also be made.  For
example, a typical sand and gravel would receive a rating of 8.  If the
sand and gravel was coarse-grained, very well sorted, and contained only a
small percentage of silt and clay, the user would assign a rating of 9 to
this media.  If the sand and gravel was poorly sorted, and contained some
significant amounts of fine-grained materials, the user would assign a
rating of 6 to the media.  A complete discussion of the use of media ranges
for aquifers and vadose media may be found in Section 3, DRASTIC:  A
Description of the Factors under Aquifer Media and Vadose Zone Media.

HOW TO EVALUATE CONFINED AQUIFERS

     The evaluation of a confined aquifer requires the use of special
definitions for several of the DRASTIC factors. The presence of a confining
l,ayer restricts contaminant movement into the aquifer.  The associated
reduction in pollution potential can be incorporated into the system by
modifying several DRASTIC parameters to reflect the conditions which affect
pollution movement.

     The confined aquifer may have either an upward or downward leakage
component.  Hydraulic gradients which result in upward flow are not taken
into consideration because a) the aquifer already has a degree of
protection and b) upward gradients are easily reversed by local pumpage.
Therefore, for purposes of the DRASTIC Index, the worst case scenario of a
gradient into the aquifer is always assumed.

                                     76

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      A judgement  must  be  made  in several  of  the DRASTIC  factors  as to the
 proper way to  evaluate that  factor  in the specific setting.   A detailed
 discussion of  the impacts of confined aquifers  on the DRASTIC parameters of
 depth to  water, net  recharge,  aquifer media  and the impact  of the  vadose
 zone media may be found in Section  3, DRASTIC:   A Description of the
 Factors.   Factors that must  be varied,  and the  guidance  for  making the
 judgement of variation are as  follows:

      1.   Depth to Water - For  a confined  aquifer, depth  to water is defined
 as  the depth from the  ground surface  to the  top of the aquifer.   This depth
 also corresponds  to  the base of the confining layer.   The presence of a
 restrictive layer will limit the migration of contaminants into  the
 aquifer.   The  confining layer  will  also restrict the  rate of water movement
 thus providing additional time for  contaminant  attenuation.

      2.   Net Recharge  - Values of net recharge  may be adjusted to  reflect
 restrictions in recharge  to  the aquifer due  to  the presence  of the
 confining layer.   If the  user  is uncertain as to whether the aquifer is
 truly confined, the  aquifer  should  be evaluated as~unconfined.  Recharge
 areas are often located miles  away  from the  confining aquifer. Values of
.net recharge can  be  chosen to  reflect the amount of water which  may
 actually  recharge the  aquifer.   In  portions  of  some confined aquifers, the
 ground-water gradients are upward from the confined aquifer  into the
 confining layer.   In this situation,  recharge to the  confined aquifer is
 negligible and a  low recharge  value may be chosen.

      3.   Aquifer  Media -  The user must make  a judgement, based on  available
 information, whether an aquifer is  confined  or  unconfined.   The  hydraulic
 conditions of  an  aquifer  may exhibit  spatial variation.  Varying degrees of
 confinement are not  uncommon particularly when  the aquifer is of large
 areal extent.

      4.   Impact of the Vadose  Zone  Media  - When evaluating a confined
 aquifer,  the user must choose  "confining  layer"  as the impact of the vadose
 zone media. The  impact of the vadose zone media reflects the ability of
 the geologic materials to affect a  contaminant  moving from the base of the
 soil to the top of the aquifer.   Because  the confining layer is  the media
 which most significantly  impacts pollution potential, the user is  choosing
 the true  impact of the vadose  zone.   Confining  layer  is  used regardless of
 the other media composition  within  the  vadose zone.

      From this discussion, it  can be  seen that  the vulnerability of an
 aquifer can be significantly impacted by  the presence of a confining layer.
 The modifications to the  DRASTIC parameters  under confined conditions
 produce a lower DRASTIC Index,  thus suggesting  a reduced vulnerability to
 ground-water contamination.  Under  confined  conditions,  the  methodology
 assumes that the  confining layer significantly  limits the migration of
 fluids, either contaminants  or  water  across  the  restrictive  layer.   In many
 areas confining layers are not  truly  impermeable,  but are leaky  or
 semi-confining.   Because  the methodology  does not  allow  the  evaluation of a
 semi-confined  aquifer,  the user  must  choose  to  evaluate  the  aquifer as
 either confined or unconfined.   The user  must evaluate the degree  of
 confinement of the aquifer.

                                    77

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     The effects of evaluating an aquifer as confined  versus unconfined  can
be illustrated using the following example.   Setting 7Ac,  Glacial  Till Over
Solution Limestone is typified by conditions in northeastern Indiana.  The
aquifer is a solution limestone overlain by  varying thicknesses  of glacial
till.  The till is comprised of unsorted deposits of sand,  silt  and  clay
which may be interbedded with localized lenses  of sand and  gravel.
Surficial deposits have weathered to a clay  loam.  Although the  limestone
is the principal aquifer, the overlying till may also  be  saturated.
Despite the restrictive permeability of the  till, recharge  to the  limestone
aquifer is relatively high.   The glacial till is in direct  hydraulic
connection with the aquifer  and serves as a  source of  recharge to  the
limestone.

     The low permeability glacial till partially confines  the limestone
aquifer. Because DRASTIC cannot be used to evaluate semi-confined  aquifers,
the aquifer must be evaluated as either confined or unconfined.  If  the
limestone is treated as an unconfined aquifer,  the depth  to water  will be
the depth from the ground surface to the water  table.   In  this setting,  the
depth to water would be the  depth to the level  of saturation of  the  till.
A typical depth to water might be 30 feet which would  have  a rating  of (5).
The aquifer would still be evaluated as karst limestone and be assigned  a
rating of (10).  The hydraulic conductivity  would also be  high.  A typical
value for high hydraulic conductivity might  be  2000+ gallons per day per
square foot with an associated rating of 10. Soil media  would typically be
a clay loam with an associated rating of (3).  Topography  would  be 2 to  6
percent with an associated rating of (9). The  vadose  zone  would be
represented by the till and  the vadose zone  media would be  called  silt/clay
with a typical rating of (3).  The DRASTIC Index can be calculated to be
139 (Table 16).

     It is also possible to  evaluate a similar  aquifer for confined
conditions.  Based on the modifications necessary for  confined aquifers,
several parameter ratings must be changed.  Depth to water  is now
considered to be the depth from the ground surface to  the  top of the
aquifer.  In this setting, the depth to the  aquifer is 60  feet.  The rating
for depth to water would change from a (5) to a (3).  Because net  recharge
may be limited by the confining layer, recharge values might be  adjusted
from 4 to 7 inches per year  (6) to 2 to 4 inches per year  (3).  The  impact
of the vadose zone media must now become "confining layer"  with  a  rating of
(1).  The other parameter ratings remain unchanged.   The  DRASTIC  index  can
now be calculated to be 107  (Table 17).

     By comparing the two indexes for this setting, 139 (unconfined) versus
107 (confined), the impact of evaluating an  aquifer as confined  is
demonstrated.  The confined  aquifer is less  vulnerable to  contamination
than the unconfined aquifer.  Although the geology of  the  site is
unchanged, there is a major  difference in the hydrogeology of the  two
examples and thus the relative degree of confinement affects the pollution
potential of the area.
                                   78

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    TABLE 16. CHART FOR EXAMPLE SETTING 7Ac — GLACIAL TILL OVER SOLUTION
             LIMESTONE SHOWING UNCONFINED CONDITIONS

Setting 7Ac Glacial Till Over Solution Limestone
Feature
Depth to water
Net recharge
Aquifer media
Soil media
Topography
Impact vadose zone
Hydraulic conductivity
Range
30-50
4-7
Karst limestone
Clay loam
2-6%
Silt/clay
2000+
General
Weight
5
4
3
2
1
5
3
Rating
5
6
10
3
9
3
10
Drastic Index
Number
25
24
30
6
9
15
30
139

    TABLE 17. CHART FOR EXAMPLE SETTING 7Ac - GLACIAL TILL OVER SOLUTION
             LIMESTONE SHOWING CONFINED CONDITIONS
Setting    7Ac Glacial Till Over Solution Limestone
Feature
Depth to water
Net recharge
Aquifer media
Soil media
Topography
Impact vadose zone
Hydraulic conductivity
Range
50-75
2-4
Karst limestone
Clay loam
2-6%
Confining layer
2000+
Weight
5
4
3
2
1
5
3
Rating
3
3
10
3
9
1
10
Drastic Index
Number
15
12
30
6
9
5
30
107
General
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SINGLE FACTOR OVERRIDES

     In some instances, it will be found that the DRASTIC Index cannot
adequately compensate for a single parameter that is so dominant that it
overrides all other parameters.  This may be a consideration that is
glaringly apparent, as in a highly-fractured surficial karst area, or it
may be a much more subtle consideration that involves design or policy
decisions.

     Tables 18 and 19 provide the DRASTIC ratings for two actual areas
referenced as Maco I and Maco II.  These areas are both located in the
glacial till plain portion of the Glaciated Central Region approximately
five miles apart.  Based on the available data, both areas are underlain by
25 to 40 feet of dense glacial till containing a few discontinuous lenses
of "dirty" sand and gravel that rarely exceed four inches in thickness.  In
the absence of fracturing or stratification, the horizontal and vertical
permeabilities of the glacial tills average 10-6 to 10~7 gallons per
day per square foot.

     In area Maco I, the glacial till overlies fractured limestone which
serves as a regional aquifer and has a hydraulic conductivity which
averages 300 to 700 gallons per day per square foot.  Water in the
limestone is semi-confined and the regional water levels approximate 30
feet.  The overlying glacial till is saturated only in association with the
occasional discontinuous lenses of sand and gravel.  These zones can be
considered "perched."

     In the Maco II area, the glacial till overlies dense, fractured shale.
The hydraulic conductivity of the shale is less than 1 gallon per day per
square foot.  Because the shale is relatively impermeable, the overlying
glacial till is saturated from a depth of approximately 5 feet, even though
the elevation, topography and soils are similar in the two areas.

     It can be seen by comparing Tables 18 and 19, that Maco II has a
slightly more favorable rating than Maco I.  The principal reason is
because there is no significant aquifer at risk at Maco II.  However, Maco
II has a water table at a depth of approximately 5 feet.  In the Maco I
area, a landfill, for example, could be properly designed and operated at a
maximum depth of fifteen feet.  At this depth, the landfill would be
located within the unsaturated zone and a substantial thickness of dense,
low permeability material would be present at the base of the landfill to
protect the regional aquifer.  Construction of a landfill in the Maco II
area (with the more favorable rating) would involve operating a
saturation-zone landfill, which often would require a harder policy
decision  from the permitting agency.

     With regard to the proper application of the DRASTIC Index in this
situation, the question is, "Is the shallow, 5-foot depth to saturation of
sufficient significance to  'override' all of the other, favorable aspects
of the site?"  This should be considered for all parameters that are very
highly-rated (i.e., in the rating range of 8-10).  Another single factor
                                     80

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            TABLE 18. DRASTIC RATING FOR MACO I
MACO I
Feature
Depth to Water
Net Recharge
Aquifer Media
Soil Media
Topography
Impact Vadose Zone
Hydraulic Conductivity
Range
15-30
4-7
Massive Limestone
Clay Loam
2-6%
Silt/Clay
300-700
GENERAL
Weight
5
4
3
2 __ '
1
5
3
Rating
7
6
4
3
9
3
4
Drastic Index
Number
35
24
12
6
9
15
12
113
            TABLE 19. DRASTIC RATING FOR MACO II
MACO
Feature
Depth to Water
Net Recharge
Aquifer Media
Soil Media
Topography
Impact Vadose Zone
Hydraulic Conductivity
Range
5-15
4-7
Massive Shale
Clay Loam
2-6
Silt/Clay
1-100
Weight
5
4
3
2
1
5
3
Rating
9
6
2
3
9
3
1
Drastic Index
Number
45
24
6
6
9
15
3
108
                                              GENERAL
                           81

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override would be exposed, highly-fractured or dissolved bedrock which
would provide a direct conduit to an aquifer.  Knowledge of the area being
mapped is usually required in order to know when overrides must be
applied.

BUILD-YOUR-OWN-SETTINGS

     From the above discussion it should become obvious that for any given
area in the United States, the ground-water pollution potential can be
estimated by choosing appropriate ranges for each DRASTIC parameter without
referring to any hydrogeologic setting described in Section 7,
Hydrogeologic Settings of the United States by Ground-Water Regions.  It
becomes necessary to use both the hydrogeologic settings and the DRASTIC
Index when producing a map which will clearly describe the conditions in an
area.  The individual DRASTIC ratings and hydrogeologic settings become
important when DRASTIC will be used by other people in potentially
different applications. The inclusion of both portions of the methodology
will provide a clear and complete "picture" of the hydrogeologic and
geologic conditions in the area.  This information will enable other users
to understand how and why the DRASTIC parameters were chosen and how
setting conditions impact the pollution potential.  The geographic
relationship also helps the user evaluate the characteristics of an area
more thoroughly thereby helping create sound judgement calls and a more
realistic DRASTIC Index.

HOW TO INTERPRET A DRASTIC AND PESTICIDE DRASTIC INDEX

     The culmination of the evaluation of any hydrogeologic setting is a
numerical value termed the DRASTIC Index.  The higher the DRASTIC Index,
the greater the ground-water pollution potential.  DRASTIC is designed to
yield a relative numerical value which can readily be compared to a value
obtained for another setting either in the same region or in a different
region.  A numerical value of 160, for example, has no intrinsic meaning.
That number is of value only when compared to DRASTIC Indexes generated for
other areas.  DRASTIC Indexes range from 65 to 223 for all typical
hydrogeologic settings.

     It is also important to be able to reconstruct the ranges for each
individual DRASTIC factor that comprise the DRASTIC Index.  Frequently it
becomes necessary to consider a specific parameter in addition to just
knowing a number for ground-water pollution potential.  The charts
accompanying each hydrologic setting in Section 7, Ground-water Regions and
Hydrogeologic Settings of the United States provide a format for quick and
easy reference of the way the DRASTIC Index was derived.

     DRASTIC Indexes provide discrete numbers which can be used to evaluate
ground-water pollution potential.  The numbers, however are not gradational
between settings.  For example, the line on a map which encloses the
DRASTIC Index is not a contour line but rather a line depicting a setting
boundary.  A contour line infers that there is a gradational transition
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between two evaluated points.  A setting boundary line allows the user  to
evaluate two points but only from a relative and not gradational
perspective.  Therefore, it is important to realize that DRASTIC Index
values cannot be contoured.

     This methodology also allows the user to apply a modified Pesticide
DRASTIC to an area when the potential impact to ground-water quality from
the application of pesticides is a concern.  The weights assigned to each
parameter have been modified to reflect the potential impacts of pesticide
application on ground water.  The assumptions have been modified to reflect
a contaminant with the mobility of a generic pesticide.  For this reason,
it is not correct to compare a General DRASTIC Index with a Pesticide
DRASTIC Index of the same area.  Comparisons made between the two Indexes
would be invalid.  The user may only compare the Pesticide DRASTIC Indexes
of two different settings evaluated using Pesticide DRASTIC to draw
conclusions about the relative pollution potential of each area with
respect to pesticide application.  Pesticide DRASTIC Indexes range from 88
to 251 for all typical hydrogeologic settings.
                                     83

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                                 REFERENCES
Freeze, R.A. and J.A. Cherry, 1979.  Groundwater; Prentice-Hall, 604 pp.

Heath, Ralph C., 1984.  Ground-water regions of the United States; U.S.
Geological Survey, Water Supply Paper 2242, 78 pp.
                                    84

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                                 Section 5

                       APPLICATION OF DRASTIC TO MAPS

     Complete evaluation of any area using DRASTIC involves not only
producing a numerical score, but also delineating appropriate hydrogeologic
settings.  To fully demonstrate the use of the system and to better
illustrate the steps in producing a DRASTIC map, ten widely varied counties
were chosen for evaluation.  This exercise also provided the opportunity to
critique the methodology and make changes where necessary.

     The selection process for the demonstration counties involved
soliciting suggested counties from committee members and other interested
individuals.  The areas selected were to be representative of different
hydrogeologic scenarios and be located in all parts of the United States.
An attempt was made to select counties which had both an abundance and a
scarcity of data and represented both urban and rural areas.  The initial
areas were further evaluated based on the level of interest at the state
and county level.  The ten counties which were finally selected include:

     Cumberland County, Maine,
     Finney County, Kansas,
     Gillespie County, Texas,
     Greenville County, South Carolina,
     Lake County, Florida,
     Minidoka County, Idaho,
     New Castle County, Delaware,
     Pierce County, Washington,
     Portage County, Wisconsin and
     Yolo County, California.

     The evaluation approach for each county varied slightly but typically
contained the following elements:  1) gathering of published data and maps,
2) eliminating data gaps through personal contacts, 3) preparing draft
DRASTIC maps in the form of color-keyed overlays, 4) conducting a formal
county presentation, 5) field checking of the draft maps with selected
individuals intimately familiar with the county, 6) making changes where
necessary on the maps and 7) printing a final map and legend.  In all
instances steps 1-4 and 7 were accomplished.  Step 5 was not completed for
Minidoka County, Idaho due to inclement weather; field checking New Castle
County, Delaware was only cursorily performed because the reviewers did not
deem an in-depth field visit necessary.  Step 6 was not performed in many
counties because modifications were not necessary.
                                     85

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HOW TO PERFORM A DRASTIC EVALUATION AND PRODUCE A DRASTIC MAP

     This section contains a step-by-step discussion of the techniques
which were used to evaluate each county and produce a map.  Although each
individual who uses DRASTIC will personalize the approach, these
discussions will serve as a starting point for the user.

Drawing the Map Manually

     1)  Gather all the published or printed information available on the
chosen county for each DRASTIC parameter.  Sources of information are
listed in Table 1.

     2)  Read and evaluate the data.  Start to make preliminary choices
about which aquifer or aquifers should be evaluated.  DRASTIC permits the
user to choose either a unconfined or confined aquifer for evaluation.
This choice will determine the type of data needed for other key DRASTIC
parameters.  Depth to water and the impact of the vadose zone media are
most significantly affected.  Remember, if an aquifer is evaluated as
confined, the depth to water is chosen as the depth to the top of the
aquifer and the impact of the vadose zone is assigned the delineation.

     The user may also choose to evaluate different aquifers on the same
map.  This may be necessary where an aquifer is not continuous across a
county.  Evaluation of different aquifers may be desirable where one
aquifer does not have the same importance, either economically or
usage-wise in the county.  Care should be taken to document which aquifer
is being evaluated so that users of the final map can understand the
evaluations and relative pollution potential.  DRASTIC does not permit the
user to evaluate two separate aquifers at the same location on the same
map; two separate maps must be produced.

     3)  Identify the pertinent hydrogeologic region (Western Mountain
Ranges for example) and begin to formulate ideas about the appropriate
hydrogeologic setting.  The hydrogeologic settings can be located in
Section 7, Hydrogeologic Settings of the United States by Ground-Water
Regions.

     4)  Begin the mapping procedure by selecting a 7 1/2 minute USGS
topographic quadrangle map (or a 15 minute map if a 7 1/2 minute map is not
available).  It is recommended that mapping proceed to an adjacent
quadrangle to maintain continuity.  Starting in one corner of the county is
usually the best approach.  Although many portions of the demonstration
maps were produced using 15 minute topographic quadrangle maps, the 7 1/2
minute maps were easier to use.

     5)  Mapping is conducted by creating a series of overlays to represent
the DRASTIC parameters.  Theoretically an overlay is necessary for each
parameter; however, it was discovered during the mapping process that
                                     86

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 frequently DRASTIC factors would be closely associated.   In  some areas the
 vadose  zone and  aquifer media were the same.  In other areas,  soil and
 topography were  intimately related.  In these instances,  it  was  not
 necessary  to create seven separate overlays; frequently 2 or 3 were
 sufficient.

      6)  Once a  7  1/2 minute quadrangle is chosen, the first overlay can be
 constructed by placing a piece of matte acetate over the map and taping it
 down.   The matte side should be placed toward the mapper.  Choose a DRASTIC
 parameter  to begin the map.  It is typically easier to choose the aquifer
 media as the starting parameter because the values chosen for other
 parameters (i.e. depth to water) may depend on the choice of aquifer for
 mapping.   So that  consistency in creating the maps was maintained, a
 specified  pencil color was assigned to each DRASTIC parameter.   Table 20
 shows the  colors which were used during the demonstration project.  The
 mapper  need not  use these colors, but may find standardization
 advantageous.


	TABLE 20. PENCIL COLORS USED FOR DRASTIC MAPPING EXERCISE	

      DRASTIC Parameter                                 Color

      Depth  to Water                                     Black
      Net Recharge                                     Green
      Aquifer Media                                     Red
      Soil Media                                       Blue
      Typography                                      Violet
      Impact of the Vadose Zone Media                         Brown
      Hydraulic Conductivity of the Aquifer                       Orange
     7)  Referring  to  available information, draw boundary lines  for  the
chosen  DRASTIC  parameter using the categories provided in Tables  4 through
10.  Try to  keep  in mind that DRASTIC is best applied by recognizing  the
generalities and  combining the unimportant specifics.  This is best done  by
remembering  that  DRASTIC areas should represent areas that are 100 acres  or
larger  in  size.   On a  7  1/2 minute quadrangle map this roughly corresponds
to the  size  of  a  50 cent piece.  It is important to "lump" generalities and
not to  "split"  unnecessarily.  Frequently individuals experience  the
greatest difficulty in "lumping" where there is extremely detailed
information  available;  where data is more generalized the temptation  to
"split" is reduced.  For example, in an area of varying topographic relief,
the mapper may  see  many  areas on the topographic map which would  lend
themselves to producing  a very detailed map.  However, the mapper needs to
remember the 50 cent piece and not create areas any smaller.  Conversely,
information about hydraulic conductivity of the aquifer is typically
generalized and is  easier to resist the temptation to draw a propensity of
lines because the data is not available to support them.
                                     87

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     It is during this mapping exercise that the mapper may become acutely
aware of data gaps or data deficiencies.  It is oftentimes necessary to
supplement the printed information with professional expertise.  A
telephone call to knowledgeable individuals (consultant, government
official, driller or other) may be both desirable and necessary.

     It is also during the mapping exercise that the user will realize that
the data used to generate a pollution potential map is produced at a
variety of scales.  For example, soils are commonly mapped at a level of
detail representing 85 percent accuracy in a one or two-acre area.
However, values for hydraulic conductivity are frequently extrapolated from
only a few points of reference or simply are estimated by aquifer media.
This can be likened to using significant figures to express research
results.  When adding numbers such as .038 and .1 the result is only
properly expressed to the first decimal point.  When creating the map it is
therefore important to attempt to "justify" the scales by either making
generalizations (in the case of soil media) or finding the most detailed
available information (in the case of hydraulic conductivity).  This
process of trying to evaluate data at relatively equal scales produces a
better pollution potential map.

     8)  Label the enclosed areas with the appropriate category.  Record
the corresponding weight and rating for the area and multiply the two
numbers.  Circle the number for easy reference.  Figure 24 shows an example
of a correctly drawn and labeled map of aquifer media.

     9)  Select the next factor to evaluate.  Tape down an additional sheet
of acetate or use the same sheet as before.  Select a different colored
pencil.  Draw in the appropriate boundaries, label and circle the computed
number.  Figure 25 shows a correctly drawn and labeled map of depth to
water superimposed on Figure 24.

    10)  Continue to map all seven DRASTIC parameters with a different
colored pencil using as many sheets of acetate as necessary.  By the  time
this portion of the exercise is complete, the mapper will have  identified
areas where additional information is needed.  At this point, the mapper
may wish to record those notations for  future reference.

    11)  Overlay and align all  the sheets of acetate.  Add an additional
clean acetate sheet to the top.  Select a black  (or other appropriate)
pencil  and retrace all the boundaries that are seen through the overlain
sheets.  Remember that the final map should have no areas smaller than  a 50
cent piece (Figure 26).  This may mean  that the  mapper may not  be able  to
trace all the lines.   In this instance, the mapper needs  to employ the
technique of "lumping."  This is best done by reviewing  the parameters  that
create  this line.  This  process is made easier if a different color pencil
was used for each parameter.  The mapper should  carefully look  at
boundaries which coincide between parameters.  Where one or more  parameter
lines coincide  the importance of keeping that particular  line  is  enhanced.
The reliability  of the data which made  the  line  should also be  evaluated.
For example, if  the aquifer media was well-documented but professional
                                     88

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90

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                                  D(5-15)(45
                                  R(7-10)(5
                                  A-S/6 (21
                                  S-SL(12
                                  T (2-6) (9
                                          l-S/6 WiSi cl (35
                                          CI300-700) (l
0(15-30)
R(4-7) (24)
A-M
S-SLl2
T (2-6) 0
 I-M I (2(J
C(1-100)(3
   0(5-15)(45
   R(7-10)(32
   A-S/6 (21
   S-SlI (8
   T(2-6)(9
 I-S 6 WiSi cl(25
C(300-700) ^ ,
                   T (2-6) ^9
              I-S 6 WiSi cl(30
           C(1-100)(3
                        0(15-30)^35
                        R(4-7)(24
                       A-M I  5
                                        D(5-15)(45
                     -S/6 WiSi
                   C(300-700)
Figure 26. Hand-drawn map showing correct delineation and labeling of all DRASTIC parameters.
                                                     91

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judgement has been used to draw the net recharge line, perhaps the net
recharge boundary could share the aquifer media boundary.   Finally, the
importance of the DRASTIC parameter should be considered.   For example, it
is frequently very easy to make a detailed map using topography alone.
However, since topography has only a weight of 1 in general DRASTIC,  it may
be possible to re-evaluate those boundaries with respect to soil,  vadose
zone or aquifer boundaries.  By reasoning processes similar to this,  the
mapper is able to create a valid DRASTIC map delineating realistic areas of
pollution potential.

    12)  At this point, the mapper needs to evaluate the hydrogeologic
settings which are present on the map.   This is done by reviewing  the
descriptions in the appropriate hydrogeologic region (Section 7).   The
descriptions and block diagrams provide generalized information about the
important hydrogeologic parameters from a pollution potential standpoint.
The block diagrams provide a "typical"  range of values which might be
present somewhere in the region.  It is unlikely that the map which has
been generated will duplicate the typical chart.  Therefore, the mapper
needs to create a lettering system for  the map.  This can be done  by making
a series of blank charts.  Write the names of the hydrogeologic settings
encountered during mapping on the top of the charts.

    13)  Next, label the areas on the final maps with the  appropriate
hydrogeologic settings (i.e., 2A, 7Da,  6K).  Concurrently or later sum the
DRASTIC numbers for a selected area. This number is the DRASTIC Index and
a measure of relative pollution potential.

     The user should note that the map  produced using these steps  is  a map
which outlines areas of hydrogeologic settings and variable DRASTIC
Indexes.  However, the user should also note that the numbers are  not
contoured.  Contour lines imply a sequential progression between each line.
The DRASTIC numbers are comparative and not sequential.   This means that
each individual Index value is not related to the adjacent value but  only
serves as a means of comparison.

    14)  Record the ranges and associated ratings on the blank chart  with
the appropriate hydrogeologic setting.   Label the appropriate area on the
map as below:
                                     6K
                                    101

where

6K denotes the ground-water region and  hydrogeologic setting and

101 denotes the DRASTIC Index.

Figure 27 illustrates a correctly labeled map.  Table 21 is an example of
an accompanying chart.
                                   92

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Figure 27. Hand-drawn map showing correctly labeled
                                                ground-water pO||ution potentja|
                                       93

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               TABLE 21. CHART FOR SETTING 912 — BEDROCK UPLANDS
Setting 912 Bedrock Uplands
Feature
Depth to water
Net recharge
Aquifer media
Soil media
Topography
Impact vadose zone
Hydraulic conductivity
Range
15-30
4-7
Metamorphic/igneous
Sandy loam
2-6%
Metamorphic/igneous
1-100
General
Weight
5
4
3
2
1
5
3
Rating
7
6
3
6
9
4
1
Drastic Index
Number
35
24
9
12
9
20
3
112
    15)  Continue to sum the DRASTIC Index and label the hydrogeologic
setting for each area.  During this process, it will become obvious that
there are many different variations within a hydrogeologic setting.  For
example, it is possible to be within the setting 6D but to have the depth
to water be 15-30 feet in one area and 30-50 feet in another.  This results
in a different DRASTIC index.  It is also possible to have changes in more
than one parameter.  For purposes of charts and labeling, it becomes
desirable to delineate between the many variations.  This is best done by
labeling as follows:
     6K1
     96
6K2
103
6K3
113
where

6K1
   is the first unique combination of DRASTIC parameters encountered

6K2
    is the second set of unique DRASTIC parameters encountered, and
/I -ITO
-.„ is the third variation encountered during mapping.
                                    94

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The mapper can thus continue to label ad infinitum.  Probably no two
mappers will label the variations (i.e., 1, 2, 3, etc.), in the same order,
but the order is not really the important aspect.  The unique combination
of DRASTIC parameters and the ability of a reviewer or user to trace the
way the mapper created the DRASTIC Index and hydrogeologic setting is the
most significant milestone.

    16)  Continue to map each 71/2 minute quadrangle using the same
technique until the county is completely mapped.  Check all map boundaries
to ensure that hydrogeologic setting lines continue from map to map.
Continue to label the hydrogeologic setting variations sequentially.

Drawing the Map by Computer

     A Geographic Information Systems (CIS) is designed to display and
combine many layers of spatial data into differing formats so results may
be more easily interpreted by the user.  Since DRASTIC combines seven
layers in the form of the seven DRASTIC parameters, an attempt was made to
produce a map using a computerized CIS.  Geographic Information Systems is
a broad term for a variety of software packages capable of manipulating
spatially-oriented data.  The capabilities and output of the CIS varies
with the software package.

     New Castle County, Delaware was chosen to demonstrate the use of
DRASTIC with a CIS.  An Automated Environmental Resources Information
System (AERI) was the computer assisted information system ayailable in New
Castle County.  The information for the seven DRASTIC parameters resided in
the existing computerized data base and needed only minor manipulation to
fit the DRASTIC format.  The software used in the demonstration was GRID II
which was designed to overlay any combination of AERI data files and
produce a map with a variety of scales.  Data in the AERI files was
previously entered in 5.74 acre grid cells with cell dimensions measuring
500 feet per side.  The demonstration did not involve inputting additional
data into the data files.  The following steps were used in producing maps
on the computer.

     1)  Existing data files were reviewed to verify the format content of
the information to ensure relevance compatibility with DRASTIC.

     A data file was chosen that represented each DRASTIC parameter. The
data file was manipulated to correspond to the DRASTIC ranges.  For
example, soil was available in the data base by soil series name.  Each
soil series had to be coded to correspond to a soil texture as listed in
Table 7.  Where information already existed in ranges, it was not always
possible to use the exact DRASTIC ranges.  For example, hydraulic
conductivity of the major unconsolidated aquifer existed in the computer by
groups A, B, and C which corresponded to 748-1870 gpd/ft2, 374-561
gpd/ft2 and 1-150 gpd/ft2 respectively.  In this instance it was
necessary to adapt the DRASTIC rating numbers to correspond to these
ranges.  Although, this practice is not recommended, the alternatives would
have been to reenter all the data or abort the project.
                                    95

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     2)  The ratings associated with the assigned ranges were entered into
the computer.

     3)  A separate map was produced for each of the seven DRASTIC
parameters at a scale of I" - 6000" to allow review of each parameter.  The
output was in the format of symbols.  The symbols were then chosen to
represent ranges for the DRASTIC parameter.  Figure 28 shows a part of a
map for aquifer media in New Castle, County.  Each symbol represented a
5.74 acre grid cell.  An acetate overlay provided geographic reference
points.

     4)  When necessary, the existing data files were reassigned DRASTIC
ranges.  For example, this was necessary in the category of soil media
because the original data had been entered on such a fine scale.  The
resultant map produced a very detailed soil media map with an associated
problem (Figure 29).  Inasmuch as DRASTIC is designed to be used on areas
100 acres or larger, it would take approximately 14 consecutive grid cells
to make an area of 100 acres.  This would be the smallest area for which a
symbol should be assigned (refer to Item number 7 in drawing the map
manually).  The CIS did not contain an algorithm to weight average each
symbol and produce sets of symbols in aggregates of 14 grid cells or
larger; therefore the only way to adjust the map was to reassign ranges and
print additional maps by trial and error.

     5)  Once a tentatively acceptable map was produced for each DRASTIC
Parameter, the weights for each DRASTIC parameter were entered into the
computer.  The program performed the calculations of the weight multiplied
by the rating for each of the assigned DRASTIC parameters and combined the
individual maps into a composite DRASTIC map.  The output was displayed in
the format of symbols.  The symbols were chosen to represent ranges of
DRASTIC values.  For example, all values between 170-179 could be
delineated by the symbol o.  The computer could then re-group the values in
chosen increments limited only by the number of available symbols necessary
to map the output.  Figure 30 shows a portion of a sample output.  Once
again the computer had produced DRASTIC Indices for areas smaller than 100
acres.  By computer manipulation it was impossible to remove the small
areas and retain any confidence in the output.  Further, although the
computer had produced a numeric map, it was not possible to detail at every
point on the map the exact range chosen for each DRASTIC factor.  It was
also impossible to obtain an overview of the hydrogeology because no
hydrogeologic settings could be delineated using this system.

     6)  To produce a valid final map for the county, it was necessary to
resort to manual manipulation.  Each separate DRASTIC factor map was used
as a source of information to produce a more generalized overlay.  For
example, a piece of matte acetate was taped over the map generated for
depth to water.  Lines were hand drawn using professional judgement to make
generalizations of parameters  where necessary.  For some of the
parameters, the areas previously defined by the computer were simply
outlined as an overlay.  The entire process was very similar to producing a
map by hand.
                                     96

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Frequency attribution ol Data Point Value. In Each Ltwl
  LEVELS

  SYMBOLS

  FREQUENCY
              LOW VALUES
                   0
       »*»*>"*oooQQQpQQ iitiiiiii
                                              HIGH VALUES
                                                  7
11646
          '4006     "23061      8383       198
                                DRASTIC RATINGS FOR AQUIFER MEDIA
                                  NEW CASTLE COUNTY, DELAWARE
                                       SEPTEMBER 26,1985
                                   Ranges and RaMngt tor AquHer Media
                                       IMPACT OF AQUIFER MEDIA
Map Level
1
2
2
3
3
4
4
5
6.
Range
Metamporphic/lgneous
Metamorphic/lgneous
Metamorphic/lgneous
Sand and Gravel
Sand and Gravel
Sand and Gravel
Sand and Gravel
Sand and Gravel
Karat Limestone
Rating
2
3
3
5
5
6
6
8
9
                                     Blank = Water as Primary Land Cover
                                          Map Scale. 1" = 6,000'
     Figure 28. Computer-drawn map showing representation of aquifer media by symbols.

                                               97

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         LOW VALUES

LEVELS          o       ,


SYMBOLS
                                                                 HIGH VALUES
                                                  111!
                     DRASTIC RATINGS FOR SOIL MEDIA
                     NEW CASTLE COUNTY, DELAWARE
                          SEPTEMBER 24,1985
                       Ranges and Ratings lor Soil Media
                             SOIL MEDIA
Map Level
1
2
3
4
5
6
7
8

Range
Nonshrrnkmg and Nonaggregated Clay
Ctay Loam
Silty Loam
Loam
Sandy Loam
Shrinking and/or Aggregated Clay
Sand
Gravel, Quarries, Thin or Absent

Rating
1
3
4
5
6
7
8
9
10
                      Blank Cells = Water as Primary Land Cover
                           Map Scale 1" = 6,000'
Figure 29. Computer-drawn map showing an unacceptable detailed soils

                              98
                                                                   map.

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  Frequency Distribution of Data Point Values in Each Level

               LOW VALUES

  LEVELS

  SYMBOLS

  FREQUENCY
                  = = = s;- = -
                  ssssssss
                  SS.SSSSSS
                                        ii
                   130
493
          2608
                    7186
                             5376
                                        2599
                                                                 HIGH VALUES
                                                                     11
                  6817
                                                          1326
                      DRASTIC INDEX VALUES MAPPED IN RANGES
                          NEW CASTLE COUNTY, DELAWARE
                                DECEMBER 5,1985	
                                DRASTIC Index Ranges
                           1
                           2
                           3
                           4
                           5.
                           6.
                           7
                           8
                           9
                          10
                   94-109
                  110-119
                  120-129
                  130-139
                  140 - 149
                  150-159
                  151 - 169
                  170-179
                  180-189
                  190-204
                                  Scale. 1" = 6,000'
                            Blank = Water as Primary Land Cover
Figure 30. Computer-drawn map showing a final DRASTIC Index value map.

                                      99

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     Once overlays had been produced for the seven factors, a final
hydrogeologic setting map was produced from the overlays as per the
explanation in the previous hand mapping section.  The mapper was able to
evaluate shared lines and the importance of parameters when delineating the
final hydrogeologic setting.  The software used in this demonstration
project was not capable of incorporating this less tangible function,  in
retrospect, any software coupled with a CIS system should be able to
produce not only a numeric or symbolic map, but also be capable of
determining how best to draw final hydrogeologic setting lines with
corresponding labels.  Labeling and charts for New Castle County, Delaware
were accomplished using the step previously described in the hand mapping
section.

Final Map Production

Map Reduction

     Once the final hydrogeologic setting map has been created for each
topographic map, it is frequently desirable to display the results within a
political boundary such as a county.  However, a county is comprised of
many 7 1/2 or 15 minute quadrangles such that the resultant map would
typically cover the floor of a large room.  To more concisely display the
finished product, the overlays need to be reduced to a scale which can be
displayed on one map.  The following steps detail the process used in the
demonstration counties.

     1)  A county highway map or other suitable political base map was
selected.  The base map was reduced to fit a 20 inch by 24 inch image area
when necessary.  This size was chosen for production purposes.

     2)  Each topographic map-sized overlay was final drafted using a
rapidograph and labeled with a template.  The rapidograph line width and
letter size was chosen so that camera reduction would yield readable
letters and significant lines.

     3)  Each topographic sized overlay was professionally camera reduced
to fit the base map and printed on drafting applique film.  A typical
county contained all or part of approximately 24 topographic maps;
therefore 24 individual camera reductions were necessary.

     4)  The maps on the drafting applique film were peeled and placed on a
sheet of matte acetate to form a composite overlay.  An image deletion pen
and rapidograph were used to clean the overlay and perform boundary
adjustments due to parallax.

     5)  The pasted up overlay was photoghraphically processed into a
positive film overlay.
                                     100

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     6)  The hydrogeologic setting map with associated DRASTIC Indexes were
superimposed on the county highway map to provide geographic reference.
Since the counties varied in size from 437 square miles to 1302 square
miles, the resultant maps were produced at varying scales.

National Color Code

     Although each hydrogeologic setting map imparted a significant amount
of information when coupled with the computed DRASTIC Index for each
setting, it was difficult to perceive a general assessment of relative
pollution potential within the county.  For example, Figure 31 demonstrates
a portion of the pollution potential map for Yolo County, California.  To
assist in map readability, each demonstration map was subsequently
color-coded using the DRASTIC Index.  Colors were chosen based on a
simplified statistical evaluation of frequency of Index occurrence.  Table
22 shows the DRASTIC Index ranges and associated colors used in the
development of a National Color Code.  The colors of the spectrum were
chosen to show the levels of relative vulnerability to pollution.  The warm
colors — red, orange and yellow — indicate areas with the potentially
greatest problems; the cool colors — blue, indigo and violet — indicate
areas of lower susceptibility to ground water pollution.  Two varying
shades of green delineate the middle ranges.  Figure 32 illustrates the
superposition of the National Color Code on a portion of the hydrogeologic
setting map for Yolo County, California.  Various screens have been chosen
to simulate the color variations on the map.

     Each draft hydrogeologic setting map was color-coded to aid in the
review process.  The color overlays were created by delineating the
appropriate DRASTIC Indexes on the map according to the ranges in Table 22.
For each color range, it was necessary to cut & piece of rubylith or
amberlith with an exacto knife along the appropriate hydrogeologic setting
lines.  Once the rubylith or amberlith was cut for each color range, the
colors were photographically shot onto separate acetate overlays.  The
result was a series of overlays containing each color.  These overlays were
taped onto the base map and the hydrogeologic setting overlay was placed on
top.

         TABLE 22. NATIONAL COLOR CODE FOR DRASTIC INDEX RANGES

DRASTIC Index Range
<79
80- 99
100- 119
120- 139
140- 159
160-179
180-199
>200
Color
Violet
Indigo
Blue
Dark Green
Light Green
Yellow
Orange
Red
Printing Specification
Color
Pantone Purple C
Pantone Reflex Blue
Pantone Process Blue C
Pantone 347C
Pantone 375 C
Pantone Yellow C
Pantone 151C
Pantone 485C
                                    101

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Figure 31. Pollution potential map for a portion of Yolo County, California, showing
          hydrogeologic settings.
                                     102

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SCALE IN MILES
Figure 32. Pollution potential map for a portion of Yolo County, California, showing the superposition
          of the national color code.
                                             103

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Presentation and Field Check

     The draft pollution potential maps accentuated using the National
Color Code were used as the focus of a presentation which was given to
interested individuals.  The presentations were held within the mapped
county or in a convenient location within the state.  The purpose of the
meeting was to familiarize people with the DRASTIC methodology, explain the
efforts conducted to date in the county, solicit critical review on the
maps and educate individuals about the importance of protecting
ground-water resources.  The audience at the meetings included a
cross-section of individuals ranging from state geologists, city planners,
mayors, and county commissioners.

     The draft color-keyed maps and the full size topographic-based
overlays were also used to field check the maps.  Individuals particularly
knowledgeable about the seven DRASTIC parameters were asked to critically
review the maps.  The review consisted of an office and field component.
The reviewers represented drillers, universities, geologists, soil
scientists, and other technical experts.  Typically, five individuals spent
a very long field day verifying the ranges chosen for the DRASTIC
parameters.

Final Map and Legend

     Once the review was complete, suggested modifications to the draft
maps were made.  The final DRASTIC maps were professionally printed in 21
inch by 27 inch sheets.  A four-color printing process was^sed to color
code the appropriate DRASTIC Index ranges.  A fifty percent screened county
highway map formed the base map.  All maps contained a scale, title,
legend, and location map.

     An accompanying legend was created using a folio style.  The legend
contains a written description and block diagram for every hydrogeologic
setting encountered in the county.  The block diagram precedes DRASTIC
charts with appropriate ranges and DRASTIC Indexes for every variation
delineated in the county.  This allows the user to recreate the
decision-making process for assessing pollution potential for every area on
the map.

     The legend also contains a section designed to assist the user in
reading the map by presenting a general county description and information
on DRASTIC.  Figure 33 shows the format of a horizontally arranged legend.
A similar format was used for vertically oriented maps.  The general county
description was adapted for each county.  The text for the other
explanatory sections needed very slight modification between counties.  The
text for Portage County, Wisconsin has been reproduced below for reference
by the system user:
                                     104

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TITLE

What DRASTIC Means
General
County
Description


D
R
A
S
T
1
C

C
H
A
R
T
S















1 	 ' How to Read the Map , 	 1
How to Calculate
a DRASTIC Index






Hydrogeologic Setting Descriptions
and Block Diagrams
Followed by Charts







Figure 33. Sample format of a legend for a ground-water pollution potential map.
                                 105

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 "How to Read the Map
The DRASTIC System provides the user with information
about the hydrogeologic setting of an area and the pollution
potential. The symbols found on the map look like this:
7Bal ]     defines the hydrogeologic setting
200  ]     defines the relative pollution potential of the
          ground water.
A.  Hydrogeologic Setting
1.  The first number (7) refers to the major ground-
    water region in which the hydrogeologic setting
    is located.
2.  The letter or letters (Ba) define the hydrogeologic
    setting in more detail.
3.  The number (1) describes a certain set of DRASTIC
    parameters which are unique to this setting.  When
    parameters, such as depth to water, change enough
    to warrant a different DRASTIC Index but not
    significantly to change hydrogeologic settings, a
    new set of unique characteristics is generated and
    another number (2) is assigned.  See charts below.
B.  DRASTIC Index
    This number represents a relative measure of ground
    water pollution potential.  The map has been color-
    coded using ranges developed on the map legend.  These
    colors are part of a national color code which has
    been developed to assist the user in gaining a general
    insight into the vulnerability of ground water to
    pollution.  DRASTIC Index values range from 99 to 200
    in Portage County.
What DRASTIC Means
D - Depth to Water
R - Net Recharge
A - Aquifer Media
S - Soil Media
T - Topography
I - Impact of the Vadose Zone
C - Hydraulic Conductivity of the Aquifer
How to Calculate a DRASTIC Index
1.  Each DRASTIC parameter has been weighted with respect
    to each other and assigned a number from 1 to 5  (Table 2).
2.  Each DRASTIC parameter has been divided into ranges or
    descriptive terms and assigned associated ratings  (Tables
    4-10).
3.  A DRASTIC Index is calculated by multiplying:
    Weight X Rating for each parameter
4.  Add the results to obtain the DRASTIC Index."
                           106

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     The legend was printed on 21 inch by 27 inch sheets to correspond to
the finished map size.  Where necessary, the lengends were printed
double-sided to allow for display of all the hydrogeologic setting
descriptions and accompanying charts.

COUNTY MAPPING EFFORTS

     The level of effort required to produce a map depends on the size of
the area to be evaluated, the amount of available information and the
degree of prior knowledge of the user about the area.  In addition, the
level of hydrogeologic expertise and familiarity with the methodology will
also influence the ability of the user to quickly produce an accurate and
reliable map.

     This section is designed to familiarize the user with the application
of DRASTIC in each of the ten demonstration counties.  Each discussion
contains a generalized description of the county, significant references
used to determine DRASTIC ranges, and a description of the major
assumptions used in producing the maps.  Notations of some of the
significant changes to DRASTIC based on this testing phase of the system
are also made.

     Each county section also contains a generalized pollution potential
map screened to show DRASTIC Index ranges corresponding to the National
Color Code.  The full-scale maps delineating hydrogeologic settings
overlayed on a county highway map are displayed in Appendices D through
M.  A location map and charts corresponding to the maps art also contained
in these Appendices.  The full-scale map of Yolo County in Appendix M has
been screened to correspond to the DRASTIC Index ranges used in the
National Color Code.  By comparing the full-scale map of Yolo County with
the unscreened maps in the other appendices, the user can evaluate the
advantages of displaying the information in a variety of formats.

Cumberland County, Maine

     Cumberland County, Maine, lies within the Northeast and Superior
Uplands hydrogeologic region.  Sand and gravel aquifers are the major
ground-water resource for the county and are capable of supplying
significant yields to domestic and municipal wells.  These aquifers consist
of glacial ice-contact and outwash deposits, which occur primarily in the
valleys of major rivers and along their tributaries.  These deposits are
typically very permeable with shallow water depths.  Where sand and gravel
deposits are not present, the igneous/metamorphic aquifers are used for
water supplies.  These aquifers are typically in hydraulic connection with
overlying glacial till; however, well yields are low.

     In mapping Cumberland County, eight hydrogeologic settings were
identified and included.  Computed DRASTIC Index values range from 84 to
184.  Table 23 details the settings and ranges of associated DRASTIC
Indexes.  Also noted in the table are the number of unique DRASTIC Index
calculations which were made during the mapping effort.  The DRASTIC Index
numbers reflect evaluation of water table aquifers only.


                                     107

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      TABLE 23. HYDROGEOLOGIC SETTINGS MAPPED IN CUMBERLAND COUNTY, MAINE

Hydrogeologic Setting
(9A) Mountain Slopes
(9Da) Glacial Till Over Crystalline Bedrock
(9E) Outwash
(9F) Moraine
(9H) Swamp/Marsh
(91) Bedrock Uplands
(9J) Glacial Lake/Glacial Marine Deposits
(9K) Beaches, Beach Ridges and Sand Dunes
Range of
DRASTIC Indexes
84
118-122
152-184
151
153
98-112
98-112
160
Number of DRASTIC
Index Calculations
1
2
7
1
1
2
2
1
     Figure 34 shows a general pollution potential map for Cumberland
County.  The DRASTIC Indexes have been grouped in accordance with the
National Color Code (Table 22).  Selected screens have been used to
illustrate the variability.  The pollution potential map has been
superimposed on a base map for geographic reference.  No hydrogeologic
setting lines have been delineated on the map.

     Appendix D contains the full-size pollution potential map for
Cumberland County complete with hydrogeologic setting designations and
individual DRASTIC Index computations.  The map has been superimposed on a
base map for geographic reference.  The DRASTIC Index values have not been
grouped on the full-size map.  The map has been divided into separate
sheets which permit it to be incorporated into the document.  An Index to
the map sheets is provided for ease of geographic sheet location.  The
corresponding «..ilrts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Water level information was primarily obtained from Ground Water
Resource Maps of Cumberland County (Caswell and Lanctot, 1978); published
maps of the Sand and Gravel Aquifer Map Series including Caswell (I979b, c,
d, e, f and g) and Tepper et al. (1985); and unpublished maps of the Sand
                                    108

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o

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and Gravel Aquifer Map Series at the Maine Geological Survey.  Supplemental
information was obtained from maps and well logs within Maine Basic Data
Reports Nos. 3 and 9 (Prescott, 1967; I976a).  According to geologic
reports, water occurs in the fractures of the igneous/metamorphic bedrock
aquifers under semi-confined conditions.  Since DRASTIC does not
effectively evaluate semi-confined aquifers, the metamorphic/igneous
aquifers must be designated as either confined or unconfined.  After
consultation with Andrews Tolman (personal communication, Maine Geological
Survey, 1985), the metamorphic/igneous aquifers were treated as unconfined.
Water levels ranged from 15 to 30 feet (7) and 30 to 50 feet (5).  Sand and
gravel aquifers were also unconfined and exhibited water level depths 5 to
15 feet (9) and 15 to 30 feet (7).  Water level data in some areas were
scarce; personal communications with Andrews Tolman were helpful in
establishing reasonable ranges for depth to water.

Net Recharge

     Published references for net recharge were not located during
reference-searching in this country.  Therefore, net recharge values were
estimated based on precipitation rates and types of surficial materials.
Estimates were provided by Andrews Tolman (personal communication, Maine
Geological Survey, 1985).  Estimates were classified according to aquifers.
Sand and gravel aquifers yielding 50 gallons per minute or greater were
assigned the range of 10+ inches per year (9) while those yielding 10 to 50
gallons per minute were assigned 7 to 10 inches per year (8).  The
metamorphic/igneous aquifers were assigned a range of 4 to 7 inches per
year (6) regardless of the characteristics of the overlying deposits.

Aquifer Media

     Information on aquifer media was derived from a variety of sources
including:  Hussey and Westerman (1979); Caswell (1979a); Caswell and
Lanctot (1979); Prescott (1963; 1967; 1968;  1976); published maps from the
Sand and Gravel Aquifer Map Series including:  Caswell (1979b, c, d, e, f
and g) and Tepper et al. (1985); unpublished maps from the Sand and Gravel
Aquifer Map Series; and the Surficial Geology Series including:  Prescott
(1976b; 1977); Prescott et al. (1976); Prescott and Thompson (I976a and b;
1977a, b and c); Smith (1976a and b; 1977a,  b, c and d); Smith and Thompson
(197t>; 1980); Thompson (1976a, b, c, d, e and f; 1977); and Thompson and
Prescott (1977).  The distribution of the sand and gravel aquifers was
determined primarily from the Sand and Gravel Aquifer Maps and the
Surficial Geology series.  The sand  and gravel aquifers  producing 50
gallons per minute or greater were assigned  a typical rating of  (8); those
producing 10  to 50 gallons per minute were assigned the lower rating of
(7).   The metamorphic/igneous aquifers were  primarily evaluated using
Prescott  (1963; 1968; 1976a).  These aquifers were assigned a typical
rating of (3) due to the fracture characteristics and known and  anticipated
yields.
                                     110

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Soil Media

     Soils were mapped based on the Soil Survey of Cumberland County, Maine
(Hedstrom, 1974).  Because the soil complexes were particularly detailed,
it was necessary to generalize the soils into a workable distribution.  In
areas of glacial till, sand and gravel outwash and the sandy occurrences of
the Presumpscott Formation, the designation of sandy loam (6) was used.  In
less sandy areas of the Presumpscott Formation, the designation of silt
loam (4) was used.

Topography

     Percent slope was estimated by using 7 1/2 minute USGS topographic
quadrangle maps where available and 15 minute USGS topographic quadrangle
maps in other areas.  Only 15 minute maps were available for the northern
and northwestern portions of the county.  Contour intervals on the 7 1/2
and 15 minute maps were 20 feet.  Areas of mountain slopes, bedrock uplands
and some glacial tills averaged 6 to 12 percent (5); areas of outwash,
swamps and the remaining glacial tills averaged 2 to 6 percent (9).

Impact of the Vadose Zone Media

     Information on the vadose zone media was obtained from well logs and
discussions in Prescott (1963; 1968; 1976; and 1977) and Tepper et al.
(1985).  Surficial geology was also reviewed.  Areas underlain by sand and
gravel aquifers yielding 50 gallons per minute or greater were assigned a
sand and gravel vadose zone with a rating of (8) because the stratigraphy
was typically consistent.  Areas underlain by sand and gravel aquifers
yielding 10 to 50 gallons per minute were called a sand and gravel with
significant silt and clay and assigned a value of (7).  This media could
possibly have been called a sand and gravel; the determination was based on
the significance of the silt and clay in the deposits.  The media was still
relatively "clean" and thus received a rating of (7).  Areas of glacial
till overlying metamorphic/igneous aquifers were designated as sand and
gravel with significant silt and clay and assigned a rating of (6).  The
lower range was chosen based on the relative degree of fine material within
the deposits when compared to the previously discussed deposits.  The
Presumpscott formation, which is a glacial marine deposit, was termed a
sand and gravel with significant silt and clay (5) regardless of the
aquifer which it overlay.  The formation did not receive a (4) rating
because of the extensive fracturing of the fine-grained clay.  [The
Presumpscott formation would be delineated as a silt/clay in this updated
version of DRASTIC.  The rating would still remain a (5).]  The
metamorphic/igneous vadose zone was assigned the typical rating of (4).
The ratings assigned to each of the vadose zone media were reviewed during
the selection process by Andrews Tolman (personal communication, Maine
Geological Survey, 1985).
                                    Ill

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Hydraulic Conductivity of the Aquifer

     Hydraulic conductivity values for the various aquifer media were
estimated from the aquifer properties and through discussion with Andrews
Tolman (personal communication, Maine Geological Survey, 1985).  Very few
published values were available.  Sand and gravel aquifers yielding 50
gallons per minute or greater were assigned a range of 700 to 1000 gallons
per day per square foot (6); those yielding 10 to 50 gallons per minute
were assigned a range of 300 to 700 gallons per day per square foot (4).
The metamorphic/igneous aquifers were assigned a range of 1 to 100 gallons
per day per square foot (1) based on the generally low yields from wells
within the county.

Finney County, Kansas

     Finney County, Kansas, is situated within two ground-water regions;
the western half of the county is located in the High Plains region and the
eastern half of the county is predominantly in the Non-Glaciated Central
region.  Ground-water resources in the High Plains region of the county are
derived primarily from the poorly-sorted, unconsolidated sands and gravels
of the Ogallala Formation which has been extensively developed for
irrigation.  This usage has resulted in historicaly declining ground-water
levels.  In the northwestern corner of the county, the Ogallala is
dewatered and small domestic ground-water yields are supplied from the
underlying consolidated chalky limestone.  A shallow, unconfined river
alluvium aquifer also occurs in the Arkansas River valley.  This alluvium
aquifer is in hydraulic connection with the underlying poorly sorted clay,
silt, sand and gravel deposits south of the river.

     Within the Non-Glaciated Central ground-water region in Finney County,
ground water is primarily available in the deep confined Dakota Sandstone.
Because the aquifer is confined and deep, ground-water pollution potential
is relatively low. The area of the Pawnee River is underlain by a river
alluvium aquifer which typically yields supplies for domestic purposes.
This river alluvium serves as the only available shallow ground-water
resource in the Pawnee River drainage basin.

     In mapping Finney County, seven hydrogeologic settings were identified
and included.  Computed DRASTIC Index values range from 50 to 166.  Table
24 details the settings and ranges of associated DRASTIC Indexes.  Also
noted in the table are the number of unique DRASTIC Index calculations
which were made during the mapping effort.  Ground-water pollution
potential was computed using both confined and unconfined aquifers as
described above.
                                     112

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        TABLE 24. HYDROGEOLOGIC SETTINGS MAPPED IN FINNEY COUNTY, KANSAS
Hydrogeologic Setting
(5A) Ogallala
(5C) Sand Dunes
(5D) Playa Lakes
(5Ga) River Alluvium with Overbank Deposits
(5H) Alternating Sandstone, Limestone Shale Sequences
(6Da) Alternating Sandstone, Limestone and Shale Thin Soil
(6Fa) River Alluvium with Overbank Deposits
Range of
DRASTIC Indexes
93-121
113-151
102-122
154-166
76
51-59
126
Number of DRASTIC
Calculations
19
9
3
3
1
5
1
     Figure 35 shows a general pollution potential map for Finney County.
The DRASTIC Indexes have been grouped in accordance with the National Color
Code (Table 22).  Selected screens have been used to illustrate the
variability.  The pollution potential map has been superimposed on a county
highway map for geographic reference.  No hydrogeologic setting lines have
been delineated on the map.

     Appendix E contains the full-size pollution potential map for Finney
Cou; :y complete with hydrogeologic setting designations and individual
DRASTIC Index computations.  The map has been superimposed on a county
highway map for geographic reference.  The DRASTIC Index values have not
been grouped on the full-size map.  The map has been divided into separate
sheets which permit it to be incorporated into the document.  An Index to
the map sheets is provided for ease of geographic sheet location.  The
corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.  l
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Depth to water in the Ogallala aquifer, the chalky limestone (Fort
Hays Member of the Niobrara Formation) and in the Arkansas and Pawnee River
alluvium aquifers was mapped based on 1984 water level data reported by
Pabst and Dague (1984).  Trends in water level changes were also noted from
Pabst and Gutentag (1979).
                                    113

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LEGEND
DRASTIC Index Range
<79
80-99
100-119
120-139
140-159
160-179
Color
m*
nn
D
m
D
a
m
Figure 35. Generalized pollution potential map of Finney County, Kansas.

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     According to geologic reports, the deposits which are collectively
referred to as the Ogallala aquifer have been extensively dewatered.  North
of the Arkansas River Valley, this dewatering has lowered water levels
below the confining layer making the aquifer unconfined.  Water levels in
the area ranged from 75 to 100 feet (2) and 100+ feet (1).  In the
northwestern portion of the county, the Fort Hays Limestone of the Niobrara
Formation serves as a localized unconfined aquifer.  Water levels in this
area were 100+ feet (1).  In the north central portion of the county, a
small section of undifferentiated deposits had shallower water levels which
averaged 30-50 feet (5).  South of the Arkansas River Valley, the Ogallala
is semi-confined with the thickness of the confining layer decreasing
southward.  Since DRASTIC does not effectively evaluate semi-confined
aquifers, the aquifer must be considered either confined or unconfined.
Because the aquifer is in direct hydraulic connection with the overlying
river alluvium where present and the aquifer has a high vertical hydraulic
conductivity, the aquifer was treated as unconfined.  Water levels ranged
from 100+ feet (1) and 75 to 100 feet (2) in the majority of the area with
levels decreasing to 50 to 75 feet (3) and 30 to 50 feet (5) close to the
Arkansas River Valley.  Water levels in the Arkansas River Valley Alluvium
and the Pawnee River alluvium were 15 to 30 feet (7).

     Depth  to water in the confined Dakota aquifer was mapped as the depth
to the top  of the sandstone as reported by Gutentag, Lobmeyer, McGovern and
Long (1972).  Depth to the top of the aquifer was 100+ feet (1).

Net Recharge

     Values for net recharge were based on information found in Meyer et
al. (1970), Latta (1944) and Dunlap et al. (1985).  Additional guidance was
obtained  from Lloyd Stullken (personal communication, U.S. Geological
Survey, 1985).  The non-glaciated central ground-water region in the
northeasten part of the county was assigned a range of 0 to 2 inches (1).
The High  Plains ground-water region north of the Arkansas River was also
assigned a  value of 0 to 2 inches (1). A value of 2 to 4 inches (3) was
selected  for the Arkansas River Valley and High Plains area south of the
Arkansas River.  These higher recharge rates took into consideration
recharge  from irrigation return flows in addition to nominal recharge from
precipitation (less than 1/2 inch per year).  The higher infiltration rates
of precipitation and irrigation return flows occurred through the dune
sands and river alluvium.

Aquifer Media

     Aquifer media information for the High Plains region (which includes
the hydrogeologic settings of Ogallala, Playa Lakes and Sand Dunes) was
obtained  from Meyer et al. (1970), Latta  (1944) and Dunlap et al. (1985).
North of  the Arkansas River, the lower unit of Miocene and Pleistocene age
undifferentiated sand, gravel, silt and clay deposits was selected as the
aquifer to  map.  The deposits were called sand and gravel and were assigned
a rating  of (7) due to the presence of preferential sorting and presence of
fines.  South of the Arkansas River, the upper unit of undifferentiated
                                     115

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Miocene and Pleistocene deposits was chosen as the aquifer.  Because this
upper unit does not have the caliche layers and finer silt and clay
deposits, the aquifer media was selected as sand and gravel with a value of
(8).

     Information on aquifer media for the Fort Hays Limestone Member of the
Niobrara Formation was obtained from Gutentag et al. (1981), Meyers et al.
(1970) and Latta (1944).  The aquifer media was selected as massive
limestone and assigned a value of (6) because the fractures and solution
openings in the rock are limited both in thickness and areal extent.

     Aquifer media information in the river alluvium of the Arkansas and
Pawnee Rivers was obtained from Meyer et al. (1970), Latta (1944) and
Dunlap et al. (1985).  The Arkansas River alluvium is a well-washed sand
and gravel which was assigned a rating of (9).  The Pawnee River alluvium
is also a sand and gravel, but contains a higher percentage of fines.  This
alluvium was assigned a typical rating of (8).

     Information on aquifer media for the Dakota aquifer in the non-glacial
central ground-water region was found in Gutentag et al. (1981), Meyer et
al. (1970), Latta (1944), Gutentag et al. (1972) and Dealy et al. (1984).
Based on this data, the aquifer media was selected as massive sandstone and
assigned a value of (6) due to the fine to medium grain calcareous
composition of the sandstone.

Soil Media

     Soils were mapped based on the Soil Survey of Finney County, Kansas
(Horner et al., 1965).  Soil media was selected by referring to the general
soil association map and choosing a different soil media where more
detailed soil series information supported the-choice.  Sand (9) was used
as the soil media in the hydrogeologic setting, Sand Dunes.  The Arkansas
River Valley contained three different soil medias.  Sand (9) and sandy
loam (6) media were designated adjacent to the river channel and clay loam
(3) was selected for areas not adjacent to the river channel.  The clay
loam provided the basis for designating the river as having overbank
deposits.  This county was evaluated using only 3 feet  instead of 6 feet of
soil profile thickness.  In this updated version of DRASTIC, the soil media
choice for clay loam (3) would have been sand (9) in most areas because the
clay loam typically represented less than 20 inches of  the  soil profile and
was underlain by significant deposits of sand.  The hydrogeologic setting
designation would be river alluvium without overbank deposits.  Silt loam
(4). typified by Ulysses silt loam, was chosen in the bluff area
immediately north of the Arkansas River Valley in the western to central
part of the county.  Clay loam  (3) was chosen as the predominant soil media
in the high plains region north of the Arkansas River.  Shrinking and
aggregated clay (7) was chosen as the principal soil media  in the playa
lake settings and in the east-central section of the high plains region.
Soils  selected as shrinking and aggregated clays were characterized by
clayey subsoils with a high shrink-swell potential.  Soils  in the Pawnee
river  basin were designated as clay loam (3).  Clay loam was also selected
as the predominant soil throughout the non-glaciated central region; sandy


                                     116

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loam (6) and shrinking and aggregated clay (7) occur in minor areas.
Another minor area of shrinking and aggregated clay (1) was also identified
in the western edge of the county, north of the Arkansas River.  Areas of
sandy loam (6) were designated in the high plains area, both north and
south of the Arkansas River.  These sandy loam soils commonly occurred in
geographical proximity to sand deposits.  Major areas of clay loam (3) also
occurred in the south-central section of the county, where they interfaced
with adjacent sandy loam soils.  One isolated section of loam (5) was
identified in the north-central section of the county.  The loam comprised
part of a sand-sandy loam-loam-clay loam soil sequence.

Topography

     Percent slope was estimated by using 7 1/2 minute USGS topographic
quadrangle maps.  Contour intervals on the maps were either 5 foot or 10
foot intervals.  The entire county is relatively flat.  North of the
Arkansas River slopes were 0 to 2 percent (1) while south of the Arkansas
River slopes averaged 2 to 4 percent (3).

Impact of the Vadose Zone Media

     Information for selecting values for the vadose zone media was
obtained from the same sources listed in the aquifer media section.  For
the high plains area north of the Arkansas River, the vadose zone media
above the lower unit of the undifferentiated Miocene and Pleistocene
deposits was called sand and gravel with significant silt and clay and
assigned a value of (6).  The deposits overlying the Niobrara Formation
were also assigned this designation.  In the high plains area south of the
Arkansas River, the upper unit of undifferentiated Miocene and Pleistocene
deposits was selected as sand and gravel with significant silt and clay and
assigned a value of (7).  The higher value was assigned based on the
presence of the sandy deposits in the dune areas.

     In the Arkansas River alluvium, the deposits beneath the thin overbank
are described as coarse sand and gravel.  The vadose media was chosen as
"sand and gravel" and assigned a typical value of (8).  In the Pawnee River
alluvium, the sands and gravels are interbedded with large amounts of silts
and clays.  This area was designated as sand and gravel with significant
silt and clay and assigned a value of (7).  The typical rating of (6) was
not chosen due to the large fraction of coarser-grained materials within
the alluvium.

     The Dakota sandstone aquifer is confined by overlying sequences of
shales, siltstones and limestones.  The impact of the vadose zone media was
chosen as "confining layer" (1).  The charts accompanying the full-size
pollution potential map detail the impact of the vadose zone media as
silt/clay (1) instead of confining layer (1).  The vadose zone would be
delineated as confining layer in this updated version of DRASTIC.  The
rating would still remain a (1).  This change was made to help clarify the
use of confining layer in the methodology.
                                    117

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Hydraulic Conductivity of the Aquifer

     Information on hydraulic conductivity of the aquifer in the High
Plains region was obtained from Meyer et al. (1970) and Dunlap et al.
(1985).  According to these published reports, hydraulic conductivity
values for the undifferentiated Miocene and Pleistocene deposits ranged
from 600 to 1500 gallons per day per square foot.  Because it was not
possible to differentiate specific areas with representative hydraulic
conductivities, a range of 700-1000 gallons per day per square foot (6) was
chosen.

     A hydraulic conductivity range for the Fort Hays Limestone Member of
the Niobrara Formation was selected based on an aquifer description by
Latta (1944).  A range of 1-100 (1) gallons per day per square foot was
selected.

     Hydraulic conductivity values for the river alluvium aquifers in the
Arkansas River and Pawnee River valleys were selected based on information
found in Meyer et al. (1970) and Dunlap et al. (1985).  This information
indicated conductivity values in the Arkansas River alluvium ranged from
1000 to 2000 gallons per day per square foot (8).  Values in the Pawnee
River alluvium ranged from 300 to 700 gallons per day per square foot (4).
Hydraulic conductivity values for the Dakota Aquifer were obtained from
Dealey et al. (1984).  A range of 1 to 100 gallons per day per square foot
(1) was assigned.

Gillespie County, Texas

     Gillespie County, Texas, lies within the Nonglaciated Central
Hydrogeologic Region.  Several different aquifers occur within the county
which provide adequate municipal and domestic supplies of ground water.
The western portion of the county is covered by a thick sequence of bedded
dolomitic limestones, which contain water in solution cavities and
fractures.  The central area of the county is covered by unconsolidated
sands and silts, which provide moderate well yields from lenses of sand and
gravel.  Where these deposits are locally non-water bearing or absent,
ground water is supplied from deeper, more permeable sandstones and
limestones.  Igneous and metamorphic rocks, which outcrop in the
northeastern part of the county, contain ground water in fractures and
faults and only provide small quantities of water to domestic wells.

     In mapping Gillespie County, five hydrogeologic settings were
identified and included.  Computed DRASTIC Index values range from 63 to
126.  Table 25 details the settings and ranges of associated DRASTIC
Indexes.  Also noted in the table are the number of unique DRASTIC Index
calculations which were made during the mapping effort.  The DRASTIC Index
numbers reflect evaluation of water table aquifers only.
                                     118

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        TABLE 25. HYDROGEOLOGIC SETTINGS MAPPED IN GILLESPIE COUNTY, TEXAS
Hydrogeologic Setting
(6B) Alluvial Mountain Valleys
(6Da) Alternating Sandstone, Limestone and Shale Thin Soil
(6Fb) River Alluvium without Overbank Deposits
(6J) Metamorphic/lgneous Domes and Fault Blocks
(6K) Unconsolidated and Semiconsohdated Aquifers
Range of
DRASTIC Indexes
94
93-126
112-116
63-65
96-113
Number of DRASTIC
Calculations
1
9
2
2
3
     Figure 36 shows a general pollution potential map for Gillespie
County.  The DRASTIC Indexes have been grouped in accordance with the
National Color Code (Table 22).  Selected screens have been used to
illustrate the variability.  The pollution potential map has been
superimposed on a county highway map for geographic reference.  No
hydrogeologic setting lines have been delineated on the map.

     Appendix F contains the full-size pollution potential map for
Gillespie County complete with hydrogeologic setting designations and
individual DRASTIC Index computations.  The map has been superimposed on a
county highway map for geographic reference.  The DRASTIC In^ex values have
not been grouped on the full-size map.  The map has been divided into
separate sheets which permit it to be incorporated into the document.  An
Index to the map sheets is provided for ease of geographic sheet location.
The corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 6.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Information on the depth to water was derived from the Texas
Department of Water Resources computer printouts of well logs.  These files
contain information regarding the location, depth, producing aquifer and
the static water level of each well.  Additional water-depth information
                                    119

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IN)
O
LEGEND
DRASTIC Index Range
<79
80-99
100-119
120-139
Color
H
D
m
D
                                     Figure 36. Generalized pollution potential map of Gillespie County, Texas.

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was obtained from well logs of Virdell Drilling Company in Fredricksburg,
Texas (personal communication, Taylor Virdell, Sr. and Taylor Virdell, Jr.,
1985).  All water levels were plotted on a base map and corrected for
topography.  All aquifers were unconfined.  Water levels in the alternating
sandstone, limestone and shale sequences were assigned based on aquifer
type and elevation.  The Edwards Limestone is the major aquifer in the
Edwards Plateau region in the western portion of the county.  Where mean
sea elevations were 2100 feet or greater, water levels in the aquifer were
assigned a range of 100+ feet (1).  Where elevations were 2000 to 2100
feet, the depth to water was assigned as 75 to 100 feet (2).  Water levels
in elevations less than 2000 feet averaged 50 to 75 feet (3).  The Edwards
Limestone is the aquifer used in settings 6Dal through 6Da5.  Other
formations also serve as aquifers in the alternating sandstone, limestone
and shale sequences.  The Glen Rose Limestone is in the southern and
eastern portions of the county.  The Glen Rose is depicted as the aquifer
in setting 6Da6 and has average water-level depths of 30 to 50 feet (5).
The Ellenberger-San Saba group occurs in the northern and eastern portions
of the county.  The Ellenberger-San Saba as exemplified in settings 6Da7
and 6Da8 have water levels averaging 50 to 75 feet (3).  The Hickory
Sandstone serves as the aquifer in the northeastern portion of the county.
Setting 6Da9 delineates the Hickory Sandstone aquifer and has water levels
averaging 75 to 100 feet (2).  The Hensell sand is depicted in the
unconsolidated and semi-consolidated aquifer setting which occurs
throughout the county.  Water levels in the Hensell sand averaged 75 to 100
feet (2) in the northwest, 50 to 75 feet (3) in the northeast and 30 to 50
feet (5) in the central and southern portions of the county.  Water levels
in the unconsolidated deposits of the alluvial mountain valleys averaged 75
to 100 feet (2).  Depth to water in the river alluvium ranged from 30 to 50
feet (5).  Water levels in the metamorphic and igneous bedrock in the
northeastern portion of the county averaged 75 to 100 feet (2).

Net Recharge

     Values for net recharge were obtained from Ashworth (1983) and Muller
and Price (1979).  Recharge rates were published in units of acre feet per
year and had to be converted to inches per year.  Values for recharge were
less than two inches per year throughout the county.  The range of 0 to 2
inches per year (1) was used.

Aquifer Media

     Information on aquifer media was derived from a variety of sources
including:  Muller and Price (1970); Rose (1972); Ashworth (1983); Walker
(1979); Mount (1963); Texas Department of Water Resources (1983) and
published maps from the Geologic Quadrangle Map Series including:
                                    121

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Barnes (1952 a, b, c, d, e and f; 1954a, b, c and d;  1956a, b, c,  d,  e,  f
and g; 1965a and b; and 1967).  The Edwards Limestone group (settings 6Dal
through 6Da5) contains a basal, extremely burrowed and solutioned  limestone
unit approximately 50 feet above the base of the section.  This marly unit
is the principle water-bearing unit and may form springs where the aquifer
outcrops.  Other water-bearing zones occur higher in  the section but  little
information was available about their water-bearing characteristics.   The
aquifer media was chosen as massive limestone and assigned a rating of (8).
The Glen Rose Limestone (setting 6Da6) is a massive limestone with moderate
solutioning along faults and joints in the lower fossiliferous member.   The
aquifer media was chosen as massive limestone and the typical rating  of  (6)
was assigned.  The Ellenberger-San Saba (settings 6Da7 and 6Da8) is also a
massive, fossiliferous limestone.  Water occurs in the joints and  solution
cavities.  The aquifer was called massive limestone and assigned a rating
of (8) because the aquifer is more prolific than the Glen Rose.  The
Hickory Sandstone (setting 6Da9) is a coarse to fine-grained moderately-
sorted sandstone with a conglomerate and coarse sandstone in the lower
portion of the aquifer.  The aquifer media was chosen as massive sandstone
and assigned a typical value of (6).  The Hensell Sand (settings 6K1
through 6K3) is a semi-consolidated deposit of sand,  silt and clay.  The
aquifer media was chosen as sand and gravel and assigned a rating  of  (7)
based on the variability of the deposit.  Unconsolidated materials in the
alluvial mountain valleys (setting 6B1) and the river alluvium (settings
6Fbl and 6Fb2) were called sand and gravel and assigned a rating of (7)
based on the presence of fine materials.  The metamorphic igneous  aquifers
have low yields and were assigned the typical rating  of (3) due to a  lack
of information about the degree of fracturing.

Soil Media

     Soils were mapped based on the Soil Survey of Gillespie County,  Texas
(Allison et al., 1975).  Soils were grouped based on  the underlying major
aquifer.  Soils overlying the Edwards Limestone (settings 6Dal through
6Da5) were very thin.  The soil media was chosen as thin or absent (10).
Soils overlying the Glen Rose  (setting 6Da6) are typically silt loams (4).
Soils formed in the Ellenberger-San Saba area (settings 6Da7 and 6Da8) and
the Hickory Sandstone area (setting 6Da9) are typically loams (5).  In some
high relief areas, the soils are thin or absent (10).  Soils overlying the
Hensell Sand (setting 6K1 through 6K3) are typically  loam (5) in the
northwest portion of the county and sandy loam (6) in the remainder of the
county.  Soils formed in the alluvial mountain valleys (setting 6B1)  are
silty loam (4).  River alluvium soils (settings 6Fbl  and 6Fb2) are clay
loam (3) in the northwestern portion of the county and loam  (5) in the
remainder of the county.  Soils overlying the metamorphic/igneous  aquifer
area (settings 6J1 and 6J2) are loam (5) and sandy loam (6).

Topography

     Percent slope was estimated by using 7 1/2 minute USGS  topographic
quadrangle maps.  Contour intervals on the 71/2 minute maps are 20 feet.
Topography was influenced by the formation exposed at the surface.  Areas
                                     122

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of the Edwards group (settings 6Dal through 6Da5) are 2 to 6 percent (9) on
the top of the plateau; slopes at the plateau boundary ranged from 2 to 6
percent (9) to 6 to 12 percent (5). Typically the northern slopes are
steeper than the southern slopes.  Slopes in other areas are relatively
uniform throughout the county at 2 to 6 percent (9).  Slopes of 6 to 12
percent (5) are present in portions of the metamorphic/igneous area where
extensive faulting has occurred.  Slopes of 6 to 12 percent (5) also occur
in portions of the areas underlain by the Ellenberger-San Saba group
(setting 6Da8).

Impact of the Vadose Zone Media

     Information on the vadose zone media was obtained from Mount (1963),
Ashworth (1983), Walker (1979) and Rose (1972).  The Edwards Limestone area
(settings 6Dal through 6Da5) was called a limestone and assigned a typical
rating of (6) based on the solutioning and jointing of the formation.  The
Glen Rose (setting 6Da6) was called limestone and assigned a rating of (5)
because the limestone is more massive than the Edwards and marly in the
upper layers.  The Ellenberger-San Saba (settings 6Da7 and 6Da8) vadose
zone media was designated as limestone and assigned a typical rating of
(6).  The Hickory Sandstone (setting 6Da9) is overlain by a limestone.  The
vadose zone media was called limestone and assigned a typical value of (6).
The Hensell Sand (settings 6K1 through 6K3) vadose zone media contains
silts and clays.  The media was designated as a sand and gravel with
significant silts and clays and assigned a typical value of (6).  The
alluvial deposits in the alluvial mountain valleys (setting 6B1) were
called sand and gravel with significant silts and clays and assigned a
typical value of (6).  The river alluvium (settings 6Fbl and 6Fb2) is
better sorted than in the alluvial valleys.  A vadose zone media of sand
and gravel with significant silts and clays was chosen and assigned a
rating of (7).  The vadose zone media in the metamorphic/igneous areas
(settings 6J1 and 6J2) was called metamorphic/igneous and assigned a
typical value of (4).

Hydraulic Conductivity of the Aquifer

     Hydraulic conductivity values for the various aquifer media were
contained in Walker (1979), Muller and Price (1979) and Mount (1963).
Where no values were given, estimates were based on discussions contained
within the reports.  Hydraulic conductivities for the Edwards Limestone
(settings 6Dal through 6Da5) are 1000 to 2000 gallons per day per square
foot (8).  Glen Rose values (setting 6Da6) were estimated to be 300 to 700
gallons per day per square foot (4).  Ellenberger-San Saba values (settings
6Da7 and 6Da8) were given as 700 to 1000 gallons per day per square foot
(6).  Hydraulic conductivity values for the Hickory Sandstone (setting
6Da9) were stated as 300 to 700 gallons per day per square foot (A).
Values for the Hensell Sand (settings 6K1 through 6K3) were listed as
ranging between 300 to 700 gallons per day per square foot (4).  The
alluvial aquifers (settings 6B1, 6Fbl and 6Fb2) were estimated to range
between 300 to 700 gallons per day per square foot (4) based on the
presence of fines and the hydraulic connection to the underlying Hensell
                                    123

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sand in the river alluvium settings.  The metamorphic/igneous aquifers were
estimated to be 1 to 100 gallons per day per square foot (1) based on low
yields.  Little information is available on the metamorphic/igneous
aquifers.

Greenville County, South Carolina

     Greenville County, South Carolina, lies within the Piedmont and Blue
Ridge ground-water region.  The primary ground-water resources of the
county are derived from igneous and metamorphic rocks covered by variable
thicknesses of saprolite.  Ground water in the igneous/metamorphic aquifer
system provides moderate yields from fractures and faults.  Unconfined
ground water accumulates in the saprolite overlying the parent rock and
often serves as a recharge source for these aquifers.  Although saprolite
is an easily developed source of ground water, low yields and seasonal
fluctuations typically limit the development of this resource.  Although
limited in aerial extent, alluvial deposits of sand and gravel adjacent to
rivers and overlying the saprolite may also constitute a source of ground
water.

     In mapping Greenville County, five hydrogeologic settings were
identified and included.  Computed DRASTIC Index values range from 87 to
152.  Table 26 details the settings and ranges of associated DRASTIC
Indexes.  Also noted in the table are the number of unique DRASTIC Index
calculations which were made during the mapping effort.  The DRASTIC Index
numbers reflect evaluation of water table aquifers only.
  TABLE 26. HYDROGEOLOGIC SETTINGS MAPPED IN GREENVILLE COUNTY, SOUTH CAROLINA
Hydrogeologic Setting
(8A) Mountain Slopes
(8B) Alluvial Mountain Valleys
(8D) Regolith
(8E) River Alluvium
(8F) Mountain Crests
Range of
DRASTIC Indexes
87-113
143
105-125
152
90-99
Number of DRASTIC
Index Calculations
7
1
3
1
3

     Figure 37 shows a  general  pollution  potential  map  for  Greenville
 County.  The  DRASTIC Indexes have been  grouped  in accordance  with the
 National Color Code  (Table  22).  Selected screens have  been used  to
 illustrate the variability.  The pollution potential  map  has  been
 superimposed  on  a  county  highway map  for  geographic reference.  No
 hydrogeologic setting lines have been delineated on the map.
                                    124

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    MAP SHOWING LOCATION OF



GREENVILLE COUNTY tN SOUTH CAROLINA
LEGEND
DRASTIC Index Range
Water
80-99
100-119
120-139
140-159
Color
D
D
m
D
DQ
     Figure 37. Generalized pollution potential map of Greenville County, South Carolina.
                                            125

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     Appendix G contains the full-size pollution potential map for
Greenville County complete with hydrogeologic setting designations and
individual DRASTIC Index computations.  The map has been, superimposed on a
county highway map for geographic reference.  The DRASTIC Index values have
not been grouped on the full-size map.  The map has been divided into
separate sheets which permit it to be incorporated into the document.  An
Index to the map sheets is provided for ease of geographic sheet location.
The corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

      Computation of the DRASTIC Indexes and identification of
hydrogeologic settings relied on detailed information of the seven DRASTIC
parameters.  Specific descriptions and sources used to obtain this
information are outlined in the following discussion centering around each
DRASTIC parameter.  A complete list of references is contained at the end
of Section 6.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Water level information was primarily obtained based on well logs and
information contained in Koch (1968).  Supplemental values were estimated
based on topography and personal communication with Don Duncan (South
Carolina Department of Health and Environmental Control, 1985).
Water-level data was generally sparse.  All aquifers were treated as
unconfined.  In general, water levels averaged 5 to 15 feet (9) in the
river valleys and and alluvial mountain valleys.  Depth to water in the
regolith in the central and southern portion of the county averaged 15 to
30 feet (7) due to the presence of thin saprolite deposits.  Water levels
in the central and northern portion of the county averaged 30 to 50 feet
(5) due to the formation of thicker saprolite deposits on the
biotite-gneiss bedrock.  Water levels on mountain slopes averaged 75 to 100
feet (2) except on slopes adjacent to the Saluda River where water levels
were shallower and averaged 30 to 50 feet (5).  Wate*" levels on mountain
crests ranged from 75 to 100 feet (2) and 100+ feet (1).

Net Recharge

     Published references for net recharge were not located during
reference-searching in this county.  Net recharge rates were estimated
based on precipitation and predicted infiltration due to rock type, cover
and topography.  The estimates were supplemented by referring to other
similar areas in the Piedmont and Blue Ridge for which net recharge values
were available.  Values of 7 to 10 inches per year (8) were assigned for
areas of high relief and 10+ inches per year (9) was used in the remainder
of the county.
                                    126

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Aquifer Media

     Information on aquifer media was obtained from Koch (1968) and Padgett
and Hardee (1982).  Metamorphic/igneous bedrock was chosen as the aquifer
in the alluvial mountain valleys due to the shallow thickness of the
overlying alluvial deposits.  This area was assigned a typical rating of
(4).  In the river alluvium areas, the alluvium is sand and gravel
interbedded with lenticular clay layers.  A rating of (5) was assigned
based on the presence of the high clay content.  In the updated version of
DRASTIC, these deposits would receive a rating of (6) which is the lowest
rating for sand and gravel.  The areas as drawn on the map depicting river
alluvium were generously broad along minor tributaries and may be thinner
than depicted.  The saprolite was chosen as the aquifer in the majority of
the county.  Wells may be developed in either the underlying
me tamorphic/igneous bedrock or in the overlying saprolite.  In all areas
where the saprolite is present, it serves as a holding reservoir for the
underlying bedrock.  Based on the hydraulic interconnection of the two
medias, the saprolite was mapped as the aquifer.  An aquifer media of
weathered metamorphic/igneous rock was chosen for the saprolite.  A typical
rating of (3) was assigned in the northern portion of the county; a value
of (5) was assigned in the southern portion of the county based on
increased fracturing and higher well yields.  Bedrock type which influenced
the development of the overlying saprolite was used as the differentiation
between the two values.

Soil Media

     Soils were mapped based on the Soil Survey of Greenville County, South
Carolina (Camp, 1975).  Soils on mountain crests or soils in the northern
portion of the county which developed on mica-granite gneiss bedrock were
called loam (5).  Soils in the river alluvium and alluvial mountain valleys
were also designated as loam (5).  Soil media in the thicker regolith area
in the southern two thirds of the county were called non-shrinking and
non-aggregated clay (1).

Topography

     Percent slope was estimated by using 7 1/2 minute USGS topographic
quadrangle maps where available and 15 minute USGS topographic quadrangle
maps in other areas.  Contour intervals on the 7 1/2 minute maps were 10
feet and 40 feet; intervals for the 15 minute maps were 20 feet and 40
feet.  Areas of alluvial mountain valleys and river alluvium averaged 2 to
6 percent (9).  Slopes in the regolith areas ranged from 2 to 6 percent (9)
in wider well-developed valleys to 6 to 12 percent (5) in other areas.
Mountain slopes averaged 12 to 18 percent (3) or 18+ percent (1).  Mountain
crests ranged from 6 to 12 percent (5), 12 to 18 percent (3) and 18+
percent (1).
                                    127

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Impact of the Vadose Zone Media

     Information on the vadose zone media was obtained from Koch (1968) and
Padgett and Hardee (1982).  The river alluvium and alluvial mountain valley
deposits were called sand and gravel with significant silt and clay and
assigned a rating of (5).  This value is less than the typical value due to
the presence of interbedded clays and silts in the deposits.  The regolith
was well-developed and contained a significant fraction of fine materials.
The media was called sand and gravel with significant silt and clay and
assigned a rating of (5).  The vadose zone media in the mountain slope and
mountain crest areas consisted of more poorly weathered coarser deposits.
The media was still chosen as sand and gravel with significant silt and
clay, but was assigned a typical rating of (6).

Hydraulic Conductivity of the Aquifer

     Values for hydraulic conductivity of the various aquifer media were
not available in published reports.  Estimates were based on well yields
and aquifer characteristics as described in Koch (1968) and Padgett and
Hardee (1982).  The river alluvium was assigned a value of 300 to 700
gallons per day per square foot (4) based on the description of sand and
gravel interbedded with clay lenses.  The alluvial mountain valley areas
were assigned a range of 100 to 300 (2) gallons per day per square foot
based on the occurrence of significant fractures in the bedrock valleys.
The weathered metamorphic/igneous aquifers in the central to northern
portion of the county principally consisting of biotite and mica granite
gneiss were assigned a range of 1 to 100 gallons per day per square foot
(1).  In the central to southern portion of the county where the bedrock
consisted primarily of granite gneiss the value of 100 to 300 gallons per
day per square foot (2) was chosen due to an increased amount of
fracturing.

Lake County, Florida

     Lake County, Florida, lies within the Southeast Coastal Plain
ground-water region.  The county is characterized by low to moderate relief
with karst topography and numerous sinkholes, lakes and swampy areas.
Water depths are typically shallow and soils are highly permeable.
Ground-water resources within Lake County are derived from either a
near-surface sand aquifer or an underlying carbonate rock aquifer, which is
in hydraulic connection with the overlying sand deposits.  The aquifers are
separated by a confining bed comprised of an interbedded mixture of clayey
sand and clay.  This confining layer is extensive throughout the county,
although variable in thickness and discontinuous in local sections.  Yields
from the surficial sand aquifer are usually sufficient for domestic
purposes.  Because of the highly permeable overlying soils and shallow
water table, the surficial aquifer is vulnerable to pollution from the
surface.  The carbonate rock aquifer is referred to as the "Floridan"
aquifer and is the major ground-water resource in the county.  The
susceptibility of this aquifer to pollution from the surface depends on the
degree or confinement of the limestone aquifer and the amount of recharge
received from the more vulnerable surficial sand aquifer.


                                     128

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     In mapping Lake County, Florida, two separate evaluations were
performed:  one for the surficial aquifer and another for the confined
aquifer.  Two hydrogeologic settings were identified and included for the
surficial aquifer.  Computed DRASTIC indexes range from 134 to 190.  Two
hydrogeologic settings were also identified and included for the confined
aquifer.  Computed DRASTIC indexes range from 93 to 214.  Table 27 details
the settings and ranges of associated DRASTIC Indexes.  Also noted in the
table are the number of unique DRASTIC Index calculations which were made
during both mapping efforts.
        TABLE 27. HYDROGEOLOGIC SETTINGS MAPPED IN LAKE COUNTY, FLORIDA
Hydrogeologic Setting
Surficial
(11 A) Solution Limestone and Shallow Surficial Aquifers
(1 1C) Swamp
Confined
(11 A) Solution Limestone and Shallow Surficial Aquifers
(1 1C) Swamp
Range of
DRASTIC Indexes

134-190
166-190
102-155
93-145
Number of DRASTIC
Index Calculations

35
17
36
9
     Figure 38 shows the general pollution potential map for the surficial
aquifer in Lake County; figure 39 shows the general pollution potential for
the confined aquifer.  Selected screens have been used to illustrate the
variability.  The pollution potential maps have been superimposed on county
highway maps for geographic reference.  No hydrogeologic setting lines have
been delineated on the map.

     Appendix H contains the full-size pollution potential map for both the
surficial and confined aquifers in Lake County complete with hydrogeologic
setting designations and individual DRASTIC Index computations.  The maps
have been superimposed on county highway maps for geographic reference.
The DRASTIC Index values have not been grouped on the full-size maps.  The
maps have been divided into separate sheets which permit incorporating into
the document.  Two Indexes to the map sheets are provided for ease of
geographic sheet location.  The corresponding charts which detail the
ranges of the seven DRASTIC parameters chosen for each area and the
computation of the DRASTIC Index immediately follows the maps.
                                    129

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LEGEND
DRASTIC Index Range
ANP (Aquifer not prese'n'lf-
Water
120-139
140-159
160-179
180-199
Color
D
D
D
a
n
n
                              t
Figure 38. Generalized pollution potential map of the surficial aquifer, Lake County, Florida.
                                        130

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LEGEND
DRASTIC Index Range
Water
80-99
100-119
120-139
140-159
200+
Color
D
D
m
n
El
•
Figure 39. Generalized pollution potential map of the confined aquifer, Lake County, Florida.
                                        131

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     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Surficial Aquifer

     Depth to Water — Water levels were mapped based on general data
contained in Knochenmus and Hughes (1976).  Since no specific water-level
data was available, depth to water was frequently inferred from topographic
maps by noting differences between lake surface elevations and adjacent
land areas.  Where inferred water levels exceeded the depth to the top of
the underlying limestone aquifer, the surficial aquifer was mapped as
"aquifer not present" (ANP).  Water levels averaged 0 to 5 (10) in swamp
settings.  Depth to water was assigned values of 5 to 15 feet (9) in areas
adjacent to swamps and lakes.  Water levels averaged 15 to 30 feet (7) in
the west-central, northwestern and northeastern portions of the county.
Water levels in sections of the east-central portion of the county also
averaged 15 to 30 feet (7).  Depth to water was chosen as 30 to 50 feet (5)
in isolated areas in the east-central, southeast and northwest portions of
the county.  Water levels were estimated to be 50 to 75 feet (3) in the
upland of the east-central and southeast portions of the county.  The depth
to water exceeded the depth to the top of the underlying limestone in the
southwestern corner of the county.  The area was assigned the designation
of aquifer not present.

     Net Recharge — Values for net recharge were inferred based on annual
surface runoff data and climatological data found in Knochenmus and Hughes
(1976).  A range of 10+ inches per year (9) was selected for the majority
of the county.  Values of 7 to 10 inches per year (8) was assigned to the
northeastern portion of the county.  The lower recharge value was selected
based on greater surface runoff and the presence of strong upward
ground-water gradients in this major ground-water discharge area.

     Aquifer Media — Information on aquifer media was contained in
Knochenmus and Hughes (1976).  The surficial aquifer consists of sand and
gravel with varying amounts of clay which increase with depth.  The aquifer
media was chosen as sand and gravel and assigned a rating of (6) based on
the high clay content at depth.

     Soil Media — Soils were mapped based on the Soil Survey of Lake
County Area, Florida (Furman et al., 1975).  The soil  survey did not cover
the Ocoee National Forest.  Soil media north of Tier 17 south was inferred
based on topography.  Large submerged areas were called muck (2) and
nonsubmerged areas were called sand (9).  The principal soil media
throughout the county is sand  (9).  Peat  (8) and muck  (2) occur
interspersed with the sands in swampy areas throughout the county.  Minor
occurrences of shrinking and aggregated clay are present west of Lake
Harris along the western border of the county, east and northeast of Lake


                                     132

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Griffin and adjacent to the southeastern boundary of the St. Johns River.
This updated version of DRASTIC contains soil media designations for peat
and muck which were not included in the original document.  This addition
was made to overcome the difficulties in mapping soil in the county and for
clarification for the user.

     Topography — Percent slope was estimated by using 7 1/2 minute USGS
topographic quadrangle maps.  Contour intervals on the 7 1/2 minute maps
were 5 feet.  Areas of swamp settings throughout the county averaged 0 to 2
percent (10).  Slopes average 2 to 6 percent (9) in the majority of the
county where swamp settings are not present.  Slopes of 6 to 12 percent (5)
occur in the southeastern portion of the county.

     Impact of the Vadose Zone Media — Information on vadose zone media
was obtained from Knochenmus and Hughes (1976).  A vadose zone media of
sand and gravel was chosen and assigned a typical value of (8).

     Hydraulic Conductivity of the Aquifer — Hydraulic conductivity values
for the sand and gravel were inferred from a general description of the
aquifer media in Knochenmus and Hughes (1976).  Values of 300 to 700
gallons per day per square foot (4) were assigned for the majority of the
county.  Values of 700 to 1000 gallons per day per square foot (6) were
assigned in the St. Johns River valley and the lake region in the central
portion of the county based on estimates of less fine materials in the
deposits.
                                                          «
Confined Aquifer

     Depth to Water — The Floridan aquifer was chosen as the aquifer to
map throughout the county.  The aquifer is confined to semi-confined in
Lake County.  In some areas the confining layer is discontinuous.  Since
DRASTIC does not effectively evaluate semi-confined aquifers, the aquifer
had to be designated as either confined or unconfined.  The Floridan was
treated as confined because the confining layer is extensive throughout the
county and discontinuous primarily in areas adjacent to sinkholes.

     When evaluating a confined aquifer, the depth to water is changed to
mean the depth to the top of the aquifer.  Depth to the top of the
limestone was mapped using information contained in Knochenmus (1971).
Depths to top of the aquifer vary from 30 to 50 feet to 100+ feet.  Shallow
depths of 30 to 50 feet (5) occur in the southwest corner of the county, in
a small area south of Lake Harris, in the northwest portion of the county
and central section of the northeast portion of the county.  Intermediate
depths of 50 to 75 feet (3) occur throughout the south central portion of
the county, in the majority of the northwest portion of the county, in the
majority of the northeast portion of the county and in small sections of
the central and south-central portions of the county.  Depths of 100+ feet
(1) occur in the north-central portion of the county, the majority of the
southeastern corner of the county, and small areas in the northwest border
of the county adjacent to the St. Johns River and northern section of the
northeastern portion of the county.
                                    133

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     Net Recharge — Average values for net recharge were contained in
Knochenmus and Hughes (1976).  General information was obtained from Grubb
(1977).  Recharge values of 0 to 2 inches per year (1) were given for the
St. Johns River valley due to strong upward gradients of ground-water flow.
This is a major discharge area which has first order magnitude springs.
Net recharge values of 2 to 4 inches per year (3) were found in the north
central portion of the county in the areas surrounding Lakes Griffin, Yale,
Eustis, Dora, Harris and Little Harris.  A value of 4 to 7 inches per year
(6) was indicated for the southwest portion of the county and for the
central and northeast portion of the county.  Net recharge averaged 7 to 10
inches per year (8) in the west and west-central portion of the county.  A
value of 10+ inches per year (1) was found ..in the southeastern portion of
the county.

     Aquifer Media — Information on aquifer media was obtained from
Knochenmus and Hughes (1976), Knochenmus (1971) and Grubb (1977).  The
Floridan Aquifer occurs extensively and continuously across the county.  An
aquifer media of karst limestone was chosen'and assigned a rating of (10).

     Soil Media — Soils were mapped based on the Soil Survey of Lake
County Area, Florida (Furman et al., 1975).  The soil survey did not cover
the Ocoee National Forest.  Soil media north of Tier 17 south was inferred
based on topography.  Large submerged areas were called muck (2) and
non-submerged areas were called sand (9).  The principal soil media
throughout the county is sand (9).  Peat (8) and muck (2) occur
interspersed with the sands in swampy areas throughout the county.  Minor
occurrences of shrinking and aggregated clay are present west of Lake
Harris along the western border of the county, east and northeast of Lake
Griffin and adjacent to the southeastern boundary of the St. Johns River.
This updated version of DRASTIC contains soil media designations for peat
and muck which were not included in the original document.  This addition
was made to overcome the difficulties in mapping soil in the county and for
clarification for the user.

     Topography — Percent slope was estimated by using 7 1/2 minute USGS
topographic quadrangle maps.  Contour intervals on the 7 1/2 minute maps
were 5 feet.  Areas of swamp settings throughout the county averaged 0 to 2
percent (10).  Slopes average 2 to 6 percent (9) in the majority of the
county where swamp settings are not present.  Slopes of 6 to 12 percent (5)
occur in the southeastern portion of the county.

     Impact of the Vadose Zone Media— For the purpose of mapping, the
Floridan is designated as a confined aquifer due to the presence of the
Hawthorn Formation which is a silty confining bed as described by
Knoehcnmus (1971) and Knochenmus and Hughes (1976).  Although the Hawthorn
is thin and locally breached in the west-central lakes area and parts of
the southwestern and south-central to southeastern portions of the county,
the Hawthorn is considered as occurring extensively and continuously across
the county.  Since the Floridan was considered as a confined aquifer, the
impact of the vadose zone media was called silt/clay and assigned a rating
of 2.  In this updated version of DRASTIC, the impact of the vadose zone
media would be chosen as confining layer and assigned a rating of (1).


                                     134

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     Hydraulic Conductivity of the Aquifer — Hydraulic conductivity values
for the Floridan were Inferred from transmissivity data presented in
Knochenmus and Hughes (1976).  A range of 200CH- gallons per day per square
foot (10) was chosen for the entire county.

Minidoka County, Idaho

     Minidoka County, Idaho, lies within the Columbia Lava Plateau
ground-water region.  The majority of the county is covered by thick
deposits of basalt resulting from numerous sequences of individual lava
flows.  These igneous rocks are generally exposed throughout the northern
part of the county and are overlain by loess and alluvial deposits in the
central and southern sections of the county, respectively.

     Ground-water in Minidoka County is derived primarily from a deep,
unconfined aquifer comprised of highly permeable basalt.  This aquifer has
been developed for domestic, industrial and irrigation uses.  Along the
Snake River in the southern part of the county, the shallow, unconfined
alluvium aquifer, which is in hydraulic connection with the areal basalts,
has been developed for domestic uses.

     In mapping Minidoka County, two hydrogeologic settings were identified
and included.  Computed DRASTIC Index values range from 127 to 167.  Table
28 details the settings and ranges of associated DRASTIC Indexes.  Also
noted in the table are the number of unique DRASTIC Index calculations
which were made during the mapping effort.  The DRASTIC Ind^x numbers
reflect evaluation of unconfined aquifers only.
      TABLE 28. HYDROGEOLOGIC SETTINGS MAPPED IN MINIDOKA COUNTY, IDAHO
Hydrogeologic Setting
(3C) Hydraulically Connected Lava Flows
(3G) River Alluvium-
Range of
DRASTIC Indexes
127-167
152-166
Number of DRASTIC
Calculations
14
4
     Figure 40 shows a general pollution potential map for Minidoka County.
The DRASTIC Indexes have been grouped in accordance with the National Color
Code (Table 22).  Selected screens have been used to illustrate the
variability.  The pollution potential map has been superimposed on a county
highway map for geographic reference.  No hydrogeologic setting lines have
been delineated on the map.

     Appendix I contains the full-size pollution potential map for Minidoka
County complete with hydrogeologic setting designations and individual
DRASTIC Index computations.  The map has been superimposed on a county
highway map for geographic reference.  The DRASTIC Index values have not
been grouped on the full-size map.  The map has been divided into separate
sheets which permit it to be incorporated into the document.  An Index to
the map sheets is provided for ease of geographic sheet location.  The
corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.
                                  135

-------
Figure 40. Generalized pollution potential map of Minidoka County, Idaho.
                               136

-------
     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Water level information was obtained from U.S. Geological Survey
(1980), Mundorff et al. (1964), Lindholm et al. (1983), Crosthwaite and
Scott (1956) and Young and Norvitch (1984).  Depth to water primarily was
based on 1980 water level data.  Water levels in the Snake River basalts
were 100+ feet (1) in all parts of the county except one small area in the
southeastern corner of the county.  In this area bordering the river
alluvium, water levels were 75 to 100 feet (2).  Depths to water in the
river alluvium averaged 5 to 15 feet (9) in areas directly adjacent to the
Snake River.  Water levels in the remaining alluvium averaged 15 to 30 feet
(7).

Net Recharge

     General information on net recharge was found in Mundorff et al.
(1964).  Additional information was obtained from Gerald Lindholm (personal
communication, U.S. Geological Survey, 1985).  Values for net recharge in
the basalts ranged from 0 to 2 inches per year (1), 2 to 4 inches per year
(3), 4 to 7 inches per year (6), 7 to 10 inches per year (8) and 10+ inches
per year (9).  These variable ranges reflect irrigation and irrigation
return flow contributions in the areas of higher recharge.  Values in the
river alluvium were assigned 10+ inches per year (9) due to intensive
irrigation practices.

Aquifer Media

     Information on aquifer media was derived from Whitehead (1984),
Mundorf et al. (1964) and Crosthwaite and Scott (1956).  The basalt aquifer
was assigned a value of 10 based on the vesicular nature of the basalt, the
presence of lava tubes and the extensive interconnection between interflow
zones in the basalt flows.  The river alluvium was called a sand and gravel
aquifer media and assigned a value of (7) based on the presence of fine
silt deposits contained within the alluvium.

Soil Media

     Soils were mapped based on the Soil Survey of Minidoka County, Idaho
(Hansen, 1985).  The soil survey only covered the southern portion of the
county.  Soil media north of Tier 6 South was inferred from topographic
maps and areal descriptions to be thin or absent (10) as a result of
numerous surface basalt flows.  Soil media in the majority of the county
underlain by the basalt aquifer was silty loam (4).  A small wedge of sandy
                                     137

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loam (6) overlying the basalt aquifer is present in the southeastern corner
of the county.  Soil media overlying the alluvium ranged from sandy loam
(6) to loam (5) to silty loam (4).  The sandy loam occurs adjacent to the
river and soils increase in fine materials northward away from the river.

Topography

     Percent slope was estimated by using 71/2 minute USGS topographic
quadrangle maps where available and 15 minute USGS topographic quadrangle
maps in other areas.  Only 15 minute maps were available for the northern
portion of the county.  Contour intervals on the 7 1/2 minute maps were 5
feet, 10 feet and 20 feet; intervals for the 15 minute maps were 20 feet.
Slopes in the areas overlying the basalt ranged from 0 to 2 percent (10) in
the central portion of the county to 2 to 6 percent (9) in the majority of
the remaining area.  Slopes were 6 to 12 percent (5) along the margin of
the river alluvium and in an isolated corner in the western portion of the
county.  Slopes in the river alluvium in the southern portion of the county
were 0 to 2 percent (10).

Impact of the Vadose Zone Media

     Information for selecting values for the vadose zone media was
obtained from Whitehead (1984), Mundorf et al. (1964), Crosthwaite and
Scott (1956) and Graham (1979).  The vadose zone media in the basalt areas
are overlain with varying thicknesses of loess deposits.  In areas where
the loess deposits are less than 10 feet thick, a vadose zone media of
basalt was selected and assigned a typical rating of (9).  This rating was
chosen due to the columnar jointing in the basalt and the ability of
surface recharge to move quickly through the vadose zone.  In areas where
the loess deposits were greater than 10 feet thick, a vadose media of
basalt was still chosen but assigned a rating of (8) in recognition of the
possible attenuation properties of the loess.  In general, loess deposits
were less than 10 feet thick in the northern and western portions of the
county.  The river alluvium vadose zone media of sand and gravel with
significant silt and clay was chosen and assigned a typical rating of (6)
based on the amount of fine material and the variable degree of compaction
within the deposits.

Hydraulic Conductivity of the Aquifer

     Hydraulic conductivity values for the basalt were based on Mundorff et
al. (1964).  Information about the river alluvium was estimated based on a
review of the aquifer media descriptions and supplemented by personal
communication with Gerald Lindholm (U.S. Geological Survey, 1985).  The
hydraulic conductivity in the basalt was assigned a range of 2000+ gallons
per day per square foot (10).  The river alluvium was designated as 300 to
400 gallons per day per square foot (4) based on the high percentage of
fines.
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New Castle County, Delaware
     New Castle County, Delaware, lies within the boundaries of two
ground-water regions which are separated by the Fall Line; the northern
area is within the Piedmont and Blue Ridge, while the remainder of the
county lies within the Atlantic and Gulf Coastal Plain.  Ground-water
resources in the Piedmont and Blue Ridge region of the county are derived
primarily from igneous and metamorphic rocks covered by variable
thicknesses of saprolite.  Unconfined ground water accumulates in the
saprolite overlying the parent rock and often serves as a recharge source
for these aquifers.  Although the saprolite is an easily developed
ground-water source, low yields and seasonal fluctuations typically limit
:he development of this resource.  Ground water in the underlying
igneous/metamorphic aquifer system provides small to moderate yields from
fractures and faults.  Wells in the Hockessin-Yorklyn and Pleasant Hill
Valleys underlain by a white marble formation have much higher yields.

     Within the Atlantic and Gulf Coastal Plain ground-water region, ground
water is available in thick sequences of sand and gravel deposits which
form the coastal plain.  The Columbia deposits comprise the major
unconfined aquifer in the county and overlie a sequence of deeper aquifers.
The deeper aquifers are typically confined, but may occur under water table
conditions in limited recharge areas.  Most areas have abundant ground
water resources.

     In mapping New Castle County, four hydrogeologic settings were
identified and included.  Computed DRASTIC Index values range from 114 to
194.  Table 29 details the settings and ranges of associated DRASTIC
Indexes.  Also noted in the table are the number of unique DRASTIC Index
calculations which were made during the mapping effort.  The DRASTIC Index
numbers reflect evaluation of unconfined aquifers only.

     TABLE 29.HYDROGEOLOGIC SETTINGS MAPPED IN NEW CASTLE COUNTY, DELAWARE
Hydrogeologic Setting
(8A) Mountain Slopes
(8D) Regolith
(10Ab) Unconsolidated and Semiconsolidated
Shallow Surficial Aquifer
(10Ba) River Alluvium with Overbank Deposits
Range of
DRASTIC Indexes
117-135
114-181
112-194
166
Number of DRASTIC
Index Calculations
2
14
29
1
     Figure 41 shows a general pollution potential map for New Castle
County.  The DRASTIC Indexes have been grouped in accordance with the
National Color Code (Table 22).  Selected screens have been used to
illustrate the variability.  The pollution potential map has been
superimposed on a county highway map for geographic reference.  No
hydrogeologic setting lines have been delineated on the map.
                                    139

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         ff
         I
        &

       I
      o
      I
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   1

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  2
  2
  


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     Appendix J contains the full-size pollution potential map for New
Castle County complete with hydrogeologic setting designations and
individual DRASTIC Index computations.  The map has been superimposed on a
county highway map for geographic reference.  The DRASTIC Index values have
not been grouped on the full-size map.  The map has been divided into
separate sheets which permit it to be incorporated into the document.  An
Index to the map sheets is provided for ease of geographic sheet location.
The corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

      Computation of the DRASTIC Indexes and identification of
hydrogeologic settings relied on detailed information of the seven DRASTIC
parameters.  Specific descriptions and sources used to obtain this
information are outlined in the following discussion centering around each
DRASTIC parameter.  A complete list of references is contained at the end
of Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Water level information was generated using data stored in the
computer files at the Water Resources Agency for New Castle County,
Delaware.  Water levels in most sections of the Piedmont in the northern
portion of the county ranged from 5 to 15 feet (9) in flatter areas and 15
to 30 feet (7) in areas with greater relief.  Depth to water was 0 to 5
feet (10) in the eastern portion of the county adjacent to the Delaware
River.  Water levels in the coastal plain ranged from 0 to 5 feet (10), 5
to 15 feet (9), 15 to 30 feet (7) and 30 to 50 feet (5).  The depth to
water was generally a reflection of topographic variation.

Net Recharge

     Values for net recharge in the coastal plain were obtained from
Johnston (1973), Groot et al. (1983) and Talley (1978).  According to
Johnston (1973), net recharge averages 13.6 inches per year; Groot et al.
(1983) indicate that recharge is not less than 10.5 inches per year; Tolley
indicates recharge ranges from 13 to 16 inches per year.  Based on this
information, a value of lOf inches per year (9) was assigned for the entire
coastal plain area.' Published values for net recharge in the Piedmont area
were unavailable.  Based on information through Bob Finkle (personal
communcation, Water Resources Agency for New Castle County, 1985) a value
of 10+ inches per year (9) was also assigned for the Piedmont area.

Aquifer Media

     Aquifer media was selected by using existing information in the data
base of the Water Resources Agency for New Castle County, Delaware,
supplementing the data base with the discussions in Petty et al. (1976) and
reviewing maps by Woodruff and Thompson (1972; 1978) and Woodruff (1981).
Information for the coastal plain had been entered into the data base by
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dividing the Columbia Formation into three major categories:  A, B and C.
Aquifer media was chosen based on the descriptions of these categories.
Category A contains coarse sand with gravel beds, silty (dirty) gravels,
coarse sand and coarse to medium sand.  Category A was called sand and
gravel and assigned a rating of (8).  Category B contains fine to coarse
sand and medium sand.  The aquifer media for Category B was chosen as sand
and gravel and assigned a rating of (6).  Category C contains fine sand,
silt or clay.  The aquifer media for Category C was called sand and gravel
and assigned a rating of (5).  In this updated version of DRASTIC, Category
C would have also been assigned a rating of (6) because the range for sand
and gravel is 6 to 9.  Aquifer media information in the Piedmont area had
been entered into the data base by formation name.  The Wilmington Complex
consists of high-grade metamorphic gneisses and associated igneous rocks.
The aquifer media for the Wilmington Complex was chosen as metamorphic/
igneous and assigned a typical rating of (3).  The Bryn Mawr Formation is a
poorly sorted sand and gravel.  The aquifer media was chosen as sand and
gravel and assigned a rating of (6) based on the fine-grained material
within the deposits.  The Wissahikon Formation consists of gneisses,
schists and amphibolites.  The aquifer media was chosen as metamorphic/
igneous and assigned a typical rating of (3).  The Cockeysville Marble is a
medium to coarse-grained white marble that develops solution cavities and
is very permeable.  Although marble is a metamorphic rock, the marble
exhibits characteristics more similar to karst limestone.  The aquifer
media was chosen as karst limestone and assigned a rating of 10.
Pegmatites occur locally in the Wissahickon Schist and Cockeysville marble.
The aquifer media for Pegmatites was chosen as metamorphic/igneous and
assigned a rating of (2).  The aquifer media for river alluvium was called
sand and gravel and assigned a rating of (5).  In this updated version of
DRASTIC, th rating would have been assigned a  (6) because (6) is  the lowest
rating for aquifer media.

Soil Media

     The information on  soil for the entire county had been digitized into
the data base using  the  Soil Survey of New Castle County, Delaware
(Matthews and Lavoie, 1970).  Since the information in the data base was
entered by soil  series name, each  individual soil series was assigned a
media designation based  on the most significant  soil layer.  A map of soil
media was generated  using these soil media designations.  The map was
unacceptable because it  was  impossible  to generalize the soil media into
areas of 100 acres or larger (refer to  the discussion  in Section  5, Drawing
the Map by Computer).  The  soil media were reassigned  into groups based on
the predominant  soil media of each area.  Soil media in the Piedmont were
chosen as either silty loam  (4) or loam (5).   Soil media in the coastal
plain were chosen as clay loam  (3), silty loam (4), loam (5) and  sandy  loam
(6).
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Topography

     Percent  slope was generated from the existing data files of the Water
Resources Agency  for New Castle County, Delaware.  Information for the data
base was obtained from U.S. Geological Survey maps.  Slopes in the Piedmont
area range  from 0 to 2 percent (10), 2 to 6 percent (9), 6 to 12 percent
(5) to  12 to  18 percent (3).  Slopes in the coastal plain were generally 0
to  2 percent  (10) and 2 to 6 percent (9) with minor occurrences of 6 to 12
percent (5).

Impact  of the Vadose Zone Media

     Vadose zone media was selected based on designations existing in the
data files  of the Water Resources Agency for New Castle County, Delaware
and by  referring  to Petty, et al. (1976), Woodruff and Thompson (1972;
1978) and Woodruff (1981).  In the coastal plain, the Columbia Formation
had been previously divided into three categories,  the vadose zone media
for Category  A was chosen to be sand and gravel and assigned a typical
rating  of (8).  Vadose zone media for Category B was called sand and gravel
and assigned  a rating of (6).  Category C vadose zone media was designated
•as  sand and gravel with significant silt and clay and assigned a rating of
(4). In the Piedmont area, vadose zone media was assigned by formation.
The Wilmington Complex was called metamorphic/igneous and assigned a rating
of  (2). The  Wissahickon vadose zone media was chosen as metamorphic/
igneous and assigned a rating of (4).  The Bryn Mawr formation was
designated  as sand and gravel and assigned a rating of (5).  In this
revised version of DRASTIC, the Bryn Mawr sand and gravel vadose zone media
would have  received a rating of (6) because this is the lowest rating for
sand and gravel or would have been called a sand and gravel with
significant silt  and clay and retained the rating of (5).  The Cockeysville
Marble  was  called metamorphic/igneous and assigned a rating of (6).  The
vadose  zone media for the Pegmatites was designated as silt/clay and
assigned a  rating of (1).  In this revised version of DRASTIC, the
silt/clay would be assigned a rating of (2).  The river alluvium vadose
zone media  was called sand and gravel with significant silt and clay and
assigned a  typical value of (6).

Hydraulic Conductivity of the Aquifer

     Hydraulic conductivity values in the coastal plain were modified from
data existing in  the computer files of the Water Resources Agency of New
Castle  County, Delaware.  The Columbia Formation had previously been
divided into  three categories.  Category A had hydraulic conductivities
which ranged  from 748 to 1870 gallons per day per square foot.  Since it
was not possible  to re-group the information into designated DRASTIC
ranges, ratings were chosen to reflect a compromise.  Hydraulic
conductivity  in Category A was assigned a rating of (8) which corresponds
to  1000 to  2000 gallons per day per square foot.  In Category B, hydraulic
conductivities ranged from 374 to 561 gallons per day per square foot; a
rating  of  (4), which corresponds to 300 to 700 gallons per day per square
foot, was assigned.  Hydraulic conductivities for Category C were 1 to 150
gallons per day per square  foot; a rating of (1), which corresponds to 1 to
100 gallons per day per square foot, was assigned.  In the Piedmont,

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hydraulic conductivity values had not been previously assigned.  Hydraulic
conductivity values were estimated based on media descriptions in Petty, et
al. (1976) and from personal communication through Bob Finkle (Water
Resources Agency For New Castle County, 1985).  Values for hydraulic
conductivity in the Wilmington Complex and Wissahickon formation were
chosen as 100 to 300 gallons per day per square foot (2).   In the Bryn Mawr
Formation, a range of 700 to 1000 gallons per day per square foot (6) was
chosen.  Hydraulic conductivity in the Cockeysville Marble was assigned a
value of 1000 to 2000 gallons per day per square foot (8).  The Pegmatites
were assigned a value of 1 to 100 gallons per day per square foot (1).
Values for hydraulic conductivity in the river alluvium was chosen as 100
to 300 gallons per day per square foot (2).

Pierce County, Washington

     Pierce County, Washington, lies within the boundaries of two
ground-water regions; the western two-thirds is within the Alluvial Basins,
and the eastern one-third lies within the Western Mountain Ranges.  The
western portion of the county is within the Puget Lowland, which is filled
with very thick sequences of interbedded glacial sands, gravels and silts.
The shallow aquifer consists of medium- to coarse-grained  sands and gravels
exhibiting shallow water-table conditions.  These deposits are very
permeable and provide significant quantities of water to domestic and
municipal wells.  The shallow aquifer provides recharge to deeper sand and
gravel aquifers and is often in direct hydraulic connection with the deeper
aquifers.  Ground-water resources constitute over seventy* j-ive percent of
the drinking water used in this area.  The volcanic mudflowe and igneous/
metamorphic rocks of the Cascade Range which occur in the  ea :tern portion
of the county provide low yields to wells.  Most ground-water supplies are
derived from alluvium adjacent to river valleys.

     In mapping Pierce County, seven hydrogeologic settings were identified
and included.  Computed DRASTIC Index values range from 77 to 200.  Table
30 details the settings and ranges of associated DRASTIC Indexes.  Also
noted in the table are the number of unique DRASTIC Index  calculations
which were made during the mapping effort.  The DRASTIC Index numbers
reflect evaluation of unconfined aquifers only.

    TABLE 30. HYDROGEOLOGIC SETTINGS MAPPED IN PIERCE COUNTY, WASHINGTON

Hydrogeologic Setting
(1Ab) Mountain Slopes — West
(1D) Glaciated Mountain Valleys
(2G) Coastal Lowlands
(1H) Mud Flows
(2Ha) River Alluvium with Overbank Deposits
(21) Mud Flows
(2J) Alternating Sandstone and Shale Sequences
Range of
DRASTIC Indexes
77-79
175
130-200
114-174
176-186
112-174
104-108
Number of DRASTIC
Index Calculations
2
1
15
2
3
4
2
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     Figure 42 shows a general pollution potential map for Pierce County.
The DRASTIC Indexes have been grouped in accordance with the National Color
Code (Table 22).  Selected screens have been used to illustrate the
variability.  The pollution potential map has been superimposed on a county
highway map for geographic reference.  No hydrogeologic setting lines have
been delineated on the map.

     Appendix K contains the full-size pollution potential map for Pierce
County complete with hydrogeologic setting designations and individual
DRASTIC Index computations.  The map has been superimposed on a county
highway map for geographic reference.  The DRASTIC Index values have not
been grouped on the full-size map.  The map has been divided into separate
sheets which permit it to be incorporated into the document.  An Index to
the map sheets is provided for ease of geographic sheet location.  The
corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Water-level information was obtained from Walters and Kimmel (1968),
Hart Crowser and Associates (1984), Drost (1982), Griffin et al. (1962) and
Brown and Caldwell (1985).  Supplemental data was derived from well logs
from the Tacoma-Pierce County Health Department.  According to geologic
reports, most of the aquifers in the western portion of the county are
semi-confined.  This area is referred to as the coastal lowland
hydrogeologic setting.  Only the recessional outwash aquifer (settings 2G6
through 2G8) and the Steilacoom gravels (settings 2G10 and 2G11) were
designated as unconfined.  Since DRASTIC does not effectively evaluate
semi-confined aquifers, the aquifers must be designated as either confined
or unconfined.  Based on available information, all the aquifers in the
coastal lowland area were evaluated as unconfined.  Mud flows in the
Puyallup River valley and in the north-central portion of the county were
also semi-confined and evaluated as unconfined.  Water levels in the
coastal lowland area were evaluated based on aquifers.  In areas of the
Vashon Drift (settings 2G1, 2G2, 2G9 and 2G12 through 2G14) and the Mashel
formation (setting 2G15), water levels were extremely variable ranging from
5 to 15 feet (9), 15 to 30 feet (7), 30 to 50 feet (5) and 50 to 75 feet
(3).  Water levels in the Steilacoom gravel (settings 2G10 and 2G11)
averaged 5 to 15 feet (9) in areas adjacent to the Nisqually River and
Puget Sound and 15 to 30 feet (7) in other areas.  Depth to water in the
Salmon Springs aquifer (settings 2G3 through 2G5) ranged from 50 to 75 feet
                                    145

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O)
                     LEGEND
              DRASTIC Index Range
                                       Figure 42. Generalized pollution
                                                                                   of Pierce County, Washington.

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(3) and 75 to 100 feet (2).  Water levels in the recessional outwash
aquifer (settings 2G6 through 2G8) ranged from 15 to 30 feet (7) in areas
adjacent to river valleys to 30 to 50 feet (5) in other areas.   River
alluvium (settings 1D1 and 2Hal through 2Ha3) had water depths  which ranged
from 5 to 15 feet (9) in glacial areas to 15 to 30 feet (7) in bedrock
areas.  Water levels in the mud flows (settings 1H1, 1H2 and 211 through
214) averaged 50 to 75 feet (2) except in areas where thin mudflows
occurred in river valleys.  In these areas,  water levels averaged 15 to 30
feet (7).  Information on depth to water in the metamorphic/igneous aquifer
(settings lAbl and !Ab2) and bedded sandstone and shale aquifer (settings
2J1 and 2J2) was sparse or not available.  Water depths were estimated to
average 75 to 100 feet (2).

Ne t Re cha rg e

     Net recharge values were derived from Hart Crowser and Associates
(1984).  Since precipitation rates are high, recharge values of 10+ inches
per year (9) were assigned to the majority of the coastal lowlands area
(settings 2G1 through 2G14) in the western portion of the county.  Recharge
values were reduced to 7 to 10 inches per year (8) in the Mashel formation
(setting 2G15) due to the presence of fine-grained deposits.  The Mashel
formation occupies the south-central and east-central portions  of the
county (setting 2G15).  Net recharge was also chosen as 10+ inches per year
(9) in the river alluvium (sesttings 1D1 and 2Hal through 2Ha3).  In areas
covered by mudflows (settings 1H1, 1H2 and 211 through 214), fine-grained
deposits restrict recharge.  Values of 4 to 7 inches per yeaf (6) were
assigned in most of the areas.  Mudflows bordering the Nisqually River were
assigned a value of 10+ inches per year (9) because the fine materials were
removed by erosion. Areas of bedded sandstone and shale (settings 2J1 and
2J2) were assigned values of 7 to 10 inches per year (8) based  on the
occurrence of permeable sandstones within the unit and amount of
fracturing.  Values of 4 to 7 inches per year (6) were assigned to the
metamorphic/igneous bedrock areas.

Aquifer Media

     Information on aquifer media for the glacial deposits and  river
alluvium was obtained from Hart Crowser and Associates (1984),  Brown and
Caldwell (1985), Griffin et al. (1962), Walters and Kimrael (1968), Crandell
(1963) and Drost (1982).  The only available information for the
metamorphic/igneous aquifer was found in Crandell (1969), Hammond (1980)
and Card (1968).  This information was sparse; attempts to supplement the
data by personal communication were unsuccessful.  The Vashon drift
(settings 2G1, 2G2, 2G9 and 2G12 through 2G14), the Mashel formation
(setting 2G15), and the recessional outwash aquifer (settings 2G6 through
2G8) consist of moderately well-sorted and permeable sands and  gravels.
The aquifer media was chosen as sand and gravel and assigned a typical
rating of (8).  The Salmon Springs aquifer (settings 2G3 through 2G5) was
called sand and gravel and assigned a typical value of (8) based on the
yields of the aquifer.  The river alluvium (settings 1D1 and 2Hal through
2Ha3) was called sand and gravel and assigned a typical rating  of (8) based
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on the presence of moderate to well-sorted deposits and associated high
permeabilities.  The Steilacoom gravel aquifer (settings 2G10 and 2G11) was
called a sand and gravel and assigned a rating of (9) because the deposits
are very coarse, well-washed and thick.  In the mudflow areas (settings
IHl, 1H2 and 211 through 214), the Vashon drift which contains lenses of
sand and gravel was considered as the principal aquifer.  An aquifer media
of sand and gravel was chosen and assigned a typical rating of (8).  The
bedded sandstone and shale aquifer (settings 2J1 and 2J2) has not been
widely developed and little information was available.  The aquifer media
was chosen as thin-bedded sandstone, limestone and shale sequences and
assigned a typical rating of (6).  The metamorphic/igneous aquifer media
(settings lAbl and !Ab2) was assigned a typical value of (3) because no
information was available.

Soil Media

     Soils were mapped based on the Soil Survey of Pierce County,
Washington (Zulauf, 1979).  Soils east of Range 4E or Range 5E were not
included in the soil survey.  The glacial coastal lowland area (settings
2G1 through 2G15) are typically overlain by sandy loam (6).  Minor
occurrences of silty loam (4) are present adjacent to the Nisqually and
Puyallup Rivers and in the western portion of the county; sand (9) also is
found in small amounts.  River alluvium soil media (settings 1D1 and 2Hal
through 2Ha3) was silty loam (4) and sandy loam (6).  Areas covered by
mudflows (settings IHl, 1H2 and 211 through 214) were overlain by loam (5).
Soil information was not available for the bedded sandstone and shale
aquifer area (settings 2J1 and 2J2) or the metamorphic/igneous aquifer area
(settings lAbl and !Ab2).  Soil media in these areas were assigned loam
(5).

Topography

     Percent slope was estimated by using 7 1/2 minute USGS topographic
quadrangle maps where available and 15 minute USGS topographic quadrangle
maps in other areas.  Only 15 minute maps were available for the
north-eastern portion of the county.  Contour intervals on the 71/2 minute
maps were 20 feet, 25 feet and 40 feet; intervals for the 15 minute maps
were 80 feet.  Slopes range from 0 to 2 percent (10) and 2 to 6 percent (9)
in  the central portion of the county and increase westward and eastward.
Slopes in the western portion of the county average 6 to 12 percent (5).
Slopes in the east-central portion of the county also average 6 to 12
percent (5), but quickly rise to 12 to 18 percent (3) and 18+ percent  (1)
in  the eastern portion of the county.

Impact of the Vadose Zone Media

     Information on the vadose zone media for the glacial deposits and
river alluvium was obtained from Griffin et al. (1962), Walters and Kimmel
(1968), Drost  (1982), Brown and Caldwell (1985) and Crandell (1963).
Information  for the bedrock aquifers was found in Crandell (1969), Hammond
(1980) and Card (1968).  Vashon drift areas (settings 2G1, 2G2, 2G9 and
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2G12 through 2G14), and the Mashel formation (setting 2G15) were designated
as sand and gravel with significant silt and clay and assigned a rating of
(7) based on the amount of sand within the deposits.  Areas covered by
Steilacoom gravel (settings 2G10 and 2G11) and recessional outwash
(settings 2G6 through 2G8) were called sand and gravel and assigned a
rating of (8) because the deposits are well-sorted and very permeable.
Salmon Springs areas (settings 2G3 through 2G5) were called sand and gravel
and assigned a typical value of (8) where the aquifer media was
outcropping.  In areas where the Salmon Springs aquifer was covered by
finer-grained glacial deposits the vadose zone media was chosen as sand and
gravel with significant silt and clay and assigned a typical rating of (6).
River alluvium was chosen as sand and gravel with significant silt and clay
and assigned a rating of (7) based on the presence of coarser-grained
material within the alluvium.  Vadose zone media in mudflow areas (settings
1H1, 1H2 and 211 through 214) was chosen as sand and gravel with
significant silt and clay.  The majority of the mudflows were assigned a
typical rating of (6); in areas of the Osceola mudflow a rating of (5) was
assigned based on fines and thicker deposits; in mudflows in the
south-central portion of the county adjacent to the Nisqually River, a
rating of (7) was assigned because the materials were thinner and coarser.
Bedded sandstone and shale areas (settings 2J1 and 2J2) were assigned a
vadose zone media of bedded limestone, sandstone and shale and assigned a
typical rating of (6).  The metamorphic/igneous areas (settings lAbl and
!Ab2) were assigned a typical rating of (4).

Hydraulic Conductivity of the Aquifer

     Hydraulic conductivity values for the glacial and river alluvium
aquifers were obtained from Brown and Caldwell (1985) and Hart Crowser and
Associates (1984).  Values for the bedrock aquifers were unavailable and
estimated from available aquifer media descriptions.  Hydraulic
conductivities in the Vashon drift (settings 2G1, 2G2, 2G9 and 2G12 through
2G14), the Mashel formation (setting 2G15) and the recessional outwash
aquifer (settings 2G6 through 2G8) were approximated to average 700 to 1000
gallons per day per square foot (6) because the deposits are moderately
well-sorted sand and gravel and have moderately high well yields.  In the
area immediately adjacent to the Nisqually and Puyallup Rivers the
hydraulic conductivity values were lowered to 300 to 700 gallons per day
per square foot (4) due to the presence of greater amounts of silts in the
deposits.  Areas of Steilacoom gravel (settings 2G10 and 2G11) were highly
permeable and assigned a value of 2000+ gallons per day per square foot
(10).  The Salmon Springs aquifer (settings 2G3 through 2G5) contained more
fine materials and was assigned a value of 300 to 700 gallons per day per
square foot (4). Values for conductivities in the river alluvium (settings
1D1 and 2Hal through 2Ha3) were chosen as 1000 to 2000 gallons per day per
square foot (8) based on aquifer descriptions of moderately well-sorted
sands and gravels with significant amounts of sand and gravel.  Values of
hydraulic conductivity for the mudflow areas (settings 1H1, 1H2 and 211
through 214) were assigned based on the interbedding of fine materials with
the sand and gravel aquifer.   In the southern part of the county, values of
1000 to 2000 gallons per day per square foot (8) were chosen;  values for
the other mudflows were lower and estimated at 100 to 300 gallons per day


                                    149

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per square foot (1) and 300 to 700 gallons per day per square foot (4).
Hydraulic conductivities in the bedded sandstone and shale (settings 2J1
and 2J2) and the metamorphic/igneous aquifers (settings lAbl and !Ab2) were
estimated at 1 to 100 gallons per day per square foot (1).

Portage County, Wisconsin

     Portage County, Wisconsin, is situated within two ground-water
regions; the northwestern part of the county is located in the Northeast
and Superior Uplands and the remainder of the county is within the
Glaciated Central Region.  The water resources of the northwestern part of
the county are derived primarily from metamorphic and igneous rocks which
are in hydraulic connection with overlying thin glacial till.  This aquifer
yields supplies sufficient for domestic use only.  The majority of the
county is covered by thick sequences of glacial outwash sand and gravel
which constitutes the major ground-water resource.  These areas are
characterized by highly permeable soils and shallow water depths.

     In mapping Portage County, nine hydrogeologic settings were identified
and included.  Computed DRASTIC Index values range from 99 to 200.  Table
31 details the settings and ranges of associated DRASTIC Indexes.  Also
noted in the table are the number of unique DRASTIC Index calculations
which were made during the mapping effort.  The DRASTIC Index numbers
reflect evaluation of unconfined aquifers only.

      TABLE 31. HYDROGEOLOGIC SETTINGS MAPPED IN PORTAGE COUNTY, WISCONSIN
Hydrogeologic Setting
(7Ba) Outwash
(7C) Moraine
(7Eb) River Alluvium without Overbank Deposits
(71) Swamp/Marsh
(9Da) Glacial Till over Crystalline Bedrock
(9E) Outwash
(9Gb) River Alluvium without Overbank Deposits
(9H) Swamp/Marsh
(91) Bedrock Uplands
Range of
DRASTIC Indexes
182-200
145-161
193
160
109
134-142
155-193
126-139
99-111
Number of DRASTIC
Calculations
4
2
1
1
1
2
3
2
4
     Figure 43 shows a general  pollution  potential map  for Portage  County.
The DRASTIC Indexes have been grouped  in  accordance with  the National  Color
Code (Table 22).   Selected  screens have been used to  illustrate the
variability.  The  pollution potential  map has been superimposed on  a county
highway map for  geographic  reference.  No hydrogeologic setting lines  have
been delineated  on the map.
                                    150

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LEGEND
DRASTIC Index Range
80-99
100-119
120-139
140-159
160-179
180-199
200+
Color
D
a
a
a
m
B
•
Figure 43. Generalized pollution potential map of Portage County, Wisconsin.
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     Appendix L contains the full-size pollution potential map for Portage
County complete with hydrogeologic setting designations and individual
DRASTIC Index computations.  The map has been superimposed on a county
highway map for geographic reference.  The DRASTIC Index values have not
been grouped on the full-size map.  The map has been divided into separate
sheets which permit it to be incorporated into the document.  An Index to
the map sheets is provided for ease of geographic sheet location.  The
corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Water-level information was primarily obtained from Map number 7 in
Lippelt (1981).  Additional information was found in part 2 of Devaul and
Green (1971) and part 2 of Olcott (1968).  All surficial aquifers were
determined to be unconfined based on information found in Holt (1965) and
Bell and Sherrill (1974).  Water levels were shallow throughout most of the
county ranging from 0 to 5 feet (10), 5 to 15 (9) and 15 to 30 feet (7).
Water levels in the bedrock uplands in the northwestern portion of the
county were slightly deeper ranging from 15 to 30 feet (7) and 30 to 50
feet (5).

Net Recharge

     Net recharge values were derived from Holt (1965) and Bell and
Sherrill (1974).  High recharge values of 10+ inches per year (9) were
assigned to the outwash in the central and eastern portion of the county
because the soil, vadoze zone and aquifer materials are very permeable.
Recharge rates on the moraines were assigned a value of 7 to 10 inches  per
year (8) because the deposits contain greater amounts of silts and clays
than in the outwash area.  Recharge was also assigned a value of 7 to 10
inches per year (8) in the river alluvium because of the presence of fine
materials.  Net recharge in the swampy areas received a value of 4 to 7
inches per year (6) based on the presence of fine materials and organic
mucks.  Swamps are also local discharge areas which indicates that
ground-water gradients are toward the surface and not toward the aquifer.
However, ground-water pumpage could easily reverse the low gradients in
these areas. The glacial till area in the northwestern portion of the
county was assigned a value of 2 to  4 inches per year (3) based on the
description of fine-grained deposits in the area.  The recharge for the
thin outwash areas in the northwestern portion of the county was designated
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as 4 to 7 inches per year (6).  This value reflects better sorting  than  the
adjacent glacial till but more fine-grained materials than in the central
and eastern outwash deposits.  The bedrock uplands areas were assigned
recharge values of 2 to 4 inches per year (3) based on the permeabilities
of the underlying crystalline and sedimentary rocks and the presence of
only moderate jointing and fracturing within the bedrock.

Aquifer Media

     Information on aquifer media was derived from Holt (1965) and  Bell  and
Sherrill (1974).  Additional information on aquifer yields is contained  in
map 18 of Lippelt and Hennings (1981).  The major outwash aquifer in the
central portion of the county consists of very thick sequences of
well-sorted sands and gravels.  These deposits were called sand and gravel
and received the highest rating of (9).  Outwash and morainal aquifers in
the eastern portion of the county contained slightly more fines than the
outwash in the central portion of the county.  The media was designated
sand and gravel and assigned a typical value of (8) based on the references
and personal communication with Truman Bennett (Bennett and Williams,
1985).  Outwash aquifers in the western portion of the county were  poorly
sorted sand and gravel lenses with a significant amount of fine material.
These deposits were called sand and gravel and assigned a value of  (5).
The glacial tills in the western portion of the county containing lenses of
sand and gravel in a fine-grained matrix were also called sand and  gravel
and assigned a lower value of (4).  In this updated version of DRASTIC,  the
aquifer media in the western outwash and the glacial till would be  chosen
as glacial till and assigned the same rating.  The designation of glacial
till as an aquifer media was made to help in clarification of the system
and to provide a rating for these types of deposits.  Aquifers underlying
the swampy areas were designated as sand and gravel (8) in the glaciated
central ground-water region and sand and gravel (5) in the northeast and
Superior Upland ground-water region.  The western sand and gravels would
have been designated as glacial till and assigned a rating of (5).  River
alluvium serving as an aquifer was called sand and gravel and assigned a
typical rating of (8).  The metamorphic and igneous aquifers were
moderately weathered and fractured and were assigned a value of (5).  In
the updated version of DRASTIC, these aquifers would have received  a rating
of (4).  The sandstone aquifer received a rating of (7) due to the  presence
of moderate fracturing.

Soil Media

     Soils were mapped based on the soil survey of Portage County (Otter
and Fiala, 1978).  The soil media was assigned using the general soil
association map.  Soils formed in the outwash and moraine sands and gravels
were sandy loam (6) in the majority of the county and loam in parts of the
western portion of the county.  Soils in the silty glacial drift in the
western portion of the county were called silty loam (4).   Soils formed  in
alluvial or organic deposits were called muck (2).  The updated version  of
DRASTIC contains muck as a soil media because of the importance to
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pollution potential and because no organic soil designations were contained
in the original draft.  Soils formed in river alluvium were called sandy
loam (6).  The permeable soils and vadose zone deposits determined the
choice of the hydrogeologic setting designation as river alluvium without
overbarik deposits.  Soils formed in loamy materials and the underlying
residuum from bedrock in the western portion of the county were called loam
(5) and sandy loam (6).

Topography

     Percent slope was estimated by using 7 1/2 minute USGS topographic
quadrangle maps and adapting slope values assigned to soil series in the
soil survey (Otter and Faila, 1978).  Contour intervals on the topographic
maps were either 5 or 10 feet.  Topography averaged 0 to 2 percent (10) in
the swamp and river alluvium areas; outwash areas ranged from 0 to 2
percent (10) to 2 to 6 percent (9); moraines and bedrock uplands ranged
from 2 to 6 percent (9) to 6 to 12 percent (5).

Impact of the Vadose Zone Media

     Information on the vadose zone media was obtained from Holt (1965) and
Bell and Sherrill (1974).  The vadose zone media for the outwash area in
the central portion of the county was called sand and gravel and assigned a
typical value of (8).  The outwash in the eastern portion of the county
contained more silts and clays.  These deposits were called sand and gravel
with significant silt and clay and assigned a rating of (8).  The high
rating was assigned based on high permeabilities within the deposits.
Vadose zone deposits in the Outer and Second Moraine areas contained more
fines than the outwash area but still had a high sand content.  The vadose
zone media was chosen as sand and gravel with significant silt and clay and
assigned a rating of (7).  Vadose zone media in the Elderon and Arnott
moraines which had a higher silt and clay content were called sand and
gravel with significant silt and clay but assigned a lower rating of (5).
The vadose zone media in the river alluvium was called sand and gravel in
areas of well-washed sands and assigned a typical value of (8).  Where more
fines were present, the deposits were called sand and gravel with
significant silt and clay and assigned ratings of (7) and (6) depending on
the amount of fines.  Ratings of (6) were assigned where the alluvium was
thinner and not as well-sorted.  The vadose zone media for glacial till in
the western portion of the county was called sand and gravel with
significant silt and clay and assigned a  typical value of (6).  Vadose zone
media for the thin outwash aquifers were  called sand and gravel with
significant silt and clay based on the presence of silts and clays.  A
rating of (7) was assigned based on the higher sand content than in the
adjacent glacial tills.  Vadose zone media overlying unconsolidated
aquifers in swampy areas was called sand  and gravel with significant silt
and clay and assigned & rating of  (6).  The metamorphic/igneous vadose zone
media overlying metamorphic/igneous aquifers in swampy areas was assigned a
typical  rating of  (4).  Metamorphic/igneous vadose zone media  in the
bedrock uplands was assigned a rating of  (5) based on moderate  jointing and
fracturing.  The  sandstone vadose  zone media in the bedrock uplands was
assigned a rating  of  (7) based on  the degree of fracturing.


                                    154

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Hydraulic Conductivity of the Aquifer

     Hydraulic conductivity values were based on discussions contained in
Holt (1965), Bell and Sherrill (1974), Devaul and Green (1971) and Olcott
(1968).  The outwash aquifer in the central and eastern portion of the
county was assigned a range of 2000+ gallons per day per square foot (10)
based on available pumping test data.  Conductivity values in the Outer and
Second Moraines and in the swampy area of the glaciated central
ground-water region were assigned a range of 700 to 1000 gallons per day
per square foot (6) based on an increasing content of fine materials.  The
conductivity in the Arnott and Elderon Moraines received a range of 300 to
700 gallons per day per square foot (4) based on an even higher content of
fine materials.  River alluvium adjacent to the central outwash aquifer was
assigned a range of 2000+ gallons per day per square foot because of a lack
of fines.  Other river alluvium received ranges of 700 to 1000 gallons per
day per square foot (6) and 300 to 700 gallons per day per square foot (4)
based on increasing amounts of fine materials.  Hydraulic conductivities in
the glacial till were assigned a range of 1 to 100 gallons per day per
square foot (1) based on the presence of only localized lenses of sand and
gravel and the presence of fine materials.  The thin outwash contains
better-sorted sand and gravel lenses and was assigned a range of 100 to 300
gallons per day per square foot (2).  The thin outwash adjacent to the
river contained even better-sorted sand and gravel and was assigned a range
of 300 to 700 gallons per day per square foot (4).  Bedrock aquifers
underlying swampy areas and in the bedrock uplands were assigned a range of
1 to 100 gallons per day per square foot based on low permeabilities and
average well yields in the area.

Yolo County, California

     Yolo County, California, lies within the Alluvial Basins ground-water
region.  From west to east, the hydrogeologic settings exemplify a typical
cross section through an alluvial basin sequence.  In the western portion
of the county, marine sandstones and shales yield only small quantities of
remnant saline water.  Older continental deposits, alluvial fans and river
alluvium comprised of sands, silts and clays provide the majority of the
ground-water resources for the county.  Conductivities are variable but
typically provide significant well yields.  These aquifers are usually
unconfined and where they overlap, are hydraulically connected.
Agricultural irrigation water provides significant recharge to these
aquifers.

     In mapping Yolo County, five hydrogeologic settings were identified
and included.  Computed DRASTIC Index values range from 67.to 192.  Table
32 details the settings and ranges of associated DRASTIC Indexes.  Also
noted in the table are the number of unique DRASTIC Index calculations
which were made during the mapping effort.  The DRASTIC Index numbers
reflect evaluation of unconfined aquifers only.
                                    155

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       TABLE 32. HYDROGEOLOGIC SETTINGS MAPPED IN YOLO COUNTY, CALIFORNIA

Hydrogeologic Setting
(2A) Mountain Slopes
(2B) Alluvial Mountain Valleys
(2C) Alluvial Fans
(2Ha) River Alluvium with Overbank Deposits
(2K) Continental Deposits
Range of-
DRASTIC Indexes
67-81
148
119-160
139-192
92-112
Number of DRASTIC
Index Calculations
3
1
6
3
3
     Figure 44 shows a general pollution potential map for Yolo County.
The DRASTIC Indexes have been grouped in accordance with the National Color
Code (Table 22).  Selected screens have been used to illustrate the
variability.  The pollution potential map has been superimposed on a county
highway map for geographic reference.  No hydrogeologic setting lines have
been delineated on the map.

     Appendix M contains the full-size pollution potential map for Yolo
County complete with hydrogeologic setting designations and individual
DRASTIC Index computations.  The map has been superimposed on a county
highway map for geographic reference.  The DRASTIC Index values have not
been grouped on the full-size map.  The map has been divided into separate
sheets which permit it to be incorporated into the document.  An Index to
the map sheets is provided for ease of geographic sheet location.  The
corresponding charts which detail the ranges of the seven DRASTIC
parameters chosen for each area and the computation of the DRASTIC Index
immediately follows the maps.

     Computation of the DRASTIC Indexes and identification of hydrogeologic
settings relied on detailed information of the seven DRASTIC parameters.
Specific descriptions and sources used to obtain this information are
outlined in the following discussion centering around each DRASTIC
parameter.  A complete list of references is contained at the end of
Section 5.  The rating associated with the chosen range for each DRASTIC
parameter appears in parenthesis for ease of reference.

Depth to Water

     Water-level information was primarily obtained from published data in
California Department of Water Resources (1978; 1985).  Additional
information was found in Olmsted and Davis (1961).  In general, water
levels deepen from east to west.  Water levels in the mountain slopes in
the western portion of the county were 100+ feet (1) and averaged 15 to 30
feet (7) in the alluvial mountain valleys.  The continental deposits which
are adjacent to the mountains had water levels which ranged from 100+ feet
(1) in the northern portion of the county to 50 to 75 feet (3) in the
                                    156

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O1
LEGEND
DRASTIC Index Range
<79
80-99
100-119
120-139
140-159
160-179
180-199
Color
m
D
m
D
a
m
•
                                      Figure 44. Generalized pollution potential map of Yolo County, California.

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central and southern portions of the county.  Depth to water in the
alluvial fans ranged from 50 to 75 feet (3) in the western areas bordering
the continental deposits to 30 to 50 feet (5) in the center of the county
to 15 to 30 feet (7) bordering the flood basins (setting 2Hal) in the
eastern portion of the county.  The flood basins and river alluvium had
water levels which averaged 15 to 30 feet (7).

Net Recharge

     Values for net recharge were based on information found in Olmsted and
Davis (1961) and California Department of Water Resources (1978).  Recharge
values were calculated for township areas from the data in California
Department of Water Resources (1978).  Net recharge values reflect recharge
from precipitation and irrigation.  Mountain slopes were assigned a value
of 0 to 2 inches per year (1) based on moderate precipitation, steep slopes
and the low permeability of the deposits.  The alluvial mountain valleys
were given a value of 2 to 4 inches per year (3).  Net recharge values for
the continental deposits were chosen as 2 to 4 inches per year because the
deposits are semi-consolidated and have a moderately high silt content.
Recharge to the alluvial fans was strongly influenced by irrigation.  Net
recharge to the alluvial fans was calculated to be 2 to 4 inches per year
(3) in the northern portion of the county.  Values increased southward and
were calculated to be 4 to 7 inches per year (6) and 7 to 10 inches per
year (8).  A value of 1CH- inches per year (1) occurred in the central
portion of the county.

Aquifer Media

     Information on aquifer media was obtained from California Department
of Water Resources (1978) and Olmsted and Davis (1961).  Additional
information was found on the geologic maps of the  Sacramento Quadrangle
(Wagner et al., 1981) and the Santa Rosa Quadrangle (Wagner and Bortugno,
1982).  The mountain slopes were comprised of sedimentary sequences
deposited in a marine environment.  The aquifer media was chosen as thin
bedded sandstone, limestone and shale sequences and assigned a typical
value of (6).  Sand and gravel was chosen as the aquifer media in the
alluvial mountain valleys and assigned a typical value of (8) due to the
coarseness of  the deposits.  The continental deposits are sequences of
semi-consolidated sand, silt and clay.  The aquifer media was chosen as
sand and gravel and assigned a typical value of (8) because the deposits
are semi-consolidated sands, gravels and silts.  The alluvial fans were
called sand and gravel and assigned a typical rating of  (8).  Lenses of
sand and gravel serve as the aquifer in the flood  basins (setting 2Hal) and
the river alluvium (settings 2Ha2 and 2Ha3).  Sand and gravel was chosen as
the aquifer media and assigned a typical value of  (8).
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Soil Media

     Soils were mapped based on the Soil Survey of Yolo County, California
(Andrews, 1972).  Soils on mountain slopes in the western portion of the
county are thin or absent (10).  Other soils on mountain slopes are
predominantly clay loam (3) with minor occurrences of shrinking and
aggregated clay (7) in the northwestern portion of the county.  Soils in
the alluvial mountain valleys are silty loam (4).  Soils overlying the
continental deposits are silty loam (4) in the western portion of the
county and shrinking and aggregated clay (7) in the central portion of the
county.  Alluvial fan deposits are overlain by clay loam (3).  Soils in
flood basins (setting 2Hal) are shrinking and aggregated clay (7).  River
alluvium soil media (settings 2Ha2 and 2Ha3) are silty loam (4) in the
eastern portion of the county and sand (9) in the central portion of the
county.

Topography

     Percent slope was estimated by using 7 1/2 minute USGS topographic
quadrangle maps.  Contour intervals on the 71/2 minute maps were 5 feet,
•20 feet and 40 feet.  Slopes were 18+ percent (1) in the western and
northwestern portion of the county and gradually lessened eastward and
southward.  Slopes of 6 to 12 percent (5) and 2 to 6 percent occur in the
central portion of the county and 0 to 2 percent slopes are found in the
eastern and southeastern portions of the county.

Impact of the Vadose Zone Media

     Information on the vadose zone media was obtained from California
Department of Water Resources (1978) and Olmsted and Davis (1961).  The
vadose zone media in the mountain slope area was called bedded limestone,
sandstone and shale and assigned a typical rating of (6).  Vadose zone
media in the alluvial mountain valleys was chosen as sand and gravel and
assigned a typical rating of (8) due to the relative coarseness of the
deposits.  The continental deposits were designated as sand and gravel with
significant silt and clay and assigned a typical rating of (6) based on an
average amount of fine material and semi-consolidation of the deposits.
Alluvial fan areas were also called sand and gravel with significant silt
and clay, but were assigned a rating of (7) based on the increased sand and
gravel content of the deposits.  Vadose zone media in the flood basins
(setting 2Hal) was chosen as silt/clay and assigned a rating of (2) based
on the presence of significant amounts of fines in the deposits and the
semi-confined conditions.  In this updated version of DRASTIC, the
silt/clay would have been assigned a rating of (3).  Vadose zone media in
the river alluvium was called sand and gravel and assigned a typical value
of (8).
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Hydraulic Conductivity of the Aquifer

     Hydraulic conductivity values for the various aquifer media were based
on information in California Department of Water Resources (1978) and
Olmsted and Davis (1961).  Where no values were given, estimates of
conductivity were made from aquifer media descriptions.  The aquifer in the
mountain slopes was essentially non-water bearing and assigned a value of 1
to 100 gallons per day per square foot (1).  The hydraulic conductivity of
the sand and gravel in the alluvial mountain valleys was estimated to be
700 to 1000 gallons per day per square foot (6).  Values of conductivity in
the continental deposits were estimated to be 300 to 700 gallons per day
per square foot (4) based on moderate well yields.  The lenses of sand and
gravel in the alluvial fans are relatively coarse and moderately sorted.
These deposits were assigned a value of 700 to 1000 gallons per day per
square foot (6) based on published values and moderately high well yields.
Values for conductivity of the sand and gravel within the flood basin area
(setting 2Hal) were estimated to range from 300 to 700 gallons per day per
square foot (4).  In the river alluvium the well-sorted highly permeable
sands and gravels in the eastern portion of the county were assigned a
value of 2000+ gallons per day per square foot (10).  Hydraulic
conductivity values for the river alluvium in the central portion of the
county were chosen as 1000 to 2000 gallons per day per square foot (8).
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                                 REFERENCES

CUMBERLAND COUNTY

Caswell, W.B. and E.M. Lanctot, 1978.  Ground-water resource maps of
Cumberland county; Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979a.   Ground-water handbook for the state of  Maine;
Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979b.   Sand and gravel aquifers map no.  4, York and
Cumberland counties, Maine; Open-file no.  79-5,  Maine Geological Survey,
Department of Conservation.

Caswell, W. Bradford, 1979c.   Sand and gravel aquifers map no.  4, York and
Cumberland counties, Maine; Open-file no.  79-6,  Maine Geological Survey,
Department of Conservation.

Caswell, W. Bradford, 1979d.   Sand and gravel aquifers map no.  10,
Sagadahoc, Lincoln, and Cumberland counties, Maine; Open-file no. 79-8,
Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979e.   Sand and gravel aquifers map no.  11,
Cumberland and Androscoggin counties, Maine; Open-file no. 79-9, Maine
Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979f.   Sand and gravel aquifers map no.  12,
Cumberland, Androscoggin, and York counties, Maine; Open-file no. 79-10,
Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979g.   Sand and gravel aquifers map no.  13,  Oxford,
York, and Cumberland counties, Maine; Open-file  no. 79-11, Maine Geological
Survey, Department of Conservation.

Caswell, W.B. and E.M. Lanctot, 1979.  Ground-water resource maps county
series; Maine Geological Survey, Department of Conservation.

Hedstrom, Gary, 1974.  Soil survey of Cumberland county,  Maine;  Soil
Conservation Service, U.S. Department of Agriculture, 94  pp.

Hussey, A.M. and D. Westerman, 1979.   Maine geology; Bulletin no. 1.,
Geological Society of Maine,  59 pp.
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Prescott, Glen C., 1963.   Reconnaissance of ground-water conditions  in
Maine; U.S. Geological Survey,  Water Supply Paper 1669-T,  52  pp.

Prescott, Glen C. , 1967.   Lower Androscoggin river basin area;  Maine
basic-data report no. 3,  Ground-water series,  U.S. Geological Survey,  63
pp.

Prescott, Glen C. , 1968.   Ground water favorability areas and surficial
geology of the Lower Androscoggin river basin, Maine;  U.S.  Geological
Survey, Hydrologic Investigations HA-285.

Prescott, Glen C., I976a.  Windhatn-Freeport-Portland Area;  Maine  basic-data
report no. 9, Ground-water series, U.S. Geological Survey,  43 pp.

Prescott, Glen C., 1976b.  Ground water favorability and surficial geology
of the Portland area, Maine;  U.S. Geological Survey, Hydrologic
Investigations HA-561.

Prescott, Glen C., G.W. Smith and W.B. Thompson,  1976.   Surficial geology
of the Cumberland Center Quadrangle, Maine; Open-file  no.  76-30;  Maine
Geological Survey, Department of Conservation.

Prescott, Glen C.  and W.B. Thompson, 1976a.  Surficial geology of the  North
Windham Quadrangle, Maine; Open-file no. 76-31; Maine  Geological  Survey,
Department of Conservation.
                                                           «>
Prescott, Glen C.  and W.B. Thompson, 1976b.  Surficial geology of the  Old
Orchard Beach Quadrangle, Maine; Open-file no. 76-32;  Maine Geological
Survey, Department of Conservation.

Prescott, Glen C., 1977.   Ground water favorability and surficial geology
of the Windham-Freeport area, Maine; U.S.  Geological Survey,  Hydrologic
Investigations HA-564.

Prescott, Glen C.  and W.B. Thompson, 1977a.  Surficial geology of the
Freeport Quadrangle, Maine; Open-file no.  77-5, Maine  Geological  Survey,
Department of Conservation.

Prescott, Glen C.  and W.B. Thompson, 1977b.  Surficial geology of the  South
Harpswell Quadrangle, Maine;  Open-file no. 77-6,  Maine Geological Survey,
Department of Conservation.

Prescott, Glen C. and W.B. Thompson, 1977c.  Surficial geology of the
Yarmouth Quadrangle, Maine; Open-file no.  77-7, Maine  Geological  Survey,
Department of Conservation.

Smith, Geoffrey W., 1976a.  Surficial geology of  the Phippsburg Quadrangle,
Maine; Open-file no. 76-37, Maine Geological Survey, Department of
Conservation.
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Smith, Geoffrey W., 1976b.  Surficial geology of  the  Small  Point
Quadrangle, Maine;  Open-file no.  76-38,  Maine Geological  Survey,  Department
of Conservation.

Smith, Geoffrey W.  and W.B.  Thompson, 1976.   Surficial  geology  of the
Gorham Quadrangle,  Maine;  Open-file no.  76-42,  Maine  Geological Survey,
Department of Conservation.

Smith, Geoffrey W., 1977a.  Surficial geology map of  Freeport,  Maine;
Open-file report, Maine Geological Survey,  Department of  Conservation.

Smith, Geoffrey W., 1977b.  Surficial geology of  the  Bath Quadrangle,
Maine; Open-file no. 77-8, Maine  Geological Survey, Department  of
Conservation.

Smith, Geoffrey W., 1977c.  Surficial geology of  the  Portland Quadrangle,
Maine; Open-file no. 77-16,  Maine Geological Survey,  Department of
Conservation.

Smith, Geoffrey W., 1977d.  Surficial geology of  the  Small  Point
Quadrangle, Maine;  Open-file no.  77-17,  Maine Geological  Survey,  Department
of Conservation.

Smith, Geoffrey W.  and W.B.  Thompson, 1980.   Surficial  geology  of the
Poland Quadrangle,  Maine;  Open-file no.  80-25,  Maine  Geological Survey,
Department of Conservation.

Tepper, Dorothy H., John S.  Williams, Andrews L.  Tolman and Glenn C.
Prescott, 1985.  Hydrogeology and water  quality of significant  sand  and
gravel aquifers in parts of Androscoggin,  Cumberland, Franklin, Kennebec,
Lincoln, Oxford, Sagadahoc,  and Somerset counties, Maine; Sand  and gravel
aquifer maps 10, 11, 16, 17  and 32, Open-file no. 85-82A, Maine Geological
Survey, 106 pp.

Thompson, Woodrow B., 1976a.  Surficial  geology of the  Cape Elizabeth
Quadrangle, Maine;  Open-file no.  76-43,  Maine Geological  Survey,  Department
of Conservation.

Thompson, Woodrow B., 1976b.  Surficial  geology of the  Cornish  Quadrangle,
Maine; Open-file no. 76-44,  Maine Geological Survey,  Department of
Conservation.

Thompson, Woodrow B., 1976c.  Surficial  geology of the  Gray Quadrangle,
Maine; Open-file no. 76-45,  Maine Geological Survey,  Department of
Conservation.

Thompson, Woodrow B., 1976d.  Surficial  geology of the  Pleasant Mountain
Quadrangle, Maine;  Open-file no.  76-46,  Maine Geological  Survey,  Department
of Conservation.
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Thompson, Woodrow B., I976e.   Surficial geology  of  the  Portland  West
Quadrangle, Maine; Open-file  no.  76-46, Maine  Geological  Survey,  Department
of Conservation.

Thompson, Woodrow B., 1976f.   Surficial geology  of  the  Prouts  Neck
Quadrangle, Maine; Open-file  no.  76-48, Maine  Geological  Survey,  Department
of Conservation.

Thompson, Woodrow B., 1977.   Surficial geology of the Norway Quadrangle,
Maine; Open-file no. 77-34, Maine Geological Survey,  Department  of
Conservation.

Thompson, Woodrow B. and G.C. Prescott, 1977.  Surficial  geology of the
Portland East Quadrangle, Maine;  Open-file no. 77-40, Maine Geological
Survey, Department of Conservation.

FINNEY COUNTY

Dealy, M.T., Jack Hume and E.D.  Jenkins, 1984.  Hydrogeology and
development of the Dakota aquifer in southwest Kansas;  Proceedings of the
First C.V. Theis Conference on Geohydrology; Geohydrology of the Dakota
aquifer, National Water Well  Association,  pp.  209-220.

Dunlap, L.E., R.J. Lindgren and C.G. Sauer, 1985.  Geohydrology  and model
analysis of stream-aquifer system along the Arkansas  river in  Kearny  and
Finney counties, Southwestern Kansas;  U.S. Geological Survey,  Water Supply
Paper 2253, 52 pp.

Gutentag, E.D., D.H. Lobmeyer, H.E.  McGovern and W.A. Long, 1972.   Ground
water in Finney county, southwestern Kansas; U.S. Geological Survey,
Hydrologic Investigations Atlas HA-442.

Gutentag, Edwin D., David H.  Lobmeyer and  Steven E. Slagle, 1981.
Geohydrology of southwestern  Kansas; Kansas Geological  Survey, Irrigation
Series 7, 73 pp.

Harner, Rodney F., Raymond C. Angell,  Marion A.  Lobmeyer  and Donald R.
Jantz, 1965.  Soil survey of  Finney county, Kansas; Soil  Conservation
Service, U.S. Department of Agriculture, 91 pp.

Latta, Bruce F., 1944.  Geology and ground-water resources of  Finney  and
Gray counties, Kansas; Kansas Geological Survey, Bulletin 55,  271 pp.

Meyer, Walter R., Edwin D. Gutentag and David H. Lobmeyer, 1970.
Geohydrology of Finney county, southwestern Kansas; U.S.  Geological  Survey,
Water Supply Paper 1891, 117  pp.

Pabst, M.E. and B.J. Dague,  1984.  January 1984  water levels,  and data
related  to water-level changes, western and south-central Kansas;  U.S.
Geological Survey, Open-file  no. 84-613.
                                    164

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Pabst, Marilyn E. and Edwin D. Gutentag, 1979.  Water level changes in
southwestern Kansas, 1940-78; Kansas Geological Survey, 29 pp.

GILLESPIE COUNTY

Allison, J.E., G.W. Dittmar and J.L. Hensell, 1975.  Soil survey of
Gillespie county, Texas; Soil Conservation Service, U.S. Department of
Agriculture, 80 pp. 77 plates.

Ashworth, John B., 1983.  Ground-water availability of the lower Cretaceous
formations in the hill country of south-central Texas; Texas Department of
Water Resources, Report 273, 172 pp.

Barnes, Virgil E., 1952a.  Bear Creek Quadrangle, Gillespie, Kerr, and
Kendall counties, Texas; Geologic Quadrangle Map, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1952b.  Cain City Quadrangle, Gillespie and Kendall
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E. , 1952c.  Live Oak Creek Quadrangle, Gillespie county,
Texas; Geologic Quadrangle Map, Bureau of Economic Geology, University of
Texas.

Barnes, Virgil E., 1952d.  Morris Ranch Quadrangle, Gillespie and Kerr
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1952e.  Spring Creek Quadrangle, Gillespie county,
Texas; Geologic Quadrangle Map, Bureau of Economic Geology, University of
Texas.

Barnes, Virgil E., I952f.  Squaw Creek Quadrangle, Gillespie and Mason
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1952g.  Stonewall Quadrangles, Gillespie and Kendall
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1954a.  Dry Branch Quadrangle, Gillespie and Kerr
counties, Texas; Geologic Quadrangle Map no. 17, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1954b.  Harper Quadrangle, Gillespie county, Texas;
Geologic Quadrangle Map no. 16, Bureau of Economic Geology, University of
Texas.
                                   165

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Barnes, Virgil E., 1954c.  Klein Branch Quadrangle, Gillespie and Kerr
counties, Texas; Geologic Quadrangle Map no. 18, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1954d.  Wendel Quadrangle, Gillespie, Kerr, and Kimbel
counties, Texas; Geologic Quadrangle Map no. 15, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., I956a.  Blowout Quadrangle, Gillespie, Llano, and Blanco
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., I956b.  Crabapple Creek Quadrangle, Gillespie and Llano
counties, Texas; Geologic Quadrangle Map no. 3, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., I956c.  Fall Prong Quadrangle, Kimbel, Gillespie, and
Mason counties, Texas; Geologic Quadrangle Map no. 19, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1956d.  Hilltop Quadrangle, Gillespie and Mason
counties, Texas; Geologic Quadrangle Map no. 2, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E. , 1956e.  Alto Creek Quadrangle, Gillespie county, Texas;
Geologic Quadrangle Map no. 8, Bureau of Economic Geology, University of
Texas.

Barries, Virgil E. , I956f.  Threadgill Creek Quadrangle, Gillespie and Mason
counties, Texas;  Geologic Quadrangle Map no. 20, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., I956g.  Willow City Quadrangle, Gillespie and Llano
counties, Texas; Geologic Quadrangle Map no. 4, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., I965a.  Geology of the Hye Quadrangle, Blanco,
Gillespie, and Kendall counties, Texas; Geologic Quadrangle Map no. 27,
Bureau of Economic Geology, University of Texas.

Barnes, Virgil E., 1965b.  Geology of the Rocky Creek Quadrangle, Blanco
and Gillespie counties, Texas;  Geologic Quadrangle Map no. 29, Bureau of
Economic Geology, University of Texas.

Barnes, Virgil E., 1967.  Geology of the Cave Creek Quadrangle, Gillespie
county, Texas;  Geologic Quadrangle Map no. 32, Bureau of Economic Geology,
University of Texas.

Mount, R.J., 1963.  Investigation of ground-water resources near
Fredericksburg, Texas; Memorandum Report no. 63-03, Texas Water Commission,
101 pp.
                                   166

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Muller, D.A. and R.D. Price, 1979.  Ground-water availability in Texas,
estimates and projections through 2030; Report 238, Texas Department of
Water Resources, 77 pp.

Rose, Peter R., 1972.  Edwards group, surface and subsurface, central
Texas, Report of Investigation no. 74, Bureau of Economic Geology,
University of Texas, 198 pp.

Texas Department of Water Resources, 1983.  Underground water conservation
districts, underground water reservoir delineations and major aquifers as
of August, 1983; Texas Department of Water Resources, Austin, Texas.

Walker, Loyd E., 1979.  Occurrence, availability, and chemical quality of
ground water in the Edwards Plateau region of Texas; Report 235, Texas
Department of Water Resources, Austin, Texas, 336 pp.

GREENVILLE COUNTY

Camp, Wallace J., 1975.  Soil survey of Greenville county, South Carolina;
Soil Conservation Service, U.S. Department of Agriculture, 71 pp.

Koch, Neil C. ,  1968.  Ground-water resources of Greenville county, South
Carolina; State Development Board Bulletin no. 38, Columbia, South
Carolina, 47 pp.

Padgett, Gary G. and Harriett K. Hardee, 1982.  Preliminary designation of
aquifer systems in South Carolina; South Carolina Department of Health and
Enviro imental Control, Ground-water Protection Division, 28 pp.

LAKE COUNTY

Furman, Albert L., Horace D. White, Orlando E. Cruz, Walter E. Russell and
Buster P. Thomas, 1975.  Soil survey of Lake county area, Florida; Soil
Conservation Service, U.S. Department of Agriculture, 83 pp.

Grubb, Hayes F., 1977.  Potential for downward leakage to the Floridan
aquifer, Green Swamp area, central Florida; U.S. Geological Survey, Water
Resources Investigations 77-71.

Grubb, Hayes F. and A.T. Rutledge, 1979.  Long-term water supply potential,
Green Swamp area, Florida; U.S. Geological Survey, Water Resources
Investigations 78-99, 76 pp.

Johnson, Richard A., 1979.  Geology of the Oklawaha basin; St. Johns River
Water Management District Technical Publication SJ 79-2, 23 pp.

Knochenmus, Darwin D., 1971.  Ground water in Lake county, Florida; Bureau
of Geology, Florida Department of Natural Resources, Map series no. 44.

Knochenmus, Darwin D. and G.H. Hughes, 1976.  Hydrology of Lake county,
Florida; U.S. Geological Survey, Water Resources Investigations 76-72, 100
pp.


                                   167

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pride, R.W., F.W. Meyer and R.N. Cherry, 1966.  Hydrology of Green Swamp
area in central Florida; Florida Geological Survey Investigations no. 42,
137 pp.

MINIDOKA COUNTY

Crosthwaite, E.G. and R.C. Scott, 1956.  Ground water in the north side
pumping division Minidoka project, Minidoka county, Idaho; U.S. Geological
Survey Circular 371, 20 pp.

Graham, William G., 1979.  The impact of intensive disposal well use on the
quality of domestic ground-water supplies in southeast Minidoka county,
Idaho; Idaho Department of Water Resources, 35 pp.

Hansen, Harold, 1975.  Soil survey of Minidoka area, Idaho, parts of
Minidoka, Elaine and Lincoln counties; Soil Conservation Service, U.S.
Department of Agriculture, 72 pp.

Lindholdm, G.F., S.P. Garabedian, G.D. Newton and R.L. Whitehead, 1983.
Configuration of the water table, March 1980, in the Snake River plain
regional aquifer system, Idaho and eastern Oregon; U.S. Geological Survey,
Open-file report 82-1022 (atlas).

Mundorff, M.J., E.G. Crosthwaite and Chabot Kilburn, 1964.  Ground water
for irrigation in the Snake River basin in Idaho; U.S. Geological Survey
Water-supply paper 1654, 224 pp.

U.S. Geological Survey, 1985.  Ground-water levels, 1980, Snake river
plain, Idaho and eastern Oregon; U.S. Geological Survey, Open-file report
85-330.

Whitehead, R.L., 1984.  Geohydrologic framework of the Snake river plain,
Idaho and eastern Oregon; U.S. Geological Survey, Open-file report 84-051
(atlas).

Young, H.W. and R.F. Norvitch, 1984.  Ground-water level trends in Idaho,
1971-82; U.S. Geological Survey, Water-Resources Investigations Report
83-4245, 28 pp.

NEW CASTLE COUNTY

Groot, Johan J., Peter M. Demicco and Phillip J. Cherry, 1983.
Ground-water availability in southern New Castle county, Delaware; Delaware
Geological Survey, Open-file report no. 23, 20 pp.

Johnston, Richard H., 1973.  Hydrology of the Columbia (Pleistocene)
deposits of Delaware:  an appraisal of a regional water table aquifer;
Delaware Geological  Survey, Bulletin no. 14, 78 pp.

Matthews, Earle D. and Oscar L. Lavoie, 1970.  Soil survey of New Castle
county, Delaware; U.S. Department of Agriculture, 97 pp., 55 plates.
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Petty, Susan, Barbara Lanan and William Miller, 1976.  Map showing
potential for ground-water recharge in New Castle county, Delaware; New
Castle county areawide waste treatment management program, Delaware
Geological Survey, 24 pp.

Talley, John H., 1978.  Ground-water levels in Delaware July 1966 -
December 1977; Delaware Geological Survey, Report of investigations no. 30,
50 pp.

Woodruff, Kenneth D., R.R. Jordan, N. Spoljarlc and I.E. Pickett, 1972.
Geology and ground water, University of Delaware, Newark, Delaware;
Delaware Geological Survey, Report of investigations no. 18, 40 pp.

Woodruff, Kenneth D. and Allan M. Thompson, 1972.  Geology of the Newark
area, Delaware; Delaware Geological Survey, Geologic Map series no. 3.

Woodruff, Kenneth D. and Allan M. Thompson, 1975.  Geology of the
Wilmington area, Delaware; Delaware Geological Survey, Geologic Map series
no. 4.

Woodruff, Kenneth D., 1981.  Geohydrology of the Wilmington area, Delaware;
Delaware Geological Survey, Hydrologic Map series no. 3, sheet 1 -
basic-geology.

PIERCE COUNTY

Brown and Caldwell, 1985.  Cover/Chambers Creek geohydrologic study for the
Tacoiaa-Pierce county Health Department, Final report; Brown and Caldwell
with Subconsultants Sweet, Edwards and Associates, Robinson and Noble,
Inc., 221 pp., 71 plates.

Crandell, D.W., 1963.   Surficial geology and geomorphology of the Lake
Tapps Quadrangle, Washington; U.S. Geological Survey, Professional Paper
388-A, U.S.  Department of Interior.

Crandell, D.W., 1969.   Surficial geology of Mount Rainier National Park
Washington;  U.S. Geological Survey, Bulletin 1288, U.S. Department of
Interior, 39 pp.

Drost, B.W., 1982.   Water resources of the Gig Harbor peninsula and
adjacent areas, Washington; U.S. Geological Survey, Water Resources
Investigations, Open-file report 81-1021, U.S. Department of Interior, 148
pp.

Card, L.M.,  1968.  Bedrock geology of the Lake Tapps Quadrangle, Pierce
county, Washington; U.S.  Geological Survey, Professional Paper 388-B, U.S.
Department of Interior, 33 pp.
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Griffin, W.C., J.E.  Sceva, H.A.  Swenson and M.J.  Mundorff,  1962.   Water
resources of the Tacoma area,  Washington;  U.S.  Geological  Survey,  Water
Supply Paper 1499-B, U.S.  Department of Interior, 98 pp.

Hammond, P.E. , 1980.  Reconnaissance geologic map and cross sections  of
southern Washington Cascade Range;  Department of  Earth Sciences,  Portland
State University, Portland, Oregon, 31 pp.

Hart Crowser and Associates, 1984.   Ground-water  resource  evaluation
coordinated water system plan, Pierce county, Washington;  Seattle,
Washington, 52 pp.,  6 plates.

Walters, K.L. and G.E. Kimmel, 1968.  Ground-water occurrence and
stratigraphy of unconsolidated deposits, central  Pierce county,  Washington;
U.S. Geological Survey and Washington Department  of Water  Resources,  Water
Supply Bulletin 22,  428 pp.

Zulauf, A.S., 1979.   Soil survey of Pierce county area, Washington;  Soil
Conservation Service, U.S. Department of Agriculture, 131  pp., 55 plates.

PORTAGE COUNTY

Bell, E.A. and M.G.  Sherrill,  1974.  Water availability in central
Wisconsin - an area of near-surface crystalline rock; U.S.  Geological
Survey, Water Supply Paper 2022, 32 pp.

Devaul, R.W. and J.H. Green, 1971.   Water resources of Wisconsin Central
Wisconsin River Bisin; U.S. Geological Survey,  Hydrologic  Investigations
HA-367.

Holt, C.L.R., Jr., 1965.  Geology and water resources of Portage county,
Wisconsin, U.S. Geological Survey,  Water Supply Paper 1796, 77 pp.

Lippelt, I.D. , 1981.  Water table elevation:  Irrigable lands inventory,
phase 1 - ground water and related  information, Wisconsin Geological  and
Natural History Survey, map 7.

Lippelt, I.D. and R.G. Hennings, 1981.  Irrigable lands inventory, phase 1
ground water and related information, Wisconsin Geological and Natural
History Survey, map 18.

Olcott, P.G., 1968.   Water resources of Wisconsin Fox-Wolf river basin;
U.S. Geological Survey, Hydrologic  Investigations Atlas HA-321.

Otter, A.M. and W.D. Fiala, 1978.  Soil survey  of Portage county,
Wisconsin: U.S. Department of Agriculture, Soil Conservation Service, 96
pp.
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YOLO COUNTY
Andrews, W.F., 1972.   Soil survey of Yolo county,  California;  Soil
Conservation Service, U.S. Department of Agriculture,  102  pp.,  86 plates.

California Department of Water Resources, 1978.  Evaluation of  ground-water
resources, Sacramento Valley;  Bulletin 118-6,  California Department  of
Water Resources and U.S. Geological Survey,  136  pp.

California Department of Water Resources, 1985.  Water level data by
hydrologic basin:  State of California, The  Resources  Agency, Department of
Water Resources.

Olmsted, F.H. and G.H. Davis,  1961.  Geologic  features and ground water
storage capacity of the Sacramento Valley, California; Water Supply  Paper
1497, U.S. Geological Survey and the California  Department of  Water
Resources, 236 pp.

Wagner, D.L. and E.J. Bortugno, 1982.  Geologic  map  of the Santa Rosa
Quadrangle; Map no. 2A, Division of Mines and  Geology, California
Department of Conservation.

Wagner, B.L., C.W. Jennings, T.L. Bedrossian and E.J.  Bortugno, 1981.
Geologic map of the Sacramento Quadrangle; Map no. 1A, Division of Mines
and Geology, California Department of Conservation.
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                                    SECTION 6

                              IMPACT - RISK FACTORS
     The DRASTIC Index estimates the vulnerability  of any  setting  to  pollution
on the basis of determinable geologic and hydrologic parameters.   It  does not,
however, indicate a variety of other parameters  that often point out  the
significance of the DRASTIC Index under the influence of cultural  and physical
modifications.  For example, an area with a low  DRASTIC  Index,  indicating
moderate or low vulnerability to contamination,  may be located  very near to a
large population center.   The proximity to a population  that can be exposed
greatly increases the risk, or impact,  of an incidence of  pollution at  the
prospective site.  Thus it can quickly be noted  that not only the  size  of the
population exposed, and the human/non-human nature  of that population,  but also
the time required for the pollutant to travel from  the point of incidence to
the population at risk, is a serious consideration  within  a given  setting.
Similarly, the relative "value" of an underlying aquifer may require  special
consideration when assessing the factors which influence pollution potential.
This may become particularly important in areas  where the  aquifer  is  the only
source of ground water or where ground-water supplies are  abundant and  have not
been fully developed.

     Travel time is considered only tangentially by the  DRASTIC Index.  It is
implied by "hydraulic conductivity," but becomes interpretable, and meaningful,
only when the distance to be traveled from a source of contamination  to a point
of concern is known, and  when the gradient,  or inclination of the  water table
is considered.  Thus, the travel time of a pollutant from  point of introduction
until it reaches a population is not given by the DRASTIC  Index, but  must be
evaluated separately, by  persons with adequate data and  expertise  for each
specific site.

     In a similar manner, the risk to a given population depends on the
toxicity of the pollutant being introduced and the  degree  of exposure of the
population to the pollutant.  Obviously, if the  pollutant  being introduced is
non-toxic to the population exposed, there is little or  no risk to that
population as a consequence of the exposure.  When  the pollutant is quite
toxic, it is obvious that minimal exposure of the population may be very
serious, even where travel time as controlled by gradient,  distance,  and
hydraulic conductivity is great.

     Essentially, the DRASTIC Index for a given  setting  is derived on the basis
of the vulnerability of the site to an invasion  of  water,  hence the name
"hydrogeological setting."  Actually, the concern is not about  the
vulnerability of a setting to water, but rather  with the vulnerability  of that
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setting to contaminants.  Water forms the common baseline, but the site
vulnerability varies with the specific properties of the contaminant being
applied.  Obviously all settings cannot be mapped for all potential
contaminants, so in many instances critical judgements have to be made about
the risks involved.  Where accidental spills are involved, these judgements
must be made rapidly, conservatively, and on the basis of the best data
available.  Where design judgements are to be made, they should be made on the

basis of adequate field and laboratory testing.  It should always be kept in
mind that some substances are so toxic that there are no "safe" settings
available.

     In addition to travel time, toxicity, and population exposed, the risk is
influenced by "loading" factors.  Whether the application rate is a slug
application, as in an accidental spill; an intermittent application, as with
pesticides and fertilizers; or a continuous application, such as a leaking tank
or lagoon, has an obvious bearing upon the total load of material reaching an
exposed population.  Loading is also influenced by the concentration of the
polluting substance.  If the incident pollutant is highly concentrated, it is
apparent that the exposed population is at much greater risk than would be the
case if the pollutant were less concentrated.  All of the attenuating factors,
dilution, dispersion, sorption, filtration, reaction etc. are more effective at
lesser loading rates.

     In order to assist in the understanding of the basic risk factors, travel
time, population exposed, loading and toxicity, and how these risk factors
impact the DRASTIC Index, the following acronym is suggested:

     I    Inclination of, the fcater table (gradient)
               Direction of slope in ft/ft (feet per foot)

     M    Measured horizontal distance
               Distance to point of exposure in feet or miles

     P    Population exposed
               Human or non-human

     A    Application rate
               Slug, intermittent, or continuous

     C    Concentration
               Concentration of pollutant, often in mg/1

     T    Toxicity
               Degree of toxicity to the population exposed

     When the DRASTIC Index of a particular setting is evaluated with regard to
these parameters of impact, as a consequence of a particular pollutant, a
reasonable judgement can be made with respect to the risk to the population
exposed.
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                                 Section 7
    GROUND-WATER REGIONS AND HYDROGEOLOGIC SETTINGS OF THE UNITED STATES

     The focus of this document is to present a system which allows the
user to evaluate the ground-water pollution potential of any area in the
United States and to produce a map of the results.   The mapping application
of the methodology requires the designation of hydrogeologic settings.
This section contains descriptions of 111 hydrogeologic settings.  Although
a conscientious attempt has been made to identify all major hydrogeologic
settings in the United States, it is possible that  additional settings may
exist.

     As described in Section 2, Development of the  System and Overview, the
entire United States has been divided into 13 geographic ground-water
regions.  These ground-water regions were developed and described by Heath
(1984) (Figure 1).  This methodology uses these major ground-water regions
as a geographic framework to begin to assess ground-water pollution
potential.  This section contains an annotated description, n geographic
location map and a block diagram illustrating the major hydrogeologic
features for each ground-water region (Heath, 1984).  Table 33 provides a
summary of principal physical and hydrologic characteristics of the
ground-water regions.  Table 34 lists common ranges for the hydraulic
characteristics of the ground-water regions.

     The ground-water regions have been subdivided into mapping units
called hydrogeologic settings.  Each hydrogeologic setting contains a
written narrative, a block diagram showing the geology of the setting and
two DRASTIC charts portraying sample DRASTIC Index calculations.  Figure 45
provides a legend for the identification of the geologic materials
portrayed in the block diagrams of each hydrogeologic setting.  The charts
display the DRASTIC Index and the Pesticide DRASTIC Index for each typical
hydrogeologic setting.  These charts have been produced as examples of
conditions which might typically exist in the hydrogeologic setting within
the specific ground-water region.  The charts are intended to only be
examples and not to represent absolute values for the hydrogeologic
setting.  The significant difference between the two charts is the
difference in weights assigned for each DRASTIC factor.

     The hydrogeologic settings and  the DRASTIC Indexes from the example
charts have been grouped to assist the user in evaluating the relative
pollution potential for many hydrogeologic settings.  Tables 35 through 37
contain lists of the hydrogeologic settings and associated DRASTIC Indexes
sorted by ground-water region, ratings and setting  title respectively.
Tables 38 through 40 contain the same information  for Pesticide DRASTIC
Indexes taken from the example charts.

                                    174

-------
TABLE 33. SUMMARY OF THE PRINCIPAL PHYSICAL AND HYDROLOGIC CHARACTERISTICS OF THE
         GROUND-WATER REGIONS OF THE UNITED STATES (AFTER HEATH, 1984)






Region
No.




1
2
3
4
5
6

7

g
9

10

II
12
13






Name





Western Mountain Ranges
Alluvial Basins
Columbia Lava Plateau
Colorado Plateau and
Wyoming Basin
High Plains
Nonglaciated Central
Region
Glaciated Central
Region
Piedmont and Blue Ridge
Northeast and Superior
Uplands
Atlantic and Gulf
Coastal Plain
Southeast Coastal Plain
Hawaii
Alaska

Components of the system

Unconfined
aquifer



1


C
o
o
•o
X



X




















c
I
X

X


X

X

X
X

V

X








ant aquifer
c
o
Q

X


X










X
X
Confining
beds



«
C

2P
c
S»
o
0
-o
X
X



X




X












a
iscontmud
1










X




X
X



o

«"
vered with
n
S
c

X
X
X

X

X




V

X


Confined
aquifers



3
C

ogically in
£
x"




X










X






—
1
D.
J=
O
z
X








X
X





X


in
5


le product
3

X
X
X

X

X




X





w
5
o-
>

•o
mmant prc
•o














X


Presence and
arrangement



1


unconfmeci
c
t/5




X










X



I/I
5

3
O
t/1














X


Storage and transmission
properties
Porosity






X
&

X


X









X
X






r-t
ale (001-0
1
S
X






X


1

X



X






o
i


X
X

X



X
X






Transmissivity



„-

T3
>2.500 m
a,

X
X

X









X
X



^~~
"s

5?
ate (250-2.
•S
o
2





X

X




X



X



_


E
a
i
X


X






X









r


2
&









X







Recharge and
discharge conditions
Recharge



E
3

Is between
c
"a.
X


X

X



X
X

X

X
X







streams
c
i
X
X
X

X










X
X

tn
T3
C
C

P,
DO
3
O
a



X

X

X




X

X


Discharge



1

u
s and surfa
S
a.
c/}
X

X
X
X
X



X
X

X

X
X
X



c

s
ation and
1
UJ

X




















Ufl
her aquifer
0
o
c

X



X

X




X





-------
            TABLE 34. COMMON RANGES FOR THE HYDRAULIC CHARACTERISTICS OF GROUND WATER REGIONS OF THE UNITED STATES
                                                    (AFTER HEATH, 1984)
Region
No Region Geologic Situation

1 Western Mountain Mountains with thin soils over
Ranges fractured rocks, alternating with
narrow alluvial and, in part,
gjacialed valleys
2 Alluvial Basins Thick' alluvial (locally glacial)
deposits in basins and valleys
bordered by mountains
3 Columbia Lava Thick sequence of lava flows
Plateau mterbedded with unconsolidated
deposits and overlain by
thin soils
4 Colorado Plateau Thin1 soils over fractured
and Wyoming Basin sedimentary rocks
5 High Plains Thick alluvial deposits over
fractured sedimentary rocks
6 Nonglacialed Thin regolith over fractured
Central region sedimentary rocks
7 Glaciated Central Thick glacial deposits over
region fractured sedimentary rocks
8 Piedmont and Blue Thick regolith over fractured
Ridge crystalline and metamorphosed
sedimentary rocks
9 Northeast and Thick glacial deposits over frac-
Superior Uplands lured crystalline rocks
10 Atlantic and Gulf Complexly mterbedded sands.
Coastal Plain silts and clays
11 Southeast Coastal Thick layers of sand and clay
Plain over semiconsolidated carbonate
rocks
12 Hawaiian Islands Lava flows segmented by dikes
mterbedded with ash deposits.
and partly overlain by alluvium
13 Alaska Glacial and alluvial deposits in
part perennially frozen and over-
lying crystalline, metamorphic.
and sedimentary rocks
Common Ranges in Hydraulic Characters ics of the Dominant Aquifers
Transmissivity
m2day '
low




20


2,000



05

1,000

300

100

9


50

500

1,000


10.000


100



high
100



20,000


500,000



100

10,000

10.000

2000

200


500

10000

100 000


100.000


10.000



fl'day '
low
5



2.000


20.000



5

10.000

3,000

1.000

100


500

5,000

10,000


00000


1.000



high
5.000,000



200.000


5.000.000



1,000

100,000

100,000

20,000

2,000


5.000

100.000

1.000.000


1.000000


100,000



Hydraulic Conductivity
m day '
low
00003



30


200



0003

30

3

2

0001


2

3

30


200


30



high
15



600


3.000



2

300

300

300

1


30

100

3000


3,000


600



ft day '
low
0001



100


500



001

100

10

5

0003


5

10

100


500


100



high
50



2.000


10,000



5

1,000

1,000

1.000

3


100

400

10,000


10,000


2.000



Recharge Rate
mm yr '
low
3



003


5



03

5

5

5

30


30

50

30


30


3



high
50



30


300



50

80

500

300

300


300

500

500


1,000


300



in yr
low
01



0001


02



001

02

02

02

1


1

2

1


1


01



high
2



1


10



2

3

20

10

10


10

20

20


40


10



Well Yield
m3 mm '
low
004



04


04



004

04

04

02

02


01

04

4


04


004



high
04



20


80



2

10

20

2

2


1

20

80


20


4



gal mm '
low
10



100


100



10

100

100

50

50


20

100

1,000


100


10



high
100



5.000


20,000



1,000

3.000

5.000

500

500


200

5,000

20,000


5.000


1,000



0)

-------
H§|
        »S  Sand/Sand and Gravel


 »* Si***!
           Regolith/Soil
           Sand and Gravel
•V«*% •'*
*.«•,***«  Sand
       "."*«*

       $?$ Sand/Sandstone
       !?v\l
•*"^J»*i »*^ Sands and Silts
           Igneous, Metamorphic
  — • — • —  Sand and Silt
> /..";/•  Till
 .«««•.»»
                                            ir-T-^-^-^- Shale/Clay
  '  '
i  I  I  I  iH Limestone
      '  "
' . ' . ' . ' 7*7
 1  '  '  '  '
                            Figure 45. Map legend.
                                    177

-------
              TABLE35. HYDROGEOLOGIC SETTINGS AND ASSOCIATED DRASTIC INDEXES
                            SORTED BY GROUND-WATER REGIONS
SETTINGS
                        DESCRIPTIONS
                                                    RATING
                                                                   SETTINGS
                                                                                           DESCRIPTIONS
                                                                                                                       RATING
1Aa East   Mountain Slopes                                 65
1AbWest  Mountain Slopes                                 70
IBaEast   Alluvial Mountain Valleys                         128
IBbWest  Alluvial Mountain Valleys                         146
1Ca East   Mountain Flanks                                 83
ICBWest  Mountain Flanks   :                             106
1D        Glacial Mountain Valleys                         180
1EaEast   Wide Alluvial Valleys (External Drainage)            158
1EbWest  Wide Alluvial Valleys (External Drainage)            180
1F        Coastal Beaches                                196
1G        Swamp/Marsh                                  139
1H        Mud Flows                                     130
2A        Mountain Slopes                                 74
2B        Alluvial Mountain Valleys                         132
2C        Alluvial Fans                                   122
2D        Alluvial Basins (Internal Drainage)                  122
2E        Playa Lakes                                    110
2F        Swamp/Marsh                                  127
2G        Coastal Lowlands                               202
2Ha       River Alluvium with Overbank Deposits              163
2Hb       River Alluvium without Overbank Deposits           191
21         Mud Flows                                     149
2J        Alternating Sandstone and Shale Sequences         112
2K        Continental Deposits                             98
3A        Mountain Slopes                                 86
3B        Alluvial Mountain Valleys                         168
3C        Hydraulically Connected Lava Flows                146
3D        Lava Flows Not Connected Hydraulically            105
3E        Alluvial Fans                                   105
3F        Swamp/Marsh                                  179
3G        River Alluvium                                  147
4A        Resistant Ridges                                 88
46        Consolidated Sedimentary Rock                    87
4C        River Alluvium                                  152
40        Alluvium and Dune Sand                         102
4E        Swamp/Marsh                                  176
5A        Ogallala                                       109
5B        Alluvium                                       107
5C        Sand Dunes                                   150
5D        Playa Lakes                                    110
5E        Braided River Deposits                          185
5F        Swamp/Marsh                                  198
5Ga       Rwer Alluvium with Overbank Deposits              129
5Gb      River Alluvium without Overbank Deposits           143
5H        Alternating Sandstone, Limestone and
          Shale Sequences                                80
6A        Mountain Flanks                                103
6B        Alluvial Mountain Valleys                         152
6C        Mountain Flanks                                105
6Da       Alternating Sandstone, Limestone and Shale —
          Thin Soil                                      139
6Dd       Alternating Sand, Limestone and Shale — Deep
          Regohth                                       125
6E        Solution Limestone                             196
6Fa       River Alluvium with Overbank Deposits              126
6Fb       River Alluvium without Overbank Deposits           187
6G        Braided River Deposits                          190
6H        Tnassic Basins                                 106
61         Swamp/Marsh                                   144
6J        Metamorphic/lgneous Domes and Fault Blocks        71
6K        Unconsolidated and Semiconsolidated Aquifers       101
7Aa       Glacial Till Over Bedded Sedimentary Rock           103
7Ab       Glacial Till Over Outwash          .                137
7Ac       Glacial Till Over Solution Limestone                 139
7Ad       Glacial Till Over Sandstone                        109
7Ae       Glacial Till Over Shale                             88
7Ba       Outwash                                 ,       176
7Bb       Outwash Over Bedded Sedimentary Rock            156
7Bc       Outwash Over Solution Limestone                   186
7C        Moraine                                        135
7D        Buried Valley                                    156
7Ea       River Alluvium with Overbank Deposits              134
7Eb       River Alluvium without Overbank Deposits            191
7F        Glacial Lake Deposits                             135
7G        Thm Till Over Bedded Sedimentary Rock             121
7H        Beaches, Beach Ridges and Sand Dunes             202
71         Swamp/Marsh                                   160
8A        Mountain Slopes                                 75
8B        Alluvial Mountain Valleys                          162
8C        Mountain Flanks                                 106
8D        Regohth                                        100
8E        River Alluvium                                   176
8F        Mountain Crests                                 70
8G        Swamp/Marsh                                   120
9A        Mountain Slopes                                 75
9B        Alluvial Mountain Valley                           180
9C        Mountain Flanks                                 106
9Da       Glacial Till Over Crystalline Bedrock                113
9Db       Glacial Till Over Outwash                          139
9E        Outwash                                        190
9F        Moraine                                        166
9Ga       River Alluvium with Overbank Deposits              146
9Gb       River Alluvium without Overbank Deposits            191
9H        Swamp/Marsh                                   120
91        Bedrock Uplands                                 118
9J        Glacial Lake/Glacial Marine Deposits                120
9K        Beaches, Beach Ridges and Sand Dunes             161
10Aa     Regional Aquifers                                82
10Ab     Unconsolidated and Semiconsolidated Shallow
          Surficial Aquifer                                 184
10Ba     River Alluvium with Overbank Deposits              142
10Bb     River Alluvium without Overbank Deposits            187
10C       Swamp                                         202
11A       Solution Limestone and Shallow Surficial Aquifers     218
11B       Coastal Deposits                                 191
11C       Swamp                                         224
11D       Beaches and Bars                                190
12A       Mountain Slopes                                 164
12B       Alluvial Mountain Valleys                          184
12C       Volcanic Uplands                                165
12D       Coastal Beaches                                 201
13A       Alluvium                                        140
13B       Glacial and Glaciolacustnne Deposits of the
          Interior Valleys                                  141
13C       Coastal Lowland Deposits                         140
13D       Bedrock of the Uplands and Mountains               92
                                                              178

-------
       TABLE 36.HYDROGEOLOGIC SETTINGS AND ASSOCIATED DRASTIC INDEXES  SORTED
                     BY RATING
SETTINGS
                        DESCRIPTIONS
                                                     RATING
                                                                   SETTINGS
                                                                                           DESCRIPTIONS
                                                                                                                        RATING
1Aa East   Mountain Slopes          v                       65
8F        Mountain Slopes                                  70
1AbWest  Mountain Slopes  r                               70
6J        Metamorphic/lgneous Domes and Fault Blocks         71
2A        Mou.ntam Slopes                                  74
8A        Mountain Slopes                                  75
9A        Mountain Slopes                                  75
5H        Alternating Sandstone, Limestone and           ~    ~~
          Shale Sequences                                  80
10Aa      Regional Aquifers                                 82
ICaEast   Mountain Flanks                                  83
3A        Mountain Slopes                                  86
4B        Consolidated Sedimentary Rock                     87
4A        Resistant Ridges                                  88
7Ae       Glacial Till Over Shale                              88
13D       Bedrock of the Uplands and Mountains               92
2K        Continental Deposits                          _98_
8D        Regohth                                       Tub
6K        Unconsohdated and Semiconsolidated Aquifers        101
4D   ,    Alluvium and Dune Sand                          102
6A        Mountain Flanks                                 103
7Aa       Glacial Till Over Bedded Sedimentary Rock           103
6C        Mountain Flanks                                 105
3D        Lava Flows Not Connected Hydrauhcally             105
3E        Alluvial Fans               ^                     105
9C        Mountain Flanks                                 106
6H        Tnassic Basins                                   106
1Cb West  Mountain Flanks                                 106
8C        Mountain Flanks                                 106
5B        Alluvium                                        107
7Ad       Glacial Till Over Sandstone                        109
5A        Ogallala                                        109
2E        Playa Lakes                                     110
5D        Playa Lakes                                     110
2J        Alternating Sandstone and Shale Sequences          112
90a       Glacial Till Over Crystalline Bedrock                 113
91        Bedrock Uplands                                 118
9J        Glacial Lake/Glacial Marine Deposits                120
8G        Swamp/Marsh                                   120
9H        Swamp/Marsh                                   120
7G        Thin Till Over Bedded Sedimentary Rock             121
2D        Alluvial Basins (Internal Drainage)                   122
2C        Alluvial Fans                                     122
6Dd       Alternating Sand, Limestone and Shale — Deep      	
          Regohth                                        125
6Fa       River Alluvium with Overbank Deposits              126
2F        Swamp/Marsh                                   127
IBaEast   Alluvial Mountain Valleys                          128
5Ga       River Alluvium with Overbank Deposits              129
1H        Mud Flows                                      130
2B        Alluvial Mountain Valleys      ^                   132
7Ea       River Alluvium with Overbank Deposits              134
7F        Glacial Lake Deposits                             135
7C        Moraine                                        135
7Ab       Glacial Till Over Outwash                          137
7Ac       Glacial Till Over Solution Limestone                 139
1G        Swamp/Marsh                                   139
6Da       Alternating Sandstone, Limestone and Shale—        139
          Thin Soil
9Db       Glacial Till Over Outwash                          139
13A       Alluvium                                        140
13C       Coastal Lowland Deposits                         140
13B       Glacial and Glaciolacustnne Deposits of the Interior
          Valleys                                         141
10Ba      River Alluvium with Overbank Deposits              142
5Gb       River Alluvium without Overbank Deposits            143
61         Swamp/Marsh                                   144
9Ga       River Alluvium with Overbank Deposits              146
IBbWest  Alluvial Mountain Valleys                          146
3C        Hydrauhcally Connected Lava Flows                146
3G        River Alluvium                                   147
21         Mud Flows            "                      —1*9_
5C        Sand Dunes                                  ~~T50~
4C        River Alluvium                                   152
6B        Alluvial Mountain Valleys                          152
7Bb>.      Outwash Over Bedded Sedimentary                 156
7D        Buried Valley                                    156
1EaEast   Wide Alluvial Valleys (External Drainage)             158
71         Swamp/Marsh                                   160
9K        Beaches, Beach Ridges and Sand Dunes             161
8B        Alluvial Mountain Valleys                          162
2Ha       River Alluvium with Overbank Deposits              163
12A       Mountain Slopes                                 164
12C       Volcanic Uplands                                165
9F        Moraine                                        166
36        Alluvial Mountain Valleys                          168_
7Ba       Outwash                                     f   176
8E        River Alluvium                                   176
4E        Swamp/Marsh                                   176
3F        Swamp/Marsh                                   179
9B        Alluvial Mountain Valley                           180
1Eb West  Wide Alluvial Valleys (External Drainage)             180
1D        Glacial Mountain Valleys                          180
12B       Alluvial Mountain Valleys                          184
10Ab      Unconsohdated and Semiconsolidated Shallow
          Surficial Aquifer                                 184
5E        Braided River Deposits                            185
7Bc       Outwash Over Solution Limestone                  186
10Bb      River Alluvium without Overbank Deposits            187
6Fb       River Alluvium without Overbank Deposits            187
11D       Beaches and Bars                                190
6G        Braided River Deposits                            190
9E        Outwash                                        190
9Gb       River Alluvium without Overbank Deposits            191
11B       Coastal Deposits                                 191
2Mb       River Alluvium without Overbank Deposits            191
7Eb       River Alluvium without Overbank Deposits            191
1F        Coastal Deposits                                 196
6E        Solution Limestone                               196
5F        Swamp/Marsh                                	^I98_
12D       Coastal Beaches                              "  201
7H        Beaches. Beach Ridges and Sand Dunes             202
2G        Coastal Lowlands                                202
10C       Swamp                                         202
11A       Solution Limestone and Shallow Surficial Aquifers     218
11C       Swamp                                         224
                                                               179

-------
               TABLE 37. HYDROGEOLOGIC SETTINGS AND ASSOCIATED DRASTIC INDEXES
                            SORTED BY SETTING TITLE
SETTINGS
                        DESCRIPTIONS
                                                     RATING
                                                                   SETTINGS
                                                                                           DESCRIPTIONS
                                                                                                                        RATING
2D        Alluvial Basins (Internal Drainage)                   122
2C        Alluvial Fans                                    122
3E        Alluvial Fans                                    105
9B        Alluvial Mountain Valleys                          180
8B        Alluvial Mountain Valleys                          162
12B       Alluvial Mountain Valleys                          184
IBbWest  Alluvial Mountain Valleys                          146
2B        Alluvial Mountain Valleys                          132
6B        Alluvial Mountain Valleys                          152
3B        Alluvial Mountain Valleys                          168
IBaEast   Alluvial Mountain Valleys                          128
13A       Alluvium                                        140
5B        Alluvium                                        107
4D        Alluvium and Dune Sand                          102
6Dd       Alternating Sand, Limestone and Shale —
          Deep Regolith                                   125
2J        Alternating Sandstone and Shale Sequences          112
6Da       Alternating Sandstone. Limestone and Shale —
          Thin Soil                                        139
5H        Alternating Sandstone, Limestone and
          Shale Sequences                                  80
11D       Beaches and Bars                                190
7H        Beaches, Beach Ridges and Sand Dunes             202
9K        Beaches, Beach Ridges and Sand Dunes             161
91         Bedrock Uplands                                 118
13D       Bedrock of the Uplands and Mountains                92
6G        Braided River Deposits                            190
5E        Braided River Deposits                            185
70        Buried Valley                                    156
12D       Coastal Beaches                                 201
1F        Coastal Beaches                                 196
11B       Coastal Deposits                                 191
13C       Coastal Lowland Deposits                         140
2G        Coastal Lowlands                                202
4B        Consolidated Sedimentary Rock                     87
2K        Continental Deposits                               98
7F        Glacial  Lake Deposits                             135
9J        Glacial  Lake/Glacial Marine Deposits                120
1D        Glacial  Mountain Valleys                          180
7Aa       Glacial Till Over Bedded Sedimentary Rock           103
9Da       Glacial Till Over Crystalline Bedrock                 113
9Db       Glacial Till Over Outwash                          139
7Ab       Glacial  Till Over Outwash                          137
7Ad       Glacial Till Over Sandstone                        109
7Ae       Glacial  Till Over Shale                             88
7Ac       Glacial Till Over Solution Limestone                 139
13B       Glacial  and Glaciolacustnne Deposits of the
          Interior Valleys                                   141
3C        Hydraulically Connected Lava Flows                 146
3D        Lava Flows Not Connected Hydraulically             105
6J        Metamorphic/lgneous Domes and Fault Blocks         71
7C        Moraine                                        135
9F        Moraine                                        166
8F        Mountain Crests                                  70
6C        Mountain Flanks                                 105
8C        Mountain Flanks                                 106
ICbWest  Mountain Flanks                                 106
1Ca East   Mountain Flanks                                  83
9C        Mountain Flanks                                 106
6A        Mountain Flanks                                 103
3A        Mountain Slopes                                  86
9A        Mountain Slopes                                  75
1Aa East   Mountain Slopes                                  65
2A        Mountain Slopes                                  74
1Ab West  Mountain Slopes                                  70
12A       Mountain Slopes                                 164
8A        Mountain Slopes                                  75
21         Mud Flows                                      149
1H        Mud Flows                                      130
5A        Ogallala                                        109
9E        Outwash                                        190
7Ba       Outwash                                        176
7Bb       Outwash Over Bedded Sedimentary Rock            156
7Bc       Outwash Over Solution Limestone                  186
2E        Playa Lakes                                     110
5D        Playa Lakes                                     110
10Aa      Regional Aquifers                                 82
3D        Regolith                                        100
4A        Resistant Ridges                                  88
8E        River Alluvium                                   176
3G        River Alluvium                                   147
4C        River Alluvium                                   152
6Fa       River Alluvium with Overbank Deposits              126
9Ga       River Alluvium with Overbank Deposits              146
7Ea       River Alluvium with Overbank Deposits              134
10Ba      River Alluvium with Overbank Deposits              142
5Ga       River Alluvium with Overbank Deposits              129
2Ha       River Alluvium with Overbank Deposits              163
6Fb       River Alluvium without Overbank Deposits            187
9Gb       River Alluvium without Overbank Deposits            191
7Eb       River Alluvium without Overbank Deposits            191
10Bb      River Alluvium without Overbank Deposits            187
2Mb       River Alluvium without Overbank Deposits            191
5Gb       River Alluvium without Overbank Deposits            143
5C        Sand Dunes                                     150
6E        Solution Limestone                               196
11A       Solution Limestone and Shallow Surficial Aquifers     218
10C       Swamp                                         202
11C       Swamp                                         224
61         Swamp/Marsh                                   144
5F        Swamp/Marsh                                   198
1G        Swamp/Marsh                                   139
3F        Swamp/Marsh                                   179
8G        Swamp/Marsh                                   120
2F        Swamp/Marsh                                   127
4E        Swamp/Marsh                                   176
9H        Swamp/Marsh                                   120
71         Swamp/Marsh                                   160
7G        Thin Till Over Bedded Sedimentary Rock             121
6H        Tnassic Basins                                  106
10Ab      Unconsohdated and Semiconsohdated Shallow
          Surficial Aquifer                                 184
6K        Unconsohdated and Semiconsolidated Aquifers       101
12C       Volcanic Uplands                                165
1 Eb West  Wide Alluvial Valleys (External Drainage)             180
1EaEast   Wide Alluvial Valleys (External Drainage)             158
                                                              180

-------
       TABLE 38.HYDROGEOLOGIC SETTINGS AND ASSOCIATED PESTICIDE DRASTIC INDEXES
                     SORTED BY GROUND-WATER REGIONS
SETTINGS
DESCRIPTIONS
RATING
SETTINGS
DESCRIPTIONS
RATING
1Aa East   Mountain Slopes                                  91
TAbWest  Mountain Slopes                                  97
IBaEast   Alluvial Mountain Valleys                          166
IBbWest  Alluvial Mountain Valleys                          184
ICaEast   Mountain Flanks                                  99
ICbWest  Mountain Flanks                                 122
ID        Glacial Mountain Valleys                          214
1EaEast   Wide Alluvial Valleys (External Drainage)             192
1EbWest  Wide Alluvial Valleys (External Drainage)             214
IF        Coastal Beaches                                 221
1G        Swamp/Marsh                                   158
1H        Mud Flows                                      132
2A        Mountain Slopes                                 105
2B        Alluvial Mountain Valleys                          165
2C        Alluvial Fans                                    155
2D        Alluvial Basins (Internal Drainage)                   157
2E        Playa Lakes                                     139
2F        Swamp/Marsh                                   146
2G        Coastal Lowlands                                215
2Ha       River Alluvium with Overbank Deposits              181
2Mb       River Alluvium without Overbank Deposits            224
21         Mud Flows                                      172
2J        Alternating Sandstone and Shale Sequences          120
2K        Continental Deposits                              99
3A        Mountain Slopes                                  92
38        Alluvial Mountain Valleys                          202
3C        Hydraulically Connected Lava Flows                157
3D        Lava Flows Not Connected Hydraulically             143
3E        Alluvial Fans                                    123
3F        Swamp/Marsh                                   208
3G        River Alluvium                                   155
4A        Resistant Ridges                                 117
4B        Consolidated Sedimentary Rock                    108
4C        River Alluvium                                   176
4D        Alluvium and Dune Sand                          131
4E        Swamp/Marsh                                   213
5A        Ogallala                                        136
SB        Alluvium                                        135
5C        Sand Dunes                                     177
5D        Playa Lakes                                     139
5E        Braided River Deposits                           216
5F        Swamp/Marsh                                   229
5Ga       River Alluvium with Overbank Deposits              129
5Gb       River Alluvium without Overbank Deposits            149
5H        Alternating Sandstone, Limestone and Shale
          Sequences                                       88
6A        Mountain Flanks                                 132
6B        Alluvial Mountain Valleys                          176
6C        Mountain Flanks                                 126
60a       Alternating Sandstone, Limestone and Shale —
          Thin Soil                                        180
6Dd       Alternating Sand, Limestone and Shale — Deep
          Regolith                                        145
6E        Solution Limestone                               216
6Fa       River Alluvium with Overbank Deposits              164
6Fb       River Alluvium without Overbank Deposits            209
6G        Braided River Deposits                           221
6H        Tnassic Basins                                  135
61         Swamp/Marsh                                   165
6J        Metamorphic/lgneous Domes and Fault Blocks        96
6K        Unconsolidated and Semiconsolidated Aquifer        109
7Aa       Glacial Till Over Bedded Sedimentary Rock           125
7Ab       Glacial Till Over Outwash                          153
7Ac       Glacial Till Over Solution Limestone                 153
7Ad       Glacial Till Over Sandstone                        129
7Ae       Glacial Till Over Shale                            111
7Ba       Outwash                                        196
7Bb       Outwash Over Bedded Sedimentary Rocks           182
7Bc       Outwash Over Solution Limestone                  206
7C        Moraine                                        156
7D        Buried Valley                                    178
7Ea       River Alluvium with Overbank Deposits              157
7Eb       River Alluvium without Overbank Deposits            224
7F        Glacial Lake Deposits                             165
7G        Thin Till Over Bedded Sedimentary Rock             143
7H        Beaches, Beach Ridges and Sand Dunes             225
71         Swamp/Marsh                                   174
8A        Mountain Slopes                                 102
8B        Alluvial Mountain Valleys                          185
8C        Mountain Flanks                                 123
8D        Regolith                                        117
8E        River Alluvium                                   198
8F        Mountain Crests                                 113
8G        Swamp/Marsh                                   141
9A        Mountain Slopes                                 102
9B        Alluvial Mountain Valley                           202
9C        Mountain Flanks                                 122
9Da       Glacial Till Over Crystalline Bedrock                 142
9Db       Glacial Till Over Outwash                          161
9E        Outwash                                        210
9F        Moraine                                        180
9Ga       River Alluvium with Overbank Deposits              164
9Gb       River Alluvium without Overbank Deposits            213
9H        Swamp/Marsh                                   141
91         Bedrock Uplands                                 158
9J        Glacial Lake/Glacial Marine Deposits                146
9K        Beaches, Beach Ridges and Sand Dunes             199
10Aa      Regional Aquifers                                113
10Ab      Unconsolidated and Semiconsolidated Shallow
          Surficial Aquifer                                 206
10Ba      River Alluvium with Overbank Deposits              165
10Bb      River Alluvium without Overbank Deposits            220
10C       Swamp                                         233
11A       Solution Limestone and Shallow Surficial Aquifers     243
11B       Coastal Deposits                                 224
11C       Swamp                                         251
11D       Beaches and Bars                                225
12A       Mountain Slopes                                 177
12B       Alluvial Mountain Valleys                          192
12C       Volcanic Uplands                                 174
12D       Coastal Beaches                                 230
13A       Alluvium                                        164
138       Glacial and Glaciolacustrme Deposits of the Interior
          Valleys                                         166
13C       Coastal Lowland Deposits                         164
13D       Bedrock of the Uplands and Mountains              118
                                                              181

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        TABLE 39. HYDROGEOLOGIC SETTINGS AND ASSOCIATED PESTICIDE DRASTIC INDEXES
                     SORTED BY RATING
SETTINGS
                        DESCRIPTIONS
                                                    RATING
                                                                   SETTINGS
                                                                                           DESCRIPTIONS
                                                                                                                        RATING
5H        Alternating Sandstone, Limestone and
          Shale Sequences                                 88
1Aa East   Mountain Slopes                                 91
3A        Mountain Slopes                                 92
6J        Metamorphic/lgneous Domes and Fault Blocks        96
1Ab West  Mountain Slopes                                 97
1Ca East   Mountain Flanks                                 99
2K        Continental Deposits                             99
8A        Mountain Slopes                                102
9A        Mountain Slopes                                102
2A        Mountain Slopes                                105
48        Consolidated Sedimentary Rock                   108
6K        Unconsolidated and Semiconsolidated Aquifer       109
7Ae       Glacial Till Over Shale                           111
10Aa      Regional Aquifers                               113
8F        Mountain Crests                                113
8D        Regolith                                       117
4A        Resistant Ridges                                117
13D       Bedrock of the Uplands and Mountains             118
2J        Alternating Sandstone and Shale Sequences         120
9C        Mountain Flanks                                122
ICbWest  Mountain Flanks                                122
8C        Mountain Flanks                                123
3E        Alluvial Fans                                   123
7Aa       Glacial Till Over Bedded Sedimentary Rock          125
6C        Mountain Flanks                                126
5Ga       River Alluvium with Overbank Deposits             129
7Ad       Glacial Till Over Sandstone                       129
4D        Alluvium and Dune Sand                         131
1H        Mud Flows                                     132
6A        Mountain Flanks                                132
6H        Triassic Basins                                 135
5B        Alluvium                                       135
5A        Ogallala                                       136
2E        Playa Lakes                                    139
5D        Playa Lakes                                    139
9H        Swamp/Marsh                                  141
8G        Swamp/Marsh                                  141
9Da       Glacial Till Over Crystalline Bedrock                142
7G        Thin Till Over Bedded Sedimentary Rock            143
3D        Lava Flows Not Connected Hydraulically            143
6Dd       Alternating Sand, Limestone and Shale — Deep
          Regolith                                       145
2F        Swamp/Marsh                                  146
9J        Glacial Lake/Glacial Marine Deposits               146
5Gb       River Alluvium without overbank deposits           149
7Ab       Glacial Till Over Outwash                         153
7Ac       Glacial Till Over Solution Limestone                153
2C        Alluvial Fans                                   155
3G        River Alluvium                                  155
7C        Moraine                                       156
3C        Hydraulically Connected Lava Flows                157
7Ea       River Alluvium with Overbank Deposits             157
2D        Alluvial Basins (Internal Drainage)                  157
1G        Swamp/Marsh                                  158
91        Bedrock Uplands                               158
9Db       Glacial Till Over Outwash Deposits                 161
6Fa       River Alluvium with Overbank                      164
13A       Alluvium                                       164
9Ga       River Alluvium with Overbank Deposits              164
13C       Coastal Lowland Deposits                        164
10Ba      River Alluvium with Overbank Deposit               165
7F        Glacial Lake Deposits                            165
61         Swamp/Marsh                                  165
26        Alluvial Mountain Valleys                         165
IBaEast   Alluvial Mountain Valleys                         166
13B       Glacial and Glaciolacustrme Deposits of the Interior
          Valleys                                        166
21         Mud Flows                                     172
71         Swamp/Marsh                                  174
12C       Volcanic Uplands                               174
6B        Alluvial Mountain Valleys                         176
4C        River Alluvium                                  176
12A       Mountain Slopes                                177
5C        Sand Dunes                                    177
7D        Buried Valley                                   178
9F        Moraine                                        180
6Da       Alternating Sandstone, Limestone and Shale —
          Thm Soil                                       180
2Ha       River Alluvium with Overbank Deposits              181
7Bb       Outwash over Bedded Sedimentary                 182
IBbWest  Alluvial Mountain Valleys                         184
8B        Alluvial Mountain Valleys                         185
12B       Alluvial Mountain Valleys                         192
1Ea East   Wide Alluvial Valleys (External Drainage)            192
7Ba       Outwash                                       196
8E        River Alluvium                                  198
9K        Beaches,  Beach Ridges and Sand Dunes            199
3B        Alluvial Mountain Valleys                         202
9B     -   Alluvial Mountain Valleys                         202
7Bc       Outwash Over Solution Limestone                 206
10Ab      Unconsolidated and Semiconsolidated Shallow
          Surficial Aquifer                                206
3F        Swamp/Marsh                                  208
6Fb       River Alluvium Without Overbank Deposits          209
9E        Outwash                                       210
9Gb       River Alluvium Without Overbank Deposits          213
4E        Swamp/Marsh                                  213
1D        Glacial Mountain Valleys                         214
1 Eb West  Wide Alluvial Valleys (External Drainage)            214
2G        Coastal Lowlands                               215
5E        Braided River Deposits                           216
6E        Solution Limestone                              216
10Bb      River Alluvium Without Overbank Deposits          220
6G        Braided River Deposits                           221
1F        Coastal Beaches                                221
2Mb       River Alluvium Without Overbank Deposits          224
7Eb       River Alluvium Without Overbank Deposits          224
11B       Coastal Deposits                                224
11D       Beaches and Bars                               225
7H        Beaches, Beach Ridges and Sand Dunes            225
5F        Swamp/Marsh                                  229
12D       Coastal Beaches                                230
10C       Swamp                                        233
11A       Solution Limestone and Shallow Surficial Aquifers    243
11C       Swamp                                        251
                                                              182

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        TABLE 40. HYDROGEOLOGIC SETTINGS AND ASSOCIATED PESTICIDE DRASTIC INDEXES
                      SORTED BY SETTING TITLE
 SETTINGS
                        DESCRIPTIONS
                                                     RATING
                                                                    SETTINGS
                        DESCRIPTIONS
                                                                                                                        RATING
 2D        Alluvial Basins (Internal Drainage)                  157
 2C        Alluvial Fans                                    155
 3E        Alluvial Fans                                    123
 9B        Alluvial Mountain Valley                          202
 8B        Alluvial Mountain Valleys                          185
 12B       Alluvial Mountain Valleys                          192
 IBbWest  Alluvial Mountain Valleys                          184
 2B        Alluvial Mountain Valleys                          165
 68        Alluvial Mountain Valleys                          176
 3B        Alluvial Mountain Valleys                          202
 IBaEast   Alluvial Mountain Valleys                          166
 13A       Alluvium                                       164
 56        Alluvium                                       135
 4D        Alluvium and Dune Sand                          131
 6Dd       Alternating Sand, Limestone and Shale — Deep
           Regolith                                        145
 2J         Alternating Sandstone and Shale Sequences          120
 6Da       Alternating Sandstone, Limestone and Shale —
           Thin Soil                                       180
 5H        Alternating Sandstone, Limestone and
           Shale Sequences                                 88
 11D   •    Beaches and Bars                               225
 7H        Beaches, Beach  Ridges and Sand Dunes             225
 9K        Beaches, Beach  Ridges and Sand Dunes             199
 91         Bedrock Uplands                                158
 13D       Bedrock of the Uplands and Mountains              118
 6G        Braided River Deposits                            221
 5E        Braided River Deposits                            216
 7D        Buried Valley                                    178
 12D       Coastal Beaches                                 230
 1F         Coastal Beaches                                 221
 11B       Coastal Deposits                                224
 13C       Coastal Lowland Deposits                         164
 2G        Coastal Lowlands                                215
 4B         Consolidated Sedimentary Rock                    108
 2K         Continental Deposits                              99
 7F         Glacial Lake Deposits                             165
 9J         Glacial Lake/Glacial Marine Deposits                146
 1D        Glacial Mountain Valleys                          214
 7Aa       Glacial Till Over Bedded Sedimentary Rock           125
 9Da       Glacial Till Over Crystalline Bedrock                 142
 9Db       Glacial Till Over Outwash                          161
 7Ab       Glacial Till Over Outwash                          153
 7Ad       Glacial Till Over Sandstone                        129
 7Ae       Glacial Till Over Shale                             111
 7Ac       Glacial Till Over Solution Limestone                 153
 13B       Glacial and Glaciolacustnne Deposits of the
           Interior Valleys                                   166
3C         Hydraulically Connected Lava Flows                 157
3D         Lava Flows Not Connected Hydraulically             143
6J         Metamorphic/lgneous Domes and Fault Blocks        96
 7C         Moraine                                        156
9F         Moraine                                        180
8F         Mountain Crests                                  113
6C        Mountain Flanks                                  126
8C        Mountain Flanks                                  123
 ICbWest  Mountain Flanks                                  122
ICaEast   Mountain Flanks                                  99
 9C        Mountain Flanks                                 122
 6A        Mountain Flanks                                 132
 3A        Mountain Slopes                                  92
 9A        Mountain Slopes                                 102
 lAa East   Mountain Slopes                                  91
 2A        Mountain Slopes                                 105
 1AbWest   Mountain Slopes                                  97
 12A       Mountain Slopes                                 177
 8A        Mountain Slopes                                 102
 21         Mud Flows                                     172
 1H        Mud Flows                                     132
 5A        Ogallala                                        136
 9E        Outwash                                       210
 7Ba       Outwash              ~                        195
 7Bb       Outwash Over Bedded Sedimentary Rock            182
 7Bc       Outwash Over Solution Limestone                  206
 2E        Playa Lakes                                     139
 5D  .      Playa Lakes                                     139
 10Aa       Regional Aquifers                                113
 8D        Regolith                                        174
 4A        Resistant Ridges                                 117
 8E        River Alluvium                                   198
 3G        River Alluvium                                   147
 4C        River Alluvium                                   176
 6Fa        River Alluvium with Overbank Deposits              164
 9Ga       River Alluvium with Overbank Deposits              164
 7Ea'       River Alluvium with Overbank Deposits              157
 lOBa       River Alluvium with Overbank Deposits              165
 5Ga       River Alluvium with Overbank Deposits              129
 2Ha       River Alluvium with Overbank Deposits              181
 6Fb        River Alluvium without Overbank Deposits            209
 9Gb       River Alluvium without Overbank Deposits            213
 7Eb        River Alluvium without Overbank Deposits            224
 10Bb       River Alluvium without Overbank Deposits            220
 2Hb       River Alluvium without Overbank Deposits            224
 5Gb       River Alluvium without Overbank Deposits            149
 5C        Sand Dunes                                     177
 6E         Solution Limestone                               216
 11A        Solution Limestone and Shallow Surficial Aquifers     243
 10C        Swamp                                         233
 11C        Swamp                                         251
 61          Swamp/Marsh                                   165
 5F         Swamp/Marsh                                   229
 1G        Swamp/Marsh                                   158
 3F         Swamp/Marsh                                   208
 8G        Swamp/Marsh                                   141
 2F         Swamp/Marsh                                   146
4E         Swamp/Marsh                                   213
9H         Swamp/Marsh                                   141
71          Swamp/Marsh                                   117
 7G         Thin Till Over Bedded Sedimentary Rock             143
6H        Triassic Basins                                   135
 lOAb       Unconsolidated and Semiconsolidated Shallow
          Surficial Aquifer                                 206
6K         Unconsolidated and Semiconsolidated Aquifer        109
 12C       Volcanic Uplands                                 174
 1 Eb West  Wide Alluvial Valleys (External Drainage)             214
 1EaEast   Wide Alluvial Valleys (External Drainage)             192
                                                             183

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 1.   WESTERN MOUNTAIN RANGES GROUND-WATER REGION
lAa East    Mountain Slopes
lAb West    Mountain Slopes
IBa East    Alluvial Mountain  Valleys
IBb West    Alluvial Mountain  Valleys
ICa East    Mountain Flanks
ICb West    Mountain Flanks
ID          Glacial  Mountain Valleys
lEa East    Wide Alluvial  Valleys  (External Drainage)
lEb West    Wide Alluvial  Valleys  (External Drainage)
IF          Coastal  Beaches
1G          Swamp/Marsh
1H          Mud  Flows
                       184

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                          1.   WESTERN MOUNTAIN RANGES
    (Mountains with thin soils over fractured rocks, alternating with narrow
                   alluvial and, in part, glaciated valleys)

    The Western Mountain Ranges encompass three areas totaling 708,000 km2.
The largest area extends in an arc from the Sierra Nevada in California, north
through the Coast Ranges and Cascade Mountains in Oregon and Washington, and
east and south through the Rocky Mountains in Idaho and Montana into the
Bighorn Mountains in Wyoming and the Wasatch and Uinta Mountains in Utah.  The
second area includes the southern Rocky Mountains, which extend from the
Laramie Range in southeastern Wyoming through central Colorado into the Sangre
de Cristo Range in northern New Mexico.  The smallest area includes the part of
the Black Hills in South Dakota in which Precambrian rocks are exposed.
Summits in the Rocky Mountains and Sierra Nevada exceed 3,500 m.  The general
appearance of the Western Mountains Ranges, with the exception of the Black
Hills, is tall, massive mountains alternating with relatively narrow,
steep-sided valleys.  The summits and sides of the mountains in much of the
region have been carved into distinctive shapes by mountain glaciers.  The
ranges that comprise the southern Rocky Mountains are separated by major
lowlands that include North Park, Middle Park, South Park, and the Wet Mountain
Valley.  These lowlands occupy downfolded or down-faulted structural troughs as
much as 70 km wide and 160 km long.  The mountains in the Black Hills are lower
in altitude than most of the mountains in other parts of the region.

     As would be expected in such a large region, both the origin of the
mountains and the rocks that form them are complex.  Most of the mountain
ranges are underlain by granitic and metamorphic rocks flanked by consolidated
sedimentary rocks of Paleozoic to Cenozoic age.  The other ranges, including
the San Juan Mountains in southwestern Colorado and the Cascade Mountains in
Washington and Oregon, are underlain by lavas and other igneous rocks.

     The summits and slopes of most of the mountains consist of bedrock
exposures or of bedrock covered by a layer of boulders and other rock fragments
produced by frost action and other weathering processes acting on the bedrock.
This layer is generally only a few meters thick on the upper slopes but forms a
relatively thick apron along the base of the mountains.  The narrow valleys are
underlain by relatively thin, coarse, bouldery alluvium washed from the higher
slopes.  The large synclinal valleys and those that occupy downfaulted
structural troughs are underlain by moderately thick deposits of coarse-grained
alluvium transported by streams from the adjacent mountains.

     The Western Mountain Ranges and the mountain ranges in adjacent regions
are the principal sources of water supplies developed at lower altitudes in the
western half of the conterminous United States.  As McGuinness (1963) noted,


                                      185

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the mountains of the west are moist "islands" in a sea of desert or semidesert
that covers the western half of the Nation.  The mountains force moisture-laden
air masses moving eastward from the Pacific to rise to higher and cooler
altitudes.  As the air cools, moisture condenses into clouds and precipitates.
The heaviest precipitation falls on the western slopes; thus, these slopes are
the major source of runoff and are also the most densely vegetated.  Much of
the precipitation falls as snow during the winter, and its slow melting,
starting at the lower altitudes in early spring, maintains streamflow at large
rates until late June or early July.  Small glaciers occur in the higher
mountain ranges, especially in the northern Rocky Mountains, the Cascades, and
the Sierra Nevada; locally, as in northern Washington they also provide
significant sources of summer runoff.

     Melting snow and rainfall at the higher altitudes in the region provide
abundant water for ground-water recharge.  However, the thin soils and bedrock
fractures in areas underlain by crystalline rocks fill quickly, and the
remaining water runs off overland to streams.  Because of their small storage
capacity, the underground openings provide limited base runoff to the streams,
which at the higher altitudes flow only during rains or snowmelt periods.
Thus, at the higher altitudes in this region underlain by crystalline rocks,
relatively little opportunity exists for development of ground-water supplies.
The best opportunities exist in valleys that contain at least moderate
thicknesses of saturated alluvium or in areas underlain by permeable
sedimentary or volcanic rocks.  Ground-water supplies in the valleys are
obtained both from wells drawing from the alluvium and from wells drawing from
the underlying rocks.  The yields of wells in crystalline bedrock and wells
drawing water from small, thin deposits of alluvium are generally adequate only
for domestic and stock needs.  Large yields can be obtained from the alluvial
deposits that overlie the major lowlands and from wells completed in permeable
sedimentary or volcanic rocks.
                                       186

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WESTERN MOUNTAIN KANGES
                                                              WESTERN MOUNTAIN RANGES
(VAa) Mountain Slopes - East

This hydrogeologic setting is characterized by steep slopes
on the eldes of mountains, a thin soil cover and highly
fractured bedrock.  Ground water Is obtained primarily from
the fractures in the bedrock which may be of sedimentary,
metamorphlc or Igneous origin.  The fractures provide
localized sources of ground water and well yields are
typically Halted even though the hydraulic conductivity is
often high because of the fractures.  Due to the steep
slopes, thin soil and small storage capacity of the
fractures, runoff is significant.  Thicker weathered zones
(soils) may develop locally particularly on talus slopes
with local perched zones common.  These eastern facing
slopes are located In the rain shadow of the mountains and
only limited rainfall is derived from the moisture laden
prevailing westerly winds, thus ground water recharge rarely
exceeds 1 Inch/year.  Ground water levels are extremely
variable but are typically deep.  Most of these areas are
water deficient on an annual basis.  The migration of
pollutants introduced at the surface will be dependent on
the current climatic conditions; pollutants will tend to
Infiltrate easier and further during wet periods u opposed
to dry periods.
(Ub) Mountain Slopes - West

This setting is similar to (lAa) Mountain Slopes-East except
that ground water levels are typically more shallow and
precipitation greatly exceeds the amount which falls on  the
•••tern slopes.  Even though rainfall is more abundant,
recharge is still low due to the steepness of the slopes and
4ra*ity of the underlying bedrock and may only exceed 2
inches/year in places where precipitation is very high and
•oil cover Is unusually favorable.  Due to Increased
precipitation, pollutants may tend to migrate to the water
table more rapidly, but be more diluted, than on the
comparable eastern (lopes.
SETTING 1 Ae Mountain Elopes Cast
FEATURE
fepth to Hater
let Recharge
tqulfer Media
ioil Media
Topography
[mpact Vadose Zone
lydraulic conductivity
RANGE
100+
0-2
Metamorphic/IgneOus
Thin or Absent
181-1
Metamorphlc/ I oneous
100-300
GENERAL
WEIGHT
5
4
3
2
1
5
3
RATING
1
1
3
10
1
4
2
Drastic Index
NUMBER
5
4
S
20
1
2C
6
65
iETTING 1 Aa Mountalr Slopes East
FEATURE
Hspth to Water
let Recharge
iquifer Media
ioil Media
Topography
[•pact Vedose Zone
JydrAuIic Conductivity
RANGE
100*
0-2
Metamorphi", Igneous
Thin or Absent
ie+«
Metamorphic/Ioneous
100-300
PrET
WEIGHT
5
4
3
5
3
4
2
iciDr
RATING
1
1
3
10
1
4
2
Pesticide
Drastic Index

NUHBEI
5
4
9
50
3
U
4
91
SETTING 1 Ab Mountain Slopes nest
FEATURE
)epth to Water
let Recharge
kquifer Media
toil Media
Topography
Impact vadose zone
iydraullc Conductivity
RANGE
75-10C
0-2
^etamorphic/ Igneous
Thin or Absent
18»«
Met amor phic/ Igneous
100-300
GENERAL
HEIGHT
5
<
3
2
1
5
3
RATING
2
1
3
10
1
4
2
Drastic Index

NUMBED
10
4
>
20
1
20
6
70
SETTING 1 Ab Mountain Slopes Mest
FEATURE
tepth to Water
tet Recharge
tquifer Media
ioil Media
Topography
[•pact Vadoa-e Zone
lydraulic Conductivity
RANGE
75-100
0-2
Metamorphlc, 'Igneous
Thir. or Absent
18*%
Metamorphlc/ Igneous
100-300
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
2
1
3
10
1
4
2
Pesticide
Drastic Index
NUMBER
10
4
9
5C
3
H
4
97
                                                          187

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WESTERN MOUNTAIN RANGES
                                                                WESTERN MOUNTAIN RANGES
(IBa)  Alluvial Mountain Valleys - East

This hydrogeologic setting of eastward facing Interior
valleys Is characterized by thin, bouldery alluvium which
overlies fractured bedrock of sedimentary, metaaorphlc or
igneous origin.  The alluvium, which Is derived from the
•urroundlng steep slopes serves as a localized source of
•ater.  Where soil cover exists, It typically Is
gravel-sized and offers little protection froo pollution.
Water levels are typically moderately deep because of the
lack of precipitation on the eastern slopes and the low net
recharge.  Ground water Is obtained from the coarser-grained
deposits within the valley, but these deposits also have a
finer-grained fraction which can Influence water movement.
Ground water may also be obtained from the fractures In the
underlying bedrock which are typically In direct hydraulic
connection with the overlying alluvium.  Since these valleys
are usually structurally controlled, there Is the
possibility that any pollutants Introduced at the surface
may migrate Into the fractures beneath the alluvium and
disperse rapidly from the site of Incidence.
SETTING ' Be Alluvial Mountain Valleys
FEATURE
tepth to Mater
)«t Mcharqe
kquifer Media
ioil Media
Topography
Impact Vado»e lone
lydraulic Conductivity
RANGE
30-5C
0-2
Sand and Gravel
Gravel
2-6%
Sand aid Gravel
100-300

WEIGHT
5
4
3
2
1
5
3
GENERAL
RATING
5
1
8
10
9
8
•2
Drastic Index

NUMBER
25
4
24
20
9
40
6
126
SETTING ' B* Alluvial Mountai- Valleys
FEATURE
>eptr. to Water
»et Recharoe
kqulfer Media
Soil Media
ropogr»phy
[•pact Vadoae lone
iydraulic Conductivity
RANGE
30-5C
0-2
Sana and Gravel
Gravel
2-6%
Sand and Gravel
100-300
PE£TJCIDF
HEIGHT
S
4
3
5
3
4
2
RATING
5
1
e
10
9
t
2
Pesticide
Drastic Index
NUMBER
25
4
24
50
27
32
4
166
(IBb) Alluvial Mountain Valleys - West

This setting, which Includes coastal valleys and
westward-sloping Interior valleys, Is elmllar to  (IBa)
Narrow Alluvial Valleys-East.  Water levels are typically
shallower due to higher amounts of precipitation  and
subsequently greater ground-water recharge.  Soils tend to
be deeper with better developed soil profiles.  Bedrock
weathering is usually deeper, with Increased mass wasting
due to freeze/thaw cycles that may occur In the higher
valleys of some areas.  The migration of pollutants
introduced at the surface will, In most cases, be
predictably downgradlent In the relatively short, straight,
narrow, well-defined valleys.
SETTING 1 Bb Alluvial Mountain Valleys
FEATURE
>epth to Hater
Jet Recharge
Kjulfer Media
.oil Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
15-30 "
2-4
Sand and Gravel
Gravel
2-i«
Sand and Gravel
100-30C

WIGHT
5
4
3
2
1
5
3
GENERAL
RATING
7
3
8
10
>
6
2
Drastic Index

NUMBER
35
12
24
20
9
40
<
146 	
JETTING 1 Efc AH'-vial Mo-r.tair, Vallevt
FEATURE
>eptT. to water
*et Recharge
uguifer Media
•oil Media
Topography
Impact vadose Zone
lydraulic Conductivity
RANGE
15-3C
2-4
Sand and Gravel
Gravel
2-6%
Sand and Gravel
100-300
PESTIC1DI
WEIGHT
5
4
3
5
1
4
2
RATING
1
3
e
10
9
8
2
Pesticide
Drastic Index
NUMBEP
35
12
24
50
21
32
4
1(4
                                                          188

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WESTERN MOUNTAIN tANGES
                                                              MUTTMf MOUNTAIN RANGES
(ICa) Mountain Flank* - East

This hydrogeologic setting is characterized by moderate  to
iteep topographic relief and dipping fractured consolidated
•edi»entary rocks, which dip toward and underlie the
adjacent wide alluvial valleys.  Soil cover is usually
thicker than on the upper mountain slopes and typically  has
weathered to a sandy loam.  Alluvlun and/or talus deposit*
•re not Included in this setting.  These sedimentary rocks,
when fractured, typically have hydraulic conductivities
similar to the fractured bedrock on the mountain slopes.
Depth to the water table varies, but is typically deep due
to lack of precipitation and noderate topographic relief,
and net recharge is very low.  Pollutants that may be
introduced at the surface will tend to migrate most rapidly
along dipping bedding planes, and through fractures.
(ICb) Mountain Flanks - West

This setting is similar to (ICa) Mountain Flanks-East.
Ground water levels, however, are typically  not quite as
deep and ground-water recharge is greater due  to  the greater
aanunt of precipitation on the western elopes.  Soil depths
•re often greater, with more developed soil  profiles.   These
•oils are characterised by higher cl«y and loan content than
those that occur en the •••tern (lopes.  Analagous  to the
•••tern flanks, any pollutants that are Introduced  will tend
to migrate along tedding planes and fractures.
SETTING 1 c« Mountain
FEATURE
>epth to Utter
let Recharge
ugulfer Media
ioll Media
Topography
[•pact vadose Zone
lydraulic Conductivity

Flanks East
RANGE
75-100
0-2
Bedded SS, LS, S«
Sequences
Sandy Loam
12-181
Beaded LS, SS , SH
100-30C


HEIGHT
5
4
3
2
1
5
3
Drastii
GENERA!
RATING
2
1
C
e
3
e
2
r Index

NUMBER
1C
4
ie
12
3
30
6
83
SETTING , cb Mountain Flanks West
FEATURE
>epth to Hater
tot Recharge
tqulfer Media
Soil Media
topography
[•pact Vadose tone
iydraulic Conductivity
RANGE
30-50
2-4
Bedded SS, LS, EH
Sequences
Sandy Loam
12-18%
Bedded LS, SS, SB
100-300
GENERAL
(EIGHT
.5
4
3
2
1
5
3
RATING
£
3
6
e
3
6
2
Drastic Index
NUMBER
It
12
18
12
3
30
6
106
SETTING 1 Ca Mour.tal- Flar.ks East
FEATURE
)epth to Hater
fet Recharge
tquifer Media
•oil Media
topography
tiapact Vadoce tone
tydraullc Conductivity
RANGE
75-10C
0-2
BeddeS SS , LS, SK
Sequences
Sandy Loair.
12-18%
Bedded LS, SS, SH
100-30C
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
2
1
6
6
3
6
2
Pesticide
Drastic Index
NUMBEF
10
4
18
30
9
24
4
99
SETTING , ch f.aanttir: Flanks west
FEATURE
tepth, to Hater
iet Recharge
tqulfer Media
Soil Media
Topography
(•pact VadOfte Zone
lydraulic Conductivity
RANGE
30-50
2-4
Bedded SS, LS , SH
Seouences
Sandy Loan*.
12-181
Bedded LS, SS, SH
100-300
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
5
3
6
6
3
6
2
Pesticide
Drastic Index
NUHBEF
25
12
IE
30
5
24
4
122
                                                        189

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WESTERN MOUNTAIN RANGES

(IP) Glaciated Mountain Valleys

This hydrogeologlc setting Is characterized by moderate
topographic relief, and very coarse-grained deposits
associated with the near mountain glacial features, such at
cirques and paternoster lakes.  These deposits Bay serve as
localized sources of water.  Hater tables are typically
shallow with  coarse-grained deposits present at the
surface.  Mountain glaciers nay be present In some areas.
Although precipitation nay not be great, recharge is
relatively high when compared to other settings in the
region because of the large volumes of water produced fro*
the glaciers during the summer melting cycle.  These recent
glacial deposits are underlain by fractured bedrock of
igneous or metamorphic origin all of which are in direct
hydraulic connection with the overlying deposits.  The
fractured bedrock may also serve as a local source of ground
water.
WESTERN MOUNTAIN RANGES

(lEa) Wide Alluvial Valleys (External Drainage) - East

This hydrogeologlc setting is characterized by low relief
and moderately thick deposits of coarse-grained alluvium
deposited by water.  It is similar to (IBs) Narrow Alluvial
Mountain Valleys except that the valleys are better
developed and the streams which occupy their channels have a
•h»llower gradient.  Typically the alluvial deposits are
fleer-grained and thicker than the narrow alluvial valleys.
The alluvium In this setting serves as the major source of
(round water and is often capable of supplying large
quantities of water.  Surficlal deposits are usually
eoarse-grained and water levels are relatively shallow even
through precipitation and net recharge are low.  The
alluvium is underlain by layers of permeable sedimentary
rock which receive their primary source of recharge from the
adjacent mountain flanks.  The sedimentary sequence is
underlain by fractured bedrock of Igneous or metamorpMc
origin.  Ground water may also be obtained from Che
permeable sedimentary rocks.
SETTING 1 D Glacial Mountain Valleys
FEATURE
>epth to Hater
let Recharge
tquifcr Media
ioil Media
Topography
Impact Vadose zone
hydraulic Conductivity
RANGE
5-15
4-7
Sand and Gravel
Gravel
2-6*
Said and Gravel
700-1000
GENERAL
.(EIGHT
5
4
3
2
1
5
3
RATING
9
C
e
10
9
e
6
Drastic Index
NUMBER
45
24
24
20
5
40
18
ISC
SETTING 1 Ea Klde Alluvial Valleys
FEATURE
iepth to Hater Table
let Recharge
tquifer Media
Soil Media
Topography
Impact Vadose Zone
Hydraulic Conductivity
RANGE
15-30
2-4
Sand and Gravel
Gravel
2-6»
Sand and Gravel
700-1000
GENERAL
WEIGHT
5
4
3
2
1
5
3
RATING
7
3
8
10
9
e
6
Drastic Index
NUMBER
35
12
24
20
9
4C
16
156
SETTING 1 V Glacial Mountain Valleys
FEATURE
iepth to Water
let Recharge
tquifer Media
loll Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
5-15
4-7
Sane and Gravel
Gravel
2-6»
Sand and Gravel
700-1000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
9
6
e
10
9
i
t
Pesticide
Drastic Intex
NUMBER
45
24
24
50
27
32
12
214
JETTING ^ *-a ^ ll^e Alluvial Valleys
(Exterr.fl Dra naoe. East
FEATURE
lepth to Hater Table
let Recharge
tquifer Media
>oil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
15-3C
2-4
Sand and Gravel
Gravel
2-61
Sand and Gravel
700-1000
PESTICIDE
HEIGHT
5
4
3
5
1
4
2
RATING
7
3
6
10
9
e
6
Pesticide
Drastic Index
NUMBIR
35
12
24
50
27
32
12
192
                                                         190

-------
WESTERN MOUNTAIN RANGES
                                                              WESTERN MOUNTAIN RANGES
(lEb) Wide Alluvial Valleys (External Drainage) - West

This setting is similar to (lEa) Wide Alluvial Valleys
(External Drainage) - East except that water levels are
typically shallow because of higher precipitation and
greater ground-water recharge.  Soils tend to be
better-developed and thicker in the areas bordering the
nountain flanks, however, in the valley lowlands, gravelly
soils predoBlnate.  Pollutants Introduced at the surface in
these wide alluvial valleys tend to Migrate rapidly in the
coarser-grained deposits and travel Into and along fracture
planes.
(IT) Coastal Beaches

This hydrogeologlc setting Is characterized by  low
topographic relief, near sea level elevation and sandy
•urface soils.  These areas have very high potential
infiltration rates.  These areas are conaonly ground-vater
discharge areas, which, when utilized for fresh water
•upply, are quickly endangered by salt-water intrusion.  Due
to their very peraeable nature and thin vadoae  cone, they
are very vulnerable to pollution.  Under natural gradients,
pollution of this tone la usually discharged to the aea.
However, with Inland puaplng, flow la rapidly reversed to
the pumping center.
'ETTING 1 Eb W1de Alluvial Valleys
FEATURE
>epth to Water Table
Jet Recharge
tquifer Media
toll Media
Topography
Impact Vadose Zone
Hydraulic conductivity
RANGE
5-15
4-7
Sand arid Gravel
Gravel
2-61
5ar.^ and Gravel
700-100C,
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
9
6
e
10
9
8
6
Drastic Index
NUMBER
4S
24
24
20
S
4C
16
16C
feETTING 1 Eb Klde Allu«
FEATURE
>eptr. to Kater Table
Net Recharge
tqcifer Media
Soil Media
topography
L»p«ct Vadose Zone
kiydraulic Conductivity
jal Valleys
ttf*1 w""iT - -
RAN"
5-15
<-7
Sand and Gravel
Gravel
2-61
Sanr" and Gravel
IDC- 100:
PEST
WEIGHT
5
4
3
5
3
4
2
ICIi-'E
RATING
V
e
e
10
9
t
e
Pesticide
Dr&stic Index
i
N'UHSER
45
24
24
SO
27
32
12
21<
JETTING ! r coastal Beaches
FEATURE
lepth Co Kater
let tocharge
Iqulfer Media
loll Media
Topography
lupact Vadose gone
aydraulic Conductivity
RANGE
0-5
10*
Sand and Gravel
Sand
0-2»
Sand and Gravel
700-100C
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
10
9
e
9
10
e
6
Drastic index
NUMBER
50
36
24
IB
1C
40
1£
19'
JETTING -i r coastal Beaches
FEATURE
Xpth to Hater
Jet Recharge
tquifer Media
iOll H«di>
Topography
[•pact Vadose Zone
iydraulic Conductivity
RANGE
0-5
10->
Sari'? and Grave!
Sand
0-2i
SanS and Gravel
700-1000
Pesticide
HEIGHT
5
4
3
5
3
4
1
RATING
10
9
E
9
10
e
t
Pesticide
OrasUc Index
NUMBEf
5C
36
24
45
30
24
12
221
                                                          191

-------
WESTERN MOUNTAIN RANGES
                                                                WESTERN MOUNTAIN RANGES REGION
(1G) Swanp/Marsh

This hydrogeologlc getting IB characterized by low
topographic relief, very high water levels and high-organic
content silts and clays along the coast. In the interior
alluvial valleys, this setting may also contain evaporltlc
deposits and saline-tolerant vegetation.  In fresh-water
environments, these areas are typified by poorly drained
•oils with high water tables.  Recharge Is potentially high
and Is dependant primarily on precipitation.  The swamp
deposits very rarely eerve as significant aquifers; water  Is
usually obtained from the underlying bedrock.  However, the
swamp deposits may aerve as a source of recharge to the
aquifer.
(IB) Mud Flows

Thl* hydrogeologlc setting Is characterized by low to
moderate topography and variable thicknesses of unsorted
mixtures of boulders and pebbles in a fine-grained matrix.
The deposits originated from the adjacent mountain slopes
and tend to be thicker toward the mountains and thinner in
the valleys with no well-developed drainage pattern.  The
mud flows are typically underlain by glacial and alluvial
deposits which serve as the major aquifer.  Recharge is
moderate to low because the mud flows restrict infiltration
and may even serve to confine the underlying aquifer.
SETTING 1 G Swair.p/Marsh
FEATURE
Mpth to Hater
Mt Recharge
iquifer Media
,011 Media
topography
tmfmct V«do»e tone
Iydraulic conductivity
RANGE
0-5
4-7
Bedded SS , LS
SI1 S"qi«?nce£
Muck
0-2
i, t G w/slQ. Silt
ii! Clav
1-10C

(EIGHT
5
4
}
t
1
t
3
GENERAL
RATING
10
6
e
2
10
e
1
DruUc Index

NUMBER
SO
24
16
4
10
30
3
139
JETTING 1 II Hid Flows
FEATURE
>epth to Hater
let Recharge
tquifer MeJia
ioil Media
Topography
Impact Vedose Zone
lydraulic Conductivity
RANGE
50-75
7-10
Sand and Grave:
Silty Vxy
2-6S
SfcG w/fcjq SlH & Clay
300-700

HEIGHT
5
4
3
2
1
5
3
GENERAL
HATING
'•)
e
e
4
9
(
4
Drastic Index

NUBBEP
15
32
24
t
9
30
12
13:
IETTING 1 G Suan^'Kars!-
FEATURE
Mptfc to Hater
let Recharge
Miulfer Media
loll Media

Impact Vadoae (one
Iydraulic Conductivity

RANGE
0-5
4-7
Bedded SS, LS
SH Sequences
HKk
0-2
S fc G w/sig. Silt
and cla>
1-100
PESTICIDE
HEIGHT
!,
4
3
. 5
3
4
2
RATING
H
6
6
2
10
6
1
Pesticia*
Drastic Index
NUKBEI
SO
21
If
1C
30
24
2
151.
iETTINC 1 H MuS F10UE
FEATURE
tepth to Nater
iet Recharge
tquifer Media
Soil Media
ropoqraphy
laipact Vadoce Zone
tydraullc Conductivity
RANGE
5C-7i
7-10
PESTICIUI:
HEIGHT
5
4
Sa1 ! a-'- Grav--; 3
Siltylxiir 5
2-6V
SfcG w/aig Silt v ulay
1
4
30C-700 2
RATING
3
8
e
4
9
e
4
Pesticide
Drastic Index
NUMB£F
IS
32
24
2C
9
24
e
132
                                                            192

-------
 2.  ALLUVIAL BASINS GROUND-WATER REGION
2A
28
2C
2D
2E
2F
2G
2Ha
2Hb
21
2J
2K
Mountain Slopes
Alluvial Mountain Valleys
Alluvial Fans
Alluvial Basins (Internal Drainage;
Playa Lakes
Swamp/Marsh
Coastal Lowlands
River Alluvium With Overbank Deposits
River Alluvium Without Overbank Deposits
Mud Flows
Alternating Sandstone and Shale Sequences
Continental Deposits
                       193

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                              2.  ALLUVIAL BASINS


    (Thick alluvial deposits in basins and valleys bordered by mountains and
                           locally of glacial origin)

    The Alluvial Basins region occupies a discontinuous area of 1,025,000 km2
extending from the Puget Sound-Williamette Valley area of Washington and Oregon
to west Texas.  The region consists of an irregular alternation of basins or
valleys and mountain ranges.  From the standpoint of topography, it is useful
to contrast this region with the Western Mountain Ranges.  In the Western
Mountain ranges the high areas, the mountains, are the dominant feature.  In
the Alluvial Basins region the low areas, the basins and valleys, are the
dominant feature.  The principal exception to this generalization is the Coast
Ranges of southern California which, though included in this region,
topographically more closely resemble the Western Mountain Ranges.

     Most of the Nevada and all of the Utah parts of this region are an area of
internal drainage referred to as the Great Basin.  No surface or subsurface
flow leaves this part of the region, and all water reaching it from adjacent
areas and from precipitation is returned to the atmosphere by evaporation or by
the transpiration of plants.

     The basins and valleys are diverse in size, shape, and altitude.  They
range in altitude from about 85 m below sea level in Death Valley in California
to 2,000 m above sea level in the San Luis Valley in Colorado.  The basins
range in size from a few hundred meters in width and a kilometer or two in
length to, for the Central Valley of California, as much as 80 km in width and
650 km in length.  The crests of the mountains are commonly 1,000 to 1,500 m
above the adjacent valley floors.

     The surrounding mountains, and the bedrock beneath the basins, consist of
granite and metamorphic rocks of Precambrian to Tertiary age and consolidated
sedimentary rocks of Paleozoic to Cenozoic age.  The rocks are broken along
fractures and faults that may serve as water-bearing openings. However, the
openings in the granitic and metamorphic rocks in the mountainous area have a
relatively small capacity to store and to transmit ground water.

     The dominant element in the hydrology of the region is the thick (several
hundred to several thousand meters) layer of generally unconsolidated alluvial
material that partially fills the basins.  Except for the part of the region in
Washington and Oregon, the material was derived from erosion of the adjacent
mountains and was transported down steep-gradient streams into the basins,
where it was deposited as alluvial fans.  Generally, the coarsest material in
an alluvial fan occurs at its apex, adjacent to the mountains; the material
gets progressively finer toward the center of the basins.  In time, the fans


                                       194

-------
formed by adjacent streams coalesced to form a continuous and thick deposit of
alluvium that slopes gently from the mountains toward the center of the basins.
These alluvial-fan deposits are overlain by or grade into fine-grained flood
plain, lake, or playa deposits in the central part of most basins.  The
fine-grained deposits are especially suited to large-scale cultivation.

     The Puget Sound and Willamette Valley areas differ geologically from the
remainder of the region.  The Puget Sound area is underlain by thick and very
permeable deposits of gravel and sand laid down by streams of glacial meltwater
derived from ice tongues that invaded the area from the north during the
Pleistocene.  The gravel and sand are interbedded with clay in parts of the
area.  The Willamette Valley is mostly underlain by interbedded sand, silt and
clay deposited on floodplains by the Willamette River and other streams.

     The Alluvial Basins region is the driest area in the United States, with
large parts of it being classified as semiarid and arid.  Annual precipitation
in the valleys in Nevada and Arizona ranges from about 100 to 400 mm.  However,
in the mountainous areas throughout the region, in the northern part of the
Central Valley of California, and in the Washington-Oregon area, annual
precipitation ranges from about 400 mm to more than 800 mm.  The region also
re'ceives runoff from streams that originate in the mountains of the Western
Mountain Ranges region.

     Because of the very thin cover of unconsolidated material on the mountains
in the Alluvial Basins region, precipitation runs off rapidly down the valleys
and out onto the fans where it infiltrates into the alluvium.  The water moves
through the sand and gravel layers toward the centers of the basins.  The
centers of many basins consist of flat-floored, vegetation-free areas onto
which ground water may discharge and on which overland runoff may collect
during intense storms.  The water that collects in these areas, which are
called playas, evaporates relatively quickly, leaving both a thin deposit of
clay and other sediment transported by overland runoff and a crust consisting
of the soluble salts that were dissolved in the water.

     Studies in the region have shown that the hydrology of the alluvial basins
is more complex than that described in the preceding paragraph, which applies
only to what has been described as "undrained closed basins."  Water may move
through permeable bedrock from one basin to another, arriving, ultimately, at a
large playa referred to as a "sink" into the ground, as the name might imply,
but by evaporating, as in other playas.  In those parts of the Alluvial Basin
region drained by perennial streams, including the Puget Sound-Willamette
Valley area, the Central Valley of California, and some of the valleys in
Arizona and New Mexico, ground water discharges to the streams from the
alluvial deposits.  However, before entering the streams, water may move down
some valleys through the alluvial deposits for tens of kilometers.  A reversal
of this situation occurs along the lower Colorado River and at the upstream end
of the valleys of some of the other perennial streams; in these areas, water
moves from the streams into the alluvium to supply the needs of the adjacent
vegetated zones.
                                      195

-------
     Ground water is the major source of water in the Alluvial Basins region.
Many of the valleys in this region have been developed for agriculture.
Because of the dry climate, agriculture requires intensive irrigation.  In the
part of this region drained by the Colorado River, ground water used for
irrigation in 1975 amounted to about 6 billion cubic meters (4,864,000
acre-feet).  Most of the ground water is obtained from wells drawing from the
sand and gravel deposits in the valley alluvium.  These deposits are
interbedded with finer grained layers of silt and clay that are also saturated
with water.  When hydraulic heads in the sand and gravel layers are lowered by
withdrawals, the water in the silt and clay begins to move slowly into the sand
and gravel.  The movement, which in some areas takes decades to become
significant, is accompanied by compaction of the silt and clay and subsidence
of the land surface.  Subsidence is most severe in parts of the Central Valley,
where it exceeds 9 m in one area, and in southern Arizona, where subsidence of
more than 4 m has been observed.

     In both the Alluvial Basins and the Colorado Plateau regions, large
volumes of water are transpired by phreatophytes (water-loving plants) of small
economic value that live along streams and in other wet areas.  In an effort to
increase the amount of water available for irrigation and other uses, numerous
studies have been made to determine the volumes of water used by phreatophytes
and to devise means to control them.  A few small control efforts have been
made, but none have proven economically effective.
                                       196

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ALLUVIAL BASINS
                                                             ALLUVIAL BASINS
(2A) Mountain Slopes

This hydrogeologic Getting is characterized by steep slopes
on the side of mountains, a thin soil cover and highly
fractured bedrock.  Ground vater is obtained primarily from
the fractures in the bedrock which may be of sedimentary,
metamorphic or igneous origin.  The fractures provide only
localized sources of ground water and well yields are
typically limited even though the hydraulic conductivity may
be high because of the fractures.  Due to the steep slopes,
thin soil cover and small storage capacity of the fractures,
runoff is significant and ground-water recharge is minimal.
Ground-water levels are extremely variable, but are
typically deep.
(21) Alluvial Mountain Valleys

Tbl* hydrogeologic setting is characterized by thin bouldery
•Iluviun which overlies fractured bedrock of sedimentary,
•etaoorphic or igneous origin.  Slopes in the valley
typically range from 2 to 6 percent.  The alluvium, which is
derived from the surrounding steep slopes serves as a
localized source of water.  Water levels are moderate in
depth, but because of the low rainfall, ground-water
recharge is low.  Ground water m»y also be obtained from the
fractures la the underlying bedrock which are typically in
direct hydraulic connection with the overlying alluviu*.
SETTING 2 A Mountain Slopes
FEATURE
tepth to Water
fat Recharge
hquifer Media
.oil Media
Topography
[•pact Vadoce Zone
lydraulic Conductivity
RANGE
50-75
0-2
Me taroorpnic/ Igneous
Thin or Absent
12-181
MetaroorphJC/lqneous
1-100
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
3
i
3
10
3
4
1
Drastic Index
NUMBER
IE
4
>
20
3
20
3
li
SETTING 2 B Alluvia]
rtHTURE
Xpth to Hater
*et ftecharo*
kquifer *edia
•oil Media
Topography
[•pact Vadose Zone
lydraulic Conductivity
Mountain Valleys
RANGE
30-50
0-2
Sand and Gravel
Sand
2-6»
Said and Gravel
300-100
GENERAL
HEIGHT
S
4
3
2
1
5
3
RATING
5
1
8
9
5
e
4
Drastic Index
NUMBER
25
4
24
18
9
40
12
132
SETTING 2 A Mountair Slopes
FEATURE
)«pth tc Water
let Recharge
kqulfer Media
ioil Media
Topography
tmpact Vadose Zone
lydraulic conductivity
RANGE
50-75
0-J
Metamorphic/ Igrcoui
Thir or Abseit
12-18%
Metamorphic/Ianeoua
1-100
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
3
1
3
10
3
4
1
Pesticide
Drastic Index

NOMEEF
15
4
9
SO
9
U
2
1^
SETTING 2 B Alluvial Nountair* Valleys
FEATURE
Jepth to Mater
*et Recharge
Iquifer Media
toil Media
topography
[•pact Vadose Zone
iydraulic conductivity
RANGE
30-50
0-2
Sand ar>d Gravel
Sand
2-£«
Sand and Gravel
300-700
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
5
1
8
9
9
8
4
Pesticide
Drastic Into
NUMBEF
25
4
24
45
27
32
8
165
                                                         197

-------
ALLUVIAL BASINS
                                                              ALLUVIAL IASINS
(2C) Alluvial Fans

This hydrogeologlc setting Is characterised by gently
sloping alluvial deposits which are coarser Bear the apex In
the mountains and grade toward finer deposits Ic the basins.
Within the alluvial deposits are layers of s«nd and gravel
which extend into the central parts of the adjacent basins.
The alluvial fans serve as local sources of water and also
as the recharge area for the deposits In the adjacent basin.
The portion of the fan extending farthest into the basin Bay
function as a discharge area, especially during seasons when
the upper portion of the fan is receiving substantial
recharge.  Discharge zones are usually related to flow along
the top of stratified clay layers.  Ground-water discharge
zones are less vulnerable to pollution than recharge zones.
Where the discharge/recharge relationship is reversible the
greater vulnerability of the recharge condition must be
evaluated.  Ground-water levels are extremely variable, and
the quantity of water available Is limited because of  the
low precipitation and low net recharge.  Ground-water  depth
varies from over 100 feet near the mountains to zero in the
discharge areas.  The alluvial fans are underlain by
fractured bedrock of sedimentary, metamorphlc or igneous
origin which are typically in direct  hydraulic connection
with the overlying deposits.  Limited supplies of ground
water are available  from  the  fractures in the bedrock.
(2D) Alluvial Basins (Internal Drainage)

This hydrogeologlc setting is characterized by low
topographic relief and thick deposits of unconsolidated
alluvial material formed by coalescing alluvial fans.  The
sand and gravel deposits within the alluvium are the major
source of water in the region.  The sand and gravel is
interbedded with finer-grained layers of saturated clay and
silt which serve as a source of recharge to the sand and
gravel when head differences are significant.  The alluvium
is underlain by fractured igneous or netamorphlc rocks and
consolidated sedimentary rocks.  Although some of the
sedimentary rocks are permeable and water may be obtained
from fractures in the crystalline bedrock, the abundance of
water in the alluvium and the greater depth of the bedrock
serves to minimize uee of these sources.  Since these basins
have internal drainage, natural gradients are low near the
basin centers.  Thus, the primary direction of pollutant
migration, under normal conditions, would be downward, and
outward radially from the point of Incidence.
JETTING 2 C Alluvial fans
FEATURE
>epth to Water
let Recharge
hqulfer Media
iotl Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
50-75
0-2
Sand and Gravel
Sand
2-6%
Sand and Gravel
300-700

SETTING 2 C Alluvial Fars
FEATURE
>epth to Water
let Recharge
bquifer Media
•oil Media
Topography
Impact Vadose Zone
lydraullc Conductivity
RANGE
50-15
0-2
Sand and Gravel
sand
2-6»
Sand and Gravel
300-100
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
3
1
e
9
9
8
4
Drastic Index


NUMBER
15
4
24
16
9
40
12
122

PESTICIDE
WEIGHT
5
4
3
5
3
1
2
RATING
3
1
6
9
9
e
4
Pesticide
Drastic Indue
NONSEI
15
4
24
45
27
32
e
155
SETTING ? D Alluvial Basins
FEATURE
>epth to Water
let Recharge
Ujuifer Media
ioll Media
Topography
Impact Vadose zone
lydraulic Conductivity
RANGF
30-50
0-2
Sand and Gravel
Sand
2-6 »
S fc G w/ sig. silt
and Clay
300-100
GENERA1
tfEIGHT
5
4
3
2
1
5
3
RATING
5
1
8
9
9
6
4
Drastic Index
NUMBER
25
4
24
U
9
30
12
122
-ET-1NG 2 C Alluvial 1
=ET,ING ,irter,;a, Dra
FEATURE
>epth to Hater
Jet Recharge
hquifer Media
Soil Media
Topography
Impact Vadose zone
lydraulic Conductivity
lasiriE
naoe!
RANGE
30-50
0-2
Sa-id and Gravel
Sand
2-6«
S i G w/ sig. Silt
and Clay
300-700
PEST1CIDR
WEIGHT
5
4
3
5
3
4
2
RATING
5
1
E
9
9
6
4
Pesticide
Drastic Index

NUMBER
25
4
24
45
27
24
6
lt~
                                                           198

-------
ALLUVIAL &ASINS
                                                               ALLUVIAL 1ASINS
(2E) Playa Lakes

This hydrogeologlc setting is characterized by very low
topographic relief and thin layers of clays and other
fine-grained sediments which overlie alluvial deposit*.  Ifc*
playa areas serve as a catchment for water during periods »f
significant runoff; when the precipitation event is •ver,
the water evaporates, leaving a crust of soluble salt* on
the surface.  Ground water Is obtained from the layers of
sand which underlie the finer-grained deposits.  Water
levels are extremely variable but are typically deep.  The
playa beds are significant recharge areas due to the
ground-water "mounding" that occurs seasonally beneath the
playas.  The rate of recharge, M compared to evaporation,
is largely a function, of the permeability of the materials
forming the bed of the playa, and the precipitation
distribution over time-
Thl« hydrogeologlc setting is characterized  by low
topographic relief, very high water  levels and high  organic
content gilts and clays along the  coast.  In  the Interior
alluvial valleys, this setting may also contain evaporltlc
deposits and saline-tolerant vegetation.   In fresh-water
environments, these areas are typified by poorly drained
•oils with high water tables.  Recharge is potentially  high
and is dependant primarily on precipitation.   The swamp
deposits very rarely serve is significant aquifers;  water Is
Mtully obtained tram the underlying bedrock.   However, the
swamp deposits Bay verve as • source of recharge to  the
aquifer.
JETTING 2 E Playa Lakes
FEATURE
>epu, to Water Table
«et Recharge
icjuifer Media
toll Hedia
Topography
It pact Vadose Zone
(ydraulic Conductivity
RANGE
75-100
0-2
Sand and Gravel
Shrink/Agg. Clay
0-21
S t n w/ slg. Silt
aid clay
7&1-100C

(EIGHT
5
4
3
2
1
5
3
GENERAL
RATING
2
1
e
7
10
6
e
Drastic Index
NUMBER
10
4
24
14
10
30
It
110
SETTING 2 F Swairp/Marsh
FEATURE
>«pth to Water
tot Racharge
iqulfer Media
loll H*dl>
Topography
Lvpact Vadoae zone
lydraulic Conductivity
JUINCF
0-5
2-«
tedded SS, LE,
& Sequences
Muck
0-*
S t G w/sio. Slit
«'.-• Cla,
1-10C
GENERAL j
HEIGHT
5,
4
3
2
1
5
3
RATING
10
3
6
2
10
fe
1
Drastic Index
NUMBER
51
12
16
4
1C'
30
3
121
JETTING 2 E Plays Lakes
FEATURE
>epn. to Water Table
jet Recharge
tquifer Media
toil Media
Topography
Impact Vadose zone
Jydraulic Conductivity
RANGE
75-10C
0-2
Sand and Gravel
Shrin../Ag9. Clay
0-2«
S & G w/ slg. Silt
and Clay
700-1000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
2
1
e
7
10
c
6
Pest icidc
DrasUc Index
NUMBEF
10
4
24
35
30
24
15
13S
iETTING 2 F Swamp 'Bars*
FEATURE
Xpth to water
let Recharge
iqulfer Media
ioll Madia
Topography
[•pact Vadoae Zone
Cydraulic Conductivity
RANGE
0-5
2-4
Bedded SS, LS,
SH Soqiicive;
MucV
P-2
S fc G w/iic. Silt
and Cja_
1-100
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
10
3
t
2
10
e
i
i Pesticide
1 Drastic Inta
NUMBEI
50
12
18
10
30
24
^
14C
                                                          199

-------
ALLUVIAL JASINS

(2G) Coastal Lowlandt

This hydrogeologic setting Is characterized by thick and
very permeable deposits of gravel and sand laid down by
streams of glacial meltwater from the Pleistocene glaciers.
The gravel and sand are Interbedded with clay In parts of
the area.  Floodplain deposits and Interbedded volcanlcs are
also Included In some areas.  The are* Is characterized by
the Willamette Valley - luget Sound trough.  Recharge Is
high and water levels are thallow to moderate.  The eand and
gravels and Interbedded volcanic* both may aerve as prolific
aquifers.
 ALLUVIAL BASINS

 (2JU)  River  Alluvium With Overbank Deposits

 This hydrogeologic setting Is characterized by low
 topography and  thin to moderately thick deposits of
 flood-deposited  alluvium along portions of the river valley.
 The alluvium is  underlain by thick sequences of glacial
 materials.  Water is obtained from sand and gravel layers
 which  are interbedded with finer-grained alluvial depoilts.
I The floodplaln  is covered by varying thicknesses of
 fine-grained silt and clay called overbank deposits.  The
 overbank thickness if usually greater along major streams
 and thinner  along minor streams.   Precipitation in the
 region varies, but recharge is somewhat reduced because of
 the silty and clayey overbank soils which typically cover
 the surface. Water levels are moderately shallow.  Ground
 water  is in  direct hydraulic contact with the surface
 stream.  The alluviiw may serve as a significant source of
 water  and may alto be In direct hydraulic contact with the
 underlying glacial deposits.
SETTING 2 0 Coastal Lowlands
FEATURE
»pth to Hater

iqulfer Media
Boil H*dia



RANGE
13"- it>
iij*
sand rtn.1 CravoJ
:,,rrt
.-fc
,a.! a:.: (.?
IETTING 2 G Coastal U>ul«'
FEATURE
_ 	 '

tqulfer Mdia
•
__« — 	 —

"yaraullc Conductivity

RANGE
15-30
10-
6ar»i and Gravel
.11
Sand
	 	 •
2-6
S.i-»^ and Gravel
1000-2000
	 _«———'
PESTJClDt
HEIGHT
5
4
3
5
3
4
2
RATING
7
"
•

fc
t
Pesticide
Drastic Index
NOMBEf
-'
il
24
4^
2"
32
K
21',
JETTING 2 "" iver Ai luviurri Hit1 Ova-ban*
FEATURE
fepth to Water
let Recharge
kqul(*r Media
ioll Media
Topography
Impact Vadote zone
•fydraiilic Conductivity
RANGE
T--3L
7-10
i,jM anj Gravel
bilty Loar
0-2%
SfcG w/-.ii; bil* & Cla>
,000-2000

rfEIGHT
S
<
3
2
1
5
}
GENERAL
HATING
7
8
8
4
10
(.
8
nraxUc Inont

HOHBER
35
32
24
«
10
30
24
If
SETTING ^ llu "ivc-" AIluvliiT With Overhar.t.
FEATURE
t«pth to Water
(ct RecharQe
tqulter Media
ioil Media
Topography
[upact vadose Zone
lydraulic Conductivity
RANGE
Vj-X
7-10
Sand a'ld Grt>\'cl
bllty Ixar
0-21
MG w/i>iq Silt ( Clay
1000-2000
PESTICIDE I
WEIGHT
5
4
3
£
3
4
2
RATING
7
e
£
4
10
6
e
Pesticide
Onstlc Index
NOMBr«
3'-
32
24
20
X
24
16
IB'
                                                          200

-------
ALLUVIAL BASINS

(2Hb) River Alluvium Without Overbank Deposits

This setting is Identical to (2Ha) River A! luviun with
Overbank Deposits except that no significant fine-grained
floodplaln deposits occupy the stream valley.  This r»»ults
In significantly higher recharge where precipitation 1*
adequate and sandy soils occur at the surface.  Water levels
•re moderate to shallow in depth.  Hydraulic contact »lth
the surface stream is usually excellent, with alternating
recharge/discharge relationships varying with stream stage.
These deposits also serve as a good source of recharge to
the underlying glacial deposits.
ALLUVIAL BASINS

(21) Mud Flows

This hydrogeologic setting is characterized by low
topography and variable thicknesses of unsorted mixtures of
boulders and pebbles in a fine-grained matrix.  The deposits
originated from the adjacent mountains and tend to be
thicker toward the mountains and thinner In the valleys with
no well developed drainage pattern.  The Bud  flows are
underlain by glacial and alluvial deposits which  serve as
the major aquifer.  Recharge is moderate to low because the
mud flows restrict Infiltration and nay even  serve to
confine the underlying aquifer.
iETTING z Hb Rlver Mluvlul" without Overbank
FEATURE
Mpth to Hater
let Recharge
Klulfer Media
loll Media
•opography
[•pact Vadose lone
lydraullc Conductivity
RANGE
5-lb
10<
Sand and Gravel
Sand
o-2»
Sau-i aiiri Gravel
700-1000
GENERAL
WEIGHT
S
4
3
2
1
5
3
RATING
9
9
8
9
10
t
L
Brattle index
NUMBER
41
M
14
1b
10
40
ie
191
•rrrtNG 2 ltt> R)vl!r *!!>««• "ithwt o«srb«r*
FEATURE
>«pth to Hater
let Recharge
ujulfer Media
ioll Media
Topography
[•pact Vadote lone
lydraullc Conductivity
RANGE
5-10
10*
Sand arv? Gravel
San1
0-2V
Sand and Gravel
700-1000


• 5
4
3
5
3
4
2

•i
y
8
9
10
k
(>
Pesticide
Oraitlc Indn

45
36
24
45
30
32
12
224
SETTING 2 I ftjd Flows,
FEATURE
Mpth to Mater
let Recharqe
iqulfer Media
Mil Madi*
ropo«r*phy
Enpact vadoae tone
lydraullc conductivity
DANCE
30-50
7-10
Sort and Grsvol
Ifar
0-2.
SiG w'sj.- Silt i Clay
7UU-10K'

HEIGHT
5
4
3
2
1
5
3
GENERAL
RATING
S
t
6
5
1C
t
c
Draatlc Index
NUMBER
2.
32
24
10
10
31
It
14"-
iETTING 2 1 "Jrl rlouE
FEATURE
xpth to Hater
let Recharge
ujulfer Media
ioll Media
ropooraphy
impact Vadoce Zone
lydraullc Conductivity
RANGE
30-iu
7-10
!t.wl ancl Gr.ivrl
loam
ii-n
SkG wAiq !.i|i » Cla>
7lH)-10lt'.
PESTICIDr
WEIGHT
5
4
3
S
3
4
t
RATING
t
b
8
5
10
t
6
Pesticide
Erotic Index
NUHBEF
2j
J'
24
25
30
24
12
172
                                                          201

-------
ALLUVIAL BASINS
                                                             ALLUVIAL BASINS
(2J) Alternating Sandstone and Shale Sequences

This hydrogeologlc letting Is characterized by moderate
topographic relief and loamy soils underlain by fractured
and folded alternating layers of sedimentary rocks with a
typically high percentage of volcanic fragments-  The
bedrock nay be overlain by Interbedded unconsolldated
deposits comprised of volcanic mud flovs, alluvium, ash,
sands and silts.  The recharge Is typically high In areas of
the region where precipitation Is high.  Water levels ar«
extremely variable but are typically deep.  The bedrock
aquifer yields only small amounts of water from the
Interconnected fractures.
(2K) Continental Deposits

this hydrogeologic setting is characterized by moderate  to
lov topographic relief and thick deposits of interbedded
•and, silt and clay with discontinuous lenses of coarser
Mod and gravel which formed on broad flood plains.   The
deposits may be partially consolidated due to subsequent
deformation.  The sand and gravel deposits within the
alluvium serve as locally Important sources of water. The
deposits are underlain by sedimentary, •etamorphic and
Igneous rocks which typically do not yield significant
quantities of water.  Recharge is limited throughout most of
the area by low precipitation.
JETTING ? J Alternating Sandstone, Shale
PKATIiHi:
>epth to water
tet Recharge
tquifer Media
Soil Hedla
topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
75-100
7-U
Bed Jed SS , LS
S.I b'KTii^Hce'i
LOUT,
2-6«
Bedded LS, SS, SI
1-10C

HEIGHT
5
4
3
2
1
5
3
GENERAL
RATING
2
e
t
s
4
C
1
Drastic Index

NUMltl.K
Hi
32
16
10
9
X
3
112
.»«.,«/- 2 J Alternating Sandstone, Shale
.ETTING Se=.aences
FEATURE
>epth to water
let Recharge
tqulfer Media
ioil Media
Topography
[•pact Vadose lone
Hydraulic Conductivity
RANGE
75- IOC
7-10
PESTICIDE
WEIGHT
5
4
He=1ed S£, 1.S .
S . bcv^" icci
Loan, • 5
2-61
Br»ljr»J LS, SS, &1
1
4
1-101' 2
RATING
2
e
c
•>
9
0
1
Pesticide
Drastic Index
NUHDEf
10
32
16
25
<>
24
2
120
iETTIMC } r continental Deposits
FEATURE
>ef>th to Hater
let Recharge
tqulfer Media
toil Media
ropoijraphy
Impact Vadose Zone
lydraullc Conductivity
RANGE
15-100
0-2
Sand and Gravel
Silt Loani
6-12*
S6G w/iiq Silt fc Cld\
300-700
GENERAL
'EIGHT
5
4
3
2
1
5
3
RATING
' 2
1
8
4
5
7
4
Drastic Index
NUMBER
10
4
24
6
5
31
12
96
JETTING 2 Y Continental Deposits
FEATURE
tepth to Water
let Recharge
ujuifer Media
ioil M.dla
ropoqraphy
[•pact Vadose Zone
hydraulic Conductivity
RANGE
75-10C
0-2
IEST1C1DE
WEIGHT
5
t
Sand ajvj Gravel 3
Silt loa-i : 5
€-124
SfcG w/,,1'4 Silt t Clay
1
4
JOO-700 2
RATING
2
1
e
4
5
7
4
Pesticide
Drastic Index
NUMDEP
10
4
24
20
5
26
e
99
                                                          202

-------
 3.  COLUMBIA LAVA PLATEAU GROUND-WATER REGION
3A
3B
3C
3D
3E
3F
3G
Mountain Slopes
Alluvial Mountain Valleys
Hydraulically Connected  Lava Flows
Lava Flows Not Connected Hydraulically
Alluvial Fans
Swamp/Marsh
River Alluvium
                      203

-------
                           3.  COLUMBIA LAVA PLATEAU


 (Thick sequence of lava flows irregularly interbedded with thin unconsolidated
                      deposits and overlain by thin soils)

    The Columbia Lava Plateau occupies an area of 366,000 km2 in northeastern
California, eastern Washington and Oregon, southern Idaho, and northern Nevada.
As its name implies, it is basically a plateau standing at an altitude
generally between 500 and 1,800 m above sea level that is underlain by a great
thickness of lava flows irregularly interbedded with silt, sand, and other
unconsolidated deposits.  The plateau is bordered on the west by the Cascade
Range, on the north by the Okanogan Highlands, and on the east by the Rocky
Mountains.  On the south it grades into the Alluvial Basins region, as the area
occupied by lava flows decreases and the typical "basin and range" topography
of the Alluvial Basins region gradually prevails.  Most of the plateau in Idaho
is exceptionally flat over large areas, the principal relief being low cinder
(volcanic) cones and lava domes.  This area and much of the area in California,
southeastern Oregon, and Nevada is underlain by much of the youngest lava, some
of which is less than 1,000 years old.  In Washington the flow« are older, some
dating back to the Miocene Epoch.  Altitudes in a few of the'mountainous areas
in the plateau region exceed 3,000 m.

     The great sequence of lava flows, which ranges in thickness from less than
50 m adjacent to the bordering mountain ranges to more than 1,000 m in
south-central Washington and southern Idaho, is the principal water-bearing
unit in the region.  The water-bearing lava is underlain by granite,
metamorphic rocks, older lava flows, and sedimentary rocks, most of which are
very permeable.  Individual lava flows in the water-bearing zone range in
thickness from several meters to more than 50 m and average about 15 m.  Most
of the lava is basalt which reached the surface both through extensive fissures
and through local eruption centers.  Because basaltic lava is very fluid when
molten, it flows considerable distances down surface depressions and over
gently sloping surfaces and forms, when it solidifies, a relatively flat
surface.  Some flows are sheetlike and can be followed visually for several
kilometers along the walls of steep canyons.  Other flows, where the lava
issuing from eruption centers followed surface depressions, are lobate, or
tonguelike.

     The volcanic rocks yield water mainly from permeable zones that occur at
or near the contacts between some  flow layers.  The origin of these
flow-contact or interflow zones is complex but involves, among other causes,
the relatively rapid cooling of the top of flows, which results in formation of
a crust.  As the molten lava beneath continues to flow, the crust may be broken
into a rubble of angular fragments which  in places contain numerous holes where
gas bubbles formed and which give  the rock the appearance of a frozen froth.


                                       204

-------
The slower cooling of the central and lower parts of the thicker flows results
in a dense, flint-like rock which in the lower part contains relatively widely
spaced, irregular fractures and which grade upward into a zone containing
relatively closely spaced vertical fractures that break the rock into a series
of hexagonal columns (Newcomb, 1961).

     Periods of time ranging from less than 100 years to thousands of years
elapsed between extrusion of successive lava flows.  As a result, parts of some
flows are separated by soil zones and, at places, by sand, silt, and clay
deposited by streams or in lakes that existed on the land surface before being
buried by subsequent lava extrusions.  These sedimentary layers, where they
occur between lava flows, are commonly referred to as "interflow sediments."
Gravel, sand, silt, and clay, partly formed by the present streams and partly
of glacial origin, cover the volcanic rocks and the older exposed bedrock in
parts of the area.

     From the standpoint of th£ hydraulic characteristics of the volcanic
rocks, it is useful to divide the Columbia Lava Plateau region into two parts:
(1) the area in southeastern Washington, northeastern Oregon, and the Lewiston
area of Idaho, part of which is underlain by volcanic rocks of the Columbia
River Group; and (2) the remainder of the area, which also includes the Snake
River Plain.  The basalt underlying the Snake River Plain is referred to as the
Snake River Basalt: that underlying southeastern Oregon and the remainder of
this area has been divided into several units, to which names of local origin
are applied (Hampton, 1964).

     The Columbia River Group is of Miocene to Pliocene age and consists of
relatively thick flows that have been deformed into a series of broad folds and
offset locally along normal faults.  Movement of ground water occurs primarily
through the interflow zones near the top of flows and, to a much smaller
extent, through fault zones and through joints developed in the dense central
and lower parts of the flows.  The axes of sharp folds and the offset of the
interflow zones along faults form subsurface dams that affect the movement of
ground water.  Water reaching the interflow zones tends to move down the dip of
the flows from fold axes and to collect undip behind faults that are transverse
to the direction of movement (Newcomb, 1961).  As a result, the basalt in parts
of the area is divided into a series of barrier-controlled reservoirs which are
only poorly connected hydraulically to adjacent reservoirs.

     The water-bearing basalt underlying California, Nevada, southeastern
Oregon, and southern Idaho is of Pliocene to Holocene age and consists of
small, relatively thin flows that have been affected to a much smaller extent
by folding and faulting than has the Columbia River Group.  The thin flows
contain extensive, highly permeable interflow zones that are relatively
effectively interconnected through a dense network of cooling fractures.
Structural barriers to ground-water movement, such as those of the Columbia
River Group, are of minor importance.  This is demonstrated by conditions in
the 44,000-square-kilometer area of the Snake River Plan east of Bliss, Idaho,
which Nace (1958) thought might be the largest unified ground-water reservoir
on the North American continent.  (It is probable that this distinction is held
by the Floridan aquifer, which underlies an area of 212,000 km2 £n Alabama
Florida, Georgia, and South Carolina.  See region 11).


                                      205

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     The interflow zones form a complex sequence of relatively horizontal
aquifers that are separated vertically by the dense central and lower parts of
the lava flows and by interlayered clay and silt.  Hydrologists estimate that
the interflow zones, which range in thickness from about 1 m to about 8 m,
account for about 10 percent of the basalt.  MacNish and Barker (1976) have
estimated, on the basis of studies in the Walla Walla River basin in Washington
and Oregon, that the hydraulc conductivity along the flow-contact zones may be
a billion times larger than the hydraulic conductivity across the dense zones.
The lateral extent of individual aquifers depends on the area covered by the
different lava flows, on the presence of dikes and other igneous intrusions,
and on faults and folds that terminate the porous zones, especially in the
Columbia River Group.

     The large differences in hydraulic conductivity between the aquifers and
the intervening "confining zones" result in significant differences in
hydraulic heads between different aquifers.  These differences reflect the head
losses that occur as water moves vertically through the system.  As a result,
heads decrease with increasing depth in recharge areas and increase with
increasing depth near the streams that serve as major lines of ground-water
discharge.  The difference in heads between different aquifers can result in
the movement of large volumes of water between aquifers through the open-hole
(uncased) sections of wells.

     Much of the Columbia Lava Plateau region is in the "rain shadow" east of
the Cascades and, as a result, receives only 200 to 1,200 mm of precipitation
annually.  The areas that receive the least precipitation include the plateau
area immediately east of the Cascades and the Snake River Plain.  The areas
that receive the largest amounts of precipitation include the east flank of the
Cascades and the areas adjacent to the Okanogan Highlands and the Rocky
Mountains.  Recharge to the ground-water system depends on several factors,
including the amount and seasonal distribution of precipitation and the
permeability of the surficial materials.  Most precipitation occurs in the
winter and thus coincides with the cooler, nongrowing season when conditions
are most favorable  for recharge.  Mundorff (Columbia-North Pacific Technical
Staff, 1970) estimates that recharge may amount to 600 mm in areas underlain by
highly permeable young lavas that receive abundant precipitation.  Considerable
recharge also occurs by infiltration of water from streams that flow onto  the
plateau  from the adjoining mountains.  These sources of natural recharge are
supplemented in agricultural areas by the infiltration of irrigation water.

     Discharge from  the ground-water system occurs as seepage to streams,  as
spring flow, and by  evapotranspiration in areas where the water table is at or
near the  land  surface.  The famous Thousand Springs and other springs along the
Snake River canyon  in  southern Idaho are, in fact, among the most spectacular
displays  of ground-water discharge in the world.

     The  Columbia Lava Plateau region is mantled by mostly thin soils developed
on  alluvial and wind-laid  deposits that are well suited for  agriculture.
Because  of the arid  and semiarid  climate in most of the region, many  crops
require  intensive irrigation.   In  1970,  for  example, more than 15,000 km2
(3.75 million  acres) were  being  irrigated on the Snake River Plain.  Water for
irrigation is obtained both by diversions  from streams and by wells  that  tap


                                       206

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the lava interflow zones.  Much of the water applied for irrigation percolates
downward into the lava and then moves through the ground-water system to the
Columbia and Snake Rivers and to other streams that have deeply entrenched
channels.  The effect of this "return flow" is graphically indicated by a
long-term increase in the flow of the Thousand Springs and other large springs
along the Snake River gorge between Milner and King Hill—from about 110 m^
sec~2- in 1902, prior to significant irrigation, to more than 225 m3 sec~l
by 1942, after decades of irrigation on adjacent and upstream parts of the
plateau.  Prior to the start of irrigation, the water represented by this
increased flow reached the Snake River below King Hill through tributary
streams and natural ground-water discharge.

     The large withdrawal of water in the Columbia Lava Plateau for irrigation,
industrial, and other uses has resulted in declines in ground-water levels of
as much as 30 to 60 m in several areas.  In most of these areas, the declines
have been slowed or stopped through regulatory restrictions or other changes
that have reduced withdrawals.  Declines are still occurring, at rates as much
as a few meters per year, in a few areas.
                                      207

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COLUMBIA LAVA PLATEAU
                                                               COUMIIA LAVA PLATEAU
(3A) Mountain Slopes

This hydrogeologlc setting is characterised by steep slopes
on the side of mountains bordering the plateau, a thin soil
cover and fractured bedrock*  Steep slopes also occur on
cinder cones within the plateau.  Ground water Is obtained
primarily from the fractures In the bedrock which nay be
sedimentary, netamorphlc or Igneous origin.  The fractures
provide localized sources of ground water and well yields
are typically limited.  Due to the thin soil cover,
topography and small storage capacity of the fractures,
runoff is significant.  Ground-water levels are extremely
variable but are typically deep.  Due to lack of rainfall,
low hydraulic conductivity and steep topography, net
recharge Is very low.
SETTING 3 A Mountain Slopes
FEATURE
tepth to Hater
t*t He-charge
tquifer Media
>oil Media
Topography
Impact vadose Zone
hydraulic Conductivity
RANGE
75-100
2-4
Metanorphic/Iqneou!
Silty Loar.
12-16*
Metamorpi" ic/Jqneoji
1000-2000
GENERA:
HEIGHT
5
4
3
J
1
5
}
RATING
2
3
3
4
3
4
e
Drastic Index
NUMBER
1C
12
9
8
3
20
24
ee
(J») Alluvial Mountain Valleys

This hydrogeologlc setting Is characterized by thin bouldery
alluvium which overlies fractured bedrock of sedimentary,
metamorphlc or igneous origin.  The alluvium, which is
derived from the aourroundlng steep slopes serves as a
localized source of water.  Hater levels are typically
moderate and recharge to the (round water may be of •
significance.  Ground water may also be obtained from the
fractures in the underlying bedrock which are typically In
direct hydraulic connection with the overlying alluvium.
iETTINC 3 B Alluvial Mountain Valleys
FEATURE
tepth to Hater
Jet Recharge
Aquifer Media
Soil Media
Topography
Impact Vadose Zone
iydraulic Conductivity
RANGE
5-15
2-4
Sand ana Gravel
Gravel
3-6»
Sand and Gravel
700-100C
GENERAL
HEIGHT
5
4
3
2
1
s
3
RATING
9
1
B
10
9
a
e
Drastic Index
NUMBER
45
12
24
20
9
40
18
166
SETTING 3 A Mcsr.tain Slcf.es
FEATURE
>epth to Kater
let Recharge
aquifer Media
ioll Media
Topography
Impact Vadose lone
iydraulic Conductivity
RANGE
75-10C
2-4
Me tamer phic/Igneou:
Silty Loam
i2-ie»
Met amor phlc/loneoui
1000-200C
PEET1CIDF.
WEIGHT
5
4
3
5
3
4
2
RATING
2
3
3
4
3
4
e
Pesticide
Drastic Indent

NUMBER
1C
12
9
20
5
16
U
92
SETTING 3 E Alluvial Mountair Valleys
FEATURE
>epth to Hater
f«t Recharge
tquifer Media
ioll Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
5-15
2-4
5a^d and Gravel
Gravel
2-6>
Sand and Gravel
700-1000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
9
3
e
1C
9
e
e
Pesticide-
Drastic Index
NUMbi.fi
45
12
24
50
27
32
12
202
                                                           208

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COLUMBIA LAVA PLATEAU
                                                               COLOMBIA LAVA PLATEAU
(3C) Hydraulically Connected Lava Flows

This hydrogeologic setting is characterized by low
topographic relief, a thin sandy soil cover and a thick
sequence of successive lava flows which is irregularly
interbedded with thin unconsolldated deposits.  The lava
beds are underlain by poorly permeable bedrock of Igneous,
sedimentary or metamorphic origin.   Ground water is obtained
primarily from the interflow zones comprised of sequential,
thin, lava flows and related sedimentary deposits, cooling
fractures, lava tubes and minor structural features.  Water
levels are extremely variable but are typically deep.  Well
yields may vary from low to extremely high depending on the
characteristics of the underlying lava flows at a particular
site.  Ground-water recharge may be appreciable because the
layers of lava are interconnected hydraulically. This
setting is characterized by the deposits that occur in
southwestern Idaho (Snake River area), northern Nevada,
southeastern Oregon and extreme northeastern California,
which are of Pliocene to Holocene age.
 (3D)  L*va  Flows  Not  Connected Hydraulically

 This  hydrogeologle  setting is characterized by low
 topographic  relief,  a  thin cover of  gravel, sand,  silt  and
 clay  of  stream and  glacial origin and  a sequence of thick
 lava  flows irregularly interbedded with unconsolldated
 deposits, which  have been  deformed Into a series of folds
 and normal faults.   The lava  sequence  is underlain by poorly
 permeable bedrock of Igneous,  sedimentary or metamorphlc
 origin.  Ground  water  is obtained primarily from the
 interflow zones  of sedimentary deposits and cooling
 fractures which  occur  between  successive layers  of lava.
 Water levels are extremely  variable, but are typically  deep.
 The presence of  thick  Impermeable zones «ay produce perched
 water table conditions  or disrupt  the  hydraulic  continuity
 of water bearing zones.  The flow of ground water  is
 controlled by  locally  offset normal faults  which form a
 series of hydraulically poorly connected  reservoirs.  This
 setting is characterized by deposits that occur  in the
 Columbia River area in  southern Washington,  northern Oregon
and northern Idaho which are Miocene to Pliocene (?) in age.
•MTTkir 3 C Hydraulically Connected
>ETTING lava rlou£
FEATURE
>epth to Water
Jet Recharge
kquifer Media
Soil Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
50-75
2-4
Basalt
Silt Loam
2-6%
Basalt
2000*
GENERAL
4EIGHT
s
4
3
2
1
5
3
RATING
3
3
9
4
9
9
10
Drastic Index
NUMBER
15
12
27
8
9
45
JO
146
>M*rTur 3 D L»va Flows Not connected
.ETTING Hvar.ullcsllv
FEATURE
tepth to ffater
jet Recharge
iqulfer Media
Soil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
50-75
2-4
Bedded Ss , LS,
SH Sequences
Sand
2-6%
Bedded IS, SS, SH
1-100
GENERAL
(EIGHT
i
4
3
2
1
i
3
RATING
3
3
6
9
9
6
1
Drastic Index
NUMBED
15
12
18
18
9
30
3
105
SETTING J.v.Hjf?0™U"Uy CC™e"ed
FEATURE
jepth to Hater
Jet Recharge
"vquifer Media
soil Media
Topography
Impact Vadose 2one
hydraulic Conductivity
RANGE
50-75
2-4
Basalt
Silt Loam
2-6»
Basalt
2000*
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
3
3
9
4
9
9
10
Pesticide
Drastic Index
NUMBEC
15
12
27
20
27
16
20
157 -
'ft^rtuf 3 C- Lava Flows Not connected
.ETTING Hv<,r.ull<:illv
FEATURE
>epth to Water
4et Recharge
Aquifer Media
soil Media
Topography
Impact Vadose Zone
iydraulic Conductivity
RANGE
50-75
2-4
Bedded SS, LS ,
SH Sequences
Sand
2-61
Bedded LS, SS, SH
1-100
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
3
3
6
9
9
6
1
Pesticide
Drastic Index
NUMBER
15
12
u
45
27
24
2
145
                                                           209

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COLUMBIA LAVA PLATEAU
                                                                COUMIA UVA PLEATEAl!
(3E) Alluvial Fane

This hydrogeologic getting is characterized by alluvial
sediments which are thickest near the mountain slopes and
thin toward the Interior basin.  Topography Is steep to
moderate.  Fan sediments range from coarse, unsorted debris
on the upper slopes grading to well-sorted and stratified
gravels, sands and clays.  Recharge Is a function of
precipitation and evaporation, since the permeability of the
surface materials Is usually high.  Ground- water movement
IB generally unidirectional from the adjacent highlands
toward the basin.  Depth to ground water Is generally
moderate to deep.  These fans may serve as local sources of
water and also as the recharge area for the deposits in the
adjacent basin and the  lover extremities may  serve  as
discharge areas to local streams.
<») twmmp/Marsh

This hydrogeologic setting is characterized  by  low
topographic relief and very high water levels subject  to
seasonal drying In smaller basins.  Surflcial deposits  are
typically thin with a high organic content and  sllty or
sandy textures.  These areas commonly form where  fairly
Impermeable bedrock Impedes percolation.  Recharge  is
moderate to low because of limited precipitation  and
vertical restrictions.  These deposits do not serve as
aquifers but many provide limited recharge to the underlying
bedrock.
JETTING 3 F Alluvial Fars
PEATURP
X-pth to Hater
4et Recharge
tqulfer Media
Soil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
75-100
2-4
Sand and Gravel
Sandy Loam
6-12%
S 4 G w,' Slq. Silt
and Clay
300-700
GENERAL
HEIGHT
5
4
}
2
1
5
3
RATING
2
3
e
6
5
t
4
Drastic Index
NUMBER
10
12
24
12
5
30
12
ICC
IETTING 3 F Marsh/Swamp
FEATURE
>»pth to Hater
let Recharge
K)ulier Media
loll Media
Topography
[•pact Vadoae Cone
lydraullc Conductivity
RANGE
• 0-5
0-2
Basalt
Sand
0-2
Sand and Grav, 1
2000"
GENERAL
•EIGHT
S
4
3
2
1
S
3
RATING
•10
1
9
9
10
e
10
Draitic Index
NUMBER
sc
4
27
16
10
40
30
179
iETTINC 3 E Alluvlo
FEATURE
>epch to Hater
*et Recharge
iquifer Media
>oil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
i Fart
RANGE
75-100
2-4
Sa-.d and Gravel
Sand> Loan
6-124
S & G w/ £lg. Silt
and Clay
300-700
PESTICIDE
HEIGHT
5
4
3
f
3
4
2
RATING
2
3
8
6
5
6
4
Pesticide
Drastic Index
Nimm.i
1C
12
24
30
15
24
t
123
iCTTING 3 F Marsh/Swamp
FEATURE
topth to Natcr
let Recharge
kquifer Media
>oll Madia
Topography
[•pact Vadoae tone
lydraullc Conductivity
RANGE
0-5
0-2
Basalt
Sand
0-2
Sand and Gr«vel
2000-
PESTICIDE
WEIGHT
5
4
3
S
3
4
2
RATING
U
1
•>
i
10
a
10
Pesticide
Drastic Index
NONBEI
50
4
21
45
3C
32
20
20b
                                                              210

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COLUMBIA LAVA PLATEAU

(3G) Elver Alluvium

This hydrogeologic setting Is characterized by low
topography and deposits of alluvium along parts of valley
streams.  The alluvium yields small to moderate supplies of
ground water.  Mater Is obtained from sand and gravel layers
which are Interbedded vlth finer-grained alluvial deposits;
these are usually In direct hydraulic contact with the
stream.  Water levels are extremely variable but are
commonly moderately shallow.  Although precipitation Is low,
recharge Is significant due to the lev topography and sandy
loam soil cover.  The alluvium Is underlain by sedimentary
or igneous bedrock which My or may mot be in direct
hydraulic connection with the overlying alluvial deposits.
SETTING 3 G Fiver MluviuT
FEATURE
tepth to Water

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4.  COLORADO  PLATEAU AND WYOMING BASIS GROUND-HATER REGION
        4A
        4B
        4C
        4D
        4E
Resistant Ridges
Consolidated Sedimentary Rock
River Alluvium
Alluvium and Dune  Sand
Swamp/Marsh
                           212

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                     4.  COLORADO PLATEAU AND WYOMING BASIN


                (Thin soils over consolidated sedimentary rocks)

    The Colorado Plateau and Wyoming Basin region occupies an area of 414,000
km2 in Arizona, Colorado, New Mexico, Utah, and Wyoming.  It is a region of
canyons and cliffs; of thin, patchy, rocky soils; and of sparse vegetation
adapted to the arid and semiarid climate.  The large-scale structure of the
region is that of a broad plateau standing at an altitude of 2,500 to 3,500 m
and underlain by essentially horizontal to gently dipping layers of
consolidated sedimentary rocks.  The plateau structure has been modified by an
irregular alternation of basins and domes, in some of which major faults have
caused significant offset of the rock layers.

     The region is bordered on the east, north, and west by mountain ranges
that tend to obscure its plateau structure.  The northern part of the
region—the part occupied by the Wyoming Basin—borders the Nonglaciated
Central region at the break in the Rocky Mountains between the Laramie Range
and the Bighorn Mountains.  The region contains small, isolated mountain
ranges, the most prominent being the Henry Mountains and the La Sal Mountains
in southeastern Utah.  It also contains, rather widely scattered over the
region, extinct volcanoes and lava fields, the most prominent example being the
San Francisco Mountains in north-central Arizona.

     The rocks that underlie the region consist principally of sandstone,
shale, and limestone of Paleozoic to Cenozoic age.  In parts of the region
these rock units include significant amounts of gypsum (Calcium sulfate).  In
the Paradox Basin in western Colorado the rock units include thick deposits of
sodium- and potassium-bearing minerals, principally halite (sodium chloride).
The sandstones and shales are most prevalent and most extensive in occurrence.
The sandstones are the principal sources of ground water in the region and
contain water in fractures developed both along bedding planes and across the
beds and in interconnected pores.  The most productive sandstones are those in
which calcium carbonate or other cementing material has been deposited only
around the point of contact of the sand grains.  Thus, many of the sandstones
are only partially cemented and retain significant primary porosity.

     Unconsolidated deposits are of relatively minor importance in this region.
Thin deposits of alluvium capable of yielding small to moderate supplies of
ground water occur along parts of the valleys of major streams, especially
adjacent to the mountain ranges in the northern and eastern parts of the
region.  These deposits are partly of glacial origin.  In most of the remainder
of the region there are large expanses of exposed bedrock, and the soils, where
present, are thin and rocky.
                                      213

-------
     Erosion has produced extensive lines of prominent cliffs in the region.
The tops of these cliffs are generally underlain and protected by resistant
sandstones.  Erosion of the domes has produced a series of concentric, steeply
dipping ridges, also developed on the more resistant sandstones.

     Recharge of the sandstone aquifers occurs where they are exposed above the
cliffs and in the ridges.  Average precipitation ranges from about 150 mm in
the lower areas to about 1,000 mm in the higher mountains.  The heaviest
rainfall occurs in the summer in isolated, intense thunderstorms during which
some recharge occurs where intermittent streams flow across sandstone outcrops.
However, most recharge occurs in the winter during snowmelt periods.  Water
moves down the dip of the beds away from the recharge areas to discharge along
the channels of major streams through seeps and springs and along the walls of
canyons cut by the streams.

     The condition described in the preceding paragraph, whereby intermittent
streams serve as sources of ground-water recharge and perennial streams serve
as lines of ground-water discharge, is relatively common in this region and in
the Alluvial Basins region to the south and west.  Streams into which ground
water discharges are referred to as gaining streams.  Conversely, streams that
recharge ground-water systems are referred to as losing streams.  The gaining
streams and the losing streams may be different streams.  However, in many
areas the same stream may be a gaining stream in its headwaters, especially
where these drain the wetter mountainous areas, become a losing stream as it
flows onto the adjoining lower areas, and, ultimately, become a gaining stream
again in its lowermost reaches where it serves as a regional drain.

     The quantity of water available for recharge is small, but so are the
porosity and the transmissivity of most of the sandstone aquifers.  Because of
the general absence of a thick cover of unconsolidated rock in the recharge
areas, there is relatively little opportunity for such materials to serve as a
storage reservoir for the underlying bedrock.   The water in the sandstone
aquifers is unconfined in the recharge areas and is confined down-dip.  Because
most of the sandstones are consolidated, the storage coefficient in the
confined parts of the aquifers is very small.  This small storage coefficient
together with the small transmissivities, results in even small rates of
withdrawal causing extensive cones of depression around pumping wells.

     Springs exist at places near the base of the sandstone aquifers where  they
crop out along the sides of canyons.  Discharge  from the springs results in
dewatering the upper parts of the aquifers for some distance back from the
canyon walls.

     The Colorado Plateau and Wyoming Basin is a dry, sparsely populated region
in which most water supplies are obtained from the perennial streams that flow
across it  from the bordering mountains.  Less than 5 percent of the water needs
are supplied by ground water, and the development of even small ground-water
supplies requires the application of considerable knowledge of the occurrence
of both rock units and their structure, and of the chemical quality of the
water.  Also, because of the large surface relief and the dip of the aquifers,
wells even for domestic or small livestock supplies must  penetrate  to depths of
a few hundred meters in much of the area.  Thus, the development of


                                       214

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ground-water supplies is far more expensive than in most other parts of the
country.  These negative aspects notwithstanding, ground water in the region
can support a substantial increase over the present withdrawals.

     As in most other areas of the country underlain by consolidated
sedimentary rocks, mineralized (saline) water-that is, water containing more
than 1,000 mg/1 of dissolved solids—is widespread in occurrence.  Most of the
shales and silts tones contain mineralized water throughout the region and below
altitudes of about 2,000 m.  Freshwater—water containing less than 1,000 mg/1
of dissolved solids—occurs only in the most permeable sandstones and
limestones.  Much of the mineralized water is due to the solution of gypsum and
halite by water circulating through beds that contain these minerals.  Although
the aquifers that contain mineralized water are commonly overlain by aquifers
containing freshwater, this situation is reversed in a few places where
aquifers containing mineralized water are underlain by more- permeable aquifers
containing freshwater.
                                       215

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COLORADO PLATEAU AND WYOMING BASIN
                                                                COUMADO PLATEAU AND WYOMING BASIN
(*A) Resistant Ridges

This hydrogeologic setting Is characterized by moderate  to
steep slopes, and a very thin soil cover which overlies
dipping fractured consolidated sedimentary rocks.  The
resistant sandstones cap the cliffs and ridges and form
hogbacks.  These sane sandstone units comprise the aquifers
that are the principal sources of ground water.  The
aquifers receive recharge In the areas where the sandstone
Is exposed at the surface.  Recharge Is low because of the
topography and the lack of precipitation la the area.  Water
levels are extremely variable, but are typically deep.
(*») Consolidated Sedimentary Rocks

This bydrogeologlc setting Is characterized by  alternating
layers of moderately-dipping, fractured, consolidated,
sedimentary rocks covered by a sandy soil  layer which
commonly weathers to a sandy loam.  The sandstones  serve  as
the principal source of ground water.  The water  Is obtained
from fractures developed along bedding planes and from
within the pore spaces.  Water levels are  typically deep  and
recharge Is low because of the lack of precipitation.
Intermittent streams often serve as sources of  recharge;
however, the major source of recharge occurs In the
resistant ridges where the bedrock is exposed.  The
MBdstones My also be confined, with small storage values
and lev yield wells.
iETTING 4 A Resistant Ridaes
FEATURE
tepth to Niter
let Recharoe
kqulfer Media
Soil Media
Topography
[•pact Vadose Zone
lydraulic conductivity
RANGE
75-100
0-2
Thin Bedded SS , LS
SH Sequences
Thin or Absent
12-181
Bedded LS , SS , SH
1-100
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
2
1
6
10
3
e
i
Drastic Index
NUMBER
10
4
IE
20
3
30
3
Be
SETTING 4 B Consolidated Sedimentary '
FEATURE
Xpth to Hater
Jet Recharge
tqulfer Hedla
Soil Media
ropography
[•pact Vadose Zone
Jydraulic Conductivity
RANGE
50-75
0-2
SH Sequences
Sandy Loam
6-12»
Bedded LS, SS, SH
1-100
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
3
1
6
t
5
6
1
Drastic Index
NUMBER
15
4
18
12
5
3C
3
f
SETTING 4 A Resistant Ridges
FEATURE
)epth tc Hater
vet Recharge
Aquifer Media
Soil Media
Topography
Empact Vadose Zone
fydroulic Conductivity
RANGE
75-100
0-2
Thir Bedded SS, LS,
SK Sequences
Thir. or Absent
12-181
Bedded LS, cs, SH
1-100
PESTICIDE
HEIGHT
5
4
3
5
3
4
J
RATING
2
1
e
10
3
6
1
Pesticide
OraaUc Index
NUMBEI
10
4
18
50
9
24
2
117
SETTING * B Consolidated Sedimer.tary
FEATURE
>epth to Water
»et Recharge
Aquifer Media
Soil Media
Topography
[•pact Vadose Zone
Jydraullc Conductivity
RANGE
50-75
0-2
SK Sequences
Sandy LOarr
6-12*
Beaded LS, SS, SK
1-100
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
3
1
e
6
5
6
1
Pesticide
Orutlc Index
NUMBER
15
4
u
30
15
24
2
ioe
                                                             216

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COLORADO PLATEAU AND WYOMING  BASIN

(4C) River Alluvium

Thle hydrogeologlc getting  Is characterized  by  low
topography and deposits of  alluvium along parts of valleys
of perennial and Intermittent streams.  The  alluvium yields
small to moderate supplies  of ground water.  Water Is
obtained from aand and gravel layers which are  Interbedded
with finer- grained alluvial deposits; these are usually In
direct hydraulic contact with the perennial  or intermittent
stream.  Water levels are extremely variable but are
commonly moderately shallow.  Although precipitation la low,
recharge is significant due to the low topography and sandy
loam aoil cover.  The alluvium is underlain by consolidated
sedimentary rocks which are often in direct hydraulic
connection with the overlying deposits.
OOUBADO PLATEAU AND WYOMING BASIN

(40) Alluvium and Dune Sand

This •ya'rogeologlc aetting is characterized  by moderate
tomography derived from unconsolldated alluvial  sediments
that have formed under various deposltional  environments.
These alluvial deposits vary from lacustrine deposits  in the
Wyoming Basin area to dune sands in the Navajo area  of
northern Arizona and northwestern New Mexico.  Much  of the
entire region is covered by thin alluvium.   The  hydraulic
conductivity of the alluvium la high throughout  the  area,
including the aand dunes portion.  Recharge  is limited by
low precipitation and evaporation.  The alluvium serves as
moderate water supplies in some areas, provides  some
•tscharge to streams, and acts as atorage for recharge to
    •r aquifers.
SETTING 4 C River Alluvium
FEATURE
iepth to Water
4et Recharge
Aquifer Media
ioil Media
Topography

lydraulic conductivity
RANGE
15-30
4-7
Sand and Gravel
Sandy Loar
2-6%
E t G v/ srf , Silt
700-100C
GENERA!
HEIGHT
5
4
3
2
1
5
3
RATING
7
i
B
6
9
6
6
Drastic Index
NUMBER
35
24
24
12
9
3C
18
152
SETTING 4 D Alluviuir and Sunf Sami
FEATURE
Wpth to Water
fet Recharge
tqulfer Media
ioil Media
Topography
Impact Vadose Zone
Jydraulic Conductivity
RANGE
50-75
0-2
Sand and Gravel
Sand
6-12%
S 4 G w/ iiq. Silt
and Clay
100-300
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
3
1
e
9
S
t
2
Drastic Index
Honors
15
4
24
16
5
30
6
102
SETTING 4 C River Alluviur
FEATURE
3epth to Hater
jet Recharge
aquifer Media
>oil Hedie
Topography
Impact V*doae lone
hydraulic conductivity
RANGE
15-30
4-7
Sand and Gravel
Sandy Loatt
2-6»
S * G v/ sig. Silt
and Clay
700-1000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
9
e
e
6
9
6
6
Pesticide
Dractic Inane
NUMHEf
45
24
24
30
27
24
12
176
JETTING 4 T A^luviur an3 Dune Sand
PEMURE
>epth to Water
Jet Recharoe
Iquifer Media
toil Media
Topography
Impact Vadoae Zone
hydraulic Conductivity
RANGE
50-75
0-2
Sa:ic3 and Gravel
Sand
6-12%
S t G w/ sig. Silt
and Clay
100-300
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
3
1
e
9
s
6
2
Pesticide
Drastic Index
NUMBVF
15
4
24
45
15
24
4
131
                                                            217

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COLORADO PLATEAU AND WYOMING BASIN

(4E) Swamp/Marsh

ThiB hydrogeologic setting is characterized by low
topographic relief and very high water levels subject to
seasonal drying in smaller basins.  Surflcial deposits have
a high organic content and silty or sandy textures. These
areas commonly form where fairly Impermeable bedrock Impedes
percolation.  Large wetland areas may also be formed where
small creeks or other drainage features have been dammed by
silt or vegetation.  Recharge is potentially high and Is
dependent primarily on precipitation.  The thickness of the
unconsolldated deposits varies.  Where thick, these deposits
may serve as an aquifer.  In other areas, the underlying
deposits serve as the aquifer with the overlying deposits
providing recharge.
lETTING 4 t Swamp, Marsh
flATORE
•epth to Water
let Rachar?;*
iqulfer Media
loll Media
Topography
[•pact vadose zone
lydraullc Conductivity
RANGE
' 0-5
7-10
Sand and Gravel
Sam
0-2
S 4 G W/MU. fall'
aiil any
300-T ,a
GENERAL
*EICHT
s
4
3
1
1
5
1
RATING
1O
8
B
9
10
6
4
Drastic Index
NUMBER
50
32
24
IS
10
30
12
nt
IETTIMG 4 E SMinp/Marth
FEATURE
topth to Mater
let Recharge
kquifer Media
ioll Hajdla
topography
[•pact Vadoie tone
rjrdraullc conductivity
RANGE
0-5
1-10
Sane! and Gravel
Sand
0-2
s & G w/slg. Silt
antl Clay
300-700
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
K
b
t
d
in
(,
4
Pesticide
Pnatlc Me»
HUMBEI
50
32
24
45
10
24
t
213
                                                             218

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    5.   HIGH PLAINS GROUND-WATER REGION
5A
5B
5C
5D
5E
5F
5Ga
5Gb
5H
Ogallala
Alluvium
Sand Dunes
Playa Lakes
Braided River Deposits
Swamp/Marsh
River Alluvium With Overbank Deposits
River Alluvium Without Overbank Deposits
Alternating Sandstone, Limestone and
  Shale Sequences
                      219

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                                5.   HIGH PLAINS


           (Thick alluvial deposits over fractured sedimentary rocks)

    The High Plains region occupies an area of 450,000 km2 extending from
South Dakota to Texas.  The plains are a remnant of a great alluvial plain
built in Miocene time by streams that flowed east from the Rocky Mountains. The
plain originally extended from the foot of the mountains to a terminous some
hundreds of kilometers east of its present edge.  Erosion by streams has
removed a large part of the once extensive plain, including all of the part
adjacent to the mountains, except in a small area in southeastern Wyoming.

     The original depositional surface of the alluvial plain is still almost
unmodified in large areas, especially in Texas and New Mexico, and forms a
flat, imperceptibly eastward-sloping tableland that ranges in altitude from
about 2,000 m near the Rocky Mountains to about 500 m along its eastern edge.
The surface of the southern High Plains contains numerous shallow circular
depressions, called playas, that intermittently contain water following heavy
rains.  Some geologists believe these depressions are due to solution of
soluble materials by percolating water and accompanying compaction of the
alluvium.  Other significant topographic features include sand dunes, which are
especially prevalent in central and northern Nebraska, and wide, downcut
valleys of streams that flow eastward across the area from the Rocky Mountains.

     The High Plains region is underlain by one of the most productive and most
intensively developed aquifers in the United States.  The alluvial materials
derived from the Rocky Mountains, which are referred to as the Ogallala
Formation, are the dominant geologic unit of the High Plains aquifer.  The
Ogallala ranges in thickness from a few meters to more than 200 m and consists
of poorly sorted and generally unconsolidated clay, silt, sand, and gravel.

     Younger alluvial materials of Quaternary age overlie the Ogallala
Formation of late Tertiary age in most parts of the High Plains.  Where these
deposits are saturated, they form a part of the High Plains aquifer; in parts
of south-central Nebraska and central Kansas, where the Ogallala is absent,
they comprise the entire aquifer.  The Quaternary deposits are composed largely
of material derived from the Ogallala and consist of alluvial deposits of
gravel, sand, silt, and clay and extensive areas of sand dunes.  The most
extensive area of dune sand occurs in the Sand Hills area north of the Platte
River in Nebraska.

     Other, older geologic units that are hydrologically connected to the
Ogallala thus form a part of the High Plains aquifer include the Arikaree Group
of Miocene age and a small part of the underlying Brule Formation.  The
                                      220

-------
Arikaree Group underlies the Ogallala in parts of western Nebraska,
southwestern South Dakota, southeastern Wyoming, and northeastern Colorado.  It
is predominantly a massive, very fine to fine-grained sandstone that locally
contains beds of volcanic ash, silty sand, and sandy clay.  The maximum
thickness of the Arikaree is about 300 m, in western Nebraska.  The Brule
Formation of Oligocene age underlies the Arikaree.  In most of the area in
which it occurs, the Brule forms the base of the High Plains aquifer.  However,
in the southeastern corner of Wyoming and the adjacent parts of Colorado and
Nebraska, the Brule contains fractured sandstones hydraulically interconnected
to the overlying Arikaree Group; in this area the Brule is considered to be a
part of the High Plains aquifer.

     In the remainder of the region, the High Plains aquifer is underlain by
several formations, ranging in age from Cretaceous to Permian and composed
principally of shale, limestone, and sandstone.  The oldest of these, of
Permian age, underlies parts of northeastern Texas, western Oklahoma, and
central Kansas and contains layers of relatively soluble minerals including
gypsum, anhydrite, and halite (common salt) which are dissolved by circulating
ground water.  Thus, water from the rocks of Permian age is relatively highly
mineralized and not usable for irrigation and other purposes that require
freshwater.  The older formations in the remainder of the area contain
fractured sandstones and limestones interconnected in parts of the area with
the High Plains aquifer.  Although these formations yield freshwater, they are
not widely used as water sources.

     Prior to the erosion that removed most of the western part of the
Ogallala, the High Plains aquifer was recharged by the streams that flowed onto
the plain from the mountains to the west as well as by local precipitation.
The only source of recharge now is local precipitation, which ranges from about
400 mm along the western boundary of the region to about 600 mm along the
eastern boundary.  Precipitation and ground-water recharge on the High Plains
vary in an east-west direction, but recharge to the High Plains also varies in
a north-south direction.  The average annual rate of recharge has been
determined to range from about 5 mm in Texas and New Mexico to about 100 mm in
the Sand Hills in Nebraska, This large difference is explained by differences
in evaporation and transpiration and by differences in the permeability of the
surficial materials.

     In some parts of the High Plains, especially in the southern part, the
near-surface layers of the Ogallala have been cemented with lime (calcium
carbonate) to form a material of relatively low permeability called caliche.
Precipitation on areas underlain by caliche soaks slowly into the ground.  Much
of this precipitation collects in playas that are underlain by silt and clay,
which hamper infiltration, with the result that most of the water is lost to
evaporation.  During years of average or below average precipitation, all or
nearly all of the precipitation is returned to the atmosphere by
evapotranspiration.  Thus, it is only during years of excessive precipitation
that significant recharge occurs and this, as noted above, averages only about
5 mm per year in the southern part of the High Plains.

     In the Sand Hills area of Nebraska, the lower evaporation and
transpiration and the permeable sandy soil results in about 20 percent of the
precipitation (or about 100 mm annually) reaching the water table as recharge.

                                      221

-------
     The water table of the High Plains aquifer  has a  general  slope toward the
southeast of about 2 to 3 m per km (10 to 15  ft  per mile).  Gutentag and Weeks
(1980) estimate, on the basis of the average  hydraulic gradient and aquifer
characteristics, that water moves through the aquifer  at  a rate of about 0.3 m
(1 ft) per day.

     Natural discharge from the aquifer occurs to  streams, springs, saline
lakes and seeps along the eastern boundary of the  plains, and  by evaporation
and transpiration in areas where the water table is within a few meters of the
land surface.  However, at present the largest discharge  is probably through
wells.  The widespread occurrence of permeable layers  of  sand  and gravel, which
permit the construction of large-yield wells  almost any place  in the region,
has led to the development of an extensive agricultural economy largely
dependent on irrigation.  Gutentag and Weeks  (1980) estimate that in 1977 about
3.7 x 1010m3 (30,000,000 acre-ft) of water was pumped  from more than
168,000 wells to irrigate about 65,600 km2 (16,210,000 acres).  Most of this
water is derived from ground-water storage, resulting  in  a long-term continuing
decline in ground-water levels in parts of the region  of  as much as 1 m per
year.  The lowering of the water table has resulted in a  10 to 50 percent
reduction in the saturated thickness of the High Plains aquifer in an area of
130,000 km2 (12,000 mi2).  The largest reductions  have occurred in the
Texas panhandle and in parts of Kansas and New Mexico.

     The depletion of ground-water storage in the  High Plains, as reflected in
the decline in the water table and the reduction in the saturated thickness, is
a matter of increasing concern in the region. However, from the standpoint of
the region as a whole, the depletion does not yet  represent5**  large part of the
storage that is available for use.  Weeks and Gutentag (1981)  estimate, on the
basis of a specific yield of 15 percent of the total volume of saturated
material, that the available (usable) storage in 1980  was about 4 x I0^2m3
(3.3 billion acre-ft).  Luckey, Gutentag, and Weeks (1981) estimate that this
is only about 5 percent less than the storage that was available at the start
of withdrawals.  However, in areas where intense irrigation has long been
practiced, depletion of storage is severe.
                                     222

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HIGH PLAINS

(5A) Ogallala

This hydrogeologic setting is characterized by moderately
flat topography and thick deposits of poorly-sorted,
semi-consolidated, clay, silt, sand and gravel that may be
underlain by fractured sedimentary rock which is in
hydraulic connection with overlying deposits,  m come parts
of the High Plains, especially in the southern part, shallow
zones of the unconsolidated deposits have been cenented with
calcium carbonate.  The permeability of this caliche layer
varies with the degree of cementation, fracturing and clay
mineral content.  Precipitation averages less than 20 Inches
per year and recharge is very low throughout most of this
vater- deficient area.  The bedrock and the overlying
semi-consolidated deposits both serve as extensive sources
of ground water. Water levels are typically deep, but
extremely variable.  The Ogaliala is underlain by bedded,
unconsoiidated deposits of fractured sandstone, limestone,
volcanic ash, silty sand, sandy clay and shales.  These
formations are hydraulically connected to the Ogaliala and
the overlying alluvium, from which they derive their
recharge.
     •AIMS

(SB) Alluvium

Thin hydrogeologic vetting Is characterized by low to
moderate relief, and Is comprised of gravel, sand, silt and
clay alluvial sediments.  These deposits are variable in
thickness.  They form, where aaturated, a portion of the
High Plains aquifer, and locally all of It where the
Ogaliala Is missing.  Water levels are variable, but
typically deep.  Recharge 1* limited throughout most of the
area by low precipitation.  The shallow caliche layer of
cemented, unconsolidated deposits also develops in the
alluvium In some localities.  Similar to the Ogaliala,
recharge to the deeper sandstones Is through the alluvial
deposits'
irmieG 5 A Ogallali
FEATURE
»pth to Water
Jet Recharge
^ifer Media
loll Media
Topography
tapact Vedose zone
lydraulic Conductivity
BANGE
75-100
0-2
Sand and Gravel
Shrink/Agq. Clay
2-6%
S t G w/ Gig. Silt
ana clay
700-1000
GENERAL
•EIGHT
S
4
3
2
1
S
3
RATING
2
1
6
7
9
6
6
tn»uc Index
NUMBER
to
4
24
14
9
30
18
109
SETTING 5 A Cc.ll.lala
FEATURE
tepth to Hate:

C
e
Pesticide
(reatlc Index
HUNBEI
10
4
24
35
27
24
12
136
SETTING S B Alluvium
FEATURE
tepth to Water
let Hector?*
iqulfer Media
ioll Media
Topography
[•pact Vado*e Zone
tydraulic conductivity
RANGE
50-75
0-2
Sand and Gravel
Sandy Loatr
0-2%
S t G w/ slg.
Silt end Clay
JOO-700
GENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
3
1
e
e
10
e
4
Drastic Index
NUMBER
15
4
24
12
10
30
12
107
SETTING S B AUuviuit
FEATURE
>epth to Hater
iet Recharoe
kqulfer Kedia
Soil Media
ropogrephy
[•pact Vadose Zone
lydreullc Conductivity
RANGE:
50-75
0-2
Sar.d and Gravel
Sandy Loar
0-2%
5 1 G w/ tie.
Silt and Clay
300-700
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
3
1
e
6
10
e
4
Pesticide
Drastic Index
NUMBER
15
4
24
3C
30
24
8
135
                                                           223

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HIGH PLAINS
                                                                UGH PLAINS
(5C) Sand Dunes

This hydrogeologic setting is characterized by hilly
topography comprised of sand dunes which overlie thick
poorly-sorted sand and gravel deposits.  The sand dunes are
in direct hydraulic connection with the underlying deposits.
Because of their relatively low water table, these dunes do
not serve as sources of ground water, but serve as local
recharge areas.  In contrast to other areas of tbt ligh
Plains, recharge rates are higher due to lower evaporation
and peneable sandy soils, but are limited by available
precipitation.
(5D) riaya Lakes

This hyirogeologic setting is characterized by low
topographic relief and thin layers of clays and other
fine-grained sediments which overlie the alluvial deposits.
The playa areas serve as a catchment for water during
periods of significant runoff.  Ground water is obtained
from the layers of sand which underlie the finer-grained
deposits. Water levels are extremely variable, but are
typically deep.  The playa beds are significant recharge
•roas doe to the rainfall that collects in them.  The rate
of recharge, as compared to evaporation, is largely a
function of the permeability of the materials forming the
bed of the playa, and the precipitation distribution over
tine.
SETTING 5 C Sand Dunes
FEATURE
>epth to Hater
let Recharge
golfer Media
ioil Media
Topography
Impact Vadose Zone
lydraulic conductivity
RANGE
30-50
0-2
Sand and Gravel
Sand
2-6%
Sand and Gravel
2000*
GENERAL
WEIGHT
5
4
3
2
1
S
3
RATING
5
1
e
9
9
B
10
Drastic Index
NUMBER
25
4
24
ie
9
40
30
150
iETTING S D Playe Lakes
FEATURE
lepth to Mater
let Recftarge
iquifer Media
Soil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
75-100
0-2
Sand and Gravel
Shrink/Agq. Clay
0-2»
S fc G v/ Slo .
Silt and Cla>
700-1000
GENERAL
(EIGHT
i
t
3
2
1
S
3
RATINE
2
1
8
7
10
6
6
Drastic Index
NUMBER
10
4
24
14
10
3C
16
110
iETTING 5 C Sand Djnes
FEATURE
>eptn to water
4et Recharge
Aquifer Media
Soil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
30-50
0-2
Said and Gravel
Sand
2-64
Sand and Gravel
2000*
PESTICIDE
HEIGHT
t
4
3
5
3
4
1
RATING
5
1
G
9
9
e
10
Pesticide
Drastic Inde*
NUHBEf
25
4
24
45
27
32
20
177
iETTING 5 D Playa Lakes
FEATURE
)epth to Water
let Recharge
Aquifer Media
Soil Media
Topography
[•pact Vadose zone
lydraulic Conductivity
RANGE
75-100
0-2
Sand and Gravel
Shrink/Ago, clay
0-21
S 1 G w/ Slg.
Silt and Clay
700-1000
PESTICI2E
HEIGHT
5
4
3
5
3
4
2
RATING
2
1
E
7
10
6
6
Pesticide
Drastic Index
NUHBEf
1C
4
24
35
30
24
12
139
                                                             224

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HIGH PLAINS
                                                               HIGH PLAINS
(5E) Braided River Deposits

This hydrogeologic setting is characterized by deposits of
alluvlun which occur within the flood plain of streams and
rivers.  The stream is characterized by a low gradient, wide
channel and a series of Interconnected shallow channels
which fora a braided pattern.  Water levels are typically
shallow, and some streams nay be Intermittent.  The river
alluvium sometimes serves as a significant source of ground
water but is most important as a source of recharge since it
overlies more productive semi-consolidated deposits.  The
underlying deposits are In direct hydraulic connection with
the overlying alluvium, so the potential for pollution of
the aquifer Is high.  Although precipitation, which averages
less than 20 inches per year is a limiting factor, recharge
•ay be very high due to seasonal or perennial stream flow on
these very permeable deposits.
 (SP)  limp/Harsh

 This  hydrogeologic setting is characterized by low
 topographic  relief and high water levels In floodplalns
 Immediately  adjacent to perennial streams. The deposits
.contain moderate amounts of organic material within the
 •andy river  alluvium.   mecharge Is potentially high and Is
 dependant  primarily on river infiltration.  The deposits may
 serve as aquifers or May recharge the underlying aquifer.
JETTING 5 E Braided River Deposits
FEATURE
iepth to Water
Jet Recharge
wjuifer Media
soil Media
Topography
Impact Vadose zone
lydraulic conductivity
RANGE
5-15
4-7
Sand and Gravel
Sand
0-2«
San] and Gravel
1000-200C
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
9
t
8
9
10
6
e
Drastic Xndnt
NUMBER
45
24
24
18
10
40
24
its
IFTTING 5 r Swamp/Marsh
rtATURE
%pth to Hater
let Recharge
tqulfer Hedia
loll Media
Topography
:«t>act Vadon lone
lydraullc conductivity
RANGE
0-5
7-10
SaM and Gravel
Sand
0-2
S<*,>- a H Grave]
'000-2000
CCNtRAL
(EIGHT
5
4
i
2
1
S
3
RATING
1t
e
e
9
10
e
a
Drastic Inln
NUMBER
50
32
24
is
10
4C
24
196
SETTING 5 E Braided River Deposits
FEATURE
>epth tc Water
tet Recharge
Iquifer Media
Boil Media
Topography

Sydraulic Conductivity
RANGE
5-15
4-7
Sar.d and Gravel
Sand
0-2%
Sand and Gravel
1000-2000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
9
e
e
9
10
8
1
Pesticide
Drastic Iran
NOMBEf
45
24
24
45
30
32
16
2U
ICTTING 5 r Swar.p/Karsh
FEATURE
Xpth to Mater
let Recharge
kquiftr Media
loll Media
Topography
Imffct vaOoM tone
lydrwillc Conductivity
RANGE
0-5
7-10
Sand and Gravel
Sand
0-2
Sand and Gravel
1000-2000
PESTICIDE
WEIGHT
5
4
)
S
3
4
2
RATING
in
b
r
".
if.
b
e
Pesticide
Drutie Intax
NUKBEI
X
32
21
4:
30
32
16
229
                                                            225

-------
HIGH PLAINS
                                                               IIGH fLAINS
(5Ga) River Alluvium With OverbanV. Deposits

This hydrogeologic setting is characterized by low to
moderate topography and thin to moderately thick deposits of
alluvium along parts of river valleys.  The alluvium is
underlain by either unconsolidated deposits or fractured
bedrock of sedimentary or igneous origin.  Water is obtained
from sand and gravel layers which are interbedded with
finer-grained alluvial deposits.  The alluvium nay or Bay
not be in direct hydraulic connection with the underlying
units.  The alluvium typically serves as a significant
source of water.  The flood plain is covered by varying
thicknesses of fine-grained silt and clay, called overbank
deposits.  The overbank thickness is usually greater along
major streams and thinner along minor streams but typically
averages approximately 5 to 10 feet.  Recharge is limited
throughout most of the area by low precipitation.  Water
levels are typically moderately shallow and may be
hydraulically connected to the stream or river.
(5Cb) tiver Alluvium Without Overbank Deposits

This netting is Identical to (SGa) River Alluvium with
Overbank Deposits except that no significant fine-grained
floodplaln deposits occupy the stream valley.  This normally
would result in significantly higher recharge except that
precipitation is limited in the area.  Where Irrigation is a
factor, recharge will occur more easily in these deposits
because of the sandy (oils which occur at the surface.
Water levels are moderate to shallow where streamflow exists
because the hydraulic connection with the surface stream is
usually excellent.  Alternating recharge/discharge
relationships will vary with the stream stage.
SETTING 5 Ga River Alluvluir. With
FEATURE
fepth to Mater
Jet Recharge
tqulfer Media
>oil Media
Topography
Impact Vadoco Zone
fydraulic Conductivity
RANGE
15-30
0-2
Sand and Gravel
Silty Loair
0-2
S4G w/sjo Silt t Clay
700-10UC

HEIGHT
5
4
3
2
1
5
3
GENERAL
RATING
7
1
8
4
10
6
e
Drastic Index

NUM13! K
35 ,
4
24
e
10
30
16
I?''
;rrn»c 5 Gt River MU
FEATURE
>epth to Hater
Jet Recharge
tqulfer Media
Soil Media
Topography
Impact Vadose Zone
Hydraulic Conductivity
vium Without
RANGE
5-15
0-2
Sand and Gravel
Sandy Loam
o-:
S*G W/S.M) Silt b CLoy
700-100'-
GENERAi
HEIGHT
5
4
3
2
1
5
3
HATING
9
1
e
e
1C
e
t
Drastic Index
NUHBE)*
t'j
1
24
12
10
30
18
,«
1ETTING S Ca River ftlluviuir, with
FEATURE
>epth to Hater Table
4et Recharge
kquifer Media
Soil Media
Topography
Impact v*dose Zone
lydraulic Conductivity
RANGE
15-30
0-2
PEST1C10E
HEIGHT
5
4
Sand a-id Gravel 1 3
Silty Loam ' 5
0-2
SfcG w/t.ig Silt t i'lay
1
4
700-1000 J
RATING
•:
i
6
4
10
e
f>
F*cticide
Dractlc Index
NUHBEI
35
4
24
20
10
24
12
12S
TTTtnr 5 Gb K*ve* Alluvluir. without
FEATURE
>«pth to Hater
let Recharge
tquifer Media
loll Media
Topography
Impact vadose Zone
lydraulic Conductivity
RANGE
',-11
0-2
PESTICIDE
HEIGHT
5
4
&a*id u:id Gravl 3
Sandy Loar. < 5
0-2 | 1
b*G w/siq bilt fc Clay ! 4
700-1000 2
RATING
9
1
K
ft
1U
d
c
Pesticide
Drastic Index
NUHDEf
45
4
24
3C
10
24
12
14°
                                                              226

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HIGH PLAINS

(5H) Alternating Sandstone, Limestone and Shale Sequences

Tbl* hydrogeologlc setting IB characterized by low
topographic relief and loamy soils which overlie thick
deposits of poorly sorted, semi- consolidated clay, silt,
sand and gravel-  These unconsolidated deposits are
underlain by horizontal or slightly dipping alternating
layers of fractured consolidated sedimentary rocks.
Precipitation averages less than 20 inches per year and
recharge is very low throughout noat of this water-deficient
area.  In areas where the unconsolidated deposits are not
saturated, ground water is obtained primarily from fractures
along bedding planes or Intersecting vertical fractures.
Where the unconsolidated deposits contain water, they are
typically in direct hydraulic connection with the underlying
bedrock.
SETTING 5 K Alternatinc
FEATURE
>epth to Water
Jet Recharge
tquifer Media
>oil Media
Topography
[•pact vadote zone
lydraulic Conductivity

Sands tone ,
RANGE
100+
0-2
bedded SS, LS
SH Sequtrces
LOJJ
0-2
£4G w/fejc Ell* t Clay
1-100


WEIGHT
5
4
3
3
1
S
3
Dtacti
CENERAl
RATING
1
1
6
!>
10
6
1
c Ind«x

NUMBER
S
4
111
10
10
30
3
81
ICTTING * K Alternatiio Sandstone*
FEATURE
tepth to Hater
4et Recharge
tqulfer Media
ioll Media
Topography
[•pact Vtdoie tone
fydraullc Conductivity
RANGE
IOC"
0-2
PESTICIDE
WEIGHT
5
4
! J
SH Sequences |
LOOT
D-2
1>V3 w/slq bilt & Clay
1-100
5
»
4
2
RATING
l
1
6
i
1C
6
1
Pesticide
OntUc Inax
NUMBEI
5
4
ia
2S
10
24
2
66
                                                           227

-------
  6.
NONGLACIATED CENTRAL GROUND-WATER REGION
 6A
 6B
 6C
 6Da

 6Db

 6E
 6Fa
 6Fb
 6G
 6H
 61
 6J

6K
      Mountain Slopes
      Alluvial Mountain Valleys
      Mountain Flanks
      Alternating Sandstone, Limestone and
        Shale - Thin Soil
      Alternating Sandstone, Limestone and
        Shale - Deep Regolith
      Solution Limestone
      River  Alluvium With Overbank Deposits
      River  Alluvium Without Overbank  Deposits
      Braided River  Deposits
      Triassic Basins
      Swamp/Marsh
      Metamorphic/Igneous  Domes and Fault
       Blocks
      Unconsolidated and Semi-consolidated
       Aquifers
                     228

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                        6.  NONGLACIATED CENTRAL REGION


                (Thin regolith over fractured sedimentary rocks)

    The nonglaciated Central region is an area of about 1,737,000 km2
extending from the Appalachian Mountains on the east to the Rocky Mountains on
the west.  The part of the region in eastern Colorado and northeastern New
Mexico is separated from the remainder of the region by the High Plains region.
The Nonglaciated Central region also includes the Triassic Basins in Virginia
and North Carolina and the "driftless" area in Wisconsin, Minnesota, Iowa, and
Illinois where glacial deposits, if present, are thin and of no hydrologic
importance.  The region is a topographically complex area that ranges from the
Valley and Ridge section of the Appalachian Mountains on the east westward
across the Great Plains to the foot of the Rocky Mountains.  It includes, among
other hilly and mountainous areas, the Ozark Plateaus in Missouri and Arkansas.
Altitudes range from 150 m above sea level in central Tennessee and Kentucky to
1,500 m along the western boundary of the region.

     The region is also geologically complex.  Most of it is underlain by
consolidated sedimentary rocks that range in age from Paleozoic to Tertiary and
consist largely of sandstone, shale, carbonate rocks (limestone and dolomite),
and conglomerate.  A small area in Texas and western Oklahoma it underlain by
gypsum.  Throughout most of the region the rock layers are horizontal or gently
dipping.  Principal exceptions are the Valley and Ridge section of the Wichita
and Arbuckle Mountains in Oklahoma, and the Ouachita Mountains in Oklahoma and
Arkansas, in all of which the rocks have been folded and extensively faulted.
Around the Black Hills and along the eastern side of the Rocky Mountains the
rock layers have been bent up sharply toward the mountains and truncated by
erosion.  The Triassic Basins in Virginia and North Carolina are underlain by
moderate to gently dipping beds of shale and sandstone that have been
extensively faulted and invaded by narrow bodies of igneous rock.  These basins
were formed in Triassic time when major faults in the crystalline rocks of the
Piedmont resulted in the formation of structural depressions up to several
thousand meters deep and more than 25 km wide and 140 km long.

     The land surface in most of the region is underlain by regolith formed by
chemical and mechanical breakdown of the bedrock.  In the western part of the
Great Plains the residual soils are overlain by or intermixed with eolian
(wind-laid) deposits.  The thickness and composition of the regolith depend on
the composition and structure of the parent rock and on the climate, land
cover, and topography.  In areas underlain by relatively pure limestone, the
regolith consists mostly of clay and is generally only a few meters thick.
Where the limestones contain chert and in areas underlain by shale and
sandstone, the regolith is thicker, up to 30 m or more in some areas.  The
                                       229

-------
chert and sand form moderately permeable soils, whereas the soils developed on
shale are finer grained and less permeable.

     The principal water-bearing openings in the bedrock are fractures along
which the rocks have been broken by stresses imposed on the Earth's crust at
different times since the rocks were consolidated.  The fractures generally
occur in three sets.  The first set, and the one that is probably of greatest
importance from the standpoint of ground water and well yields, consists of
fractures developed along the contact between different rock layers, in other
words, along bedding planes.  Where the sedimentary layers making up the
bedrock are essentially horizontal, the bedding-plane fractures are more or
less parallel to the land surface.  The two remaining sets of fractures are
essentially vertical and thus cross the bedding planes at a steep angle.  The
primary difference between the sets of vertical fractures is in the orientation
of the fractures in each set.  For example, in parts of the region one set of
vertical fractures is oriented in a northwest-southeast direction and the other
set in a northeast-southwest direction.  The vertical fractures facilitate
movement of water across the rock layers and thus serve as the principal
hydraulic connection between the bedding-plane fractures.

     In the parts of the region in which the bedrock has been folded or bent,
the occurrence and orientation of fractures are more complex.  In these areas
the dip of the rock layers and the associated bedding-plane fractures range
from horizontal to vertical.  Fractures parallel to the land surface, where
present, are probably less numerous and of more limited extent than in areas of
flat-lying rocks.

     The openings developed along most fractures are less than a millimeter
wide.  The principal exception occurs in limestones and dolomites, which are
more soluble in water than most other rocks.  Water moving through these rocks
gradually enlarges the fractures to form, in time, extensive cavernous openings
or cave systems.  Many large springs emerge from these openings; one in this
region is Big Spring, in Missouri, which has an average discharge of 36.8
     Recharge of the ground-water system in this region occurs primarily in the
outcrop areas of the bedrock aquifers in the uplands between streams.
Precipitation in the region ranges from about 400 mm per year in the western
part to more than 1,200 mm in the eastern part.  This wide difference in
precipitation is reflected in recharge rates, which range from about 5 mm per
year in west Texas and New Mexico to as much as 500 mm per year in Pennsylvania
and eastern Tennessee.  Discharge from the ground,-water system is by springs
and seepage into streams and by evaporation and transpiration in areas where
the water  table is within a few meters of land surface.

     The yield of wells depends on (1) the number and size of fractures that
are penetrated and the extent to which they have been enlarged by solution, (2)
the rate of recharge, and (3) the storage capacity of the bedrock and regolith.
Yields of  wells in most of the region are small, in the range of 0.01 to 1
mSmin"1 (about 2.5 to about 250 gallons per minute), making the Nonglaci-
ated Central region one of the least favorable ground-water regions in the
                                       230

-------
country.  Even in parts of the areas underlain by cavernous limestone, yields
are moderately low because of both the absence of a thick regolith and the
large water-transmitting capacity of the cavernous openings which quickly
discharge the water that reaches them during periods of recharge.

     The exceptions to the small well yields are the cavernous limestones of
the Edwards Plateau, the Ozark Plateaus, and the Ridge and Valley section.  The
Edwards Plateau in Texas is bounded on the south by the Balcones Fault Zone, in
which limestone and dolomite up to 150 m in thickness has been extensively
faulted.  The faulting has facilitated the development of solution openings
which makes this zone one of the most productive aquifers in the country.
Wells of the City of San Antonio are located in this zone; individually, they
have yields of more than 60 m3min-l.

     Another feature that makes much of this region unfavorable for
ground-water development is the occurrence of salty water at relatively shallow
depths.  In most of the Nonglaciated Central region, except the Ozark Plateaus,
the Ouachita and Arbuckle Mountains, and the Ridge and Valley section, the
water in the bedrock contains more than 1,000 mg/1 of dissolved solids at
depths less than 150 m.  Most of the salty water is believed to be
connate—that is, it was trapped in the rocks when they emerged from the sea in
which they were deposited.  Other possible sources include: (1) seawater that
entered the rocks during a later time when the land again was beneath the sea
and (2) salty water derived from solution of salt beds that underlie parts of
the region.

     The presence of connate water at relatively shallow depths is doubtless
due to several factors, including, in the western part of the area, a .-semiarid
climate and, consequently, a small rate of recharge.  Other factors prcbably
include an extremely slow rate of ground-water circulation at depths greater
than a few hundred meters.
                                      231

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HON-GLACIATED CENTRAL
                                                                •OV-CUCIATED CENTRAL
(6A) Mountain  Slopes

This hydroseologlc  setting Is characterized by relatively
steep slopes on  the side  of mountains or hills, a thin  toll
cover and fractured bedrock.  Ground water Is obtained
primarily from the  fractures In the bedrock which may to ef
sedimentary, metamorphlc  or Igneous origin but which are
commonly alternating  sedimentary layers, and also from
bedding planes between the sedimentary layers.  The
fractures provide only localized sources of ground water and
well yields are  typically limited.  Although precipitation
may be significant  In some areas,  due to the steep slopes,
thin soil cover  and small storage  capacity of the fractures,
runoff Is significant and ground-  water recharge la low.
Water levels are extremely variable but are commonly
moderately deep.  Perched ground-water zones are common.
 These sedimentary  rocks  may range In attitude from nearly
horizontal, as In parts of the western Appalachian Plateau,
to steeply dipping, as seen In the Valley and Ridge
province, the  Wichita,  Arbuckle and Ouachlta Mountains, the
Black Hills, and on the eastern slopes of the Rockies.
 SETTING   £ A Mountain Slopes
 tepth to Hater
 *et Recharge
       FEATURE
 kqulfer Media
 Topography
 Impact Vadose Zone
 Jydraulic Conductivity
Bedded SS,  LS,
Sh Sequences
                      Thin or Absent
                     Bedded LS, SS,  SH
                                       Drastic Index   103
 iETTING   6 A Mountain Slopes
 fepth to Hater
 Jet Recharge
        fEATURE
 Topography
 [mpact Vadose Zone
 lydraulic Conductivity
                     Bedded SS,  LS,
                     SH Sequences
                       Thin or  Absent
                     Bedded LS,  SS, SH
                                        Pesticide
                                        Drastic Index
                                            (41) alluvial Mountain Valleys

                                            This hydrogeologic  setting  is characterized by thin bouldery
                                            alluvium which overlies  fractured bedrock of sedimentary,
                                            metamorphlc or igneous origin but which is commonly
                                            comprised of alternating sedimentary layers.  The alluvium,
                                            which is derived  from the surrounding slopes serves.as a
                                            localized source  of water.   Water is obtained from sand and
                                            gravel layers which are  interspersed between finer-grained
                                            deposits.  Surflcial deposits have typically weathered to a
                                            sandy loam.  Hater  levels are relatively shallow but may be
                                            extremely variable.  Ground water may also be obtained from
                                            the fractures In  the underlying bedrock which are typically
                                            in direct hydraulic connection with the overlying alluvium.
IETTING $ B Alluvial Mountain Valleys
FEATURE
>*pth to Water
Jet Recharge
kquifer Media
soil Media
Topography


hydraulic conductivity
RANGE
15-30
4-7
Sand and Gravel
Sandy Loair,
2-61
E i r, w/ sis. Silt
and Clay
700-1000
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
7
6
e
e
9
e
6
Drastic Index
iETTING t B Alluvial Moontair Valleys
FEATURE
>epth to Water
*et Recharge
Aquifer Media
Soil Media
Topography
Impact Vadose Zone
iydraulic Conductivity
RANGE
15-3C
' 4-7
Sand and Gravel
Sandy Loair.
2-6»
S 1 G w/ sic. Silt
and Clay
700-1000
NUMBER
35
24
24
12
9
30
18
152
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
7
6
6
t
9
6
e
Pesticide
Drastic Index
NUKBEI
35
24
24
30
27
24
12
176
                                                              232

-------
NON-GLACIATED CENTRAL
                                                                HON-CUCIATED CENTRAL
(6C) Mountain Flanks

This hydrogeologic setting Is characterized  by moderate
topographic relief and moderately-dipping,  fractured,
consolidated, sedimentary rocks.   Soil  cover is usually
thicker than on the mountain slopes  and typically has
weathered to a sandy  loam.  Although precipitation can be
significant, ground-water recharge is only  moderate due to
the slope .  Water' levels are typically moderately deep
although  they are  extremely variable.  The  mountain flanks
serve as  the recharge area for  aquifers which are confined
in adjacent areas.  Ground water  is  obtained from the
permeable sedimentary rocks or  from fractures In the
sedimentary rocks.  The  sedimentary rocks may be underlain
by fractured bedrock  of  Igneous,  metamorphlc or sedimentary
origin which yield little water.   Sedimentary beds may be
either horizontal  or  dipping, as  Indicated for the higher
mountain  slopes  (6A), and have  a  similar geographic
distribution.
 SETTING  6 C Mountain Flanks
 >epth to Muter
 Jet Recharge
 Kquifer Media
 'opography
 Impact Vadose Zone
 lydraulic Conductivity
Bedded SS, LS,
SH Sequences
                        Sandy Loam
                     Bedded LS, SS,  SH
                                       Drastic Index
                                                 Alternating  Sandstone,  Limestone and Shale - Thin Soil

                                           This hjrdrogeologic setting is characterized by low to
                                           •oderate  topographic  relief,  relatively thin loamy soils
                                           overlying horizontal  or slightly dipping alternating layers
                                           of fractured consolidated  sedimentary rocks.  Ground water
                                           Is obtained primarily from fractures along bedding planes or
                                           Intersecting vertical fractures.  Precipitation varies
                                           widely In the region, but  recharge Is moderate where
                                           precipitation is adequate.  Water levels are extremely
                                           variable but on the average moderately shallow.  Shale or
                                           clayey layers often form aqultards, and where sufficient
                                           relief Is present, perched  ground water zones of local
                                           domestic  Importance are often developed.
SETTING 6 Da Alternatino Sandstone,
T.epth to Water
Jet Recharge
Ujuifer Media
Soil Media
Topography
[•pact Vadoce tone
lydrauiic Conductivity
RANGE
15-30
4-7
Bedded SS , LS ,
SH Sequences
Thin or Absent
2-6»
Bedded LS, SS, SN
1-100
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
7
6
6
10
9
6
1
Pesticide
Drastic Index
NUMBEI
35
24
18
50
27
24
2
180
                                                            233

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HON-GLACIATED CENTRAL
                                                               HOW-GLACIATED CENTRAL
(6Db) Alternating Sandstone, Limestone and Shale - Deep
Regolith

This setting is Identical to (6Da) Alternating Sandstone,
Limestone and Shale - Thin Soil except that the surflclal
deposits typically have been weathered to form clay loans
which grade into weathered bedrock.  This weathered zone
helps retard the novenent of pollutants through the (round
to the water table.  These thick soil deposits are usually
In direct, hydraulic connection with the underlying
fractured sedimentary deposits.
(*E) Solution Limestone

This hydrogeologlc setting Is characterized by moderate,  but
variable, topographic relief and deposits of limestone which
have been partially dissolved along bedding and  fracture
planes to foro a network of solution cavities and caves.
foil is usually thin or absent, but where present is
eommonly a clayey loam.  Recharge is usually greater than 10
Inches per year because the region receives significant
amounts of rainfall which is easily recharged through the
solution channels.  Runoff return through solution channels
Into surface watercourses is sometimes very high.  Water
levels are typically moderately deep.  The limestone serves
•s a significant source of ground water because  of the high
hydraulic conductivity of the solution channels.  Caves
related to this setting are widespread, but their greatest
concentration occurs In a band 200-400 miles wide extending
from central Missouri through western Virginia.
SETTING 6 Dt> Alternating sandstone,
^Hmfltflr*- pftal*" " °«*D Beoollth
FEATURE
fepth to Hater
Jet Recharge
iqulfer Media
soil Media
Topography
latpact Vadoae Zone
lydraulic Conductivity
RANGE
15-30
4-7
Bedded SS, LS,
SH Sequences
Clay Loam
2-6%
Bedded LS , SS, EH
1-100
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
7
6
e
3
9
e
i
Drastic Index
NUMBER
35
24
ie
e
9
30
3
125
SETTING 6 E Solution Limestone
FEATURE
Jepth to Hater
Jet Recharge
tquifer Media
soil Media
Topography
Impact Vadose Zone
iydraulic Conductivity
RANGE
30-5C
10*


Thin or Absent
6-12%
Karst Limestone
2000-
GENERAL
*EIGHT
5
4
3
2
1
5
3
RATING
5
9
10
10
5
10
10
Drastic Index
NUMBER
25
36
30
20
5
5C
3C
19E
SETTING * Eb Alternative sandstone,
Lin*etor.e. S^le - Deen Rear.lith
FEATURE
lepth to Hater
Jet Recharge
tquifer Media
Soil Media
Topography
Impact Vadose zone
lydraulic Conductivity
RANGE
15-30
4-7
Bedded SS , LS,
SB Sequences
Clay Loam
2-6%
Bedded LS, SS, SH
1-100
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
7
6
6
3
9
t
1
Pecticiae
Drastic Index
NUMBEI
35
24
16
15
27
24
2
145
SETTING 6 E Solution Limestone
FEATURE
Jepth to Water
Jet Recharge
aquifer Media
loll Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
30-50
10*
Karst Limestone
Thin or Absent
6-121
Varst Limestone
2000*
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
5
9
10
10
5
10
10
Pesticide
Drastic Index
NUMBER
25
36
30
50
15
40
20
216
                                                           234

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HON-GLACIATED CENTRAL

(6Fa) giver Alluvium with Overbank Deposits

This hydrogeologlc getting is characterized by Ion
topography and deposits of alluvium along parts of stream
valleys.  Water is obtained from sand and gravel layers
which are interbedded with finer-grained alluvial deposits.
The floodplain is covered by varying thicknesses of
fine-grained silt and clay called overbank deposits.   The
overbank thickness is usually thicker along major streams
(commonly as much as 40 feet), and thinner along minor
streams.  Precipitation varies widely over the region, but
recharge is somewhat reduced because of the impermeable
nature of the overbank deposits and subsequent clayey loam
•oils which typically cover the surface.  There is usually
substantial recharge, however, due to infiltration from the
associated stream, water levels are typically moderately
shallow.  The alluvium is commonly in direct hydraulic
connection with the underlying sedimentary rocks.
•OH-CLACIATED CENT&AL

(*rb) Hv«r Alluvium without Overbank Deposits

This setting is identical to (6Fa) River Alluvium with
Overbank Deposits except that no significant fine-grained
floodplain deposits occupy the stream valley.  This results
in significantly higher recharge where precipitation is
adequate and sandy loam soils occur at the surface.  Water
levels are typically closer to the surface because-the
floe-grained onrarbank deposits are not present.
SETTING * F* River Alluvium with Overbank
n*»r\n«i »-e
FEATURE
fepth to Hater
*et Recharge
iquifer Media
Soil Media
topography
Impact Vadoce Zone
lydraulic Conductivity
RANGE
15-30
7-10
Sand and Gravel
Clay Loam
0-2%
Silt/Clay
1000-2000
GENERAL
HEIGHT
S
4
3
2
1
5
3
RATING
7
e
e
3
1C
3
8
Drastic Index
HUMEES
35
32
24
t
10
15
24
126
>ETT1NG Overbad Deposits
FEATURE
>epth to Water
let Recharge
iqulfer Media
ioil Media
Topography
Impact Vadose tone
lydraulic Conductivity
RANGE
5-15
7-10
Sand and Gravel
Sandy Loam
0-2»
Sand and Gravel
1000-2000
GENERAL
'EIGHT
S
4
3
2
1
5
3
RATING
9
e
a
e
10
e
e
Efrastic Index
NUMBER
45
32
24
12
10
40
24
167
SETTING 6 F* River Alluvium with Overbank
He p.- c i » c
FEATURE
Jepth to Hater
vet Recharge
^qulfer Media
•oil Media
Topography
Impact Vadoce Zone
lydraulic Conductivity
RANGE
15-30
7-10
Sand and Gravel
Clay Loam
0-2«
Silt/Clay
1000-2000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
7
8
8
3
10
3
*
Pesticide
Oraiue Index
NDNBEH
35
32
24
15
30
12
1C
1t4
JETTING ' Fb RJv«r"ATI
ITJNC Over bark DSDOS
FEATURE
>epth to Water
Jet Recharge
iquifer Media
loll Media
Topography
Impact VadOEe zone
lydraulic Conductivity
it!
RANGE
5-15
7-1C
Sand and Gravel
Sandy Loan
0-21
Sand and Gravel
1000-2000
PESTICIDE
HEIGHT
5
4
3
5
3
4
3
RATING
9
8
8
e
10
8
8
Pesticide
teas tic Index
NUMBER
45
32
24
30
30
32
H
20S
                                                          235

-------
NON-GLACIATED CENTRAL
                                                                •XW-CIACIATED OCMTUL
(M) Braided River Deposits

This hydrogeologlc setting Is characterized by deposit! of
alluvium vhlch occur within the flood plain of streams and
rivers.  The stream Is characterized by a low gradient, wide
channel and series of Interconnected shallow channels vhlch
form a braided pattern.  Water levels are typically shallow.
This setting Is found only In the western portion of this
ground- water region.  The river alluvium does not serve as
• significant source of ground water where It overlies more
productive seal-consolidated deposits.  However, recharge
from the river Is substantial and the underlying deposits
are in direct hydraulic connection with the overlying
alluvium; therefore the potential for pollution of the
aquifer is high.  Although precipitation commonly averages
less than 20 Inches per year, recharge is relatively high
due to the flat topography and sandy surficlal deposits.
(M) Trlasslc Basins

This hydrogeologlc setting is characterized by moderately
dipping, highly faulted beds of sandstone, shale and sllty
limestone.  Conglomerltic deposits occur  In some areas.
These basins tend to be bounded by high angle faults, with
the basins being elongate in the NE-SW directions.  The
sedimentary beds may be cut by narrow igneous intrusions
(dikes, etc.), and are sometimes indurated by the Intrusive
activity.  The Trlasslc formations are often red in color
*ue to high iron concentrations, but green colors are also
common. These deposits may serve «s a localized source of
mater end water levels are variable.
SETTING C C Braided River De.xislts
FEATURE
Xpth to Hater
let Recharge
Iquifar Media
Soil Media
Topography
[mpact Vadose Zone
lydraulic Conductivity
RANGE
0-5
4-7
Sand and Gravel
Sani
0-2%
Sand and Gravel
1000-2000
GENERAL
HEIGHT
5
1
3
2
1
i
3
RATING
10
<
8
9
10
8
8
Draitic Index
NUMBER
SO
24
24
18
10
40
24
19C
SETTING 6 H Triassic Basins
FEATURE
tepth to Hater
let Recharge
hqulfer Media
toil Media
Topography
impact Vadose Zone
lydraulic Conductivity
RANGE
75-100
4-7
Massive Sandstone
Sandy LOar
2-6»
Bedded LS , SS , SF
1-100
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
2
6
6
6
9
6
1
Drastic Index
NUMBER
10
24
18
12
o
30
3
ioe
JETTING 6 G Braided Biver Depcsits
FEATURE
>*pth to Hater
«t Recharge
tqulfer Media
ioil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
0-5
4-7
Sand and Gravel
Sand
0-2%
Sand and Gravel
1000-2000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
10
6
8
9
10
8
1
Pesticide
Drastic Index
NUHBEI
50
24
24
45
30
32
1C
221
SETTING 6 H Triassic Basins
FEATURE
>epth to Water
let Recharge
ujuiter Media
Soil Media
Topography
[•pact Vadose zone
lydraulic conductivity
RANGE
75-100
4-7
KaSElve Sandstone
Sar.dy Loar
2-6%
Bedded LS, SS , SK
1-100
PIST1C1DT
HEIGHT
5
4
3
5
3
4
2
RATING
2
t
6
6
9
6
1
Pesticidt-
Drastic Index
NUNBLR
1C
24
U
3C
27
24
2
13E
                                                           236

-------
NON-GLACIATED CENTRAL
                                                               MOM-GLACIATED CENTRAL
(61) Swamp/Mar§h

ThiB hydrogeologic setting Is characterized by low
topographic relief and high water levels with high organic
content in the sandy clay deposits.  The high water tables
are a result of either restricted vertical conductivity or
restricted drainage patterns.  Recharge is highly variable
but is typically moderate to high where precipitation and/or
streamflow permit.  These deposits may serv* •• aquifers or
may eerve as recharge to the underlying aquifer.
(*J) Netamorphic/ Igneous Domes and Fault Blocks

This hydrogeologic setting is characterized by metamorphic
and igneous rocks exposed at the surface.  The rocks are
typically more highly fractured and faulted along the flanks
of the domes.  The domes are flanked by gently dipping
deposits of sedimentary rocks which may also be faulted
adjacent to the dome.  Soil is typically thin or ab'sent and
water levels are extremely variable.  Recharge rates are
typically low because of excessive surface runoff and low
permeabilities.  Water yields are extremely variable
depending on the degree of folding and faulting but
typically are higher along the more fractured flank tones.
Where few fractures exist, water yields are very low or
•on-exiatent .
SETTING 6 I Swamp/Marsh
FEATURE
>cpth to Hater
let Recharge
tqulf«r Media
soil Media
Topography
taipact Vado>« Zone
lydraulJc Conductivity
RANGE
0-f.
4-1
Bedded SS , LS ,
EH Srv.ie'ices
Cld> LOdTT.
0-2
S t C w/- ic. Sjlt
fl'i • Ci.r
10I.-30C
GENERAL
HEIGHT
5
4
}
2
1
5
3
RATING
U
6
6
3
10
6
2
Drastic Indax
NUMBER
50
2«
It
6
10
30
C
14<
SETTING ' J Metamorpnic/lgneous Domes
»-r> Fa,,11- Plrv-V.
FEATURE
lepth to Water
Jet Recharge
aquifer Media
ioll Media
Topography
[•pact Vadoce Zone
tydraulir Conductivity
RANGE
75-100
0-2
Hetanorphic/IgoeouE
Thin or Absent
6-12
Metanorph ic/Igneojs
1-100
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
2
1
3
10
5
4
1
Drastic Index
NUMBER
1C
4
o
2C
5
20
3
7'
tETTING f, I Suap^/Marsr.
FEATURE
tepth to Hater
'et M*charge
kquifer Media
ioll Media
Topography
[•pact VadOM lone
lydraullc Conductivity
RANGE
0-5
4-7
Bedded SS , LS ,
SH Sequences
Clay Loar
0-2
5 fc G w/sig. Silt
ami Clay
100-300
PESTIC1DF
WEIGHT
5
4
3
5
3
4
2
RATING
U
6
(
1
1.,
f,
2
Pesticide
OtMtic Index
NUMBEI
SG
2<
Ifc
15
30
21
4
16?
	 an; rai.: Blockt
FEATURE
Jeptt. to Water Tahle
iet Recharge
Aquifer Media
ioll Media
Topography
[•pact Vadoce Zone
lydraullc conductivity
RANGE
75-1 OC
0-2
Hetairorphi=/Igieoj£
PESTICIDE
HEIGHT
5
4
3
Thir, or Absent ' 5
6-12
MetairDrphic/lgneoijE
1-10C
1
4
1
RATING
2
1
3
10
S
4
1
Pesticide
Drastic Index
NUMBER
10
4
9
5C
5
16
2
»G
                                                         237

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NON-GLACIATED CENTRAL

(6K) Unconeolidated and Semi-Consolidated Aquifers

This hydrogeologic setting is characterized by moderately
low topographic relief and interbedded deposits which
consist primarily of sand, silt and clay.  Although soils
are typically loamy or sandy, recharge IE limited because of
only moderate precipitation and high evapotranspiration.
Water levels are extremely variable but are typically not
less than SO feet.  Hydraulic conductivities are also
extremely variable also depending on the amount of fine
materials which are Interbedded with the sands.
JETTING 6 K UncOnscll
FEATURE
Jepth to Hater
Jet Recharge
Aquifer Media
>O!l Media
Topography
Impact Vadoae Zone
lydraulic Conductivity

dated »nd Semi-
RANGE
75-100
0-2
Sand and Gravel
Sandy Loan
2-6»
SfcG w/sic Silt fc Clay
300-70C



-------
 7.   GLACIATED CENTRAL GROUND-WATER REGION
7Aa
7Ab
7Ac
7Ad
7Ae
7Ba
7Bb
7Bc
7C
7ti
7Ea
7Eb
7F
7G
7B
71
Glacial Till Over Bedded Sedimentary Rock
Glacial Till Over Outwash
Glacial Till Over Solution Limestone
Glacial Till Over Sandstone
Glacial Till Over Shale
Outwash
Outwash Over Bedded Sedimentary Rock
Outwash Over Solution Limestone
Moraine
Buried Valley
River Alluvium With Overbank Deposits
River Alluvium Without Overbank Deposits
Glacial Lake Deposits
Thin Till Over Bedded Sedimentary Rock
Beaches, Beach Ridges and Sand Dunes
Swamp/Marsh
                      239

-------
                          7.   GLACIATED CENTRAL REGION
              (Glacial deposits over fractured sedimentary rocks)

    The Glaciated Central region occupies an area of 1,297,000 km2 extending
from the Triassic Basin in Connecticut and Massachusetts and the Catskill
Mountains in New York on the east to the northern part of the Great Plains in
Montana on the west.  The part of the region in New York and Pennsylvania is
characterized by rolling hills and low, rounded mountains that reach altitudes
of 1,500 m.  Westward across Ohio to the western boundary of the region along
the Missouri River, the region is flat to gently rolling.  Among the more
prominent topographic features in this part of the region are low, relatively
continuous ridges (moraines) which were formed at the margins of ice sheets
that moved southward across the area one or more times during the Pleistocene.

     The Glaciated Central region is underlain by relatively flat-lying
consolidated sedimentary rocks that range in age from Paleozoic to Tertiary.
They consist primarily of sandstone, shale, limestone, and dolomite.  The
bedrock is overlain by glacial deposits which, in most of the area, consist
chiefly of till, an unsorted mixture of rock particles deposited directly by
the ice sheets.  The till is interbedded with and overlain by sand and gravel
deposited by meltwater streams, by silt and clay deposited in glacial lakes,
and, in large parts of the North-Central States, by loess, a well-sorted silt
believed to have been deposited primarily by the wind.

     On the Catskill Mountains and other uplands in the eastern part of the
region, the glacial deposits are typically only a few to several meters thick,
but localized deposits as much as 30 m thick are common on southerly slopes.
In much of the central and western parts of the region, the glacial deposits
exceed 100 m in thickness.  The principal exception is the "driftless" area in
Wisconsin, Minnesota, Iowa, and Illinois, where the ice, if it invaded the
area, was too thin to erode preexisting soils or to deposit a significant
thickness of till.  Thus, the bedrock in this area is overlain by thin soils
derived primarily from weathering of the rock.  This area, both geologically
and hydrologically, resembles the Nonglaciated Central region and is,
therefore, included as part of that region.

     The glacial deposits are thickest in valleys in the bedrock surface;
thicknesses of 100 to 300 m occur in the valleys of the Finger Lakes in New
York.  In most of the region westward from the Ohio to the Dakotas, the
thickness of the glacial deposits exceeds the relief on the preglacial surface,
with the result that the locations of valleys and stream channels in the
preglacial surface are no longer discernible from the land surface.  The
glacial deposits in valleys include, in addition to till and lacustrine silts
and clays, substantial thicknesses of highly permeable sand and gravel.

                                       240

-------
     Ground water occurs both in the glacial deposits and in the bedrock.
Water occurs in the glacial deposits in pores between the rock particles and in
the bedrock primarily along fractures.  The dominant water-bearing fractures in
the bedrock are along bedding planes.  Water also occurs in the bedrock in
steeply dipping fractures that cut across the beds and, in some sandstones and
conglomerates, in primary pores that were not destroyed in the process of
cementation and consolidation.

     Large parts of the region are underlain by limestones and dolomites in
which the fractures have been enlarged by solution.  Caves are relatively
common in the limestones where the ice sheets were relatively thin, as near the
southern boundary of the region and in the "driftless" area.  A few caves occur
in other parts of the region, notably in the Mohawk River valley in central New
York, where they were apparently protected from glacial erosion by the
configuration of the bedrock surface over which the ice moved.  However, on the
whole, caves and other large solution openings, from which large springs emerge
and which yield large quantities of water to wells in parts of the Nonglaciated
Central region, are much less numerous and hydrologically much less important
in the Glaciated Central region.

     The glacial deposits are recharged by precipitation on the interstream
areas and serve both as a source of water to shallow wells and as a reservoir
for recharge to the underlying bedrock.  Precipitation ranges from about 400 mm
per year in the western part of the region to about 1,000 mm in the eastern
part.  Recharge also depends on the permeability of the glacial deposits
exposed at the land surface and on the slope of the surface.  On sloping
hillsides underlain by clay-rich till, the annual rate of recharge, even in the
humid eastern part of the region, probably does not exceed 50 mm.  In contrast,
relatively flat areas underlain by sand and gravel may receive as much as 300
mm of cecharge annually in the eastern part of the region.  Recharge of the
ground-water system in the Glaciated Central region occurs primarily in the
fall, after plant growth has stopped and cool temperatures have reduced
evaporation, and again during the spring thaw before plant growth begins.  Of
these recharge periods, the spring thaw is usually dominant except when fall
rains are unusually heavy.  Minor amounts of recharge also may occur during
midwinter thaws and during unusually wet summers.

     Ground water in small to moderate amounts can be obtained anyplace in the
region,-both from the glacial deposits and from the bedrock.  Large to very
large amounts are obtained from the sand and gravel deposits and from some of
the limestones, dolomites, and sandstones in the North-Central States. The
shales are the least productive bedrock formations in the region.

     As is the case in the Nonglaciated Central region, mineralized water
occurs at relatively shallow depth in the bedrock in large parts of this
region.  Because the principal constituent in the mineralized water is sodium
chloride (common salt), the water is commonly referred to as saline or salty.
The thickness of the freshwater zone in the bedrock depends on the vertical
hydraulic conductivity of both the bedrock and the glacial deposits and on the
effectiveness of the hydraulic connection between them.  Both the freshwater
                                      241

-------
and the underlying saline water move toward the valleys of perennial streams to
discharge.  As a result, the depth to saline water is less under valleys than
under uplands, both because of lower altitudes and because of the upward
movement of the saline water to discharge.  In those parts of the region
underlain by saline water, the concentration of dissolved solids increases with
depth.  At depths of 500 to 1,000 m in much of the region, the mineral content
of the water approaches that of seawater (about 35,000 mg/L).  At greater
depths, the mineral content may reach concentrations several times that of
seawater.

     Because the Glaciated Central region resembles in certain aspects both the
Nonglaciated Central region (region 6) to the south and the Northwest and
Superior Uplands region (region 9) to the north, it may be useful to comment on
the principal differences among these three regions.  First, and as is already
apparent, the bedrock in the Glaciated Central and the Nonglaciated Central
regions is similar in composition and structure.  The difference in these two
regions is in the composition and other characteristics of the overlying
unconsolidated material.  In the Nonglaciated Central region this material
consists of a relatively thin layer that is derived from weathering of the
underlying bedrock and that in any particular area is of relatively uniform
composition.  In the Glaciated Central region, on the other hand, the
unconsolidated material consists of a layer, ranging in thickness from a few
meters to several hundred meters, of diverse composition deposited either
directly from glacial ice (till) or by meltwater streams (glaciofluvial
deposits).  From a hydrologic standpoint, the unconsolidated material in the
Nonglaciated Central region is of minor importance both as a source of water
and as a reservoir for storage of water for the bedrock.  In contrast, the
glacial deposits in the Glaciated Central region serve both as a source of
ground water and as an important storage reservoir for the bedrock.

     The Glaciated Central region and the Northeast and Superior Uplands region
are similar in that the unconsolidated material in both consists of glacial
deposits.  However, the bedrock in the two regions is different. The bedrock in
the Glaciated Central region, as we have already seen, consists of consolidated
sedimentary rocks that contain both steeply dipping fractures and fractures
along bedding planes.  In the Northeast and Superior Uplands, on the other
hand, the bedrock is composed of intrusive igneous and metamorphic rocks
(nonbedded) in which most water-bearing openings are steeply-dipping fractures.
As a  result of the differences in fractures, the bedrock in  the Glaciated
Central region is, in general, a more productive and more important source of
ground water  than the bedrock in the Northeast and Superior  Uplands region.

     The largest fresh-water supply in North America, the Great Lakes, is
located in this region.  Bordering the Great Lakes, there are abandoned beach
ridges, present-day beaches and sand dunes, all of which are very sensitive
environmental areas.
                                       242

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GLACIATED CENTRAL

(7Aa) Glacial Till Over Bedded Sedimentary Rocks

This hydrogeologlc setting Is characterized by low
topography and relatively flat-lying, fractured sedimentary
rocks consisting of sandstone, shale and  limestone which are
covered by varying thicknesses of glacial till.  The till  Is
principally unsorted deposits which may be interbedded with
loess or localized deposits of sand and gravel.  Although
ground water occurs in both the glacial deposits and In the
Intersecting bedrock fractures, the bedrock Is typically the
principal aquifer.  The glacial till serves as a source of
recharge to the underlying bedrock.  Although precipitation
Is abundant in most of the region,  recharge is moderate
because of the glacial till and soils which are  typically
clay  loams.  Depth to water is extremely  variable  depending
In part on the thickness  of the glacial  till, but  averages
around 30 feet.
Tur 7 Aa Glaciai
SBIepth to Hater
Jet Recharge
(quifer Media
soil Media
Topography
[mpact Vadose Zone
iydraulic Conductivity
ock
RANGE
30-50
4-7
Bedded SS , LS,
SK Sequences
Clay Loam
2-6%
Silt/Clay
100-300

•EIGHT
5
4
3
2
1
5
3
GENERAL
RATING
5
6
t
3
9
3
2
Drastic Index

NUMBER
25
24
18
t
9
15
e
103
GETTING I^i^/R
FEATURE
>epth to Water
let Recharge
kquifer Media
ioil Media
Topography
[•pact Vadose Zone
Iydraulic conductivity


RANGE
30-5C
4-7
Beddec SS , LS ,
SH Sequences
Clay Loair
2-6«
Silt/Clai
100-300

HEIGHT
5
4
3
5
3
4
2
RATING
5
6
6
3
9
3
2
Pesticide
Drastic Index
HUMBEF
25
24
18
IS
27
12
4
125
GLACIATED CENTRAL

(7Ab) Glacial Till Over Outwash

This hydrogeologlc setting Is characterized  by  low
topography and outwash materials which are covered  by
varying thicknesses of glacial till.  The till  Is
principally unsorted deposits which may be Interbedded with
loess or localized deposits of sand and gravel.  Surflclal
deposits have usually weathered to a clay loan.  Although
ground water occurs In both the glacial deposits and In  the
underlying outwash, the outwash typically serves as the
principal aquifer because the fine-grained deposits have
been renoved by glacial meltwater.  The outwash Is  In direct
hydraulic connection with the glacial till and  glacial till
serves as a source of recharge for the underlying outwash.
This setting Is similar to (7Aa) Glacial Till Over  Bedded
Sedimentary Rock and (7Ac) Glacial Till Over Solution
Limestone In that although preclpltlon Is abundant  In most
of the region, recharge Is moderate because  of  the
relatively low permeability of the overlying glacial till.
Depth to water Is extremely variable depending  In part on
the thickness of the glacial till, but averages around 30
feet.
SETTING 7 Ab Glacial Till Over Outuash
FEATURE
>epth to Water
•tct Recharge
tquifer Media
Soil Media
Topography
Impact Vadose Zone
lydraullc Conductivity
RANGE
15-30
4-7
Sand and Gravel
Clay Loar
2-6%
Silt/Clay
1000-200C
GENERAL
HEIGHT
5
4
3
1
1
5
3
RATING
7
e
8
3
9
3
e
Drastic Index
NUMBER
3'.
24
24
t
9
15
24
13-
iETTING '7 Ab Glarlal Till Over Outuash
FEATURE
>epth to Hater

kquifer Media
ioil Media
Topography
Impact Vadose Zone
Iydraulic Conductivity

RANGE
15- JC
4-7
Sa-.d ani Gravel
Clay Loor
2-6%
Silt/Clay
1000-200C
PESTICIDE
HEIGHT
5
4
3
5
3
4
2

7
6
e
3
9
3
8
Pesticide
Drastic Index

35
24
24
15
27
12
U
I*1
                                                           243

-------
GLACIATED CENTRAL
                                                                GLACIATED MUTUAL
(7Ac) Glacial Till Over  Solution  Limestone

This hydrogeologlc setting  Is  characterized by lov
topography and solution  limestone which are covered by
varying thicknesses of glacial till.   The till is
principally unsorted deposits  which nay be Interbedded with
Iocs* or localized deposits  of sand and gravel.  Surflclal
deposits have usually weathered to a clay loam.  Although
ground water occurs in both  the glacial deposits and In the
underlying Huestone, the limestone,  which typically
contains solution cavities,  typically serves as the
principal aquifer.  The  limestone Is in direct hydraulic
connection with the glacial  till  and the glacial till serves
•a a aource of recharge  for  the underlying limestone.  This
setting Is similar to (7Aa)  Glacial Till Over Bedded
Sedimentary Rock and (7Ab)  Glacial Till Over Outvash In that
although precipitation is abundant In most of the region,
recharge is moderate because of the relatively low
permeability.of the overlying  glacial till.  Depth to water
le extremely variable depending In part on the thickness of
the glacial till, but is typically moderately deep.
 iETTING  ' *c  Glacial  Till Over Solution
 >epth  to Water
 let Recharge
       FEATURE
fcqulfer Media
Boil  Media
Topography
 it.pact Vadose  Zone
Hydraulic Conductivity
                                      4EIGHT  RATING NUMBER
                      Xarst Limestone
                         Clay Loar,
                         Silt/Clay
                                      Drastic Index
(7Ad) Glacial Till Over  Sandstone

This hydrogeologlc setting  Is characterized by low
topography and relatively flat-lying,  fractured sandstones
which are covered by  varying thicknesses of glacial till.
The till is principally  unsorted  deposits which may be
interbedded with loess or localized deposits of sand and
gravel.  Although ground water occurs  in both the glacial
deposits and in the intersecting  bedrock fractures, the
bedrock Is typically  the principal aquifer.  The glacial
till serves as a source  of  recharge to the underlying
bedrock.  Although precipitation  Is abundant In most of the
region, recharge la moderate because of the glacial tills
which typically weather  to  clay loam.   Depth to water Is
extremely variable, depending in  part  on the thickness of
the glacial till, but averages around  40 feet.
irTTlNG 7 Ad Glacial Till Over Sandstone
FEATURE
Xpth to Hater
<*t R*charge
hqulf«r Media
ioil Media
Topography
[•pact Vadose Zone
iydraulic Conductivity
RANGE
30-50
4-7
Massive Sandstone
Clay Loan
2-61
Silt/Cla)
JOO-700
GENERAL
HEIGHT
5 '
4
3
2
1
S
3
RATING
5
6
6
3
9
3
4
Drastic Index
NUMBER
25
24
ie
6
9
15
12
ICt
JETTING 7 *c Glacial Till Over Solutior
FEATURE
ieptl- to Hater
det Recharge
Iquifer Media
Soil Media
Topography
[•pact Vadose Zone
iydraulic Conductivity
RANGE
30-5C
4-^
rarst Limesto-ie
Clay Loar.
2-61
Silt/Clay
2000-
PESTICIDr
HEIGHT
5
4
3
S
3
4
2
RATINE
5
6
10
3
9
3
10
Pesticide
Drastic Index
NUMBEF
25
2<
30
15
27
12
20
153
JETTING 7 Ad Glacial Till Over Sandstone
FEATURE
Xcpth to Hater
*«t Recharge
hquifer Media
ioil Media
ropostaphy
[•pact Vadose Zone
Iydraulic Conductivity
RANGE
30-50
4-7
Massive Sandstone
Clay Lca-r.
Z-6»
Silt/Clay
300-700
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
5
6
6
3
9
3
4
Pesticide
Drastic Index
NUMEtl
25
'24
ie
15
27
12
t
12!>
                                                          244

-------
GLACIATED CENTRAL

(7Ae) Glacial Till Over Shale

This hydrogeologlc setting is similar to (7Ad) Glacial Till
Over Sandstone except that varying thickness of till overlie
fractured, flat-lying shales. The till is principally
unsorted deposits with interbedded lenses of loess and ond
and gravel.  Ground water is derived from either localised
sources in the overlying till or from deeper, more permeable
formations.  The shale Is relatively Impermeable and toes
not serve as a source of ground water.  Although
precipitation IB abundant, recharge Is minimal from the till
to deeper formations and occurs only by leakage of water
through the fractures.
SETTING 7 Ae Glacial Till Over Shale
FEATURE
Jepth to Water
let Recharge
hquifer Media
>oll Media
ropogr.phy
tnpact vedose Zone
iydraulic Conductivity
RANGE
30-50
4-7
Massive Shale
Clay Loam
2-6%
Silt/Clay
1-100
GENERAL
(EIGHT
S
4
3
2
1
5
3
RATING
5
e
2
3
9
3
1
Dractic Index
NUMBER
25
24
e
e
9
15
3
ee
SETTING 7 Ae Glacial Till Over Shale
FEATURE
lepth to Hater
4et Recharge
Iquifer Media
Soil Media
Topography
Impact v«dose Zone
lydraulic conductivity
RANGE
30-5C
4-7
Massive Shale
Clay Loam
2-61
Silt/Clay
1-100
PESTICIDE
HEIGHT
S
4
3
5
3
4
2
RATING
5
6
2
3
9
3
1
Pesticide
Drastic Index
NUKBEF
25
24
6
15
27
12
2
1 1 1
GLACIATED CENTRAL

(71a) Outwash

This hydrogeologic Betting is characterized by moderate to
low topography and varying thicknesses of outwash which
overlie sequences of fractured sedimentary rocks.  The
outwash consists of water-washed deposits of Band and gravel
which serve as the principal aquifer In the area.  The
outwash also serves as a source of recharge to the
underlying bedrock.  Precipitation Is abundant throughout
most of the area and recharge Is moderate to high.  Recharge
Is somewhat restricted by the Bandy loam soil which
typically develops in this setting.  Water levels are
extremely variable, but relatively shallow.  Outwash
generally refers to water-washed or ice-contact deposits,
and can include a variety of morphogenlc forms.  Outwash
plains are thick sequences of sands and gravels that are
laid down in sheet-like deposits from sediment-laden waters
draining off, and from within a glacier.  These deposits are
well-sorted and have relatively high permeabilities.  Kames
and eskers are ice-contact deposits. A kame is an isolated
hill or mound of stratified sediments deposited in an
opening within or between ice blocks, or between ice blocks
and valley walls.  An eaker IB a sinuous or meandering ridge
of well-sorted sande and gravels that are remnants of
streams that existed beneath and within the glaciers.  These
deposits may be in direct hydraulic connection with
underlying fractured bedrock.
SETTING , B. outwash
FEATURE
Jepth to Hater
Jet Recharge
iguifer Media
soil Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
1S-30
7-10
Sand and Gravel
Sandy Loajn
2-6%
Sand *ne Gravel
1000-200C
GENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
7
8
a
6
9
e
e
ttrastic Index
NUMBER
35
32
24
12
9
40
2<
176
JETTING 7 Ba Outwash
FEATURE
>epth to Water
let Recharge
iqulfer Media
Boil Media
topography
Inpact Vadose Zone
'ydraullc Conductivity

RANGL
15-30
7-10
Sand and Gravel
Sandy Loan
2-6t
Sand and Gravel
1000-2000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
7
e
e
e
9
e
t
Pesticide
Drastic Index
NUMBEF
35
32
2<
30
27
32
16
9C
                                                         245

-------
GLACIATED CENTRAL
                                                              GLACIATED CENTRAL
(7Bb) Outwash Over Bedded Sedimentary Rock

This hydrogeologlc setting is characterized by moderate to
low topography and relatively flat-lying, fractured
sedimentary rocks consisting of sandstones, shales and
limestone which are covered by varying thicknesses of
glacial outvash.  The outwash consists of a variety of
water-washed deposits of sand and gravel which serve as the
principal aquifer in the area.  The Outwash also serves as a
source of recharge to the underlying bedrock.  Precipitation
la abundant throughout most of the area and recharge is
moderate to high.  Water levels are extremely variable, but
typically shallow.
(7»c) Outvash Over Solution Limestone

This hydrogeologlc setting is characterized by low
topography and solution limestone which Is covered by
varying thicknesses of glacial Outwash.  The outwash
consists of varying types of water-washed deposits that
typically weather to sandy loan soils.  Both the outwash and
the solution limestone serve as principal aquifers in the
area.  The solution limestone is in direct hydraulic
connection with the glacial outwash and the outwash serves
as a source of recharge for the underlying limestone.  Water
levels are extremely variable and In part dependent on the
thickness of the overlying outwash.
._-TTMr 1 Bb Outwash Over Bedded
>tiuNij sedimer.tarv Sock
FEATURE
>epth to Water
let Recharge
ujuller Media
ioil Media
Topography
Impact Vadose Zone
iydraulic Conductivity
RANGE
15-3C
101
Bedded SS , LS ,
SH sequences
Sandy Loan
2-6»
Sand and Gravel
100-300
GENERAL
HEIGHT
5
«
3
2
1
5
3
RATING
7
9
6
6
9
e
2
Drastic Index
NUMBER
35
36
IE
12
»
4C
e
156
SETTING 7 Be Outwash Over Solution
FEATURE
>epth to Water
let Recharge
kquifer Media
Soil Media
topography
Impact Vadose Zone
iydraulic Conductivity
RANGE
15-30
10+
Karst Limes rone
Sandy Loair
2-6 »
Said and Gravel
1000-2000
GENERA'.
(EIGHT
5
t
3
2
1
5
3
RATING
1
9
10
6
9
8
8
Drastic Index
NUMBER
35
36
30
12
9
40
24
186
• ri^Tu,- ' Bt 6utw«r 6ver Bedded
>LTU!"j Sedimentary Roci.
FEATURE
iepth to Water
Jet Recharge
tqulfer Media
>oll Media
Topography
[•pact Vadose Zone
lydrauiic Conductivity

RANGE
1i-3C
10*
Beddi-d SS , LE ,
SH Sequences
Sandy Loar
2-6%
Sand and Gravel
100-300
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
7
9
6
6
9
e
2
Pesticide
Drastic Index
NUMBEF
35
36
16
30
27
32
4
182
SETTING 7 Be Outwash Over Solution
FEATURE
>epth to Water
4et Recharge
iquifer Media
ioil Media
Fopogr aphy
Input Vadose Zone
iydraulic Conductivity
RANGE
15-30
10*
Karst Limestone
Sandy Loam
2-6*
Sand and Gravel
1000-2000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
7
9
10
6
9
e
e
Pesticide
Drastic Index
NUMBER
35
36
30
30
27
32
16
20C
                                                           246

-------
GLACIATED CENTRAL
                                                              OLftCUTID CENTRAL
(7C) Moraine

This hydrogeologlc setting is characterized by moderate to
moderately steep topography and varying thicknesses of mixed
glacial deposits which overlie sequences of relatively
flat-lying fractured sedimentary rocks.  This setting Is
similar to (7Ba) Outwash in that the sand and gravel within
the morainal deposits may be well-sorted and serve as the
principal aquifer in the area.  These deposits also serve as
a source of recharge for the underlying bedrock.  Moraines
also contain sediments that are typically unsorted and
unstratified; these deposits contain more fines than outw««h
deposits, are less permeable and characteristic of glacial
till.  Moraines are typically mounds or ridges of till which
were deposited along the margin of a stagnant or retreating
glacier.  Surficial deposits often weather to sandy loam.
Precipitation is abundant throughout the region and
ground-water recharge is Moderate,  ttater levels are
extremely variable, based in part on the thickness of the
glacial till, but are typically fairly shallow.
 (78) Burled Valley

 This hydrogeologlc setting is characterized by thick
 deposits of sand and gravel that have been deposited In a
 former topographic low (usually a pre-glaclal river valley)
 by glacial meltwaters.  These deposits are capable of
 yielding large quantities of ground water.  The deposits My
 •r aay not underlie a present-day river and nay or may not
 he In direct hydraulic connection with a stream.  Glacial
..till or recent alluvium often overlies the burled valley.
 usually the deposits are several times more permeable than
 Che surrounding bedrock, with finer-grained alluvium
 covering the underlying sand and gravel.  Soils are
 typically a sandy loam. Recharge to the sand and gravel Is
 ••derate and water levels are commonly relatively shallow,
 although they may be quite variable.
SETTING 7 c Moraine
FEATURE
)epth to Water
4et Recharge
tquifer Media
Soil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
15-30
7-10
Sand and Gravel
Sandy Loan-
6-121
Silt/clay
300-700
GENERAL
•EIGHT
5
4
3
2
1
5
3
RATING
7
8
8
6
5
3
4
Qraatlc Index
NUMBER
35
32
24
12
5
15
12
135
SETTING 7 D Buried Valley
FEATURE
tepth to Mater
let Recharge
ugulfer Media
loll Media
topography
[•pact Vadose zone
lydraulic Conductivity
RANGE
30-50
7-10
Sand and Gravel
Sandy Loam
2-ei
S t G w/sig. Silt
and Clay
1000-2000
GENERAL
HEIGHT
S
4
3
1
1
S
3
RATING
5
e
8
6
9
6
e
Drastic Index
NUMBER
25
32
24
12
S
30
24
156
SETTING 7 C Korai.-e
FEATURE
Jepth to Water
4et Recharge
tquifer Media
Soil Media
Topography
Impact Vadose Zone
iydraulic Conductivity
RANGE
15-30
7-10
Sand and Gravel
Sandy Loar
6-124
Silt/Clay
300-700
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
7
e
e
6
5
3
4
Pesticide
Drastic Index
NUMBEF
35
32
24
30
15
12
1
156
IETTING 7 D Buried Valley
FEATURE
>epth to Hater
let Recharge
Kjulfer Media
loll Media
•opography
Iiapact vadoae tone
lydraulic Conductivity
RANGE
30-50
7-10
Sand and Gravel
Sandy Loar,
2-6%
E t G w/sig. Silt
and Clay
1000-200C
PESTICIDE
WEIGHT
5
4
3
S
3
4
t
RATING
5
e
£
6
9
6
e
Pesticide
Drastic Index
NUMBEf
25
32
2<
30
27
24
16
176
                                                         247

-------
GLACIATED CENTRAL

(7Ea) River Alluvium With Overbank Deposits

This hydrogeologlc setting is characterized by low
topography and thin to moderately thick deposits of
flood-deposited alluvium along portions of the river valley.
The alluvium is underlain by fractured bedrock of
sedimentary, metamorphlc or igneous origin.  Water is
obtained from sand and gravel layers which are Interbedded
with finer-grained alluvial deposits.  The floodplaln la
covered by varying thicknesses of fine-grained silt and clay
called overbank deposits.  The overbank thickness is usually
greater along major streams (as much as 40 feet) and thinner
along minor streams.  Precipitation in the region varies,
but recharge Is somewhat reduced because of the sllty and
clayey overbank soils which typically cover the surface.
Water levels are moderately shallow.  Ground water may he in
direct hydraulic contact with the surface stream-  The
alluvium may serve as a significant source of water and may
also be In direct hydraulic with the underlying sedimentary
rocks.
GLACIATED CENTRAL

(7lb) River Alluvium Without Overbank Deposits

this aetting Is identical  to (6Fa) River Alluvium with
Ovcrbank Deposits except that no significant  fine-grained
floodplain deposits occupy the stream valley.  This results
in •i«nificantly higher recharge where precipitation is
4»it)4juate and sandy soils occur at the surface.  Water levels
•re moderate to shallow in depth.  Hydraulic  contact with
toe surface stream Is usually excellent, with alternating
r«charge/discharge relationships varying with stream «tage.
These deposits also serve as a good source of recharge to
the underlying fractured bedrock.
SETTING 7 Ea Rlvcr Alluvium With Overbarik
Depot i t«
FEATURE
>epth to Hater
let Recharge
Iquifer Media
Boil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
15-30
4-7
Sand and Gravel
Silty Loan
0-2%
Silt/Clay
700-1000
GENERAL
HEIGHT
5
4
3
2
1
t
3
RATING
7
e
6
4
10
3
6
Drastic Index
NUMBER
35
24
24
e
10
15
16
134
•ETTING 7 Ea Rlvcr Alluviuit Hith Overbank
DeDOs it*
FEATURE
>epth to Kater
let Recharge
kquifer Media
Mill Media
Topography
[a^act Vadose Zone
lydraulic Conductivity
RANGE
15-3C
4-7
Sand and Gravel
Silty Loan
0-21
Silt/Clay
700-1000
PESTICIDE
HEIGHT
S
4
3
5
3
4
2
RATING
7
e
e
4
10
3
t
Pesticide
Drastic Index
NUMEEf
3i
24
24
20
30
12
12
157
SETTING ' Et> River Al
FEATURE
>epth to Hater
let Recharge
Iqulfer Media
•oil Media
Topography
Impact Vadose Zone
lydraullc Conductivity
luviun Without
RANGE
5-15
10*
Send and Gravel
Sand
0-2*
Sand and Gravel
700-1000

SETTING 7 EL River Al
Cvprh= A Dear,
FEATURE
tepth to Water
let Recharge
iquifer Media
toil Media
Topography
[•pact Vadoie Zone
lydraulic Conductivity
luviuir. Without
its
RANGE
5-15
10*
Sand and Gravel
Sand
0-21
Sand and Gravel
700-1000
GENERAL
(EIGHT
5
4
3
2
1
S
)
RATING
9
9
e
9
10
e
6
Prattle Index

NUMBER
45
36
24
18
1C
4C
16
191

PESTICIDE
HEIGHT
5
4
3
5
2
4
2
RATING
9
9
I
9
10
S
e
Pesticide
Drastic Index
NUMBEF
45
3t
24
45
30
32
12
224
                                                          248

-------
GLACIATED CENTRAL
                                                              GLACIATED CENTRAL
(7F) Glacial Lake Deposits

This hydrogeologlc setting Is characterized by flat
topography and varying thicknesses of fine-grained sediments
that overlie sequences of fractured sedimentary rocks.  The
deposits are composed of fine-grained silts and clays
Interlayered with fine sand that settled out In glacial
lakes and exhibit alternating layers relating to seasonal
fluctuations.  As a consequence of the thin, alternating
layers there Is a substantial difference between the
vertical and horizontal permeability with the horizontal
commonly two or more orders of magnitude greater than the
vertical.  Due to their fine-grained nature, these deposits
typically weather to organic-rich sandy loams with a range
In permeabilities reflecting variations in sand content.
Underlying glacial deposits or bedrock serve as the major
source of ground water In the region.  Although
precipitation Is abundant, recharge Is controlled by the
permeability of the surface clays; however, in all Instances
recharge Is moderately high because of the Impact of the low
topography.  Hater levels are variable, depending on the
thickness of the lake sediments and the underlying
materials.
(70) Thin Till Over ledded Sedimentary Rock

This hydrogeologlc setting Is characterized  by moderate  to
low topography and deposits of thin, patchy  glacial  till
overlying alternating layers of fractured consolidated
sedimentary rocks.  The till, where present, is  primarily
unsorted deposits of clay, sand and gravel.  Although ground
water occurs in both the till and In the Intersecting
fractures of the bedrock, the bedrock is the principal
aquifer.  The glacial till serves as a source of recharge to
the underlying bedrock.  Although precipitation  is abundant
in most of the region, recharge is moderate  because  of the
glacial tills and clayey (oils.  Water levels are extremely
variable, but usually moderate.
SETTING 7 F Glacial Lake Deposits
FEATURE
>epth to Hater
Jet Recharge
kquifer Media
Soil Media
Topography
[Kpact Vadose Zone
^draulic Conductivity
RANGE
15-30
4-7
Bedded SS, LS,
SH Sequences
Sandy Loam
0-2%
S & G w/ Sig . Silt
and clay
100-300
GENERAL
HEIGHT
5
4
3
1
1
5
3
RATING
7
6
t
6
10
6
2
Drastic Index
NUMBER
35
24
18
12
10
35
6
135
SETTING ^ T Glacial Lake Deposits
FEATURE
>eptn to Water
Jet Recharge
Kjuifer Media
soil Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
15-30
4-7
Bedded SS , LS ,
SH Sequences
Sandy Loam
0-2*
S t G w/ sig. Silt
and Clay
100-300
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
7
t
6
1
10
6
2
Pesticide
Drastic Irtex
NUMfiEI
35
24
18
30
30
24
4
165
SETTING ' c Thin Till
FEATURE
tepth to Hater
let Recharge
ujuller Media
ioil Media
Topography
[•pact Vadose Zone
lydraulic conductivity

Over Bedded
pvk
RANGE
15-30
7-10
Bedded SS, LS,
SN Sequences
Clay Loan
2-61
Eilt/Clay
100-3CC


»EJ6MT
5-
4
3
2
1
5
3
Drastu
GENERA!
RATING
7
e
6
3
9
3
2
: Index

NUMBER
35
32
18
6
i
15
e
121
SETTING 7 G Tnl" Till Over Bedded
FEATURE
>epth to water
let Recharge
kquifcr Media
ioil Media
topography
[•pact Vadose lone
lydraulic conductivity
RANGE
15-30
7-10
Bedded SS, LS,
SK Sequences
Clay Loam
2-6»
Silt/Clay
100-300
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
^
l
e
3
9
3
2
Pesticide
Drastic Index
NUMBES
35
32
1C
15
27
12
4
143
                                                         249

-------
GLACIATED CENTRAL
                                                              6LACIATED CENTRAL
(7R) Beaches, teach Ridges and Sand Dunes

This hydrogeologlc setting Is characterized by low relief,
sandy surface soil that is predominantly silica sand,
extremely high infiltration rates end low sorptlve capacity
in the thin vadose zone.  The water table is very shallow
beneath the beaches bordering the Great Lakes.  These
beaches are connonly ground-vater discharge areas.  The
water table Is slightly deeper iMBMth the rolling dune
topography and the vestigial Inland Wach ridges.  All of
these areas serve as recharge sources for the underlying
sedimentary bedrock aquifers, and they often serve as local
sources of water  supply.
(71) Swamp/Marsh

This hydrogeologic setting is characterized by low
topographic relief, high water levels and high organic silt
and clay deposits.  These wetlands occur along the courses
of floodplains and in upland areas as a result of vertically
restricted drainage.  Conaon features of upland wetlands
include those characteristics attributable to glacial
activity such as fllled-ia glacial lakes, potholes and
cranberry bogs.  Recharge is moderate In nost of the region
4ue to restriction by clayey aoils and Halted by
precipitation.  The swamp deposits very rarely serve as
significant aquifers but frequently recharge the underlying
sand and gravel or bedrock aquifers.
IETTING ^ H lc*SnSE ' Beack R^dgeE and
fEKTORl
tepth to Hater
let Recharge
tqulfxr Hedla
Mil Manila
Topography
tatpact Vadose Zone
lydraulic Conductivity
RANGE
0-5
10*
Sand And Gravel
Sana
0-2»
Sar^d and Gravel
1000-2000

wriGHT
S
4
3
2
1
S
3
GENERAL.
RATING
10
9
a
9
10
e
t
Drastic Index

NUMBER
50
36
24
16
10
40
24
202
SETTING 7 1 swamp/Marsh
FEATURE
Mtpth to Hater
let Recharge
kqulfer Media
toll Media
ropography
[«pact vedoae tone
lydraullc Conductivity
RANGE
0-5
4-7
Sairf and Grove)
HKV
0-2
S fc G w/siq. silt
and Cloy
700-100G
GENERAL
HEIGHT
5
4
9
1
1
5
3
RATING
10
6
e
2
10
t
(
traiUc Index
NUMBER
51
24
24
4
10
3C'
18
IfO
iETTJNG 7H Baches,
fEATURE
lepth to Nater
lat Recharge
kqulfer Media
•oil Madia
Topography
(•pact vadoie lone
hydraulic Conductivity
Beach Ridgec and
BS . . . 	
RANGE
0-5
10-
Sa'.d an2 Gravel
Sand
0-2»
Sand and Gravel
1000-2000
PESTICIDE
HEIGHT
5
4
3
i
3
4
2
RATING
10
9
8
9
10
6
e
Pesticide
Drastic Index
NUMBEF
50
36
24
45
30
24
It
225
lETTINC 7 j Swamp/Marsh
FEATURE
lepth to Mater
let Recharge
kqulfer Media
Oil Media
ropooraphy
la?aet Vadoac lone
lydraulic conductivity
RANGE
0-5
4-7
Sand arid Gravel
Hick
0-2
S t G w/sig. Silt
and Clay
700-1000

WEIGHT
5
4
3
5
3
t
2
PE5T1C1
RATING
11,
L
b
•"
tu
c
I.
Oraitlc Index
K
NUMBEF
50
24
2<
1C
30
24
12

                                                          250

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6.  PIEDMONT BLUE  RIDGE GROUND-WATER REGION
        6A
        8B
        8C
        8D
        8E
        8F
        8G
Mountain Slopes
Alluvial Mountain Valleys
Mountain Flanks
Regolith
River Alluvium
Mountain Crests
Swamp/Marsh
                     251

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                         8.  PIEDMONT BLUE RIDGE REGION


          (Thick regolith over fractured crystalline and metamorphosed
                               sedimentary rocks)

    The Piedmont and Blue Ridge region is an area of about 247,000 km2
extending from Alabama on the south to Pennsylvania on the north.   The Piedmont
part of the region consists of low, rounded hills and long, rolling,
northeast-southwest trending ridges whose summits range from about a hundred
meters above sea level along its eastern boundary with the Coastal Plain to 500
to 600 m along its boundary with the Blue Ridge area to the west.   The Blue
Ridge is mountainous and includes the highest peaks east of the Mississippi.
The mountains, some of which reach altitudes of more than 2,000 m, have
smooth-rounded outlines and are bordered by well-graded streams flowing in
relatively narrow valleys.

     The Piedmont and Blue Ridge region is underlain by bedrock of Precambrian
and Paleozoic age consisting of igneous and metamorphosed igneous and
sedimentary rocks.  These include granite, gneiss, schist, quartzite, slate,
marble, and phyllite.  The land surface in the Piedmont and Blue Ridge is
underlain by clay-rich, unconsolidated material derived from in situ weathering
of the underlying bedrock.  This material, which averages about 10 to 20 m in
thickness and may be as much as 100 m thick on some ridges, is referred to as
saprolite.  In many valleys, especially those of larger streams, flood plains
are underlain by thin, moderately well-sorted alluvium deposited by the
streams.  When the distinction between saprolite and alluvium is not important,
the term regolith is used to refer to the layer of unconsolidated deposits.

     The regolith contains water in pore spaces between rock particles.  The
bedrock, on the other hand, does not have any significant intergranular
porosity.  It contains water, instead, in sheetlike openings formed along
fractures (that is, breaks in the otherwise "solid" rock).  The hydraulic
conductivities of the regolith and the bedrock are similar and range from about
0.001 to 1 m day~l.  The major difference in their water-bearing
characteristics is their porosities, that of regolith being about 20 to 30
percent and that of the bedrock about 0.01 to 2 percent.  Small supplies of
water adequate for domestic needs can be obtained from the regolith through
large-diameter bored or dug wells.  However, most wells, especially those where
moderate supplies of water are needed, are relatively small in diameter and are
cased through the regolith and finished with open holes in the bedrock.
Although, as noted, the hydraulic conductivity of the bedrock is similar to
that of the regolith, bedrock wells generally have much larger yields than
regolith wells because, being deeper, they have a much larger availble
drawdown.
                                      25:

-------
     All ground-water systems function both as reservoirs that store water and
as pipelines (or conduits) that transmit water from recharge areas to discharge
areas.  The yield of bedrock wells in the Piedmont and Blue Ridge region
depends on the number and size of fractures penetrated by the open hole and on
the replenishment of the fractures by seepage into them from the overlying
regolith.  Thus, the ground-water system in this region can be viewed, from the
standpoint of ground-water development, as a terrane in which the reservoir and
pipeline functions are effectively separated.  Because of its larger porosity,
the regolith functions as a reservoir which slowly feeds water downward into
the fractures in the bedrock.  The fractures serve as an intricate
interconnected network of pipelines that transmit water either to springs or
streams or to wells.

     Recharge of the ground-water system occurs on the areas above the flood
plains of streams, and natural discharge occurs as seepage springs that are
common near the bases of slopes and as seepage into streams.  With respect to
recharge conditions, it is important to note that forested areas, which include
most of the Blue Ridge and much of the Piedmont, have thick and very permeable
soils overlain by a thick layer of forest litter.  In these areas, even on
steep slopes, most of the precipitation seeps into the soil zone, and most of
this moves laterally through the soil in a thin, temporary, saturated zone to
surface depressions or streams to discharge.  The remainder seeps into the
regolith below the soil zone, and much of this ultimately seeps into the
underlying bedrock.

     Because the yield of bedrock wells depends on the number of fractures
penetrated by the well, the key element in selecting well sites is recognizing
the relation between the present surface topography and the location of
fractures in the bedrock.  Host of the valleys, draws, and other surface
depressions indicate the presence of more intensely fractured zones in the
bedrock which are more susceptible to weathering and erosion than are the
intervening areas.  Because fractures in the bedrock are the principal avenues
along which ground water moves, the best well sites appear to be in draws on
the sides of the valleys of perennial streams where the bordering ridges are
underlain by substantial thicknesses of regolith.  Wells located at such sites
seem to be most effective in penetrating open water-bearing fractures and in
intercepting ground water draining from the regolith.  Chances of success seem
to be somewhat less for wells on the flood plains of perennial streams,
possibly because the alluvium obscures the topographic expression of bedrock
fractures.  The poorest sites for wells are on the tops of ridges and mountains
where the regolith cover is thin or absent and the bedrock is sparsely
fractured.

     As a general rule, fractures near the bedrock surface are most numerous
and have the largest openings, so that the yield of most wells is not increased
by drilling to depths greater than about 100 m.  Exceptions to this occur in
Georgia, South Carolina and North Carolina and some other areas where
water-bearing, low-angle faults or fractured zones .are present at depths as
great as 200 to 300 m.
                                      253

-------
     The Piedmont and Blue Ridge region has long been known as an area
generally unfavorable for ground water development.  This reputation seems to
have resulted both from the small reported yields of the numerous domestic
wells in use in the region that were, generally, sited as a matter of
convenience and from a failure to apply existing technology to the careful
selection 6f well sites where moderate yields are needed.  As water needs in
the region increase and as reservoir sites on streams become increasingly more
difficult to obtain, it will be necessary to make more intensive use of ground
water.
                                       254

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PIEDMONT AND SLUE RIDGE
                                                               FXIHiDNT AMD H.OE KIDGE
(8A) Mountain Slopes

This hydrogeologlc setting is characterized by steep slopes
on the side of mountains, a thin soil cover and fractured
bedrock.  Ground water is obtained primarily from the
fractures in the bedrock which may be of sedimentary,
metamorphic or igneous origin, but which is commonly
•etamorphlc or igneous.  The fractures provide localized
sources of ground water and well yields are typically
limited.  Although precipitation is abundant, due to the
•teep slopes, thin soil cover and small storage capacity of
the fractures, runoff is significant and ground-water
recharge is only moderate.  Water levels are extremely
variable but are commonly deep.
(•» Alluvial Mountain Valleys

This hydrogeologic setting is characterized by thin,
bouldery alluvium which overlies fractured bedrock of
sedimentary, metamorphic or igneous origin.  The alluvium,
which includes both mass-wastage and water-sorted debris, is
derived from the surrounding slopes, and serves as a
localized source of water.  Water is obtained from sand and
gravel layers which are interspersed between finer-grained
deposits.  Surflclal deposits have typically weathered to a
learn.  Hater levels are usually relatively shallow but are
extremely variable.  Ground water is also obtained from the
fractures In the underlying bedrock, which are typically in
direct hydraulic connection with the overlying alluvium.
SETTING 8 A Mountain slopes
FEATURE
>epth to Hater
4et Recharge
tquifer Media
ioil Media
Topography
[•pact Vadoie zone
lydraulic Conductivity
RANGE
75-100
2-4
Met amor phic/ Igneous
Thir. or Absent
18*
Metamorpwic/3gneou!
1-100

GENERAL
'EIGHT
5
4
3
2
1
5
3
RATING
2
3
3
10
1
4
1
DraiUc Index
NUMBER
10
12
9
20
1
2C
3
75
SETTING S A Kov.r.tain Slopes
FEATURE
>epth to Hater
4et Recharge
iqulfer Media
ioil Media
Topography
[•pact Vadote zone
lydraulic Conductivity
RANGE
75-10C
2-4
Me tancrph ic /Igneous
Thir. or Absent
18*
Metamorpfcic/Jgneoui
1-100
PESTICIDE
HEIGHT
5
4
3
S
3
4
2
RATING
2
3
3
10
1
4
1
Pesticide
Ik-aatic Inda>
NUMBEF
10
12
9
50
3
H
2
102
iETTJHG B B Alluvial Mountain Valleys
FEATURE
>*pth to Water
let Recharge
tquifer Media
ioil Media
Topography
Impact Vadose tone
iydraullc Conductivity
RANGE
5-15
7-10
Sand and Gravel
Loam
2-6%
S 4 G w,' sig. Silt
and Clay
300-700
GENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
9
e
8
5
9
t
4
Drastic Index
NUMBER
45
32
24
10
9
30
12
162
BETTING e B Alluvial MOdr.taln Valleys
FEATURE
>epth to Water
4et Recharge
Aquifer Media
Soil Media
Topography
Inpact Vadoie Zone
lydraulic Conductivity
DANCE
5-15
7-10
Sand and Gravel
Loairi
2-61
S I G w/ ng. silt
and Clay
300-700
PESTICIDE
WEIGHT
:
4
3
S
3
4
2
RATING
5
t
8
5
9
6
4
Pesticide
Drastic Index
NUMBEI
45
32
24
25
27
24
8
185
                                                         255

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PIIDMON1 AND BLOT RIDGE
                                                               FIUMONT AND BLUE RIDGE
(8C) Mountain Flanks

This hydrogeologlc setting IB characterized by moderate
topographic relief and moderately-dipping, fractured,
consolidated sedimentary rocks.  Soil cover Is usually
thicker than on the mountain slopes and typically has
weathered to a sandy loam or loam.  Although precipitation
Is abundant, ground-water recharge Is moderate due to the
soil cover and slope.  Utter levels are typically
moderately-deep although they are extremely variable.  The
mountain flanks serve a« the recharge area for aquifers
which are typically confined le adjacent valley areas.
(8D) Kegolith

This hydrogeologlc setting Is characterized by moderate to
low slopes covered by regolith and underlain by fractured
bedrock of igneous, sedimentary or metamorphic origin.  The
regolith is typically clay-rich but may also serve as a
source of ground water for low-yield wells.  The regolith
functions as a reservoir for ground-water recharge to the
bedrock which is in direct hydraulic connection with the
•flurlying regolith.  the bedrock typically yields larger
•counts of ground water than the regolith when the well
Intersects fractures In the bedrock-
lETTIKG g c Mountain Flanks
FEATURE
>epth to Hater
let Recharge
iqulfer Media
ion Media
Topography
Impact Vadoae Zone
lydraullc Conductivity
RANGE
30-SO
2-4
Bedded 55, LS,
SH Sequences
Loam
6-121
Bedded LS, SS, SH
100-300
GENERAL
*EIOHT
i
4
3
2
1
S
}
HATING
5
3
e
5
S
(
2
BnaUc Index
NUMBER
25
12
ie
10
5
30
e
106
SETTING 8 C Regolith
FEATURE
tepth to water
*et Recharge
Aquifer Media
ioil Media
Topography
[•pact Vadoae tone
tydraullc Conductivity
RANGE
5-15
4-7
Weathered Meta./Ig.
Clay Loam
6-12»
Silt/Clay
1-100
GENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
'$
C
4
3
i
1
1
Drastic Index
NUMBER
45
24
12
6
5
5
3
IOC
TOTTING 8 C Mountain Flanks
FEATURE
lepth to Water
Jet Recharge
iqulftr Media
ioil Media
Topography
Impact Vadoae Ion*
lydraulic conductivity
RANGE
30-50
2-4
Bedded SS, LS,
SH Sequences
Loan
e-m
Bedded LS, SS, SH
100-300
PESTICIDE
HEIGHT
i
t
3
t
•)
t
)
RATING
5
3
C
S
5
<
2
l&ikc't.W
•omci
25
12
1C
25
IS
24
4
123
SETTING 8 C Regolltfi
FEATURE
>epth to Water
let Recharge
iquifer Media
ioil Media
Topography
[atpact Vadoae Zone
lydraullc Conductivity
RANGE
5-15
4-1
Weathered Keta./Ig
Clay Loam
6-12*
Silt/Clay
1-100
PESTICIDE
WEIGHT
i
4
3
5
3
4
2
RATING
S
e
4
3
5
1
1
Pesticide
Drastic Index
NUMBEC
45
24
12
15
1 5
4
2
117
                                                            256

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PIEDMONT AND BLUE RIDGE
                                                                rttMONT AND BLUE RIDGE
(8E) River Alluvium

This hydrogeologic setting Is characterized by low
topography and deposits of varying thickness of alluvium
along parts of stream valleys.  The alluvium is underlain by
fractured igneous, metanorphic or consolidated sedimentary
rocks.  Water is obtained from sand and gravel which is
overlain and interbedded with finer-grained alluvial
deposits.  Surficial deposits usually weather to a sandy
loam.  The sand and gravel within the alluvium serves as the
principal aquifer, but the alluvium also serves as the
source of ground-water recharge for the underlying aquifer.
Precipitation is abundant and recharge Is moderately high,
limited only by the loamy surficial deposits.  Hater levels
are extremely variable, but are typically moderately
shallow.
(if) Mountain Crests

This hydrogeologic setting is characterized by moderate to
steep topography on the crests of mountains with thin soil
cover and exposed fractured bedrock.  Ground water is
obtained primarily from the fractures In the bedrock which
may be of sedimentary, metamorphic or igneous origin but
which la commonly metamorphic or igneous.  The fractures
provide localized sources of ground water and well yields
are typically limited.  Although precipitation is Abundant,
due to the (lopes, thin soil cover and small storage
capacity of the fractures, runoff Is significant and
ground-water recharge is low.  Hater levels are extremely
variable but commonly deep.
BETTING 6 r River Alluvium
FEATURE
iepth to Hater
let Recharge
Aquifer Media
ioll Media
Topography
Impact Vadose Zone
hydraulic Conductivity
RANGE
5-15
7-10
Sand and Gravel
Sandy Loam
2-6%
£ 1 G w/ sic. Silt
and Clay
1000-2000
GENERAL
tfEICHT
5
4
3
2
1
5
3
RATING
9
8
e
e
9
c
>
erotic Intex
NUMBER
45
32
24
12
9
30
24
176
iETTING ( r Mountain
FEATURE
Mpth to Water
let Recharge
iquifer Media
ioil Media
•opoeraphy
[•pact vadoae zone
lydraulic conductivity
Crests
RANGE
100*
0-2
Metamorphic/lgneoui
Thin or Absent
2-6»
Metamorpt- ic/Igneoui
1-10C
GENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
1
1
3
10
9
4
1
Drastic Index
NUMBER
&
4
a
20
9
20
3
70
SETTING 6 i Flver A.J.H.
FEATURE
Jepth to Water
vet Recharge
kquifer Media
Soil Media
Topography
Impact Vadote tone
lydraulic Conductivity
-•lur
RANGE
5-15
7-10
Sand and Gravel
Sandy Loan
2-6 «
S t G w/ sig. Silt
and Clay
1000-2000
PESTICIDE
HEISMT
5
4
2
S
1
4
2
RATING
9
8
e
e
•
6
a
Pesticide
Drastic Index
NUMBEf
45
32
24
30
27
24
16
198
SETTING e f Mountain
FEATURE
Mpth to Water
wt Recharge
iguifer Media
ioll Media
Topography
[•pact Vadose tone
lydraulic conductivity
Crests
RANGE
100*
0-2
Metamorphic/lgneou
Thin or Absent
2-6%
Metwnorphic/Igneoui
1-100
1 PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
1
1
3
10
9
4
1
Pesticide
Drastic Index
NUHBEI
S
4
9
SO
27
16
2
113
                                                          257

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PIEDMONT AND BLUE RIDGE

(8G) Swa*p/Marsh

This hydrogeologlc setting is characterized by low
topographic relief, high water levels and high organic silt
and clay deposits'  These wetlands occur along the courses
of floodplalns and in upland areas as a result of vertically
restricted drainage.  Recharge is conmonly low to Moderate
as a result of low topography and low conductivities even
though rainfall is high.  These areas nay be discharge tones
or aay alternate as recharge and discharge zones as Masons
change.
ItTTIHG $ c Swamp/Marsh
FEATURE
lepth to Hater
Jet Recharge
iqolfer Media
soil Media
topography
[•pact Vadoae Zone
lydraulic Conductivity
RANGE
0-5
4-7
Netairorpl > ic/ Igneous
Muck
0-2
Mctarorf* ic/Igioous
1-100
GENERAL
(EIGHT
S
4
3
2
1
5
3
RATING
10
6
3
2
10
4
1
tr**Uc Index
NUMBER
SC
24
9
4
10
20
3
120
[fTTING e c SwalrF/Kar
KATURE
Mpth to Water
let Recharge
ujuifer Media
ioil Media
Topography
[•pact Vadoae lone
lydreullc conductivity
h
RANGE
r-5
4-7
Mcta orpine/ 1 < irtaut-
Muck
0-2
H-u.^n-.K.vm^-.
1-10C
PESTICIDE
HEIGHT
S
4
3
5
3
4
2
RATING
lu
f.
3
2
10
4
1
Pecticide
ttmtic InJe*
•UHBEI
50
24
9
1C
30
V.
'
141
                                                            258

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9.  HORTHEAST  AND SUPERIOR UPLANDS GROUND-WATER REGION
      9A
      9B
      9C
      9Da
      9Db
      9E
      9F
      9Ga
      9Gb
      9H
      91
      9J
      9K
Mountain Slopes
Alluvial Mountain Valleys
Mountain Flanks
Glacial Till Over Crystalline Bedrock
Glacial Till Over Outwash
Outwash
Moraine
River Alluvium With Overbank Deposits
River Alluvium Without Overbank Deposits
Swamp/Marsh
Bedrock Uplands
Glacial Lake/Glacial Marine Deposits
Beaches, Beach Ridges and Sand Dunes
                             259

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                       9.  NORTHEAST AND SUPERIOR UPLANDS ,
                                                        ^

              (Glacial deposits over fractured crystalline rocks)

    The Northeast and Superior Uplands region is made up of two separate areas
totaling about 415,000 km2.  The Northeast Upland encompasses the Adirondack
Mountains, the Lake Champlain valley, and nearly all of New England.  The parts
of New England not included are the Cape Cod area and nearby islands, which are
included in the Atlantic and Gulf Coastal Plain region, and the Triassic
lowland along the Connecticut River in Connecticut and Massachusetts, which is
included in the Glaciated Central region.  The Superior Upland encompasses most
of the northern parts of Minnesota and Wisconsin adjacent to the western end of
Lake Superior.  The Northeast and Superior Uplands are characterized by rolling
hills and low mountains.  Land-surface altitudes in the Northeast Upland range
from sea level to more than 1,500 m on some of the peaks in the Adirondacks and
White Mountains.  In contrast to the mountainous areas in the Northeast, the
Superior Upland is in an area of rolling hills whose summits reach altitudes of
only 300 to 600 m.

     Bedrock in the region ranges in age from Precambrian to Paleozoic and
consists mostly of granite, syenite, anorthosite, and other intrusive igneous
rocks and metamorphosed sedimentary rocks consisting of gneiss, schist,
quartzite, slate, and marble.  Most of the igneous and metamorphosed
sedimentary rocks have been intensely folded and cut by numerous faults.

     The bedrock is overlain by unconsolidated deposits laid down by ice sheets
that covered the areas one or more times during the Pleistocene and by gravel,
sand, silt, and clay laid down by meltwater streams and in lakes that formed
during the melting of the ice.  The thickness of the glacial deposits ranges
from a few meters on the higher mountains, which also have large expanses of
barren rock, to more than 100 m in some valleys.  The most extensive glacial
deposit is till, which was laid down as a nearly continuous blanket by the ice,
both in valleys and on the uplands.  In most of the valleys and other low
areas, the till is covered by glacial outwash consisting of interlayered sand
and gravel, ranging in thickness from a few meters to more than 20 m, that was
deposited by streams supplied by glacial meltwater.  In several areas,
including parts of the Champlain valley and the lowlands adjacent to Lake
Superior, the unconsolidated deposits consist of clay and silt deposited in
lakes that formed during the melting of the ice sheets.

     Ground-water supplies are obtained in the region from both the glacial
deposits and the underlying bedrock.  The largest yields come from  the sand and
gravel deposits, which in parts of the valleys of large streams are as much as
60 m thick.  Other sand and gravel deposits, not thick or productive enough to
                                       260

-------
be included in the Alluvial Valleys region, occur locally in most valley and
lowland areas in the Northeast and Superior Uplands region and serve as
important sources of water.

     Water occurs in the bedrock in fractures similar in origin, occurrence,
and hydraulic characteristics to those in the Piedmont and Blue Ridge region.
In fact, the primary difference in ground-water conditions between the Piedmont
and Blue Ridge region and the Northeast and Superior Uplands region is related
to the materials that overlie the bedrock.  In the Piedmont and Blue Ridge,
these consist of unconsolidated material derived from weathering of the
underlying bedrock.  In the Northeast and Superior Uplands the overlying
materials consist of glacial deposits which, having been transported either by
ice or by streams, do not have a composition and structure controlled by that
of the underlying bedrock.  These differences in origin of the regolith between
the Northeast and Superior Uplands and the Piedmont and Blue Ridge are an
important consideration in the development of water supplies, as is discussed
in the following paragraphs.

     Recharge from precipitation generally begins in the fall after plant
growth stops.  It continues intermittently over the winter during thaws and
culminates during the period between the spring thaw and the start of the
growing season.  Precipitation on the Northeast Upland, about 1,200 mm per
year, is twice that on the Superior Upland, with the result that recharge, both
to the glacial deposits and to the underlying bedrock, is largest in the
Northeast.  The glacial deposits in the region serve as a storage reservoir for
the fractures in the underlying bedrock, in the same way the saprolite
functions in the Piedmont and Blue Ridge region.  The major difference is that
the glacial deposits on hills and other upland areas are much thinner than the
saprolite in similar areas in the Piedmont and Blue Ridga and, therefore, have
a much smaller ground-water storage capacity.

     Water supplies in the Northeast and Superior Uplands region are obtained
from open-hole drilled wells in bedrock, from drilled and screened or open-end
wells in sand and gravel, and from large-diameter bored or dug wells in till.
The development of water supplies from bedrock, especially in the Superior
Upland, is more uncertain than from the fractured rocks in the Piedmont and
Blue Ridge region because the ice sheets that advanced across the region
removed the upper, more fractured part of the rock and also tended to obscure
many of the fracture-caused depressions in the rock surface with the layer of
glacial till.  Thus, use of surface depressions in this region to select sites
of bedrock wells is not as satisfactory as in the Piedmont and Blue Ridge.

     Most of the rocks that underlie the Northeast and Superior Uplands are
relatively insoluble, and, consequently, the ground water in both the glacial
deposits and the bedrock generally contains less than 500 mg/1 of dissolved
solids.  Two of the most significant water-quality problems confronting the
region, especially the Northeast Upland section, are acid precipitation and
pollution caused by salts used to de-ice highways.  Much of the precipitation
now falling on the Northeast (in 1982) has a pH in the range of 4 to 6 units.
Because of the low buffering capacity of the soils derived from the rocks
underlying the area, there is relatively little opportunity for the pH to be
                                      261

-------
increased.  One of the results of this is the gradual elimination of living
organisms from many lakes and streams.  The effect on ground-water quality,
which will develop much more slowly, has not yet been determined.  The second
problem—that of de-icing salts—affects ground-water quality adjacent to
streets and roads maintained for winter travel.
                                       262

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NORTHEAST AND SUPERIOR UPLANDS

(9A) Mountain Slopes

This hydrogeologic setting is characterized by steep elopes
on the side of mountains, a thin soil cover and fractured
bedrock.  Ground water is obtained primarily from the
fractures in the bedrock, which nay be of sedimentary,
metamorphic or igneous origin but which Is commonly
•etamorphic or igneous.  The fractures provide localized
sources of ground water, and well yields are typically
limited.  Although precipitation is abundant, due to the
steep slopes, thin «oil cover and null storage capacity of
the  fractures, runoff is significant aod ground-water
recharge  is moderate.  Mater levels are extremely variable
but  are commonly deep.
MRTREAST AND SUPERIOR UPLANDS

(»») Alluvial Mountain Valleys

This hydrogeologic setting Is characterized by  thin,
kouldery alluvium which overlies fractured bedrock of
sedimentary, metamorphlc or igneous origin but  which are
commonly alternating sedimentary layers.  The alluvium,
which Is derived from the surrounding slopes serves as a
localised source of water.  Hater Is obtained from aand and
gravel layers which are Interspersed between fine-grained
deposits.  Surflclal deposits have typically weathered to a
sandy loam.  Hater levels are relatively shallow but may be
extremely variable.  Ground water may also be obtained from
the fractures In the underlying bedrock which are usually In
direct hydraulic connection with the overlying  alluvium.
SETTING 9 A Mourtain Slopes
FEATURE
>epth to Nater
Jet Recharge
kquifer Media
ioil Media
ropography
Impact Vadose zone
Jydraulic Conductivity
RANGE
75-100
2-<
Metamorphlc/Igneou!
Thin or Absent
16»
Metar.orpnic/Icneou:
1-100
GENERAL
WEIGHT
•>
4
3
2
1
5
3
RATING
2
3
3
10
1
4
1
Drastic Index
NUMBER
10
12
9
20
1
20
3
75
SETTING 9 A Mountain sloper
FEATURE
Jepth to Water
let Recharge
uguifer Media
ioil Media
ropography
laipact Vadoie tone
lydraulic Conductivity
RANGE
75-100
2-4
Me tatnorphic/ Igneous
Thin or Absent
18*
Hetamorphic/Igneou
1-100
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
2
3
3
10
1
4
1
Pesticide
Drastic Index
NUMBEC
10
12
9
5u
3
U
2
102
iCTTING 9 B Alluvial Mount* in Valleys
FEATURE
ttpth to Water
let Recharge
ujulfer Media
ioil M*dla
topography
[•pact Vadose Zone
lydraullc Conductivity
RANGE
5-15
7-10
Sand and Gravel
Sandy Loan
2-6%
Sand and Gravel
700-1000
GENERAL
•EIGHT
s
4
3
2
1
5
3
RATING
9
8
8
6
9
e
t
Drastic Index
S UMBER
45
32
24
12
9
4C
U
18C
JETTING 9 6 Alluvial Mountain Valleys
FEATURE
>epth to Hater
let Recharge
hqulfer Media
ioil Media
ropography
[•pact Vadoae Zone
lydraullc Conductivity
RANGE
5-15
7-10
Sand and Gravel
Sandy Loam
2-i»
Sand and Gravel
700-1000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
9
8
e
f
9
e
e
Pesticide
Drastic Index
NUMBEf
45
32
24
30
11
32
12
202 _
                                                          263

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NORTHEAST AND SUPERIOR UPLANDS

(9C) Mountain Flanks

This hydrogeologlc setting is characterized by moderate
topographic relief and moderately dipping, fractured,
consolidated sedimentary rocks•  Soil cover is usually
thicker than on the mountain slopes and typically has
weathered to a sandy loam.  Although precipitation can be
significant, ground-water recharge is moderate due te the
slope.  Water levels are typically moderately deep, although
they are extremely variable.  The mountain flanks serve as
the recharge area for aquifers which are confined in
adjacent lowland areas.  Ground water is obtained from the
permeable sedimentary rocks or from fractures and bedding
planes in the sedimentary rocks.  The sedimentary rocks may
be underlain by fractured bedrock of Igneous, metamorphlc or
sedimentary origin which yield little water.
        T AMD SUPERIOR UPLANDS

(•Da) Glacial Till Over Crystalline Bedrock

This hydrogcologic setting is characterized by moderately
low topographic relief and varying thicknesses of glacial
till overlying severely fractured, folded and faulted
bedrock of Igneous and metamorphic origin with minor
»ccurrences of bedded sedimentary rocks.  The till is
principally unsorted deposits which may be interbedded with
localized deposits of sand and gravel.  Although ground
water occurs in both the glacial deposits and fractured
bedrock, the bedrock is typically the principal aquifer.
The glacial till serves as a recharge source.  Although
precipitation is abundant, recharge is only moderately high
because of the low permeability of the glacial till and the
surficial deposits which typically weather to loan.  Depth
to water is extremely variable depending in part on the
thickness of the glacial till, but is typically moderately
shallow.
JETTING 9 c Mountain FlanKE
FEATURE
>«pth to Hater
let Recharge
kquifer Media
•oil Media
Topography
[npact Vadose Zone
lydraulic Conductivity
RANGE
30-50
2-4
Bedded SS, LS,
SH Sequences
Sar.dy Loar
12-18S
Beddei L£ , SS , SP
100-30C
GENERAL
(EIGHT
S
4
3
2
1
S
3
RATING
'5
3
C
6
3
e
2
Drastic Index
NUMBER
25
12
16
12
3
3C
f
106
SETTING "fcPtiHKftt^
FEATURE
>epth to Mater
i*t Kvcharge
ujuifer Media
toil Media
Topography
Impact Vftdose lone
lydraulic Conductivity
sr-ic*v"
RANGE
15-30
7-10
Metamorphic/Igneou:
Loam
2-6«
Silt/Clay
1-100
GENERAL
•EIGHT
5
4
3
2
1
5
3
RATING
^
e
3
5
9
3
1
Drastic Index
NUMBER
35
32
9
10
9
15
3
113
SETTING 9 c rountai" Flanks
FEATURE
>epth to Water '
let Recharge
kquifer Media
ioil Media
Topography
[•pact Vadoae Zone
iydraulic Conductivity
RANGE
30-50
2-4
Bedded S£ , LS ,
ss- Sequences
Sandy Loar.
12-16%
Bedded LS, SS, SH
100-300
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
5
3
e
t
3
<
2
Pesticide
Drastic Index
NUHBEF
25
12
IB
10
9
24
4
122
iETTIKG gr5|tiitlJi|-Bl^oc9--«
FEATURE
>«pth to Water
Jet Recharge
iquifer Media
ioil Media
Topography
laujtact Vadose Zone
Hydraulic Conductivity
RANGE
15-3C
7-10
Meta-iorphic/Icneou
Loarr
2-6*
Silt/Clay
1-100
PESTICIDE
HEIGHT
5
4
3
5
t
4
2
RATING
7
i
3
5
9
3
1
Pesticide
Drastic Index
NUMEER
36
32
9
25
27
12
2
14:
                                                          264

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NORTHEAST AND SUPERIOR UPLANDS

(9Db) Glacial Till Over Outwash

This hydrogeologlc Betting is characterized by low
topography and outwash naterlals which are covered by
varying thicknesses of glacial till.  The till Is
principally (inserted deposits which Bay be Interbeddcd with
localized deposits of sand and gravel-  Surflclal deposits
have usually weathered to a loam.  Although ground water
occurs In both the glacial till and in the underlying
outwash, the outwash typically serves as the principal
aquifer because the fine grained deposits have been moved
by glacial neltwater.  The outwash Is In direct hydraulic
connection with the glacial till and the glacial till servos
as a source of recharge for the underlying outwash.
Precipitation Is abundant in the region but recharge Is
noderate because of the relatively low permeability of the
overlying glacial till.  Depth to water is extremely
variable depending In part on the thickness of the glacial
till, but averages around 30 feet.
NORTHEAST AND SUPERIOR UPLANDS
                                                         \
(»E) Outwash

This hydrogeologlc setting is characterized by moderate
topographic relief and varying thickness of outwash which
overlie fractured bedrock of sedinentary, metanorphic or
igneous origin.  The outwash consists of water- washed
deposits of sand and gravel which often serve as the
principal aquifers in the area, and which typically have a
sandy loam surficlal layer. The outwash also serves as a
source of recharge to the underlying bedrock.  Recharge is
abundant and ground-water recharge is high.  Hater levels
•re cxtreaely variable, but are relatively (hallow.
JETTING 9 Ob Glacial Till Over Outwash
FEATURE
>epth to Water
let Recharge
kquifer Hedia
ioil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
DANCE
30-50
7-10
Sand and Gravel
Loafr
2-6«
Silt/Clay
1000-2000
GENERAL
(EIGHT
S
4
3
2
1
5
3
RATING
5
t
e
5
9
3
8
Drastic Index
NUMBER
25
32
24
10
9
15
24
139
SETTING 9 £ Outwash
FEATURE
)epth to Water
let Recharge
tqulfer Media
>oll Media
Topography
Impact Vadose Zone
iydraullc Conductivity
RANGE
5-15
10+
Sand and Gravel
Sandy Loam
2-6*
Sand and Gravel
1000-2000
GENERAL
•EIGHT
S
4
3
2
1
5
3
RATING
9
9
8
6
9
e
e
Drastic Index
NUMBER
45
36
24
12
9
40
24
19C
SETTING 9 Db Glacial Till Over Outwash
FEATURE
>epth to Hater
let Recharge
iquifer Media
Soil Media
Topography
rmpact Vadose Zone
fydraulic Conductivity
RANGE
30-50
7-10
Sand and Gravel
Loam
2-61
Silt/Clay
1000-2000
PESTICIDE
HEIGHT
S
4
3
S
3
«
2
RATING
5
8
8
S
9
3
8
Pesticide
Drastic Index
NUMBEI
25
32
24
25
27
12
16
161
SETTING 9 E Outwas!"
FEATURE
ieptb to Water
4et Recharge
kquifer Media
Soil Media
Topography
[•pact Vadose Zone
lydraulic Conductivity

RANGE
5-15
10+
Sand and Gravel
Sandy Loar.
2-6»
Sand and Gravel
1000-2000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
S
9
8
6
9
e
8
Pesticide
Drastic Index
NUMBER
45
36
24
30
27
32
16
210
                                                         265

-------
NORTHEAST AND SUPERIOR UPLANDS
                                                              NORTHEAST AND SUPERIOR UPLANDS
(9F) Moraine

This hydrogeologlc setting Is characterized by moderate
topography and varying thicknesses of mixed glacial deposits
which overlie fractured bedrock of sedimentary, igneous or
netamorphic origin.  This setting is similar to (9E) Outwsh
in that the sand and gravel within the morainal deposits Is
well-sorted and serves as the principal aquifer in the «r««.
These deposits also serve as a source of recharge for the
underlying bedrock.  Moraines also contain sediments that
are typically unsorted and unstratifled; these deposits
contain more fines than outwash deposits, are less permeable
and characteristically more like glacial till. Moraines are
typically mounds or ridges of till which were deposited
along the margin of a stagnant or retreating glacier.
Surflclal deposits often weather to a sandy loam.
Precipitation is abundant throughout the region and ground-
water recharge Is moderately high.  Hater levels are
extremely variable, based in part on the thickness of the
glacial till, but are typically fairly  (hallow.
(»Ga) River Alluvium With Overbank Deposits

This hydrogeologlc setting Is characterized by low
topography and thin to moderately thick deposits of alluvium
along parts of river valleys.  The alluvium Is underlain by
fractured bedrock of sedimentary, metamorphlc or Igneous
origin.  Water is obtained from eand and gravel layers which
•re Interbedded with finer-grained alluvial deposits.  The
floodplaln is covered by varying thicknesses of fine grained
silt and clay, called overbank deposits.  The overbank
thickness is usually greater along major streams (as Much as
40 feet) and thinner along minor streams.  Precipitation is
abundant, but recharge is somewhat reduced because of the
sllty overbank deposits and subsequent clayey loam soils
which typically cover the surface.  Water levels are
typically moderately shallow and may be hydraullcally
connected to the stream or river.  The alluvium may serve as
a significant source of water and Is also usually in direct
hydraulic connection with the underlying bedrock.
SETTING s F Moraine
FEATURE
Jepth to Hater
let Recharge
tquifer Media
loll Media
Topography
Impact Vadose zone
lydraullc conductivity


RANGE
15-30
7-10

Sandy Loan;
6-12%
Sand and Gravel
700-1000


WEIGHT
5
4
3
1
1
S
3
DtttU
GENERAL
RATING
7
8
a
6
5
8
6
c Index

NUMBER
35
32
24
12
5
40
18
m
SETTING 9 F Moraine ' PESTICIDE
FEATURE
>epth to Kater
let Recharge
uguifer Media
ioil Media
Topography
Impact Vadose Zone
lydraullc conductivity

RANGE IWEICHT
15-30
7-10
Sand and Gravel
Sandy Loam
6-12*
Sand and Gravel
700-1000
5
4
3
5
3
4
2
RATING
7
8
8
6
5
e
6
Drastic Index

35
32
24
30
15
32
12
180
lETTING Overharik Deposits
FEATURE
Septh to Mater
let Recharge
Iquifer Media
Soil Media
topography
L»pact Vadose Zone
lydraulic Conductivity
RANGE
15-30
7-10
Sand and Gravel
Clay Loam
0-2%
Silt/Clay
1000-2000
GENERAL
(EIGHT
5
4
3
1
1
5
3
RATING
1
8
e
3
10
3
8
Drastic Index
NUMBER
35
32
24
6
1C
15
24
146
.__..„,. 9 Ga Kiver Alluviuit, Kith
|E7'ING Overbad. Deposits
FEATURE
>epth to Water
let Recharge
tquifer Media
soil Media
Topography
Impact Vadose Zone
lydraullc conductivity
RANGE
1S-3C
7-10
Sand and Gravel
Clay Loar.
0-2*
Silt/Clay
1000-2000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
7
8
8
3
10
3
8
Pesticide
Drastic Index
(iUHEEf
3£
32
24
15
3C
12
16
164
                                                           266

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NORTHEAST AND SUPERIOR UPLANDS
                                                                     IT AMD  SUPERIOR UPLANDS
(9Gb) River Alluvium Without Overbank Deposits

This hydrogeologlc setting Is Identical to (9Ga) River
Alluvium With Overbank Deposits except that no significant
fine-grained floodplaln deposits occupy the stream valley.
This results in significantly higher recharge where
precipitation is adequate and sandy soils occur at the
(urface.  Water levels are moderate to shallow in depth.
Hydraulic contact with the surface stream is usually
excellent, with alternating recharge/discharge relationships
varying with stream stage.  These depotlts serve as a good
source of recharge to the underlying fractured bedrock.
(*H) fcnap/Marsh

This hydrogeologlc setting is characterized by low
topographic relief, high water levels and high organic silt
and clay deposits.  These wetlands occur along the courses
of floodplalns and in upland areas as a result of vertically
restricted drainage.  Common features of upland wetlands
Include those characteristics attributable to glacial
activity such as fllled-ln glacial lakes, potholes and
cranberry bogs.  Recharge is moderate in most of the region
due to restriction by clayey soils.  The swamp deposits very
rarely serve as significant aquifers but frequently recharge
the underlying sand sad gravel or bedrock aquifers.
SETTING 8 Gb River Allu
TEXTURE
)epth to Hater
let Recharge
tquifer Media
(oil Media
ropoqraphy
[mpact vadose zone
fydraulic Conductivity
vium without
RANGE
5-15
10<
Sand and Gravel
Sandy Loam
0-21
Sand and Gravel
1000-2000
GENERAL
HEIGHT
s
4
3
2
1
5
3
RATING
9
9
8
6
10
8
8
Drastic Index
NUMBER
45
36
24
12
10
40
24
191
IETTING 9 H Swamp/Harsh
FEATURE
Xpth to Mater
let Recharge
iqulfer Media
•oil Madia
Topography
[•pact Vadose Zone
lydraulic Conductivity
RANGE
0-5
4-7
Metara-phic/Igneous
Mick
0-2
Metancrphic/IgneouE
1-10C
GENERAL
(EIGHT
5
4
3
2
1
5
}
RATING
10
6
3
2
10
4
1
Drastic Index
NUMBER
50
24
9
4
10
20
3
12C
lETTING 9 Gt River Allu\ lu- KltnC--.
Ovprh»-l. rijspr.e *c
FEATURE
>epth to Hater
Jet Recharoe
Iqulfer Media
ioil Media
Topography
[mpact Vadose Zone
lydraulic Conductivity
RANGF
5-15
10-
Sand and Grevel
Sar.dy Loam
0-2%
Sand and Gravel
1000-2000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
9
9
8
6
10
e
I
Pesticide
Drastic Index
NUMBEI
45
36
24
30
30
32
16
213
lETTING » H Swamp/Marth
FEATURE
Mtpth to Hater
let Recharge
iqulfer Media
>oll Media
repooraphy
[•pact Vados* tone
lydraulic Conduct 1. .ty
RANGE
0-5
4-7
Mt . fiL-rphic/lti icou-.
MxrK
0-2
Mt?t3flDr|j| . 1C/ Iu- HJOU >.
1-10t,
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
1f<
f
3
2
1C
4
1
Pesticide
Drastic Intel
NUMBEI
5C
24
9
10
30
16
2
141
                                                         267

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NORTHEAST AND SUPERIOR UPLANDS

(91) Bedrock Dpi and«

This hydrogeologic Betting Is characterized  by moderately
low topographic relief and exposed fractured,  folded and
faulted bedrock of Igneous and low-grade metamorphic origin
with minor occurrences of bedded sedimentary rocks.
Recharge is primarily controlled by precipitation but is
limited by the hydraulic conductivity of the rock.  Where
present, soils are commonly sandy.  These areas typically
serve as limited aquifers.
•OKTUAST AND SUPERIOR UPLANDS

(*J) Glacial Lake/Glacial Marine Deposits

This hydrogeologic setting is characterized by relatively
flat to gently rolling topography and varying thicknesses of
fine-grained sediments that overly sequences of fractured
Igneous and metamorphic rocks.  The deposits are composed of
fine-grained silts and clays interlayered with fine sand
that settled out in glacial lakes and submerged coastal
areas and exhibit alternating layers relating to seasonal
fluctuations.  Due to their fine- grained nature, these
deposits range In permeabilities reflecting variations in
sand content.
IETTING 9 I Bedrock uplands
FEATURE
»pth to Hater
let Recharge
tquife-r Media
toll Madia
•opoqraphy
•pact Vadoae tone
lydraulic Conductivity
RANGE
11-30
4-7
Metanorphic/lcraoua
Saiact vadoa* Zone
lydraulic Conductivity
RANGE
15-30
4-7
Metarorf*i ic/ 3 gneous
Sand
2-6
Metancrphic/IgneouE
1-100
PESTICIDE
HEIGHT
S
4
3
S
3
4
2
RATING
7
f
3
1

24
9
45
27
Id
2
ISh
SETTING ' J Glacial Lake/Glacial Marine
D*t>nft Its
FEATURE
>epth to Hater
let Recharge
kquifer Media
ioil Media
topography
[•pact Vadoac Zone
lydraulic Conductivity
RANGE
15-30
4-7
MetaRorFtiic/lgneous
LOOT
2-«
StG w/sio Silt b Clay
1-1 00
GENERAL
(EIGHT
5
4
)
2
1
5
3
RATING
7
6
3
5
9
6
1
Drastic Index
NUMBER
35
2t
9
1C
9
3C
3
12C

FEATURE
>epth to Hater
let Recharge
iquifer Media
ioil Media
ropooraphy
Impact vadoae Zone
lydraulic Conductivity
RANGE
15-30
4-7
PESTICIDI-
HEIGHT
5
4
MetsiDrphic/lgneous 3
Loair. , 5
2-61
StG w/sig Silt l Clay
3
4
1-100 ! 2
RATING
7
6
3
5
9
6
1
Pesticide
Drastic Index
NUMBER
35
24
9
25
27
24
2
146
                                                       268

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NORTHEAST AND SUPERIOR UPLANDS

(9K) Beaches, Beach Ridges and Sand Dunes

This hydrogeologic setting Is characterized by a low relief,
sandy surface soil that Is predominantly silica sand,
extremely high Infiltration rates and  low sorptive capacity
in the thin vadose zone.   The water table is very shallow
beneath the beaches boarding the coastal areas.  The water
table is slightly deeper  beneath the rolling dune topography
and the vestigial inland  beach ridges.  All of these «re««
serve as recharge sources for the underlying sedimentary
bedrock aquifers, and they may serve as local sources of
water supply.
JETTING ' K Bea-hes . Beach Ridges and
	 £im3 Dune
FEATURE
>epth to Water
tft Recharge
kqulfcr Media
loll Media
ropoqraphy
[•pace Vadose Zone
lydraulic Conductivity
RANGE
5-15
10*
Metarorphic/lgneous
Sand
0-2«
Sand and Gra\-el
1-100
GENIRU.
(EIGHT
5
4
3
1
1
S
3
RATING
9
9
3
9
10
8
1
Draitic index
NUMBER
a
X
9
16
10
40
3
161
SETTING ^ * Beaches,, Beach Pidges and
_Siad Dune
FEATURE
>epth to Water
'c* Recharge
tqulfer Media
ioll Media
Topography
Impact Vadoce Zone
lydraullc conductivity
RANGE
5-15
10»
PESTICIDE
WEIGHT
S
4
MetanDrphic/lgneOus 3
Sand i 5
0-2«
Sand and Gravel
1-100
3
4
2
RATING
9
9
3
i
10
e
1
Pesticide
Drastic Index
NUMBEI
45
36
9
45
30
32
2
199
                                                     269

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10. ATLANTIC AND GULF COASTAL PLAIN  GROUND-WATER REGION
         lOAa
         lOAb

         lOBa
         lOBb
         IOC
Regional Aquifers
Unconsolidated  & Semi-Consolidated
  Shallow Surficial Aquifer
River Alluvium  With Overbank Deposits
River Alluvium  Without Overbank Deposits
Swamp
                              270

-------
                      10.  ATLANTIC AND GULF COASTAL PLAIN


                  (Complexly interbedded sand, silt, and clay)

     The Atlantic and Gulf Coastal Plain region is an area of about 844,000
km2 extending from Cape Cod, Massachusetts, on the north to the Rio Grande in
Texas on the south.  This Region does not include Florida and parts of the
adjacent States; although those areas are a part of the Atlantic and Gulf
Coastal Plain physiographic province, they together form a separate
ground-water region.  (See region 11, "Southeast Coastal Plain").

     The Atlantic and Gulf Coastal Plain region ranges in width from a few
kilometers near its northern end to nearly a thousand kilometers in the
vicinity of the Mississippi River.  The great width near the Mississippi
reflects the effect of a major downwarped zone in the Earth's crust that
extends from the Gulf of Mexico to about the confluence of the Mississippi and
Ohio Rivers.  This area is referred to as the Mississippi embayment.

     The topography of the region ranges from extensive, flat, coastal swamps
and marshes 1 to 2 m above sea level to rolling uplands, 100 to 250 m above sea
level, along the inner margin of the region.

     The region is underlain by unconsolidated sediments that consist
principally of sand, silt, and clay transported by streams from the adjoining
uplands.  These sediments, which range in age from Jurassic to the present,
range in thickness from less than a meter near the inner edge of the region to
more than 12,000 m in southern Louisiana.  The greatest thicknesses are along
the seaward edge of the region and along the axis of the Mississippi embayment.
The sediments were deposited on floodplains and as deltas where streams reached
the coast and, during different invasions of the region by the sea, were
reworked by waves and ocean currents.  Thus, the sediments are complexly
interbedded to the extent that most of the named geologic units into which they
have been divided contain layers of the different types of sediment that
underlie the region.  These named geologic units (or formations) dip toward the
coast or toward the axis of the Mississippi embayment, with the result that
those that crop out at the surface form a series of bands roughly parallel to
the coast or to the axis of the embayment. The oldest formations crop out along
the inner margin of the region, and the youngest crop out in the coastal area.

     Within any formation the coarsest grained materials (sand, at places
interbedded with thin gravel layers) tend to be most abundant near source
areas. Clay and silt layers become thicker and more numerous downdip.
                                       271

-------
     Although sand, silt, and clay, as noted above, are the principal types of
material underlying the Atlantic and Gulf Coastal Plain, there are also a small
amount of gravel interbedded with the sand, a few beds composed of mollusk
shells, and a small amount of limestone present in the region.  The most
important limestone is the semi-consolidated Castle Hayne Limestone of Eocene
age which underlies an area of about 26,000 km2 in eastern North Carolina, is
more than 200 m thick in much of the area, and is the most productive aquifer
in North Carolina. A soft, clayey limestone (the chalk of the Selma Group) of
Late Cretaceous age underlies parts of eastern Mississippi and western Alabama,
but instead of being an aquifer it is an important confining bed.

     From the standpoint of well yields and ground-water use, the Atlantic and
Gulf Coastal Plain is one of the most important regions in the country.
Recharge to the ground-water system occurs in the interstream areas, both where
sand layers crop out and by percolation downward across the interbedded clay
and silt layers.  Discharge from the system occurs by seepage to streams,
estuaries, and the ocean.  Movement of water from recharge areas to discharge
areas is controlled, as in all ground-water systems, by hydraulic gradients,
but in this region the pattern of movement is complicated by down-dip
thickening of clay which hampers upward discharge.  As a result, movement down
the dip of the permeable layers becomes increasingly slow with increasing
distance from the outcrop areas. This causes many flow lines to converge on the
discharge areas located on major streams near the downdip part of outcrop
areas. These areas of concentrated ground-water discharge are referred to as
"artesian-water gaps" by LeGrand and Pettyjohn (1981).

     Wells that yield moderate to large quantities of water can be constructed
almost anywhere in the region. Because most of the aquifers consist of
unconsolidated sand, wells require screens; where the sand is fine-grained and
well sorted, the common practice is to surround the screens with a coarse sand
or gravel envelope.

     Withdrawals near the outcrop areas of aquifers are rather quickly balanced
by increases in recharge and (or) reductions in natural discharge.  Withdrawals
at significant distances downdip do not appreciably affect conditions in the
outcrop area and thus must be partly or largely supplied from water in storage
in the aquifers and confining beds.

     The reduction of storage in an aquifer in the vicinity of a pumping well
is reflected in a decline in ground-water levels and is necessary in order to
establish a hydraulic gradient toward the well.  If withdrawals are continued
for long periods in areas underlain by thick sequences of unconsolidated
deposits, such as the Atlantic and Gulf Coastal Plain, the lowered ground-water
levels in the aquifer may result in drainage of water from layers of silt and
clay.  The depletion of storage in fine-grained beds results in subsidence of
the land surface.  Subsidence in parts of the Houston area totaled about 9 m as
of 1978.  Subsidence near pumping centers in the Atlantic Coastal Plain has not
yet been confirmed but is believed to be occurring, though at a slower rate
than along the Texas Gulf Coast.
                                       272

-------
     The depletion of storage in confining beds is permanent, and subsidence of
the land surface that results from such depletion is also permanent.  On the
other hand, depletion of storage in aquifers may not be fully permanent,
depending on the availability of recharge.  In arid and semiarid regions,
recharge rates are extremely small, and depletion of aquifer storage is, for
practical purposes, permanent.  Depletion of storage in aquifers in these
regions is referred to as mining.  In humid regions, recharge is sufficient to
replace aquifer storage rather quickly, once withdrawals are stopped, so that
depletion of aquifer storage in these areas is not considered to be mining.
The important point is that depletion of storage in the confining layers of
silt and clay in both arid and humid regions is permanent but is not normally
considered to be ground-water mining.  The term "mining" is applied by most
ground-water hydrologists only to areas in which aquifer storage is being
permanently depleted.

     Depletion of storage in the aquifers underlying large areas of the
Atlantic and Gulf Coastal Plain is reflected in long-term declines in
ground-water levels.  These declines suggest that withdrawals in these areas
are exceeding the long-term yield of the aquifers.

     This is a water-management problem that will become more important as
rates of withdrawal and the lowering of water levels increase.  Solutions to
this problem include (1) concentrating withdrawals as close as possible to
outcrop (recharge) areas, (2) dispersing withdrawals in regions remote from the
outcrop areas over the widest possible area, and (3) increasing withdrawals
from surficial aquifers to the maximum possible extent.

     Another problem that affects ground-water development in the region
concerns the presence of saline water in the deeper parts of most aquifers.
The occurrence of saline water is controlled by the circulation of freshwater
which, as noted previously, becomes increasingly slow down the dip of the
aquifers.  Thus, in some of the deeper aquifers, the interface between
freshwater and saltwater is inshore, but in parts of the region, including
parts of Long Island, New Jersey, and Mississippi, the interface in the most
intensively developed aquifers is a significant distance offshore.  Pumping
near the interfaces has resulted in problems of saltwater encroachment locally.

     Another significant feature of the ground-water system in this region is
the presence of "geopressured" zones at depths of 1,800 to 6,100 m in Texas and
Louisiana which contain water at a temperature of 80°C to more than 273°C.
Water in these zones contains significant concentrations of natural gas, and
the water in some zones is under pressures sufficient to support a column of
water more than 4,000 m above land surface.  Because the elevated temperature,
natural gas, and high pressures are all potential energy sources, these zones
are under intensive investigation.
                                      273

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ATLANTIC AND GULF COASTAL PLAIN
                                                                ATLANTIC AND  GULF  COASTAL PLAIN
(lOAa) Regional Aquifer

This hydrogeologlc letting Is characterized by moderately
low topographic relief and gently dipping, complexly
Interbedded unconsolidated and semi-consolidated deposits
which consist primarily of sand, silt and clay.  Outcrops of
these deposits form a aeries of bands roughly parallel to
the coast or to the axis of the Mississippi Embayment.  The
outcrop areas and overlying semi-permeable beds are the
principal sources of recharge to the formations which serve
as regional aquifers.  Precipitation Is abundant and
recharge Is moderately high in the outcrop areas but low
regionally to deep zones.  Surficlal deposits typically
weather to a sandy loam.  Large quantities of water are
obtained from the sand and gravel and sand deposits within
the aquifer.  Water levels are extremely variable and
typically are shallower toward the shoreline.  When ground
water ie heavily pumped near the shoreline, these aquifers
are very susceptible to salt-water Intrusion. Since the
shallow aquifers are very vulnerable to pollution due to
their permeable nature, and the deeper aquifers are
recharged from the shallow ones, the entire system Is
somewhat susceptible to ground-water pollution.  The degree
of vulnerability varies according to the nature of the
deposits and the amount of recharge.
iCTTING 10 Aa Confined Regional Aquifers
FEATURE
Mpth to Hater
let Recharge
kquifer Media
loll Hedia
Topography
:*pact Vadoae tone
lydraullc Conductivity
RANGE
100«
0-2
Sand and Gravel
Sandy Loam
0-2%
Silt and Clay
JOO-700
GENERAL
•EIGHT
5 •
4
3
2
1
5
. J
RATING
•l
1
e
t
10
3
4
Draatic Index
NUMBER
5
4
24
12
10
15
12
12
(lOAb) Onconsolidated & Semi-Consolidated Shallow Surficlal
Aquifer

This setting is very similar to (lOAa) Confined Regional
Aquifers except that the principal aquifer is the shallow
surficial deposits which serve as a local source of water
and typically provide recharge for the regional aquifer.
Water Is obtained from the surficial sand and gravel which
may be separated from the underlying regional aquifer by a
confining layer.  This confining layer typically "leaks"
providing recharge to the deeper zones.  Surficlal deposits
are sandy loams. Water levels tend to be quite shallow,
•specially near the coast.  Precipitation Is abundant and
recharge to the ground water is high.  These deposits are
very vulnerable to ground-water pollution due to their
permeable nature.
SETTING 10 Ab Unconsolld
Oijkllra^ eiM"fl<-la
FEATURE
>epth to Hater
Jet Recharge
iquifer Hedia
soil Hedia
Topography
Impact Vadose Zone
lydraullc conductivity
ated l Soni-Coisolidatac
1 A^lMffr
RANGE
5-15
10*
Sand and Gravel
Sandy Loam
2-61
Sand and Gravel
700-1000
GENERAL
WEIGHT
5
4
3
2
1
5
3
RATING
9
9
8
6
9
B
c
Drastic Index
NUMBER
45
36
24
12
9
40
IS
18<
SETTING 10 Aa Confined Regional Aquifers
FEATURE
Mpth to Hater
let Recharge
kquifer Media
Soil Hedia
Topography
[npact vadose Zone
lydraullc Conductivity
RANGE
100<
0-2
Sand and Gravel
Sandy Loam
0-2%
Silt and Clay
300-700
PESTICIDE
NCIGHT
5
4
3
5
3
4
2
RATING
1
1
8
6
10
3
4
Peaticide
Draatic Intel
NUHBEi
5
4
24
30
30
12
8
113
SETTING 10 to Unconsoli£
Bh.11,,.. 5,,-f..r,_
FEATURE
Jepth to Hater
let Recharge
iqulfer Media
Soil Hedia
Topography
[•ipact Vadoae Zone
lydraulic Conductivity
ated i Semi-Consolldatec
|1 touiff-r
RANGE
5-15
10*
Sand and Gravel
Sandy Loa-.
2-6%
Sand and Gravel
700-1000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
9
9
8
6
9
e
6
Pesticide
Drastic Index
NUMDEF
45
36
24
30
27
32
12
206
                                                           274

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ATLANTIC AND GULF COASTAL PLAIN
                                                               ATLANTIC AMD GDLF COASTAL PLAIN
(lOBa) River Alluvium with Overbank Deposits

This hydrogeologic setting is characterized by low
topography and thin to moderately thick deposits of alluvium
along parts of river valleys.  The alluvium is underlain by
consolidated and semi-consolidated sedimentary rocks.  Water
is obtained from sand and gravel layers which are
interbedded with finer-grained alluvial deposits.  The
floodplain is covered by varying thicknesses of
fine-grained, silty deposits called overbank deposits.  The
overbank thickness is usually greater along major streams
(as much as 40 feet) and thinner along minor streams.
Precipitation in the region is abundant, but recharge is
somewhat reduced because of the silty overbank deposits and
subsequent silty soils which typically cover the surface.
Water levels are typically moderately shallow.  The alluvium
may serve as a significant source of water and may be in
direct hydraulic connection with the underlying sedimentary
rocks.  The alluvium may also serve as a source of recharge
to the underlying bedrock.
(1Mb) River Alluvium without Overbank Deposits

This catting is identical to (lOBa) River Alluvium with
Overbank Deposits except that no significant fine-grained
floodplain deposits occupy the stream valley.  This results
In significantly higher recharge and sandy soils at the
surface.  Water levels are typically shallow In depth and
throughout much of this region there Is an abundance of
coarse-grained material.  Hydraulic connection with the
surface stream Is usually excellent, with alternating
recharge/discharge relationships varying with stream (tace.
These «*po*lts provide a good source of recharge to the
Ukterlvlm*, eemaolidated and seal-consolidated bedrock.
iETTING ^ BB River Alluvium With Over-
FEATURE
>epth to Water
4«t Recharge
kqulfer Media
ioll Madia
Topography
Impact Vadose zone
epth to Mater
*et Recharae
Iquifer Media
Soil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
15-30
7-10
Sand and Gravel
Silty Loam
0-2«
Silt/Clay
700-1000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
7
8
e
4
10
3
(
Pesticide
Drastic Index
NUNBEF
35
32
24
20
30
12
12
1CS
ICTTtNG ov«rb«nk Depo
FEATURE
tepth to Water
let Recharge
tqulfer Media
Soil Media
Topography
Impact Vadoie Zone
lydraulic Conductivity

its
RANGE
5-15
10*
Sand and Gravel
Sand
0-2%
5 & G w/ clg. Silt
and Clay
1000-2000


WEIGHT
S
4
3
2
1
5
3
Drastu
GENERA!
RATING
9
9
e
9
10
6
e
c Index

NUMBER
45
36
24
18
10
3C
24
167
•FTTTMr ic Bb River Alluviutr. Without
.tnini* overbank Deposits
FEATURE
tepth to Water
fet Recharae
tqulfer Media
ioll Media
Topography
tmpact Vadose Zone
lydraulic Conductivity
RANGE
5-15
10*
Sand and Gravel
Sand
0-2%
S 4 C w/ sig. Silt
and Clay
1000-2000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2 .
RATING
9
9
e
9
1C
(
$
ettlift.
NUMBE!
45
36
24
45
30
24
U
220
                                                            275

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ATLANTIC AND GULF COASTAL PLAIN

(IOC) Swamp

This hydrogeologlc letting it characterized  by  low
topographic relief and deposits of sand,  and sand and
gravel, which overlie consolidated and  semi-consolidated
sedimentary rocks.  Precipitation is  abundant and potential
recharge is high.  Water levels are typically at or near the
surface during the majority of the year.   Surficlal deposits
are typically sand nixed with organic material. The
surflcial sands are usually In hydraulic  connection with the
underlying aquifers and nay serve as  a  source of recharge.
However, a swamp is frequently a ground-water discharge tone
and in this case would not be especially  vulnerable to
pollution.  It should also be noted that  a slight reversal
In gradient would easily convert the  swamp into a
ground-water recharge lone.  Thus, It Is  potentially highly
vulnerable to ground-water pollution.
IETTING ,0 c SvamF
flATURE
xpth to niter
let Recharge
tquifer Media
loll Media
Topography
Impact Vadose Zone
lydraulic conductivity
RANGE
0-5
10*
Sand and Gravel
Sand
0-2%
Sand and Gravel
1000-2000
GENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
10
9
e
9
10
8
e
Drastic Index
NUMBER
SO
36
24
18
10
40
24
202
!ETT:NC ,0 c Swamp
FEATURE
>epth to Water
Jet Recharge
tqulfer Media
Soil Media
Topography
Impact Vadoae lone
lydraulic Conductivity

RANGE
0-5
10*
Sand and Gravel
Sand
0-21
Sand and Gravel
1000-2000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
10
9
e
9
10
e
t
Pesticide
Druuc Index
NUMBEI
sc
36
24
45
30
32
16
233
                                                           276

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11. SOUTHEAST COASTAL PLAIN GROUND-WATER REGION
          I    -I — 	 I 	 	  '    ^ 	 _^-"- •
         '    i     i  "L   T  /-T-r^:;'
  11A

  11B
  11C
  11D
Solution Limestone and Shallow Surficial
  Aquifers
Coastal  Deposits
Swamp
Beaches  & Bars
                      277

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                          11.   SOUTHEAST COASTAL PLAIN
     (Thick layers of sand and clay over semi-consolidated carbonate rocks)

     The Southeast Coastal Plain is an area of about 212,000 km2 in Alabama,
Florida, Georgia, and South Carolina.  It is a relatively flat, low-lying area
in which altitudes range from sea level at the coast to about 100 m down the
center of the Florida peninsula and as much as 200 m on hills in Georgia near
the interior boundary of the region.  Much of the area, including the
Everglades in southern Florida, is a nearly flat plain less than 10 m above sea
level.

     The.land surface of the Southeast Coastal Plain is underlain by
unconsolidated deposits of Pleistocene age consisting of sand, gravel, clay,
and shell beds and, in southeastern Florida, by semiconsolidated limestone.
From the coast up to altitudes of nearly 100 m, the surficial deposits are
associated with marine terraces formed when the Coastal Plain was inundated at
different times by the sea.  In most of the region the surficial deposits rest
on formations, primarily of middle to late Miocene age, composed of interbedded
clay, sand, and limestone.  The most extensive Miocene deposit is the Hawthorn
Formation.  The formations of middle to late Miocene age and, where those
formations are absent, the surficial deposits overlie semiconsolidated
limestones and dolomites that are as much as 1,500 m thick.  These carbonate
rocks range in age from early Miocene to Paleocene and are generally referred
to collectively as Tertiary limestones.

     The Tertiary limestone that underlies the Southeast Coastal Plain
constitutes one of the most productive aquifers in the United States and is the
feature that justifies treatment of the region separately from the remainder of
the Atlantic and Gulf Coastal Plain.  The aquifer, which is known as the
Floridan aquifer, underlies all of Florida and southeast Georgia and small
areas in Alabama and South Carolina.  The Floridan aquifer consists of layers
several meters thick composed largely of loose aggregations of shells of
foraminifers and fragments of echinoids and other marine organisms interbedded
with much thinner layers of cemented and cherty limestone.  The Floridan, one
of the most productive aquifers in the world, is the principal source of
ground-water supplies in the southeast Coastal Plain region.

     In  southern Florida, south of Lake Okeechobee, and in a belt about 30 km
wide northward along the east coast of Florida to the vicinity of St.
Augustine, the water in the Floridan aquifer contains more than 100 mg/1 of
chloride.  In this area, most water supplies are obtained from surficial
aquifers, the most notable of which underlies the southeastern part of Florida
and which in the Miami area consists of 30 to 100 m of cavernous limestone and
                                       278

-------
sand referred to as the Biscayne aquifer.  The Biscayne is an unconfined
aquifer which is recharged by local precipitation and by infiltration of water
from canals that drain water from impoundments (conservation areas) developed
in the Everglades.  It is the principal source of water for municipal,
industrial, and irrigation uses and can yield as much as 5m3min-l (1,300
gal min~l) to small-diameter wells less than 25 m deep finished with open
holes only 1 to 2 m in length.

     The surficial aquifers in the remainder of the region are composed
primarily of sand, except in the coastal zones of Florida where the sand is
interbedded with shells and thin limestones.  These surficial aquifers serve as
sources of small ground-water supplies throughout the region and are the
primary sources of ground water where the water in the Floridan aquifer
contains more than about 259 mg/1 of chloride.

     The Floridan aquifer, as noted above, is the principal source of ground
water in the region.  Ground water in the upper part of the aquifer is
unconfined in the principal recharge areas in Georgia and in west-central
Florida.  In the remainder of the region, water in the aquifer is confined by
clay in the Hawthorn Formation and in other beds that overlie the aquifer.
Recharge occurs where the potentiometric surface of the Floridan aquifer is
1'ower than the water table in the overlying surficial aquifer.  The principal
recharge areas include a broad area along the west side of Florida extending
from the central part of the peninsula to south-central Georgia and an area
extending from west-central Florida through southeast Alabama into southwest
Georgia.  In these areas, recharge rates are estimated to exceed 120 mm yr~^
(5 in. yr~l).  Recharge occurs by infiltration of precipitation directly into
the limestone, where it is exposed at the land surface, and by seepage through
the permeable soils that partly mantle the limestone in the outcrop areas.
Considerable recharge also occurs in the higher parts of the recharge areas
through permeable openings in the confining beds, where these beds have been
breached by the collapse of caverns in the limestone during the process of
sinkhole formation.  Thus, the land surface in most of Florida north of Lake
Okeechobee is marked by thousands of closed depressions ranging in diameter
from a few meters to several kilometers.  The larger depressions, which
represent a more advanced stage of solution of the limestone and collapse of
the overlying material, are occupied by lakes generally referred to as sinkhole
lakes.

     Discharge from the Floridan aquifer occurs through springs and by seepage
to streams.  Considerable discharge also occurs by diffuse seepage across the
overlying confining beds in areas where the potentiometric surface of the
aquifer stands at a higher altitude than the water table.  In most of these
areas, which include the southern third of the Florida peninsula, the east
coast area and major stream valleys of Florida, and the coastal zone and major
stream valleys of Georgia and South Carolina, wells open to the aquifer will
flow at the land surface.  Such wells are called "flowing artesian wells."  The
most spectacular discharge from the Floridan aquifer is through sinkholes
exposed along streams and offshore.  Florida has 27 springs of the first
magnitude at which the average discharge exceeds 2.83 m^sec"! (100
        ).  The largest is Silver Springs, which has an average discharge
                                       279

-------
of 23.2 m3sec-l (530 million gallons per day) and reached a maximum
discharge of 36.5 mSsec"1 on September 28, 1960.  Heath and Conover (1981)
estimate that the combined discharge from Florida's springs is 357 m3sec-l
(8 billion gallons per day).

     The marked difference in ground-water conditions between the Southeast
Coastal Plain and the Atlantic and Gulf Coastal Plain and the Atlantic and Gulf
Coastal Plain regions is apparent in the response of ground-water levels to
withdrawals.  In the Atlantic and Gulf region most large withdrawals are
accompanied by a pronounced continuing decline in ground-water levels.  In the
Southeast Coastal Plain, on the other hand, large withdrawals have
significantly lowered ground-water levels in only a few areas.
                                      280

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SOUTHEAST COASTAL PLAIN
                                                                MOIBAST COASTAL PLAIN
(HA)  Solution Lines tone and Shallow Surflcial Aquifers

This bydrogeologlc setting Is characterised by low to
moderate topographic relief and deposits of limestone which
have been partially dissolved to form a network of solution
cavities and caves.  Surflcial deposits typically consist of
sands which may serve as localized aquifers.  The underlying
limestone typically serves as the principal aquifer due to
the high yields.  The shallow surflclal aquifer may not be
present in all areas.  Precipitation is abundant and
recharge is high.  Water levels are variable but are usually
moderate in the limestone and shallow In the overlying
Surflcial sands.  These sands also serve as an important
source of recharge for the limestones.  Due to the presence
of a shallow water table and direct recharge to the
limestone these surficial sands are very vulnerable to
pollution.  Near the coast, these aquifers are very
susceptible to salt water intrusion.
(Ill) Coastal Deposits

TMe hydrogeologlc setting Is characterized by flat
topography and unconsolldated deposits of carbonate, sand,
gravel, clay and shell beds which overlie semi-consolidated
carbonate rocks.  The surficial deposits serve as direct
sources" of ground vater and also serve as recharge for the
underlying carbonate rocks where the gradient Is downward
toward the earkoMtea.  The carbonates serve as a source of
ground rater bat My contain saline water In tome aroas.
Precipitation la abundant and recharge Is high.  Hater
level* s»y very, but are typically close to the aurface.
SETTING 11 A Solution Limestone
FEATURE
>epth to Hater
4et Recharge
tquifer Media
Soil Media
ropoqraphy
Impact vadoae Zone
lydraulic Conductivity
RANGE
5-15
10-
Xarst Limestone
Sand
2-6*
Karst Limestone
2000*
GENERAL
HEIGHT
5
4
3
2
1
5
3
RATING
9
9
10
9
9
10
10
Drastic Index
NUMBER
4E
36
30
IE
9
50
3C
216
SETTING 11 B Coastal Deposits
FEATURE
Xpth to Mater
let Recharge
tquifer Media
ioil Media
ropoqraphy
[impact Vadoce Zone
lydraulic Conductivity
RANGE
5-15
10*
Sand and Gravel
Sand
0-2*
Sand and Gravel
700-100C
GENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
9.
9
6
9
10
«
6
Drastic Into
NUMBER
45
36
24
IB
10
40
16
191
iHTTING 11 A solution Limestone
FEATURE
>epth to Water
Jet Recharge
\quifer Media
ioil Media
ropoqraphy
Impact Vadose Zone
lydraulic conductivity
DANCE
5-15
10->
Karst Limestone
Sand
2-6 >
Kar&t Limestone
2000-1
PESTICIDE
HEIGHT
5
4
3
5
}
4
2
RATING
9
9
10
9
9
10
10
Pesticide
Drastic Index
NUMOKK
45
36
30
45
27
40
20
243
irTTING 11 B Coastal Deposits , PESTICIDE
FEATURE
>epth to Water
let Recharge
tquifer Media
.oil Media
Topography
Impact Vadoae Zone
lydraulic conductivity
RANGE
5-15
10*
Sand and Gravel
Sand
0-2%
Sand and Gravel
700-1000
WEIGHT
5
4
3
S
3
4
2
RATING
9
9
6
9
10
e
6
Pesticide
Drastic Index
NUHDM
45
36
24
45
30
32
12
224
                                                            281

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SOUTHEAST COASTAL PLAIN

(11C) Swamp

This hydrogeologlc setting Is characterized by flat
topographic relief, very high water levels and deposits of
limestone which have partially been dissolved to form a
network of solution cavities and caves.  Soils are typically
sand and recharge may be high due to the abundant
precipitation.  The lines tone typically serves as the Bajor
regional aquifer.  These swamps also serve as discharge
areas, but due to their environmental vulnerability, and
possible gradient reversal, they should be regarded as areas
of maximum (potential) recharge.  Hater levels are typically
at or above the surface during the majority of the year.
•OCTOAST COASTAL PLAIN

(Itt) »«ach«« and Bars

This tiydrogeologic setting Is characterized by moderate to
fist topographic relief and unconsolldated deposits of
mater-washed sands.  These eands sre well-sorted and very
permeable, and may serve as localized sources of ground
mmter.  These deposits also serve as a source of recharge to
the underlying unconsolldated coastal deposits.
Precipitation Is abundant and recharge Is high.  Water
levels may vary, mat are typically shallow.  These areas are
highly susceptible to pollution due to their high
permeabilities.
iETTING 11 C Swamp
FEATURE
topth to Water
let Recharge
kquifer Media
ioll Madia
Topography
[•pact vadoae Zone
lydraulic Conductivity


RANGE
0-5
10*

Sand
0-2%
Karst Linestone
2000"


HEIGHT
S
4
3
2
1
t
J
Gra»U
GENERAL
RATING
10
9
10
9
10
10
10
c Inont

NUMBER
SO
36
30
16
10
SO
30
224
SETTING 11 D Beaches and Bars
FEATURE
>epth to Hater
Jet Recharge
tquifer Media
toil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
5-15
10+
Sand and Gravel
Sand
2-6%
Sand and Gravel
700-1000
GENERAL
HEIGHT
5
4
3
2
1
i
3
RATING
9
9
8
9
9
8
6
Drastic Index
NUMBED
45
36
24
16
9
40
18
190
iETTING 11 C Swamp
FEATURE
Xpth to Water
let Recharge
iqulfer Media
ioil Media
Topography
Impact Vadoae tone
rydraulic Conductivity
RANGE
0-5
10*
Karst Limestone
Sand
0-2%
Xarst Limestone
2000+
PESTICIDE
HEIGHT
S
4
3
S
3
4
2
RATING
10
9
10
9
10
10
10
Pesticide
Drastic Index
HUMSEI
SO
36
30
45
30
40
20
251
irTTJNG 11 D Beaches and Bars
FEATURE
>epth to Water
Jet Recharge
Iquifer Media
ioil Media
Topography
[•pact Vadoae Zone
lydraulic Conductivity
RANGE
5-15
10->
Sam] and Gravel
Sand
2-6%
Sand and Gravel
700-1000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
9
9
S
9

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12. HAWAIIAN ISLANDS GROUND-WATER REGION
       100
                               too
           r^-9-
                       HAW;
                          ,IIAN
                PA C
                    ; FI c
                        ISlAND

                          0 CE A I
    12A
    12B
    12C
    12D
Mountain Slopes
Alluvial Mountain Valleys
Volcanic Uplands
Coastal Beaches
                     283

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                             12.  HAWAIIAN ISLANDS


     (Lava flows segmented in part by dikes, interbedded with ash deposits,
                        and partly overlain by alluvium)

     The Hawaiian Islands region encompasses the State of Hawaii and consists
of eight major islands occupying an area of 16,707 km^ in the Pacific Ocean
3,700 km southeast of California.  The islands are the tops of volcanoes that
rise from the ocean floor and stand at altitudes ranging from a few meters to
more than 4,000 m above sea level.  Each island was formed by lava that issued
from one or more eruption centers.  The islands have a hilly to mountainous
appearance resulting from erosion that has carved valleys into the volcanoes
and built relatively narrow plains along parts of the coastal areas.

     Each of the Hawaiian Islands is underlain by hundreds of distinct and
separate lava flows, most of which are composed of basalt.  The lavas issued in
repeated outpourings from narrow zones of fissures, first below sea level, then
above it.  The lavas that extruded below the sea are relatively impermeable.
Those formed above sea level tend to be highly permeable, with interconnected
openings that formed as the lava cooled, cavities and openings that were not
filled by the overlying flow, and lava tubes (tunnels).  The central parts of
the thicker flows tend to be more massive and less permeable; the most common
water-bearing openings are joints and faults that formed after the lava
solidified.  Thin layers of ash and weathered volcanic rock occur irregularly
between some of the flows that formed above sea level.  The lava flows in
valleys and parts of the coastal plains are covered by a thin layer of alluvium
consisting of coral (limestone) fragments, sand-size fragments of basalt, and
clay.

     The fissures through which the lava erupted tend to cluster near eruption
centers.  Flows from the fissures moved down depressions on the adjacent slopes
to form layers of lava that dip at angles of 4 to 10 degrees toward the margins
of the volcanoes.  The result, prior to modification by erosion, is a broad,
roughly circular, gently convex mountain similar in shape to a warrior's
shield.  Thus, volcanoes of the Hawaiian type are referred to as shield
volcanoes.  When eruption along a fissure ceases, the lava remaining in the
fissure solidifies to form a dike.

     All of the islands have sunk, to some extent, as a result of a downward
flexing of the Earth's crust caused by the weight of the volcanoes.  This has
resulted in flows that formed above sea level being depressed below sea level.
The upper parts of these flows contain freshwater that serves as an important
source of water.
                                      284

-------
     In mineral composition and nature of the water-bearing openings, the lavas
that form the Hawaiian Islands are very similar to those in the Columbia
Plateau region.  Thus, from these two standpoints, these regions could be
combined into one.  There is, however, one important difference that justifies
their treatment as separate regions.  This difference relates to the presence
of seawater around and beneath the islands, which significantly affects the
occurrence and development of water supplies.

     From the standpoint both of description and of development, it is useful
to divide the ground-water system of the Hawaiian Islands into three parts.
The first part consists of the higher areas of the islands in the vicinity of
the eruption centers.  The rocks in these areas are formed into a complex
series of vertical compartments surrounded by dikes developed along eruption
fissures.  The ground water in these compartments is referred to as
dike-impounded water.  The second, and by far the more important, part of the
system consists of the lava flows that flank the eruption centers and that
contain fresh ground water floating on saline ground water.  These flank flows
are partially isolated hydraulically from the vertical compartments developed
by the dikes that surround the eruption centers.  The fresh ground water in
these flows is referred to as basal ground water.  In parts of the coastal
areas the basal water is confined by the overlying alluvium.  The third part of
the system consists of fresh water perched, primarily in lava flows, on soils,
ash, or thick impermeable lava flows above basal ground water.

     The ground-water system is recharged by precipitation which ranges
annually from about 160 mm to more than 11,000 mm.  This wide range in
precipitation reflects the effect of the islands on the moist northeast trade
winds.   As the moisture-laden winds are deflected upward by the mountains,
precipitation falls on the higher elevations.  Precipitation is heaviest on
mountains below 1,000 m and lightest in the coastal areas on the leeward side
of the islands and at elevations above 1,000 m on the islands of Maui and
Hawaii.  The average annual precipitation on the islands is estimated to be
about 1,800 mm.  Because of the highly permeable nature of the volcanic soils,
it is estimated that about 30 percent of the precipitation recharges the
ground-water system.

     Some discharge of dike-impounded ground water doubtless occurs through
fractures in the dikes into the flanking lava flows.   This movement must be
small,  however, because water stands in the compartments at levels hundreds of
meters  above sea level and the principal discharge occurs as springs on the
sides and at the heads of valleys where erosion has removed parts of the dikes.
Both the basal ground water and the perched ground water in the lava flows
surrounding the dike-bounded compartments is recharged by precipitation and by
streams leaving the dike-bounded area.  Discharge is  to streams and to springs
and seeps along the coast.

     The basal water is the principal source of ground water on the islands.
Because the freshwater is lighter (less dense) than seawater, it floats as a
lens-shaped body on the underlying seawater.  The thickness of the freshwater
zone below sea level essentially depends on the height of the freshwater head
above sea level.  Near the coast the zone is thin, but several kilometers
                                      285

-------
inland from the coast on the larger islands it reaches thicknesses of at least
a few hundred meters.  In parts of the coastal zone, and especially on the
leeward side of the islands, the basal ground water is brackish.

     Forty-six percent of the water used in Hawaii in 1975, or 3.1 x
        "1. was ground water.  It is obtained through horizontal
tunnels and through both vertical and inclined wells.  Tunnels are used to
obtain supplies of basal water near the coast where the freshwater zone is
thin.  Tunnels are also used to tap dike-impounded water.  These tunnels
encounter large flows of water when the principal impounding dike is penetrated
and it is necessary to drain most of the water in the saturated zone above the
tunnel before construction can be completed.  Thereafter, the yield of the
tunnel reflects the rate of recharge to the compartment tapped by the tunnel.
To avoid a large initial waste of water and to preserve as much storage as
possible, the Honolulu Board of Water Supply has begun to construct inclined
wells to obtain dike-impounded water.  Vertical wells are used to obtain basal
water and perched ground water in inland areas where the thickness of the
freshwater zone permits the use of such wells.
                                       286

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HAWAII
                                                               MNAI1
 (12A) Mountain Slopes

This hydrogeologlc setting IE characterized  by  «t*«p  dope*
composed of volcanic lava flows, breccia and  related
extrusive magmatlc rocks.  Soils are thin, but  highly
permeable where present.  Rubble alluvial deposits are
common.  Because of the steep topography and  elevation the
water table Is typically deep.  Water occurs  In the
fractures and vesicular zones of the basaltic lava flows,
and along the relatively horizontal inter-flow  zones.
Overall, hydraulic conductivity is moderately high, due to
the density of fracture zones.  Perched water table zones
are common, where water In an Inter-flow zone between
successive lava flows Is delayed from moving downward by a
dense layer of clayey material or basalt.  The  dense  layer
act* a« an aqultard.   Rainfall is high, and with permeable
surface material recharge Is alao high.
(121) Alluvial Mountain Valleys

This hrdrogeologlc setting Is characterized by narrow,
steep-walled valleys, with moderate to steep seaward  slope.
The valleys contain alluvial material varying typically  from
zero to a few tens of feet In thickness.  Waterfalls  and
related features are common near the ocean.  The alluvium
consists of basaltic debris and associated weathered
products.  Soils are moderately developed, thin and quite
permeable.  Rainfall is high, recharge Is high, and
vegetation is lush.  The alluvium below stream grade  la
generally saturated at a shallow level, and may be
hvdraullcally connected to the permanent water table  or
perched •ones,  lydraullc conductivity of both the alluvium
•md vnderlrlnf aquifers Is high.
iCTTING 12 A Mountain Slopes
TEATURE
>epth to Hater
ft Recharge
! alter Media
ion Media
Topography
Impart Vadose Zone
hydraulic Conductivity
RANGE
100»
10+
Basalt
Thin or Absent
i8«i
Basalt
JOOO-
CENERAL
(EIGHT
5
4
3
2
1
5
3
RATING
1
9
9
10
1
9
10
Drastic Index
NUMBED
5
36
27
20
1
45
30
1«4
JETTING IJ B Alluvial Mountain Valleys
rtATURE
Xpth to Hater
4et Recharge
tquifer Media
Soil Media
Topography
iMpact Vadose Zone
lydraullc Conductivity
RANGE
5-15
10*
Sand and Gravel
Sandy Loam
12-18«
Sand and Gravel
1000-2000
GENERAL
•EIGHT
5
4
3
2
1
5
3
RATING
9
9
8
6
3
e
B
Drastic Index
NUMBER
45
36
24
12
3
40
24
164
il'TUNG 12 A Mountain Slopes
fEATURE
Xpth to Hater
Jet Recharqe
vqulfer Media
>oil Media
Topography
Impact Vadose Zone
fydraulic Conductivity
RANGE
100-.
10t
Basalt
Thin or Absent
18«*
Basalt
2000*
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
1
9
9
10
1
9
10
Pesticide
Drastic Index
NUHBH
5
36
27
50
3
36
20
177
SETTING 12 B Alluvial Mountain Valleys
FEATURE
>«pth to Mater
Jet Recharge
tqulfer Media
jell Media
Topography
Impact Vadose zone
lydraullc Conductivity
RANGE
5-15
10*
Said and Gravel
Sandy Loam
12-1BI
Sand and Grovel
1000-2000
PESTICIDE
HEIGHT
s
4
3
5
3
4
2
RATING
9
9
8
6
3
e
E
Pesticide
Drastic Index
NUMOfF
45
36
24
30
9
31
16
192
                                                           287

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HAWAII

(12C) Volcanic Uplands

This hydrogeologlc setting Is characterized by moderately
rolling topography, at medium elevations, and rich, dark,
soils developed from the basaltic bedrock.  The soils are
permeable, rainfall Is high and recharge Is high.  Bedrock
Is composed primarily of alternating extrusive basaltic lava
flows and Interlayered weathered zones formed between flows.
Ground water occurs at moderate to deep depths, and aquifer
yield Is controlled by fracture zones, vesicular zones (both
primarily cooling features) and the inter-flow weathered
zones.  Hydraulic conductivity Is high.  As with other
settings in Hawaii, heavy pumping stresses often result in
salt-water Intrusion.  This Is a reflection of the fact that
each Island is surrounded by and underlain by epth to Mater
Jet Recharge
tqulfer Media
Soil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
75-100
10*
Basalt
Sandy Loarc
6-12%
Basalt
2000*
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
2
9
9
6
5
9
10
Pesticide
Drastic Index
NUMBKfi
10
36
27
30
15
36
20
174
SETTING 12 D Coastal Beaches
FUTURE
>epth to Mater
let Recharge
Aquifer Hedia
ioil Media
Topography
Impact Vadose zone
lydraulic Conductivity
RANGE
0-5
10«
Sand and Gravel
Sand
2-6%
Sand and Gravel
1000-2000

GENERAL
HEIGHT
S
4
3
2
1
5
3
RATING
10
9
e
9
9
e
e
Drastic Index
NUMBER
50
36
24
ie
9
40
24
201
SETTING 12 D coastal Beaches
FEATURE
>cpth to Mater
4et Recharge
tquifer Media
Soil Media
Topography
Impact Vadose Zone
tydraulic Conductivity
RANGE
0-5
10 +
Sand and Gravel
Sand
2-6%
Sand and Gravel
1000-2000
PESTICIDE
HEIGHT
5
4
3
5
3
4
2
RATING
10
9
e
9
9
8
8
Pesticide
Drastic Index
NUMDlf
50
36
24
45
27
32
16
230
288

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      13.  ALASKA GROUND-WATER REGION
13A
13B

13C
13D
Alluvium
Glacial and Glaciolacustrine  Deposits
  of the Interior Valleys
Coastal Lowland Deposits
Bedrock .of the Uplands and  Mountains
                     289

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                                  13.  ALASKA


      (Glacial and alluvial deposits, occupied in part by permafrost, and
 	        overlying crystalline, metamorphic, and sedimentary rocks)

     The Alaska region encompasses the State of Alaska, which occupies an area
of 1,519,000 km2 at the northwest corner of North America.  Physiographical-
ly, Alaska can be divided into four divisions—from south to north, the Pacific
Mountain System, the Intermontane Plateaus, the Rocky Mountain System, and the
Arctic Coastal Plain.  The Pacific Mountain System is the Alaskan equivalent of
the Coast Range, Puget Sound Lowland, and Cascade provinces of the
Washington-Oregon area.  The Intermontane Plateaus is a lowland area of plains,
plateaus, and low mountains comparable to the area between the Cascades-Sierra
Nevada and the Rocky Mountains.  The Rocky Mountain System is a continuation of
the Rocky Mountains of the United States and Canada, and the Arctic Coastal
Plain is the geologic equivalent of the Great Plains of the United States and
Canada.  The coastal areas and lowlands range in altitude from sea level to
about 300 m, and the higher mountains reach altitudes of 1,500 to 3,000 m.  Mt.
McKinley in the Pacific Mountain System is the highest peak iruNorth America,
with an altitude of about 6,300 m.

     As would be expected of any area its size, Alaska is underlain by a
diverse assemblage of rocks.  The principal mountain ranges have cores of
igneous and metamorphic rocks ranging in age from Precambriam to Mesozoic.
These are overlain and flanked by younger sedimentary and volcanic rocks. The
sedimentary rocks include carbonates, sandstones, and shales. In much of the
region the bedrock is overlain by unconsoliated deposits of gravel, sand, silt,
clay, and glacial till.

     Climate has a dominant effect on hydrologic conditions in Alaska.  Mean
annual air temperatures range from -12°C in the Rocky Mountain System and the
Arctic Coastal Plain to about 5°C in the coastal zone adjacent to the Gulf of
Alaska.  The present climate and the colder climates that existed
intermittently in the past have resulted in the formation of permafrost, or
perennially frozen ground.  Permafrost is present throughout the State except
in a narrow strip along the southern and southeastern coasts.  In the northern
part of the Seward Peninsula, in the western and northern parts of the Rocky
Mountain System, and in the Arctic Coastal Plain, the permafrost extends to
depths as great as 600 m and is continuous except beneath deep lakes and in the
alluvium beneath the deeper parts of the channels of streams.  South of this
area and north of the coastal strip, the permafrost is discontinuous and
depends on exposure, slope, vegetation, and other factors.  The permafrost is
highly variable in thickness in this zone but is generally less than 100 m
thick.
                                       290

-------
     Much of the water in Alaska is frozen for at least a part of each year:
that on the surface as ice in streams and lakes or as snow or glacier ice and
that below the surface as winter frost and permafrost.  Approximately half of
Alaska, including the mountain ranges and adjacent parts of the lowlands, was
covered by glaciers during the Pleistocene.  About 73,000 km2f or
one-twentieth of the region, is still occupied by glaciers, most of which are
in the mountain ranges that border the Gulf of Alaska.  Precipitation, which
ranges from about 130 mm yr~l in the Rocky Mountain System and the Arctic
Coastal Plain to about 7,600 mm yr-1 along the southeast coast, falls as snow
for 6 to 9 months of the year and even year-round in the high mountain regions.
The snow remains on the surface until thawing conditions begin, in May in
southern and central Alaska and in June in the arctic zone. "During the period
of subfreezing temperatures, there is no overland runoff, and many streams and
shallow lakes not receiving substantial ground-water discharge are frozen
solid.

     From the standpoint of ground-water availability and well yields, Alaska
is divided into three zones.  In the zone of continuous permafrost, ground
water occurs beneath the permafrost and also in small, isolated, thawed zones
that penetrate the permafrost beneath large lakes and deep holes in the
channels of streams.  In the zone of discontinuous permafrost, ground water
occurs below the permafrost and in sand and gravel deposits that underlie the
channels and floodplains of major streams.  In the zone of discontinuous
permafrost, water contained in silt, clay, glacial till, and other fine-grained
deposits usually is frozen.  Thus, in this zone the occurrence of ground water
is largely controlled by hydraulic conductivity.  In the zone not affected by
permafrost, which includes the Aleutian Islands, the western part of the Alaska
Peninsula, and the southern and southeastern coastal areas, ground water occurs
both in the bedrock and in the relatively continuous layer of unconsolidated
deposits that mantle the bedrock.

     Relatively little is known about the occurrence and availability of ground
water in the bedrock.  Permafrost extends into the bedrock in both the zones of
continuous and discontinuous permafrost, but springs that issue from carbonate
rocks in the Rocky Mountain System indicate the presence of productive
water-bearing openings.  Small supplies of ground water have also been
developed from sandstones, from volcanic rocks, and from faults and fractures
in the igneous and metamorphic rocks.

     Recharge of the aquifers in the Alaska region occurs when the ground is
thawed in the areas not underlain by permafrost. This period generally lasts
only from June through September.  Because the ground, even in nonpermafrost
areas, is still frozen when most snowmelt runoff occurs, relatively little
recharge occurs in interstream areas by infiltration of water across the
unsaturated zone.  Instead, most recharge occurs through the channels of
streams where they flow across the alluvial fans that fringe the mountainous
areas and in alluvial deposits for some distance downstream.  Because of the
large hydraulic conductivty of the sand and gravel in these areas, the rate of
infiltration is large.  Seepage investigations along Ship Creek near Anchorage
indicate channel losses of 0.07 m3sec~lkm~1, which gives an infiltration
rate through the wetted perimeter of about 0.4 m day-1.
                                      291

-------
     Discharge from aquifers occurs in the downstream reaches of streams and
through seeps and springs along the coast.  The winter flow of most Alaskan
streams is sustained by ground-water discharge.  In the interior and northern
regions, this discharge is evidenced by the buildup of ice (referred to locally
as "icings") in the channels of streams and on the adjacent flood plains.

     Unlike the 12 regions which comprise the contiguous United States, both
Alaska and Hawaii are political subdivisions, not discrete ground-water
regions.  Hawaii can be treated as a single region because of its smaller size
and relative geologic simplicity.  Alaska, however, due to its size and
complexity includes several major ground-water regions.  For purposes of this
document, these regions are considered hydrogeologic settings.
                                       292

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ALASKA
                                                               ALASKA
(UA) Alluvium

This hydrogeologlcal setting Includes floodplalns, terraces
•nd alluvial fans of both major valleys and upland and
mountain valleys.  Braided streams are present In the major
valley floodplalns.  Heavy silt/rock flour loading In
streams results In substantial silt and clay deposition
•long with the alluvial sands and gravels.  Ground-water
levels are usually shallow near the streams, Into which the
ground water discharges, and considerably deeper along the
higher terraces.  Recharge to the ground water Is seasonal,
following snow melt and thawing of frozen areas.  Except for
the south coastal area, precipitation Is light to moderate
and usually In the font of snow.  Topography Is moderate,
with a unidirectional downstream ground-water movement.
Hydraulic conductivities are moderate to very high In the
cleaner portions of the sand and gravel aquifers.
(IS!) Glacial and Claclolacustrlne Deposits of the Interior
Valleys

This hydrogeological setting Is characterized by tills and
associated outwash deposits, as well as glacier-related  lake
deposits of Interbedded sand, silt and clay.  Ground-water
levels are relatively shallow.  Surface tolls are typically
organic sandy loans with moderate conductivity.  Recharge is
moderate to low, primarily limited by the period of thaw and
annual precipitation.  Topography is moderate, and the
hydraulic conductivity of the outwash aquifers is generally
high.
SETTING 13 A Alluvium
FEATURE
tepth to Mater
let Recharge
kquifer Media
ioil Media
Topography
Impact Vadose Zone
lydraulic Conductivity
RANGE
15-30
2-4
Sand and Gravel
Sandy Loam
2-6%
S t G w/ fiig. Silt
and Clay
700-1000
GENERAL
(EIGHT
...I-
4
3
2
1
5
3
RATING
1
3
e
6
9
6
6
Draatic Index
NUMBER
35
12
24
12
9
30
IB
140
[fi-i-Tur 11 n Glacial i Glaciolacustrine
SETTING 13 B Deposlts. interior Valleys
FEATURE
tepth to Hater
let Recharge
Icjuifer Media
ioil Media
Topography
[•pact Vadoce tone
lydraulic Conductivity
RANGE
5-15
2-4
Sand and Gravel
Sandy Loam
2-6%
Silt/Clay
1000-2000
GENERAL
4EIGHT
5
4
3
1
1
5
3
RATING
9
3
t
6
9
3
e
Drastic Index
NUMBER
45
12
24
12
9
15
24
141
SETTING 13 A Alluvium
FEATURE
>opth to Hater
Jet Recharge
kquifer Media
ioil Media
Topography
Impact v«do»e Zone
lydraulic Conductivity

RANGE
15-30
2-4
Sand and Gravel
Sandy Loam
2-6%
S t C «/ tig. Silt
and Clay
700-1000
PESTICIDE
WEIGHT
5
4
3
5
1
4
2
RATING
7
3
e
6
9
6
6
Pesticide
Drastic Index
NUMBKf
35
12
24
30
21
24
12
1(4
•ETTING 13 B DepOsits: interior Valleys
FEATURE
>epth to Hater
Jet Recharge
tquifer Media
ioil Media
Topography
[•pact Vadose zone
lydraulic Conductivity
RANGE
5-15
2-4
Sand and Gravel
Sandy Loam
2-6%
Silt/Clay
1000-2000
PESTICIDE
WEIGHT
5
4
3
5
3
4
2
RATING
9
3
B
e
9
3
8
Pesticide
Drastic Index
NUKDI.I
45
12
24
30
27
12
16
166
                                                            293

-------
ALASKA
                                                                ALAtKA
(13C) Coastsl-Lowland Deposits

This hydrogeologlc setting Includes coastal plains, aeltalc
deposits of major streams, beaches and nearshore bars and
spits, and deposits of deep alluvial coastal basins and
valleys.  Permafrost severely affects the northernmost
portions of this setting, which Is within the  permanent
permafrost tone.  Where not permanently  frozen, recharge
rates are seasonally high, particularly  along  streams which
are hydraullcally connected to the ground-water.
Ground-water depths are at or near the elevation of the
•urface streams, and topographic  slopes  are low to moderate.
The primary aquifers In this setting are the alluvial sands
and gravels that are Interbedded  with silts and clays.
Thick sequences of all types of materials are  co
(13D) Bedrock of the Uplands and Mountains

This hydrogeologlc setting Is characterized by deposits  of
carbonate rocks, limestone, sandstone, volcanlcs and  other
l(n«oue and metamorphlc rocks.  These  formations underlie a
thin veneer of alluvium beneath a large portion of  the
•tate.  Water levels within this setting are variable, but
•amorally deep.  Exceptions to this are discharge zones
•long the flanks of many mountains.  The most notable
••ample of this are springs discharging from carbonate rocks
•long the flank* of mountains.  Recharge is limited by
precipitation, topography and predominant permafrost.  Soils
•r* tcnarally thin and poorly developed.  Aquifer
comductlvltlet vary frosi low in some of the fractured
mctemorptilcs to very high in the solution-dissolved
carbonates.
SCTTIHG U C Coastal Lowland Deposits
FEATURE
>epth to Hater
iet Recharge
ugulfer Media
soil Media
Topography
[•pact Vado»e zone
lydraulic Conductivity
RANGE
15-30
2-4
sand and Gravel
Sandy Loaft
2-6%
S 4 C w/ sig. Silt
and Clay
700-1000

HEIGHT
S
4
3
2
1
5
3
GENERAL
RATING
7
3
e
e
9
e
6
Oraatic Index

NUMBER
35
12
24
12
9
30
18
140
•PTTIHC 17 c Bedrock of the UPiands
.ETTIHC 13 D ind Hoant.ms
FEATURE
lepth to Hater
let Recharge
Kjuifer Media
ioil Media
Topography
Impact Vadose Zone
iydraulic conductivity

RANGE
100*
0-2
Bedded SS, LS,
SH Sequences
Thin or Absent
12-18S
Bedded Li, SE , £11
300-700

WEIGHT
5
4
3
2
1
5
3
GENERAL
RATING
1
1
6
10
3
6
4
Drastic Index

NUMBER
5
4
ie
20
3
30
12
92
1CTTING 13 C coastal Lowland Deposits
FEATURE
)epth to Hater
let Recharge
vquifer Media
toll Media
Topography
[•pact Vadoie lone
lydraulie conductivity
RANGE
15-30
2-4
Sand and Gravel
Sandy Loarc
2-6%
S i G vl sig. Silt
and Clay
700-1000
PESTICIDE
HEIGHT
S
4
3
5
3
4
1
RATING
7
3
e
6
9
6
t
Pesticide
Beetle Index
NUHDCH
35
12
24
30
27
24
12
164
TTTING 11 n Bedrock of the Uplands
• ETTING 13 D mf Bollntnln,
TEATURE
>epth to Mater
let Recharge
aquifer Media
>oil Media
Topography
[a^>act Vadote tone
lydraulic Conductivity
RANGE
100+
0-2
Bedded SS , LS ,
SK Sequences
Thin or Absent
12-18%
Bedded LS, SS, SI!
300-700
PESTICIDE
HEIGHT
5
4
3
S
3
4
2
RATINC
1
<
6
10
3
e
4
Pesticide
Drastic Index
NUHDI.F
5
4
16
50
9
24
t
116
                                                              294

-------
                                   REFERENCES
Gutentag, E.D. and J.B. Weeks, 1980.   Water table in the High Plains Aquifer  in
1978 in parts of Colorado, Kansas,  Nebraska, New Mexico, eklahoma,  South
Dakota, Texas and Wyoming; U.S. Geological Survey Hydrologic Investigations
Atlas 642.

Hampton, E.R., 1964.  Geologic factors that control the occurrence  and
availability of ground water in the Fort Rock Basin, Lake County, Oregon;  U.S.
Geological Survey Professional Paper 383-B, 29 pp.

LeGrand, H.E. and W.A. Pettyjohn, 1981.   Regional hydrogeologic concepts of
homoclinal flanks; Ground Water, vol. 19, no. 3, pp. 303-310.

Luckey, R.R. and E.D. Gutentag, 1981.  Water-level and saturated-thickness
changes, predevelopment to 1980, in the High Plains Aquifer in parts of
Colorado, Kansas, Nebraska, New Mexico,  Oklahoma, South Dakota, Texas and
Wyoming; U.S. Geological Survey Hydrologic Atlas 652.

MacNish, R.D. and R.A. Barker, 1976.   Digital simulation of a basalt aquifer
system, Walla Walla River Basin, Washington and Oregon; Washington  Department
of Ecology, Water Supply Bulletin 44.

McGuiness, C.L., 1963.  The role of ground water in the national water
situation; U.S. Geological Survey Water Supply Paper 1800, 1121 pp.

Nace, R.L., 1958.  Hydrology of the Snake River basalt; Washington  Academy of
Science Journal, vol. 48, no. 4, pp.  136-138.

Newcomb, R.C., 1961.  Storage of ground water behind subsurface dams in  the
Columbia River basalt, Washington,  Oregon and Idaho; U.S. Geological Survey
Professional Paper 383-A, 15 pp.

Weeks, J.B. and E.D. Gutentag, 1981.   Bedrock geology, altitude of  base  and
1980 saturated thickness of the High Plains Aquifer in parts of Colorado,
Kansas, Nebraska, New Mexico, Oklahoma,  South Dakota, Texas and Wyoming; U.S.
Geological Survey Hydrologic Investigations Atlas 648.
                                      295

-------
                             MASTER REFERENCES

Abrams, E.F., D. Derkics, C.V. Fong, D.K. Guinan and K.M. Slimak, 1975.
Identification of organic compounds in effluents from industrial sources;
National Technical Information Service PB-241641, 211 pp.

Ahmad, Moid U., 1974. Coal mining and its effect on water quality;  Water
Resources Problems Related to Mining, Proceedings no. 18, American Water
Resources Association, pp. 138-148.

Alberts, E.E. and R.G. Spomer, 1985.  Dissolved nitrogen and phosphorus  in
runoff from watersheds in conservation and conventional tillage; Journal of
Soil & Water Conservation, vol. 40, no. 1, pp. 153-157.

Aller, Linda, 1984.  Methods for determining the location of abandoned
wells; EPA-600/2-83-123, Office of Research and Development, 130 pp.'

Allison, J.E., G.W. Dittmar and J.L. Hensell, 1975.  Soil survey of
Gillespie county, Texas; Soil Conservation Service, U.S.  Department of
Agriculture, 80 pp. 77 plates.

American Petroleum Institute, 1979.  Installation of underground petroleum
storage systems; API Publication 1615, 12 pp.

American Petroleum Institute, 1980.  Underground spill cleanup manual; API
Publication 1628, 34 pp.

American Petroleum Institute, 1983.  Cathodic protection of underground
petroleum storage tanks and piping system; API Publication 1632, 20 pp.

Anderson, M.P.,  1984.  Movement of contaminants in groundwater: groundwater
transport - advection and dispersion; Groundwater Contamination, National
Academy Press, pp. 37-45.

Andrews, W.F., 1972.  Soil survey of Yolo county, California;  Soil
Conservation Service, U.S. Department of Agriculture, 102 pp., 86 plates.

Ashworth, John B., 1983.  Ground-water availability of the lower Cretaceous
formations in the hill country of south-central Texas; Texas Department  of
Water Resources, Report 273,  172 pp.

Atkins, A.S. and F.D. Pooley, 1982. The effects of biomechanisms on acidic
mine drainage in coal mining; International Journal of Mine Water,  vol.  1,
pp. 31-44.
                                    296

-------
Baker, J.L. and J.M. Laflen, 1983.  Water-quality consequences of
conservation tillage; Journal of Soil and Water Conservation, vol. 38, no.
3, pp. 186-193.

Barker, J.C., 1973.  The effects of surface irrigation with dairy manure
slurries on the quality of groundwater and surface runoff; University of
Tennessee, Ph.D. dissertation, 99 pp.

Barnes, Virgil E., 1952a.  Bear Creek Quadrangle, Gillespie, Kerr, and
Kendall counties, Texas; Geologic Quadrangle Map, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1952b.  Cain City Quadrangle, Gillespie and Kendall
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1952c.  Live Oak Creek Quadrangle, Gillespie county,
Texas; Geologic Quadrangle Map, Bureau of Economic Geology, University of
Texas.

Barnes, Virgil E., 1952d.  Morris Ranch Quadrangle, Gillespie and Kerr
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1952e.  Spring Creek Quadrangle, Gillespie county,
Texas; Geologic Quadrangle Map, Bureau of Economic Geology, University of
Texas.

Barnes, Virgil E., 1952f.  Squaw Creek Quadrangle, Gillespie and Mason
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1952g.  Stonewall Quadrangles, Gillespie and Kendall
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1954a.  Dry Branch Quadrangle, Gillespie and Kerr
counties, Texas; Geologic Quadrangle Map no. 17, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1954b.  Harper Quadrangle, Gillespie county, Texas;
Geologic Quadrangle Map no. 16, Bureau of Economic Geology, University of
Texas.

Barnes, Virgil E., 1954c.  Klein Branch Quadrangle, Gillespie and Kerr
counties, Texas; Geologic Quadrangle Map no. 18, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1954d.  Wendel Quadrangle, Gillespie, Kerr, and Kimbel
counties, Texas; Geologic Quadrangle Map no. 15, Bureau of Economic
Geology, University of Texas.
                                    297

-------
Barnes, Virgil E., 1956a.  Blowout Quadrangle, Gillespie, Llano, and Blanco
counties, Texas; Geologic Quadrangle Map, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1956b.  Crabapple Creek Quadrangle, Gillespie and Llano
counties, Texas; Geologic Quadrangle Map no. 3, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1956c.  Fall Prong Quadrangle, Kimbel, Gillespie, and
Mason counties, Texas; Geologic Quadrangle Map no. 19, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1956d.  Hilltop Quadrangle, Gillespie and Mason
counties, Texas; Geologic Quadrangle Map no. 2, Bureau of Economic Geology,
University of Texas.

Barnes, Virgil E., 1956e.  Alto Creek Quadrangle, Gillespie county, Texas;
Geologic Quadrangle Map no. 8, Bureau of Economic Geology, University of
Texas.

Barnes, Virgil E., 1956f.  Threadgill Creek Quadrangle, Gillespie and Mason
counties, Texas;  Geologic Quadrangle Map no. 20, Bureau of Economic
Geology, University of Texas.

Barnes, Virgil E., 1956g.  Willow City Quadrangle, Gillespie and Llano
counties, Texas; Geologic Quadrangle Map no. 4, Bureau of Ec
-------
Baxter, K.M. and L. Clark, 1984.   Effluent recharge;  Water Research Centre
Technical Report TR-199, United Kingdom,  60 pp.

Beck, Barry, F., Loris Asmussen and Ralph Leonard, 1985.   Relationship of
geology, physiography, agricultural land  use,  and ground-water quality in
southwest Georgia; Ground Water,  vol.  23, no.  5,  pp.  627-634.

Bedient, P.B., N.K. Springer, E.  Baca, T.C. Bouvette, S.R. Hutchins and
M.B. Tomson, 1983.  Ground water transport from wastewater infiltration;
Journal of Environmental Engineering,  vol. 109, no.  2, pp. 485-501.

Bell, E.A. and M.G. Sherrill, 1974.  Water availability in central
Wisconsin - an area of near-surface crystalline rock; U.S. Geological
Survey, Water Supply Paper 2022,  32 pp.

Blank, Horace R. and Melvin C. Schroeder, 1973.   Geologic classification  of
aquifers; Ground Water, vol. 11,  no. 2,  pp. 3-5.

Blevins, R.L., M.S. Smith, G.W. Thomas and W.W. Frye, 1983.  Influence of
conservation tillage on soil properties;  Conservation, vol. 38, no. 3, pp.
301-305.

Blomquist, Peter K., 1984.  Abandoned  water wells in  southeastern
Minnesota; National Water Well Association, Proceedings of the Seventh
National Ground Water Quality Symposium,  pp. 33-342.

Borman, R.G., 1981.  Effects of a cattle  feedlot  on ground-water quality  in
the South Platte River Valley near Greeley, Colorado; U.S. Geological
Survey Water Resources Investigation 80-83, 78 pp.

Borrelli, J., R.D. Burman, R.H. Delaney,  J.L.  Moyer,  H.W. Hough and B.L.
Weand, 1978.  Land application of wastewater under high altitude
conditions; U.S. EPA Office of Research  and Development,  EPA 600/2-78-139,
92 pp.

Bouwer, Herman, 1978.  Groundwater Hydrology;  McGraw-Hill Book Company, New
York, 479 pp.

Bouwer, Herman, 1985.  Renovation of wastewater with  rapid infiltration
land treatment systems; Artificial Recharge of Groundwater, Butterworth
Publishers, pp. 249-282.

Bouwer, Herman, R.C. Rice, E.D. Escarcega and  M.S. Riggs, 1972.  Renovating
secondary sewage by ground water  recharge with infiltration  basins; U.S.
EPA, Office of Research and Monitoring,  pp. 1-81.

Bouwer, E.J., P.L. McCarty and J.C. Lance, 1981.   Trace organic behaviour
in soil columns during rapid infiltration of secondary wastewater; Water
Research, vol. 15, no. 1, pp. 151-159.

Bouwer, E.J., B.E. Rittmann and P.L. McCarty,  1981.   Anaerobic degradation
of halogenated 1- and 2-carbon organic compounds; Environmental Science
& Technology, vol. 15, no. 5, pp. 596-599.

                                   299

-------
Bremner, J.M., G.W. McCarty and C.  Gianello,  1986.   Reduction of  nitrate
pollution of ground water by nitrogen fertilizers;  Proceedings of the
Agricultural Impacts on Ground Water - A Conference,  National Water  Well
Association, pp. 467-481.

Bremner, John M. and Jane C. Yeomans, 1986.   Effects  of  pesticides on
denitrification of nitrate by soil  microorganisms;  Proceedings of the
Agricultural Impacts on Ground Water - A Conference,  National Water  Well
Association, pp. 445-456.

Brenoel, Michael and Richard A. Brown, 1985.   Remediation of  a leaking
underground storage tank with enhanced bioreclamation;  Proceedings of the
Fifth National Symposium and Exposition on Aquifer  Restoration and Ground
Water Monitoring, Nationa,! Water Well Association,  pp.  527-536.

Broscious, John A., Vedat Batu and  Matthew C. Plautz, 1986.   Recovery of
petroleum product from a highly permeable aquifer under the effects  of
municipal water supply wells; Proceedings of  the Sixth National Symposium
and Exposition on Aquifer Restoration and Ground Water Monitoring, National
Water Well Association, pp. 493-509.

Brown and Caldwell, 1985.  Cover/Chambers Creek geohydrologic study  for the
Tacoma-Pierce county Health Department, Final report; Brown and Caldwell
with Subconsultants Sweet, Edwards  and Associates,  Robinson and Noble,
Inc., 221 pp., 71 plates.

Brown, K.W., G.B. Evans, Jr. and B.D. Frentrop, editors, 1983.  Hazardous
waste land treatment; Butterworth Publishers, 692 pp.

Bruck, Glen R., 1986.  Pesticide and nitrate  contamination of ground water
near Ontario, Oregon; Proceedings of the Agricultural Impacts on Ground
Water - A Conference, National Water Well Association, pp. 597-612.

Brunner, D.R. and D.J. Keller, 1972.  Sanitary landfill design and
operation; EPA SW-65ts, Office of Solid Waste Management Programs, 54  pp.

Burke, Michael R. and Dan C. Buzea, 1984.  Unique technology  applied to  the
cleanup of hydrocarbon product from a low permeability formation in  a
residential neighborhood, St. Paul, Minnesota; Proceedings of the Petroleum
Hydrocarbons and Organic Chemicals in Ground  Water  - Prevention,  Detection
and Restoration, National Water Well Association, pp. 377-399.

Bush, P.W., 1979.  Connector well experiment to recharge the  Floridan
aquifer, East Orange county, Florida; U.S. Geological Survey, Water
Resources Investigations 78-73, 40 pp.

California Department of Water Resources, 1978.  Evaluation of ground-water
resources,  Sacramento Valley; Bulletin 118-6, California Department  of
Water Resources and U.S. Geological Survey, 136 pp.
                                  300

-------
California Department of Water Resources, 1985.  Water level data by
hydrologic basin:  State of California, The Resources Agency, Department of
Water Resources.

Callahan, M., M. Slimak, N. Gabel, I. May, F. Fowler, R. Freed, P.
Jennings, R. Duffee, F. Whitmore, B. Maestri, W. Mabey, B. Holt and C.
Gould, 1979.  Water related fate of 129 priority pollutants, vol. 1 -
introduction and technical background, metals and inorganics, pesticides
and PCBS; U.S. EPA-440/4-79-029a, pp. 2-1 through 2-14.

Camp, Wallace J., 1975.  Soil survey of Greenville county, South Carolina;
Soil Conservation Service, U.S. Department of Agriculture, 71 pp.

Canter, L.W., 1984.  Problems of abandoned wells; Proceedings of the First
National Conference on Abandoned Wells:  Problems and Solution, Sponsored
by the National Water Well Association and Environmental and Ground Water
Institute, University of Oklahoma, pp. 1-16.

Canter, L.W. and R.C. Knox, 1985.  Septic tank system effects on ground
water quality; Lewis Publishers, Chelsea, Michigan, 336 pp.

Caswell, W.B. and Lanctot, E.M. , 1978.  Ground-water resource maps of
Cumberland county; Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979a.  Ground-water handbook for the state of Maine;
Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979b.  Sand and gravel aquifers map no. 4, York and
Cumberland counties, Maine; Open-file no. 79-5, Maine Geological Survey,
Department of Conservation.

Caswell, W. Bradford, 1979c.  Sand and gravel aquifers map no. 4, York and
Cumberland counties, Maine; Open-file no. 79-6, Maine Geological Survey,
Department of Conservation.

Caswell, W. Bradford, 1979d.  Sand and gravel aquifers map no. 10,
Sagadahoc, Lincoln, and Cumberland counties, Maine; Open-file no. 79-8,
Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979e.  Sand and gravel aquifers map no. 11,
Cumberland and Androscoggin counties, Maine; Open-file no. 79-9, Maine
Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979f.  Sand and gravel aquifers map no. 12,
Cumberland, Androscoggin, and York counties, Maine; Open-file no. 79-10,
Maine Geological Survey, Department of Conservation.

Caswell, W. Bradford, 1979g.  Sand and gravel aquifers map no. 13, Oxford,
York, and Cumberland counties, Maine; Open-file no. 79-11, Maine Geological
Survey, Department of Conservation.
                                    301

-------
Caswell, W.B. and E.M. Lanctot, 1979.  Ground-water resource maps county
series; Maine Geological Survey, Department of Conservation.

Ceroici, W.J., 1985.  Ground water contamination associated with waste
disposal in a water-filled open-pit coal mine; Proceedings of the Second
Canadian/American Conference on Hydrogeology, Alberta Research Council and
the National Water Well Association, pp. 196-201.

Chang, A.C. and A.L. Page, 1979.  Fate of inorganic micro-contaminants
during groundwater recharge; Proceedings of the Wastewater Reuse for
Groundwater Recharge, Office of Water Recycling, California State Water
Resources Control Board, pp. 118-136.

Cheng, H.H. and W.C. Koskinen, 1985.  Processes and factors affecting
transport of pesticides to ground water; American Chemical Society
Symposium Series #315, Evaluation of Pesticides in Ground Water; pp. 1-13.

Cheremisinoff, P.N., J.G. Casana and R.P. Ouellette, 1986.  Special Report:
Underground storage tank control; Pollution Engineering, vol. 18, no. 2,
pp. 22-29.

Cheremisinoff, P.N., J.G. Casana and H.W. Pritchard, 1986.  Special Report:
update on underground tanks; Pollution Engineering, vol. 18, no. 8, pp.
12-25.

Cherry, J.A., R.W. Gillham and J.F. Barker, 1984.  Contaminants in
groundwater: chemical processes; Groundwater Contamination, National
Academy Press, pp. 46-66.

Glaus, D. and N. Walker, 1964.  The decomposition of toluene by soil
bacteria; Journal General Microbiology, vol. 36, pp. 107-122.

Cohen, S.Z., S.M. Creeger, R.F. Carsel and C.G. Enfield, 1984.  Potential
for pesticide contamination of ground water resulting from agricultural
uses;  American Chemical Society Symposium Series #259, Treatment Disposal
of Pesticide Wastes, Krueger and Seiber, editors, Washington, B.C., 27 pp.

Cohen, S.Z., C. Eiden and M.N. Lorber, 1986.  Monitoring ground water for
pesticides  in Evaluation of Pesticides in Ground Water, W.Y. Garner, R.C.
Honeycutt and H. Nigg, editors, American Chemical Society Symposium Series
#315,  Washington, D.C., pp. 170-196.

Council for Agricultural Science and Technology, 1985.  Agriculture and
groundwater quality; ISSN; 194-4088; no. 103, 62 pp.

Counts, Harlan B. and Ellis Donsky, 1963.  Salt-water encroachment geology
and ground-water resources of Savannah area Georgia and South Carolina;
U.S. Geological Survey, Water Supply Paper 1611, 100 pp.
                                    302

-------
Crandell, D.W., 1963.  Surficial geology and geomorphology of  the Lake
Tapps Quadrangle, Washington;  U.S.  Geological Survey,  Professional Paper
388-A, U.S. Department of Interior.

Crandell, D.W., 1969.  Surficial geology of Mount Rainier National Park
Washington; U.S. Geological Survey, Bulletin 1288, U.S.  Department of
Interior, 39 pp.

Creech, J.R., 1986.  Class I injection well design considerations using
fiberglass tubulars and epoxy cement;  Proceedings of the International
Symposium on Subsurface Injection of Liquid Wastes, National Water Well
Association, pp. 113-132.

Crites, Ronald W., 1985.  Micropollutant removal in rapid infiltration;
Artificial recharge of groundwater, Butterworth Publishers, pp.  579-608.

Crosthwaite, E.G. and R.C. Scott, 1956.  Ground water in the north side
pumping division Minidoka project,  Minidoka county, Idaho;  U.S.  Geological
Survey Circular 371, 20 pp.

Dalton, Matthew G., Ronald Wilson and  C. Hugh Thompson,  198A.   Recovery of
petroleum product within a complex hydrogeologic environment;  Proceedings
of the Petroleum Hydrocarbons and  Organic Chemicals in  Ground Water -
Prevention, Detection and Restoration, National Water Well Association, pp.
344-352.

Davis, K.E., 1986.  Factors affecting  the area of review for hazardous
waste disposal wells; Proceedings of the International Symposium on
Subsurface Injection of Liquid Wastes, National Water Well Association, pp.
148-194.

Davis, K.E. and T.L. Hineline, 1986.  Two decades of successful hazardous
waste disposal operation - a compilation of case histories; Proceedings of
the International Symposium on the Subsurface Injection  of Liquid Wastes,
National Water Well Association, pp. 295-308.

Davis, S.N. and R.J. DeWiest,  1966.  Hydrogeology; John  Wiley  & Sons, 463
PP-

Dealy, M.T., Jack Hume and E.D. Jenkins, 1984.  Hydrogeology and
development of the Dakota aquifer in southwest Kansas; Proceedings of the
First C.V. Theis Conference on Geohydrology; Geohydrology of the Dakota
aquifer, National Water Well Association, pp. 209-220.

Dee, Norbert, Janet Baker, Neil Drobny, Ken Duke, Ira Whitman  and Dave
Fahringer, 1973.  An environmental evaluation system for water resource
planning; Water Resources Research, vol. 9, no. 3, pp. 523-535.

Detroy, Mark G., 1986.  Areal and vertical distribution  of nitrate and
herbicides in the Iowa river alluival  aquifer, Iowa county, Iowa;
Proceedings of the Agricultural Impacts on Ground Water  - A Conference,
National Water Well Association, pp. 381-398.


                                   303

-------
Deutsch, M., 1963.   Groundwater contamination and  legal  controls  in
Michigan:  U.S. Geological Survey,  Water Supply Paper 1691,  pp. 46-47.

Devaul, R.W. and J.H.  Green,  1971.   Water resources  of Wisconsin  Central
Wisconsin River Basin; U.S.  Geological Survey, Hydrologic  Investigations
HA-367.

Dick, Warren A., William M.  Edwards and Fraz Haghiri, 1986.   Water movement
through soil to which no-tillage cropping practices  have been continuously
applied; Proceedings of the  Agricultural Impacts on  Ground Water  - A
Conference, National Water Well Association, pp. 243-252.

Dinchak, W.G., 1983.  Consider a soil-cement/synthetic membrane  liner  for
containment of sanitary landfill leachate; Sixth Annual  Madison
Conference on Municipal and  Industrial Wastes, Madison,  Wisconsin, pp.
126-137.

Dohnalek, D.A. and J.A. Fitzpatrick, 1983.  The chemistry  of reduced sulfur
species and their removal from ground water supplies; Journal of  American
Water Works Association, vol. 75, no. 6, pp. 298-308.

Drost, B.W. , 1982.   Water resources of the Gig Harbor peninsula and
adjacent areas, Washington;  U.S. Geological Survey,  Water  Resources
Investigations, Open-file report 81-1021, U.S. Department  of Interior,  148
pp.
                                                          «
                                                        5
Dunlap, I.E., R.J.  Lindgren and C.G. Sauer, 1985.   Geohydrology  and  model
analysis of stream-aquifer system along the Arkansas river in Kearny and
Finney counties, Southwestern Kansas; U.S. Geological Survey, Water  Supply
Paper 2253, 52 pp.

Eklund, Bart and Walt Crow,  1986.  Results for survey of vendors  of
external petroleum leak monitoring devices for use with  underground  storage
tanks; U.S. EPA no. 68-02-3994, pp. 1-1 through 4-31.

Emrich, Grover H. and Gary L. Merritt, 1969. Effects of  mine drainage  on
ground water; Ground Water,  vol. 7, no. 3, pp. 27-32.

Engineering-Science, 1985.  Installation restoration program, phase  1:
records search Grissom AFB,  Indiana, Appendix G:  USAF installation
restoration program hazard assessment rating methodology and Appendix  H:
site hazard assessment rating forms; Engineering-Science,  Atlanta,  Georgia,
pp. G-l-11 and H-l-14.

Erlich, G.G., D.F. Goerlitz, E.M. Godsy and M.F. Hult, 1982.  Degradation
of phenolic contaminants in ground water by anaerobic bacteria:  St.  Louis,
Minnesota; Ground Water, vol. 20, no. 6, pp. 703-710.

Exner, M.E. and R.F. Spalding, 1985.  Ground water contamination and well
construction in southeast Nebraska; Ground Water,  vol. 23, no. 1, pp.
26-34.
                                   304

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Farb, D. , 1978.  Upgrading hazardous waste disposal sites:   remedial
approaches; U.S. EPA #SW-677, Cincinnati, Ohio,  40 pp.

Fenn, Dennis G., Keith J. Hanley and Truett V. DeGeare, 1975.   Use of the
water balance method for predicting leachate generation from solid waste
disposal sites; U.S. EPA Solid Waste Report no.  168, Cincinnati,  Ohio, 40
pp.

Fetter, C.W., 1980.  Applied Hydrogeology; Charles E.  Merrill  Publishing
Company, 448 pp.

Field, R., E.J. Struzeski, Jr., H.E. Masters and A.N.  Tafuri,  1973.  Water
pollution and associated effects from street salting;  U.S.  EPA National
Environmental Research Center, EPA R2-73-257, 47 pp.

Field, R.E., J. Struzeski, Jr., H.E. Masters and A.N.  Tofuri,  1974.  Water
pollution and associated effects from street salting;  Journal  Environmental
Engineering Division, American Society of Civil  Engineers,  vol. 100, EE2,
pp. 459-477.

Flipse, W.J., B.C. Katz, J.B. Linder and R. Markel, 1984.   Sources of
nitrate in ground water in a sewsred housing development, central Long
Island, New York; Ground Water, vol. 22, no. 4,  pp. 418-426.

FMC Corporation, 1983.  Industrial waste treatment with hydrogen peroxide;
Industrial Chemical Group, Philadelphia, Pennsylvania, 23 pp.

Forseth, J.M. and P. Kmet, 1983.  Flexible membrane liners  for solid and
hazardous waste landfills - A-state-of-the-art-review; Sixth Annual Madison
Conference on Municipal and Industrial Wastes, Madison, Wisconsin,
pp. 138-166.

Franks, B.J., 1981.  Land application of domestic wastewater in Florida -
Statewide assessment of impact on ground-water quality; U.S. Geological
Survey Water Resources Investigations, 81-3, 37  pp.

Freeze, R.A. and J.A. Cherry, 1979.  Groundwater; Prentice-Hall,  604 pp.

Fryberger, John S. and Richard M. Tinlin, 1984.   Pollution  potential from
injection wells via abandoned wells; Proceedings of the First  National
Conference on Abandoned Wells:  Problems and Solution, National Water Well
Association, Environmental and Ground Water Institute, University of
Oklahoma, pp. 118-124.

Fujioka, R.S. and L.S. Lau, 1984.  Assessing the quality of ground water
near a coastal plain used for agricultural and discharge of sewage;
Proceedings Second International Conference on the Quality  of  Ground Water
Research, Oklahoma State University, pp. 101-104.
                                    305

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Fuller, W.H. and J. Artiola,  1978.   Use of limestone to limit contaminant
movement from landfills;  Proceedings Fourth Annual Research Symposium,  Land
Disposal of Hazardous Wastes, U.S.  EPA-600/9-78-016,  pp.  282-298.

Furman, Albert L.,  Horace D.  White, Orlando E.  Cruz,  Walter E.  Russell  and
Buster P. Thomas, 1975.  Soil survey of Lake county area,  Florida;  Soil
Conservation Service, U.S. Department of Agriculture, 83  pp.

Card, L.M., 1968.  Bedrock geology of the Lake  Tapps Quadrangle,  Pierce
county, Washington; U.S.  Geological Survey, Professional  Paper 388-B, U.S.
Department of Interior, 33 pp.

Gass, Tyler, E., Jay H. Lehr  and Harold W. Heiss,  Jr., 1977.   Impact  of
abandoned wells on ground water; EPA-600/3-77-905, Office of Research and
Development, 52 pp.

Gburek, W.J., J.B.  Urban and  R.R. Schnabel, 1986.   Nitrate contamination of
ground water in an upland Pennsylvania watershed;  Proceedings of  the
Agricultural Impacts on Ground Water - A Conference,  National Water Well
Association, pp. 352-380.

George, C. and B. Thomas, 1986.  Cementing to achieve zone isolation  in
disposal wells; Proceedings of the International Symposium on Subsurface
Injection of Liquid Wastes, National Water Well Association,  pp.  77-89.

Gerba, Charles P.,  Craig Wallis and Joseph Melnick, 1975.   Fate of
wastewater bacteria and viruses in soil; Journal of the Irrigation  and
Drainage Division,  American Society of Civil Engineers, vol.  101, pp.
157-174.

Gerba, Charles P. and J.  Clarence Lance, 1980.   Pathogen removal  from
wastewater during ground water recharge; Proceedings of the Wastewater
Reuse for Ground Water Recharge, Office of Water Recycling, California
State Water Resources Control Board, pp. 137-144.

Gerba, C.P., 1985.   Microbial contamination of the subsurface;  Ground Water
Quality, C.H. Ward, W. Giger and P.L. McCarty,  editors, John Wiley  and
Sons,, pp. 53-67.

Gerba, Charles P. and Sagar M. Goyal, 1985.  Pathogen removal from
wastewater during ground water recharge; Artificial Recharge of Ground
Water, Butterworth Publishers, pp. 283-318.

Gibb, James P., Michael J. Barcelona, Susan C.  Schock and Mark W. Hampton,
1983.  Hazardous waste in Ogle and Winnebago Counties:  potential risk  via
ground water due to past and present activities; Illinois Department  of
Energy and Natural Resources, Document no. 83/26,  66 pp.

Gibson, D.T., 1978.  Microbial transformation of aromatic pollutants;
Transformations and biological effects, Proceedings of the Second
International Symposium on Aquatic Pollutants,  Noordwijerhout, Amsterdam,
Netherlands, Pergamon Press,  519 pp.

                                   306

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Gish, T.J., C-S. Helling and P.C. Kearney,  1986.   Simultaneous leaching  of
bromide and atrazine under field conditions;  Proceedings of the
Agricultural Impacts on Ground Water - A Conference,  National  Water Well
Association, pp. 286-297.

Goldthorp, G.D. and D.V. Hopkin, 1972.  Migration of  liquid industrial
waste from a gravel pit:  Ground Water Pollution  in Europe, Water Research
Association Conference Proceedings,  Reading,  England, pp.  296-298.

Gordon, W. and J. Bloom, 1986.  Deeper problems limited to underground
injection as a hazardous waste disposal method; Proceedings of the
International Symposium on Subsurface Injection of Liquid  Wastes, National
Water Well Association, New Orleans, Louisiana, pp. 3-50.

Graham, William G., 1979.  The impact of intensive disposal well use on  the
quality of domestic ground-water supplies in  southeast Minidoka county,
Idaho; Idaho Department of Water Resources,  35 pp.

Gregg, Dean 0., 1971.  Protective pumping to  reduce aquifer pollution,
Glynn County, Georgia; Ground Water, vol. 9,  no.  5, pp. 21-29.

Griffen, R. , R. Clark, M. Lee and E. Chian,  1978.  Disposal and removal  of
polychlorinated biphenyls in soil;  Proceedings Fourth Annual Research
Symposium, Land Disposal of Hazardous Wastes, U.S. EPA-600/9-78-016, pp.
169-181.

Griffin, W.C., J.E.  Sceva, H.A. Swenson and M.J.  Mundorff, 1962.   Water
resources of the Tacoma area, Washington; USGS Water  Supply Paper 1499-B,
U.S. Department of Interior, 98 pp.

Groot, Johan J., Peter M. Demicco and Phillip J.  Cherry, 1983.  Ground-
water availability in southern New Castle county, Delaware; Delaware
Geological Survey, Open-file report no. 23,  20 pp.

Grubb, Hayes F., 1977.  Potential for downward leakage to  the  Floridan
aquifer, Green Swamp area, central Florida; U.S.  Geological Survey,  Water
Resources Investigations 77-71.

Grubb, Hayes F. and A.T. Rutledge,  1979.   Long-term water  supply potential,
Green Swamp area, Florida; U.S. Geological  Survey, Water Resources
Investigations 78-99, 76 pp.

Gutentag, E.D., D.H. Lobmeyer, H.E.  McGovern  and  W.A. Long, 1972.  Ground
water in Finney county, southwestern Kansas;  U.S. Geological Survey,
Hydrologic Investigations Atlas HA-442.

Gutentag, E.D. and J.B. Weeks, 1980.  Water table in  the High  Plains
aquifer in 1978 in parts of Colorado, Kansas, Nebraska, New Mexico,
Oklahoma, South Dakota, Texas and Wyoming; U.S. Geological Survey,
Hydrologic Investigations Atlas 642.
                                    307

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Gutentag, Edwin D., David H.  Lobmeyer and Steven E.  Slagle,  1981.
Geohydrology of southwestern Kansas;  Kansas Geological Survey,  Irrigation
Series 7, 73 pp.

Hackett, G.G., 1984.  The threat of bacterial contamination of  ground water
from septic tanks; Proceedings of the 1984 Ohio Conference on Home Sewage
and Water Supply, Columbus, Ohio, pp. 94-106.

Hallberg, George R., 1986.  Overview of agricultural chemicals  in  ground
water; Proceedings of the Agricultural Impacts on Ground Water  - A
Conference, National Water Well Association, pp. 1-63.

Hallberg, George R., James L. Baker and Gayles W. Randell, 1986.  Utility
of title-line effluent studies to evaluate the impact of agricultural
practices on ground water; Proceedings of the Agricultural Impacts on
Ground Water - A Conference,  National Water Well Association, pp.  298-326.

Hammond, P.E., 1980.  Reconnaissance geologic map and cross sections of
southern Washington Cascade Range; Department of Earth Sciences, Portland
State University, Portland, Oregon, 31 pp.

Hampton, E.R. , 1964.  Geologic factors that control the occurrence and
availability of ground water in the Fort Rock Basin, Lake County,  Oregon;
U.S. Geological Survey, Professional Paper 383-B, 29 pp.

Hannon, J.B. , 1980.  Underground disposal of storm water runoff; Office of
Research and Development, Federal Highway Administration FHWA-TS-80-218,
United States Department of Transportation, 215 pp.

Hansen, Harold, 1975.  Soil survey of Minldoka area, Idaho,  parts  of
Minidoka, Elaine and Lincoln counties; Soil Conservation Service,  U.S.
Department of Agriculture, 72 pp.

Haque, R. , D.W. Schmedding and V.H. Freed, 1974.  Aqueous solubility,
adsorption and vapor behaviour of polychlorinated biphenyl Arochlor 1254;
Environmental Science & Technology, vol. 8, pp. 139-142.

Hardie, M.G., J.C. Jennett, E. Bolter, B. Wixson and N. Gale, 1974.  Water
resources problems and solutions associated with the New Lead Belt of
south-east Missouri; Water Resources Problems Related to Mining,
Proceedings No. 18, American Water Resources Association, pp. 109-122.

Harkin, John M., Gordon Chesters, Frank A. Jones, Riyadh N. Fathulla, E.
Kudjo Dzantor and David G. Kroll, 1986.  Fate of aldicarb in Wisconsin
ground water; Technical report PB86-215936, National Technical  Information
Service, 54 pp.

Harner, Rodney F., Raymond C. Angell, Marion A. Lobmeyer and Donald R.
Jantz, 1965.  Soil survey of Finney county, Kansas;  Soil Conservation
Service, U.S. Department of Agriculture, 91 pp.
                                   308

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Harsh, K., 1975. In-situ neutralization of an acrylonitrile spill;  Ohio
Environmental Protection Agency, Dayton, Ohio, pp. 187-189.

Hart Crowser and Associates, 1984.  Ground-water resource evaluation
coordinated water system plan, Pierce county, Washington; Seattle,
Washington, 52 pp., 6 plates.

Heath, Ralph C., 1984.  Ground-water regions of the United States;  U.S.
Geological Survey, Water Supply Paper 2242, 78 pp.

Hedstrom, Gary, 1974.  Soil survey of Cumberland county, Maine;  Soil
Conservation Service, U.S. Department of Agriculture, 94 pp.

Helling, Charles S. and Timothy J. Gish, 1985.  Soil characteristics
affecting pesticide movement into ground water; American Chemical Society
Symposium Series #315, Evaluation of Pesticides in Ground Water,
pp. 14-28.

Helling, Charles S., 1986.  Agriculture pesticides and ground water
quality; Proceedings of the Agricultural Impacts on Ground Water. Issues,  A
Conference, National Water Well Association, pp. 161-175.

Higgins, A.J., 1984.  Impacts on groundwater due to land application of
sewage sludge; Water Resources Bulletin vol. 20, no. 3,  pp. 425-434.

Hinchee, Robert E. and H. James Reisinger, 1985.  Multi-phase transport of
petroleum hydrocarbons in the subsurface environment:  Theory and practical
application;  Proceedings of the Petroleum Hydrocarbons and Organic
Chemicals in Ground Water - Prevention, Detection and Restoration,  National
Water Well Association, pp. 58-76.

Holden, Patrick W., 1986.  Pesticides and groundwater quality:  issues and
problems in four states; National Academy Press, 124 pp.

Holt, C.L.R., Jr., 1965.  Geology and water resources of Portage county,
Wisconsin, U.S. Geological Survey, Water Supply Paper 1796, 77 pp.

Houzim, V., J. Vavra, J. Fuksa, V. Pekney, J. Vrba and J. Stribral, 1986.
Impact of fertilizers and pesticides on ground water quality;  Impact of
Agricultural Activities on Ground Water, vol. 5, pp. 89-132.

Hubbard, R.K., L.E.  Asmussen and H.D. Allison, 1984.  Shallow groundwater
quality beneath an intensive multiple-cropping system using center  pivot
irrigation; Journal of Environmental Quality, vol. 13, no.  1,  pp. 156-161.

Hubert, J.S.  and L.W. Canter, 1980.   Effects of acid rain on ground water
quality; Report No.  NCGWR 80-7, National Center for Ground  Water Research,
Oklahoma State University, 226 pp.
                                   309

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Hughes, J.L. and S.G. Robson, 1973.   Effects of  waste percolation on
groundwater in alluvium near Barston, California;  Second International
Symposium on Underground Waste Management and Artificial Recharge,
Sponsored jointly by the American Association of Petroleum Geologists, the
United States Geological Survey, and the International Association of
Hydrological Sciences, Sept. 26-30,  1973, New Orleans, Louisiana, pp.
91-115.

Hussey, A.M. and D. Westerman, 1979.  Maine geology;  Bulletin no. 1.,
Geological Society of Maine, 59 pp.

Hutchins, S.R. and C.H. Ward, 1984.   Microbial removal of trace organics
during rapid infiltration recharge of ground water;  Proceedings Second
International Conference on Ground Water Quality Research, Oklahoma State
University, pp. 18-21.

Hutchinson, Wayne, R. and Jeffrey L. Hoffman, 1983.   A ground water
pollution priority system; New Jersey Geological Survey Open-file Report
no. 83-4, Trenton, New Jersey, 32 pp.

Idelovitch, E. , R. Terkaltoub, M. Butbul, M. Michail and R. Friedman,  1979.
Groundwater recharge with municipal  effluent; Second recharge year - 1978;
annual report, Dan Region Project, Tel Aviv, 34 pp.

Idelovitch, Emanuel and Medy Michail, 1985.  Groundwater recharge for
wastewater reuse in the Dan Region Project:  Summary of £, .*e year
experience, 1977-1981; Artificial Recharge of Groundwater, Butterworth
Publishers, pp. 529-540.

Jhaveri, V. and A.J. Mazzaua, 1983.   Bio-reclamation of ground and
groundwater - case history; Proceedings of the National Conference on
Management of Uncontrolled Hazardous Waste Sites,  Washington, D.C.,
pp. 242-247.

Joel, A.H., 1926.  Changing viewpoints and methods in soil classification;
reprinted in soil classification, Charles W. Finkl,  Jr., editor (1982),
Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania, pp. 52-59.

Johnson, Richard A., 1979.  Geology of the Oklawaha basin; St. Johns River
Water Management District Technical Publication SJ 79-2, 23 pp.

Johnston, Richard H.,  1973.  Hydrology of the Columbia (Pleistocene)
deposits of Delaware:  an appraisal of a regional water table aquifer;
Delaware Geological Survey, Bulletin no. 14, 78 pp.

Jones, P.H., 1981.  Snow and ice control and the transport environment;
Environmental Conservation, vol. 8,  no. 1, pp. 33-38.

Kaap, James D., 1986.  Implementing best management practices to reduce
nitrate levels in north-east Iowa groundwater; Proceedings of the
Agricultural Impacts on Ground Water - A Conference, National Water Well
Association, pp. 412-427.


                                  310

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Karickhoff, S.W., D.S. Brown and T.A.  Scott,  1979.   Sorption of  hydrophobia
pollutants on natural sediments; Water Research,  vol.  13,  no. 3, pp.
241-248.

Kashef, Abdel-Aziz I., 1983.  Salt-water intrusion in the  Nile Delta;
Ground Water, vol. 21, no. 2, pp. 160-167.

Kaufmann, R.F., G.C. Eadie and C.R.  Russell,  1975.   Ground-water quality
impacts of uranium mining and milling  in the  Grants Mineral Belt, New
Mexico; Office of Radiation Programs,  Technical Note ORP/LV-75-4-, U.S.
Environmental Protection Agency, 70 pp.

Keenan, C.W. and J.H. Wood, 1971.  General  college  chemistry; Harper & Row,
717 pp.

Keith, L.A. and W.A. Telliard, 1979.  Priority pollutants, I-A perspective
view; Environmental Science & Technology, vol. 13,  no. 4,  pp. 416-423.

Kelly, Richard, George R. Hallberg,  Lauren  G. Johnson, Robert D. Libra,
Carol A. Thompson, Roger C. Splinter and Mark G.  Detroy,  1986.  Pesticides
in ground water in Iowa; Proceedings of the Agricultural  Impacts on Ground
Water - A Conference, National Water Well Association, pp. 622-647.

Kelly, W.E. , 1976.  Modelling ground-water  flow near landfills and gravel
pits for water quality studies; Ground Water  Quality - Measurement,
Prediction and Protection, Proceedings of the Water Research Centre
Conference, Reading, Berkshire, England, Support Paper U.

Kent, R.T., D.R. Brown and M.E. Bentley, 1986.  Subsurface injection in
Ontario, Canada; Proceedings of the International Symposium on the
Subsurface Injection of Liquid Wastes, National Water Well Association,  pp.
380-398.

Keswick, B.H. and C.P. Gerba, 1980.  Viruses  in groundwater; Environmental
Science and Technology, vol. 14, no. 11, pp.  1290-1295.

Kimmel, G.E. , 1972.  Nitrogen content  of ground water in  Kings County, Long
Island, New York; U.S. Geological Survey, Professional Paper 800-D, pp.  D
199-D203.

Kimrey, J.O., 1978.  Preliminary appraisal  of the geohydrologic  aspects  of
drainage wells, Orlando area, Central  Florida; U.S. Geological Survey Water
Resources Investigations Report 78-37, 24 pp.

Kimrey, J.O. and L.D. Fayard, 1984.   Geohydrologic  reconnaissance of
drainage wells in Florida; U.S. Geological  Survey,  Water  Resources
Investigations Report 84-4021, 67 pp.
                                    311

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Klemt, B., S. Pole and R. MacKinnon, 1986.   Industrial  waste disposal  wells
"mechanical integrity"; Proceedings of the  International Symposium on
Subsurface Injection of Liquid Wastes, National  Water Well Association,  pp.
90-112.

Kmet, P. and P.M. McGinley, 1982.   Chemical characteristics of leachate
from municipal solid waste landfills in Wisconsin:   Fifth Annual Madison
Conference on Applied Research and Practice on Municipal and Industrial
Waste, Madison, Wisconsin, pp. 225-254.

Knochenmus, Darwin D., 1971.  Ground water  in Lake  county, Florida;  Bureau
of Geology, Florida Department of  Natural Resources,  Map series no.  44.

Knochenmus, Darwin D. and G.H. Hughes, 1976.  Hydrology of Lake county,
Florida; U.S. Geological Survey, Water Resources Investigations 76-72> 100
pp.

Knowlton, H.E. and J.E. Rucker, 1979.  Landfarming  shows promise for
refinery waste disposal; Oil and Gas Journal, vol.  77,  no. 20, pp. 108-116.

Knox, R.C., 1979.  Effects of land disposal of sewage sludge on ground
water quality; National Center for Ground Water Research, Report No. NCGWR
79-2, Norman, Oklahoma.

Kobayashi, H. and B.E. Rittmann, 1982.  Microbial removal of hazardous
organic compounds; Environmental Science &  Technology,  vol. 16, no.  3, pp.
170A-183A.

Koch, D.H., J.R. Stetson and B.R.  Genes, 1982.  Assessment of ground and
surface water effects around coal  and mineral storage areas; Bureau of
Mines, Open-file Report 12-83, 306 pp.

Koch, Neil C., 1968.  Ground-water resources of Greenville county, South
Carolina; State Development Board  Bulletin no. 38,  Columbia, South
Carolina, 47 pp.

Lappenbusch, W.L.  1984.  Health effects of drinking water contaminants;
Proceedings of the Thirty-first Ontario Industrial  Waste Conference,
Ontario Ministry of the Environment, Ontario, Canada, pp. 271-291.

Latta, Bruce F., 1944.  Geology and ground-water resources of Finney and
Gray counties, Kansas; Kansas Geological Survey, Bulletin 55, 271 pp.

Lavy, T.L., J.D. Mattice and T.C.  Cavalier, 1985.  Analyses of ground  water
for trace  levels of pesticides; National Technical  Information Service,
PB86-158219, 17 pp.

Leach, S.D. and R.G. Grantham, 1966.  Salt-water study  of the Miami River
and its tributaries, Dade County,  Florida;  Florida  Geological Survey,
Report of  Investigations No. 45, 36 pp.
                                   312

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LeGrand, H.E. and W.A. Pettyjohn, 1981.  Regional hydrogeologic concepts of
homoclinal flanks; Ground Water, vol. 19, no.  3,  pp.  303-310.

LeGrand, Harry E., 1983.  A standardized system for evaluating waste-
disposal sites; National Water Well Association,  Worthington,  Ohio, 49 pp.

Lehman, J.P., 1986.  An outline of EPA's Subtitle D Program; Waste Age,
vol. 17, no. 2, pp. 55-57.

Lehr, Jay H., Wayne A. Pettyjohn, Truman Bennett, James R.  Hanson and
Laurence E. Sturtz, 1976.  A manual of laws, regulations and  institutions
for control of ground water pollution, U.S.  EPA-440/9-76-006,  432 pp.

Lehr, Jay H., David M. Nielsen and John J. Montgomery,  1984.   U.S. federal
legislation pertaining to ground water protection; Groundwater Pollution
Microbiology, Gabriel Bitton and Charles P.  Gerba, editors, John Wiley &
Sons, pp. 353-371.

Leonard, Ralph A., 1986.  Agriculture and ground  water  quality; Proceedings
of the Focus Conference on Southeastern Ground Water  Issues,  National Water
Well Association, pp. 125-144.

Letey, J. and P.F. Pratt, 1984.  Agricultural  pollutants and  groundwater
quality; Ecological Studies, vol. 47, pp. 211-221.

Libra, Robert D., George R. Hallberg, Bernard  E.  Hoyer  and  Loren G.
Johnson, 1986.  Agricultural impacts on ground water  quality:   the Big
Spring Basin study, Iowa; Proceedings of the Agricultural Impacts on Ground
Water - A Conference, National Water Well Association,  pp.  253-273.

Lindholdm, G.F., S.P. Garabedian, G.D. Newton  and R.L.  Whitehead, 1983.
Configuration of the water table, March 1980,  in  the  Snake  River plain
regional aquifer system, Idaho and eastern Oregon; U.S. Geological Survey,
Open-file report 82-1022 (atlas).

Lippencott, W.T. , A.B. Garrett and F.H. Verhoek,  1978.   Chemistry; John
Wiley & Sons, pp. 646-697.

Lippelt, I.D., 1981.  Water table elevation:  Irrigable lands  inventory,
phase 1 - ground water and related information, Wisconsin Geological and
Natural History Survey, map 7.

Lippelt, I.D. and R.G. Hennings, 1981.  Irrigable lands inventory, phase 1
ground water and related information, Wisconsin Geological  and Natural
History Survey, map 18.

Liu, D., W. Strachan, K. Thomson and K. Kwasniewska,  1981.  Determination
of the biodegradability of organic compounds;  Environmental Science &
Technology, vol. 15, no. 7, pp. 788-793.
                                   313

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Longmire, P., 1984.  Geochemistry and alteration processes  of  uranium
tailings in ground water, Grants Mineral Belt,  New Mexico;  Proceedings
First Canadian/American Conference on Hydrogeology, Practical  Applications
of Ground Water Chemistry, National Water Well  Association, pp.  190-199.

Lorimor, J.C., L.N. Mielke, L.F. Elliot and J.R. Ellis,  1972.   Nitrate
concentrations in groundwater beneath a beef cattle feedlot; Water
Resources Bulletin, vol. 8, no.5, pp. 999-1005.

Luckey, R.R. and E.D. Gutentag, 1981.  Water-level and saturated-thickness
changes, predevelopment to 1980, in the High Plains aquifer in parts  of
Colorado, Kansas, Nebraska, New Mexico, Oklahoma,  South Dakota,  Texas and
Wyoming; U.S. Geological Survey, Hydrologic Atlas 652.

Lusczynski, N.J. and W.V. Swarzenski, 1966.  Salt-water encroachment  in
southern Nassau and southeastern Queens counties Long Island,  New York;
U.S. Geological Survey, Water Supply Paper 1613-F, 76 pp.

MacNish, R.D. and R.A. Barker, 1976.  Digital simulation of a  basalt
aquifer system, Walla Walla River Basin, Washington and Oregon;  Washington
Department of Ecology, Water Supply Bulletin 44, 51 pp.

Madison, Robert J. and Jilann 0. Brunett, 1984.  Overview of the occurrence
of nitrate in ground water in the United States, National Water Summary
1984; U.S. Geological Survey, Water Supply Paper 2275, pp.  93-105.

Marin, P.A. and E.X. Droste, 1986.  Contamination of ground water as  a
result of agricultural use of ethylene dibromide (EDB);  Proceedings of the
Third Annual Eastern Regional Ground Water Conference, National Water Well
Association, pp. 277-306.

Martin, Harry W. and William R. Mills, Jr., 1976. Water pollution caused  by
inactive ore and mineral mines - a national assessment;  Industrial
Environmental Research Laboratory, Office of Research and Development, U.S.
EPA, EPA-600/2-76-198, 185 pp.

Matthess, G., 1981.  In situ treatment of arsenic contaminated ground
water; The Science of the Total Environment, no. 21, pp. 99-104.

Matthess, G. and J.C. Harvey, 1982.  Properties of groundwater;  John
Wiley & Sons, pp.  73-114.

Matthews, Earle D. and Oscar L. Lavoie, 1970.  Soil survey of  New Castle
county, Delaware;  U.S. Department of Agriculture, 97 pp., 55 plates.

McBee, J.M. and M.P. Wanielista, 1986.  Application of concepts of
engineering  to an  unusual hydrologic problem:  The stormwater drainage
wells of Orlando,  Florida; Proceedings of the Focus Conference on
Southeastern Ground Water Issues, National Water Well Association, Tampa,
Florida, pp. 145-163.
                                    314

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 McCarty, Perry L., Bruce E. Rittmann and Martin Reinhard, 1980.  Processes
 affecting the movement and fate of trace organics in the subsurface
 environment; Proceedings of the Wastewater Reuse for Groundwater Recharge,
 Office of Water Recycling, California State Water Resources Control Board,
 pp. 93-117.

 McCollum, M.J. and H.B. Counts, 1964.  Relation of salt-water encroachment
 of the major aquifer zones Savannah area, Georgia and South Carolina; U.S.
 Geological Survey, Water Supply Paper 1613-D, 26 pp.

 McCurry, Gordon N. and Henry W. Rauch, 1986. Characterization of ground
 water contamination associated with coal mines In West Virginia;
 Proceedings of the Sixth National Symposium and Exposition on Aquifer
 Restoration and Ground Water Monitoring, National Water Well
 Association, pp. 669-685.

 McGuiness, C.L., 1963.  The role of ground water in the national water
 situation; U.S. Geological Survey Water Supply Paper 1800, 1121 pp.

 McLin, S.G. and P.L. Tien, 1982.  Hydrogeologic characterization of seepage
.from a uranium mill tailings impoundment in New Mexico; Proceedings of the
 Second National Symposium on Aquifer Restoration and Ground Water
 Monitoring, National Water Well Association, pp. 343-358.

 McWhorter, D.B., R.K. Skogerboe and G.V. Skogerboe, 1974.  Potential of
 mine and mill spoils for water quality degradation; Water Resources
 Problems Related to Mining, Proceedings No. 18, American Water Resources
 Association, pp. 123-137.

 Meinzer, Oscar E., 1923.  Outline of ground-water hydrology; United States
 Geological Survey, Water Supply Paper 494, 71 pp.

 Mele, L.M., P.F. Prodan and J.P. Schubert, 1982.  Characterization of
 runoff water from coal-waste disposal sites in southwestern Illinois;
 International Journal of Mine Water, vol. 2, June 1982, pp. 1-14.

 Meyer, Walter R., Edwin D. Gutentag and David H. Lobmeyer, 1970.
 Geohydrology of Finney county,  southwestern Kansas; U.S. Geological Survey,
 Water Supply Paper 1891, 117 pp.

 Michigan Department of Natural Resources, 1983.  Site assessment system
 (SAS) for the Michigan priority ranking system under the Michigan
 Environmental Response Act; Michigan Department of Natural Resources,
 91 pp.

 Miller, C., T.A. Fisher II, J.E. Clark, C.H. Hales, W.M. Porter, and J.N.
 Tilton, 1986.  Flow and containment of injection wastes; Proceedings of the
 International Symposium on the Subsurface Injection of Liquid Wastes,
 National Water Well Association, pp. 520-559.
                                     315

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Miller, D.W. (editor), 1980.  Waste Disposal Effects on Ground Water;
Premier Press, Berkeley, California, 512 pp.

Miller, D.W., F.A. DeLucia and T.L. Tessier, 1974.  Ground water
contamination in the northeast states; U.S. EPA Office of Research and
Development, EPA 600/2-74-056, pp. 185-198.

Miller, John C. and David A. Fischer, 1986.  Deep dedicated pump
installation Florida EDB contamination investigation; Proceedings of the
Focus Conference on Southeastern Ground Water Issues, National Water Well
Association, pp. 27-37.

Miller, W.D., 1971.  Infiltration rates and ground-water quality beneath
cattle feedlots, Texas High Plains (abstract); U.S. EPA Program 16060 EGS
01/71, Water Pollution Control Research Series Report, Water Quality
Office, 55 pp.

Mink, Leland, Roy E. Williams and Alfred T. Wallace, 1971. Effect of early
day mining operations on present day water quality; Ground Water, vol. 10,
no. 1, pp. 17-26.

Moe, C.L., C.G. Coggerpond and M.D. Sobsey, 1984.  Viral and bacterial
contamination of groundwater by on-site wastewater treatment systems in
sandy coastal soils; Proceedings Second International Conference on Ground
Water Quality Research, Oklahoma State University, pp. 132-134.
                                                           «
                                                         «
Mount, R.J., 1963.  Investigation of ground-water resources near
Fredericksburg, Texas; Memorandum Report no. 63-03, Texas Water Commission,
101 pp.

Muller, D.A. and R.D. Price, 1979.  Ground-water availability in Texas,
estimates and projections through 2030; Report 238, Texas Department of
Water Resources, 77 pp.

Mundorff, M.J., E.G. Crosthwaite and Chabot Kilburn, 1964.  Ground water
for irrigation In the Snake River basin in Idaho; U.S. Geological Survey
Water-supply paper 1654, 224 pp.

Murphy, R.C., 1986.  Putting wastewater to work; Civil Engineering, vol.
56, no. 6, pp. 77-79.

Nace, R.L., 1958.  Hydrology of the Snake River basalt; Washington Academy
of Science Journal, vol. 48, no. 4, pp. 136-138.

National Academy of Sciences, 1983. Transportation of hazardous materials:
towards a national strategy; Transportation Research Board Special Report
No. 197.

National Fire Protection Association, 1983.  Underground leakage of
flammable and combustible liquids; NFPA 329, pp. 329-1 - 329-23.
                                    316

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National Research Council, 1981. Coal mining and ground-water resources in
the United States, summary of impacts; Committee on Ground-Water Resources
in Relation to Coal Mining, Board on Mineral and Energy Resources,
Commission on Natural Resources, National Academy Press, Washington, D.C.,
197 pp.

Newcomb, R.C., 1961.  Storage of ground water behind subsurface dams in the
Columbia River basalt, Washington, Oregon and Idaho; U.S. Geological
Survey, Professional Paper 383-A, 15 pp.

Newport, Bob D., 1977.  Salt water intrusion in the United States,
EPA-600/8-77-Oil, Office of Research and Development, 30 pp.

New York State Department of Environmental Conservation, 1985.  Technology
for the storage of hazardous liquids; a state-of-the-art review; Division
of Water, Bureau of Water Resources, 223 pp.

Nielsen, D.M. and L. Aller, 1984.  Mathods for determining the mechanical
integrity of Class II injection wells; EPA-600/2-84-121, Office of Research
and Development, United States Environmental Protection Agency, 263 pp.

Nightingale, Harry I. and William C. Bianchi, 1977.  Ground water turbidity
resulting from artificial recharge;  Ground Water, vol. 15, no. 2, pp.
146-152.

Norbeck, P.N. , L-L. Mink and R.E. Williams, 1974.  Ground water leaching of
jig tailings deposits in the Coeur D'Alene district of northern Idaho;
Water Resources Problems Related to Mining, Proceedings No. 18, American
Water Resources Association, pp. 149-157.

O'Connor, M.J., A.M. Wofford and S.K. Ray, 1984.  Recovery of subsurface
hydrocarbons at an asphalt plant:  Results of a five-year monitoring
program; Proceedings of the Petroleum Hydrocarbons and Organic Chemicals in
Ground Water - Prevention, Detection and Restoration, National Water Well
Association, pp.  359-076.

O'Hare, Margaret P., Deborah M.  Fairchild, Paris A. Hajali and Larry W.
Canter, 1986.  Artificial recharge of ground water, status and potential in
the contiguous United States;  Lewis Publishers, Inc., Chelsea, Michigan,
419 pp.

O'Leary, P. and B.  Tansel, 1986a.  Land disposal of solid wastes:
Protecting health and environment; Waste Age, vol. 17,  no. 3, pp. 68-77.

O'Leary, P. and B.  Tansel, 1986b.  Leachate Control and Treatment;  Waste
Age, vol. 17, no.  5, pp. 68-85.

Oaksford, Edward  T., 1985.  Artificial recharge:  methods, hydraulics,  and
monitoring;  Artificial Recharge  of Groundwater, Butterworth Publishers, pp.
69-128.
                                   317

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Oberts, G.L., 1986.   Pollutants associated with sand  and salt  applied  to
roads in Minnesota;  Water Resources Bulletin,  vol.  22,  no.  3,  pp.  479-483.

Office of Technology Assessment, 1984.   Protecting  the  nation's  groundwater
from contamination,  vol. 1,  2; U.S. Congress,  Washington,  B.C.,  503  pp.

Ohneck, R.J. and G.L. Gardner, 1982.   Restoration of  an aquifer
contaminated by an accidental spill of organic chemicals;  Proceedings
of the Second National Symposium on Aquifer Restoration and Ground Water
Monitoring, National Water Well Association,  Columbus,  Ohio, pp. 339-342.

Olcott, P.G. , 1968.   Water resources  of Wisconsin Fox-Wolf  river basin;
U.S. Geological Survey, Hydrologic Investigations Atlas HA-321.

Olmsted, F.H. and G.H. Davis, 1961.  Geologic features  and  ground  water
storage capacity of  the Sacramento Valley, California;  Water Supply  Paper
1497, U.S. Geological Survey and the  California Department  of  Water
Resources, 236 pp.

Olson, R.A., 1986.  Agricultural practices for minimizing  nitrate  content
of ground water; Proceedings of the Agricultural Impacts on Ground Water -
A Conference, National Water Well Association, pp.  428-444.

Otter, A.M. and W.D. Fiala,  1978.  Soil survey of Portage  county,
Wisconsin: U.S. Department of Agriculture, Soil Conservation Service,  96
pp.

Owe, M., P.J. Craul  and H.W. Halverson, 1982.   Contaminant  levels  in
precipitation and urban surface runoff:  Water Resources Bulletin, vol.  18,
no. 5, pp. 863-868.

Pabst, Marilyn E. and Edwin D. Gutentag, 1979.  Water level changes  in
southwestern Kansas, 1940-78; Kansas Geological Survey, 29  pp.

Pabst, M.E. and B.J. Dague,  1984.  January 1984 wat i levels,  and  data
related to water-level changes, western and south-central  Kansas;  U.S.
Geological Survey, Open-file no. 84-613.

Padgett, Gary G. and Harriett K. Hardee, 1982.  Preliminary designation  of
aquifer systems in South Carolina; South Carolina Department of  Health and
Environmental Control, Ground-water Protection Division, 28 pp.

Page, A.L., 1974.  Fate and effects of trace elements in sewage  sludge when
applied to agricultural lands; U.S. EPA 670/2-74-005, Office of  Research
and Development, 96 pp.

Paque, M.J., 1986.  Class I injection well performance survey; Ground  Water
Monitoring Review, vol. 6, no. 3, pp. 68-69.

Parker, L.V., T.F. Jenkins and B.T. Foley, 1984.  Impact of slow-rate  land
treatment on groundwater quality; U.S. EPA Office of  Research  and
Development, EPA 600/2-84-097, 36 pp.

                                   318

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Peffer, J.R.,  1982.   Fly ash disposal in a limestone quarry;  Ground Water,
vol. 20, no. 3, pp.  267-273.

Peterson, N.M., 1983.  1983 Survey of landfills;  Waste Age, pp.  37-40,
March, 1983.

Petty, Susan,  Barbara Lanan and William Miller,  1976.   Map showing
potential for  ground-water recharge in New Castle county,  Delaware; New
Castle county  areawide waste treatment management program, Delaware
Geological Survey, 24 pp.

Pettyjohn, Wayne A., 1981.  Introduction to artificial ground water
recharge; NWWA/EPA Series, Office of Research and Development, 44 pp.

Peterec, L. and C. Modesitt, 1985.  Pumping from multiple  wells  reduces
water production requirements: recovery of motor vehicle fuels,  Long
Island, New York; Proceedings of the NWWA/API Conference on Petroleum
Hydrocarbons and Organic Chemicals in Ground Water - Prevention,  Detection
and Restoration, pp. 358-373.

Piet, G.J. and B.C.J. Zoeteman, 1985.  Bank and  dune infiltration of
surface water  in The Netherlands; Artificial Recharge  of Groundwater,
Butterworth Publishers, pp. 529-540.  .

Pionke, Harry  B. and James B. Urban, 1985.  Effect of  agricultural land use
on ground-water quality in a small Pennsylvania  watershed; Ground Water,
vol. 23, no. 1, pp.  68-80.

Pionke, Harry  B., Dwight E. Glotfelt and James B. Urban, 1986.  Pesticide
contamination  of ground water in a rural Pennsylvania  watershed;
Proceedings of the Agricultural Impact on Ground Water - A Conference,
National Water Well Association, pp. 542-563.

Pollock, S.J.  and L.G. Tober, 1973.  Effects of  highway de-icing salts  on
groundwater and water supplies in Massachusetts;  Highway Research Record
No. 425, Highway Research Board, National Research Council, pp.  17-22.

Pollock, S.J.  and L.C. Stevens, 1985.  Effectiveness of highway  drainage
systems in preventing salt contamination of ground water;  Proceedings
Fifth National Symposium and Exposition on Aquifer Restoration and Ground
Water Monitoring, National Water Well Association Exposition, Columbus,
Ohio, pp. 709-733.

Pound, C.E. and R.W. Crites, 1973.  Wastewater treatment and  reuse by  land
application, vol. 1 - Summary; U.S. EPA Office of Research and Development,
EPA -660/2-73006a, 80 pp.

Powers, W.L. ,  G.W. Wallingford and L.S. Murphy,  1975.   Research  status  on
effects of land application of animal wastes; U.S. EPA-660/2-75-010,
National Environmental Research Center, Office of Research and Development,
88 pp.
                                   319

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Prescott, Glen C-, 1963.   Reconnaissance of ground-water  conditions  in
Maine; U.S. Geological Survey,  Water Supply Paper 1669-T,  52  pp.

Prescott, Glen C. , 1967.   Lower Androscoggin river basin  area;  Maine
basic-data report no. 3,  Ground-water series,  U.S. Geological Survey,  63
pp.

Prescott, Glen C. , 1968.   Ground water favorability areas and surficial
geology of the Lower Androscoggin river basin, Maine;  U.S.  Geological
Survey, Hydrologic Investigations HA-285.

Prescott, Glen C., 1976a.  Windham-Freeport-Portland Area;  Maine  basic-data
report no. 9, Ground-water series, U.S. Geological Survey,  43 pp.

Prescott, Glen C., 1976b.  Ground water favorability and  surficial geology
of the Portland area, Maine;  U.S. Geological Survey, Hydrologic
Investigations HA-561.

Prescott, Glen C., G.W. Smith and W.B. Thompson,  1976.   Surficial geology
of the Cumberland Center Quadrangle, Maine; Open-file no.  76-30;  Maine
Geological Survey, Department of Conservation.

Prescott, Glen C.  and W.B. Thompson, 1976a.  Surficial geology of the  North
Windham Quadrangle, Maine; Open-file no. 76-31; Maine Geological  Survey,
Department of Conservation.

Prescott, Glen C.  and W.B. Thompson, 1976b.  Surficial geology of the  Old
Orchard Beach Quadrangle, Maine; Open-file no. 76-32; Maine Geological
Survey, Department of Conservation.

Prescott, Glen C.  1977.  Ground water favorability and surficial  geology  of
the Windham-Freeport area, Maine; U.S. Geological Survey, Hydrologic
Investigations HA-564.

Prescott, Glen C.  and W.B. Thompson, 1977a.  Surficial geology of the
Freeport Quadrangle, Maine; Open-file no.  77-5, Maine Geological  Survey,
Department of Conservation.

Prescott, Glen C. and W.B. Thompson, 1977b.  Surficial geology of the  South
Harpswell Quadrangle, Maine;  Open-file no. 77-6,  Maine Geological Survey,
Department of Conservation.

Prescott, Glen C.  and W.B. Thompson, 1977c.  Surficial geology of the
Yarmouth Quadrangle, Maine; Open-file no.  77-7, Maine Geological  Survey,
Department of Conservation.

Preul, H.C., 1968.  Contaminants in groundwaters  near waste stabilization
ponds; Journal Water Pollution Control Federation, vol. 40, no. 4, pp.
659-669.
                                   320

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Prickett, T.A., D.L. Warner and D.D.  Runnells,  1986.   Application of  flow,
mass transport, and chemical reaction modeling  to subsurface  liquid
injection; Proceedings of the International Symposium on the  Subsurface
Injection of Liquid Wastes, National  Water Well Association,  pp.  447-463.

Pride, R.W., F.W. Meyer and R.N. Cherry,  1966.   Hydrology of  Green Swamp
area in central Florida; Florida Geological Survey Investigations no. 42,
137 pp.

Pye, V.I., R. Patrick and J. Quarles, 1983.  Groundwater contamination in
the United States; University of Pennsylvania Press,  314 pp.

Pye, Veronica I. and Jocelyn Kelley,  1984.  The extent of groundwater
contamination in the United States;  Groundwater Contamination,  National
Academy Press, pp. 23-33.

Reddell, D.L., G.E. Wise, R.E. Peters and P.J.  Lyerly, 1973.  Water quality
hydrology of lands receiving farm animal  wastes; Technical Report no. 50,
Texas Water Resources Institute, NTIS PB-222-181, 110 pp.

Reichenbaugh, R.C., D.P. Sown and C.I. Goetz, 1979.   Results  of testing
land spreading of treated municipal  wastewater  at St. Petersburg, Florida;
U.S. Geological Survey, Water Resources Investigations 78-110,  47 pp.

Ricca, V.T. and R.R. Schultz, 1979.   Acid mine  drainage modeling  of surface
mining; Proceedings of the First International  Mine Drainage  Symposium,
G.O. Argall Jr., and C.O. Brawner, editors, pp. 651-670.

Riley, John A., Dale R. Ralston and  Roy E. Williams,  1984. The  hydrology of
an underground lead-zinc mine:  water flow and  quality characteristics;
Proceedings of the National Water Well Association Conference on  the  Impact
of Mining on Ground Water, National  Water Well  Association, Denver,
Colorado, pp. 113-128.

Ritter, W.F., 1984.  Influence of nitrogen application and irrigation on
ground-water quality in the coastal  plain; U.S. Department of Commerce,
National Technical Information Service, PH85-225852,  pp. 1-22.

Ritter, W.F. and A.E.M. Chirnside, 1984.   Impact of land use  on ground
water quality in southern Delaware;  Ground Water, vol. 22, no.  1, pp.
38-47.

Rittmann, Bruce E., Perry L. McCarty  and  Paul V. Roberts, 1980.  Trace-
organics biodegradation in aquifer recharge; Ground Water, vol. 18, no. 3,
pp. 236-243.

Roberts, Paul V., Joan Schreiner and  Gary D. Hopkins, 1980.  Field study of
organic water quality changes during  groundwater recharge in  the  Palo Alto
Baylands; Proceedings of the Wastewater Reuse for Groundwater Recharge,
Office of Water Recycling, California State Water Resources Control Board,
pp. 283-316.
                                   321

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Roberts, P.V., 1981.  Nature of organic contaminants in ground water and
approaches to treatment; American Water Works Association Seminar
Proceedings, Organic Chemical Contaminants in Ground Water:  Transport and
Removal, pp. 47-66.

Roberts, Paul V. , 1985.  Field observations of organic contaminant behavior
in the Palo Alto Baylands; Artificial Recharge of Groundwater, Butterworth
Publishers, pp. 647-680.

Rose, Peter R. , 1972.  Edwards group, surface and subsurface, central
Texas, Report of Investigation no. 74, Bureau of Economic Geology,
University of Texas, 198 pp.

Rott, U., 1981.  Protection and improvement of ground water  quality by
oxidation processes in the aquifer; Quality of Ground Water, Proceedings of
an International Symposium, The Netherlands, Elsevier Scientific
Publication Company, pp. 1073-1076.

Sawhill, G.S., 1977.  The effect of spray irrigation of secondary treated
effluent on the vegetation, soils, and groundwater quality in a New Jersey
Pine Barrens Habitat; Rutgers University, Ph.D. dissertation, 183 pp.

Sawyer, C.N. and P.L. McCarty, 1978.  Chemistry for environmental
engineering; McGraw-Hill, pp. 94-163.

Scalf, M.R. , W.J. Dunlap and J.F. Kreissel, 1977.  Enviro* >ntal effects of
septic tank systems; Office of Research and Development, EPA-600/3-77-096,
34 ip.

Scarano, Louis J., 1986.  The Massachusetts aldicarb well water survey;
Proceedings of the Third Annual Eastern Regional Ground Water Conference,
National Water Well Association, pp. 261-276.

Schmidt, Kenneth D., 1986.  DBCP in ground water of the Fresno-Dinuba Area,
California; Proceedings of the Agricultural Impacts on Ground Water - A
Conference, National Water Well Association, pp. 511-529.

Schneider, A.D.,  M. Asce and O.R. Jones, 1983.  Basin recharge of playa
water; Journal of Irrigation and Drainage Engineering, vol.  109, no. 3.,
pp. 309-316.

Schubert, J.P., 1979.  Groundwater contamination problems resulting from
coal refuse disposal; Proceedings of the First International Mine Drainage
Symposium, G.O. Argall Jr., and C.O. Brawner, editors, pp. 757-780.

Scrivner, N.C., K.E. Bennett, R.A. Pease, A. Kopatsis, S.J.  Sanders, D.M.
Clark and M. Rafal, 1986.  Chemical fate of injected wastes; Proceedings of
the International Symposium on the Subsurface Injection of Liquid Wastes,
National Water Well Association, pp. 560-609.
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 Seiber, James N.,  1983.   General principles governing the fate of  chemicals
 in the environment;  Beltsville Symposia in Agricultural Research,
 Beltsville Agricultural  Research Center pp. 389-402.

 Seifert, Gregory  G., August 1984.  Hydrogeochemical  Impacts of  coal strip
 mining in Macon County,  Missouri;  Proceedings  of  the  National  Water Well
 Association Conference on the Impact  of Mining on Ground Water,  National
 Water Well Association,  Denver,  Colorado,  pp.  33-50.

 Seitz, H.R. ,  A.M.  Lasala and J.R.  Moreland, 1977.   Effects_of  drain wells
 on the ground-water  quality of the western Snake  Plain aquifer,  Idaho;  U.S.
 Geological Survey, Open-file Report 76-673, 34 pp.

 Seller, L.E.  and  L.W.  Canter, 1980.  Summary of selected ground-water
 quality impact assessment methods;  National Center  For Ground  Water
 Research Report no.  NCGWR 80-3,  Norman, Oklahoma, 142 pp.

 Sgambat, Jeffrey  R., Elaine A. LaBella and Sheila Roebuck,  1980. Effects of
 underground coal  mining  on ground  water in the eastern United  States;
• EPA-600/7-80-120,  Industrial Environmantal Research Laboratory,  Office  of
 Research and  Development, 182 pp.

 Shaffer, K.A., D.D.  Fritton and  D.D.  Baker, 1979.   Drainage water  sampling
 in a wet, dual-pore  soil system;  Journal of Environmental  Quality, vol.  8,
 no. 2, pp.  241-246.

 Sheibac>i, R.  Bruce,  Roy  E.  Williams and Benjamin  R. Genes,  1982.
 Controlling acid  mine  drainage from the Picher mining district,  Oklahoma,
 United States; International Journal  of Mine Water, vol. 1, pp.  45-52.

 Sherman, C.R.  and  P.L. Craig, 1986.  Fluid sealed Class I  injection wells;
 Proceedings of the International Symposium on  the Subsurface Injection  of
 Liquid Wastes, National  Water Well Association, pp. 195-210.

 Shimek, S.J.  and  D.J.  Hermann, 1985.   Effect of acidic leachate  on clay
 permeability:   Eighth  Annual Madison  Waste Conference on Municipal and
 Industrial  Wastes, Madison, Wisconsin,  pp.  303-314.

 Slack, Larry  J.,  1983. Hydrology of an abandoned  coal-mining area  near
 McCurtain,  Haskell County,  Oklahoma;  U.S.  Geological  Survey Water-
 Resources Investigations Report  83-4202, 117 pp.

 Smith, Geoffrey W.,  1976a.   Surficial geology  of  the  Phippsburg  Quadrangle,
 Maine; Open-file no. 76-37, Maine  Geological Survey,  Department  of
 Conservation.

 Smith, Geoffrey W.,  1976b.   Surficial geology  of  the  Small  Point
 Quadrangle, Maine; Open-file no. 76-38,  Maine  Geological Survey, Department
 of Conservation.
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Smith, Geoffrey W. and W.B.  Thompson,  1976.   Surficial  geology of  the
Gorham Quadrangle, Maine;  Open-file no.  76-42,  Maine Geological Survey,
Department of Conservation.

Smith, Geoffrey W., 1977a.  Surficial  geology map of Freeport,  Maine;
Open-file report,  Maine Geological Survey,  Department of  Conservation.

Smith, Geoffrey W., 1977b.  Surficial  geology of  the Bath Quadrangle,
Maine; Open-file no. 77-8, Maine Geological Survey,  Department of
Conservation.

Smith, Geoffrey W., 1977c.  Surficial  geology of  the Portland Quadrangle,
Maine; Open-file no. 77-16,  Maine Geological Survey, Department of
Conservation.

Smith, Geoffrey W., 1977d.  Surficial  geology of  the Small Point
Quadrangle, Maine; Open-file no. 77-17,  Maine Geological  Survey, Department
of Conservation.

Smith, Geoffrey W. and W.B.  Thompson,  1980.   Surficial  geology of  the
Poland Quadrangle, Maine;  Open-file no.  80-25,  Maine Geological Survey,
Department of Conservation.

Smith, William, 1985.  Advantage of utilizing multiple  recovery wells  for
aquifer restoration; Proceedings of the  Petroleum Hydrocarbons and Organic
Chemicals in Ground Water -  Prevention,  Detection and Restoration, National
Water Well Association, pp.  406-420.

Snoeyink, V.L. and D. Jenkins, 1980.  Water chemistry;  John Wiley  & Sons,
463 pp.

Soil Conservation Service, 1951.  Soil survey manual; U.S. Department  of
Agriculture, 503 pp.

Soil Conservation Service, 1960.  Soil classification:  a comprehensive
system, 7th approximation; United States Department  of  Agriculture, 265  pp.

Soil-Conservation Service, 1975.  Soil taxonomy:   a  basic system of soil
classification for making and interpreting soil surveys;  United States
Department of Agriculture Handbook no. 436, 754 pp.

Solley, Wayne B., Edith B. Chase and William B. Mann, 1983.  Estimated use
of water in the United States in 1980; U.S. Geological  Survey, Circular
1001, 56 pp.

Solomons, T.W., 1980.  Organic chemistry; John  Wiley &  Sons, pp. 634-639.

Sonntag, W.H., 1980.  Water-quality data for canals  in  eastern Broward
county, Florida,  1975-78;  U.S. Geological Survey, Open-file Report 80-68,
161 pp.
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State of California, 1978.  Health aspects of wastewater recharge, a
state-of-the-art review; Water Information Center, Inc., Huntington, N.Y.,
pp 173-204.

Stegman, R., 1982.  The pollution potential of sanitary landfills;
International Association of Hydrological Sciences Pub. No.  139,  Effects of
Waste Disposal on Groundwater and Surface Water, pp. 125-135.

Steichen, James, James Koelliker and Doris Grosh, 1986.  Kansas farmstead
well survey for contamination by pesticides and volatile organics;
Proceedings of the Agricultural Impacts on Ground Water - A conference,
National Water Well Association, pp. 530-542.

Sterrett, R.J., G.D. Barnhill and M.E. Ransom, 1985.  Site assessment and
on-site treatment of a pesticide spill in the vadose zone:  Proceedings  of
the National Water Well Association Conference on Characterization and
Monitoring of the Vadose Zone, Denver, Colorado, pp. 255-271.

Stewart, B.A., F.G. Viets, G.L. Hutchinson and W.D.  Remper,  1967.   Nitrate
and other water pollutants under fields and feedlots (abstract);
Environmental Science and Technology, vol. 1, no. 9, pp. 736-739.

Stimpson, K., S. Springer and R. Lillich, 1984.  Bennett's Quarry:  A case
study of an immediate removal of PCB wastes under Superfund; Seventh Annual
Madison Waste Conference on Municipal and Industrial Wastes, Madison,
Wisconsin, pp. 219-232.

Stover, E.L. aid D.F. Kineannon, 1983.  Contaminated ground water
treatability - a case study; Journal of American Water Works Association,
vol. 75, no. 6, pp. 292-298.

Stroud, J.L. Spellman,  R.R. Potts and A.J. Oakley, 1985.  Chemistry and
apparent quality of surface water and ground water associated  with coal
basins, Publication no. 113, Arkansas Water Resources Research Center,
University of Arkansas, 88 pp.

Tabak, H.H., S.A.  Quave, C.I. Mashni and E.F. Earth, 1980.
Biodegradability studies with priority pollutant organic compounds;
Staff Report, Wastewater Research Division, U.S. EPA Research  Center,
Cincinnati, Ohio,  42 pp.

Talley, John H., 1978.   Ground-water levels in Delaware July 1966  -
December 1977;  Delaware Geological Survey, Report of investigations no.  30,
50 pp.

Tepper, Dorothy H. , John S. Williams, Andrews L. Tolman and  Glenn C.
Prescott, 1985.   Hydrogeology and water quality of significant sand and
gravel aquifers in parts of Androscoggin, Cumberland,  Franklin, Kennebec,
Lincoln, Oxford, Sagadahoc, and Somerset counties, Maine;  Sand and gravel
aquifer maps 10, 11, 16, 17 and 32,  Open-file no.  85-82A,  Maine Geological
Survey, 106 pp.
                                   325

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Texas Department of Water Resources, 1983.  Underground water conservation
districts, underground water reservoir delineations and major aquifers as
of August, 1983; Texas Department of Water Resources, Austin, Texas.

Thomas, Grant W. and Ronald E. Phillips, 1979.  Consequences of water
movement in macropores; Journal of Environmental Quality, vol. 8, no. 2,
pp. 149-152.

Thomas, Grant W., 1983.  Environmental significance of minimum tillage;
Agricultural Chemicals of the Future, Beltsville Symposia in Agricultural
Research, Beltsville Agricultural Research Center, p. 411-423.

Thomas, Harold E., 1952.  Ground water regions of the United States - their
storage facilities; Interior and Insular Affairs Committee, U.S. House of
Representatives, 76 pp.

Thompson, C.A., Robert D. Libra and George R. Hallberg, 1986.  Water
quality related to ag-chemicals in alluvial aquifers in Iowa; Proceedings
of the Agricultural Impacts on Ground Water - A Conference, National Water
Well Association, pp. 224-242.

Thompson, Woodrow B., 1976a.  Surficial geology of the Cape Elizabeth
Quadrangle, Maine; Open-file no. 76-43, Maine Geological Survey, Department
of Conservation.

Thompson, Woodrow B., 1976b.  Surficial geology of the Cornish Quadrangle,
Maine; Open-file no. 76-44, Maine Geological Survey, Department of
Conservation.

Thompson, Woodrow B., 1976c.  Surficial geology of the Gray Quadrangle,
Maine; Open-file no. 76-45, Maine Geological Survey, Department of
Conservation.

Thompson, Woodrow B., 1976d.  Surficial geology of the Pleasant Mountain
Quadrangle, Maine; Open-file no. 76-46, Maine Geological Survey, Department
of Conservation.

Thompson, Woodrow B., 1976e.  Surficial geology of the Portland West
Quadrangle, Maine; Open-file no. 76-46, Maine Geological Survey, Department
of Conservation.

Thompson, Woodrow B., 1976f.  Surficial geology of the Prouts Neck
Quadrangle, Maine; Open-file no. 76-48, Maine Geological Survey, Department
of Conservation.

Thompson, Woodrow B., 1977.  Surficial geology of the Norway Quadrangle,
Maine; Open-file no. 77-34, Maine Geological Survey, Department of
Conservation.

Thompson, Woodrow B. and G.C. Prescott, 1977.  Surficial geology of the
Portland East Quadrangle, Maine; Open-file no. 77-40, Maine Geological
Survey, Department of Conservation.

                                    326

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Thompson, W.E., R.L. Hoye and J.S. Greber, 1984.  Evaluation of management
practices for mine solid waste storage, disposal, and treatment;
Proceedings of the Seventh National Ground Water Quality Symposium,
National Water Well Association, pp. 224-234.

Thompson, W.E., W.V. Swarzenskl, D.L. Warner, G.E. Rouse, O.F.  Carrington
and R.Z. Pyrih, 1978. Ground-water elements of in-situ leach mining of
uranium; NUREG/CR-0311, Division of Fuel Cycle and Material Safety, Office
of Nuclear Material Safety and Safeguards, U.S. Nuclear Regulatory
Commission, 173 pp.

Thornthwaite, S.W. and J.R. Mather, 1957.  Instructions and tables for
computing potential evapotranspiration and the water balance; Drexel
Institute of Technology, Laboratory of Climatology, Publications in
Climatology, Centerton, New Jersey, vol. 10,  no. 3, 3J1 pp.

Todd, D.K., 1980.  Groundwater hydrology; John Wiley & Sons, 535 pp.

Tolman, A., A. Ballestero, W. Beck and G. Emrich, 1978.  Guidance manual
for minimizing pollution from waste disposal sites; U.S. EPA-600/2-78-142,
pp. 328-331.

Tolman, Andrews L. and Craig D. Neil, 1986.  Statewide pesticide
monitoring;  Proceedings of the Third Annual Eastern Regional Ground Water
Conference,  National Water Well Association,  pp. 234-250.

Tomson, Mason B., J. Dauchy, S. Hutchins, C.  Curran, C.J. Cook  and C.H.
Ward, 1981.   Groundwater contamination by trace level organics  from a rapid
infiltration site; Water Research, vol. 15, no. 9, pp. 1109-1116.

Toran, L. and K.R. Bradbury, 1985. Hydrogeologic and geochemical evolution
of contaminated groundwater near abandoned mines; Technical Report WIS WRC
85-01, Water Resources Center, University of Wisconsin, 34 pp.

Traylor, Robert L., 1984. Impacts of historic mining on water quality in
the Walsenburg coal field of Colorado; Proceedings of the National Water
Well Association Conference on the Impact of Mining on Ground Water,
National Water Well Association, pp. 24-32.

United Nations, 1975.  Ground-water storage and artificial recharge;
National Resources/Water Series No. 2, Department of Economic and Social
Affairs, United Nations, 270 pp.

United States Environmental Protection Agency, 1973a.  Ground water
pollution from subsurface excavations; Office of Air and Water  Programs,
EPA-430/9-73-012, 217 pp.

United States Environmental Protection Agency, I973b.  Identification and
control of pollution from salt water intrusion; EPA-430/9-73-013.  Office
of Air and Water Programs, 94 pp.
                                   327

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United States Environmental Protection Agency,  1975.   Inactive & abandoned
underground mines, water pollution prevention & control;  EPA-440/9-75-007,
Office of Water and Hazardous Materials,  338 pp.

United States Environmental Protection Agency,  1978a.   Chemical and
physical effects of municipal landfills on underlying  soils  and
groundwater;  EPA-600/2-78-096,  Office of Research and Development, 139  pp.

United States Environmental Protection Agency,  1978b.   Surface impoundments
and their effects on ground water quality in the United States - A
preliminary survey; EPA 570/9-78-004,  Office of Drinking Water, 275 pp.

United States Environmental Protection Agency,  1979a.   A Guide to the
Underground Injection Control Program; Office  of Drinking Water WH-550,
29 pp.

United States Environment...I Protection Agency,  1979b.   Methods of
preventing, detecting, and dealing with surface spills of contaminants
which may degrade underground water sources for public water systems;
Office of Drinking Water, EPA 570/9-79-018, 112 pp.

United States Environmental Protection Agency,  1980.   Lining of waste
impoundment and disposal facilities;  EPA  500-870, MERL, Office of Research
and Development, 285 pp.

United States Environmental Protection Agency,  1983.   Surface Impoundment
Assessment National Report  U.S.  EPA 570/9-84-002, 200 pp.

United States Environmental Protection Agency,  1984.   The hydrologic
evaluation of landfill performance (HELP) model, vol.  1.   User's Guide  for
Version 1; EPA/53-SW-84-009,  Office of Solid Waste and Emergency Response,
120 pp.

United States Environmental Protection Agency,  1986a.   Criteria for
identifying areas of vulnerable  hydrogeology under the Resource
Conservation and Recovery Act, U.S. EPA,  Office of Solid Waste and
Emergency Response, Washington,  DC, 491 pp.

United States Environmental Protection Agency,  1986b.   RCRA  orientation
manual; EPA/530-SW-86-001, Office of Solid Waste, pp.  II-l through 11-10.

United States Environmental Protection Agency,  1986c.   Septic systems and
ground-water protection a program manager's guide and  reference book;
Office of Ground Water Protection, Washington,  D.C., 152 pp.

United States Environmental Protection Agency,  1986d.   Summary of state
reports on releases from underground storage tanks; U.S.  EPA No.
600/M-86/020, Office of Underground Storage Tanks, 50  pp.
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United States Environmental Protection Agency, 1986e.  Underground motor
field storage tanks:  A National survey vol. 1; U.S. EPA No. 560/5-86-013,
Office of Pesticides and Toxic Substances, pp. 1-1 through 10-15.

United States Geological Survey, 1985.  Ground-water levels, 1980, Snake
river plain, Idaho and eastern Oregon; U.S. Geological Survey, Open-file
report 85-330.

Van der Leeden, F., L.A. Cerrillo and D.W. Miller, 1975.  Ground water
pollution problems in the northwestern United States; U.S. EPA Office of
Research and Development, EPA -660/3-75-018, pp. 245-254.

van Ee, J. Jeffrey, Linda Aller, Kristen K. Stout, Frank Frischknecht and
Deborah Fairchild, 1984.  Summary and comparisons of three technologies for
locating abandoned wells in central Oklahoma; Proceedings of the Seventh
National Ground Water Quality Symposium, National Water Well Association,
pp. 330-342.

Van Voast, Wayne A., 1974. Hydrologic effects of strip coal mining in
southeastern Montana - emphasis:  one year of mining near Decker; Bulletin
93, Bureau of Mines and Geology, Montana College of Mineral Science and
Technology, 24 pp.

Wagner, B.L., C.W. Jennings, T.L. Bedrossian and E.J. Bortugno, 1981.
Geologic map of the Sacramento Quadrangle; Map no. 1A, Division of Mines
and Geology, California Department of Conservation.

Wagner, D.L. and E.J. Bortugno, 1982.  Geologic map of the Santa Rosa
Quadrangle; Map no. 2A, Division of Mines and Geology, California
Department of Conservation.

Walker, L.W., A.K. Turner and D.G. Vanselow, 1979.  Inflow to ground water
from a large cattle feedlot in Victoria; Proceedings of The Groundwater
Pollution Coni rence, Perth, Western Australia; C.R. Lawrence and R.J.
Hughes, editor,, pp. 375-389.

Walker, Loyd E., 1979.  Occurrence, availability, and chemical quality of
Around water in the Edwards Plateau region of Texas; Report 235, Texas
Department of Watt-r Resources, Austin, Texas, 336 pp.

Walker, W.H., 1973.  Where have all the toxic chemicals gone?; Ground
Water, vol. 11, no. 2, pp. 11-20.

Wallace,  William J. , 1984.  Seawater intrusion in the San Juan Islands;
Second International Conference on Ground Water Quality Research
Proceedings, Oklahoma State University, University Printing Services, pp.
155-157.

Walter, B., 1986.   Remediation of ground-water contamination resulting from
the failure of a Class I injection well:  A case history;  Proceedings of
the International  Symposium on the Subsurface Injection of Liquid Wastes,
National  Water Well Association, pp. 357-379.

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Walter, Gary R., Robert E.  Kidd and George M. Lamb, 1979.   Ground-water
management techniques for the control of salt-water encroachment in Gulf
Coast aquifers:  a summary report;  Geological Survey of Alabama, Division
of Water Resources, 84 pp.

Walters, K.L. and G.E. Kimmel, 1968.  Ground-water occurrence and
stratigraphy of unconsolidated deposits, central Pierce county,  Washington;
U.S. Geological Survey and Washington Department of Water  Resources, Water
Supply Bulletin 22, 428 pp.

Warner, D.L. and J.H. Lehr, 1981.  Subsurface wastewater injection; Premier
Press, Berkeley, California, 344 pp.

Warnken, D., 1984.  Abandoned wells in man-made reservoirs;  Proceedings of
the First National Conference on Abandoned Wells:  Problems and  Solutions,
Environmental and Ground Water Institute, National Water Well Association
and United States Environmental Protection Agency, pp.  118-124.

Weast, R.C., editor, 1983.   CRC handbook of chemistry and  physics;  CRC
Press, Inc., 2303 pp.

Weber, J.B., 1972.  Interaction of organic pesticides with particulate
matter in aquatic and soil systems; Advances in Chemistry Series, no. Ill,
American Chemical Society;  pp. 55-120.

Weber, J.B. and S.B. Weed,  1974.  Effects of soil on the biological
activity of pesticides; Journal Series of the North Carolina State
University Agricultural Experiment Station, Paper no. 4087,  pp.  223-256.

Weeks, J.B. and E.D. Gutentag, 1981.  Bedrock geology,  altitude  of base and
1980 saturated thickness of the High Plains aquifer in parts of  Colorado,
Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas and  Wyoming;
U.S. Geological Survey, Hydrologic Investigations Atlas 648.

Wehtje, G., L.N. Mielke, J.R.C. Leavitt and J.S. Schepers, 1984.  Leaching
of atrazine in the root zone of an alluvial soil in Nebraska; Technical
report, Journal of Environmental Quality, vol. 13, no.  4,  pp. 507-513.

Weldon, R.A., 1979.  Biodisposal farming of refinery oily wastes; reprinted
from American Petroleum Institute Oil Spill Conference Proceedings, March
19-22, 1979.

Welling, Robert, John Troiano, Richard Maykoski and George Loughner, 1986.
Effects of agronomic and geologic factors on pesticides movement in soil;
comparison of two ground water basins in California; Proceedings of the
Agricultural Impacts on Ground Water - A Conference, National Water Well
Association, pp. 666-685.

Wengel, R.W. and G.F. Griffin, 1979.  Potential ground water pollution from
sewage sludge applications on agricultural land; Office of Water Research
and Technology, NTIS PB80-102957, 17 pp.
                                    330-

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Wetherold, R.G., D.D. Rosebrook and E.W. Cunningham, 1981.  Assessment of
hydrocarbon emissions from land treatment of oily sludges; Proceedings of
the Seventh Annual Research Symposium, Land Disposal: Hazardous Waste,
U.S. EPA-600/9-81-002b, pp. 213-223.

Whitehead, R.L., 1984.  Geohydrologic framework of the Snake river plain,
Idaho and eastern Oregon; U.S. Geological Survey, Open-file report 84-051
(atlas).

Whiteside, R.F. and S.F. Raef, 1986.  Mechanical integrity of Class I
injection wells; Proceedings of the International Symposium on Subsurface
Injection of Liquid Wastes, National Water Well Association, pp. 57-76.

Whittle, G.P., T.A. Carlton and H.R. Henry, 1984.  Permeability changes in
clay liners of hazardous waste storage pits; Seventh Annual Madison
Conference on Municipal and Industrial Wastes, Madison, Wisconsin, pp.
364-372.

Williams, J.S., 1984.  Road salt - silent threat to ground water; Maine
Environmental News, vol. 11, no. 3, pp. 4-5.

Williams, J.S., 1986.  Prioritization of ground water contamination
problems at sand-salt storage sites in Maine; Proceedings of the Third
Annual Eastern Regional Ground Water Conference, National Water Well
Association, pp. 630-637 and Proceedings of the Eastern Regional Ground
Water Conference, National Water Well Association, pp. 208-233.

Williams, J.S., A.L. TtIman and C.W. Fontaine, 1984.  Geophysical
techniques in contamination site investigations:  Usefulness and problems;

Williams, R.E., 1975.  Waste production and disposal in mining, milling,
and metallurgical industries; Miller Freeman Publications, Inc. 489 pp.

Williams, R.E. and J.L. Osiensky, 1983.  Hydrogeologic analysis of uranium
mill tailings sites; Oak Ridge National Laboratory, Union Carbide, Nuclear
Division, Contract no. 7949, Oak Ridge, Tennessee, pp. 2-1 to 2-21.

Wilmoth, B.M., 1972.  Salty ground water and meteoric flushing of
contaminated aquifers in West Virginia; Ground Water, vol. 10, no. 1, pp.
99-106.

Wilson, Barbara H. and John F. Reese, 1985.  Biotransformation of gasoline
hydrocarbons in methanogenic aquifer material; Proceedings of the Petroleum
Hydrocarbons and Organic Chemicals in Ground Water - Prevention, Detection
and Restoration, National Water Well Association, pp. 128-139.

Wilson, J.L., R.L. Lenton and J. Porras, editors, 1976.  Groundwater
pollution:  technology, economics and management; Department of Civil
Engineering, Massachusetts Institute of Technology, Report no. TR 208, pp.
17-21.
                                    331

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Wilson, John L. and Stephen H.  Conrad,  1984.   Is  Physical  displacement  of
residual hydrocarbons a realistic possibility in  aquifer restoration;
Proceedings of the Petroleum Hydrocarbons and Organic Chemicals  in
GroundWater - Prevention, Detection and Restoration,  National Water Well
Association, pp. 274-298.

Wilson, L.G., C.P. Gerba, M.W.  Bolton and J.B. Rose,  1984.  Subsurface
transport of urban run off pollutants;  Proceedings of the  Second
International Conference on Ground Water Quality  Research, Oklahoma State
University, pp. 158-160.

Wilson, William E. , 1982.  Estimated effects  of projected  ground-water
withdrawals on movement of saltwater front in the Floridan Aquifer,
1976-2000, west^central Florida,; U.S. Geological  Survey, Water Supply Paper
2189, 24 pp.

Wirries, Dana L. and Archie J.  McDonnell, 1983. Drainage quality at deep
coal mine sites; Water Resources Bulletin, vol. 19, no.  2, pp. 235-240.

Wood, Warren W. and Randy L. Bassett, 1975.  Water quality changes related
to the development of anaerobic conditions during artificial recharge;
Water Resources Research, vol.  11, no.  4, pp. 553-558.

Woodruff, K.D., R.R. Jordan, N. Spoljaric and I.E. Pickett, 1972.  Geology
and ground water, University of Delaware, Newark, Delaware; Delaware
Geological Survey, Report of investigations no. 18, 40 pps

Woodruff, Kenneth D. and Allan M. Thompson, 1972.  Geology of the Newark
area, Delaware; Delaware Geological Survey, Geologic  Map series no. 3.

Woodruff, Kenneth D. and Allan M. Thompson, 1975.  Geology of the
Wilmington area, Delaware; Delaware Geological Survey, Geologic Map series
no. 4.

Woodruff, Kenneth D., 1981.  Geohydrology of the Wilmington area, Delaware;
Delaware  Geological Survey, Hydrologic Map series no. 3,  sheet 1 - basic-
geology.

Wuellner, W.W., D.A. Wierman and H.A. Koch, 1985.  Effect  of landfill
leachate  on the permeability of clay soils; Eighth Annual  Madison Waste
Conference on Municipal  and Industrial Wastes, Madison, Wisconsin, pp.
287-302.

Yaniga,  Paul M. and David J. Demko,  1983.  Hydrocarbon contamination of
carbonate aquifers; assessment and abatement; Proceedings  of the Third
National  Symposium on Aquifer Restoration and Ground-Water Monitoring,
National  Water Well Association, pp. 60-65.
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Yaniga, Paul M. 1984.  Hydrocarbon retrieval and apparent hydrocarbon
thickness:  Interrelationships to recharging/di scharging aquifer
conditions; Proceedings of the Petroleum Hydrocarbons and Organic Chemicals
in Ground Water - Prevention, Detection and Restoration, National Water
Well Association, pp. 299-329.

Yaniga, Paul M. and James Mulry, 1984.   Accelerated aquifer restoration:
In-situ applied techniques for enhanced free product recovery/absorbed
hydrocarbon reduction via bioreclamation;  Proceedings of the Petroleum
Hydrocarbons and Organic Chemicals in Ground Water - Prevention, Detection
and Restoration, National Water Well Association, pp. 421-440.

Yaniga, Paul M., Charlton Matson and David J. Demko, 1985.   Restoration of
water quality in a multiaquifer system via in-situ biodegradation of  the
organic contaminants; Proceedings of the Fifth National Symposium and
Exposition on Aquifer Restoration and Ground Water Monitoring,  National
Water Well Association, pp. 510-526.

Young, H.W. and R.F. Norvitch, 1984.  Ground-water level trends in Idaho,
1971-82; U.S. Geological Survey, Water-Resources Investigations Report
83-4245, 28 pp.

Young, J.A., L.L. Cadwell, H.D. Freeman and K.A. Hawley, 1986.   Long-term
surveillance and monitoring of decommissioned uranium processing sites and
tailings piles; Division of Radiation Programs and Earth Sciences,
NUREG/CR-4504, Office of Nuclear Regulatory Research, 33 pp.

Young, Wen S. , 1986.  Vapor diffusions  in  soil;  Proceedings of  the
Conference on Southwestern Ground Water Issues,  National Water  Well
Association, pp.  426-439.

Zulauf, A.S. , 1979.   Soil survey of Pierce county area,  Washington;  Soil
Conservation Service, U.S. Department of Agriculture, 131 pp.,  55 plates.
                                   333

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                                   APPENDIX A

        PROCESSES AND PROPERTIES AFFECTING CONTAMINANT FATE AND TRANSPORT
     Most potential ground-water contaminants are released at or slightly above
the water table as a result of various industrial, agricultural and other human
activities.   The attenuation of contaminants as they travel through the
unsaturated  zone and ground-water system is affected by a variety of naturally
occurring physical processes and chemical reactions that often cause the
contaminant  to change its physical state or chemical form.  This change may
result in removal of the contaminant from the ground-water system.  The extent
of these reactions is dependent on hydrogeochemical conditions present in the
ground water such as pH, redox-potential and solid surface area.  However, the
chemical processes within dynamic ground-water systems are complex, and are
highly dependent on site-specific aquifer and soil characteristics as well as
the effects  of individual contaminants in the system (Cherry et al., 1984).
Therefore, although the importance of these chemical reactions in attenuation
of contaminants is widely recognized, prediction of the amount of attenuation
of a contaminant in any environment is still very difficult.

     Attenuation includes those mechanisms that lessen the severity or amounts
of contaminants.  The components wh. ch affect attenuation are the physical and
chemical processes and properties including density, solubility, sorption,
biodegradation, oxidation-reduction, dilution, hydrolysis, dispersion,
viscosity, mechanical filtration, ion exchange, volatilization and buffering or
neutralization.  The degree of attenuation that occurs is dependent on:  1) the
time that the contaminant is in contact with the material through which it
passes, 2) tne grain size, and physical and chemical characteristics of the
material through which it passes, and 3) the distance which the contaminant has
traveled.  For most materials, the longer the time, the greater the surface
area and the greater the distance of travel, the greater the degree of
attenuation.  Movement of ground water is slower in rocks with high surface
areas, such as found in a fine-grained porous medium, than in rocks where water
movement is primarily through fault and fracture channels or solution openings.
Additionally, flow velocity decreases with lower gradients and increasing
depth; subsequently ground water is in prolonged contact with rock materials
(Matthess and Harvey, 1982).

     Another factor affecting attenuation includes surface area in the aquifer
media.  The greater the surface area of the material through which the
contaminant passes, the greater the potential for sorption of the contaminant.
Likewise, the greater the reactivity of the material through which the
contaminant passes, the greater the potential for attenuation.
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     The many physical processes and chemical reactions present in a
ground-water system may work individually or in combination to provide varying
degrees of attenuation depending on the hydrogeochemical conditions and the
particular contaminant.  The following discussion addresses each physical and
chemical process and describes the respective impact on contaminants.

DENSITY

     The density of any substance is defined as mass per unit volume.  The
movement of a contaminant in an aquifer is directly affected by the density of
the fluid with respect to the density of the ground water.  Low density
contaminants float on top of the water table; high density contaminants sink to
the bottom of the aquifer.

     Once a contaminant has entered an aquifer, it will be transported as a
function of density in the direction of ground-water flow.  Under the ideal
condition of a homogeneous aquifer media, the contaminant will begin to
disperse forming an elliptical plume (Pye et al., 1983; Todd, 1980).  Movement
and dispersion of the plume is affected by the density of the contaminant, the
character of the geologic formation through which the contaminant passes and
the reactive nature of the contaminant.  In a uniform geologic formation, the
more dense the contaminant, the greater will be the downward migration of that
contaminant and the slower the contaminant will travel in relation to the
velocity of ground-water flow.

SOLUBILITY

     As a contaminant is introduced into an aquifer, the contaminant is
generally partially dissolved in water, forming either miscible or immiscible
solutions.  A potential contaminant may also remain insoluble, depending on the
chemical characteristics of the contaminant.  The solubility of a substance is
defined as the mass of a substance that will dissolve in a unit volume of
solute under specified chemical conditions (Freeze and Cherry, 1979).  The
solubility of a constituent in water is dependent on variations in temperature,
pressure, pH, redox potential (Eh) and the relative concentrations of other
substances in solution.  The interactions of these chemical parameters make it
difficult to predict the solubilities of many substances in ground water (Davis
and DeWiest* 1966; Snoeyink and Jenkins, 1980).

     Substances are dissolved in water, or become soluble, because the water
molecule exhibits a charge which attracts other molecules in solution.  When.
the attractive forces that hold a substance together are less than or equal to
the attractive force of the water molecule, the substance will dissolve.
Conversely, those substances that are held together by attractive forces
stronger than the attraction of the water molecule do not dissolve to any
appreciable degree in water, thus forming immiscible liquids or solids.  A good
example is oil and water; the two substances do not mix because the oil is only
slightly soluble in water.  Substances that have been dissolved may be
reprecipitated as a consequence of equilibria shifts and deposited in the void
spaces of the aquifer.  In addition, immiscible fluids may be transformed
through similar changes in solubility.
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     The chemical reaction which transforms a dissolved substance to  a  solid
form is precipitation.   The precipitation of a dissolved substance may  be
initiated by changes in pressure,  temperature, pH,  concentration, or
oxidation-reduction.  In addition,  the introduction of  another  substance that
changes the equilibrium concentrations in the solution, or which reacts
chemically with the dissolved substance may cause precipitation.   The resultant
solid is deposited in the void spaces of the aquifer,  thereby reducing  the
space available for transport of the ground water.

     Several types of contaminants  can be effectively  removed from the  ground
water through precipitation.  Calcium salt solutions have been  shown  to
effectively precipitate free fluorides (Tolman, et  al., 1978).   Alkalis and/or
sulfides may precipitate heavy metals.  Stover and  Kincannon (1983) have
conducted successful experiments with regulated pH  conditions,  demonstrating
the precipitation of metals using lime.  Since oxidation-reduction reactions
may change the chemical state of a  substance by rendering it insoluble, this
reaction has proven effective in changing dissolved chromium to a less  soluble
state thereby removing it from the  ground water (Tolman et al., 1978; Fuller
and Artiola, 1978).  The FMC Corporation (1983) has conducted extensive studies
using hydrogen peroxide to oxidize  various sulfide  compounds and initiate
precipitation.  Vapors escaping from a contaminated site may cause heavy metals
to be transported and re-deposited.  Each of these  chemical reactions provides
a method of changing the solubility of a substance, thereby removing  the
contaminant from the ground water and precipitating it  in the void spaces of
the aquifer.  Even though the contaminant has changed  form, the precipitate may
be re-dissolved and the process repeated.  When a precipitate re-dissolves, the
contaminant may not be in its original form and may form a different  solute
which may or may not be harmless.

SORPTION

     Sorption is a combination of two processes, adsorption and absorption.
Adsorption occurs when molecules or ions are attached  to the surface  of charged
particles by weak Van der Waals or  covalent bonds.   Adsorption  differs  from
absorption in that the latter involves penetration by  the absorbed substance
(Keenan and Wood, 1971; Matthess and Harvey, 1982).  Sorption occurs  on all
surfaces where bonding conditions are present.  Sorption increases with
increasing surface area, which is usually a function of decreasing grain  size.
Colloidal particles range in diameter size from 10~3 to 10~6 mm.  These
particles tend to have a large charge relative to their surface area  (Freeze
and Cherry, 1979).  Porous geologic materials that are composed of an
appreciable amount of collodial-sized particles exhibit a higher capability to
sorb constituents onto the particle surfaces.

     The subsurface materials that exhibit sorptive properties  include  clay
minerals, hydrous iron, manganese,  aluminum oxides, organic substances
(particularly humus), glauconites and the rock-forming minerals mica, feldspar,
aluminous augite and hornblende (Matthess and Harvey,  1982; Freeze and  Cherry,
1979; Davis and DeWiest, 1966).  These minerals are commonly present  in
colloidal form and contain especially large surface areas available for
sorption.
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     The surface charge on a mineral in the saturated or unsaturated zone
creates an attractive force.  This charge may be due to 1) imperfections or
substitutions in the crystal lattice of the particle or 2) chemical reactions
at the surface of the particle involving weak hydrogen bonding, due to the
presence of water.  The pH of the water and the crystal structure of the
mineral have a direct affect on the charge of the particle surface; waters with
a high pH and highly crystalline materials typically produce net negative
charges on the particle surface thus favoring the sorption of positive
constituents or cations (Matthess and Harvey, 1982).  There is a direct
relationship between the quantity of a substance sorbed on a particle surface
and the quantity of the substance suspended in solution.  In general, an
increase in the concentration of the substance in solution will increase the
quantity sorbed.

     The presence of organic matter in porous materials appears to be an
important factor in the sorption of non-ionic organic substances.  Those
organic substances that are nonpolar (not attracted to water) and relatively
insoluble are frequently absorbed by soils and sediments containing clays and
organic carbon.  The sorption of nonpolar aromatic and chlorinated hydrocarbons
has been shown to increase with decreasing particle size and subsequently
increasing organic carbon content (Karickhoff et al., 1979).  Sorption of polar
organics primarily occurs through weak hydrogen bonds to mineral particles
(Cherry et al., 1984; Brown et al., 1983).  Studies by Haque et al. (1974) and
Griffen et al. (1978) indicate that sorption of PCBs was enhanced in materials
with greater surface area and higher organic content.  The sorptive
capabilities of clays and soils appear promising for attenuation of some
contaminants, however further experimentation is necessary due to the
complexity of chemical reactions that occur in the sorption process.

ION EXCHANGE

     The process of ion exchange is similar to sorption, however, stronger
ionic bonding occurs on the particle surfaces.  Ion-exchange processes are
virtually limited to colloidal size particles because these particles have
large electrical charges with respect to their surface areas.  Colloidal
particles range in diameter size from 10~3 to 10~6 mm.

     Ion exchange occurs when there is a surface charge imbalance.  These
surface charges are a result of 1) imperfections or ionic substitutions within
the crystal or particle, or 2) chemical dissociation reactions at the particle
surface.  Upon exposure to water the charged molecules attract hydroxyl groups
(OH-) to the surface.  When these hydroxyl groups break down, the resulting
charge imbalance attracts oppositely charged particles (Freeze and Cherry,
1979).  Ionic substitutions within particle surfaces also cause a charge
imbalance that attracts oppositely charged ions.  These ions comprise an
adsorbed layer that is interchangeable; thus the process is reversible.  An
example of ionic substitutions occurs within silicate minerals.  Aluminum ions
tend to substitute for the silica ions, forming an unbalanced charge on the
mineral surface.  The nature of the surface charge that develops is dependent
on pH; positively charged surfaces develop at low pH and a negatively charged
                                       337

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surface prevails with a high pH.  Clay minerals are the primary geologic
materials of colloidal size that exhibit surface charges as a result of ionic
substitutions.  Organic materials such as humus and plant roots in soils and
recent sediments also exhibit high ion-exchange capacities (Davis and DeWeist,
1966; Matthess and Harvey, 1982).

     The most common ion exchange involves the transfer of cations on charged
surfaces.  Cation exchange capacity is the capability of a charged surface
layer to attract positive ions in the zone adjacent to that charged surface
(Freeze and Cherry, 1979).  The affinity for attraction of cations varies with
the valence, or charge, of the ion and the ionic size.  Other things being
equal, the affinity for ion exchange is greater when the ion has a higher
valence.  For ions of the same valence, the affinity for exchange increases
with atomic number and decreases with increasing hydrate radius (Matthess and
Harvey, 1982).

     Other colloidal particles that exhibit ion-exchange capacities include
hydrated oxides of iron and manganese.  Hydrated oxides of iron selectively
sorb zinc, copper, lead, mercury, chromium, molybdenum, tungsten and vanadium
through ion exchange.  Similarly, hydrated oxides of manganese will bond to
copper, nickel, cobalt, chromium, molybdenum, and tungsten (Matthess and
Harvey, 1982).  Clay minerals tend to preferentially bond zinc, copper, lead,
mercury and radioactive elements such as rubidium, cesium, and strontium.
Certain organic dyes are firmly bonded to clays by strong electrostatic bonds
(Matthess and Harvey, 1982).  For cationic organic substances, increasing
valence will tend to increase the capacity for bonding to els ^surfaces, and
vice versa for anionic organic constituents (Brown et al., lb»63).

     Ion exchange can provide a means for attenuation of heavy metals and
certain organic substances if the bonding is sufficiently strong to prevent
reversal of the chemical reaction and release of - the contaminant back into the
ground-water system.

OXIDATION-REDUCTION

     Oxidation and reduction (redox) are geochemically important processes
because together with pH, they control the solubility, and thus the presence of
many substances in water.  These reactions involve the transfer of electrons
between dissolved, gaseous and solid substances in the water.  As a result of
this electron transfer, there is a change in the oxidation state of the
substance.  A redox reaction consists of two parts or half reactions.  In the
oxidation reaction, the substance loses, or donates electrons; in the reduction
reaction, the substance accepts, or gains electrons.  Oxidation and reduction
reactions are always coupled; no free electrons can exist in solution and
electrons must be conserved (Snoeyink and Jenkins, 1980).

     Deposits above the water table contain voids which are usually filled with
atmospheric gases containing oxygen.  Percolating water carries dissolved
atmospheric oxygen to the water table where the processes of diffusion and
dispersion can carry it to deeper water levels (Matthess and Harvey, 1982).
The presence or absence of dissolved oxygen in the ground water is one factor
                                       338

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which controls whether oxidizing or reducing conditions will predominate.
Oxidation may be initiated in ground water by the presence or introduction of
an oxidizing agent, such as potassium permanganate, or a change in valence
state of ions such as Fe+3 and Mn+3.  In general, oxidation processes are
increased in warm climates, and are more complete in humid and humid/arid
climates than in arid climates.

     Microorganisms are responsible for a large proportion of redox reactions
which occur in ground water.  The principal microorganisms involved in redox
processes are bacteria which contain enzymes.  Bacteria and their enzymes
utilize redox processes to provide energy for cell synthesis-and maintenance
(Freeze and Cherry, 1979).  Bacteria that require oxygen are known as aerobic
bacteria, while anaerobic bacteria cannot tolerate dissolved oxygen in the
water.

     In many contaminated ground-water systems, dispersion exerts a strong
influence on the redox state of the ground water.  Dispersion causes a
continuous mixing of waters that are different in chemical composition and
redox potential.  The mixing of these waters by dispersion affect the redox and
pH conditions and may instigate other chemical reactions within the system.

     The use of oxidation-reduction reactions for the attenuation of
contaminants has proven effective for both inorganic and organic substances.
The introduction of oxidizing agents into ground water is the most important
mechanism of oxidation after microorganisms.  Detoxification through oxidation
of cyanides (Farb, 1978) and organic cyanides (Harsh, 1975) has been
accomplished through the application of sodium hypochloride in conjunction with
pH adjustments to produce substances that are insoluble.  Dohnalek and
Fitzpatrick (1983) documented removal of hydrogen sulfide from ground water in
laboratory studies using oxidants.  The FMC Corporation (1983) has conducted
extensive experimentation using hydrogen peroxide to oxidize various sulfides
and organic sulfides thereby rendering them insoluble.  Certain organic
compounds such as phenols, aldehydes, hydroquinine, as well as chlorine
compounds and cyanides can also be oxidized by hydrogen peroxide (FMC, 1983).
Matthess (1981) achieved treatment of arsenic-contaminated ground water by
accelerating the natural precipitation process through the injection of the
oxidant potassium permanganate.  The soluble arsenic compounds were oxidized to
the less soluble arsenate state and precipitated as iron and manganese
arsenates and hydroxides, thus removing the arsenic from the ground water and
eliminating the contamination problem.  Injection of oxygenated water into an
aquifer has also been shown to improve water quality by stimulating iron and
manganese bacteria. The bacteria then provided the adsorption-oxidation
mechanism that precipitated the iron and manganese hydroxides (Rott et al.,
1981).  Other chemicals susceptible to oxidation include phenols, aromatic
amines and dienes (Cherry et al., 1984).  The application of a strong reducing
agent has also proven effective in changing the oxidation state of chromium
causing the formation of an insoluble chromium product.
                                      339

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      The mechanisms  of  oxidation  and  reduction  provide  a means  for  reducing  the
 solubility and  causing  subsequent  precipitation through several  reactions.
 Those most effective  reactions  for reducing  solubility  include  a change  in
 oxidation state, the  formation  of  new compounds, and the enhancement of
 naturally occurring  bacterial processes.

 BIODEGRADATION

      Biodegradation  results from  the  enzyme-catalyzed transformation of  organic
 compounds by microbes,  principally bacteria, fungi, actinomycetes,  algae and
 yeasts.  Biological  treatment can  eliminate  hazardous organic wastes by
 transforming them into  innocuous  forms, degrading them  by mineralization to
 carbon dioxide  and water, or by anaerobically decomposing them  to carbon
 dioxide and methane  (Kobayashi and Rittmann, 1982).  Bacteria and other
 microbes require nutrients to produce the necessary enzymes that use or  attack
 the organic compounds.  Most microbes require oxygen, water and  nutrients such
 as carbon, nitrogen,  phosphorus and trace metals.  Aerobic bacteria require the
 presence of free oxygen; anaerobic bacteria  require the absence  of  dissolved
 oxygen.  The metabolic  processes of both types  of bacteria are energy efficient
 and tend to enhance certain critical  reactions.  Reactions such  as  reductive
 dehalogenation, nitroreduction and  reduction of sulfoxides are catalyzed by
 anaerobic bacteria (Kobayashi and  Rittman, 1982).

      Biodegradation of  a broad range  of organic compounds particularly those
 that  are man-made, have been demonstrated in laboratory studies.  It is
 difficult to predict  the exact transformations  that may occur in the subsurface
 due to the complexity of chemical  reactions  present in  natural systems of mixed
 microbes and organic  compounds (Cherry et al.,  1984; Kobsyashi and  Rittmann,
 1982).  Biodegradation  is dependent on interactions in  a natural environment
 such as redox potential, dissolved oxygen, pH,  temperature, presence of  other
 compounds, salinity,  other competing  organisms, and the concentrations of
 compounds and organisms.  Organic  compounds need to be  fairly soluble in water
 in order to be utilized by microbes.  Biodegradation can be limited if there
 are antagonistic interactions between two types of microbes, such as bacteria
 and fungi (Kobayashi  and Rittmann,  1982).  In addition, very low compound
 concentrations in a substrate may  pose problems; certain organisms require
 minimal threshold values for survival and/or production of necessary enzymes.

     Certain man-made organic compounds are  refractory or resistant to
 biodegradation.  This resistance is generally due to the presence of chemical
 substituents such as nitrogroups,  chlorines and amines, that are attached to
 the parent compound.   Generally, larger molecules are less degradable than
 smaller ones (Kobayashi and Rittmann, 1982).  Other important refractory
 compounds are halogenated organics which are very resistant to biodegradation
 (Brown et al., 1983).  These halogenated organics include pesticides,
 plasticizers, solvents and trihalomethanes.   Chlorinated compounds such as DDT
 and other pesticides have been the most frequently studied compounds.  The
 first step in degradation of halogenated organics involves dehalogenation by
 several biological mechanisms.  Anaerobic reductive dehalogenation  is an
 important mechanism in degradation of pesticides and certain halogenated
aliphatic compounds.
                                     340

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     Kobayashi and Rittmann (1982) and Tabak et al. (1980), indicate that most
man-made organic compounds will undergo biodegradation to some extent.
Actinomycetes and fungi are known to attack a wide variety of complex organic
compounds.  These microbes can grow under low nutrient conditions, wide
temperature ranges and wide pH ranges.  Actinomycetes break compounds down into
groups that can be utilized by other organisms.  Certain types of fungi are
able to degrade complex hydrocarbons including the degradation of DDT.  Fungi
are believed to be capable of degrading PCB's more efficiently than bacteria
(Gibson, 1978).  Fungal metabolism is generally incomplete and requires other
microbes for complete degradation.  Bacteria have been found to degrade a wide
variety of compounds under aerobic conditions.  Bacteria are the major agents
in the degradation of hydrocarbons and heterocyclic compounds (Kobayashi and
Rittmann, 1982; Jhaveri and Mazzacca, 1983; Weldon, 1979; Tabak et al., 1980;
Liu et al., 1981; Glaus and Walker, 1964; Cherry et al., 1984).

     Anaerobic bacteria degrade organic compounds to carbon dioxide and methane
under oxygen-deficient conditions.  Although little is known about these
bacteria, four groups that utilize each of the metabolic products are
responsible for degradation of the other groups.  These bacteria are capable of
dehalogenation, nitrosamine degradation, reduction of epoxide groups, reduction
of nitro groups and the breakdown of aromatic structures (Kobayashi and
Rittmann, 1982; Tabak et al., 1980).  In a study conducted by Ehrlich et al.
(1982) an aquifer contaminated by phenols and polynuclear aromatic hydrocarbons
such as naphthelene showed significant reductions in these contaminants within
1000 m of the contamination source. Contaminant attenuation has been attributed
to anaerobic degradation of the hydrocarbons by bacteria.  Laboratory studies
indicate that anaerobic bacteria are capable of degrading certain halogenated
1- and 2-carbon organic compounds such as trihalomethanes, chloroform and
trichlorethylene (Bouwer et al., 1981).

HYDROLYSIS

     The breakdown of substances by water and its ionic species H+ and OH~
is known as hydrolysis.  The breakdown of minerals by hydrolysis is an
important reaction that occurs in the ground water, causing relatively
insoluble minerals to form new minerals while releasing ions into solution.
The hydrolysis process is dependent on pH, a measure of the concentration of
H+ and OH~ ions in solution, in addition to the oxidation-reduction
potential (Matthess and. Harvey, 1982).  Hydrolysis is most effective at high
temperatures, low pH and low redox potential.  Hydrolysis is the basic reaction
in the weathering processes which acts upon rocks and aids in the production of
clays and soils.

     Hydrolysis of an organic compound involves the introduction of a hydroxyl
group (-OH) into the chemical structure, usually with the loss of a chemical
group (X).  The rate of hydrolysis of organic compounds is dependent on pH
conditions and the presence of metal ions.  A common hydrolysis reaction
involves the replacement of halogens (X) by a hydroxyl group (Cherry et al.,
1984).  The occurrence of hydrolysis may aid in contamination attenuation.
Certain organic compounds may be broken down by hydrolysis into simpler
                                     341

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compounds that may then be easily assimilated through other processes.  An
example would be the hydrolysis of esters into a simple  alcohol  and  acid  that
would comprise less harmful constituents in the ground water.

     Hydrolysis is an important process in the attenuation of  pesticides.   It
may be used to help predict the rate of decay of pesticides in the  soil (Cohen
et al., 1984; Cherry et al., 1984).  Hydrolysis of  atrazine and  other  pesticide
derivatives has been shown to operate faster when humic  material is  present.
Hydrolysis rates for breakdown of pesticides have been determined for  certain
organic groups (Cherry et al., 1984; Callahan et al., 1979; Cohen,  1984).

VOLATILIZATION

     Volatilization is defined as the loss of a compound to the  atmosphere.
This process provides an attenuation mechanism for  those compounds  that are
resistant to degradation and/or weakly absorbed, and to  those  that  exhibit  low
solubilities and high vapor pressures (Callahan et  al.,  1979;  Brown et al.,
1983).  Organic constituents with high vapor pressures are more  easily
volatilized from the soil.  Compounds that are not  soluble tend  to  be  available
for volatilization longer because they are not readily removed by water.
Persistent organic constituents that are not easily removed by other processes
may tend to volatize after a period of time.  Organic compounds  tend to
volatize more easily if they are less strongly sorbed by the soil.

     Factors that affect volatilization include vapor pressure,  water
solubility, soil moisture, adsorption, wind speed,  turbulence, temperature,
depth below land surface and time (Brown et al., 1983; Callahan  et al., 1979).
Studies indicate that the highest volatilization of organics occurs within
minutes of application and decreases substantially  within one hour (Wetherold
et al., 1981).

     Volatilization of organics is generally restricted  to the purgable or
volatile organic compounds.  These compounds include hydrocarbons,  compounds
with simple functional groups such as alcohols, halides, and sulfur-containing
compounds, and compounds containing unsaturated functional groups such as
aldehydes, ketones and esters.  Increasing air humidity, soil temperature and
soil moisture have been shown to increase volatilization rates (Wetherold et
al.,  1981).

BUFFERING AND NEUTRALIZATION

     Buffering and neutralization are chemical reactions which are similar.
Neutralization is achieved by balancing the pH or activity of the hydrogen ion
concentration so that a neutral solution is produced.  Buffering refers  to  the
ability of a substance to maintain a constant pH over a wide range of
concentrations.  The neutralization of an acid or base produces  water and
neutral salts.  Lime is effective  in neutralization of acidic wastes.
                                    342

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     Many biological processes rely on maintaining neutral pH levels to enhance
biodegradation of organic constituents (Brown et al., 1983).  Neutral pH levels
are maintained in soils by their natural buffering capacity.  Aluminum ions in
the surface of clay colloids maintain an equilibrium of hydroxide ions in the
soil solution.  The actual pH range of a soil may vary according to the
predominant clay constituent present (Brown et al., 1983).  Neutralization of
contaminants through pH adjustment is generally achieved by the addition of an
acid or base, precipitation and oxidation reduction.

     A buffer solution is comprised of a weak acid or base plus a salt of that
acid or base.  A solution of this type will maintain a relatively constant pH
even though a strong acid or base is added.  A common example of this is the
acetic acid-sodium acetate solution which will maintain a relatively constant
pH when HC1 is added, due to the H+ ions from the HC1 combining with the
acetate ions, as follows:

                        +
    Na2C.jH20   	^   Na +

         HC1   	.     Cl~+

Therefore, no change occurs in the hydrogen ion concentration.

     Carbonate systems provide very effective buffering effects in natural
waters and waste waters (Snoeyink and Jenkins, 1980).  The system is
essentially based on a weak acid, carbonic, and sodium bicarbonate.  As a
consequence of the natural equilibria established between these parameters a
relatively constant, near neutral pH is maintained for most ground water,
making many important biological processes possible.

     The precipitation of chromium from water is directly controlled by
variable pH values by providing suitable electron donors to change the chromium
to a less soluble oxidation state (Tolman et al., 1978; Fuller and Artiola,
1978).  The use of variable pH levels enables the detoxification of cyanide
through oxidation and subsequent precipitation of insoluble cyanide compounds
(Farb, 1978).

DILUTION

     The dilution of ground-water contaminants occurs through the addition of
water by precipitation or other sources, introduced into the ground-water
system.  Dilution is an integral mechanism of dispersion occurring on a
microscopic and macroscopic scale (Todd, 1980).  These mixing mechanisms
produce longitudinal and transverse dispersion of the contaminant such that the
concentration decreases with the distance from the point of introduction.
According to Todd (1980), dilution may be the most important mechanism for
attenuation after the pollutant enters the ground-water system.
                                     343

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DISPERSION

     A porous medium is composed of particles of varying sizes, shapes and
orientations.  As water flows through a porous medium, the velocity varies
across pore space and around particles.  As a result, when a contaminant is
introduced into a ground-water system, it spreads, or disperses, so as to
gradually occupy an increasing volume of that flow system.  Thus dispersion
constitutes a non-steady, irreversible mixing process by which the contaminant
disperses within the surrounding ground water (Todd, 1980).

     Dispersion has two components, longitudinal and transverse.  Longitudinal
dispersion occurs in the direction of flow and is caused by differences in
macroscopic velocities as the water moves across pore spaces and around
particles winding a tortuous path through the media in the direction of flow.
Transverse dispersion occurs in two dimensions normal to ground-water flow and
results from repeated division and deflection of the water flow by the
particles (Todd, 1980; Bouwer, 1978).  Figure A-l illustrates transverse and
longitudinal dispersion in a saturated porous medium.

     Dispersion is a phenomenon that is caused by a combination of two
processes, molecular diffusion and mechanical dispersion that occurs with
laminar flow in a porous medium (Todd, 1980; Wilson et al., 1976).  The result
of these processes produces a contaminant plume with distinctly different
characteristics dependent on the way the contaminant is introduced into the
system.  Figure A-2(a) illustrates the configuration of a plume that forms from
the continuous input of a contaminant, whereas Figure A-2(b) represents input
of a contaminant in pulses.  The contaminant plume develops £a expanding
elliptical shape with declining concentration per unit mass of aquifer because
of the process of dispersion (Freeze and Cherry, 1979).

     The relative rates of dispersion and the subsequent configuration of the
contaminant plume are dependent on the homogeneity of the aquifer.  Most
laboratory testing of dispersion has been restricted to homogeneous, sandy
mediums.  Heterogeneous aquifer media present a complex dispersion pattern
related to the respective hydraulic conductivities of the individual
stratigraphic units.  High conductivity units dominate the flow of contaminants
in the ground-water system as well as provide zones of migration where
contaminants would move more quickly than through adjacent units of low
conductivity (Freeze and Cherry, 1979).  The predomination of heterogenous
geologic units that serve as aquifers has necessitated the quantification of
contaminant transport through mathematical models (Freeze and Cherry, 1979;
Bouwer, 1978; Roberts, 1981; Anderson, 1984).  These models have been extended
to include molecular diffusion, the adsorption of solutes by the media and the
decay  of radioactive materials.  The primary emphasis of these models is  to
provide an effective means of predicting the extent of contaminant dispersion,
contaminant  flow velocities, and concentrations at various points within  the
plume.  Most modeling efforts are  constrained by  the  lack of adequate control
data.
                                      344

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    A *-
                                                     Longitudinal dispersion occurs
                                                     when a contaminant enters at
                                                     A or B.

                                                     Longitudinal and transverse
                                                     dispersion occurs when a
                                                     contaminant enters at C.
Figure A-1. Schematic of pathlines showing longitudinal and transverse dispersion (Bouwer, 1978).
                                       345

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    Uniform flow
 Continuous
 point source
 of tracer
                                       (a)
    Uniform flow
                                        (b)
Figure A-2.  Plume configuration based on contaminant input (Freeze and Cherry, 1979).

                                       346

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VISCOSITY

     The viscosity of a fluid is the property of resistance to relative motion
and shear deformation during flow.  The more viscous the fluid, the greater the
shear stress, and thus, the resistance to flow.  Viscosity is affected by
temperature; the higher the temperature, the lower the viscosity, the easier it
will be for a fluid to move.through the pores in a media.  Viscosity of water
has a direct affect on hydraulic conductivity that can be quantified as an
inverse linear relationship (Bouwer, 1978).  Reducing the viscosity by half
will double the hydraulic conductivity.

     Thus, the viscosity of a contaminant will partially control the rate of
migration.  More viscous contaminants will not move as easily through porous
media.  Consideration of contaminant viscosity if it differs significantly from
water viscosity, in conjunction with other applicable chemical reactions, may
be necessary for prediction of contaminant migration.

MECHANICAL FILTRATION

     Mechanical filtration removes contaminants which are larger than the pore
spaces of the host medium.  This process is most effective in finer-grained
materials such as clay or soil, but can occur in coarse-grained media depending
on the particulate sizes being filtered.  The effects of mechanical filtration
increase with decreasing pore and/or channel size within the media.  Retention
of larger particles may effectively reduce the permeability of the media.
Chemical reactions such as precipitation may form larger, insoluble particles
that are retained by the media, thereby affecting porosity and permeability.
The effectiveness of mechanical filtration for removal of contaminants is tlus
dependent on grain size and sorting of the media, hydraulic conditions within
the media, and the particulate size of the contaminant being transported
through the medium.
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                                   REFERENCES

Anderson, M.P., 1984.  Movement of contaminants in groundwater:  groundwater
transport - advection and dispersion; Groundwater Contamination, National
Academy Press, pp. 37-45.

Bouwer, E.J., B.E. Rittmann and P.L. McCarty, 1981.  Anaerobic degradation of
halogenated 1- and 2-carbon organic compounds; Environmental Science &
Technology, vol. 15, no. 5, pp. 596-599.

Bouwer, Herman, 1978.  Groundwater hydrology; McGraw-Hill, 480 pp.

Brown, K.W., G.B. Evans, Jr. and B.D. Frentrop, editors, 1983.  Hazardous waste
land treatment; Butterworth Publishers, 692 pp.

Callahan, M., M. Slimak, N. Gabel, I. May, F. Fowler, R. Freed, P. Jennings, R.
Duffee, F. Whitmore, B. Maestri, W. Mabey, B. Holt and C. Gould, 1979.  Water
related fate of 129 priority pollutants, vol. 1 - introduction and technical
background, metals and inorganics, pesticides and PCBS; U.S. EPA-440/4-79-029a,
pp. 2-1 through 2-14.                                       ,  '

Cherry, J.A., R.W. Gillham and J.F. Barker, 1984.  Contaminants in ground
water:  chemical processes; ground water contamination, National Academy Press,
pp. 46-66.

Glaus, D. and N. Walker, 1964.  The decomposition of toluene by soil bacteria;
Journal General Microbiology, vol. 36, pp. 107-122.

Cohen, S.Z., S.M. Creeger, R.F. Carsel and C.G. Enfield, 1984.  Potential for
pesticide contamination of ground water resulting from agricultural uses;
American Chemical Society Symposium Series #259, Treatment Disposal of
Pesticide Wastes, Krueger and Seiber, editors, Washington, B.C., 27 pp.

Davis, S.N. and R.J. DeWiest, 1966, Hydrogeology; John Wiley & Sons, 463 pp.

Dohnalek, D.A. and J.A. Fitzpatrick, 1983.  The chemistry of reduced sulfur
species and their removal from ground water supplies; Journal of American Water
Works Association, vol. 75, no. 6., pp. 298-308.

Erlich, G.G., D.F. Goerlitz, E.M. Godsy and M.F. Hult, 1982.  Degradation of
phenolic contaminants in ground water by anaerobic bacteria:  St. Louis,
Minnesota; Ground Water, vol. 20, no. 6, pp. 703-710.
                                     348

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Farb, D., 1978.  Upgrading hazardous waste disposal sites:  remedial
approaches; U.S. EPA #SW-677, Cincinnati, Ohio, 40 pp.

FMC Corporation, 1983.  Industrial waste treatment with hydrogen peroxide;
Industrial Chemical Group, Philadelphia, Pennsylvania, 23 pp.

Freeze, R.A. and J.A. Cherry, 1979.  Groundwater; Prentice-Hall, 604 pp.

Fuller, W.H. and J. Artiola, 1978.  Use of limestone to limit contaminant
movement from landfills; Proceedings of the 4th Annual Research Symposium, Land
Disposal of Hazardous Wastes, U.S. EPA-600/9-78-016, pp. 282-298.

Gibson, D.T., 1978.  Microbial transformation of aromatic pollutants;
Transformations and biological effects, Proceedings of the Second International
Symposium on Aquatic Pollutants, Noordwijerhoust, Amsterdam, Netherlands,
Pergamon Press, 519 pp.

Griffen, R., R. Clark, M. Lee and E. Chian, 1978.  Disposal and removal of
polychlorinated biphenyls in soil; Proceedings of the Fourth Annual Research
Symposium, Land Disposal of Hazardous Wastes, U.S. EPA-600/9-78-016, pp.
169-181.

Haque, R., D.W. Schmedding and V.H. Freed, 1974.  Aqueous solubility,
adsorption and vapor behaviour of polychlorinated biphenyl Arochlor 1254;
Environmental Science & Technology vol. 8, pp. 139-142.

Harsh, K., 1975.  In situ neutralization of an acrylonitrile spill; Ohio
Environmental Protection Agency, Dayton, Ohio pp. 187-189.

Jhaveri, V. and A.J. Mazzaua, 1983.  Bio-reclamation of ground and groundwater
- case history; Proceedings of the National Conference on Management
of Uncontrolled Hazardous Waste Sites,  Washington, D.C., pp. 242-247.

Karickhoff, S.W., D.S. Brown and T.A. Scott, 1979.  Sorption of hydrophobic
pollutants on natural sediments; Water Research, vol. 13, no. 3, pp. 241-248.

Keenan, C.W. and J.H. Wood, 1971, General college chemistry; Harper & Row, 717
pp.

Kobayashi, H. and B.E. Rittmann, 1982.   Microbial removal of hazardous organic
compounds; Environmental Science & Technology, vol. 16, no. 3, pp. 170A-183A.

Liu, D., W. Strachan, K. Thomson and K. Kwasniewska, 1981.  Determination of
the biodegradability of organic compounds; Environmental Science & Technology,
vol. 15, no. 7, pp. 788-793.

Matthess, G., 1981.  In situ treatment of arsenic contaminated ground water;
The Science of the Total Environment, no. 21, pp. 99-104.

Matthess, G. and J.C. Harvey, 1982.  Properties of groundwater; John Wiley &
Sons, pp. 73-114.
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Pye, V.I., R. Patrick and J. Quarles, 1983.  Groundwater contamination in the
United States; University of Pennsylvania Press, 314 pp.

Rott, U. , 1981.  Protection and improvement of ground water quality by
oxidation processes in the aquifer; Quality of Ground Water, Proceedings of an
International Symposium, The Netherlands, Elsevier Scientific Publication
Company, pp. 1073-1076.

Roberts, P.U., 1981.  Nature of organic contaminants in ground water and
approaches to treatment; American Water Works Association Seminar Proceedings,
Organic Chemical Contaminants in Ground Water:  Transport and Removal, pp.
47-66.

Snoeyink, V.L. and D. Jenkins, 1980.  Water chemistry; John Wiley & Sons, 463
pp.

Stover, E.L. and D.F. Kineannon, 1983.  Contaminated ground water treatability
- a case study; Journal AWWA, vol. 75, no. 6, pp. 292-298.

Tabak, H.H., S.A. Quave, C.I. Mashni and E.F. Earth, 1980.  Biodegradability
studies with priority pollutant organic compounds; Staff Report, Wastewater
Research Division, U.S. EPA Research Center, Cincinnati, Ohio, 42 pp.

Todd, D.K., 1980.  Groundwater hydrology; John Wiley & Sons, pp. 316-352.

Tolman, A., A. Ballestero, W. Beck and G. Emrich, 1978.  Guidance manual for
minimizing pollution from waste disposal sites; U.S. EPA-600/2-78-142, pp.
328-331.

Weldon, R.A., 1979.  Biodisposal farming of refinery oily wastes; reprinted
from API Oil Spill Conference Proceedings, March 19-22, 1979.

Wetherold, R.G., D.D. Rosebrook and E.W. Cunningham, 1981.  Assessment of
hydrocarbon emissions from land treatment of oily sludges; Proceedings of the
Seventh Annual Research Symposium, Land Disposal:  Hazardous Waste, U.S.
EPA-600/9-81-002b, pp. 213-223.

Wilson, J.L., R.L. Lenton and J. Porras, editors, 1976.  Groundwater pollution:
technology, economics and management; Department of Civil Engineering,
Massachusetts Institute of Technology, Report no. TR 208, pp. 17-21.
                                      350

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                                   APPENDIX B

             CHARACTERISTICS OF SELECTED GROUND-WATER CONTAMINANTS
     Contaminants have been divided into inorganic compounds and organic
compounds.  For purposes of this discussion, inorganic compounds are  subdivided
into metals and nonmetals, while organic compounds are separated into groups
bearing similar molecular structures which influence those processes  affecting
the fate and transport of ground-water contaminants.

INORGANIC METALS

     The mobility and attenuation of metals in any hydrogeologic setting  is a
function of the hydrochemical ground-water environment.  Metals of primary
importance include cadmium, chromium, copper, lead, mercury, manganese, silver,
zinc and iron for which maximum Federal Drinking Water Standards have been
established.  With the exception of iron, metals typically occur naturally in
the environment in concentrations below 1 mg/1.  Concentrations are low due to
the processes of adsorption, hydrolysis, precipitation and oxidation-reduction.

     Metals tend to be hydrolized by water and exist as one or more ionic
species.  These metals combine readily with ligands to form ionic or  neutral
aqueous complexes.  These ligands may be inorganic ions such as

HCO ~  C03~2, S04~2, Cl~, F~, and N03~  (Freeze and Cherry et al., 1979).  Any

dissolved organic constituents that are present may also cause complexation or
chelation.  Increases in the concentrations of these anions increase  the
concentrations of the complexes that are formed.  The occurrence of a complexed
species is dependent on the pH and the equilibrium of a particular complex in
the aqueous solution.

     The oxidation-reduction potential of the ground water directly affects the
oxidation state of the metal and may also affect the nonmetallic anions with
which it forms complexes.  Changes in the oxidation state of a metal may
control the relative solubility or insolubility in water.  The mechanism  of
sorption of trace metals is dependent on redox potential and pH.

     Sorption of trace metals is an important process which may maintain  metal
concentrations far below that provided through solubility constraints.
Trace-metal sorption occurs due to the presence of colloidal size clay
                                      351

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particles, organic matter, and iron and manganese hydroxides.  In most
oxidizing environments, the iron and manganese oxides occur as surface coatings
on grains thereby increasing their ability to sorb trace metals (Freeze and
Cherry, 1979).  This is particularly effective for Co, Ni, Cd and Zn in soils
and freshwater sediments.

     The hydrochemical environment of a ground-water system exhibits many
effects on trace metals making the prediction of transport and migration
difficult and complex.  In general, the processes of sorption and precipitation
cause the trace metals to migrate very slowly with respect to ground-water flow
velocities.  Thus, the occurrence of generally localized contamination by trace
metals is common.

Cadmium (Cd)

     Cadmium-contaminated wastes are generated as byproducts of cadmium-nickel
battery production, pigments for plastics, enamels and paints, fumicides and in
electroplating and metal coatings.  The solubility and sorption of cadmium are
controlled by pH.  Under acidic or low pH conditions, cadmium solubility
increases while sorption by colloids decreases (Brown et al., 1983).
Precipitation of cadmium carbonates and cadmium phosphates may reduce cadmium
concentrations at low pH values.  Precipitation of cadmium sulfides occurs in
reducing environments.  The primary mechanism for cadmium attenuation is
through sorption to organic matter in soils as organic-metallic complexes.  The
contaminant level as established in the Federal Primary Drinking Water
Standards is 0.01 mg/1.

Chromium (Cr)

     Chromium is present in waste streams as a consequence of its use as a
corrosion inhibitor, production of refractory bricks to line metallurgical
furnaces, plating operations, topical antiseptics and astrigents, and the
tanning and dye industries (Brown et al., 1983).  The oxidation-state of the
chromium ion directly affects its toxicity; chromium is the most toxic and
mobile at an oxidation state of +6.  This is the most common form of chromium
in industrial wastes, thus making chromium a concern.  The soluble salts of
chromium such as sulfate and nitrate, are more toxic than the insoluble salts
of oxides and phosphates.  The solubility of chromium will vary at different pH
values in the presence of suitable electron donors, changing the oxidation
state from 4-6 to +3 (Tolman et al. , 1978; Fuller and Artiola, 1978).  The +3
chromium is less toxic and generally immobile in ground water because it will
readily precipitate with carbonates, hydroxides and sulfides to form insoluble
compounds.  The maximum contaminant level as established in the Federal Primary
Drinking Water Standards is 0.05 mg/1.

Copper (Cu)

     Industrial wastes from textile mills, cosmetics manufacturing and
hardboard production contain significant amounts of copper.  The sorption of
copper onto colloids is a function of pH; sorption increases at higher pH
values.  Organic matter present in soils forms very stable complexes with
                                     352

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copper (Brown et al., 1983).  These include complexation with carboxyl and
phenolic groups where sorption is high when iron and manganese oxide
concentrations are low.  Experiments indicate that copper is sorbed appreciably
by quartz and even more strongly by clays.  Copper is also beneficial because
low concentrations are necessary for the metabolic processes of decomposition
by bacteria.  The maximum contaminant level as established in the Federal
Secondary Drinking Water Standards is 1.0 mg/1.

Lead (Pb)

     Lead is found in wastes from the manufacture of lead-acid storage
batteries, gasoline additives, ammunition, pigments, paints, herbicides and
insecticides.  Lead may precipitate as sulfates, hydroxides and carbonates.
The presence of free lead ions depends on the stability of the lead complex at
varying pH values.  At high pH levels, lead is less soluble and preferentially
sorbed onto clay surfaces.  Under reduced conditions, lead becomes mobile and
may form insoluble complexes with organic compounds (Brown et al., 1983).  The
maximum contaminant level as established in the Federal Primary Drinking Water
Standards is 0.05 mg/1.

Mercury (Hg)

     Mercury is present in a wide variety of industrial wastes such as
electrical apparatus manufacturing, production of chlorine and caustic soda,
Pharmaceuticals, paints, plastics, paper products and mercury batteries.  Many
pesticides have metals as part of their composition.  Of these pesticides, over
40 percent use mercury as the major metal component (Brown et al., 1983).
Mercury in the +2 oxidation state is rapidly and strongly complexed by covalent
bonding to sulfur-containing organic compounds and inorganic soils.  Colloidal
particles of clay, iron and manganese oxides, fine sands and organic matter
readily absorb mercury.  Sorption by clay particles is most effective at high
pH values.  The solubility of various mercury ionic complexes can be affected
by changes in pH and/or oxidation-reduction.  Insoluble precipitates of
mercury, sulfates, hydroxides and nitrates form at high pH conditions.
Insoluble mercury sulfide occurs in reducing conditions, whereas, insoluble
mercury chlorides favor oxidizing conditions.

     Organic mercury compounds such as phenyl, alkyl and methoxyethyl mercury
used as fungicides may be degraded by certain bacteria.  However, other
bacterial forms tend to produce toxic mercury compounds with organic matter
(Brown et al., 1983).  The most toxic form of mercury occurs as methyl mercury
and poses a contamination problem for the aquatic food chain.  The maximum
contaminant level as established in the Federal Primary Drinking Water
Standards is 0.002 mg/1.

Manganese (Mn)

     The major source of manganese-contaminated waste waters are  from the iron
and steel industries and from the manufacture of paints, disinfectants and
fertilizers.  The manganese ion commonly occurs as Mn +2, which is soluble and
mobile, and Mn +4, which is insoluable and thus non-mobile.  Under reduced
                                      353

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conditions, Mn +2 is strongly sorbed to clay minerals and organic matter, but
becomes less soluble as pH increases.  Under oxidizing conditions several
stable manganese compounds will form (Brown et al., 1983).  Manganese is
considered a secondary constituent under Federal Drinking Water Standards;
maximum contaminant levels are set at 0.05 mg/1.

Silver (Ag)

     Silver is found in the waste streams of a variety of industrial processes
including photographic, mirror and electroplating manufacturing (Brown et al.,
1983).  Silver may be adsorbed on clay minerals, hydrous oxides of iron or
manganese and organic matter.  Precipitation with common inorganic anions such
as carbonate sulfates and chlorides or complexation with organic compounds can
reduce silver concentrations in ground water.  The solubility of silver is
largely controlled by the pH and redox conditions present in the ground water
system.  The maximum contaminant level as established in the Federal Primary
Drinking Water Standards is 0.05 mg/1.

Zinc (Zn)

     Industrial wastes containing zinc are a byproduct of brass and bronze
alloy production, galvanized metals for pipes, utensils, insecticides, glues,
rubber, inks and glass (Page, 1974).  Zinc can be attenuated through
precipitation, absorption and ionic substitution (Brown et al., 1983).  Zinc
may be ionically substituted for aluminum, iron or magnesium in many clay
minerals.  Zinc is primarily sorbed onto organic colloids whi<*k are very
soluble and mobile.  Zinc may be sorbed onto the particle surfaces of alloys
and is generally immobile.  The solubility of zinc precipitates is dependent on
the stability of the complex that forms under variable pH conditions.  The only
insoluble zinc precipitate is zinc sulfate.  All other precipitates of zinc are
soluble.  Zinc is rendered insoluble in soils and water with a pH greater than
6.5.  The maximum contaminant level as established in the Federal Secondary
Drinking Water Standards is 5.0 mg/1.

Iron (Fe)

     Iron, under oxidizing conditions in ground water, forms hydrous oxides
which provide a major attenuation mechanism  for the sorption of trace metals
such as cobalt, nickel, copper and zinc in soils and freshwater sediments.
When this oxide occurs as coatings on grains of a media, it can greatly
increase the sorptive capacity of that medium.  Iron compound stabilities are
dependent on pH and oxidation-reduction potential.  Iron in reduced form is
soluble and remains in solution.  However, either very small-scale variations
in the pH/Eh relationship or in bacterial activity can result in precipitation
of iron in the hydrous oxide form.  The maximum contaminant level as
established in the Federal Secondary Drinking Water Standards is 0.3 mg/1.
Unlike most other limits, the level for iron was not set because of associated
health risks, but rather for water quality problems associated with staining
and color.  Iron oxides precipitate and stain due to their relative
insolubility.
                                      354

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INORGANIC NONMETALS

     The chemical behavior of non-metallic substances in water has  a
significant effect on ground-water quality.   Most non-metals  tend to be  fairly
mobile in the ground-water system as ionic species.   The type and amount of
each species present is a function of temperature,  pressure,  pH, redox
potential, dissolved concentrations, reactivity and  microbial activity.

     The following discussion focuses on the major nonmetallic chemicals
occurring in ground water.  For each chemical,  information is presented  on the
source(s) of the chemical and its water chemistry characteristics.   These
nonmetallic chemicals can occur either naturally in  ground water or as a result
of human activities.

Nitrogen

     The most common inorganic contaminant is dissolved nitrogen in the  form  of
nitrate (N03~).  Dissolved nitrogen also occurs in the form of ammonium
(NH4+), ammonia (NH3~), nitrite (N02~), nitrogen (N2>, and nitrous
oxide (N20).  Common sources of nitrate in ground water are from the burial
of.nitrogen-rich wastes, application of fertilizers  and disposal of sewage.
When nitrogen-rich compounds are added to the environment, nitrogen is
converted to different forms.  The processes of nitrification [conversion or
(NH4+) to (N03~) by oxidation] and ammonification [conversion of organic N
to (NH^-)] generally occur above the water table where oxygen and organic
matter are abundant (Freeze and Cherry, 1979).

     Concentrations of (N03~) are not limited by solubility.   Thus, this
anionic form is very mobile and stable under oxidizing conditions.   (N03~) is
not easily retarded or transformed by chemical  processes.   The presence  of
reducing conditions may initiate denitrification, a  process where (N03~) is
converted to N2 or N20-  These resulting forms  are of less concern  from  a
ground-water pollution standpoint because they  pose  no health risk.  A maximum
contaminant level of 10 mg/1 as N or 45 mg/1 as (N03~) has been established
for nitrates because of health concerns in infants when this  level  is exceeded.

Phosphorous

     Phosphorous is not generally considered to be an intrinsically harmful
constituent in ground water in normal concentrations, but  its presence can
cause significant environmental problems by decreasing available oxygen  through
accelerated algae and aquatic vegetative growth.  The most common source of
phosphorous contamination is by agricultural activity, decomposition of  organic
wastes and septic tank effluent.  Dissolved phosphorous can occur in many forms
depending on the pH of the water.  Hydrolysis and mineralization can convert
insoluble forms of phosphates to the soluble phosphate ion for use  by plants
and organisms (Brown et al., 1983).  Degradation and mobilization of
phosphorous by microbes accounts for a portion  of its attenuation.   Under
certain conditions, phosphorous will precipitate as  iron-,-aluminum  or calcium
phosphate or be sorbed by iron and aluminum oxides and hydroxides.
                                    355

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jtoron

     Boron is released during the decomposition of organic materials.   Partial
sorption of boron may occur on iron and aluminum hydroxyl compounds  and clays.
The sorption of boron to these materials is pH dependent;  sorption will not
occur at high pH levels.  The amount of boron that will be sorbed  is dependent
on surface area and appears to be irreversible due to the formation  of  covalent
bonds.  No drinking water standards for human consumption of  boron have been
set.

Sulfur

     Sulfur is moderately abundant in the earth's soils and is an  important
plant nutrient.  Sulfur, in some form, is widespread in industrial waste from
processes such as kraft mills, sugar refining, petroleum refining, and  copper
and coal extraction (Brown et al., 1983).  Sulfur is commonly found  in  two
forms; as sulfate (804-2) in oxidizing conditions, and as sulfide  (HS~)
or (H2S) under reducing conditions.  Sulfides are toxic and produce  an  odor
in water.  The FMC Corporation (1983) has conducted extensive laboratory
testing using hydrogen peroxide to oxidize sulfides to sulfur and  water.
Hydrogen peroxide has been shown to be effective in neutralizing other  sulfur
compounds that are common industrial waste effluents.  These  include
polysulfides, sulfites, thiosulfates, polythionates, dithionites and
dithionates.  Sulfates are relatively mobile in the ground-water system as
anions.  Some clays have the capability to sorb sulfate onto  their particle
surfaces (Brown et al., 1983).  Sulfates also tend to form inorganic ligands
and complex with metal ions increasing their solubility.  A maximum  contaminant
level for sulfates is established in the Federal Secondary Drinking  Water
Standards at 250 mg/1.

Fluoride

     The mobility of fluoride depends on the types and quantities  of cations
present in the water that have formed salts with the fluoride ion.  Sodium
salts of fluoride (NaF) have high solubilities as opposed to  calcium salts
(Ca?2) which have low solubilities.  Fluoride may be a natural constituent of
ground water produced from the dissolution of fluoride-bearing rocks or from
industrial wastes such as the production of phosphatic fertilizers,  hydrogen
fluoride and fluorinated hydrocarbons (Brown et al., 1983).  Fluoride may also
tend to complex with metallic ions.  Soils with high cation exchange capacities
are capable of retaining fluoride.  The limit for concentration of fluoride  has
been established at 4.0 mg/1 in the Federal Primary Drinking  Water Standards
based on possible adverse health effects and at 2.0 mg/1 in Secondary Standards
for aesthetic purposes.

Chloride

     Chloride is very soluble and thus highly mobile in ground water.   Chloride
in ground water results from the dissolution of chloride-bearing rocks  such  as
halite, and is a common product or byproduct (e.g. chlorinated hydrocarbon
wastes) in most industrial wastes.  Common causes of chloride contamination


                                    356

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result from spillage or leakage of brines that are produced in oil and gas
drilling operations, and from the widespread use and application of highway
de-icing salts in many states.  Chlorides introduced at the surface are readily
transported into the ground water by recharge from precipitation.  Excessive
chloride concentrations in soils can also occur in areas of intensive
irrigation due to leaching in the root zone and high rates of
evapotranspiration.  The maximum contaminant level as established in the
Federal Secondary Drinking Water Standards is 250 mg/1.

Arsenic

     Arsenic is contained in wastes from the production of herbicides,
pesticides, pigments and wood preservatives (Freeze and Cherry, 1979; Brown et
al., 1983).  Arsenic in natural ground water occurs in four oxidation states
which exist as many different species under variable conditions.  In general,
most forms of arsenic tend to become soluble under oxidizing conditions.
Solubility is controlled by pH and redox potential.

     The movement of arsenic in the environment is affected by sorption to
soils and volatilization.  Sorption and/or precipitation by soil colloids is an
important attenuation mechanism.  These colloids include iron and aluminum
hydroxides or clays.  Sorption increases with increasing pH, clay and hydroxide
content.  Levels of arsenic as low as 10 mg/1 have been shown to be toxic
(Brown et al., 1983).  The maximum contaminant level as established in the
Federal Primary Drinking Water Standards is 0.05 mg/1.

Selenium

     Sources of selenium which can cause ground-water contamination include
glass, electronics, steel, rubber and photographic industries.  Selenium has
properties which are similar to sulfur.  Selenium has three oxidation states.
These typically form selenites and selanates of sodium and calcium, and soluble
selenium salts.  Selenium anions form selanates with mercury, copper and
cadmium which are very insoluble (Brown et al., 1983).  Selenium in ground
water is least soluble under acid conditions.  Mechanisms for selenium
attenuation include sorption onto hydrous iron oxides and precipitation to the
insoluble ferric oxide selenite.  The maximum contaminant level as established
in the Primary Federal Drinking Water Standard is 0.01 mg/1.

ORGANIC COMPOUNDS

     The contamination of ground-water resources by organic compounds has
resulted in the initiation of studies on their occurrence and behavior in the
ground-water system.  Many organic compounds of environmental concern are at
trace levels, parts per million, billion or trillion.  However, even these
minute levels may exhibit toxic effects on aquatic and mammalian life forms.
The United States Environmental Protection Agency (EPA) has developed a list of
what are considered to be the 129 priority pollutants and the relative
frequency of these materials in industrial waste waters (Keith and Telliard,
1979) (Table B-l).
                                     357

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TABLE B-1. EPA LIST OF 129 PRIORITY POLLUTANTS AND THE RELATIVE FREQUENCY OF
         THESE MATERIALS IN INDUSTRIAL WASTEWATERS (KEITH AND TELLIARD, 1979)
Percent Number of
of Industrial
samples3 categories'1
Percent Number of
of Industrial
samples3 categories'1
31 are purgeable organics
1 2
27
291
293
167
77
50
65
102
1 4
77
1 9
42
04
1 5
402
5
10
25
28
24
14
10
16
25
8
17
12
13
2
1
28
Acrolem
Acrylonitnle
Benzene
Toluene
Ethylbenzene
Carbon tetrachlonde
Chlorobenzene
1,2-Dichloroethane
1 , 1 , 1-Trichloroethane
1.1-Dichloroethane
1 , 1 -Dichloroethylene
1,1 2-Tnchloroethane
1 , 1,2,-Tetrachloroethane
Chloroethane
2-Ghloroethyl vinyl ether
Chloroform
21
1 0
342
1 9
01
1 9
43
68
03
25
102
105
02
77
01

5
5
25
6
1
12
17
11
4
15
19
21
2
18
2

1 ,2-Dichloropropane
1,3-Dichloropropane
Methylene chloride
Methyl chloride
Methyl bromide
Bromoform
Dichlorobromomethane
Trichlorofluoromethane
Dichlorodifluoromethane
Chlorodibromomethane
Tetrachloroethylene
Trichloroethylene
Vinyl chloride
1,2-trans-Dichloroethylene
bis(Chloromethyl) ether

46 are base/neutral extractable organic compounds

60

05
02
1 1
1 0
04
106
09
1 5
1 8
1 1
1 5
004
41 9
64
58
76
189

9

5
1
7
6
3
18
9
13
9
3
9
1
29
12
15
20
23
{1,2-Dichlorobenzene
1,3-Dichlorobenzene
1,4-Dichlorobenzene
Hexachloroethane
Hexachlorobutadiene
Hexachlorobenzene
1.2,4-Tnchlorobenzene
bis(2-Chloroethoxy) methane
Naphthalene
2-Chloronaphthalene
Isophorone
Nitrobenzene
2,4-Dmitrotoluene
2,6-Dmttrotoluene
4-Bromophenyl phenyl ether
bis(2-Ethylhexyl) phthalate
Di-n-octyl phthalate
Dimethyl phthalate
Diethyl phthalate
Di-n-butyl phthalate
57
72
5 1
78

106
23
16
1 8
32
08
02
06
01
0
02
1 1
08
01
1 2
11
12
9
14

16
6
6
6
8
4
4
7
2
0
4
4
7
1
5
Fluorene
Fluoranthene
Chrysene
Pyrene
i Phenanthrene
( Anthracene
Benzo(a)anthracene
Benzo(b)fluoranthene
Benzo(k)fluoranthene
Benzo(a)pyrene
lndeno(1,2,3-c,d)pyrene
Dibenzo(a.h)anthracene
Benzo(g,h,i)perylene
4-Chlorophenyl phenyl ether
3 3'-Dichlorobenzidme
Benzidme
bis(2-Chloroethyl) ether
1,2-Diphenylhydrazme
Hexachlorocyclopentadiene
N-Nitrosodiphenylamme
                                                                   (continued)
                                    358

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TABLE B-1.  (continued)
Percent Number of
of Industrial
samples3 categories"
45
42
85

26 1
23
22
IB
1 1
69

03
04
02
06
08
02
05
05
01
004
01
02

02
02

181
199
14 1
307
537
555
438

334
12
14
13

25
11
9
6
6
18

3
4
2
4
6
4
3
5
3
1
2
2

3
2

20
19
18
25
28
28
27

19
Acenaphthylene
Acenaphthene
Buty benzyl phthalate
11
Phenol
2-Nitrophenol
4-Nitrophenol
2,4-Dimtrophenol
4,6-Dimtro-o-cresol
Pentachlorophenol

«-Endosulfan
/i-Endosulfan
Endosulfan sulfate
o-BHC
/J-BHC
ft-BHC
7-BHC
Aldrm
Dieldrin
4.4'-DDE
4.4'-DDD
44'-DDT

Endrin
Endnn aldehyde

Antimony
Arsenic
Beryllium
Cadmium
Chromium
Copper
Lead

Total cyanides
Percent
of
samples9
01
01
1 4
are acid extractable organic compounds
1 9
23
33
46
52

26 are pesticides/PCB's
03
01
02
02
06
05
09
08
06
06
05




13 are metals
165
347
189
229
192
546

Miscellaneous
Number of
Industrial
categories"
1
2
6

8
10
12
12
15


3
1
4
2
2
1
2
3
2
3
1





20
27
21
25
19
28


Not available
Not available
N-Nitrosodimethylamme
N-Nitrosodi-n-propylamine
bis(2-Chloroisopropyl) ether

p-Chloro-m-cresol
2-Chlorophenol
2.4-Dichlorophenol
2,4,6-Trichlorophenol
2,4-Dimethylphenol


Heptachlor
Heptachlor epoxide
Chlordane
Toxaphene
Aroclor 1016
Aroclor 1221
Aroclor 1232
Aroclor 1242
Aroclor 1248
Aroclor 1254
Aroclor 1260
2.3.7,8-Tetrachlorodibenzo-p-dioxin
(TCDD)



Mercury
Nickel
Selenium
Silver
Thallium
Zinc


Asbestos (fibrous)
Total phenols
  The percent of samples represents the times this compound was found in all samples in which i! was analyzed for divided by the total as of 31 August 1978 Numbers of
  samples ranged from 2 532 to 2 998 with the average being 2617
b A total of 32 industrial categories and subcategones wore analyzed for organics and 28 for metils as of 31 August 1978
                                                                 359

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     There are several chemical and biochemical reactions that are recognized
as having a potential to significantly control contamination migration or
attenuation in ground-water systems.  These mechanisms include sorption,
hydrolysis, oxidation-reduction and biodegradation.  A discussion of  these
processes is contained in Appendix A, Processes and Properties Affecting
Contaminant Fate and Transport.

     The solubility of organic compounds may be divided into two broad groups:
polar and nonpolar. Polar organics exhibit an affinity for water, and therefore
do not bond or sorb to particle surfaces.  Non-polar organics are not attracted
to water and therefore tend to be easily sorbed.  The solubility of an organic
substance also affects its ability to be oxidized, hydrolyzed and biodegraded.
These properties differ between the organic groups and those interactions are
often strongly dependent on the hydrogeochemical environmental factors
including the pH, redox potential and other constituent concentrations in the
water.

     The study of organic compounds, known as organic chemistry, deals with the
compounds of carbon (Sawyer an,:1 McCarty, 1978).  All organic compounds contain
carbon in combination with one or more elements, most commonly, hydrogen,
oxygen, nitrogen, phosphorous and sulfur.  Organic compounds generally exhibit
several properties that make them different from inorganic substances.   Organic
compounds are generally combustible, less soluble in water and have  lower
boiling and melting points.  Reactions of organic compounds are generally
molecular so they tend to be slower than most other chemical reactions.  All
organic compounds are either natural, synthetic or fermentative in origin.
Organic wastes ar-, often produced from the processing of  natural and  synthetic
organic materials and fermentation at industrial facilities.

     The basis of an organic compound is the element carbon.   Carbon  is  diverse
because it maintains four covalent bonds in addition to  the ability  of  the
carbon atoms to  link together by covalent bonding in a wide variety  of ways
(Sawyer and McCarty, 1978).  These bonds may occur as a  continuous  chain, a
branched chain,  a cyclic ring or as chains or rings containing other  elements
(Figure B-l ) .  These structures serve as the basis for classification of
organic compounds.  For example, aliphatic compounds contain chains  or branched
chains of carbon atoms and aromatic compounds have carbon atoms  linked  in a
six-member carbon ring which contains three double bonds  that  give  them
stability.  Each of these compounds can be subdivided into groupings  or
homologous series where each member in the series differs from other  members by
the addition of  an extra carbon group.
        I   I    1    I   I           !    I_^_J       '\/^    -

                                        I              A            I

          Straight chain             Branched chain           Ring        Aromatic ring

           Figure B-1.  Covalent bonding arrangements of carbon atoms (Lippencott et al., 1978).

                                      360

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     The naming of organic compounds is complex.  The details of nomenclature
may be found in a standard chemistry text or the CRC Handbook of Physics and
Chemistry (Weast, 1983).  The Office of Technology Assessment, (1984) provides
a comprehensive list of organic compounds that are known to occur in ground
water, their ranges of detected concentrations, examples of uses and
quantitative estimates of carcinogenic potency and noncarcinogenic toxicity
(Table B-2).  This list has been subdivided according to characteristic organic
classes:  aromatic hydrocarbons, oxygenated hydrocarbons, hydrocarbons with
specific elements (N,S,P,Cl,I,F,Br) and "others".  The "others" group generally
corresponds to the aliphatic hydrocarbons which includes many petroleum
products.  The following discussions use this classification for simplicity,
but expands upon the groups found within these classes.

Aliphatic Compounds

     A hydrocarbon is a basic organic compound of carbon and hydrogen that may
be of two types:  saturated and unsaturated.  A saturated hydrocarbon has
adjacent carbon atoms joined by single covalent bonds with all other bonds to
hydrogen atoms.  Unsaturated hydrocarbons have at least two carbon atoms joined
by more than one covalent bond with all other bonds satisfied by hydrogen
(Sawyer and McCarty, 1978; Lippencott et al., 1978).

     Saturated compounds range from a compound with one carbon atom, to those
with each successive compound containing an additional carbon atom.  These
compounds are known as the alkanes or the methane series and are relatively
inactive.  The principal source of alkanes is petroleum.  Mixtures of these
compounds comprise gasoline and diesel fuel.  Some other alkanes include ethane
and propane.  Methane is the simplest hydrocarbon (City) and is a major end
product of anaerobic treatment processes as well as a constituent of natural
gas.

     In the alkane series, butane has two isomers.  An isomer is a compound
that has the same molecular formula, but different structural formulas
(Lippencott et al., 1978).  Many organic compounds exhibit this property.
Compounds containing rings of saturated carbon atoms are known as cycloalkanes;
they are more reactive due to the strained structure of the small ring.  These
are commonly known as the napthenes and have cyclo-prefixes.

     The unsaturated hydrocarbons can lose hydrogen to bond with other elements
or compounds.  The alkene or ethylene series of compounds all have one double
bond between two adjacent carbon atoms.  The compounds are commonly called
olefins and are formed in large quantities during the processing of petroleum
products.  The most important reaction of the alkenes is polymerization, where
small molecules unite to form giant molecules or polymers.  The most common
reaction is the polymerization of ethylene to form polyethylenes.  The
alkadienes or alkapolyenes contain more than two carbon-carbon double bonds.
Those hydrocarbons containing triple bonds between carbon atoms are known as
the alkyne or acetylene series.  These compounds represent starting substances
for many synthetic fibers.
                                      361

-------
                     TABLE B-2. SUBSTANCES KNOWN TO OCCUR  IN GROUND WATER, RANGES OF DETECTED
                                   CONCENTRATIONS, EXCEEDED STANDARDS,  EXAMPLES OF USES, AND QUANTITATIVE
                                   ESTIMATES OF CARCINOGENIC POTENCY AND NONCARCINOGENIC TOXICITY (OTA.1984)
W
O>
M
                     Contaminant
                                                      Concentration
                                                     (parts per billion)
                                                                    Standard
                                                                           Examples of uses
                                                      Carcmo-  Noncai-
                                                      genic   cinogenic
                                                     potency    toxicity
Aromatic hydrocarbons
Acetamlide
Alkyl benzene sulfonates
Aniline
Anthracene                            18
Benzene                            0 6-20 230
Benzidme
Benzyl alcohol

Butoxymethylbenzene
Chrysene                              10
Creosote mixture
Dibenzja h ]anthracene
Di-butyl-p-benzoqumone
Dihydrotnmethylquinoline
4 4-Dmitrosodiphenylamine
Ethylbenzene                        09-4000
Fluoranthene                           31
Fluorene
Fluorescein
Isopropyl benzene                     290
4,4'-Methylene-bis-2-chloroanilme
  (MOCA)
Methylthiobenzothiazole
Napthalene                          6 7-82

o-Nitroanilme

Nitrobenzene
4-Nitrophenol
n-Nitrosodiphenylamme
Phenanthrene                        18-471
n-Propylbenzene
Pyrene                                48
Intermediate manufacturing. Pharmaceuticals dyestuffs
Detergents
Dyestuffs. intermediate, photographic chemicals
  Pharmaceuticals, herbicides fungicides petroleum
  refining explosives
Dyestuffs intermediate semiconductor research
Detergents, intermediate, solvents antiknock gasoline
Dyestuffs reagent  stiffening agent in rubber compounding
Solvent  perfumes and flavors, photographic developer inks
  dyestuffs. intermediate
NA
Organic synthesis
Wood pteservatives disinfectants
NA
NA
Rubbei antioxidant
NA
Intermediate solvent
NA
Resinous products dyestuffs insecticides
Dyestuffs
Solvent, chemical manufacturing
Curing agent for polyurethanes and epoxy resins
                                                                             Solvent, lubricant, explosives  preservatives intermediate
                                                                               fungicide, moth repellant
                                                                             Dyestuffs intermediate, interior paint pigments chemical
                                                                               manufacturing
                                                                             Solvent, polishes, chemical manufacturing
                                                                             Chemical manufacturing
                                                                             Pesticides retarder of vulcanization of rubber
                                                                             Dyestuffs. explosives, synthesis of drugs, biochemical research
                                                                             Dyestuffs solvent
                                                                             Biochemical research
                                                                                                                                     Low
                                                                                                                                     High
                                                                                                                                             Low
                                                                                                                                    Low
                                                                                                                                             Low
                                                              Moderate
                                                                                                                                     (continued)

-------
                       TABLE B-2.  (continued)
Co
O>
CO
                       Contaminant

                       Aromatic hydrocarbons (cont'd)
                       Styt^ne (vinyl benzene)
                       Toluene


                       1 J 4-Tnmetnylbi'Mzenc

                       Xylones (m o p)                        007-300
Oxygenated hydrocarbons
Acetic acid

Acetone                              10-3000

Benzophenone
Butyl acetate
N-Butyl-benzylphthalate                 10-38
Di-n-butyl phthalate                      470

Diethyl ether

Diethyl phthalate
Dilsopropyl ether                        20-34
2.4-Dimethyl-3-hexanol
2.4-Dimethyl phenol
                       Di-n-octyl phthalate                       23
                       1.4-Dioxane                            2.100
                      Ethyl acrylate
                      Formic acid

                      Methanol (methyl alcohol)
                      Methylcyclohexanone
                      Methyl ethyl ketone
                                   Concentration   Standard
                                   (parts per billion)

                                     01-6400
                    Examples of uses
Carcino-   Noncar-
 genic    cmogenic
potency   toxicity
Plastics, resins  protective coatings intermediate
Adhesive solvent in plastics, solvent  aviation and high octane
  blending stock  dilutent and thinner, chemicals
  explosives detergents
Manufacture of dyestuffs. Pharmaceuticals, chemical
  manufacturing
Aviation gasoline  protective coatings, solvent  synthesis of
  organic chemicals
Fno'1 additives plastics dye- tuffs  pharnaci-uticals
  p1 >toqiaptiir '  'Tni': i's  \>  feticides
Dyestuffs. solvent, chemical manufacturing, cleaning and
  drying of precision equipment
Organic synthesis, odor fixative, flavoring, Pharmaceuticals
Solvent
Plastics, intermediate
Plasticizer, solvent, adhesives, insecticides, safety glass inks,
  paper coatings
Chemical manufacturing, solvent  analytical chemistry.
  anesthetic, perfumes
Plastics, explosives, solvent, insecticides, perfumes
Solvent, rubber cements, paint and varnish removers
Intermediate, solvent, lubricant
Pharmaceuticals, plastics disinfectants, solvent, dyestuffs.
  insecticides, fungicides, additives to lubricants and
  gasolines
Plasticizer for polyvmyl chloride and other vinyls
Solvent, lacquers, paints, varnishes, cleaning and detergent
  preparations, fumigants.  paint and varnish removers,
  wetting agent, cosmetics
Polymers, acrylic paints, intermediate
Dyeing and finishing, chemicals, manufacture of fumigants,
  insecticides, solvents, plastics, refrigerants
Chemical manufacturing, solvents, automotive antifreeze, fuels
Solvent, lacquers
Solvent, paint removers, cements and adhesives, cleaning
  fluids, printing, acrylic coatings
             Low



             Low

             Low

             Low


             Low
                                                                                                                                High
                                                                                                                                                (continued)

-------
                      TABLE B-2.  (continued)
Co
O)
                      Contaminant
                      Oxygenated hydrocarbons (cont'd)
                      Methylphenyl acetamide
                      Phenols (e g  p-Tert-butylphenol)

                      Phthalic acid
                      2-Propanol
 Concentration   Standard
(parts pot billion)

   10-234.000
                                                                               Examples of uses
                                                         Carcmo-  Noncar-
                                                          genic    cmogenic
                                                        potency    toxicity
 2-Propyl-1 -heptanol
 Tetrahydrofuran                                    Solvent
 Varsol

 Hydrocarbons with specific elements
 (e.g.. with N.P.S.CI.Br.l.F)
 Acetyl chloride
 Alachlor (Lasso)                      190-1700         *
 Aldicarb (sulfoxide and sulfone          36-405          *
   Temik)
 Aldrm                                                 •
 Atrazine                                              •
 Benzoyl chloride
 Bromacil                              72-110          *
 Bromobenzcne                        1  9-5 8
 Bromochloromethane
 Bromodichloromethane                 14-110          *
 Bromoform                            24-110
 Carbofuran                            4-160           *
 Carbon tetrachlonde                 0*5-18 "00         *

 Chlordane                                             •
 Chlorohenzene                        27-41           •
 Chloroform                           14-1.890          *
 Chlorohexane
Chloromethane (methyl chloride)           44

Chloromethyl sulfide                                 NA
 NA
 Resins, solvent. Pharmaceuticals, reagent dyestuffs and
   indicators, germicidal paints
 Dyestuffs. medicine perfumes reagent
 Chemical manufacturing solvent, deicmg agent.
   Pharmaceuticals, perfumes, lacquers, dehydrating agent.
   preservatives
 Solvent

 Paint and varnish thinner
                                                                                 Dyestuffs. Pharmaceuticals, organic preparations
                                                                                 Herbicides
                                                                                 Insecticide, nernatocide
                                                                                                                                           High
 Insecticides
 Herbicides, plant growth regulator, weed control agent
 Medicine, intermediate
 Hoi bit ides
 Solvent motor oils, oiganic synthesis
 Fire extinguishers, organic synthesis
 Solvent, fire extinguisher fluid mineral and salt separations
 Solvent, intermediate
 Insecticide nernatocide
 Degreasers. refrigerants and propellants  fumiaants chemical
  manufacturing                                         Moderate
 Insecticides, oil i>muKions
 Stiver/  petricid ;s. c'<°mu  ,il manufacturing
 Plastics, fumigants. insecticides, refrigerants and propellants
 NA
Refrigerants, medicine, propellants. herbicide, organic
  synthesis
                                                                  Moderate
                                                                    High
                                                                                                                                                  Moderate

                                                                                                                                                  Moderate
                                                                                                                                                  Moderate

                                                                                                                                                    Low
                                                                                                                                                  Moderate
                                                                                                                                                  Moderate
                                                                                                                                                 Moderate
                                                                                                                                                    Low
                                                                                                                                             (continued)

-------
                      TABLE B-2.  (continued)
CO
O)
Oi
                      Contaminant
                                                        Concentration   Standard
                                                                                                    Examples of uses
                      Hydrocarbons with specific elements
                      (e.g., with N,P,S,CI,Br,l,F) (cont'd)    (parts per billion)
                      2-Chloronaphthalene                    83
                                                                                                                   Carcino-   Noncar-
                                                                                                                    genic    cinogenic
                                                                                                                  potency    toxicity
Chlorpynfos
Chlorthal-methyl (DCPA, or Dacthal)
o-Chlorotoluene
p-Chlorotoluene
Dibromochloromethane
Dibromochloropropane (DBCP)
Dibromodichloroetnylene
Dibromoethane (ethylene
  dibromide, EDB)
Dibromomethane
Dichlofenthion (DCFT)
o-Dichlorobenzene

p-Dichlorobenzene

Dichlorobenzidme
Dichlorocyclooctadiene
Dichlorodiphenyldichloroethane
  (ODD. TDE)
Dichlorodiphenyldichloroethylene
  (DDE)
Dicnlorodiphenyltnchloroethane
  (DDT)
1.1-Dichloroethane
1 2-Dichloroethane
                      Dichloroethyl ether
  24

2 1-55
1 -137

35-300

 449

  2 7

06-07
                                                           001-08
                                                          005-022
                                                          05-11 330
                                                           250-847
                                                           1 2-4 000
 1 1-Dichloroethylene (vmyhdiene
  chloride)
 1,2-Dichloroethylene (cis and trans)      0 2-323
                                       1.100
Oil  plasticizer, solvent for dyestuffs, varnish gums and
  lesins  waxes
  Wax moisture-, flame-, acid- and insect-proofing of
  fibrous materials, moisture- and flame-proofing of
  electrical cable, solvent (see oil)
NA
Herbicide
Solvent, intermediate
Solvent, intermediate
Organic synthesis
Fumigant, nematocide
NA
Fumigant. nematocide. solvent, waterproofing preparations
  organic synthesis
Organic synthesis, solvent
Pesticides
Solvent fumigants, dyestuffs, insecticides  degreasers
  polishes, industrial odor control
Insecticides moth repellant. germicide space odorant
  intermediate, fumigants
Intermediate curing agent for resins
Pesticides
Insecticides

Degradation product of DDT found as an impurity in
  DDT residues

Pesticides
Solvent fumiqants medicine
Solvent, degreasers, soaps and scouring compounds organic
   synthesis, additive in antiknock gasoline, paint and
   finish removers
Saran  (used in screens upholstery, fabrics, carpets, etc )
   adhesives synthetic fibers
Solvent, perfumes, lacquers, thermoplastics, dye extraction,
   organic synthesis, medicine
Solvent, organic synthesis, paints, varnishes, lacquers, finish
   removers, drycleaning, fumigants
                                                                                                                                                  Moderate
                                                                                                                                                  Moderate
                                                                                                                                         Moderate
                                                                                                                                                    Low
                                                                               High
                                                                                                                                           Low
                                                                                                                                         Moderate
                                                                                                                                             (continued)

-------
                      TABLE B-2.  (continued)
Co
0)
O)
                      Contaminant
                                                        Concentration   Standard
                                                                                                    Examples of uses
                                                                                                                                         Carcmo-  Noncar-
                                                                                                                                          genic   cmoqenic
                                                                                                                                         potency    toxicity
Hydrocarbons with specific elements
(e g.. with N.P.S.CI.Br I.F) (contd)   pail, pet :nlli
Dichloroiodomethane                  28-41
Dichloroisopropylether ( bis-2-
  chloroisgpropylether)
Dichloromethane (methylene            4-8400
  chloride)
Dichloropenta'liene                      036
2 4-Dichlorophenol
2 4-Dicnlorophenoxyacetic acid         1-85 000
  124-D)
1  ?-Dichloropropane                     46-60

Dioldnn
Diiodomethane                         20
D:isopropyl nethyl phosphonate
  IDIMP)
Dimethyl disulfide
Dimethylfor'iamide
2 4-Dmotrophenol (Dinoseb, DNBP)      124-400
Dioxms(eg TCDD)
Dodecyl mercaptan (lauryl
  mercaptan)
Endosulfan                             08
Endrin
Ethyl chloride

Bis-2-ethylhexyiphthalate               12-170
Di-2-ethylhexylphthalate
Fluorobenzene                          67
Fluoroform                             3 5
Heptachlor
Heptachlorepoxide
Hexachlorobicycloheptadiene            2 2
Hexachlorobutadiene                    2 53
d-Hexachlorocyclohexane                6
  (= Benzenehexachlonde,  or
  «-BHC)
/j-Hexachlorocyclohexane (ft-BHC)       3 8
  /<-BHC)
NA
Solvont paint and varnish removers cleaning solutions

Solvent plastics  paint removers propellants  blowing agent
  1 i  foams
N/>'
Organic synthesis
Herbicides

Solvent, intermediate scouring compounds fumigant
  nematocide. additive tor antiknock fluids
Insectides                                                 High
Organic synthesis
NA

NA
Solvent organic synthesis
Herbicides
Impurity in the herbicide 2 4,5-T                             High
Manufacture of synthetic rubber and plastics
  Pharmaceuticals insecticides fungicides
Insecticides
Insecticides
Chemical manufacturing anesthetic solvent refrigerants,
  insecticides
Plastics                                                   Low
Plasticizers
Insecticide and larvicide intermediate
Refrigerants intermediate blowing agent for foams
Insecticides                                              Moderate
Degradation product of heptachlor also acts as an insecticide
NA
Solvent transformer and hydr uffir fluid  he,it-transfef liquid
insecticides
                                                                                 Insecticides
                                                                                                                                                  Moderate
                                                                                                                                                  Moderate
                                                                                                                                                    High
                                                                                                                                                    High
                                                                                                                                             (continued)

-------
                       TABLE B-2.  (continued)
u
O)
                       Contaminant
                                                         Concentration   Standard
                                                                                                     Examples of uses
                       Hydrocarbons with specific elements
                       (e.g.. with N,P.S.CI,Br,I.F) (cont'd)  (parts p^r billion)

                        7-Hexachlorocyclohexane              05-43
                        (7-BHC, or Lindane)
                        Hexachlorocyclopentadiene               —
Hexachloroethane

Hexachloronorbomadiene
Kepone
Malathion
Methoxychlor
Methyl bromide
Methyl parathion
Parathion
Pentachlorophenol (PCP)

Phorate (Disulfoton)
Polybrommated biphenyls (PBBs)
Polychlorinated biphenyls (PCBs)

Prometon
RDX (Cyclonite)
Simazine
Tetrachlorobenzene
Tetrachloroethanes
  (1.1.1.2& 1,1.2,2)

Tetrachloroethylene (or  perchlo-
roethylene, PCE)

Toxaphene
Tnazine
1,2,4-Tnchlorobenzene

Trichloroethanes (1,1,1 and 1.1,2)
1,1,2-Tnchloroethylene (TCE)
                                                               46
                                                               74
                                                               46
                                                              8-40
                                                              3400

                                                              5,000
                                                               4
                                                            717-2405

                                                              1-570
                                                               2
                                                               37

                                                           0 2-26,000
                                                           210-37.000
Insecticides

Intermediate for resins, dyestuffs, pesticides, fungicides,
   Pharmaceuticals
Solvent, pyrotechnics and smoke devices, explosives,
   organic synthesis
NA
Pesticides
Insecticides
Insecticides
Fumigants  pesticides, organic synthesis
Insecticides
Insec'icidos
Insecticides, fungicides, bactencides, algicides. herbicides,
   wood preservative
Insecticides
Flame retardant for plastics, paper, and textiles
Heat-exchange and insulating fluids in
   closed systems
Herbicides
Explosives
Herbicides
NA
Degreasers, paint removers, varnishes, lacquers,
   photographic film organic synthesis, solvent    insecti-
cides  fumigants. weed killer

Degreasers, drycleaning, solvent, drying agent, chemical
   manufacturing, heat-transfer medium, vermifuge
Insecticides
Herbicides
Solvent, dyestuffs, insecticides, lubricants,
   heat-transfer medium (e g , coolant)
Pesticides, degreasers. solvent
Degreasers, paints, drycleaning,  dyestuffs. textiles, solvent.
   refrigerant and heat exchange liquid, fumigant,
   intermediate, aerospace operations
                                                                                                                   Carcmo-  Noncar-
                                                                                                                    genic   cmogenic
                                                                                                                  potency    toxicity
          Moderate



   Low


            High

          Moderate
                                                                                                                                                      High
                                                                                                                                                    Moderate
                                                                                                                                                      Low
Moderate


Moderate

Moderate



  Low

Moderate
  Low
  Low
                                                                                                                                                (continued)

-------
                       TABLE B-2.  (continued)
W
O>
00
                       Contaminant
                                                         Concentration   Standard
                                                                                                      Examples of uses
                                                                                                                     Carcmo-  Noncar-
                                                                                                                      genic   cinogenic
                                                                                                                    potency    toxicity
                       Hydrocartx>ns with specific elements
                       (e.g., with N,P,S,CI,Br,l,F) (cont'd)     (parts per billion)
                      Trichlorofluoromethane (Freon 11)         26
                      2,4 6-Trichlorophenol
                      2.4 5-Tnchlorophenoxyacetic acid
                         (2.4.5-T)
                       2 4.5-Tnchlorophenoxypropionic
                         acid (2,4,5-TP or Silvex)
                       Tnchlorotrifluoroethane                 35-135

                       Trinitrotoluene (TNT)                  620-12,600

                       Tns-(2.3-dibromopropyl) phosphate
                       Vinyl chloride                          50-740
Other hydrocarbons
Alkyl sulfonates
Cyclohexane                            540
1,3,5 7-Cyclooctatetraene
Dicyclopentadiene (DCPD)

2.3-Dimethylhexane
Fuel oil
Gasoline                            2,000-9.000
Jet fuels
Kerosene                              243,000
Lignm                                  7,500'

Methylene blue activated                  11
  substances (MBAs)
Propane                                —
Tannin                                 7,500'

4,6,8-Tnmethyl-1-nonene                 —
Undecane                               —

Metals and cations                (parts per million)
Aluminum                            01-1.200
                                                            Solvent  refrigerants, fire extinguishers, intermediate
                                                            Fungicides, herbicides, defoliant
                                                            Herbicides, defoliant

                                                            Herbicides and plant growth regulator

                                                            Drycleanmg, fire extinguishers, refrigerants, intermediate.
                                                            drying agent
                                                            Explosives intermediate in dyestuffs and photographic
                                                              chemicals
                                                            Flame retardant
                                                            Organic synthesis polyvmyl chloride and copolymers
                                                              adhesives
Detergents
Organic synthesis, solvent, oil extraction
Organic research
Intermediate for insecticides, paints and varnishes  flame
   retardants
NA
Fuel heating
Fuel
Fuel
Fuel, heating, solvent, insecticides
Newsprint, ceramic binder, dyestuffs. drilling fuel additive,
   plastics
Dyestuffs, analytical chemistry

Fuel, solvent, refrigerants, propellants, organic synthesis
Chemical manufacturing, tanning, textiles, electroplating,
   inks, Pharmaceuticals, photography, paper
NA
Petroleum research, organic synthesis
                                                                                 Alloys, foundry, paints, protective coatings, electrical
                                                                                    industry, packaging, building and construction, machinery
                                                                                    and equipment
                                                                  Moderate
                                                                     Low
                                                                  Moderate

                                                                     High
                                                                                                                                             Low
                                                                                                                               High
                                                                                                                                              (continued)

-------
                 TABLE B-2.  (continued)
to
O)

-------
                        TABLE B-2. (continued)
C*>
^i
O
                        Contaminant

                        Metals and cations (cont'd)
                        Titanium
                        Vanadium

                        Zinc
Nonmetals and anions
Ammonia

Boron
Chlorides

Cyanides

Fluorides
Nitrates
Nitrites
Phosphates
Sulfates
Sulfites

Micro-organisms
Bacteria (cohform)
Viruses

Radionuclides

Cesium 137
Chromium 51
Cobalt 60
Iodine 131
                       Iron 59
                       Lead 210
Concentration   Standard

(parts per million)

      243

    0 1-240



     1-900


   1 0-49,500

    1 05-14

    0 1-250
    1 4-433

    04-33
  02-32,318
                                                          (picocunes per
                                                             mililiter)
                                                               64
                                                                                Examples of uses
                                                         Carcmo-  Noncar-
                                                          genic    cmogenic
                                                         potency   toxicity
                                                            Alloys, structural materials, abrasives, coatings
                                                            Alloys, catalysts, target material for x-rays

                                                            Alloys, electronics, automotive parts, fungicides, roofing,
                                                               cable wrappings, nutrition
Fertilizers, chemical manufacturing, refrigerants, synthetic
  fibers, fuels, dyestuffs
Alloys, fibers and filaments, semi-conductors, propellants
Chemical manufacturing, water purification, shrink-proofmg.
  flame-retardants. food processing
Polymer production (heavy duty tires), coatings, metallurgy,
  pesticides
Toothpastes and other dentrifices, additive to drinking water
Fertilizers, food preservatives
Fertilizers, food preservatives
Detergents, fertilizers, food additives
Fertilizers, pesticides
Pulp production and processing food preservatives
                         Gamma radiation source for certain foods
                         Diagnosis of blood volume, blood cell life, cardiac output, etc
                         Radiation therapy, irradiation, radiographic testing, research
                         Medical diagnosis, therapy, leak detection, tracers (e g , to
                           study efficiency of mixing pulp fibers, chemical reactions,
                           and thermal stability of additives to food products),
                           measuring film thicknesses
                         Medicine, tracer
                         NA
                                                                     Low
                                                                    High,
                                                                   moderate
                                                                   Moderate
                                                                                                                                                        High

                                                                                                                                                      Moderate
                                                                                                                                               (continued)

-------
                      TABLE B-2.  (continued)
u
•g
                      Contaminant
                                                             Concentration    Standard
                                                                                                                 Examples of uses
                                                                                             Carcino-   Noncar-
                                                                                               genic    cinogenic
                                                                                             potency    toxicity
                      Radionuclides (cont'd)

                      Phosphorous 32

                      Plutonium 238, 243
                      Radium 226
                      Radium 228
                      Radon 222
                      Ruthenium  106
                      Scandium 46
                      Strontium 90

                      Thorium 270
                      Tritium
                      Uranium 238
                      Zinc 65
                     Zirconium 95
(picocuries per
   milliliter)
   0.8-25
     125
    0817
   150-353
   10-500
Tracer, medical treatment, industrial measurements (e g  , tire
   tread wear and thickness of films and ink)
Energy source, weaponry
Medical treatment, radiography
NA
Medicine, leak detection, radiography, flow rate measurement
Catalyst
Tracer studies, leak detection, semi-conductors
Medicine, industrial applications (e g., measuring
   thicknesses, density control)
NA
Tracer, luminous instrument dials
Nuclear reactors
Industrial tracer (e.g , to study wear in alloys, galvanizing,
   body metabolism, function of oil additives in lubricating oils)
                                                                                          NA
               ''Basedon Auiams.etai 1975 Bryant etal 198.4 Harris etal nd O'Brien and Fisher. 1983 Tucker. 1981, University olOklahoma 1983,Hawley 1977. ConsidmeandConsidine, 1983 Lewis and Tatken 1980 and Wmdholz.et
                al  1982
               "Concentrations represent single reported concentrations of ranges of reported groundwater or domestic well concentrations from references surveyed they generally do not include concentrations at hazardous waste sites
                Dash (—} indicates contaminant detected but concentration not reported Note that units differ among categories, units are defined at the beginning of each contaminant category
               c Solid bullet means that a( least one type of standard exists for the substance  Asterisk means that at least one standard is known to have been exceeded Note that these refer to standards tor individual substances, standards for
                groups of substances or other measurements such as BOD are listed in app C
               d Listed uset, are primarily industrial applications Some substances occur naturally in groundwater and may not be a result of human activities
               e Absence of an entry does not necessarily mean that no adverse health effects are associated with that substance, rather, entries reflect data available to OTA In addition, if a value was found for carcinogenic potency of a
                substance no search for non-cannogemc toxicity of that substance was made
               ' Carcinogenic potency is measured either according to unit risks developed by EPA Carcinogen Assessment Group or according to estimated unit risk based on assessment by EPA Office of Pesticides and Toxic Substances (as
                reported in Environ Corp  1983), carcinogens are listed only if peer-reviewed unit risk data are available Unit risk = risk per unit of exposure, where unit of exposure is defined as lifetime average daily intake Estimates of lifetime
                risk are obtained by multiplying unil risk by actual exposure Potency categories are defined as (Environ  Corp  1983)
                    High potency  unit risk greater than 5 (mg/kg/day)'1
                    Medium potency  unit risk equal to 0 1-5 (mg/kg/dayr1
                    Low potency  unit risk less than 0 1 (mg/kg/day) 1
               qNoncarcmogenic toxicity is measured by Minimum Effective Dose (MED, the minimum dose known to cause adverse impact, Environ Corp , 1983)
                    High  MED less than 10 mg/kg body weight, day                                                                                                     '
                    Moderate = MED 10-100 mg/kg body weight day
                    Low  MED greater than 100 mg/kg body weight/day
               h Value for combined anthracene and phenanthrene
               1 NA ~ information on use not available in standard references that were consulted
               I Value for combined Itgnm and tannin

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Oxygenated Hydrocarbons

     Oxygenated hydrocarbons refer to any organic compound that contains an
(OH) group, an oxygen group or responds as an acid in a solution.  These may
include both aromatic and aliphatic hydrocarbon groups.

     Alcohols or hydroxy alkyl compounds are considered to be a step in the
primary oxidation product of hydrocarbons.  The alcohols are classified into
three groups:  primary, secondary and tertiary, depending on the location of
the (OH) group.  The common alcohols are methyl, ethyl, isopropyl and n-butyl.
Methyl alcohol is used in the synthesis of organic compounds and in antifreeze.
Ethyl alcohol is used in the production of beverages, synthesis of organic
compounds and in medicines.  Isopropyl alcohol is used extensively in organic
synthesis as is n-butyl alcohol.  Short chain alcohols are soluble in water and
may be volatized and biodegraded (Brown et al., 1983).  Polyhydroxyl alcohols
contain two hydroxyl groups per molecule and are known as glycols.  These are
commonly used as radiator anti-freeze compounds and are very toxic.  Glycerol
is a trihydroxy alcohol used extensively in soaps, foods, cosmetics and
medicines.  Most alcohols are easily oxidized by oxidizing agents and many
microo rgani sms.

     Primary alcohols are oxidized to aldehydes, while secondary alcohols
oxidize to ketones.  Common aldehydes include formaldehyde and acetaldehyde.
Formaldehyde is used extensively in organic synthesis, and is toxic to
microorganisms, however, under dilute concentrations it can be used as food by
microorganisms and oxidized to carbon dioxide and water.  Thf- chemical names of
all aldehydes end in -al.  Many of the aromatic aldehydes exhibit fragrant
odors, such as coumarin and vanillan.  The ketones are used as industrial
solvents and in the synthesis of organic products.  The most common ketone is
acetone.  Both aromatic and aliphatic ketones are easily oxidized by
microorganisms.

     Organic acids represent the highest oxidation state possible in an organic
compound; further oxidation produces carbon dioxide and water (Sawyer and
McCarty, 1978).  All organic acids contain a carboxyl group.  Thus, acids with
one carboxyl group are known as monocarboxylic acids and so on.  A wide variety
of saturated and unsaturated acids occur in nature as constituents of waxes,
fats and oils.  These are known as fatty acids which are typically straight
chain structures.  The lower members of the saturated acid series are liquids,
ranging in order from the sharp odors of formic and acetic acid to the
unpleasant odors of butyric and valeric acids.  Butyric acid gives rancid
butter its disagreeable odor.  Industrial wastes from the dairy industry must
be treated to prevent formation of these acids.  These acids range from being
completely soluble in water to relatively insoluble.  The unsaturated acids
include acrylic, oleic and linoleic acids which are the general constituents of
the glycerides of most fats and oils (Sawyer and McCarty, 1978; Lippencott et
al., 1978).  Organic acids are utilized by microorganisms through oxidation
processes and are converted to carbon dioxide and water.  Biodegradation of
higher acids may be limited by their solubility in water.  A wide variety of
aromatic carboxylic acids are known such as benzoic acid, a preservative,
salycilic acid, a constituent of aspirin, and phthalic acid, an important
intermediate in the manufacture of organic compounds.  These acids are also
subject to biodegradation by microorganisms to carbon dioxide and water.

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     The degradation of aliphatic hydrocarbons by microorganisms depends on
molecular weight, water solubility, number of double bonds, degree of
branching, and whether the compound is an open chain or cyclic compound.  Thus,
the simplest compounds such as a straight chain hydrocarbon will be the  most
easily degraded as opposed to a more complex cyclic compound (Brown et al.,
1983).  The degradation rate decreases with either a decreasing number of
double bonds or with the number and size of alkyl groups.   Sediments containing
aliphatic hydrocarbons are generally deficient in nitrogen and phosphorous.
Addition of these fertilizers greatly enhances biodegradation rates (Brown et
al. , 1983).  Volatilization of low molecular weight hydrocarbons is a mechanism
that occurs with increasing temperature and soil moisture  content.

Aromatic Compounds

     The aromatic compounds contain stable ring structures, or cyclic groups,
with very stable bonds which are hybrids of single and double bonds.  Thus,
aromatic compounds do not bond to substances by addition,  but rather by
substitution of a hydrogen atom for an element or compound.  The simplest
aromatic ring is made up of six-ringed carbon atoms bonded to six hydrogen
atoms and is known as benzene or the benzene ring.  Substitutions may occur at
one or more hydrogen atom sites.  The benzene series constitutes a single ring
with alkyl substitutions; these include toluene and xylene and the respective
isomers of xylene.  These products are found in coal tar and crude petroleum
and are used primarily as solvents.

     The phenols are an important aromatic hydrocarbon. They consist of a
basic ring hydrocarbon or benzene with an attached (OH) group.  Phenols  are
generally known as carbolic acid which is widely used as a disinfectant, and  in
concentrated solutions is toxic to bacteria.  Phenols occur as natural
constituents of industrial wastes from coal and petroleum  processing.  Until
recently, phenol was thought to be toxic to bacteria for biodegradation
applications.  However, more recent studies suggest that bacteria may be able
to degrade low concentrations (Erlich et al., 1982; Tabak  et al., 1980).
Studies by the FMC Corporation (1983) indicate that hydrogen peroxide  is
capable of oxidizing phenols in the presence of a catalyst to produce carbon
dioxide and water.

     The next higher group of phenols are cresols.  They are found in coal  tar
and exhibit even higher germicidal properties than phenols, but are less toxic.
Cresols are commonly found in spray disinfectants such as  lysol and in
creosote, used in wood preservation.  Phenols with more than one (OH)  group are
termed polyhydric.  Three industrially important isomers of polyhydric phenols
include the catechols, resorcinals and hydroquinone.  These isomers are  readily
oxidized by microorganisms (Sawyer and McCarty, 1978).   Other biodegradation
mechanisms for benzenes and phenols occur through hydroxylation of the double
bonds to produce dicarboxylic acid.  These aromatic acids  may be further
biodegraded to simple compounds.
                                    373

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     A polyring aromatic hydrocarbon consists of one or more cyclic rings that
are bonded through shared carbon atoms.  These carbon atoms do not have
hydrogen atoms attached.  The polyring aromatic compounds include naphthelene
and anthracene used in the manufacture of dyes, and phenanthracene, an
important constituent of alkaloids such as morphine and vitamin D.  Halogenated
and nitrogenous aromatics will be discussed in the next section.

     Aromatic compounds are usually present in wastes generated by petroleum
refineries, organic chemical plants, rubber industries and waste streams
associated with combustion proceses (Brown et al., 1983).  Most aromatic
hydrocarbons are toxic and/or carcinogenic and fairly resistant to
degradation.  The decomposition rate of aromatic hydrocarbons is typically
substance dependent; however, simple compounds typically degrade more easily.
In addition, the more soluble compounds are more easily degraded by
microorganisms (Tabak et al., 1980).

Hydrocarbons With Specific Elements

     The final group of hydrocarbons may be either aliphatic or aromatic, but
has one or more additional groups with specific elements as substituents,
namely, nitrogen, sulfur and phosphorous and the halogens, chlorine, fluorine,
iodine and bromine.  The halogenated organics have received the most attention
as ground-water contaminants.  These compounds are refractory, or very
resistant to degradation.  This is thought to be due to the presence of a
halogen; its location and type determine the relative persistence of the
compound (Kobayashi and Rittmann, 1982).  These compounds range from simple
alkyl halides to polyhalogen compounds to complex halogenated hydrocarbons such
as DDT.  Common halogenated compounds include methyl chloride, ethyl chloride,
ethylene dibromide, chloroform, carbon tetrachloride, tetrachloroet rylene,
chlorobenzene and freon (dichlorodifluoromethane).  Methyl and ethyl chloride
were once used as refrigerants; ethyl chloride is used in the manufacture of
tetraethyl lead, an antiknock gasoline additive.  Chloroform has been found in
drinking water due to the reaction of chlorine with natural organic substances
in water.  Freon is an extensively used refrigerant due to its non-toxic and
non-flammable properties (Sawyer and McCarty, 1978).

     Chlorinated hydrocarbons were formerly used extensively as various types
of pesticides, many of which are very resistant to degradation.  These include
dioxin,'DDT, DDE, Aldrin, Dieldrin, Endrin, Lindane, Chlordane, Toxaphene, 2,
4-D and 2,4,5 TP Silvex which have been banned from usage or greatly restricted
because of their toxicity and carcinogenic potentials (Solomons, 1978; Brown et
al., 1983; Abrams et al., 1975).  These products were used extensively for
agricultural and defoliant purposes.  Other pesticides have been studied to
determine their potential for attenuation through hydrolysis, reductive
dehalogenation and biodegradation.

     Hydrolysis is a reaction in which a bond is broken by water.  Often, an
(OH) group replaces a halide ion or ester.  Hydrolysis rates are dependent on
pH, the presence of humic materials and individual compounds (Cherry et al.,
1984; Cohen et al., 1984).  Reductive dehalogenation involves the removal of
the halogen through oxidation-reduction reactions in low redox  state ground
                                      374

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water (Cherry et al., 1984) and by certain microorganisms (Kobayashi and
Rittmann, 1982).  Biodegradation of halogenated hydrocarbons has been
documented under both aerobic and anaerobic conditions (Kobayashi and Rittman,
1982; Cherry et al,, 1984; Bouwer et al., 1981; Tabak et al., 1980; Brown et
al., 1983).  Hexachloroethene was shown to disappear with a 40 day half life in
a sand aquifer.  Supporting laboratory data indicated the compound was reduced
to tetrachlorethylene through microbial biodegradation (Griddle et al., 1986).

     Other types of pesticides include organic phosphorous and carbamate
pesticides.  Organic phosphorous pesticides include parathion, which is very
toxic, and malathion which has low toxicity for mammals.  Phosphorous
pesticides tend to hydrolyze quickly at or above a neutral pH, thus losing
their toxic properties.  Carbamate pesticides typically have moderate to high
water solubilities and are often volatile.  These include IPC, a herbicide,
captan, a fungicide and ferbam and sevin as insecticides.  Aldicarb and
carbofuron are toxic carbamate pesticides which have been found in ground water
in many states.

     As a rule, chlorinated aromatics are less degradable and less soluble than
their aliphatic counterparts.  This has proven true for the chlorinated
benzenes including hexachlorobenzene (HCB) and its derivatives.  These are
found as by-products of industrial processes, and in chlorinated solvents and
pesticides.  The rates of degradation of these compounds are slow; they may
persist in the soil and water for several years without significant
degradation.  Certain plants such as lettuce, carrots, grasses and potatoestend
to absorb HCBs from the soil (Brown et al., 1983).  Rates of degradation are
variable depending on the degree of chlorination; in general, the less
chlorinated, the more degradable (Tabak et al., 1980).

     Another widely publicized group of halogenated organics are the
polychlorinated biphenyls (PCBs).  These are biphenyl molecules with the
presence of one or more chlorine atoms at several locations on the phenyl
structures.  These mixtures have been commercially produced since 1929 with a
total of 210 possible compounds.  PCBs are classified according to chlorine
content with most industrial mixtures containing 40 to 60 percent chlorine
(Solomons, 1980).

     PCBs had many uses including heat exchangers in transformers, in
capacitors and thermostats, plasticizers in food bags and polystyrene cups, in
printing inks and in waxes.  Because the PCBs are highly persistent and fat
soluble, they tend to collect in the tissues of many animals and humans.  The
EPA banned the manufacture, processing and distribution of PCBs in 1979
(Solomons, 1980).

     Degradation of PCBs has been found to be affected by the nature of the
chlorine substituents with respect to the substitution or relative position of
the chlorine atom within the compound (Brown et al., 1983).  Degradation tends
to increase as the amount of chlorine substitution decreases; the relative
position of the chlorine also affects rates of degradation.  In general, the
lower chlorinated compounds were found to be degradable in mixed microbial
populations (Kobayashi and Rittmann, 1982).
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     Other hydrocarbons with specific elements have the nitrogen group as
substituents.  These include the amines, amides, anilines and nitriles.  The
amines are alkyl derivatives of ammonia and may be primary, secondary or
tertiary depending on the number of hydrogen ammonia atoms that are replaced.
The amines are found in industrial wastes from fish and beet-sugar industries,
and little is known about their susceptibility to biodegradation.  The amides
are derived from organic acids and ammonia under special conditions.  The
nitriles are organic cyanides that are extensively used in the manufacture of
synthetic fibers (Sawyer and McCatty, 1978).  The most commonly used nitriles
include acrylonitrile and acetonitrile.  Attenuation of nitriles occur through
oxidation reactions at specified pH values (Harsh, 1975).  The primary form of
amines are known as analines and are important compounds for organic synthesis
and in dyes.  The amines were shown to range in ease of biodegradability
depending on the individual compound (Tabak et al., 1980; Kobayashi and
Rittmann, 1982).

     Mercaptans or thiols are aliphatic compounds that contain sulfur and have
a structure similar to alcohols.  Mercaptans are known to have  disagreeable
odors and are typically byproducts of kraft pulping and petroleum processing.
The FMC Corporation (1983) has shown that thiols are readily oxidized under
acid conditions to insoluble products.
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                                   REFERENCES
Abrams, E.F., D. Derkics, C.V. Fong, D.K. Guinan and K.M. Slimak, 1975.
Identification of organic compounds in effluents from industrial sources; NTIS
PB-241641, 211 pp.

Bouwer, E.J., B.E. Rittmann and P.L. McCarty, 1981.  Anaerobic degradation
of halogenated 1- and 2-carbon organic compounds; Environmental Science &
Technology, vol. 15, no. 5, pp. 596-599.

Brown, K.W., G.B. Evans, Jr. and B.D. Frentrop, editors, 1983.  Hazardous waste
land treatment; Butterworth Publishers, 692 pp.

Cherry, J.A., R.W. Gillham and J.F. Barker, 1984.  Contaminants in groundwater:
chemical processes; Groundwater Contamination, National Academy Press, pp.
46-66.

Cohen, S.Z., S.M. Creeger, R.F. Carsel and C.G. Enfield, 1984.  Potential for
pesticide contamination of ground water resulting from agricultural uses;
American Chemical Society Symposium Series #259, Treatment Disposal of
Pesticide Wastes, Krueger and Seiber, editors, Washington, D.C.

Erlich, G.G., D.F. Goerlitz, E.M. Godsy and M.F. Hult, 1982.  Degradation of
phenolic contaminants in ground water by anaerobic bacteria:  St. Louis,
Minnesota; Ground Water, vol. 20, no. 6, pp. 703-710.

FMC Corporation, 1983.  Industrial waste treatment with hydrogen peroxide;
Industrial Chemical Group, Philadelphia, Pennsylvania, 23 pp.

Freeze, R.A. and J.A. Cherry, 1979.  Groundwater; Prentice-Hall, 604 pp.

Fuller, W.H. and J. Artiola, 1978.  Use of limestone to limit contaminant
movement from landfills; Proceedings of the 4th Annual Research Symposium on
Land Disposal of Hazardous Wastes, U.S. EPA-600/9-78-016, pp. 282-298.

Harsh, K., 1975.  In situ neutralization of an acrylonitrile spill; Ohio
Environmental Protection Agency, Dayton, Ohio, pp. 187-189.

Keith, L.A. and W.A. Telliard, 1979.  Priority pollutants, I-A perspective
view; Environmental Science & Technology, vol. 13, no. 4, pp. 416-423.

Kobayashi, H. and B.E. Rittmann, 1982.  Microbial removal of hazardous organic
compounds; Environmental Science & Technology, vol. 16, no. 3, pp. 170A-183A.
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Lippencott, W.T., A.B. Garrett and F.H. Verhoek, 1978.  Chemistry; John Wiley &
Sons, pp. 646-697.

Office of Technology Assessment, 1984.  Protecting the nation's groundwater
from contamination, vol. 1, 2; U.S. Congress, Washington, D.C., 503 pp.

Page, A.L., 1974.  Fate and effects of trace elements in sewage sludge when
applied to agricultural lands; U.S. EPA-670/2-74-005, Office of Research and
Development, 96 pp.

Sawyer, C.N. and P.L. McCarty, 1978.  Chemistry for environmental engineering;
McGraw-Hill, pp. 94-163.

Solomons, T.W., 1980.  Organic chemistry; John Wiley & Sons, pp. 634-639.

Tabak, H.H., S.A. Quave, C.I. Mashni and E.F. Earth, 1980.  Biodegradability
studies with priority pollutant organic compounds; Staff Report, Wastewater
Research Division, U.S. EPA Research Center, Cincinnati, Ohio, 42 pp.

Tolman, A., A.  Ballestero, W. Beck and G. Erarich, 1978.  Guidance manual for
minimizing pollution  from waste disposal sites; U.S. EPA-600/2-78-142, pp.
328-331.

Weast, R.C., editor,  1983.  CRC handbook of  chemistry and physics; CRC Press,
Inc., 2303 pp.
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                                 APPENDIX C

                   SOURCES OF GROUND-WATER CONTAMINATION  '

     The quality of the ground water may be altered by a wide variety of
human activities and naturally occurring phenomena.  The innumerable waste
materials and byproducts of man's activities provide potential for
ground-water contamination through a variety of mechanisms.

     Ground-water quality problems that are attributed to man's influence
are commonly related to:  (1) water-soluble products that are placed on the
land surface and in streams or surface impoundments, (2) substances that
are deposited in the ground above the water table, and (3) disposal,
storage, or extraction of materials below the water table (Lehr et al.,
1976).  Sources of ground-water pollution are associated with a broad range
of industrial, agricultural, commercial and domestic activities.  Many of
the problems that arise from wastes as a result of these activities are not
well understood, due to their complexity.  Technical solutions are
available for many ground-water quality problems through planning,
management, and/or prevention practices.

     The application of a rating system designed to estimate potential for
ground-water contamination is of concern with regard to individual
contamination situations.  Because ground-water contamination may occur
from a variety of sources, it may be necessary to consider and possibly
reevaluate the importance of a rating factor as the scale of the area being
evaluated changes.

     Soil attenuation characteristics such as sorptive capabilities,
microorganisms, degradation capacities and textures are of major importance
when considering the placement of wastes on the surface of the land (e.g.
stockpiles, sludge, wastewater) and the subsequent potential for
ground-water pollution.  However, the effect of soil is relatively
unimportant for situations where the soil has been removed,  such as at a
landfill, or where contaminants are buried beneath the soil  surface (e.g.
storage tanks).  Thus, engineering and other practical considerations of an
area can obviate the application of DRASTIC parameters.

     Dry contamination sources that are implaced on the land surface, such
as stockpiles, fertilizers and pesticides are dissolved and  disseminated by
rainfall resulting in the generation of ground-water pollution.  Evaluation
of the DRASTIC parameters suggests that the most important parameters with
regard to this category of activities are:  Depth to Water,  which controls
contact time of the pollutant with the unsaturated zone; Net Recharge,
which limits the quantity of leachate generated; Soil Media, which affects
boLh organic and inorganic attenuation mechanisms; and the Vadose Zone
Media, which also directly affects attenuation properties.  Parameters of

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lesser impact for this category of activities include:  Aquifer Media and
Hydraulic Conductivity of the Aquifer, since these are impacted less by
surface-applied pollutants.  Topography may be important for surface
storage facilities, but most agricultural activities are confined to
relatively flat terrain.

     Wet contamination sources emplaced on the land surface include
wastewater, irrigation water and spills.  In this situation, the most
important parameters are Depth to Water, Soil Media, Impact of the Vadose
Zone Media and Topography which will affect the attenuation and
infiltration rates of the liquid contaminants.  Again, because the source
is on the surface, Hydraulic Conductivity of the Aquifer and Aquifer Media
are less important.  Net Recharge has a less negative effect since the
contaminant is already liquid.  High net recharge may result in dilution.

     This type of rationale can also be applied to either liquid or dry
sources emplaced below the surface which may or may not intersect the water
table.  The potential for liquid sources below the water table to cause
contamination, such as leaking underground storage tanks or drainage wells,
is affected primarily by the Depth to Water, the Impact of the Vadose Zone
Media, Hydraulic Conductivity of the Aquifer, and the Aquifer Media.  These
factors are directly related to attenuation and migration rates of the
contaminant.  Surface characteristics such as Topography, Net Recharge and
Soil Media would subsequently be of lesser importance for potential
pollution evaluations.

     Lastly, for dry contaminant sources emplaced below the surface (e.g.
landfills and quarries) it is necessary to consider Net Recharge in terms
of volumes of leachate generated; the Hydraulic Conductivity of the Aquifer
in relation to migration rates; and Aquifer Media for possible attenuation
of contaminants, dispersion, dilution and routing.  Again, surface
characteristics are of lesser importance; Topography, Soil Media, and
Impact of the Vadose Zone Media.

     Thus, man's activities and the intensity of these activities present
many potential contamination problems.  The impact of these activities is
discussed in Section 6, Impact - Risk Factors.  Activities are not directly
involved in the determination of the DRASTIC Index, but their impact is
always of serious concern.  These activities may be categorized according
to their relative position with respect to the ground water; Table 11
represents a comprehensive list of activities that are potential sources of
contamination and their respective modes of emplacement.  Each of these
sources will be discussed individually in relation to their effects and
potential for ground-water contamination.

GROUND WATER QUALITY PROBLEMS THAT ORIGINATE ON THE LAND SURFACE

Land Disposal

     One of the major causes of ground-water pollution is the disposal of
solids or liquid waste materials directly onto the land surface in either
individual deposits or spread over the land.  Any soluble products present
in the waste can be transported into the ground water either with the

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liquid portion of the wastes or as a consequence of precipitation.  Land
disposal practices include the application of sewage sludge, manure,
garbage, industrial wastes, waste tailings and spoil piles.  These
activities are capable of producing a wide variety of contaminants,
including organic chemicals, inorganic chemicals and reactive ions.

Stockpiles and Mine Tailings

     The presence of material stockpiles, mine tailings and spoils poses a
potential source of ground-water contamination.  Contamination of ground
and surface water occurs from the infiltration of precipitation, seepage of
leachate into the subsurface and from runoff into streams and rivers.  The
Office of Technology Assessment (1984) estimates that approximately 20
percent of total mining materials production is stored in stockpiles.
Commonly stockpiled materials that may affect ground-water quality include
salt, coal, various metallic ores (e.g. copper, uranium, titanium,
vanadium, silver, lead, zinc), phosphates and gypsum (Koch et al., 1982).

     Because these stockpiles are commonly stored uncovered, precipitation
falling onto the stockpiles may dissolve or react with soluble constituents
to produce leachate that can percolate into the ground water or runoff to
surface streams and water bodies.  In particular, sulfide bearing minerals,
including coal, lead, zinc, molybdenum, nickel and copper stored as ore
stockpiles are capable of producing sulfuric acid from reactions with
infiltrated water.  The acidic leachate produced also may dissolve other
constituents from the ores of these minerals.  Coal which is used
extensively by electric utilities, coke plants and industrial users is the
most commonly stockpiled mineral.  Koch et al. (1982) estimated coal
stockpiles alone at 185 million tons in 1980.  Table C-l lists substances
present in coal piles which have the potential to leach into the ground
wa ter.
              TABLE C-1. &1AJOR SUBSTANCES PRESENT IN COAL ORE STOCK-
                       PILES AND SPOIL PILES (AFTER KOCH ET AL.,1982)
Major Constituents
Aluminum
Iron
Calcium
Magnesium
Sodium
Potassium
Manganese
Sulfur
Phosphate




Trace Amounts
Arsenic
Cadmium
Mercury
Lead
Zinc
Uranium
Copper
Cobalt
Antimony
Barium
Beryllium
Boron
Selenium
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Mining

     The disposal of mining wastes through spoil piles and tailings can
also degrade the quality of ground water.  Both types of waste are usually
stored on the land surface and exposed to weathering and precipitation.
Water moving through the waste piles will mobilize many hazardous
constituents, depending on the nature of the materials and the chemical
conditions within the pile.

     Spoil piles are composed of the disturbed soils and overburden from
surface mining, and the waste rock removed from underground mining (Miller,
1980).  Some reclamation techniques use spoils to reclaim the area after
mining, but in the past the mined areas were often left in their original
state.  The principal contaminants generated from mine wastes include
acids, dissolved solids, metals and radioactive materials.

     The generation of acid mine drainage and related contaminant products
is associated with the mining of coal and other sulfide-bearing minerals.
Upon exposure to the atmosphere, iron sulfides associated with coal and
mineral ores oxidize and produce soluble hydrous iron sulfates.  Water from
precipitation and run-off react with the sulfates to produce sulfuric acid
and ferrous sulfate, decrease the pH of the water and release substantial
quantities of iron to the water (Miller, 1980; National Research Council,
1981).  Acid formation may also be influenced by the presence of certain
species of iron bacteria which catalyze and accelerate the oxidation rate
above that typically found in natural systems (Koch et al., 1982; National
Research Council, 1981; Atkins and Pooley, 1982).  Accelerated acid
formation and lower pH will enhance the dissolution of metals frequently
associated with metallic ore deposits such as copper, zinc, cadmium,
aluminum and manganese.  Common minor elements may be released through
dissolution, complexation and colloidal suspension contributing to total
dissolved solids and turbidity (National Research Council, 1981).  In
addition to the trace constituents listed in Table C-l, other trace
compounds associated with coal and sulfide mining include: nickel,
zirconium, titanium, rubidium, lithium, chromium, gallium, germanium,
lanthanum and tungsten (Miller, 1980; National Research Council, 1981).

     Acid mine drainage from coal spoil piles alone represents a
significant threat to ground-water quality in areas where coal reserves are
mined  (National Research Council, 1981).  Degradation of ground-water
quality from mine spoils has also been documented at lead-zinc mines
(Sheibach et al., 1982; Miller, 1980; Hardie et al., 1974), and uranium
mines  (Kaufman et al., 1975; Williams and Osiensky, 1983).

     The presence of limestones and dolomites in mining areas, particularly
in the western states, serves to neutralize acid mine drainage which
develops from spoil piles.  Under basic conditions most heavy metals form
insoluble salts, however, the water can still be highly mineralized due to
an increase in sulfate salts of calcium, magnesium and sodium.
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     The total Impact of mine spoils is dependent on the mineralogic
characteristics, size and configuration of the spoils, the climate of the
area, the hydrogeology of the mine site and the control technology
implemented at the site to prevent the development and infiltration of
leachate.  Ground-water contamination from mine spoils leachate has been
documented at several sites (Van Voast et al., 1974; McWhorter et al.,
1974; Mele et al., 1982; Walker, 1973; Ricca and Schultz, 1979; Schubert,
1979).

     Tailings piles and ponds result from the disposal of mining wastes
generated from the on-site processing operations of cleaning and
concentrating the ore.  Tailings are transported as a slurry from the
processing site via ditch or pipeline to the tailings pond along with
process wastewater and mine drainage.  The suspended solids in the slurry
are allowed to settle to the floor of the ponds.  The remaining wastewater
is either recovered for reuse, lost to evaporation, discharged to surface
streams or infiltrates to the ground water.

     Tailings ponds may be located in natural depressions or in constructed
excavations with perimeter dikes to contain the liquids.  Tailings ponds
are typically unlined, allowing for unrestricted seepage into the ground
water (Miller, 1980).  Some tailings may be used to construct the pond
embankments if the materials are capable of preventing pond leakage and
supporting the weight of the structure to minimize embankment failure
(Williams, 1975).  Fully sedimented tailings ponds are usually abandoned,
and the remaining tailings piles are left uncovered.  Precipitation that
infiltrates these deposits may dissolve soluble constituents and carry
these contaminants into the ground water.  Ground-water contaminants
associated with tailings piles and ponds include acids, metals, dissolved
solids and radioactive materials.

     The process of ore concentration or beneficiation typically utilizes
the techniques of flotation and acid/alkaline extraction (Williams, 1975).
Spent acid (sulfuric) or alkaline (sodium carbonate and biocarbonate) leach
liquids are often discharged to the tailings ponds in addition to minerals
associated with the metallic compound being recovered. The major dissolved
species found in tailings ponds wastewater includes sulfate, iron,
aluminum, sodium, chloride, manganese, calcium and magnesium; minor amounts
of arsenic and selenium may also be present (Williams and Osiensky, 1983).
Depending on the specific metal being recovered and the chemical nature of
the waste stream, other metals may be found as dissolved or suspended
species in the tailings ponds.  Waste disposal from uranium-thorium mills
may contain dissolved radionuclides of radium, thorium, uranium and lead.
The typical pH of tailings ponds averages 1.8 for acid leach extraction and
10.2 for alkaline leach processes (Williams and Osiensky, 1983).

     Incidences of ground-water contamination from seepage through tailings
ponds and piles has been documented.  Contamination from uranium mill
tailings has been found in the Grants Mineral Belt, New Mexico (Kaufmann et
al., 1975; McLin, 1982; Thompson et al., 1984; Longmire, 1984), as well as
in Colorado, Wyoming, Utah and Washington (Williams and Osiensky, 1983;
                                    383

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Young et al., 1986).  Hydrologic investigations at some sites have
discovered contamination severe enough to prompt the implementation of
ground-water "pumpback" systems by the Nuclear Regulatory Commission.
Ground-water pumpback systems intercept the contaminant plume, withdraw the
water and return it to a tailings or evaporation pond (Williams and
Osiensky, 1983).

     Additional examples of contamination can also be found in the
literature.  For example, early day lead-zinc mining operations coupled
with present-day mining activities are now affecting ground-water quality
at several sites in the Coeur d'Alene district in Idaho (Mink et al., 1971;
Norbeck et al., 1974).  Gold and silver tailings ponds in Nevada and South
Dakota have contaminated the local ground water with cyanides, sulfates,
chlorides, metals and dissolved solids (Thompson et al., 1984).  Clay slime
ponds from phosphate mines in Florida have increased concentrations of
phosphorous, chloride, fluoride and total dissolved solids in the water
table aquifer near mine disposal areas (Thompson, et al., 1984).

Salt

     The improper storage of road salt for highway de-icing has caused
contamination problems in many of the Midwest and Northeastern snowbelt
states.  Although pure salt is usually stored in watertight buildings, the
source of contamination is often uncovered piles of mixed sand and salt at
highway maintenance lots.  An average size sand-salt pile contains 3000
cubic yards of sand and 150-250 tons of salt (Williams, 198A).  The salt is
usually commercial rock or marine salt with ferric ferrocyauide and sodium
ferrocyanide added to reduce caking of the salt piles.  Chromate and
phosphate may also be added to reduce the corrosivity of the  salt (Bouwer,
1978).  Salt additives may also contribute to ground-water contamination;
sodium ferrocyanide is water soluble and can generate cyanide when exposed
to sunlight, while chromate can produce high concentrations of hexavalent
chromium in run-off water (Field et al., 1974).

     The dissolution of salt in sand-salt piles and subsequent infiltration
into the ground water has caused elevated levels of chloride  in more than
150 domestic wells in the state of Maine (Williams, 1984; Williams, 1986).
Contaminant plumes generated by sand-salt storage piles have  been
successfully delineated through the use of resistivity  soundings and
terrain conductivity profiling (Williams et al., 1984).  Chloride
contamination of domestic wells from sand-salt  piles has also been
documented in Massachusetts, Michigan and Connecticut (Field  et al., 1974).
A five-year study in Monroe County, West Virginia showed an increase of
chloride in wells located 1500 feet away from a stockpile (Wilmoth, 1972).
When the salt piles were enlarged, an  increase  of chloride concentrations
in the ground water sampled from the wells was  noted.   Conversely, removal
of the salt piles caused chloride levels in the wells to decline within  two
months.

Disposal of Sewage and Sludge

     The collection, treatment and disposal of  large quantities of
municipal and industrial wastewater constitutes a major problem in many

                                    384

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communities.  Towns with older combined sanitary and storm water collection
systems are often confronted with a hydraulically overloaded treatment
facility during periods of heavy runoff or meltwater.  Deicing salts,
litter and other street debris from storm water runoff may also adversely
impact the operation of the treatment facility.  Land application of
stabilized wastewater and sewage sludge is often used as an alternative to
more costly conventional treatment and disposal processes.

Wastewater

     The adverse impact of sewage disposal on ground-water quality can
originate during the collection and transport of sewage to the treatment
facility.  Sanitary and storm water sewer systems are designed to provide a
watertight passage for the conveyance of waste to a treatment facility.  If
the sewer pipe is non-watertight, sewage may either leak out of the pipe or
ground water may infiltrate into the pipe.  Where ground-water levels are
lower than the wastewater level in a cracked pipe, the wastewater can
impact the ground-water quality by leakage into the ground.  As an example,
ground-water contamination by nitrates from leaky sewer systems has been
documented on Long Island, New York (Kimmel, 1972).  Conversely where
ground-water levels are higher than the wastewater level in the pipe,
leaking pipes allow ground water to enter the pipe.  This additional volume
of water must be treated at the treatment facility and may cause
overloading of the system.  Overloading the system may result in inadequate
treatment of the effluent or bypassing of certain treatment phases before
discharging to surface water.

     In addition to leaking sewers, another inadvertent impact of sewage on
ground-water quality may be infiltration from wastewater stabilization
ponds.  Wastewater stabilization ponds are primarily used for settlement of
suspended solids and biological treatment of primary and secondary
effluent.  The function of the ponds will vary depending on the basic
design, but commonly employs biological treatment under aerobic and/or
anaerobic conditions (Miller, 1980).  Leakage from unlined ponds may be
significant and cause potential pollution problems.  The presence of
detergents and nitrates have been detected under waste stabilization ponds
in sandy to silty soils (Preul, 1968).

     Impacts on ground-water quality by sewage disposal may also occur as a
result of the intentional land application of wastewater.  The use of
disposal practices may include discharging partially treated wastewater to
the land surface for final treatment in disposal, the application of
treated effluent for ground-water recharge and the irrigation and
fertilization of agricultural land.  Degradation of water quality occurs
when the effluent infiltrates into the ground water without sufficient
attenuation of desirable constituents.

     Land spreading of wastes for the purposes of treatment, irrigation,
and recharge is achieved by three basic application techniques:  1) spray
irrigation, 2) overland flow and 3) infiltration-percolation basins.
Irrigation of croplands using sewage effluent may be accomplished through
the use of sprayers, ridge and furrow or flood techniques.  The type of


                                   385

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irrigation system utilized is dependent on soil permeability, topography,
crop type and cost (Pound and Crites, 1973).   Loading rates are calculated
based on crop nutrient uptake, soils, climate and wastewater
characteristics.  Typical loading rates range from 1.5 to 4.0 inches per
week.  In general, effluent irrigation is capable of removing significant
amounts of nitrogen, suspended solids and fecal coliform (Pound and Crites,
1973; Murphy, 1986).  Soils with significant organic and clay content have
been shown to attenuate heavy metals, phosphorous and certain types of
viruses through adsorption and complexation (Pound and Crites, 1973;
Keswick and Gerba, 1980).  Sandy and silty loam soils at slow rate
irrigation test sites have been shown to remove trace organic constituents
in wastewater through adsorption, biodegradation and volatilization
(Parker et al., 1984).  However, ground-water contamination from nitrates,
phosphorous, chlorides and fecal coliform during irrigation have also been
documented (Barker, 1973; Sawhill, 1977; Reichenbaugh et al., 1979; Franks,
1981).

     Overland flow techniques are suitable for soils with limited
permeability such as silts and clays.  Wastewater flows sheetlike over a
vegetated surface and runoff must be collected.  Overland flow systems have
provided effective removal of BOD, suspended solids, nitrogen and partial
removal of phosphorous through crop fixation, biological uptake and
adsorption (Pounds and Crites, 1973).

     Infiltration-percolation of treated effluent in spreading basins has
become a popular mode of disposal for waste treatment and ground-water
recharge.  Successful use of infiltration-percolation systems requires
soils with infiltration rates of 4 inches per day to 2 feet per day or more
(Pound and Crites, 1973).  Infiltration systems may be low rate (4 to 60
inches per week) or rapid rate (5 to 10 feet per week) systems.  Rapid rate
infiltration systems generally require pretreated or secondarily treated
wastewater to maintain a high loading rate.  Spreading basin surfaces may
contain bare soils, gravel or vegetation.  The intermittent inundation of
spreading basins has proven successful for maintaining aerobic/anaerobic
conditions for  removal of nitrates,  phosphorous, BOD, suspended solids and
fecal coliform  (Bouwer et al., 1972).

     The attenuation and removal of  wastewater constituents has been shown
to occur by  the processes of filtration, chemical transformation,
adsorption,  dilution and biodegradation (Bouwer et al.,  1972; Borrelli et
al., 1978; State of California,  1978; Idelovitch et al., 1979; Baxter and
Clark, 1984).   The removal of trace  organics through biodegradation,
sorption and volatilization at rapid rate infiltration sites has also been
demonstrated (Bouwer et  al.,  1981; Hutchins and Ward, 1984; Parker et al.,
1984).

     Certain contaminants, however,  are not  totally attenuated  in  the
subsurface.  Ground-water contamination from rapid rate  infiltration sites
has  caused increased elevations  in dissolved solids and  detergents  (Hughes
and  Robson;  1973; Van der Leeden et  al.,  1975; Fujioka and Lau, 1984),
                                    386

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nitrates, phosphorous (Baxter and Clark, 1984), trace organics (Tomson et
al., 1981; Bedient et al., 1983), and bacteria and viruses (Keswick and
Gerba, 1980; Moe et al., 1984).  The discharge of primary sewage effluent
has caused ground-water  contamination at several treatment sites in England
(Baxter, 1985).  Table C-2 illustrates the effects of ground-water recharge
by municipal effluent on a calcareous sandstone separated by silt and clay
layers in the Dan Region, Israel (Idelovitch et al., 1979).

     Municipal and industrial wastewater can be classified according to
their physical, chemical and biological characteristics.  Table C-3 lists
municipal wastewater characteristics at various stages of treatment (Pound
and Crites, 1973).  Industrial wastewater contains many of the same
constituents as municipal wastewater but varies by industry, product and
the processing technique utilized (Pound and Crites, 1973).  Wastes
produced by chemical-related industries exhibit a wide variability in waste
constituents and may contain any number of organic compounds.

Sludge

     Sludge is the by-product or residue from the chemical, physical or
biological treatment of  industrial and municipal waste.  Municipal sludge
contains a mixture of sewage from metabolic wastes, industrial wastes,
household wastewater, and in some cases, storm water run-off.  The
composition of municipal sludge typically contains partially decomposed
organic compounds, inorganic salts, heavy metals, bacteria and viruses.
Industrial sludge compositions may vary widely depending on industry type
and waste treatment practice.  The constituents of concern relative to
ground-water contamination in typical municipal sludge include:  nitrogen,
phosphorous, heavy metals and trace metals, organic compounds and
pathogens.

     The most common disposal method for municipal and industrial sludge is
land spreading of waste or placement in a sanitary landfill.  Land
spreading is the application of solid or liquid sludges to forested or
agricultural lands.  Sludge can also be utilized for land reclamation in
strip mine areas.

     The nitrogen content of municipal sludge varies from 1 to 7 percent
according to the type of sewage treatment utilized.  Approximately half of
this amount occurs as organic nitrogen and the other half as ammonia which
is directly available for uptake by plants (Knox, 1979; Miller, 1980).  In
addition, organic nitrogen is converted to ammonia by mineralization at a
rate of 15 to 30 percent the first year and 3 percent per year thereafter.
Nitrogen applied in excess of crop uptake is available for leaching into
the ground water.  The factors which affect nitrogen absorption into the
environment and thus the rate of application of the sludge are:
volatization, denitrification, climate, soil and crop type.  Research
indicates that proper farm management practices allow for repeated sludge
applications with minimal nitrate impact on ground water (Higgins, 1984;
Wengel and Griffin, 1979).  Municipal sludge applications have also
resulted in nitrate contamination problems in the ground water (Wengel and
Griffin, 1979; Higgins,  1984).


                                    387

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TABLEC-2.COMPARISON OF EFFLUENT QUALITY PRIOR TO RECHARGE AND AFTER FLOW TO
         OBSERVATION WELLS (IDELOVITCH ET AL., 1979)
Parameter
Basic Wastewater
BOD
COD
DOC
KMn04 Consumption
Ammonia, as N
Total Nitrogen
Phosphorus
Irrigation
Chloride
Electrical conductivity
Sodium
SAR
Boron
Copper
Fluoride
Selenium
Drinking
Detergents
Hardness, as CaC03
Calcium
Nitrate, as N
Fluoride
Copper
Selenium
Cadmium
Lead
Phenol
Units

mg/l
mg/l
mg/l
mg/l
mg/l
mg/l
mg/l

mg/l
/Limhos/cm
mg/l
mg/l
/ug/l
Aig/l
/ug/i
//g/t

mg/l
mg/l
mg/l
mg/l
ug/\
jug/i
/>g/i
W3/I
/wg/i
Aig/i
Recharge Effluent3

8
50*
15
13
3
4c-10d*
1

205b
950
152b
6.5"
460
16
300
7

1.4
103
36
0.11
300
16
7
4
25
5
Effluent in Observation
Wells 61 & 63

<1
6-20
1.5-4.5
1.5-5
<0.02
2-8
0.005-0.060

175-240
920-1070
25-170
0.8-6.5
40-430
3-4
<100
1

<001-06
120-440
40-150
06-7
<100
3-4
1
3
10-25
<1-4
aWeighted average — January 1977 to December 1978
b Weighted average — January 1977 to August 1978
cApproximate average — June to September, 1977 and 1978
Approximate average — December to March, 1977 and 1978
'Based on results from Tahal Laboratory, Azur
                                   388

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TABLE C-3. MUNICIPAL WASTEWATER CHARACTERISTICS (POUND AND CRITES, 1973)
mg/L (except as noted)
Constituent
Physical
Total solids
Total suspended solids
Chemical
Total dissolved solids
pH, units
BOD
COD
Total nitrogen
Nitrate-nitrogen
Ammonia-nitrogen
Total phosphorus
Chlorides
Sulfate
Alkalinity (CaCO3)
Boron
Sodium
Potassium
Calcium
Magnesium
Sodium adsorption ratio
Biological
Cohform organisms, MPN/100 ml
Virus PFu/L
Untreated
Sewage

700
200

500
7 0+0.5
200
500
40
0
25
10
50
—
100
—
—
—
—
—
—

106
0-1 04
Typical Secondary
Treatment Effluent

425
25

400
70±05
25
70
20
—
—
10
45
—
—
1.0
50
14
24
17
2.7

—
0-102
Actual Quality
Applied to Land

760-1,200
10-100

750-1,100
68-81
10-42
30-80
10-60
0-10
1-40
7.9-25
40-200
107-383
200-700
0-1 0
190-250
10-40
20-120
10-50
4.5-7.9

2.2-1 06
—
                                 389

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     Phosphorous is found in municipal sludges at lower concentrations than
nitrogen.  Phosphorous is not a threat to ground-water quality because
phosphorous that is not immediately utilized by plants is attenuated
through fixation by soils.

     The heavy and trace metals content of sludge varies with the types of
wastes accepted at treatment facilities.  Heavy metals present in domestic
sewage are derived from:  1) metals excreted by humans (including chromium,
cobalt, copper, iron, manganese, molybdenum, selenium and zinc), 2) metals
from the dissolution of plumbing (lead, copper, and zinc) and 3) metals
present in storm runoff (cadmium, lead and zinc).  A variety of heavy
metals and trace constituents may be added by industrial wastes.

     The metals of most concern for land application purposes include lead,
copper, zinc, nickel and cadmium.  The total concentration of these metals
will limit the length of time an area may receive sludge.  The removal of
heavy metals in soils is dependent on the organic content of the soils,
soil texture and pH.  Metals are removed primarily through adsorption by
anion and cation exchange or chelation by organic compounds (Knox, 1979).
Certain metals are utilized by plants during the growth cycle, while others
in increasing concentrations become toxic to both plants and humans that
consume the plant products.  Leaching of metals may occur when the sorption
capacity of the soil is exceeded or when other chemical factors affect
metal solubilities.

     Pathogenic organisms, primarily bacteria and viruses associated with
domestic sewage, may be present in municipal sludge.  The ability of
nathogens to contaminate ground water depends on survival and transport of
the organism through the soil system.  The survival of pathogenic organisms
in the subsurface is influenced by organism type, soil texture, moisture
temperature and the presence of antagonistic organisms (Keswick and Gerba,
1980; Knox, 1979; Gerba, 1985).  The migration of pathogenic organisms is
dependent on the permeability and composition of the soil and vadose zone,
pH, subsurface flow rate and presence of soluble organics and cations.
Research indicates that bacteria and virus removal occurs primarily through
the processes of filtration and adsorption (Keswick and Gerba,  1980; Gerba,
1985).  Despite the presence of these processes, bacteria and viruses have
been detected in both the vadose zone and ground water beneath  sludge
application sites (Miller, 1980; Keswick and Gerba, 1980; Gerba, 1985).
Stabilization or pre-treatment of sludge prior to application may
significantly reduce the potential for  the migration of pathogens into the
subsurface.  In some cases, land application of sludge has proven effective
in removing certain bacteria and viruses (Freeze and Cherry, 1979; Bouwer,
1978; Miller, 1980; Knox, 1979).
                                    390

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     Several industries commonly employ land spreading for the disposal of
sludges and wastes.  For example, the canned fruit and vegetable industry
produce wastes such as simple carbohydrates, starch and cellulesic
substances that are readily biodegradable.  The petroleum refining industry
generates sludges that contain not only oily wastes, but also oil-free
sludges resulting from water conditioning.  Chemical sludges are produced
from the refining process, and biotreatment sludges are generated during
the pretreatment waste processes.  Many of these wastes are biodegradable
by soil microorganisms or are useful for soil conditioning (Knowlton and
Rucker, 1979).  However, heavy metals present in refinery sludges may
effectively limit land application of these wastes.  Fly ash and water
treatment additives are common wastes from the coal fired, steam electric
power industry.  Fly ash is often used as soil conditioner, but land
application may be limited by the boron and heavy metal content of the ash.
Wastes produced from the pulp and paper industry include natural organic
compounds such as sugars, tannins, resins and lignins as well as inorganic
sulfur compounds.  Pulp and paper sludges are commonly land spread because
of their biodegradability.

Salt Spreading

     The application of large quantities of anti-skid sand and de-icing
salt to improve winter driving conditions has become a common practice in
many of the snowbelt states.  Excessive salt application to-highways has
increased levels of chlorides, sodium and other related constituents in
ground water.  In addition to direct dissolution of the salts on the road
surface and roadside by precipitation, accumulated  snow piles along
roadsides can release constituents during melting periods to road surface
runoff.

     The de-icing salts consist principally of commercial rock salt and
marine salt (Bouwer, 1978).  The addition of calcium chloride for chemical
de-icing has become more widespread, particularly in Europe, due to its
superior ice control properties.  Common salt or sodium chloride is
ineffective for melting ice below -12°C; whereas, the addition of calcium
chloride extends the melting range to -29°C (Jones, 1981).  As an additive
to common salt, calcium chloride improves the rate  and extent of melt,
prevents freezing of sand-salt mixtures and reduces salt loss from
mechancial bouncing off the road during application.

     Other types of additives are commonly blended  with the sand-salt
mixtures to increase useability.  Ferric  ferrocyanide and sodium
ferrocyanide are often added to sand-salt piles to  minimize caking during
storage and application (Field et al., 1973).  Sodium ferrocyanide is water
soluble and can generate cyanide in excessive concentrations in the
presence of sunlight.  Chromate and phosphates are  also added to de-icing
salts as corrosion inhibitors.  Consequently, increased levels of sodium
chromate, hexavalent chromium and table chromium were detected in snowbelt
samples during the winter of 1965-66 in the Minneapolis - St. Paul area
(Field et al., 1973).
                                    391

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     A recent study suggests that certain elements present in sampled
snowmelt could be correlated to the source of the sand and salt applied
(Oberts, 1986).  Increased levels of lead, zinc, phosphorous and total
dissolved solids were detected in sand-salt mixtures sampled in the
Minneapolis metropolitan area.  The source of dissolved solids and
phosphorous appeared to be related to local quarries where the sand was
acquired.  Levels of lead and zinc were correlated with salt concentrations
in the sand/salt mixtures.  The source of salt for the area was from
various suppliers in the southern United States.

     Serious ground-water contamination problems have occurred in many
areas of the northern United States from the application of de-icing salts.
The state of New Hampshire in 1965 reported replacement of over 200
roadside wells due to increased concentrations of chloride and sodium from
contamination by road salts (Field et al., 1973).  Road salt contamination
has occurred in more than 60 communities in Massachusetts, as well as in
Maine, Connecticut, Michigan and Ontario (Field et al., 1973; 1974; Pollock
and Toler, 1973; Miller et al., 1974; Jones, 1981).  Seasonal fluctuations
in chloride concentrations have been documented due to infiltration of
runoff during spring melt periods (Miller et al., 1974).

     Alternative practices to reduce the amounts of de-icing salts applied
to highways are currently being implemented and evaluated.  These include
the development of effective management strategies combined with optimum
mixture and application plans as related to the physical conditions of
weather and the road surface.  Improved highway drainage systems to prevent
the infiltration of road runoff are currently being evaluated in
Massachusetts  (Pollock and Stevens, 1985).  The development of experimental
road surfaces, such as Verglimit (a chemical defroster added to the upper
layer of asphalt), which reduce the bonding of  ice  to road surfaces, may
also allow for a reduction in the use of de-icing salts (Jones, 1981).

Animal Feedlots

     Leachate  from large quanitites of animal wastes at feedlots or seepage
from animal waste lagoons are point sources of contamination.  The
principal contaminant from animal waste is nitrogen in the form of organic
nitrogen or ammonium.  Nitrogen in these  forms  is readily oxidized in the
vadose  zone to produce nitrates.  Other contaminants of concern include
phosphates, bacteria and chlorides.  The  characteristics of the
contaminants generated from animal feedlots will vary depending on feedlot
management practices, feeding methods, feedlot  surface (paved or unpaved)
and slope  (Miller, 1980).

     The most  significant volume of wastes are  produced by cattle  feeding
operations, however, sheep, poultry and hog operations also represent
potential  contamination  sources.  Cattle  feedlot operations are
concentrated throughout  the Corn Belt and  Northern  Plains regions; poultry
raising  is located primarily  in  the  South, hogs  in  the Midwest and sheep  in
the West and  Southwest  (Miller,  1980).  The  traditional disposal method  for
manure  is  land application as a  fertilizer and  soil conditioner.
                                    392

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     The potential for contamination from feedlots is dependent  on several
factors including the stocking rate, manure removal management and waste
treatment facilties.  Natural factors such as depth to water, soil texture
and permeability and the net recharge to ground water will  also  influence
the occurrence of contamination.  Frequent removal of manure combined  with
low stocking rates allows for increased aeration of manure, and  thus higher
rates of nitrate production (Walter et al., 1979).  Infrequent removal of
manure can alter the underlying soil characteristics by decreasing soil
permeabiity and infiltration capacity (Miller, 1971; Powers et al., 1975).
The development of an impermeable manure pack in addition to soil clogging
can restrict infiltration of leachate.  Studies suggest that the presence
of anaerobic conditions beneath the pack allow denitrification and may
limit the quanities of nitrate present in the ground water  beneath the
feedlots (Borman, 1981; Walker et al., 1979).                    ^~

     The variations in research regarding nitrate leaching  may be explained
partially through differences in soil properties.  In general,
coarse-textured soils have a greater potential for nitrate  movement after
waste application.  Finer-textured soils that exhibit restricted drainage
have a lower potential for nitrate leaching due to reduced  infiltration or
anaerobic conditions which cause denitrification (Powers et al., 1975).
Another factor which affects the potential for nitrate leaching  is climatic
conditions.  The potential for nitrate movement also increases with higher
rates of waste application.

     Contamination of ground water by phosphorous and bacteria beneath
feedlots has not yet been documented.  Phosphates bound to  organic
molecules or as nitrophosphates have low water solubilities. Bacteria
populations in soils that receive applied wastes increase initially, then
decrease with time (Kansas State University, 1975).  Ground-water
contamination from the leaching of nitrates, however, has been shown to
occur under animal feedlots and land application sites'(Powers et al.,
1975; Reddell et al., 1973; Walker et al., 1979;  Stewart et al., 1967;
Lorimor et al. , 1972; Ritter and Chirnside, 1984).  A ground- water quality
monitoring study in southern Delaware identified increased  nitrate
concentrations in ground water within 825 feet of poultry farms  in several
areas (Ritter and Chirnside, 1984).  Increased levels of chlorides and
copper in the ground water were also detected in the samples.  The
occurrence of these contaminants was correlated with the poultry farming
practice; animal and human wastes both contain chlorides while copper  is
used in the broiler feed.  Highest concentrations of all constituents  were
located in areas of well drained soils.

Fertilizers and Pesticides

     The increased use of agricultural chemicals during the past decade to
obtain greater crop yields has contributed to increased levels of nitrates
and pesticides in ground water in the United States and other agricultural
countries (Madison and Brunett, 1984; Hallberg, 1986; Holden, 198.6).   An
accurate characterization of the overall impact from agricultural nonpoint
source pollution has been difficult to assess due to the complex
interaction between crop management and tillage practices,  chemical type
and application, and soil and climatic conditions.

                                   393

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Fertilizers

     The addition of organic and inorganic fertilizers to agricultural
lands supplements the natural supplies of nutrients in the soils necessary
to sustain crop growth.  Organic fertilizers, such as solid and liquid
manure and compost, contain the essential nutrients (nitrogen, potassium
and phosphorous), as well as important growth-stimulators and microbes
necessary for proper utilization of the nutrients by plants (Houzim et al.,
1986).  Organic fertilizers typically account for 40 percent of the humus
component in agricultural soils.  Increased humus content of soils improves
soil water capacity, adsorptive capability and resistance to acidification.
Soils deprived of organic fertilizers exhibit losses in biological activity
and fertility over time.  Thus, organic fertilizers are combined with
inorganic fertilizers to provide optimum growth conditions.  Inorganic
fertilizers include nutrients such as nitrogen, potash and phosphate and
lesser amounts of fluorine, cadmium, calcium, magnesium, cobalt and
molybdenum (Houzim et al., 1986).  Lime and gypsum are also added to
farmland to reduce cumulative soil acidity.

     The solubility, adsorptive capability, decomposition and mobility of
fertilizers directly influence fertilizer impact on ground-water quality.
Most nitrogen fertilizers do not readily adsorb into soils and are
moderately to very soluble in water; thus, they are quickly leached to the
ground water under a variety of conditions and constitute a major concern
for contamination in agricultural areas (Hallberg, 1986).  Granulated,
coated and multi-component fertilizers dissolve more slowly than pulverized
fertilizers.  Phosphates and potash not assimilated by plants are readily
sorbed oato cl^iy particles or complexed with humus (Houzim et al. , 1986;
CAST, 1985; Letey and Pratt, 1984).

     Nitrogen movement  through the biosphere is controlled by a series of
complex processes.  In  general, most crops utilize nitrogen in the
inorganic form of nitrate or ammonium.  Organic nitrogen  in the soil  is
transformed into inorganic forms by microorganisms.  Ammonium is the  first
transformation compound.  In the presence of oxygen, the  subsequent
transformation to nitrate will occur.  Nitrate not utilized by crops  will
either continue  to leach through the soils under aerobic  conditions,  or be
converted to nitrogen gas through denitrification under anaerobic
conditions.

     Ground-water contamination problems are thus manifested when nitrate
concentrations in soils  exceed crop uptake and significant nitrate losses
occur beneath the root  zone.  Recent studies indicate  that nitrogen
recovery by agronomic crops seldom exceeds 50 percent  of  available nitrogen
and more typically approximates 35 percent or less for grain crops
 (Hallberg,  1986).  Extensive research  over the past several years has
clearly shown a  direct  relationship between  excessive  nitrogen
 fertilization and subsequent increases in nitrogen concentrations in  ground
water, particularly in  shallow, fresh  water  aquifers (CAST, 1985; Pionke
and Urban,  1985; Beck et al.,  1985; Thompson et al., 1986; Libra et al.,
 1986; Ritter, 1984).   Results  of these studies indicate  that  three major
 factors affect the concentration of nitrate  which reaches the ground  water

                                    394

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including:  1) the amount of nitrogen available, 2) the quantity of
infiltrating water (dependent on the hydraulic conductivity of the
materials), and 3) the presence of denitrification processes in the
subsurface.

     Increases in nitrogen concentrations have been related to agricultural
land practices in many areas of the United States (Beck et al., 1985; CAST,
1985; Letey and Pratt, 1984; Alberts and Spomer, 1985; Thompson et al.,
1986; Libra et al., 1986; Bruck, 1986; Detroy, 1986; Gburek et'al,, 1986;
Ritter, 1984; Pionke and Urban, 1985).  The implementation of best
management practices to reduce the quanitites of nitrate available for
leaching have been studied.  Suggested practices for nitrate reduction
include the determination of residual soil nitrates in the crop and rooting
zone coupled with the application of nitrogen during periods of greatest
crop intake (Olson, 1986; OTA, 1984).  A study involving nine Iowa farmers
showed how potential nutrient losses could be reduced by establishing
realistic yield goals in conjunction with best management practices (Kaap,
1986).  Other practices include improved irrigation water management to
prevent excessive percolation (Hubbard et al., 1984) and the use of
compounds which inhibit the oxidation of fertilizer ammonium to nitrate by
microorganisms (Bremner et al., 1986).  Agricultural practices such as
cropping and tillage can also affect nitrate losses to the subsurface.  The
continuous culture of nonleguminous crops, such as corn and cotton,
promotes the increased use of nitrogen fertilizers thus affecting nitrogen
losses through leaching to ground water.  Losses of nitrate can be
minimized by alternating the planting of nonleguminous crops with soybeans,
which utilize both organic and inorganic nitrogen and do not require
additional nitrogen fertilization (CAST, 1985).  Some studies suggest that
the implementation of conservation or no-tillage practices serve to
increase nitrate leaching (CAST, 1985; Thomas, 1983; Alberts and Spomer,
1985; Baker and Laflen, 1983).  Conventional tillage enhances the release
of nitrate from organic matter, but also promotes soil erosion.
Conversely, while conservation tillage reduces soil erosion, the soil
moisture is increased, and evaporation decreases (Blevins et al., 1983).
Although less nitrate is released than soil organic matter, increased
infiltration rates under conservation tillage fields provides the
conditions for greater losses of nitrate to the ground water.  In addition,
conservation tillage minimizes the disturbance of soil structure thereby
enhancing surface water infiltration through soil macropores (Thomas, 1983;
Dick et al., 1986).

Pesticides

     Pesticides are chemicals used for the control of insects, fungi or
other undesirable organisms and weeds.  At the beginning of the century,
the use of mercury and arsenical compounds for pest control became
widespread.  Pesticide usage rapidly increased with the advent of new
synthetic organic compounds.  There are currently more than 32,000
different compounds with over 1800 active ingredients now used for
agricultural applications (Houzim et al., 1986).  Recent United States
Environmental Protection Agency studies cite the presence of more than
50,000 different formulated products with only 1200 active ingredients


                                    395

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(personal communication,  Stuart Cohen, Biospherics,  Inc.,  1987).
Agricultural activities account for 69 to 72 percent  of  pesticide use;
government agencies  and industries use 21 percent; home  and garden uses
constitute the remainder.

     Despite the  large quantities of pesticides applied  yearly to
agricultural lands,  public attention had focused  on  other  sources of toxic
chemicals found in ground  and surface water.  Contamination from pesticides
was largely unexpected; those pesticides in use were  assumed to degrade or
volatize rapidly, or to bind to soil particles (Holden,  1986).  The
discovery of DBCP (dibromochloropropane) and aldicarb in wells in
California and New York respectively, in 1979, prompted  extensive
ground-water monitoring for pesticides which has  led  to  the discovery of at
least 17 pesticides  in ground water in 23 states  (Table  C-4) (Cohen et al.,
1986).
             TABLE C-4. TYPICAL POSITIVE RESULTS OF PESTICIDE GROUND-
                      WATER MONITORING IN THE U.S.t (COHEN ET AL, 1986)

Pesticide
Alachlor
Aldicarb (sulfoxide ana
sulfone)

Atrazine
Bromacil
Carbofuran
Cyanazme
DBCP
DCPA (and acid products)
1 ,2-Dichloropropane
Dinoseb
Dyfonate
EDB

Metolachlor
Metnbuzin
Oxamyl
Simazine
1,2,3-Tnchlorc-
propane
Use'
H
I, N


H
H
I, N
H
N
H
N
H
I
N

H
H
I, N
H
K
(impurity)
State (s)
MD, IA, NE, PA
AR, AZ, CA, FL, MA, ME.
NC, NJ. NY, OR, Rl, TX,
VA, WA, Wl
PA, IA, NE, Wl, MD
FL
NY, WI.MD
IA, PA
AZ, CA, HI, MD, SC
NY
CA, MD, NY, WA
NY
IA
CA, FL, GA, SC, WA, AZ,
MA. CT
IA. PA
IA
NY, Rl
CA, PA, MD
CA, HI

Typical
Positive, ppb
01-10
1-50


0.3-3
300
1-50
01-10 j
0.02-20
50-700
1-50
1-5
01
0 05-20 '

01-04
1 0-43
5-65
0.2-3.0
01-50

              tTotal ol 17 different pesticides in a total of 23 different states.
              * H = herbicide
               I = insecticide
               N = nematicide
                                     396

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     Numerous studies now document the relationship between the use of
agricultural chemicals and their occurrence in ground water, particularly
in areas located over shallow unconfined aquifers with permeable soils
throughout the country (Holden, 1986; Cohen et al., 1984; Cohen et al.,
1986; Hallberg et al., 1986; Welling et al., 1986; Schmidt, 1986;  Steichen
et al. , 1986; Pionke et al., 1986; Wehtje et al., 1984; Kelley et  al.,
1986; Harkin et al., 1986; Miller and Fischer, 1986; Tolman and Neil, 1986;
Marin and Droste, 1986; Scarano, 1986).  Pesticide contamination has also
been found in other hydrogeologically vulnerable areas such as karst
terrains (Leonard, 1986; Holden, 1986).  In contrast, a recent sampling  of
irrigation wells over time in intensively agricultural areas of silt loam
to clay soils in Arkansas revealed no positive presence of pesticides in
the ground water (Lavy et al., 1985).

     Attempts to accurately characterize pesticide fate and movement have
been complicated by the wide variability in soil and vadose zone
properties, climate, agronomic management and the physical and chemical
nature of every pesticide.  Seiber (1983) has grouped behavior and fate
processes according to three major components including:  1) the
environmental compartments (i.e. air, soil, water) in which the pesticide
is found; 2) the transfer processes which affect pesticide movement, and 3)
attenuation by transformation processes (i.e. chemical and biological
degradation.  Table C-5 lists the major factors which affect the fate and
movement of various pesticides based on their chemical classification.

     The properties of the soil media and the external effects of  climate
both influence the movement and transformation of pesticides in the soil.
The adsorptive capabilities of soil colloids and organic matter has been
recognized as an importan  factor in the attenuation of ionic and  nonionic
pesticides (Helling, 1986; Helling and Gish, 1985; Weber and Weed, 1974;
Weber, 1972).  Soil texture and the hydraulic conductivity of the  soil also
affect pesticide leaching.  Studies confirm that a pesticide introduced
into sandy coarse-textured soils will penetrate farther and faster than in
finer-textured soils (Helling and Gish, 1985; Weber and Weed, 1974;
Helling, 1986).  The presence of soil structure, (in particular, the role
of macropores), is being recognized as a possible rapid transport  mechanism
which reduces the opportunity for significant attenuation processes to take
effect (Thomas and Phillips, 1979; Shaffer et al., 1979).  Preferential
flow through soil structure has been found to occur in all types of soils
and accounts for solute transport several times greater than that
recognized by traditional transport theories.  Agronomic practices such as
conservation or no-tillage, which advocates minimal soil disturbance has
been shown to promote the development of extensive macropores in the soils.
The presence of the macropores was related to increased infiltration rates
in those fields under study (Dick et al., 1986; Gish et al., 1986).

     Increasing soil moisture content is generally associated with
increased adsorption and degradation.  The moisture and temperature of the
soil and soil pH, combined with climatic effects also influence pesticide
behavior directly through adsorption, volatilization and photo
decompositon, and indirectly through the chemical and microbial degradation
processes (Weber and Weed, 1974).

                                   397

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     The transfer and transformation processes which affect pesticides are
dependent on the physiochemical nature of the pesticide and the interaction
of these factors with the soil and climatic system.   These processes have
been reviewed by Sieber (1983), Cheng and Koskinen (1985) and Helling
(1986).  The significant properties which affect pesticide behavior
include: ionizability, water solubility, volatility, presence of functional
groups, molecular size and stability (Weber, 1972).   The leaching of
pesticides to ground water involves the consideration of both adsorption
and degradation. In general, pesticides which are absorbed by the soil are
not readily available for leaching; those pesticides not strongly absorbed
are then susceptible to microbial and chemical degradation.  For most
pesticide groups, the adsorptive capacity is directly related to
solubility; as pesticide solubility increases, adsorption to soil colloids
and organic matter decreases (Houzim, et al., 1986).  Cohen et al. (1984)
suggest that pesticides with the following mobility  and persistence
properties have the greatest potential to leach to ground-water:  1) water
solubilities greater than 30 parts per million, 2) soil binding constants
(Kd values) less than 5, 3) root zone half lives greater than 2 to 3 weeks
and 4) hydrolysis half lives of less than 6 months.   Table C-5, Column 11
ranks the mobility of various pesticides according to various groups.

     Pesticide fate is also influenced by agronomic  practices such as
tillage and irrigation.  As previously discussed, tillage practices
directly influence runoff and infiltration of pesticides.  Extensive
irrigation of fields also has been associated with increased pesticide
leaching below the root zone (Helling, 1986).  The use of improved
irrigation practices such as drip irrigation, helps prevent excessive water
percolation and subsequent pesticide movement into the subsurface.

Acciden tal S pi11s

     A variety of hazardous and non-hazardous materials are transported
throughout the country by truck, rail and aircraft and transferred at
handling facilities such as airports and loading docks.  Improper handling
or accidents often results in spills of these solutions.  Ground-water
contamination resulting from these spills constitutes a significant problem
which only recently has received attention by state, federal and  industrial
authorities.  The National Academy of Sciences  (NA.S) estimates that
approximately 16,000 spills occur annually, involving a variety of
materials such as hydrocarbons (i.e. gasoline and jet fuel), paint
products, flammable compounds, various acids and anhydrous ammonia (NAS,
1983).  Of all accidental releases, petroleum products are the most
frequently spilled or leaked (U.S. EPA, 1979b).

     The potential impacts of an accidental spill on ground-water quality
depends on:  1) the site specific hydrogeologic conditions, 2) the natural
capacity for attenuation and/or degradation of  the natural materials  at  the
site, 3) the characteristics of the chemical(s) spilled, and 4) any
remedial actions undertaken by authorities at the time of  the  spill.
                                    398

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TABLE C-5.  FACTORS AFFECTING ADSORPTION OF SELECTED GROUPS OF PESTICIDES AND THEIR LEACHING INTO GROUND WATER
           (HOUZIMETAL, 1986)

1 2
345
6 7
8
9 10
11
Adsorption to Bond to
Adsorption
I Chemical Group Mechanism
I Ionic Pest
1 Cationic Pest e/d/g
| 2 Acidic Pest f/g

3 Basic Pest c/d/e/f/g/

| 4 Miscellaneous g/
Ionic Pest

II Nonionic Pest
5 Chlorinated a/b/d/
Hydrocarbons
6 Organophosph a/b/c/d/e
W
CD 7 Substituted a/b/d/
*•' Anilines
8 Phenylureas a/b/c/d/f/
I
9 Phenylcarbonates and a/b/c/d/
Carbonates
10 Amides a/b/d/

1 1 Thiocarbonates alb/61
Carbothioates
Acetamides
1 12 Phenylamides a/b/d/
13 Benzunitnles a/b/d/
I
Column 2 a/ Van der Waals attractions
b/ Hydrophobic bonding
c/ Hydrogen bonding
d/ Charge transter
e/ Ion exchange
f/ Ligand exchange
g/ lon-dipole and dipole-dipole
Organic Clay Organic
Matter Minerals Matter

+ d/ + e/d strong
* - weak

+ c/d/e/f/ + d/e/ weak

+ - weak



+ a/d/ + very
strong
+ b/d/ + c/ very
strong
+ b/d/ + strong

+ b/d/ + c/f/ medium

+ b/d/ - c/ medium

+ b/d/ - weak

+ b/d/ + strong


+ b/d/ - strong
+ b/d/ + strong

Column 3, 4

Column 7

Column 8


Clay Soil pH
Minerals Effect
very
strong small
very >PKa
weak
medium 
-------
     Documentation on spill incidents which includes information about the
cause, chemical name, volume spilled and suspected or documented
pre-existing contamination problems is usually insufficient.  In many
cases, little emphasis is placed on ground-water protection during spill
clean-up activities until contaminants are detected in nearby domestic or
municipal water supply wells.

     Reported spill volumes range from a few gallons to several million
gallons.  Current methods to quickly and adequately clean up spills have
improved over the past few years but are still limited to quick response
to contain and recover the substance.  For example, spill areas are
frequently flushed with water to quickly remove spilled liquid.  This is
particularly true in tanker truck accidents where removal of the spilled
liquids from road surfaces helps prevent further hazards to life and
property.  However, these contaminants then infiltrate through adjacent
soils and may possibly contaminate ground-water supplies.

     A successful program for spill remediation involves several steps for
containment and recovery of the contaminant.  This was illustrated during
an actual spill of 130,000 gallons of organic chemicals which entered a
shallow unconfined aquifer (Ohneck and Gardner, 1982).  Initial action at
the site involved immediate containment and collection of the surface
liquids.  Chemicals were then properly identified for disposal.  Air
monitoring systems were established to identify the presence of toxic
fumes.  Information was collected on the hydrogeology of the site and test
borings were performed to identify the extent of the contamination.
Monitoring wells were installed to determine site specific hydrogeologic
characterisitcs and for later use ii, ground-water sampling.  An effective
in-situ reclamation program combined with a ground-water recovery and
treatment program resulted in complete clean-up of the spill site.   Other
successful cases of accidental  spill clean ups of organic chemicals have
been documented by Harsh (1975) and Sterret, et al. (1985).

Particulate Matter from Airborne Sources

     Fallout of particulate matter from the atmosphere is a relatively
minor, but potential  source of  ground-water contamination.  Particulate
materials fall  to the surface of the earth and are transferred as soluble
or insoluble products by water  to the subsurface.  The primary source of
atmospheric  pollution is automobile emissions and various industrial
processes.   The major contaminants from these emissions  include sulfur and
nitrogen compounds, asbestos and heavy metals (Owe et al.,  1982).  The
distribution of particulates in the atmosphere and on the surface depends
on their size when released, weather patterns and climate.  The attenuation
of these pollutants depends  on  the site-specific hydrogeochemical
characteristics, location  of pollutant fallout and chemical nature  of the
pollutant.

      The infiltration of airborne contaminants  is  typically higher  in
heavily  industrialized areas (Lehr, et  al.,  1976).  Concentrations  of lead,
cadmium and  mercury which  exceeded EPA  maximum  allowable concentrations  in
                                    400

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 drinking water have been  detected  in  the precipitation of mountain regions
 of  New England.  Precipitation recharging the aquifers in these areas could
 lead  to potential contamination of  these aquifers  (Miller,  1980).  Airborne
 chromium from an electroplating firm  in Michigan has been suspected as a
 source of  ground-water contamination  of nearby wells.  Chromium-laden dust
 discharged through ventilators on the roof and settled to the ground.  The
 dust  was carried by precipitation  into the subsurface where it directly
 impacted the ground-water quality  (Deutsch,  1963).

      The major environmental concern  today related  to airborne contaminants
 is  the effect of acid rain on the surface and subsurface water quality.
 Acid  rain  is divided into two categories, wet deposition or dry deposition.
 Wet deposition refers to  atmospheric  pollutants that are deposited with
 rain  and snow in the form of acids  (mainly sulfuric and nitric).  Dry
 deposition includes those solid or  gaseous pollutants deposited on the
 surface of the earth (Hubert and Canter, 1980).  The occurrence of acid
 rain  near  heavily industrialized and  urbanized areas has impacted
 vegetation and surface-water quality.  Infiltration of acid precipitation
 and the solubilization of dry particulates which may be transported to the
 ground water can impact ground-water quality.  The  potential effects of
 sulfur/sulfur dioxide compounds, nitrogen/nitrogen  dioxide compounds,
 hydrogen ions and heavy metals in acid rain as they enter the ground water
 will  decrease the pH of the water and raise the concentrations of these
 compounds  above safe consumption levels (Hubert and Canter, 1980).  These
 substances may also undergo secondary and tertiary  reactions in the
 subsurface to form other  potentially  toxic compounds.

 GROUND WATER QUALITY PROBLEMS THAT  ORIGINATE IN THE GROUND ABOVE THE WATER
 TABLE

 Septic Systems, Cesspools and Privies

      On-site sewage disposal systems are used to treat and dispose the
 domestic wastewater from approximately one-third of the homes in the United
 States.  Each year, an estimated one  trillion gallons of effluent is
 discharged into the environment by  approximately 22 million on-site sewage
 disposal systems (U.S.  EPA, 1986c).  Of these individual on-site disposal
 units, conventional septic tank-soil absorption systems constitute 85
 percent of the systems in use, while alternative systems (i.e. aerobic
 treatment  systems,  filter beds, mounds, etc.) and unregulated systems (i.e.
 cesspools) comprise the rest (Scalf et al., 1977).

     The basic on-site sewage disposal system consists of a septic tank
 with an accompanying soil absorption and treatment field.  The septic tank
 separates  the floating and settable solids from the liquid portion of the
 wastewater.  Solids settling to the bottom of the tank (i.e. sludge)
 undergo partial anaerobic decomposition in the tank.  Sludge builds up in
 the tank and must be periodically removed to prevent these solids from
 discharging out of  the tank along with the liquid effluent.   Septic tanks
 typically are designed  and sized to retain the anticipated daily volume of
wastewater from the home for 24 to 48 hours.   This is accomplished by using
                                   401

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a single compartment tank, double portioned tank or multiple single
compartments tanks in series.  These latter tank designs are favored for
their improved solids removal capabilities (Canter and Knox, 1985).  Septic
tanks may be constructed from a variety of materials, including reinforced
concrete, steel, plastic or fiberglass.  The effluent from the septic tank
discharges into a soil absorption and treatment field.  The soil absorption
and treatment field is designed to distribute the septic tank effluent into
the soil for final treatment and disposal.  Soil absorption and treatment
fields are commonly designed as gravel-lined trenches or beds containing
perforated distribution tile or pipe (Canter and Knox, 1985).  Seepage
pits, above-ground mounds or other innovative designs may also be used in
lieu of conventional soil absorption fields.

     On-site sewage disposal systems provide safe and effective disposal of
domestic waste when the system is correctly designed, installed, operated,
maintained and located in appropriate environment conditions.  However,
sewage effluent may be a significant potential source of ground-water
contamination where regulations do not adequately address these elements or
where proper regulations are inadequately enforced.  The potential for
ground-water contamination by on-site systems may also exist where the
density of these systems exceeds the capacity of the soil to adequately
treat the sewage effluent before it reaches the ground water.  This is
especially a concern with certain soluble salts, such as chlorides,
nitrates and sulfates, which are not readily removed by the soil treatment
and absorption system.  Canter and Knox (1985) estimate that septic system
densities exceeding 40 systems per square mile may constitu*% a significant
potential ground-water contamination problem.

     General site criteria must be examined prior to designing and locating
the on-site system.  Suitability of the soil for treating and disposing of
wastewater is often evaluated by digging  soil ,test pits and/or conducting
percolation tests.  Soil test pits are used to evaluate soil properties,
such as  texture and structure, the occurrence of seasonally high water
tables or perched water tables, depth  to  bedrock and depth  to apparent
ground-water.  Percolation tests may also be conducted as a rough,
empirical method  of evaluating the capability of the  soil to absorb sewage
effluent.  In general, a minimum depth of four feet  of permeable,
unsaturated soil  should be present between  the bottom of the absorption
trench or bed and the  top of the seasonal water table and/or bedrock  (Scalf
et  al.,  1977).  Proper isolation distances  between septic tanks and water
wells must be maintained  to  prevent contamination of  domestic water wells
by  the sewage effluent.

     The  potential  for ground-water contamination by  septic  tanks  depends
on  the quality  of the  effluent discharging  from the  system  and  the capacity
 for the  soils and unsaturated  zone materials  to effectively attenuate and
degrade  these  substances.  Wastewater  constituents which are a  primary
concern  to  ground-water quality  include biological contaminants  (i.e.
bacteria and  viruses), phosphates, nitrates,  heavy metals,  and  synthetic
organic  and inorganic  compounds.  The  transport and  fate of  these
 contaminants  depends  on  the  efficiency of the  physical, chemical  and
biological attenuation mechanisms in  the  unsaturated zone  including
 filtration, adsorption and microbial .degradation.

                                    402

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     Biological contamination of ground water from septic systems is widely
recognized.  Bacterial movement in unsaturated soils is generally limited
by the physical filtering capability of the soils and adsorption onto soil
particles.  The filtration and adsorptive capacity of the soil depends on
various soil factors including:  soil pH, moisture content, temperature,
oxidation-reduction potential, the size and shape of interstitial voids of
the soil and the permability and related velocity of flow through the soil
(Canter and Knox, 1985; Bauder, 1984).  Unsaturated flow conditions beneath
the absorption trench or bed provide increased contact and detention time
between the bacteria and the soil (Hackett, 1984).  Bacteria survival times
depend on several soil conditions, including pH,  temperature and moisture
content.  Survival times of up to 2 to 3 months in soil have been
documented (Gerba et al., 1975).  These extended  survival times of bacteria
are important when considering that bacteria adsorbed to the soil particles
beneath the adsorption trench can remain viable and penetrate deeper into
the soil should suitable flow conditions develop  (Hackett, 1984).

     With regard to other potential wastewater pollutants, phosphorus is
typically attenuated by chemical precipitation and adsorption.  Ammonium is
removed primarily through adsorption, cation exchange or volatilization.
Nitrogen and ammonium converted to nitrates move  readily through the soil
system unless other processes such as denitrification or uptake by plants
occur.  Heavy metals discharged in septic effluent may be attenuated by the
soils through adsorption, ion exchange, chemical  precipitation and
complexation with organic substances (Canter and  Knox, 1985).  Synthetic
organic compounds from various household wastes may be attenuated through
the physical and chemical processes of adsorption, hydrolysis,
complexation, volatilization, and most irnportartly by microbial
degradation.  One of the most frequently detected contaminants in ground
water, trichloroethylene (an industrial solvent and degreaser), is also
used as a septic tank cleaner.

     In order to provide effective removal of wastewater contaminants,
proper septic system design and soil conditions must exist.  Contamination
of both regional and localized ground water due to septic system discharges
has been documented (Canter and Knox, 1985; Flipse et al., 1984; Scalf et
al., 1977).  Contamination problems commonly occur from improper
construction and maintenance causing a significant percentage of systems to
fail prior to their expected design life (Scalf et al., 1977).  The direct
discharge of untreated sewage wastes into gravel  beds, fractured bedrock or
solution channels which is still practiced in some areas of the United
States may also cause ground-water contamination.  Other contamination
problems occur when the soil adsorption systems are located beneath the
biologically active zone, effectively excluding the process of biological
degradation.  High densities of septic tanks in areas where permeable soils
exist have caused regional contamination of aquifers in Nassau and Suffolk
Counties, New York, and in Dade County, Florida (Flipse et al., 1984).  The
installation of public sewers in high density septic system areas will
                                   403

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alleviate some ground-water contamination problems but at a  considerable
cost.  Other alternatives to improve septic systems and help  prevent
degradation of ground-water quality include the use of specialized  systems
such as percolation and evapotranspiration mounds in areas with thin or
unsuitable soils or in areas of fractured or impermeable strata.

Surface Impoundments and Lagoons

     Surface impoundments are used by farms, industries and municipalities
for the treatment, retention, and/or disposal of non-hazardous and
hazardous liquid wastes.  Holding ponds, surface impoundments and lagoons
present a significant potential for ground-water contamination because of
their relative numbers and size.  A recent Surface Impoundment Assessment
(SIA), conducted by the U.S. Environmental Protection Agency, located over
180,000 impoundments at approximately 80,000 sites (U.S. EPA, 1983).  Table
C-6 lists six major categories which show the nationwide distribution of
sites and impoundments, both active and abandoned.  Agricultural
impoundments are associated with farming, crop production and animal
husbandry.  Uses of impoundments on farms range from manure  and dairy waste