&EPA
           United States
           Environmental Protection
           Agency
Off Ice of Solid Waste
and Emergency Response
Washington DC 20460
July 1986.
           Solid Wane
          Criteria for Identifying
          Areas of Vulnerable
          Hydrogeology Under the
          Resource Conservation
          and Recovery Act
          Appendix D

          Development of Vulnerability
          Criteria Based on Risk
          Assessments and
          Theoretical Modeling
          Interim Final

-------
        GUIDANCE CRITERIA FOR IDENTIFYING
         AREAS OF VULNERABLE HYDROGEOLOGY
                    APPENDIX D
      DEVELOPMENT OF VULNERABILITY CRITERIA
BASED ON RISK ASSESSMENTS AND THEORETICAL MODELING
              Office of Solid Waste
            Waste Management Division
       U.S. Environmental Protection Agency
                401 M Street, S.W.
             Washington, D.C.  20460
                     July 1986

-------
                        TABLE OF CONTENTS
                                                            Page
List of Tables	 iv
List of Figures	 v
1.0  Introduction ..........................................  1-1


2.0  Theoretical Considerations Affecting Discharge
     and Exposure Potential ...............................  2-1

          2.0.1  Relationship between TOTioo and the
                 Potential Size of a Plume .................  2-2

          2.0.2  Analysis of Peak Concentration as a
                 Function of TOT   ........... ; ........... '•  2-4
          2.0.3  Application of the Liner Location Model...  2-14

     2.1  Potential for Exposure Through a Ground-Water
          Resource .................. ' ............... . .......  2-19

          2.1.1  Theoretical Relationship between TOTioo
                 and Well Yield... .........................  2-20

          2.1.2  Frequency Distribution of TOTioo among
                 Well-studied Aquifers .....................  2-22

          2.1.3  Contamination of High Capacity Production
                 Wells ....................................   2-25

          2.1.4  Contamination of Individual  Drinking  Water
                 Wells .....................................  2-26

     2.2  Potential for Exposure to Contaminated Surface
          Water ................. ...........................  2-27

          2.2.1  Surface Water Exposure Pathway:  Hydro-
                 geologic Settings .........................  2-27

          2.2.2  Contamination of Potable Surface Water
                 Supplies ..................................  2-28

          2.2.3  Contamination of Surface Water Ecosystems.  2-28

          2.2.4  Bedrock Springs Contamination .............  2-29

     2.3  Potential for Exposure Through the  Basement
          Seepage Pathway ...... . ...........................  2-30

-------
          2.3.1  Description of Condition	 2-30

          2.3.2  Representative Hydrogeologic Settings	 2-30

     2.4  Considerations for Location and Unit Design	 2-31

          2.4.1  Controlling Discharge from a Unit	 2-32

          2.4.2  Considerations for Unit De-sign	 2-34

          2.4.3  Considerations for Storage and Disposal
                 Units	 2-35

3.0  Case Study Examples and Exposure Estimation Methods... 3-1

     3.1  Case Studies:  Three Exposure Pathways	 3-2

        •  3.1.1  Ground-Water Resource Pathway: Chemical
                 Plant Site	 3-3

          3.1.2  Ground-Water Resource Pathway: Abandoned
                 Gravel  Pit/Landfill	 3-4

          3.1.3  Potable Surface Water: Multi-Source Waste
                 Site	 3-5

          3.1.4  Surface Water Ecosystems:  Mining and Ore
                 Processing Facility	 3-6

          3.1.5  Bedrock Seeps and Springs: Municipal and
                 Industrial Landfill	 3-9

          3.1.6  Basement Seepage Pathway:  Quarry/Landfill
                 Site	 3-10

          3.1.7  Basement Seepage Pathway:  Chemical Landfill
                 Site	 3-11

     3 . 2  Health Risk Assessment Methods	 3-12

          3.2.1  Assessment Methodology	 3-17

          3.2.2  Methods for Interpreting Results	 3-23

          3.2.3  Results of Preliminary Exposure and Health
                 Risk Assessments	 3-24

     3.3  Case Studies:  Health Risk Assessment	 3-25

          3.3.1  Case Study D-l	 3-27
                                ii

-------
          3.3.2  Case Study D-2	 3-43

          3.3.3  Case Study D-3	 3-62

          3.3.4  Case Study D-4	 3-71

          3.3.5  Case Study D-5	 3-79

          3.3.6  Case Study D-6	 3-87


4.0  Estimating the Number of Facilities located in
     Vulnerable Ground-Water Settings	 4-1

     4.1  Methodology	 4-1.

     4 . 2  Results	 4-6

     4.3  Continuing Efforts . .,	 4-8


5.0  References	 5-1
Attachment 1:  Application of Liner Location Model
               to the Analysis of Time-of-Travel Criteria
               for Siting of New Land Disposal Facilities
                               iii

-------
                             LIST OF TABLES


   2.0-1   Hydrogeologic Data Colleted from Liner-location
           Project Literature Survey	 2-5

   2.0-2   Critical Times and Peak Concentrations and
           100-foot Travel Times for Twelve Scenarios	 2-18

   3 . 3-1   Estimated Flow Rates and Volumes	 3-35

   3.3-2   Contaminant Concentration	 3-42

   3.3-3   Summary of Pumping Test Results	 3-51

   3.3-4   Contaminant Concentrations at Selected Wells	 3-56.

   3 . 3-5   Tabulation of Carcinogenic Risks	 3-58

   3.3-6   Tabulation of Hazard Indices for Systemic
           Toxicants	 3-60

   3.3-7   Results of Benzene Plume Simulation	 3-69

   3.3-8   Concentration of Metals in Monitoring Wells	 3-74

   3 . 3-9   Tabulation of Carcinogenic Risks	 3-77

   3.3-10  Chemical Analyses for Selected Organic
           Contaminants in Ground Water at a Depth of
           18.3 Meters at Sites 1 and 3 through 7	 3-83

   3.3-11  Data from Installation of Monitoring Wells	 3-94

   3.3-12  Laboratory Analytical Results of Groundwater
           Quality Monitoring	 3-105

   3.3-13  Incremental Carcinogenic Risk Associated
           with Lifetime Consumption of Trichloroethylene
  -         and 1,1,1-Trichloroethane	 3-106

   4.2-1   Distribution of Facilities by Region	 4-7
C ~ . '
   4.3-1   Geologic Settings	 4-9

   4. 3-2   Regolith Systems	 4-10

   4.3-3   Bedrock Systems	 4-11
                                   iv

-------
                         LIST OF FIGURES

2.0-1   Potential Areal Extent of a Plume as a Function
        of TOT Per Unit Time	  2-10

2.0-2   Ratio of Peak to Steady State Concentrations as a
        Function of Time of Travel	  2-15

2.1-1   Locations of Literature Survey Study Areas in
        Relation to the Lower 48 States and 10 USGS
        Ground-water Regions	  2-23

2.1-2   Histogram of Ground-water Velocities Generated in
        Literature Survey in the Liner-location Project....  2-24

2.4-1   Schematic Illustrations of Unit Design	  2-38

3.1-1   Site Map Showing Location of E-W Transect and
        Major Surficial Features at Love Canal	  3-13

3.1-2   West-East Cross-Section of Love Canal	  3-14

3.2-1.  Hypothetical Well Locations Used in Risk
      .' Assessments	  3-16

3.3-1   Waste Units	  3-28

3.3-2   Geologic Cross Section	  3-31

3.3-3   Glaciolacustrine Aquifer Potentiometric Contours...  3-34

3 . 3-4   Schematic Flow Diagram	  3-37

3.3-5   Well and Piezometer Location Plan and Formation
        Intervals	  3-39

3 . 3-6   Facility Location	  3-45

3.3-7   Hydrogeologic Cross Sections A-A1  and B-B'	  3-46

3.3-8   Flow Net Analyses for the Alluvial Aquifer,
        August 1984	  3-47

3.3-9   Iso-Specific Conductance Map for the Alluvial   .    •'-
        Aquifer, June - July 1984	  3-53

3.3-10  Ground-water Dewatering Plan and Location of
        Corrective Action and Compliance Point
        Monitoring Wells	  3-54

3.3-11  Location of Deep Well Borings, and Geologic
        Sections	  3-63

3. 3-12  Geologic Section A-A1	  3-65

-------
3. 3-13  Geologic Section B-B'	 3-66

3.3-14  Well Pattern and Plume Outline	 3-73

3.3-15  Cross-section of Ground-Water Plume	 3-75

3.3-16  Location of Monitoring Sites	 3-80

3.3-17  Hydrogeologic Cross-Section	 3-81

3.3-18  Site Plan	,.	 3-89

3.3-19  Locations of Off-Site Monitoring Wells	 3-90

3.3-20  On-Site Sub-Surface Soil Boring Locations and
        Locations of Site Soil Sections	 3-91

3.3-21  Site Section A-A1	 3-92

3 .3-22  Site Section B-B'	 3-93

3.3-23  Inferred Surficial Aquifer Plume from Section A-A'. 3-98

3.3-24  Subsurface Cross-Section A-A'  from Site to River... 3-99

3.3-25  Inferred Bedrock Potentiometric Surface from 1982
        Data with 1984 Data Superimposed	 3-100

3.3-26  Inferred Bedrock Aquifer Plume for
        1,1,1-Trichloroethane (1984 Data Superimposed)	 3-101

3.3-27  Inferred Surficial Aquifer Plume for
        1,1,1-Trichloroethane (1984 Data Superimposed)	 3-104
                                VI

-------
                       1.0   INTRODUCTION


      This  Appendix  presents the  results of  the  analyses  that  EPA

 performed  in  developing  the definition  of ground  water vulnerability,

 In  developing the vulnerability  definition,  EPA's primary  goal was

 the identification  of  locations  where the potential  for  exposure

 to  releases of hazardous waste or waste constituents  could be

 significant in the  event of the  failure or  absence of engineered

 containment barriers or  monitoring  and  response activities.

      The Agency  examined the effect on  ground-water  quality from
                                                   *
 a number of land-based hazardous waste  management units  located

.in  a variety  of  hydrogeologic settings.  This examination

 identified three generic potential  pathways  in  the saturated

 zone through  which  the public or the environment  could be  ad-

 versely affected; these  pathways are discussd in  Section 2.0

 of  the main text of this guidance.   EPA believes  that results

 from these hydrogeologic assessments show that  exposure  potential

 is  not minimized at locations where any of  the  three  pathways

 exist.  The vulnerability definition therefore  must be able to

 identify these three pathways so that further steps can  be taken

 to  minimize potential  exposure to human health  and the environment

 in  the event  of  a release.

      Location vulnerability is determined for hazardous  waste

 landfills, surface  impoundments, and waste  piles  by  calculating

 the time of travel  of  water along 100 feet  of a ground-water  flow

 line originating at the  base of  a hazardous  waste management

 unit (TOT]_oo)-   For landfills and surface impoundments used
                                1-1

-------
for disposal, TOT]_oo values less than on the order of 100 years



are considered to indicate vulnerable settings.  For those land



storage or treatment facilities where wastes will be definitely



be removed at closure, the vulnerability of the ground water



will be determined by comparing the TOT^QO to the time that would



be necessary to correct a problem in the event that design and



operating controls in place at the facility failed.  Determination



of this time is site specific, and the permit writer should



first ascertain that wastes and contaminated soils will be removed



from the site at closufe before considering a value for TOT^QO



that is less than on the order of 100 years.



     The case studies and theoretical modeling analyses described



in this Appendix discuss how the vulnerability definition can be



used to recognize these pathways and thereby minimize potential



exposure to the environment and human health by triggering further



investigation of the location and reevaluation of design or



operation considerations.



     Chapter 2 of this Appendix describes the theoretical consid-



rations affecting discharge and exposure potential, and how the



concept of TOT^QO incorporates these considerations.   Using examples



and plume modeling,  it examines the relationship between TOTj_oo



contaminant discharge and travel through each of the three routes



of exposure.  The final section in Chapter 2 discusses overall



site design and location strategy based on the objective of



maximizing TOT^oO and minimizing contaminant access to exposure



pathways.



     Chapter 3 of this Appendix presents illustrations of the
                               1-2

-------
three exposure pathways, and a health-risk and exposure estimation



method for the the ground-water resource pathway.  Ground-water



quality data for actual or simulated ground water plumes were



analysed to determine if any health risks might exist at a variety



of hypothetical exposure points.  Finally, case studies are



included that illustrate the TOTioo criteria and the health-risk



assessment for the ground-water resource pathway.



     Chapter 4 of this Appendix provides estimates on the



number of facilities located in vulnerable settings.
                               1-3

-------
            2.0  THEORETICAL CONSIDERATIONS AFFECTING
                 DISCHARGE AND EXPOSURE POTENTIAL


     This chapter describes a series of exposure conditions that

may result from ground-water contamination.  The experience gained

from investigations of CERCLA (Superfund) sites and the case studies

described later in this Appendix has been used to identify and

illustrate these exposure conditions.

     Sections 2.0-1 through 2.0-3 examine the theoretical con-

siderations affecting discharge of ground water and potential for

exposure.  The relationship between TOT and plume size is discussed,

and an analysis of peak concentration in the plume versus TOT is

described, using the Liner Location Model.

     Section 2.1 discusses for the ground-water pathway the

relationship between TOT and well yield and the TOT distribution

among aquifers.  The section contains a general discussion of the

hydrogeologic settings where contamination can spread to high

capacity production wells and individual drinking water wells.

     Section 2.2 describes exposure potential through the second

pathway, surface water contamination.  Included are general

examples illustrating the correlation between short TOT^oO set-

tings and the contamination of potable surface water supplies and

surface water ecosystems, and the occurrence of contaminated

seeps and springs.

     Section 2.3 illustrates how exposure can occur through the

basement seepage pathway.   Section 2.4 discusses overall siting

design and location strategies to minimize the potential for

exposure through any of the three pathways.
                               2-1

-------
     Although the three pathways have been separately explained

in this chapter, one must remember that they are closely linked

in actuality. -For example, contaminated ground water can

discharge to surface water; leachate migrating along a shallow

basement seepage pathway can discharge to drainage swales. Hence,

the separation of the three pathways is a simplification to

facilitate description and illustration of each route for the

purposes of this appendix.
2.0.1  Relationship between TOT^QO an<^ t^6 Potential Size of a
       Plume

     The potential size of a plume is a function of the hydro-

geologic characteristics of a location and the properties of the

constituents released from the wastes.  The potential rate of

growth of a plume can be described by TOT^QO'

     TOT].oo measured for water should describe the rate of growth

of a plume unless constituents that move faster than water are

present, such as when immiscible fluids are placed in the unit.

However, EPA believes that these situations are atypical of most

hazardous waste management units.  When immiscible fluids are

known to be present, their TOTiQO can be easily calculated by

converting the hydraulic conductivity (K) to a conductivity for

the fluid of concern.  This conversion requires a knowledge of

the dynamic viscosity (/-c, kg/m sec) and density ( /j , kg/m3) of

the fluid.  The relationship is given by (Freeze and Cherry, 1.979):
                               2-2

-------
where g is the acceleration due to gravity (m/sec2) and k is the

specific or intrinsic permeability (m2), which is a function of

the porous medium alone and which includes all the textural

characteristics of the medium (i.e./  mean grain diameter, grain

size distribution, sorting coefficient, sphericity and roundness

of grains, and the nature of their packing configuration).

However, such a recalculation of TOTiQO should not fundamentally

change the interpretation of the plume isolation properties of

the location, or of the.potential for the hydrogeologic setting

to be used as a ground-water resource.  TOT^QO calculated for

water provides a simple means for comparing the natural contain-

ment characteristics of any hydrogeologic setting, thus providing

a descriptive baseline for comparing the exposure potential at a

facility.  Where appropriate, the TOT^QO f°r immiscible constit-

uents can be calculated for the purpose of comparison.

     The maximum potential extent of plume growth in ground water
                                                                  *
is described by the size of the ground-water flow cell, which is

the distance between recharge and natural discharge zones.  Flow

cell characteristics can be related to geologic settings, and the

dimensions can also be related to topographic position within the

setting.  In some settings, such as coastal plain deposits, the

flow cell can be quite large, on the order of tens of miles or

more.  Other settings, such as low-permeability glacial till

deposits with hummocky topography, have fairly short distances

(on the order of hundreds of feet, depending on the topographic

position).  Table 2.0-1 lists the sizes of the flow systems at the

sites studied in the Liner Location Project (which is discussed


                               2-3

-------
in more detail in Section 2.1.2).  Freeze and Cherry  (1979,


Chapter 6) presents a more comprehensive discussion on flow


systems.


     Figure 2.0-1 shows that potential plume size is directly


related to TOT^QO'  However, the maximum extent of a plume in


ground water will be limited by any natural discharge zone.


Except where such boundaries to the flow cell e.xist, the oppor-


tunity for exposure to a plume increases when TOT increases


because the plume will underlie a greater area of land.  Of


course, when a plume's growth is limited by a natural discharge
                                          »

zone, the potential impact of the contaminated ground water on


surface water quality must be considered.


2.0.2  Analysis of Peak Concentration as a Function of TOT]_QO


     EPA examined whether there is a direct relationship between


TOT^oO an^ risk, to determine if waste disposal in certain hydro-


geologic settings presents inherently less risk than in others.


This analysis used peak concentrations as a proxy for risk because


a common factor in all risk assessments is a comparison of con-


stituent concentration data with toxicity guidelines for those


constituents.  The other factor in risk assessments is an evalu-


ation of exposure potential; this factor is considered separately


in the analyses presented in this Appendix.


     The theoretical analysis of peak concentration versus TOT


considers four contaminant release scenarios:  continuous release


at a constant release rate,  continuous release at a rate deter-


mined by the ground-water flow velocity, constant rate contaminant


release for a limited time period, and flow controlled contaminant
                               2-4

-------
to
01
                                                          TABLE 2.0-1

                            HYDROGEOLOGIC DATA COLLECTED FROM LINER-LOCATION PROJECT LITERATURE SURVEY
Unsaturatcd lone
Stuly
Area
1-1


1-2

2-1

2-2


2-3


2-4

2,3-1
3-1


3-2
3-3



4-i

4-2

5-1

Earth
Hitcrlal
gravel


gravel, sand

alluvium

gravel, sand


gravel, sand
Silt

clay, silt
sand, gravel
-
sand, gravel


sand, gravel
—



sandstone

.

sandstone

Myor
Ihickness
(ft)
_c


_

10-20

50-100


50-100


100-250

-
20-200


200
—



0-300

—

20-80

Earth
Material
gravel
silt, clay
sand, gravel
gravel, sand, silt
basalt
alluvlus

gravel, sand, silt
clay
gravel, sand, silt
gravel, sand, silt
clay, silt
sandstone
clay, silt
sand, gravel
sand, gravel
sand, groveli
clay, silt
basalt
silt, sand
sediment, basalt



sandstone
faulted sandstone
sandy clay
sandstone
sandstone

Saturated Zone
Layer
Thickness
(ft)
25
300
>400
0-3000
400-1000
30-40

150
60
600
300
200
MOO
>200

30-60
200
100
>100
>1200
5000



0-700
>100
0-135
70
>300

flow Velocity
Mln Max
Vh
25
-
0.01
2.8
65
4.5

0.15
-
0.70
1.7
-
0.9
0.63

0.21
67
-
0.08
0.38
5



0.11
5.6.
0.025
0.43
0.09
'
V« V V.
tit/day)" '
110
0.006
0.04
6.3
- - -
_ _ _

- 2.10 -
3.6x10 ' - 6*10 *
2.10
5.0
2-6
1.8 -
1.6

-
-. . 220 -.
4a - id"
0.21
0.64
25 -



0.22
12.0
-
_
0.60

flow Syr.tra
Distance m»
Itech. to Ulccjiy
Boundaries'*
(ft)
21.000

40,000 .
_
-
* -

42,000
-
-
21,000
-
—
27,000

-
32,000
32,000
32.000
53,000
_



21,000
~
-
-
-
•
Pr iKiry
. lUdc ol
Discharge
river
aquifer :
river
river
river
river

river
aquifer

wolls
nquifer
aquifer
well

river
lake
« fuller
aquifer
wells
_



spring
—
wells
wells
wells

Guicr ic
Seating
1
.1

5
l
I 1
1
1


1


1

1
7


1
1



1

6

1

Source
Konizeskl et al.
(1968)

Dion (1969)

Price (1962)

UMkXfilst (19UI)


llardt et. al
(I960)

Anderson (1972)

Bertoldi (1971)
Tanuka et al.
(1974)

Newcunb et al.
(1972)
Barracluuqh,
et al.(1976)
lubcrtson.
et ol. (1974)
Luidy (1978)

Ri^nond 1 ,
et al. (1983)
U«.fy et al.
(1967)
                                                     continued

-------
TABLE 2.0-1  (continued)
stilly
Area
5-2
«-l
6-2


6-3

6-4

6-5

6-6
to
1
°* 6-7


6-8
6-9

6-10

6-11


7-1

7-2
7-3
Unsaturatcd Sane
earth layer
Hiterlal Thickness
(ft)
sandstone 50-100
Kscitont 0-500
•and. silt, 10
gravel
sandstone 20-50
•and. silt.
gravel
sandstone 50-200

6-10

fractured 0-200
llsttctone

lUwstone


-


karstlc
lloestone
Ehale


sand, gravel 10

-
sand, gravel
' Saturated Zone
Parch Layer
Hater lal Thickness
(ft)
sands torn
liacstofw
sandstone

coal
sand, silk, gravel

sandstone

1 Ues tone

fractured llaestone


binristane
shale, liaestone
sandstone
karstlc llaestona
karstlc dolomite

karstlc limestone

shale, slltstone
saw Is tone
ahale
sand, gravel
• granite
sand, gravel, silt
sand, gravel
ISO
550
20

70
15

300

50

600


100
SO
100
-
—

)1,000

40
40
>100
150
-
-
90
t
Flow Syst
t»


Flow Velocity Distance frui Primary
Min Max tech. to Dlochg. Node of Generic
V v* V. Va Boundaries*
h fft/day)" * (ft) '
0.27 -
0.04 -
_

0.61
0.10

0.20

0.49

0.13


0.04 - -,
talO'30
0.06
26
1.9

24

0.002d
0.03 - .
o.ooad
0.02
* -.
1
0.64
3.0 - 21,000
0.4 - 53,000
•3,000

3.0
5.3 - 6,000

0.40 - 16,000

_ _ -

0.24


0.16 - „
2x10 ~
0.26
5.000
2.6

180

- 0.003d
0.26 - .
- 0.01d
0.05 - 53.000
— — —
3
1.3 - 10.000
Discharge Settling
stream
aquifer
strca


river

tell

spring

spring


anuiter
aquifer
aquifer
stream
—

spring

aquifer
t^jf in)
Oftilr.f
spring
™
-
river
1
I
1


1

1

1

1


7


1
1

1

3


1

1
1
Source
luison 11965)
Kunlkow |1976)
Davis (1975)


Konikow (1*76)

Ttauqer et al.
(1964)
lurk et al.
(1971)
Klant* Ct al.
(1979)

Hall rt al.
(197S)

Harvey et al.
Skelton et al.
(1979)
Harvey (1980)

Zchner (1983)


Baker et al.
(1967)
Otton (1972)
ftothrock et al.
(1947)
         continued

-------
                                              TABLE 2.0-1 (continued)
to
StuJy
Area
™

7-5

7-6

7-7

7-1
7-9
7-10
7-11



7-12


7-13

7-14



8-1

8-2


9-1

Unsaturatcd lone
Earth . Layer
Material ThickiMM
(ft)

till, sand I

_ _

..

•and, gravel

-
•tit
-
•lit, clay



sand, gravel 10


•aid, gravel, 10
silt
till 10-20



•aprollte 3-17

gneiss
(weathered)

•lit, clay 10

Saturated Zone
Earth
Material
till, sand
•hale
ll*c»ton*
•and, gravel

sand

•and, gravel
dolcnite
•and, gravel
clay, silt
Bond, gravel
.sand, gravel
silt, clay
sand, gravel
limestone
•and, gravel
silt, clay
•and, gravel
aandctono
Clay till
till
dolcnite
dolomite
shale
eaprolite

gneiss
(weathered)

silt, clay
dolcnite
Layer
IMckneea
(ft)
>1000
200
25-260
90

75-130

50
200

50
-
40
60
50
100
30
100
20
74
20-217
30
IS
60
>50
0-50

100


100
MOO
Flow Velocity D
Min Kax Rei
V. V V. V*
h tft/dav)h
•
0.025 -
3.4

1.9

. _
0.21 -
0.04 >
0.15
1
»•> - -5
1 txlO *
1.4
~ —
0.01
0.001
o.a
18
-
0.0055 -
0.055
0.03 s -
i«io- -
0.023 -

0.56


0.002 -
0.17
-
0.51
. _

1

_ _
0.43. -
0.27 -
l.B
-
«•• -.4
- 6*10 *
4.8
— ~
0.10
0.002
1.6
51
• •
_ • _
- -
_ -
-
0.043

3.1


0.01
0.69
Flow System
i stance (ton
cf). to Dischg.
Boundaries b
(ft)
-
-
16,000

130,000 .

-
•
-
(00
-
^ •
-
—
"
_
-
-
16,000
•
5,200
5,200
5,200
4,200
-

5,000


10,500
10,500
Primary
Made of Generic
Discharge Settling
aquifer
-
river

river

.
well*
-
stream
-
river
aquifer
-
~
creek
aqui lei
underflow
river

rlvor
river
river
river
stre.au

stream

1
river

I

1

1

1

1
1
1
.1



2


1

3



2

1


1

Source
Kent ct.al.
(1972)

Kj>mlck et al.
(1VUI)
kJthsrhtld
ct al. (19U2)
leixcl ft al.

tt ton (1972)
Glbb (1978)
Otton (1972)
Planert (1980)



Petti John (1977)


tutinotf et al.
(1*02) ,.
Hr.lld ct al.
(19U2)

)
rurylond DLP
(1981)
McCrcevy and
Sloto (1980)

Trainer et al.
(1*62)





















sgr,
^fcs'
rf-^ S
Kl' s

3
00
i^
00
^~
• SB
' 1
                                                        continued

-------
TABLE 2.0-1 (continued)

Unsaturated tone
Study tarth Layer
Area Material Thickness
(ft)
9-2
9-3

9-4

10-1

10-2

10-3

ro 10-4
00

10-5

10-«

10-7

lo-i
10-,
10-10


sand, gravel
sond, gravel 10

•and, Bllt,
clay
— _

•and ISO

•and

clay, sand 10-30


_ »

_ .

— —

Saturated lone
Earth
Miter lal
sand, gravel
sand, silt, clay
crystalline rock
sand, silt, clay
basalt
sand

•and

•and, gravel
^
clay. Band
•and
•and
•llty clay
luKBtona

llacstone

und, clay

Layer
ttilckneu
(ft)
35
80
>SOO
200
WOO
1000

>400

>1000

20
100
ISO
75
100

>1000

23

•.•mtatone. lutestone 100
•and
•and, gravel 30


sand
clay
Band, gravel
clay
•Ant, gravel
crystalline cock
100
30
200
200
100
MOO
Flow Velocity -
Min Max
Vh
1.9
2.4
-
0.36
—
0.006

0.21

0.05

0.042
0.02
0.02
-
o.sa

9.011

9.0035

1.1
0.53
0.24
0.10
-
Vu Vh
Tft/dayr
6.2
14
—
3.0
— -
0.29

0.47

0.2

B.4
4.3
0.2
-
.

0.011

0.001

3.5
1.1
- . 0.64
U10'5 -
0.26
•• ~
Flow System
Distance Frui Prinary
Rech. to Oischg. Hide of
V" Boundaries b Discharge
v (It)
creek
3.200 river
aquifer
2,000 river
— — —
- -

streon

• - %«!!•

3,000 Cfrlnjs
-• 3,000 sprlnja
3,000 creek
- - -
52.000 creek

» - ocean

.

*MI
MllB
MllS
6xlO~* - aquifer
aquifer
— —
Vcncric
Setttlni
1
1

1

1

1

1

S


1

I

2

1
1
7


Source
Qjr.luic et al.
llarni (l»78)

LaSala (1968)
.
K-wson et al.
(19b7)
Mri.wicr at al,
(1966)
Hx>t rt al.
(196S)
Ohlll { 1902)


Knollin et al.
(1964)
llonr^.w et al.
(196S)
llutchinson
et al. (1978)
M..,t ||V«|
North Carolina
D.N.M. (1978)
Mack (1962)


     continued

-------
                                                                                TABLE  2.0-1
K)
Utsaturatod lone
Sluly
Area
10-11
•
10-12

10-13


10-14

11-1

11-2
11-3



'.1-4

11-5
11-6

11-7

11-a

r.irth Layrr
Material Ihickness
(ft) .
-

sand.

sand.


sand.
clay
sand.

sand.
sand.



sand.

-
•and.

sand.
clay
sand.

-

gravel 10-20

gravel 10-100


silt, 90

gravel

gravel
gravel



gravel

-
gravel

•lit.

gravel

Saturated lone Flow Systra
Earth Layer
Material Hilckness
(ft)
sandstone

Bond, gravel
schist
said, gravel
clay
sand, gravel
sand
•ilty clay
sand, gravel
lumlatona
sand, gravel
sand, gravel
fine sand
sand, gravel
Eliale
sand, gravel
Itarstone
cand, gravel
sand, gravel
ohale
sand, silt, clay

cand, gravel
cltale* schist
•0

200
>100
90
20
200
10
100
150
>200
100
30
100
30
>50
100
-
-
100
>200
75

200
>500
flow Velocity Distance Mru»
Mln MOM Hech. to UlccJig
vh
0.64

0.03

0.16
-
0.04
1.3
-
0.64
-
0.32
0.22
-
1.3
-
0.4S
—
5
0.45
"
21

27

V* V. V. Boundaries0
Yft/day)5 ' (It)
...

0.10 - 42,000

- . 0.72 - SS.OOd
iKlO"* - S»10~*
0.19
2.1
- - - -
- ' 1.3 - 10,000
- - -
0.64
- d 0.45 - . 2,000
0.04° - l.f 100
2.2
-
3.0 - 13,000
...
.
3.0 - 5,000
- - •
- 55 - 15,000

- 80

Primary
. Hide o(
Discharge


well

stream
a^iiter
well
strcon
-
river
-
-
river
aquifer
river
-
river
-
river
well

river

wells

Gittcric
betttlng
1

1

1

1
|
'l

1

1
a



i

i
i

i

i

Source
UvxfcTkrr et al.
(1979)
LMwillc et al.
(19bl|
Luzier (1900)

Getzcn (1972)


SfrinJUe (1978)

Croft (1973)

Dalsln (1978)
Marie (1975)



flonort et al.
(1979)
teutb (1970)
Hilton ct al.
(1960)
Kllnuth (19*4)

Ktnslow et al.

                 * Vertical groundwater flow U toward unless otherwise Indicated
                   Mailimn horlnntal distance fccn recharge to discharge groundwater divide*
                 c A dash indicates that  Information MS not reported
                   Onward groundwater Clow

-------
        FIGURE  2.0-1
         POTENTIAL AREAL EXTENT OF A  PLUME  AS  A FUNCTION
         OF TOT PER UNIT TIME
         c
        •o *-.
         4) 4J
        — t+-
         « *-*

         HJ I/)
         u u
        *J HJ
           0)
         V >>
         
-------
release for a limited time period.  The first of these scenarios

shows increasing steady state concentrations with increasing TOT,

the second and_third show peak or steady state concentrations to

be unrelated to TOT and the fourth shows decreasing peak concen-

trations with increasing TOT.

Steady State

     If the release of a contaminant into an aquifer for a finite

period of time is assumed to occur at a point, then the following

equation describes the variation of contaminant concentration

with time and distance along the direction of the flow:

                                -(x-V(t-l
                    Q(t') exp (
       C(x,t)
t-t'))2\
(t-t1) J
Q(t') exp      4Dx(t-t') /   dt1 (2)*
                      8 n0VlT3(t-t')3DxDyDz
where
     C(x)   =  Concentration (grams/meter^)
               distance x (meters);

     Q(t')  =  Time dependent contaminant release rate
               (grams/second) to the aquifer at point.x = 0;

     V      =  Seepage velocity for the aquifer (meters/year);

     Dx     =  Dispersion in the direction of flow
               (meters2/year);

     Dy     =  Dispersion in the horizontal direction
               perpendicular to the direction of flow
               (meters^/year);

     Dz     =  Dispersion in the vertical direction
               (meters^/year); and,

     ne     =  Effective porosity  (0 < ne _f.l);
*Equation (2) is modified by GCA Corporation from Freeze and Cherry
(1979) equation 9.6 (on page 395) for the case y = z = 0.


                               2-11

-------
This equation describes the effects of hydrodynamic dispersion

It does not consider the effects of contaminant degradation or

sorption to soil particles.

     For a release rate Qo, which does not vary with time, the

steady state concentration (t—? °° ) is given by:
                    4-ff x ne y DyDz
                                               (3)
                                                 **
     In the analysis, the following assumption/definitions are

also made:

     Cmax(x) = Maximum concentration at distance x considering
               all values of C(x,t)

     Time of Travel  (TOT) = x
                            V
     Dv =  c< Tv

     Dz =  XTV


The values ° have units of

meters.  The contaminant release rate, Qo, used in Equation (3)

can be written as follows:

     Qo  =   JV                                 (4)

where

     j = either a constant or a variable  (units of g/m)
         depending on whether or not the  release rate, Qo,
         is  flow dependent.



** Equation  (3) is from Hunt (1978).
                               2-12

-------
Equation (3) can then be written as:



     C(x, oO )  = 	jv	
                  41T x ne v  «T °^L           (5)
                  4TT x



     If the release rate is constant with respect to velocity,



then the source term Qo is constant and j is inversely proportional



to V.  In this case, as TOT increases, j increases and the peak



concentration increases.  With constant contaminant release, the



steady state concentration at distance x is higher for longer TOT.



     If the release rate is flow-controlled (proportional to the



flow velocity within the aquifer), then Qo is proportional to V,



and j is constant.  In this case, the steady state concentration



at distance x is independent of velocity and,  therefore, TOT.



Releases Over a Limited Time Period



     Some releases may only last for a period Tr.  In this case,



the time dependent release rate Q(t') used in Equation (2) is



given by:



     Q(t')  - jV  for 0Tr



For a constant release rate Qo over a finite period Tr, the term



jV will be constant and the peak concentration Cmax(x) at a



distance x will be independent of the TOT.



     For flow-controlled releases having a. finite period, the



peak concentration, Cmax(x), at a distance x will actually



decrease with increasing TOT.  The amount of this decrease will



depend upon the period of release and the distance from the





                               2-13

-------
source.  This relationship is illustrated in Figure 2.0-2, which



shows the ratio of maximum to steady state concentration for



different values of TOT and release period.  In this example, the



distance x has been chosen as 30 meters and the longitudinal and



traverse dispersivities, 
-------
 4)
 4)
 O
 o
 II
 X
 L.
 o
 8
X
 X
 E
 O
                        Time of Travel to Reach 100 Feet (Years)

           Symbols  (Period of Release)
            •    1 YR.
            a    2 YR.
            T    3 YR.
            O    5 YR.
            *    7 YR.
            A   10 YR.
      FIGURE  2.0-2  Ratio of Peak to Steady State Concentration  as  a Function  of
                   Time of Travel (TOT) and Period of Release at a Distance of
100 Feet from the Release Point (
«
                                                               0.1)
                                        2-15

-------
problem can be isolated for examination by holding other aspects



constant.



     Modeling also provides an opportunity to examine the effects



of hazardous waste management in hydrogeologic settings with



long TOTs.  The steady-state characteristics of plumes in these



settings cannot be thoroughly examined using case studies, simply



because insufficient time has passed since facility operations



began in those settings for a plume to mature to such dimensions.



Modeling provides a method for estimating when such dimensions



might be reached, and what the characteristics of such a plume



and its relationship to an uppermost aquifer might be.



     The model selected for this work is the Liner Location Model



developed by EPA to assess the contaminant concentrations and



health risks associated with a range of TOT^oO conditions (as well



as other characteristics) at hypothetical sites.  The model has a



number of subroutines, including ones for ground-water flow and



solute transport.  The version of the model used in this analysis



was not designed for site-specific use; EPA is refining the model



and plans to make it adaptable for site-specific use.



Results of Model Use



     This effort examined six generic, vertically-oriented ground-



water flow fields covering a range of ground-water flow velocities



from 100 feet in 10 years to 100 feet in 1,000 years.  Peak con-



centrations were determined for a point 100 feet along the ground-



water flow line from the source.  The hydrologic subroutine is



described in Attachment 1.



     Different scenarios were generated for each setting by varying





                               2-16

-------
key parameters, as follows:



  0 Two contaminant mobilities were examined.  These were class 1,



    retardation factor of 1.3, and class 2, retardation factor of



    32.



  0 Two source loading mechanisms were examined:  equal mass



    input and flow field controlled mass input.  Equal mass



    inputs could be controlled by either the facility design/



    failure mode or an underlying unsaturated zone.  Flow



    field controlled inputs are masses released at a rate



    determined by the flow field which continue for a fixed



    time period.  The total mass released varies with flow



    field velocity.



     The principal results of the hydrologic model are summar-



ized in Table 2.0-2,  which shows peak contaminant concentrations



and 100-foot travel time for the six generic settings.  Variations



are shown for the two chemical mobility classes and for the two



source loading assumptions.  For the hydrogeologic settings



considered, there is no clear relationship between peak concen-



trations produced by instantaneous equal mass releases at the



source and velocity or TOTioO-  This is consistent with the dis-



cussion in Section 2.0.2 which showed these variables to be



independent.  Variations in concentration shown in Table 2.0-2



are due to variations in other variables such as porosity and



the influence of multilayer velocities in scenarios M, N, and O.



Where time-limited mass releases are controlled by the flow field



(including diffusion-controlled transport with high velocity



contrasts), peak concentrations decrease with increasing
                             2-17

-------
                      TABLE 2.0-2  CRITICAL TIMES AND PEAK CONCENTRATIONS AND 100-FOOT TRAVEL TIMES
                                   FOR TWELVE SCENARIOS
ro
H*
OD
Scenario
identification
J-1-100
J-2-100
K- 1-100
K-2-100
L-1-100
L-2-100
M-1-100
M-2-100
N-1-100
N-2-100
0-1-100
0-2-100

Start
(yr)
300
8,000
35
800
k
80
250
8,000
120
3,000
5
150
Critical
End
(yr)
5,000
110,000
1»50
11,000
53
1,100
120,000
360,000
800
20,000
120
3,500
times
Peak time
(yr)
1,250
32,270
115
3,000
12
320
1,360
33,000
260
6, MO
21.5
550
Peak concentrations
Standard load
(mg/1)
k2.k
1.80
19.5
.92
20.5
.87
1.2
.0
-------
     The difference in relationships between peak concentration



and velocity/TOT^QO highlights the importance of the source term



in the model. _This modeling study also shows that the lowest con-



centrations are associated with settings that include very low



velocity surficial layers with diffusion-controlled transport



overlying an aquifer that would otherwise have received



higher inputs of contaminants and would not have met the current



TOTiQO criterion.



Conclusions of Preliminary Use of Liner Location Model



     This preliminary analysis supports the use of the TOT^oO



criterion where source removal or corrective action can limit the



duration of the contaminant releases.  In this circumstance, the



magnitude or mass loading of the release is controlled by the



low-velocity flow field.



     This analysis also shows that zero concentration cannot be



achieved for nondegrading constituents as long as a waste source



exists.  Contaminants will move, albeit slowly and in minimal



volume, through low-velocity flow fields.  These constituents can



eventually reach aquifers and, hence, points of potential exposure.



However,  as shown in Table 2.0-2, these times may be far into the



future, on the order of thousands of years.  This result further



supports the view that the TOT]_go criterion describes settings



that minimize the potential for exposure to releases.



2.1  POTENTIAL FOR EXPOSURE THROUGH A GROUND WATER RESOURCE



     The potential for exposure to contamination through a ground



water resource can be described by two main factors.  The first



factor relates to the plume character, which includes its potential
                               2-19

-------
size and the peak concentration of contaminants, as discussed

in Section 2.0.  The second factor in potential exposure is

related to the"probability that the saturated zone could supply a

sufficient volume of water for residential use or other purposes.

As described in this section, the vulnerability criterion,  TOT^oO'

provides a measure for potential exposure because it incorporates

a consideration of these factors.

2.1.1  Theoretical Relationship between TOT^QO and Well Yield

     This section discusses the theoretical relationship between
                       *
TOT^oo of ground water within a saturated zone and the potential

yield (Q) of a discharging well in the same zone.



Time of Travel

     The technical analysis examined well-documented mathematical

expressions, commonly used by hydrogeologists to analyze travel

time and well yield.

     The general expression for calculating TOT in a homogeneous,

isotropic media through which ground water is flowing under the

influence of a uniform hydraulic gradient is:



           TOT = Lne                       (7)
                 KT~



where      TOT = time of travel, (T)

           L   = length of flow path,  (L)

           ne  = effective porosity, (dimensionless)

           K   = hydraulic conductivity, (L/T)

           i   = hydraulic gradient, (dimensionless).

     Equation (7) is used in the definition of ground-water


                               2-20

-------
                                                       ruuu




                                                 8472 • 00-  2A



vulnerability when L is set equal to 100 feet.  It shows that TOT



is inversely proportional to both hydraulic conductivity and



hydraulic gradient.  A long TOT can be associated with very low



permeability materials, very low hydraulic gradient,  or both.



Well Yield



     The steady radial flow to a discharging well in  a confined



aquifer is described by (Thiem, 1906):



           Q = ?TTKh  h - hw               (8)

                     In (r/rw)



where      Q = constant well yield,  (L^/T)



           K = hydraulic conductivity, (L/T)



           b = constant aquifer thickness, (L)



           h = hydraulic head at radial distance r,  (L)



          hw = hydraulic head at the well, (L)



           r = radial distance associated with h, (L)



          rw = radius of the well,  (L)



     A more general form of the equation can be obtained by



letting r = rl, rw = r2,  while h = 'hi and hw = h2.  Equation (8)
                                            •


can then be rearranged to obtain an expression for the hydraulic



conductivity (Todd, 1959,  page 83):
           K
               Q In (r2/rl)
               2^Tb (h2-h1)



     Consideration of the equations for TOT and well yield can be



taken further by substituting Equation (9)  for K in Equation (7).



This yields the following expression:




           TOT = 2TT L n b (h2-hj)          (IQ)

                  Q In (r2/ri)i
                               2-21

-------
Both well yield and TOT are sensitive to hydraulic conductivity.



A very low conductivity regime will tend to have both long TOT



and low well yields.  Facilities located in such "non-aquifers"



(i.e., aquitards) should have a minimal potential for exposing



human and environmental resources to contaminants released to



ground water because the chances for aquifer exploitation are



minimal.



     However, the relationship between yield and TOT is also



influenced by porosity, well drawdown, aquifer thickness and



hydraulic gradient.  A setting with a high hydraulic conductivity



and a very low hydraulic gradient can have both long TOT and high



potential well yields.  This occurrence illustrates the importance



of considering changes in hydraulic gradient due to aquifer



exploitation in evaluating TOT, as discussed in Section 3.2.2



of the main text of this guidance.



2.1.2  Frequency Distribution of TOT Among Well-studied Aquifers



     This section summarizes information on 67 case studies of



existing hazardous waste land treatment, storage, and disposal



facilities reviewed during Phase I of the Liner Location Project



for the Office of Solid Waste (EPA, 1983).  The location of the



67 facilities is shown in Figure 2.1-1.



      Figure 2.1-2 is a histogram that presents the frequency of



occurrence of horizontal ground-water velocities collected in the



survey.  Table 2.0-1 summarizes the basic data for each case



study.  Because the majority of cases represented well-studied



aquifers that were also well developed for water supply, the



velocities may be biased toward the high end of the range of
                               2-22

-------
NJ

10
OJ
      EXPLANATION
        • 6-1
              Groundwater region
Location and designation of
groundwater study area
                                                                                                       10-8
                                                                                             0   WO  tOO  MO  400   MO Mllll
                  FIGURE 2.1-1   LOCATIONS  OF LITERATURE SURVEY STUDY AREAS IN RELATION TO  THE
                                 LOWER 48 STATES AND 10 USGS GROUND-WATER REGIONS

-------
o
ec
ec
o

>•
S*
Oi
U.
50 -
30 -
20 -
10 .
0 -
<
yjiy
c
IX'X'X'X-X
x:::x ::x::-::x:x:::
o


•--^•--1
EXPLANATION
Frequency based on
1 i terature survey
o Frequency of value used
in model scenarios

<
10 
-------
possible velocities.  In addition, some, but not most, case



studies represent confined aquifers, not the uppermost aquifer.



Consequently, there is some question about how representative this



data-base is of conditions underlying RCRA facilities.



     A TOT]_QQ scale is shown at the bottom of Figure 2.1-2 in order



to show the relationship of the criteria to the aquifer-oriented



database.  Clearly, TOTiQO values on the order of 100 years occur


infrequently among the 67 case studies  (about 4%).



     This information suggests important conclusions:  TOT^QO

                                         *
values on the order of .100 years or more are uncharacteristic of
                                •

aquifers, and facilities located in nonvulnerabie settings are



unlikely to discharge to geologic formations that supply a sig-



nificant quantity of water for sustained uses.


2.1.3 Contamination of High Capacity Production Wells



     A common condition resulting in risk and exposure occurs



when contaminated ground water is intercepted by high capacity


production wells.  The public is at risk when municipal wells are



contaminated, while the potential for worker exposure exists when



industrial wells are threatened by contamination.  If irrigation


wells become contaminated, the irrigated crops may also take up



the contaminants, which can result in contamination of the entire



food chain.


      The conditions described above are most likely to occur in



areas with high-yield aquifers in which high-production wells are



likely to be located.  In general, these aquifers consist of thick



deposits of unconsolidated sands and gravels, or other highly


porous media, such as fractured or poorly cemented sedimentary
                               2-25

-------
rocks, or fractured limestones.  Often, the well fields are situ-



ated near streams and rivers, where induced recharge from surface



waters supplements the available ground-water supply.  The TOT^oo



in these types of hydrogeologic settings is always very short



because such productive aquifers are highly permeable.



     Because continuous pumping of significant quantities of



water at these well fields can alter the pre-existing flow paths



and even create reversals in the direction of ground-water flow,



sources of contamination may be very difficult to identify.



Pumping may also shorten TOT^QO if it has been calculated under



natural conditions, because the cone of depression around such



wells will increase the hydraulic gradient, which is also directly



proportional to velocity.



2.1.4  Contamination of Individual Drinking Water Wells



     Contamination of domestic water supplies is becoming in-



creasingly more common.  In 1970, nearly 20 percent of the United



States population relied on individual wells for drinking water



and domestic use.  In rural areas, many contaminated domestic



wells have had to be abandoned due to releases from hazardous



waste management facilities.



     Individual drinking wells can be located in many kinds of



hydrogeologic settings because even aquifers with very small



yields (as low as half a gallon per minute) can provide sufficient



quantities of water for domestic use.  The geologic settings



range from fractured crystalline bedrock to highly permeable sand



and gravel deposits.  TOT^oO is highiy variable because of the wide



range of hydrogeologic settings.  Well depths range from only a
                               2-26

-------
few feet to over a thousand feet, although the majority of wells

are between 100 and 300 feet deep.  In general, domestic wells

located in unconsolidated materials are shallow, depending on the

depth to the water table.  These wells are the most susceptible

to ground-water contamination because most hazardous waste facil-

ities are located at or near the surface; hence, contaminants

will often be most concentrated near the top of the aquifer.

Exceptions would include contamination from underground injection

wells that dispose of wastes to deeper portions of the aquifer,
   v
and contamination by constituents that are much denser than water.


2.2 POTENTIAL FOR EXPOSURE TO CONTAMINATED SURFACE WATER

     The theoretical discussions of ground water contamination

presented in Sections 2.0 and 2.1 also relate to the second pathway

of exposure, surface water contamination, because contaminated

ground water can discharge to surface water bodies through springs,

seeps, and baseflow.

     This section describes conditions and representative hydro-

geologic settings that can lead to contamination of surface water.

2.2.1 Surface Water Exposure Pathway: Hydrogeologic Settings

     Surface waters and ground waters are interdependent compo-

nents of the hydrologic cycle; a change in one of these components

may have a significant impact on the other.  Contamination may be

transported from ground water to surface water in discharge areas,

which occur in topographic lows.  These situations arise when the

net saturated flow of ground water is toward the water table,

which is often at or very near to the ground surface.
                               2-27

-------
     If the discharge rate is low or flow occurs over a large area



diffuse seepage may occur, moistening the ground.  However, seepage



along streams or lake banks may produce a volume sufficient to



provide a main source of stream flow during dry periods (baseflow).



     Surface water bodies may also receive ground water from



springs.  Springs arise when a discharge from an aquifer is



concentrated in a small area, and they commonly occur in areas of



fractured bedrock or karst topography.



     Discharge of ground water is related to precipitation and



will vary seasonally with the amount of water that is stored in



the saturated zone and, therefore, with the slope of the potentio-



metric surface.  Nested piezometers may be installed to determine



if an area has an upward component of flow characteristic of a



discharge area.



2.2.2 Contamination of Potable Surface Water Supplies



     An example of a situation that presents a risk to human health



is the contamination of surface water bodies, such as lakes,
                                       •


reservoirs, ponds,  or rivers, that serve as drink'ing water supplies.



A risk can also exist if creeks, streams, rivers, or their tributar-



ies that eventually empty into a drinking supply are contaminated.



Surface water may become contaminated by direct discharge of con-



taminants from a point source to the water body or by contaminated



runoff.  Contaminated ground water may also be a source of surface



water contamination if it discharges to the surface water body.



2.2.3  Contamination of Surface Water Ecosystems



     When a body of surface water becomes contaminated, it poses



a risk to aquatic organisms or the entire ecosystem that it
                               2-28

-------
hosts.  Humans are also at risk if they have contact with the


contaminated water through recreational activities or if they


ingest aquatic life/ such as fish, that dwell in the water.


Animals may also be exposed if they drink the water or ingest any


aquatic organisms.


2.2.4 Bedrock Springs Contamination


     In some cases, the identification of contaminated ground


water is first made in areas where springs are visibly contam-


inated.  Indications of contaminated springs or seeps include


noxious odors, dead or dying vegetation or animals near the
                                                    »

springs, and the presence of oil.   The presence of a contaminated


spring is usually a strong indication of a much larger problem.


     In general, springs and seeps occur where the water table


intersects the surface.  Several types of springs can occur,


depending on the hydrogeologic setting.  A depression spring is


likely to occur in a topographic low spot, thereby creating a


local discharge zone.  Contact springs are likely to occur at the


contact between a high permeability layer and an underlying low


permeability layer.  Faulting can create a similar condition when


a low permeability layer is juxtaposed with a high permeability


layer.  In areas underlain by limestone, springs are very common


because of the creation of solution features, such as caverns and


sinkholes.  Springs are also common in areas with fractured, low


permeability rock.  Water movement occurs along the joints and


fractures, and spring water discharges where the fractures intersect


the surface.

     Given otherwise similar hydrogeologic settings, the
                               2-29

-------
will nearly always be shorter where springs and seeps are present

than where they are absent.  Springs and seeps often reflect the

presence of pathways of low resistance, such as solution channels

in limestones or joints in crystalline rocks, along which ground

water tends to flow.  Abandoned mine shafts create a similar

condition, in which rapid transport of contaminants occurs in

water-filled shafts.

2.3  POTENTIAL FOR EXPOSURE THROUGH THE BASEMENT SEEPAGE PATHWAY

2.3.1 Description of Condition

     Exposure can occur when contaminants enter basements of homes

and buildings through ground-water seepage or vapor phase transport

of methane and other toxic gases.  To anyone living in the area,

this condition poses a serious threat through exposure 'to toxic

chemicals and fumes and through the potential for fires and

explosions resulting from highly combustible gases.

2.3.2  Representative Hydrogeologic Settings

     This condition can occur in a variety of hydrogeologic
 •
settings.  .However, the risk from contaminants seeping into

basements is most likely to be present in areas where the water

table is permanently or seasonally above the level of the basement

floor or where an upper isolated saturated zone exists.  Vapor

phase transport is a more serious problem in settings where there

are interconnected pathways between the contaminated aquifer and

the surface, such as fractured bedrock or porous unconsolidated

sand and gravel deposits.  The presence of noxious odors is often

the first indication of a problem.

            varies in settings where basement seepage occurs.


                                2-30

-------
The pathways themselves may be localized features with short



TOTioo values that provide the path of least resistance for con-



taminant transport in a predominantly long TOT^QO setting.  For



instance, such pathways may consist of sand lenses, permeable



topsoil, or man-made conduits such as buried utility lines or



gravel-^f illed drainage swales.



     When a facility is underlain predominantly by a low perm-



eability layer (where TOTioo ^s long), increased recharge, both



artificial and natural, could cause ground-water mounding.  This



elevation of the water table may create the opportunity for



contaminants to travel through previously inaccessible pathways



(the 'bathtub effeet'),. unless that pathway is already accessible



due to a high water table.  One must also examine the potential



impact of artificial containment barriers installed to lengthen



TOT100' or tne failure or stripping off of a cover, in causing a



bathtub effect (see Section 3.1 for examples of contaminant



transport through the basement seepage pathway).  The potential



for this pathway to exist may be recognized by examining flow



patterns that would result from the greatest hydraulic head that



could occur at a unit.  Section 3.2.2 of the main text discusses



how these heads can be determined.  If the pathway could exist,



modifications in unit design might prevent migration, as discussed



in the next section.



2.4   CONSIDERATIONS FOR LOCATION AND UNIT DESIGN



     The optimum nonvulnerable setting for a hazardous waste man-



agement unit is one that minimizes the potential for exposure to
                                2-31

-------
human health or the environment by limiting waste migration

potential through each of the three pathways: exposure to a

contaminated ground water resource, exposure to surface water

contaminated by discharging ground water, and exposure through

the "basement seepage" (near-surface flow) pathway.  The vulner-

ability definition is an important trigger for evaluating overall

site performance under several major design scenarios.

2.4.1  Controlling Discharge from a Unit

     The hydrogeologic characteristics of a location can control
                                              *
the amount of fluid released to the saturated zone from a landfill,

surface impoundment, or waste pile, thereby helping to control a

plume at its source.  An effective design evaluation includes an

assessment of how natural controls can be used to minimize fluid

discharge, in addition to engineered components such as liners

and caps.

     The volume of fluid discharged across an area within the

saturated zone per unit time (Q) can be calculated as:

           Q = -KiA,                       (11)

where      Q = flow (L3/T)
           K = hydraulic conductivity (L/T)
           i = hydraulic gradient
           A = cross-sectional area of flow (L2).


Because   Q o<_  K    and    Q oi i,  settings with low hydraulic

gradients and low hydraulic conductivities (i.e.,  long TOT^QO

values) can minimize discharge from the waste management unit

depending upon whether the discharge is controlled by the flow

field.  This can best be understood by considering the potential
                               2-32

-------
performance differences of a unit in the unsaturated and saturated




zones.



Unsaturated Zone



     The potential discharge from the facility located wholly



above the water table equals the amount of infiltration passing



through the cover (or direct precipitation, if no cover is present)



and the bottom liner (if any), plus the volume of any run-on and



fluids present within the unit.  If the liner and the cover are



truly impermeable, there should be no discharge.  If this condition



is not satisfied, the discharge will be as high as the infiltration



through the cover, or the fluid volume placed within the unit



plus 'incident precipitation and run-on during unit operation.



Consequently, prevention or minimization of discharge requires



both advanced design considerations and long-term, .active unit



maintenance.



     When a discharge occurs from a unit in the unsaturated zone,



the hydraulic gradient along' the flow path from the unit to the



ground-water table will be high (close to 1.0).  If the discharge



is substantial, a ground-water mound might be created beneath the



unit; mounding can increase the pre-existing hydraulic gradient



within the saturated zone as well, with a consequent increase



in Q and reduction of TOT^QQ•



     The relationship between TOTj^oO an^ peak concentration (or



risk) for such cases is discussed in Section 2.0.2 under the



descriptions for the constant release scenario, in which peak



concentration increases with increasing TOT^QO f°r a continuous



release.  A release occurring over a limited time period displays






                               2-33

-------
a peak concentration unrelated to



Saturated Zone



     This discussion applies only to below-grade units, in which



the maximum elevation of waste placement is below the top of the



saturated zone.  At closure, the final cover would fill the



excavation to the original grade.



     At a facility where waste is located entirely within the



saturated zone, the potential discharge through the liner (if



any), can be limited to the natural flux of ground water passing



across the boundary of the unit.  The discharge would be greater



only when the hydraulic gradient is increased by either fluid



addition during operation (assuming no impermeable liner) or



infiltration through the cover in excess of pre-existing conditions



In addition, the seepage velocity of ground water would be equal



to pre-site velocity unless the gradient is increased.



     This situation corresponds to the flow field controlled



scenarios described in Section 2.0.2,  in which peak concentrations



(and hence,  risk) are reduced as TOTiQO increases.  The success of



a unit located entirely within a low-permeability saturated zone



primarily depends on the ability of the final cover to limit



infiltration to levels that are not significantly greater than



those prior to unit construction; failure of the cover to perform



properly could allow mounding and migration along the third



pathway.



2.4.2 Considerations for Unit Design



     Limiting access to the three exposure pathways is critical



for optimal unit design.  One design scenario for a unit in a





                               2-34

-------
low-permeability nonvulnerable setting would be to:

     0  review the impact of passive flow barriers that may be
        installed,

     0  keep wastes well below grade to prevent formation of the
        basement seepage pathway or leachate springs (see Figure
        2.4-1), and

     0  maintain the integrity of the cover so that excess
        infiltration does not create a bathtub effect.

This design scenario optimizes the use of passive methods to

minimize the potential for exposure to releases that occur due

to human oversight and the failure or absence of man-made barriers.

It highlights the other major option for minimizing exposure

potential, which is to provide long-term (perpetual) monitoring

and response.  For example, if such active controls were ensured

through an institutionalized oversight and response program,

hydrogeologic setting would be less critical in long-term exposure

minimization.

2.4.3 Considerations for Storage and Disposal Units

     Unit design and location considerations can be affected by

whether a unit is operated and closed as a storage unit or as a

disposal unit.

Storage Units

     Because wastes are removed from storage units at closure,  a

release from a storage unit can occur only during a limited

period of time.  Because the owner or operator is responsible

for ground-water monitoring and corrective action during this

period (the active period of the storage unit), any release that

occurs should be detected and corrected as necessary, in response

to the permitting standards of 40 CFR 264 Subpart F.  As discussed


                               2-35

-------
                                                     OSWER POLICY DIRECTIVE K
                                                   9472•00-2A
                       '*!'.•-*.".'-*.''-•-'>'.
                                                               X
                                                          I
  3}

                                                   CLAY
FIGURE 2.4-1  Schematic illustrations of unit design.   Figure A
               shows waste disposed above grade.   The high
               hydraulic head  causes flow along  the  near surface
               silty layer as  well as vertically into the clay.
               Figure 3 shows  the optimal unit desiqn,  with wastes
               deposited below grade,, with a thick cap  filling the
               excavation, thus inhibiting access through the basement
               seepage pathway.
                                   2-36

-------
in Section 2.0.2, such limited time releases can occur under



either a constant release or a flow-controlled release scenario.



A constant release scenario, typical of a unit placed in the



unsaturated zone, yields a peak concentration that is unrelated to



TOTiQO*  A storage unit located in an unsaturated zone should not



pose a risk of exposure if the setting provides an adequate time



period for plume detection and implementation of corrective



action.



     A storage unit placed in the saturated zone would be



characterized by a flow-controlled release, in which peak con-



centration decreases as TOT^QO increases. While the long TOT^oO"



saturated zone setting may be more protective in the event of a



release, the major location consideration is to provide adequate



time for plume detection and response.  In fact, a longer TOT^QO



setting may impede the efficiency of a corrective action, owing to



increased sorption capacity of fine-grained sediments and the



decreased ability of collection wells to capture and remove the



plume rapidly.



Disposal Units



     Because wastes are not removed from disposal units at



closure, the potential exists for continuous and long-term release



of contaminants to the environment.  A disposal unit could have



either a flow-controlled continuous release, or a constant con-



tinuous release.



     As discussed in Section 2.4.2, a leaking disposal facility



located in an unsaturated zone would correspond to a constant



release scenario; the magnitude of the constant rate of flow






                               2-37

-------
from the unit depends on the degree of failure of the unit



design, is complicated by ground-water mounding, and thus is



generally unpredictable.



     Releases occurring from disposal units located in the sat-



urated zone may be controlled by the natural ground-water flow



velocities.  Although the peak concentration in flow-controlled



releases is unrelated to TOT^oO' tne size of the plume is limited



in a long TOT100 setting (Section 2.0.1), and discharges from the



unit would be minimal and predictable (Section 2.1.1).  Thus, a



long TOT^oO setting is especially important for disposal facilities
              *


where the absence of long term care necessitates a setting that



minimizes the potential for exposure to future releases.  Isolation



of wastes completely within saturated, low-permeability materials



offers this potential.
                               2-38

-------
     3.0 CASE STUDY EXAMPLES AND EXPOSURE ESTIMATION METHODS






     This chapter uses case studies to illustrate exposure and



health risk estimates for each exposure pathway in a variety of



hydrogeologic settings.  The case studies show that exposure to



ground-water contamination is most frequently documented at



locations with hydrogeologic settings exhibiting short TOT^Q'  Tne
vast majority of ground-water contaminant plumes and their ultimate



threat to human health and the environment have resulted from



hazardous waste disposal in locations where ground-water flow is



rapid and contaminants may be transported to a well, spring, or



surface water body.  In hydrogeologic settings with predominantly



long TOTiQO values, observed health threats have resulted from the



failure to recognize and prevent seepage of contaminated ground



water and associated toxic vapors along near-surface, short



TOTiQO pathways into basements and subsurface utilities.



     However, evidence of contamination in short TOT^oO



settings is expected because many existing hazardous waste sites



located in settings with long TOT^gO values would not be expected



to have ground water contaminated to the point where a problem



would have been detected.  Conversely, sites exhibiting short



TOT100 values would develop ground-water plumes rapidly as a result



of improper or ill-considered waste disposal activities and con-



sequently are much more likely to cause detectable contamination



that subsequently would be investigated.



     Because plume detection may be biased towards short TOTioo



settings, and because of the occurrence of basement seepage path-



ways, long TOTiQO settings should not be considered automatically




                               3-1

-------
safe for siting.  The examples presented in this section suggest
strongly that regional hydrogeologic settings and related land
and water uses surrounding the hazardous waste management facility
site should be evaluated thoroughly during the facility permitting
process.
     The brief case descriptions in Section 3.1 illustrate the
relationship between TOTioo and tne three exposure pathways.
Exposure and risk through the potential pathways are discussed
for each case in qualitative terms, because sufficient data
were not readily available for quantitative risk assessments.
An exception is the example in Section 3.1.7 for which more
quantitative information was available for the third pathway
analysis.
     As an example of the type of health risk methodology that
can be applied to a specific pathway, Section 3.2 discusses
assessment methods that can evaluate the potential health threat
to humans exposed to contamination through potable ground water.
     Finally, case studies illustrating the application of this
health risk assessment for ingestion of contaminated drinking
water are presented in Section 3.3; other pathways are indicated
when present.
3.1  CASE STUDIES: THREE EXPOSURE PATHWAYS
     These case studies are general summaries designed to il-
lustrate the relationship between TOT]_oo an^ a^ three exposure
pathways.  No rigorous health assessment methodology has been
used for these case studies.
                               3-2

-------
 3.1.1 Ground-Water Resource Pathway: Chemical  Plant  Site
 Description of Condition
     A  large  chemical plant was operated at the site until 1982.
 Nearby  residents have filed complaints about odors and irritants
 in the  air since 1973.  The town drilled five  highly productive
 wells in the  area, but odors in the water from these wells indi-
 cated the presence of contaminants.  Local and state authorities
 conducted a more detailed investigation of the company's disposal
 practices in  1978 after the company submitted  a proposal for
 expansion at  the site.  The investigation resulted in the shutdown
 of two  town wells as a precautionary measure,  which reduced the
 town's  drinking water supply by 40%.  The company has agreed to
 clean up the  contaminated areas and restore the quality of the
 aquifer supplying the town wells.
 Hydrogeologic Setting
     The site occupies about 500 acres and is  underlain by
 unconsolidated sands and gravels deposited near the end of the
 Wisonsin Glaciation.  These deposits have been extensively mined,
 especially in the southern portion of the property.  The plant
 and associated landfill are located on the northern part of the
 property.
     The stratified glacial deposits range in  thickness from a
 few tens of feet to about 120 feet.  A thin discontinuous layer
 of till separates the sands and gravels from the underlying meta-
 morphic gneiss bedrock.   The ground water in the gneiss occurs
primarily in the joints and fractures in the uppermost portion of
 the formation.  The hydrogeologic investigation of the site showed
                               3-3

-------
that  there  is a hydraulic connection between  the  ground water  ij
the bedrock and the overlying aquifer.
      Based on existing hydraulic conductivity data, an average
hydraulic gradient of .004, and an effective porosity of 20 per-
cent, velocities were determined to range  from 3  ft/day (sand and
gravel) to  .2 ft/day (silty fine sand).  Therefore, the shortest
TOT^QO would be about 33 days and the longest would be 500 days.
      In addition to the very short TOT^oO' the original flow
paths have been altered significantly by interference from
multiple pumping wells in the area.  Furthermore, the ground
water flow paths are subject to change, depending on the rates of
recharge and pumping. This variation makes a reasonable long
term prediction of contaminant migration very difficult in this
type of setting.
3.1.2 Ground-Water Resource Pathway: Abandoned Gravel Pit/Landfill
Description of Condition
     This site in the northeastern U. S. includes two landfills
located in an abandoned gravel pit on a lake shore.  Both municipal
and industrial wastes, including chemical wastes, were disposed of
for nearly 50 years.  Twenty-one homes adjacent to the landfill were
obtaining drinking water from private wells when the contamination
was discovered in 1979.   In 1980, volatile organic compounds
were detected in a residential well south of the site.  The lake
and the domestic wells are seriously threatened by the landfills.
Hydrogeologic Setting
     The site is located in unconsolidated sand and gravel deposits
where TOTjoO values would be expected to be short, underlain by an
                               3-4

-------
irregular bedrock surface.  A deep bedrock trough containing as



much as 150 feet of glacial and marine sediments underlies the



northeastern part of the site.  The general direction of ground-



water flow is eastward toward the lake; however, local flow



patterns are much more complex and vary temporally with fluctua-



tions in rainfall and the lake level.



3.1.3 Potable Surface Water: Multi-Source Waste Site



Description of Condition



     The site area, located within a valley, provides an example



of a long-term, multi-source contamination problem.  Seepage from



industrial and municipal waste impoundments is the major source of



ground-water contamination.  However, leaking sewers and storage



tanks, use of sewage sludge as fertilizer, and spills of contam-



inated fluids in commercial and industrial areas have added to



the problem.  The ground water flows toward the east and discharges



to a shallow narrow stream that drains into a major reservoir on



the river that supplies about half of the total water used in



the valley.  Elevated concentrations of total dissolved solids



are present in ground water and surface water sampled in the



stream and its tributaries.  The dissolved solids consist of



high concentrations of iron, chromium, lead, lithium, strontium



and zinc.  A plume of nitrate-rich ground water extends to the



stream from a large industrial park, 3 to 4 miles downgradient



from the site.  The continued movement of contaminated water



poses a potential threat to the water quality of the lake.



Hydrogeologic Setting



     The site area lies within a bedrock valley that is partly
                               3-5

-------
filled with unconsolidated deposits consisting of beds and l



of sand, silt, gravel, and clay up to several thousand feet



thick.  The bedrock valley is comprised of relatively imper-



meable igneous and sedimentary rocks.




     The unconsolidated deposits form several major hydrogeologic



units at the site.  The uppermost aquifer isjsomposed of sand



and gravel; the water table within this aquifer ranges from land



surface near the stream, to as much as 50 feet below land surface



elsewhere in the valley.  Underlying this uppermost aquifer is a



confining unit composed of silt, clay, and fine sand; several



artesian aquifers are interfingered with these confining beds.



Regional ground-water flow is from the recharge areas along the



bordering highlands to the discharge areas in the lowlands, where



water from both the shallow and underlying deep aquifers seeps




into the stream.  TOTiQO for this setting is estimated to be short



through the unconsolidated sands and gravels of the uppermost



aquifer.



3.1.4 Surface Water Ecosystems: Mining and Ore Processing Facility



Description of Condition



     An abandoned mining and ore processing facility produced



titanium dioxide for paint pigments between 1931 and 1971.



During its period of operation, the facility either disposed of



acidic wastes in sedimentation ponds or discharged these wastes,



untreated, into a nearby river.  Between 1977 and 1980,  four major



fish kills occurred in the river; the State has attributed these



fish kills to the facility.  Although the acidic waste liquids



are no longer present in the evaporation ponds,  ground water and
                               3-6

-------
soils still exhibit acidic conditions.  Residual sludges and



other materials are buried on the site; some unreacted ore and



ferrous sulfate is located within the soil in evaporation ponds



or scattered at the surface.



     Surface water runoff from the site exhibits low pH values



(acidity) and high metals concentrations; ground-water sampling



has also revealed low pH values, elevated metals concentrations,



and sulfate contamination.  Human exposure from the facility is



considered to be low, given the remote location of the site.  The



nearest drinking well is located to the north upgradient of the



site; when tested,  the water did not contain metals or other con-



taminants above ambient background levels.  The closest drinking



water source downstream of the river is 40 miles away.



     The two environments at risk of exposure are terrestrial



flora and fauna around the clay-lined iron sulfate pit and the



aquatic ecosystem of the river.  The primary routes of exposure



to these receptors are ground-water discharge and surface water



runoff.  The forest areas.located in the path of ground-water



flow and surface runoff, and benthic flora and fauna in the river



downstream of the site, face the highest risk.  Water having



certain low pH values has been shown to be acutely toxic to



aquatic species.



Hydrogeologic Setting



     The facility lies in the foothills of the Blue Ridge



Mountains along a river; and occupies approximately 510 acres.



The facility is set on a hillside within the river drainage



basin.  Soils are composed of clay and silty clay.   The soil is
                               3-7

-------
a dark reddish clay loam with a low permeability.  Soils of this
type commonly exhibit permeabilities of 10~5 to 10~9 cm/sec
(Freeze and Cherry, 1979).  Borings taken in November of 1982
indicate that sand and gravel materials exist/ either within the
clay and silt matrix, or in thin lenses interspersed between
clay and silt, and the soil gradually changes with depth into
saprolite, a decomposed clay with a rich igneous horizon.  Most
of the horizon contains mica flakes and rock fragments.  The
saprolite material becomes coarser with depth and changes into
silt-sized particles.
     Bedrock consists of anorthosite, a gray, plutonic rock of
Precambrian age that contains titanium-rich minerals in this
locality.  The bedrock strikes northeast and dips steeply to the
southeast, and occurs at a depth of about 40 feet at the site.
     Although limited data are available on the site hydrogeologj^
ground-water flow is apparently controlled by the geology of the
valley.  The inference is that the potentiometric surface slopes
toward the river; hence, ground-water discharges to the river.
Areas upgradient and north of the site appear to be free of
ground-water contamination.  Two wells located north and north-
west of the site revealed no contamination.  However, ground-water
samples on and downgradient from the waste burial site showed
contamination.  Ground-water contamination is also evidenced by
vegetative stress in the area.
     The primary surface water of concern is the eastward-flowing
river, which discharges into another river approximately 3.5 miles
downstream.  The surface water runoff from all six areas of
                               3-8

-------
 concern  discharges  into  this  river.   Several seeps  have developed



 from the iron  sulfate  disposal  area  and  apparently  contaminate



 surface  runoff.flowing off  the  area  and  toward  the  river.






 3.1.5  Bedrock Seeps and Springs:  Municipal and  Industrial Landf;



 Description of Condition



     The site  was used as a municipal  landfill  and  an industrial



 waste disposal site from 1966 to 1974.   Materials were  disposed of



 in unlined pits on the site,'  resulting in contamination of local<



 soil, surface  water, and ground water  by organic and inorganic



 compounds.



 Hydrogeologic  Setting



     The site  lies on  a plateau and  is underlain by a sandstone,



 shale, and limestone formation.  The bedrock  stratigraphy beneath



 the  site consists of the fractured and weathered sandstone under-



 lain by  the soft, grey-brown  to reddish  shale and claystones.  A



 limestone lies below the shale resting conformably  on "red beds."



 Soils at the site are  10-14 feet thick and con-sist  mainly of



 silts and sands, probably derived from the bedrock.



     The  sandstone and the unconsolidated material  overlying it



 constitute the uppermost aquifer.  The limestone that underlies



 the shale is also an a'quifer; although its water-bearing properties



have not been  directly investigated at the site, it is  thought



 to be an  unconfined aquifer.



     Seeps have been identified at the contact of the sandstone



 and shale; the seeps are the  result of infiltrating water that



 is unable to percolate through the less permeable shale and
                               3-9

-------
discharges on the slopes at the sandstone/shale contact.  Seeps



have also been identified at elevations typical of the limestone



in the site area.  Samples collected from one of the offsite seeps



revealed concentrations of benzene, ethylbenzene, 1,3-dichloro-



propane, vinyl chloride, and trichloroethylene.  This seep likely



results from ground-water discharged at the sandstone/shale



contact.



     A contaminated spring also emerged at a neighboring farm.



The elevation of the spring is typical of the elevation of the



limestone; however, this unit has not been confirmed the source



of discharge.





3.1.6 Basement Seepage Pathway: Quarry/Landfill Site



Description of Condition



     A 125-acre site located in the Ohio River floodplain was



an active sand and gravel quarry both before and during the period



when the landfill was in operation from 1948 to 1975.  In 1975,



flash fires around water heaters were reported by families .living



in homes adjacent to the landfill.  Seven families eventually had



to be evacuated when explosive levels of methane gas were detected



in the area.  The presence of other toxic gases as well as methane



were documented by Federal, State, and local authorities.   In



February of 1980, over 50 chemicals were identified when approxi-



mately 400 exposed drums were discovered on the river bank adjacent



to the landfill.  A venting system was installed in 1980 and the



wastes were removed in 1981.
                               3-10

-------
Hydrogeologic Setting




     The  site is underlain by relatively permeable alluvial



deposits  consisting of unconsolidated sands and gravels.  Because



of the site's proximity to the river, the water table is rela-



tively close to the surface.  The gases, such as methane that



are generated by the decaying wastes  tend to accumulate at or



near the  top of the aquifer.



3.1.7 Basement Seepage Pathway:  Chemical Landfill Site



Description of Condition



     A canal, originally designed as part of a system to generate



hydroelectric power, was used from the 1920s until the 1950s as a



landfill  for chemical wastes.  Over 21,000 tons of various chemi-



cals were dumped in the canal before the landfill was closed and



covered in 1952.  An elementary school and numerous homes were



constructed near the site, and odors and residues were first



reported during the 1960s.  As the water table rose during the



1970s,  these reports increased,  and contaminated ground water



began to  seep out of the ground.   Residents were relocated,  the



school was demolished, and millions of dollars have been spent



on efforts to clean up the site.



Hydrogeologic Setting



    The hydrogeology of the site includes both shallow and deep



groundwater flow systems.   The shallow system, where most of the



contamination occurred, consists of interbedded layers of silts



and fine sands underlain by leaky confining beds of lacustrine



clays and glacial till.  The lower aquifer is a fractured dolomite



bedrock,  which overlies a relatively impermeable shale.   Because
                               3-11

-------
of the  relatively  low permeability of  the  shallow  system, a




relatively long TOT^QO to tne deeper flow  system is present at



the site.  Contaminated ground-water seepage occurred at  the



surface because of the "bathtub effect" described  in Section 2.3.2



A detailed flow net that included the  effects of engineered



barriers, removal of the cover, and changes in infiltration rates



would have revealed this shallow flow  path and the potential for



exposure.  Refer to Figures 3.1-1 and  3.1-2.






3.2 HEALTH RISK ASSESSMENT METHODS



     The health risk assessment methodology presented in this



appendix focuses on the risks associated with the consumption of



contaminated ground water.   Although site-specific data were used



to generate the risk estimates, the health assessments should not



be construed to represent potential or actual risks to exposed



populations.  The risks associated with exposure to contaminants



either on-site or off-site may be quite different from the risks



projected here.  The methodology does  not quantitatively con-



sider the exposure pathways of surface water and the basement



seepage route.  Also,  several health risk routes of exposure



(inhalation, skin absorption, ingestion) and other environmental



media (air,  soil) may be important factors in assessing risk for



a particular site.   Additional environmental impacts such as



aquatic toxicity or damage to wetlands may be significant for a



particular facility.   However, for the purpose of evaluating a



parameter to describe ground water vulnerability such as TOT^oO'



the health risk assessment methodology provides a way to perform
                               3-12

-------
                                      LEGEND
HIGH.  RELATIVE ELECTROMAGNETIC CONDUCTIVITY
LOW

      MODERATELY HIGH CONDUCTIVITY

      EXTREMELY HIGH CONDUCTIVITY
                                                     SUSPECTED SWALE

                                                     SUSPECTED SAND LENS
Figure 3.7-1.   Sice map  showing location of  E-W transect and major surficial

                features  at  Love Canal.  (Adapted from EPA 600/4-82-030a).
                                    3-13

-------
                                                                            • SEASONAL HI0H WATER TABLE
PERMEABILITY!

Iff7 to 10 §cm/i
     H1
     •t»
                                SILT FILL -PERMEABILITY: >10 Bcm/i
                   SILTY SAND -PERMEABILITY:  >W**n/t
                         •7th ST.
                                                                                                  BASEMENT
                                                                                                            Wth ST.
   LOVE
   CANAL
iORIO. DiPTHj
           /
                                                                                                                             OROUi
                                                                                                                             1.B-2
                                                                                                                             4.0 -e
                                                                                                                             8.0ft.
                                                                                                                             12.0ft.
                                                                                                                          — 23.0 ft.
                LEGEND: BURIED UTILITIES ARE


                      8 —STORM SEWER


                     A - SANITARY SEWER


                     W- WATER MAIN

                      	>- PRESUMED FLOW PATH FOR LEACHATE
                                                                                                                          — 3a.o h.
                             ACTUAL FLOW PATH FOR LEACHATE
               Lgure  3.7-2.   West-East  cross  section of

-------
preliminary conservative risk calculations for ground-water

contamination.

     To facilitate the assessment of health risk, points of

hypothetical exposure were chosen.  Point B in Figure 3.2-1

represents background (or upgradient) ground-water quality.

Individuals would be exposed to this water quality if no release

from a hazardous waste management unit occurred.  Hydrogeologic

conditions at the site are assessed carefully to ensure that

Point 3 does in fact represent an appropriate background position

since it must be outside the influence of any potential ground-watei

mound associated with the unit.  Point C represents ground-water

quality at the RCRA "point of compliance" monitoring points (see

40 CFR 264.95).  Point A is located at the end of a 100-foot-long

ground-water flow line that originates beneath the unit.  Where

actual monitoring data are not available at a site for this

point, data from the monitoring well located downgradient from

the unit that is closest to Point A are used.  Point D is site-
       •                                           '
specific,  just within the leading edge of the plume.

     Wherever possible,  actual ground-water monitoring data for

RCRA facilities are used in conjunction with well-characterized

hydrogeologic descriptions.  These data are available for a number

of facilities within relatively fast ground-water flow regimes.

Where such data are not available for important geologic settings,

modeling techniques are used to estimate likely concentrations at

steady-state conditions.  Conservative assumptions for important

parameters, such as dispersion, are used when modeling is necessary.
                               3-15

-------
               FIGURE 3.2-1:   HYPOTHETICAL WELL LOCATIONS
                              USED IN RISK ASSESSMENTS





_.., / UASTF \
w ^v s
\
1001





?
PLUME ::..'. ~
Stream

\ <^-
;
f
where:
     B - background water quality
     C » compliance point water quality ("uppermost aquifer")
     A * point 100 feet along flowline
     D m point within leading edge of plume (point D may be within a stream)
      NOTE:  The distance from point C to point A need not be
             measured in the horizontal plane.
                                    3-16

-------
     The objectives of these analyses are to determine:

     ' how large the plume is or may become,

     0 what the quality of water is within this plume,

     0 what the health risk would be to an individual
       withdrawing water from various locations in this
       plume for drinking purposes,

     0 whether the contamination has reached or will reach the
       uppermost aquifer,

     0 when the potential for exposure (and hence potential
       for adverse risk) could or did occur at these points.

3.2.1  Assessment Methodology

     The health risk assessment case studies are based on analyti-

cal data available from ground-water monitoring at well-documented

sites and ground-water quality data from computer simulation at

partially or poorly documented sites.  These data are listed in

tables, along with the maximum actual or simulated concentration

of significant contaminant compounds found at various monitoring

points at each site.  Ground-water quality data corresponding to

positions A-D shown in Figure 3.2-1 are used to the extent

possible in the health risk assessments.

     The health risk assessment in this appendix does not consider

actual or potential site-specific exposure of humans to ground-

water,  but instead considers a hypothetical exposure to ground-

water at the positions indicated by points A-D at the sites.

The risk calculation is intended to assess the potential health

risk to individuals using ground water withdrawn at these points,

and not to determine actual or potential risks to any populations

residing near a land storage or disposal facility.

     The hypothetical exposure scenario to be used for each risk
                                3-17

-------
calculation includes the following parameters:
     0 70 kg  (150 pound) adult,
     8 per capita consumption equals 2 liters of water
       per day,
     0 lifetime exposure (70 years), and
     0 consumption of untreated ground water.
     These factors are used to determine the dose of chemicals
that a person drinking water withdrawn from wells at points A-D
would receive.  The dose is defined as the amount of chemical
taken into the body and is expressed in milligrams per kilogram
body weight per day (mg/kg/day) or micrograms per kilogram body
weight per day ( g/kg/day).  Only intake from drinking water is
considered, although intake may occur from other sources, such
as air and food.  Intake is divided by the body weight in order
to permit comparison.   Pharmacokinetic factors such as absorption,
body distribution, metabolism, and excretion are not considered
in the calculation of dose.  One hundred percent absorption is
conservatively assumed for all contaminants.
The hypothetical exposure is calculated by multiplying the con-
centration of chemical in the ground water at the monitoring
point (analytical data or simulated concentration) by 2 liters
per day, and dividing by 70 kilograms.  For example, drinking 2
liters per day of water containing 6 ppm of a contaminant would
result in the following exposure:
           6 ppm = 6  rag/liter
           6  mg/liter x 2 liter/day  » 0.16 mq/kg/day
                       70 kg
     After hypothetical exposures are calculated, conventional
measures of human health risk are applied to the obtained values
                               3-18

-------
to assess hypothetical risks that humans would experience if



they drank ground water withdrawn from wells at these positions.



Health risks are calculated for each chemical found or predicted



for which applicable health standards or guidelines exist.  In



addition to risk assessments for individual compounds, risks due



to mixtures of noncarcinogenic compounds are calculated.



Noncarcinogenic risks are considered to be independent of each



other and additive.  It is not possible to estimate, with any



degree of confidence, the risks associated with exposure to



multiple carcinogens; therefore, carcinogenic risks for single



compounds only will be presented.



     The health risk assessment methodology used in this



appendix is considered conservative.  However, caution should



be exercised when assuming that determination of the dose of chemica.



to a hypothetical person drinking water withdrawn from points A-D



is a conservative estimate of risk.   Points A-D may not reflect



worst case dose estimates at any particular time.  In addition,



only risk from ingestion is considered and intake from other



sources may increase overall risk.  While .the methodology for



noncarcinogens considers at additivity, synergistic and antagon-



istic effects are not considered and may result in different



levels of risks.  Again, assuming the methodology is employed



only to give a measure of the magnitude of a hypothetical risk



rather than to predict actual or potential risk to specific



populations at specific sites, the methodology can be considered



conservative and appropriate.



     Two risk assessment methods are used, one for carcinogens and
                               3-19'

-------
one  for  systemic toxicants.  Carcinogens are defined as substances
evaluated as human carcinogens or potential human  carcinogens by^P
the  U.S. EPA Carcinogen Assessment Group (CAG, 1984) for which
carcinogenic potencies have been developed.  This  list currently
includes approximately 54 chemicals.  The carcinogenic potency is
used in a linear multi-stage model procedure for low-dose extrap-
olation  (U.S. EPA, 1980).  The risk estimates are  calculated
using the formula: Risk = Exposure x Potency.  The model leads to
a plausible upper limit (upper 95 percent confidence limit) of
carcinogenic risk.  It is based on a 70 kilogram person who
drinks 2 liters of water per day over a 70-year lifetime.  The
risk value obtained represents increased carcinogenic risk over a
person's lifetime from a single chemical.
      For systemic toxicants, the analysis uses Acceptable Daily
Intakes  (ADIs) as contained in the Summary of Acceptable Daily
Intakes  (ADI) for Oral Exposure.  (May, 1985).  Some of the ADIs
are  considered interim by the EPA and are noted as such here.  In
some instances, two ADIs were presented for a single constituent.
                                                             •
Where this was encountered for the constituents examined in the
case studies, the more stringent ADI was used.  Current EPA
policy is to use ADIs for risk assessments involving systemic
toxicants; in this appendix, ADIs are not calculated for carcinogens
or suspected carcinogens.
     ADIs are based upon laboratory animal studies and upon actual
human exposure data where available.  The ADI is usually calculated
from a subchronic or chronic No Observable Adverse Effect Level
(NOAEL) or Lowest Observable Adverse Effect Level  (LOAEL) in
                                3-20

-------
laboratory  studies.  The NOAEL  is the  dose  at which  no  toxic



effects are observed in laboratory animals  under  experimental



conditions.  The LOAEL is the lowest dose at which an adverse



response is observed.  The NOAEL is a  safer endpoint and the



LOAEL is used only if a no effect dose has  not been  determined.



The ADI is obtained by dividing the NOAEL or LOAEL by a "safety



factor" of usually 10, 100, or  1,000,  depending upon the quality



and confidence level of the data.  the most sensitive effect seen-



in a test animal is the toxic endpoint chosen for calculating



ADIs.



     To assess the effect of exposure  to mixtures of systemic



toxicants, the Hazard Index was used (Federal  Register (Vol. 50,



No. 6, pp 1170 -1176)).  For a  single  substance, this index is



the ratio of the estimated daily intake to  the ADI.  For a mixture



of toxic substances, these ratios are  summed.  A Hazard Index in



excess of 1.0 is considered to  be unacceptable.  The following



equation represents a Hazard Index for a mixture of systemic



toxicants:



          HI » Ei/ALi + E2/AL2  +...+ Ej./ALi



where,



          E^ - exposure level to the itn toxicant, and



         AL^ = maximum acceptable levels for the itJl toxicant





     At some sites, very high concentrations of chemicals (such as



3,4 dimethylphenol) that do not have specifically quantified toxi-



city values are present in ground water.  Assessing the toxicity



of these chemicals is done, when appropriate, by assuming toxicities



equal to that of an isomer, if  quantified,  or to the most toxic





                                3-21

-------
member of the chemical family, if quantified.


     The risk values calculated for exposure to carcinogens and

systemic toxicants determine whether hypothetical exposure to

ground-water at each site represents a potential threat to human

health.


     For carcinogens, data are presented as per person incremental.

risks given as negative powers of 10.  A risk of 1 x 10~6 means

that, upon lifetime exposure to two liters of water per day


containing the specified concentration of the carcinogen, a person

incurs an.increased risk of developing cancer of one in 1 million.

A risk of 4.3 x lO'S, fOr example, means an increased risk of

4.3 in one hundred thousand.  A 1 in 1 million increased risk

means that each individual who is exposed to the ground water over

his or her lifetime has an additional (i.e., incremental) chance


of getting cancer of 1 in 1 million.

     There is no current EPA policy as to the level of risk that

is acceptable.  In its Ambient Water Quality Criteria, EPA
             •
calculated concentrations of carcinogens in water that would give

increased incremental risks of 1 x 10"5,  1 x 10~6,  and 1 x 10"7 to

people exposed to such water over their lifetimes.   The selection

of these risk levels did not imply their acceptability.  Because

carcinogens are assumed not to have a threshold dose (a level

below which exposure does not elicit a response), any exposure to

a carcinogen carries with it a risk of developing cancer.

     Systemic toxicants, on the other hand, have threshold dose-

response curves; a threshold dose exists below which a toxic

response is not seen (the NOAEL).  The.chronic or subchronic
                               3-22

-------
NOAEL divided by a safety factor is assumed to provide an adequate

margin of safety for lifetime human exposure.  Therefore, any

daily exposure lower than the ADI is assumed to carry no risk of

toxic effects in the general population, based upon currently

available data.  A daily exposure greater than the ADI (a Hazard

Index equal to or greater than 1.0) carries some risk of toxicity

upon chronic exposure.

3.2.2  Methods for Interpreting Results

     Hypothetical risks are calculated for monitoring points A/

C, and D to determine the incremental contributions made by the
                        •
hazardous waste management units.  After this calculation, the

potential for actual human exposure to ground-water at points A,

C, and D is assessed.  The known or modeled spatial distribution

of the plume over this distance is compared with the hydrogeologic

characteristics of the site to determine whether the plume is

associated with geologic units that have a reasonable chance of

serving as a source of drinking water, of transmitting the plume

to surface waters,  or of entering nearby streams.

     The lateral extent of the plume (as determined by the loca-

tion of Point D) at steady-state conditions also serves as an

indicator of the potential for exposure.  These distances are

compared qualitatively for a variety of geologic settings to des-

cribe those settings that offer the greatest and least potential

for exposure.  Sites are grouped into two categories.  The first

consists of those at which a potential for exposure exists and

in which ground-water quality poses an adverse risk to a hypo-

thetical user. The second consists of sites at which the plume
                                3-23

-------
will remain entrained for a very long time in a geologic unit


that is not a reliable source of water and at which the other


pathways of exposure do not appear to be significant.  These


ratings are compared with the TOTioo values calculate for the


cases to evaluate how well the TOT^QO test results correlated


with these categories.  This comparison is used to refine the


definition of vulnerability.


     The hydrogeologic information and data used in the case


study evaluations are not all-inclusive.  That is, the information


presented may not necessarily describe the entire facility«area.


For instance, only one or two "representative" cross-sections


were used in each case study.  Because there are on-going


investigations at these sites, full sets of data are not yet


available.  The case study interpretations and evaluations are
                                                      »'

not meant to replace or be equivalent to comprehensive Part B


permit application reviews for meeting the ground-water protection


requirements of 40 CFR Part 264, Subpart F.


3.2.3 Results of Preliminary Exposure and Health Risk Assessments


     OSW is compiling and studying information drawn from a


collection of 228 hazardous waste management facilities across


the U.S. and is categorizing these facilities by geologic setting.


This study will include an examination of flow patterns and an


assessment of current and future health risk to potential ground-


water users.  Time of Travel and the maximum potential dimensions


(distance between the unit and point D) of plume growth for


facilities representative of the various settings will also be


estimated.
                                3-24

-------
     Section 3.3 presents information for six facilities.  Health



risk assessments for potential ground-water users at five of



these facilities were made using actual monitoring data.  An



analytical model has been used to describe potential contaminant



concentrations at the sixth site and to supplement the moni-



toring data at one of the other sites.



3.3  CASE STUDIES: HEALTH RISK ASSESSMENT



     The following case studies discuss the health risk



assessments using the detailed assessment methodology described



in Section 3.2, primarily for the ground water pathway.  However,



when exposure through surface water or the basement seepage



pathway is possible, this- fact is noted.



Summary of Case Studies



     The case studies presented below describe a range of TOT^QO3



and exposure potentials.  Case study D-l illustrates horizontal



flow in a shallow glacial till aquifer where a long TOT]_QO and



naturally saline ground-water correspond'to a very low exposure



potential.  Case study D-2 describes a plume that travels through



an alluvial aquifer and discharges to a nearby river;  TOTj.00 ^s



short, and potential exposure via the first pathway would be high



except for the restricted aquifer use and an industrial setting.



The full impact on the second pathway is unknown.  Case study D-3



shows how a very long TOT^QO through a thick chalk sequence yields



a very low exposure potential for all pathways.  A short TOTioo



through an unconfined upper aquifer is illustrated in case study



D-4; however, exposure is limited due to surrounding land use.



Case study D-5 shows how a short TOTiQO *n an unconfined aquifer





                                3-25

-------
causes contamination of a nearby bay and a high exposure



for the first two pathways.  Case study D-6 shows a complex



setting of a recharge zone where fractured bedrock strongly



affects ground-water flow, and where a short TOT^oo corresponds to



known exposures through the first pathway to nearby residents.



     Although the case studies do not include an example of a



long TOT^oo setting where exposure potentials are high, EPA is



investigating further.  The possibility exists that a site initially



characterized as a long TOT^oo location could have exposure potentia



due to unforeseen channeling of ground-water through the third



pathway.  This channeling could occur through thin sand lenses,



fissures, and manmade conduits.  Although thorough characterization



of the hydrogeology of the site should preclude this happening, a



long TOTj.00 setting may need further evaluation to eliminate the



possibility of exposure through a hidden pathway.
                               3-26

-------
3.3.1 Case Study D-l                              ^  . Q Q
Facility Description



     The facility is located near a major river in'~"the Great



Lakes Region and has been used since 1942 for a variety of



industrial purposes including commercial hazardous waste disposal.



The site was used during 1942 and 1943 for the manufacture of



trinitrotoluene (TNT).  Subsequently, it was used for:  the stor-



age and transport of chemicals and ammunition, the storage and



burial of radioactive materials, and the burial and burning of



wastes from the development of high energy fuels.  Figure 3.3-1



depicts some of the waste unit locations .



     The current facility operations include the treatment,



recovery, disposal and transfer of hazardous and industrial



wastes.  The waste units include a waste receiving area, metal



hydroxide storage ponds, chemical treatment facilities, biolo-



gical treatment lagoons, transfer stations and nine landfills,



one of which is presently in operation.  The operating landfill



is the major source of potential ground-water contamination.



     Leachate data from the landfills indicate that the most



common organic constituents are methylene chloride,  toluene,



trichloroethene, 1, 1,1-trichloroethene, benzene, tetrachloroethene



and chloroform.  Methyl ethyl ketone, tetrahydrofuran, phenol and



some PCB compounds were also detected.
                                3-27

-------
                                             ^^rsi^r• • *^ • i • f * H  • ^  •
                                                              ~
                                             :;Ix&Wmtf'.' *  v ••
 »»^*^^^^» ^ • •• c. ~^^^ • • ^ » • ^^/ •     •
 NO. 8  ;il^::?W^   *M
     J^MIjtox^v U>  ^-
 !..   ••^*--X>»z *•*'_!Iv/  r.^
  O-^-. A'^-^rS
                                                          j^ ---•» «••
                                                        8r  ..^4
                                                        ?fc'" -5.1
                                                        v ' •.••• Jj3
\K>L^^.
^fP^?
            N'POND
            POND N0-7
             POND

PONDS

SECURE LANDFILLS 2-6
    SN^5  LAGOONS  1,2,5,6
                    FIGURE 3.3.1  WASTE UNITS


                             3-28

-------
Topography/Climate




     The facility lies on the lowland area of a lake plain.  The



lake plain has a gentle slope of approximately 0.3 percent toward



the north; the slope begins at an elevation of 375 feet at the



base of an escarpment and drops to an elevation of 275 feet.  The



plain varies in width from about 6.5 miles to 10 miles.  The



facility is located in an area of low relief.  The site slopes



between 0.1 and 0.2 percent toward the north; surface drainage is



generally the north through several small creeks.



     Precipitation is fairly uniformly distributed throughout the



year; the wettest month is August, which accounts for approxi-



mately 12 percent of the total precipitation.  Data for the area



indicate about 31.5 inches of precipitation for water year 1983,



while the potential evapotranspiration was estimated at 25.4



inches for the same year.



Regional Geology/Hydrology



     The bedrock units in this region are comprised of a series of



Upper Devonian to Silurian aged shales,  limestones and dolostones.



The rock units are relatively flat-lying with a regional dip of



approximately 0.75% south - southwest.



     The unconsolidated deposits include alluvium overlying



glacial deposits from several major periods of glaciation.   In



some areas, these deposits have been re-distributed by streams.



In addition,  the irregularity of the glacial deposits has led



to a varied drainage pattern with many lakes, ponds,  bogs and



marshes.  The major drainage direction in the region is toward



the Great Lakes and the St. Lawrence River.
                               3-29

-------
     The glacial deposits constitute the best aquifers within the
region; limited ground water is available from bedrock aquifers
in areas where the unconsolidated deposits are absent, thin, or
of low permeability.
Site Geology
     The geology of the site area has been characterized by
information gathered during several field investigations.  More
than 450 borings and test pits from several site studies were
used by the permit applicant to describe the geology of the area.
Figure 3.3-2 is a geologic cross section drawn from the northwest
to the southeast portion of the^site.
Surficial Geology
     The facility is underlain by about 30 to 60 feet of glacial
deposits overlying shale bedrock.
     The uppermost unit at the site is a low permeability glacial
till sequence that is about 10-25 feet thick in the site area.
The till is underlain by a glaciolacustrine clay, 20-30 feet thick
in most areas, which is in turn underlain by a glaciolacustrine
silt/sand unit.  Beneath these units is a lodgement till that
overlies the shale bedrock.
     At the northwestern portion of the site the glaciolacustrine
clay unit is divided into an upper and lower member by a silt till
that was apparently deposited during a local oscillation of the
advancing glaciers.
                                3-30

-------
                                            FIGURE 3.3-2  GEOLOGIC CROSS SECTION
to

10
                NORTHWEST

         ELEVATION
          FEET MSL
       320  _,
                BOREHOLE     LANDFILL NO.  7
                  G-8        AND NORTH  POND
       300
       280  J
       260  J
       240  J
       220  H
       200  J
                                                                                                  SOUTHEAST
UPPER ALLUVIUM

     LAGOON'S
                               UPPER


                         UPPER CIACIOLACUSTRIME CLA»

                     MIDDLE SILT TILL
  PARTIALLY WEATHERED
    SHALE BEDROCK
(QUEENSTON FORMATION)
                                  _ 260
                                  L 240
                                                                                                                U220
                                  L200
                                                   HORIZONTAL SCALE IN FEET

                                                VERTICAL EXAGGERATION 30 TIMES
              NOTE:   This figure Is a schematic representation
                     of the geologic stratigraphy made by straight
                     line Interpolation between boreholes G-l and
                     G-8.  Some of the strata shown are
                     discontinuous.

-------
Bedrock Geology
     Bedrock encountered during drilling in the site area is a
reddish-brown shale that is approximately 1000 feet thick.  Rock
samples were cored from some of the borings on the site.  The
cores reveal that the rock is generally a red fissile shale that
has occasional bands of green shale ranging from 1/2 to 24 inches
thick, and gypsum nodules 1/2 inch to 1 inch in diameter.
     The top 5 to 10 feet of the shale unit is highly weathered
and fragmented.  Although some cores showed that the shale was
broken parallel to bedding, it was difficult to determine whether
this'was due to natural bedding features of the rock or if it was
induced by drilling.  Some high angle joints which were not a
result of drilling were observed in some of the unweathered cores.
     The surface of the bedrock is undulating; it slopes from an
elevation of about 275 feet MSL, in the southeastern part of the
site, to 250 feet MSL in the northwestern portion of the site.
    .The average values for hydraulic conductivity are 1 x 10~5
cm/sec in the shallow rock and 5 x 10"^ cm/sec in the deeper rock
zones.
Site Hydrology
     Shallow ground water occurs in the upper glacial till
sequence at a depth of about 3 to 5 feet.  Potentiometric contours
in the upper glacial till indicate that the shallow ground water
moves horizontally north - northwest.   Vertical flow in the
upper glacial till is minimal due to the underlying less permeable
glaciolacustrine clay.  The glaciolacustrine clay is the main
retarding layer to downward vertical flow in the site area.
                                3-32

-------
Vertical gradients across the glaciolacustrine  clay  unit range



from 0.1 to 0.58 with a mean of 0.35.



     Flow in the glaciolacustrine silt/sand aquifer  is essentially



horizontal to the north and west.  The most transmissive portion



of the aquifer is its thickest portion, where a coarser sub-unit



is present.  As the ground water flows northward, it moves toward



the areas of higher transmissivity.  Figure 3.3-3 depicts flow



directions in the glaciolacustrine silt/sand aquifer.



     Flow within the basal red till is controlled by pressure



differences within the glaciolacustrine silt/s"and aquifer and the



underlying bedrock.  The shallow bedrock exhibits flow that is



predominantly horizontal toward the north and west, similar to



flow in the glaciolacustrine silt/sand aquifer.  The shallow bed-



rock has low hydraulic conductivity and is not considered a sig-



nificant water-producing zone when compared to the glacial aquifer.



     The average values for flow rates for the geologic units



at the site as presented in the Part B application are given in



Table 3.3-1.  The flow velocities were calculated using values



for hydraulic conductivities, hydraulic gradients, and effective



porosity.  Conductivities of the geologic formations were



determined in the field .through variable head tests and in the



laboratory.  Gradients were established using ground-water level



measurements obtained from wells and piezometers at the site.



A value of oil for effective porosity was supplied by the applicant



and is applied to all the units.  Since it is unlikely that all



the units would have the same effective porosity, TOT values
                               3-33

-------
    OJ
    J,
    •U  I
FIGURE 3.3-3
 Glftclolacustrine Aquifer
              •
Potentionetric  Contour*
'*~~l t ^'^M^'^t-'r-^^^^
                                                   ^-.js^-' >.- .  . • •• »«*a».»MM»<..
                                                   C^^^<--*-l^niteiF=^v=::::K:ijl;:P •
                                                   "*^" I TJT^'l 1 MBkAVV TT   '   • J-a . •-. • •» l'l >1*^> •
                                                   ^ .TT^yy*^*-^—rivj.^id.iTit.^l.fj^r*.
                                                   ^M;_:-.- I   -  g
                                                   —T.~       ^        ft J
                                                       ' Jl .    ' •  1:     ^^•"^
                                  •IrJ^X X^-y^^tkJ^^jP^^f
                                   •/••'•^v&^.'iP-*-*..  •-  -•/
                                   /.-  :.•.,•:.%;•'/•£  -./..- JT
                                   /.....-.•.•...•  .••  -r"^ ^._ ..»•••*...   ••    i- •WHT=»C?H

-------
                                      TABLE 3.3-1  ESTIMATED FLOW RATES AND VOLUMES
U)
OJ
01
GEOLOGIC*1* PERMEABILITY,
FORMATION (cm/s)

UGT
GC
MST
GSS
BRT
SR
NOTES
(1)
Horizontal Vertical
2x10~6 6x10~7*6*
5x!0"8 2xlO"8
3x10 Ixio"7
4xlO~8 3xlC"8
Ixio"5

Formation Designations
K GRADIENT, 1
(ft. /ft.)
Horizontal Vertica
0.002 0.012
0.001 0.35
0.005 0.07
0.007 6x10 l
0.00/4 0.0/4
0.004

*
•
FLOW AREA, A
(ft.2)
1 Section*3*
80,000
40,000
60,000
7* 90,000
40,000
160, OOO*9*


Plan
I6x106
I6xl06
7x10
I6xl06
15xlOb
-


FLOW VOLUME ****
Q. (ft.Vday)
Horizontal
1.0
0.006
3
360
0.02
18.1


Vertical
320
320
50
60
-


FLOW RATE, v*5*
(ft./yr.)
Horizontal Vertical
0.04 0.07
0.0005 0.07
0.16 0.07
14.5 0.01
0.002 0.01
0.4.


           UGT - Upper Glacial  Tills
           GC  - Glaciolacustrlne Clay
           MST - Middle Silt TIM
           GSS - Glaclolacustrine Silt/Sand
           BRT - Basal Red Till
           SR  - Shallow Rock
     (2)   Exit gradient from property.
     (3)   Cross section area along.north or north and west perimeter for each formation.
     CO   Q = klA.
     (5)   V - kl/n  . with n  - O.I.
     (6)   k
           V
     (7)   Estimated to maintain continuity.
     (8)   Coarse portion of aquifer with k
     (9)   Assumed 20 feet thick.
kl/n , with n
    e-7
 6x10   cm/s due to structural discontinuities. (See text Sections 7.1 and 8.3.)

-------
calculated with this input should be considered to be only estimates
A second TOT has been calculated using default values for effective
porosity for each unit.
     A contaminant can be traced from the point of release at the
surface through the geologic formations in the site area.  Hori-
zontal and vertical flow rates can be added, using vector addition,
to get the resultant flow rate vector through the different units
(see Figure 3.3-4).  Figure 3.3-4 also depicts two different
profiles of flow, for the northwest and the southeast sides of
the facility.  Ground-water time of travel through the geologic
units varies between these opposing sides of the facility because
of different unit thicknesses and the presence of the middle silt
till at the northwest side of the facility.  The middle silt till
is absent at the southeast side of the facility.
     At the southeast side of the facility, the upper glacial .
till layer is thinner (approximately 11 feet thick) than at the
northwest side (approximately 16 feet thick).  Using average flow
rates derived from vector addition, the ground water would take
150 years to flow through that layer.  At the northwest side, the
ground water would take 230 years to flow through the upper
glacial till unit, because of the greater unit thickness.
     Flow within the upper glacial till is toward the north-
northwest.  Assuming that a particle is released and will be
carried with the ground water without being affected by advective
or dispersive forces, after 100 years, the particle will still be
traveling through the upper glacial till layer toward the north-
northwest.  The time that the particle would take to reach the
                                3-36

-------
                              WATER TABLE
                         0.081  FT/YR
                           230  YEARS
                                               20'
                           0.07 FT/YR
                            100 YEARS
                                   7'
                                     0.17 FT/YR
                                      220 YEARS
             0.07 FT/YR  kO YEARS
             H.5  FT/YR  1000 YEARS TO
             FLOW  ACROSS THE AQUIFER
                (1A.500 FT)
U)
\°
               .01  FT/YR   500 YEARS
                                       16' UPPER GLACIAL TILLS
UPPER GLACIO-
LACUSTRINE CLAY
                                       15'
      MIDDLE
       SILT
       TILL
                                       3'LOWER  GLACIOLACUSTRINE
                                                     "     CLAY
                                      10 ' CLACIOLACUSTRINE SILT/SAND
                                              AQUIFER
                                                                                                 N
3' BASAL RED TILL
                 0.4I  FT/YR
                                         BEDROCK
1 WATER TABLED
\ 0.12 FT/YR
NJ50 YEARS
X. 13'
0.0? FT/YR
290 YEARS
YEARS TO flOVI AC*
IFER (725 FT.)


tOSS THE ~]
I 0.01 FT/YR
\ 500 YEARS

UPPER GLAC
GLAC 10-
LACUSTRIN
20' CLAY

1« US FT/YR
J GLAC IOLACUS TRINE SI
3 'BASAL RED TIL
                                                                                                                    TILLS
                                                                                0.<«1 FT/YR
                                                                                         BEDROCK
                     NORTHWEST SIDE OF FACILITY

                     (Velocities from TABLE 2.3-1
                      Scale -  1" = 10' HOR.
                              I" = 10' VER.
                                                                    SOUTHEAST SIDE OF FACILITY

                                                                    (Velocities from TABLE 2.3-1 except
                                                                     UPPER GLACIAL TILLS and AQUIFER
                                                                     velocities based on horizontal
                                                                     gradients  0.005 and 0.0007
                                                                     respectively)
                                                                     Scale - 1" = 10' HOR.
                                                                             I" = 10' VER.
                                           FIGURE 3.3-4  SCHEMATIC FLOW DIAGRAM

-------
glaciolacustrine silt/sand aquifer is  590 years  for  the northwest

side of the facility and 440 years for the southeast side of the

facility.

TOTiQO Calculation

     TOT^oo can b® calculated by adding the number of years as

shown in Figure 3.3-4 to travel through the geologic units under-

lying the site.  It wil~l~'take 590 years to travel 55 feet along a

flow path to the glaciolacustrine silt/sand unit at the northwest

side of the facility.  When it reaches this unit, the ground water

moves horizontally at a rate of 14.5 ft/year.  To complete the

total distance of 100 feet, ground water must travel an additional

45 feet through the unit.  At a rate of 14.5 ft/year, the added

travel time is three years.  Thus, the total estimated travel time

over 100 feet at the northwest side of the facility is 593 years.

TOT^QO calculation using ne default values

                                Effective Porosity
                                Default Values           TOT

Upper Glacial Tills                  0.05             115 years

Upper Glaciolacustrine Clay          0.01              10 years

Middle Silt Till                     0.10             220 years

Lower Glaciolacustrine Clay          0.01               4 years

Glaciolacustrine Silt/Sand           0.15             4.5 years

                                         TOT100 =   353.5 years

Using default values of effective porosity (see Table 3.2-2 of

the main text) for each layer rather than a constant effective

porosity of 0.1 throughout produced a difference in TOT^QQ of

239.5 years.  As such the percent error involved is too large
                               3-38

-------
  N

,                       r
r  .                 TA
l] .; -i r**4«- . ... '-U?  mW!) *\
Ki: •,,••!. .••-, ••   ,   x \i£
i1- •« •  *••! - - ' JL  __JlW3CSS^ij£.- *-.. t .:.^**-J)«J^ »j
^^^te^^iw7^^':^^^
!-iii>~ ;^^^TOK»^'^  ^v-?n
 .••^: -.. dF« - »^mKrf* •.-    .. • t-r -:
l^fEM^py
^^:C^S»H
r-r
                                  ••/i; o
                                        • rniantTiii at VKL
                                        3Ill:iATt01

                                       • rtltontTit 01 vtu LOCit:
                                      >oti«T;aii iti!:inT:;t
                                       arrtt »ALBTICII
                                      BCT crm euetAi
                                      CC CIACIOIACIITIIM IlI/IASD
                                      IIT lilAL 1CJ TtLt
                                      it iiAiiov toes
                                      oi :tu laa

                                      lOtt: »-• «OT LOCtTIO.
                                   SCALE IN
             FIGURE 3.3-5
                    WELL AND PIEZOMETER LOCATION
                    PLAN AND FORMATION INTERVALS

                       3-39

-------
(when using a constant effective porosity value) to recommend its use

Plume Information
     The monitoring well network at this site consists of over
50 shallow and deep wells located to serve a detection monitoring
function.  The shallow wells draw from the upper glacial till
layer and the deep wells draw from the various deeper formations.
Ground-water monitoring has been performed on a monthly basis for
two years, drawing samples from a selection of the monitoring
wells on the site.  There is no conclusive evidence of a contam-
inant plume at this site, but isolated contamination has been
observed at individual wells.
     Only one well has shown contamination in repeated samples
that is not explained by laboratory error or solvents used in well
grouting materials.  This well, shallow well Z-3 (screened in the
upper glacial till), is considered to be point C in this case
study.  The nearest downgradient well, point A also screened in
the upper glacial till aquifer, is represented by well Z-21,
300 feet north of Z-3.  These wells are located between secure
landfill (SLF) 7 and SLF 11, shown in the upper portion of
Figure 3.3-5.  The observed contaminant levels at these well are
presented in Table 3.3-2.
     There are no suitable wells to represent points B or D.   No
wells are located offsite or far  enough downgradient from the
facility to characterize contaminant migration.  However, since
no contaminant plumes have been detected, this is not necessary.
                             3-40

-------
Likewise, no wells are located far enough upgradient from the

potential sources of contamination to serve as background wells.

However, background concentrations for the constituents reported

in Table 3.3-2, are clearly below the limits of detection.

Health Risk Assessment

     Of the two contaminants observed at well Z-3, one is recog-

nized as a carcinogen and the other is a systemic toxicant.

Trichloroethylene is a carcinogenic substance with a potency,

recommended by  the Carcinogen Assessment Group (CAG),  of 1.9 x

10~2.  Lifetime ingestion of 2 liters per day of water with an

average trichloroethylene concentration of 668 ppb (the average

of the three samples) represents a 3.6 x 10~4 probability of

contracting cancer.

     The acceptable daily intake for 1,2-trans-dichloroethylene
                                                      •'
is 0.001 mg/kg/day.  The highest of the concentrations observed

at well Z-3 corresponds to an exposure of 0.0027 mg/kg/day and a

hazard index of 2.7.  This concentration would therefore pose an

unacceptable health risk if it were present in a drinking water

supply.

     Several of the deeper wells on the site showed barium

concentration in excess of the 1 ppm, National Interim Primary

Drinking Water Standards value.  However, these concentrations

appear to be a background condition since some of these wells are

located upgradient of the hazardous waste management units, and

since the travel time to some of the deep wells is over 500 years.
                             3-41

-------
Exposure Assessment

     The exposure potential at this facility is considered to be

very low.  There is no known contaminant plume, the TOT is very

long, and the ground-water beneath the facility is very saline,

in excess of state drinking water standards.  The ground waters

are not currently used as a source of drinking water, and no such

use is expected in the future.


          Table 3.3-2:  Contaminant Concentration (ppb)


                                    Point C                Point A
Constituent	(Well Z-3)	        (Well Z-21)

1,2
Tri<

Trans-dichloroethylene
rhloroethylene
6/84
ND
1290
11/84
60
496
12/84
95
258
6/84
ND
. ND
11/84
ND
ND
12/8
ND
ND
ND denotes not detected.  The limits of detection were 10 ppb.
                               3-42

-------
3.3.2 Case Study D-2



Facility Description



     The facility started operations in 1952 and covers an area



of approximately 2.4 sq. miles in the southeastern U.S. (see



Figure 3.3-6).  This area contains manufacturing facilities in



conjunction with past, present, and proposed waste treatment,



storage, and disposal units.  Some of the units currently onsite



consist of an incinerator, numerous storage tanks,  a landfill,



and a biological sludge landfill.



     No information was available concerning the types of wastes



disposed of in the landfill unit.  However, it is known that ope-



rations at this facility have contaminated the uppermost alluvial



aquifer? therefore,  the facility is implementing a Corrective



Action Plan as specified under 40 CFR 264.100.  This plan proposes



closure of many of the units in an attempt to eliminate the source



or sources of contamination and installation of a pumping well



system to contain contaminant migration.



Site Topography



     The site consists of rolling topography with gentle slopes to



the southeast toward the river.  Many small streams and drainage



ditches dissect the site.  Surface water flow from northwest of



the property is diverted through drainage ditches to the east



into the river.  Surface flow from within the site follows the



site topography to the southeast into the river.
                               3-43

-------
Site Climate

     The climate of the area is very humid and sub-tropical.


There are very long, hot, and humid summers with mild wet winters.

The average annual precipitation is 59 inches, with December

through April being the wettest and August through November being

the driest.  The average temperature for this area is 65°F January

averages 498F while July averages 80*F.

Regional Geology


     The site is located in the Gulf Coastal Plain Physiographic

province adjacent to the river.  The area is underlain by alluvium

and terrace deposits of Pleistocene age.  Deposits also included

in this area are undifferentiated Miocene sand, clay, and gravelly

sand.  Total thickness of these unconsolidated flood plain terrace

deposits are over 700 feet.

Site Geology

     Data from previous and recent test drilling indicate that

the plant site is built on a flood plain terrace, whereas the

lower portion of the facility located near the river is built on

flood plain deposits.  A pervasive clay layer is reported at the

surface of the facility.  This is reportedly well documented from

previous reports; however, the large distances between wells as

shown in Figure 3.3-7 indicate that very little control in the

form of wells or borings is available for interpretatipn of the
                                                               j
cross sections. Cross section locations are shown on Figure 3.3-8.

Directly below this surficial clay are lenticular deposits of silt,

sand, and clay.  Previous reports (May 1981) allude to the fact

that there may be a hydraulic connection through the clay between
                               3-44

-------
liiiiiiiilMil  PLANT SITE
                     FIGURE 3.3-6   FACILITY LOCATION
                                      3-45

-------
     to
     •
     u>

     -J
    o
    70
    O
    CD
    CT
    •— i
OJ  O


£  <">


     o

     CD
     I
     CO
              "
              "

-------
      WELL LOCATION, NUMBER, AND
o...   WATER SURFACE ELEVATION  IN
•••°   FEET ABOVE MEAN SEA LEVEL
-,0   PRODUCTION WELL  LOCATION
/-'4   CONTOUR INTERVAL IS 1  FOOT
                                                FLOW LINE SHOWING DIRECTION
                                                OF GROUND WATER MOVEMENT
     FIGURE 3.3-8  FLOW NET ANALYSES FOR THE ALLUVIAL AQUIFER, AUGUST 1984
                                    3-47

-------
the water table and fluids in the reservoir.  The basis for this



statement is reportedly from water level data, but these data



were not available for review.



     The surficial clay materials are underlain by Recent and



Pleistocene shallow terrace and alluvial deposits.  As shown in



the cross sections (Figure 3.3-7), this unit is the uppermost



aquifer and consists of alternating, interbedded layers of sand, .



gravel, and clay.  Underlying this alluvium is a sequence of



Miocene clays and sandy clays with thicknesses ranging from 30 to



more than 100 feet.  Below these clays are alternating layers of



Miocene age sand, clay, and gravel over 700 feet thick.  This



unit is the second aquifer identified in the area.  There is no



mention of the bedrock underlying this facility.  The Miocene



clay layer is reported to be a confining layer separating the



upper alluvial aquifer from the lower Miocene sandy aquifer.



Site Hydrology



     Ground water parameters have been defined at the site through



the use of many existing wells (M series wells) from previous



studies and through the installation of nine 2 inch diameter



observation wells (OW-1 through OW-9).  Most of the observations



contained in this report are directed at the uppermost alluvial



aquifer.  The only mention of the surficial clay layer is that



permeabilities range from 0.7 x 10~° to 1.9 x 10~' cm/sec.  There



is no discussion in the report addressing to what extent the clay



layer impedes flow into the alluvial aquifer.  However, the



application indicates a "water surface" in the cross-section



(Figure 3.3-7) which is described as the alluvial aquifer water
                                3-48

-------
table.  It can be seen in the cross section that an area labeled

effluent stream is in direct contact with the alluvial aquifer.

This may be a pathway for migration as evidenced by elevated

contaminant concentrations in well M-6.

     Ground water in the uppermost aquifer is reported to be under

semi-confined conditions and flowing to the southeast towards the

river  (see Figure 3.3-8).

     The underlying Miocene aquifer is also confined and reported

to contain highly mineralized water.  Due to the overlying low

permeability Miocene clay layer  (10~"^/sec) the applicant states

that the upper alluvial and Miocene aquifers are not hydraulicaLly

connected.  Therefore, contamination in the uppermost aquifer

would not migrate to the Miocene aquifer for a long time.

     Due to pumping from wells at the facility and adjacent
                                                      »'    .  '
property, the hydraulic head.in the Miocene and alluvial aquifers

have been greatly impacted.  Prior to ground-water development,

the potentiometric surface in the Miocene aquifer was higher than

that in the alluvial aquifer.  Today, the Miocene potentiometric

•surface elevations are below that of the upper alluvial aquifer.

Flow directions in the Miocene aquifer are also reported to be

somewhat influenced due to its development as a ground-water

resource.

     Field tests were performed in an attempt to define the

hydraulic parameters of the alluvial aquifer.  Twelve hour

specific capacity tests were performed on wells M-3, M-4, M-6

and M-12, with results ranging from 14.15 to 25.5 gallons per

minute per foot of drawdown.
                                3-49

-------
     Aquifer  (pump) tests  (96 hours) were performed on wells W-3

and W-12 in order to define transmissivity, hydraulic conductivity

and coefficients of storage.  A summary of the test results is

presented in Table 3.3-3.  These wells are reported to be screened

in the uppermost alluvial  aquifer, and, therefore, listed para-

meters are indicative of this unit.

Time of Travel

     A worst case TOTiQO was calculated for flow in the uppermost

alluvial aquifer using the following parameters:

                                                    Default Value
                             Worst case   Average     (Freeze &
	K Value	K Value   Cherry, 1979)

Hydraulic Conductivity (K)   288 ft/day   90 ft/day   10~1cm/sec
     Time drawdown and
     recovery tests (Pump
     tests)
Hydraulic gradient (i)
     water level
     measurements

Effective Porosity
     EPA default value
.01
.20
                                            .01
                                            .20
.01
.20
Ground water velocity (v)   14.4 ft/day  4.5 ft/day   14.2 ft/day
TOT10o
                        7  days
                              7 days      22 days

     The above TOT^QO does not take into account the surficial

clay layer due to the fact that the effluent stream shown in the

cross sections (Figure 3.3-8) is in direct connection with the

alluvial aquifer.  Due to this feature, contamination could reach

the alluvial aquifer without moving through the clay layer.

However, there are hazardous waste units located in the clay that

do not breach through to the alluvium.  Therefore,  a TOT incorpor-

ating the clay is presented below:
                                3-50

-------
                                        TABLE 3.3-3  SUMMARY  OF PUMPING  TEST  RESULTS
U)
I

Well
Number
M-3


M-4
M-6
M-12
MW-11

Distance
from . ,
Discharge PW to EW -
Q r
(gpm) (feet)
78
78
78
90
88
75.5
75.5
75.5 22.5

Saturated
Tb ickness
m
(feet)
38
-
-
25.8
34.56
22
22
AVERAGE :
Coeff i cient
of
Transmi ss i vi ty
T
(gpd/ft)
1,117
3,973
8,939
55,751
49,200
4,326
9,832
18,026
18,895.5
Coefficient
of
Permeab i 1 i t
K
(gpd/ft )
29
104
235
2,161
1,424
197*
447
819
676.8?
Coefficient
of
y Storage
S
(-) Remarks
Time- drawdown
T 1 me- d rawdown
Ti me- recovery
Time- drawdown
Time-drawdown
Time -drawdown
Time- recovery
6.33 x 10 Time-drawdown

      —   PW, pump ing well;

          EW, evaluation well

-------
     K = 1.9 x 10~7cm/sec         Permeability value stated in
         (lab methods)            the May 1981 report.

     n = .01                      Default value from EPA location
                                  guidance for effective porosity.

     i = 1.0                      Assuming vertical flow through
                                  the clay layer (worst case).

Using the expression, v =     Ki   , a velocity of  .05 ft/day was
                              ne

calculated.  Assuming that the clay unit is 20 ft. thick it would

take approximately 400 days for groundwater to travel through

this unit into the uppermost aquifer.

Plume Information

     The indicator parameters used to delineate the plume consist

of specific conductance, total organic carbon (TOC) and total

organic halogen (TOX).  Figure 3.3-9 shows results of the specific

conductance testing, while Figure 3.3-10 shows locations of wells

tested and compliance point monitoring wells.  From the various

monitoring results there appears to be a line of contamination

with two lobes of increased contamination.  One appears to be

concentrated near the manufacturing area with its source presum-

ably being an abandoned effluent pond.  There is no discussion

concerning the nature of this pond and, therefore,  very few

conclusions can be drawn concerning the contamination.  Due to

the fact that contamination is lower in OW-1 than OW-2, it is

possible that the plume has past and there is not a continued

source.   However,  without historical monitoring data,  no definite

conclusion can be drawn concerning this issue.  The other plume

appears to be in the area of the effluent stream (Figure 3.3-9).
                               3-52

-------
 OWT  WELL LOCATION,  NUMBER, AND
•"••  GROUND-WATER SPECIFIC
      CONDUCTANCE IN
   .   CONTOUR INTERVAL IN pMHOS
 jS   AS  SHOWN (DASHED WHERE
I     INFERRED)
NOTE:  Ground-water collection data
       M Wells:  June 13-21,
      OW Wells:  July 17-20, 1984
             •00   ItOO  ItOO

          KALI IN rut
               FIGURE 3.3-9  ISO-SPECIFIC CONDUCTANCE MAP FOR THE
                             ALLUVIAL AQUIFER,  JULY-JUNE 1984

                                      3-53

-------
                                                                               LINE OF
                                                                               COMPLIANCE
                                                                         \    POINTS
'** LOCATION AND NUMBER OF 300 GPM
O MAXIMUM CAPACITY OEWATERING WELLS

••-« LOCATION AND NUMBER OF 200 GPM
O MAXIMUM CAPACITY OEUATERING WELLS

..-• LOCATION AND NUMBER OF 100 GPM
 O MAXIMUM CAPACITY OEWATERING WELLS

c»-i LOCATION AND NUMBER OF MONITORING
 6 WELL FOR CORRECTIVE ACTION PROGRAM

-• LOCATION AND NUMBER OF COMPLIANCE
 O POINT MONITORING WELL
   FIGURE 3.3-10  GROUND-WATER DEWATERING PLAN  AND  LOCATION OF
                      CORRECTIVE  ACTION AND  COMPLIANCE  POINT  MONITORING.  WELLS.

                                          3-54

-------
It is interpreted that contamination has been released from

various waste management units in this area.

     Well M-2 is located upgradient of the facility and is

designated as well B (background) in the A, B, C, D configuration,

Since there are two plumes or plume sources, wells OW-1 (point

C-l) and OW-2 (point A-l) will be used to identify the plume from

the manufacturing area while well M-6 (point C-2) and well M-12

(point A-2) will be used to identify the plume on the eastern

side of the facility.  No D wells at this facility have been

designated.  Table 3.3-4 shows contaminant concentrations at
                                                        *
selected wells.

B.  Health Risk Assessment

     Several hazardous constituents have been observed in the two

plumes originating at this site.  Table 3.3-4 presents concentra-

tions of hazardous constituents observed in selected monitoring

wells M-2 (point B) OW-1 (point C-l), OW-2 (point A-l), M-6

(point C-2) and M-12 (point A-2).

     Carcinogenic constituents were observed in wells M-6, OW-2

and M-12.  The carcinogenic risks are tabulated in Table 3.3-5

for each of these wells.  The most significant risk at each of

these well is due to high levels of arsenic.  (Arsenic has been

associated with skin cancer in epidemiological studies.)  The

highest risk, 4.6 x 10~2 was observed at well OW-2, a few hundred

feet downgradient from the compliance well near the manufacturing

facility.  In the plume originating at the hazardous waste manage-

ment unit, the compliance point (M-6) shows a carcinogenic risk
                               3-55

-------
      TABLE 3.3-4  CONTAMINANT CONCENTRATIONS AT SELECTED WELLS (ppb)
Constituents                 M2
                           (6/8*0
Purge & Trap Compounds

Benzene                      ND
Carbon disulfide             NO
Chloroethane                 NO
Chlorobenzene                NO
Chloroform                   ND
1,2-Trans-dichloroethylene   ND
Methylene chloride           ND
trans-1,3-Dichloropropene    ND
Methyl ethyl ketone          ND
Carbon tetrachloride         ND
Toluene                      ND
Trichloroethylene            ND
Tetrachloroethylene          ND
  M6        M6       M12
(*/8*)    (6/8*)    (*/8*)
                 118
                  *0.6
                  *3.8
                  NO
                 1*0.8
                <10
                  *0.*
                  ND
                 11*.*
                  ND
                93**
                  3*.5
                  NO
                                   OW2
                                  (6/8*)
                            838
                             ND
                          29*69.6
                           938.8
                             ND
                             10.2
                            2*.6
                            306.6
                            17
                            ND
Acid/B/N/Pest Compounds

Aniline                      ND
bis(2-Ethylhexyl)phthalate   ND
1 ,3,5-Trichlorobenzene       ND
2,3f5,6-Tetrachlorophenol     ND
2,3,*,5-Tetrachloropheno.l     ND
o-Cresol                     ND
a+p-Cresol                   ND
Di-n-butyl phthalate         ND
1 ,2-Di chlorobenzene          ND
1 ,3-Di chlorobenzene          ND
1 ,*-Di chlorobenzene          ND
Aldicarb                     ND
Nap tHa lene                   ND
Nitrobenzene                 ND
Phenol                       ND
1, 2, *-Tri chlorobenzene       ND
                  ND
                  10
                  ND
                  3*
                  ND
                  ND
                  ND
                  ND
                 1*7
                  ND
                  13
                  ND
                             ND
                             ND
                             ND
                             ND
                             ND
                             ND
                             96
                           < 1-9
                            28*
                             ND
                             ND
                             87
                             ND
                           < 1.9
Pest..& Herb. Compounds

A-BHC                        ND
G-BHC                        NO
                  ND
                  ND
                             ND
                              6.0
DAI HPLC Compounds

Haleic hydrazide
Nicotine acid
ND
ND
           ND
           ND
  ND
<900
                                      3-56

-------
TABLE 3.3-4   (continued)
Const!tuents
Extractable HPLC Compounds

Benzidine
3 ,.3' ~Di ch 1 orbenzi dene
3.3'~Dimethoxybenzidene
m-phenylenediamine
p-pheny1ened i ami ne
To 1 uene- 2 ,_3- D i am i ne
Metals & Cyanides
Aluminum
Arsen ic
Barium  *
Be ry 1 1 i urn
Cadmium
Calcium
Chromi urn
Copper
Total Cyanide
I ron
N i eke 1
Osmium
Potass ium
Sodi urn
S t ron t i urn
Thai 1ium
Vanadi urn
Zinc
M2
(6/8'

NO
<25
<25
NO
NO
NO
NO
20
NO
NO
2800
NO
NO
<25
NO
<20
<800
590
1*300
NO
NO
NO
10
M6
*) (V8i»

--
--
--
—
""

50
200
—
5
--
530
--
—
550,000
—
--
—
3,273,000
--
--
--
--
M6
) (6/81*)
NO
NO
NO
NO
NO
NO
61,500
20
110
6

-------
                                                        •00-2A
TABLE 3.3-5:  Tabulation of Carcinogenic RisksJ
Constituent
Well Numbers (hypothetical exposure points)
                     M2 (B)  OW1 (Cl)  OW2 (Al)  M6 (C2)   M12 (A2)
Benzene                ND

Chloroform             ND

Methylene Chloride  .   ND

Carbon Tetrachloride   ND

Tetrachloroethylene    ND

Arsenic                ND
          NA    1.2xlO-3  1.8xlO-4     NA

          NA    1.9x10-3  2.8x10-4     NA

          NA    1.8xlO-7  7.3xlO-7     NA

          NA    1.1x10-3     ND        NA

          NA       ND        ND        NA

          NA    4.2x10-2  1.5x10-2  7.7x10-3
*Risk measurements based upon average of observed concentrations
ND - constituent analyzed,  but not detected or below detection
     limits.
NA - not analyzed.
                               3-58

-------
of 1.5 x 10~2 while the downgradient well (M-12) has a risk of



7.7 x 10-3.



     Systemic toxicants have also been observed in both plumes.



The tabulation of hazard indices for these wells is shown in



Table 3.3-6.  Well OW-2 has a very high concentration of chloro-



benzene.  This level of contamination relates to a hazard index



of 84.2, or more than 80 times the maximum acceptable level.



Well M-6 has high levels of toluene, chromium and barium.  The



total hazard index depends upon the valence state of the chromium.



If the chromium is hexavalent, the HI is 28.2, as shown in



Table 3.3-6, but if it is trivalent, the HI is 21.1.  In either



case a toxic risk is posed.



     Both plumes pose significant carcinogenic risks, and contain



unacceptable levels of systemic toxicants.  The plume originating



at the manufacturing facility has no compliance point data, but



the downgradient well, OW-2, has high levels of arsenic and



chlorobenzene.  In the plume originating at the hazardous waste



management unit, both the compliance point well and the down-



gradient well would pose significant health risks if used as



sources of drinking water.  Monitoring has not been done to



determine the downgradient extents of these plumes.



     A simple analytical model was used to describe contaminant



transport toward the river.  The model results show that steady



state concentrations at 100 feet are reached in one week.  Steady



state concentrations at the river edge are reached in roughly



one year.  The steady state concentrations are extremely dependent
                               3-59

-------
        TABLE 3.3-6  TABULATION OF HAZARD INDICES FOR SYSTEMIC TOXICANTS
Const!tuent
Chlorobenzene
Methyl Ethyl Ketone
Toluene
1,2 Dichlorobenzene
1,4 Dichlorobenzene
Phenol
Ch rom i urn
Nickel
Barium
Zinc

Total
Wei 1 Numbers (hypothetical exposure points)
M2 (B)
ND
NO
ND
ND
ND
ND
ND
<.06
1.97
.001
OWI (Cl)
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
OW2 (Al)
84.2
.034
.002
.021
.08
ND
.93*
.257
1.67
.004
M6 (C2)
ND
.156
.921
ND
ND
.004
7.07*
.286
19.7**
.018
M12 (A2)
NA
NA
NA
NA
NA
NA
ND
NA
<9.85
NA
2.0
NA
8774
25.2
NA
NA - not avai table
 * Assumed to be hexavalent.  Report identifies only total  chromium.
** Hazard .index based on the higher of the measured values.
                                  3-60

-------
upon the dispersivity assumptions.  With a dispersivity of 1.0 m,



the concentration at the edge of the river is 14.5 percent of that



at 100 feet.  Because the concentrations of systemic toxicants at



points A-l and C-2 are both over 14.5 times the recommended ADI



for some constituents, the ground water at the river edge is



likely to exceed ADI for these constituents.



Exposure Assessment



     The plumes originating at this facility will discharge into



the nearby river.  Parts of these plumes will pass outside of the



facility property before discharging to the river; however they



will pass beneath the property of another chemical manufacturing



facility.  No supply wells are in the path of the plumes.  The



river is used as a source of drinking water, though the degree of



surface water contamination and the location of drinking water



intakes was not provided in the materials reviewed for this case



study.



     From velocity values for the alluvial aquifer of 14.4 and



4.5 ft/day, it can be approximated that the contamination would



have traveled to the river (3600 ft) within a range of 250 days



to slightly more than 2 years.  This assumes that all the water



in the aquifer discharges into the river, thereby preventing



underflow.  Further analysis of ground-water flow in the area of



the river would be necessary in order to adequately characterize



its movement.
                               3-61

-------
3.3.3  Case Study D-3



Facility Description



     A hazardous waste landfill has been operated at this site



since 1977 on approximately 300 acres of the site's 2500 acres



(see Figure 2.3-11).  Previously, wastes were disposed of in



trenches ranging in depth from 30 to 50 feet.  Current practice



consists of burial of non-liquid containerized and



non-containerized wastes in trenches up to 175 feet deep and up



to 8 acres in area.  It is believed that most listed hazardous



wastes have been disposed in this facility.



Climate



     Average precipitation in the area is about 50 inches/year.



Monthly average precipitation ranges between about 6.2 inches in



the winter and spring months to about 2.2 inches in the late



summer to early fall.  Watersheds in the area are characterized



by high amounts of evapotranspiration and widely varying amounts



of runoff depending on the surficial geology.  Area temperatures



are moderate with below freezing temperatures occurring only



during short periods.  Therefore, accumulations of snow and ice



are not a consideration in runoff or water balance calculations.



Regional Hydrogeology



     The site is located in the Coastal Plain physiographic pro-



vince.  The rocks in this area generally consist of Upper Cretaceous



sediments which dip to the southwest.  The facility is located



on chalk/marl which is a relatively homogeneous low permeability



unit.  The chalk was presumably deposited in a clear sea of
                               3-62

-------
NOTE:   Borings from State
       Inventory Wei 1
                        1
0123
                 •i

   SCALE IN MILES
       FIGURE 3.3-11  LOCATION OF DEEP WELL BORINGS AND GEOLOGIC SECTIONS


                                     3-63

-------
moderate depths.  The uppermost aquifer lies directly beneath



the chalk/marl and local ground water is believed to flow east to



northeast.  The uppermost aquifer is the first stratigraphic unit



with the ability to transmit groundwater at a sufficient rate and



yield to be used as a water supply.



Site Geology



     The chalk/marl group (650-750 feet thick) consists of a



chalky limestone with a minerologic makeup of 50% calcium



carbonate, 44% clay minerals and approximately 6% sand.  The



lower member of the group is a uniform thin bedded chalky marl



with a thickness of approximately 250 feet.  The chalk/marl, as



previously stated,  is reported to be quite homogeneous with very



little structure and a low permeability.  There is some discussion



in the application concerning faulting in the chalk/marl group.-



The presence of faulting or fractures could greatly effect the



migration of contaminants within the chalk/marl group.



     The uppermost aquifer formation is approximately 400 feet



thick beneath the site and generally consists of thin clay and



sand beds with thick and coarse sand and gravel beds at its base.



This formation is divided into three units with the upper 100 feet



being a sand member.  Figures 3.3-12 and 3.3-13 represent schematic



sections in the area of the site.



Site Hydrology



     The potentiometric surface of the chalk/marl is generally 10



to 30 feet below the ground surface.  However, because evaporation



is greater than precipitation, dry trenches have been excavated



to over 100 feet.  From water level measurements in the uppermost
                               3-64

-------
                              sw
u>

&
tn
                                N-3
                                                                                         NE
            o
            z
                  500 _
                    0 _
                 -500 -
                -1000
                -1500 -
3   -2000 -

i—



    -2500-





    -3000-
                        EL.-2225
                                                                 NATURAL GROUND LEVEL
                                                                                            1-8
                                                                                 A1

                                                                                 EL.  110
                                                   UPPERMOST] AQUIFER FORMATION
                                                                                             EL.-1770
                            NOTE:  See FIGURE 2.3-11 for Location of Section and Scale
r  500





-  0





- -500





  -1000





  -1500





  -2000





  -2500





  -3000
                                                                                                     m
                                                                                                     r~
                                                                                                     m
                                                                                                     o
                                 FIGURE 3.3-12  GEOLOGIC SECTION A-A1 NORMAL TO STRIKE

-------
                                NW
                                   J-]k
                                                                            SE
                                                                               N-8
00


cr>
                   500 -,
                     0 -
                  -500 .
                 -1000 -
                          EL.
         EL.-465




             EOB
              o
              z
             ^  -1500
-2000 -
                 -2500 -
                 -3000 -
                 -3500 J
NATURAL GROUND LEVEL
CHALK/MARL
UPPERMOST AQUIFER FORMATION

'


ITE: See FIGURE 2. 3-11. for Location of Section and Scale
B'
EL 200

EL. -510
ft _ft~7fi
tL . -0/U
Cl 1 1f\f\
tL . - 1 3UU
ci -on^n

EOB

- 500
- 0
. -500
m
m
<:
--1000 ^
z
--1500 ^
-H
-?nnn 1^
--2500
--3000
--3500
                                            FIGURE 3.3-13  GEOLOGIC SECTION B-B'

                                                           PARALLEL TO STRIKE

-------
aquifer, a downward gradient into the aquifer was observed from



the chalk/marl in the eastern portion of the site.  In the western



portion of the site, however, an upward gradient from the upper-



most aquifer into the chalk/marl was observed.  Head differences



reach a maximum of 80 feet in the eastern portions of the site



and a maximum of 20 feet in the site western portions.  Although



the application states that vertical gradients do exist (approxi-



mately .11) and ground-water movement occurs, the actual movement



is believed to be negligible.  Field permeability values are



reported to range from 5.7 x 10"^ to 1 x 10"^ cm/sec.   Also, a



laboratory determined effective porosity of 33.4% was reported.



Plume Information



     There was no information available concerning existing



monitoring well locations, nor were any monitoring data presented.



However, considering the low permeability values and thickness



of the chalk/marl, migration into the uppermost aquifer may be



unlikely except over extremely long time periods.  This statement



appears true even though much of the actual waste disposal occurs



below the water table in the chalk/marl unit.



     There is some discussion in the application regarding



proposed monitoring well installations in the chalk/marl.   Sixteen



core holes will be placed around the unlined trenches used during



interim status.  These core holes will be completed as wells



screened across selected fractures in the chalk.  An additional



18 wells will be screened below the base of adjacent trenches.



This shallow monitoring system will encircle the landfill trenches.



Two background wells away from active landfilling will also be
                                3-67

-------
installed to depths of 100 feet.

Time of Travel

     Using the following application-supplied values, a vertically

downward ground-water velocity was calculated.  (K values were

obtained from packer and well recovery tests).

          Hydraulic Conductivity (K)     1 x 10""^ cm/sec
          Hydraulic Gradient (i)             .11
          Effective Porosity (ne)_           .33
          Ground Water Velocity (V)       .034 ft/yr

From a ground water velocity of .034 ft/yr a TOT]_QO °f approxi-

mately 3000 years can be expected.   There is 550 feet between the

uppermost aquifer and the base of the waste management unit at

the site.  Considering the previously listed velocity, the

contamination would take approximately 16,200 years to reach the

uppermost aquifer.

Health Risk Assessment

     The contaminant plume at this facility is hypothetical.  The

simulation model assumed a steady state source release rate of

1.0 g/yr of benzene from a point at the facility.   The resulting

concentrations and hypothetical health risks are shown in

Table 2.3-8 at distances of 100 feet and 550 feet.  At 100 feet,

the plume reaches steady state after 7500 years with a concentra-

tion- of 0.805 ppb and a hypothetical carcinogenic risk of 1.1 x

10~5.   At 550 feet, the plume reaches steady state after 33,000

years with a concentration of 0.87 ppb and a risk of 1.24 x 10"^.

     The health risk indicated in this table is the hypothetical

risk associated with the small 1.0 g/yr assumption.  At 1 x 10"^,

the steady state risk is approximately at the threshold of

acceptability at both 100 and 550 feet.


                               3-68

-------
Table 3.3-7:   Results of Benzene Plume Simulation
Time (years)
500
1000
5000
7500
8000
10,000
15,000
20,000
30,000
33,000
Benzene Concentration (ppb) Health
100 ft 550 ft Risk
0
3.72 x 10-3 5.3
6.33 x 10-1 9.0
8.05 x 10-1 1.15
6.58 x 10-5 9.4
1.04 x 10-2 1.49
1.68 x 10-1 2.4
5.74 x 10-1 8.2
8.61 x 10-1 1.23
8.68 x 10-1 1.24
0
x
X
X
X
X
X
X
X
X

10-9
10-7
10-6
10-11
10-8
10-7
10-7
10-6
10-6
                       3-69

-------
Exposure Assessment



     Based on available information, there is no plume at this



facility.  If one does develop, it will not pose much of a risk



because the hydraulic conductivity of the chalk/marl is so low



that it would take an extremely long time for exposure to occur.



Such a plume would travel very slowly, on the order of one foot



in 300 years and would not be expected to reach the uppermost



aquifer for over 15,000 years.  Furthermore, the chalk/marl for-



mation is not pumped for any domestic, commercial, or agricultural



purposes.
                               3-70

-------
3.3.4   Case Study D-4



Facility Description



    A plume of ground water contaminated by liquid metal-plating




effluent has formed downgradient from an industrial park on Long




Island, New York.  Discharges from the plant to the shallow



aquifer began in the 1940s.  Waste water treatment was installed




in 1958, and the operations ceased in 1970.  While the facility



was in operation the plume contained elevated chromium and cadmium



concentrations extending approximately 4,300 feet downgradient



from the waste disposal basins and discharged into a small creek.



Hydrology



    The area is underlain by the upper glacial (water table)




aquifer, and the Magothy aquifer, which supplies all the drinking



water to the area.  The aquifer of concern is the upper glacial



aquifer which, in the study area, ranges from 80 to 140 feet




thick.  The water table in the area ranges from 0 to 25 feet



below land surface.  This aquifer consists chiefly of medium to



coarse sand with lenses of fine sand and gravel.   Locally, beneath




and immediately west of the stream, the rate of movement of the



leading edge of the plume may be as low as 0.5 feet/day, owing



to the smaller hydraulic gradient in that area.  The TOT for



100 feet is therefore less than 200 days.



Plume Information



    Maximum concentrations of hexavalent chromium determined



during successive investigations ranged from 40 mg/1 in 1949 to



10 mg/1 in 1962.  Cadmium concentrations ranged from 0.01 to



10 mg/1, but in most places, were less than 1 mg/1.  Maximum
                               3-71

-------
observed concentrations of cadmium and chromium in the creek were



0.1 and 2.9 mg/1, respectively.  Concentrations of both cadmium



and hexavalent chromium in most of the plume and in part of the



the creek exceeded the limits of 0.01 and 0.05 mg/1, respectively,



as stated in the National Interim ,Primary Drinking Water Standards.



     The location of the monitoring wells is depicted in



Figure 3.3-14.  No background well was available.   Point D, the



leading edge of the plume, is interpreted as Well #62.  Well #2



was chosen as point A, even though it lies 700 feet along the flow



line.  No monitoring well was installed at compliance point C.



    Analysis of the single samples taken in the fall of 1975 from



the observation wells at the site are reported in Table 3.3-8.



Well #2, the closest well to the disposal basins,  showed the



highest concentration of contaminants.  Figure 3.3-15 presents a



cross-section of the area and the plume,  along the axis of flow



toward the creek.



Health Risk Assessment



    The concentrations of the constituents used in the following



assessments may not represent the largest values passing through



the hypothetical exposure points, because ground-water quality



sampling has occurred between 10 and 20 years after waste water



treatment operations had reduced the concentrations of hazardous



constituents entering the ground water.



     No oral carcinogens were identified at this site.  Cadmium



and chromium VI have been identified as inhalation carcinogens,



but no oral carcinogenic risks have been demonstrated.  Cadmium,



chromium VI and chromium III are all recognized as systemic
                              3-72

-------
                  500    looo FCET
                100  iee  100 MI Tins
FIGURE  3.3-14  WELL PATTERNS AND PLUME  OUTLINE



                      3-73

-------
Table 3.3-8:  CONCENTRATION OF METALS  IN MONITORING WELLS  (ppb)
Compound
Trivalent chromium
Hexavalent chromium
Cadmium
Point D
(Well 162)
110
0
440
Point A
(Well #2)a
366
24
6,900
aWell #2 is located approximately 700 feet from the disposal
 basins.
                                3-74

-------
MA* SHOWING LOCATION Or SCCTION
                                              t'U

    FIGURE 3.3-15  CROSS-SECTION OF GROUND-WATER PLUME
                            3-75

-------
toxicants on EPA's listing of ADI's.  The remaining constituents

appearing at elevated concentrations  (iron, manganese and zinc)

are neither carcinogenic nor recognized systemic toxicants.

     The hazard indices for cadmium and chromium are presented

in Table 3.3-9.  This table shows that the concentrations of

cadmium represent a significant toxic hazard, because ingestion

of 2 litres per day of water at the contamination levels observed

at points A or D represents a cadmium ingestion of many times the

ADI.  The hazard index for point D is 25.  Neither hexavalent nor

trivalent chromium concentrations have hazard indices in excess

of 1.0.

Exposure Assessment

     Prior to discovery of the contaminant plume in the early

1940's, the shallow aquifer was widely used as a source of
                                                      »*
drinking water.  The yield probably exceeds 10 gallons.per minute

in nearby shallow local wells.  In addition, the contaminated

portion of this aquifer underlies an area of approximately

77 acres.  The leading edge of the plume appears to be influenced

by the position of the creek,  although Figure 3.3-15 suggests

that part of the plume may flow under and beyond the Creek.

     Use of this contaminated ground water for drinking purposes

does not appear to occur because the many residences overlying

the plume are served by municipal water.  If the area were not

urbanized,  there would be a greater chance that the ground water

would be used for drinking purposes.  Also,  because the plume is

well documented, potential users would likely be warned by local

authorities to avoid consuming this ground water.
                               3-76

-------
Table 3.3-9:  Tabulation of Hazard Indices
Constituent
    ADI        Exposure (mg/kg/day)    Hazard Index
(mg/kg/day)	A	D	     A     D
Cadmium
  .0005
 0.197
0.0126
 394    25.2
Chromium III
  1.60
.0105
.0031
.0066  .0019
Chromium VI
 .0021
.0007
              .33
Total
                                       394    25.2
                                 3-77

-------
Conclusions



    The cadmium concentration at points A and D represent



significant toxic risk if they are ingested in drinking water.



The exposures that would result from drinking water use exceed



acceptable daily intake thresholds by a factor of 394 at point A



and a factor of 25 at point D.



    This case demonstrates that a large-scale plume can develop



within a hydrogeologic setting that fails the TOTiQO criterion.



The potential for exposure to this plume is high because the



plume occupies a large portion of an aquifer that has a large



sustained yield.  An opportunity for large-scale, direct exposure



to this plume appears to be prevented only by the highly urban



character of this area.  Were the site more rural in character,



significant use of the ground water would be expected.  Impact



on stream quality has not been assessed in this case study.
                               3-78

-------
3.3.5  Case Study D-5

Facility Description

    This case study concerns ground-water contamination associated

with several unlined surface impoundments containing creosote

wastes in Florida.  The site began operation in 1902; operations

ceased around 1981.  Figure 3.3-16 shows the locations of the

facility and the monitoring wells used in this assessment.

Figure 3.3-17 is a hydrogeologic cross-section of the site.   As

shown by monitoring data, the plume extends approximately

1,000 feet from the impoundments towards a bay.  The plume length
                9
for .phenols is considerably less than anticipated by theoretical

calculations. [Such calculations project the. phenol plume to have

migrated 4 to 5 kilometers downgradient from the site beneath the

bay.]  However, there are no apparent monitoring wells "beyond

300 meters south of the site that verify these calculations.

Although many of the expected waste components are absent or

extremely dilute near the bay,  a dark sludge band has been

observed on the beach at low tide.  This suggests transport to

the bay through the ground-water system.

Hydrogeology

    The site overlies an upper sand and gravel aquifer that is

approximately 90 meters thick at the site area.  The water table

is within 1.2 meters of the land's surface near the impoundments.

Contamination has been found only within the upper 30 meters of

the aquifer, due probably to the retarding influence of the silt/

clay lens shown in the cross-section at a depth of approximately

10 feet.  TOTjLoO ^s estimated to be 25 days.
                                3-79

-------
                PLANT
                OVERFLOW  PONDS
                                         0  50. 100 150 METERS
                                         i   i
  6

 1.5
MONITORING SITE AND NUMBER
ALTITUDE OF WATER TABLE. CONTOUR
INTERVAL 0.5 METER. DATUM IS SEA LEVEL
      •A*  GEOLOGIC SECTION LINE A -A1
FIGURE 3.3-16 LOCATION OF MONITORING SITES (WELLS)

                      3-30

-------
                FIGURE 3.3-17   HYDROGEOLOGIC CROSS-SECTION  OF SITE
                                 (January 1984)
SEA LEVEL
                                           3 PONDS	
                                                                          A1
                                                                        METERS
                                                                         r-10
            .ju;—~-r CLAY rj
                                                                         -SEA LEVEL
                                                                         -10
                                                                         Mo
                          GENERALIZED SECTION. NOT TO SCALE
            k       MULTIPLE DEPTH WELL SITE
                           •* *
           •2.0	ALTITUDE OF POTENTIOMETRIC SURFACE,
                   CONTOUR INTERVAL 0.5 METER.  DATUM
                   IS SEA LEVEL.  DASHED WHERE
                   APPROXIMATE
                                      3-81

-------
Plume Information

     Monitoring data are available for 33 chemicals falling into

five groups.  These groups are:  phenols, polycyclic aromatic

hydrocarbons, nitrogen heterocyclics, sulfur heterocyclics, and

oxygen heterocyclics.  These data are presented for six well loca-

tions in Table 3.3-10.  For the purpose of this analysis, well 1

is designated as point B, well 3 as point C (compliance), well 4

as point A  (although it lies some 250 feet from the compliance

point) and well 7 as point D, the downstream edge of the plume.

The location of these wells is shown in Figure 3.3-20.

Health Risk Assessment

    These monitoring data are analyzed for adverse health risks

to hypothetical users in accordance with established toxicity

factors for carcinogens and systemic toxicants, and by analogy

with constituents with unknown toxicities to similar constituents

with known toxicities.  The latter method is used here because

extremely high levels of a compound are present for which no

toxicity values are available.

     1.  Standard procedure-

         a.  Carcinogens

             Of the constituents listed in Table 2.3-10, only
             Benzo-(a)-pyrene is known to be carcinogenic,
             and it was not detected at any of the wells.

         b.  Toxicants

             Several of the constituents have known toxic
             risks, and include:  phenol, biphenyl,
             pentachlorophenol, and fluoranthene.  The
             estimated Hazard Index for each of these is as
             follows:
                               3-82

-------
    TABLE 3.3-10  CHEMICAL ANALYSES FOR SELECTED  ORGANIC  CONTAMINANTS
           IN GROUND WATER AT A DEPTH OF 18.3  METERS  AT SITES
                            1 AND 3 THROUGH 7*
Compound
Phenols
Phenol
2-methyl phenol
2, 4-dimethyl phenol
3, 5-dimethyl phenol
2,3,5-trimethylphenol
1-naphthol
2-naphthol
Pentachlorophenol
Total phenols
Polycyclic aromatic
hydrocarbons
Indane
Naphthalene
2-methyl naphthalene
1-methyl naphthalene
Biphenyl
Acenaphthene
Fluorene
Phenanthrene
Anthracene
Fluoranthene
Pyrene
Benzo(a)pyrene
Total polycyclic
aromatic hydrocarbons
Nitrogen heterocycles
2,4-dimethylpyridine
Qu incline
2-methlyqu incline
2-quinolinone
Acridine
Carbazole
Acridinone
Total nitrogen
heterocycles
Well
1
B

ND
ND
ND
ND
ND
ND
ND
ND
ND


ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND
ND


ND
ND
ND
ND
ND
ND
ND
ND

1 numbers/hypothetical exposure points
3 4 5 6 7
C A D

13.3
456
1,835
1,666
317
360
317
11.6
4,976


19.0
1,976
159
91.1
22.0
157
82.1
57.2
3.2
2.8
1.6
ND
2,571


ND
3.5
ND
1,217
1.0
339
12.4
1,573


ND
7.8
623
548
36.5
ND
ND
ND
1,215


ND
27.3 1
1.1
0.5
--
1.2
1.2
1.6
ND
0.2
0.2
ND
33


ND
ND
ND
125
ND
13.5
ND
139


ND
15.9
83
13.5
35.9
111
2.4
ND
262


54.7
,038
87.3
44.7
7.8
44.9
17.3
2.9
ND
ND
ND
ND
1,298 1


ND
ND
ND
214
ND
52.5
2.2
?69~~


ND
44.7
178
999
218.8
216
13.3
ND
17770


435
271 1
437
260
53.2
246
103.4
49.4
3.0
ND
ND
ND
,858 1


ND
ND
2.7
517
ND
299
11.4
S30~


ND
2.3
405
6.6
60.9
138
81.1
ND
694


186
,072
156
81.3
15.4
75.9
34.5
12.5
ND
ND
ND
ND
,634


ND
ND
ND
94
ND
104
2.4
Ioo~

Concentrations in micrograms per liter; ND, not detected.
                                  3-83

-------
TABLE 3.3-10  CHEMICAL ANALYSES FOR SELECTED ORGANIC CONTAMINANTS
              IN GROUND WATER AT A DEPTH OF 18.3 METERS AT SITES
              1 AND 3 THROUGH 7 (Continued)*
                              Well numbers/hypothetical exposure points
                              1       3       4       56       7
Compound                      B       C       A                       D

Sulfur heterocycles

Benzo(b)thiophene             ND     268      6.0     82.7  442      157
Dibenzothiophene              ND       3.6    0.5      4.9    4.4      1.1
Total sulfur                  ND     272      7       88    446      158
  heterocycles

Oxygen heterocycles

Dibenzofuran                  ND       89.3   O.J     15.1  101.1     31.4
Total oxygen                  ND       89     1    .   15   . 101       31
  heterocycles


*  Concentrations in micrograms per liter; ND, not detected
                                     3-84

-------
                                A       B       C        D

         Biphenyl              ND      ND     .013     .009
         Phenol                ND      ND     .004      ND
         PCP                   ND      ND     .011      ND
         Fluoranthene         .006     ND     .013      ND

         Total Hazard Index   .009    ND      .25      .12

         ND - not detected

     2.  Estimation of unknown toxicities by analogy

         Extremely high concentrations of 2,4-dimethylphenol,

         3,5-dimethyiphenol,  and 2,3,5-trimethylphenol have

         been observed at this site, but these compounds do

         not have assigned EPA toxicity values.   EPA does,

         however, list ADIs for 2,6-dimethylphenol and

         3,4-dimethylphenol of 0.00019 and 0.00044 mg/kg/day,

         respectively.  We have chosen the lower of the two,

         0.00019, as a conservative estimate of  the ADI for

         2,4-di, 3,5-di, and  2,3,5-trimethylphenol.

                                        A     B      C     D

         Total Concentration  (mg/1)   1.20   ND    3.83  0.47
         Hazard Index                  185   ND     588  72.3

Exposure Assessment

     The potential for exposure to contaminants  at this site could

be great due to the potentially high yield of the aquifer as shown

by nearby production wells (e.g., 5,500 gallons  per minute) and

the areal extent of the plume (approximately 7.4 acres).  There

is, however, no present indication that ground water in the area

of the plume is being used for drinking water purposes.  A study

is underway to determine if there have been any detrimental

environmental effects to the  bay.
                               3-85

-------
Conclusions



     The evidence of significant toxic risk at this site is



convincing, although the substances of concern are not explicitly



represented on the ADI list for systemic toxicants.  The EPA list



of ADIs shows 2,6-dimethylphenol to be one of the most toxic



substances on that list, with an ADI of.. 0.00019 mg/kg/day.



Application of this toxicity threshold to chemically similar



2,4-dimethylphenol, 3 , 5-dimethylphenol and 2, 3-, 5-trimethylphenol



observed at this site is a reasonable procedure, though it is



conservative and may tend to overestimate risk.  However, the
                                                        •


concentrations at this site are so high that" even an ADI of



0.0019 mg/kg/day (i.e., 100 times less toxic than



2,6-dimethylphenol) would show significant risks.



     The ground water characterized by this risk extends for a



substantial distance from the site (approximately 1,000 feet).



The opportunity for exposure is high; the sustained yield of the



geologic unit containing the plume can exceed 5,500 gpm.  The



site clearly fails the proposed TOT]_oo criterion.
                              3-86

-------
3.3.6  Case Study D-6


Facility Description


     A facility which handled hazardous wastes is located at a


former sand and gravel pit operation.  The facility's operations


have resulted in the release of hazardous constituents to the


ground water beneath the site.  The facility currently consists


of a fenced enclosure with an incinerator, a concrete block


building, and an asphalt lined lagoon (see Figure 3.3-24).


Outside of the fenced enclosure is an undeveloped area partially


enclosed by second fence constructed to restrict vehicular access.


Prior to 1972 the site was a sand and gravel pit, which was


allegedly used to store and dispose of contaminated by-products


from tank cleaning.


     The on-site asphalt lagoon was originally constructed in 1972
                                                      »'

to accommodate waste generated by a marine oil spill of


100,000 gallons of industrial fuel.  The existing incinerator was


also upgraded at that time.  In addition to the oil spill wastes,


the owner also accepted tank bottoms of number 6 and number 4 oil,


septic tank wastes, and industrial process wastes.  Approximately


100,000 to 200,000 gallons were received annually by the facility


between 1972 and 1977.


     The facility was operated as a transfer station for the


wastes listed above.  Initially, the incinerator with afterburners


and pollution control equipment was used to dispose of oil


impregnated refuse (seaweed from the oil spill, rags, etc.).


However, the incinerator was not used after 1975.  The typical


method of operation was to accumulate wastes in large tanks until




                           3-87

-------
sufficient quantities were obtained for shipment to refiners or



off-site disposal.  Contents of the lagoon were then transferred to



the large tanks.  Subsequently, the tanks leaked.  Also, numerous



accounts allege that rinse waste and oily wastes were applied directly



to the ground surface.  The area between the inner fenced area and



the adjacent road was once allegedly used for dumping and burning



and contains buried drums.  This area has since been filled to



grade by the site owner.





Environmental Setting



     The topopgraphy of the site is relatively flat west of the



adjacent road witn" the fenced enclosure and the areas to the



west and north lying in a excavated area.  Off-site, the land



slopes steeply eastward to the river.   Elevations range from



approximately 300 feet mean sea level (MSL) at the site to less



than 200 feet MSL at the river, approximately 3/4 mile due east.



     Site area surface and groundwater discharge to the river and



its tributary brook.  The State's department of environmental



protection has classifed the river as B-2,  acceptable for



recreation, including water contact.  Class B-2 waters may also



be used for industrial and potable supply after treatment.



     Site surface drainage is contained on-site and the water



either evapotranspirates or percolates into the soil.  The



percolation rates through the contaminated soils at the site



are likely to be approximately twice as high as usual for the



state, creating little or no run-off.
                               3-88

-------
           (MONITORING
           WELL ITTPI
                                  WATER
                                 IWELL
                      *|	S3 SAL. DRUMS
               ASPHALT  i— GATE
                 RAMP
                             VERTICAL TANK (7YP.)
                          I CHAIN LINK
                          I FENCE
                  BOTTOM OF SLOPE
                  'TOP OF SLOPE
APPROXIMATE  SCALE:  |"= 100*
                               TRUE
SITE  PLAN
                                                        FIGURE 3.3-18
                             3-89

-------
           HAND
   • GRAVEL PIT
                                                                                                1*=1000'
LOCATIONS OF OFF-SITE MONITORING WELLS
        MAP FnOM U9Q8      QUAOnANQLE)
                                                                      N
FIGURE U-19

-------
               • I • —••».«
         I  II   III  II   I \L  I  I   I   I   I
                                                                       KEY
                                                                  DOMING LOCATIONS
      i   i   i  riii   i   i  i  i   i  'i   i
                 ___.«_-.
ON-SITE SUB SURFACE SOIL BORING LOCATIONS AND
LOCATIONS OF SITE SOIL SECTIONS
                                                        f\J
TRUE
~~1
                                                                          FIGURE 3.3-20

-------
SITEECTION A-A'
FI
1.3-21

-------
       MO DETECTABLE TOTAL VOLATILE onOANICO 
-------
                        TABLE
                              2.3-n
 B-l
 B-l
 B-2A
. B-2S
  B-2C
  B-3 (soil)
  B-3 (rodO
   B-4
   B-5  (soil)
   B-5 (rocO
SSSSaSL&ai
    .209.0 - 224.8
    188.6  - 204.9
    131.5 -  1«.5
     153.9 - I50'8  •
     187.5- IV'*
     171.2-  IBS-1
      145.6.- 161-6
       28.5 -  65-1
       150.5 - 153.4
       132.5 - 1*7.6
                                                     Groundwater
                                                      Elevation
                                                      (ft HSL)
                                                   3/6/8A
1.7 x 10~4
4 5 x 10" -
^ • »
8.3 x 10"6
TO'2
» 10
,n-3
1.7. x 10
1 4 x 10"4
1 • ^ *^
2.6 x 10"5
fa • ^
.5
9.3 x 10 .
2.8 x 10'5
. - - ,n-5
223.6
. 219.*
192.1
200.9

frozen
176.8
170.3
99.8

170.5
170.4
224.1
21&.8
193.4
203.0

203.1
176.5
.153.9
97.0

171.0
170.9
                                    3-94

-------
Surficial Geology



     The study area is located on a glacial outwash plain comprised



of stratified sand, gravel, and boulders.  Three major subsurface



units are noted to be present near the site.  These units consist



of glaciomarine fine sands and gravels, reported overlying glacio-



fluvial (deltaic) stratified sands and gravels.  Glacial till is



noted to underlie the stratified sands.



     Beneath the site the predominant soil type is a medium grained



sand with lenses of silt and clay (see Figure 3.3-26 through 3.3-28)



Approximately forty feet of these medium coarse grained sands



beneath the site are unsaturated.  An effective porosity of 0.2



(default value) was used for these sediments when saturated.



     The glaciomarine fine sands, silts and clay silts reportedly



overlie the sand and till along the steep slopes that lie adjacent



to the river and its tributary brook.  It was noted that the clayey



glaciomarine deposits have apparently presented a barrier to



ground water flow from the sand and gravel deposits (sand and till).



Springs and seeps were noted to occur where this ground water



flowing from the sand and gravel escapes to the surface through the



clayey deposits.





Bedrock Geology



     The topography of the bedrock surface generally slopes to the



east, toward the river as shown in Figure 3.3-32.  The bedrock



surface forms a broad northeast-trending trough to the west of



the site; the surface rises south of the site.  This peculiar



topography of the bedrock surface is a significant factor, which



results in movement of groundwater toward the north away from the





                           3-95

-------
site.

     The bedrock beneath the site is reportedly composed of granit^

pegmatite or schistose migmatite, possibly transected locally by

thin, tabular mafic dikes.  Cores from the monitoring wells drilled

in 1984 show moderately to heavily fractured rock with softening

and iron staining due to weathering along the fractures.  It was

noted that ground water is transported through the bedrock apparently

to the northwest in fractures, and to the north/northeast along the

dikes.  Calculated permeabilities from falling head permeability
                                                                *
tests in the upper zone of the bedrock were reported to vary from

10~5 to 2.5 x 1CT6 cm/sec.


Site and Near Site Hydrology

     General information on the ground water hydrology of the

surficial and bedrock aquifers in the vicinity of the ^site was

noted to be given in a previous report, conducted in 1982.  A

study conducted in 1984 was designed to better define the

ground water flow and to verify the inferences made relative to

the hydrogeologic parameters of the area from the 1982 study.

To this end, five monitoring wells were installed (B1-B5), in

addition to the four previous monitoring wells installed

in 1982 (B101-104).  Figure 3.3-25 shows the location of the

monitoring wells from both studies.   Also note Table 3.3-16 on

Well Data (1984).

     Wells Bl through B5 were installed in order to expand and

address the need for further well data.  This well information

was intended to confirm the presence and migration of the

contaminant plume, to delineate areas of high permeability,  to


                          3-96

-------
assist in model calibration, and define areas of low permeablility
thought to exist near the site.
     The general path of ground water flow in the surficial aquifer
was noted"to be northwestward from the site,  eventually turning
eastward through an east-west trending coarse gravel deposit toward
the "springs" (see Figures 3.3-29 and 3.3-30).  Figure 3.3-31 gives
the inferred bedrock potentiometric surface;  flow direction was
inferred to move to the northwest, as indicated by the arrows.
     The aquifers are hydraulically connected as indicated by
the presence of contaminants in the bedrock aquifer.  Downward
vertical gradients (i.e. a recharge zone) through the surficial
aquifer were indicated by all the 1984 boring sites with multiple
well installations.

Plume Information
                                                      »•
     The path of contaminants leaving the site appears" to be in a
north-northwesterly direction; the contaminants then appear to
take a larger radius turn (larger then that predicted by the 1982
study), before curving eastward and finally southeastward to
intersect the river at the springs.  Refer to the section on site
and near site hydrology for well data used to confirm the contam-
inant plumes path.  Also see Figures 3.3-29 through 3.3-32.  The
report also noted that most of the bedrock ground water that
originates at the site is discharged to the overlying gravel
deposits in the vicinity of the springs.
                           3-97

-------
;-'
                   .,
/~V o'    sorf   IOOQ' (
.^) »       '"^ ./ *
INFERRED SURFICIAL AQUIFER PLUME FROM
•becAw ^-^l
N

FIGURE 3.3-23

-------
                                                                               LEGEND

                                                       .3- 30IL IIOnillQ LOCATION      - - WITIIOnAWAL WELL l.OCATIOII
                                                         - onoiiMowAicn LEVEL   .... ....... APPROXIMATE TOP OF IIEOIIOCH
   WATER SAMPLE
  -TAKEN AT OEPIII
   06 pp»» 1.1.1-TIIICIILOnOETIIAHC.
   1.000 ppb TCE
                                                                                    HO-OELOW DETECTAULE LEVELS
                                                                                    SPRIIIQS-i
         III
                                                                                                    RIVER
                           1000
                                         2000
3000    I'EET    4000
                                                                                    6000
                                                                                                  0000
sunsunrAcn CROSS^GECTION A-A FROM SITE TO
(ooo rifliiro2.323for  Croao-Socllon Locnllon)
                                      FIGURE 3.3-24

-------
&

                                                                            -     c
                                                                   —   •.      •
                                                                     q  •>•  .-- 7
                                                                   ;        •
-188* POTENTIOMETER   ;-


"SURFACE ELEVATION (f««O
INFERRED BEDROCK POTENTIOMETRIC
SURFACE FROM (1982) WITH
1984 DATA. SUPERIMPOSED
,j± -. • ~. ---', FIGURE 3.3-25
                                  3-100

-------
        SC/UE
.a
             *  mr
                           /'•• .  s.  - DM  .
 LEGEND

MONITORING WELL DG
1004 CONCENTRATION
    (6ppb)
              0EDROCK AQUIFER PLUME FROM  1^02
WITH THE 1004 1,1,1-TniCIILOnOETIIANE ODQEHVED DATA OUPEniMPOBED |
                                                                           FIGURE 3.3-26

-------
 Time of Travel-TOT]_QO

      Approximately 40 feet of unsaturated medium-textured sands a

 encountered cirectly beneath the site.  The analytical approach to

 solving for TOT within the unsaturated zone was based on a

 single-layered system of a single material type.  This solution

 assumes that the hydraulic gradient is equal to 1.1  A steady state

 flow of moisture through the unsaturated zone is also assumed.

 Steady state flux (q) is assumed to be equal to net precipitation

 where evapotranspiration and run-off are assumed nonexistent.  This

 provides the maximum flux for the site.
                                       >
       0 Unsaturated Zone

          TOTunsat.= L0         L = Length of unsaturated column
                     q          0 = Volumetric water content
                                    approximately equal to porosity
                                q = Flux

          TOTllr,a_«. = (1.22 x 103 cm) (0.395 cm3/cm3)
             unsciu.           , _ _   /
                              107 cm/year

          TOTunsat.= 4'5 years

       0 Saturated Zone

          V = Ki       K « 3.28 x 10~4  ft/sec (default value)2
              ne       i = 0.02 average from field data
                      ne = 0.2 (default value)

          V= 3.28 x 10"5 ft/sec

          TOT100 = 	100 ft        = 3.05 x 106 sec = 9.67 x 10~2 yrs
                   3.28 x ID"5 ft/sec

          TOT100 = TOTunsat. + TOTsat.
          TOT]_oo = 4.6 years


1 - Derived from Technical Support for Developing Guidance for
    Calculating Time of Travel (TOT)in the Unsaturated Zone;
    December,  1984, Section 3.

2 - Default value for hydraulic conductivty taken from Freeze & Cherry,
    1979.   K selected for clean sand is 1 x 10~2 cm/sec. Conversion
    factor for ft/sec = 3.28 x 10"2.

                              3-102

-------
Health Risk Assessment


     This health risk assessment characterized hypothetical risks


associated with the lifetime consumption of ground water contaminated


with trichloroethylene (TCE) and 1,1,1-trichloroethane, the major


contaminants for this site.  While actual contamination of private


well water supplies near the site has occurred, these data were not


available for use in this case study and therefore the potential


risks to residents who were exposed to contaminated drinking water


will not be evaluated here.


     Hypothetical risks associated with the lifetime consumption


of ground water containing TCE and 1,1,1-trichloroethane (two


potential human carcinogens) will be based on the maximum contaminant


concentrations identified in 1984 in a bedrock monitoring well (B-l)


located in the centerline of the plume.  Figure 3.3-33 shows the
                                                      »*

location of B-l and Table 3.3-17 contains the sampling-results.


Contaminant concentrations are generally higher in the bedrock


aquifer than in the surficial aquifer.  Well B-l is located

                                       *
off-site at roughly 1000 feet northeast of the si.te; it corresponds


to a well location between points A and D on Figure 3.2-1.   Well


B-l data were collected in 1984.  Drinking water has been obtained


from both the bedrock and surficial aquifers.  Thus, using the


data available in the RI for this, site, worst-case risk estimates


will be produced.


     For 1,1,1-trichloroethane, and additional risk esimate was


made based on the maximum isoconcentration line shown in


Figure 3.3-33; the concentration gradients shown in Figure 3.3-33


apply to the surficial aquifer and are based on historical and
                           3-103

-------
(-.
o
               LEGEND
     |fll   MONITOniNQWELLD1

     •'if70 I  100^ CONCENTRATION.
                                               lsocon:*.i  TPII
    ;>iriovc-ii**ii'.!l.te02>j    •*
    ''	  •     x 'I /•;-••>
j : 1 -,j. j. ' ..-../ . • . . .
'^[ii:. INFERRED SUnFICIAL AQUIFER PLUME FROM 1983 T>AT&
WITH THE 10IM 1,1,1-TIlllcnUOnOETIIAHE OD3ERVED DATA OUPEniMPOSED,
• .*
N
FIGURE
3.3-27

-------
                           TABLE  3.3-12
                     LABORATORY ANALYTICAL  RESULTS
                   OF GROUNDWATER QUALITY MONITORING
Location
B-l (shallow soil)
B-l (bedrock)
B-2 (shallow soil)
B-2 (deep soil )
B-2 (bedrock)
B-3 (shallow soil)
B-3 (bedrock)
B-4 (deep soil ) '
5-5 (deep soil )
B-5 (bedrock)
Date
(1984)
3/21
3/21-
3/22
3/22
3/22
3/20
3/20
3/21
3/20
3/16
1,1,1 Trichlo'roethane
(oob)
170** (230)
470** (500)
9
16
5
65
3
ND
NO (ND)*
7 (8)*
Trichloroethylene (TCE)
(oob) . '
16,000
29,000
91
160
56
1,800
120
ND
ND (ND)*
190 (177)*
duplicate
ND « not detected   .

These samples were  diluted for the analysis of trichloroeth/lene.  The
companion  results in  parentheses for 1,1,1-trichloroethane are for the;
•undiluted  sample.   .             •                                   '
                           3-105

-------
     TABLE 3.3- 13.  INCREMENTAL CARCINOGENIC RISK ASSOCIATED WITH LIFETIME
    CONSUMPTION OF TCE  AND 1,1,1-TRICHLOROETHANE CONTAMINATED GROUND WATER
                                   Average Daily    CAG Potency   Incremental
                   Concentration   Lifetime Dose*    Estimate     Carcinogenic
Contaminant (ppb)
Trichloroethylene 29,000
1,1,1-Trichloroethane 500
1,000
(mg/kg/day)
0.83
0.014
0.028
(mg/kg/day )'1
1.9 x 10'2
1.6 x 10'3
1.6 x 10"3
Risk
1.6 x ID'2
2.2 x 10'5
4.4 x 10'5
* Assumes lifetime ingestion of 2 liters/day of drinking water by a 70 kg.
  adult
                                   3-106

-------
current (1984) data.
     The carcinogenic risks associated with the lifetime consumption
of TCE and 1,1,1-trichloroethane are given in Table 3.3-18.  The
risk from TCE ingestion over a lifetime is estimated at 1.6 x 10~2,
which is extrememly high.  For 1,1,1-trichloroethane,  the estimated
risk is 2.2 and 4.4 x 10"5.
     While the concentrations of contaminants found in the sixteen
private wells that were closed in 1977 are not reported in the RI,
it can be assumed that by virtue of the wells being capped, the
risks were considered to be unacceptable.     ,
                                     •
Exposure Assessment
     Exposure to ground water contaminants from this site has
occurred.   As previously stated, 16 private wells in the path
of the plume -were closed in 1977.' In 1978 a public water supply
was provided as replacement for these wells.  Future exposure via
ground water ingestion is unlikely because of the provision of
this new water supply.  However, unless land use controls are
instituted to prevent utilization of the contaminated aquifer,
exposure could occur in the future from well water installatipn.
     The plume is migrating to the north and northwest and
eastward to a river and brook.  Based on data in the site RI report,
no contamination has been found in these downgradient surface
waters.  Potential future risks associated with the river and
brook would depend on the remedial actions taken on the site, where
significant soil contamination exists that could contribute to
overland flow and infiltration to ground water.  The brook (as Class
B-2 water) could theoretically, under state regulations, be used for

                           3-107

-------
drinking water if treated.  Relatively low-level contamination of



a spring adjacent to the river has occurred, the spring being a



discharge point for the contaminated ground water.   The potential



for exposure to contaminants in the spring is not known from



information provided in the RI.
                          3-108

-------
      4.0  ESTIMATING THE NUMBER OF FACILITIES LOCATED IN
           VULNERABLE GROUND-WATER SETTINGS
     The analytical approach and methodology followed to

estimate the number of hazardous waste land treatment, storage,

and disposal (TSD) facilities located in vulnerable ground-water

settings, and the results obtained, are discussed in this

Section.

     The optimal approach to determine the number of hazardous

waste TSD facilities in vulnerable settings would be to eval-

uate the ground-water vulnerability of each facility in the

U.S. on a facility-specific basis.  However, an evaluation of

all facilities was not possible due both to the lack of available

hydrogeologic data on TSD facilities and to the time constraint

placed on the completion of the analysis.  As a result, a praq-

matic approach was developed necessarily that uses only currently

available data.


4.1  METHODOLOGY

     Ground-water vulnerability is evaluated in terms of

TOTiQOf the time of travel of ground water along a 100-foot

flow line originating at the water table at the base of the

hazardous waste unit.  In the absence of facility-specific

information for all facilities in the U.S., other readily

available databases containing information useful for the

analysis were identified.  Several databases were reviewed

for hydrogeologic information that could be used to calculate

       and evaluate ground-water vulnerability.
                                   4-1

-------
     As described in detail in the guidance criteria, the




calculation of TOTiQO requires data on hydraulic conductivity,



hydraulic gradient, and the effective porosity of the geologic



media underlying the facility.  These data are explicitly



required in a Part B application, and are used to calculate the



average linear velocity (V) of ground-water flow.  Based upon



the criteria outlined in the guidance, travel distance is set



at 100 feet; therefore, ground-water velocity essentially



dictates whether a facility pases the TOTiQO criteria.



     Additional data requirements for the analysis were EPA



facility ID number, address, and latitude and longitude.  These



data are necessary to identify facility location and ascertain



overlap between the various databases.  The following databases



were identified as being potentially useful for characterizing



ground-water vulnerability:



     0 HWDMS database - the hazardous waste data manage-



       ment system database includes information on



       process codes based on Part A permit application



       data, and regional updates.  This database



       provides the best representation of the "universe"



       of RCRA hazardous waste TSD facilities, including



       landfills, surface impoundments, and waste piles.



     0 1982 GCA Study - GCA Corporation prepared a



       comprehensive database of geographical, geological,



       and hydrological variables to characterize the



       hydrogeology of 346 sites.
                               4-2

-------
0 1983 G&M Study - Geraghty & Miller designed 18 flow



  field scenarios to correspond to the 18 generic



  hydrogeologic settings developed by GCA Corporation



  (1982) based on data for 346 existing sites.   G&M



  established a rational basis for simulating flow



  rates and patterns by applying flow system theory,



  professional experience, and literature reviews.



  Selected pairs of flow fields having similar  hydro-



  geologic characteristics were clustered into  flow



  systems, reducing the total number of flow systems



  from 18 to 14.



0 WA23 Database - EPA's Office of Solid Waste (OSW)



  and Pope-Reid Associates collected data from  Part B



  applications to develop a worst-case hydrogeologic



  scenario.   Sufficient data were collected from



  163 hazardous waste disposal facilities nationwide



  to create a computer database.  The database



  contains two files; a ground-water characteristics



  file and a stratigraphic (soil) conditions file.



0 1985 GCA Study - GCA is currently conducting  a



  study for OSW.  They have collected data on approx-



  imately 225 sites (RCRA, CERCLA, USGS, municipal)



  and are analyzing the data for quantitative



  information that can be used in calculating TOT,



  and risk or environmental performance criteria.



  Approximately 60 of the sites have been analyzed,



  of which 37 are RCRA facilities.
                          4-3

-------
     0 EPA Case Studies - case studies for 10 RCRA-permitted


       hazardous waste land TSD facilities and one Superfund


       remedial action site were developed and included as

       Technical Methods for Evaluating Facility Locations:


       Technical Resource Document.


     The databases were evaluated in terms of the information

that they could provide on hydrogeology on the sites, aquifer


type, ground-water quality, location, and facility type.


Facility types analyzed are limited to landfills, surface


impoundments (treatment, storage, and disposal), and waste


piles.  Other facility types such as deep well injection, are


not considered.

     A review of available information and relevant databases


revealed three potential approaches for determining TOT^go-

The first approach, to review all available RCRA hazardous

waste land TSD facility Part B permit applications and calculate


TOT100 f°r eacl-1 facility, would have yielded the most accurate
      *
results because it employed detailed facility-specific data.

However,  it was rejected for two reasons:  (1) the relatively

small number of Part B applications available (roughly 150);

and (2) the time necessary to carry out the approach.  Gathering

the needed data from EPA Regional Offices would have required

more time than was available for this analysis.


     The second approach was to use the,1982 GCA and 1983 G&M

studies to calculate TOT^oO f°r ^ aquifer flow regimes, based

on data from the 346 land TSD facilities, and project the
                               4-4

-------
findings for these facilities to the HWDMS universe by



statistical methods.  This approach was also rejected because



it was based entirely on the generic flow regimes for the



determination of TOT^QQ, an<^ failed to employ any facility-



specific data.



     The third approach, which was selected, was to augment the



second approach by combining 173 generic TOT^QO calculations



with as many (55) facility-specific determinations as could be



made from available data, short of analyzing Part B applications.



This approach balances the desire to maximize the number of



facilities measured" with the need to rely as heavily as possible



on facility-specific data.



     All three approaches are less than ideal in that they



require the extrapolation of results from a facility sample



to estimate the number of facilities that are in vulnerable



settings.  The statistical validity of any such extrapolation



is unclear since insufficient information exists to determine



what would be a hydrogeologically representative sample of



facilities.  However, the third approach has the advantage of



employing both facility-specific and flow regime classification



data.  This approach allowed evaluation of the more generic



flow regime approach by comparing the results of the flow



regime analysis to the results of the facility-specific analysis,



while making the best use of the available data.  Therefore,



the third approach was judged to be the best available procedure



for estimating the total number of facilities potentially



subject to the ground-water vulnerability criterion.
                               4-5

-------
     The vulnerability designation was determined by comparing


EPA vulnerability guidelines to the TOTioo of the facility.  A


designation of vulnerable, non-vulnerable, or non-vulnerable


(storage) was assigned to each facility.


     "Vulnerable" facilities are those for which TOTioo is less


than on the order of 100 years for disposal facilities or, for


treatment facilities, for which TOTioo is too short to implement


a Corrective Action Plan.  "Non-vulnerable" facilities were


divided into two categories.  "Non-vulnerable (storage)" repre-
                                                       *

sents those treatment or storage facilities located over ground


water in settings where TOTioo exceeds the time in which a


Corrective Action Plan can be implemented.  "Non-vulnerable"


represents the remainder of non-vulnerable facilities, i.e.,


those in settings where TOTioo exceeds oh the order of 100 years



4.2  RESULTS


     TOT^oo was determined for 228 facilities including 55


facilities for which facility-specific data were used and 173


for which the G&M flow regimes served as the basis for generic


TOTioo calculations.  However, some of these facilities have


lost interim status (LOIS) as a result of failure to certify


compliance with certain ground-water monitoring requirements


of the Hazardous and Solid Waste Amendments of 1984.  The


HWDMS database provides information on facilities that have


survived LOIS.  A July 21, 1986 HWDMS printout indicated that


171 of the 228 facilites for which TOTioo was determined were


still accepting wastes.  Table 4-2-1 presents by EPA Regions


the vulnerability status of these 171 facilities.



                               4-6

-------
TABLE 4.2-1 DISTRIBUTION OF FACILITIES BY REGION  (VULNERABLE,
            NON-VULNERABLE, NON-VULNERABLE  (STORAGE))
Region  tVulnerable   ftNon-vulnerable    #Non-vulnerable  (storage
1
2
3
4
5
6
7
8
9
10
11
7
10
18
17
26
5
8
14
4
-
1
2
1
8
19
1
-
2
1
-
-
-
1
10
4
-
-
1
_
  Totals   120              35                      16
                               4-7

-------
     The results indicate that the majority (120, or 70%) of



the 171 facilities are located in vulnerable ground-water



settings.  The vulnerability status may be affected by errors



in the TOT100 calculations and errors that may be caused by



variations in the quality of hydrogeologic data in the databases.



Some errors in classification have already been identified and



are being corrected.  TOTioo values for the sites included in the



analysis vary from much less than one year to more than 1000



years, but insufficient information is available to warrant the
                 9


rigorous construction of a distribution of TOTiQO values, which



would perhaps allow the effect of TOTiQO on vulnerability to be



evaluated stochastically.





4.3. CONTINUING EFFORTS



     The EPA will continue to examine specific hazardous waste



land TSD facilities in various hydrogeologic settings to further



the facility location standards development program.  Currently,



a preliminary classification scheme has been designed for the



purpose of selecting the possible settings that may adequately



correspond to a wide range of TOTioO3-  Therefore, rather than


covering all hydrologic/physiographic/hydrogeologic provinces,



the scheme covers all the physical settings that govern TOT^go



from the surface to the uppermost aquifers or close receptors.



     The classification scheme considers two basic systems:  an



unconsolidated overburden (Regolith) and an underlying bedrock



system.  As applied to the TOT^QO concept, each system is classified



according to its ability to allow water to flow through it.




                               4-8

-------
                 TABLE 4.3-1  GEOLOGIC SETTINGS
Regolith Systems
Bedrock System
1.  Thin or absent
2.  Alluvium/Aeolian
3.  Alluvium/Aeolian with confining
    layer

4.  Clay
5.  Clay over unconsolidated aquifer
6.  Unsaturated sand
7.  Permeable Glacial
8.  Impermeable Glacial
 a)  Aquifer
 b)  Aquitard

 a)  Aquifer
 b)  Aquitard

 a)  Aquifer
 b)  Aquitard

 a)  Aquifer
 b)  Aquitard

 a)  Aquifer
 b)  Aquitard

 a)  Aquifer
 b)  Aquitard

 a)  Aquifer
 b)  Aquitard

 a)  Aquifer
 b)  Aquitard
                               4-9

-------
                           TABLE 4.3-2

                         Regolith Systems
     (Unconsolidated soils sediment cover overlying bedrock)
1.  Thin or absent:  Is not a factor in water infiltration

2.  Alluvium/ Aeolian:  Unconsolidated material overlying bedrock.
                       Capable of allowing water to infiltrate
                       and be stored or move.  Deltaic, fluvial,
                       coastal, aeolian sands, gravel, loam, -
                       non-glacial in origin.  May contain silt/
                       clay lenses, overbank deposits.  Can be
                       the uppermost aquifer, and also reach
                       great thicknesses.
   »
    Alluvium/Aeolian with confining layer:  Similar to (2) above,
                       but with a confining layer (Unconsolidated)
                       between it and bedrock, such that it will
                       restrict flow to bedrock locally.

    Clay:  Any considerable thickness of clay size material
           overlying bedrock.  Can be saprolite, lake deposits,
           peat, etc.  It impedes infiltration to bedrock.
3.
    Clay over Unconsolidated aquifer:
                                       Similar to (4) above.  The
                                       implication is that it is
                                       not a recharge area for
                                       the underlying aquifer.
    Unsaturated sand:
    Permeable glacial
                       Similar in texture to (2) above, but lack
                       of recharge makes it unsaturated.

                        Glacier related sediments with varying
                        degree of permeability.  Includes outwash,
                        eskers, stratified drift, sandy/bouldery
                        till, glaciofluvial, glaciomarine, brittle
                        glacial till, etc.
8.  Impermeable glacial:
                          "Tight" glacial deposits such as clayey
                          till, lacustrine deposits, etc.
                               4-10

-------
                  TABLE 4.3-3  BEDROCK SYSTEMS


A.  Bedrock Aquifers

    1.  Includes sedimentary and crystalline rocks that exhibit
        secondary porosity due to:

        - Faults
        - Fractures, joints, and cleating (coal)
        - Foliation and schistocity
        - Karst (limestone, dolomite, gypsum)        	
        - Weathered horizons (& unconformities)
        - Narrow intrusion (dikes)

    2.  Poorly cemented and bedded sandstone and carbonate
        rocks

    3.  Thin bedded sequences of sedimentary rocks

    4.  Basalt flows

B.  Bedrock Aquitards

    1.  Well cemented,  unaltered elastic and chemical sediment

    2.  Unaltered crystalline rock
                               4-11

-------
Table 4.3-1 shows the eight different classes in the Regolith



system and the two classes of bedrock that can be applied to



each overburden class.  Table 4.3-2 presents the conceptual



definition of each Regolith class/ and Table 4.3-3 presents the




conceptual definition of each Bedrock Class.



     These preliminary combinations cover a wide range of TOTjoo3



Since the classification scheme is not based on geographical



location, a site can be furt-her described as belonging in a



specific location, such as the "glaciated Appalachian Region."



One may find a second case study that fits the same TOT^QQ classi-



fication, but is located in the "glaciated Central Region."  In



such a case, there will be no need to include both sites as case



studies since that specific TOTlOO setting is represented by



either one.



     The intent of this continuing effort is to determine



whether case study or modeled characterizations exist for each



of the major geologic categories.  If characterizations are



lacking, they will be formulated and refined during the location



standards development process.
                              4-12

-------
                              5.0 REFERENCES


GAG (Carcinogen Assessment Group), 1984.  Relative Carcinogenic
  Potencies Among 54 Chemicals Evaluated by the Carcinogen
  Assessment Group as Suspect Human Carcinogens, Health
  Assessment Document for Polychlorinated-Dibenzo-pDioxins.
  EPA-600/8-84-041A, May 1984.

Freeze, A. R. and J. A. Cherry, 1979.  Groundwater.  Prentice
  Hall, Inc., Englewood Cliffs, N.J.

Todd,  David K., 1959.  Ground Water Hydrology, John Wiley & Sons,
  New York, 336 pp.

Theis, C. V., 1935.  The relation between the- lowering of the
  piezometric surface and the rate and duration of discharge of
  a well using ground-water storage, Trans. Amer. Geoph. Union,
  volume 16, pp. 519-524.

Thiem, G., 1906.  Hydrologische Methoden, Gebhardt, Leipzig, 56 pp,

U.S. Environment Protection Agency, 1980.  Water Quality Criteria
  Documents; Availability.  Federal Register 45:79318-79357,
  November 28, 1980.

U.'S. Environment Protection Agency, July 1983. Liner/Locational
  Analysis Project. Prepared by: Ertec Atlantic, Inc.
                               5-1

-------
               ATTACHMENT 1

  APPLICATION OF LINER LOCATION MODEL TO
 THE  ANALYSIS OF  TIME-OF-TRAVEL CRITERIA
FOR SITING OF NEW LAND DISPOSAL FACILITIES

    Prepared  by Geraghty  i Miller,  Inc.

-------
Geraghry & Milic:. Inc.
                      APPLICATION OF LINER-LOCATION MODEL
                  TO THE ANALYSIS OF TIME-OF-TRAVEL CRITERIA
                  FOR SITING OF NEW LAND DISPOSAL FACILITIES
                             DRAFT FINAL REPORT
                               Prepared For:

                   U.S.  ENVIRONMENTAL PROTECTION AGENCY
                           LAND DISPOSAL BRANCH
                           OFFICE OF SOLID WASTE
                          Washington, D.C.  20460
                          EPA CONTRACT 68-01-6871
                           WORK ASSIGMENT NO. 34
                                    By:
                          GERAGHTY & MILLER, INC.
                         ANNAPOLIS/  MARYLAND 21401
                               January 1985

-------
Gcraghty Sc Miller, Inc
                                 PREFACE
           This  report  was prepared  by Geraghty  &  Miller,  Inc.
      (G&M)  in  fulfillment of work Assignment  34  under the  U.S.
      Environmental  Protection  Agency (EPA) Contract  68-01-6871.
      It  will  be  incorporated  by GCA  Corporation  into a  larger
      report that will deal with  the  technical  issue of selecting
      criteria that control the siting of new hazardous waste  land
      disposal  facilities.   The work  is  being  performed for  the
      Office of Solid  Waste  (OSW)  which  has  the objective of
      establishing a scientific basis  for a working definition of
      the  term  "vulnerable ground  water".    The  present working
      definition is  based  on  a  time-of-travel (TOT) to a standard
      distance  measured  along a  ground-water flow line.   Ground
      water  under  landfills  and disposal surface  impoundments is
      considered non-vulnerable if the TOT  is equal to or greater
      than 100 years.  Ground water under storage  impoundments and
      waste  piles  is considered non-vulnerable  if  the  travel  time
      is equal to or greater than  10  years.

           Both  hypothetical  studies  and real  site  case studies
      are  being developed  in  order to examine the  health risks of
      exposure  to  various  chemicals  and a  range of hydrogeologic
      settings that would bracket  the  above  TOT  criteria. G&M and
      ICF,  Inc., are performing model  studies with  .the  liner-
      location  model, while  Geotrans  is performing site-specific
      model  studies to assist GCA  in  their analyses.

           The  EPA  technical  project  monitor for  this  study  was
      Mr.  Seong Hwang of  the Land Disposal Branch  (LOB)  under
      the  direction  of  Mr. Arthur Day.   The Project  Manager and
      Quality  Assurance Officer for G&M  were Don A. Lundy  and
      Jeffrey P. Sgambat,  respectively.  Other  members  of the G&M
      team  included  Messers.  Glenn  Duffield and  Robert Wright.
      G&M  also  acknowledges  significant  input  from  the Project
      Manager at GCA Corporation,  Mr. Alfred Leonard and at  ICF,
      Mr. Baxter Jones.

-------
Geraghty 6t Miller, Inc
                             TABLE OF CONTENTS


                                                              Page
      PREFACE	       i

      SUMMARY	       1

      INTRODUCTION	       4

      CONCLUSIONS	       6

      METHODOLOGY  	       7

           Scenario Development	       7
           Randon-Walk Model Development 	      13

      RESULTS	      22

           Random-Walk Model Output. ...» 	  .      22
           Liner-Location Model Output ..........      22
           Relationship Between Ground-Water
              Velocity/Time-of-Travel and Peak
              Concentrations 	      24

      REFERENCES	      29

      APPENDICES

           A. TABLES OF RANDOM-WALK MODEL OUTPUT 	    A-1

           B. GRAPHS OF RANDOM-WALK MODEL OUTPUT 	    B-1
                                   11

-------
Gcraghty & Miller, Inc.
                               LIST OF FIGURES
     1.  Orientation of a Generic Flow Field With
         Respect to the Contaminant Source and the
         Surface Water Outflow Boundary
         (From Geraghty & Miller, 1984) 	     8

     2.  Nine Generic Ground-Water Flow Fields
         Used in the Liner-Location Transport
         Model Scenario	     9

     3.  Six Generic Flow Fields Used to Study
         the Time-of-Travel Criteria	    11

     4.  Examples of Standard Breakthrough Curve
         and How It May Be Adjusted to Simulate
         Larger Mass Inputs and Biodegradation	    19

     5.  Comparison of Random-Walk Model Output
         With Two Analytical Solutions	    21

     6.  Plot of Contaminant Concentrations vs.
         100-ft TOT for Standard Mass Load Input
         Scenarios	    26

     7.  Plot of Peak Contaminant Concentration
         vs. 100 ft. TOT for Adjusted Load (Flow
         Field-Controlled) Input Scenarios	 .    27
                                 iii

-------
Gcraghty & Miller, Inc.
                                LIST OF TABLES


                                                              Face
      1.  Contaminant Velocities, Dispersivities,
          and Effective Porosities for Twelve
          Transport Model Scenarios. . .	   12

      2.  Source-Term Characteristics for Six
          Generic Flow Fields	   16

      3.  Critical Times and Peak Concentrations
          of Breakthrough Curves and 100-ft TOTs
          for Twelve Scenarios 	   23
                                    iv

-------
Gcraghty & Miller, Inc.
                                SUMMARY
          Geraghty &  Miller,  Inc.,  (G&M)-worked  with ICF, Inc.,
     and  GCA Corporation to  adapt and apply  an existing  set
     of  computer models  developed  for  the  1984 liner-location
     project of the  Economics Analysis Branch of  OSW  for  the
     assessment  of health  risks associated with a range of time-
     of-travel  (TOT)  conditions on hypothetical sites.

          G&M developed  six  generic vertically-oriented ground-
     water  flow fields  and  a standardized contaminant source
     term for  simulation of  contaminant  mass  transport to a
     downgradient monitor  well.   A range  of ground-water velo-
     cities  was  selected to  represent a  range of TOTs to a well,
     i.e.,  for  travel  along  a  100-ft ground-water flow line that
     originates  at the center of  the source and terminates at a
     monitor well.

          The source  term is conceptualized as a  line source
     with dimensions  of 1-foot  wide  and 32.8  ft  (10  m) long.
     This  source has  mass loading characteristics  of  either a
     generic landfill or a  storage  surface impoundment.  The
     source  life and  strength for  the  landfill  source  is e^ti-
     mated  assuming  an original  mass  in storage of 6 kg/ft , a
     leaching rate determined  by  an assigned  contaminant  concen-
     tration in  the  concentration in the leachate and ^facility
     leakage rate  controlled  by  ground-water  velocities in  the
     underlying flow  field.  The  source life  for the surface
     impoundment source  is  arbitrarily  set  to  30 years;  source
     strength  is controlled  by an  assigned contaminant  concen-
     tration and a  leachate release rate  dictated  by  the flow
     field.

          To simulate  these  conditions,  G&M  used  the Random-Walk
     particle tracking code  of Prickett, et al.  (1981).  A stan-
     dard mass   input  of one kilogram  over a one-year time step
     produces a standard breakthrough curve of  concentration
     vs.  time at the well  for each flow field.   Contaminants
     are  assumed to  have one  of  two mobilities  based on  earlier
     work in the  liner-location  project.   , Each mobility class
     represents  three specific contaminants selected by GCA  for
     risk analyses:

             Mobility Class 1           Mobility Class 2
                (Rd =  1.3)                 (Rd -  32)

             Acrylonitrile                  Benzene
             Phenol                         Xylene
             Chromium VI                    Nickel

-------
Gcraghty & Miller, Inc.
          With  input  from  G4M,  ICF adjusted the  standard  break-
     through curves to account for the following:

             Concentration in the leachate
             (either  equal  to  saturation  or 1/10  saturation
             concentration)

             Leachate release rate
             (controlled by the underlying flow field)

          .  Dispersion in the third dimension
             (at a  right angle  to  the  vertical  plane of  the  flow
             field)

          Attenuation and time delays caused by transport through
     the  unsaturated  zone  and   biodegradation  in the  saturated
     zone are  ignored in  the  analysis.   With  a  modified  liner-
     location  model code,   ICF  simulated contaminant  concentra-
     tions  and  individual  health  risks  at  the  end  of  the  fol-
     lowing time periods:  50, 100, 200,  500, and 1000  years,  and
     at  steady  state, for  the  landfill  and surface  impoundment
     sources with the above two source concentration  assumptions.
                                                       •*
          G&M studied the  relationship of  peak concentrations to
     ground-water  velocities  and TOT  under both equal  and  flow
     field-controlled mass  input conditions.   Equal mass  inputs
     could  be  controlled  by  either the  facility  design/failure
     mode or an  underlying unsaturated zone.   Unequal  flow field
     controlled  inputs  would be the  expected  result  of  a  low-
     permeability and/or low-flux environment.

          For all hydrogeologic settings  considered,  except those
     involving  diffusion-controlled transport  with  large  (two-
     orders-of-magnitude)  contrasts between  multilayer  veloci-
     ties/ peak concentrations produced by equal mass releases at
     the  source  are inversely  related  to velocity and  positively
     related  to TOT.   Where  mass  releases are  controlled  by
     the  flow  field/  concentrations  are  positively related  to
     velocity  and  inversely related  to TOT  for all  settings,
     including diffusion-controlled  transport  with high  velocity
     contrasts.

          The  apparent   reversal  of  relationships  between  con-
     centration and  velocity/TOT  points up  the importance of
     the  source term in  the  model.  It also  raises an  issue
     concerning to what degree low-velocity  flow  fields will
     actually  limit  mass  loadings  from facilities located in
     these  settings.    G&M  believes  that  in most  cases mass
     loading rates  are  controlled  by  the underlying flow  field.

-------
Gcraghcy & Miller, Inc.
           Prom  this modeling study,  it  is clear that the  lowest
      concentrations are  associated  with  settings  that  involve
      very low  velocity surficial layers (with diffusion-con-
      trolled  transport)  overlying  an  aquifer  that would  otherwise
      have received  higher  inputs  of  contaminants  and would not
      have met current  TOT criteria.

-------
Gcraghty & Miller, Inc.
                              INTRODUCTION.

          This  report will document the application of a Random-
     Walk mass  transport model for estimating concentrations of
     contaminants at hypothetical  wells  downgradient of a leaking
     generic  landfill or storage  surface impoundment.   The model
     application  is  an  extension  of an earlier modeling study by
     G4M which  constituted part of Phase I of the  liner-location
     project  for  the Economic  Analysis  Branch (EAB)  -(Geraghty &
     Miller,  Inc.,  1984).  The current  study  for Land Disposal
     Branch  (LDB) draws  heavily from the previous  study which is
     now documented  in  a draft  final  report entitled  "Liner-
     Location Risk Analysis Model".  Several significant changes
     were required in applying  the model  to the current study, as
     documented below.

          Model scenarios developed in  the liner-location project
     were based  in  part on a national  survey of water-supply
     aquifer  characteristics.   Ground-water  velocities assigned
     to model  flow  fields in that project ranged  from about 1.6
     to  33,000 ft/yr  (0.5 to 10,000  m/yr).  For that  reason,
     they  essentially  represented  100-ft  time-of-travel  (TOT)
     scenarios  that  would have  ranged  from  0.003 to  63 years.
     New scenarios  developed  for the  current study  represent
     100-ft  TOTs  that  range  from  about  10  to 1083 years.  Based
     on data generated   in G&M's  aquifer  survey,  these new sce-
     narios  represent underdeveloped  aquifers  in arid  regions
     associated  with  low recharge  settings,  or what  is  more
     likely, low-permeability   non-aquifers in  all climatic
     settings.

          Within  the constraints  of  this  project, low-velocity
     hydrogeologic  settings  had  to  be  conceptualized as  being
     composed of one or  two  layers of  homogenous,  isotropic
     porous  media.   Real-world  complexities  such as  natural
     variations  in  layer geometry  and permeability were  not
     simulated.  The processes  of  flow and transport  within
     an unsaturated zone were also not  simulated.

          Our modeling  effort  is  further limited  by significant
     assumptions  concerning the source  of contamination.  Sources
     behave  in simple  predictable ways,  and do  not  alter the
     assumed  natural  rate  of ground-water flow through the model
     flow  fields.   Moreover,  sources  are   small with  simple
     geometries,  and do not create the  magnitude of mass loadings
     that could be simulated for  large  areal  sources.

-------
    Miller, Inc.
     The models used  in  this study are  limited  in  repre-
senting  all complexities  that  can  be  observed on  real
sites.   However,  they  are very useful  in a comparative
analysis which has the objective  of  identifying general
and  fundamental relationships between  velocity/TOT  and
concentrations/risks.

     There  are  two primary  objectives  to G&M's scope  of
work.  The first objective  was  to develop new scenarios and
provide  ICF with  model output that  would be used  in the
liner-location  model (or some derivative of  that model)  that
would provide  numerical  estimates of health risks  to  a
hypothetical exposed  population.   The  second objective was
to establish the general  relationships between TOT and
concentration  of  contaminants  observed  at  a  specified
distance downgradient.  The specified distance was set at an
arbritary 100-ft length measured along a centrally  located
flow line orignating  from  the  source  of  contamination and
terminating  at  a  monitor  well.   Because the ground-water
velocity (not  the  contaminant  velocity)  is the  key  model
variable  that  controls  TOT,  the relationship between
velocity and concentration  is equally  important • and was
studied.

-------
Gctaghty & Miller, Inc.
                             CONCLUSIONS

          Liner-location  model  runs  by G&M indicate a very  wide
     range of concentrations  resulting from  six ground-water
     contaminants  emanating  from two contaminant  sources  located
     within six hydrogeologic  settings.   Based   on  Random-Walk
     transport  model simulations, the  following  conclusions  can
     be drawn concerning  TOT/  ground-water velocities and  peak
     contaminant concentrations:

          1.  Peak concentrations decrease with  increasing  TOTs
              (with  decreasing  ground-water velocities) when the
             contaminant  mass  input  is  rate-limited  by  the
             underlying  ground-water flow  field,  all other
             parameters  held equal.

          2.  Peak concentrations increase with  increasing  TOTs
              (with  decreasing ground-water velocities) when  mass
             input  at  the source and all other model parameters
             are  held equal.

          3.  A  low-velocity,  near-surface  layer can signifi-
             cantly increase  the  TOT from a facility to  any
             given  distance in  an  underlying  uppermost  aquifer
             and  also  decrease peak concentrations in the  same.

-------
t
eraght? i"c Miller, Inc.
                              METHODOLOGY

            The technical approach used by G&M- to meet the project
       objectives  proceeded  through  the following  four  steps:

                Developed new model scenarios with  input  from LDB

                Examined  the existing  liner-location models  to see
                if  they were suitable  in present form for applica-
                tion to the  new  scenarios

                Made model changes,  performed the simulations, and
                delivered output  to ICF for  their  risk estimates

                Analyzed  the output  from the Random-Walk model and
                identified basic relationships between TOT/ground-
                water velocity and peak contaminant concentrations
                and breakthrough times.

                            Scenario Development

            Scenarios are  identified  in this project by- the same
       characteristics  that  were  used  in the  previous  liner-
       location  project.   A mass  transport model  scenario  is
       identified  on  the basis  of  three characteristics  --  a
       generic  ground-water  flow field,  a  contaminant  mobility
       class,  and a distance to  an exposure point.

            The flow  field  is conceptualized as a  two-dimensional
       vertical plane  extending  beneath the contaminant source to
       a depth  that  represents  the  base  of  shallow ground-water
       circulation beneath  the  site. ' Unlike the  flow  systems of
       the liner  location project,  the unsaturated  zone  is elim-
       inated  in the  current  analyses.   The velocity field within
       the generic flow system was not simulated, nor was it based
       on a  national  survey  as was done  with  the liner-location
       project.   Rather,  a  range  of velocities and  dimensions
       were arbitrarily assigned  to the generic settings  in order
       to bracket  the TOT  criteria currently  under consideration
       by LDB.

            Figure  1  shows the  conceptual  orientation  of  a flow
       field with  respect  to  a  source area and  a generic exposure
       point developed  in the  liner-location  project.    Figure  2
       shows  the  nine generic flow  fields used  in  the  liner-
       location project;  these  were developed from a survey of 67

-------
                                             MODEL
                                           SOURCE AREA>
                                     TOTAL FACILITY
                                      SOURCE AREA
                                   PARTICLE PLUME;
      te	___
Figure 1.
Orientation  of  a Generic Flow  Field with Respect
to  the  Contaminant  Source  and  the  Surface Water
Outflow  Boundary (from Geraghty & Miller, 1984).
                             8

-------

OIM/Y
MM
IO M/Y • .
1 M/Y
MM
IOOM/Y • i
10 M/Y
MM
lOOOM/Y • .
IOOM/Y
30 M
10,000 M/Y -. .
1000 M/Y
 ISM
MM
   x Voos M/Y — y /.//' .
    IOOM/Y
\
               t M/Y
           EXPLANATION
                        50 M
                        tOM








1
1
:OM/Y

I
01 M/Y
    boundary
       )OM
               -
                Woitr toblt boundary



\
IM/Y
                          boundary
             No-llOw '
             boundort
                                                 ISM
                                                 15 M





\ M/Y

1
1M/Y
                                                                        MM
                                                                        MM
                                                                        MM
                                                                             IOM/Y •
                                                                                      O.S M/Y
                                                                             IOOM/Y
                  AVERAGE UNEAR GSCUNOwATER VELOCITY VECTORS
                  ^ETERS/YEifl) THROUGH £iCM LitER OF SATURATED
                  MATERIAL WITH CONSTANT THICKNESS (METERS).

                  CROSS-HATCH USES INDICATE LAYER IS A NON-AQUIFER.
                                                                                        I M/Y
      Figure 2.  Nine Generic Ground  Water Flow Fields  Used  in
                   the  Liner-Location Transport Model  Scenarios.

-------
uglny -& Miller, Inc.
   case studies of  regional water-supply aquifers in all major
   ground-water regions  of the  U.S.  (as defined by  the U.S.
   Geological  Survey;  McGuiness, 1963).   Although  useful for
   studying  risks  of  ground-water  exposure  from contaminated
   aquifers, the generic settings  in  Figure 2  all  have TOT
   values  to 100-ft distances  that are less  than  100 years.

        Figure 3 shows six additional generic  flow fields devel-
   oped for  the  current  study.   Two generic flow fields shown
   in  Figure 3 were developed  to provide  a way  of  testing
   risks  at the TOT values  that are  equal  to  the  proposed
   criteria  of  100  years  for landfills  and  disposal surface
   impoundments, and 10 years for  storage  surface impoundments
   and waste piles  (flow fields  K,  L, respectively).   Four
   other new flow  fields  were created to provide  concentration
   and risk estimates for TOT  values  that were larger than
   these (flow fields J,  M, N,  and 0).

        Three  ground-water contaminants  from  each of  two
   mobility classes were  selected  by GCA  for the  current
   analysis.   In  Mobility  Class 1, defined  by   a  retardation
   factor  (Rd) equal to  1.3,  acrylonitrile,  phenol, and chro-
   mium VI were selected.   In   Mobility Class 2, having a Rd
   equal  to 32,  GCA  selected   benzene,  xylene, and  nickel.

        The  six  generic  flow fields  and  two mobility classes
   combine to  make 12  mass transport model scenarios for
   simulation.  Table  1  shows additional model parameters that
   were used for  these scenarios.   Contaminant velocities were
   calculated with  the ground-water  vel .cities shown in  Figure
   3  and  the two  Rd factors  discussed  above.   Dispersivities
   are  estimated  on the  basis   of  literature  values  and work
   performed in  the liner-location project,  allowing for some
   adjustment of low velocity,  diffusion-controlled  movement to
   be  discussed later.  Effective  porosities  are  also based on
   work done in the liner-location project (Geraghty & Miller,
   1984).  \s shown  in Table 1,  "Layer  1"  refers  to the  single
   layer of  flow  fields J, K,  and L,  or  the upper layers of
   flow fields M,  N, and 0.  This  layer is consistently  equal
   to  20-ft  thick  in the single layer  classes and  10-ft  thick
   in  the  double layer classes.  Layer  2,  the  underlying  layer
   in  flow fields M,  N,  and 0,  is consistently set to  20-ft
   thick.
                               10

-------
 Gcraghty-& Miller, Inc.
                                          K
             FT/YR
                  t.OI FT/YR
1 FT/YR
t
1 FT/YR
10 FT/YR
t
1 FT/YR
                                                               20 ft
                M
                       N
.01 FT/YR
n
1 FT/YR
" I
.01 FT/YR
.1 FT/YR
.1 FT/YR
I.I FT/YR
1 FT/YR
f.l FT/YR

1 FT/YR
- 1 1 FT/YR
10 FT/YR
t.l FT/YR
10 ft
20 ft
     EXPLANATION


    War* taut.
Out-flow  «4-
Boundory
            10 FT/YR.
       Contaminant Source



        — Ground-water Velocity
I FT/YR
                             10  ft     Layer  thickness
                        -f- In-flow Boundary
                ^•No-flow Boundary


        Figure 3.   Six Generic  Flow  Fields  Used  to Study  the
                     Time-of-Travel  Criteria.
                                          11

-------
    Gcraghcy,& Miller, Inc.
                                          TABLE 1.
                    CONTAMINANT VELOCITIES, DISPERSIVITIES, AND EFFECTIVE
                       POROSITIES FOR TWELVE TRANSPORT MODEL SCENARIOS
   Scenario
 Gratification
     Horizontal
Contaminant Velocity
Dispersivity
Effective Porosity
Number3
J-1-100
J-2-100
K-1-100
K-2-100
L-1-100
L-2-100
tt-1-100
l*-2-100
N-1-100
N-2-100
0-1-100
0-2-100
Layer 1
(ft/yr)
7.7x10"^
3.1x10"-*
7.7x10*2
3.1x10"
7.7
3.1x10"'
7.7x10"^
3.1x10~4
7.7x10",
3.1x10"-*
7.7x10"!
3.1x10"^
Layer 2
(ft/yr)
—
_
— —
—
—
7.7x10"}
3.1x10"^
7.7x10"!
3.1x10"^
3!lx10"1
Laver 1
Long. Trans.
(ft) (ft)
6.6
6.6
6.6
6.6
6.6
6.6
1.0
1.0
.33
.33
6.6 •
6.6
6.6
6.6
6.6
6.6
6.6
6.6
.70
.70
.13
.13
.66
.66
Layer 2
Long. Trans.
(ft) (ft)
i
__
—
__
—
6.6
6.6
6.6
6.6
6.6
• 6.6
-
— —
—
^_
—
.66
.66
.66
.66
.66
.66
Layer 1
(percent)
10
10
20
20
.20
' 20
, 5
5
10
10
20
20
Layer 2
(percent)
—
^^
—
__
—
20
20
20
20
20
20
* Identification number = flow field - mobility class - exposure point distance, in feet


  Long.  * Longitudinal dispersivity, in direction that is parallel to ground-water flow


  Trans. » Transverse dispersivity, in direction that is orthogonal to ground-water flow
                                              12

-------
Gcraghty _& Miller, Inc.
          To  maintain  some  consistency  for  comparison  with
      the  liner-location  model runs,  the  source  term is treated
      as  a  line-source positioned  at the upgradient  end  of the
      flow field  (Figure  3).  The  source is arbitarily  set at
      32.8 ft (10m)  long  and one  ft wide.   In the  Random-Walk
      model  runs,  a  standard mass input of  one kilogram  (Kg)
      (represented by  1,000 particles)  is  input over  a  1-year
      time step.   Breakthrough of the  one Kg mass of  contaminants
      is  tracked  through  the  flow fields  to the hypothetical
      exposure well which  fully  penetrates  the layer of interest
      (the  higher velocity layer  in two-layer  flow  fields).

                      Random-Walk Model  Development

          Because of several significant  differences  between
      the  previous and  current application  of the mass transport
      and  liner-location  models,  both G&M and  ICF  were required
      to  further  develop  the models  before they could  be  run.
      The  following  discussion will  focus on  those  changes  that
      were made in G&M's particle tracking  code which  utilizes the
      Random-Walk  model of Prickett, Naymik,  and Lonnquist • (1981).

          Minor  code changes were  required  because  of  the low
      velocity generic  flow fields  and  because  the  source  terms
      are  handled  differently from the liner-location  application.
      More specifically, the changes  were made in order to handle
      the  following factors:

             Longer simulation times

             Shorter exposure distances

             Slower ground-water velocities

             Generic flow field-limited  mass  loading

             Changes in scaling factors.

          Longer  simulation times   and  short  exposure distances
      were  handled with  trivial  changes and  require  no further
      discussion  here.   The effects  of slower velocity on the
      dispersion  term  and  changes in the scaling factors applied
      by ZCF were  non-trivial and are discussed below.
                                  13

-------
Gcraghty-& Miller, Inc.
      Velocity  and Dispersion

           The   spreading  of contaminants  through  subsurface
      materials  is  caused both  by mechanical  dispersion  and
      molecular diffusion.   Under most aquifer conditions,  where
      ground-water  velocities  are greater than  one foot  per
      year, the  molecular diffusion  component can  be  ignored.
      Such was the case  in  the  previous  application  for  the
      liner-location  project.   At  very  low  velocities,  such
      as those  seen in  Figure  3  for  flow field M,  mechanical
      dispersion  is negligable  relative  to  molecular diffusion
      and this  must  be  accounted  for  in  the mathematical  model
      (Freeze and Cherry, 1979).

           Because  the Random-Walk  model generally  assumes  that
      diffusion is  negligable,  and  relies  on only a  dispersivity
      term,  it  was  necessary to define a new term called "effec-
      tive  dispersivity"  defined as follows:
                   ae
      where:

          a   »  Effective dispersivity (L)

          a   =   Longitudinal  (or  tranverse)  dispersivity,  (L)

          V  =   Average linear ground-water velocity  (L/T)
          *                            2
          D   »  Diffusion coefficient, (L /T)


          In the current  scenario  simulations,  only  flow field
      M was   significantly affected by  the diffusion coefficient.
      Values  of dispersivity listed in Table  1  include  the dif-
      fusion  term.

      Source  Term

          In the previous liner-location  project,  a  separate
      submodel  developed by  Pope Reid Associates was  used  to
      simulate  the  stochastic process of facility failure  and
      mass release of contaminants from a hypothetical facility.
                                 14

-------
Gewghty. & Miller, Inc.
      Release rates from the Pope Reid model were generally small
      enough  so that  the project  team could  ignore  hydraulic
      changes  in the  underlying generic flow  fields.   it  was
      assumed that  leachate drained  freely  from  the liner system
      and, while delayed by passing  through the unsaturated zone,
      the  leachate release  rate was not  limited by underlying
      earth materials  or by  low ground-water velocities.   This
      methodology was  considered acceptable  since  generic  flow
      fields A through I  (Figure  2) had  relatively large values of
      velocity.

           ICF's original liner-location model reads the standard
      breakthrough  concentrations  from G&M's  model output  and
      scales the data  according  to the  size  of  the facility.   It
      then creates  future scenarios  by  adding the adjusted stan-
      dard concentration  curves  in   a sequence determined  by  the
      failure and  leakage  history of the  Pope  Reid model.   ICF
      modified this code  to  by pass  the Pope Reid simulation  and
      assume a more simplified  life expectancy of  the source term.
      They also  deleted  the  scaling  factor for  the facility size
      and  added  a  new term  to handle dispersivity  in  the third
      dimension  oriented at  right  angles  to the vertical  flow
      fields.

           In the current application by ICF, the Pope Reid model
      was  replaced  with  an  assumption  that the  underlying hydro-
      geologic materials  would have  a  control on the volumetric
      release  rate of leachate  from the  source.  Time  and*'re-
      sources did  not permit  simulating this  rigorously  under a
      set  of  hydraulic  parameters and  boundary conditions.
      Rather,  we assumed that  the  vertical leakage  rate  from
      the  source was  equal  to the  vertical  seepage velocity
      within the underlying  flow  field.

           Table 2  lists for each  of  the six  flow fields  the
      critical source  term characteristics.that affect the leach-
      ate  release   rate  from  the 32.8  ft  area.  As  shown/  we
      assumed a contamination concentration of 100,000 mg/1 in the
      leachate in order  to  show  how  the mass  load can range over
      three orders  of magnitude  (from  .045  to   18  kg/yr).   This
      high concentration  is  slightly  larger than  the most soluable
      species considered,  phenol  (with solubility  of  93,000 mg/1),
      and  therefore the  mass  loading rates represent a conserva-
      tive upper-bound estimate.

           To meet  G&M's  project  objectives,  it  was necessary to
      evaluate the  effects  of  both  the  standard  and flow field-
      adjusted mass load source  strengths.   The  interpretation
                                   15

-------
Gcraghty, & Miller, Inc
                                TABLE  2.
         SOURCE-TERM CHARACTERISTICS FOR  SIX  GENERIC  FLOW FIELDS
Flow
Field
J
K
L
M
N
0
Vertical
Ground-Water
Velocity
(ft/yr)
.01
.1
1.
.01
.1
1.
Effective
Porosity
(percent)
10
20
20
5
10
20
Recharge
Per Unit
Area
(ft/yr)
.001
r
.020
.200
.0005
.010
.200
Leachate
Release
Rate
(ftVyr)
.033
.656
6.560
.016 .
.328
6.560
Mass .
Loading
(kg/yr)
.092
1.8
18.
.045
.92
18. -
     Release rate is the flow  field-controlled  volumetric discharge
     of leachate over a strip  source  area  with  dimensions of
     1  ft x 32.8 ft.


     Hypothetical examples assuming a contaminant  concentration of
     100/000 mg/1 in the leachate.
                                      16

-------
Geraghty .«Sc Miller, Inc
      of these  two conditions  deserves  some  discussion.   The
      standard  mass input  to  all flow  field  scenarios  can be
      conceptualized as one of the following:

           .  The facility  is  engineered and fails in a consistent
             way that creates an  equal release of mass  that is
             input directly  to  the  saturated zone of  each flow
             field.

           .  An  unsaturated  zone  serves to spread, dilute, atten-
             uate,  etc.  releases  of different  magnitudes  and
             thereby converts  them all  to  equal inputs  to the
             saturated zone.

      The  flow  field-controlled, adjusted  mass  input  can be
      conceptualized as follows:

           .  The facility is engineered  and fails in  a  variety
             of  ways, however,  a low  rate  of  flux through the
             cover materials  or  a  low  permeability of host mater-
             ials  coiGterols  the  actual release of mass  and the
             subsequent  direct  input to the  saturated  zone.

           .  An  unsaturated  zone  serves  to convert  releases of
             equal magnitude  to  inputs  of  variable magnitude  that
             are  controlled  by the  low-flux,  low-permeability
             setting.

      In G&M's opinion,  the  flow field-controlled situations will
      be more common in low-velocity settings.

           The source  life for the landfill  strip was calculated
      by assuming an initial  total mass and  storage per unit
      area  and  calculates  the  time to deplete  the  mass   through
      leaching.   Based on mail survey data studied  by ICF in the
      liner-location  project,  G&M  and  ICF  assumed an  average
      contaminant  density in  landfilled  wastes of  0.30   kg/ft .
      The average  thickness  of  landfilled  waste was assumed to be
      20 feet, thereby creating  a  mass  storage per unit area of 6
      kg/ft .  The  leaching rate was set  equal  to the product of
      the seepage  velocity of the underlying flow field, the  area
      of the source,  and  the concentration  of the particular
      chemical  constituent.   The life  of  the storage  surface
      imp9undment  source was assumed to be 30 years.  Mass  release
      was  assumed  to  be  the product of  seepage  velocity  of the
      underlying flow field, area  of  the source,  and concentra-
      tions assumed for the particular contaminant.
                                  17

-------
Geraghty &. Miller, Inc.
          The  standard breakthrough curve generated from a  1-kg
      input  of  contaminant mass at  the source  is  adjusted to  fit
      the  particular mass  loading conditions for each contaminant.
      Figure  4  shows how  the  amplitude of  the  breakthrough  curve
      can  be adjusted  upward  to simulate  a  loading rate of  1 .8
      kg/yr, corresponding  to a  leachate  with  a contaminant
      concentration  of  100,000 mg/1  for  flow  field K  (Table  2).

          Figure  4 also  shows this  effect of  biodegradation  on
      concentrations of  the  standard  breakthrough curve.   The
      example  shown is  for  a  species  that was  loaded at  the
      standard  rate of  1  kg/yr but has  biodegraded with a  half-
      life of 20,000 days.   As shown,  the peak  concentration  is
      not  only  smaller but  occurs  earlier  in  time.  For most  of
      the  small velocity scenarios considered  in our study,  a
      relatively  slow  rate  of biodegradation  could yield signi-
      ficant  reductions in concentration  at hypothetical  exposure
      points.   Unfortunately,  time  and  resources  did  not permit
      establishing  a half-life for  the organic species which  are
      known  to  biodegrade, especially  benzene  and acrylonitrile.
      The  estimates of  concentrations  are, therefore,  conserva-
      tively  large  for  these species.

      Transverse Dispersion

          One  of  the  limitations  of the  earlier  application  of
      the  Random-Walk  model   is that  dispersion   of  contaminants
      was  limited  to the  vertical  plane and transverse  dispersion
      at  right  angles  to the  plane  was  not simulated.   Because
      the  exposure  points are  centrally  located along an axis
      that divides  the source  area into  two  equal parts, this
      does not  read to  major errors  with large  areal sources
      (simulated in the liner-location  project).   For  the current
      application,  however,  it is necessary to consider  dispersion
      in the  third direction.

          A  correction factor was  determined  empirically.  This
      was  accomplished  by comparing  several analytical  solutions
      to  the Random-Walk model output.   The  solutions for  an
      instantaneous  mass input at  a point source for one-  and
      two-dimensional cases  (Hunt,  1978)  are  used  for this pur-
      pose.   The  one-dimensional  equation can  be converted  to
      a  quasi  two-dimensional solution  by  dividing the  concen-
      tration by the thickness of the aquifer in question. Figure
      5  illustrates how,  for  scenario  K-1-100, the 1-0  solution
      adjusted  by  thickness  is a very  close match  to the Random-
      Walk output  (scatter of  points).   The two-dimensional  equa-
      tion can  similarly  be converted  to quasi three-dimensional
                                  18

-------
\
o
6
C
o

*>
0
C
«*
C
f>
u
C
o
u
      Scenario  K-1-IC3




ground water velocities  (ft/


        horizontal- 1


         v«rt tea!-  .1

    retardation factor-  1.3




         EXPLANATION



     •  Ooia computed by moaii

   —— Standard Srtonthrougn eurv«

   ^— — Source-ierm adiusted curvt

   — • — Biod«qrca«d curve
                                                                              450
                                     t ime  (years)
     Figure 4.   Examples  of  Standard  Breakthrough  Curve  and  How
                  It  May  be Adjusted  to Simulate Layer Mass  Inputs
                  and-Biodegradation.
                                       19

-------
Geraghcy. & Miller, Inc
     by dividing  by  thickness.   Figure 5  illustrates  the  break-
     through  curve  for  the  2-D solution  adjusted for  vertical
     thickness, which  has a concentration that  is  small  than
     the quasi  two-dimensional  solution  by a factor  that  ranges
     from about 1/8 to 1/15.  This  relationship  of  concentrations
     for the  1-D and 2-D cases appears to hold., for  other velocity
     fields  considered  in  our  analyses.    For  this  reason,  and
     because  risks  are  being examined at  the  order-of-magnitude
     level,  G&M  advised  ICF  to adjust  the Random-Walk model
     standard curves downward by a  factor  of  1/10  to  account for
     dispersion in the third dimension.
                                   20

-------
\
cj
c
o
c
0
u
c
o
u
                                              Sc«n»rto  K-1-IB0
 ~	— • •• D«ta gen«r»tad by


         R»ndom-W»lk mod«1


(Rt1 solutions h«v« *»m« m»ss lotding


   per unit «re»,  .830 kg/sq.ft)
           as   sa   75   laa  125  isa  i?s  zee 225  2se  2?s  aea  325  ase 375 430
                                   Ti me  (yrs)
    Figure 5.  Comparison  of   Random-Walk  Model  Output  With

                Two Analytical Solutions.
                                    21

-------
Gcraghcy. £ Miller, Inc.
                               RESULTS

          Appendix  A  includes  tables  of  output  produced  by
     the Random-Walk model  which show  concentration  vs.  time
     resulting from a standard  1-Kg mass  input for  12 scenarios.
     Mass  loading  to a  surface  stream is  included  for  each
     scenario as a  check on  the concentration breakthrough.
     Appendix B presents  the same  output  in graphical format and
     includes the best fit curve to the scatter of data which is
     typical of"particle  tracking code  output.

                        Random-Walk Output

          Table 3  shows  .the critical  times  and  peak concentra-
     tions  of. the standard  breakthrough  curves   and  for break-
     through  curves  resulting  from  an  adjusted,  flow  field-
     controlled mass  release (Table 2).   Table 3 also shows for
     each of  the  12  scenarios,  the  TOT  to  the  100-ft exposure
     point.   Under the proposed TOT criteria,  flow fields L and 0
     constitute vulnerabl-e conditions  for landfills and disposal
     impoundments.  All  flow  fields would meet the TOT criteria
     for non-vulnerable  conditions for storage impoundments and
     waste piles.

          The  adjusted  load  breakthrough curves  represent data
     used by  ICF  in  their simulations  of future  concentrations.
     It is  important  to  note that  the  critical time of  starting,
     ending, and peaking  of the curves  are not  adjusted, only the
     magnitude of the concentration is  adjusted.

          General observations  based  on the one-yr mass input to
     the flow  fields  should  hold true  for other transient cases
     involving longer simulation times.   If  time  is  considered to
     be a  relevant  measure of  risk,  scenarios involving the
     lowest  velocities  and least mobil constituents must be
     associated with  the  lowest  risks.   If  concentration is the
     major control on  risk,  Table  3  suggests  that  the hydrogeo-
     logic setting/mobility combination,  which  is  best suited for
     reducing risks,  is  also  sensivitive  to the  strength of the
     source term.

                      Liner-Location Model Output

          The  original  liner-location model  developed  by ICP
     simulates  a  concentration  and  corresponding  risk profile
     over a  400-year simulation  period.    Individual  risks are
     computed on the assumption of  a 70-year  lifetime with a dose
                                  22

-------
     craghcy. & Miller, Inc
                                         TABLE 3.
                 CRITICAL TIMES AND PEAK CONCENTRATIONS OF BREAKTHPOUGH
                      CURVES AND 100-ET TOT'S FOR TWELVE SCENARIOS
Critical Times
Scenario
Identification
J-1-100
J-2-100
K- 1-1 00
• K-2-100
L-1-100
L-2-100
^M-1-100
M-2-100
N-1-100
N-2-100
0-1-100
0-2-100
Start
(yr)
300
8,000
35
800
4
80
250
8,000
120
3,000
5
150
Peak Concentrations K Time of Travel
End Peak Time Standard Load" A
(yr) (yr) ' (mg/1)
5,000
110,000
450
11,000
53
1,100
120,000
360,000
800
20,000
120
3,500
1,250
32,270
115
3,000
12
320
1,360
33,000
260
6,440
21.5
550
42.4
1.80
19.5
.92
20.5
.87
1.2
.048
14.7
.63
9.9
.45
d justed Load"
(mg/1)
3.9
.17
35.
1.7
370.
16.
.054
.0022
4.8
.21
65.
2.9
To 100-ft
(yr)
1000
1000
100
100
10
10
1083
1083
186
186
18.6
18.6
a Standard mass load of one kilogram for one year ever the strip  source area (32.8  ft )

  Standard mass load adjusted by flow field-controlled leachate relase  rates (Table 2).
                                              23

-------
Geraghty & Miller, Inc.
     based  on a  running  average concentration over  any  70-year
     period.   In  the  current  study,  simulation times were  much
     longer than 400  years  and  it seemed  reasonable  to  compute
     concentrations  at greater intervals, assuming  that the point
     of concentration  represents a 70-year average.

         In  this study,  concentrations  and risks are  provided
     by G&M and  ICF,  respectively,  for landfills and surface
     impoundment  sources  at the  following  time intervals:  50,
     100,  200, 500,  and  1,000 years and  at steady state.   Al-
     though the calculated  source  life  of  both source  types  is
     limited  to several  thousand years,  it  was necessary in some
     cases  to extend  this  in order to reach the  hypothetical
     steady-state  case.   The project team  composed of G&M,  GCA,
     and LDB personnel agreed that the time factor begins to take
     on more importance  than  concentrations  beyond  1,000  years,
     and no additional  time steps between  1,000  years and  the
     hypothetical  steady-state case are calculated.

         Concentrations and  risks  vary over  many orders-of-
     magnitude  and represent a total  of  72  separate scenarios (2
     source strength terms  x 2 source types x 6  contaminants x 6
     flow  fields  x 6 time intervals).   GCA Corporation  will
     discuss  the significance of  these  with respect to  the TOT
     criteria^.

       Relationship  of TOT  and Velocity to Peak Concentrations

         The  relationships of TOT and velocity to  peak concent
     tratiorvs  are highly  depended  on  the source  term.   trus
     is because   the  advection-dispersion-retardation  models
     (both  analytical, numerical and particle  tracking)  require
     that  the  concentration  at  any downgradient location  is
     directly proportional to  both contaminant  concentration
     and volumetric  release  rate of  leachate at the source.
     Because  the  assumption of the concentration of contaminants
     at the source being  equal to the saturated concentration (in
     pure water)  is  considered highly conservative,  an additional
     set of runs were  created  where  the mass  in storage and
     contaminant  concentration in  the  leachate  is reduced  by a
     factor of  ten.  This yields a 10-fold decrease in concentra-
     tions  for all 72  scenarios.

         Changing the concentration at the  source  impacts peak
     concentrations but is completely independent of TOT and
     velocity.  The  other half of the source term,  the volumetric
     leachate  release rate  can  be  related  to TOT  and velocity.
                                  24

-------
Gcraghty- & Miller, Inc.
     For  the  somewhat  limited  instances where  mass loading  is
     independent of  the setting  (i.e.,  the  same  for each  sce-
     nario), two relationships  are  observed.   First, in  single-
     layer  flow systems, the  concentration  tends  to  decline  with
     increasing velocity  to  a  certain  point,  beyond which  the
     concentration becomes  essentially steady and the  potential
     exposure  time  decreases with  increased  velocity.    Second,
     when a lower velocity  layer  is  positioned  above the  aquifer
     of  interest  (compare  settings  M  and N to K; and  compare  0
     to  L), peak  concentrations are  reduced  because  of  the
     slow,  controlled  release of  contaminants to  the underlying
     layer in which the hypothetical  well is screened.

          For the more  prevalent  situations where  the mass  input
     is allowed to be controlled by  the hydrogeologic setting and
     the  adjusted  leachate  release  rates prevail, the  relation-
     ship of  velocity  to  concentration changes  somewhat.   In
     single-layer cases, peak concentrations  increase  in direct
     proportion to  increased  horizontal  velocities.   If  low
     velocity layers are positioned  above higher velocity  layers,
     peak concentrations within the  latter  are reduced,  as  they
     are with the standard  load input.

          Figures 6 and 7 show the  general  relationships  between
     peak concentrations and  TOTs for the  standard  and  adjusted
     mass load input scenarios.  Figure 6 shows that  peak  concen-
     trations generally  increase  with  increasing  TOT.    A  note-
     worthy exception  to  this  relationship  is apparent  for
     scenarios  involving  flow field M.   The  order-of-magnitude
     decrease in peak concentration  for  scenarios  M-1 and M-2 is
     attributed  to  diffusion-controlled transport  in the  upper
     layer and to the two order-of-magnitude contrasts in  veloci-
     ty  between  the upper  and lower  layers  of the  flow field.
     When these  conditions   prevail,  peak  concentrations become
     less sensitive to the  mass loading rate.

          Figure 7  shows a  more  consistent   relationship  where
     peak concentrations decline with increasing TOT  values.   The
     change in  slope of the line between  scenarios 0  and  N to
     scenarios involving flow field  M  is attributed  to the  same
     characteristics identified above.   Apparently,  flow  field M
     has a  distinct advantage for minimizing  contaminant  concen-
     trations in an underlying  velocity  layer.   This observation
     is consistent with previous work done for the liner-location
     project in which it was  shown that  the effect of adding low
     velocity layers above  the  aquifer of interest is to  greatly
     reduce peak concentrations  and spread out  the  breakthrough
     curve over longer periods of  time.
                                   25

-------
«*•
0

c
o

+*
10
i.

C
I)
o
c
o
u
m
u
D.
    \
    O)
X
O)

o
k
X
CQ


T3
10
0
    •0
    t.

    •o
    c
    U)
           100
            10
            .1
           .01
           001
         .0001
                                                . J-l
                          . L-l
                                               \.J-2
                                                  M-2
                                                        e1
                         10
                                    100
                                           1000
10000
                     Time o-f Travel to  100 ft  (yrs)



   Figure 6.   Plot of Contaminant Concentrations  vs.  100-ft
             TOT for  Standard  Mass  Load Input  Scenarios.
                             26

-------
          1Q20
C
O
(0
I
O
C
O
O
ID
•)!
CLj
    \
    O)
    E
    CD
    3
    O
    u
    O
    _J

    T3
    V
    
-------
Gerighcy,& Miller, Inc.
           The  apparent  reversal  of  relationships  between  TOT/
      velocity  and  concentrations  is  largely  a  function of  the
      source  term  in  the model.   It  also  raises an issue  con-
      cerning  to what degree  low-velocity flow fields  will  act-
      ually limit mass loadings from facilities located  in  these
      settings.   However,  it is clear  that  the lowest concentra-
      tions  are associated  with  settings that involve  very  low
      velocity  surficial  layers (with  diffusion-controlled trans-
      port) overlying  an  aquifer that, by itself, would not  have
      an  acceptable   velocity  to  meet   current  TOT  criteria.
                                  28

-------
Gcraghty & Miller, Inc.
                                REFERENCES
      Freeze, A.R., and Cherry,  J.A.,  1979; Groundwater, Prentice-
           Hall, Englewood Cliffs,  New Jersey.

      Hunt, B.,  1978;  Dispersive  Sources in Uniform Ground-Water
           Flow.   Journal of the  Hydraulics  Division,  ASCE 104:
           75-85.

      Geraghty "& Miller, Inc.,  1984; Appendix  B-Subsurface Trans-
           port Modeling,  in  Liner Location  Risk Analysis Model,
           report  prepared by  Sobatka  & Co.  fo'r OSW  under EPA
           Contract No. 68-01-6621, Work  Assignments 51  and 53, 61
           pp.

      McGuiness,  C.L.,  1963;  The Role  of Ground Water  in the
           National  Water Situation, U.S. Geol. Survey,  Water
           Supply Paper 1800,  1121  pp.

      Prickett, T.A.,  Naymik,   T.C.,  and Lonnquist,  C.G.,   1981;
           A  "Random-Walk"  Solute Transport  Model  for Selected
           Groundwater  Quality  Evaluations;  Bulletin  165,  111.
           State Wtr. Sur., 103  pp.
                                  29

-------