PB84
EVALUATION OF SEPTIC TANK SYSTEM EFFECTS ON GROUND WATER QUALITY
National Center for Ground Water Research
Norman, OK
Jun 84
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
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l-PA-600/2-84-107
June 1984
EVALUATION OF SEPTIC TANK SYSTEM EFFECTS
ON GROUND WATER QUALITY
by
Larry Canter
Robert C. Knox
National Center for Ground Water Research
University of Oklahoma
Norman, Oklahoma 73019
Cooperative Agreement No. CR-806931
Project Officers
Ronald t". Lewis
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
Marion R. Scalf
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
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TECHNICAL REPORT DATA
(I'll a\i trail /tulfiiciiiun mi llic n rrnr hcjitri-i
1 RfrPORT NO
EPA-600/2-H4-107
•> I I [ I I /\NI) Mill I I 1 I I
Evaluation ol Septic Tank System Effects
on Ground Writer Quality
7 AUTHOR(S)
Larry Canter and Robert C. Knox
National Center for Ground Water Research
.1 RECIPIENT'S ACCESSION NO
m com DAI i
.lu.u- 1«)«-'.
!> I'l IU UMMINr, OIU,ANIMATION COOh
8 PERFORMING ORGANIZATION REPORT NO
9 PERFORMING ORGANIZATION NAME AND ADDRESS
National Center for Ground Water Research
University of Oklahoma
Norman, OK 73019
10 PROGRAM ELEMENT NO.
CBPC1A
11 CONTRACT/GRANT NO
CR-806931
12 SPONSORING AGENCY NAME AND ADDRESS
13 TYPE OF REPORT AND PERIOD COVERED
Robert S. Kerr Environ. Research Laboratory
U.S. EPA, ORD
P.O. Box 1198
Ada. OK 74820
14 SPONSORING AGENCY CODE
EPA 600/15
IB SUPPLEMtNTARY NOTES
IB ABSTRACT
This study summarizes literature concerning the types and mechanisms of ground-water
pollution from septic tank systems and provides information on methodologies for eval-
uating the ground water pollution potential. The conclusions are: (l)septic tank
systems represent a significant source of ground-water pollution in the United States
since many systems are exceeding their design life, the usage of synthetic organic
chemicals in the household is increasing, and larger-scale systems are being designed
and used; (2) a key issue is related to understanding the transport and fate of system
effluents in the subsurface environment; (3) no specific technical methodology exists
for evaluating ground water effects of septic tank systems, however, application of
two empirical assessment methodologies (surface impoundment assessment and waste-sci'I-
site interaction matrix) adjusted for annual wastewater flow and analytical method
(Hantush) for determining water table rise, and a solute-transport model (Konikow and
Bredehoeft) for ground water flow and pollutant concentrations has met with some suc-
cess; (4) the empirical assessment methodology (adjusted SIA method) could be used i
permitting or evaluation procedures for systems serving individual homes and subdivi-
sions and large-scale systems, the analytical model could be used for subdivisions and
large-scale systems, and the solute-transport model could be used for large-scale
systems.
17
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Ground Water
Septic Tanks
Water Pollution
b IDENTIFIERS/OPEN ENDED TERMS
percolation
sewage treatment
COSATI I'icld/Cruiip
68D
18 DISTRIBUTION STATEMENT
Public Release
19 SECURITY CLASS (This Report)
Unclassified
21 NO. OF PAGES
38/
20 SECURITY CLASS (Thispage)
Unclassified
22 PRICE
EPA Form 2220-1 (9-73)
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NOTICE
THIS DOCUMENT HAS BEEN REPRODUCED
FROM THE BEST COPY FURNISHED US BY
THE SPONSORING AGENCY. ALTHOUGH IT
IS RECOGNIZED THAT CERTAIN PORTIONS
ARE ILLEGIBLE, IT IS BEING RELEASED
IN THE INTEREST OF MAKING AVAILABLE
AS MUCH INFORMATION AS POSSIBLE.
I -
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DISCLAIMER
Although the research described in this report has been funded whollv
or in part by the United States Environmental Protection Agency through
Cooperative Agreement CR-806931 to the National Center for Ground Water
Research, it has not been subjected to the agency's peer and policy review
and therefore does not necessarily reflect the views of the agency and no
official endorsement should be inferred, nor docs mention of trade names
or commercial products constitute endorsement or reconmendntion for use.
ii
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FOREWORD
The Environmental Protection Agency was established to coordinate admin-
istration of the major Federal programs designed to protect the quality of our
environment.
An important part of the Agency's effort involves thr search for informa-
tion about environmental problems, mlin.i>>,i>mi>nL techni ques, anil new technologies
through which optimum use of the N.it ion's l.nul .mil w.iter resources ciin he
;jH8ured Hixl the lhre.il \>n I 1 lit i on post's lo the well.ire ol [lie Ann1 r if.in people
c.'in be mini mi /.'-(I.
EPA's Officf.1 of Ki-se.irch and Dr-ve I .>pment conducts this se.irch through .1
nationwide network of research facilities.
As one of these facilities, the Robert S. Kcrr Environmental Research
Laboratory is the Agency's center of expertise for investigation of the soil
and subsurface environment. Personnel .it the laboratory are responsible for
management of research programs to: (a) determine the fate, transport and
transformation rates of pollutants in the soil, the unsaturated zone and the
saturated zones of the subsurface environment; (b) define the processes to be
used in characterizing the soil and subsurface environment as a receptor of
pollutants; (c) develop techniques for predicting the effect of pollutants on
ground water, soil and indigenous organisms; and (d) define and demonstrate
the applicability and limitations of using natural processes, indigenous to
the soil and subsurface environment, for the protection of this resource.
This report contributes to that knowledge which is csstMiti.il IP or dor
for EPA to establish and enforce pollution control standards which are
reasonable, cost effective, and providi adequate environmental protection
for the American public.
Clinton W. Hall
I)i rector
Robert S. Kerr Environmental
Research Laboratory
iii
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PREFACE
The principal authors of "Evaluation of Septic Tank System Effects
on Ground Water Quality" are Dr. Larry W. Canter, Professor and Co-
Director, and Dr. Robert C. Knox, Environmental Engineer, National
Center for Ground Water Research (NCGWR). The U.S. Environmental
Protection Agency (EPA) established the Center in September, 1979, as a
consortium of the University of Oklahoma, Oklahoma State University, and
Rice University. Drs. Canter and Knox are located at cht» University of
Oklahoma in Norman, Oklahoma.
The primary focus of the NCGWR is to address the four major issues
identified by the EPA as problem areas that persist in ground water
protection. These include transport and fate of pollutants,
characterization of the rate-determining factors in the subsurface
environment, development of methods for ground water quality assessment
and protection, and information transfer.
If you are interested in receiving more information about the
NCGWR, please contact:
Dr. L.W. Canter, Co-Director
National Center for Ground Water Research
University of Oklahoma, Oklahoma State University,
and Rice University
200 Felgar Street
Norman, Oklahoma 73019
(Phone: 405/325/5202)
iv
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ABSTRACT
This study summarizes literature concerning the types and
mechanisms of ground water pollution from septic tank systems and
provides information on methodologies for evaluating the ground water
pollution potential. The conclusions are: (1) septic tank systems
represent a significant source of ground water pollution in the United
States since many systems are exceeding their design life, the usage of
synthetic organic chemicals in thu household is increasing, and larger-
scale systems are being designed .md used; (2) a key issue is related to
understanding the transport and fate of system effluents in the
subsurface environment; (3) no specific technical methodology exists for
evaluating the ground water effects of septic tank systems, however,
application of two empirical assessment methodologies (surface
impoundment assessment and waste-soil-site interaction matrix) adjusted
for annual wastewater flow and analytical method (Hantush) for
determining water table rise, and a solute-transport model (Konikow and
Bredehoeft) for ground water flow and pollutant concentrations has met
with some success; (4) the empirical assessment methodology (adjusted S1A
method) could be used in permitting or evaluation procedures for systems
serving individual homes and subdivisions and large-scale systems, the
analytical model could be used for subdivisions and large-scale systems,
and the solute-transport model could be used for large-scale systems;
and (5) a specific empirical assessment methodology should be developed
for septic tank system areas, with the methodology using some factors
from both the SIA method and the interaction matrix, and additional
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factors such as wastewater flow, percolation rate, septic tank density,
and average life of septic tank systems.
This report was submitted in fulfillment of Cooperative Agreement
No. CR-806931 by the National Center for Ground Water Research under the
sponsorship of the U.S. Environmental Protection Agency.
vi
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CONTENTS
Page
Foreword ill
Preface iv
Abstract v
List of Figures x
List of Tables xii
Conversions xvi
1. INTRODUCTION 1
SEPTIC TANK SYSTEM REGULATION 8
OBJECTIVE OF STUDY 15
SCOPE OF STUDY 15
ORGANIZATION OF REPORT 16
2. DESIGN OF SEPTIC TANK SYSTEMS 18
OVERVIEW OF SEPTIC TANK SYSTEMS 18
SEPTIC TANK DESIGN 21
SOIL ABSORPTION SYSTEM DESIGN 33
OVERVIEW OF SEPTIC TANK-MOUND SYSTEMS 63
3. GROUND WATER POLLUTION FROM SEPTIC TANK SYSTEMS .... 67
POTENTIAL POLLUTANTS FROM SYSTEM EFFLUENTS 67
MECHANISMS OF GROUND WATER CONTAMINATION
FROM SEPTIC TANK SYSTEMS 85
Soil Systems 89
Ground Water Systems 90
vii
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Page
TRANSPORT AND FATE OF BIOLOGICAL CONTAMINANTS. ... 92
Bacteria in Soils 92
Viruses in Soils 99
Bacteria and Viruses in Ground Water 105
TRANSPORT AND FATE OF INORGANIC CONTAMINANTS .... 107
Phosphorus 107
Nitrogen 112
Chlorides 119
Metals and Other Inorganic Contaminants .... 119
TRANSPORT AND FATE OF ORGANIC CONTAMINANTS 124
GROUND WATER POLLUTION CONTROL MEASURES 129
GROUND WATER MONITORING 132
SEPTAGE — A SPECIAL CONCERN 143
4. SEPTIC TANK SYSTEM MODELING 148
CONCEPT OF AREA SOURCE 149
PREVIOUS USAGE OF MODELS 149
SELECTION CRITERIA FOR MODELS 157
EMPIRICAL ASSESSMENT METHODOLOGIES 160
Surface Impoundment Assessment 161
Central Oklahoma Study Area 167
Waste-Soil-Site Interaction Matrix 174
Comparison of Empirical Assessment
Methodologies 195
HANTUSH ANALYTICAL MODEL 200
KONIKOW-BREDEHOEFT NUMERICAL MODEL 206
Study Area Near Edmon 1, Oklahoma 210
Hydrogeology of Study Area 212
Input Data for Model 218
Results and Discussion 229
HIERARCHICAL STRUCTURE FOR MODEL USAGE 231
viii
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Page
5. SUMMARY AND CONCLUSIONS 235
References 250
Appendices
A. Annotated Bibliography A-l
B. Characteristics of Septic Tank Areas in Central
Oklahoma B-l
C. Phillips, Nathwani and Mooij Assessment Matrices. . . . C-l
D. Error Function in Hantush Analytical Model D-l
E. Fortran IV Program for Konikow-Bredehoeft Solute
Transport Model E-l
ix
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LIST OF FIGURES
Figure Page
1 Population Using Septic Tanks (Anonymous, 1979). ... 2
2 Schematic Cross-Section Through a Conventional
Septic Tank Soil Disposal System for On-Site
Disposal and Treatment of Domestic Liquid
Waste (Bouma, 1979) 4
3 Typical On-Site System (Scalf, Dunlap and
Kreissl, 1977) 20
4 Typical Two Compartment Septic Tank (Cotteral
and Norris, 1969) 22
5 Plan and Section Views of Two Compartment Septic
Tank (U.S. Environmental Protection Agency,
October, 1980) 30
6 Typical Trench-type Soil Absorption System
(U.S. Environmental Protection Agency, October
1980) 36
7 Details of Drainfield Trench Layout (Cotteral
and Norris, 1969) 38
8 Typical Bed-type Soil Absorption System (U.S.
Environmental Protection Agency, October 1980) .... 39
9 Soil Moisture Content (U.S. hnvironmental
Protection Agency, September 1978) 50
10 Hydraulic Conductivity of Soils (U.S. Environmental
Protection Agency, September 1978) 51
11 Typical Time-Rate Infiltration Curve for Soil
Absorption System (Cotteral and Norris, 1969) 53
12 Typical Wisconsin Mound System (Harkin, et al.,
1979) 64
13 Effect of Clogged Absorption Field on Nearby
Well (Scalf, Dunlap and Kreissl, 1977) 86
14 Effect of a Pumping Well on Contaminated Water
Movement (Scalf, Dunlap and Kreissl, 1977) 88
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Figure Page
15 Removal of Poliovirus (added Co septic tank
effluent) in Sand-columns at Two Differenct
Flow Regimes (Bouma, 1979) 101
16 Form and Fate of Nitrogen in the Subsurface
Environment (Freeze and Cherry, 1979) 114
17 Segregation of Household Wastewater (Siegrist,
1977) 133
18 Comparison of the Effectiveness of Sampling
Plans in Detecting System Failure (Nelson
and Ward, 1982) 141
19 Comparison of the Effectiveness of Sampling
Plans as Measured by Temporary Overload Detection
(Nelson and Ward, 1982) 142
20 Surface Geology of Study Area 168
21 Septic Tank Areas in Central Oklahoma 171
22 Map Shows Residential Areas Which Are Served By
Septic Tank Systems in Modeled Area 211
23 Geologic Map of Modeled Area 213
24 Cross Section of the Garber-Wellington Aquifer
in Edmond, Oklahoma, Showing Upper (Water-Table)
Aquifer 215
25 Diagrammatic West-East Cross-section of Modeled
Area Showing Land Surface and Saturated Thickness
of Upper Part of Garber-Wellington Aquifer Above
Assumed Layer for this Study 217
26 Possible Transformations and Pathways of Nitrogen
from Septic Tank Systems (Tanji and Gupta, 1978;
and Freeze and Cherry, 1979) 224
27 Finite-difference Grid Used to Model the Study
Area 228
XI
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LIST OK TABLES
Table Page
1 Densities of Septic Tank Systems and Cesspools
for Counties with More than 50,000 Housing
Units Served by These Systems 6
2 Maximum Contaminant Levels for Inorganic
Chemicals (U.S. Environmental Protection
Agency, 1976) 11
3 Maximum Contaminant Levels for Organic
Chemicals (U.S. Environmental Protection Agency,
1976) 12
4 Maximum Bacteriological Contaminant Levels
(U.S. Environmental Protection Agency, 1976) 13
5 Single Household Unit Septic Tank Liquid Volume
Requirements (U.S. Environmental Protection
Agency, October 1980) 25
6 State Requirements for Single Household Unit
Septic Tank Size and Water Depth (Senn, 1978) 26
7 Setback Requirements for Septic Tanks (Cotteral
and Norris, 1969) 34
8 Site Criteria for Trench and Bed Systems
(U.S. Environmental Protection Agency, October
1980) 40
9 Falling Head Percolation Test Procedure (U.S.
Environmental Protection Agency, October 1980) .... 44
10 Estimated Hydraulic Characteristics of Soil
(U.S. Environmental Protection Agency, October
1980) 46
11 Soil Absorption System Area Requirements for
Single Housing Units (U.S. Public Health Service,
1967) 47
12 Recommended Rates of Wastewater Application for
Trench and Bed Bottom Areas (U.S. Environmental
Protection Agency, October 1980) 48
xii
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Table Page
13 Setback Requirements for Drainfields (Cotteral
and Norris, 1969) 57
14 Design Factors for Trench System Drainfields
(Cotteral and Norris, 1969) 60
15 Summary of State Setback Requirements and Design
Factors for Trench Systems (Senn, 1978) 61
16 Characteristics of Influent Wastewaters to
Septic Tank Systems (Bauer, Conrad and Sherman,
1979) 69
17 Typical Characteristics of Domestic Sewage in the
United States (Council on Environmental Quality,
1974) 70
18 Comparison of Septic Tank Influent Wastewater
with Community Domestic Wastewater 71
19 Summary of Treatment Efficiency of a Septic
Tank (Viraraghavan, 1976) 74
20 Summary of Treatment Efficiencies of Two Septic
Tanks (Lawrence, 1973) 76
21 Summary of Effluent Quality from Seven Septic
Tanks (University of Wisconsin, 1978) 77
22 Summary of Effluent Quality from Various Septic
Tank Studies (U.S. Environmental Protection
Agency, October, 1980) 79
23 Summary of Bacteriological Character of Household
Septic Tank Effluents 80
24 Characteristics of Septic Tank Effluent Applied
to Study Site (Viraraghavan and Warnock, 1976) .... 83
25 Movement of Bacteria through Soil (Gerba, 1975). ... 94
26 Factors Affecting Survival of Enteric Bacteria
in Soil (Gerba, 1975) 96
27 Factors Thay May Influence Removal Efficiency
of Viruses by Soil (Gerba, 1975) 100
xidi
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Table Page
28 Survival of Bacteria in Ground Water (Gerba,
1975) 106
29 Ground Water Pollution Control Measures for
New Septic Tank Systems (U.S. Environmental
Protection Agency, 1973) 131
30 Characteristics of Black Water (Bauer, Conrad
and Sherman, 1979) 134
31 Characteristics of Grey Water (Bauer, Conrad
and Sherman, 1979) 135
32 Characteristics of Domestic Septage (U.S.
Environmental Protection Agency, October 1980) .... 144
33 Indicator Organism and Pathogen Concentrations in
Domestic Septage (U.S. Environmental Protection
Agency, October 1980) 146
34 Summary Features of Empirical Assessment
Methodologies (Canter, 1981) 151
35 Comparison of Study Methodologies to Selection
Criteria 159
36 Rating of the Unsaturated Zone in the SIA Method
(U.S. Environmental Protection Agency, 1978) 162
37 Rating Ground Water Availability in the SIA Method
(U.S. Environmental Protection Agency, 1978) 164
38 Rating Ground Water Quality in the SIA Method
(U.S. Environmental Protection Agency, 1978) 165
39 Examples of Contaminant Hazard Potential Ratings
of Waste Classified by Source in the SIA Method
(U.S. Environmental Protection Agency, 1978) 166
40 Populations Served by Septic Tank System Areas in
Central Oklahoma Study Area 170
41 Assessment of Septic Tank Sy tern Areas by Surface
Impoundment Assessment Method (Canter, 1981) 173
42 Waste Factors in Waste-Soil-Site Interaction
Matrix (Phillip, Nathwani and Mooij, 1977) 175
xiv
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Table Page
43 Soil-Site Factors in Waste-Soil-Site Interaction
Matrix (Phillips, Nathwani and Mooij , 1977) 178
44 Example of Waste-Soil-Site Interaction Matrix
(Phillips, Nathwani and Mooij, 1977) 179
45 Toxicity Values for Waste-Soil-Site Interaction
Matrix (Phillips, Nathwani and Mooij, 1977) 181
46 Waste-Soil-Site Interaction Matrix Assessment for
Arcadia, Oklahoma County, Oklahoma 193
47 Assessment of Septic Tank System Areas by Waste-
Soil-Site Interaction Matrix Methodology 194
48 Comparison of Rank Order of Septic Tank System
Areas 196
49 Well Samples and Analysis for Septic Tank System
Areas 199
50 Data for Example Problem Using Hantush Analytical
Model 203
51 Calculation Procedure for Hantush Analytical Model
(Kincannon, 1981) 204
52 Water Table Rise Under Mound-type Septic Tank
System 205
53 Hierarchical Structure for Septic Tank System
Modeling 233
xv
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Conversion from Customary to Metric Units
Multiply Customary Unit
acre
inch
inch
foot
million gallon
mile
square mile
foot per minute
cubic foot per
square foot
Abbreviation
ac
in
in
ft
MG
mile
sq mile
ft/mi n
cu ft/
sq ft
By
0.4047
25.4
2.54
0.3048
3.785 x 103
1.609
2.590
5.080
0.3048
To Obtain Metric Unit
ha (hectare)
rmi
cm
m
m3
km
km2
mm/s
m /m or m
gallon per day gpd/ft
per square foot
4.074 x 10
~2 m3/m2-d or m/d
xv i
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CHAPTER 1
INTRODUCTION
The first reported use of a septic tank for serving the wastewater
disposal needs of a household was in France about 1870. Septic tanks
were introduced in the United States in 1884 through the use of a two-
chamber tank utilizing an automatic siphon for intermittent effluent
disposal (Cotteral and Norris, 1969). Since their introduction in the
United States, septic tanks systems have become the most widely used
method of on-site sewage disposal, with over 70 million people depending
on them (Hershaft, 1976). Approximately 17 million housing units, or
1/3 of all housing units, dispose of domestic wastewater through the use
of septic tank systems. About 25% of all new homes being constructed in
the United States use septic tank systems for treatment prior to
disposal of the home-generated wastewater (U.S. Environmental Protection
Agency, October 1980). Figure 1 is a summary of the population in the
United States utilizing septic tank systems (Anonymous, 1979). As can
be seen, the greatest densities of usage occur in the east and southeast
as well as the northern tier and northwest portions of the country.
A septic tank system includes both the septic tank and the
subsurface soil absorption system. Approximately 800 billion gallons of
wastewater is discharged annually to the soil via tile fields following
the 17 million septic tanks (Scalf, Dunlap and Kreissl, 1977). Of all
ground water pollution sources, septic tank systems and cesspools rank
highest in total volume of wastewater discharged directly to soils
overlying ground water, and they are the most frequently reported
-1-
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Percentage of
Households Using
Septic Tanks
Figure 1: Population Using Septic Tanks (Anonymous, 1979)
-2-
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sources of contamination (U.S. Environmental Protection Agency, 1977).
Figure 2 displays the components of the septic tank system and indicates
the general relationship between the soil absorption system and
underlying ground water (Bouma, 1979). In sparsely-populated urban and
rural areas, septic tank systems that have been properly designed,
constructed, and maintained are efficient and economical alternatives to
public sewage disposal systems. However, due to poor locations for many
septic tank syntema, an well as poor designs and construction and
maintenance practices, septic tank systems have polluted, or have the
potential to pollute, underlying ground waters. It is estimated that
only 40% of existing septic tanks function in a proper manner
(Anonymous, 1979). A major concern in many locations is that the
density of the septic tanks is greater than the natural ability of the
subsurface environment to receive and purify system effluents prior to
their movement into ground water. A related issue is that the design
life of many septic tank systems is in the order of 10-15 years. Due to
the rapid rate of placement of septic tank systems in the 1960's, Che
usable life of many of the systems is being exceeded, and ground water
contamination is beginning to occur.
A type of ground water pollution of historical as well as current
concern is associated with bacterial contamination. Contamination of
drinking supplies by malfunctioning septic tank systems has caused
outbreaks of waterborne communicable diseases (Anonymous, 1979).
Documented cases of infectious hepatitis (Hepatitis a) have been traced
to contaminated water. In central Appalachia, where few people are
served by sewers and septic tank systems often malfunction, the
-3-
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wtll
PRODUCTION PRfcTRlATMENT
_. .illi
-it-1 septic lank
TE :•_-:.-«
DISPOSAL
t
ivipoutnspitMion
Ji I *4S ..-•L,
i
i
soil etisorplion
purification •
1_J_—^
ground water
60cm
streams, lakes
Figure 2: Schematic Cross-Section Thiough a Conventional Septic
Tank Soil Disposal System !ir On-Site Disposal and
Treatment of Domestic Liquid Waste (Bouma, 1979)
-4-
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occurrence of infectious hepatitis is high. Many other pathogens, such
as typhoid, cholera, streptococci, salmonella, poliomyelitis, and
protozoans are also transmitted by septic tank system overflows. Many
of these pathogenic organisms have a slow die-off rate in the subsurface
environment.
While localized incidents of ground water pollution from septic
tank systems are of concern, regional problems have also been recognized
in areas of high septic tank system density. Within the United States
there are four counties (Nassau and Suffolk, New York; Dade, Florida;
and Los Angeles, California) with more than 100,000 housing units served
by septic tank systems and cesspools. In addition, there are 23
counties with more than 50,000 housing units served by septic tank
systems and cesspools (U.S. Environmental Protection Agency, 1977).
Table 1 summarizes relevant county statistics and the density (number
per square mile) of septic tank systems and cesspools (U.S. Department
of Commerce, 1980; and Newspaper Enterprise Association, Inc., 1982).
Densities range from as low as 2 to greater than 346 per square mile.
It should be noted that the densities were calculated based on assuming
an even distribution of the septic tank systems and cesspools throughout
the county. If they are localized in segments of the county the actual
densities could be several times greater than those shown in Table 1.
Density ranges can be considered as low (less than 10 per square mile or
3.8 per square kilometer), intermediate (between 10 and 40 per square
mile, or 3.8 and 15 per square kilometer), and high (greater than 40 per
square mile or 15 per square kilometer). Areas with more than 40 per
square mile can be considered to have potential contamination problems.
-5-
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Table 1: UenHitien of Septic Tank System-, and Cesspools for Counties with More
than 50,000 Housing Units Served by These Systems.
County
Jefferson, Alabama (1)
Riverside, California
San Bernardino, California
Falrfleld, Connecticut
Hartford, Connecticut
New Haven, Connecticut
Broward, Florida
Duval, Florida
Hillsborough, Florida
Jefferson, Kentucky
Bristol, Massachusetts
Middlesex, Massachusetts
Norfolk, Massachusetts
Plymouth, Massachusetts
Worcester, Massachusetts
Genesee, Michigan
Oakland, Michigan
Monmouth, New Jersey
Multnomah, Oregon
Westmoreland, Pennsylvania
Davidson, Tennessee
King, Washington
Pierce, Washington
County
1980
Population
(xlO3)
671
660
878
807
808
761
1,006
571
641
685
475
1,367
607
405
646
450
1,012
503
563
392
478
1,270
486
Statistics
iy»U
Housing
Units
(xlO3)
260
295
3f>8
3. '8 ( 0
3.'8 (.!)
309 ( })
482
227
264
266
193 (3)
556 (3)
247 (3)
105 (3)
2<>3 (3)
163
373
186
229 (3)
148
194 (3)
526
187
Area
(sq. mi.)
1,115
7,176
20,117
632
739
610
1,219
766
1,038
375
554
825
394
654
1,509
642
867
476
423
1,024
501
2,128
1,676
Housing
Units With
Septic Tank
Systems or
(%) Cesspools
19-38 (2)
17-34
14-27
15-30
15-30
16-32
10-21
22-44
19-38
19-38
26-52
9-18
20-40
30-61
19-38
31-61
13-27
27-54
22-44
34-68
26-52
10-19
27-53
Density of
Septic Tank
Systems or
Cesspools
(No. /mi2)
45- 90 (2)
7- 14
2- 4
79-158
68- 1 35
82-164
41- 82
65-130
48- 96
133-266
90-180
61-122
127-254
76-153
33- 66
78-156
58-115
105-210
118-236
49- 98
100-200
23- 47
30- 60
-6-
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Table 1 Continued
County
Los Angeles, California
Dade, Florida
Nassau, New York
Suffolk, New York
County
1980
Population
(xlO3)
(4) 7,745 2
1,574
1,322
1,284
Statistics
1980
Housing
Units
(xlO3) (sq
,854 4
657 2
434
432
Area
. mi.)
,069
,042
289
929
Housing
Unity With
Septic Tank
Systems or
(%) Cesspools
>4
>15
>23
>23
Density of
Septic Tank
Systems or
Cesspools
(No. /mi2)
> 25
> 49
>346
>108
(1) Counties from Jefferson, Alabama through Pierce, Washington have more than
50,000 housing units, but less than 100,000 housing units, served by septic
tank systems.
(2) First number is based on 50,000 housing units served by septic tank systems,
and second number by 100,000 housing units served by septic tank systems.
(3) Calculated based on 2.46 persons per housing unit; this value based on
reported data for counties of Jefferson, Alabama; Riverside and San Bernardino,
California; Broward, Duval, and HiJIsborough, Florida; Jefferson, Kentucky;
Genesee and Oakland, Michigan; Monmouth, New Jersey; Westmoreland, Pennsyl-
vania; and King and Pierce, Washington.
(4) Counties from Los Angeles, California through Suffolk, New York have more
than 100,000 housing units served by septic tank systems.
-7-
-------
Actual densities in areas with documented problems have considerably
exceeded the arbitrary 40 per square mile indicator (U.S. Environmental
Protection Agency, 1977). Another means of expressing density is by the
number per acre, with 40 per square mile equalling 0.062 per acre. The
maximum density shown in Table 1 is 346 per square mile, or 0.54 per
acre. Considering septic tank system localization within a county, or
non-uniform distribution, it would be possible for several counties
listed in Table 1 to have densities of greater than 1 septic tank system
per acre.
SEPTIC TANK SYSTEM REGULATION
Several types of institutional arrangements have been developed for
regulating septic tank system design and installation, operation and
maintenance, and failure detection and correction. Most of the
regulatory activities are conducted by state and local governments.
Design and siting regulations exist in most states for both individual
housing unit systems as well as systems serving clusters of up to
several hundred housing units (U.S. Environmental Protection Agency,
1977). Site inspection and installation permit issuance is handled
either by the state, regional authority, county, or town, or by a joint
effort by two or more of these entities. A state or local governmental
entity may regulate all domestic and industrial septic tank system
installations; or it may regulate only systems serving multiple housing
units and/or industries; or it may regulate only installations in certain
critical areas. Where regulations exist, the associated inspections may
range from minimal checking to comprehensive evaluations. State
-8-
-------
regulation and inspection of septic tank installation is generally
considered to be more effective than local regulation (U.S. Environmental
Protection Agency, 1977).
Operation and maintenance of single housing unit septic tank
systems is largely not regulated and left to the judgment of the system
owner. Systems serving multiple housing units or industries may be
subject to routine inspections and reporting requirements. Failure
detection and correction is difficult to regulate and is typically
handled on an individual complaint basis or when a health hazard arises
(U.S. Environmental Protection Agency, 1977).
In terms of protection of ground water quality, this is best
accomplished by system design, site selection, and installation
regulations. Consideration should also be given to the septic tank
system density in an area. The U.S. Environmental Protection Agency can
become a participant in the regulatory process based on the provision of
funding for septic tank systems. Sections 201 (h) and (j) of the Clean
Water Act of 1977 (P.L. 95-217) authorized construction grants funding
of privately-owned treatment works serving individual housing units or
groups of housing units (or small commercial establishments), provided
that a public entity (which will ensure proper operation and
maintenance) apply on behalf of a number of such individual systems
(Bauer, Conrad, and Sherman, 1979). One of the major concerns related
to funding applications is to evaluate the ground water pollution
potential of the proposed system or systems. This issue becomes even
more important for larger systems serving several hundred housing units.
To serve as an illustration of possible system size, the U.S.
-9-
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Environmental Protection Agency has funded a system located in the
northeastern United States with a design flow of 100,000 gallons per day
(Thomas, 1982).
To provide a basis for evaluation of the ground water pollution
potential of septic tank systems, the U.S. Environmental Protection
Agency requires that the ground water quality resulting from land
utilization practices (septic tank systems) meet the standards for
chemical quality (inorganic chemicals) and pesticides (organic
chemicals) specified in the EPA Manual for Evaluating Public Drinking
Water Supplies in the case of ground water which potentially can be used
for drinking water supply. In addition to the standards for chemical
quality and pesticides, the bacteriological standards (microbiological
contaminants) specified in the EPA Manual for Evaluating Drinking Water
Supplies are required in the case of ground water which is presently
being used as a drinking water supply (U.S. Environmental Protection
Agency, 1976). Tables 2, 3, and 4 summarize the inorganic, organic, and
bacteriological standards, respectively, which should be used in the
evaluation process. Current and potential ground water usage should be
considered in the evaluation of septic tank systems. The U.S.
Environmental Protection Agency requirements have been stated in terras
of three cases (U.S. Environmental Protection Agency, 1976):
Case I: The ground water can potentially be used for drinking
water supply.
(1) The maximum contaminant levels for inorganic chemicals and
organic chemicals specified for drinking water supply systems
as shown in Tables 2 and 3 should not be exceeded.
(2) If the existing concentration of a parameter exceeds the
maximum contaminant levels for inorganic chemicals or organic
-10-
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Table 2: Maximum Contaminant Levels Eor Inorganic Chemicals
(U.S. Environmental Protection Agency, 1976).
Contaminant :
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Nitrate (as N)
Selenium
Silver
Level
(mg/ft)
0.05
1.
0.010
0.05
0.05
0.002
10.
0.01
0.05
The maximum contaminant levels for flouride are:
Temperature
Degrees Fahrenheit1
53.7 and below
53.8 to 58.3
58.4 to 63.8
63.9 to 70.6
70.7 to 79.2
79.3 to 90.5
Degrees Celsius
12 and below
12.1 to 14.6
14.7 to 17.6
17.7 to 21.4
21.5 to 26.2
26.3 to 32.5
Level
(mg/4)
2.4
2.2
2.0
1.8
1.6
1.4
1Annual average of the maximum daily air temperature,
-11-
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Table 3: Maximum Contaminant Levels for Organic Chemicals
(U.S. Environmental Protection Agency, 1976).
Level
Chemical
Chlorinated hydrocarbons
Endrin (1,2,3,4,10,10-Hexachloro-
6,7 - epoxy - l,4,4a,5,6,7,8,8a-oc-
tahydro-1,4-endo,endo - 5,8,-di-
methano naphthalene) 0.0002
Lindane (1,2,3,4,5,6 - Hexachloro-
cyclohexane, gamma isomer) 0.004
Methoxychlor (1,1,l-Trichloro-2,
2-bis {p-methoxyphenyl} ethane) 0.1
Toxaphene (CioHioCLs - Technical
chlorinated camphene, 67 to 69
percent chlorine) 0.005
Chlorophenoxys
2,4-D (2,4-Dichlorophenoxyacetic
acid) 0.1
2,4,5-TP Silvex (2,4,5-Trichloro-
phenoxypropionic acid) 0.01
-12-
-------
Table 4: Maximum Bacteriological Contaminant Levels
(U.S. Environmental Protection Agency, 1976).
The maximum contaminant levels for coliform bacteria, applicable to
community water systems and non-community water systems are as follows:
(a) When the membrane filter technique is used, the number of
coliform bacteria shall not exceed any of the following:
(1) One per 100 milliliters as the arithmetic mean of all samples
examined per month.
(2) Four per 100 milliliters in more than one sample when less than
20 or more are examined per month.
(3) Four per 100 milliliters in more than five percent of the sam-
ples when 20 or more are examined per month.
(b) (1) When the fermentation tube method and 10 milliliter
standard pertions are used, coliform bacteria shall not be present in any
of the following:
(i) More than 10 percent of the portions in any month;
(ii) Three or more portions in more than one sample when less than
20 samples are examined per month; or
(iii) Three or more portions in more than five percent of the
samples when 20 or more samples are examined per month.
(2) When the fermentation tube method and 100 milliliter standard
portions are used, coliform bacteria shall not be present in any of the
following:
(i) More than 60 percent of the- portions in any month;
(ii) Five portions in more than one sample when less than five
samples are examined per month; or
(iii) Five portions in more than 20 percent of the samples when
five or more samples are examined per month.
(c) For community or non-community systems that are required to
sample at a rate of less than 4 per month, compliance with Paragraphs
(a), (b) (1), or (2) shall be based upon sampling during a 3 month period,
except that, at the discretion of the State, compliance may be based upon
sampling during a one month-period.
-13-
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chemicals, there should not be an increase in the
concentration of that parameter due to land utilization
practices.
Case II: The ground water is used for drinking water supply.
(1) The criteria for Case I should be met.
(2) The maximum microbiological contaminant levels specified for
drinking water supply systems as shown in Table 4 should not
be exceeded in cases where the ground water is used without
disinfection.
Case III: Uses other than drinking water supply.
(1) Ground water criteria should be established by the EPA
Regional Administrator based on the present or potential use
of the ground water.
The EPA Regional Administrator in conjunction with the appropriate
State officials and the grantee shall determine on a site-by-site basis
the areas in the vicinity of a specific land utilization site where the
criteria in Case I, II, and III shall apply. Specifically determined
shall be the monitoring requirements appropriate for the project site.
This determination shall be made with the objective of protecting the
ground water for use as a drinking water supply and/or other designated
uses as appropriate and preventing irrevocable damage to ground water.
Requirements shall include provisions for monitoring the effect on the
native ground water (U.S. Environmental Protection Agency, 1976).
Tables 2 through 4 are based on the National Interim Primary
Drinking Water Regulations (40 CFR 141). Any amendments of the National
Interim Primary Drinking Water Regulations and any National Revised
Primary Drinking Water Regulations hereafter issued by EPA prescribing
standards for public water system relating to inorganic chemicals,
organic chemicals or microbiological contamination shall automatically
-14-
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apply in the same manner as the National Interim Primary Drinking Water
Regulations (U.S. Environmental Protection Agency, 1976).
OBJECTIVE OF STUDY
Based upon the needs of the U.S. Environmental Protection Agency to
evaluate the ground water pollution potential of septic tank systems
i
being considered for grant funding, and also the needs of engineering
designers and state and local regulatory officials for similar relevant
information, the objective of this study is to summarize existing
literature relative to the types and mechanisms of ground water
pollution from septic tank systems, and to provide information on
technical methodologies for evaluating the ground water pollution
potential of septic tank systems.
SCOPE OF STUDY
The scope of work involved in this study included a survey of
published literature on the identification and evaluation of ground
water pollution from septic tank systems; and selection and evaluation
of two empirical assessment methodologies, one numerical model, and one
analytical model for their applicability to septic tank systems. The
empirical assessment methodologies and numerical model were tested on
septic tank system areas in central Oklahoma, while hypothetical
calculations were made to demonstrate usage of the analytical model for
quantifying potential ground water quality effects from septic tank
systems. The literature survey was based on the conduction of computer-
based literature searches using the DIALOG system of Lockheed
Corporation. Appropriate descriptor words for septic tank systems were
-15-
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identified, and Che data bases searched included the National Technical
Information Service, Pollution Abstracts, Compendex (Engineering Index),
Enviroline, Biosis, and Smithsonian Science Information Exchange.
Selection of the methodologies and models was based on considering their
previous or potential use for septic tank systems; likely availability
of required input data; resource requirements in terms of general
personnel and technical specialists, computational equipment, and time
or ease of implementation; understandability by non-technical persons;
and previous documentation for prediction of pollutant transport.
ORGANIZATION OF REPORT
Chapter 1 of this report provides an introduction to the study and
includes background information on the use of septic tank systems.
Chapter 2 summarizes septic tank system design practices, site selection
and evaluation criteria, and operation and maintenance procedures for
minimizing ground water pollution concerns. Chapter 3 includes
information on the types of pollutants and mechanisms of contamination
via migration of pollutants through the unsaturated zone into the ground
water system. The transport and fate of bacteria and viruses in soils
and ground water are addressed along with similar information on
inorganic contaminants such as phosphorus, nitrogen, chlorides, and
metals. Information is also included on the transport and fate of
organic contaminants.
Chapter 4 represents the focal chapter in terms of the evaluation
of septic tank system effects on ground water quality. Information on
the Surface Impoundment Assessment methodology and the Soil-Waste
-16-
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Interaction Matrix methodology are included along with descriptions of
the Hantush Analytical Model and the Konikow and Bredehoeft Numerical
Model. Applications of the two methodologies to 13 septic tank system
areas in central Oklahoma are described along with information from a
cursory field sampling program at 4 locations. Usage of the Hantush
Analytical Model is demonstrated by example calculations for a system
serving one household unit. Finally, the advantages and limitations of
the Konikow and Bredehoeft Numerical Model are demonstrated through its
application to one geographical area served by septic tank systems near
Edmond in central Oklahoma.
Chapter 5 contains the summary of the study and recommendations for
additional research. Selected references are included along with five
appendices. Appendix A is an annotated bibliography of published
reference materials on septic tank systems and ground water modeling.
Appendix B provides information on the characteristics of 13 septic tank
system areas located in central Oklahoma, while Appendix C provides
specific information on the use of the matrix empirical assessment
methodology for these 13 areas. Appendix D contains the error function
used in the Hantush Analytical Model. Finally, Appendix E has the
Fortran IV program for the Konikow and Bredehoeft Numerical Model.
-17-
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CHAPTER 2
DESIGN OF SEPTIC TANK SYSTEMS
Septic tank systems consist of the septic tank and associated soil
absorption system. Sound principles of engineering should be used in
designing both system components. In addition, site suitability criteria
should be applied for system location, and routine operational checks
and maintenance activities should be conducted. The purpose of this
chapter is to summarize design factors, locational criteria, and
operational and maintenance measures for septic tank systems. The focus
will be on those factors, criteri.i, and measures which will provide
appropriate ground water quality protection. The chapter will begin with
some general information on septic tank systems and be followed by
sections on septic tank design and operation and subsurface disposal
system design and operation. The final section will address a variation
of the basic system — the septic tank-mound system popularized in
Wisconsin.
OVERVIEW OF SEPTIC TANK SYSTEMS
The basic septic tank system consists of a buried tank where
waterborne wastes are collected, and scum, grease and settleable solids
are removed from the liquid by gravity separation; and a subsurface
drain system where clarified effluent percolates into the soil. System
performance is essentially a function of the design of the system
components, construction techniques employed, characteristics of the
wastes, rate of hydraulic loading, climate, areal geology and topography,
physical and chemical composition of the soil mantle, and care given to
-18-
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periodic maintenance (Cotteral and Norris, 1969). A typical on-site
system is shown in Figure 3 (Scalf, Dunlap and Kreissl, 1977). The
system consists of a building sewer, laid to specified grade, which
discharges to the inlet of a septic tank. The septic tank effluent
discharges to a series of distribution pipes laid in trenches
(absorption trenches) or to a single large excavation (seepage) bed.
The system as displayed in Figure 3 is basically for a single
housing unit. Similar systems have been applied at industrial plants
and for multiple housing units in a given area, and for small
communities with wastewater flows as large as 100,000 gallons per day
(Thomas, 1982). The basic components of larger systems are similar to
those for the individual home system; namely, a septic tank and a soil
absorption system. Primary differences are associated with the size of
the components of the system.
The general advantages of septic tank systems include the
following:
1. Minimal maintenance is required for the system, with potential
pumpage of septage required every three to five years. While
there are requirements for removal of septage, there is less
sludge produced per person through use of a septic tank system
than through use of a centralized mechanical plant such as an
activated sludge plant.
2. The cost of individual or community septic tank systems is
less than the cost of central wastewater collection facilities
and treatment plants.
3. The septic tank system represents a low technology system,
thus the possibility for long-term operation without extensive
periods of shut-down is enhanced.
4. The energy requirements of septic tank systems are low in
comparison to centralized wastewater treatment facilities.
-19-
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NON PERFORATE
TILE
ABSORPTION
FIELD.
TILE
DRAINAGE
LINES
Figure 3: Typical On-Site System (Scalf, Dunlap and Kreissl, 1977)
-20-
-------
The general disadvantages of septic tank systems include:
1. The potential for ground water pollution depending upon the
soil characteristics and density of systems in a given
geographical area.
2. System overflows and pollution of adjacent water wells and
surface water courses if the systems are not properly
maintained.
3. Cleaners used for maintenance of septic tank systems may
create difficulties in terms of ground water pollution,
particularly cleaners that have organic solvent bases.
These advantages and disadvantages of septic tank systems must be
considered as general statements, with the specific decision to locate a
system in a given geographical area based on site suitability and costs
relative to other on-site disposal options and central collection and
treatment systems.
SEPTIC TANK DESIGN
Septic tanks are buried, water-tight receptacles designed and
constructed to receive wastewater from one to multiple housing units or
industrial processes. A typical two-compartment septic tank for a
housing unit is shown in Figure 4 (Cotteral and Norris, 1969). Heavier
sewage solids in the influent settle to the bottom of the tank forming a
blanket of sludge. The lighter solids, which includes fats and greases,
rise to the surface and form a layer of scum. A considerable portion of
the sludge and scum is liquified through decomposition and digestion
processes. Gas is liberated from the sludge in this process, carrying
some of these solids to the surface where they accumulate with the scum.
Further digestion may occur in the scum, and part of the solids may
settle again to the sludge layer below. This process may be retarded if
-21-
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. kf-^-'-^—- —:-- - '^ --v- ---A:.•.-/., -'I- ' j'j,r>'
?: *.u_
, i.t.\;;TH
t> • SLUOGf CifJff it'ACf (II INCMLS ViMMuV
C • «O* OF LIQUID SfPTH
Figure 4: Typical Two Compartment Septic Tank (Cotteral and Norris,
1969)
-22-
-------
there is an excess of grease in the scum layer. The partially-clarified
liquid between the sludge and scum flows through an outlet located below
the scum layer. Proper use of baffles within the septic tank will
minimize scum outflow to the soil absorption system. In summary, the
septic tank provides for separation of sludges and floatable materials
from the wastewater, and an anaerobic environment for decomposition of
both retained sludge and non-settleable materials within the scum layer.
Some anaerobic decomposition of tho intermediate liquid layer also
occurs.
Design considerations rel.ited to a septic tank include
determination of the appropriate volume, a choice between single and
double compartments, selection of the construction material, and
placement on the site. The septic tank must be designed to ensure
removal of almost all settleable solids in the influent wastewater. Key
design considerations basic to this removal from wastewaters from
individual housing units include (U.S. Environmental Protection Agency,
October 1980):
(1) Liquid volume sufficient for a 24-hr fluid retention time at
maximum sludge depth and scum accumulation.
(2) Inlet and outlet devices to prevent the discharge of sludge or
scum in the effluent.
(3) Sufficient sludge storage space to prevent the discharge of
sludge or scum in the effluent.
(4) Venting provisions to allow for the escape of accumulated
methane and hydrogen sulEide gases.
It is important that septic tanks be sized based on the wastewater
to be handled. A factor of safety should be provided to allow for
variations in wastewater loading and future changes in the character of
-23-
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household wastes. Oversized tanks will not he cost-effective and
undersized ones will yield effluent discharges which have not received
the level of treatment necessary for optimum usage of the soil
absorption system. The first step in selecting the appropriate tank
volume is to determine the average daily volume of wastewater produced
from the source or sources to be handled. This determination should be
based on measurements of actual wastewater flows; however, measurements
will not be possible for housing units, commercial establishments, or
industrial plants which are under construction. The design volume for
septic tanks serving single housing units can be based on the number of
bedrooms per home and the average number of persons per bedroom. The
average wastewater contribution is about 45 gpcd (170 Ipcd). As a
safety factor, a value of 75 gpcd (284 Ipcd) can be coupled with a
potential maximum dwelling density oC two persons per bedroom yielding a
theoretical design flow of 150 gal/bedroom/day (570 I/bedroom/day). A
theoretical tank volume of 2 to 3 times the design daily flow is common,
resulting in a total tank design capacity of 300 to 450 gal per bedroom
(1,140 to 1,700 1 per bedroom) (U.S. Environmental Protection Agency,
October 1980). Single household unit septic tank liquid volume
requirements recommended by the Federal Housing Authority, U.S. Public
Health Service, and Uniform Plumbing Code are shown in Table 5 (U.S.
Environmental Protection Agency, October 1980). State requirements for
tank size and minimum water depth are summarized in Table 6 (Senn,
1978). Tank length to width ratios of at least 2 to 1 and not over 3 to
1 have been used for several decades (Senn, 1978).
-24-
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Table 5: Single Household Unit Septic Tank Liquid Volume Requirements
(U.S. Environmental Protection Agency, October 1980).
Minimum, gal
1-2 bedrooms, gal
3 bedrooms, gal
4 bedrooms, gal
5 bedrooms, gal
Additional bedrooms
Federal
Housing
Authority
750
750
900
1,000
1,250
(ea), gal 250
U.S. Public
Health
Service
750
750
900
1,000
1,250
250
Uniform
Plumbing
Code
750
750
1,000
1,200
1,500
150
-25-
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Table 6: State Requirements for Single Household Unit Septic Tank Size
and Water Depth (Senn, 1978).
States
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Tank Size in
Number of
1 2 3
1000 1000 1000
750 750 900
960 960 960
_
- - -
750 750 900
1000 1000 1000
_
750 750 900
750 750 900
- - -
750 750 900
_ _ _
750 750 900
750 750 1000
_
750 750 900
500 750 900
750 750 900
-
-
-
-
— _
Gallons
Bedrooms
4 5
1200 1400
1000 1250
1200 1500
-
-
1000 1250
1250 1500
-
1000 1200
1000 1250
-
1000 1250
-
1100 1250
1250 1500
-
1000 1250
1150 1400
1000 1250
-
-
-
-
« _
Minimum
Water Depth
(Feet)
4
4
4
-
-
No Minimum
1.5
-
1.5
No Minimum
-
4
-
1.5
-
None
2
-
-
-
-
_
-26-
-------
Table 6 Continued
States
Missouri
Montana
Nebraska
Nevada
New Hampshire
Tank
Size in Gallons
Number of Bedrooms
1 2
-
750 750
750 750
1000 1000
750 750
3 A 5
_
900 1000 1250
900 1000 1250
1000 1000 1250
900 1000 1250
Minimum
Water Depth
(Feet)
-
4
4
4
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
750
1000
750
900
750
1000
750
750
750
1000
750
900
750
1000
750
750
900
1500
900
900
900
1000
900
900
1000
2000
1000
1000
1000
1250
1000
1000
1250
2000
1250
1100
1250
1500
1250
1250
1.5
4
3
4
4
30 hour Detention 100 Gallons Per Day
750 750 900 1000 1250
750 750 900 1000 1250
No Minimum
3
4
-27-
-------
Table 6 Continued
States
Tank Size in Gallons
Number of Bedrooms
12345
Minimum
Water Depth
(Feet)
Wisconsin
Wyoming
750
750
750
750
975
900
1200
1000
1375
1250
3
4
-28-
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Septic tanks for commercial, institutional, or industrial sources,
or for multiple housing units, must also be sized for daily wastewater
flows. For septic tanks being planned for existing sources the flow
should be measured to determine average daily flows and peak flows. For
multiple housing units, if the total measured flow cannot be measured,
the individually measured or estimated flows based on the expected
population and the generation rate of 45 gal/cap/day (170 1/cap/day)
from each unit must be summed to determine the design flow (U.S.
Environmental Protection Agency, October 1980). For flows between 750
and 1,500 gal per day (2,840 to 5,680 1 per day), the capacity of the
tank should equal to 1-1/2 days wastewater flow. For flows between
1,500 and 15,000 gpd (5,680 to 56,800 Ipd), the minimum effective tank
capacity can be calculated as 1,125 gal (4,260 1) plus 75% of the daily
flow; or
V = 1,125 + 0.75Q
where:
V = net volume of the tank (gal)
Q = daily wastewater flow (gal)
Early trends in septic tank design focused on single compartment
tanks. More recent trends favor multiple compartment tanks due to
resultant improvements in biochemical oxygen demand (BOD) and suspended
solids removals. Figure 4 displayed some of the features of a two-
compartment tank (Cotteral and Norris, 1969), and Figure 5 shows still
others (U.S. Environmental Protection Agency, October 1980). Benefits
of the design shown in Figure 5 are due largely to hydraulic isolation,
and to the reduction or elimination of intercompartmental mixing.
-29-
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-i r
H
D
Access
Manholes
Plan
Sanitary
Tee.
Inlet
Outlet
Longitudinal Section
Figure 5: Plan and Section Views of Two Compartment Septic Tank
(U.S. Environmental Protection Agency, October 1980)
-30-
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Mixing can occur by two means — water oscillation and true turbulence.
Oscillatory mixing can be minimized by making compartments unequal in
size (commonly the second compartment is 1/3 to 1/2 the size of the
first), reducing the flow-through area, and using an ell to connect
compartments. In the first compartment, some mixing of sludge and scum
with the liquid always occurs due to induced turbulence from entering
wastewater and the digestive process. The second compartment receives
the clarified effluent from the first compartment. Most of the time it
receives this hydraulic load at a lower rate and with less turbulence
than does the first compartment, and thus, better conditions exist for
settling low-density solids. These conditions lead to longer working
periods before pump-out of solids is necessary, and they improve overall
performance.
Septic tanks should be w.iter-tight, structurally sound, and
reasonably durable. The water-tight requirement is to preclude
infiltration into the tank which will cause hydraulic overloading and
lead to poor quality discharges to soil absorption systems at a rate
greater than the system design. In addition, the material of
construction should be such that the tank is cost-effective. The
Federal Housing Authority and Uniform Plumbing Code indicate that the
materials of construction should be durable; the U.S. Public Health
Service indicates usage of either concrete or metal (Cotteral and
Norris, 1969). Reinforced concrete is the most commonly used septic
tank construction material. Most single housing unit septic tanks have
been precast for easy installation at the site (U.S. Environmental
Protection Agency, October 1980). The walls have thicknesses of 3 to 4
-31-
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in. (8 Co 10 cm), and the tanks are sealed for watert ightness after
installation with two coats of bituminous coating. Care must be taken
to seal around the inlet and discharge pipes with a bonding compound
that will adhere both to concrete and to the inlet and outlet pipe.
When steel is used as the construction material it must be treated to be
able to resist corrosion and decay. Such protection includes bituminous
coating or other corrosion-resistant treatment. However, despite a
corrosion-resistant coating, tanks deteriorate at the liquid level.
Past history indicates that steel tanks have a short operational life
(less than 10 years) due to corrosion (U.S. Environmental Protection
Agency, October 1980). Other construction materials which have been or
are being used include redwood and cedar (Cotteral and Norris, 1969) and
polyethylene and fiberglass (U.S. Environmental Protection Agency,
October 1980). Plastic and fiberglass tanks are very light, easily
transported, and resistant to corrosion and decay. While these tanks
have not had a good history due to structural failures, some
manufacturers are now producing tanks with increased strength. This
minimizes the chance of damage during installation or when heavy
machinery moves over them after burial. A well-designed and maintained
concrete, fiberglass, or plastic tank should last for 50 years. Because
of corrosion problems, steel tanks can be expected to last no more than
10 years (U.S. Environmental Protection Agency, October 1980).
Placement of the septic tank on the site basically involves
consideration of the site slope and minimum setback distances from
various natural features or built structures. A typical minimum lot
size for a septic tank system serving a single household unit is one
-32-
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acre (Cotteral and Morris, 1969). This lot size takes into account
areas unsuitable for drainfields by reason of local variation in soil
conditions, and it will normally be sufficient for the required initial
drainfield and its replacement, and leave space for standard setbacks
and construction of the residence. As noted in Chapter 1, numerous
areas within the United States have septic tank densities greater than
one per acre. If the site slope is greater than 5%, it is desirable to
increase the minimum lot size to make allowance for additional
construction difficulties on slopes, and to take precautions to prevent
slides or downhill surfacing of system effluents. Based upon drainfield
area slope, that is, the maximum slope across a minimum 1/2 acre area
containing both the required drainfield and the replacement drainfield
area, the following minimum lot sizes should be required: 5 to 10% —
1.25 acres; 10 to 20% — 1.50 acres; and over 20% — 2.0 acres (Cotteral
and Norris, 1969). Minimum setback distances used by the Federal
Housing Authority, Uniform Plumbing Code, and several California
counties are listed in Table 7 (Cotteral and Norris, 1969). Setback
information for drainfields will be presented in the next section.
SOIL ABSORPTION SYSTEM DESIGN
Proper designs of soil absorption systems are critical to the
successful operation of septic tank systems. Laak, Healy and Hardisty
(1974) identified three aspects in the rational design of soil
absorption systems. The first is associated with hydraulic
characteristics. This means that the flow regime and the storage and
water-carrying capacity of the receiving soil should be measured before
-33-
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Table 7: Setback Requirements Tor Septic Tanks
(Cotteral and Morris, 1969).
Setback Requirements (feet)
Buildings
Property lines
Wells
Creeku or streams
Cuts or embankments
Pools
Water lines
Walks and drives
Large trees
Federal Uniform San
Housing Plumbing Mateo
Authority Code County
Septic
5 55
10 5 10
50 50 50
•>() 20
25
10 5 -
10 -
Santa Santa
Cruz Clara
County County
Tanks To:
5 5
5 10
50 100
50
15
5
Contra Mar in
Costa County
County
10 5
5 5
50 50
50 1 0
50 15
10
10
5
10
-34-
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design. A soil with a coefficient of permeability of less than 10"^
ft/min (5 x lO'-' cm/sec) suggests, for example, that the hydraulic
capacity of the system governs the size of the subsurface leaching field.
Seasonally high water tables or impervious strata may retard the flow
and reduce the quantity of wastewater that can be carried away from the
subsurface disposal area. The second consideration concerns the
biological mat in leaching fields. Leaching fields can be designed with
higher loadings in soils having a greater coefficient of permeability
than 10~4 ft/min (5 x 10~5 cm/sec) if increased pretreatment is used. A
mathematical relationship can be used for reducing the size of leaching
fields for effluents with a 8005 plus suspended solids less than 250
mg/1. The third design consideration is related to preserving ground
water quality. A chief factor is the type of subsurface soil and
distance to the top of the water table from the soil absorption system.
Soil absorption systems include the design and usage of trenches
and beds, seepage pits, mounds, fills and artificially drained systems
(U.S. Environmental Protection Agency, October 1980). Trench and bed
systems are the most commonly used methods for on-site wastewater
treatment and disposal. A typical trench system is shown in Figure 6
(U.S. Environmental Protection Agency, October 1980). Trenches are
shallow, level excavations, usually 1 to 5 ft (0.3 to 1.5 m) deep and I
to 3 ft (0.3 to 0.9 m) wide. The bottom is filled with 6 in (15 cm) or
more of washed crushed rock or gravel over which is laid a single line of
perforated distribution piping. Additional rock is placed over the pipe
and the rock covered with a suitable semiperraeable barrier to prevent
the backfill from penetrating the rock. Both the bottoms and sidewalls
-35-
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Backfill
Perforated
Distribution
Pipe
Barrier
Material
3/4 - 2-V? in. Rock
Water Table or
Creviced Bedrock
Figure 6: Typical Trench-type Soil Absorption System (U.S. Environ-
mental Protection Agency, October 1980)
-36-
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of the trenches are infiltrative surfaces. Additional details on
drainfield trench layouts are in Figure 7 (Cotteral and Norris, 1969). A
typical bed system is shown in Figure 8 (U.S. Environmental Protection
Agency, October 1980). Beds differ from trenches in that they are wider
than 3 ft (0.9 m) and may contain more than one line of distribution
piping. Thus, the bottoms of the beds are the principal infiltrative
surfaces. Site criteria for trench and bed systems are shown in Table 8
(U.S. Environmental Protection Agency, October 1980). These criteria
are based upon factors necessary to maintain reasonable infiltration
rates and adequate treatment performance over many years of continuous
service.
Specific sites used for soil absorption systems must meet certain
basic criteria. A soil is considered suitable for the absorption of
septic tank effluent if it has an acceptable percolation rate, without
interference from ground water or impervious strata below the level of
the absorption system. For a septic tank system to be approved by a
local health agency, several criteria normally must be met: a specified
percolation rate, as determined by a percolation test; and a minimum 4-
ft (1.2 m) separation between the bottom of the seepage system and the
maximum seasonal elevation of ground water. In addition, there must be
a reasonable thickness, again normally 4 ft, of relatively permeable
soil between the seepage system and the top of a clay layer or
impervious rock formation (U.S. Environmental Protection Agency, 1977).
Bouma (1980) summarized specific limits in a health code for on-site
subsurface disposal of septic tank effluent as follows: (1) the
percolation rate of the soil should be more than 60 cm per day; (2)
-37-
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T»tHC" SPfflMt
P
t
J
,s£
• c
V-
O fl
o »
["-
WIDTH
L
*— nor ton tntt
SECTION A-l
x t Htrtr MCM t eicrn
r/ew (nwf
//
2
£
O'tlHflflO r»CNCHtS-S
PARALLEL DISTRIBUTION
•rurvn OIVIHSIOH to*
stPLtctucur gauarifio
SERIAL DISTRIBUTION
HO 1CM.C
Figure 7: Oecails of Drainfleld Trench layout (Cotteral and Norris,
1969)
-38-
-------
Distribution
Box
;«fo^ .
^^^^fe^:, :
6:12 in of
'•/•.-2V2 inch dta Rock
2-4 ft. mm
Water Table or
Creviced Bedrock
Figure 8: Typical Bed-type Soil Absorption System (U.S. Environ-
mental Protection Agency, October 1980)
-39-
-------
Table 8: Site Criteria Cor Trench and Bed Systems
(U.S. Environmental Protection Agency, October 1980).
Item
Criteria
Landscape Position'
Slope*
Typical Horizontal Separation
Distances
Water Supply Wells
Surface Waters, Springs
Escarpments, Manmade Cuts
Boundary of Property
Building Foundations
Soil
Texture
Level, well drained areas, crests of
slopes, convex slopes most desirable.
Avoid depressions, bases of slopes and
concave slopes unless suitable surface
drainage is provided.
0 to 25%. Slopes in excess of 25% can
be utilized but the use of construction
machinery may be limited (7). Bed
systems are limited to 0 to 5%.
50
50
10
5
10
100 ft
100 ft
20 ft
10 ft
20 ft
Soils with sandy or loamy textures are
best suited. Gravelly and cobbley
soils with open pores and slowly
permeable clay soils are less
desirable.
Structure
Color
Layering
Strong granular, blocky or prismatic
structures are desirable. Platy or
unstructured massive soils should be
avoided.
Bright uniform colors indicate
well-drained, well-aerated soild.
Dull, gray or mottled soild indicate
continuous or seasonal saturation and
are unsuitable.
Soild exhibiting layers with distinct
textural or structural changes should
be carefully evaluated to insure water
movement will not be severely restrir.tfd.
-40-
-------
Table 8 Continued
Item Criteria
Unsaturated Depth 2 to 4 ft of unsaturated soil should
exist between the bottom of the system
and the seasonally high water table or
bedrock (3) (A) (8).
Percolation Rate 1-60 min/in. (average of at least 3
percolation tests). Systems can be
constructed in soils with slower
percolation rates, but soil damage
during construction must be avoided.
Landscape position and slope are more restrictive for beds because of the
depths of cut on the upslope side.
Intended only as a guide. Safe distance varies from site to site, based
upon topography, soil permeability, ground water gradients, geology, etc.
f*
Soils with percolation rates <1 min/in. can be used for trenches and beds
if the soil is replaced with a suitably thick (>2 ft) layer of loamy sand
or sand.
-41-
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bedrock should be at least 90 cm below the surface on 80% of the lot
area and at least 180 cm below on the remainder; (3) the lot slope
should be less than 10 to 20%, depending on the percolation rate; (4)
the highest ground water level, or depth to the water table, should be
at least 90 cm below the bottom of the seepage system; and (5) the lot
should not be subject to flooding. Health codes typically list required
seepage areas as a function of the soil percolation rate.
Cotteral and Norris (1969) identified the four most important
factors affecting the performance of a septic tank drainfield as
percolative capacity, infiltrative capacity, soil particle size, and
drainfield loading rate. Percolative capacity is a measure of the rate
at which effluent can be transmitted through the pores or interstices of
the soil. Infiltrative capacity is a measure of the rate at which
effluent can enter the soil through the surface on which it is applied.
Soil particle size refers to a soil characteristic which influences both
infiltrative capacity and percolative capacity; the common definition of
soil particle size is "effective size," which describes a soil
containing ten percent by weight of particles smaller than the stated
size. Loading rate is the rate of application of effluent to the
drainfield infiltrative surface; loading rate is normally expressed as
cubic feet of liquid per square foot of surface area per day, sometimes
shortened to feet per day.
Percolative capacity has traditionally been one of the basic design
factors for soil absorption systems. While it is true that the
percolative capacity of a soil acts as a limiting factor on the ability
of a drainfield to dispose of septic tank effluent, it is the
-42-
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infiltrative capacity of the liquid-soil interface which ultimately
determines the life of the drainfield (Cotteral and Norris, 1969). The
percolative capacity of the soil must be great enough to transport the
effluent away from the system liquid-soil interface at a rate at least
equal to the rate at which the liquid enters the soil. The key test
used to determine the percolative capacity of the soil is the
percolation test which was developed over 50 years ago. The percolation
test procedure is described in Table 9 (U.S. Environmental Protection
Agency, October 1980). Estimated percolation rates for various soil
textures and permeabilities are given in Table 10 (U.S. Environmental
Protection Agency, October 1980). Table 11 summarizes the absorption
area requirements for single housing units based on measured soil
percolation rates (U.S. Public Health Service, 1967). Experience has
shown that design hydraulic application rates can sometimes be
correlated with soil texture. Table 12 summarizes this experience and
it meant only as a guide. Soil texture and measured percolation rates
will not always be correlated as indicated, due to differences in
structure, clay mineral content, bulk densities, and other factors in
various areas of the country (U.S. Environmental Protection Agency,
October 1980).
It is recognized that the percolation test has a high degree of
variability in terms of measuring the saturated conductivity of the soil
(Otis, Plews and Patterson, 1978). In one series of tests, variability
was as high as 90 percent, therefore, if the percolation rate is the
only criterion used for sizing the soil absorption system, failures may
occur due to the high variability of the test results and their
inappropriate usage in system design. Saturated hydraulic conductivity
-43-
-------
Table 9: Falling Head Percolation Test Procedure
(U.S. Environmental Protection Agency, October 1980).
1. Number and Location of Tests
Commonly a minimum of three percolation tests are performed within the
area proposed for an absorption system. They are spaced uniformly
throughout the area. If soil conditions are highly variable, more tests
may be required.
2. Preparation of Test Hole
The diameter of each test hole is 6 in., dug or bored to the proposed
depths at the absorption systems or to the most limiting soil horizon.
To expose a natural soil surface, the sides of the hole are scratched
with a sharp pointed instrument and the loose material is removed from
the bottom of the test hole. Two inches of 1/2 to 3/4 in. gravel are
placed in the hole to protect the bottom from scouring action when the
water is added.
3. Soaking Period
The hole is carefully filled with at least 12 in. of clear water. This
depth of water should be maintained for at least 4 hr and preferably
overnight if clay soils are present. A funnel with an attached hose or
similar device may be used to prevent water from washing down the sides
of the hole. Automatic siphons or float valves may be employed to
automatically maintain the water level during the soaking period. It
is extremely important that the soil be allowed to soak for a sufficiently
long period of time to allow the soil to swell if accurate results are to
be obtained.
In sandy soils with little or no clay, soaking is not necessary. If,
after filling the hole twice with 12 in. of water, the water seeps
completely away in less than ten minutes, the test can proceed immediately.
4. Measurement of the Percolation Rate
Except for sandy soilds, percolation rate measurements are made 15 hr hut
no more than 30 hr after the soaking period began. Any soil that sloughed
into the hole during the soaking period is removed and the water level is
adjusted to 6 in. above the gravel (or 8 in. above the bottom of the hole).
At no time during the test is the water level allowed to rise more than
6 in. above the gravel.
Immediately after adjustment, the water level is measured from a fixed
reference point to the nearest 1/16 in. at 30 min intervals. The test is
continued until two successive water level drops do not vary by more than
1/16 in. At least three measurements are made.
-44-
-------
Table 9 Continued
After each measurement, the water level is readjusted to the 6 in. level.
The last water level drop is used to calculate the percolation rate.
In sandy soils or soils in which the first 6 in. of water added after
the soaking period seeps away in less than 30 rain, water level measure-
ments are made at 10 min intervals for a 1 hr period. The last water
level drop is used to calculate the percolation rate.
5. Calculation of the Percolation Rate
The percolation rate is calculated for each test hole by dividing the
time interval used between measurenents by the magnitude of the last
water level drop. Tliia calculation n-sults in n percolation rate in
terms of mln/ln. To determine the pcieolation race Tor the area, the
rates obtained from each hole are .iveraged. (If tests in the area vary
by more than 20 min/in., variation:, in soil type are indicated. Under
these circumstances, percolation r.'tes should not be averaged.)
Example: If the last measured drop in water level after 30 min is 5/8 in.,
the percolation rate = (30 min)/(5/8 in.) = 48 min/in.
-45-
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Table 10: Estimated Hydraulic Characteristics of Soil
(U.S. Environmental Protection Agency, October 1980).
Soil Texture Permeability Percolation
(in./hr) (min/in.)
Sand >6.0 <10
Sandy loams
Porous silt loams 0.2-6.0 10-45
Silty clay loams
Clays, compact
Silt loams <0.2 >45
Silty clay loams
-46-
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Table 11: Soil Absorption System Area Requirements for Single Housing Units
(U.S. Public Health Service, 1967).
Percolation Rate (Time Required Absorption Area3, in
Required for Water to Square Feet per Bedroom , for
Fall 1 in.) (minutes) Standard Trenchc and Seepage
Pitsd
1 or less
2
3
A
5
10
15
30e
A5e
60e'f
70
85
100
115
125
165
190
250
300
330
a
Provides for garbage grinders and automatic-sequence washing machines.
In every case, sufficient area should be provided for at least two
bedrooms.
Absorption area for standard trenches is figures as trench-bottom area.
Absorption area for seepage pits is figured as effective side-wall area
beneath the inlet.
g
Unsuitable for seepage pits if ov< r 30.
Unsuitable for leaching systems if over 60.
-47-
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Table 12: Recommended Rates of Wastew.iter Application for Trench and
Bed Bottom Areas (U.S. Environmental Protection Agency,
October 1980).
Percolation
Soil Texture Rate
(min/in. )
Gravel, coarse sand <1
Coarse to medium sand 1-5
Fine sand, loamy sand 6-15
Sandy loam, loam 16-30
Loam, porous silt loam 31 - 60
Silty clay loam, clay loam 61 -120
Application
Rate5.
(gpd/fO
Not suitable
1.2
0.8
0.6
0.45
0.2e
May be suitable estimates for sidewall infiltration rates.
Rates based on septic tank effluent from a domestic waste source.
A factor of safety may be desirable for wastes of significantly
different character.
Q
Soils with percolation rates <1 min/in. can be used if the soil is
replaced with a suitably thick (>2 ft) layer of loamy sand or sand.
Soild without expandable clays.
A
These soils may be easily damaged during construction.
-48-
-------
does not reveal how the soil will conduct wastewater under prolonged use,
because once the surface mat is formed, the liquid movement is through
unsaturated soil below. As noted in Table 10, the percolation rate is
related to soil texture and permeability (hydraulic conductivity).
Classes of soil permeability have been defined, with the class limit
values representing saturated or maximum permeability (Otis, et al.,
1977). If the moisture content of the soil decreases the permeability
also decreases; therefore, soils can have an infinite number of
permeabilities. Sand has relatively large pores that drain abruptly at
relatively low tensions, whereas clay releases only a small volume of
water over a wide tension range due to its very fine pores. Figure 9
shows soil moisture retention for four different soil materials (U.S.
Environmental Protection Agency, September 1978). Figure 10 shows
hydraulic conductivity as a function of soil moisture tension (U.S.
Environmental Protection Agency, September 1978). A field method has
been developed to directly measure the unsaturated hydraulic
conductivity of soils. However, it is a complex technique that requires
both time and trained technicians. Therefore, the short-term
traditional percolation test is still used for most soil evaluations
prior to soil absorption system desLgn and installation (Otis, Plews and
Patterson, 1978).
It has been well demonstrated chat the infiltrative capacity of the
liquid-soil interface controls the long-terra capacity of the drainfield
system, and that this infiltration rate, due to the various clogging
effects which occur, will always be less than the percolation rate of
the soil (Cotteral and Norris, 1969). A typical time-rate infiltration
curve representing three distinct phases in the infiltration process can
-49-
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60
50
40
z
8 30
IU
-------
IOOO-:
_ IOO-
2
O
8
10-
0-
0 I-
249 -
2O 4O CO 80 100
SOIL MOISTURE TENSION (MBAR)
DRYING »
Figure 10: Hydraulic Conductivity of Soils (U.S. Environmental
Protection Agency, Septt-mber 1978)
-51-
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be defined as shown in Figure 11. Phase 1 reflects Che initial loss of
infiltration rate due to slaking of the soil caused by the affinity of
the internal soil surface for water and the breakdown of cohesive forces
which hold the soil together. Phase 2 represents an increase due to the
removal of entrapped air by solution in the percolation water. Phase 3
represents a long-term decrease due primarily to microbial action in the
soil. Although in reality no equilibrium rate is ever reached, a
reasonably stable rate may be expected after a period of from 5 months
to 1 year. It has further been shown that the long-term infiltration
rate of sewage into permeable soils eventually declines to about the same
negligible quantity regardless of the difference in soil permeabilities
in the beginning.
The process of soil clogging and resultant loss of infiltrative
capacity as shown in Figure 11 occurs as a result of combined physical,
chemical and biological factors. Physical factors include the
compaction of the soils by ponded water or equipment, smearing of soil
surfaces by excavating equipment, and physical movement of fines into the
voids of the infiltrative surface. The most important chemical factor
is the deflocculation of soils when they are irrigated with high-sodium-
percentage waters. A high percentage of sodium in the wastes, either
naturally occurring or resulting from water softener regeneration, may in
effect preclude the use of soil absorption systems. Biological factors
are the most important influencing the clogging phenomenon. The major
reduction of infiltrative capacity shown as Phase 3 in Figure 11 results
from the formation of an organic mat about 5 mm thick at the liquid-soil
interface. It is within this zone that the major biological activity
-52-
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10
10
30
iO
6tj
Figure 11: Typical Time-Rate Infiltration Curve for Soil Absorption
System (Cotteral and Norris, 1969)
-53-
-------
occurs, and it is here Chat the processes of deposition of suspended
materials, bacterial build-up, and decomposition of organic material by
bacterial action continually modify the infiltrative capacity.
Anaerobic conditions within the clogging zone will lead to further
clogging through the growth of slimes and the deposition of ferrous
sulfide in an even deeper zone of 2 in. to 3 in. beyond the surface
(Cotteral and Norris, 1969).
Healy and Laak (1974) conducted a literature survey and concluded
that there is a long-term acceptance rate, which is a function of the
soil permeability, at which septic tank effluent can be absorbed
indefinitely. This acceptance rate is independent of whether the soil
is continuously or intermittently flooded, and varies from approx 0.3
gpd/sq ft for a soil with a permeability of 0.0002 ft/min (6 x 10~5
m/min) to approx 3.0 gpd/sq ft (12 cm/day) for a soil with a
permeability of 0.1 ft/min (0.03 m/min).
In a related matter to general soil absorption system clogging, it
has been determined that the sidewall area of a trench is the major
infiltrative surface, and that the bottom area is of minor importance.
The effects of slaking of the soil particles and the more rapid clogging
of bottom surfaces by sedimentation contribute to this phenomenon. The
finding leads to the conclusion that deep, narrow trenches are the most
effective. The minimum desirable width of drainfield trenches appears
to be determined primarily by practical considerations of construction
(Cotteral and Norris, 1969).
The percolative and infiltrative capacity of a soil cannot be
predicted by comparing its particle size characteristics with those of
-54-
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other soils for which these capacities have been established.
Nevertheless, there are several broad observations which can be made
concerning the effect of soil particle size on absorption field
performance. Where small soil grain size makes the effects of surface
tension and capillarity a major consideration, a minimum length of soil
column becomes necessary to produce complete draining of the soil
adjacent to infiltrative surface areas. Failure to provide this minimum
soil column length, by construction, for example, in an area with a high
ground water table, will lead to continued inundation and failure. If
drainage is to take place at all, the infiltrative surface must be
sufficiently above the ground water surface to overcome capillary forces.
The critical distance varies from soil to soil, but is on the order of 3
ft in many fine-grained soils having good percolative capacity (Cotteral
and Norris, 1969).
The topographic and geological characteristics of the soil
absorption system site can affect performance. Examples of factors which
should be considered in determining the suitability of a given site are
the ground slope, ground water level, depth of the soil mantle, and
location in relation to surface water streams and wells. The ground
slope can affect the stability of hillside trenches, the cost of
construction of the soil absorption system, and the distance that the
effluent from the system will travel through the soil without surfacing.
The ground water level should be low enough to assure that the minimum
soil depth necessary to prevent inundation of the drainfield is
maintained throughout the year. As inundation may lead to irreversible
clogging of the infiltrative surface, suitability should be determined
-55-
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on Che basis of the maximum height of the ground water table during the
wet season. The depth of the soil mantle at the site should be
sufficient to receive and transport the effluent from the piping system.
Consideration should be given to the depth and profile of the underlying
rock formation to ensure that it will not contribute to the inundation
of the drainfield nor short-circuiting and subsequent surfacing of the
effluent from the system piping (Cotteral and Norris, 1969).
As was the case for septic tank placement, location of the soil
absorption system on the site involves consideration of minimum setback
distances from various natural features or built structures. Minimum
drainfield setback distances used by the Federal Housing Authority,
Uniform Plumbing Code, and several California counties are listed in
Table 13 (Cotteral and Norris, 1969).
The pollutional strength and volume of the wastewater should be
considered prior to designing the soil absorption system. Three types
of drainfield loading can be utilized, including continuous ponding,
dosing and resting,and uniform application without ponding. In the
continuous ponding method the infiltrative surface is covered at all
times with wastewater. This method has the advantage of increasing the
effective infiltrative area by submerging the sidewalls of the
drainfield trenches. It also increases the hydraulic gradient across
the infiltrative surface and this in turn may increase the infiltration
rate. However, since clogging occurs at the infiltrative surface there
will be no aeration at the surface and this may cause subsequent
problems in terms of both hydraulic flow and biological decomposition.
-56-
-------
Table 13: Setback Requirements for Dr.iinfields
(Cotteral and Norris, 1969).
Setback Requirements
Federal
Housing
Authority
Uniform
Plumbing
Code
San
Mateo
County
Santa
Cruz
County
(feet)
Santa
Clara
County
Contra
Costa
County
Marin
County
Drainfields To:
Buildings 5
Property lines 5
Wells 100
Creeks or streams
Cuts or embankments
Pools
Water lines 10
Walks and drives
Large trees
8
5
50
50
5
10
75
20
20
25
5
5
100
100
15
10
10
100
10
10
5
50
50
50
10
5
10
10
5
100
25
25
25
-57-
-------
To overcome some of the concerns related to continuous ponding,
dosing and resting can be utilized. This approach provides reaeration in
that periods of loading are followed by periods of resting. The resting
phase allows the soil to drain and reaerate, thus encouraging
degradation of the clogging mat which may build up at the infiltrative
surface.
The process of alternate dosing and resting of a drainfield can
therefore markedly prolong the effective life of the system. For
practical purposes the resting period required for restoration appears
to be on the order of several months (Cotteral and Norris, 1969). In
uniform application without ponding the liquid is distributed uniformly
over the entire infiltrative surface at a rate lower than that which the
soil can accept liquid. Therefore, the soil always remains unsaturated
and aerobic conditions prevail at the infiltrative surface. When these
aerobic conditions prevail, the resistance of the clogging mat is
minimized.
As mentioned earlier, trench and bed systems are the most commonly
used designs for soil absorption systems. Bed systems usually require
less total land area and are less costly to construct. However, trench
systems can provide up to five times more sidewall area than do bed
systems for identical bottom areas. Less damage is likely to occur to
the soil during construction because the excavation equipment can
straddle the trenches so it is not necessary to drive on the infiltrative
surface. On sloping sites, trench systems can follow the contours to
maintain the infiltrative surfaces in the same soil horizon and keep
excavation to a minimum. Bed systems may be acceptable where the site
-58-
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is relatively level and the soils are sandy and loamy sands. Trench
system design factors utilized by the Federal Housing Authority, U.S.
Public Health Service, and Uniform Plumbing Code are summarized in Table
14 (Cotteral and Norris, 1969). Table 15 summarizes state setback
requirements and design factors for trench systems (Senn, 1978).
Design of trench and bed soil absorption systems for small
institutions, commercial establishments, and clusters of dwellings
generally follows the same design principles as for single dwellings. In
cluster systems serving more than about five homes, however, peak flow
estimates can be reduced because of flow attenuation, but contributions
from infiltration through the collection system must be included.
Flexibility in operation should also be incorporated into systems
serving larger flows since a failure can create a significant problem.
Alternating bed systems should be considered. A three-field system can
be constructed in which each field contains 50% of the required
absorption area. This design allows flexibility in operation. Two beds
are always in operation, providing 100% of the needed infiltrative
surface. The third field is alternated in service on a semi-annual or
annual schedule. Thus, each field is in service for one or two years
and "rested" for 6 months to one year to rejuvenate. The third field
also acts as a standby unit in case one field fails. The idle field can
be put into service immediately while a failed field is rehabilitated.
Larger systems should utilize some dosing or uniform application to
assure proper performance (U.S. Environmental Protection Agency, October
1980).
-59-
-------
Table 14: Design Factors for Trench System Drainfields
(Cotteral and Norris, 1969).
Data
Percolation test used
Surface used for design
Federal
Housing
Authority
yes
bottom
U.S. Public
Health
Service
yes
bottom
Uniform
Plumbing
Code
as req'd3
bottom
Trench width required, in
inches
12-36
12-36
18-36
Gravel depth below tile, in
inches
Minimum sidewall area,
in square feet
Sidewall area, in square
feet per bedroom
15 min per inch
percolation rate
30 min per inch
percolation rate
60 min per inch
percolation rate
Minimum trench spacing,
in feet
Replacement area req'd,
as a percentage
190
250
330
140
190
250
330
200
80
120
50
As required by the Health Department
Where design is based on bottom area, sidewall area was calculated
based on minimum depth and width requirements.
-60-
-------
Table 15: Summary of State Setback Requirements and Design Factors
for Trench Systems (Senn, 1978).
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Setbacks
Well
50-75
50-100
50-100
-
-
100
75
-
75-100
100
-
100
-
50-100
100-200
-
100
100-300
-
-
-
-
-
-
100
100
100
75
-
-
-
-
-
50
-
50-100
100
100
-
100
50
-
100
-
35-100
75-100
100
50-100
100
(fi-Ct)
Surface
Water
50-100
100
-
-
50
50
-
50
50
-
100-300
-
50
25
-
50-100
-
-
-
-
-
-
100
50
100
75
-
-
—
_
-
-
50-100
50
50
-
100
50
-
100
-
50-100
100
100
50
50
Minimum
Spacing
(Feet)
6
6
6
-
-
6
6-9
-
6-8
10
-
6
-
6-7.5
7.5
-
10
-
-
-
-
-
-
6
6
6
6-7.5
-
-
_
_
_
6
—
10
6
6
-
6
6
—
6-7.5
-
6-9
6
6
10
6-7.5
Minimum
Cover
(Inches)
6
12
12
-
-
12
6
-
12
12
—
12
-
12
12
-
None
6-12
2-6
-
-
-
-
-
-
12
6
4-6
6
-
-
_
_
_
6
_
6
12
12
_
12
—
12
—
None
6
12
12
6-12
-61-
-------
Table 15 Continued
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
Minimum
Percolation
Restrictions
None
None
None
-
-
None
None
-
None
None
-
None
-
None
None
-
None
None
-
-
-
-
-
-
Yes
No
Yes
None
-
-
-
-
-
None
-
None
Yes
None
-
Yes
None
-
None
-
None
Yes
None
None
None
Trench
Widths
(Inches)
18-36
12-36
12-18
-
-
18-36
18-36
-
18-24
18-36
-
12-36
-
18-36
18
-
12-18
24
-
-
-
-
-
-
12-36
10-36
12-24
12-36
-
-
-
-
-
8-30
-
24
12-36
18
-
18-36
-
12-36
-
18-36
18-36
12-36
18-36
12-36
Sizing
Perc
Perc & Soils
Perc
-
-
Perc
Perc
-
Pure & Soils
Perc & Soils
-
Perc & Soils
-
Perc
Perc
-
Perc
Perc
Soils
-
-
-
-
-
-
Perc & Soils
Perc
Perc
Perc
—
-
-
-
-
Soils
-
Soils
Perc
Perc
-
Perc
Perc & Soils
-
Perc
-
Perc & Soils
Perc & Soils
Perc
Perc & Soils
Perc
-62-
-------
OVERVIEW OF SEPTIC TANK-MOUND SYSTEMS
Many soils in the United States are not suited for on-site disposal
of wastewaters using conventional septic tank systems. Examples are
slowly permeable soils (defined as having a percolation rate slower than
60 min./inch), thin-layered permeable soils over very permeable creviced
bedrock, and soils with periodic or permanent high ground water. A
general requirement for on-site waste disposal is the availability of at
least 3 feet of sufficiently permeable unsaturated soil below the bottom
of the seepage bed. An estimated 50 percent of the soils of Wisconsin
do not meet this requirement and are thus unsuitable for on-site
disposal. An engineering modification of the conventional septic tank-
soil absorption system can be used to overcome natural soil limitations,
with the modification known as the septic tank-mound system. The mound
system is essentially an elevated soil absorption system. The main
components of a septic tank-mound system include the septic tank, a
pumping chamber, and the mound itself. Most of the developmental work on
septic tank-mound systems has been done in Wisconsin.
The septic tank in a septic tank-mound system is sized in the same
manner as the septic tank in the conventional septic tank system. A pump
then elevates the effluent from the tank and pressurizes the
distribution within the mound. A siphon may replace the pump if the
mound is located downslope (Converse, 1978). Figure 12 depicts a typical
Wisconsin mound system (Harkin, et al., 1979). The mound is comprised
of a fill material (usually medium-textured sand), an absorption area, a
distribution system, a cap, and topsoil. The effluent flows through the
fill material where it is purified before entering the natural soil.
-63-
-------
FROV
HOUSE R-ri
/- WATER
/ LEVEL
ft
PERFORATED PVC PIPE
SAND FILL
CLAY FILL OR TOPSOIL
TOPSOIL
SEPTIC TANK
STONE FILL-
PLOWED SURFACE
"* *«
HIGH WATER
ALARM SWITCH
PUMP
x PUMP SW'TCH
PUMPING CHAMBER
Figure 12: Typical Wisconsin Mound System (Harkin, et al., 1979)
-------
The cap, which is usually comprised of topsoil or subsoil, provides
frost protection, serves as a barrier to infiltration, retains moisture
for vegetation, and promotes runoff of precipitation. A minimum of 24
inches of unsaturated natural soil under the mound is recommended
(Converse, 1978). This natural soil provides additional purification and
acts as a buffer protecting ground water from potential contamination.
There are several advantages and disadvantages of a septic tank-
mound system. The advantages are .is follows:
1. The topsoil can be selected to be more permeable than the
subsoil.
2. There is less chance of changing the hydraulic characteristics
of the soil during compaction as construction is eliminated in
the wetter subsoil.
3. Slimes that develop in the bottom of the absorption area do
not clog the fill as readily as they do in less permeable
natural soil.
4. A smaller absorption area is required for a given quantity of
wastewater when compared to the traditional septic tank
system.
5. There is a reduction in the nitrate nitrogen leaving the
system due to denitrification processes.
In contrast to the advantages enumerated above, the septic tank-
mound system has certain disadvantages as follows:
1. Septic tank mound systems exhibit increased cost over
traditional septic tank systems due to the cost of the fill
material and its placement.
2. Construction of the mound will change the landscape and
possibly the visual quality of the environmental setting.
3. Even though the absorption area within the mound is smaller,
the mound itself may comprise a larger area than the soil
absorption system would encompass in the conventional septic
tank system.
-65-
-------
In summary relative to septic tank-mound systems, they represent an
alternative approach to the traditional septic tank system in areas
where the soil characteristics are insufficient for use of the
conventional system. Care must be taken to appropriately evaluate the
features and characteristics of the septic tank-mound system and
determine its applicability in a given geographical area.
-66-
-------
CHAPTER 3
GROUND WATER POLLUTION FROM SEPTIC TANK SYSTEMS
One of the key concerns associated with the design and usage of
septic tank systems is the potential for inadvertently polluting ground
water. This concern is increased when considerating systems serving
multiple housing units. This chapter begins with the identification of
constituents of potential concern in the effluents from septic tank
systems. Mechanisms of ground water contamination from septic tank
systems are addressed, including the migration of pollutants through soil
and ground water systems. The transport and fate of biological
contaminants are described, with information included on both bacteria
and viruses. The transport and fate of inorganic chemicals are also
described, with emphasis given to phosphates and nitrogen compounds as
well as chlorides, metals, and other inorganic contaminants. Brief
information is included on the transport and fate of organic
contaminants; the brief coverage is due to the lack of extensive
information in the published literature. Some information on pollution
control measures is presented. Ground water monitoring for septic tank
systems is also addressed. Finally, a special section is included on
the handling of septage.
POTENTIAL POLLUTANTS FROM SYSTEM EFFLUENTS
Potential ground water pollutants from septic tank systems are
primarily those associated with domestic wastewater. Contaminants
originating from system cleaning can also contribute to the ground water
pollution potential of septic tank systems. The volume of wastewater
-67-
-------
introduced to a septic tank system from a typical household unit ranges
from 40 to 45 gpd/person (150 to 170 liters/day/person) (U.S.
Environmental Protection Agency, 1977). Typical sources of household
wastewater, expressed on a percentage basis, are: toilet(s) — 22 to
45%; laundry — 4 to 26%; bath(s) — 18 to 37%; kitchen — 6 to 13%; and
other — 0 to 14%. The quality characteristics of wastewater entering
septic tank systems are summarized in Table 16 (Bauer, Conrad and
Sherman, 1979). The data in Table 16 excludes contributions from
garbage disposal units and home water softeners. Garbage disposal
contributions are excluded since they can contribute substantial
quantities of pollutants which can be effectively disposed of as solid
wastes without entering septic tank systems.
To provide a basis for comparison of quality characteristics, Table
17 summarizes the typical composition of community domestic wastewater
in accordance with weak, medium, and strong concentrations of a variety
of constituents (Council on Environmental Quality, 1974). Table 18
displays the average characteristics of septic tank influents in
relation to medium strength domestic wastewater. The physical and
chemical constituents are reasonably comparable in their concentrations,
although individual studies of septic tank influents may indicate that
the organic strength of household wastewater (septic tank influent) is
greater than the organic strength of medium community wastewater
(Viraraghavan, 1976). Bacterial counts in household wastewater tend to
be lower than in community wastewater, with a possible cause being a
shorter incubation time from the house (source) to the septic tank in
-68-
-------
Table 16: Characteristics of Influent Wastewaters to Septic Tank Systems*
(Bauer, Conrad, and Sherman, 1979).
Constituent
(B/cap/dV
BOD
BOD5 filtered
COD
TOC
TOC filtered
TS
TVS
SS
VSS
TKN
NH3-N
N03-N
N02-N
TP
PO.-P
4
Oil & Grease)
MBAS
flow (Ipcd)
Investigator
Olson
Karlgren, and
Tullander
45
-
120
-
-
130
83
48
40
12.1
-
-
-
3.8
-
-
-
131.5
re
(0
48.7
-
119.4
-
-
-
-
-
-
-
3.2
0.1
-
-
4.0
-
-
156.7
Bennett and
Lindstedt
34.8
-
121.5
-
-
146.3
74.6
47.3
41.6
6.5
-
-
-
-
3.7
-
-
165.3
CO
•H
(J
00
^
0
- 09
JJ
4J "0
•H C
Z£ «J
49.5
30.4
-
32.1
22.0
113.4
63.1
35.4
26.6
6. 1
1.3
0.1
-
4.0
1.4
14.6
-
119.4
C/J
in
49.5
30.4
-
32.1
22.0
113.4
63.1
35.4
26.6
6. 1
1.3
0.1
-
4.0
1.4
-
-
161.2
Weighted Value
48
30
120
32
22
125
70
40
31
6
2
0.1
-
4
1.4
15
3
160
Constituent
(mg/O
300
188
750
200
138
781
438
250
194
38
12
0.6
-
25
8.8
94
19
Also excludes garbage disposal conti ibutions
Data have been rounded
-69-
-------
Table 17: Typical Characteristics of Domestic Sewage in the United States
(Council on Environmental Quality, 1974).
Constituent
Weak
Medium
Strong
i
>j
o
Color (nonseptic)
Color (septic)
Odor (nonseptic)
Odor (septic)
Temperature- F (average)
Total solids* (mg/1)
Total volatile solids (mg/1)
Suspended solids (mg/1)
Volatile suspended solids (mg/1)
Settleable solids-(ML)
L
pH (units)
Cl, SO^, Ca, Mg, etc.*
Total nitrogen (mg/1)
Organic nitrogen (mg/1)
Ammonia nitrogen (mg/1)
Nitrate nitrogen (mg/1)
Total phosphate-PO^ (mg/1)
Total bacteria
Total coliform
( MPN )
100 ml
Biochemical oxygen demand
Physical Characteristics
Gray
Gray-Black
Musty
Mugty-H2S
450
250
100
75
2
Chemical Characteristics
6.5
15
5
10
Biological Characteristics
1 x 108
1 x
100
Gray
Blackish
Musty
H2S
55°-90°
800
425
200
130
5
7.5
40
14.5
25
0.5
15
30 x 108
200
Gray
Blackish
Musty
1200
800
375
200
7
8.0
60
19
40
1.0
30
100 x 10e
100 x
450
* Quite variable depending on natural water quality of region.
-------
Table 18: Comparison of Septic Tank Influent Wastewater with Community
Domestic Wastewater
Constituent
Community
Wastewater (1)
Septic Tank
Influent
Wastewater (2)
Total solids (mg/1)
Total dissolved solids (mg/1)
Total suspended solids (mg/1)
5-day BOD (mg/1)
Total organic carbon (mg/1)
Total nitrogen (as N, mg/1)
Organic
Ammonia
Nitrate
Total phosphorus (as P, mg/1)
Total bacteria (counts/100ml)
Total coliform (MPN/100ml)
Fecal coliform (MPN/100ml)
Fecal streptococci (MPN/100ml)
Enteric Virus (PFU/1)
800
600
200
200
200
40
14.5
25
0.5
15
30 x 108
30 x 106
n.d.
n.d.
7000 (4)
781
531
250
300
200
50
38
12
0.6
25
5.6-8 x 107 (3)
2 x 106 (3)
3 x 104 (3)
3 x 101* (3)
32 - 7000 (5)
(1) Based on medium strength wastewater as shown in Table 17.
(2) Based on averages shown in Table 16.
(3) Viraraghavan (1976).
(4) Vilker (1978).
(5) Siegrist (1977).
-71-
-------
comparison with the time from the source to the community treatment
plant.
In regard to the virological characteristics of individual
household wastewater, very little characterization research has been
conducted (Siegrist, 1977). Virus are generally not part of the normal
microbial flora of healthy individuals and unlike the bacteria, appear
to be shed in significant concentrations only as a result of an
infection. Assuming a viral concentration of 10^ PFU/wet gram of feces
for a typical individual experiencing an intestinal viral infection, it
can be estimated that the concentration in the individual's wastewater
could reach 10? PFU/liter. As expected, investigations of raw municipal
wastewater have demonstrated considerably lower levels. One
investigator estimated the level of virus to be about 7000 PFU/liter,
while another reported recoveries of only 32 to 107 PFU/liter (Siegrist,
1977).
Of concern in terms of ground water pollution is the quality of the
effluent from the septic tank portion of the system, and the efficiency
of constituent removal in the soil underlying the soil absorption
system. Those constituents which pass through the septic tank and the
unsaturated soil beneath the drainfield represent ones of concern
relative to ground water pollution. Numerous studies have been made of
the treatment efficiencies and effluent qualities from septic tanks,
with fewer reported studies related to soil absorption system
efficiencies.
The septic tank serves several important functions such as solid-
liquid separation, storage of solids and floatable materials, and
-72-
-------
anaerobic treatment of both stored solids as well as non-settleable
materials. Viraraghavan (1976) reported on a study of a household two-
compartment septic tank serving 12 persons. The tank volume was 200
ft^, with 148 ft^ in the first compartment and 52 ft^ in the second.
The average flow rate was 327 gal/day (27.3 gal/person/day), thus the
theoretical detention time was 4.6 days (not accounting for sludge
accumulation). Table 19 summarizes the statistics associated with the
treatment efficiency of the sepi Lc tank. The BOD and COD removal
efficiencies were in the order of 50% on the average, with the TSS
removal less than 25%.
Lawrence (1973) reported on the efficiencies of two single chamber
septic tanks each having a liquid capacity of 740 gal. Tank 1 received
domestic and laundry wastes from a family of six. The household water
supply was a hard, high-iron water taken from a private well and treated
by ion exchange. Waste brine from regeneration was not allowed to enter
the system. At the time of this study, the tank had been in continuous
operation for five years and, with the exception of scum removed after
the first two years of operation, had not been cleaned prior to this
investigation. Tank 2 served a family of five and received only
domestic wastes without laundry discharge. Household water was from a
municipal supply softened by the cold lime process. At the time of this
study the tank had been in service five years and had not been serviced
since its installation. Observations on water consumption by each
household revealed an average daily flow of 186 gpd (31 gpd/capita) for
the first and 245 gpd (49 gpd/capita) for the second. This indicates
theoretical detention times of four and three days, respectively;
-73-
-------
Table 19: Summary of Treatment Efficiency of a Septic Tank
(Viraraghavan, 1976).
->l
4>
Characteristics (1)
Influent
Time Equal to
or Less Than:
15%
50%
85%
Effluent
Time Equal to
or Less Than;
15%
50%
85%
Efficiency
Time Equal to
or Less Than:
15%
50%
85%
pH (units)
TSS
BOD
COD
SOC
PO^-P
NH3-N
NO^-N
Total soluble iron
Chlorides
Total coliform/100 ml
Fecal coliform/100 ml
Fecal streptococci/ 100 ml
SPC per milliliter (35°C)
SPC per milliliter (20°C)
Psuedomonas aeruginosa/ 100ml
6.45
80
362
350
70
0.0
17.0
0.0
0.0
0.0
2.2xl05
1.5xl03
l.SxlO3
1.3xl05
1.4xl05
-
7.60
200
520
1000
280
14.0
47.0
0.10
1.50
130.0
2xl06
3x10-*
3x10**
5.6xl05
8xl05
150
8.7
320
670
1650
470
32.0
75.0
0.19
3.0
260
1.6xl07
6.6xl05
5.6xl05
2.5xl06
4.7xl06
4xl03
6.65
80
170
300
35
6.5
80
0.0
0.0
35
3.7xl05
IxlO1*
2.2X101*
SxlO1*
4.2xl05
<2
6.90
165
280
550
70
10.5
92
0.02
2.25
50
2.3xl06
1.6xl05
l.lxlO5
3xl05
8.2xl05
28
7.15
250 nil 18
350 53 46
800 14 45
105 50 75
14.0
105
0.04
4.75
67
1.45xl07
2.6xl06
S.lxlO5
1.7xl06 o2 46
1.6xl06
520 81
22
48
52
78
32
87
(1) mg/1 unless noted otherwise.
-------
however, due to Che sludge and scum volume and the fact that quite
frequently, two-thirds of the daily flow of wastewater was generated in
less than four hours, the effective detention time for both tanks was a
matter of a few hours. Table 20 summarizes the measured efficiencies.
The wide range in influent and effluent quality and efficiencies may be
attributed to the difference in water consumption (both total and per
capita) between the two households and the fact that household laundry
wastes were excluded from tank 2 but not tank 1. The suspended solids
removals were in the order of 35 to 45%, with the BOD removals being 15%
or less.
The quality of the effluent from a septic tank is of greater
importance in terms of ground water pollution than its treatment
efficiency. A summary of the physical and chemical parameter effluent
qualities measured for 7 septic tank systems is in Table 21 (University
of Wisconsin, 1978). Additional summary information from a study of 34
more tanks is in Table 22 (U.S. Environmental Protection Agency, October
1980). Based on the composite information in Tables 21 and 22, the
following represent typical physical and chemical parameter effluent
concentrations from septic tanks:
Suspended solids 75 mg/1
BOD5 140 mg/1
COD 300 mg/1
Total nitrogen 40 mg/1
Total phosphorus 15 mg/1
Table 23 summarizes the bacteriological character of household
septic tank effluent (Siegrist, 1977; and University of Wisconsin,
1978). The quantities of indicator bacteria such as fecal coliform are
high, and pathogenic bacteria such as Pseudomonas aeruginosa, have
-75-
-------
Table 20: Summary of Treatment Efficiencies of Two Septic Tanks
(Lawrence, 1973).
Tank No. Parameter
Total solids
Volatile solids
Suspended solids
Volatile suspended solids
1 BOD
Settleable solids
PH
Detergents
Grease
Total solids
Volatile solids
Suspended solids
Volatile suspended solids
2 BOD
Set table solids
PH
Detergents
Grease
Influent
1128
483
200
159
241
4.4
7.5
43
21
512
249
126
108
146
0.7
7.2
3.7
16
Effluent
1034
420
130
107
224
0.2
7.5
49
26
505
239
70
73
124
0.06
7.2
5.0
8.5
Percentage
Reductance
8
13
35
33
7
85
0
0
1
4
44
32
15
91
0
47
-76-
-------
Table 21: Summary of Effluent Quality from Seven Septic Tanks
(University of Wisconsin, 1978).
Parameter and Statistics
Results(1)
Suspended Solids, mg/L
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
Volatile Suspended, mg/L
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
BOD5 (Unfiltered) mg/1
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
BOD5 (filtered), mg/L
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
COD, mg/L
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
Total Phosphorus, mg-P/L
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
Orthophosphorus, mg-P/L
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
Total Nitrogen, mg-N/L
Mean (// of Samples)
Coeff. of Variation
95% Conf. Int.
Range
49(148)
0.16
44-54
10-695
35(148)
0.18
32-39
5-320
138(150)
0.42
129-147
7-480
190(130)
0.47
100-118
7-330
327(152)
0.33
310-344
25-780
13(99)
0.34
12-14
0.7-99
11(89)
0.36
10-12
3-20
45(99)
0.40
41-49
9-125
-77-
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Table 21 Continued
Parameter and Statistics Results(1)
Ammonia Nitrogen, mg-N/L
Mean (// of Samples 31(108)
Coeff. of Variation 0.46
95% Conf. Int. 28-34
Range 0.1-91
Nitrate Nitrogen, mg-N/L
Mean (// of Samples) 0.4(114)
Coeff. of Variation 6.7
95% Conf. Int. <0.1-0.9
Range <0.1-74
(1) Data from seven sites and collected over time period from May 1972
December 1976.
-78-
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Table 22: Summary of Effluent Quality from Various Septic Tank Studies
(U.S. Environmental Protection Agency, October, 1980).
Parameter
Suspended Solids
Mean, mg/1
Range, mg/1
No. of Samples
BOD5
Mean, mg/1
Range, mg/1
No. of Samples
COD
Mean, mg/1
Range, mg/1
No. of Samples
Total Nitrogen
Mean, mg/1
Range, mg/1
No. of Samples
7 Tanks
49
10-695
148
138
7-480
150
327
25-780
152
45
9-125
99
10 Tanks
155a
43-485
55
138a
64-256
44
-
-
-
-
-
™
19 Tanks
101
-
51
140
-
51
-
-
-
36
-
51
4 Tanks
V.
95b
48-340
18
240b
70-385
21
-
-
—
-
-
™
1 Tank
39
8-270
47
120
30-280
50
200
71-360
50
-
-
"
Sample-
Weighted
Average
77
142
296
42
Calculated from the average values from 10 tanks, 6 series of tests.
Calculated on the basis of a log-normal distribution of data.
-------
Table 23: Summary of HacU'rJ illogical CharacLi-r of ilousi-liolil Septic
Tunic Effluents
Reference
1
1
I
2
1
2
1
Organism
Total
bacteria
Total
coliform
Fecal
coliform
Fecal
coliform
Fecal
streptococci
Fecal
streptococci
Pseudomonas
aeruginosa
Number
of
Samples
88
91
94
151
97
155
33
Mean
(No./ 100 ml)
a
3.4 x 10
A
3.4 x 10
5
4.2 x 10
A
5.0 x 10"
3
30 v i n
.OX 1U
4.U X LU
q
8.6 x 10J
95%
Confidence
Interval
(no./ 100 ml)
g
2.5 to 4.8 x 10
g
2.6 to 4.4 x 10
5
2.9 to 6.2 x 10
6^
7
Z.5 x W to 1.0 x 10
3
2.0 to 7.2 x 10
3e
S
e.u x lu to 2.0 x 10
•»
3.8 to 19.0 x 10
Reference 1 = Siegrist (1977) data from 5 tanks.
Reference 2 = University of Wisconsin (1978) - - data from 7 tanks.
-80-
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commonly been isolated. In addition, results of analyses for
Staphylococcus aureus and salmonellae have indicated their presence in
septic tank effluents, but only infrequently and in much lower
concentrations (ten homes, 6 of 63 samples positive at 10-1000/100 ml
and eleven homes, 2 of 55 samples positive at 3.4-220/100 ml,
respectively) (Siegrist, 1977). Viruses in septic tank effluents are
high only if infections have occurred. Salmonellae have been detected
in 59% of 17 different septic tank pumpout sludges, which shows clearly
that septic effluents need to be purified before release to either
ground water or surface water (Bouraa, 1979).
Viraraghavan and Warnock (1976) conducted a field investigation
with the primary objective of determining the efficiency of a soil
absorption (drainfield tile) system. By "efficiency" is meant the
reduction in concentration of various parameters achieved between the
point at which the septic tank effluent was distributed to the tile and
the various depths in the soil at which soil water samples were
collected. The environmental effects of air and soil temperatures and
unsaturated depth of soil on the efficiency of the septic tile were
studied as a part of this investigation. The site of the study was near
Ottawa, Ontario, Canada. Significant climatic conditions in this region
that affected the study are low winter temperatures, usually with snow
cover, and a period of melting snow in the spring when ground water
levels are usually high. A visual examination of the soil samples taken
from various depths at the site indicated that the soil was sandy clay
for the initial depth of 2 ft (0.61 m), followed by clay with less sand
at depths of 2 to 5 ft (0.61 to 1.53 m). The characteristics of the
-81-
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septic tank effluent applied to the study site are listed in Table 24.
The results of the field study conducted from December, 1972, to
February, 1974 indicated the following for a 5 ft. deep traverse of the
underlying soil:
1. The soil had the ability to reduce a high percentage (75 to 90
percent) of the TSS, BOD, COD, and soluble organic carbon
present in the septic tank effluent.
2. Reductions of phosphates were usually in the 25 to 50 percent
range, much lower than those reported in the literature. This
has special significance for lake shore septic tank systems
since substantial amounts of phosphorus in the form of
phosphates may be added to lakes, thereby causing
eutrophication.
3. High ammonia reductions (80 to 90 percent) were observed; with
an increase in ammonia reduction, corresponding increases in
nitrification were generally observed. Nitrification leads to
nitrate build-up in ground water and nearby lakes, thus
causing possible health hazards and eutrophication.
4. Efficiency was influenced by seasonal variations. There were
greater efficiencies (80 to 90 percent) for the various
parameters during the late summer and early fall, extending
from September to November when the unsaturated depth of soil
was greater. These efficiencies tended to decrease to about
70 to 75 percent with respect to BOD and TSS, and to 20 to 35
percent for ammonia nitrogen, during the winter period when
the water levels started to rise. Nitrate nitrogen levels
also showed a declining trend during the winter months.
Based on the above-listed minimum and maximum percentage reductions
relative to the average effluent characteristics as shown in Table 24,
the following concentrations passed the 5 ft. depth (if the top of the
water table were at the 5 ft. depth, these would be the concentrations
entering the ground water):
TSS 18 - 53 mg/1
BOD 28 - 84 mg/1
COD 57 - 142 mg/1
SOC 7-18 mg/1
Total phosphates 6 - 9 mg/1
Ammonia nitrogen 10 - 78 mg/1
-82-
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Table 24: Characteristics of Septic Tank Effluent Applied to Study Site
(Viraraghavan and Warnock, 1976).
Characteristic
pH
TSS
BOD
COD
Soluble organic carbon
Total phosphates (PO.-P)
Ammonia nitrogen
Nitrate-N
Total soluble iron
Chlorides
Range
6.53
68
140
240
24
6.25
77
0.00
0.00
37
- 7.45
- 624
- 666
- 2,026
- 190
- 30.0
- Ill
- 0.10
- 20.0
- 101
Mean
Value
6.90
176
280
568
73
11.6
97
0.026
2.63
53
All values except pH are milligrams per liter.
-83-
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In addition Co the above constituents, others of concern relative
to ground water pollution from septic tank systems include:
Nitrates — Excessive concentrations of nitrates in drinking water
may cause a bitter taste. Water from wells containing more than 45
mg/1 of nitrates has been reported to cause methemoglobenemia in
infants. Organic and ammonia nitrogen in wastewater can be
converted to nitrate nitrogen within the septic tank system.
Organic contaminants — Within recent years there have been several
reported instances of organic contamination of ground water, with
some cleaning solvents for septic tank systems being identified as
potential sources (U.S. Environmental Protection Agency, May 1980).
The chief concern relating to organic contaminants is that many of
these substances are persistent within the subsurface environment
and they are known to be carcinogenic above certain concentration
levels. An example of one of these contaminants is
trichloroethylene.
Metals (lead, tin, zinc, copper, iron, cadmium, and arsenic) — The
concern relating to various metals is associated with their
potential toxic effects in excessive concentrations. This is
pertinent in terms of ground water usage as drinking water and the
movement of gound water into surface waters and subsequent effects
on the aquatic ecosystem.
Inorganic contaminants (sodium, chlorides, potassium, calcium,
magnesium, and sulfates) — These inorganic constituents in
excessive concentrations may cause undesirable health consequences
ranging from laxative effects to aggravated cardiovascular or renal
disease. These concerns are pertinent in terms of ground water
usage as drinking water.
In summary relative to the potential pollutants from septic tank
systems, there are a variety of pollutants of concern. Most of the
literature deals with bacterial and viral contamination along with the
introduction of nitrates in the ground water system. Additional
pollutants becoming increasingly important include organic contaminants
and several metals.
-84-
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MECHANISMS OF GROUND WATER CONTAMINATION FROM SEPTIC TANK SYSTEMS
Ground water degradation has occurred in many areas having high
densities of septic tank systems, with the degradation exemplified by
high concentrations of nitrates, bacteria, and other contaminants.
Recent studies indicate that significant amounts of organic contaminants
have been introduced into ground water through septic tank systems (U.S.
Environmental Protection Agency, May 1980). Septic tank problems are
magnified by the fact that in many areas, especially rural communities,
a substantial reliance on subsurface disposal systems is paralleled by a
reliance on private wells for drinking water supplies.
It has been estimated that as many as one-half of all septic tank-
soil absorption systems are not operating satisfactorily (Scalf, Dunlap
and Kreissl, 1977). One common failure is when the capacity of the soil
to absorb effluent from the tank has been exceeded, and the waste added
to the system moves to the soil surface above the lateral lines. This
type failure results from soil clogging and loss of infiltrative
capacity, and is caused by combined physical, chemical, and biological
factors. When system failure does occur from soil clogging and
wastewaters do seep to the surface, overland flow from rainfall may
carry contaminants directly to a stream or lake or into an inadequately
sealed well. This transport is shown in Figure 13 (Scalf, Dunlap and
Kreissl, 1977).
Another type of failure which is potentially of more significance
is when pollutants move too rapidly through soils. Many soils with high
hydraulic absorptive capacity (permeability) can be rapidly overloaded
-85-
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Reproduced from
bos! available COPY.
PRECIPITATION
tei
m~
r^i-
tiri* .
i .. . .. ,
GRAVEL PACK
CONTAfv'I.MATED ^ TOO CLOSE
WATER JT] f TO SURFACE
:—» '^L-^.
AQUIFER
i
r>- i i \t_oi i vir*-'.i L.II
•3^
~-:AQUICLUDE-~-r-
Figure 13: Effect of Clogged Absorption Field on Nearby Well
(Scalf, Dunlap, and Kreissl, 1977)
-86-
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with organic and inorganic chemicals and microorganisms, thus permitting
rapid movement of contaminants from the lateral field to the ground water
zone. This transport is shown in Figure 14 (Scalf, Dunlap and Kreissl,
1977). This type of system failure has been largely ignored until recent
years. The type and thickness of subsurface material is a major
determinant for this kind of failure (Scalf, Ounlap and Kreissl, 1977).
In considering ground water contamination from septic tank systems,
attention must be directed to the transport and fate of pollutants from
the soil absorption system through underlying soils and into ground
water. Physical, chemical and biological removal mechanisms may occur in
both the soil and ground water systems (Loehr, 1978). As septic tank
system effluent moves through the soil pores, suspended solids are
removed by filtration. The depth at which removal occurs varies with the
size of the particles, soil texture, and rate of water movement. The
larger the hydraulic application rate and the coarser the soil, the
greater the distance the particles will move. Adsorption, ion exchange,
and chemical precipitation are the most important chemical processes
governing the movement of constituents in the septic tank system
effluent. A key soil parameter is the cation exchange capacity (CEC);
the CEC of soils can range from 2 to 60 meq/100 grams of soil, with most
soils having a CEC value between 10 and 30. The differences occur
because soils vary widely in their humus and clay content, the
components that have the highest CEC. The biological transformations
that occur in the soil include organic matter decomposition and nutrient
assimilation by plants. Greater biological activity can be anticipated
in the upper layers of soil underneath the soil absorption system.
-87-
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CONTAMINATED WATERtQ LAND SURFACED
FRESH WATER
RECHARGE
*
Figure 14: Effect of a Pumping Well on Contaminated Water
Movement (Scalf, Dunlap, and Kreissl, 1977)
-88-
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While the focus of this discussion is on ground water contamination
from septic tank systems, pertinent: information from other sources such
as sanitary and chemical landfill leachates will also be included as
appropriate. The mechanisms of contamination are independent of
pollutant sources and dependent on pollutant types and soil and ground
water characteristics in the vicinity of the source.
Soil Systems
Pollutants have been found to interact with natural organic matter,
clays, and microorganisms in soils and sediments, and it is these
interactions that may render the chemical constituents in landfill
leachates more or less mobile (Van Hook, 1978). However, contaminants
have been found to travel several hundred meters beyond their point of
origin despite the attenuating characteristics of the soil (Lofty, et
al., 1978). The fate of pollutants in soils can be estimated by knowing
the characteristics of different soil types. Chun, et al. (1975),
conducted a two-year study to determine the removal characteristics of
selected Oahu soils with respect to the substances found in landfill
leachates. Soil ion exchange capacity was primarily responsible for
altering the concentration of inorganic substances, and microbial
degradation appeared to be the major mechanism in removal of organic
substances. The importance of the cation exchange capacity of soil was
first discussed by Bower, Gardner and Goetzen (1957).
A good soil system for receiving septic tank system effluents
should absorb all effluent generated, provide a high level of treatment
before the effluent reaches the ground water, and have a long, useful
-89-
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life (Otis, Flews and Patterson, 1978). Ideally, a soil should be able
to convert a pollutant into an unpolluted state at a rate equal to or
greater than the rate at which it is added to the soil (Andrews, 1978).
Bradford (1978) studied trace-elements in soil-plant-water systems and
attempted to determine how trace-element concentrations are modified
upon passage of water through the soils. Removal of elements in the
soil through plant uptake is another potential mechanism of pollutant
attenuation. Chemical reactions such as adsorption, fixation,
precipitation, and other soil interactions, all influence the transport
process. LeGrand (1972) studied the hydrogeological factors controlling
pollutant movement. Pertinent factors include the presence of clays to
retard movement and facilitate sorption, and the distance to the water
table to provide an opportunity for .ittenuation to occur.
Ground Water Systems
Ground water typically moves in the direction of the slope of the
water table, that is, from the area of higher water table to areas of
lower water table. Since the water table usually follows the general
contours of the ground surface, septic tanks should be located downhill
from wells or springs. Information on the mechanisms of pollutant
movement in ground water systems can be considered independent of the
specific waste source. In other words, nitrates within ground water
will move with certain typical characteristics irrespective of whether
the nitrates originate from a septic tank system or a landfill leachate.
Information in this section will be drawn from a variety of source
-90-
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types, with the principles applicable to the movement of contaminants
from septic tank systems within the ground water system.
The transport and fate of pollutants in ground water was discussed
by Muir (1977). Pollutants addressed included inorganic and organic
nitrogen compounds, bacteria and viruses. A general discussion on the
chemistry and movement of ground water was presented by Vandenberg, et
al. (1977) with reference to a subsurface waste disposal project and its
potential for ground water contamination. Sampling strategies for
determining pollutant transport and fate in ground water have been
discussed by Pimentel, et al. (1979).
Changes in ground water geochemistry through the influence of
liquid wastes and changes in certain constituents of wastewater as they
move through an aquifer have been discussed by Ku, Ragone and Vecchioli
(1975). Water quality transformations resulting from the passage of
reclaimed water through an aquifer may be due to adsorption,
precipitation, ion exchange, dissolution, chemical oxidation,
nitrification and denitrification, degradation of organic substances,
mechanical dispersion, and filtration (Roberts, et al., 1978).
General references on the transport of pollutants and plume
migration in ground water are given by Lakshraan (1979); Childs and
Upchurch (1976); Childs, Upchurch and Ellis (1974); and Anonymous
(1975). Specific discussions on the underground movement of chemical
and bacterial pollutants are presented by Butler, Orlob and McGaughey
(1954) and Roberts, et al. (1978). Substances like ammonia, trace
metals, and trace organic compounds move slowly in an aquifer when
-91-
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compared with chloride ions. Exler (1972) found that the elements from
a garbage deposit could be found up to 3,000 meters away from the
source.
TRANSPORT AND FATE OF BIOLOGICAL CONTAMINANTS
The potential for biological contamination of ground water by
percolation from such sources as surface spreading of untreated and
treated wastewater, sludge landspreading, septic tank systems and
landfill leachates is high (Vilkcr, 1978). Biological contaminants
(pathogens) have a wide variety of physical and biological
characteristics, including wide ranges in size, shape, surface
properties, and die-away rates. This section will address the transport
and fate of bacteria and viruses in soils and ground water. Information
resulting from specific studies associated with septic tank systems will
be presented along with pertinent information from studies of other
source types.
Bacteria in Soils
Brown, et al. (1979) studied the movement of fecal coliforms and
coliphages from a septic tank system through undisturbed soil to ground
water. Samples taken 1 and 2 years after system start-up indicated
limited mobility and survival of fecal coliforms in the soils.
Coliphages were present in the samples in very low concentrations
immediately after spiking the applied sewage. At the end of 2 years,
the soils below the soil absorption system lines were dissected and
sampled in a grid pattern. On only a few occasions were fecal coliforms
-92-
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present in samples collected 120 cm. below the soil absorption system
lines.
In a study by Reneau and Pettry (1975) of total and fecal coliform
bacteria from septic tank system effluents in Virginia coastal plain
soils, the most probable number (MPN) of both total and fecal coliforms
decreased with horizontal distance and depth from the soil absorption
system lines. They concluded th.-it coliform bacteria were unlikely to
move into the ground water system. However, extensive movement of
coliform bacteria is possible depending upon soil and geological
features in a given area. For example, Rahe, et al. (1978) found that
in a perched water table fecal bacteria moved at a rate of 15 m./hour
through a western Oregon hill slope soil. Strains of Escherichia coli
survived in large numbers for at least 96 hours in the soils examined.
Table 25 summarizes some information on the movement of bacteria
through soil (Gerba, 1975). The distance of travel of bacteria through
soil is of considerable significance since contamination of ground or
surface water supplies may present a health hazard. A number of
environmental factors can influence the transport rate, and certain
design considerations can be based on experimental results and studies
of removal mechanisms. Environmental factors include rainfall; soil
moisture, temperature, and pH; and availability of organic matter.
Design considerations are related to soil type and depth as well as the
hydraulic loading rate from the soil absorption system.
Hagedorn, Hanson and Simonson (1978) found that the numbers of
bacteria peaked in sampling wells in association with rainfall patterns,
and the populations required longer periods to peak in wells farthest
-93-
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Table 25: Movement of Bacteria through Soil (Gerba, 1975)
I
VO
Nature of
pollution
Canal water on perco-
lation beds
Sewage introduced
through a perforated pipe
Oxidation pond effluent
Secondary sewage
effluent on percolation
beds
Diluted settled sewage
into injection well
Tertiary treated
wastewater
Tertiary treated
wastewater
Lake water and diluted
sewage
Primary and treated
sewage effuent
Secondary sewage
Organism
E._coli
coliforms
colifonns
fecal coliforms
coliforms
coliforms
fecal coliforms
and streptococcus
B. stearo-
thermophilis
coliforms
coliforms
Media
sand dunes
fine-grained sands
sand-gravel
fine loamy sand
to gravel
sand and pea
gravel aquifer
fine to medium sand
coarse gravel
crystalline
bedrock
fine sandy loam
sandy gravels
Maximum
observed
distance Time of
of travel travel
(ft) (days)
10
6
2,490
30
100
20
-
1,500 2
94 1.25
13
3
-------
from inoculation pits. This study supports the fact that bacterial
movement through unsaturated soil is influenced by local infiltration,
while bacterial movement in ground water is influenced by local ground
water movement rates and direction.
Table 26 (Gerba, 1975) delineates several environmental factors
that affect survival of enteric bacteria in soil. Gerba (1975) reported
that under adverse conditions survival of enteric bacteria seldom
exceeded 10 days; under favorable field conditions survival may extend
up to approximately 100 days. The principle factor determining the
survival of bacteria in soil is moisture (Peavy, 1978). Temperature,
pH, and the availability of organic matter can also influence enteric
bacteria survival. Survival in all types of soil tested was found to be
greatest during the rainy season. In sand where drying was rapid due to
its low moisture-retaining power, survival time was short — between 4
days and 7 days during dry weather (Peavy, 1978). In soils that retain
a high amount of moisture, such as loam and adobe peat, the organisms
persisted longer than 42 days. Temperature changes, the presence of
oxygen, a reduction in readily available food supply, and predation by
native soil organisms can create unsuitable conditions for bacterial
growth. Periodic or partial drying of the soil increases the death
rate. Also, bacteria seem to survive longer in cool soils than in warm
soils, while low pH, low organics and low moisture content increase the
death rate. It was surmised that low pH could not only act to adversely
affect the viability of the organisms but also the availability of
nutrients; pH could also interfere with the action of inhibiting agents.
-95-
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Table 26: Factors Affecting Survival of Enteric Bacteria in Soil
(Gerba, 1975).
Factor
Remarks
Moisture content
Moisture holding capacity
Temperature
PH
Sunlight
Organic matter
Antagonism from soil microflora
Greater survival time in moist soils
and daring times of high rainfall
Survival time is less in sandy soils
than in soils with greater water-
holding capacity
Longer survival at low temperatures;
longer survival in winter than in summer
Shorter survival time in acid soils
(pH 3-5) than in alkaline soils
Shorter survival time at soil surface
Increased survival and possible regrowth
when sufficient amounts of organic
matter are present
Increased survival time in sterile soil
-96-
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Several mechanisms combine to remove bacteria from water
percolating through the soil. The physical process of straining (chance
contact) and the chemical process of adsorption (bonding and chemical
interaction) appear to be the most significant. Additional mechanisms
include competition for nutrients and the production of antibiotics by
high populations of actinoraycetes, Pseudomonas, and Bacillus in the
aerated zone beneath the clogged layer formed at the soil-trench or
soil-bed interface in a soil absorption system. These antibiotics have
been suggested as playing an important role in the rapid die-off of
fecal coliforms and streptococci (Bouma, 1979).
Physical straining occurs when the bacteria are larger than the
pore openings in the soil. Partial clogging of soil pore space by
organic particles in the septic tank system effluent increases the
efficiency of straining. Finer soil materials such as clay and silt
generally function better for bacterial straining due to their small
pore spaces (Peavy, 1978). Studies using sandy soils of various
effective porosity concluded that removal of bacteria from a liquid
percolating through a given depth is inversely proportional to the
particle sizes of the soil. The same study also found that the greatest
removal occurred on the mat (top 2 to 6 mm) that formed the soil surface
(Gerba, 1975). When suspended particles, including bacteria, accumulate
on the soil surface, these particles can act as a filter. Such a filter
is capable of removing even finer particles, by bridging or
sedimentation, before they reach and clog the original soil surface.
Removal is accomplished largely by mechanical straining at the soil
surface and sedimentation of bacterial clusters.
-97-
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Adsorption is the other major mechanism in the removal of bacteria
by soil. The process of adsorption appears to be significant in soils
having pore openings several times larger than typical sizes of
bacteria. Since most soils also carry a net negative charge, one might
expect rejection rather than attraction of bacteria on soils. This
adsorption takes place in spite of the fact that bacteria are
hydrophilic colloids which possess a net negative charge at the surface.
Adsorption will occur in water with high ionic strength and neutral or
slightly acidic pH; these are typical characteristics of septic tank
effluents. Cations (Ca++, Mg++, Na*, H+) in water neutralize and
sometimes supersaturate the surface of the bacteria, thus making them
susceptible to adsorption by negatively charged soil particles (Peavy,
1978).
Both physical straining/filtration and adsorption can be influenced
by the flow rate of the septic tank system effluent. Bouaa (1979)
suggested that the removal of fecal bacteria from percolating effluent
is very strongly a function of the flow regime. Rapid movement
decreases the travel time and contact between the bacteria, soil, and
liquid phase constituents. Better purification was achieved when system
effluent was applied at a rate of 5 cm./day to a sand as compared to a
rate of 10 cm./day. Laboratory studies have indicated that perhaps 60
cm., but certainly 90 cm., of sand can be effective in removing both
pathogenic bacteria and viruses from septic tank effluent if the loading
rate does not exceed 5 cm./day and if temperatures do not become too low
(Bouma, 1979). Decreased removals at low temperatures suggest
biological mechanisms in the removal.
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Viruses in Soils
In a literature review by Allen (1978) it was reported that viruses
have been found to migrate in soils to distances greater than 600 feet
from their source, and that continued use of septic tank systems and
cesspools have resulted in localized pollution. Viruses are more
resistant to environmental changes and have a longer life span in the
soil than bacteria. Virus survival times of up to 170 days have been
reported. It has been shown that viruses attached to clay particles are
still infective. Studies show that virus removal, like bacteria
removal, is enhanced by low pH and high ionic strength water (Gerba,
1975). Table 27 lists factors that may influence the removal efficiency
of viruses by soil (Gerba, 1975).
The first factor listed in Table 27 is flow rate, with less than
1/64 gpm/ft^ corresponding to less than 91 cm/day (Gerba, 1975). The
general point is that the lower the hydraulic flow rate, the better the
virus removal rate. This point w.-is also found by Bouma (1979) when he
indicated that polio-virus type 1 (strain CHAT), when added to septic
tank effluent and applied to 60 cm. long sand columns, was effectively
removed if the hydraulic flow rate did not exceed 5 cm./day. These
results are shown in Figure 15 (Bouma, 1979).
The most important mechamism of virus removal in soil is by
adsorption of viruses onto soil particles (Drewry and Eliassen, 1968).
Virus adsorption is greatly affected by the pH of the soil-water system.
This effect is due primarily to the amphoteric nature of the protein
shell of the virus particles. At low pH values, below 7.4, virus
adsorption by soils is rapid and effective. Burge and Enkiri (1978)
-99-
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Table 27: Factors Thay May Influence Removal Efficiency
of Viruses by Soil (Gerba, 1975).
Factors
Remarks
Flow rate
Cations
Clays
Soluble organics
pH
Isoelectric point of virus
Chemical composition of soil
Low flow rates (99%) in clean waters. As flow rate
increases, virus retention decreases
proportionally.
Cations, especially divalent cations,
can act to neutralize or reduce repulsive
electrostatic potential between negatively
charged virus and soil particles, allowing
adsorption to proceed.
This is the active fraction of the soil.
High virus retention by clays results
from their high ion exchange capacity
and large surface area per volume.
Soluble organic matter has been shown
to compete with viruses for adsorption
sites on the soil particles, resulting
in decreased adsorption or elution of
an already adsorbed virus.
The hydrogen ion concentration has a
strong influence on virus stability
as well as adsorption and elution.
Generally, a low pH favors virus ad-
sorption while a high pH results in
elution of adsorbed virus.
The most optimum pH for virus adsorption
is expected to occur at or below its
ioelectric point, where the virus
possesses no charge or a positive charge.
A corresponding negative charge on a
soil particle at the same pH would be
expected to favor adsorption.
Certain metal complexes such as magnetric
iron oxide have been found to readily
absorb viruses to their surfaces.
-100-
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10
20 30
deplh into inil column
iOcm'day
SO
60
Figure 15: Removal of Poliovirus (added to septic tank
effluent) in Sand-columns at Two Different
Flow Regimes (Bouma, 1979)
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noted Chat coarser soils with higher pH values were less effective in
adsorbing viruses. Higher pH values considerably decrease the
effectiveness of virus adsorption by soils because of increased
ionization of the carboxyl groups of the virus protein and the
increasing negative charge on the soil particles. Virus adsorption by
some soils is greatly enhanced by increasing the cation concentration of
the liquid phase of the soil-water system. The cations in the water
neutralize or reduce the repulsive electrostatic potential (the negative
charge) on either the virus particles or the soil particles, or both,
and allow adsorption to proceed. This study further indicated that
adsorption of virus particles by soils increases with increasing clay
content, silt content, and ion-exchange capcity (Drewry and Eliassen,
1968). Experiments by Drewry (1969) with different-sized soil particles
showed that finer soils are more efficient in removing viruses from
water.
As noted above, virus adsorption is influenced by soil pH, liquid
phase constituents, and other soil characteristics such as clay content,
silt content, ion exchange capacity and particle size. Adsorption also
differs as a function of virus type. Gerba and Goyal (1978) conducted a
study to determine if poliovirus adsorption to soil truly reflected the
behavior of other members of the enterovirus group, including recently
isolated strains. It quickly became evident that, while poliovirus to a
large extent reflects the behavior of most reference laboratory strains
of enteroviruses in adsorption to soil, it was not reflective of many
strains recently isolated from sewage-polluted waters. In the initial
screening of enteroviruses, the adsorption of laboratory strains to soil
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from Flushing Meadows, New York, was evaluated. Of the 27 different
enterovirus types, only echo 1, echo 12 and echo 29 adsorbed
significantly less than the other reference enteroviruses. In addition,
the rate of echo 1 adsorption was found to be less than that of polio 1.
No difference in adsorption was observed between the laboratory and
natural isolates of poliovirus, but a great deal of variability was
observed between the natural isolates of echo 1 and coxsackie B4.
Adsorption of echo 1 strains to Flushing Meadows soil ranged from 99 to
0%. Polioviruses are the enteroviruses most commonly isolated from
sewage because of the widespread use of oral poliovirus vaccine. From
this work it is apparent that virus adsorption to soil is highly
dependent on the strain of virus. Differences in adsorption between
different strains of the same virus type might result from variability
in the configuration of proteins in the outer capsid of the virus, since
this will influence the net charge on the virus. The net charge on the
virus would affect the electrostatic potential between virus and soil,
and thereby could influence the degree of interaction between the two
particles.
Vilker (1978) has conducted experimentation and developed equations
for the prediction of breakthrough of low levels of virus from
percolating columns under conditions of both adsorption (application of
wastewater to uncontaminated beds) and elution (application of clean
water to contaminated beds). This breakthrough is described by the ion
exchange/adsorption equations with the effects of external mass transfer
and nonlinear adsorption isotherms included. Predictions are in
qualitative agreement with reported observations from the experiments
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which measured virus uptake by columns packed with activated carbon or a
silty soil.
While the actual mechanism of viral adsorption to soils is not
known, two general theories have been proposed. Both are based on the
net electronegativity of the interacting particles. Bacteriophage T2
adsorption to natural clay particles is highly dependent on the
concentration and type of cations present in solution. It was shown
that maximum adsorption of T2 was about 10 times greater for divalent
cations than monovalent cation at the same concentration in solution.
In addition, no definite relationship between the degree of virus
adsorption to clay particles and electrophoretic mobility was evident.
This led to the conclusion that a clay-cation-virus bridge was operating
to link the two negatively-charged particles. Therefore, a reduction in
cation concentration results in a breakdown of the bridging effect and
desorption of the virus (Gerba, 1975). The second theory of adsorption
is that fixation of multivalent cations onto the ionizable groups on the
virus particle is accompanied by a reduction of the net charge of the
particle. This reduction or elimination of the electric charge on the
particle allows the solid and the virus to come close enough for
intermolecular van der Waals forces to interact. The predictability of
this process, however, is complicated by the existence of considerable
variation in the affinity of inorganic cations toward the different
functional groups on the virus. In addition, ions that enhance
adsorption at low concentration may cause desorption at higher
concentrations (Gerba, 1975).
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From the two proposed theories it can be concluded that virus
adsorption cannot be considered a process of absolute immobilization of
the virus from the liquid phase. Any process that results in a
breakdown of virus association with solids will result in their further
movement through porous media. For example, it has been demonstrated
that organic matter in the water phase will compete with viruses for
adsorption sites, thus resulting in either decreased virus adsorption or
elution of previously adsorbed viruses from clay particles (Gerba,
1975).
Bacteria and Viruses in Ground Water
In a study on the fate of bacteria in ground water, lake water
containing Salmonella typhimurium was passed through columns of sand.
Results showed that S_^ typhimurium could noc multiply under these
conditions and that die-off continued for 44 days, after which no
bacteria were detected (Gerba, 1975). However, £_._ coli bacteria have
been found to survive and even multiply on organic matter filtered from
lake water during underground recharge projects in Israel. Table 28
shows the survival times of several types of bacteria in ground water
(Gerba, 1975).
As noted by Gerba (1975), Lefler and Kott studied the survival of
£2 bacteriophage and poliovirus 1 in sand saturated with distilled
water, distilled water containing cations, tap water, and oxidation pond
effluents. The poliovirus titer was lost between 63 days and 91 days
after the start in distilled water, while f2 bacteriophage survived
longer than 175 days. The viruses survived even longer in distilled
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Table 28: Survival of Bacteria in Ground Water (Oerba, 1975).
Organism
Survival time
Media
E. coli
Salmonella
ShigeJla
E_. coli
E. coli
Coliforms
Shigella flexneri
Vibrio cholerae
63 days
44 days
24 days
3-3.5 months
4-4.5 months
17 hr/50% reduction
26.8 hr/50% reduction
7.2 hr/50% reduction
recharge well
water infiltrating sand
columns
water Infiltrating sand
columns
ground wafer in the field
ground water held in the lab
well water
well water
well water
-106-
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water containing cations. When tap water or oxidation pond effluent was
used, it was noted that a very high initial kill of virus occurred, but
poliovirus particles could still be detected after 91 days. In this
media, f2 particles again survived in excess of 175 days (Gerba, 1975).
In summary, while this information is not specifically related to ground
water, the results can be considered as indicative of potential survival
timea in ground water.
TRANSPORT AND FATE OF INORGANIC CONTAMINANTS
Potential inorganic contaminants from septic tank systems include
phosphorus, nitrogen, chlorides and metals. This section will address
the subsurface movement and fate of these contaminants, with the
information primarily based on, but not limited to, studies on septic
tank systems.
Phosphorus
As shown in Table 16, the total phosphorus in influent wastewaters
to septic tank systems serving single household units averages 25 mg/1,
with 8.8 mg/1, or 35%, being in the inorganic, or orthophosphate form,
and 65% being in the organic form. The anaerobic digestion process
occurring in the septic tank converts most of the influent phosphorus,
both organic and condensed phosphate forms, to soluble orthophosphate.
Bouma (1979) reported on studies by others who found that more than 85%
of the total phosphorus in septic tank effluents was in the soluble
orthophosphate form. Total phosphorus concentrations in the effluents
from seven septic tanks monitored in a field study averaged 13 mg/1,
with 85%, or 11 mg/1, in the orthophosphate form (University of
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Wisconsin, 1978). In a separate study of septic tank treatment
efficiency, the orthophosphates in the tank effluent averaged 10.5 mg/1
(Viraraghavan, 1976). Therefore, the septic tank portions of septic
tank systems are not highly efficient in phosphorus removals. As noted
based on data from studies of 41 septic tank systems presented in Tables
21 and 22, the typical total phosphorus concentration entering the soil
absorption system is IS mg/1.
While phosphorus can move through soils underlying soil absorption
systems and reach ground water, this has not been a major concern since
phosphorus can be easily retained in the underlying soils due to
chemical changes and adsorption. In a study by Jones, et al. (1977) it
was confirmed that phosphorus from septic tank wastewater disposal
system effluent is not usually transported through the soil to ground
water.
Phosphate ions become chemisorbed on the surfaces of Fe and Al
minerals in strongly acid to neutral systems and on Ca minerals in
neutral to alkaline systems. As the concentration in the soil solution
is raised, there comes a point above which one or more phosphate
precipitates may form. In the pH range encountered in septic tank
seepage fields, hydroxyapatite is the stable calcium phosphate
precipitate. However, at relatively high phosphorus concentrations
similar to those found in septic tank effluents, dicalciura phosphate or
octacalcium phosphate are formed initially, followed by a slow
conversion to hydroxyapatite (Bouma, 1979). Therefore, both chemical
precipitation as well as chemisorption is involved in phosphorus
retention in soils. Phosphates can be removed at practically all pH
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ranges (Peavy, 1978). These removal mechanisms have been found by many
investigators, including Enfield, et al. (1975) who determined that the
ability of soil to remove wastewater orthophosphate from a solution
passing through a soil matrix is primarily related to the formation of
relatively insoluble phosphate compounds of aluminum, iron, and calcium.
Studies to confirm phosphorus retention in soils have also been made,
with Bouma (1979) reporting on a study in central Wisconsin where it was
determined that phosphorus extracted from sandy soils beneath septic
tank seepage fields which had operated for several years ranged from
about 100 to about 300 ug/gm.
The rate at which phosphorus is sorbed from solution onto the
surfaces of soil constituents has been shown to consist of a rapid
initial reaction followed by an important, much slower, reaction which
appears to follow first order kinetics (Bouma, 1979). Since the removal
involves chemisorption, it is possible to exceed the sorptive capacity
of the soil based on either long term use of a septic tank system or the
application of high hydraulic loading rates such as might occur for a
system serving multiple housing units. Sawhrey and Starr (1977)
described two laboratory experiments which illustrate how sorptive
capacity can be exceeded. Wastewater containing 6 to 9 mg/1 phosphorus
was applied to 75-cm long soil columns for 240 days at the rate of 20
cm/day for 2 hours a day. The concentration of phosphorus in the
effluent solution reached 0.1 mg/1 in the column filled with 0.1 to 0.25
mm soil particles, whereas in the effluent from a column containing 0.25
to 5.0 mm particles it reached a concentration of 5.8 rag/1. In another
experiment a septic tank system effluent containing 18 mg/1 phosphorus
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was applied at a rate of 8 cm/day to columns containing 60 cm of sandy
fill underlain by 30 cm of silt loam. Concentrations in the effluent
were very low during the first 20 days and then continued to increase
with time. Obviously, movement of phosphorus through soil columns is
minimum until "sorption sites" are occupied. Thereafter, movement
through the soil continues to increase, depending upon the application
rate, percolation rate, and the pH of the soil.
Measurements of phosphorus in ground water underlying septic tank
systems have generally confirmed that only minimal concentrations are
introduced from these systems. Sawhrey and Starr (1977) described two
studies by others of the phosphorus introduced into ground water from
septic tank systems. One study of five systems in sandy soils was
conducted in August, October, and November, 1971. Dissolved inorganic
phosphorus concentrations as high as 1.9 mg/1 was observed in the
underlying ground water in August. During the two remaining periods,
concentrations of soluble phosphorus in the ground water were less than
0.25 mg/1 in systems with no perched water table. Another study focused
on the phosphorus concentrations in ground water in Varina and Goldsboro
soils where plinthic horizons (iron-rich hardpan) were 54 and 132 cm
below the drainline and produced a seasonal perched water table. In the
Varina soil, a concentration of 1.05 mg/1 was observed in the perched
water 36 cm below and 15 cm away from the drainline while only 0.01 mg/1
of phosphorus was observed in soil solution within the plinthic horizon.
On the other hand, in the Goldsboro soil, the concentration in the
perched water was only 0.01 mg/1 while in the soil solution from the
plinthic horizon, the concentration of phosphorus was 0.91 mg/1. The
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higher concentration in the plinthic horizon in Goldsboro soil was
attributed to the movement of phosphorus in water under saturated flow
to the plinthic horizon when the water table was low.
In summary relative to the literature, phosphorus in septic tank
system effluents is effectively retained in underlying soils, and only
low concentrations will be typically introduced into ground water.
There will be exceptions in localized situations based on geohydrology
and the soil barrier. For example, Viraraghavan and Warnock (1976)
indicated phosphate concentrations ranging from less than one to in
excess of 20 mg/1 in ground water beneath a tile field, with the higher
concentrations corresponding to periods of high ground water. In
addition, Peavy (1978) reported on minimal attenuation of phosphate 50
feet from a tile field.
If phosphate contamination of ground water becomes a problem, it is
possible to reduce the phosphorus concentration in system effluents
through chemical additions to septic tanks (Brandes, 1977). Aluminum
sulfate (alum), lime, and ferric chloride have been widely used in
municipal wastewater treatment plants in North America and Europe for
removal of phosphates, BOD, and suspended solids. Phosphorus can be
completely removed from solution when aluminum is present in large
excess. Additional benefits of the use of alum is the removal of
coliform organisms (about 80 percent) and intestinal parasite ova and
protozoa. In accordance with the stoichiometry of the reaction between
the alum and the orthophosphates of the domestic wastewater, a solid
product (A1P04) is formed:
A12(S)4)3 + 2P04 " 2A1P04 i+ 3S04 (1)
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which precipitates to the bottom of the septic tank. The chemical
reaction and the precipitation process are affected by the A1:P ratio in
the solution and by the pH. Other reaction products like Ca^0(P04)g
(OH>2 (hydroxyapatite) and FeP04'2H2 (strengite) are also formed as a
result of the affinity between multivalent metal ions and
orthophosphates. All the above precipitated solids and floes are
components of the sludge that is removed later from the septic tank.
Based on the stoichiometry of reaction (1), it would take 0.87 gm. of
aluminum to precipitate 1.0 gm. of phosphorus. Due to its composition,
it would take 11.0 gm. of alum to get 1 gm. of aluminum; therefore,
based on stoichiometric considerations, it would take 9.57 gm. of alum
to precipitate 1.0 gm. of phosphorus. In practice, however, the
recommended aluminum: phosphorus ratio is in the order from 2 to 3,
depending on the phosphorus concentration in the wastewater and on the
phosphorus concentration permitted in the final effluent. Using a ratio
of 2, it would take 22.0 gm. of alum to precipitate 1.0 gm. of
phosphorus. Periodic usage of alum during periods of high ground water
might be justified in order to minimize the phosphorus concentration in
the ground water.
Nitrogen
As shown in Table 16, the total Kjeldahl nitrogen (organic plus
ammonia) in influent wastewaters serving single household units averages
38 mg/1, with 12 mg/1 (32%) in the ammonium (Nfy*) form. Anaerobic
conditions prevail in the septic tank and organic nitrogen is converted
to the ammonium form. Nitrogen in tink effluents averages about 40 mg/1
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and consists of about 75% in the ammonium form and 25% in the organic
form. Therefore, the septic tank is ineffective in nitrogen removal,
but it does cause conversion of organic nitrogen to ammonium ions. The
nitrates concentration in septic tank effluents is low due to the lack
of oxygen in septic tanks (anaerobic conditions).
Nitrogen contamination of ground water has occurred as a result of
septic tank systems. On Long Island, New York, it was determined that
the major sources of nitrogen in the recharge water for the aquifers was
lawn fertilizers and septic tank systems (Shoemaker and Porter, 1978).
Several recent studies have reported on the extent of nitrate
contamination of ground water adjacent to septic tank seepage beds.
Nitrogen is a key nutrient of concern because it contributes to
eutrophication of surface water, and excess nitrogen reaching ground
water can be a health hazard.
The transport and fate of nitrogen in the subsurface underneath a
septic tank system is dependent upon the form of the entering nitrogen
and various biological conversions which may take place. Figure 16
displays the forms and fate of nitrogen in the subsurface environment
(Freeze and Cherry, 1979). As noted earlier, the predominant nitrogen
form entering the soil from the soil absorption system is the ammonium
form. Some organic nitrogen will also be introduced. The fate of the
introduced nitrogen is dependent upon its initial form as well as
biological conversions in the soil and ground water. Nitrates (NC>3~)
can be formed by nitrification involving ammonium ion conversion to
nitrites and then to nitrates. Nitrification (Nfy* •* N02~ •* N03~) is an
aerobic reaction performed primarily by obligate autotrophic organisms
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Ground water
[oenilnfieoiion m reducing zones}
Figure 16: Form and Fate of Nitrogen in the Subsurface
Environment (Freeze and Cherry, 1979)
-114-
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and NO-} is Che predominant end product (Bouma, 1979). Nitrification is
dependent on the aeration of the soil, which, in turn, is dependent on
soil characteristics, percolation rate, loading rate, distance to
impervious strata, and distance to ground water (Peavy, 1978).
Effluents from septic tank systems located in sandy soils can be
expected to undergo predominantly aerobic reactions; this has been
demonstrated to be the case in field systems located in sands and
laboratory column studies employing sands. However, incomplete
nitrification may occur in more clayey soils, such as silt loams and
clays (Bouma, 1979).
Denitrification is another important nitrogen transformation in the
subsurface environment (soils and ground water) underlying septic tank
systems. It is the only mechanism by which the N(>3~ concentration in
the percolating (and oxidized) effluent can be decreased.
Denitrification or the reduction of N(>3~ to ^2° or N2 is a biological
process performed primarily by ubiquitous facultative heterotrophs. In
the absence of 02, N03~ acts as an acceptor of electrons generated in
the microbial decomposition of an energy source. However, in order for
the denitrification to occur in soils beneath a home waste disposal
system, the nitrogen must usually be in the N03~ form and an energy
source must be available. Therefore nitrification, an aerobic reaction,
must occur before denitrification. Therefore, knowing the aeration
conditions beneath a seepage bed will provide information as to the
probable nitrogen forms present (Bouma, 1979).
Based upon the forms of nitrogen in septic tank system effluents,
and the biological transformations which can occur in the subsurface
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environment, there are two forms of major concern relative to ground
water pollution — ammonium ions (NH^+) and nitrates (N03~). Ammonium
ions can be discharged directly from soil absorption system drainage
tiles into the subsurface environment, or they can be generated within
the upper layers of soil from the ammonification process (conversion of
organic nitrogen to ammonia nitrogen). The transport and fate of
ammonium ions may involve adsorption, cation exchange, incorporation
into microbial biomass, or release to the atmosphere in the gaseous
form. Adsorption is probably the major mechanism of removal in the
subsurface environment.
Anaerobic conditions will normally prevail below the upper layers
of soil beneath a soil absorption system. Under these conditions,
positively charged ammonium ions (NH^*) are readily adsorbed onto
negatively charged soil particles. This adsorption is essentially
complete in the first few inches oC soil. After the adsorption capacity
of the first few inches of soil is reached, the ammonia must travel
through saturated soil to find unoccupied sites. This movement will go
farther if there are still anaerobic conditions. Since anaerobic
conditions in soils are usually associated with saturated soils, some
movement of ammonia with ground water can occur if the effluent is
transmitted through a continuously saturated soil into the aquifer.
This movement will be slow, however, since adsorption continues to occur
onto soil particles in the aquifer (Peavy, 1978). To illustrate the
adsorption process, Viraraghavan and Warnock (1976) conducted an
analysis of a soil absorption system located in fine soil (D^g ranging
from 0.0010 to 0.0062 mm and D60 from 0.051 to 0.41 mm in the top 1.5
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meters) over high ground water. The ground water fluctuated from near
the ground surface to a maximum depth of 3.05 meters. Percolation rates
of approximately 1.2 inches/hour were found. The predominant species of
nitrogen in the ground water under this drainfield was ammonia during
periods of operation. During periods when loading ceased for a period
of a few weeks, the concentration of ammonia decreased with a
corresponding rise in the concentration of nitrate. An attenuation of
ammonia with distance away from the system was observed. The
concentration dropped from approximately 40 rag/1 beneath the tiles to
less than 5 mg/1 at 10 feet. The adsorption of ammonium ions may be
aided by the presence of organic matter; however, the exact chemical
nature of this organic-ammonia complex is not well understood.
Cation exchange may be involved along with adsorption in the
retention of ammonium ions in soils underneath septic tank systems.
However, just as the adsorption capacity of a soil can be exceeded, the
cation exchange capacity can also be exhausted. Under these conditions
the cation exchange sites in the soil beneath a seepage bed would become
equilibrated with the cations in the effluent. The effluent would then
move to the ground water with its cation composition essentially
unchanged (Bouma, 1979). Ammonia nitrogen can be incorporated into
microbial or plant biomass in the subsurface environment; however, this
is probably not a major removal mechanism relative to nitrogen in septic
tank system effluents. Finally, ammonia gas can be released to the
atmosphere as a function of the soil-liquid pH conditions. When the pH
is neutral or below, most of the nitrogen is in the ammonium ion form.
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As Che pH become basic the NH^+ is transformed into ammonia and can be
released from the soil as a gas.
Nitrate ions can also be discharged directly from soil absorption
system drainage tiles into the subsurface environment, or they can be
generated within the upper layers of soil from the nitrification
process. The transport and fate of nitrate ions may involve movement
with the water phase, uptake in plants or crops, or denitrification.
Since nitrate ions (N(>3~) have a negative charge, they are not attracted
to soils which also possess negative charges. Accordingly, nitrates are
more mobile than ammonium ions in both unsaturated and saturated soils.
Immobilization of nitrates by plants in the immediate vicinity of
disposal fields can occur as indicated by the characteristic lush growth
often seen near septic tank systems. But this amount is minor inasmuch
as the amount of nitrogen in system effluents greatly exceeds that which
can be utilized by nearby plants (Bouma, 1979). Some of the nitrates
could be removed by crops needing nutrient materials. Nitrogen uptake
by crops grown on the drainfield site is an effective way to reduce the
nutrient content of the system effluent. Removal of nitrates depends on
plant roots into the effluent-laden layer of soil. A crop should be
selected that has a long growing season and a high nitrogen requirement.
Denitrification can also remove nitrates from soils underlying
septic tank systems. Denitrificarion occurs in soils which contain an
abundance of denitrifying bacteria that can use free oxygen or nitrate
as a substitute hydrogen acceptor if free oxygen is absent. In the
denitrification process bacteria convert nitrates back to nitrites and
then to nitrogen gas, N2- This gas can be released from the soil.
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Nitrogen in the form of nitrate usually reaches ground water, and
becomes very mobile because of its solubility and anionic form.
Nitrates can move with ground water with minimal transformation. They
can migrate long distances from input areas if there are highly
permeable subsurface materials which contain dissolved oxygen. The only
condition which can effect this process is a decline in the redox
potential of the ground water. In this case, the denitrification
process can occur.
Chlorides
Chlorides are natural constituents in surface and ground water, and
they are also found in household and community wastewaters. Both septic
tank systems and conventional community wastewater treatment plants are
ineffective for chlorides removal. The chlorides concentrations in
septic tank system effluents will be variable depending on the natural
quality of the water supply. To serve as an example, the concentrations
of chlorides in septic tanks, and thus in the effluent discharged to the
soil through soil absorption systems, have been reported by Peavy (1978)
to range from 37 to 101 mg/1. Due to their anionic form (Cl~) and
mobility with the water phase, chlorides can be useful as a tracer or
indicator of septic tank system pollution.
Metals and Other Inorganic Contaminants
Metals in the effluents from septic tank systems may be responsible
for contamination of shallow water supply sources. Sandhu, Warren and
Nelson (1977), in a random survey of Chesterfield County, South
Carolina, showed that metallic contamination was quite common from
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septic tank systems. The levels of arsenic, iron, lead, mercury and
manganese were, in some cases, higher than recommended limits. Lower
and more acceptable concentrations of cadmium, copper, and zinc were
found in the study. The lead and cadmium found in the ground water may
have originated from corrosion of antiquated plumbing in old houses
being served by septic tank systems.
A review of the transport and fate of heavy metals in the
subsurface environment has been prepared by Batrs (1980). The L'our
major reactions that metals may be involved in with soils are
adsorption, ion exchange, chemical precipitation and complexation with
organic substances. Of these four, adsorption seems to be the most
important for the fixation of heavy metals. Ion exchange is thought to
provide only a temporary or transitory mechanism for the retention of
trace and heavy metals. The competing effects exhibited by more common
metal ions such as Ca+2, Na+, H* and K+ limit the cation exchange sites
available for heavy metal removal (Jenne, 1968). Precipitation
reactions as a mechanism of metciL fixation in soils have been well
documented (Jenne, 1968; Hahne and Kroontje, 1973; Kee and Bloomfield,
1962; and Lindsay, 1972). This type of reaction is greatly influenced
by pH and concentration, with precipitation predominantly occurring at
neutral to high pH values and in macro-concentrations (Bingham, et al.,
1964). Organic materials in soils may immobilize metals by complexation
reactions or cation exchange. Organic materials have a very high cation
exchange capacity, therefore proving more available exchange sites than
most clays. Complexation reactions between metals and organic
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substances, although definitely serving to fix the metals, may only
provide for temporary immobilization. If the organic complex is
biodegradable, the metal may be subsequently released back to the soil
environment. Fixation of heavy metals by soils by either of these four
mechanisms is dependent on a number of factors including soil
composition, soil texture, pH and the oxidation-reduction potential of
the soil and associated ions (Bates, 1980).
Soil type or composition is a very important factor in all heavy
metal fixation reactions. Clays are extremely important in adsorption
reactions because of their high cation exchange capacity. In addition,
soils high in humus or other organic matter also exhibit good exchange
capacity. The type of clay mineral present is, in addition, an
important factor. Many sorption reactions take place at the surface of
iron and aluminum hydroxides and hydroxy oxides and, therefore, the iron
and aluminum content of soils becomes an essential factor governing the
ability of a soil for heavy metal immobilization. A. number of studies
have been conducted on the retention of zinc, copper, cadmium, lead,
arsenic, mercury and molybdenum by various soil types (Bates, 1980).
Soil texture or soil particle size is another factor that can
influence the fixation of metals by soils. In general, finely-textured
soils immobilize trace and heavy metals to a greater extent than coarse-
textured soils. Also, finely-textured soils usually have a greater
cation exchange capacity which is ai important factor in heavy metal
fixation. Soil texture has been fo md to influence the transport of
mercury, lead, nickel, and zinc (Bates, 1980).
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Soil pH plays a very important role in the retention and mobility
of metals in soil columns (Korte, et al., 1976; Zimdahl and Skogerboe,
1977). The pH is a controlling factor in sorption-desorption reactions
and precipitation-solubilization reactions. In addition, the cation
exchange capacity of soils generally increases with an increase in pH.
Even with a soil that has a high affinity for a specific metal, the
degree to which the metal is fixed is a function of pH. Soil pH has
been determined to be a major factor along with cation exchange capacity
for the fixation of lead by soils. Soil pH also influences the
retention of zinc, molybdenum, mercury and copper (Bates, 1980).
The oxidation-reduction or redox potential of a soil is very
important in determining which species of an element is available for
sorption, precipitation, or complexation. In general, the reduced forms
of a metal are more soluble than the oxidized forms. The redox
potential of a soil system is usually altered through biological
activity and a change in redox potential is many times correlated with
changes in pH. Reducing conditions may be associated with a low pH
resulting from the formation of C02 and organic acids from the microbial
degradation of organic matter. A reducing environment typically exists
in saturated soils underneath septic tank systems. The anaerobic
conditions would enhance the mobility of metals in system effluents.
Iron is a good example of a metal which readily undergoes redox
reactions. In the oxidized or ferric state, iron may form insoluble
compounds of Fe(OH>3 or FeP(>4. However, when iron is reduced under
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anoxic conditions, the ferrous form, which is more soluble, predominates
(Bates, 1980).
Another factor affecting the retention or mobility of metal ions is
competing ions. The presence of phosphate affects the retention of both
arsenic and zinc. Arsenic tends to become more mobile in the presence
of phosphate and zinc is more highly retained. The effects of chlorides
on the mobility of several heavy metals have also been investigated.
For example, the presence of chloride decreases the adsorption of
mercury (II) and enhances its mobility. Doner (1978) conducted studies
on the effect of chlorides on the mobilities of nickel (II), copper (ll)
and Cd (II) in soils. Cadmium forms stable complexes with chloride
while nickel and copper form weak chloride complexes. Using a sandy
loam soil, Doner found that chloride increased the rate of mobility of
nickel, copper and cadmium through soil. Of the three metals, copper
was held more strongly than nickel or cadmium and the mobility of
cadmium was increased more than that of nickel or copper.
In summary relative to the transport and fate of metals in septic
tank system efluents, a number of mechanisms and influencing conditions
are involved. Although generalities can be drawn with respect to the
soil types and textures favorable for optimum metal retention, other
factors such as pH, redox potential, and the presence of specific
associated ions makes the chemistry of each metal ion in the soil column
unique. Of particular concern is the influence of anaerobic conditions
and associated ions in increasing the mobility of metals in the
subsurface environment. These factors can increase the possibility of
ground water contamination by heavy metals from system effluents.
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TRANSPORT AND FATE OF ORGANIC CONTAMINANTS
Recent evidence indicates that many aquifers have been contaminated
by organic chemicals. Some of these chemicals are known to be
carcinogenic, and thus they pose a public health threat. Studies have
also demonstrated that these contaminants have entered some ground water
systems through septic tank systems. For example, a municipal landfill
in Jackson Township, New Jersey, was licensed to receive wastewater
sludges and septic tank wastes, but it now appears that dumping of
chemicals has also occurred at the site. As a result of the variety of
potential ground water pollutants, approximately 100 wells surrounding
the landfill have been closed due to organic chemical contamination. It
is impossible to determine whether the chemicals were from sludges,
septic tank wastes, or other indiscriminate dumping. Water analyses
revealed the presence of chloroform (33 micrograms per liter), methylene
chloride (3000 micrograms per liter), benzene (330 micrograms per
liter), toluene (6400 micrograms per liter), trichloroethylene (1000
micrograms per liter), ethylbenzene (2000 micrograms per liter), and
acetone (3000 micrograms per liter) (U.S. Environmental Protection
Agency, May 1980). One additional example of the movement of organic
chemicals into ground water is based on a study of subsurface migration
of hazardous chemical constituents at 50 land disposal sites that had
received large volumes of industrial wastes (Miller, Braids and Walker,
1977). The facilities included la-idfills, lagoons, and combinations of
the two, both active and abandoned. They were located in 11 states east
of the Mississippi River. At 43 of the 50 sites migration of one or
more hazardous constituents was confirmed. Migration of heavy metals
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was confirmed at 40 sites; selenium, arsenic and/or cyanide at 30 sites;
and organic chemicals at 27 sites. Eighty-six wells and springs used
for monitoring yielded water containing one or more hazardous substances
with concentrations above background.
The most frequently found organic contaminant in ground water is
trichloroethylene, an industrial solvent and degreaser which is also
used as a septic tank cleaner. Other volatile organics include
tetrachloroethylene, 1,I,1-trichloroethane, 1,1-dichloroethane, and
dichloroethylene (U.S. Environmental Protection Agency, May 1980).
The transport and fate of organic contaminants in the subsurface
environment is a relatively new topical area of concern, thus the
published literature is sparse. A variety of possibilities exist for
the movement of organics, including transport with the water phase,
volatilization and loss from the soil system, retention on the soil due
to adsorption, incorporation into microbial or plant biomass, and
bacterial degradation. The relative importance of these possibilities
in a given situation is dependent upon the characteristics of the
organic, the soil types and characteristics, and the subsurface
environmental conditions. This very complicated topical area is being
actively researched at this time. One study is being conducted at a
ground water recharge facility being operated by the Santa Clara Water
District in California (Roberts, 1980). Effluent from a 2 mgd advanced
waste treatment plant is used ii the recharge system. The study
objectives are to acquire quantitative data regarding the removal of
organic micropollutants (chlorinated and nonchlorinated trace organic
compounds) during aquifer passage; obtain evidence that processes such
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as adsorption and biodegradation influence the transport of such
pollutants relative to the velocity of the injected water; estimate the
field capacity of the aquifer for retaining specific pollutants; and
ascertain to what degree extreme concentration fluctuations are
attenuated by aquifer passage.
Griffin and Chow (1980) studied the adsorption, mobility, and
degradation of polybrominated biphenyls (PBBs) and hexachlorobenzene
(HCB) in soil materials and in a carbonaceous adsorbent. The aqueous
solubilities of both materials wen- low (< 16 ppb), but solubilities were
higher in river water and landfill leachate than in distilled water.
The solubilities can be directly correlated with the level of dissolved
organics in the waters. The PBBs and HCB were immobile in all soils
studied when leached with deionized water and landfill leachate; they
were highly mobile in all soil materials when leached with organic
solvents. The PBBs and HCB were found to be strongly adsorbed by the
carbonaceous adsorbent and by soil materials, with HCB being adsorbed to
a greater extent than PBBs. The adsorption capacity and mobility of
PBBs and HCB were highly correlated with the organic carbon content of
the soil materials. In a soil incubation study, it was found that PBBs
and HCB persisted for 6 months in soil with no significant microbial
degradation. Because of their low water solubilities, strong
adsorption, and persistence in soils, these two compounds are highly
resistant to aqueous phase mobility through earth materials; however,
they are highly mobile in organic solvents.
Considerable research has been conducted on the transport and fate
of organic pesticides and herbicides in soils. It is possible for
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pesticides to be introduced into septic tank systems through normal
household use and disposal practices. A bibliography of published
literature on the transport, transformation, and soil retention of
pesticides is available (Copenhover and Benito, 1979). Based on studies
involving the infiltration of aldrin, a chlorinated hydrocarbon
insecticide, through columns of Ottawa sand, it was determined that
aldrin penetrability through soils is dependent upon the type of
formulation applied, frequency of its application, soil conditions, and
the frequency and rate of rainfall or irrigation (Robertson and Kahn,
1969).
Several studies have been conducted on the movement and
biodegradation of large concentrations of pesticides in soils.
Davidson, Ou, and Rao (1976) examined the factors affecting pesticide
mobility from hazardous waste disposal sites containing high pesticide
concentrations. Major consideration was given to the influence of the
shape of the adsorption isotherm on pesticide mobility. Equilibrium
adsorption of the dimethylamine salt of (2, 4-D (2, 4-Dichlorophenoxy)
acetic acid)} on Webster silty clay loam was measured in the
concentration range of 0-5000 pg/ml. The adsorption sites for 2, 4-D on
the Webster soil were not saturated even in the presence of 5000 pg/ml
of 2, 4-D. The adsorption isotherm was non-linear in shape with the
Freundlich equation exponent being 0.71. The mobility of 2, 4-D in the
Webster soil at various 2, 4-D concentrations was simulated with a
numerical solution to the solute transport model. These simulations
revealed that pesticide mobility increased as solution concentration
increased when the Freundlich equation exponent was less than 1.0.
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However, an increase in solution concentration when the exponent was
greater than 1.0 resulted in a decreased mobility. Serious errors may
be introduced by assuming a linear adsorption isotherm when predicting
pesticide transport under waste disposal sites where high pesticide
concentrations exist. A procedure for estimating the arrival time of a
selected pesticide concentration at various soil depths below a disposal
site was developed by Davidson, Ou and Rao (1976).
Additional studies by Davidson, et al. (1980) revealed equilibrium
adsorption isotherms of the non-linear Freundlich type for atrazine,
methyl parathion, terbacil, trifluralin, and 2, 4-D and four soils.
Pesticide solution concentrations used in the study ranged from zero to
the aqueous solubility limit of e.-ich pesticide. The mobility of each
pesticide increased as the conceniration of the pesticide in the soil
solution phase increased. These results were in agreement with the
equilibrium adsorption isotherm data. Biological degradation of each
pesticide was measured by ^CC^ evolution resulting from the oxidation
of uniformly ^C ring-labeled pesticides, except trifluralin which was
labeled at !^CF3. Technical grade and formulated forms of each
pesticide at concentrations ranging from zero to 20,000 Pg/g of soil
were used in the biological degradation experiments. Pesticide
degradation rates and soil microbial populations generally declined as
the pesticide concentration in the soil increased; however, some soils
were able to degrade a pesticide at all concentrations studied, some
soils degraded a pesticide at a low concentration but not a higher
concentration, while others remained essentially sterile throughout the
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incubation period. Several pesticide metabolites were formed and
identified in various soil-pesticide systems.
The movement of 2, 4-D in three soils was studied by Dregne, Gomez
and Harris (1969) to determine the extent to which herbicides applied in
the field enter ground water systems. Adsorption isotherms,
breakthrough curves, leaching studies, and bioassays indicate that 2, 4-
D in the acid or salt form, is only slightly adsorbed by soil particles.
It is easily leached if the soils are permeable. Virtually 100% of
applied 2, 4-D was recovered from a sandy loam in six and one-half hours
of leaching. Only 38% was recovered from a slowly permeable silty clay
loam over a period of ten months. Degradation products of 2, 4-D were
leached as easily as 2, 4-D itself.
Schneider, Wiese and Jones (1977) conducted a field study of the
movement of three herbicides in a fine sand aquifer. Low concentrations
of atrazine, picloram and trifluraline, and a NaN(>3 tracer were injected
into a sand aquifer through a dual-purpose well. Recharge by injection
continued for 10 days at an average rate of 81.8 cu ra/hour. After a 10-
day pause, the well was pumped for 12 days to determine if the
herbicides and tracer could be recovered. Water samples were pumped
from observation wells located 9, 20, and 45 m from the dual-purpose
well. Herbicides were detected in the 9- and 20-m distant wells, but
none of the herbicides or the tracer was detected in the 45-m distant
well.
GROUND WATER POLLUTION CONTROL MEASURES
Several measures can be identified to minimize the possibility for
undesirable ground water pollution to result from septic tank system
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usage. Examples include proper system design and site selection,
establishment of institutional requirements, and consideration of
influent wastewater segregation. Siting criteria and design features
for septic tanks and soil absorption systems were addressed in Chapter
2. Some control measures can be used for existing septic tank systems
experiencing problems with overloaded soil absorption fields. One
approach would be to require any existing subdivision subject to septic
tank system failures to join sewage districts with specific collection
and treatment facilities. Another approach is to require householders
to connect to sewers as urban development occurs and sewers are
provided.
Table 29 summarizes several positive actions that can be used for
new septic tank systems (U.S. Environmental Protection Agency, 1973).
One is to require approval of the site and design by competent
hydrogeologists, soil scientists and engineers. Another approach is to
construct percolation systems by methods which do not compact the
infiltrative surface. There are some operational practices which can
minimize the potential for ground water pollution. These include
alternately loading and resting the percolation system, inspecting and
removing scum and grease from septic tanks, and cleaning of septic tanks
by withdrawal of only one-half the sludge rather than the entire
contents. A final suggestion for control of septic systems is the use
of zoning and other land management controls in urban areas to prevent
installations in unsuitable soils. Unsuitable soils are those that are
too impervious to accept effluents, or too coarse or fractured to
maintain the required biological and physical treatment.
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Table 29: Ground Water Pollution Control Measures for New Septic Tank
Systems (U.S. Environmental Protection Agency, 1973).
Require approval of the site and design by competent hydrogeologists,
soil scientists and engineers before septic systems are approved for any
subdivision, recognizing that simple percolation tests and standard codes
offer only partial criteria for the design of a septic system.
Construct percolation systems by methods which do not compact the
infiltrative surface.
Operate septic systems effectively by:
Alternately loading and resting one-half the percolation system;
the cycle to be determined by the onset of ponding in the system
at the observation well.
Inspecting and rcmovin;-. scum and grease from septic tanks annually.
Drawing off half of the sludge rather than pumping out the entire
contents of tanks.
Use of zoning and other land management controls to prevent septic
system installations in unsuitable soils (i.e., soils too impervious to
accept effluents, or too coarse or fractured to maintain a biological and
physical treatment system).
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Another measure to minimize the ground water pollution potential of
septic tank systems is to reduce the wastewater strength entering the
systems. Segregation of household wastewaters is depicted in Figure 17
(Siegrist, 1977). Various wastewater streams within the household unit
can be divided into two major fractions: the toilet wastes, commonly
referred to as "black water"; and the other household wastewaters,
commonly referred to collectively as "grey water". The characteristics
of the black water and grey water streams are summarized in Tables 30
and 31, respectively (Bauer, Conrad and Sherman, 1979). On the average,
the black water contributes about 30% of the BOD, 50% of the suspended
solids, 70% of the total Kjeldahl nitrogen, 17% of the total phosphorus,
and 30% of the flow from a household unit. Removal of the black water
from the household waste stream through use of a non-conventional toilet
system (e.g. composting, incinerating, recycle, low volume flush/holding
tank), would reduce the wastewater loading to the septic tank and the
soil absorption system.
GROUND WATER MONITORING
As noted in Chapter 1, ground water monitoring may be required for
septic tank systems funded by the U.S. Environmental Protection Agency.
Monitoring is of greater importance for geographical areas with high
septic tank densities, and for specific systems serving large numbers of
housing units. The first requirement for a ground water monitoring
program should be the clear delineation of monitoring objectives.
Nelson and Ward (1982) suggested two basic objectives based on system
failure detection: (1) the detection of temporary overloads of high
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TOILET HKITCHENW DISH \f BATH- UCLOTHESU MISC
SINK IIWASHLRHSHOWERHWASHER
Figure 17: Segregation of Household Waste-
water (Siegrist, 1977)
-133-
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Table 30: Characteristics of Black Water (Bauer, Conrad, and Sherman, 1979)
Parameter
(g/cap/d)
BOD5
BOD5 filtered
COD
TOG
TOG filtered
TS
TVS
SS
VSS
TKN
NH3-N
N03-N
N02-N
TP
PO.-P
4
Oil and Grease
MBAS
PH
Total Bacteria
(///cap/d)
Total coliform
(///cap/d)
Fecal coliform
(#/cap/d)
Fecal strep
Flow (Ipcd)
Investigator
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8.9
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3.8xl09
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23.5
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67.8
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2.78
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74.9
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6.9
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65
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76.5
55.8
36.5
31
5.2
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5.6
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28.5
19.7
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0.03
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0.55
0.31
3.35
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26.6
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10.7
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7.8
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0.55
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3
-
-
—
-
-
-
50
* Study households equipped with vacuum toilets.
-134-
-------
Table 31: Characteristics of Grey Water (Bauer, Conrad, and Sherman, 1979).
Parameter
(g/cap/d)
BOD5
BOD5 filtered
COD
TOC
TOC filtered
TS
TVS
SS
VSS
TKN
NH3-N
N03-N
N02-N
TP
P04-P
Oil and Grease
MB AS
PH
Total Plate
Count (///cap/d)
Total coliform
(///cap/d)
Fecal coliform
(///cap/d)
Fecal strep
(///cap/d)
Flow (Ipcd)
Investigator
Olsson, Karlgren,
and Tullander
25
-
48
-
-
77
44
18
15
1.1
-
-
trace
2.2
-
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7.6xl010"
1.3x10™
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121.5*
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38.8
24.1
-
24.4
17.2
85
43
22.6
16.5
1.9
0.16
0.04
-
3.43
1.10
11.3
-
-
_
6500**
550**
94**
92.8
C/)
38.8
24.1
-
24.4
17.2
85
43
22.6
16.5
1.9
0.16
0.04
-
3.43
1.10
-
-
-
—
6500**
550**
94**
126.5
Weighted Value
33
24
52
24
17
80
40
20
15
2
0.2
0.05
-
3
1.1
11
3
7.2
-
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_
_
110
* Excluding garbage disposal and water softner.
+ Based on bath/shower, dishwashing, and laundry only.
// Based on kitchen and bath/shower data only.
**Based on laundry and bath/shower data only.
-------
polllutant concentrations in ground water; and (2) the detection of
permanent overloads of high concentration.
The three primary components of a septic tank system monitoring
program are: (1) determination of the sampling locations; (2) selection
of parameters to be monitored; and (3) selection of the required number
of samples (Nelson and Ward, 1982). Since the treatment system consists
of the septic tank, the soil absorption system, and the unsaturated soil
zone beneath the drainage tiles, the most logical sampling location is
in the upper portion of the saturated zone directly beneath the field
lines. Sampling at this location should be most representative of the
input to the ground water aquifer. Location of the sampling points in
the upper portion of the saturated zone entails possible physical
difficulties associated with collecting samples at varying depths as the
water table fluctuates. This problem can be circumvented by using
either a cluster of wells installed at various depths or a ground water
profile sampler. This particular sampler consists of a well point
filled with sand and divided into sections with partitions made of
caulking. A sampling probe is located within each section and tubing
extends from each probe to the ground surface. One advantage of using a
cluster of wells is that they can be located at various points in the
leach field to give more extensive areal coverage. The degree to which
more areal coverage is required will depend on the homogeneity of the
soil in the leach field and the uniformity of effluent distribution.
More sampling wells will be required if the soil is nonhomogeneous
and/or the effluent distribution is nonuniform (Nelson and Ward, 1982).
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A number of parameters could be measured as a part of a ground
water monitoring program for a septic tank system. Tables 16 and 18
illustrate the variety of physical, chemical and biological constituents
in septic tank system wastewaters. Parameters of importance in terms of
monitoring include those which might be considered health hazards,
including bacteria, viruses, and nitrates.
Since bacteriological testing is easier and less expensive than
virological testing, the former should be given precedence (Nelson and
Ward, 1982). Fecal coliforms and fecal streptococci can serve as
suitable indicators of bacterial or viral contamination of ground water
by septic tank systems. Nitrate monitoring is important since the
unsaturated zone is not effective in nitrogen removal. An adequate
depth of unsaturated flow, necessary for bacteriological and virological
treatment and for phosphorus removal, also establishes conditions which
allow for rapid nitrification within the first few centimeters of the
unsaturated zone. Nitrate is then transported uninhibited to the ground
water. Simple dilution of the nitrate with the ground water provides
adequate reduction of the nitrate concentrations if the density of
septic tanks in a given area is sufficiently low. However, high
densities could result in significant increases in nitrate
concentrations in the ground water (Nelson and Ward, 1982).
The number of parameters included in a ground water monitoring
program is typically limited by budgetary and time constraints. As
noted above, routine monitoring for fecal coliforms, fecal streptococci,
and nitrates would be reasonable in most instances. It might be
desirable to monitor for total solids, dissolved solids, and chlorides
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if the background concentrations are low for these constituents. Due to
the growing importance of metals and organic constituents in septic tank
system effluents, it may become increasingly important to monitor for
these constituents, particularly for systems serving multiple household
units.
Sampling location and parameter selection is envisioned to be
similar for detection of either temporary or permanent overloads of high
pollutant concentrations in ground water. Sampling frequency is more
dependent on whether the objective is to detect temporary or permanent
overloads. Nelson and Ward (1982) used a mathematical model to
determine the sampling frequency required to achieve a specific
probability of failure detection. The mathematical model was based on
detection of nitrates alone. This approach was used since on-site
systems are least effective in the removal of nitrate. Also, the
modeling of nitrate flow through a porous medium has been well
documented. Since most of the bacteria, viruses, and phosphorus will be
removed before reaching the ground water, the statistical variability
associated with these variables should be much lower than that of
nitrate. Therefore, if the sampling frequency for all variables
considered in the monitoring program can be taken as the frequency
determined for nitrate, then the resulting precision of the estimates
for all variables will be at least as good as the precision for
nitrates.
The mathematical model used b? Nelson and Ward (1982) to determine
sampling frequencies consisted of a mass transport model which described
the flow of nitrates through the leach field, and a simulation model
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which was used to establish input concentrations. The convective-
dispersion equation was used in the mass transport portion of the model
and model parameters were selected to represent different soil types. A
number of random components associated with water use patterns in a
house were included in the simulation portion of the model.
Consequently, varying results were obtained on each simulation run. The
output resulting from each simulation was superimposed with a sampling
plan in order to determine the effectiveness of that plan. Major
emphasis in the modeling was placed on the detection of a permanent
system failure. In this case it was assumed that the assimilative
capacity of the ground water reservoir is such that a failure of a
temporary nature is not severe. Hence, the monitoring objective was to
detect a permanent system failure while avoiding the classification of a
temporary overload as a permanent failure. Three sampling plans were
evaluated by Nelson and Ward (1982) to determine their effectiveness in
meeting this objective:
Plan I — Samples were taken at equally spaced intervals at
frequencies of 1, 3, 5, 10, 15, and 20 samples per
year. If a concentration above the detection limit was
found, system failure was assumed and sampling was
terminated.
Plan II — Primary samples were taken at the frequencies given in
Plan I. However, if a concentration above the
detection limit was found, the primary sample was
followed by one secondary sample one week later. If
both the primary and secondary samples were above the
detection limit, system failure was assumed and
sampling was terminated.
Plan III — Primary samples were taken at the frequencies given in
Plan I. However, if a concentration above the
detection limit was found, the primary sample was
followed by two secondary samples 3 days and 6 days
-139-
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later. If all three samples were above the detection
limit, system failure was assumed and sampling was
terminated.
From the description of the various sampling plans considered, it
is obvious that the primary objective of plans II and III is to avoid
classifying a detection as a permanent failure when it is actually a
temporary overload. For each sampling plan and sampling frequency
several quantities were determined. For purposes of this discussion the
most important are percent permanent failure detection and percent
temporary overload detection. As shown in Figure 18, sampling plan III
is the most effective in detecting system failure. With this plan a
sampling frequency of at least 7 samples per year is necessary to detect
a system failure 90% of the time on the average. Figure 18 also
indicates that an increase in sampling frequency beyond this point would
not be very beneficial in terms of increased failure detection. It is
also noted that sampling plan I reaches a maximum percent failure
detection at a frequency of 3 or 4 samples per year and higher
frequencies actually reduce the effectiveness. The reason for this
apparent anomaly is that higher frequencies tend to begin detecting an
increasing number of temporary system overloads as indicated in Figure
19 (Nelson and Ward, 1982). The results shown in Figures 18 and 19
indicate that sampling plan I would be inadequate in detecting a system
failure given the characteristics of the system that was modeled.
Sampling plans II and III provide significant improvement. Plan III
requires more samples, and consequently, would be more costly. The
choice between plan II and III would be dependent on the value a
management agency is willing to accept as the probability of making an
-140-
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10
Figure 18: Comparison of the Effectiveness of
Sampling Plans in Detecting System
Failure (Nelson and Ward, 1982)
-141-
-------
90
I I0
\ '°
I *°
I
|
I *°
c 10
O *l» I
a n« a
(J Plan m
Figure 19: Comparison of the Effectiveness of
Sampling Plans as Measured by Tem-
porary Overload Detection (Nelson
and Ward, J982)
-142-
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error by classifying a detection as failure when it is actually a
temporary overload (Nelson and Ward, 1982).
SEPTAGE — A SPECIAL CONCERN
Septic tanks serving single or multiple household units must be
periodically cleaned to remove septage. Septage refers to the mixture
of sludge, fatty materials, and wastewater removed during the pumping of
a septic tank (U.S. Environmmcal Protection Agency, October 1980).
Tank clean-out and septage removal may occur every 3 to 5 years or more
frequently as needed depending upon wastewater loading. Septage is
often highly odoriferous and may contain significant quantities of grit,
grease, and hair that may make pumping, screening, or settling
difficult. Of particular importance is the high degree of variability
of this material, some parameters differing by two or more orders of
magnitude. This is reflected to some extent by the variability in mean
values from different studies presented in Table 32 (U.S. Environmental
Protection Agency, October 1980). In general, the heavy metal content
of septage is low relative to municipal wastewater sludge, although the
range of values may be high. Table 33 presents typical concentration
ranges for indicator organisms and pathogens in septage (U.S.
Environmental Protection Agency, October 1980). These values are not
unlike those found for raw primary wastewater sludge. It is evident
that septage may harbor disease-causing organisms, thus demanding proper
management to protect public health.
While it is beyond the scope of this study to address the ground
water pollution potential of septage, it should be noted that
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Table 32: Characteristics of Domestic Scptago (U.S. Environmental
Protection Agency, October 1980).
Parameter
Mean Value
(mg/1)
Total Solids
Total Volatile Solids
Suspended Solids
Volatile Suspended Solids
BOD
COD
PH
Alkalinity (CaCO-)
TKN
22,400
11,600
39,500
15,180
8,170
27,600
2,350
9,500
21,120
13,060
1,770
7,650
12,600
8,600
4,790
5,890
3,150
26,160
19,500
60,580
24,940
16,268
6-7 (typical)
610
1,897
410
650
820
472
59
100
120
92
153
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Table 32 Continued
Mean Value
Parameter (mg/1)
Total Phosphorus 190
214
172
351
Grease 3,850
9,560
Aluminum 48
Arsenic 0.16
Cadmium 0.1
0.2
9.1
Chromium 0.6
1.1
Copper 8.7
8.3
Iron 210
160
190
Mercury 0.02
0.4
Manganese 5.4
4.8
Nickel 0.4
<1.0
0.7
Lead 2.0
8.4
Selenium 0.07
Zinc 9.7
62
30
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Table 33: Indicator Organism and Pathogen Concentrations in Domestic
Septage (U.S. Environmental Protection Agency, October 1980),
Parameter
Typical Range
(number/100ml)
Total Coliform
Fecal Coliform
Fecal Streptococci
Ps. aeruginosa
Salmonella sp.
Parasites
Toxacara, Ascaris
Lumbricoides.
Trichuris trichiura.
Trichurls vulpis
10 - 10'
10" - 10'
10 -
10
101 -
- 10
Present
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inappropriate disposal of septage can cause ground water quality
programs. Septage is typically disposed into sanitary landfills, thus
the issues of concern are associated with leachate formation and
transport to ground water. As noted earlier, leachates from the Jackson
Township, New Jersey landfill probably contain constituents from septage
(U.S. Environmental Protection Agency, May 1980). Due to the increasing
usage of septic tank systems, a study to determine the national
magnitude of septage disposal effects on ground water would be desirable
not only in terms of current practices, but also in relation to positive
future actions which could be taken to minimize the undesirable impacts.
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CHAPTER 4
SEPTIC TANK SYSTEM MODELING
One of Che objectives of this study is to provide information on
technical methodologies for evaluating the ground water pollution
potential of septic tank systems. This evaluation is desirable prior to
installation of new systems; it is required based on the Section 201 (h)
and (j) provisions of the Clean Water Act of 1977 (P.L. 95-217) which
authorized construction grant funding of privately-owned treatment works
serving individual housing units or groups of housing units, provided
that a public entity apply on behalf of a number of such individual
systems (Bauer, Conrad and Sherman, 1979). As noted earlier, this
evaluation is of greater importance for larger systems serving up to
several hundred housing units. Evaluations may also be necessary for
single systems up to several hundred individual systems in a given
geographical area.
Technical methodologies range from empirical index approaches to
sophisticated mathematical models. Models can range from analytical
approaches addressing ground water flow to numerical approaches which
aggregate both flow and solute transport considerations. Technical
methodologies vary in input data requirements and specificity of output-
oriented calculations. Only minimal work has been done on modeling of
the ground water effects of septic tank systems; therefore, the major
focus of this chapter will be on the application of existing technical
methodologies not previously applied to septic tank systems. The
initial section will describe the septic tank system as an area source
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of ground water pollution. Previous usage of models and selection
criteria for this study will be summarized. Information will then be
presented on two empirical assessment methodologies and their
application in a central Oklahoma study area; the Hantush analytical
model; and the Konikow and Bredehoeft numerical model. Finally, a
suggested heirarchical structure for model usage will be presented.
CONCEPT OF AREA SOURCE
An important consideration in selecting technical methodologies is
the source type to be modeled, i.e., is it a point source, line source,
or area source? A point source would be represented by a pipe discharge
to the subsurface environment; a very shallow brine disposal well would
be an example. A line source would represent discharges to the
subsurface along either a horizontal or vertical line. An example of a
horizontal line source would be a series of closely-spaced recharge
wells; a vertical line source example would be a corroded oil production
pipeline penetrating the fre-.h ground water zone. Area sources
represent potential ground water pollution sources that range in
geographical size from small surface ponds to aquifer recharge areas.
Septic tank systems can be considered as area sources of ground water
pollution, with the rectangular dimensions of the drainage field
representing the source boundaries. Waste stabilization ponds (surface
impoundments), and sanitary and chemical landfills also can be
considered as potential area sources of ground water pollution.
PREVIOUS USAGE OF MODELS
Empirical assessment methodologies refer to simple approaches for
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development of numerical indices of the ground water pollution potential
of man's activities. Several methodologies have been developed for
evaluating the ground water pollution potential of wastewater ponds and
sanitary and chemical landfills. Table 34 summarizes the general
features of empirical assessment methodologies (Canter, 1981).
Methodologies typically focus on a numerical index, with larger numbers
used to denote greater ground wat<-r pollution potential; however, some
methodologies encourage the grouping or ranking of pollution potential
without extensive usage of numerical indicators. Methodologies
typically contain several factors for evaluation, with the number and
type, and importance weighting, varying from methodology to methodology.
Methodologies also include descriptions of measurement techniques for
the factors, with information provided on the scaling of importance
weights (points). Final integration of information may involve
summation of factor scores or their multiplication followed by
summation. Empirical assessment methodologies should be utilized for
relative evaluations and not absolute considerations of ground water
pollution. Considerable professional judgment is needed in the
interpretation of results. However, they do represent approaches which
can be used, based on minimal data input, to provide a structured
procedure for preliminary source evaluation, site selection, and
monitoring planning.
Ground water models can be classified into flow models and solute
transport models. Ground water modeling begins with a conceptual
understanding of the physical problem. The next step in modeling is
translating the physical system .into mathematical terms (Mercer and
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Table 34: Summary Features of Empirical Assessment Methodologies
(Canter, 1981)
Numerical Indices of Ground Water Pollution Potential
Multiple Factors and Relative Importance Weighting
Measurement Techniques for Factors and Scaling (Scoring)
of Importance Weights
Indices Based on Summation of Factor Scores or Products of Scores
Need for Careful Interpretation with Professional Judgment
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Faust, 1980). In many cases Che equations are simplified, using site-
specific assumptions, to form a variety of equation subsets. An
understanding of these equations and their associated boundary and
initial conditions is necessary before a modeling problem can be
formulated. Prickett (1979) identified the following four main groups
of flow models: (1) sand tank models which are a scaled down
representation of an aquifer, including its boundary configuration and
usually its hydraulic conductivity; (2) analytical models, where the
behavior of an aquifer is described by differential equations which are
derived from basic principles such as the laws of continuity and
conservation of energy; (3) analog models, which can be subdivided into
the three major categories of viscous fluid models, electrical models,
and miscellaneous models and techniques; and (4) numerical models, which
can be subdivided into four groups — finite-difference, finite-element
variational, finite-element Galerkin, and miscellaneous.
Several studies reviewing the applicability of various ground water
models have been conducted. Prickett and Lonnquist (1971) presented
information on generalized digital computer program listings that can
simulate one-, two-, and three-dimensional nonsteady flow of ground
water in heterogeneous aquifers under water table, nonleaky, and leaky
artesian conditions. Programming techniques involving time varying
pumpage from wells, natural or artificial recharge rates, the
relationships of water exchange between surface waters and the ground
water reservoir, the process of ground water evapotranspiration, and the
mechanism of converting from artesian to water table conditions are also
included. The discussion of the digital techniques includes the
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necessary mathematical background, documented program listings,
theoretical versus computer comparisons, and field examples. Also
presented are sample computer input data and explanations of job set-up
procedures. A finite difference approach is used to formulate the
equations of ground water flow.
Appel and Bredehoeft (1976) discussed the types of problems for
which models have been, or are being, developed, including ground water
flow in saturated or partially unsaturated material, land subsidence
resulting from ground water extraction, flow in coupled ground water-
stream systems, coupling of rainfall-runoff basin models with soil
moisture-accounting aquifer flow models, interaction of economic and
hydrologic considerations, predicting the transport of contaminants in
an aquifer, and estimating the effects of proposed development schemes
for geothermal systems. The status of modeling activity for various
models is reported as being in a developmental, verification,
operational, or continued improvement phase. Bachmat, et al. (1978)
assessed the present status of 250 numerical models as a tool for ground
water related water resource management. Among the problem areas
considered were the accessibility of models to users, communications
between managers and technical personnel, inadequacies of data, and
inadequacies in modeling. The 250 models were categorized as
prediction, management, identification, and data management models.
Prediction of the movement of contaminants in ground water systems
through the use of models has been given increased emphasis in recent
years because of the growing trend toward subsurface disposal of wastes.
Anderson (1979) reviewed the formulation of contaminant transport
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models, their application to field problems, the difficulties involved
in obtaining input data, and the current status of modeling efforts.
Contaminant transport models which include the effects of dispersion
have been applied to several field studies. Regional size models which
limit the effects of dispersion have had limited success because of the
scarcity and poor quality of field data. Another difficulty in the
development of contaminant transport models is the current lack of
knowledge regarding the quantification of chemical reaction terms.
Several examples of solute transport models which have, or could
have, applicability to septic tank systems, can be cited. Khaleel and
Redell (1977) developed a three-dimensional model describing two-phase
(air-water) fluid flow equations in an integrated saturated-unsaturated
porous medium. Also, a three-dimensional convective-dispersion equation
describing the movement of a conservative, non-interacting tracer in a
nonhomogeneous, anisotropic porous medium was developed. Finite
difference forms of these two equations were solved using an implicit
scheme to solve for water or air pressures, an explicit scheme to solve
for water and air saturations, and the method of characteristics with a
numerical tensor transformation to solve the convective-dispersion
equations. The inclusion of air as a second fluid phase caused the
infiltration rate to decrease rapidly to a value well below the
saturated hydraulic conductivity when the air became compressed. This
is in contrast to one-phase fluid flow problems in which the saturated
hydraulic conductivity is considered to be the lower bound for the
infiltration rate. A field-size problem describing the migration of
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septic tank wastes around the perimeter of a lake was also considered
and solved using the total simulator.
Pickens and Lennox (1976) described the use of the finite element
method based on a Galerkin technique to formulate the problem of
simulating the two-dimensional transient movement of conservative or
nonconservative wastes in a steady state saturated ground water flow
system. The convection-dispersion equation was solved in two ways: in
the conventional Cartesian coordinate system; and in a transformed
coordinate system equivalent (•> the orthogonal curvilinear coordinate
system of streamlines and normals to those lines. The two formulations
produced identical results. Examples involving the movement of
nonconservative contaminants described by distribution coefficients, and
examples with variable input concentration are given. The model can be
applied to environmental problems related to ground water contamination
from waste disposal sites.
A final example of a solute transport model is the one developed by
Konikow and Bredehoeft (1978). The model simulates solute transport in
flowing ground water, and it was used in a field application described
later in this chapter. The model is applicable to one-or two-
dimensional problems having steady-state or transient flow. The model
computes changes in concentrations over time caused by the processes of
convective transport, hydrodynauic dispersion, and mixing (or dilution)
from fluid sources. The model assumes that the solute is non-reactive
and that gradients of fluid density, viscosity, and temperature do not
affect the velocity distribution. However, the aquifer may be
heterogeneous and (or) anisotropic. The model couples the ground water
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flow equation with the solute-transport equation. The digital computer
program uses an alternating-direction implicit procedure to solve a
finite-difference approximation to the ground water flow equation, and
it uses the method of characteristics to solve the solute-transport
equation. The model is based on a rectangular, block-centered, finite-
difference grid. It allows the specification of any number of injection
or withdrawal wells and of spatially varying diffuse recharge or
discharge, saturated thickness, transmissivity, boundary conditions, and
initial heads and concentrations. An analysis of several test problems
indicated that the error in the mass balance will be generally less than
10 percent. The test problems demonstrated that the accuracy and
precision of the numerical solution is sensitive to the initial number
of particles placed in each cell and to the size of the time increment,
as determined by the stability criteria. Mass balance errors are
commonly the greatest during the first several time increments, but tend
to decrease and stabilize with time.
In addition to general ground water flow and solute transport
equations, specific predictive equations have been developed for virus
removal in the subsurface environment beneath soil absorption systems.
Sproul (1973) discussed methods of predicting the capacity of a septic
tank-soil absorption system for removing viruses. Vilker (1978)
conducted experiments and developed models for predicting the
breakthrough of low levels of viruses from percolating columns under
conditions of adsorption and elution. Breakthrough of viruses was
illustrated by ion exchange/adsorption equations. Predictions were in
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qualitative agreement with observations from experiments that measured
virus uptake by activated carbon or silty soil in columns.
SELECTION CRITERIA FOR MODELS
Septic tank systems may range from isolated systems to high
densities (greater than one system per acre) serving single housing
units. In addition, larger septic tank systems have been designed to
serve up to several hundred housing units. Ground water modeling can be
useful for evaluation of specific sites for systems, or even larger
geographical areas that may be served by hundreds of systems. Modeling
could be used to exclude septic- tank system location on specific sites
or in larger geographical areas. In addition, modeling can be useful in
planning ground water monitoring programs for specific sites or
geographical areas. As previously mentioned, available technical
methodologies range from empirical assessment approaches to ground water
flow and solute transport models. These^me'thodologi~es> differ in their
input requirements, output characteristics, and general useability.
Accordingly, certain selection criteria were identified as basic to the
selection of technical methodologies (TM) used in this study. The
criteria statements were as follows:
1. The TM should have been previously used for evaluation of
septic tank systems.
2. The TM should be potentially useable, or adaptable for use,
for evaluation of septic tank systems.
3. If the TM needs to be calibrated prior to use, the necessary
data for calibration should be readily available.
4. The input data required for the TM should be readily
available, thus the use of the TM could be easily implemented.
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5. The resource requirements for use of the TM should be minimal
(resource requirements refer to personnel needs and personnel
qualifications, computer needs, and the time necessary for TM
calibration and usage).
6. Usage of the TM for prediction of pollutant transport in the
subsurface environment should have been previously documented.
7. The conceptual framework of the TM as well as its output
should be understandable by non-ground water modeling
specialists.
No single technical methodology (TM) which met all seven criteria
was identified. Table 35 summarizes the criteria met by the technical
methodologies selected for use in this study. The Surface Impoundment
Assessment and Waste-Soil-Site Interaction Matrix are empirical
assessment methodologies. These two methodologies (1) provide indices
of ground water pollution potential, (2) allow for direct comparison of
different sites, (3) have their greatest utility in preliminary
assessments, (4) are relatively easy to implement, (5) have low resource
requirements, (6) are easily understood by non-technical persons, and
(7) can be easily adapted to septic tank systems due to their previous
usage for projects with similar geometric configurations (area sources)
such as waste stabilization ponds and chemical and sanitary landfills.
The empirical assessment methodologies can be applied to septic tank
systems serving single housing units, to larger systems serving multiple
housing units, or to geographical areas characterized by high system
densities, e.g., greater than one system per square mile.
The Hantush analytical model listed in Table 35 (1) provides a
quantitative prediction of the ground water flow increase, (2) allows
for estimation of the qualitative changes in concentrations for
conservative pollutants in ground water, (3) can be easily programmed
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Table 35: Comparison of Study Methodologies to Selection Criteria
vo
I
Criteria
Previous Usage
Potential for Usage
Available Calibration
Data
Available Input Data
Minimal Resource
Requirements
Documentation of
Prediction Usage
Understandable
Surface Waste-Soil-Site Hantush
Impoundment Interaction Analytical
Assessment Matrix Model
0 00
3 3 3
n.a. n-a- n-a-
3 2 2
3 2 2
n.a. n-a- 3
3 2 2
Konikow
Bredehoc
Numerical
0
2
1
1
1
3
1
and
ift
Model
3 = high likelihood for satisfying criteria; 2 = moderate likelihood; 1 = low likelihood;
0 = criteria not satisfied.
-------
for hand calculators, (4) has relatively low resource requirements, (5)
does not have extensive input data requirements, (6) is generally
understandable by non-technical personnel, and (7) can be adapted to
septic tank systems due to its basic orientation to projects with
similar geometric configuration. The Hantush analytical model can be
applied to septic tank systems serving single housing units, or to
larger systems serving multiple houHing units. The Konikow and
Bredehoeft numerical model listed in Table 35 (1) could provide the most
accurate calculations for quantitative and qualitative changes to ground
water resulting from septic tank systems, (2) requires extensive field
data for model calibration and usage, (3) has extensive resource
requirements, (4) is fully documented for prediction of pollutant
transport, and (5) is difficult to understand by non-technical persons.
The Konikow and Bredehoeft model can be applied to septic tank systems
serving single housing units, to larger systems serving multiple housing
units, or to geographical areas with high system densities.
EMPIRICAL ASSESSMENT METHODOLOGIES
This section will provide a description of the two selected
methodologies — surface impoundment assessment (U.S. Environmental
Protection Agency, June 1978), and waste-soil-site interaction matrix
(Phillips, Nathwani and Mooij, 1977). Both methods were applied to 13
septic tank system areas in central Oklahoma. Since neither methodology
considers the total quantity of wastewater being discharged into the
subsurface environment, a pollutant quantity adjustment factor was
developed for the central Oklahoma areas. Finally, this section will
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summarize the results of a cursory field sampling program which was
conducted in 4 of the 13 septic tank system areas in central Oklahoma.
Surface Impoundment Assessment
The surface impoundment assessment (SIA) method is based on work by
LeGrand (1964). The method was developed for evaluating wastewater
ponds (U.S. Environmental Protection Agency, June 1978) and it yields a
sum index with numerical values ranging from 1 to 29. Due to the
geometric similarity between pond leakage entering ground water and soil
absorption system effluent entering ground water, the SIA method can be
used for evaluating the ground water pollution potential of septic tank
systems. The index is based on four factors — the unsaturated zone,
the availability of ground water (saturated zone), ground water quality,
and the hazard potential of the waste material (septic tank system
effluent in this case). Numerical values for the unsaturated zone range
from 0 to 9, for the availability of ground water from 0 to 6, for
ground water quality from 0 to 5, and for hazard potential of waste from
1 to 9.
The unsaturated zone rating is based on considering earth material
characteristics as well as zone thickness. Table 36 provides the basis
for the evaluation, with the categories of earth materials based on
permeability and secondarily upon sorption character. In rating a
particular locality where hydrologically dissimilar layers exist, the
septic tank system effluent is more likely to move through the more
permeable zones and avoid the impermeable zones. In such cases the
earth material should be rated as the more permeable of the two or more
layers which might exist. The availability of ground water factor
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Table 36: Rating of the Unsaturated Zone in the SIA Method
(U.S. Environmental Protection Agency, 1978)
Earth Material
Category
Unconsolidatcd
Rock
Consolidated
Rock
Representative
Permeability
in g?d/ft2 -
in or./sec -
I
Gravel,
Medium to
Coarse Sand
Cavernous or
Fractured
Lines tone,
Evaporites,
Basalt Lava
Fault Zones
>200
>io-2
II
Fine to Very
Fine Sand
Fractured
Igneous and
Ketanorphic
(Except Lava)
Sandstone
(Poorly
Cencnted)
2 - 200
10-* - io-2
III
Sand with
<15% clay.
Silt
Sandstone
(Moderately
Cemented)
Fractured
:*6hale
0.2 - 2
io-5 - xo-*
XV
Sand with
>15X but
<50Z clay
Sandstone
(Well
Cemented)
<0.2
ao-5
V
Clay with
<50Z sand
Siltstone
<0.02
<10"6
•"• 1
VI
Clay |
I
Unfracturcd
Shale,
Igneous and
Mctamorphie
Rocks
<0.002
^io-7
RATING MATRIX
22 >3°
^3 >10 < 30
o -a *-*
3 < 10
M i £;3
-« n c
£2~ >Q
-------
considers the ability of the aquifer to transmit ground water, thus it is
dependent upon aquifer permeability and saturated thickness. Table 37
provides information on the types of earth material and thicknesses for
various ratings. The letters accompanying the rating matrices in Tables
36 and 37 are for the purpose of identifying the origin of the rating
and documenting the process.
The ground water quality factor is based upon criteria associated
with the Underground Injection Control program of the U.S. Environmental
Protection Agency. Table 38 contains information on the rating (U.S.
Environmental Protection Agency, June 1978). If ground water has high
total dissolved solids (TDS) the rating is lower since potential ground
water uses which would be curtailed would be limited. If the ground
water is serving as a drinking water supply the rating is 5 regardless
of the TDS concentration. The waste hazard potential factor is
associated with the potential for causing harm to human health.
Examples of hazard potential ratings of waste materials classified by
source are in Table 39. The ratings consider toxicity, mobility,
persistence, volume, and concentration. Table 39 includes a range of
ratings for several sources, with the concept being that in cases where
there is considerable pretreatment, the rating may be lowered to the
bottom of the range. The waste hazard potential rating based on wastes
classified by type can also be used (U.S. Environmental Protection
Agency, June 1978). While no specific waste hazard rating was listed
for septic tank system effluents, a rating of 5 can be used based on the
fact that a rating of 4 to 8 was suggested for municipal sludges from
conventional biological sewage treatment plants (U.S. Environmental
Protection Agency, June 1978).
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Table 37: Rating Ground Water Availability in the SIA Method
(U.S. Environmental Protection Agency, 1978)
Earth
Material
Category
Unconsolidated
Rock
Consolidated
Rock
Representative
Permeability
in gpd/ft2
in cm/sec
Thickness i 30
of Saturated
Zone 3-30
(Meters)
^3
I
Gravel or sand
Cavernous or
Fractured Rock,
Poorly Cemented
Sandstone,
Fault Zones
>2
>io-4
II
Sand with £50%
clay
Moderately to
Well Cemented
Sandstone,
Fractured Shale
0.02 - 2
io-6 - io-4
III
Clay with < 50%
sand
Siltstone,
Unfractured
Shale and other
Impervious Rock
<-0.02
-------
Table 38: Rating Ground Water Quality in the S1A Method (U.S. Envi-
ronmental Protection Agency, 1978)
Rating
A
3
2
1
0
Quality
-500 mg/1 IDS or a current drinking water
source
>500 - ^ 1000 mg/1 IDS
> 1000 - £ 3000 mg/1 IDS
> 3000 - ^ 10,000 gm/1 IDS
> 10,000 mg/1 IDS
No ground water present
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Table 39: Examples of Contaminant Hazard Potential Ratings of Waste
Classified by Source in the SIA Method (U.S. Environmental
Protection Agency, 1978)
Hazard Potential
SIC Number Description of Waste Source Initial Rating
02 AGRICULTURAL PRODUCTION - LIVESTOCK
021 Livestock, except Dairy, Poultry and 3
Animal Specialties (5 for fecdlots)
024 Dairy Farms 4
025 Poultry and Eggs 4
13 OIL AND GAS EXTRACTION
131 Crude Petroleum and Natural Gas 7
132 Natural Gas Liquids 7
1381 Drilling Oil and Gas Wells 6
20 FOOD AND KINDRED PRODUCTS
201 Meat Products 3
202 Dairy Products 2
203 Canned and Preserved Fruits
and Vegetables 4
204 Grain Mill Products 2
28 CHEMICALS AND ALLIED PRODUCTS
2812 Alkalies and Chlorine 7-9
2813 Industrial Gases
2816 Inorganic Pigments 3-8
2819 Industrial Inorganic Chemicals,
not elsewhere classified 3-9
29 PETROLEUM REFINING AND RELATED INDUSTRIES
291 Petroleum Refining 8
295 Paving & Roofing Materials 7
299 Misc. Products of Petroleum & Coal 7
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Summation of the ratings for each of the four factors in the SIA
method yields an overall evaluation for the source. An additional
consideration is the degree of confidence of the investigator as well as
data availability for the specific site. An overall evaluation of the
final rating is suggested, with the ratings being either A, B, or C.
The rating of A denotes high confidence and is given when the data used
has been site specific. Ratings of B and C denote moderate and low
confidence, respectively, and are given when data has been obtained from
a generalized source, or extrapolated from adjacent sites.
Central Oklahoma Study Area
The main aquifer in this study of two empirical assessment
methodologies was the Garber-Wellington aquifer in central Oklahoma.
The surface area bounding the outcrop and underlying portions of the
aquifer includes Oklahoma and Cleveland Counties as well as portions of
Logan, Lincoln, Pottawatomie, McClain, Canadian, and Kingfisher
Counties. This area is shown in Figure 20 (Canter, 1981). The Garber-
Wellington aquifer contains over 50 million acre-feet of fresh water,
with approximately two-thirds potentially available for development.
The thickness of the fresh water zone ranges from about 50 to 275
meters. Water well depths range from about 75 to 325 meters, with the
deeper wells located in the western half of the study area.
There are additional aquifers potentially influenced by septic tank
system areas in central Oklahoma. For example, in Canadian County the
Garber-Wellington aquifer is overlain by Permian-age rock formations
such as the Hennessey shale and the El Reno group (Mogg, Schoff, and
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5W
3W_ 2W 1W IE 2E 3E
KINGFISH
16N
15N
CANADI/
LECEHP;
-—*": Outcrop Interface
?cd : El Reno Group
Pjj : Hennessey Group
P, : Garber-Wellfngfon
Formation
PO : Oscar Group
Qal : Alluvial Deposit
Qg : Terrace Deposit
5N
Figure 20: Surface Geology of Study Area.
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Reed, 1969). Saturated zone thicknesses are generally greater than 35
meters. In Logan, Oklahoma, and Cleveland Counties, septic tank system
areas are surrounded and underlain by alluvial or terrace deposits.
Where the alluvial or terrace deposits are underlain by the Hennessey
Shale, as in Norman, Moore, and the western parts of Oklahoma City, the
Garber-Wellington aquifer is confined (Bingham and Moore, 1975). The
alluvial and terrace deposits in these areas are between 3 and 35 meters
thick. The eastern half of Figure 20 represents the outcrop area for
the Garber-Wellington aquifer (Bingham and Moore, 1975; Burton and
Jacobsen, 1967).
There are 13 identifiable areas served by numerous individual
septic tank systems in central Oklahoma. These areas were identified
through discussions with Health Department personnel in Canadian, Logan,
Oklahoma, and Cleveland Counties; and with personnel at the Oklahoma
State Department of Health. Table 40 summarizes the populations served
in the areas, and Figure 21 displays the general locations of the areas.
The populations range from 150 (Sunvalley Acres) to over 12,000 (Midwest
City). Assuming that an average of 4 persons is served by a septic tank
system, the number of systems ranges from about 40 to 3000. In addition
to population information there are five other characteristics common to
all septic tank system areas that are required for usage in one or both
of the empirical assessment methodologies. These characteristics are:
(1) Soil type in area and permeability measured in inches per
hour.
(2) The depth from the soil surface to the water table measured in
feet.
(3) The land or water table gradient (slope) and the direction of
flow.
-169-
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Table 40: Populations Served by Septic Tank System Areas in
Central Oklahoma Study Area.
Location of System Area
Estimated Population
Served and Year
Arcadia
Oklahoma County
Arrowhead Hills
Oklahoma County
Crutcho
Oklahoma County
Del City
Oklahoma County
Forest Park, Lake Hiwassee, and Lake Alma
Oklahoma County
Green Pastures
Oklahoma County
Midwest City
Oklahoma County
Mustang
Canadian County
Nicoma Park
Oklahoma County
Norman (east of 24th Street)
Cleveland County
Seward Area
Logan County
Silver Lake Estate
Oklahoma County
Sum/alley Acres
Canadian County
410 (1975)
488 (1975)
587 (1977)
246 (1975)
1,200 (1975)
2,313 (1977)
12,040 (1975)
3,550 (1975)
3,000 (1975)
8,000 (1980)
2,247 (1980)
325 (1975)
150 (1975)
-170-
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(4) The distance from the septic tank area to the nearest public
or private drinking water source (water well or lake) measured
in feet.
(5) Thickness of the porous layer between the soil surface and
bedrock measured in feet.
Data for these characteristics have been collected for 13 septic
tank areas in the central Oklahoma study area and are presented in
Appendix B. Interpolation and engineering judgment had to be used in
determining some of the characteristics for several of the septic tank
areas. When information on specific characteristics was unavailable, a
"worst case" condition was used.
Application of the surface impoundment assessment method to the
general information about the 13 septic tank system areas yielded
composite scores ranging from 12 to 24, with the specific results shown
in Table 41 (Canter, 1981). Variations in the scores are primarily
reflective of the geological features of the areas. Ten septic tank
system areas are located on terrace deposits or in the Garber-Wellington
outcrop area, and they received scores ranging from 22 to 24. The
remaining three systems are located on outcrops of the Hennessey or El
Reno groups, and they had scores between 12 and 15. An additional factor
which could be utilized for evaluation of the pollution potential is the
service area or estimated total flows into septic tank systems. Table
41 also contains estimates of the total wastewater flows for the
i
respective service areas. The estimates were developed by multiplying
the average wastewater flow per person by the number of persons served by
septic tanks in the area. A flow of 52 gal ./person/day was used in
determining the total flow for a septic tank area (U.S. Environmental
-172-
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MAP SHEET
8
9
1C
OGAN COUNTY
OKLAHOMA COUNTY
CANADIAN COUNTY
LAKE
OVERHOLSE
OKLAHOMA COUNTY
CLEVELAND COUNTY
OMOORE
LAKE \
DRAPER \
Boundary of Garber
Wellington Aquifer
E;
Tat-lTOERBIRD
0LEXINGTON
LEGEND
1. Sevard Area
2. Midwest City
3. Arcadia
4. Crutcho
5. Sunvalley Park
6. Green Pastures
7. Nicoma Park
Arrowhead Hills
Mustang
East Norman
11. Forest Park, Lake Hiwasse, Lake Alma
12. Silver Lake Estates
13. Del City
Figure 21: Septic Tank Areas in Central Oklahoma.
-171-
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Table 41: Assessment of Septic Tank System Areas by Surface
Impoundment Assessment Method (Canter, 1981).
Area
(Underlying Aquifer)
Maximum Value
Minimum Value
Confidence Level
,
(U 4J
4-1 >H
CO r-l
3 -H
•O cfl
C r-4
3 -H
O CO
Wi >
0 <
6
0
C
00
C
J-l -1-1
Q) 4-1
4J C3
CO p£
»^
"O 4J
C -H
3 —I
o n
l-i 3
o cy
5
0
B
"O
i^
CO
N
CO
00
0) C
u -H
(A 4J
CC CO
3 a:
9
1
B
i
CO
•O C i-l
C -H CO
3 e •*
O ^0 ^^
I-l 4-1 C
U C (U
O 4-1
^H U 0
^-l Pu
CO »-i
t-i Q> C
QJ 4-1 O
> CO -H
O 3 •!-«
29
1
——
0) ^
4J >>
S "^
V CO
u 00
10
(0\O
3 O
^^
^J ^^^
CO
3 ?
B 0
C ^^
•< ffcl
x Arcadia (G-W)*
x Seward (G-W)
Arrowhead Hills (G-W)
Crutcho (T, G-W)
Forest Park (G-W)
Green Pastures (T, G-W)
x Midwest City (G-W)
Nicoma Park (T, G-W)
East Norman (T, G-W)
Del City (G-W)
x Sunvalley Acres (ER)
Mustang (ER)
Silver Lake Estates (H)
8B
8B
7B
7B
7B
7B
7B
7B
6B
6B
5D
4D
2E
6A
6A
6A
6A
6A
6A
6A
6A
6A
6A
2E
2E
2E
5
5
5
5
5
5
5
5
5
5
3
4
3
5
5
5
5
5
5
5
5
5
5
5
5
5
24
24
23
23
23
23
23
23
22
22
15
15
12
8
175
9
11
27
44
228
57
152
5
3
67
6
x Denotes sampling conducted in area.
* G-W = Garber-Wellington, T = terrace deposits, ER = El Reno group,
H = Hennessey group.
-173-
-------
Protection Agency, September 1978). To serve as an illustration, the
estimated population in the Arcadia area served by septic tank systems
is 410 people. The flow expressed on an annual basis is: (410
people)(52 gal./person/day)(365 day/yr) = 7.8 x 106 gal/yr (use 8 x
106).
Based on considering the anticipated annual flows along with the
ground water contamination potential rating, the following priority
listing was obtained — Midwest City (highest potential), Seward, East
Norman, Nicoma Park, Green Pastures, Mustang, Forest Park, Crutcho,
Arrowhead Hills, Arcadia, Del City, Silver Lake Estates, and Sunvalley
Acres (lowest potential).
Waste-Soil-Site Interaction Matrix
The waste-soil-site interaction matrix was developed for assessing
industrial solid or liquid waste disposal on land (Phillips, Nathwani
and Mooij, 1977). Septic tank system effluent (liquid) is discharged to
soil through the soil absorption system, hence this matrix is considered
to be potentially applicable to the evaluation of septic tank system
areas. The method involves summation of the products of various wacte-
soil-site considerations, with the resultant numerical values ranging
from 45 to 4,830. The methodology includes ten factors related to the
waste, and seven factors associated with the site of potential waste
application. Table 42 contains a description of the waste factors and
their numerical scores, and Table 43 lists the soil-site factors with
their associated weights. Table 44 represents an example interation
matrix resulting from this methodology, with the total summation of the
products being 990. Ten classes used for interpretation are as follows
-174-
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Table 42: Waste Factors in Waste-Soil-Site Interaction Matrix
(Phillip, Nathwani, and Mooij, 1977).
Group
Factor
Effects
Behavioral
(Behavioral Performance)
Human Toxicity (Ht) — ability of a substance
to produce injury once it reaches a susceptible
site in or on the body. Based on severity of
effect all substances grouped into those with
no toxicity, slight toxicity, moderate
toxicity, and severe toxicity. The Ht values
range from 0 (no toxicity) to 10 (maximum
toxicity).
Ground Water Toxicity (Gt) — related to
minimum concentration of waste substance in
ground water which would cause damage or injury
to humans, animals, or plants. The Gt value is
a function of the lowest concentration which
would cause damage or injury to any portion of
the ecosystem; the Ct values range from 0 (non-
toxic) to 10 (very toxic).
Disease Transmission Potential (Dp) —
considers mode of disease contraction,
pathogen life state, and ability of the
pathogen to survive. Disease contraction
includes direct contact, infection through
open wounds, and infection by vectors (usually
insects). Pathogen life state includes
pathogenic microorganisms with more than one
life state (virus and fungi), one life state
(vegetative pathogens), and those which cannot
survive outside their host. The ability of the
pathogen to survive includes survival in air,
water, and soil enviornraents. The Dp values
range Crom 0 (no effect) to 10 (maximum
effect).
Chemical Persistence (Cp) — related to the
chemical stability of tox'c components in the
waste. Consideration is given to the
concentration of toxic components after one-
day and iiix-days contact with coil Cnm
potential disposal site. The Cp values range
from 1 (very unstable toxic component) Lo 5
(very stable toxic component).
-175-
-------
Table 42 (continued)
Group Factor
Biological Persistence (Bp) — related to the
biodegradability of the waste as determined by
biochemical oxygen demand (BOD) and
theoretical oxygen demand (TOD). The Bp values
range from 1 (very biodegradable) to 4 (non-
biodegradable) .
Sorption (So) — related to the mobility of the
waste in the soil environment. Consideration
is given to initial concentration of toxic
component(s) in waste and well as one-day
following mixing with soil from potential
disposal site. The So values range from 1
(very strong sorption) to 10 (no sorption).
Behavioral
(Behavioral Properties) Viscosity (Vi) — related to the flow of the
waste toward the water table. Consideration is
given to the waste viscosity measured at the
average maximum temperature of the site during
its proposed months of use. The Vi values
range from 1 (very viscous) to 5( viscosity of
water).
Solubility (Sy) — along with sorption,
solubility relates to the mobility of the waste
in the soil environment. Waste solubility is
measured in pure water at 25°C and pH of 7. The
Sy values range from 1 (low solubility) to 5
(very soluble). In case the wasta is miscible
with water, Sy is equal to 5.
Acidity/Basicity (Ab) — considers the
influence of acidic or basic wastes on the
solubility of various metals. Acidic wastes
tend to solubilize metals whereas basic wastes
tend to immobil i.ze metals through
precipitation. The Ab values range from 0 (no
effect) to 5 (maximum effect).
-176-
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Table 42 (continued)
Group Factor
Capacity Rate Waste Application Rate (Ar) — related to the
volumetric application rate of the waste at the
site, the sorption characteristics of the site
(NS to be discussed in Table 7), and the
concentration of toxic component(s) in the
waste. The Ar values range from 1 (low
volumetric application rate of a low
concentration waste to a site having high
sorptive properties) to 10 (high volumetric
application rate of a high concentration waste
to a site having low sorptive properties).
-177-
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Table A3: Soil-Site Factors in Waste-Soil-Site Interaction Matrix
(Phillips, Nathwani, and Mooij, 1977).
Group
Factor
Soil
Hydrology
Site
Permeability (NP) — relates to permeability of site
materials. Clay is considered to have poor permeability, fine
sand moderate permeability, and coarse sand and gravel good
permeability. The NP values range from 2.5 (low permeability)
to 10 (maximum permeability).
Sorption (NS) — relates to sorption characteristics of site
materials. The NS values range from 1 (high sorption) to 10
(low sorption).
Water Table (NWT) — considers the fluctuating boundary free
water level and its depth. The zone of aeration occurs above
the water table and is important to oxi.dative degradation and
sorption. The NWT values range from 1 (deep water table) to 10
(water table near surface).
Gradient (NG) — relates to the effect of the hydraulic
gradient on both the direction and rate of flow of ground
water. The NG values range from 1 (gradient away from the
disposal site in a desirable direction) to 10 (gradient toward
point of water use).
Infiltration (NI) — relates to the tendency of water to enter
the surface of a waste disposal site. Involves consider-ation
of the maximum rate at which a soil :an absorb precipitation or
water additions. A site witli a large amount of infiltration
will have greater ground water pollution potential. The NI
values range from 1 (minimum infiltration) to 10 (maximum
infiltration).
Distance (NO) — relates to th.» distance from the disposal
site to the nearest point of water use. The greater the
distance the less chnnce of contamination because waste
dilution, sorption, and degradation increase with distance.
The ND values range Crom 1 (long .-libtnnce from disposal site to
use site) to 10 (disposal sico oJose tn us« site).
Thickness of Porous T..iyor (NT) — refers co porous laynr at the
disposal site. The NT values r.nige from 1 («Yoout 100 ft. or
more of depth) to 10 (about 10 ft. of dcprh).
-178-
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Table 44: Example of Waste-Soil-Site Interaction Matrix
(Phillips, Nathwani, and Mooij, 1977).
i
•
0
5
•si
£
*jd
f
I1
•i
*" o»
y
t
e^
•*?»•*
35
\
^V SOIL
\^
WASTtX
Hunan
Toilclty
Ht
(0-10)
GroundMler
Toilclty
Gt
(0-10)
Dliutl
Transmission
Potential
(0-10)
Persistence
Cp
(1-5)
Biological
Persistence
Bp
(1-4)
Sorptlon
So
(1-10)
Viscosity
VI
d-Sl
Solubility
Sy
d-S)
Acidity/
Basicity
Ab
(0-5)
Wast*
Application
Rat*
Ar
(1-10)
TOUI
X
8
5
0
3
4
5
2
1
1
4
33
SOU GROUP
Perccablluy
NP
(ZS-10)
5
40
25
15
.
20
25
10
5
S
20
165
Sorptton
NS
(1-10)
4
32
20
12
16
20
8
4
4
•
16
132
HYOROLOCT G10UP
Water Table
«T
(1-10)
5
40
25
15
20
25
10
S
5
20
165
Gradient
KG
(1-10)
2
16
10
6
8
10
4
2
2
8
66
Infiltration
Nl
(1-10)
6
43
30
18
24
30
12
6
6
24
198
SITE GROUP
Distance
NO
(I- 10)
7
56
35
21
28
35
14
7
7
28
231
Thickness of
Porous Layer
NT
(1-10)
1
8
b
3
4
5
2
1
1
1+
33
Otil
30
240
150
90
120
ISO
60
30
30
125
990
• P • point score
-179-
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— Class 1 (45-100 points), Class 2 (100-200), Class 3 (200-300), Class 4
(300-400), Class 5 (400-500), Class 6 (500-750), Class 7 (750-1000),
Class 8 (1000-1500), Class 9 (1500-2500), and Class 10 (greater than
2500). Classes 1-5 are considered acceptable, and classes 6-10
unacceptable. In the following detailed discussion the method for
calculating each pertinent factor for the central Oklahoma study area is
presented.
1. Effects Group
a. Human Toxicity (Ht): Human toxicity is based on
classifying wastes or waste constituents into four
categories regardless of the concentration of the waste.
These categories are shown in Table 45, and the Ht value
is determined as follows.
Ht = a Sr
where Ht is the human toxicity rank, a is a constant, and
Sr represents the toxicity rating. In the methodology a
is considered to have a value of 10/3, and Sr can range
from 0 to 3. Due to the potential for nitrates to cause
methemoglobinemia in infants, an Sr of 3 was used for all
13 septic tank systems in the study area; therefore, the
Ht value was 10 (maximum toxicity). Using an Sr of 3
represents a worst case approach.
b. Ground Water Toxicity (Gt): Ground water toxicity is
measured in terms of concentration of the waste or waste
constituents. The concentration is the critical value
which results in a detrimental effect on the ecosystem.
Thus, a critical concentration is defined in terms of
human toxicity, aquatic toxicity or plant toxicity, or
the minimum concentration which would cause damage to
humans, animals, or plants. The use of concentration in
the toxicity term ensures that no overlap occurs with the
human toxicity rank, which is based on severity of
effect.
For toxicity to humans, the critical concentration can be
chosen at the maximum allowable concentration in drinking
water. For aquatic toxicity, the critical concentration
can be taken as the lethal concentration (LCso) value for
fish in a standard bioassay. For plant toxicity, the
critical concentration must be taken as the maximum
-180-
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Table A5: Toxicity Values for Waste-Soil-Site Interaction Matrix
(Phillips, Nathwani, and Mooij, 1977).
1. Sr-0, no toxicity,
Applied for w:i<.UC!s that arc c;ii.i.'gori^cd .is follows:
(a) ".itcrials Lh.-it rauso no harm under .my conditions of use; or
(b) Materials vhich produce lcv:ic effects on hui 1.111? only under the
most unusual cor.ii itions or overwhelming dosage.
2. Sr=l, slight toxicii.y
Materials produce chin^Pb in the liun.in body which are readily
reversible and which uill di.Tvip;)u.ir follo"LiT; Lcrmiuation of ex-
posure, cither with or without ir.udic.il treatment.
3. Sr-2, node rate toxj«:iLy
M.uei uils that pro.'.iicc irroviM •• M>]e .as well .1*; reversible effects
in the human bcily out iio uoL tliii.il.c-n life or c.ui'.c ^crioub per-
manent hrfiCeTj ipi i v
A. Sr=3, severe to.:icity
Materials th.it when absorbed info the body by inhnl.ition,
ingestion, or through the skin -..-ill cduse injury or illness of
such severity to threaten life or to caur.e pcrmar.cni. uhysic.il
or disfigurement.
-181-
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concentration tolerated by the most sensitive plant in
the area. Since any one of toxicity to humans, aquatic
life, or plants may be limiting, the smallest critical
concentration of the set is used to define the ground
water toxicity, which is given by:
Gt - ^ (4 - loglo Cc)
where Gt is the ground water toxicity rank, and Cc
represents the smallest critical concentration in
milligrams per liter (rag/1) for humans, aquatic life or
plants. When Cc is larger than 10^ rag/1, Gt will be
equal to zero, and for Cc less than 10~3 mg/1, Gt will be
equal to ten. Therefore, the range of Gt will be from 0
(nontoxic) to 10 (very toxic). In this study Cc was
assumed to be 10 mg/1 for nitrates in ground water;
therefore, Gt was uniform at 4.3 for all 13 septic tank
system areas.
Disease Transmission Potential (Dp): This factor is
evaluated according to three specific disease
transmission properties of the waste, denoted subgroup A,
B and C. Subgroup A represents the mode of disease
contraction, subgroup B represents the pathogen life
state, and subgroup C represents the ability of the
pathogen to survive. The final disease transmission
potential factor is the sum of the contributions from the
three groups. The estimation of each contribution from
the three groups is as follows:
Subgroup A: mode of disease contraction; maximum
value of factor is 4. Selection of one of the
following three possible modes is made:
(a) direct contact: assigned a value of up to 4 on
account of immediate threat;
(b) infection through open wounds: assigned a
value of up to 3;
(c) infection by vector (usually insect): assigned
a value of up to 1*5 since site control can
minimize this.
Subgroup B: pathogen life state; maximum value of
factor is 3. Selection of one of the following
three life state categories is made:
(a) pathogenic micro-organisms with more than one
life state (virus, fungi): assigned a value of
up to 3;
-182-
-------
(b) pathogenic micro-organisms with only one life
state (vegetative pathogens): assigned a value
of up to 2;
(c) pathogenic micro-organisms which cannot survive
outside their host: assigned zero value.
Subgroup C: ability of pathogen to survive in
various environments; maximum value of factor is 2%.
Selection is made as follows:
(a) able to survive in air: assign value of 1.5;
(b) able to survive in water: assign value of 1;
(c) able to survive in soil: assign value of 1/2.
A uniform Dp value of 8.5 was used for each of the 13
septic tank system areas in the central Oklahoma study
area. The value of 8.5 was derived by considering that
bacterial and viral contamination of nearby wells can
occur from septic tank systems. The 8.5 points resulted
from 4 points from direct contact as the mode of disease
contraction, 3 points from more than one pathogen life
state, and 1.5 points due to pathogen ability to survive
in water and soil. Again, this represents a worst case
approach.
2. Behavioral Group (Behavioral Performance Subgroup)
a. Chemical Persistence (Cp): This factor relates to the
persistence over time of chemical constituents in the
waste. The factor is expressed by assuming that the decay
of the toxic component(s) of a waste can be specified by
a single parameter. This is chosen to be a pseudo-first
order rate constant k. Then the chemical persistence
factor Cp will be given by:
Cp = 5 exp (-kt), but if Cp < 1 then Cp = 1
where t is the time and k is determined from the
following equation:
CS/GI = exp (-kt)
where GI is the concentration of toxic component(3) at
one day, and C& is the concentration of toxic
component (s) at 6 days. A mixture of waste and soil in
question is prepared to make a 50% by weight soil mixture
used to determine Cj and Cf,. The contact must occur at
-183-
-------
Che average minimum temperature for the site, and the
mixture must be in the open. The chemical persistence
factor Cp will then range from 1 (for very unstable toxic
component) to 5 (for a very stable toxic component). No
laboratory studies were made to determine Cp in this
study. Instead, a worst case approach was used in that a
Cp value of 5 was used for all 13 septic tank system
areas.
Biological Persistence (Bp): This factor relates to the
biodegradability of waste components over time.
Biological degradability is measured in terms of
biochemical oxygen demand, BOD, usually measured over 5
days. For highly biodegradable waste, the BOD is
approximately equal to the theoretical oxygen demand, TOD,
measured by chemical oxidation methods. The ratio of
BOD:TOD is then a measure of degree ot biodegradability.
The following equation expresses the biological
persistence in quantitative values:
Bp = 4 (1 - BOD/TOD)
but if Bp is less than 1, then use Bp = 1. The range of
values of this factor is from 1 (very biodegradable) to 4
(unbiodegradable). No laboratory studies were conducted
to determine Bp in this study. However, several other
published studies have indicated that the BOD of septic
tank effluent is about 60% of the TOD; therefore, a Bp
value of 1.6 was used for all 13 septic tank system areas.
Sorption (So): This factor reflects the adsorption
properties of both the waste and the soil receiving the
waste. It is measured in the same manner as the chemical
persistence factor with a 50% by weight mixture of waste
and soil. The only difference between the two factors is
the length of time between measurements of the waste
concentration. The function for determination of the
sorption parameter is:
So = 11 - Co/Ci
where Co = concentration of toxic components in waste
initially, and CL = concentration of toxic components in
waste after 1 day. This short length of time effectively
eliminates the effect of rate processes. If Co/Ci is
larger than 10, then So is set equal to 1. The range of
this factor is, therefore, from 1 (very strong adsorption)
to 10 (no adsorption). The sorption parameter receives a
high point value because it is an important determinant
of the capacity of a site for neutralizing wastes. No
laboratory studies were conducted to determine So in this
-184-
-------
study. In order to present the worst case approach, an So
value of 10 was used for all 13 septic tank system areas.
No adsorption was assumed based on the general mobility
and low adsorption of nitrates in soils and ground water.
3. Behavioral Group (Behavioral Properties Subgroup)
a. Viscosity (Vi): This factor is a measure of the ability
of the waste for rapid or slow movement through the soil
to the water table. The flow of the waste towards the
water table is a function of the waste viscosity. Wastes
with low viscosities will more rapidly contaminate ground
water. This factor is defined as follows:
Vi = 5 -
where p is the viscosity of the waste in centipoises, but
if g is larger than 10, then Vi should equal to one (Vi =
1) and for p less than one, Vi is equal to 5 (Vi = 5).
The viscosity is measured at the average maximum
temperature of the site during its proposed months of use.
The range of Vi is from 1 (very viscous) to 5 (viscosity
of water). No laboratory studies were conducted to
determine Vi in this study. Since water is the primary
medium in septic tank effluents, a Vi value of 5 was used
for all 13 septic tank system areas. Use of a Vi of 5
represents a worst case approach.
b. Solubility (Sy): This factor reflects the solubility of
the waste in water and is a measure of waste mobility with
the water phase in the subsurface environment. The
solubility factor is defined as follows:
Sy = 3 + 0.5 logio S
where S is the solubility of waste in pure water at 25°C
and pH of 7, S is measured in milligrams per liter. If S
is less than 10"^ mg/1, then Sy is equal to one, and if S
is larger than 10^ mg/1, then Sy = 5. Therefore, the
solubility term has a range of 1 (low solubility) to 5
(very soluble). In case the waste is miscible with water,
Sy is equal to 5, the maximum value. The term is equally
applicable to dissolved solids and dissolved liquids. No
laboratory studies were conducted to determine Sy in this
study. Since nitrates are highly soluble in water, an Sy
value of 5 was used for all 13 septic tank system areas.
Use of an Sy value of 5 represents a worst case approach.
c. Acidity/basicity (Ab): Highly acidic or basic wastes are
undesirable in the environment. Highly acid wastes will
-185-
-------
solubilize heavy metal precipitates and allow them to
migrate and enter the ground water, while highly basic
wastes will precipitate the metals and thus immobilize
them. The acidity/basicity factor, Ab, can be determined
as follows:
pH of waste - 0 1 2 3 4 5 6 7 8 9 10 11 12 13 - 14
Ab value 55543210011223 3
The range of the acidity/basicity factor is then from 0
(no effect) to 5 (maximum effect). In case the waste is a
solid, the pH of a 50% by weight mixture of the waste in
water is measured and used to deduce the factor Ab. No
laboratory studies were conducted to determine Ab in this
study. However, since the pH of septic tank effluents is
in the range of 7 to 8, an Ab value of 0 was used for all
13 septic tank system areas.
4. Capacity Rate Group
Waste application rate (Ar): This factor measures the
attenuation effect of the soil based on the waste load
that is being applied. If the waste loading rate is too
high, then the attenuating ability of the soil will be
exceeded, causing the excess waste to penetrate deeper
into the soil and eventually to the ground water. The
quantity of contaminant per unit volume of waste
multiplied by the volumetric rate of application of the
waste per unit area is equal to the application rate of
the contaminant (quantity applied per unit area per unit
time). The waste application rate factor is defined as
follows:
Ar = (9/2) Iog10 ((Rf • Co)5* • NS) + 1
where Ar is the waste application rate, NS is the
sorption parameter for site (defined later), Rf is the
volumetric rate factor determined from the following
table:
Rf 1 2 3. 456739 JO
Volumetric <0.1 0.1-0.3 0.5-1.0 1-2 2-3 3-/« 4-5 5-6 6-7 >7
application
rate gal/ft
day
and Co is the function of concentration of toxic
component in waste, determined from:
Co = 5 + 1.25 logio C
-186-
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where C is the concentration of waste in mg/1. But if C
is less than 10~4 mg/1, then Co is equal to 1, and if C
is larger than 10^ mg/1, then Co is equal to 10. The
concentration term Co has a range of from 1 (low
solubility) to 10 (high solubility), and the waste
application rate factor (Ar) ranges from 1 (low
volumetric application rate of a low concentration waste
to a site having high sorptive properties) to 10 (high
volumetric application rate of a high concentration waste
to a site having low sorptive properties). If one
contaminant in a mixture of wastes has a dominant effects
factor, then the waste behavior may be based on that
component, otherwise each component should be considered
separately. For this study a volumetric application rate
of 4 gal/ft2/day was used, thus Rf is 6. Since nitrates
are of concern, a value of C of 34.6 mg/1 was used since
this represents an average tank effluent concentration
(U.S. Environmental Protection Agency, September 1978).
Therefore, the Co value is 6.9. The value for NS will be
subsequently discussed. Substitution of the Rf and Co
values into the above equation yields the following:
Ar = | log {(6 x 6.9)** x NS} + 1
Ar = | log (6.4 x NS) + 1
5. Soil Group
Permeability (NP): In this method the ranges in
permeability are broadly estimated. Clay is assigned a
poor permeability, fine sand a moderate permeability, and
coarse sand and gravel good permeability. It should be
noted that good permeability denotes poor conditions in
terms of ground water quality protection. The sites
considered in this study fall into two categories: (1)
the one-medium site with disposal in loose granular earth
materials extending to about 100 ft below ground surface;
and (2) the two-media site with disposal in
unconsolidated granular materials at the ground surface
underlain at shallow depths by dense rocks and linear
openings. The normalized permeability factor is defined
as:
NP =
where NP is the normalized permeability factor, P is the
permeability point score from the below charts, and Pmax
is the maximum value of P from LeGrand. For loose
granular single and two media sites, Pmax is equal to 3.
-187-
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p
I
Cloy SHI or
Oorty Fmo fond Coort* Coo.*
•end tond
Single-Media Sites
p
_J ! I
Cloy Sill or Cloyty Flno fond Fractured Coortc tond Clean
tondy cloy tond rack
Double Media Sites
Therefore, NP ranges from 2.5 (low permeability) to 10
(maximum permeability). In this study, 11 of the 13
septic tank system areas were underlain by fine sand, and
2 areas were underlain by clayey sand. The NP values for
the fine sand areas were 5.9, while for the areas with
soils nearer clayey sand the NP values ranged from 2.5 to
3.1.
b. Sorption (NS): The normalized sorption value is
determined as follows:
NS = sdrrr (Sraax + 1 ~s)
where NS is the normalized sorption factor, S is the
sorption point score (LeGrand) determined from the below
charts, and Smax is the maximum value of S from LeGrand.
For loose granular site or for two-media site Smax is
equal to 6.
* . *' . i v I 4
CoorM Smoll on.ounu of Sill Equal oirounit of Clot
clean ton) . etaf in tond cloy anti tond
Loose Granular Sites
Fractured Coorti clean Small amounts of Equal amount* ol Clay
rock tond cloy in tond do* and tond
Two-Media Sites
The range of NS is therefore from 1 (high sorption) to 10
(low sorption). In this study, 10 of the 13 septic tank
system areas were characterized by small amounts of clay
in sand, thus the NS values equalled 7.1. Two of the 13
areas had equal amounts of clay and sand, thus the NS
values equalled 5.7. Finally, one area with silt had an
NS value of 5.0. The NS values are also used in the
waste application rate factor (Ar). Based on the above
discussion of Ar, the Ar values were 8.5 when NS was 7.1,
8.0 when NS was 5.7, and 7.8 when NS was 5.0.
-188-
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6. Hydrology Group
Water Table (NWT): The water table is the fluctuating
boundary free water level and its depth is determined by
observing the free water in a well. The zone of aeration
generally occurs above the water table and is important
to oxidative degradation and sorption. The normalized
water table value used in this method is given by:
° (WTraax * l ~ WT)
WTmax +
where NWT is the normalized water table factor, WT is the
water table point score (LeGrand) from the below chart,
and WTmax is the maximum value of WT from LeGrand. For
loose granular and two-media sites, WTmax is equal to 10.
WT
t f i t * "! 1 1 «
DOMna bikM bou of frtpoui unit--"
Loose Granular Materials
WT
0 I 1 > • 9 « Tl » »
I '. I ', ' I \ r-1 H r1 1 ' 1
» e » to *o 90 nioo no «**>
Dittonci bito. bou of dura* i»it--fi
Two-Media Sites
The range of NWT is therefore from 1 (best case: deep
water table) to 10 (worst case: water table near
surface). In this study the WTmax is equal to 10, hence
NWT = jy (11 - WT)
In this study the NWT values range from 2.4 to 9.5. For
an NWT of 2.4, the WT is about 8.3, and the distance below
the septic tank area to the water table is about 150 ft.
For an NWT of 9.5, the WT is about 0.5, and the distance
to the water table is about 7 ft. Data on the depth to
the water table for each of the 13 septic tank system
areas is in Appendix B.
Gradient (NG): The gradient has an effect on both the
direction and the flow rate of ground water. Movement of
water away from the septic tank system area is much more
desirable than movement towards it. A water table may be
lowered by pumping from a well, thus increasing the
gradient and flow rate. The gradient for the matrix is
given by:
NG =
where NG is the normalized gradient factor, G is the
gradient point score (LeGrand) from the chart below, and
-189-
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Gmax is the maximum value of G from LeGrand. Gmax is
equal to 7 for loose granular and two media sites.
Loose Granular Materials
Two-HeJla Sites
Therefore, NG ranges from 1 (gradient away from the
disposal site in a desirable direction) to 10 (gradient
towards point of water use). It should be noted that in
large septic tank system areas there could be some
locations with gradients away from the site, nnd other
locations with gradients toward points of water use. In
this study the Gmax is equal to 7, hence
NG - •*§ (8 - G)
In this study the NG values range from 3.0 to 5.6. For
an NG of 3.0, the G value is 5.6, and the percentage of
gradient slope is about 7%. For an NG value of 5.6, the
G value is 3.5, and the percentage of gradient slope is
about 2%. Data on the land and water table gradient
slope is in Appendix B for the 13 septic tank system
areas.
Infiltration (NI): This factor describes the tendency of
moisture from precipitation to enter the surface of a
disposal site. The application of this factor to septic
tank systems is analogous to the percolation test to
determine the rate at which water will percolate or
infiltrate the soil in inches per hour. A septic tank
site with a high percolation rate or infiltration rate
(in/hr) is more likely to contaminate ground water than a
site with a low infiltration rate. The infiltration
factor as included in this method represents the tendency
of water to enter the surface of a waste disposal site.
The infiltration (i) is the maximum rate at which a soil
can absorb precipitation or water additions. In the case
of seepage beds or fills, it would be considered as the
maximum rate that liquid or fluid enters the soil at the
bed interface. The normalized infiltration factor used
in this method is determined as follows:
-190-
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i. inches <2 2-4 4-6 6-8 8-10 10-12 12-14 14-16 16-18 18-20
Nl 1122334455
t inches 20-22 22-24 24-26 26-28 28-30 30-32 32-34 34-36 36-38 38-40 >40
Nl 6 6 7 .7 8 8 9 9 10 10 10
Thus the range of the infiltration factor is from 1
(minimum infiltration) to 10 (maximum infiltration). The
infiltration (i) for the central Oklahoma study area is
estimated at 2 inches per year due to the moderate
precipitation and high evaporation on an annual basis.
Therefore, an Nl value of 1.0 was used for all 13 septic
tank system areas in this study.
7. Site Group
Distance (ND): This factor is a measure of the distance
from a disposal site to any point of water use, e.g.
lake, city water well, or private water well. The
greater the distance from the disposal site to the point
of use the less will be the chance of contamination.
This is because dilution occurs with distance traveled,
sorption becomes more complete, time of travel increases
with distance, and thus decay or degradation is more
complete, and the water table gradient tends to decrease
so that the velocity of flow decreases. The normalized
distance factor is given by:
ND = _ 10 — r (Draax + 1 - D)
Draax + 1
where ND is the normalized distance factor, D is the
distance point score (LeGrand) determined from the chart
below, and Dmax is the maximum value of D from LeGrand.
Draax is equal to 11 for loose granular single media sites
and two-media sites.
o
«Tlt
-I—I I I ' I 1 1—I—+-
» » n 100 IM too MO 9*3 ooi
-Fwl
Loose Granular Materials
1
1 :,
0 I
1 1
90 100
I
.«
F»l
1
100
1 ? t
900 OOD 1900
I • «
1 tun -
Two-Media Sites
The range of ND is from 1 (long distance from disposal to
effect site) to 10 (disposal site close to effect site).
In this study the Dmax is equal to 11, hence
ND = (12 - D)
-191-
-------
In this study the ND values range from 2.5 to 9.2. For
an ND value of 2.5, the D value is 9, and the distance
from the site to the nearest water use is about 5 miles
for a two-media site. For an ND value of 9.2, the D
value is about 1, and the distance from the site to the
nearest water use is about 50 ft. for loose granular
material, and 100 ft. for two-media sites. Data on
distances to public/private water wells is included in
Appendix B for each of the 13 septic tank system areas.
Thickness of porous layer (NT): This factor is a measure
of the unsaturated zone above the bedrock at each site.
The porous layer is defined as being greater than 100 ft.
In case the layer is less than 100 ft in thickness, then
the site is classified as a two-media site, the underlying
media being considered relatively impermeable. In the
second case, an additional rating factor is needed,
defined as follows:
x - T)
where NT is the thickness of porous layer factor (less
than 100 ft thick) for two-media sites, T is the thickness
point count (LeGrand) determined from the chart below,
and Tmax is the maximum value of T from LeGrand. Tmax is
equal to 6.
T
? ! ' ' '
i . . i .
>0«OM«0!OMMIOO
rm
Two-Media Sit PS
NT ranges from 1 (about 100 ft of depth porous layer) to
10 (about 10 ft of depth of porous layer). In this study
the Tmax is equal to 6, hence
NT = ±y (7 - T)
In this study an NT value of 10 was used for all 13
septic tank system areas since the thickness of the porous
layer to bedrock was typically less than 10 ft. Specific
information is included in Appendix B for the 13 septic
tank system areas.
Application of the waste-soil-site interaction matrix to the 13
septic tank system areas in central Oklahoma yielded composite scores
ranging from 2005 to 2641. Table 46 displays the matrix results for the
Arcadia area, and Table 47 lists the assessment scores for all 13 areas.
The interaction matrices for the other 12 areas are in Appendix C. Ten
-192-
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Table 46: Waste-Soil-Site Interaction Matrix Assessment for Arcadia,
Oklahoma County, Oklahoma.
^^ Soil
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
Sy
Ab
Ar
TOTAL
^x?
p^s.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
7.3
73
31
62
37
12
73
37
37
0
62
424
G
3
30
13
26
15
~5
30
15
15
0
26
175
I
1
10
4
9
5
2
10
5
5
0
9
59
D
9.2
92
40
78
46
15
92
46
46
0
78
533
T
10
100
43
85
50
16
100
50
50
0
85
579
TOTAL
435
187
370
219
70
435
219
219
0
370
2524
P = normalized score
-193-
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Table 47: Assessment of Septic Tank System Areas by Waste-Soil-Site
Interaction Matrix Methodology
Area
(Underlying Aquifer)
XSunvalley Acres (ER)
Crutcho (T, G-W)
XArcadia (G-W)*
xSeward (G-W)
Arrowhead Hills (G-W)
Green Pastures (T, r,-W)
Midwest City (G-W)
Nicoma Park (T, G-W)
Forest Park (G-W)
Mustang (ER)
Silver Lake Estates (H)
Del City (G-W)
East Norman (T, G-W)
Assessment Score
2641
2556
2524
2479
2.179
2366
2363
2319
2310
2288
2203
2030
>005
Annual Wastewater Flow
(106 gal/yr)
3
11
8
175
9
44
228
57
27
67
6
5
152
Denotes sampling conducted in area.
*G-W = Garber-Wellington, T = terrace deposits, ER = El Reno group,
H = Hennessey group
-194-
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of the 13 areas are rated in Class 9 (1500-2500) for interpretation, and
three are in Class 10 (greater than 2500). The lowest score represents
the area least likely to contaminate the ground water, and the highest
score represents the area most likely to contaminate the ground water.
Based on the normal usage of the waste-soil-site interaction matrix,
both Classes 9 and 10 would be unacceptable as waste sites. However,
since the areas are already being used for septic tank systems, the
assessment scores can be viewed as indicating ground water pollution
potential, with the areas with lower scores having lower potential.
Based on considering the assessment scores along with the anticipated
annual wastewater flows into the septic tank systems, the following
priority listing was obtained: Midwest City (highest ground water
pollution potential), Seward, East Norman, Mustang, Nicoma Park, Green
Pastures, Forest Park, Crutcho, Arrowhead Hills, Arcadia, Silver Lake
Estates, Del City, and Sunvalley Acres (lowest potential).
Comparison of Empirical Assessment Methodologies
Table 48 provides a comparative display of the rank order ground
water pollution potential of the 13 septic tank system areas as
determined by the two selected empirical assessment methodologies
adjusted by considering the annual wastewater flows in the areas. The
two adjusted methodologies provided similar rank orderings of the 13
septic tank system areas. Midwest City, Seward, and East Norman were
ranked as having the highest ground water pollution potential, while
Sunvalley Acres was ranked as the lowest. Following are some summary
comments relative to these two methodologies:
-195-
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Table 48: Comparison of Rank Order of Septic Tank System Areas
Adjusted Surface Impoundment
Assessment Methodology
Adjusted Waste-Soil-Site
Interaction Matrix Methodology
*Midwest City (1)
xSeward
East Norman
Nicoma Park
Green Pastures
Mustang
Forest Park
Crutcho
Arrowhead Hills
xArcadia
Del City
Silver Lake Estates
XSunvalley Acres (2)
Midwest City (1)
Seward
East Norman
Mustang
Nicoma Park
Green Pastures
Forest Park
Crutcho
Arrowhead Hills
Arcadia
Silver Lake Estates
Del City
XSunvalley Acres (2)
"Denotes ground water sampling conducted.
(1) Highest ground water pollution potential.
(2) Lowest ground water pollution potential.
-196-
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(1) The final ranking of the 13 septic tank system areas is
largely dependent upon the annual wastewater flow in the area,
and this is directly related to the number of persons and
septic tank systems in the area.
(2) Both the surface impoundment assessment method and the waste-
soil-site interaction matrix can be used to develop a priority
ranking of existing or planned septic tank system areas. Since
the surface impoundment assessment method has 6 items of
needed information versus 17 items in the interaction matrix,
the SIA. method is easier to use. However, it should be noted
that neither methodology accounts for wastewater flow, and
this is an important factor which should be given consideration
in the use of either method for septic tank system areas.
(3) A methodology specifically developed for septic tank system
areas would be useful. The methodology could use some factors
from both the SIA method and the interaction matrix, and should
include some additional factors such as wastewater flow,
percolation rate, septic tank density, and average life of
septic tank systems. The development of a methodology for
septic tanks would require a separate study.
As part of the study reported herein, a modest field sampling
program was conducted to evaluate the pollution potential predictions for
4 of the 13 septic tank systems areas in the study area. The program
consisted of locating 11 existing wells in the A areas, pumping the wells
for several minutes, and then collecting one-liter samples. Field
measurements included pH, salinity, and conductivity. Subsequent
laboratory analyses were performed for orthophosphates, total
phosphorus, Kjeldahl (organic) nitrogen, nitrate-nitrogen, alkalinity,
hardness, and TDS. Specific areas monitored during the program are
identified in Table 48. Two areas had high ground water pollution
potential (Midwest City and Seward), and two had lower potential
(Arcadia and Sunvalley Acres). The following criteria were used in
interpreting the key analytical results (U.S. Environmental Protection
Agency, July 1976):
-197-
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pH — value should be between 6.5 - 8.5
Orthophosphate — 4 mg/1 represents weak domestic sewage
Total phosphorus — 6 mg/1 represents weak domestic sewage
Nitrate nitrogen — 10 mg/1 is drinking water standard
TDS — 500 mg/1 is drinking water standard
Eleven wells were sampled in the four septic tank system areas, and
the results are in Table 49. All wells were within the septic tank
system areas, and none can be considered as background wells. Seven of
the 11 wells exceeded the Oklahoma nitrate-nitrogen standard; 4 wells
exceeded the USPHS TDS standard, and 9 wells had organic phosphorus
concentrations of greater than 1 mg/1 (weak domestic sewage has 2 mg/1).
Therefore, ground water contamination appears to be occurring in each of
the four septic tank system areas. In terms of rank ordering of the
areas and considering nitrates only, the average concentrations for the
wells sampled were as follows:
Midwest City 25 mg/1 (3 wells)
Seward 39 mg/1 (3 wells)
Arcadia 13 mg/1 (3 wells)
Sunvalley Acres 9 mg/1 (2 wells)
As noted earlier, Midwest City and Seward were considered to have
higher ground water pollution potential than Arcadia and Sunvalley
Acres. Both Midwest City and Seward exhibited higher nitrates in ground
water than did Arcadia and Sunvalley Acres. However, it is stressed
that this was a cursory sampling program, and a more extensive and
systematic field sampling program should be conducted to confirm the
general assumptions of the utilized empirical assessment methodologies.
-198-
-------
Table 49: Well Samples and Analysis for Septic Tank System Areas
LOCATION
^^"^^•^Jluinbe r
Parameter ^"~*~^^
pH
Salinity
-------
HANTUSH ANALYTICAL MODEL
The Hantush analytical model was developed to determine the rise
and fall of the water table under circular, rectangular, or square
recharge areas; it does not address ground water quality (Hantush, 1967).
A septic tank system serving an individual home can be considered as a
rectangular recharge area since it introduces septic tank effluent into
the soil through a subsurface drain system. A larger septic tank system
serving up to several hundred homes can also be considered as a
rectangular recharge area due to its subsurface drain system. The
assumptions basic to the Hantush model are:
(1) the aquifer is homogeneous, isotropic, and resting on a
horizontal impermeable base;
(2) the formation coefficients are constant in time and space; and
(3) the constant rate of deep percolation relative to the
hydraulic conductivity is so small that the vertically downward
percolation is almost completely refracted in the direction of
the tilt of the water' table.
The rise of the water table In response to a vertically downward
uniform rate of recharge that is supplied from a rectangular area can be
estimated with the following equation (Hantush, 1967):
M
[
l.37(ft., -
-200-
-------
where
h^ = initial height of water table above aquiclude, in feet
hm = height of water table above aquiclude with recharge, in feet
Wm = recharge rate, in gpd per unit area
m = 0.5 (h£ + hm), in feet
t B time after recharge starts, in days
Sy ° specific yield of aquifer, fraction
bm " one-half width of recharge area, in feet
x,y = coordinates of observation point in relation to center of
recharge area, in feet
T = coefficient of transmissibility, in gpd/ft
&TH = one-half length recharge area, in feet
The function of W* is defined by
The Hantush analytical model was developed based on the assumption
of a uniform recharge rate. The effluent from a septic tank system is
not uniform; however, the results from applying the model to septic tank
systems can be considered conservative, i.e., the actual rise of the
water table will be less than or equal to that predicted by the Hantush
mode1.
To illustrate the application of the Hantush analytical model an
example will be presented for an individual, mound-type septic tank
system. This example was chosen since mound-type systems are used in
areas with high water tables, thus the water table rise would be of
particular concern. The data used in the following example are
-201-
-------
hypothetical, however, they are typical for the Wisconsin area where
mound-type septic tank systems are used (Harkin, et al., 1979).
Problem: A 3-bedroom home with a daily wastewacer load of 450
gallons is to use a mound-type septic tank system. Using the
recommended loading rate of 1.2 gal/day/ft2, the derived bottom area
of the mound is calculated to be 375 ft2. Using a 20 ft by 20 ft
square mound system, calculate the water table rise under the
system. The mound system will be located on low permeable (P = 100
gal/day/ft2) sand, 2 feet above the water table that extends down 5
feet. The specific yield of the aquifer is assumed to be 0.1; and
the coefficient of transmissibility is assumed to be 500
gal/day/ft. Calculate the rise in the water table after 3 days at
distances up to 20 ft downgradient from the system recharge area.
The key data for solving the problem is summarized in Table 50.
Solution: A seven step procedure for using the Hantush analytical
model has been developed and is listed in Table 51 (Kincannon,
1981). Applying this procedure to the data for the example problem
shown in Table 50 yielded the calculated water table rises as shown
in Table 52.
As seen from Table 52, the maximum water table rise after 3 days
will be 0.375 ft (4.5 inches). An increase in the time after recharge
of more than 30-fold (to 100 days) does not even double the rise in the
water table. This suggests that the water table rise will approach some
equilibrium value somewhere around 3 or 4 months after initiation of
discharge. Although the water table rise in any case only approaches a
maximum of 8 inches, this becomes a significant rise in view of the fact
that mound systems are used in areas of high water tables. Actual
loadings by septic tanks will be intermittent which will decrease the
actual rise of the water table, however increases in loading rates
(either by malfunctioning or overloaded systems) could increase the
water table rise.
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Table 50: Data for Example Problem Using Hantush Analytical Model
Recharge Rate (W ) - 1.2 gal/day/ft
m
Time after recharge (t) - 3 days
Specific Yield (S ) - 0.1
1/2 width of recharge area (b ) - 10 ft.
m
1/2 length of recharge area (a ) - 10 ft.
Transmissibility (T) - 500 na
Y coordinate of observation well - 0 ft.
X coordinate of observation well - from 0 to 20 ft,
-203-
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Table 51: Calculation Procedure for Hantush Analytical Model
(Kincannon, 1981)
Step 1. Collect the following data:
A) Recharge rate (Wrn)
B) Net time after recharge starts (t)
C) Specific yield of aquifer (Sy)
D) One-half width of rechorgp area (b,n)
E) One-half length of recharge area (am)
F) Coefficient of transmissibility (T)
G) Coordinates of observation point in relation to the
center of recharge area (x»y)
Step 2. Calculate a, and (s.
A) o, = 1.37 (bm + x)
<*2 = T-37 (bm - x) /-f
B) B, = 1.37 (a,,,* y) /-^-
B2 = 1.37 (am - y) /-yjr
Step 3. Obtain W* (a\, BI) from the Tables in Appendix D.
Step 4. Repeat steps 2 and 3 for
W* (ai,B2), W* (a2,B,) ?s.d W* (a2, B2) -
Step 5. Calculate the rise in water table
W t
(hm - h.:) by mijltiplyino the totcil of Steps ^ and 4 by --,,vc~
JU by
Step 6. Repeat the above strps for var>ino values of x and y until a
rise in the water trible of O.G foot is achieved
Step 7. Plot the rise in the water tnhli.1 versus the distance to the
observation well.
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Table 52: Water Table Rise Under Mound-type Septic Tank Svstem
Observation Well Coordinates (ft)
x y
20 0
16 0
12 0
8 0
4 0
2 0
0 0
Water Table Rise* (ft)
(hm - hi)
.19
.23
.26
.31
.34
.35
.375 (.552n)(.656b)
*after 3 days unless otherwise noted
a = after 50 days
b = after 100 days
-205-
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KONIKOW-BREDEHOEFT NUMERICAL MODEL
The Konikow-Bredehoef t (K-B) numerical model was applied to a
septic tank system study area near Edmond, Oklahoma, to determine its
usefulness in predicting nitrate concentrations in ground water from this
source type. The K-B model is a two-dimensional solute transport model
which has been used in the analysis of ground water pollution from a
variety of source types. The K-B model, which exists as a packaged
program available for the user, muse solve both Che flow equation and the
solute transport equation. A general discussion of these two equations
is as follows.
The equation describing the transient ground water flow in two
dimensions (areal flow) for an inhomogeneous anisotropic confined
aquifer may be written as follows (Bredehoeft and Finder, 1971):
e j. IT/> ..>>
y^J =SaI + W
-------
where the second term on the right, X(x,y,t) (LT~1), is the direct
withdrawal or recharge, such as pumpage from a well, well injection,
precipitation, or evapotranspiration. The third term on the same side,
Ka
— (H8 - h), shows a steady state leakage bed, in which Ks is the
vertical hydraulic conductivity of the confining layer, stream bed, or
lake bed (LT~1), m(L) is the thickness of the confining layer, stream
bed, or lake bed, and Hs is the hydraulic head in the source bed, or
lake. T = T(x,y) is the transmissivity (L2/T).
The dispersion of a tracer in fluid flow through saturated
homogeneous porous media (solute transport) may be described by the
differential equation as (Khaleel and Reddell, 1977):
S
where
C is the tracer concentration
DJ; is the coefficient of hydrodynamic dispersion (L^/T), (a
second-order tensor),
Vi is the component of velocity vector (L/T),
i and j subscripts are used to denote tensor, where i and j = 1,2,3,
and
x£,x: are the Cartesian coordinates (L).
The differential equation used to provide a model for studying
ground water pollution patterns in a given aquifer system is a
combination of two equations: (1) ground water flow (2), and (2)
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convection-dispersion (3). As mentioned previously, these two equations
must be solved simultaneously because both convective transport and
hydrodynamic dispersion are functions of the ground water flow velocity.
After the ground water flow velocity is obtained from the head
distribution, it is used as an input parameter in the solute-transport
model. The following is the combination of two equations, (1) and (3),
which describe the two-dimensional solute-transport in a transient ground
water flow (Konikow and Grove, 1977):
ar i •> / ar \ ar cl" S -|f + W - n I-1/] - C'W
A? . I ? [ bn if-1- v •— + L at iU
at b axjV ij 3xJ vi axt nb
i.J-1,2 (4)
where
C is the concentration of the dissolved chemical species in the
aquifer (M/L3),
t is the time (T),
b is the saturated thickness of the aquifer (L),
D^j is the coefficient of hydrodynamic dispersion (a second order
tensor) (L2/T),
V£ is the velocity component in the x and y direction (L/T),
h is the hydraulic head (L),
W is the sink/source term (L/T),
n is the effective porosity (dimensionless),
C' is the concentration of the dissolved chemical in a source
(when it gets into ground water) or sink fluid (M/L3), and
S is the storage coefficient (dimensionless).
The key to all the available ground water models is to represent
Equation 4 in a finite difference form, i.e., to approximate the partial
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derivatives with finite differences between two points. If this
operation is applied to a collection of points (represented by a grid) in
the area of interest, a set of simultaneous equations results. The
various models usually differ in their approach to solving this set of
equations. The terms W and C* are characteristics of the septic tanks
that will have to be determined and inserted into the model as input. As
noted previously, these two terms are not always readily available and
may represent a significant detriment to the use of numerical models for
septic tank systems.
As noted earlier, the K-B model exists as a packaged computer
program available in Fortran IV from the U.S. Geological Survey (Konikow
and Bredehoeft, 1978). A complete listing of the program and
definitions of selected program variables is in Appendix E. This
program was used in this study. The objective of this portion of the
overall study was to determine the feasibility of modeling the effects
of septic tank systems on ground water quality by direct application of
the K-B solute transport model to an existing situation. The scope of
this analysis involved three phases. First, all available information
concerning a selected area of intense septic tank use and its underlying
aquifer had to be gathered. Second, any information gaps had to be
identified and filled as accurately as possible through the use of
estimates or assumptions. Third, the information and data gathered on
the study area was used as input to a model for predicting the long term
effects of the septic tank systems on the ground water quality (Sohrabi,
1980).
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Study Area Near Edmond, Oklahoma
The area selected for this study is located from Latitude 35°36" to
35°42'15", and from Longitude 97O23'15" to 97O27'30", in T14N, T13N,
R2W, Edmond, Oklahoma County (see Figure 22). The east and west
boundaries of the study area are the Edmond City limits both east and
west of 1-35 (about two miles west and east); the north boundary is one
and one-half miles from the Logan County line; and the south boundary is
one-half mile south of Memorial Road. The study area includes about 28
square miles. Homes are located on one-half to one-acre lots;
approximately 17,000 people live in the selected area, with 73 percent
served by septic tank systems and individual wells.
This area was thought to be appropriate for this study because:
(1) it has been classified as having concentrated areas of septic tanks
which are potential sources of nitrate contaminants into the Garber-
Wellington aquifer; (2) the hydrogeology of the area is fairly well
understood; and (3) the area is in the outcrop region of the Garber-
Wellington aquifer. Being located in the outcrop region places the
study area in a recharge zone for the Garber-Wellington aquifer, thus
the septic tank systems represent a potential threat to the ground water
quality. A significant portion of Edmond, especially the east side of
the city, is served by septic tank systems. The use of the septic tank
systems raises some significant issues which must be addressed in water
quality management planning because of the importance of ground water in
future development of the region. In Edmond, 100 percent of the needed
water is supplied by well water. The main sources of nitrate
contamination in the study area are from septic tank systems.
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97' 23' 15"
EDMOND
M Medium Density Area
L Low Density Area
31 Section numbers
Y///A Reported Septic Tank*
Concentrated Area (Square
mile)
Figure 22: Map Shows Residential Areas Which Are Served By Septic
Tank Systems in Modeled Area, (areas showing reported
septic tanks, have not been drawn to scale).
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The nitrate levels of the deeper artesian (confined) aquifer in the
Edmond area range from about 1.0 to 14.3 mg/1 (measured in 1971). High
nitrate concentrations (18 mg/1 N03) have been reported near the
Arrowhead Hills development in the study area. The Arrowhead Hills
development has a number of septic tank systems. While 18 mg/1 nitrates
is not a dangerous concentration, it could be an indication of the
beginning of nitrate contamination of the water table aquifer by septic
tank systems. If the trend toward housing additions with septic tanks
is continued, it is possible that health effects from such contamination
will be experienced.
At present, a large percentage of the public water supply in Edmond
is obtained from the confined portion of the Garber-We11ington aquifer.
However, future growth will necessitate greater use of the unconfined
portion as the confined portion is pumped beyond safe and economical
limits. Edmond is now using almost 20 percent of the water from the
unconfined portion, and this is going to increase as a result of city
development toward the east side. Areas of potentially high nitrate
concentration due to present or proposed densities using septic tank
systems are shown in Figure 22.
Hydrogeology of Study Area
The study area is underlain everywhere by the Garber Sandstone and
Wellington Formation, which have a combined maximum thickness of about
340 feet as determined by geophysical logs (Figure 23). The Garber and
Wellington constitute a single aquifer, or water-bearing unit. The
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R2W
U)
EXPLANATION
mam
Garber-Wellington
Formation
Alluvium
Trrace Deposits
Pumping Test
Wells
Base from Oklahoma Geological Survey
5 Klltt
Figure 23: Geologic Map of Modeled Area
-------
regional dip is 30-35 feet: per mile westward and southward toward the
Anadarko Basin (Wood and Burton, 1968). These two units, Permian in
age, were deposited under similar conditions, and both consist of
lenticular beds of sandstone, siltstone and shale that may vary greatly
in thickness within short lateral distances (see Figure 24). The two
units have similar hydrologic properties and are hydrologically
interconnected (Carr, 1977). The sandstone layers are fine to very
fine-ground and loosely cemented and crumble easily. None of the sand
in the Garber and Wellington is coarser than 0.35 mm (millimeter), and
the average diameter of the grains is 0.155 mm. The sandstone is
composed almost entirely of subangular to subrounded fragments of fine-
grained quartz (Wood and Burton, 1968).
The study area overlies an aquifer outcrop characterized by
rolling-steep-sided hills that are forested with scrub oak and other
small, slow-growing deciduous trees (Wood and Burton, 1969). The
Hennessey Group, which overlies the Garber-Wellington aquifer in the
western part of the study area (Figure 24), consists of shale,
siltstone, and thin beds of very fine grained sandstone. In general,
the unit thickens to the west and south. The thickness about 4 miles
west of the study area is about 90 feet, but it increases to about 400
feet at the Canadian County line (Carr and Marcher, 1977).
The Hennessey-Garber contact is a plane between the two formations
which separates them from each other in the region. This contact can be
a determining line for classifying aquifers. The available data from
well logs suggest that the upper part of the aquifer is not saturated in
a belt of about 400 miles west of and parallel to the Hennessey-Garber
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Figure 24: Cross Section of the Carber-Wellington Aquifer in Edmond,
Oklahoma, Showing Upper (Water-Table) Aquifer
rrr7.- ^ \
Sand (water
producing zone)
Shale
KXX X A
Hennessey
deposit
Soil and Clay
(Loose)
wa'er- table
(upper aquifer)
water table
(tower aquifer)
-------
contact (Carr and Marcher, 1977). As a result, water in this belt is
under water table or semi-artesian conditions (Figure 23). West of this
belt, the aquifer is fully saturated and the Hennessey serves as a
confining layer so that artesian conditions prevail. But from the
contact toward the east, unconfined conditions prevail at depths of less
than 250 ft where the aquifer is exposed at the surface (Carr and
Marcher, 1977). In addition, wells drilled east of the contact
encounter water under water-table conditions. Most wells in the Edmond
study area, where the aquifer crops out at the surface, are drilled to
depths ranging from 600 to 750 feet. The thickness of the saturated
portion of the aquifer in the study area, which was determined by
examining the geophysical logs of water wells, ranges from about 50 to
215 feet in the area (see Figure 25). The hydrology of the Gar be r-
Wellington aquifer is not that of a continuously uniform saturated body
of rock, each with its own capacity to store and transmit water to
wells. Almost one-third of the thickness has a significaiit role in
transmitting water (Engineering Enterprises, Inc., data on file, 1980).
This thickness is from the first effective shale layer, which is assumed
to be an impermeable layer for the selected upper water-table aquifer,
to the phreatic surface.
Water in the upper part of the aquifer has two components of
movement: (1) lateral movement from areas of recharge to points of
discharge, which is the principal component; and (2) vertical movement
downward due to differences between the piezometrie and potentiometric
heads of the confined and unconfined zones, respectively. The rate of
downward movement is probably very slow under natural conditions in most
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EXPLANATION
Wa:or-tob!8il973)
Unnd sufface(l9SG',
f/A Soluraletl Ihicknes'
Shale (assumed
bedrock layer}
Figure 25: Diagrammatic Best-Ease Cross-section of Modeled Area Showing Land Surface and Saturated
Thickness of Upper Part of Garber-Wellington Aquifer Above Assumed Layer for this Study
-------
places because the upper and lower parts of the aquifer are
interconnected by a shale bed of low hydraulic conductivity (Carr and
Marcher, 1977).
About one mile of the Deep Fork River in the southwest corner of
the Edmond study area and its two tributaries, Coffee and Spring Creeks,
drain the surface waters in the area. Coffee and Spring Creeks are
seasonal streams and most of the year are dry. The Deep Fork River had
an average of 30.9 cfs discharge at the Arcadia gaging station in the
spring of 1977. Almost all of the water discharged in it is from
industrial manufacturers and wastewater treatment plants.
Input Data for Model
The model selected for determining the effects of the septic tank
systems on ground water quality was the two-dimensional model of solute
transport and dispersion developed by Konikow and Bredehoeft (1978) for
the U.S. Geological Survey. Like all solute transport models, the K-B
model must solve both the ground water flow equation and the mass
transport equation. The structure of the Konikow-Bredehoeft (K-B) model
is such that the flow equation is solved by employing a finite-
difference approximation to the partial differential equation and an
alternating direction implicit procedure for solving the resulting
simultaneous equations. The mass transport equation is solved in two
parts: (1) first, the effects of convective transport are evaluated
using the method of characteristics; and (2) the effects of hydrodynamic
dispersion are evaluated using a finite-difference scheme. The
structure of the K-B model is such that the outermost nodes of the grid
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approximating the aquifer are designated as "constant head" or "no-
flow". Sources of constant recharge and constant solute concentration
can also be designated. The model also allows two direction hydraulic
conductivities (Kx and Ky) and dispersivities (DL and D?) to be
specified. The input information needed for the K-B model, and the
approaches or assumptions associated with obtaining the information, is
delineated in the following sub-sections.
(1) Hydraulic Conductivity
The hydraulic conductivity of the aquifer was assumed to be
constant and uniform over time and space at a value of 15 gallons per
day per square foot. This constant value was determined from pump tests
performed in the area in 1979.
(2) Transmissivity, Aquifer Thickness and Water Table Elevation
The transmissivity values ot the aquifer were calculated within the
model by multiplying the hydraulic conductivity by the saturated
thickness of the aquifer. The saturated thickness of the aquifer was
determined from analysis of seven available drillers' logs. The
thickness of the aquifer was computed as about 214 feet on the west
side, and was assumed to decrease at a uniform rate to about 70 feet on
the east side of the study area. Water table elevations were obtained
from an interpolated potentiometric surface plotted by Carr and Marcher
(1977).
(3) Specific Yield
Little information is available on the specific yield of the
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Garber-WelLington aquifer; therefore, it was estimated from the Upper
Permian Rush Springs Sandstone which is similar to the study aquifer.
The conservatively estimated value of specific yield for the Garber-
Wellington aquifer is 0.20 (Carr and Marcher, 1977). The specific yield
determined from 32 analyses in the similar aquifer has an average value
of 0.22.
(4) Effective Porosity
There was no data available to describe this parameter in the study
area. Therefore, the effective porosity was assumed to be 0.35 based on
estimates provided by the U.S. Geological Survey.
(5) Dispersivity
The value of the longitudinal dispersivity (100 meters) and the
ratio of transverse to longitudinal dispersivities ("x/^L = 0.33) were
estimated on the basis of review of available literature. No
determinations of this parameter (by either field or laboratory
analysis) have been done in the Edmond study area.
(6) Recharge and Discharge
The most important source of recharge in the study area is
precipitation. The estimated percolation into the ground water basin is
about 10 percent of the annual precipitation, or 3.6 inches per year
(Carr and Marcher, 1977). This value is assumed to be uniform over the
study area despite the fact that parts of the area (streets, highways,
impervious top soil, etc.) do not contribute to the natural
replenishment of the aquifer. According to the Association of Central
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Oklahoma Governments and the Edmond Water Department, there are no
intensive agricultural activities in the study area; therefore, no
return flow from irrigation sources was considered.
The other source of recharge is return flow from septic tanks;
however, this is minimal from a quantitative viewpoint, in comparison to
precipitation. Evapotranspiration losses (annually 87 inches from a
Class A Pan) from soil absorption field systems which lie under the
ground surface have a significant role in decreasing effluent
percolation through the soil column. Septic tank system effluents are
subject to two processes in the subsurface environment: (1) part of the
applied septic tank effluent is consumed by crops or grasses and by
evapotranspiration, and (2) part percolates below the root zone. A
large part of the cumulative percolate may be stored in the unsaturated
zone, and the recharge of the zone of saturation by this effluent is
very small (this value is estimated as 1% based on information obtained
from the State Health Department and a literature review). As mentioned
previously, this amount exerts only a small effect from a quantitative
viewpoint; however, it does have significant effect from a qualitative
viewpoint.
Presently, the principal means of discharge from the aquifer in the
study area is believed to be pumping from seven domestic water supply
wells; the rates have ranged from approximately 150 to 350 gpm (AGOG and
Oklahoma Water Resources Board, data on file, 1980). The other means of
discharge from the aquifer is believed to be a segment of the Deep Fork
River which serves as a gaining reach. Specific discharge (the volume
of water flowing per unit time through a unit cross-sectional area)
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through this natural boundary was estimated as 1.052 x 10~9 ft/a by use
£Vi
of Darcy's Law, q = Kg^i where q is the specific discharge, K is the
3h
hydraulic conductivity, and "gj is the hydraulic-head gradient. The area
of the stream bed was less than the area of the stream bed nodes by a
ratio of 1 to 100, and it was considered in the calculation of the
discharge. The Edmond study has some houses with individual wells
having yields ranging from about 30 to 50 gpd. The reported annual
pumpage, assuming pumps are in operation 20 hours per day, was used in
the K-B model for domestic water supply wells instead of using the
reported yield (Edmond Water Department, data on file, 1980).
Another means by which ground water can leave the aquifer is by
evaporation, but this process has an insignificant effect because of the
relatively low water-table in the investigated area.
(7) Concentration of Sinks and Sources
No nitrate data for septic tank effluents existed for the Edmond
study area. Therefore, reported literature was used to approximate the
concentration of nitrates in septic tank system effluents when it
reaches the ground water. It is assumed that only nitrates leaching
from dense numbers of septic tank systems may have a significant future
impact on the ground water in the Edmond study area. Nitrogen in the
effluent from septic tanks is primarily in the form of organic nitrogen
(25Z) and ammonium ions (Nfy) (75%) (Peavy, 1978). Several studies have
been conducted which show that the range of ammonia-nitrogen and
nitrate-nitrogen in septic tank effluents is between 77-111 mg/1 and
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0.00-0.10 mg/1, respectively (the mean values were 97 mg/1 and 0.026
mg/1) (Viraraghavan, 1976).
The major part of the nitrogen reaching the water table from septic
tanks is in the form of negatively-charged nitrate ions (N03~). Figure
26 displays the sources, transformations and pathways of nitrogen in the
subsurface environment. Ammonia-nitrogen is converted to nitrate when
aerobic conditions exist. Since nitrates are quite soluble they remain
dissolved in the water as they percolate through the soil.
The transit time of pollutants from the land surface to the ground
water table was developed for the percolation of irrigation water in the
sandstone coastal aquifer of Israel (Mercado, 1976). This aquifer has a
total thickness of 51 feet and consists of sand and calcareous sandstone
layers of Plio-Pleistocene age, intersected with clay and loam layers.
The transit time formula for irrigation water pollutants may be written
as (Mercado, 1976):
T ~ Lo
1 = — r
where
T is the retention time of pollutants in the unsaturated soil
column (T),
L is the average depth of the water table below the land surface
(L),
0 is the relative volumetric moisture content (dimensionless),
R is the precipitation rate (L/T),
qir is the irrigation rate (L/T), and
<5 is the return flow ratio (dimensionless).
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SEWAGE
to
N>
*•
I
LAND
SURFACE
N.^H'4-^RHHH
KK6
KK
GROUND WATER
Note: Subscripts K and KK denote rate constants, while subscripts
e, s, p, i and g respectively refer to exchangeable,
solution, plant, immobilized, and gaseous phase.
NO,
Figure 26: Possible Transformations and Pathways of Nitrogen from Septic
Tank Systems (Tanji ami Gupta, 1978; and Freeze and Cherry, 1979)
-------
To approximate the retention time for septic tank effluent
percolation into ground water, equation (5) is modified as:
Lo
(6)
s
where
R+ q e
s
qa is the septic tank effluent (L/T), and
c is the evapotranspiration coefficient.
The transit time for septic tank effluent is calculated on the
basis of the following information from the Edmond study area:
L = 42 feet for the node at i = 6, j = 16
o = 12% (Fisher, et al., 1969)
R =36.13 inches per year
qs = 6.09 inches per year (based on calculation)
e = 40% (estimated value)
According to equation (6) and the above information, the septic tank
effluent as influenced by precipitation takes about 1.6 years to reach
the ground water. In Mercado's (1976) study concerning nitrate pollution
of aquifers, he assumed the relationship between nitrogen quantities
released in the surface and nitrogen quantities reaching the water table
to be linear. The assumed linear relationship between potential nitrogen
on the surface and actual contributions to the aquifer is expressed by
sewage contribution = B (SWG) (7)
where
6 is the linear proportion coefficient for sewage contribution
(@5.1) (dimensionless) , and
SWG is the sewage disposal concentration (mg/1).
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The following estimation of the concentration of the septic tank
effluent when it reaches the ground water is based on the Mercado studies
on nitrate pollution in aquifers in Israel in 1976. The mean value of
ammonia-nitrogen in the septic effluent is 97 mg/1, and the 6 value is
assumed to be 70% for the study area; therefore, according to equation
(7) i the nitrogen contribution to the ground water will be 67.9 mg/1
(NH/t-N). In order for ammonia-nitrogen to be converted to nitrate
(N03), the following chemical reactions will occur (assuming all the
contributed ammonia-nitrogen will be converted to nitrates):
NH4 -*• N02 -*• N03 (nitrification process)
The resulting concentration was 300 mg/1 (N03). Once again,
according to the Mercado studies, nitrate removal in the unsaturated
soil column will consist of a 50% loss by uptake in surface vegetation,
and a 33% loss due to denitrification, adsorption, and fixation. Only
16% of the total nitrates will reach the aquifer (50 mg/1).
The locations and number of septic tanks in each grid was
determined by using an existing land-use map and communication with the
city engineer in Edmond. The following assumptions were made in the use
of the existing land-use map:
(1) in low-density areas there is one dwelling unit per acre with
3 persons per house;
(2) in medium-density areas there are two dwelling units per acre
with 3 persons per house;
(3) in high-density areas there are five dwelling units per acre
with 3 persons per house; and
(4) a minimum allowable lot size of one acre is needed to provide
an area for dilution of septic tank effluents. This was
assumed based on a percolation rate of 2 to 6.30 inches per
hour (sandstone bedrock is about 1 foot below the land
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surface, therefore, there will be less percolation through
this bedrock) (Fisher, et al., 1969).
(8) Boundary and Initial Conditions
In order to obtain a specific solution for the K-B model, it is
necessary to define the boundary and initial conditions for the aquifer.
Two types of boundary conditions were used in the K-B model: (1) no-
flow (a specific case of constant-flux boundary conditions); and (2) a
constant-head. The K-B model requires that the project area be
surrounded by a no-flow boundary because of the applied numerical
procedure (Konikow and Bredehoeft, 1978). A constant-head boundary was
specified for a portion of the Deep Fork River which passes through the
southwestern corner of the modeled area. It is a physical boundary and
a gaining reach.
Constant-head and no-flow boundaries used in the modeled area and
their locations are shown in Figure 27. A zero flux boundary was
created by assigning a value of zero transmissivity to nodes surrounding
the Edmond study area, and the head values used for the constant-head
boundary were taken from the 1973-1974 potentiometric surface map.
After existing water-level contours (1973-1974) were interpolated from
50 foot intervals to 10 foot intervals, the head values were determined
for each node on the basis of this modification. They were used as
initial heads in the model for 1973. According to verbal communication
with the U.S. Geological Survey in Oklahoma City, the water level data
between 1973 and 1974 showed minimal differences.
Initial nitrate concentrations were obtained from the Edmond Water
Department. This data was taken from wells number 16 and 17 in 1971
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CO
0)
t
w
-------
(the nitrate concentration was 1 mg/1 in both wells). Because of lack
of data from the other wells, it is assumed that the aquifer had a
uniform concentration during this year.
Results and Discussion
The results of analysis by the K-B model of the Edmond study area
must be classified as disappointing and frustrating. Disappointment
stems from the fact that the model was unable to be calibrated, even for
ground water flow (water levels). Frustration stems from the fact that
the difficulties encountered with the model were due solely to the lack
of and questionable validity of input data. These points are examined
in detail below.
The first task in the K-B model usage was to calibrate the model,
i.e., manipulate the input data so that the results produced by the
model parallel those actually measured. As stated previously, the model
was unable to be calibrated for ground water flow, hence, attempts to
calibrate it for solute transport were not made. The model actually
reproduced some moderately accurate head values for the southwestern
part of the study area, but this positive note was more than offset by
the fact that ground water levels were predicted to be above the ground
surface in the southeastern part of the region.
Difficulties in calibrating the model can be attributed to two main
sources: (1) aquifer characterization information; and (2) input data.
The ability to transform the hydrologic behavior of the aquifer into a
numerical description for the computer model is critical. Placement of
no-flow and constant-head boundaries such that they accurately reflect
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Che aquifer and/or they do not adversely affect the results of the
numerical analysis is important. The initial status of the aquifer (in
terms of heads, concentrations, etc.) also needs to be accurately
identified. Both of these aspects of characterization are dependent upon
not only a firm grasp of the study area hydrogeology, but also a firm
understanding of the relationships and complexities within the numerical
model.
The K-B model, like most ground water models, also requires the
input of a number of specific aquifer parameters. These parameters
should accurately reflect the aquifer. In other words, a parameter
determined from a particular test in a particular spot may be accurate
but may not reflect the gross properties of the aquifer. The input
parameters are not set in stone and, in fact, are the values manipulated
in order to calibrate the model. However, if the calibration procedure
requires that certain values be manipulated out of the range of real
life values, it must be concluded that errors exist somewhere. Such is
the case in this analysis. As discussed previously, most of the input
data was either estimated, assumed or obtained from minimal information.
The total uncertainty of these values defeated the calibration process.
In summary, the analysis of this study area was precluded by a
combination of the detailed input data requirements of the model and the
lack of accurate information concerning this study area.
The only conclusion to be drawn concerning the applicability of
sophisticated ground water models to the problem of septic tank systems
is that the utility of the models may be outweighed by their significant
data requirements. In other words, before an analysis of the septic
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tank systems can ever begin, the aquifer must be understood in great
detail.
Even though water quality considerations were foregone in this
analysis, a few comments can be made concerning the knowledge of the
influence of septic tank systems on ground water quality. As seen in the
development of the input data for the septic tank areas, the actual
functioning of a septic tank system is understood theoretically, but
quantitative information on the various subsurface processes is almost
non-existent. Only two parameters concerning septic tank system behavior
are needed for the K-B model — the amount and concentration of recharge
reaching the ground water. Both of these parameters had to be
calculated using estimates for input data. A better understanding of the
subsurface behavior of septic tank system effluents would be needed for
any detailed ground water quality modeling study.
HIERARCHICAL STRUCTURE FOR MODEL USAGE
Three types of models for evaluating the potential effects of
septic tank systems on ground water have been described in this chapter.
The three types of models are:
(1) An empirical assessment model for developing a ground water
pollution potential index based on site hydrogeological
information, wastewater characteristics and flows. Two
existing models were described (surface impoundment assessment,
and waste-soil-site interaction matrix), and it was suggested
that both be modified by including consideration of the annual
wastewater flow in prioritizing the ground water pollution
potential of septic tank system areas. Further, it was
determined that the SIA model was perhaps a better choice since
it required less site and wastewater information, and it
yielded essentially the same priority ranking of 13 septic
tank system areas in a central Oklahoma study area as did the
interaction matrix model. The site and wastewater information
needed for the SIA model should be fairly readily available,
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or it can be based on defensible assumptions. However, it was
noted that the SIA model was developed for surface
impoundments containing liquids, and although similar in
physical arrangements to a septic tank system (liquids
introduced to the subsurface from a surface or near-surface
source), the model does not focus on some key issues relevant
to septic tank systems. Accordingly, an empirical assessment
model specific for septic tank systems and system areas needs
to be developed. This model should include such factors as
percolation rate, septic tank density, septic tank age,
wastewater flow, depth to ground water, distance to nearest
water well and gradient relationship to well.
(2) An analytical model developed by Hantush for determining the
rise in the water table underneath a circular, rectangular, or
square recharge area. This model can be used to predict water
table rises, with these rises being of particular importance
in areas with shallow ground water. This model does not
address quality considerations. The basic site and source
information needed for use of -this model for septic tank
system areas should be fairly readily available, or it can be
based on defensible assumptions.
(3) A solute-transport model developed by Konikow and Bredehoeft
for addressing ground water flow and pollutant transport in
the subsurface environment. The K-B model is mathematically
sophisticated and, although it is available in a packaged
computer program, it requires extensive field information,
both current and historical, for calibration and subsequent
usage. An attempt was made to use the K-B model in a septic
tank system study area near Edmond, Oklahoma; however,
necessary input data was simply unavailable. This suggests
that special field studies will be necessary in order to
gather the input data necessary for use of solute-transport
models for evaluation of septic tank systems or system areas.
An hierarchical structure for usage of the three models (types of
models) is in Table 53. The potential usage is shown at three levels:
(1) a septic tank system serving an individual home; (2) several hundred
individual septic tank systems being used in a subdivision; and (3) a
large-scale septic tank system serving several hundred homes, with the
daily wastewater flow being upwards of 100,000 gallons. The empirical
assessment model could be used as part of the permitting procedure for
all three levels; however, its greatest usage should probably be for the
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Table 53: Hierarchical Structure for Septic Tank System Modeling
Model
Key Characteristics
of Model
Usage
Individual Home
Septic Tank
System
Subdivision
with Several
Hundred Septic
Tank Systems
Large-Scale
Septic Tank
System
Empirical Assessment*
Provides ground water
pollution potential index;
data needs minimal
Analytical
Predicts water level rise;
data needs minimal
X
Solute Transport
Predicts ground water flow
and concentrations of
pollutants; need field
studies to get input data
*Either the adjusted SIA model or a new model specifically developed for septic tank systems
-------
first two levels. The analytical model could be used for subdivisions
and large-scale systems, with the greatest usage probably associated with
the former. Finally, the solute-transport model should be used for
large-scale systems since their potential for ground water pollution
could justify the conduction of the necessary field studies to gather
appropriate input data.
In addition to using the structure suggested in Table 53 as part of
the permitting process, the models could also be used to evaluate
existing septic tank systems or system areas. This evaluation can be
useful in ground water pollution identification, monitoring planning, and
development of ground water quality management strategies.
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CHAPTER 5
SUMMARY AND CONCLUSIONS
Septic tanks were introduced in the United States in 1884, and
since then septic tank systems have become the most widely used method
of on-site sewage disposal, with over 70 million people depending on
them. Approximately 17 million housing units, or 1/3 of all housing
units, dispose of domestic wastewater through these systems, and about
25% of all new homes being constructed are including them. The greatest
densities of usage occur in the east and southeast as well as the
northern tier and northwest portions of the United States. A septic tank
system includes both the septic tank and the subsurface soil absorption
system. Aproximately 800 billion gallons of wastewater is discharged
annually to the soil via tile fields following the 17 million septic
tanks.
Septic tank systems that have been properly designed, constructed,
and maintained are efficient and economical alternatives to public sewage
disposal systems. However, due to poor locations for many septic tank
systems, as well as poor designs and construction and maintenance
practices, septic tank systems have polluted, or have the potential to
pollute, underlying ground waters. A major concern in many locations is
that the density of the septic tanks is greater than the natural ability
of the subsurface environment to receive and purify system effluents
prior to their movement into ground water. A related issue is that the
design life of many septic tank systems is in the order of 10-15 years.
Due to the rapid rate of placement of septic tank systems in the 1960'a,
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the usable life of many of the systems is being exceeded, and ground
water contamination is beginning to occur.
Septic tank systems are frequently reported sources of localized
ground water pollution. Historical concerns have focused on bacterial
and nitrate pollution; more recently, synthetic organic chemicals from
septic tank cleaners have been identified in ground water. Regional
ground water problems have also been recognized in areas of high septic
tank system density. Within the United States there are four counties
with more than 100,000 housing units served by septic tank systems and
cesspools, and an additional 23 counties with more than 50,000 housing
units served by these systems. Densities range from as low as 2 to
greater than 346 per square mile based on assuming an even distribution
of the septic tank systems and cesspools throughout the county. If they
are localized in segments of the county the actual densities could be
several times greater. An often-cited figure is that areas with more
than 40 systems per square mile can be considered to have potential
contamination problems.
Several types of institutional arrangements have been developed for
regulating septic tank system design and installation, operation and
maintenance, and failure detection and correction. Most of the
regulatory activities are conducted by state and local governments. The
U.S. Environmental Protection Agency can become a participant in the
regulatory process based on the provision of funding for septic tank
systems. Sections 201 (h) and (j) of the Clean Water Act of 1977 (P.L.
95-217) authorized construction grants funding of privately-owned
treatment works serving individual housing units or groups of housing
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units (or small commercial establishments), provided that a public entity
(which will ensure proper operation and maintenance) apply on behalf of
a number of such individual systems. One of the major concerns related
to funding applications is to evaluate the ground water pollution
potential of the proposed system or systems. This issue becomes even
more important for larger systems serving several hundred housing units.
To serve as an illustration of possible system size, the U.S.
Environmental Protection Agency has funded a system located in the
northeastern United States with a design flow of 100,000 gallons per day.
Based upon the needs of the U.S. Environmental Protection Agency to
evaluate the ground water pollution potential of septic tank systems
being considered for grant funding, and also the needs of engineering
designers and state and local regulatory officials for similar relevant
information, the objective of this study has been to summarize existing
literature relative to the types and mechanisms of ground water pollution
from septic tank systems, and to provide information on technical
methodologies for evaluating the ground water pollution potential of
septic tank systems. The scope of work included a survey of published
literature on the identification and evaluation of ground water pollution
from septic tank systems; and selection and evaluation of two empirical
assessment methodologies, one numerical model, and one analytical model
for their applicability to septic tank systems. Selection of the
methodologies and models was based on considering their previous or
potential use for septic tank systems; likely availability of required
input data; resource requirements in terms of general personnel and
technical specialists, computational equipment, and time or ease of
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implementation; understandability by non-technical persons; and previous
documentation for prediction of pollutant transport.
The basic septic tank system consists of a buried tank where
waterborne wastes are collected, and scum, grease and settleable solids
are removed from the liquid by gravity separation; and a subsurface drain
system where clarified effluent percolates into the soil. System
performance is essentially a function of the design of the system
components, construction techniques employed, characteristics of the
wastes, rate of hydraulic loading, climate, areal geology and topography,
physical and chemical composition of the soil mantle, and care given to
periodic maintenance.
Design considerations related to a septic tank include
determination of the appropriate volume, a choice between single and
double compartments, selection of the construction material, and
placement on the site. Placement of the septic tank on the site
basically involves consideration of the site slope and minimum setback
distances from various natural features or built structures. Soil
absorption systems include* the design and usage of trenches or beds,
seepage pits, mounds, fills and artificially drained systems. Trench
and bed systems are the most commonly used methods for on-site
wastewater treatment and disposal. Site criteria which must be met for
septic tank system approval include: a specified percolation rate, as
determined by a percolation test; and a minimum 4-ft (1.2 m) separation
between the bottom of the seepage system and the maximum seasonal
elevation of ground water. In addition, there must be a reasonable
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thickness, again normally 4 ft, of relatively permeable soil between the
seepage system and the top of a clay layer or impervious rock formation.
One of the key concerns associated with the design and usage of
septic tank systems is the potential for inadvertently polluting ground
water. This concern is increased when considering systems serving
multiple housing units. Potential ground water pollutants from septic
tank systems are primarily those associated with domestic wastewater,
unless the systems receive industrial wastes. Contaminants originating
from system cleaning can also contribute to the ground water pollution
potential of septic tank systems. The typical wastewater flow from a
household unit is about 150 to 170 liters/day/person. Typical sources
of household wastewater, expressed on a percentage basis, are:
toilet (s) — 22 to 45%; laundry ~ 4 to 26%; bath(s) — 18 to 37%;
kitchen — 6 to 13%; and other — 0 to 14%. Of concern in terms of
ground water pollution is the quality of the effluent from the septic
tank portion of the system, and the efficiency of constituent removal in
the soil underlying the soil absorption system. Based on a number of
studies, the following represent typical physical and chemical parameter
effluent concentrations from septic tanks: suspended solids — 75 mg/1;
BODs ~ 140 mg/1; COD — 300 rag/1; total nitrogen — 40 rag/1; and total
phosphorus — 15 mg/1. Studies of the efficiency of soil absorption
systems have indicated the following typical concentrations entering
ground water: suspended solids — 18-53 mg/1; BOD — 28-84 mg/1; COD —
57-142 mg/1; ammonia nitrogen — 10-78 mg/1; and total phosphates — 6-9
mg/1. In addition, other wastewater constituents of concern include
bacteria, viruses, nitrates, synthetic organic contaminants such SB
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trichloroethylene, metals (lead, tin, zinc, copper, iron, cadmium, and
arsenic), and inorganic contaminants (sodium, chlorides, potassium,
calcium, magnesium, and sulfates).
Ground water degradation has occurred in many areas having high
densities of septic tank systems, with the degradation exemplified by
high concentrations of nitrates and bacteria in addition to potentially
significant amounts of organic contaminants. One common reason for
degradation is that the capacity of the soil to absorb effluent from the
tank has been exceeded, and the waste added to the system moves to the
soil surface above the lateral lines. Another reason of greater
significance to ground water is when pollutants move too rapidly through
soils. Many soils with high hydraulic absorptive capacity
(permeability) can be rapidly overloaded with organic and inorganic
chemicals and microorganisms, thus permitting rapid movement of
contaminants from the lateral field to the ground water zone. In
considering ground water contamination from septic tank sysrems,
attention must be directed to the transport and fate of pollutants from
the soil absorption system through underlying soils and into ground
water. Physical, chemical and biological removal mechanisms may occur
in both the soil and ground water systems. Transport and fate issues
must be considered in terms of biological contaminants (bacteria and
viruses), inorganic contaminants (phosphorus, nitrogen, and metals), and
organic contaminants (synthetic organics and pesticides).
Biological contaminants (pathogens) have a wide variety of physical
and biological characteristics, including wide ranges in size, shape,
surface properties, and die-away rates. The distance of travel of
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bacteria through soil is of considerable significance since
contamination of ground supplies may present a health hazard. A number
of environmental factors can influence the transport rate, including
rainfall; soil moisture, temperature, and pH; and availability of
organic matter. Environmental factors affecting the survival of enteric
bacteria in soil include soil moisture content and holding capacity,
temperature, pH, sunlight, organic matter, and antagonism from soil
microt'lora. The physical process of straining (chance contact) and the
chemical process of adsorption (bonding and chemical interaction) appear
to be the most significant mechanisms in bacterial removal from water
percolating through soil. Factors influencing the removal efficiency of
viruses by soil include flow rate, cation concentrations, clays, soluble
organics concentrations, pH, isoelectric point of the viruses, and
general chemical composition of the soil. The most important mechanism
of virus removal in soil is by adsorption of viruses onto soil
particles.
While phosphorus can move through soils underlying SOL! absorption
systems and reach ground water, this has not been a major concern since
phosphorus can be easily retained in the underlying soils due to
chemical changes and adsorption. Phosphate ions become chemisorbed on
the surfaces of Fe and Al minerals in strongly acid to neutral systems
and on Ca minerals in neutral to alkaline systems. In the pH range
encountered in septic tank seepage fields, hydroxyapatite is the stable
calcium phosphate precipitate. However, at relatively high phosphorus
concentrations similar to those found in septic tank effluents,
dicalcium phosphate or octacalcium phosphate are formed initially,
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followed by a slow conversion to hydroxyapatite. Ammonium ions can be
discharged into the subsurface environment, or they can be generated
within the upper layers of soil from the ammonification process
(conversion of organic nitrogen to ammonia nitrogen). The transport and
fate of ammonium ions may involve adsorption, cation exchange,
incorporation into microbial biomass, or release to the atmosphere in
the gaseous form. Adsorption is probably the major mechanism of removal
in the subsurface environment. Nitrate ions can also be discharged
directly or generated within the upper layers of soil. The transport
and fate of nitrate ions may involve movement with the water phase,
uptake in plants or crops, or denitrification. Nitrates can move with
ground water with minimal transformation.
The four major reactions that metals may be involved in with soils
are adsorption, ion exchange, chemical precipitation and complexation
with organic substances. Of these four, adsorption seems to be the most
important for the fixation of heavy metals. Ion exchange is thought to
provide only a temporary or transitory mechanism for the retention of
trace and heavy metals. Precipitation reactions are greatly influenced
by pH and concentration, with precipitation predominantly occurring at
neutral to high pH values and in macroconcentrations. Organic materials
in soils may immobilize metals by complexation reactions or cation
exchange. Fixation of heavy metals by soils by either of these four
mechanisms is dependent on a number of factors including soil
composition, soil texture, pH and the oxidation-reduction potential of
the soil and associated ions.
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The transport and fate of organic contaminants in the subsurface
environment is a relatively new topical area of concern, thus the
published literature is sparse. A variety of possibilities exist for the
movement of organics, including transport with the water phase,
volatilization and loss from the soil system, retention on the soil due
to adsorption, incorporation into microbial or plant biomass, and
bacterial degradation. The relative importance of these possibilities in
a given situation is dependent upon the characteristics of the organic,
the soil types and characteristics, and the subsurface environmental
conditions. This very complicated topical area is being actively
researched at this time. Several studies have been conducted on the
movement and biodegradation of large concentrations of pesticides in
soils.
One of the objectives of this study was to provide information on
technical methodologies for evaluating the ground water pollution
potential of septic tank systems. Technical methodologies range from
empirical index approaches to sophisticated mathematical models. Models
can range from analytical approaches addressing ground water flow to
numerical approaches which aggregate both flow and solute transport
considerations. Septic tank systems can be considered as area sources of
ground water pollution, with the rectangular dimensions of the drainage
field representing the source boundaries. Waste stabilization ponds
(surface impoundments), and sanitary and chemical landfills also can be
considered as potential area sources of ground water pollution.
Empirical assessment methodologies refer to simple approaches for
development of numerical indices of the ground water pollution potential
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of man's activities. Several methodologies have been developed for
evaluating the ground water pollution potential of wastewater ponds and
sanitary and chemical landfills. Methodologies typically contain several
factors for evaluation, with the number and type, and importance
weighting, varying from methodology to methodology.
Ground water models can be classified into flow models and solute
transport models. Of interest herein are analytical models and numerical
models. Analytical models include those where the behavior of an
aquifer is described by differential equations which are derived from
basic principles such as the laws of continuity and conservation of
energy. Numerical models are actually analytical models that are so
large they require the use of digital computers, capable of multiple
iterations, to converge on a solution. The applicability of ground water
models has been the subject of a number of studies. Prediction of the
movement of contaminants in ground water systems through the use of
models has been given increased emphasis in recent years because of the
growing trend toward subsurface disposal of wastes.
Ground water modeling can be useful for evaluation of specific
sites for systems, or even larger geographical areas that may be served
by hundreds of systems. Modeling could be used to exclude septic tank
system location on specific sites or in larger geographical areas. In
addition, modeling can be useful in planning ground water monitoring
programs for specific sites or geographical areas. As noted earlier,
available technical methodologies for addressing the ground water effects
of septic tank systems range from empirical assessment approaches to
ground water flow and solute transport models. These methodologies
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differ in their input requirements, output characteristics, and general
useability. Accordingly, certain selection criteria were identified as
basic to the selection of technical methodologies (TM) used in this
study. The criteria statements were as follows:
1. The TM should have been previously used for evaluation of
septic tank systems.
2. The TM should be potentially useable, or adaptable for use,
for evaluation of septic tank systems.
3. If the TM needs to be calibrated prior to use, the necessary
data for calibration should be readily available.
4. The input data required for the TM should be readily
available, thus the use of the TM could be easily implemented.
5. The resource requirements for use of the TM should be minimal
(resource requirements refer to personnel needs and personnel
qualifications, computer needs, and the time necessary for TM
calibration and usage).
6. Usage of the TM for prediction of pollutant transport in the
subsurface environment should have been previously documented.
7. The conceptual framework of the TM as well as its output
should be understandable by non-ground water modeling
specialists.
No single technical methodology (TM) which met all seven criteria
was identified. However, two empirical assessment methodologies
(Surface Impoundment Assessment and Waste-Soil-Site Interaction Matrix),
one analytical model (Hantush), and one solute-transport model (Konikow
and Bredehoeft) was chosen for examination in this study. The two
empirical methodologies were used to determine the ground water
pollution potential of 13 septic tank system areas in central Oklahoma.
The rank order of the ground water pollution potential of the 13 areas
was determined by the two methodologies adjusted by considering the
annual wastewater flows in the areas. The two adjusted methodologies
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provided similar rank orderings of the 13 septic tank system areas. Key
findings from this part of the study were:
(1) The final ranking of the 13 septic tank system areas was
largely dependent upon the annual wastewater flow in the area,
and this is directly related to the number of persons and
septic tank systems in the area.
(2) Both the surface impoundment assessment method and the waste-
soil-site interaction matrix can be used to develop a priority
ranking of existing or planned septic tank system areas.
Since the surface impoundment assessment method has 6 items of
needed information versus 17 items in the interaction matrix,
the SIA method is easier to use. However, it should be noted
that neither methodology accounts for wastewater flow, and
this is an important factor which should be given
consideration in the use of either method for septic tank
system areas.
The Hantush analytical model was developed to determine the rise
and fall of the water table under circular, rectangular, or square
recharge areas; it does not address ground water quality. This model
was applied to a mound-type septic tank system analogous to those used
in Wisconsin, and it was determined that the water table rise only
approaches a maximum of 8 inches; however, this could be a significant
rise in view of the fact that mound systems are used in areas of high
water tables. Actual loadings from septic tank systems will be
intermittent and this will decrease the actual rise of the water table;
however, increases in loading rates (either by malfunctioning or
overloaded systems) could increase the water table rise.
The Konikow-Bredehoeft (K-B) numerical model was applied to a
septic tank system study area near Edmond, Oklahoma, to determine its
usefulness in predicting nitrate concentrations in ground water from
this source type. The K-B model is a two-dimensional solute transport
model which has been used in the analysis of ground water pollution from
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a variety of source types. The objective of this portion of the overall
study was to determine the feasibility of modeling the effects of septic
tank systems on ground water quality by direct application of the K-B
solute transport model computer package to an existing situation. The
results of analysis by the K-B model of the Edmond study area must be
classified as disappointing and frustrating. Disappointment stems from
the fact that the model was unable to be calibrated, even for ground
water flow (water levels). Frustration stems from the fact that the
difficulties encountered with the model were due solely to the lack of
and questionable validity of input data. The only conclusion to be
drawn concerning the applicability of sophisticated ground water models
to the problem of septic tank systems is that the utility of the models
may be outweighed by their significant data requirements. This suggests
that special field studies will be necessary in order to gather the
input data necessary for use of solute-transport models for evaluation
of septic tank systems or system areas.
Based on the results of this study, an hierarchical structure for
usage of the three types of technical methodologies has been developed.
Potential usage can be considered for three types of septic tank
systems: (1) a septic tank system serving an individual home; (2)
several hundred individual septic tank systems being used in a
subdivision; and (3) a large-scale septic tank system serving several
hundred homes, with the daily wastewater flow being upwards of 100,000
gallons. The empirical assessment methodology (adjusted SIA method)
could be used as part of the permitting procedure for all three types;
however, its greatest usage should probably be for the first two types.
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The analytical model could be used for subdivisions and large-scale
systems, with the greatest usage probably associated with the former.
Finally, the solute-transport model should be used for large-scale
systems since their potential for ground water pollution could justify
the conduction of the necessary field studies to gather appropriate input
data.
The conclusions from this study of the effects of septic tank
systems on ground water quality are:
1. Septic tank systems represent a significant source of ground
water pollution in the United States. The significance of this
source type is expected to increase since:
(1) many existing systems are becoming older and exceeding
their design life by several-fold;
(2) the usage of synthetic organic chemicals in the household
and for system cleaning is increasing; and
(3) larger-scale systems are being designed and used, with
flows up to 100,000 gallons/day.
2. A key issue associated with septic tank systems is related to
understanding the transport and fate of system effluents in
the subsurface environment. There is a considerable body of
knowledge relative to the transport and fate of biological and
inorganic contaminants in the subsurface environment.
However, considerable research is needed relative to the
subsurface movement and disposition of many synthetic organic
chemicals of current concern. Examples of needed research
include:
(1) Development of a classification scheme for synthetic
organic chemicals in terms of their transport and fate in
the subsurface environment.
(2) Determination of the influence of aerobic and anaerobic
conditions on transport and fate processes.
(3) Development of information on intermediate and by-
products of degradation processes which may be of greater
concern to ground water pollution than the original
synthetic organic chemicals.
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3. No specific technical methodology exists for evaluating the
ground water effects of septic tank systems based on the
following desirable criteria for such a methodology: (1)
should have been previously used for evaluation of septic tank
systems; (2) should be potentially useable, or adaptable for
use; (3) the necessary data for calibration, if needed, should
be readily available; (4) input data should be readily
available; (5) the resource requirements should be minima1; (6)
usage for prediction of pollutant transport in the subsurface
environment should have been previously documented; and (7) the
conceptual framework and output should be understandable by
non-ground water modeling specialists.
4. Application of two empirical assessment methodologies adjusted
for annual wastewaLer flow, an analytical method for
determining water table rise, and a solute-transport model for
ground water flow and pollutant concentrations has met with
some success. Usage of these approaches should be keyed to
the following three types of septic tank systems: (1) a septic
tank system serving an individual home; (2) several hundred
individual septic tank systems being used in a subdivision; and
(3) a large-scale septic tank system serving several hundred
homes, with the daily wastewater flow being upwards of 100,000
gallons. The empirical assessment methodology (adjusted SIA
method) could be used as part of the permitting or evaluation
procedure for all three types; the analytical model could be
used for subdivisions and large-scale systems; and the solute-
transport model could be used for large-scale systems.
5. A usable type of methodology for septic tank system evaluation
is the empirical assessment methodology directed toward
developing an index of ground water pollution potential. A
specific methodology should be developed for septic tank system
areas. The methodology could use some factors from both the
SIA method and the interaction matrix, and should include some
additional factors such as wastewater flow, percolation rate,
septic tank density, and average life of septic tank systems.
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Anderson, M.P., "Using Models to Simulate the Movement of Contaminants
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Andrews, W.F., "Soil as a Media (sic) for Sewage Treatment", Third
Annual Illinois Private Sewage Disposal Symposium, Feb. 1978, pp. 18-20.
Anonymous, "New Technology for Groundwater Protection", Ground Water,
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Anonymous, "Septic Tanks Currently Limited for Federal Clean Water
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Appel, C.A. and Bredehoeft, J.D., "Status of Ground Water Modeling in
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Bachmat, Y., et al., "Utilization of Numerical Groundwater Models for
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Bates, M.H., "Fate and Transport of Heavy Metals", Proceedings of the
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Bauer, D.H., Conrad, E.T. and Sherman, D.G., "Evaluation of On-Site
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Bouma, J., "Subsurface Applications of Sewage Effluent", in Planning the
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Bouma, J., "Use of Soil Survey Data for Preliminary Design of Land
Treatment Systems and Regional Planning", Ch. 22 in Simulating Nutrient
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1980, John Wiley and Sons, Inc., New York, New York.
Bower, C.A., Gardner, W.P. and Goetzen, J.O., "Dynamics of Cation
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Bradford, G.R., "Trace Element Study of Soil-Plant-Water Systems",
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Brandes, M., "Effective Phosphorus Removal by Adding Alum to Septic
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Bredehoeft, J.D. and Finder, G.F., "Mass Transport in Flowing Ground
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Brown, K.W., et al., "Movement of Fecal Coliforms and Coliphages Below
Septic Lines", Journal of Environmental Quality, Vol. 8, No. 1, Jan.-
Mar. 1979, pp. 121-125.
Burge, W.D. and Enkiri, N.K., "Virus Adsorption by Five Soils", Journal
of Environmental Quality. Vol. 7, 1978, pp. 73-76.
Burton, L.C. and Jacobsen, C.L., "Geologic Map of Cleveland and Oklahoma
Counties, Oklahoma", 1967, Oklahoma Geological Survey, Norman, Oklahoma.
Butler, R.G., Orlob, G.T. and McGaughey, P.H., "Underground Movement of
Bacterial and Chemical Pollutants", Journal of American Hater Works
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Canter, L.W., "Methods for the Assessment of Ground Water Pollution
Potential", Oct. 1981, First International Conference on Ground Water
Quality Research, Rice University, Houstin, Texas, 51 pages.
Carr, J.E. and Marcher, M.V., "A Preliminary Appraisal of the Garber-
Wellington Aquifer Southern Logan and Northern Oklahoma Counties
Oklahoma", Open File Report 77-278, May 1977, U.S. Geological Survey,
Oklahoma City, Oklahoma.
Carriere, G.D., "Priority Ranking of Septic Tank Systems in the Garber-
Wellington Area", NCGWR 80-32, Nov. 1980, 148 pages.
Childs, K.E. and Upchurch, S.B., "Documenting Ground Water Contamination
from Surface Sources", Presented at NWWA 96th Annual Conference; Water
Supply Management Resources and Operations. Vol. 1, June 20-25, 1976,
New Orleans, Louisiana.
-251-
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ChiIds, K.E., Upchurch, S.B. and Ellis, B., "Sampling of Variable Waste-
Migration Patterns in Ground Water", Ground Water, Vol. 12, No. 6, Nov.-
Dec. 1974, pp. 369-371.
Chun, M.J., et al.f "Groundwater Pollution from Sanitary Landfill
Leachate, Oahu, Hawaii", Hawaii University, Honolulu, Water Resources
Research Center, OWRT-A-040-HlU), Apr. 1975, 87 pp.
Clark, J.W., et al., Water Supply and Pollution Control, Dun-Donnally,
New York, 1977.
Converse, J.C., Design and Construction Manual for Wisconsin Ponds,
University of Wisconsin, Madison, Wisconsin, 1978.
Copenhover, E.D. and Benito, K.W., "Movement of Hazardous Substances in
Soil: A Bibliography. Volume 2. Pesticides", EPA/600/9-79/024B, Aug.
1979, U.S. Environmental Protection Agency, Municipal Environmental
Research Laboratory, Cincinnati, Ohio.
Cotteral, J.A., Jr. and Norris, D.P., "Septic Tank Systems", ASCE
Journal Sanitary Engineering Division, Vol. 95, No. SA4, 1969, pp. 715-
746.
Council on Environmental Quality, "Evaluation of Municipal Sewage
Treatment Alternatives", Feb. 1974, Washington, D.C., 402 pages.
Davidson, J.M., Ou, L.T. and Rao, P.S.C., "Behavior of High Pesticide
Concentration in Soil Water Systems", Hazardous Waste Research Symposium
on Residual Management by Land Disposal, University of Arizona, 1976,
pp. 206-212.
Davidson, J.M., et al., "Movement and Biological Degradation of Large
Concentrations of Selected Pesticides in Soils", Disposal of Hazardous
Wastes; Proceedings of the 6th Annual Symposium, Chicago, Illinois,
EPA-600/9-80-010, Mar. 1980, U.S. Environmental Protection Agency, Solid
and Hazardous Waste Research Division, Washington, D.C., pp. 93-107.
Doner, H.E., "Chloride as a Factor in the Mobilities of Ni (.11), Cu
(II), and Cd (II) in Soil", Soil Sci. Soc. Am. J., Vol. 42, 1978, pp.
882-885.
Dregne, H.E., Gomez, S. and Harris, W., "Movement of 2,4-D in Soils",
New Mexico Agricultural Experiment Station Western Regional Research
Project, Progress Report, Nov. 1969, New Mexico State University, Las
Cruces, New Mexico.
Drewry, W.A., "Virus Movement in Groundwater Systems", OWRR-A-005-ARK
(2), 1969, 85 pp., Water Resources Research Center, University of
Fayetteville, Arkansas.
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Drewry, W.A. and Eliassen, R.S., "Virus Movement in Ground Water",
Journal of Water Pollution Control Federation, Vol. 40, No. 8, 1968, pp.
R247-R271.
Edmond Water Department, Edmond, Oklahoma, 1980.
Enfield, C.G., et al., "Fate of Water Phosphorus in Soil", Journal of
Irrigation and Drainage Division, Vol. 101, No. IR3, Sept. 1975, pp.
145-155.
Engineering Enterprises, Inc., Norman, Oklahoma, 1980.
Exler, H.J., "Distribution and Reach of Groundwater Pollution in the
Subflow of a Sanitary Landfill", Gar-Wasserfach, Wasser-Absasser, Vol.
113, No. 3, 1972, pp. 101-112.
Fisher, C.F., et al., "Soil Survey of Oklahoma County, Oklahoma", Feb.
1969, United States Department of Agriculture (Soil Conservation
Service) in cooperation with Oklahoma Agricultural Experiment Station.
Freeze, R.A. and Cherry, J.A., Ground Water, Prentice-Hall, Inc.,
Englewood Cliffs, New Jersey, 1979.
Gerba, C.P., "Fate of Waste Water Bacteria and Viruses in Soil", Journal
of the Irrigation and Drainage Division, Vol. 101, No. IR3, Sept. 1975,
pp. 157-173.
Gerba, C.P. and Goyal, S.M., "Adsorption of Selected Enteroviruses to
Soils", Proceedings of International Symposium on Land Treatment of
Wastewater, Vol. 2, 1978, U.S. Army Corps of Engineers Cold Regions
Research and Engineering Laboratory, Hanover, New Hampshire, pp. 225-
232.
Griffin, R.A. and Chow, S.J., "Disposal and Removal of Halogenated
Hydrocarbons in Soils", Disposal of Hazardous Wastes; Proceedings of
the Sixth Annual Symposium, Chicago, Illinois, EPA 600/9-80-010, Mar.
1980, Southwest Research Institute/Solid and Hazardous Waste Research
Division, U.S. Environmental Protection Agency, pp. 82-92.
Hagedorn, C., Hansen, D.T. and Simonson, G.H., "Survival and Movement of
Fecal Indicator Bacteria in Soil Under Conditions of Saturated Flow",
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59.
Hahne, H.C.H. and Kroontje, W., "The Simultaneous Effect of pH and
Chloride Concentration Upon Mercury (II) as a Pollutant", Soil Sci. Soc.
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Hantush, M.S., "Growth and Decay for Groundwater-Mounds in Response to
Uniform Percolation", Water Resources Research, Vol. 3, 1967, p. 227.
-253-
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Harkin, J.M., et al., "Evaluation of Mound Systems for Purification of
Septic Tank Effluent", Technical Report WIS WRC 79-05, 1979, Madison,
Wisconsin.
Healy, K.A. and Laak, R., "Site Evaluation and Design of Seepage
Fields", ASCE Journal of Environmental Engineering Division, Vol. 100,
No. 5, Oct. 1974, pp. 1133-1146.
Hershaft, A., "The Plight and Promise of On-Site Wastewater Treatment",
Compost Science, Vol. 17, No. 5, Winter 1976, pp. 6-13.
Jenne, E.A., "Controls on Mn, Fe, CO, Ni, Cu and Zn Concentrations in
Soils and Water: The Significant Role of Hydrous Mn and Fe Oxides", Adv.
in Chem. Ser.. Vol. 73, 1968, pp. 337-387.
Jones, R.A., et al., "Septic Tank Disposal Systems as Phosphorus Sources
for Surface Waters", Report No. EPA-600/3-77-129, Nov. 1977, U.S.
Environmental Protection Agency, Ada, Oklahoma.
Kee, N.S. and Bloomfield, C., "The Effect of Flooding and Aeration on
the Mobility of Certain Trace Elements in Soils", Plant and Soil, Vol.
16, No. 1, 1962, p. 108.
Khaleel, R. and Redell, D.L., "Simulation of Pollutant Movement in
Ground Water Aquifers", OWRT-A-030-Tex(l), May 1977, 261 pp., Water
Resources Institute, Texas A&M University, College Station, Texas.
Kincannon, D.F., Draft Final Report on Land Application of Wastewater,
Oklahoma State University, Stillwater, Oklahoma, 1981.
Konikow, L.F. and Bredehoeft, J.D., "Computer Model of Two-Dimensional
Solute Transport and Dispersion in Ground Water", Techniques of Water-
Resources Investigations of the United States Geological Survey, Book 1,
Chapter 2, 1978, U.S. Geological Survey, Washington, D.C.
Konikow, L.F. and Grove, D.B., "Derivation of Equations Describing
Solute Transport in Ground Water", Water-Resources Investigations #77-
19, 1977, U.S. Geological Survey, Washington, D.C.
Korte, N.E., et al., "Trace Element Movement in Soils: Influence cf
Soil Physical and Chemical Properties", Soil Science, Vol. 122, 1976,
pp. 350-359.
Ku, H.F.H., Ragone, S.E. and Vecchioli, J., "Changes in Concentration of
Certain Constituents of Treated Wastewater During Movement through the
Magothy Aquifer, Bay Park, New York", Journal of Research of the U.S.
Geological Survey, Vol. 3, No. 1, Jan.-Feb. 1975, pp. 89-92.
Laak, R., Healy, K.A. and Hardisty, D.M., "Rational Basis for Septic
Tank System Design", Ground Water, Vol. 12, No. 6, Nov.-Dec. 1974, pp.
348-351.
-254-
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Lakshman, 15. T., "Faulty Waste Disposal Practices Endanger Groundwater
Quality", Water and Sewage Works, Vol. 126, No. 6, July 1979, pp. 94-98.
Lawrence, C.H., "Septic Tank Performance", Journal of Environmental
Health, Vol. 36, No. 3, Nov.-Dec., 1973, pp. 226-228.
LeCrand, H.E., "Hydrogeologic Factors Controlling Pollutant Movement in
Shallow Ground", Geological Society of America, Vol. 4, No. 2, 1972, pp.
86-87.
LeGrand, H.E., "System of Reevaluation of Contamination Potential of
Some Waste Disposal Sites", Journal American Water Works Association,
Vol. 56, Aug. 1964, pp. 959-974.
Lindsay, W.L., "Inorganic Phase Equilibria of Micronutrients in Soil",
in J.S. Hortuedt, P.M. Giordano, W.L. Lindsay (ed), Micronutrients in
Agriculture, Madison, Wisconsin, 1972, p. 41.
Loehr, R.C., "Pretreatment Requirements for Land Application of
Wastewater", Proceedings of International Symposium on Land Treatment of
Wastewater, Vol. 1, 1978, U.S. Army Corps of Engineers Cold Regions
Research and Engineering Laboratory, Hanover, New Hampshire, pp. 283-
287.
Lofty, R.J., et al., "Environmental Assessment of Subsurface Disposal of
Municipal Wastewater Treatment Sludge", June 1978, 380 pp., SCS
Engineers, Long Beach, California, EPA/530/SW-167C.
Mercado, A., "Nitrate and Chloride Pollution of Aquifers: A Regional
Study with the Aid of a Single-Cell Model", Water Resources Research,
Vol. 12, No. 4, Aug. 1976, pp. 731-747.
Mercer, J.W. and Faust, C.R., "Ground Water Modeling: Mathematical
Models", Ground Water, Vol. 18, No. 3, May-June 1980, pp. 212-227.
Miller, D.W., Braids, O.C. and Walker, W.H., "The Prevalence of
Subsurface Migration of Hazardous Chemical Substances at Selected
Industrial Waste Land Disposal Sites", PB-272 973, Sept. 1977, National
Technical Information Service, Springfield, Virginia.
Mogg, J.L., Schoff, S.L. and Reed, E.W., "Ground Water of Canadian
County", Bulletin 87, 1969, Oklahoma Geological Survey, Norman,
Oklahoma.
Muir, K.S., "Initial Assessment of the Groundwater Resources in the
Monterey Bay Region, California", Report No. USGS/WRD/WRI-77/053, Aug.
1977, U.S. Geological Survey, Menlo Park, California.
Nelson, J.D. and Ward, R.C., "Ground Water Monitoring Strategies for On-
Site Sewage Disposal Systems", Proceedings of the Third National
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Symposium on Individual and Small Community Sewage Treatment, ASAE
Publication 1-82, 1982, American Society of Agricultural Engineers, St.
Joseph, Michigan, pp. 301-308.
Newspaper Enterprise Association, Inc., World Almanac and Book of Facts,
1982, New York, New York.
Oklahoma Water Resources Board, Oklahoma City, Oklahoma, 1980.
Otis, R.J., et al., "Effluent Distribution", Proceedings of the Second
National Home Sewage Treatment Symposium, American Society of
Agricultural Engineers, 1977, pp. 61-85.
Otis, R.J., Plews, G.D. and Patterson, D.H., "Design of Conventional
Soil Adsorption Trenches and beds", Third Annual Illinois Private Sewage
Disposal Symposium, Toledo Area Council of Governments, Toledo, Ohio,
1978, pp. 52-66.
Peavy, H.S., "Groundwater Pollution from Septic Tank Drainfields", June
1978, Montana State University, Montana.
Phillips, C.R., Nathwani, J.S. and Mooij, H., "Development of a Soil-
Waste Interaction Matrix for Assessing Land Disposal of Industrial
Waste", Water Research, Vol. 11, Nov. 1977, pp. 859-868.
Pickens, J.F. and Lennox, W.C., "Numerical Simulation of Waste Movement
in Steady Ground Water Flow Systems", Water Resources Research, Vol. 12,
No. 2, Apr. 1976, pp. 171-184.
Pimentel, K.D., et al., "Sampling Strategies in Groundwater Transport
and Fate Studies for In Situ Shale Retorting", Conf-7903-34-Si Jana
1979, Lawrence Liverraore Lab., California University, Livermore,
California.
Prickett, T.A. and Lonnquist, C.G., "Selected Digital Computer
Techniques for Ground Water Resources Evaluation", Bulletin 55, 1971,
Illinois Water Survey, Urbana, Illinois.
Prickett, T.A., "State-of-the-Art of Groundwater Modeling", Water Supply
and Management. Vol. 3, No. 2, 1979, pp. 134-141.
Rahe, T.M., et al., "Transport of Antibiotic-Resistant Escherichia Coli
through Western Oregon Hillslope Soils Under Conditions of Saturated
Flow", Journal of Environmental Quality, Vol. 7, No. 4, Oct.-Dec., 1978,
pp. 487-494.
Reneau, R.B. and Pettry, D.E., "Movement of Coliform Bacteria from
Septic Tank Effluent through Selected Coastal Plain Soils of Virginia",
Journal of Environmental Quality, Vol. 4, No. 1, Jan.-Mar. 1975, pp. 41-
45.
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Roberts, P.V., et al., "Direct Injection of Reclaimed Water into an
Aquifer", Journal of American Society of Civil Engineers, Environmental
Engineering Division, Vol. 104, No. EE5, Oct. 1978, pp. 933-949.
Roberts, P.V., "Organic Contaminant Behavior During Ground Water
Recharge", Journal Water Pollution Control Federation, Vol. 52, No. 1,
Jan. 1980, pp. 161-171.
Robertson, J.B. and Kahn, L., "The Infiltration of Aldrin through Ottawa
Sand Columns", Professional Paper 650-C, 1969, U.S. Geological Survey,
Idaho Falls, Idaho, pp. C219-C223.
Sandhu, S.S., Warren, W.J. and Nelson, P., "Trace Inorganics in Rural
Potable Water and Their Correlation to Possible Sources", Water
Research. Vol. 12, 1977, pp. 257-261.
Sawhrey, B.L. and Starr, J.L., "Movement of Phosphorus from a Septic
System Drainfield", Journal Water Pollution Control Federation, Vol. 49,
No. 11, Nov. 1977, pp. 2238-2242.
Scalf, M.R., Dunlap, W.J. and Kreissl, J.F., "Environmental Effects of
Septic Tank Systems", EPA-600/3-77-096, Aug. 1977, U.S. Environmental
Protection Agency, Ada, Oklahoma.
Schneider, A.D., Wiese, A.F. and Jones, O.R., "Movement of Three
Herbicides in a Fine Sand Aquifer", Agronomy Journal, Vol. 69, No. 3,
May-June 1977, pp. 432-436.
Senn, C.L., "Current Status of On-Site Wastewater Management", Journal
of Environmental Health, Vol. 40, No. 5, Mar.-Apr. 1978, pp. 279-284.
Shoemaker, C.A. and Porter, K.S., "Recharge and Nitrogen Transport Model
for Nassau and Suffolk Counties, New York", NTIS BP-276 906/55, Jan.
1978, Cornell University, Ithaca, New York.
Siegrist, R., "Waste Segregation as a Means of Enhancing Onsite
Wastewater Management", Journal of Environmental Health, Vol. 40, No. 1,
July-Aug. 1977, pp. 5-8.
Sohrabi, T.M., "Digital-Transport Model Study of Potential Nitrate
Contamination from Septic Tank Systems Near Edraond, Oklahoma", NCGWR 80-
38, Nov. 1980, 107 pages.
Sproul, O.J., "Virus Movement Into Ground Water from Septic Tank
Systems", Paper No. 12, Sept. 1973, Rural Environmental Engineering
Conference on Water Pollution Control in Low Density Areas Proceedings,
University Press of New England, Hanover, New Hampshire.
Tanji, K.K. and Gupta, S.K., "Computer Simulation Modeling for Nitrogen
in Irrigated Croplands", Nitrogen in the Environment, Vol. 1, Academic
Press, Inc., New York, New York, 1978.
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Thomas, R.E., 1982, personal communication.
U.S. Department of Commerce, Bureau of the Census, State and
Metropolitan Area Data Book 1979 — A Statistical Abstract Supplement,
1980, Washington, D.C.
U.S. Environmental Protection Agency, "Ground Water Pollution from
Subsurface Excavations", EPA-430/9-73-012, 1973, Washington, D.C.
U.S. Environmental Protection Agency, "Alternative Waste Management
Techniques for Best Practicable Waste Treatment", Federal Register, Vol.
41, No. 29, Feb. 11, 1976, pp. 6190-6191.
U.S. Environmental Protection Agency, "Quality Criteria for Water", July
1976, U.S. Government Printing Office, Washington, D.C.
U.S. Environmental Protection Agency, "The Report to Congress: Waste
Disposal Practices and Their Effects on Ground Water", EPA 570/9-77-001,
June 1977, Washington, D.C., pp. 294-321.
U.S. Environmental Protection Agency, "A Manual for Evaluating
Contamination Potential of Surface Impoundments", EPA 570/9-78-003, June
1978, Office of Drinking Water, Washington, D.C.
U.S. Environmental Protection Agency, "Management of Small Waste Flows",
Report No. EPA-600/2-78-173, Sept. 1978, Cincinnati, Ohio.
U.S. Environmental Protection Agency, "Planning Workshops to Develop
Recommendations for a Ground Water Protection Strategy, Sections I, II
and III", May 1980, Washington, D.C.
U.S. Environmental Protection Agency, "Design Manual — Onsite
Wastewater Treatment and Disposal Systems", EPA 625/1-80-012, Oct. 1980,
Cincinnati, Ohio.
U.S. Public Health Service, "Manual of Septic Tank Practice", Pub. No.
526, 1967, Washington, D.C.
University of Wisconsin, "Management of Small Wastewater Flows", EPA-
600/2-78-173, Sept. 1978, U.S. Environmental Protection Agency,
Cincinnati, Ohio, pp. 19-20.
Vandenburg, A., et al., "Subsurface Waste Disposal in Lambton County
Ontario - Piezometric Head in the Disposal Formation and Ground Water
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Van Hook, R.I., "Transport and Transportation Pathways of Hazardous
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Vol. 27, Dec. 1978, pp. 295-308.
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Vi.lk.cr, V.L., "An Adsorption Model for Prediction of Virus Breakthrough
from Fixed Beds", Proceedings of International Symposium on Land
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Regions Research and Engineering Laboratory, Hanover, New Hampshire, pp.
381-388.
Viraraghavan, T., "Septic Tank Efficiency", ASCE Journal Environmental
Engineering Division, Vol. 102, No. EE2, Apr. 1976, pp. 505-508.
Viraraghavan, T. and Warnock, R.G., "Efficiency of a Septic Tile
System", Journal Water Pollution Control Federation, Vol. 48, No. 5, May
1976, pp. 934-944.
Wood, P.R. and Burton, L.C., "Ground-Water Resources Cleveland and
Oklahoma Counties", Circular 71, 1968, Oklahoma Geological Survey,
Oklahoma University, Norman, Oklahoma.
Zimdahl, R.L. and Skogerboe, R.N. , "Behavior of Lead in Soil,
Environmental Science and Technology, Vol. 11, 1977, pp. 1202-1207.
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APPENDIX A
ANNOTATED BIBLIOGRAPHY
A-l
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Anderson, M.P., "Using Models to Simulate the Movement of Contaminants
Through Ground Water Flow Systems", Critical Reviews in Environmental
Control. Vol. 91, Nov. 1979, pp. 97-156.
Prediction of the movement of contaminants in ground water
systems through the use of models has been given increased emphasis
in recent years because of the growing trend toward subsurface
disposal of wastes. Prediction is especially critical when nuclear
wastes are involved. Contaminant transport models which include
the effects of dispersion have been applied to several field
studies. Regional size models which limit the effects of
dispersion have had limited success because of the scarcity and
poor quality of field data. Another difficulty in the development
of contaminant transport models is the current lack of knowledge
regarding the quantification of chemical reaction terms. This
review examines the formulation of contaminant transport models,
application to field problems, difficulties involved in obtaining
input data, and current status of modeling efforts.
Andreoli, A., et al., "Nitrogen Removal in a Subsurface Disposal
System", Journal of the Water Pollution Control Federation. Vol. 51, No.
4, Apr. 1979, pp. 841-855.
The effects of subsurface waste disposal on ground water
quality in Long Island, N.Y., are assessed. Residents of Long
Island depend on ground water for their entire water supply. The
geology of Long Island is reviewed. Described are the design,
construction, and operation of a full scale system consisting of a
conventional septic tank-leaching field wastewater disposal system
combined with a subsurface system using natural soil treatment
mechanisms for nitorgen removal. The septic tank reduces the
inorganic nitrogen concentration of raw wastewater by 20%. About
36% of the total nitrogen applied to the soil is removed after 2 ft
of travel through the soil. Nitrification occurs within 2-4 ft. of
vertical travel in Long Island soil.
Andrew, W.F., "Soil as a Media (sic) for Sewage Treatment", Third Annual
Illinois Private Sewage Disposal Symposium, Feb. 1978, pp. 18-20.
In the selection of a site for a septic tank absorption field,
the pollution abatement potential must be considered. Compared to
air and water, soil is a very good medium for the treatment of
septic tank effluent. Ideally, a soil should be able to convert a
pollutant to an unpolluted state at a rate equal to or greater than
the rate at which it is added to the soil. Several soil
characteristics affect the soil's pollutant abatement potential.
Septic tank installation is not recommended in soil subject to
flooding. Where soil is shallow to bedrock or cemented pan, the
volume of absorptive soil is reduced; the only alternative is to
A-2
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increase Che size of the field. A high water table reduces the open
pore space of the soil, reducing its absorptive capacity. It also
reduces the 02 in the soil and, consequently, the microbial
capacity. Permeability of the soil reflects the ability of air and
water to move through it. If movement is too slow, the field needs
to be enlarged; if too rapid, there is danger of ground water
contamination. Where soil is sloping, there is a danger of uneven
distribution of the effluent, and the possibility of some coming to
the surface. Coarse fragments cause installation problems and
reduce the overall volume per area. Subsidence can be a severe
problem. Filter lines may shift, causing blockage and excessive
concentration of effluent. Depressions may occur over the lines and
cause surface water to accumulate.
Anonymous, "New York Seeks to Curb Solvents in Ground Water", Chemical
Week. Vol. 124, No. 14, Apr. 4, 1979, p. 24.
Evidence that on Long Island commercial products for cleaning
cesspools and septic tanks are the source of ground water
contamination by trichloroethane and methylene chloride has prompted
New York State to move to limit use of these products. A
preliminary injunction against Jancyn Manufacturing Corporation of
Central Islip, New York, asks that Jancyn be enjoined from selling
its product, Drainz, which contains 1/3, 1,1,1-trichloroethane, 1/3
methylene chloride, and other organic solvents. A single 2-gal
dose of Drainz is enough to contaminate 40 million gal of ground
water, based on the state's limit of 50 ppb of trichloroethane and
methylene chloride. From 1976 to 1978, 193 public wells were
closed in Suffolk and Nassau counties: of those in Suffolk, 53%
were contaminated with trichloroethane, and of those in Nassau, 33%
contained the chemical. The legislature is considering a measure
to prohibit sale and use in the state of cesspool cleaners
containing a variety of chemicals.
Appel, C.A. and Bredehoeft, J.D., "Status of Ground Water Modeling in
the U.S. Geological Survey", Circular No. 737, 1976, U.S. Geological
Survey, Washington, D.C.
Types of problems for which models have been, or are being,
developed include: ground water flow in saturated or partially
unsaturated material, land subsidence resulting from ground water
extraction, flow in coupled ground water-stream systems, coupling
of rainfall-runoff basin models with soil moisture-accounting
aquifer flow models, interaction of economic and hydrologic
considerations, predicting the transport of contaminants in an
aquifer, and estimating the effects of proposed development schemes
for geothermal systems. The status of modeling activity for
various models is reported as being in a developmental,
verification, operational, or continued improvement phase.
A-3
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Bachmat, Y., et al., "Utilization of Numerical Groundwater Models for
Water Resource Management", EPA-600/8-78/012, June 1973, U.S.
Environmental Protection Agency, Ada, Oklahoma.
The study assessed the present status of international
numerical models as a tool for ground water related water resource
management. Among the problem areas considered are: the
accessibility of models to users; communications between managers
and technical personnel; inadequacies of data; and inadequacies in
modeling. The report, which is directed toward the nontechnical
reader, describes 250 models. These are categorized as prediction,
management, identification, and data management models.
Brown, K.W., et al., "The Movement of Fecal Coliforms and Coliphages
Below Septic Lines", Journal of Environmental Quality, Vol. 8, No. 1,
1979, pp. 121-125.
A two-year lysimetric study utilizing 3 undisturbed soils was
conducted to investigate the movement of fecal coliforms and
coliphages to the ground water. Septic tank effluent was applied
to each of the 3 soils at appropriate design rates via subsurface
septic lines. The soils included had sand contents of 80, 41 and
7.6%. Indigenous concentrations of fecal coliforms in the effluent
were more than sufficient to assure detectability. During the
winter the levels of indigenous coliphages decreased, and on
several occasions the septic effluent was spiked with cultured
coliphages. The remainder of the year, indigenous levels were
sufficient to allow adequate detection. Leachate samples were
analyzed on a continuous basis, and at the end of the study the
soils below the septic lines were dissected and sampled on a grid
pattern. They were analyzed for both fecal col forms and
coliphages. On only a few occasions were fecal coliforms present
in leachate collected 120 cm below the septic lines. Subsequent
samples in from the same locations did not indicate the presence of
fecal coliforms so that the few samples that were collected shortly
after application began may have been a result of contamination, or
they may be indicative of greater mobility before organic residue
built up in the soil. Soil samples taken 1 and 2 years after
application began indicated limited mobility and survival of fecal
coliforms in all 3 soils. Coliphages were present in the leachate
only in very low concentrations immediately after spiking of the
applied sewage with 10^ times more organisms than were applied.
Soil samples also confirmed the limited mobility of coliphages.
Thus, 120 cm of any of the soils tested appeared to be sufficient
to minimize the possibility of ground water pollution by fecal
coliform or coliphages from septic effluent disposal.
A-4
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Brown, R.J., "Septic Tank and Household Sewage Systems Design and Use:
(Citations from the Engineering Index Data Base), 1970-1979", NTIS/PS-
79/0458, 1979, NTIS, Springfield, Virginia.
The bibliography provides worldwide research reports on septic
tanks and other sewage treatment units used for household sewage
systems. Construction materials, design, service life, and a
comparison of systems are described. The suitability of soils for
drainage and adsorption to prevent pollution of ground water from
bacteria and viruses are discussed. Purification processes and the
environmental constraints of disposal systems are included. This
updated bibliography contains 159 abstracts, 9 of which are new
entries to the previous edition.
Carlile, B.L., Stewart, L.W. and Sobsey, M.D., "Status of Alternative
Systems for Septic Wastes Disposal in North Carolina", Proceedings of the
Second Annual Illinois Private Sewage Disposal Symposium, Champaign,
Illinois, 1977, 16 pp.
Dye studies indicate that septic tank systems in the study
area contribute significant contamination to nearby shellfish
harvesting waters via surface and subsurface flow. Surface ponding
of septic tank effluent during periods of rainfall constitute a
potential health hazard through possible direct contact with these
wastes. Continued dependence on conventional septic tank systems
for area waste treatment will result in further degradation of area
water resources. Studies such as these and from evidence of vast
acres of shellfish waters closed, provide convincing evidence that
the "carrying capacity" or use potential of land sites have already
been exceeded in many coastal areas of the state. If septic tanks
are indiscriminately installed in the area, then a reasonable
estimate is that approximately 90% will not function properly and
will fail to some degree within the first year's use. Ultimately, a
research goal is to define the carrying capacity of soil types to
identify the basic soil limitations in determining loading
intensities for conventional and alternative systems of septic
waste disposal which would allow developments to proceed without
creating additional pollution loads on surface and ground waters.
Childs, K.E., Upchurch, S.B. and Ellis, B., "Sampling of Variable Waste-
Migration Patterns in Ground Water", Ground Water, Vol. 12, No. 6, Nov.-
Dec. 1974, pp. 369-371.
A survey of waste-migration patterns from septic-tank/tile-
field systems surrounding Houghton Lake, Michigan, indicates that
sampling plans designed to detect and quantify waste migration in
ground water should be predicated on the concept that the waste
plume may be complex and that the plume may not follow regional,
ground water flow. The waste-migration plumes at Houghton Lake
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range from simple, multichemical plumes that move with regional
flow to complex plumes that bifurcate, that show different
migration patterns for different chemicals, and that move up the
regional gradient for short distances.
Cotteral, J.A. and Norris, D.P., "Septic Tank Systems", American Society
of Civil Engineering, Journal of Sanitary Engineering Division, Vol. 95,
No. SA4, Aug. 1969, pp. 715-746.
A review of history and theory of septic tank systems allows
the establishment of guidelines for the design and construction of
satisfactory and economical systems. While survival curves show
that system life is usually short, proper design and construction
supplemented by regular inspection and maintenance can adequately
extend the expected life. It is recommended that a single
drainfield design loading rate be applied to all installations
meeting minimum topographical and geological requirements. Control
should be exercised by a county regulatory agency and should be
based upon engineering control of design in lieu of a codified
approach. Periodic county inspection and regular maintenance by
homeowners is essential, and csn be implemented by an enforcement
program based upon annually renewable septic tank use permits. An
adequately designed, constructed and maintained septic tank system
is more expensive than complete community sewerage, but is
nevertheless economically feasible.
Crosby, J.U., III, et al. , "Investigation of Techniques to Provide
Advance Warning of Ground Water Pollution Hazards with Special Reference
to Aquifers in Glacial Outwash", NTIS No. PB-203 748, Aug. 197i,
Washington State University, Pullman, Washington.
Findings are recorded of a six-year investigation of pollution
hazards involved with the use of septic tanks and drainfields in
the Spokane Valley of eastern Washington. The geological setting
of the study area was investigated by gravimetric and refraction
seismic methods. The results of these studies indicated a
generally simple, U-shaped valley incised in ancient granitic and
metamorphic rocks. Valley fil materials appears to be almost
entirely glaciofluvial sands and gravels. Previously postulated
basalt flows and Latah clays are probably not present in
significant amounts. Drilling and sampling of local drainfields
revealed that the upper moist and wet valley fill materials pass
into dry sands and gravels at depth. This phenomenon prompted a
postulate that drainfield fluids must be moving laterally rather
than vertically. Confirmatory laboratory measurements of soil
moisture tension showed all of the soils, at depth, to be in a
state of high moisture deficiency. Routine geophysical logging of
monitor wells indicated that moisture movement and variations were
confined to upper soil layers. Infiltration tests substantiated
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other findings concerning the movement of soil moisture. Extensive
sampling and analysis of surface and ground waters revealed no
evidence of ground water contamination. Surface waters are
generally of good quality east of Spokane but are seriously
degraded in the immediate Spokane area.
Drewry, W.A., "Virus Movement in Ground Water Systems", OWRR-A-005-
ARK(2), 1969, Water Resources Research Center, University of Arkansas,
Fayetteville, Arkansas.
The study investigates the extent to which soil acts as an
agent in the transmission of waterborne viruses. Since many
waterborne outbreaks of viral diseases have involved small well-
water supplies contaminated by effluents from subsurface wastewater
disposal systems, there is a great need for such information.
Results show that virus adsorption by soils is greatly affected by
the pH, ionic strength, and soil-water ratio of the soil-water
system and various soil properties. It is shown that one cannot
predict the relative virus adsorbing ability of a particular soil
based on the various tests normally used to characterize a soil.
It is shown that virus movement through a continuous stratum of
common soil under gravity flow conditions and with intermittent
dosing should present no health hazard if usual public health
practices relating to locating water supply wells are followed.
Test results also indicate no greater or lesser movement of virus
through soils with a highly polluted water than with a non-polluted
water.
Ettesvold, W.L., "On-Site Wastewater Treatment Versus Collection Sewers:
A Local Health Department Veiwpoint", Journal of Environment.:.!. Health,
Vol. 41, No. 6, May-June 1979, pp. 321-324.
The cost effectiveness of retaining, repairing, anil improving
onsite wastewater treatment units and collector sewers is compared.
Septic tanks and drainfields are not likely to be cost effective in
densely developed areas if the costs of maintenance, inspection,
pumping, sludge disposal, and ground water protection are
considered. It is suggested that one large septic tank and
drainfield be constructed on suitable soil in an area distant from
lakes, streams, or wells.
Fetter, C.W., Jr., Sloey, W.E. and Spangler, F.L., "Potential
Replacement of Septic Tank Drain Fields by Artificial Marsh Waste Water
Treatment Systems", Ground Water, Vol. 14, No. 6, Nov.-Dec. 1976, pp.
396-403.
Use of emergent marsh vegetation planted in a gravel substrate
in a plastic-lined trench to treat septic tank effluent is
demonstrated. Treatment of unchlorinated primary municipal
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effluent reduces 6005 by 77%, COD by 71%, orthophosphate by 35%,
total phosphorus by 37%, nitrate by 22%, and coliform bacteria by
99.9%. The method is useful at summer cottages, camping areas,
resorts, and roadside rest areas. Marsh treatment systems are
inexpensive to operate and virtually automatic.
Fey, R.T., "Cost-Minded Community Chooses Small Diameter Gravity
System", Water and Sewage Works. Vol. 125, No. 6, June 1978, pp. 58-62.
In 1975, a small town in Wisconsin decided to install a small
diameter gravity system for wastewater treatment because of the
system's environmental compatibility and cost effectiveness. The
system has a small scale force main and septic tanks, which
discharge into a common absorption field. Typical plugging
ingredients are eliminated in the system, and the septic tanks
retain the solids. Monitoring wells in and around the absorption
field are used to determine any change in ground water quality
attributable to the septic effluent.
General Accounting Office, "Community-Managed Septic Systems - A Viable
Alternative to Sewage Treatment Plants", CED-78-168, Nov. 1978,
Community and Economic Development Division, Washington, D.C.
This report discusses the benefits and obstacles concerning
septic systems as viable waste water treatment alternatives to
central treatment processes. Properly operating septic systems can
be as permanent and effective as central treatment facilities, at
considerably less cost.
Goldstein, S.M., et al., "A Study of Selected Economic and Environmental
Aspects of Individual Home Wastewater Treatment Systems", Report No.
M72-45, Mar. 1972, Mitre Corp., McLean, Virginia.
The report evaluates the potential effectiveness of individual
home waste treatment systems and estimates the cost implications of
increased use of individual systems. A review of previous research
into septic tank system failures is summarized. Economic factors
which can govern the choice between individual and collective
systems are reviewed. The results of several economic analyses of
the problem are discussed. A MITRE-developed economic model is
used to generate both the time stream and the total present value
of future costs of sewage treatment on a national basis for
projected new individual homes. Simultaneous consideration is
given to individual and central systems for a variety of
independently specified parameters.
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Hagedorn, C., et al., "Survival and Movement of Fecal Indicator Bacteria
in Soil Under Conditions of Saturated Flow", Journal of Environmental
Quality. Vol. 7, No. 1, Jan.-Mar. 1978, pp. 55-59.
Antibiotic-resistant fecal bacteria were used to monitor the
degree of movement and subsequent ground water contamination by
septic tank effluent discharged into a drainfield under saturated
conditions. Two pits of different depths were constructed to
simulate drainfield beds, and ground water samples were removed
during 32-day sampling intervals from sampling wells installed at
set distances from each inoculation pit. The bacteria added to the
deep pit were released into a B2t horizon which contained a higher
clay content than the A horizon in which the shallower pit was
installed. Streptomycin-resistant strains of Escherichia coli and
Streptococcus faecalis amended to each pit site moved in a
directional manner, required more time to reach sampling wells when
inoculated into the deeper of the two pits, and moved relatively
long distances when considering that the area where the sites were
located had only a 2% slope. Bacterial numbers peaked in the
sampling wells in association with major rainfall patterns and the
populations required longer periods to peak in the wells furthest
from the inoculation pits. The results indicated that antibiotic-
resistant bacteria eliminated the problem of differentiating
between the amended bacteria and those nonresistant strains already
in the soil, and the potential is excellent for including this type
of microbiological procedure for assessing the suitability of a
soil site for septic tank and wastewater drainfield installations.
Healy, K.A. and Laak, R., "Site Evaluation and Design of Seepage
Fields", ASCE Journal of Environmental Engineering Division, Vol. 100,
No. 5, Oct. 1974, pp. 1133-1146.
A re-evaluation of previous work by others indicated that soil
can absorb septic tank effluent indefinitely if the application
rate is kept below a certain level, which is a function of soil
permeability. This long-term acceptance rate is independent of
whether the soil is continuously or intermittently flooded, and
varies from approxiamtely 0.3 gpd/sq. ft. (0.01 m/day) for clay loam
and silt to approximately 0.8 gpd/sq. ft. (0.03 m/day) for sand. A
study of the ground water flow pattern below a seepage field showed
that it is, in many cases, the hydraulic conductivity of the ground
surrounding the field, as determined by the external water table,
soil permeability, and impervious strata, that controls the size of
the field required. Reliable techniques for site evaluation of
soil permeability, depth to water table, and depth to any impervious
strata are presented, and a chart is given for designing a seepage
field based on this information. Design examples are included.
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Holzer, T.L., "Limits to Growth and Septic Tanks", Proceedings of the
Rural Environmental Engineering Conference on Water Pollution Control in
Low Density Areas. University Press of New England, Hanover, New
Hampshire, 1975, pp. 65-87.
Appraisal of the potential pollution of ground water by septic
tank systems requires an understanding of the ground water system
into which the effluent is discharged. Flow paths of ground water
and recharge areas must be delineated. Quantity of ground water
recharge must be estimated because the recharge is a measure of the
amount of water available for dilution of effluent. Capability of
the natural system to renovate effluent from septic tank systems
must be known. Data are presented in graphical and tabular form.
Jaovich, B.A. and Couillard, D., "Septic Tanks: Consitfefatidhs About
Drainage", Eau du Quebec. Vol. 11, No. 2, Apr. 1978, pp. 77-80.
Language: French.
Percolation or water infiltration tests are normally performed
on soils intended for septic tank installations, but these tests
present problems of reproducibility and representativity because of
their empiric nature and the phenomenon of clogging. Clogging
layers often develop in septic tanks within 10 months of use.
Other tests — tensiometry and electric resistivity - have been
developed which take into account the factors of clogging and soil
water content. In general, it is best to use a clogging test in
conjunction with some sort of infiltration test. The infiltration
and purification capacity of soils can be improved by intermittent
addition and good distribution of effluents over the entire
receiving surface.
Jones, E.E., "Improving Subsurface Disposal System Performance", Journal
of Environmental Health. Vol. 40, No. 4, Jan.-Feb. 1978, pp. 186-19K
Onsite domestic waste disposal facilities can have nearly
infinite life at reasonable cost. It is economically prohibitive
to install sewers for low density populations, so improved design
and maintenance of septic tanks can be as valuable as public
sewerage systems. Current technologies are reviewed. Domestic
waste disposal facilities can be engineered to: reduce ground
water pollution; provide greater service life; lower annual costs;
and make more beneficial use of effluent water and nutrients. An
essential factor is soil aeration or oxidation potential, which is
required by certain organic compounds for decomposition. Most new
management systems need adequate soil drainage for proper
functioning. Service life figures for five eastern soils are
included.
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Jones, R.A. and Lee, G.F., "Septic Tank Wastewater Disposal Systems as
Phosphorus Sources for Surface Waters", Journal of the Water Pollution
Control Federation. Vol. 51, No. 11, Nov. 1979, pp. 2764-2775.
A 4-year ground water monitoring study was conducted in the
immediate vicinity of an active septic tank system in northwestern
Wisconsin to determine the potential for septic tank effluent to
contribute to the excessive fertilization of area surface waters.
During the course of this study, movement of septic tank effluent in
the ground water was indicated by measured values of several
conservative parameters. However, there was no evidence of the
transport of the phosphate from septic tank effluent through the
ground water even at the monitoring point closest to the tile field
(about 15 m down ground water gradient from the tile field). The
results of this confirmed the conclusions drawn from similar studies
in other areas reported in the literature, namely, that phosphorus
from septic tank waste water disposal system effluent is usually not
readily transported through the ground water.
Khaleel, R. and Redell, D.L., "Simulation of Pollutant Movement in
Groundwater Aquifers", OWRT-A-030-Tex (1), May 1977, Water Resources
Institute, Texas A&M University, College Station, Texas.
A three-dimensional model describing the two-phase (air-water)
fluid flow equations in an integrated saturated-unsaturated porous
medium was developed. Also, a three-dimensional convective-
dispersion equation describing the movement of a conservative, non-
interacting tracer in a nonhomogeneous, anisotropic porous medium
was developed. Finite difference forms of these two equations were
solved using an implicit scheme to solve for water or air
pressures, an explicit scheme to solve for water and air
saturations, and the method of characteristics with a numerical
tensor transformation to solve the convective-dispersion equations.
The inclusion of air as a second fluid phase caused the
infiltration rate to decrease rapidly to a value well below the
saturated hydraulic conductivity when the air became compressed.
This is in contrast to one-phase fluid flow problems in which the
saturated hydraulic conductivity is considered to be the lower
bound for the infiltration rate. A typical two-dimensional
drainage problem in agriculture was solved in a nonhomogeneous,
integrated saturated-unsaturated medium using the total simulator
of fluid flow and convective-dispersion equations. A variety of
outputs, such as an equipotential map or a solute concentration
map, were obtained at selected time steps. A field-size problem
describing the migration of septic tank wastes around the perimeter
of a lake was also considered and solved using the total simulator.
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Klein, S.A., "NTA Removal in Septic Tank and Oxidation Pond Systems",
Journal of Water Pollution Control Federation, Vol. 46, No. 1, Jan.
1974, pp. 78-88.
Four pilot-scale septic tank and leaching field systems were
used to determine the survival of trisodium nitrilotriacetate (NTA)
in ground waters and its removal by household treatment systems.
Results indicated a 20% removal of NTA in the septic tank and
complete removal for the total system when the percolation fields
were aerobic.
Konikow, L.F. and Bredehoeft, J.D., "Computer Model of Two-Dimensional
Solute Transport and Dispersion in Ground Water", Techniques of Water-
Resources Investigations of the United States Geological Survey, Book 1,
Chapter 2, 1978, U.S. Geological Survey, Washington, D.C.
This report presents a model that simulates solute transport
in flowing ground water. The model is both general and flexible in
that it can be applied to a wide range of problem types. It is
applicable to one- or two-dimensional problems having steady-state
or transient flow. The model computes changes in concentration
over time caused by the processes of convective transport,
hydrodynamic dispersion, and mixing (or dilution) from fluid
sources. The model assumes that the solute is non-reactive and that
gradients of fluid density, viscosity, and temperature do not
affect the velocity distribution. However, the aquifer may be
heterogeneous and (or) anisotropic. The model couples the ground
water flow equation with the solute-transport equation. The digital
computer program uses an alternating-direction implicit procedure
to solve a finite-difference approximation to the ground water flow
equation, and it uses the method of characteristics to solve the
solute-transport equation. The report includes a listing or the
computer programs, which is written in FORTRAN IV and contains about
2,000 lines. The model is based on a rectangular, block-centered,
finite-difference grid. It allows the specification of any number
of injection or withdrawal wells and of spatially varying diffuse
recharge of discharge, saturated thickness, transmissivity,
boundary conditions, and initial heads and concentrations. The
accuracy of the model was evaluated for two idealized problems for
which analytical solutions could be obtained. In the case of one-
dimensional flow the agreement was nearly exact, but in the case of
plane radial -flow a small amount of numerical dispersion occurred.
An analysis of several test problems indicates that the error in
the mass balance will be generally less than 10 percent. The test
problems demonstrated that the accuracy and precision of the
numerical solution is sensitive to the initial number of particles
placed in each cell and to the size of the time increment, as
determined by the stability criteria. Mass balance errors are
commonly the greatest during the first several time increments, but
tend to decrease and stabilize with time.
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Kreissl, J.F., "Status of Pressure Sewer Technology", EPA Technology
Transfer Report, Mar. 1977, U.S. Environmental Protection Agency,
Cincinnati, Ohio.
Although sewage pumping has been practiced for years in
municipal systems in the form of lift stations and force mains to
avoid excessive depths of cut, and in many individual homes in the
form of ejector or sump pumps, the wholesale use of small diameter
pressure collection systems did not emerge until the lacer part of
the 1960's. Pressure sewer systems are a viable alternative
technology and should be considered in any cost-effective analysis
of alternative wastewater management systems in rural communities.
Pressure sewers offer many advantages in areas where population
density is low, severe rock conditions exist, high ground water or
unstable soils prevail, or undulating terrain predominates. The
most serious impediment to wider adoption of pressure sewer
technology is the lack of comprehensive long-term operation and
maintenance data and treatment information. The two types of
pressure sewer system designs — grinder-pump systems and septic
tank effluent pumping systems — are detailed.
Lotse, E.G., "Septic Tank Effluent Movement Through Soil", NTIS No. PB-
261 368/5ST, June 1976, University of Maine at Orono, Orono, Maine.
The rate and extent of phosphorus and nitrogen movement in
selected Maine soils were studied under continuous and intermittent
loading. Conditions approximating those of septic tank absorption
fields were simulted. For intermittently operated columns, there
was no breakthrough of phosphorus when 8.0, 12.4, and 15.0 pore
volumes of effluent, respectively, had been collected. For
continuously operated columns, however, breakthrough occurred at
10.8 and 11.2 pore volumes, respectively. The greater the
hydraulic loading, the greater was the rate of phosphorus movement
through a given soil. Septic tank absorption field systems should
have several trenches and large total length of trench in order to
minimize the movement of phosphorus and contamination of ground
waters.
McGrail, J.W., et al., "A Cost Comparison of Underground Disposal of
Wastewater Versus Public Sewerage for Rural and Suburban Towns", New
England Water Pollution Control Association. Vol. 12, No. 1, Apr. 1978,
pp. 4-19.
A nonpoint source water quality model was developed, applied,
and verified. Private sewage disposal may have only a minor effect
on the trophic condition of many lakes, especially those draining
large watersheds. Inadequate private sewage disposal may cause
pathogen contamination in lakes and streams, and high P
concentrations in nearshore lake waters. The installation of
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interceptor sewers along rural shorelines is often not cost-
effective. The interceptor-induced shoreline development may
result in a net increase in P loading to the lake from increased
runoff. Where technically feasible, a program to inspect, correct,
and maintain rural private sewage disposal systems can minimize the
potential for pathogen- or F-related septic tank problems at a cost
lower than that for sewers. A proposed on-lot disposal system
control program represents a new level of local government
involvement in wastewater disposal. Communities which choose a
private sewage disposal control program over public sewerage should
be considered for federal and state funding.
Melien, W.L., "Site Evaluation for Seepage Fields", Third Annual
Illinois Private Sewage Disposal Symposium, Lake County Health
Department, Waukegan, Illinois, 1978, pp. 1-8.
Before designing an individual sewage disposal system, it is
necessary to determine if the soil is suitable for the absorption of
septic tank effluent. Several conditions must be met. The maximum
seasonal elevation of the ground water table should be 2 ft. below
the bottom of the trench. The most important clue to seasonal high
water table is the color of the soil. If it has a uniform reddish-
brown to yellow color, due to oxidation of Fe compounds, it
indicates free alternate movements of air and water in and through
the soil. Such a soil has desirable absorption characteristics. To
determine impervious stratas, it may be necessary to run
percolation tests in the routine manner and also at a depth of 12
in. lower than the original test. The ground slope has an effect
on the site's suitability and the type of distribution. Soils in
humid areas of the country should have a one ft. fall within Che
septic field area, and serial distribution or a dropbox system
should be used. Level areas are subject to supersaturation from
building runoff and sump pumps during heavy spring rains.
Mercer, J.W. and Faust, C.R., "Ground Water Modeling: Mathematical
Models", Ground Water. Vol. 18, No. 3, May-June 1980, pp. 212-227.
Ground water modeling begins with a conceptual understanding
of the physical problem. The next step in modeling is translating
the physical system into mathematical terms. In general, the final
results are the familiar ground water flow equation and transport
equations. These equations, however, are often simplified, using
site-specific assumptions, to form a variety of equation subsets.
An understanding of these equations and their associated boundary
and initial conditions is necessary before a modeling problem can
be formulated.
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Otis, R.J., et al., "On-Site Disposal of Small Wastewater Flows", EPA
Technology Transfer Report, 1977, U.S. Environmental Protection Agency,
Washington, D.C.
A noncentral facility consisting of several treatment and
disposal systems serving isolated individual residences or clusters
of residences in rural areas offers an economical solution to the
problem of waste disposal in those areas where conventional central
facilities are impractical. Individual or shared septic tank
systems could provide onsite treatment and disposal where wastes
are generated. Noncentral facilities are also more ecologically
sound than centralized systems, since the dispersed systems dispose
of wastes over wider areas. Through this practice, the environment
is able to assimilate the waste discharge more readily, thereby
reducing the need for mechanical treatment and the associated energy
consumption. Various treatment and disposal systems that would be
applicable to the noncentralized theory are described, and
potential problems associated with each system are reviewed.
Otis, R.J., Plews, G.D. and Patterson, D.H., "Design of Conventional
Soil Absorption Trenches and Beds", Third Annual Illinois Private Sewage
Disposal Symposium, Toledo Area Council of Governments, Toledo, Ohio,
1978, pp. 52-66.
A good soil absorption system should absorb all effluent
generated, provide a high level of treatment before the effluent
reaches the ground water, and have a long, useful life. To meet
these goals, proper site selection is necessary. Factors to be
considered include the hydraulic conductivity characteristics of
the soil, the unsaturated depth of the soil, the distance to
bedrock, characteristics of the bedrock, the landscape position,
slope of the land, and proximity to surface waters, wells, road
cuts, buildings, etc. Trench and bed designs are discussed in
detail with reference to the "Manual of Septic Tank Practice" of the
USPHS. Probably the most frequent cause of early failure of
properly designed systems is poor construction. Absorption of
waste effluent requires that soil pores remain open. If these are
sealed during construction by compaction, smearing, or puddling, the
system may be rendered useless. Careful construction techniques
will minimize these causes of soil clogging.
Pickens, J.F. and Lennox, W.C., "Numerical Simulation of Waste Movement
in Steady Ground Water Flow Systems", Water Resources Research, Vol. 12,
No. 2, Apr. 1976, pp. 171-184.
The finite element method based on a Galerkin technique ia
used to formulate the problem of simulating the two-dimensional
transient movement of conservative or nonconservative wastes in a
steady state saturated ground water flow system. The convection-
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dispersion equation is solved in two ways: in the conventional
Cartesian coordinate system, and in a transformed coordinate system
equivalent to the orthogonal curvilinear coordinate system of
streamlines and normals to those lines. The two formulations
produce identical results. A sensitivity analysis on the dispersion
parameter 'dispersivity* is performed, establishing its importance
in convection-dispersion problems. Examples involving the movement
of nonconservative contaminants described by distribution
coefficients and examples with variable input concentration are also
given. The model can be applied to environmental problems related
to ground water contamination from waste disposal sites.
Pitt, W.A.J., Jr., "Effects of Septic Tank Effluent on Ground Water
Quality, Dade County, Florida: An Interim Report", Ground Water, Vol.
12, No. 6, Nov.-Dec. 1974, pp. 353-355.
At each of the 5 sites, where individual (residence) septic
tanks have been in operation for at least 15 years and where septic
tank concentration is less than 5 per acre, a drainfield site was
selected for investigation to determine the effects of septic tank
effluent on the quality of the water in the Biscayne Aquifer. At
each site 2 sets of multiple depth wells were drilled. The
upgradient wells adjacent to the drainfields in most places, were
constructed so that the aquifer could be sampled at 10, 30, 40, and
60 feet below the land surface.
Prickett, T.A. and Lonnquist, C.G., "Selected Digital Computer
Techniques for Ground Water Resources Evaluation", Bulletin 55, 1971,
Illinois Water Survey, Urbana, Illinois.
Generalized digital computer program listings are given that
can simulate one-, two-, and three-dimensional nonsteady flow of
ground water in heterogeneous aquifers under water table, nonleaky,
and leaky artesian conditions. Programming techniques involving
time varying pumpage from wells, natural or artificial recharge
rates, the relationships of water exchange between surface waters
and the ground water reservoir, the process of ground water
evapotranspiration, and the mechanism of converting from artesian to
water table conditions are also included. The discussion of the
digital techniques includes the necessary mathematical background,
documented program listings, theoretical versus computer
comparisons, and field examples. Also presented are sample computer
input data and explanations of job setup procedures. A finite
difference approach is used to formulate the equations of ground
water flow. A modified alternating direction implicit method is
used to solve the set of resulting finite difference equations. The
programs included are written in FORTRAN IV and will operate with
any consistent set of units.
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Prickett, T.A., "State-of-Che-Art of Groundwater Modeling", Water Supply
and Management, Vol. 3, No. 2, 1979, pp. 134-141.
Outline for ground water modeling techniques within the
categories of mathematical, sand tank, analog and numerical models
is presented. The models discussed are one of two types: ground
water 'flow1 or 'transport' models. The term 'flow1 refers to the
type of model used to provide answers to the quantitative side of
ground water problems; typical 'flow' models would solve problems
related to safe yields of well fields, interference effects of
nearby wells and surface-water-ground-water relationships. The
'transport1 model is a water quality type; typical 'transport'
models might include energy considerations, dispersion and
diffusion processes, chemical exchange reactions, or multiple fluid
effects. Mathematical solutions are models of the particular
conditions defined; their applications to field problems are
therefore somewhat limited. Four main groups of flow models are
discussed: (1) Sand tank models which are a scaled down
representation of an aquifer, including its boundary configuration
and usually its hydraulic conductivity. (2) Analog models, where
the behavior of an aquifer is described by differential equations
which are derived from basic principles such as the laws of
continuity and conservation of energy. (3) Analog models, which
can be subdivided into the three major categories of viscous fluid
models, electrical models, and miscellaneous models and techniques.
(4) Numerical models, which have been powerful tools in aiding
hydrologists in evaluating ground water resources. Development of
the digital computer has made possible the practical use of the
techniques in ground water flow modeling. Numerical models can be
subdivided into four groups: finite-difference, finite-element
variational, finite-element Galerkin, and miscellaneous.
Rahe, T.M., et al., "Transport of Antibiotic-Resistant Escherichia Coli
Through Western Oregon Hillslope Soils Under Conditions of Saturated
Flow", Journal of Environmental Quality, Vol. 7, No. 4, Oct.-Dec., 1978,
pp. 487-494.
Field experiments using strains of antibiotic resistant
Escherichia coli were conducted to evaluate the events which would
occur when a septic-tank drainfield became submerged in a perched
water table and fecal bacteria were subsequently released into the
ground water. Three separately distinguishable bacterial strains
were inoculated into three horizontal lines installed in the A, B,
and C horizons of two western Oregon hillslope soils. Movement was
evaluated by collecting ground water samples from rows of modified
piezometers (six piezometers/row) placed at various depths and
distances downslope from the injection lines. Transport of E. coli
differed at both sites with respect to movement rates, zones in the
soil profiles through which major translocation occurred, and the
relative numbers of cells transported over time. Movement rates of
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at least 1,500 cm/hour were observed in the B horizon at one site.
The strains of E. coli survived in large numbers in the soils
examined for at least 96 hours and appeared to be satisfactory as
tracers of subsurface water flow. The concept of partial
displacement (or turbulent flow through macropores) is discussed as
an explanation of the rapid movement of substantial numbers of
microbial cells through saturated profiles.
Rea, R.A. and Upchurch, S.B., "Influence of Regolith Properties on
Migration of Septic Tank Effluent", Ground Water, Vol. 18, No. 2, Mar.-
Apr. 1980, pp. 118-125.
An investigation of waste-migration patterns from a septic
tank system indicates that complex patterns result from minor
variations in regolith adsorptive capacity and texture, local
hydrology, and possibly soil microbiology. The existence of multi-
chemical, bifurcating plumes suggest that monitor wells arranged up
and downgradient and capable of multilevel sampling are essential
to adequately delineate contaminant migration in ground water. The
data also indicate that sampling for a single constituent could
yield misleading information about the nature and distribution of
other ground-water contaminants. The ability for chemical removal
by the regolith is in direct response to minor variations in siit-
and clay-sized particle content and corresponds to Langmuir
adsorption isotherms. Silt- and clay-sized particles are
dominantly organic in origin. Minor iron and aluminum
hydroxyoxides and clays are present. Substrate samples, when
collected at regular intervals and analyzed for adsorbed
constituents and textural variability, provide an integrated
picture of the distribution of waste chemicals through tine. Such
samples also provide insight into the mechanics of plume
configuration and flow characteristics within the regolith. The
study shows that regolith adsorption data are essential to the
determination of life expectancy of the regolith as a contaminant
treatment system.
Reneau, R.B., "Changes in Concentrations of Selected Chemical Pollutants
in Wet, Tile-Drained Soil Systems as Influenced by Disposal of Septic
Tank Effluents", Journal of Environmental Quality, Vol. 8, No. 2, Apr.-
Jun. 1979, pp. 189-197.
Investigations at three Virginia locations determined on site
changes in several chemical constituents of septic tank effluent in
shallow ground waters and soils. Changes were related to distance
traveled, soil properties, and seasonal variation between
subsurface absorption fields and a subsurface tile drainage system.
Fluctuations in phosphorus, ammonium, nitrate, nitrogen dioxide,
chlorine, pH, and methylene blue active substances were measured.
Most of the chemical constituents monitored had lowered to
acceptable levels by the time effluent was intercepted by the tile
A-18
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drain. Effective soil volume, as determined by distance to and
depth of drainage system and by soil type, was directly related to
effluent purification. Techniques for improving water quality are
suggested.
Reneau, R.B., et al., "Distribution of Total and Fecal Coliform
Organisms from Septic Effluent in Selected Coastal Plains", Public
Health Reports. Vol. 92, No. 3, May-June 1977, pp. 251-260.
Distribution of total and fecal coliform bacteria in three
Atlantic Coastal Plain soils was monitored J_n situ for three years.
The soils studied were V/irina, Goldsboro, and Beltsville sandy
loams. These soils are found extensively in the populous U.S.
Atlantic seaboard, which is considered only marginally suitable for
septic tank installation because the restricting soil layers result
in the subsequent development of seasonal perched water tables. As
distance from the drainfield increased, large reductions in total
and fecal coliform bacteria were noted in the perched ground waters
above the restricting layers. These restricting soil layers appear
to be effective barriers to the vertical movement of indicator
organisms. The reduction in the density of the coliform bacteria
above the restriction soil layers probably can be attributed to
dilution, filtration, and dieoff as the bacteria move through the
natural soil system.
Reneau, R.B. and Pettry, D.E., "Phosphorus Distribution from Septic Tank
Effluent in Coastal Plain Soils", Journal of Environmental Quality, Vol.
5, No. 1, Jan.-Mar. 1976, pp. 34-40.
Phosphorus concentrations in perched ground waters around
septic tank drainfields are determined. The influence of disposal
of septic tank effluent on soil phosphorus fractions and their
distribution in natural soil systems is described. Contamination
of a permanent ground water table via vertical movement is a
limited possibility at Varina and Goldsboro soil locations.
Reneau, R.B., Jr., "Changes in Inorganic Nitrogeneous Compounds from
Septic Tank Effluent in Soil with a Fluctuating Water Table", Journal of
Environmental Quality. Vol. 6, No. 2, Apr.-Jun. 1977, pp. 173-178.
Changes in ammonia and nitrates were monitored in situ during
1972, 1973, 1974, and 1975 in a Virginia Coastal Plain soil with a
fluctuating water table. Samples of soil solution above and in a
very slowly permeable plinthic horizon were analyzed for the above-
mentioned inorganic N fractions. Ammonium-N in solution above the
plinthic horizon decreased with increased distance from the
drainfield in the direction of ground water flow. Decreases were
attributed to the processes of adsorption and nitrification.
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Nitrite and nitrate concentrations did not change significantly with
distance above the plinthic horizon, but did accumulate in the
plinthic material beginning at a 1.27-m distance from the
drainfield.
Reneau, R.B., Jr., "Influence of Artificial Drainage on Penetration of
Coliform Bacteria from Septic Tank Effluents into Net Tile Drained
Soils", Journal of Environmental Quality, Vol. 7, No. 1, Jan.-Mar. 1978,
pp. 23-30.
The bacteria were monitored in ground waters at selected
distances from the septic tank drainage fields in the direction of
ground water flow and were compared to coliform densities in control
wells and in tile outfalls. Fecal coliform densities were
approximately 105/100 ml in ground waters adjacent to the disposal
area as compared to 101-103/100 ml 152 cm from the agricultural tile
and less than 3.0/100 ml in control wells. The outfall from the
study area was normally less than 200 fecals/100 ml compared to
less than 3.0/100 ml in outfall waters from a control area. Fecal
coliform densities of the outfall from the study area were some
tenfold less than the bacterial quality of the receiving stream.
Coliform densities in ground waters decreased as a logarithmic
function of distance. In these soils, artificial drainage systems
apparently lowered the seasonal fluctuating water tables to such a
degree that individual wastewater treatment systems did not fail as
a result of untreated or partially treated effluent coming to the
surface. It is more difficult to assess the adequacy of artificial
drainage with respect to penetration of coliform organisms present
in the wastewaters.
Russelman, H.B. and Turn, M.P., "Management of Septic Tank Solids",
Third Annual Illinois Private Sewage Disposal Symposium, Toledo Area
Council of Governments, Toledo, Ohio, 1978, pp. 9-17.
Septage from septic tanks is biodegradable waste capable of
affecting the environment through water and air pollution. Proper
control of its disposal requires knowing the number of tanks
installed and the rate of new installations; the quantity of
septage being hauled and by whom; Lhe generally used disposal
practices and problems associated with them; and the regulatory
framework controlling the disposal. A private sewage disposal
program which attempts only to assure proper effluent disposal does
not adequately address problems inherent in the ultimate disposal
of the residue. To assure a more complete role in the
implementation of a disposal control program, a community should
establish a licensing fee consistent with administrative costs.
This would help prevent irresponsible scavengers from operating and
also provide revenue to offset costs of inspection. It should
require periodic inspection of all hauling vehicles and permit the
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use only of disposal sites found result in no contravention of
surface and ground water quality requirements. It can permit the
utilization of experimental sites if the absence of public health
hazards is determined from monitoring operations. Since land
application is the most common and economical method available to
contractors, septage application rates should be studied and
contractors should be guided in achieving the most cost-effective
methods consistent with public health criteria.
Sawhney, B.L., "Predicting Phosphate Movement through Soil Columns",
Journal of Environmental Quality, Vol. 6, No. 1, Jan.-Mar. 1977, pp. 86-
89.
To assess the potential pollution of ground water with P from
septic tank drainfields, sorption capacities of various soils were
determined over an extended period of time and related to P
movement through soil columns using solutions having P
concentrations similar to waste wters. The amounts of P sorbed by
fine sandy loam (fsl) and silt loam (sil) soil columns before
breakthrough occurred were approximately equal to the sorption
capacities determined from isotherms obtained over a sufficiently
long reaction time of about 200 hours. In Merrimac fsl,
breakthrough occurred after about 50 pore volumes of waste water
had passed through the column while about 100 pore volumes passed
through Buxton sil before the breakthrough occurred.
Sawhney, B.L. and Starr, J.L., "Movement of Phosphorus from a Septic
System Drainfield", Journal Water Pollution Control Federation, Vol. 49,
No. 11, Nov. 1977, pp. 2238-2242.
Movement of phosphorus (P) from a septic tank drainfield
through the surrounding soil to ground water and its eventual
discharge to surface waters were investigated. Suction probes and
tensiometers were intalled at various distances below and beside
the drainfield to obtain effluent solutions and moisture
distribution. Soon after the septic tank was put into use, ponding
of the effluent in the trench began. Movement of P from the trench
occurred in both downward and the horizontal directions.
Scalf, M.R., Dunlap, W.J. and Kreissl, J.F., "Environmental Effects of
Septic Tank Systems", Report No. EPA/600/3-77/096, Aug. 1977, Robert S.
Kerr Environmental Research Laboratory, Ada, Oklahoma.
Septic tank-soil absorption systems are the most widely-used
method of on-site domestic waste disposal. Almost one-third of the
United States population depends on such systems. Although the
percentage of newly constructed homes utilizing septic tanks is
decreasing, the total number continues to increase. Properly
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designed, constructed, and operated septic tank systems have
demonstrated an efficient and economical alternative to public
sewer systems, particularly in rural and sparsely developed
suburban areas. However, because of their widespread use in
unsuitable situations, they have also demonstrated the potential
for contamination of ground and surface waters.
Shoemaker, C.A. and Porter, K.S., "Recharge and Nitrogen Transport
Models for Nassau and Suffolk Counties, New York", NTIS PB-276 906/5ST,
Jan. 1978, Cornell University, Ithaca, New York.
Ground water aquifers underlying Long Island are the only
source of drinking water for more than 2.5 million people in Nassau
and Suffolk Counties in Long Island, New York. Due to residential
and agricultural land use, the ground water is being contaminated by
nitrogen. In order to quantify both the amount of recharge water
and the nitrogen concentration in the recharge, a simulation model
has been developed. The model calculates a mass balance of water
and nitrogen on 762 cells, each of which is 1.5 miles square. The
calculations which are computed daily or monthly are based upon land
use, soil type, temperature, precipitation and sewerage in each
grid. Detailed soil moisture data were collected at several sites.
Data from the early part of the year were used to calibrate the
model. Validation was achieved by comparison with independent data
collected in the late part of the year. The average recharge of
precipitation for Nassau and Suffolk Counties was estimated by the
model to be 1140 million gallons per day or 20.5 inches per year.
Lawn fertilizer and septic systems were the major sources of
nitrogen in the recharge water.
Sproul, O.J., "Virus Movement Into Ground Water from Septic Tank
Systems", Paper No. 12, Sept. 1973, Rural Environmental Engineering
Conference on Water Pollution Control in Low Density Areas Proceedings,
University Press of New England, Hanover, New Hampshire.
Viruses can be recovered from any water that has been
subjected to viral contamination. In situations where wastewater is
to be discharged to the local environment, e.g., one's backyard, as
with the septic tank system, the concern of che homeowner should be
obvious, especially if his water supply is a private well only a
few feet from the septic tank system. Viruses from these supplies
are routinely involved in outbreaks of infectious hepatitis and
gastroenteritis. Methods of predicting the capacity of a septic
tank-soil absorption system to remove viruses and to develop
criteria to assess this capacity are discussed.
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Troyan, J.J. and Norris, D.P., "Cost-Effectiveness Analysis of
Alternatives for Small Wastewater Treatment Systems", EPA Technology
Transfer Report, Mar. 1977, U.S. Environmental Protection Agency,
Washington, D.C.
Information pertinent to the cost-effectiveness analysis of
sewerage systems for both small communities and rural residential
areas is presented. Procedures for use in determining the
feasibility and desirability of employing four onsite systems and
four types of community collection systems are described. Major
objectives of the study include: identifying the problem conditions
that must be considered in selecting sewerage alternatives;
outlining the advantages, drawbacks, and limitations of the onsite
and community collection alternatives presented; reviewing a
procedure for screening and analyzing costs of alternatives for
individual homes; and examining a set of case histories taken from
recent sewerage reports and facilities plans.
Uttormark, P.O., Chapin, J.D. and Green, K.M., "Estimating Nutrient
Loadings of Lakes from Non-Point Sources", EPA 660/3-74-020, Aug. 1974,
University of Wisconsin, Madison, Wisconsin.
Data describing nutrient contributions from nonpoint sources
were compiled from the literature, converted to kg/ha/yr, and
tabulated in a format convenient for estimating nutrient loadings
of lakes. Contributing areas are subdivided according to general
use categories, including agricultural, urban, forested, and
wetland. Data describing nutrient transport by ground water
seepage and bulk precipitation are given along with data for
nutrient contributions from manure handling, septic tanks, and
agricultural fertilizers.
Vilker, V.L., "An Adsorption Model for Prediction of Virus Breakthrough
from Fixed Beds", Presented at Land Treatment of Waste Water
International Symposium, Hanover, New Hampshire, Aug. 1978, pp. 381-389.
Laboratory and field studies have demonstrated the potential
for biological and chemical contamination of U.S. ground water
supplies by percolation from land application of untreated and
treated wastewater, sludge land spreading, septic tanks, and
landfill leachates. Experiments were conducted and mathematical
models were developed to predict the breakthrough of low levels of
virus from percolating columns under conditions of adsorption and
elution. Breakthrough of viruses was illustrated by ion
exchange/adsorption equations. Predictions were in qualitative
agreement with observations from experiments that measured virus
uptake by activated carbon or silty soil in columns.
A-23
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Vilker, V.L., et al., "Water - 1977 (Application of Ion Exchange/Adsorp-
tion Models to Virus Transport in Percolating Beds)", AICHE Symposium
Series. Vol. 74, No. 178, 1978, pp. 84-92.
Ground water currently constitutes 95% of the U.S. freshwater
supply. This supply is subject to biological and chemical
contamination by percolation from surface spreading of untreated and
treated wastewater, sludge land spreading, septic tanks, and
landfill leachate. Examined is the magnitude of the threat of
virus contamination of ground water supplies that is presented by
these waste disposal practices. Described are initial experimental
and mathematical modeling efforts to predict breakthrough of low
levels of virus from percolating columns under conditions of
adsorption and elution. This breakthrough is described by the ion
exchange/adsorption equations that include the effects of external
mass transfer and nonlinear adsorption isotherms. Predictions
qualitatively agree with reported observations from experiments
that measured virus uptake by columns packed with activated carbon
or a silty soil.
Viraraghavan, T., "Influence of Temperature on the Performance of Septic
Tank Systems", Water, Air and Soil Pollution, Vol. 7, No. 1, Jan. 1977,
pp. 103-110.
Air, liquid and soil temperatures are important environmental
factors that influence the operation of septic tank-soil absorption
systems. An investigation conducted near Ottawa, Ont., on the
efficiency of an experimental tile system did not show any specific
trend between soil temperatures (depth dependent) and efficiency;
this can be attributed to the fact that the depth factor carries
with it other elements such as proximity to ground water table, and
oxygen penetration that significantly influence the efficiency of
the system.
Viraraghavan, T., "Travel of Microorganisms from a Septic Tile", Water,
Air, and Soil Pollution, Vol. 9, No. 3, Apr .1978, pp. 355-362.
An investigation was carried out to monitor the horizontal
travel of indicator microorganisms from the end of a 7.93-m-long
septic tile in the direction of ground water flow. Ground water
samples were collected on 2 occasions at distances of 0, 2.10,
3.05, 9.15, 12.20, and 15.25 m from the end of the septic tile by
putting down bores about 2 m deep and analyzed for indicator
organisms (coliforms, fecal coliforms, and fecal streptococci).
The analyses were performed as per Standard Methods. The
microorganism levels exhibited a declining trend with distance away
from the tile end. Because the unsaturated depth of soil available
for microorganisms vertical travel was limited, relatively high
A-24
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levels of organisms were found in the ground water even at a
horizontal distance of 15.25 m from the end of the septic tile.
Viraraghavan, T. and Warnock, R.G., "Groundwater Pollution from a Septic
Tile Field", Water, Air and Soil Pollution, Vol. 5, No. 3, Apr. 1976,
pp. 281-287.
The characteristics of the ground water below an existing
septic tile field were studied during the summer of 1973. The
concentrations for chemical constituents were found to be much
lower in the ground watr>r compared to the septic tank effluent;
however, these were quit.- high compared to background levels for
the ground water in the tren, indicating the pattern of pollution
that is taking place.
Walker, W.G., et al., "Nitrogen Transformations During Subsurface
Disposal of Septic Tank Effluent in Sands: II. Ground Water Quality",
Journal of Environmental Quality, Vol. 2, No. A, 1973, pp. 521-525.
Ground water observation wells were installed in the immediate
vicinity of four septic tank effluent soil disposal systems.
Potentiometric maps were constructed from measurements of the
ground water level at each site to establish the direction of
movement. Ground water samples were pumped from each well to
establish patterns of N enrichment in the ground water around the
seepage bank and to evaluate the performance of these disposal
systems in sands in terms of N removal. Soil disposal systems of
septic tank effluent in sands were found to add significant
quantities of nitrate (N03~N), formed by nitrification of Nl^-N,
the dominant N form in the effluent, to underlying gvound water.
The data obtained suggest that in sands, the only active merhanioir,
of lowering the N03~N content is by dilution with uncontaminated
ground water. Relatively large areas of 0.2 ha (0.5 sere) down
gradient were needed in the studied systems before concentrations
in the top layer of the ground water were lower than 10 rag/1. The
average N input per person was 8 kg (10 Ib.) per year. Essentially
complete nitrification in the soil results in addition of
approximately 33 kg NC^-N (73 Ib. ) to the ground water per year for
an average family of four.
Waltz, J.P., "A System for Geologic Evaluation of Pollution Potential at
Mountain Dwelling Sites", NTIS PB-240 820/2ST, Jan. 1975, Colorado State
University, Fort Collins, Colorado.
Development of mountain homesites is accelerating in the Rocky
Mountains of central Colorado. These homesites often require
individual water wells and sewage disposal systems. Unfortunately,
the widely used septic tank-leach field system generally is not
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suited for use in Che mountainous terrain where soils are thin or
missing. Although current federal regulations call for six feet or
more of soil at the leach field site, many of the individual sewage
disposal systems now in operation in the Rocky Mountain Region of
Colorado fail to meet this requirement. Sewage effluent at these
sites may directly enter bedrock fractures and travel large
distances without being purified. As a consequence, contamination
of streams, lakes, and ground water from these malfunctioning leach
fields has become a problem of increasing magnitude.
Investigations of geologic, topographic, and hydrologic conditions
at over 100 homesites in the Rocky Mountains of north-central
Colorado have resulted in the development of objective criteria for
evaluating pollution potential at mountain homesites.
Weeter, D.W., "The Use of Evapotranspiration as a Means of Wastewater
Disposal", Report No. 70, May 1979, NTIS, Springfield, Virginia.
A laboratory study, mattn'matLeal models, and a literature
search were employed to determine the applicability of evapotrans-
piration to treat on-site disposal of septic tank effluent and
aerobically treated effluent. The relative fate of some trace
metals within the evapotranspiration rates (outflow) and the
infiltration rates (inflow) of the proposed evapotranspiration bed.
A literature search related soil-ground water parameters to the
inflow-outflow rates and attempted to determine the effective life
of the system. Results of the study show that evapotranspiration
rates of aerobically digested water are equal to the rates for
septic tank effluent; that evapotranspiration is independent of the
dry plant matter produced; and the two feed solutions showed equal
metal uptake rates. It is concluded that the cost of this method is.
economically justifiable in certain circumstances.
Willis, R. and Dracup, J.A., "Optimization of the Assimilative Waste
Capacity of the Unsaturated and Saturated Zones of an Unconfined Aquifer
System", Report No. UCLA-NEG-7394, Dec. 1973, School of Engineering and
Applied Science, University of California, Los Angeles, California.
A mathematical model to optimize the assimilative waste
capacity of unconfined aquifers is formulated. The aquifer is to be
used conjunctively with surface sources as a source of water
supply. Waste waters may be introduced into the ground water
aquifer system by either well injection or by basin spreading of
waste waters. In the model, three treatment processes are
available to reduce constituent concentrations present in waste
waters: (1) dilution; (2) surface treatment of each constituent;
and (3) the assimilative capacity of the unsaturated and saturated
zones of the aquifer system. The total cost for supplying the
dilution water and the cost for surface treatment of each
constituent is minimized by the model.
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APPENDIX B
CHARACTERISTICS OF SEPTIC TANK AREAS TN CENTRAL OKLAHOMA
B-l
-------
Data Sheet
Site; Arcadia, Oklahoma County, Oklahoma
Permeability
(a) soil type
(b) in/hr
Depth to water table (ft)
Land/water table gradient
(slope - %)
Distance to Public/Private
water source (ft)
Thickness of Porous
Layer to Bedrock (ft)
Population of Area
(a) year of census
(b) Estimated Application
rate (MG/Yr)
- Darncll-Stephenville fine sandy loam
- high percolation
- 24
- 3-12% (land)
< 100 (private wells)
- estimate <• 2
- 410
- 1975
7.8 (52 gal/person-day)
B-2
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Data Sheet
Site; Arrowhead Hills. Oklahoma County, Oklahoma
Permeability
(a) soil type
(b) in/hr
Depth to water table (ft)
Land/water table gradient
(slope - %)
Distance to Public/Private
water source (ft)
Thickness of Porous
Layer to Bedrock (ft)
Population of Area
(a) year of census
(b) Estimated Application
rate (MG/Yr)
Darnell-Stephenville fine sandy loam
high percolation
- 50
- 3-12% (land)
< 100 (private wells)
< 1 (severely eroded)
- 488
- 1975
- 9.3 (52 gal/person-day)
B-3
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Data Sheet
Site; Crutcho, Oklahoma County, Oklahoma
Permeability
(a) soil type
(b) in/hr
Depth to water table (ft)
Land/water table gradient
(slope - %)
Distance to Publie/Private
water source (ft)
Thickness of Porous
Layer to Bedrock (ft)
Population of Area
(a) year of census
Stephenville fine sandy loam
high permeability
34
3-5% (land)
- < 100 (private wells)
- 3-4
- 587 (3522/6)
- 1977 (estimated)
(b) Estimated Application
rate (MG/Yr) - 11.1 (average 52 gal/person-day)
B-4
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Data Sheet
Site; Del City, Oklahoma County, Oklahoma
Permeability
(a) soil type - Renfrew clay loam
(b) in/hr - 0.06
Depth to water table (ft) - 14° to 18°
Land/water table gradient - l~yx> (land)
(slope - %)
Distance to Public/Private
water source (ft) - < 200 (public water wells in area)
Thickness of Porous
Layer to Bedrock (ft) - 1 to 4 -
Population of Area - 246
(a) year of census - 1975
(b) Estimated Application
rate (KG/Yr) - 4.7 (52 gal/person-day)
B-5
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Data Sheet
Site; Forest Park, Lake Hiwassee, and Lake Alma, Oklahoma County,
Oklahoma
Permeability
(a) soil type
(b) in/hr
Depth to water table (ft)
Land/water table gradient
(slope - %)
Distance to Publie/Private
water source (ft)
Thickness of Porous
Layer to Bedrock (ft)
Population of Area
(a) year of census
Darnell-Stepher.ville fine sandy loam
_ high percolation
- 65-100
_ 3-12% (land)
< 100 (private wells)
- 1
-• 1200
- 1975
(b) Estimated Application
rate (MG/Yr) - 27.0 (52 gal/person-day)
B-6
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Data Sheet
Site: Green Pastures, Oklahoma County, Oklahoma
Permeability
(a) soil type - Darnell-Stephenville fine sandy loaia
(b) in/hr - very raPid percolation
Depth to water table (ft) - 50 to 60
Land/water table gradient - 3~12%
(slope - %)
Distance to Public/Private ,„„,_, ,, s
water source (ft) - < 10° (P^vate wells)
Thickness of Porous
Layer to Bedrock (ft) - l
Population of Area - 2313
(a) year of census - 1977 (estimate)
(b) Estimated Application
rate (MG/Yr) - 43.9 (52 gal/person-day)
B-7
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Data Sheet
Site; Midwest City, Oklahoma County, Oklahoma
Permeability
(a) soil type
(b) in/hr
Depth to water table (ft)
Land/water table gradient
(slope - %)
Distance to Publie/Private
water source (ft)
Thickness of Porous
Layer to Bedrock (ft)
Population of Area
(a) year of census
- Darnell-Stephenville fine sandy loam
- high percolation
_ 36 to 44
_ 3-12% (land)
_ < 200 (public water wells in area)
- 1 to 4 -
- 12040
- 1975
(b) Estimated Application
rate (MG/Yr) - 228.5 (52 gal/person-day)
B-8
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Data Sheet
Site; Mustang, Canadian County, Oklahoma
Permeability
(a) soil type - Binger Line sandy loam
(b) in/hr - hiSh percolation
Depth to water table (ft) - 20
Land/water table gradient - 1~5 (land)
(slope - %)
Distance to Public/Private
water source (ft) - 5 miies (Lake Overholser)
Thickness of Porous
Layer to Bedrock (ft) - 3-4
Population of Area - 3550
(a) year of census - 1975
(b) Estimated Application
rate (MG/Yr) - 67.4 (52 gal/person-day)
B-9
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Data Sheet
Site; Nicoma Park; Oklahoma County, Oklahoma
Permeability
(a) soil type
(b) in/hr
Depth to water table (ft)
Land/water table gradient
(slope - %)
Distance to Public/Private
water source (ft)
Thickness of Porous
Layer to Bedrock (ft)
Population of Area
(a) year of census
(b) Estimated Application
rate (MG/Yr)
Darnell-Stephenville fine sandy loam
high percolation
- 62 to 83
- 3-12%
< 100 (private wells)
- < 1
- 3000
- 1975
57 (52 gal/person-day)
B-10
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Data Sheet
Site: East Norman, (Ea-t of 24th Street), Cleveland County, Oklahoma
Permeability
(a) soil type - Darnell-Stephenville fine sandy loam
(b) in/hr - high percolation
Depth to water tabl« (ft) - 145 to 18r) (Low due to water well
drawdown)
Land/water table gradient - 3_]2% (Llnd)
(slope - %)
Distance to Public/Private
water source (ft) - < 1/2 mile (public water well)
Thickness of Porous
Layer to Bedrock (ft) - 2 to 3 -
Population of Area - estimate 8000 (Koscinski, 1980)
(a) year of census - 1980
(b) Estimated Application
rate (MG/Yr) - 151.8 (52 gal/person-day)
B-ll
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Data Sheet
Site: Seward Area (South of Guthrie to Oklahoma County Line) Logan County,
Oklahoma
Permeability
(a) soil type - Darnell-Stephenville fine sandy loam
(b) in/hr - high percolation
Depth to water table (ft) - 13 to 31
Land/water table gradient - estimate 3-12 (land)
(slope - %)
Distance to Publie/Private
water source (ft) - < 200 (private wells)
Thickness of Porous
Layer to Bedrock (ft) - 2 to 3-
Population of Area - 2247 (Gaiuher, 1980)
(a) year of census - !980
(b) Estimated Application
rate (MG/Yr) - 174.6 (52 gal/person-day)
B-12
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Data Sheet
Site; Silver Lake Estates, Oklahoma County, Oklahomi
Permeability
(a) soil type
(b) in/hr
Vernon-Zaneis soil
slow percolation - 0.06
Depth to water table (ft)
Land/water table gradient
(slope - %)
Distance to Publie/Private
water source (ft)
Thickness of Porous
Layer to Bedrock (ft)
Population of Area
(a) year of census
(b) Estimated Application
rate (MG/Yr)
-. 12
- 3-5%
0.25 miles to Lake Hefner
- < 4
- 325
- 1975
6.2 (52 gal/person-day)
B-13
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Data Sheet
Site: Sunvalley Acres, Canadian County, Oklahoma
Permeability
(a) soil type - Rcinach fine sandy loam
(b) in/hr - moderate; to rapid percolation
Depth to water table (ft) - 7
Land/water table gradient - 1-3 (land)
(slope - %)
Distance to Publie/Private
water source (ft) - < 10° (private wells)
Thickness of Porous
Layer to Bedrock (ft) - estimatre 3 to 4
Population of Area - 150
(a) year of census - 1975
(b) Estimated Application
rate (MG/Yr) - 2.85 (52 gal/person-day)
B-14
-------
APPENDIX C
PHILLIPS, NATHWANI, AND MOOI.J ASSESSMENT MATRICES*
*Results from Carriere (1980)
C-l
-------
Site; Arrowhead Hills, Oklahoma County, Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
\s. Soil
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
Sy
Ab
Ar
TOTAL
"XP
p \.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
4.8
48
21
41
24
8
48
24
24
0
41
279
G
3
30
13
26
15
~5
30
15
15
0
26
175
I
I
10
4
9
5
2
10
5
5
0
9
59
D
9.2
92
40
78
46
15
92
46
46
0
78
533
T
10
100
43
85
50
16
100
50
50
0
85
579
TOTAL
410
177
349
206
66
410
206
206
0
349
2379
normalized score
C-2
-------
Site; Crutcho, Oklahoma County, Oklahoma
Phillips, Nathvani, Mooij Interaction Matrix
^S. Soil
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
sy
Ab
Ar
TOTAL
X.P
p \».
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
7.1
71
31
60
36
11
71
36
36
0
60
412
G
3.75
38
16
32
19
'6
38
19
19
0
32
219
I
1
10
4
9
5
2
10
5
5
0
9
59
D
9.2
92
40
78
46
15
92
46
46
0
78
533
T
10
100
43
85
50
16
100
50
50
0
35
579
TOTAL
441
190
374
222
70
441
222
222
0
374
2556
normalized score
C-3
-------
Site; Del City, Oklahoma County, Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
^X. Soil
WASTE
Ht
Gt
Dp
Cp
Bp
So
VI
Sy
Ab
Ar
TOTAL
XP
pX.
10
4.3
8.5
5
1.6
10
5
5
0
7.8
NP
3.1
31
13
26
16
5
31
16
16
0
24
178
NS
5
50
22
43
25
8
50
25
25
0
39
287
WT
2.4
24
10
20
12
4
24
12
12
0
19
137
G
5.6
56
24
48
28
9
56
28
28
0
44
321
I
1
10
4
9
5
2
10
5
5
0
8
58
D
8.3
83
36
71
42
13
83
42
42
0
65
^77
T
10
100
43
85
50
16
100
50
50
0
78
572
TOTAL
354
152
302
178
57
354
178
178
0
277
2030
P = normalized score
C-4
-------
Site; Forest Park, Lake Hiwassee, and Lake Alma, Oklahoma County,
Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
WASTE
Ht
Ct
Dp
CP
Bp
So
Vi
sy
Ab
Ar
TOTAL
Soil
\P
P\.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
N?
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
3.6
•J6
16
31
18
6
36
18
18
0
31
210
G
3
30
13
26
15
"5
30
15
15
0
26
175
I
1
10
4
9
5
2
10
5
5
0
9
59
D
9.2
92
40
78
46
15
92
46
46
0
78
533
T
10
100
43
85
50
16
100
50
50
0
85
579
TOTAL
398
172
339
200
64
398
200
200
0
339
2310
normalized score
C-5
-------
Site: Green Pastures, Oklahoma County, Oklahoma
Phillips, Mathwani, Mooij Interaction Matrix
^N. Soil
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
Sy
Ab
Ar
TOTAL
^X. P
p\.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
UP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
4.6
46
20
39
23
7
46
23
23
0
39
266
G
3.0
30
13
26
15
5
30
15
15
0
26
175
I
1
10
4
9
5
2
10
5
5
0
9
59
D
9.2
92
40
78
46
15
92
46
46
0
78
533
T
10
100
43
85
50
16
100
50
bO
0
85
579
TOTAL
s
408
176
347
205
65
408
205
205
0
347
2366
P = normalized score
C-6
-------
Site; Midwest City, Oklahoma County, Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
^\. Soil
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
Sy
Ab
Ar
TOTAL
\p
P\.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
5.4
54
23
46
27
9
54
27
27
0
46
313
G
3
30
13
26
15
"5
30
15
15
0
26
175
I
1
10
4
9
5
2
10
5
5
0
9
59
D
8.3
83
36
71
42
13
83
42
42
0
71
483
T
10
100
43
85
50
16
100
50
50
0
85
579
TOTAL
407
175
347
205
65 .
407
205
205
0
347
2363
normalized score
C-7
-------
Site; Mustang, Canadian County, Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
Sy
Ab
Ar
TOTAL
Soil
\P
P^v
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
7.9
79
34
67
40
13
79
40
40
0
67
459
G
5
50
22
43
25
~8
50
25
25
0
43
291
I
1
10
4
9
5
2
10
5
5
0
9
59
D
2.5
25
11
21
13
4
25
13
13
0
21
146
T
10
100
43
85
50
16
100
50
50
0
85
5/9
TOTAL
394
170
335
199
63
394
199
193
0
335
2288
P = normalized score
C-8
-------
Site; Nicoma Park, Oklahoma County, Oklahoma
Phillips, Nathwar.i, Mooij Interaction Matrix
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
sy
Ab
Ar
TOTAL
Soil
\P
P \.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
50
412
WT
3.8
38
16
32
19
6
38
19
19
0
32
219
G
3
30
13
26
15
"5
30
15
15
0
26
175
I
1
10
4
9
5
2
10
5
5
0
9
59
D
9.2
92
40
78
46
15
92
46
46
0
78
533
T
10
100
43
85
50
16
100
50
50
0
85
579
TOTAL
400
172
340
201
64
400
201
201
0
340
2319
P = normalized score
C-9
-------
Site: East Norman (East of E. 24th Street), Cleveland County,
Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
\^
WASTE
lit
Gt
Dp
Cp
Bp
So
Vi
Sy
Ab
Ar
TOTAL
Soil
\P
P \.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
WT
2.4
24
10
20
12
4
24
12
12.
0
20
138
G
3
30
13
26
15
5
30
15
15
0
26
175
L
1
10
4
9
5
1
10
5
5
0
9
59
D
5.2
52
22
44
26
8
52
26
26
0
44
300
T
10
100
43
85
50
16
100
50
50
0
85
579
TOTAL
346
148
294
174
55
346
174
174
0
294
2005
normalized score
C-10
-------
; Scward Aren (South of Outhrie to Oklahoma County Line) Logan
County, Oklahoma
Phillips, Natlivani, Mooij Interaction Matrix
WASTE
Ht
Gt
Dp
CP
Bp
So
Vi
Sy
Ab
Ar
TOTAL
Soil
\P
P^S.
10
4.3
8.5
5
1.6
10
5
5
0
8.5
NP
5.9
59
25
50
30
9
59
30
30
0
50
342
NS
7.1
71
31
60
36
11
71
36
36
0
60
412
UT
/.4
74
32
03
37
12
74
57
37
0
63
429
G
3
30
13
26
15
"5
30
15
15
0
26
175
f
1
10
4
9
5
2
10
5
5
0
9
59
D
8.3
83
36
71
42
13
83
42
42
0
71
483
T
10
100
43
85
50
16
100
50
50
0
85
576
TOTAL
427
184
364
215
68
427
215
215
0
364
2479
P = normalized score
C-ll
-------
Site; Silver Lake Estates, Oklahoma County, Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
sy
Ab
Ar
TOTAL
Soil
\, p
P^SX.
10
4.3
8.5
5
1.6
10
5
5
0
8
NP
2.5
25
11
21
13
4
25
13
13
0
20
145
NS
5.7
57
25
49
29
9
57
29
29
0
46
330
WT
8.9
89
38
76
45
14
89
45
4r>
0
71
512
G
4.4
44
19
37
22
"7
44
22
22
0
35
252
I
1
10
4
9
5
2
10
5
5
0
8
58
D
5.8
58
25
49
29
9
58
29
29
0
46
332
T
10
100
43
85
50
16
100
50
50
0
80
574
TOTAL
383
165
326
193
61
383
193
193
0
306
2203
normalized score
C-12
-------
Site; Sunvalley Acres, Canadian County, Oklahoma
Phillips, Nathwani, Mooij Interaction Matrix
WASTE
Ht
Gt
Dp
Cp
Bp
So
Vi
Sy
Ab
Ar
TOTAL
Soil
VX?
P Vs.
10
4.3
8.5
5
1.6
10
5
5
0
8
W
5.C
59
25
50
22
9
59
22
22
0
47
315
NS
5.7
57
25
49
29
9
57
29
29
0
46
330
WT
9.5
9j>
41
81
48
15
95
48
48
0
76
547
G
5
50
22
43
25
~8
50
25
25
0
40
288
I
1
10
4
9
5
2
10
5
5
0
8
58
D
9.2
92
40
78
46
15
92
46
-'to
0
74
529
T
10
100
43
85
50
16
100
50
50
0
80
574
TOTAL
...
463
200
395
225
74
463
225
225
0
371
2641
P = normalized score
C-13
-------
APPENDIX I)
F.KROK FUNCTION IN HANTIJSII ANALYTICAL MODEL
D-l
-------
A ~
a
I. OK.
t.Oii-
O.C>2(
C.030
G.04C
0.051
C.OM'
0.070
C.CBO
0.090
0.100
0.110
0.120
0.110
0.140
0.150
0.160
0.170
0.180
0.190
0.200
0.210
D.22D
0.230
0.240
0.250
0.260
0.270
0.280
0.290
0.300
0.3)0
0.320
0.330
0.340
6.350
0.340
C.370
0.380
0.390
0.400
0.410
0.42D
0,005
O.ODO:
0. 000s
0.001*
O.OOIS
0.0023
0.0017
O.OON
C. 0033
0.003t
G.003E
0.0040
0.0042
0.0045
0. 0046
0.0050
0.0052
0.0054
O.OOSt
0.005F
0.0060
0.0062
0.0063
0.006!)
0.0066
0.006B
0.0069
0.0070
0.0071
0.0073
0.0074
0.0075
0.007t>
0.0077
0.007E
0.0079
0.0080
O.OOB2
0.0082
O.OOB4
0.0065
0.0086
O.ODBc
O.MB7
O.OIb
0.000*
O.OOli
0.002:-
(-.003:
<'.(»04<
0.004:
0.005*
0.006C
0.0066
0.007)
0.0076
O.OOBD
O.OOB6
0.0090
0.0095
0.0099
0.010?
0.0107
0.0111
0.0115
o.om
0.0122
0.0125
0.0126
0.0131
0.0134
0.0136
0.0139
0.0142
0.0144
0.0147
0.0119
0.0151
0.0153
0.0156
0.015E
0.016C
0.0162
0.0165
0.0167
0.016B
0.0170
0.0171
0.020
G.OC04
0. OCI3
0.0041
0. OC57
c.007:
0. OOE7
0.010)
0.0113
0.0125
0.013*
0.0146
0.0154
0.0)65
0.0174
0.0163
0.0191
0.0200
0.020E
0.02U
C.022J
0.0230
0. 0237
0.0243
0.0250
0.0256
0.026)
0.0267
0.0272
0.0277
0.0282
0.0287
G.0292
0.0297
0.0301
0.0306
0.0310
0.0314
0.031E
0.0325
0.0126
0.0331
0.0334
C.0337
0.030
G.OOJe
0.0032
&.005:
O.OOB;
o.oio;
0.0125
0.0145
0.016*
0.0181
0.0197
0.0212
t>.0226
0.0241
0.0255
0.026B
0.02B1
0.0293
0.0305
0.0317
0.0328
0.0336
0.0349
O.K5B
0.036B
0.0377
0.0385
0.0373
0.0401
0.0409
0.0417
0.0424
0.0431
0.0436
0.0445
0.0452
0.045E
0.0465
0.0471
0.04BO
0.0485
0.04S9
0.0494
0.0495
0.040
1). 0021
G.OMt
O.OOT:
0.0103
0.013?
O.Olol
0.015'
0.021?
0.0215
0.0257
0.0277
0.0295
0.0315
0.0333
0.0350
0.0367
0.038!
C'.OW
0.0415
0.042'
0.0443
0.0457
0.0470
0.046;
0.0494
0.0506
0.0517
0.0527
0.053B
0.054B
0.0556
0.0567
0.0577
0.0586
0.0595
0.0603
0.0612
0.0620
0.0653
0.0639
0.0645
0.0651
6. 0457
O.C50
0.0027
o.oc<:
0.0057
0.0125
0.0)63
C.C!95
c.c:r
&.C25E
0.02E7
0.0313
0.033B
0.0362
0.0385
0.040B
0.0430
0.045)
O.P47J
0.0491
0.0510
0.052t
0.0546
0. 0562
O.C57S
0.0594
0.060°
0.0623
0.0637
0.0650
0.0663
0.0676
0.06BB
0.0700
0.0712
0.0723
0.0734
0.074b
0.075t
0.076e
0.0781
(l.MB1!
0.0791
0.0304
O.OB11
0.060
O.Otol-
t.OC'5*
o.GJo;
fc.014f
O.OIB'
C.C22-
O.C2b(
o.(-3o:
t,'.03it
O.C36?
0.0396
0.0425
0.0453
0.0480
0.0506
0.0531
0.0555
0.0579
0.060?
C.062:
6.0b4<
0.06&5
O.OSE'.
0.070?
0.0720
0.0737
0.0754
0.0769
0.0785
O.OBOO
0.0815
O.OB30
O.QB44
0.0857
O.OB71
O.PES3
O.OE96
C.090E
0.0527
0.0?3t
0.0945
0.0954
0.0963
C.07d
6.0G33
t. 0060
0.0113
C..P16*
0.0:1:
C.{?5F
o. esc:-
C.0343
0.03.E2
0.0411?
0.0454
0.04B6
0.0519
0.055P
o.oseo
0.0609
0.0637
0.0664
0.069C
0.07 It
0.074(-
0.0764
O.OJBi
b.OBOB
O.GB2E
O.OB4B
0.0867
O.OBB6
0.0904
0.0921
0.0935
0.0956
0.0972
0.09BE
0,100;
0.101B
0.1033
G.l(>47
G.lObB
O.IG7S
0.10B9
0.1100
O.nib
n o
c-.oso c.090 e.i&c
b.003t C.OC-3E 1.004C-
O.OGo: 0.0('": C.007:
1-.012! &.G!3* C.u«c
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0.2312 0.2465 0.2615
0.2331 0.2486 0.2638
0.234? 0.2506 0.2659
0.2366 0.2574 0.2676
0.23B2 0.2541 0.2696
0.2396 C.255t 0.2713
0.2411 0.2572 0.2729
0.2425 0.258fc 0.2745
0.2437 0.2600 0.2760
0.2449 0.2613 0.2773
0.2461 0.2625 0.2786
0.2471 0.2636 0.2798
0.2481 0.2647 0.2809
0.2490 0.2656 0.2820
0.249E 0.2665 0.2829
0.2506 0.2674 C.283B
0.2513 0.26B2 0.2847
0.2566 0.273B 0.2907
0.25B6 0.2760 0.293!
0.2600 0.2775 0.2947
0.260B 0.27B3 0.2956
0.2611 0.27B6 0.2959
0.2611 0.2787 0.2959
0.2611 0.2787 0.2959
0.2611 0.27B7 0.2959
0.2611 0.2767 0.2959
0.2611 0.2767 0.2959
0.2309
C.233?
C.235:
C.2379
C.240I
G.242e
0.244=
0.2471
C.251E
G.2554
0.258E
0.2621
0.2652
0.26B2
0.2710
0.2737
0.2763
0.2786
0.2809
0.2829
0.2849
0.2866
0.2884
0.2903
0.2916
0.2931
0.2944
0.2957
0.2969
0.2980
0.2990
0.3000
0.3009
0.3073
0.3099
0.3115
0.3125
0.312B
0.3128
0.312E
0.312E
0.3J2B
0.3128
0.2426
0.2453
0.2476
0.250C
0.2525
0.255C.
0.2575
0.259?
0.264E
0.2t>8r
0.2722
0.2757
0.2790
0.2822
0.2B52
0.2BBO
0.2907
0.2932
0.2955
0.297;
0.2996
0.3017
0.3035
0.3053
0.3070
0.3085
0.3099
0.3113
0.3125
0.3137
0.3148
0.315B
0.3166
0.3236
0.3263
0.32B1
0.329!
0.3295
0.3295
0.3295
0.3295
0.3295
0.3295
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0.2774
0.2814
0.2853
0.2890
0.2925
0.295P
0.2990
0.3020
0.304E
0.307i
0.3096
0.312:
0.31"
0.3164
0.3184
0.3203
0.3220
0.3236
0.3251
0.3266
0.3279
0.3291
0.3303
0.3314
0.3324
O.J39i
0.3425
0.3443
0.345*
0.345E
0.3458
C.3456
0.3458
0.345E
0.345E
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0.3019
0.3056
0.3091
0.3125
0.3156
0.3186
0.3214
0.3240
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0.3267
G.330E
0.3329
0.3349
0.3367
C.3384
0.3400
0.3415
0.3429
0.3442
0.3454
0.3466
0.3476
0. 3552
0.355:
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0.3613
0.3617
0.3617
0.3617
0.3617
0.3617
0.3617
C.2761
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1.2B4F
0.267'
C.25CS
0.2=3'
0.29i;
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0.3063
0.3105
0.3146
0.3185
0.322!
0.3256
0.3290
0.3321
0.3350
0.337E
0.3403
O.J427
0.3450
0.3471
0.3491
0.3511
0.3529
0.3546
0.3561
0.3576
0.3590
0.3602
0.361'
0.3626
0.3705
0.3737
0.3758
0.3769
0.3774
0.3774
0.3774
0.3774
0.3774
0.3774
0.2Ec"
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0.304:
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0.3137
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0.32Z7
0.3270
0.3310
0.3349
0.3385
0.3420
0.3453
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0.3512
0.353*
0.35M
C.358B
0.3611
0.3t>32
0.3652
0.3671
0.368E
0.3705
0.3720
0.3734
0.3745
0.3760
0.3772
0.3B55
0. 38B9
0.3911
0.3923
0.3927
0.3927
0.3927
0.3927
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0.3723
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0.3769
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0.3855
0.3880
0.3903
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0.3945
0.3964
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0.4014
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0.4042
0.4055
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0.4163
0.4206
0.4219
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0.340'
C.3472
0.3525
0.3575
0.3623
0.3669
0.3712
0.3754
0.3793
0.3830
0.3865
0.3897
0.3928
0.395fc
0.3984
0.4009
0.4033
0.4056
0.4077
0.4097
0.4115
0.4133
0.4149
0.4164
0.4176
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0.3475
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0.3913
0.3950
0.3986
0.4020
0.4051
0.4080
0.4110
0.4136
0.4161
0.4184
0.4206
0.4227
0.4246
0.4264
0.4281
0.4297
0.4312
0.4325
0.4423
0.4464
0.4489
0.4503
0.4509
0.4509
0.4509
0.4509
0.4509
0.4509
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C.010
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0.030
0.0*0
C.050
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0.070
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0.090
0.100
0.110
0.120
0.130
0.140
0.1 50
0.160
0.170
0.180
0.190
0.200
0.210
0.220
0.230
0.240
C.250
0.260
0.270
0.280
0.290
0.300
0.310
0.320
C.330
0.340
0.350
0.360
0.370
0.380
0.390
0.400
0.410
0.420
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0.0070
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0.026T
C.0393
0.0517
0.0637
0.0754
0.0867
0.0977
0.1084
0.1188
0.1288
0.1364
0.1476
0.1570
0.1660
0.1748
0.1833
0.1916
0.1 99c
0.2074
0.2150
0.2223
0.2294
0.2343
0.2429
0.2494
0.2556
0.2617
0.2677
0.2735
0.2792
0.2847
0.2901
0.2954
0.3004
0.3054
0.3102
0.3174
0.3210
0.3247
0.32B3
0.3320
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0.0527
0.065C
0.0769
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0.099B
0.1 10B
0.1214
0.1317
0.1415
0.1511'
0.1607
0.1699
0.1789
0.1876
0.1961
0.20"
0.2124
0.2202
0.2278
0.2351
0.2422
0.2490
0.2556
0.2621
0.2684
0.2745
0.2805
0.2B64
0.2921
0.2976
0.3030
0.3083
0.3134
0.3183
0.3257
0.3295
0.3333
0.3371
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0.0073
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0.0277
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0.1019
0.1131
0.1240
0.1345
0.1446
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0.1642
0.1737
0.1829
0.1919
0.2006
0.2091
0.2173
0.2253
0.2331
0.2406
0.2479
0.2549
0.2617
0.2684
0.2749
0.2812
0.2874
0.2934
0.2993
0.3050
0.3105
0.3159
0.3212
0. 3263
0.3340
0.337B
0.3417
0.3456
0.3495
0.290
0.0074
0.0144
0.028?
0.0417
0.054F
0.067e
0.0800
0.0921
0.1039
0.1154
0.1265
0.1373
0.1476
0.1577
0.1677
0.1774
0.186B
0.1960
0.204S
0.2136
0.2221
0.2303
G.23B3
0.2460
0.2535
0.2607
0.2677
0.2745
0.2B12
0.2877
0.2940
0.3002
0.3063
0.3121
0.3179
0.3234
0.328B
0.3341
0.3420
0.3460
0.3500
0.3540
0.3580
0.300 0.310
0.0075 0.0076
0.014" 0.014C
0.02S7 0.025:
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0.055E 0.056?
0.06BE 0.0701
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0.1289 0.1313
0.1399 0.1425
0.1505 0.1533
0.1609 0.1640
0.1710 0.1743
0.1810 0.1845
0.1906 0.1943
0.2000 0.2039
0.2092 0.2133
0.2181 0.222*
0.2268 0.231?
0.2352 0.2399
0.2433 0.2483
0.2513 0.256'
0.2589 0.2642
0.2664 0.2719
0.2735 0.2792
0.2B05 0.2864
0.2874 0.2934
0.2940 0.3002
0.3006 0.3069
0.3069 0.3134
0.3131 0.3196
0.3191 0.3260
0.3250 0.3320
0.3307 0.3379
0.3363 0.3436
0.3417 0.3491
0.349B 0.3575
0.3539 0.3617
0.3581 0.3659
0.3622 0.370?
0.3663 0.374»
0.320
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0.0297
0.043F
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0.0712
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0.1336
0.1451
0.1561
0.1669
0.1775
0.1879
0.1979
0.2078
0.2173
0.2267
0.2357
0.7445
0.2531
0.2614
0.2694
0.2772
0.2847
0.2921
0.2993
0.3063
0.3131
0.319B
0.3263
0.3326
0.338B
0.3448
0.3507
0.3564
0.36*9
0.3693
0.37J6
0.3780
0.3823
0.330
0.007P
0.0153
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0.0*45
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0.0727
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0.1 236
0.1359
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0.2400
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0.3574
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0.1402 0.1422
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0.1754 0.1780
0.1866 0.189*
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0.2082 0.2114
0.21 St. 0.2220
0.2287 0.2323
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0.248? 0.2522
0.2576 0.2617
0.2667 0.2710
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0.2924 0.2972
0.3004 0.3054
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0.3159 0.3212
0.3234 0.32BE
0.3307 0.3363
0.3379 0.3436
0.344P 0.3507
0.3516 0.3576
0.359! 0.3644
0.3647 0.3710
0.3710 0.3774
0.3770 0.3836
0.3862 0.3929
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0.705B
0.7144
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0.77B3
0.7B26
0.7B90
0.7950
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0.8056
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0.8197
0.8236
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0.83(5
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0.3769
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0.4526
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0.4979
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0.1754
0.1930
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0.3070
0.3220
0.3367
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0.3652
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0.3924
0.4056
0.4185
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0.5009
0.5117
0.5223
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0.2449 0.2461 0.2471
0.2613 0.2625 0.2636
0.2773 0.2786 0.279E
0.2931 0.2944 0.2957
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0.4695 0.4719 0.4741
0.4811 0.4636 0.4859
0.4925 0.4950 0.4974
0.5036 0.5062 0.50B6
0.5145 0.5172 0.5157
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0.5356 0.5384 0.5410
0.5457 0.5486 0.5513
0.5557 0.5566 0.5613
0.5701 0.5731 0.5759
0.57BO 0.5810 0.5839
0.5855 0.5890 0.5915
0.593E 0.5970 0.5999
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0.4133
0.4264
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0.5242
0.5351
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0.3746
0.3B90
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0.4164
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0.3236
0.339*
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0.3705
0.3855
0.4002
0.4Mb
0.4266
0.4424
0.4558
0.4689
0.4816
0.4545
0.5069
0.5190
0.5309
0.5426
0.5540
0.5651
0.5760
0.5867
0.6021
0.6106
0.6191
0.6776
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0.2244
0.2415
0.2597
0.2772
C.2943
0.3111
0.3275
0.3437
0.3595
0.3750
0.3902
0.4050
0.4195
0.4337
0.4475
0.4611
0.4745
0.4876
0.5004
0.5130
0.5254
0.5375
0.5493
0.5609
0.5722
0.5B32
0.5941
0.6094
0.6182
0.6769
0.1356
0.6443
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0.430
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C.46C-
0.470
0.460
0.49(
0.500
0.520
0.540
0.56J
0.580
0.600
0.620
0.640
0.660
0.690
0.700
0.720
0.740
0.760
0.780
0.800
0.820
0.840
0.860
D.B80
0.900
0.920
0.940
0.960
0.980
1.000
1.200
1.400
1.600
1.800
2.000
2.200
2.400
2.600
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3.000
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0.6060
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0.6214
0.629!
0.636B
0.6445
0.6521
0.6664
0.6789
0.6909
0.7024
0.7134
0.723E
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0.7432
0.7521
0.7605
0.7664
0.775B
0.7827
0.7894
0.7959
0.8019
0.8076
0.8129
0.8179
0.8225
0.8269
0.8310
0.8349
0. 8365
0.841E
0.8663
0.8764
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O.B878
0.887B
0.8876
O.BB78
O.B20
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0.6101
0.617?
0.625:
0.633'
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0.64S?
0. 656'
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0.681"
0.695B
0.7074
0.7184
0.7290
0.7390
C.74B6
0.7576
0.7o61
0.7741
0.7816
0.7885
0.7955
0.8019
0.8080
0.8136
0.8190
0.8240
0.8288
0.8332
0.8374
0.8413
0.8450
0.8484
0.8731
O.BE33
0.8B9B
C.B935
0.8949
0.8949
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0.8949
0.8949
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0.6530
0.6609
0.6755
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0.7536
0.7627
0.7713
0.7794
0.7E70
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0.8011
0.807*
0.8136
0.8194
O.B24B
0.8298
0.8346
0.8391
0.8434
O.B473
O.B511
0.8546
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O.BB9E
0.8965
0.9001
0.9016
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0.6096
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1.6333
0.6411
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0.9073
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0.8803
0.9064
0.9173
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0.7406 0.7605 0.7706
0.7524 0.7726 0.7829
0.7637 0.7845 0.794B
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0.7943 0.8164 0.8274
0.8034 0.6260 O.B374
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0.6604 0.6855 0.8980
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0.8B46 0.9108 0.9242
0.8866 0.9151 0.9286
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t.9190 0.9472 0.9615
0.9302 C.959C 0.9739
0.9374 0.9666 0.9817
0.9414 0.9709 0.9660
0.9430 0.9725 0.9877
0.9430 0.9726 0.9877
0.9430 0.9726 0.9877
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0.9430 0.9726 0.9B77
0.9430 0.9726 0.9877
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D-15
-------
AI'I'T-NUrX F.
FORTRAN IV PROGRAM FOR KON1KOW-BRKDEHOEFT
SOLUTE TRANSPORT MODEL
E-l
-------
FORTRAN IV Program Listing
.««*•*»•»»•»•**•****•**»•••*••••
•
SOLUTE TRANSPORT AND DISPERSION IN A POROUS MEDIUM •
NUMERICAL SOLUTION METHOD OF CHARACTERISTICS *
PROGRAMMED BY J. D. BREDEHOEFT AND L. F. KONIKOW •
*
DOUBLE PRECISION DMIN1,DEXPsDLOG*DABS
REAL *8TMRXsVPRM»HI«HR«HC«HK*WT/REC«RECH«TIM«AOPT,TITLE
REAL •8XOEL,YDEL/S,AREA,SUMT,RHO,PARA«,TEST,TOL,PINT,HMIN,PYR
REAL *8TINT,ALPHA1,ANITP
COMMON /PRMI/ NTIM»NPMP»NPNT/NITP,N,NX,NY/NP,NREC»INT,NNX»NNY,NUMO
1BS,NMOV»IMOV,NPMAX»ITMAX,NZCRIT,IPRNT,NPTPND»NPNTMV»NPNTVL»NPNTD,N
2PNCHV,NPDELC
COMMON /PRMK/ NODE ID(20*20) »NPCELL(20*20)*LIMBO(500)• IXOBSt5>/IYOB
1S(5>
COMMON /HEDA/ THCK(20,20 ) »PERM{20,20),TMUL<5,50)«TMOBS<50>,ANFCTR
COMMON /HEDB/ TMRX(20*20/2)»VPRM(20/20)»HI(20*20)»MR(20*20)»HC(20,
1 20)»HIC< 20* 20),WT( 20*20) »REC (20*20>»RECH(20«20> « T IM(100) «AOPT(20)«T
2ITLE(1 0>«XDEL»VDEL»S«AREA«SUHT«RHO,PARAM»TEST»TOL«PINT»HMIN«PYR
COMMON /CHMA/ PART(3*3200),CONC(20/20),TMCN(5»50)»VX<20/20)*VY(20»
120)/CONINT(20«20)«CNRECH(20«20)rPOROS»SUnTCH«BETA/TIMV«STORM»STORH
2I»CMSIN»CMSOUT«FLMIN»FLMOT»SUMIO»CELDIS«DLTRAT/CSTORM
•••*••
•**»•*»»••»••••»»•**»»
--- LOAD DATA ---
INT«0
CALL PARLOO
CALL GENPT
•••••••••*••••*••*•••••••••*•••••*••»•*••**••**•*••••••••••••••
--- START COMPUTATIONS ---
--- COMPUTE ONE PUMPING PERIOD ---
DO ISO INT*1,NPMP
IF (INT.GT.1) CALL PARLOD
--- COMPUTE ONE TIME STEP ---
00 130 N«1,NTIM
IPRNT'O
--- LOAD NEW DELTA T ---
TINT«SUMT-PYR«(INT-1)
TOEL*DMIN1
SUMT-SUMT«TDEL
TIM(N)-TDEL
REMN=MOO (N,NPNT )
••*»•*•••*•*••••»•»•*••«•*•••»»»•»»*****
CALL ITERAT
IF (REMN.EQ.O.O.OR.N.EQ.NTIM) CALL OUTPT
CALL VELO
CALL MOVE
*•»••*••••*••*»•»•»*•**«
**»»»»**»•*
•»••**»
•»*••»•»•*•»»»*•»*»**
WELL DATA
GO TO 120
O) GO TO 120
110
--- STORE OBS.
IF (S.EQ.0.0)
IF (NUMOBS.LE
JaMOD(N,SO>
IF (J. EQ.O) J-50
TM08S( J)»SUMT
DO 110 I«1«NUMOBS
TMULCI /J >-HK< IXOBS < I)* I Y08S< I) >
TMCN (I /J)«CONC(IXOBS(I )«IYOBS(I»
CONTINUE
FOR TRANSIENT FLOW PROBLEMS ---
10
20
30
40
50
60
70
80
90
100
110
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400
410
420
430
440
450
460
470
480
490
500
510
520
530
540
550
560
570
580
E-2
-------
FORTRAN IV program listmg—Continued
_ • r Qf>
C OUTPUT ROUTINES ^_ 600
120 IF (HEMN.EO.O.O.OR.N.EO.NTIM.OR.MOD(N,50) .EQ.O) CALL CHMOT — ^ 610
IF (SUMT.GE.(PYR*INT)) GO TO 140 620
130 CONTINUE 630
C SUMMARY OUTPUT 650
140 CONTINUE 660
1PRNT-1 670
CALL CHHOT ^ 680
ISO CONTINUE 690
Jf\f\
STOP 710
END * ••••••• * •" * 7jo
SUBROUTINE PARLOD B 10
DOUBLE PRECISION DM INl,DEXP,DLOG,DABS B 20
REAL *8TMRX,VPRH,HI,HR,HC,HK,WT,REC,RECH,TIM,AOPT,TITLE B 30
REAL •8XDEL»YDEL,S»AREA,SUMT,RHO,PARAM, TEST,TOL,PINT,HMIN,PYR B 40
REAL *8FCTR,TIMX,TINIT,PIES,YNS,XNS,RAT,HMX,HMY B SO
REAL *8TINT,ALPHA1,ANITP B 60
COMMON /PRMI/ NTIM,NPMP,NPNT,NITP,N,NX,NY,NP,NREC,INT,NNX,NNY,NUMO B 70
1BS,NNOV,IMOV,NPMAX,ITMAX,NZCRIT,1PRNT,NPTPND,NPNTMV,NPNTVL»NPNTD,N 8 80
2PNCHV,NPDELC B 90
COMMON /PRMK/ NODEID(20,20),NPCELL ( 20,20),LIMBO(500),1XOBS(5), I YOB B 100
1S<5) B 110
COMMON /HEDA/ THCK<20,20),PERM(20,20),TMWL<5,50)»TMOBS(50>,ANFCTR B 120
COMMON /HEDB/ TMRX(20,20,2),VPRM(20,20),HI(20,20),HR(20,20),HC(20* B 130
120),HK(20,20),WT(20,20),REC(20,20),RECH(20,20),TIH(100),AOPT(20),T B 140
2ITLE(10)»XDEL,YOEL,S,AREA,SUMT,HHO,PARAM,TEST,TOL,PINT,HMIN,PYR B 150
COMMON /CHHA/ PART<3,3200),CONC(20,20),TMCN(5,50),VX(20,20),VY(20, B 160
120),CONINT(20,20),CNRECH(20,20),POROS,SUMTCH,BETA,TIMV,STORM,STORM B 170
2I,CMSIN,CMSOUT,FLMIN,FLMOT,SUMIO,CELDIS,DLTRAT,CSTORM B 180
COMMON /BALM/ TOTL8 B 190
COMMON /XINV/ DXINV,DY1NV,ARINV,PORINV B 200
COMMON /CHMC/ SUMC(20,20),VXBDY(20,20),VYBDY(20,20) B 210
C ••»•*•»•••»•••••••*•******•••••************•*****•***•**•****** B 220
IF (INT.GT.1) GO TO 10 B 230
WRITE (6,750) B 2*0
READ (5,720) TITLE 3 250
WRITE (6,730) TITLE S 260
C INITIALIZE TEST AND CONTROL VARIABLES B 280
STORMI-0.0 B 290
TEST-0.0 B 300
TOTL8-0.0 8 310
SUMT»0.0 B 320
SUMTCH»0.0 B 330
INT»0 B 340
IPRNT*0 B 350
NCA-0 B 360
N«0 B 370
IMOV'O B 380
NMOV«0 B 390
C LOAD CONTROL PARAMETERS B 410
READ (5,740) NTIM,NPMP,NX,NY,NPMAX,NPNT,NITP,NUM08S,ITMAX,NREC,NPT 8 420
1PND,NCODES,NPNTNV,NPNTVL,NPNTD,NPDELC,NPNCHV B 430
READ (5,800) PINT,TOL,POROS,BETA,S,TI*X,TINIT,XDEL,YDEL,DLTRAT,CEL B 440
1DIS,ANFCTR B 450
PYR»PINT*86400.0*365.25 B 460
NNX«NX-1 B 470
E-3
-------
FORTRAN IV program lifting—Continued
NNY»NY-1
NP'NPMAX
OXINV>1.0/XOEL
DVINV-1.0/VOEL
ARINV*DXINV*DYINV
PORINV"!.0/POROS
PRINT CONTROL PARAMETERS
WRITE (6,760)
NX*NY*XDEL,YDEL
NTIM*NPMP*PINT*TIMX»TINIT
S*POROS*BETA*DLTRAT,ANFCTR
NITP*TOL* ITHAX*CELDIS,NPHAX*NPTPND
4.0R.NPTPND.GT.9.0R.NPTPND.EQ.6.0R.NPTPND.E0.7)
(6*770)
(6*780)
(6*790)
(6*870)
.LT,
WRITE
WRITE
WRITE
WRITE
IF (NPTPND
1£ (6*880)
WRITE (6*890)
WRIT
NPNT»NPNTMV,NPNTVL*NPNTD*NUMOBS,NREC,NCODES*NPNCHV,N
FOR SUBSEQUENT
1PDELC
IF (NP'NTMV.EQ.O) NPNTMV-999
GO TO 20
C READ DATA TO REVISE TIME STEPS AND STRESSES
C PUMPING PERIODS
10 READ (5,1060V ICHK)
IF (ICHK.LE.O') RETURN
READ (5*1070) NTIM*NPNT*NITP*ITNAX*NREC,NPNTMV*NPNTVL,NPNTD*NPDELC
1,NPNCHV*PINT*TIMX*TINIT
WRITE (6*1080) INT
WRITE (6*1C90) NTIM*NPNT*NITP*ITMAX*NREC*NPNTMV*NPNTVL,NPNTD,NPDEL
1C*NPNCHV*PINT*TIMX*TINIT
C ••••*•*•••****•****•****••••*••*•»******«**•*«•****»***»*****»*
C LIST TIME INCREMENTS
20 DO 30 J*1,100
TIM(J)»0.0
30 CONTINUE
40
50
60
IF (S.EO.0.0) GO TO 50
DO 40 K-2*MTIM
TIH(IC)«TIMX*TIM(K-1 )
WRITE (6*470)
WRITE (6*490) TIM
GO TO 60
TIM(1)«PVR
WRITE (6,480) TIM(1)
I*****************************
INITIALIZE
IF (INT.GT.1)
DO 70 IY*1,NY
DO 70 IX=1,NX
VPRMd X*IY>*0.0
PERM(IX,IY)=0.0
THCK(IX*IY)aO.O
RECH(IX*IY)«0.0
CNRECH(IX*IY)>0.0
REC(IX*IV)*0.0
NODEID(IX*IY)*0
TMRX(IX*IY*1)«0.0
TMRX(IX,IY,2)"0.0
HI(IX*IY)«0.0
MATR ICES
GO TO 100
HR
HC
HK
WT
VX
IX*IY)«0.0
IX*IV)«C.O
IX*IY)-0.0
IX,IY)-0.0
IX*IY)«0.0
B 480
B 490
8 500
B 510
B 520
B 530
B 540
B 550
B 560
B 570
B 580
B 590
B 600
B 610
B 620
B 630
B 640
B 650
B 660
8 670
B 680
B 690
B 700
B 710
B 720
B 730
B 740
B 750
B 760
B 770
B 780
B 790
B 800
B 810
B 820
B 830
B 34C
B 850
G 860
B 8'C
8 880
B 890
8 900
B 910
B 920
B 930
B 940
S 950
B 960
B 970
B 980
8 990
81000
81010
B1020
81030
81 040
B1050
B1060
81070
81080
81090
E-4
-------
FORTRAN IV program lifting—Continued
80
90
C
c
C
c
100
110
120
ISO
140
ISO
160
WY(1X,IY)=0.0
VXBDY(JX,IY)=0.0
VYBDV(IX*IY)«0.0
CONC(IX,IY)«0.0
CONINT(IX*IY)«0.0
SUMC(IX,IY)«0.0
70 CONTINUE
ft***************************************************************
READ OBSERVATION WELL LOCATIONS
IF (NUMOBS.LE.O) GO TO 100
WRITE (6*900)
DO 80 J»1*KUMOBS
READ (5*700)' IX,IV
WRITE (6*810) J*IX*IV
IXOBS(J)«IX
IVOBS(J)«1V
DO 90 1-1/NUHOBS
DO 90 J«1*50
TMWLU ,J)«0.0
TMCN(I,J)»0.0
•*•****••••»«»**«•••*»**«••*•••*****••*•*«»»••»•»••»«*»*•»*•**•*
READ PUMPAGE DATA -- (X-Y COORDINATES AND RATE IN CFS)
SIGNS : WITHDRAWAL * POS.; INJECTION • NEG.
IF INJ. WELL* ALSO READ CONCENTRATION OF INJECTED WATER
IF (NREC.LE.O) GO TO 120
WRITE (6*910)
DO 110 I»1*NREC
READ (5*710) IX*IV*FCTR*CNREC
IF (FCTR.LT.0.0) CNRECH(IX*IY)"CNREC
REC(IX*IV)«FCTR
WRITE (6*820) IX*IV*REC(IX*IY)*CNRECH(IX*IV)
•••••••<
IF (1NT.GT.1) RETURN
AREA»XDEL*VDEL
WRITE (6*690) AREA
WRITE (6*600)
WRITE (6*610) XDEL
WRITE (6*610) VDEL
READ TRANSM1SSIVITY IN FT**2/SEC INTO VPRM ARRAY
— FCTR • TRANS'MISSIVITV MULTIPLIER —> FT«»2/sEC—
WRITE (6*530)
READ (5*550) INPUT,FCTR
DO 160 IY»1,NY
IF (INPUT.E0.1) READ (5*560) ( VPRM( IX,1 V)* IX«1,NX)
DO ISO IX«1,NX
IF (INPUT.NE.1) GO TO 130
VPRM(IX*IY)>VPRM(IX*IY)*FCTR
GO TO 140
VPRM(IX*1Y)«FCTR
IF (IX.£0.1.OR.IX.EO.NX) VPRM(I X*1V)"0.0
IF (IV.E0.1.0R.IV.EQ.NY) VPRM(I X, IV)-0.0
CONTINUE
WRITE (6,520) (VPRH(IX,IV)*IX-1*NX)
i •»***»*»<
>••««••••••••••••*
170
SET UP COEFFICIENT MATRIX BLOCK-CENTERED GRID
AVERAGE TRANSMISSIVITV HARMONIC MEAN
IF (ANFCTR.NE.0.0) 60 TO 170
WRITE (6*1050)
ANFCTR»1.0
PIES-3. 141 5927.3.1*15927/2.0
TNS«NY«NY
81100
6111Q
81120
B1130
B1140
B11SO
81160
81170
81180
B119C
81200
B1210
B1220
81230
81240
61250
61260
B1270
B1280
81290
81300
81310
81320
B1330
81340
81350
81360
81370
81380
81390
81400
81410
81420
81430
81440
81450
81460
81470
81480
81490
B1500
81510
81 520
B1S30
B1S40
81SSO
B1S60
81570
81 580
81590
81600
81610
81620
81630
81640
81650
81660
81670
81680
81690
81700
81710
E-5
-------
FORTRAN IV program toting—Continued
XNS"NX*NX
HMiN-2.0
00 180 IY-2,NNY
DO 180 IX»2,NNX
IF (VPRM*VPRM(IX»1,I V)/(VPRM(IX,IY)*XDEL*VPRM
1(1X41,IY)»XDEL>
TNRX(IX,IY,2)«2.0*VPRM(IX,IY>*VPRM(IX,IY«1)/(VPRM(IX,IY)*rDEL«VPRM
1OX,IY*1)*YDEL)
C ADJUST COEFFICIENT FOR ANISOTROPY
THR-XCI X,l V,2)*TMRX (IX,IY,2)*ANFCTR
C COMPUTE MINIMUM ITERATION PARAMETER (HMIN)
IF (TMRX(IX,IY,1).EQ.O.O) GO TO 180
IF (TNRX(IX,IV,2).EO.O.O) 60 TO 180
RAT«TMRX(IX,IV,1)*YDEL/(TMRX(IX,IY,2)*XDEL)
HNX»PI.ES/(XNS*(1.0 + RAT))
HHY«PIES/(YNS«(1.0*(1.0/RAT)))
IF (HMX.LT.HMIN) HMIN"HMX
IF (HNV.LT.HMIN) HMIN»HMY
180 CONTINUE
C READ AQUIFER THICKNESS
WRITE (6*510)
READ (5,550) INPUT,FCTR
DO 210 IY«1,NY
IF (INPUT.EQ.1) READ (5,540) (THCK(I X,IY),IX»1,NX )
DO 200 IX«1,NX
IF (INPUT.NE.1) GO TO 190
THCK(IX,IY)»THCK(IX,IV)*FCTR
60 TO 200
190 IF (VPRH(IX,IY).NE.O.O) THCK(IX,IV)*FCTR
200 CONTINUE
210 WRITE (6,500) (THCK(IX,IY),IX»1,NX)
•»••*****•*********•••<
•A**********************
220
230
240
C
C
C
C
250
260
READ DIFFUSE RECHARGE AND DISCHARGE
WRITE (6,830)
READ (5,550) INPUT,FCTR
DO 240 IY«1,NY
IF (INPUT.E0.1) READ (5,560) (RECH(IX,IY),IX*1,NX>
DO 230 IX»1,NX
IF (INPUT.NE.1) GO TO 220
RECH(IX,IY)«RECH(IX,IY)<»FCTR
GO TO 2*0
IF (THCK(IX,IY).NE.O.O) RECH(I X,I V)>FCTR
CONTINUE
WRITE (6,840) (RECH(IX,IY),IX«1,NX)
•A**************************************************************
COMPUTE PERMEABILITY FROM TRANSMISSI V ITY
COUNT NO. OF CELLS IN AQUIFER
SET NZCR1T « 2X OF THE NO. OF CELLS IN THE AQUIFER
DO 250 IX-1/NX
DO 250 IY-1/NY
IF (THCK(IX,IY).EQ.O.O) GO TO 25G
PERM(IX,IY)«VPRM(IX,IY)/THCK(IX,IY)
NCA-NCA+1
VPRNU X,I Y)*0.0
AAQ«NCA*AREA
NZCRIT«
-------
FORTRAN IV program listing—Continued
WRITE (6*630) NCA,AAO,NZCR1T
370
280
290
300
310
320
330
340
350
C
c
360
370
380
READ NODE IDENTIFICATION CARDS
SET VERT. PERM., SOURCE CONC., AND DIFFUSE RECHARGE-
SPECIFY CODES TO FIT YOUR NEEDS
WRITE (6,570)
READ (5,550) INPUT,FCTR
DO 280 IY«1,NY
IF (INPUT.E0.1) READ (5,640) (NODEID(I X,IY),I X*1,NX)
DO 270 IX«1,NX
IF (INPUT. NE.1. AND. IHCKdX, IY) .NE. 0.0) NODE I D (1 X , I Y ) = F C T R
WRITE (6,580) (NODEID(IX,1Y),IX=1,NX>
WRITE (6,920) NCODES
IF (NCODES.LE.O) GO TO 310
WRITE (6,930)
DO 300 IJ«1,NCODES
READ (5,850) ICODE,FCTR1,FCTR2,FCTR3,OVERRD
DO 290 IX»1,NX
DO 290 IY«1,NY
IF (NODEID(IX,IY).NE.ICODE) GO TO 290
VPRM(IX,IY)>FCTR1
CNRECH(IX,1V)»FCTR2
IF (OVERRD.NE.O) RECH(I X,IY)>FCTR3
CONTINUE
WRITE (6,860) ICODE,FCTR1,FCTR2
IF (OVERRD.NE.O) WRITE (6,1100) FCTR3
WRITE (6,590)
DO 320 IY«1,NY
WRITE (6,520) (VPRMdX, IV), IX«1 , NX)
A****************************************************
READ WATER-TABLE ELEVATION
WRITE (6,670)
READ (5,550) INPUT,FCTR
DO 350 IT=1,NY
IF (INPUT.EQ.1) READ (5,660) I WT(I X,IY),1X«1,NX )
DO 340 IX«1,NX
IF (INPUT.NE.1) GO TO 330
WTdX,IY)«bT(IX,IY)«FCTR
GO TO 340
IF (THCK(IX,IY).NE.O.O) WT(IX,IY)*FCTR
CONTINUE
WRITE (6,680) (WT(IX,IY),IX-1,NX)
••••*••••••••*•*«•••••••<
SET INITIAL HEADS
DO 360 IX«1,NX
DO 360 IY«1,NY
HI(IX,IY)«WT(IX,IY)
HC(IX«IY)*HI(IX,IY)
HR(IX,IY)«HI(IX,IY)
HK(IX,IY)«HI(IX,IY)
CALL OUTPT
COMPUTE ITERATION PARAMETERS
DO 370 I0«1,20
AOPT(ID)«0.0
CONTINUE
ANITP«NITP-1
ALPHA1»DEXP(DLOG(1.0/HMIN)/ANITP)
AOPT(1)»HMIN
DO 380 IP«2,NITP
AOPT(IP)«AOPT(IP-1)*ALPHA1
82340
B2350
B2360
82370
B2380
B2390
B2400
B2410
82420
82430
B244G
B2450
B2460
B2470
B2480
B2490
B2500
B2510
B2520
B2S30
B2540
B2550
B2560
B2570
B2580
B2590
B2600
B2610
82620
B2630
B2640
B2650
B2660
B2670
B2680
82690
82700
82710
82720
82730
82740
B2750
B2760
82770
82780
82790
82800
82810
82820
82830
82840
B2850
82860
82870
B2880
82890
82900
82910
B2920
82930
82940
62950
E-7
-------
FORTRAN IV program lifting—Continued
WRITE
WRITE
(6,450)
(6*460)
AOPT
l*****»«*******»*****»*»********»**»**»********
C READ INITIAL CONCENTRATIONS AND COMPUTE INITIAL MASS STORED
READ (5*550) INPUT,FCTR
00 420 IV»1,NY
IF (INPUT.EQ.1) READ (5,660) (CONC(IX,IY),IX»1,NX)
DO 410 IX-1,NX
IF (INPUT.NE.1) GO TO 390
CONC(IX,IV)*CONC(IX*IY)*FCTR
GO TO 400
390 IF (THCKdX, IV). NE.0.0) CONC ( I X, I Y) »FC TR
400 CONINT(IX*IY)«CONC(IX,IV)
410 STORHI»STORMI+CONINT(IX,IY)*THCK(IX,IV)*AREA*POROS
420 CONTIN.UE
C *••••••••••••»••**••••*•••*•**••••»*•»»•»*»•••••••••»*•»•*••*»••
C CHECK DATA SETS FOR INTERNAL CONSISTENCY
00 440 IX«1*NX
DO 440 IY«1*NV
IF (THCKdX,IV).GT.0.0) GO TO 430
IF (TMRXdX, IV*1). GT.0.0) WRITE (6,940) IX,IV
IF (TMRXdX,IV,2).GT.0.0) WRITE (6,950) IX,IY
IF (NOOEIDdX*! V).GT.O) WRITE (6,960) IX,IY
IF (WT(IX,IY).NE.0.0) WRITE (6,970) IX,IV
IF (RECHdX,IV) .NE.0.0) WRITE (6,980) IX,IV
IF (REC(IX*IY).NE.0.0) WRITE (6,990) IX,IY
430 IF (PERM(IX,IY).GT.0.0) GO TO 440
IF (NODEIDdX, IV). GT.0.0) WRITE (6,1000) IX,IY
IF (WT(IX,IV).NE.0.0) WRITE (6*1010) IX,IY
IF (RECHdX,IY).NE.0.0) WRITE (6,1020) IX, IV
IF (RECdX,IV).NE.0.0) WRITE (6,1030) IX,IY
IF (THCKdX,IV).GT.0.0) WRITE (6,1040) IX,IV
440 CONTINUE
C »•*•*•*»**•••••**«*••*»••*«•••••*••••»»••««««••••««»«•»»»•»•»»••
RETURN
C «•••**•*•»•••**•*••**»**•»•••«»•»•••»*•»•**••*»»»»••»•***••*****
C
C
C
450 FORMAT (1H1,20HITERATION PARAMETERS)
460 FORMAT (3H ,1G20.6)
470 FORMAT (1H1,27HTIME INTERVALS (IN SECONDS))
480 FORMAT (1H1,15X,17HSTEADY-STATE FLOW//5X,57HTI ME
* ,612.5)
INTERVAL (IN SEC)
(FT))
(FT*FT/SEC>)
1 FOR SOLUTE-TRANSPORT SIMULATION
490 FORMAT (3H ,10G12.5)
500 FORMAT (3H ,20F5.1>
510 FORMAT (1H1,22HAQUIFER THICKNESS
520 FORMAT (3H ,20F5.2)
530 FORMAT (1H1,30HTRANSMISSIVITY MAP
540 FORMAT (20G3.0)
550 FORMAT (11,610,0)
560 FORMAT (20G4.1)
570 FORMAT (1H1,23HNODE IDENTIFICATION
580 FORMAT (1H ,2015)
590 FORMAT ( 1 H1 ,45HVE R T I C AL PERME ABI L IT Y /THI C KNE SS
600 FORMAT (1HO,10X,12HX-Y SPACING:)
610 FORMAT (1H ,1 2X ,1 OG1 2. 5 ).
620 FORMAT (1H1,24HPERMEABILTY MAP (FT/SEC))
630 FORMAT (1MO,////10X,«4HNO. OF FINITE-DIFFERENCE CELLS
1 ,I4//10X,28HAREA OF AQUIFER IN MODEL • ,G12.5,10H
20X,4?HNZCRIT (MAX
MAP//)
( FT /( F T*SE C ) »
B2960
82970
82980
B2990
B3000
83010
83020
83030
83040
83050
83060
83070
83080
83090
83100
83110
83120
83130
83140
83150
83160
83170
83180
B3190
B3200
B3210
B3220
83230
83240
83250
83260
83270
B3280
83290
83300
83310
83320
83330
B3340
83350
B 3.560
83370
83380
B3390
83400
83410
B3420
83430
NO. OF CELLS THAT CAN BE VOID
IN AQUIFER •
SO. FT.////1
OF /20X , 5 6HPART I
83450
83460
83470
83480
B3490
83500
83510
83520
B3S30
B3540
83550
B3S60
83570
E-8
-------
FORTRAN IV program lifting—Continued
3CLES;
640 FORMAT
650 FORMAT
660 FORMAT
670 FORMAT
680 FORMAT
690 FORMAT
700 FORMAT
710 FORMAT
720 FORMAT
730 FORMAT
740 FORMAT
750 FORMAT
IF EXCEEDED, PARTICLES ARE REGENERATED)
(2011)
(3H ,20F5.3)
(20G4.0)
(1H1,11HWATER TABLE)
(1H ,20F5.0)
(1HO,10X,19HAREA OF ONE CELL = ,G12.4)
(212)
(212/268.2)
» /I4/>
(1HO,10A8>
(1714)
(1H1,77HU.S.G.
1 TRANSPORT IN GROUND
760 FORMAT (1HO,21X,21HI
S. ME T HOD-OF -CH AR AC T E R I S T I C S MODEL FOR SOLUTE
WATER)
NPUT DATA)
770 FORMAT (1HO,23X,16HGRID DESCRI PTORS// 1 3X/ 30HNX (NUMBER OF COLUM
1NS) * , 14/13X,28HNY (NUMBER OF ROWS) = , 1 6 / 1 3 X , 29HX DE L (X
2-DISTANCE IN FEET) = / F 7 . 1 / 1 3X , 29HYDEL (V-DISTANCE IN FEET) * ,F7
3.1)
780 FORMAT < 1 HO/23X ,1 6H T IHE PARAME TE RS// 1 3X, 40HNT I M (MAX. NO. OF TI
1ME STEPS) * ,I6/13X,40HNPMP (NO. OF PUMPING PERIODS)
2 * ,I6/13X,39HP1NT (PUMPING PERIOD IN YEARS) « , F 1 0 . 2/1 3X,3 9
3HTIMX (TIME INCREMENT MULTIPLIER) *>• F 1 0. 21 1 3X ,39MT I N IT UNIT
4IAL TIME STEP IN SEC.) «,F8.0)
790 FORMAT ( 1 H0,1 4X, 34 HH YDROLOG1 C AND CHEMICAL P A R A ME T E fiS / / 1 3 X , 1 H S *7X ,
129MSTORAGE COEFFICIENT) «, 5X, F9. 6/ 1 3 X, 28HPOROS (EFFECTIVE
2 POROSITY), 8X,3H» ,F8.2/13X,39HBETA (CHARACTERISTIC LENGTH)
3 » ,F7.1 /13X,31 HDLTRAT (RATIO OF TRANSVERSE TO/21 X , 30HLONGI TUD I
4NAL DI SPERSIVITY) - , F 9 . 2/1 3X , 39HANF C T R (RATIO OF T-YY TO T-XX)
5 • ,F12.6)
12G5.0)
1H ,16X,I2,5X,I2»4X,12)
1H ,7X,2I4,3X,F7.2,5X,F7.1)
1H1,39HDIFFUSE RECHARGE AND DISCHARGE (FT/SEC))
1H ,1P10E10.2)
(I2,3G10.2*I2>
(1HO,7X,I2,7X,E10.3,5X,F9.2)
(1HO,21X,20HEXECUTION P AR AMETE RS / / 1 3X , 39 HN I TP (NO. OF 1TE
PARAMETERS) = , I 4 /1 3X, 39HTOL (CONVERGENCE CRITERIA - ADI
4/13X,39H ITMAX (MAX. NO. OF ITERATIONS - ADIP) - »14/12X,3
- M.O.C. )
800 FORMAT
810 FORMAT
820 FORMAT
830 FORMAT
840 FORMAT
850 FORMAT
860 FORMAT
870 FORMAT
1RATION
2P) » ,F9
34HCELDIS
(MAX.CELL DISTANCE PER MOVE/24X,28HOF PARTICLES
4 • ,F8.3/13X,30HNPMAX (MAX. NO. OF PARTICLES),7X,2H« ,I4/12Xs3
S2H NPTPND (NO. PARTICLES PER NODE),6X,3H« ,14)
880 FORMAT <1HO»5X»47H*•• WARNING •** NPTPND MUST EGUAL 4,S^8, 03 9.)
890 FORMAT (1HO,23X,1 5HPROGRAM OPT 1ONS//1 3X,3OHNPNT (TIME STEP INTER
1VAL FOR/21X,18HCOMPLETE PRINTOUT),7X,3H» ,14/13X,31HNPNTMV (MOVE
2INTERVAL FOR CHEM./21X»28HCONCENTRATION PRINTOUT) * , I 4 /1 3X,29HN
3PNTVL (PRINT OPTION-VELOCITY/21X,24HOcNO; 1*FIRST TIME STEP;/21X,1
47H2*ALL TIME STEPS),8X,3H» ,I4/13X,31 HNPNTD (PRINT OPT ION-DISP.C
50£F./21X,24hO=»NO; 1«FIRST TIME ST EP.'/ 21 X , 1 ?H2«A L L TIME STEPS),8X,3
6H» ,14/13X,32HNUMOBS (NO. OF OBSERVATION WELLS/21X,28HFOR HYDROGR
7APH PRINTOUT) * ,I4/13x,35HNREC (NO. OF PUMPING WELLS) « ,15
8/13X,24HNCOOES (FOR NODE I DENT.),9X,2H* ,I 5/13X,25HNPNCHV (PUNCH V
9ELOCITIES),8X«2H* ,I 5/13X,36HNPOELC (PRINT OPT.-CONC. CHANGE) • r
S14)
900 FORMAT (1HO,10X,29HLOCATION OF OBSCRVATION WELLS//17X,3HNO.,5X,1HX
1,5X,1HY/)
910 FORMAT (1HO,10X,28HLOCATION OF PUMPING WELLS//1 1 X,28HX Y RA
1TE(IN CFS) CONC./)
920 FORMAT (1HO,5X,37HNO. OF NODE IDENT. CODES SPECIFIED * ,12)
930 FORMAT (1HO,10X,41HTHE FOLLOWING ASSIGNMENTS HAVE BEEN MADE:/5X,51
IHCODE NO. LEAKANCE SOURCE CONC. RECHARGE)
B3580
B3590
B3600
B3610
B3620
B3630
83640
636SO
B3660
B3670
8368G
B3690
B3700
B3710
83720
B3730
B3740
B3750
B3760
83770
B3780
B3790
B3800
B3810
B3820
63830
63840
6 38 50
83860
63870
63880
83890
63900
B3910
63920
63930
63940
63950
B3960
53970
039feO
33990
B4000
B4010
64020
84030
64040
84050
64060
64070
84080
64090
64100
64110
84120
B4130
64140
64150
B4160
64170
84180
64190
E-9
-------
FORTRAN IV program lifting—Continued
••• THCK.EO.0.0 AND TMRX(X).GT.0.0
••• THCK.EQ.0.0 AND TMRX(Y).GT.0.0
••• THCK.EQ.0.0 AND NODE 10.GT.0.0
•** THCK.EO.0.0 AND WT.NE.0.0 AT N
*•* THCK.EQ.0.0 AND RECH.NE.0.0 AT
**• THCK.EQ.0.0 AND REC.NE.0.0 AT
••• PERM.EQ.0.0 AND NODE ID.GT.0.0
**« PERM.EQ.0.0 AND WT.NE.0.0 AT N
••• PERM.EQ.0.0 AND RECH.NE.0.0 AT
• •• PERM.EQ.0.0 AND REC.NE.0.0 AT
ANFCTR
1.0)
940 FORMAT (1H ,5X/61H«*« WARNING
1 AT NODE IX «,I4,6H, IV -,I4)
950 FORMAT <1H /5X/61H*** WARNING
1 AT NODE IX *,I4,6H, IV *»I4)
960 FORMAT (1H ,5X,6lH«*« WARNING
1 AT NODE IX »,I4,6H, IV «,I4)
970 FORMAT <1H ,SX,56H**» WARNING
10DE IX «,I4,6H, IV «,I4>
980 FORMAT <1H /5X/58H*** WARNING
1 NODE IX «,I4,6H, IV »,I4>
990 FORMAT (1H /5X,58H**« WARNING
1 NODE IX «,I4,6H, IV -r!4>
1000 FORMAT <1H »5X,61H«** WARNING
1 AT NODE IX «/I4,6H, IV »,I4)
1010 FORMAT (1H ,5X,56H*** WARNING
10DE IX «»I4,6H, IV »»I4>
1020 FORMAT <1H ,5X,58H**« WARNING
1 NODE IX «,I4,6H, IV «,I4>
1030 FORMAT (1H ,5X,58H*«* WARNING
1 NODE IX »,14,6H, IV -,I4>
1040 FORMAT (1H »5X,58H«*« WARNING ••• PERM.EQ.0.0 AND THCK.GT.0.0 AT
1 NODE IX »/I4,6H* IV «,I4>
1050 FORMAT (1HO»5X*45H«*» WARNING •••
1X»3tHDEFAULT ACTION: RESET ANFCTR
1060 FORMAT (11)
(1014,365.0)
(1H1,5X/25HSTART PUMPING PERIOD NO.
STEP* PUMPAGE* AND PRINT PARAMETERS
(1HC/14X,9HNTIM > ,I4/15X,9HNPNT
1I4/15X,9HITMAX « ,I4/15X,9HNREC = , I 4/ 1 5X,9HNPNTHV * ,I4/15X,9H
2NPNTVL * •I4/15X/9HNPNTD • ,1471SX/9HNPDELC * ,14/15X,9HNPNCHV =
3»I4/15X/9HPINT • ,F10.3/1SX*9HTIMX = /F10.3/15X,9HTIN IT • ,F1
40.3/)
1100 FORMAT (1H ,46X,E10.3)
END
SUBROUTINE ITERAT
DOUBLE PRECISION DMIN1,0EXP,DLOG,DABS
REAL *8TMRX,WPRM,HI«HR»HC«HK«WT,REC«RECH,TIM,AOPT,TITLE
REAL *8XOEL»YOEL»S*AREA*SUMT,RHO»PARAM/TEST,TOL*PINT,HMIN,PYR
REAL *8B/G/W»A,C/E»f»OR»I>C/T8AR,Tmc^COEF»eLH*BRK/CHK,QL»BRK
COMMON /PRMI/ NTIM,NPMP*NPNT,NITP,N,NX,NY,NP,NREC*INT/NNX,NNY,NUHO
1BS»NMOV«IMCV»NPMAX,ITMAX«NZCRIT,IPRNT,NPTPNO,NPNTMV/NPNTVL«NPNTD/N
2PNCHW,NPOELC
COMMON /PRKK/ NODEID(20«20)/NPCELL(20«20)«LIMBO<500)tIXOBS<5)/IYOB
1S(5)
COMMON /HE DA/ THCK(20*20 ) »P£RM(20*20)»TMWL<5»50>/TMQBS(50)»ANFCTR
COMMON /HEDB/ TMRX<20*20*2 ) /VPRM<20,20)»HI(20,20),HR(20*20)»HC(20,
120)*HK<20,20),WT(20,20),REC(20,20),RECH(20*20),TIH(100),AOPT<20)/T
21TLE(10>,XDEL«YAEL*S«AREA,SUMT,RHO,PARAM,TEST,TOI,PINT,HMIN,PYR
COMMON /BALM/ TOTLQ
COMMON /XINV/ DXINV«DVINV«ARINV«PORINV
DIMENSION b(20), 8(20), G<20>
1070 FORMAT
1080 FORMAT
1C TIME
1090 FORMAT
WAS SPECIFIED AS 0.0/23
/I2//2X,75HTHE FOLLOWIN
HAVE BEEN REDEFINED:/)
• /I4/15X,9HNITP « ,
>•*•**••*.*»«**•,
KOUNTaQ
--- COMPUTE ROW AND COLUMN ---
--- CALL NEW ITERATION PARAMETER ---
10 RENNaMOD(KOUNT,N!TP>
IF (REMN.EO. 0) NTH-0
NTH»NTH*1
PARAMa AOPT (NTH)
B4200
B4210
B4220
B4230
B4240
B42SO
84260
B4270
B4280
B4290
B4300
B4310
B4320
B4330
B4340
64350
B4360
B4370
B4380
B4390
B4400
64410
B4420
84430
B4440
B4450
84460
B4470
84480
84490
B4500
B4S10
B4520
B4530
B4S40-
10
20
30
40
50
60
70
80
90
100
110
120
--- ROW COMPUTATIONS ---
140
150
160
170
180
190
200
C 210
C 220
230
240
250
260
270
E-10
-------
FORTRAN IV program hating—Continued
TEST*0.0 C 280
RHO=S/TIM(N> C 290
BRKB-RHO C 300
DO SO 1Y»1,NY C 310
00 20 M*1,NX C 320
W(H)*0.0 C 330
B(M>*0.0 C 340
G(H)«0.0 C 350
20 CONTINUE C 360
DO 30 IX=1,NX C 370
IF GO TO 30 C 380
COEF-VPRM(IX,IY> C 390
Ol«-COEF*HT(IX,IY) C 400
A-TMRX(IX-1«IV»1)*DXINV C 410
C«THRX*DXINV c 420
E'THRX(IX,IV-1«2)«DYINV C 430
F«T«RXBRH*HC(IX«IY)+BRK*HK(1X,IY)-E*HC(IX,IY-1)-F*HC(IX,IY*1>+QL«RECH C 490
KIX/I V)*REC(1X»]Y)*AR1NV C 500
W(IX)*BLH-A*B(IX-1 ) C 510
B(IX)«C/W(1X> C 520
GUX)«(DR-A*G(IX-1 »/W< IX) C 530
30 CONTINUE C 540
C 550
BACK SUBSTITUTION C 560
DO 40 J*2,NX C 570
1J*J-1 C 580
IS'NX-U C 590
40 MR(IS, IY)«G(IS)-B(IS)*HR(IS + 1^1 Y) C 600
50 CONTINUE C 610
••••••••••••••••••A******************************************** C 620
COLUMN COMPUTATIONS C 630
DO 90 1X-1,NX C 640
DO 60 M»1,NY C 650
U(M)«0.0 C 660
8(M)»0.0 C 670
60 G(M>*0.0 C 683
DO 70 1Y«1,NY C 690
IF .EQ.O.O) GO TO 70 C 700
COEf«VPRM( IX/1V) C 710
OL«-COEF*MT(IX,IY) C 720
A«TWRX( IX,IY-1»2)«OYINV C 730
C»THRX( IX,lY/2)*OYfNV C 740
E-TMRX(IX-1,IY,1)*OXINV C 750
F-TMRX (IX,1Y/1)*DXINV C 760
TBAR«A*C+E*F C 770
TMK>TBAR*PARAM C 780
BLH»A-C-RHO-COEF-TMK C 790
BRH»E*F-TNK C 800
DC"BRH*MR(IX,IY)*BRK*Ht((IX,IY)-E*HR(IX-1,IY)-F*HR(IX»1/IY)»OL»RECH 810
1
-------
FORTRAN IV program listing—Continued
IJ-J-1
IB-NY-IJ
HC(IX,I8)»G(I8)-B(IB)*HC(IX,IB*1)
IF
COMPUTE LEAKAGE FOR MASS BALANCE
IF (VPRM(IX,IY).EQ.0.0) GO TO 130
OELO«VPRMdX,IV)«AREA«(WT(IX,IV)-HK ,114)
ISO FORMAT (1H ,2X,23HNUM8ER OF ITERATIONS • ,114)
160 FORMAT (1HO,5X,64H«*« EXECUTION TERMINATED -- MAX. NO. ITERATION
1S EXCEEDED *«*/26X,21HF INAL OUTPUT FOLLOWS:)
END
SUBROUTINE GENPT
REAL *BTMRX,VPRM,HI,HR,HC,HK,WT,REC,RECH,TIM,AOPT,TITLE
REAL •8XDEL,YDEL,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HMIN,PYR
COMMON /PRMI/ NTIM,NPMP,NPNT,NITP,N,NX,NY,NP,NREC,I NT,NNX,NNY,NUMO
1BS,NMOV,IMCV,NPMAX,ITMAX,NZCRIT,IPRNT,NPTPND,NPNTNV,NPNTVL,NPNTD,N
2PNCHV,NPDELC
COMMON /PRMK/ NOOEID(20,20),NPCELL(20,20),LIMBO(500),IXOBS(S),IVOB
1S(5)
COMMON /HE DA/ THCK <20,20),PERM<20,20),TMWL(5,50),TMOBS(50),ANFCTR
COMMON /HE OS/ TMRX(20,20,2),VPRM(20,20),HI(20,20),HR(20,20),HC<20,
120>,HK(20,20),WT(20,20),REC(20,20),RECH(20,20),TIM(100),AOPT(20),T
21TLE(10),XDEL,YDEL,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HMIN,PYR
COMMON /CHMA/ PART(3,3200>,CONC(20,20),TMCN(5,50),VX(20,20),VY(20,
120)*CONI NT (20,20),CNRECH(20,20),POROS,SUMTCH,8ETA,TIMV,STORM,STORM
900
910
920
930
940
950
960
970
980
990
C1000
C1010
C1020
C1030
C1040
C10SO
C1060
C1070
C1080
C1090
C1100
C1110
C1120
C1130
C1140
C115O
C1160
C1170
C1180
C1190
C1200
C1210
C1220
C1230
C1240
C1250
C1260
C1270
C1280
C1290
C1300
C1310
C1320
C1330
C1340
C1350
C1360
C1370-
10
?0
30
40
SO
60
70
80
90
100
110
120
130
140
E-12
-------
FORTRAN IV program lifting—Continued
2I,CMSIN,CMSOUT,FLMIN,FLMOT,SUM10»CELDIS»DLTRAT,CSTO»M 0 150
DIMENSION RP<8>/ RMS), IPT<8> D 160
••••••••••••••••••••••••••••••••••••••••••••••••••••••••A****** o 170
F1«0.30 D 180
F2*1.0/3.0 D 190
IF (NPTPND.EQ.4) F1=0.25 D 200
IF (NPTPNO.EQ.9) Fla1.0/3.0 0 210
IF (NPTPND.EQ.8) F2=0.25 D 220
NCHK«NPTPND D 230
IF (NPTPNO.EQ.5.OR.NPTPNO.EQ.9) NCHK*NPTPND-1 0 240
IF (TEST.6T.98.) GO TO 10 D 250
•••••••••••*••••••**•••••••*•••**«*•••**••*•*•**•*****•**•***** o 260
INITIALIZE VALUES 0 270
STORM*0.0 0 280
CMSIN«0.0 0 290
CMSOUTsO.O 0 300
FLHIN*0.0 0 310
FLMOT*0.0 D 320
SUMIOaO.O D 330
••••••••••••••••A********************************************** 0 340
10 00 20 10-1,3 D 3SO
DO 20 IN«1,NPMAX D 360
20 PART(ID,1N>»0.0 D 370
DO 30 I A*1,8 D 380
RP(1A)»0.0 D 390
RN1.0 D 610
IF (THCK(IX«1,IV*1).EQ.O.O.OR.THCK(IX^1,IY-1) .EQ.0.0.OR.THCK(IX-1, D 620
11Y»1).E8.0.0.OR.THCK(1X-1,IY-1).EQ.0.0) TEST2*1.0 0630
IF «THCIC(IX,IV*1) . EQ. 0. 0. OR-. T HC K< I X, 1 Y-1 ). EQ.0.0. OR. THCK ( I X*1 »I Y ) D 640
1.EQ.O.O.OR.THCK(IX-1,IY).EO.O.O).AND.NPTPND.GT.5) TEST2=1.0 0 650
CNODE«C1*(1.0-F1) 0 660
IF (TEST.LT.98.0.OR.TEST2.6T.0.0) GO TO 70 0 670
SUMC»CONC(1X*1,IY)+CONC(IX-1,I Y)*CONC(IX,IY*1) + CONC(IX,IY-1) 0 680
IF (NCHK.Ea.4) GO TO 60 0 690
SUMC-SUHC + CONC(IX*1,IY*1)*CONC < I X*1 , I Y- 1 )*CONC(IX-1,1Y41)+CONC(I X- D 700
11,IV-1 ) 0 710
60 AVC'SUMC/NCHK 0 720
IF (AVC.GT.C1) METH'2 0 730
D 740
PUT 4 PARTICLES ON CELL DIAGONALS 0 750
70 DO 140 IT«1,2
E-13
-------
FORTRAN IV program lifting—Continued
EV6T«<-1 .0>*MT
DO 140 ISM,2
EVES«<-1.0)**1S
PART(1,INO)-IX*F1*EVET
PART(2/IND)«IY*F1*EVES
PART(2/INO)«-PART<2/IND)
PART(3,INO)»C1
IF (TEST.LT.98.0.OR.TEST2.GT.0.0) GO TO 130
IXO»IX*EVET
IVD*IV»EVES
KR«KR+1
IPT(KR)»INO
IF (METH.EQ.2) GO TO 80
PART(3/1ND)«CNOOE+CONC(IXO/IVD)*F1
GO TO 90
80 PART(3/IND)«2.0*C1•CONC(IXD/IYD)/
RN(KR)«C1-PART(3/INO)
GO TO 130
110 RP(KR)«0.0
RN(KR)*0.0
GO TO 130
120 RP(KR>-C1-PART(3/INO>
RN(KR)«CONC(IXO/IYO)-PART(3/INO)
130 INO»INO*1
140 CONTINUE
IF (NPTPNO.EQ.S.OR.NPTPND.EQ.9) GO TO ISO
GO TO 160
PUT ONE PARTICLE AT CENTER OF CELL
ISO PARTd,1NO--IX
PART(2/IND)«-IY
PART(3,IND)*C1
IND»IND»1
PLACE NORTH/ SOUTH/ EAST/ AND WEST PARTICLES"
160 IF (NPTPNO.LT.B) GO TO 290
CNODE*C1*<1.0-F2)
00 280 IT-1/2
EVET«<-1.0)**IT
PART(1/IND)'IX«F2*EVET
PART(2/1NO)«-1Y
PART(3/IND)*C1
IF (TEST.LT.98.0.OR.TEST2.GT.0.0) GO TO 220
IXO-IX»EVET
KR«KR+1
IPT(KR)>INO
IF (METH.EQ.2) GO TO 170
PART(3,IND)*CNODE+CONC(IXD/IY)*F2
GO TO 180
170 PART(3/INO>«2.0*C1*CONC(IXD/IV)/(C1*CONC(IXD/IY))
180 IF (C1-CONC(IXD,IY)) 190/200/210
190 RP(KR)-CONC(IXO/IY)-PART(3/IND)
RN(KR)>C1-PART(3/IND)
GO TO 220
200 RP(KR>-0.0
RN(KR)«0.0
GO TO 220
210 RP(KR)-C1-PART(3/INO)
RN
-------
FORTRAN IV program listing—Continued
PART(2»IND)»IY+F2*EVET
PART(2*IND)<:-PART(2*IND)
PART(3*IND)EC1
IF (TEST.UT.98.0.OR.TEST?.GT.0.0) GO TO 280
lYOalY+EVET
KR*KR«1
IPT(KR>cIND
IF (HETH.EQ.2) GO TO 230
PART(3»IND)sCNODE+CONC(IX*IYD> «F2
GO TO 240
230 PART(3»IND)*2.0*C1*CONC(1X*IYD)/(C1*CONC(IX*1YD))
240 IF (CI-CONCdX/ITD) > 250,260*270
2SO RP(KR)«CONC(IX,IYD)-PART (3*I NO)
RN(KR)cC1-PART(3«IND)
GO TO 280
260 RP(KR)-0.0
RN(KR)»0.0
GO TO 280
270 RP(KR)«C1-PART(3»I NO)
RN(KR)«CONC(IX*1YD)-PART(3*IND)
280 IND«IND«1
290 IF (TEST.LT.98.0.OR.TEST2.GT.0.0) GO TO 410
SUMPT-0.0
COMPUTE CONC. GRADIENT WITHIN CELL
DO 300 KPT'1*NCHK
IK«IPT(KPT)
300 SUMPTsPART(3*IK)*SUMPT
CBAR«SUNPT/NCHK
CHECK MASS BALANCE WITHIN CELL AND ADJUST PT. CONCS.
SUMPT-O.O
IF (CBAR-C1) 310*410*330
310 CRCT«1.0-(C8AR/C1 )
IF (METH.E0.1) CRCT»CBAR/C1
DO 320 KPT*1,NCHK
1K=IPT(KPT)
PART(3»IK)'PART(3«IK)«RP(KPT)*CRCT
320 SUMPTaSUMPT+PART(3*IK>
CBARN=SUMPT/NCHK
GO TO 3SO
330 CRCT«1,0-(C1/CBAR)
IF (METH.E0.1) CRCT=C1/CBAR
DO 340 KPT«1/NCHK
IKelPT(KPT)
PART(3»IK)«PART(3»IK)*RN(KPT)«CRCT
340 SUMPT«SUMPT+PART(3/1K)
CBARN«SUHPT/NCHK
350 IF (CBARN.E8.C1> GO TO 410
CORRECT FOR OVERCOMPENSATI ON
CRCT-C1/CBARN
DO 380 KPT«1»NCHK
U-IPT(KPT)
PART(3,U)«PART(3,IK)*CRCT
CHECK CONSTRAINTS
IF (PART(3«IK)-C1> 360*380*370
360 CLIH«C1-RP(KPT)*RN(KPT)
IF (PART(3*IK).LT.CLIM) GO TO 390
GO TO 380
370 CLIM«C1+RPUPT)-RNUPT)
IF (PART(3*IK).GT.CLIM) GO TO 390
380 CONTINUE
GO TO 410
D1390
D1400
01410
01420
DUSO
01440
01450
D1460
D1470
01480
01490
01500
01510
01520
01530
01540
01550
01560
01570
01580
01590
01600
01610
D1620
01630
01640
01650
01660
01670
01680
01690
01700
01710
D1720
01730
01740
01750
01760
01770
01780
D1790
01800
01810
01820
01830
01840
01850
01860
01670
01880
01890
01900
01910
D1920
01930
01940
01950
01960
01970
01 980
01990
02000
E-15
-------
FORTRAN IV program, listing—Continued
390 TEST2»1.0 02010
00 tOO KPT«1,NCHK 02020
IK'IPT(KPT) 02030
400 PART(3,IK)«C1 02040
410 CONTINUE D20SO
NP'INO 02060
IF (1NT.EQ.O) CALL CHMOT 02070
RETURN 02090
••••••••••*•*••»**•••*•••••*••**•*•**»*»*••****•**«•**********•* 02100
END 02110-
SUBROUTINE VELO E 10
OOU8LE PRECISION OMIN1 ,DEXP,DLOG,OABS E 20
REAL »8THRX,VPRM,HI,HR,HC,HK,WT,REC»RECH,TIM,AOPT,TITLE E 30
REAL »8XDEL,YO£L,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HMIN,PYR E 40
REAL *8RATE,SLEAK,DIV E SO
COMMON /PRMI/ NTIM,NPMP,NPNT,NITP,N,NX,NY,NP,NREC,INT,NNX,NNy,NUMO E 60
18S,NMOV,IMCV,NPMAX,ITMAX,NZCRIT,IPRNT,NPTPNO,NPNTMV,NPNTVL,NPNTO,N E 70
2PNCHV,NPDELC E 80
COMMON /PRMK/ NODE I 0(20,20),NPCELL(20,20),LIMBO<500)•IXOBS(5>,IYOB E 90
1S(S) . E 100
COMMON /HEDA/ THCK(20,20),PERM(20,20),TMWL(5,50>,TMOBS<50),ANFCTR E 110
COMMON /HEOB/ TMRX(20,20,2),VPRM{20,20),HI(20,20>,HR(20,20)»HC(20, E 120
120),HK(20,20),WT<20,20),R£C(20,20),RECH(20,20),TIM<100),AOPT(20),T E 130
21TLE(10),XOEL,YOEL,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HMIN,PYR E 1 40
COMMON /XINV/ OXINV,OYINV,ARINV,PORINV E ISO
COMMON /CHMA/ PART(3,3200),CONC(20,20>,TMCN(5,50>,VX(20,20),VY(20, E 160
120),CONINT(20,20),CNRECHC20,20),POROS,SUMTCH,BETA,TIMV,STORM,STORM E 170
2I,CMSIN,CMSOUT,FLMIN,FLMOT,SUMIO,CELOIS,DLTRAT,CSTORM E 180
COMMON /CHrC/ SUMC(20,20),VXBOV(20,20),VVBOY(20,20) E 190
COMMON /OIFUS/ OISP(20,20,4) E 200
••»•••••••«•••••••••••••••••••*•••*•***•••••*••••*••**•••••**•• E 210
COMPUTE VELOCITIES ANO STORE E 220
VHAX=1.OE-10 E 230
VMAY»1.0E-10 E 240
VMX8D*1.OE-10 E 2SO
VMYBO=1.OE-10 E 260
M(N> E 270
E 280
C E 290
00 20 IX«1,NX E 300
00 20 IY=1,NY E 310
00 10 IZ"1,« E 320
10 DISP(IX,IY,m»0.0 E 330
C E 340
IF (THCK(IX/IY).EQ.O.O) GO TO 20 E 3SO
RATE«REC(IX,IY)/AREA E 360
SLEAK»(HK(IX,IY)-WT(IX,IY))*VPRM(IX,IY) E 370
OIV»RATE*SLEAK*RECH(IX,IY) E 380
C E 390
C VELOCITIES AT NODES--- E 400
C X-DIRECTION E 410
GROX-(HK(IX-1,IY)-HK(IX*1,IY))*OXINV*0.50 E 420
IF (THCK(IX-1,IY).EO.0.0) GROX»(HK(IX,IY)-HK(I X * 1 * IY»«OXINV E 430
IF (THCK(IX + 1,IY).EQ.O.O) GROX"(HK(IX-1,I V)-HK(I X,IY))•OXINV E 440
IF (THCKUX-1,1 Y).EO.0.0.ANO.THCK(IX»1,IY).EQ.0.0) GROX=0.0 E 450
VX(IX,IY)«PERM(IX,IY)*GROX«PORINV E 460
ABVX«A8S(VX(IX,IY)) E 470
IF (ABVX.GT.VMAX) VMAX=ABVX E 480
C Y-OIRECTION-— E 490
GROY»(HK
-------
FORTRAN IV program htttnff—Continued
20
c
c
80
90
100
110
IF (THCK( 1X,IY*1).EQ.0.0) GRDY«(HK>
VXBDV(IX/IY)=PERMX*GRDX*POR1NV
GRDV*(HK(IX,IY)-HK(IX/IY + 1»*DYINV
PERNY=2.0*PERM(IX,IY)*PERM(IX,IV*1)/ABVY
IF (DIV.GE.0.0) GO TO 20
TDIV»(POROS*THCK(IX/IY))/DABS(DIV)
IF (TDIV.LT.TMV) TMV*TDIV
CONTINUE
i»»•*»•
PRI
NT VELOCITIES
IF (NPNTVL.EQ
IF (NPNTVL.EQ
IF (NPNTVL.EQ
30
40
50
60
70
GO TO
WRITE
WRITE
DO 40
WRITE
WRITE
DO 50
WRITE
WRITE
WRITE
DO 60
WRITE
WRITE
DO 70
WRITE
80
(6/220)
(6/330)
IY»1,NV
(6/350)
(6/340)
IVal ,NY
(6,350)
(6/360)
(6/330)
IY»1 /NY
(6/350)
(6/340)
IV'1/NY
(6/350)
.0) GO TO
.2) GO TO
.1 .AND.N.
(VX(IX/I
(VXBDVCI
(VV( IX/I
80
30
EQ
Y)
X,
V)
(VYBDYdX/
.1) GO TO
,IX*1/NX)
IY),IX«1 ,
,IX«1/NX)
IY)/IX«1,
30
NX)
NX)
PUNCH VELOCITIES
IF (NPNCHV.EO.O) GO TO 110
IF (NPNCHV.E0.2) GO TO 90
IF (NPNCHV.E0.1.AND.N.EQ.1) GO TO 90
GO TO 110
WRITE (7/510) NX/NY/XDEL/YDEL/VMAX/VNAY
DO 100 1Y«1/NY
WRITE (7/520) (VX(IX/IY)/IX»1/NX)
WRITE (7/520) (VV(IX/IY)/IX-1,NX)
COMPUTE NEXT TIME STEP
WRITE (6/390)
WRITE (6/400) VNAX/VNAY
WRITE (6/410) VNXBD/VNYBD
TDELX«CELOIS*XDEL/VMAX
TDELV«CELD1S*YDEL/VMAY
TDELXB-CELDIS*XDEL/VNXBD
TDELVB"CEIDIS*YDEL/VMVBD
TIMV-AMINKTDELX/TDELY/TDELXB/TDELVB)
WRITE (6/310) TNV/TIHV
E S20
E 530
E S40
E SSO
E 560
E 570
E 580
E 590
E 600
E 610
E 620
E 630
E 640
E 650
E 660
E 670
E 680
E 690
E 700
E 710
E 720
E 730
E 740
E 750
E 760
E 770
E 780
E 790
E 800
E 810
E 820
E 830
E 840
E 850
E 860
E 870
E 880
E 890
E 900
E 910
E 920
E 930
E 940
E 950
E 960
E 970
E 980
E 990
E1000
E1010
E1020
E1030
El 040
E1050
El 060
E1070
E108C
E109U
E 1100
E1110
E1123
E1130
E-17
-------
FORTRAN IV program lifting—Continued
120
130
140
IF (TMV.LT.TIHV) GO TO 120
LIM--1
60 TO 130
TINV-TNV
LIM-1
NTINV«TIH(N)/HMV
NMOV«NTIHV»1
WRITE (6,420) TINV«NTIMV»NMOV
TIMV*TIM(N)/NMOV
WRITE (6*370) TIN(N)
WRITE (6,380) TIMV
IF (BETA. EO. 0.0) 60 TO 200
•••••••A**
--- COHPUTE DISPERSION COEFFICIENTS---
ALPHA-BETA
ALNG-ALPHA
TRAN«DLTRAT*ALPHA
XX2«XDEL*XDEL
YY2«YDEL*YOEL
XY2*4.Q*XOEL*VDEL
00 ISO IX-2/NNX
00 ISO IY«2»NNY
IF (THCK(IX,IY).EQ.O.O> GO TO ISO
VXE«VXBDY(IX,IY>
VYS«VYBDY (IX,I Y)
IF (THCK(IX«1»IY).Ea.O.O> GO TO 140
--- FORWARD COEFFICIENTS: X-DIRECTION ---
VYE-(VYBDY(IX,IY-1 ) * VVBO Y ( I X + 1 , I Y-1 ) *V Y S» V YBO Y ( IX«1,IY))/4.0
VXE2-VXE*VXE
VVE2»VVE*VYE
VMGEZSQRT(VXE2«'VVE2)
IF (VHGE.LT.1.0E-20) GO TO 140
DALN-ALNG*VMGE
OTRN-T RAN*tfMGE
VnGE2>VMCE*VMGE
--- XX COEFFICIENT ---
DISP(IX,IV,1)»(DALN*VXE2+DTRN*VYE2)/(VMGE2*XX2)
--- XY COEFFICIENT ---
OISP(IX*IV*3)*(DALN-DTRN)*VXE*VYE/(VMGE2*XY2)
--- FORWARD COEFFICIENTS: Y-OIRECTION ---
IF (THCK( IX,IY+1).EQ.O.O) GO TO ISO
130
VYS2»VYS*WYS
VXS2=VXS»VXS
VMGS«SQRT(VXS2*VYS2)
IF (VMGS.LT.1.0E-20) GO TO 150
OALN-ALNG*VMGS
OTRN=TRAN*tfMGS
VMGS2>VMGS*VMGS
--- YY COEFFICIENT ---
OISP(IX*IY,2)*(DALN»VYS2+DTRN*VXS2)/(VMGS2*YY2)
--- YX COEFFICIENT ----
DISP. £0.0.0. OR. THCK(IX*1,IY-1).EO. 0.0) D I SP ( I X / I Y / 3 ) «0.0
IF (THCK(IX»1,1Y).EO.O.O.OR.THCK(IX*1,IY»1).EQ.O.O.OR.THCK
-------
FORTRAN IV program lifting—Continued
1).EQ.O.O.OR.THCK(IX-1*1Y*1).EO.O.O)
160 CONTINUE
DISP(1X*IV*4)»0.0
170
180
••»•••••**•••*»••••••••*•••»••»••••»•»•••••••••••*•»•»••••«•••••
--- CHECK FOR STABILITY OF EXPLICIT HETHOO ---
TIHDIS«0.0
00 170 IX-2*NNX
DO 170 IY=2*NNY
TDCO=DISP(1X*IY*1 )*DISP(IX*IY,2)
IF (TDCO.GT.T1HOIS) TIHDIS=TDCO
T IHDC=0.5/TIMOI S
WRITE (6*440) TIMOC
NT1HO=TIM(N)/TIMDC
NDISP*NT1MD*1
IF (NO 1SP.LE.NMOV) GO TO 180
NMOV«NDISP
TIMV=T IM(N)/NMOV
LIH-0
WRITE (6/430) T IMV * NT I HO / NMOV
190
200
210
220
230
240
ADJUST DISP. EQUATION COEFFICIENTS FOR
DO 190 IX«2*NNX
DO 190 IY«2»NNY
BAVX*0.5*(THCK(IX*IY>*THCK(IX*1*IY))
BAVY»0.5*(THCK(IX*IY)»THCK(1X,1Y*1))
DISP(IX*IY,1)»DISP(IX,1Y,1)«BAVX
DISP(IX*1Y*2)>DISP(IX*IY*2)*BAVY
DISP(IX*IY»3)>DlSP(IX*IVr3)*BAVX
DISP(IX,ir,4)»DISP(IX*IY,4)*8AVY
A*
IF (LIH) 210/220*230
WRITE (6*530)
GO TO 240
WRITE (6,540)
GO TO 240
WRITE (6*550)
>•••*•*••*•**»***
SATURATED THICKNESS
a**********************************************
C
C
C
C
PRINT DISPERSION EQUATION COEFFICIENTS
IF (NPNTO.EQ.O) GO TO 300
IF (NPNTD.EQ.2) GO TO 250
IF (NPNTD.EQ.1.AND.N.£0.1 ) GO TO 250
GO TO 300
250 WRITE (6*450)
WRITE (6*460)
DO 260 IY«1*NY
260 WRITE (6*500) (01SP(1X * IY*1)* IX«1*NX)
WRITE (6*470)
00 270 IV»1*NY
270 WRITE (6,SCO) (DISP(I X*IY*2)* IX«1*NX)
WRITE (6*480)
DO 280 IY«1*NV
280 WRITE (6*500) (01SP(I X * IY*3)* IX«1*NX)
WRITE (6*490)
DO 290 IV«1*NV
290 WRITE (6*500) (DISP(IX,IY*4)*IX-1*NX>
300 RETURN
**•***•«•••»**•••«•••••*••••••**»**•••«»*••«•••,
310 FORMAT
112.5)
(IN *19H THV (MAX. INJ.) • *G12.5/20H TIHV (CELDIS) • *G
E1760
E1770
E1780
E1790
E1800
E.1810
E1820
E1830
£1840
£1850
E1860
E1870
E1880
E1890
E1900
E1910
E1920
E1930
E1940
E1950
E1960
E1970
E1980
El 990
E2000
E2010
E2020
E2030
E2040
E2050
E2060
E2070
E2080
E2090
E2100
E2110
£2120
E2130
E2140
E21SO
E2160
E2170
E2180
E2190
£2200
E2210
E2220
E2230
£2240
E2250
E2260
E2270
E2280
E2290
E2300
E2310
E2320
£2330
E2340
£2350
£2360
E2370
E-19
-------
FORTRAN IV program luting—Continued
320
330
3*0
3SO
360
370
380
390
400
410
420
430
440
4SO
460
470
480
490
500
510
520
530
540
550
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
1/CGRID
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
1ECTION
(1H1/12HX VELOCITIES)
(1H ,25X,8HAT NODES/)
<1HO,25X,13HON BOUNDARIES/)
C1H ,10612.3)
<1H1,12HV VELOCITIES)
(3H ,11HTIM (N) « ,1612.5)
<3H ,11HTIMEVELO - ,1612.5)
<1H1,10X,29HSTABILITY CRITERIA M.O.C.//)
(1HO/8H VMAX • ,1PE9.2,5X,7HVMAY * ,1PE9.2)
(1H ,8H VMXBD" ,1PE9.2,5X,7HVMVBD» ,1PE9.2)
(1HO,8H TIMV - ,1PE9.2,5X,8HNTIMV • ,15,5X,7HNMOV - ,I5/)
(1HO/8H TIMV • ,1PE9.2,5X,8HNTIMD • ,15,5X,7HNMOV • ,15)
<5H ,11HTIMEDISP - ,1E12.S)
<1H1,32HDISPERSION EQUATION COEFFICIENTS,10X,25H«(0-IJ ) *(B>
FACTOR)}
COEFFICIENT/)
COEFFICIENT/)
COEFFICIENT/)
COEFFICIENT/)
(1H
(1H
(1H
C1H
,35X,14HXX
,3SX,14HYY
,35X,14HXY
,3SX,14HVX
,1P10E8.1)
(2I4,2F10.1,2F10.7)
(8F10.7)
(1HO,10X,42HTHE LIMITING
(1HC,10X,40HTHE LIMITING
(1HO,10X,58HTHE LIMITING
RATE)
STABILITY
STABILITY
STABILITY
CRITERION
CRITERION
CRITE RION
IS
IS
IS
CELDIS)
BETA)
MAXIMUM
INJ
END
SUBROUTINE MOVE
REAL •8TMRX,VPRM, HI, HR,HC,HK,UT,REC,RECH,TIM,AOPT, TITLE
REAL »8XOEL,YDEL,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HMIN,PYR
COMMON /PRMI/ NTIM,NPMP,NPNT,NITP,N,NX,NY,NP,NREC,INT,NNX,NNY,NUMO
1BS,NMOV,IMOV,NPMAX, ITMAX,NZCRIT,IPRNT,NPTPND»NPNTMV,NPNTVL,NPNTD,N
2PNCHV,NPDELC
COMMON /PRMK/ NODE 10(20,20), NPCELL( 20, 20), LIMBO (500* , I XOBS( 5 ) , I YOB
1S(5)
COMMON /HE DA/ THCK(20,20),PERM(20,20),TMWL(5,50),TMOBS(50),ANFCTR
COMMON /HE OB/ TMRX(20,20,2),VPRM(20,20),HI(20,20),HR(20,20) ,HC(20,
120),HK(20,20>,WT(20,20),REC(20,20),RECH(20,20),TIM(100),AOPT(2C),T
2ITLEUO) ,XDEL,YDEL,S,AREA,SUMT,RHO,PARAM, TEST, TOL, PINT, HMIN,PYR
COMMON /XINV/ DXINV,DY I N V,ARI NV,PORI NV
COMMON /CHMA/ PART ( 3,3200) , CON C ( 20,20 ), TMCN ( 5, 50) ,VX < 20, 20) ,VY(20,
120), CON INT (20, 20 ), C NRE CM (20,20 > ,POROS ,SUM TC H,B ETA, TIMV, STORM, STORM
2I,CMSIN,CMSOUT,FLMIN,FLMOT,SUMIO,CELOIS,DLTRAT,CSTORM
COMMON /CHMC/ SUM C ( 20, 20 ) , VXBD V ( 2 0,20) , V VBD Y ( 20 ,20 )
DIMENSION XNEWC4), YNEUU), DISTC4)
0.299
0.333
10
WRITE (6,680) NMOV
SUMTCH=SUMT-TIM(N)
F1*0.249
IF (NPTPND.EQ.5) F1
IF (NPTPND.EQ.9) F1
CONST1 *TIMV*DXINV
CONST2«TIMV*OY INV
--- MOVE PARTICLES 'NMOV1 TIMES ---
00 650 IMOV=1,NMOV
NPTM>NP
--- MOVE EACH PARTICLE ---
DO 590 IN»1/NP
IF (PART(1,IN).EO.O.O) GO TO 590
KFLAG-0
E2380
E2390
E2400
E2410
E2420
E2430
E2440
E2450
E2460
E2470
E2480
E2490
E2500
E2510
E2S20
E2530
E2540
E2550
E2560
•£2570
E2S80
E2590
E2600
E2610
E2620
E2630
E2640-
10
20
30
40
SO
60
70
80
90
100
110
F 120
COMPUTE OLD LOCATION
130
140
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
E-20
-------
FORTRAN IV program luting—Continued
JFLAG«1 F 360
IF (PART(1,IN).GT.O.O) GO TO 20 f 370
JFLAG«-1 F 380
PARTM / IN)«-PART(1 /IN) F 390
20 XOLD«PART<1,1N> F 400
1X«XOLD*0.5 F 41Q
1FLAG-1 F 420
IF (PART(2/IN).GE.O.O) GO TO 30 F 430
IFLAG--1 F 440
PART(2«1N)*-PART(2/IN) F 4SC
30 YOLO'PART<2»IN) F 460
IY«YOLD*0.5 F 47Q
If (THCKUX,IV).EQ.0.0) GO TO 560 F 480
C •••••••••••••»»••••»•»•••*•••«*»•»••**•»••••••**••*•*••••*»•*•• f 49Q
C COMPUTE NEW LOCATION AND LOCATE CLOSEST NODE F 500
C LOCATE NORTHWEST CORNER F 510
IVX>XOLD F 520
IVV-YOLD F 530
IXE-IVX+1 F 540
1YS-IVY*1 F 550
C »•»••••*«»•••*•*•»*•»*••**••«*»••»»*»*«*••••••**«*****»**»***•• f 560
C LOCATE QUADRANT* VEL. AT 4 CORNERS* CHECK FOR BOUNDARIES F 570
CELDX-XOLO-1X F 580
CELDY=YOLD-IY F 590
IF (CELDX.EO.O.O.AND.CELDY.EO.O.O) GO TO 280 F 600
IF (CELDX.GE.O.O.OR.CELDY.6E.O.O) GO TO 70 F 610
C PT. IN NU QUADRANT F 620
VXNW*VXBDY(IVX,IVV> F 630
VXNE-VX(IXErlVY) F 640
VXSW'VXBDYUVX*IYS) F 650
VXSE'VXd XE,I YS> F 660
VYNU«VYBDY(1VX,IVY) F 670
VYNE'VYBDYdXE, IVY) f 680
VYSWEVVdVXsIYS) F 690
VVSEeVVdXE'IYS) F 700
IF (THCKdVX,IVY).EQ.0.0) GO TO 50 F 710
IF (REC(IXE/IVY).EQ.0.0.AND.VPRH(IXE, IVY).LT.0.09) GO TO 40 F 720
VXNE=VXNU F 730
40 IF (REC.EQ.0.0.AND.VPRH<1VX, I YS).LT.0.09) GO TO 50 F 740
VYSW-VYNM F 750
50 IF (REC.EO.0.0) GO TO 60 F 770
VXSE'VXSW F 780
60 IF (THCK(IXE,IVY).EQ.0.0) GO TO 270 F 790
VYSE-VYNE F 800
GO TO 270 F 810
C F 820
70 IF (CELOX.LE.O.O.OR.CELDV.GE.O.O) GO TO 130 F 830
C PT. IN ME QUADRANT F 840
80 VXNW«VX(IVX»IVY) f 850
VXNE«VXBDY(IVX,IVY) F 860
VX$W-VX(IVX/IYS) F 870
VXSE*VXBDY(IVX«IYS) f 880
VVNU*VYBDV(IVX,IVY) f 890
VYNE«VYBDY(IXE,IVY) F 900
VYSW«VY(IVX,IYS) f 910
VY$E«VY(IXE,1YS) F 920
IF (CELDX.EQ.0.0) GO TO 120 F 930
IF (THCK( IXErlVV).EQ.0.0) GO TO 100 F 940
IF (RECUVX,IVY).EO.0.0.AND.VPRMUVX,IVY).LT.0.09) GO TO 90 F 950
VXNU-VXNE F 960
90 IF (REC
-------
FORTRAN IV program lifting—Continued
VYSE-VYNE
100 IF .LT.0.09) GO TO 270
IF (THCK(IXE»IYS).EQ.O.O) GO TO 110
VXSU*VXSE
110 IF (THCK(IVX,IVY).EQ.O.O) GO TO 270
VTSU*VVNU
60 TO 270
120 IF. . EG. 0.0. AND. VPRM .LE. 0.09) GO TO 270
IF (THCK(IVX,IVV>.EQ.O.O) GO TO 270
VYSW'VVNU
60 TO 270
130 IF (CELOY.LE.O.O.OR.CELDX.GE.O.O) GO TO 190
PT. IN SW QUADRANT
140 VXNW«VXBDV(IVX/IVY)
VXNE«VX< IXE'IVV>
VXSU«VXBOYVV(1VX,IVV>
VVNE*VY(IXE/IVY)
VYSM-VYBDY (IVX,IVY)
VYSE-VYBOY (1XE/IVY)
IF (CELDY.EO.0.0) GO TO 180
IF (THCK(1VX*1VS).EQ.O.O> GO TO 160
IF (REC(1VX/IVV).EQ.O.O.AND.VPRM(IVX,IVY).LT,
VYNU*VVSW
IF (REC(IXE/IYS).EQ.O.O.AND.VPRM(IXE*IYS>.LT.
VXSE-VXSW
IF (REC GO TO 170
VXNE'VXNW
IF (THCK(IXE«IYS).EO.O.O> GO TO 270
VYNE'VYSE
GO TO 270
IF (REC(IXE»IVV).EQ.O.O.AND.VPRM(IXE»IVY>.LE,
IF (THCK(IVX/IVY).EQ.0.0) GO TO 270
VXNEsyXNU
GO TO 270
150
160
1 70
180
190
200
210
220
230
0.09) GO TO ISO
0.09) GO TO 160
0.09) GO TO 270
0.09) GO TO 270
IF (CELDY.LE.O.O.OR.CELDX.LE.O.O) GO TO 260
PT. IN SE QUADRANT
VXNW»VX( IVX,IVY>
VXNE'VXBOY( IVX«IVY)
VXSU*VX( IVXsIYS)
VXS£«tfX80Y(IVX/IYS)
VVNU*VY( IVXxIVY)
VVME«VY( IXE^IVY)
VVSV»VY80Y( IVX»IVY)
VVSE'VYBOY( IXE,IVY)
IF (CELDY.EQ.0.0) GO
IF (CELOX.EQ.0.0) GO
IF (THCK(IXE»IYS).EQ
IF (REC(IXE»IVY).EQ.O.O
VYNE'VYSE
IF {REC( IVX, IYS).EQ.O.O
VXSU-VXSE
IF GO TO 270
VYNU'VYSU
CO TO 27Q
TO 240
TO 250
0.0) GO TO 220
,AND.VPRMCIXE,IVY).LT,
,AND.VPRM(IVX,IYS>.LT,
0.09) GO TO 210
0.09) GO TO 220
0.09) GO TO 270
F 980
F 990
F1000
F1010
F1020
F1030
F1040
F10SO
F1060
F1070
F1080
F1090
F1100
•F1110
F1120
F1130
F1140
F1150
F1160
F1170
F1180
F1190
F1200
F1210
F1220
F1230
F1240
F12SO
F1260
F1270
F1280
F1290
F1300
F1310
F1320
F1330
F1340
F1350
F1360
F1370
F138C
F1390
F1400
F1410
F1420
F1430
F1440
F14SO
F1460
F1470
F1480
F1490
F1500
F1510
F1520
F1530
F1540
F1550
F1S60
F1570
F1580
F1590
E-22
-------
FORTRAN IV program l\»tmg—Continued
240
250
260
270
280
290
300
IF (REC(1VX,IVY>. EO. 0.0. AND. VPRMUVX, IVY) .LE. 0.09)
IF (THCK(IXE, IVY). f 0.0.0) GO TO 270
VXNW'VXNE
GO TO 270
IF .EQ.0.0) YVEL*VYb
i ••*«••••
--- BOUNDARY CONDITIONS ---
TEMPX«XOLO*OISTX
TEMPY« YOLD«DISTY
INX»TEHPX«O.S
INY-TEMPY40.5
IF (TMCK( INX/INY) .GT.0.0) GO TO 330
««»«»««««««
--- X BOUNDARY ---
IF (THCK( INX/IY). EO.0.0) GO TO 300
PARTU ,IN)-TEMPX
GO TO 310
BEYON»TEMPX-IX
IF (BEVON.LT.0.0) BEYON»BEYON+0.5
IF (BEYON. GT.0.0) BE YON«BE YON-0. 5
PARTd »IN)»TEHPX-2.0*BE YON
F1600
F1610
F1620
F1630
F1640
F1650
F166C
f 1670
F1680
71690
?1700
F1710
F1720
F1730
F174Q
F1750
F1760
F1770
F1780
F1790
F1800
F1810
F1820
F1830
F1840
F1C50
F1860
F1870
F1880
F1890
F1900
F1910
F1920
F1930
F1940
F1950
F1960
H970
Ft 980
M990
F2000
F2010
F2020
F2030
F2040
F20SO
F2060
F2070
F2080
F2090
F2100
F2110
F2120
F2130
F2UO
F21SO
F2160
F2170
F2180
F2190
F2203
F2210
E-23
-------
FORTRAN IV program litting—Continued
INX«PART<1,IN>*0.5
310
•*•*•*••*«•**•****•••***»••»*****»*«*»•*****••**»*•**{
- — Y BOUNDARY ---
IF 60 TO 320
PART(2,IN)«TEMPV
GO TO 340
(»»*•««,
320
330
3*0
BEYON«TENPY-IY
IF (BE YON.LT.0.0) BEYON-BEVON+0.5
IF (BEYON.GT.0.0) BEYOM«6EYON-0.5
PART<2*IN)«TEMPY-2.0*BEYON
INV»PART(2,IN>*0.5
TEHPV*PART(2«IN>
60 TO 340
PARTd ,IN)»TEMPX
PARTC2*IN)«TEMPY
CONTINUE
*••••«••••••*••••••*•••***••**•*•<
--- SUM CONCENTRATIONS AND COUNT PARTICLES
SU«C»SUMC
NPCELL»1
IF
IF
IF
IF
IF
IF
GO
--- CHECK FOR CHANGE IN CELL LOCATION ---
(IX.EO.INX.AND.1Y.EO.INY) GO TO 580
--- CHECK FOR CONST. -HEAD BOY. OR SOURCE
(REC GO TO 540
(UT.GT.HK(IX/IY>) GO TO 350
(WT (1X»IV>.LT.HK) GO TO 360
TO S40
AT OLD LOCATION
A***************************************************************
350
360
370
NEW PARTICLES
GO TO 550
GO TO 370
380
C
c
CREATE NEW PARTICLES AT BOUNDARIES
IF (IFLAG.GT.O)
KFLAG'1
DO 370 1L«1»500
IF (LIM80( ID.EQ.O)
IP«LIMBO.Ea.O.O.OR.THCK,
1EQ.O.O.OR.THCKUX/IY-1).EQ.O.O> GO TO 520
IF (THCKC1X*1»IY*1) .EQ.O.O.OR.THCK(IX+1,I Y-1).EQ.0.0.OR.THCK(I X-1
II Y*1).EO.O.O.OR.THCKSQRT((AD*AD)»(AN*AN))
IF (AD.EQ.0.0) GO TO 410
SLOPE-AN/AD
F2220
F2230
F2240
F2250
F2260
F2270
F2280
F2290
F2300
F2310
F2320
F2330
F2340
F2350
F2360
F2370
F2380
F2390
F2400
F2410
F2420
F2430
F2440
F2450
F2460
F2470
F2480
F2490
F2500
F2510
F2520
F2530
F2540
F2SSO
F2560
F2570
F2S80
F2S90
F2600
F2610
F2620
F2630
F2640
F2650
F2660
F2670
F2680
F2690
F2700
F2710
F2720
F2730
F2740
F2750
F2760
F2770
F2780
F2790
F2800
F2810
F2820
F2830
E-24
-------
FORTRAN IV program luting—Continued
too
i
410
420
430
440
4SO
460
470
480
490
SOO
S10
520
NEW COORDINATES AND VERIFY
420
BI-YOLD-SLOPE*XOLD
XC1«IX-F1
XC2«IX*M
YC1-IY-F1
YC2«IY»F1
COMPUTE
DO 400 !Ka1,4
YNEW(1K)«0.0
XNEW(1K)-0.0
DIST(IK>*0.0
YNEWd)«(SLOPE*XC1)+8I
XNEUd )-XC1
YNEW(2)*(SLOPE*XC2)+8I
XNEU(2)«XC2
IF (SLOPE.EO.0.0) GO TO
YNEU<3)"YC1
XNEU(3)««YC2
XNEU(4)*(VC2-BI >/SLOPE
GO TO 430
YNEWd>»I Y-F1
XNEWd ) = XOLD
VNEW<2)«IY4M
XNEW(2)=XOLD
JJ'2
DO 440 11«1,JJ
DISTd I)»SQRT((XNEW(II>-TEHPX)•*2 + (YNEW( I 1>-TEHPY>*«2)* 1.00001
IACC'0
DISTCK-2.0
DO 460 IG«1*JJ
IF (DIST(IG).GE.OlSTMV.ANO.OIST(IG).LT.OISTCK) GO TO 4SO
GO TO 460
IXC«XNEW(1G>*0.50
IYC»YNEU(I6)*0.50
IF ( IXC.NE.IX.OR.IYC.NE.IY) GO TO 460
IACC»I6
DISTCK'DIST(IG)
CONTINUE
IF (IACC.LT.1.0R.IACC.GT.4) GO TO 510
(XNEW(IACC).EQ.XCI.OR.XNEU(IACO.EO. XC2) GO TO 470
(YNEW(IACC).EQ. YC1.0R. YNEW( IACO.EQ. VC2) GO TO 430
TO S10
YNEWUACO-YC1
YNEU(IACC)"YC2
IF
IF
GO
IF
IF
GO
IF
IF
,YC1>
,YC2)
(VNEW(IACC).LT
(YNEU(IACC).GT
TO 490
(XNEW(IACC).LT.XCI)
(XNEU(IACC).GT.XC2)
PARTd ,IP)«XNEW(IACC)
PART(2«IP)>YNEU(IACC)
GO TO 530
PARTd ,1P)«-IX
PART(2»IP)»IV
GO TO 530
PARTd,IP)«XOLD
PART(2,IP)-YOLD
GO TO 530
IF EDGE SOURCE OR
X POSITION
DLX-INX-IX
PARTd,IP)»TEMPX-DLX
V POSITION
OLY»INY-IV
XNEW(IACC)*XC1
XNEW(1ACC)*XC2
SINK
F2840
F2850
F2860
F2870
F2880
F2890
F2900
F2910
F2920
F293C
F2940
F2950
F2960
F2970
F2980
F2990
F3000
F3010
F3020
F3030
F3040
F3050
F3060
F3070
F3080
F3090
F3100
F3110
F3120
F3130
F3140
F3150
F3160
F3170
F3180
F3190
F3200
F3210
F3220
73230
F3240
F3250
F3260
F3270
F3280
F3290
F3300
F3310
F3320
F3330
F3340
F3350
F3360
F3370
F3380
F3390
F3400
F3410
F3420
F3430
F3440
F3450
E-25
-------
FORTRAN IV program lifting—Continued
530
PART<2,IP)"TEMPY-DLY
IF (KFLA6.6T.O) 60 TO 530
IF SINK
SUMCCIX,IY)»SUMC
NPCELL»0.0
PART(2,IN>«0.0
PART(3,1N)«0.0
DO 570 10-1*500
IF (LIMBO(ID).GT.O) GO TO 570
LIMBO( ID)*IN
60 TO 590
CONTINUE
570
580
590
PART<2,IN)»-T£MPY
PART(1,IN>«-TEMPX
PT. LIMIT EXCEEDED
IF (IFLAG.LT.O)
IF (JFLAG.LT.O)
CONTINUE
C END OF LOOP
C •••••••••••»•••••••••••••••»••••••
GO TO 620
C RESTART MOVE IF
600 WRITE (6/700) IMOV/IN
TEST*100.0
CALL GENPT
DO 610 IX*1,NX
DO 610 IY-1/NY
SUHC(IX,IY>»0.0
610 NPCELL (IX ,IV)*0
TEST-0.0
GO TO 10
C A***************************!
• ••**** ft**********************
620
•A*********************************
SUMTCH=SUMTCH*-TIMV
ADJUST NUMBER OF PARTICLES
NPsNPTM
WRITE (6/670) NP/IMOV
•••****••*•*••*•*••*•*•»***»•**•****•**••**•******•••**•**•*•**•
CALL CNCON
A********************************************************
WELL DATA
TO 640
GO TO 640
630
640
---- STORE OBS.
IF (S.GT.0.0) 60
IF (NUMOBS.LE.O)
J»MOD( IMOV/50)
If (J.EQ.O) J«50
TMOBSC J)>SUMTCH
00 630 I»1,NUM08S
THWL»CONC< ixossd >/iYo»s(i
— PRINT CHEMICAL OUTPUT— -
IF (IMOV.GE.NMOv) GO TO 660
FOR STEADY FLOW PROBLEMS
F3460
F3470
F3480
F3490
F3500
F3510
F3S20
F3530
F3540
F3550
F3560
F3570
F3S80
F3590
F3600
F3610
F3620
F3630
F3640
F3650
F3660
F3670
F3680
F3690
F3700
F3710
F3720
F3730
F3740
F3750
F3760
F3770
F3780
F3790
F3800
F3810
F3820
F3830
F3B4C
F3850
F3860
F3870
F3880
F3890
F3900
F3910
F3920
F3930
F3940
F3950
F3960
F3970
F3980
F3990
F4000
F4010
F4020
F4030
F4040
F4050
F4060
F4070
E-26
-------
FORTRAN IV program littinp—Continued
650 IF •*«•«
660
RETURN
**••••
»»»•*»•••»»»**
670 FORMAT ( 1 HC,2X,2HNP,7X,2H« ,8X, I 4,1 OX,11HI MOV » ,8X,I4>
680 FORMAT (1HO/10X/61HNO. OF PARTICLE MOVES REQUIRED TO COMPLETE THIS
1 TIME STEP = , I4//>
690 FORMAT <1HO/SX,53M••• WARNING ••• QUADRANT NOT LOCATED FOR PT.
1 NO. ,I5/11H , IN CELL /2I4>
700 FORMAT (1HO,5X,17H • •• NOTE •••,10X,23HNPTM.EQ.NPMAX IHOV=
1/I4/5X/8HPT. NO.=/I«/5X,10HCALL CENPT/)
END
SUBROUTINE CNCON
REAL •8TMRX/VPRM/HI/MR,HC/HK,WT,REC,RECH/T1M,AOPT,TITLE
REAL •8XOEL,YDEL/S/AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HHIN,PYR
REAL *8FLW
COMMON /PRMI/ NTIM/NPMP,NPNT,NITP,N/NX/NY,NP,NREC,INT,NNX,NNY,NUHO
1BS/NMOV/IMOV/NPMAX,ITMAX/NZCRIT,IPRNT,NPTPND/NPNTMV/NPNTVL/NPNTD/N
2PNCHV/NPDELC
COMMON /PRMK/ NODE I 0(20,20),NPCELL(20,20),LIM80<500)•\XOBS(5)» IYOB
1S(5)
COMMON /HE DA/ T HCK ( 20, 20 ),PERM (20,20 ) , T MWL ( 5, 50 ) ,TMOBS ( 50 ) , ANF CT R
COMMON /HED8/ TMRX(20,20,2),VPRM<20,20),HI<20,20),HR(20,20),HC(20»
1 20),HK(20*20),WT(20»20),REC(20,20)*RECH(20,20),TIM<100),AOPT(20),T
2ITLEC10),XDEL,YDEL,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HMIN,PYR
COMMON /XIKV/ DXINV,DYINV,ARINV,PORINV
COMMON /CHHA/ PART(3,3200),CONC(20,20),TMCN(5,50),VX(20,20),VY(20,
1 20),CONINT(20*20),CNRECH(?0,20),POROS,SUMTCH,BETA,T1MV,STORM,STORM
2I,CMSIN,CMSOUT,FLMIN,FLMOT,SUMIO,CELOIS»OLTRAT,CSTORM
COMMON /DIFUS/ DISP(20,20,4)
COMMON /CHMC/ SUMC<20,20),VXBOY(20,20),VY80Y(20,20)
DIMENSION CNCNC(20»20), CNOLD(20,20)
A**************************************************************
ITEST-0
DO 10 1X=1,NX
DO 10 IY«1,NY
CNOLD(IX,IY)«CONC(IX,IY)
10 CNCNCCIX, IY)-0.0
APC-0.0
NZERO-0
TVA«AREA*T1NV
ARPOR»AREA*POROS
C •••••••••••••••••••»••*••*•••••*•*»•*•*•***•
C CONC. CHANGE FOR 0.5*TIMV DUE TO:
C RECHARGE/ PUMPING/ LEAKAGE/ DIVERGENCE OF
CONST-0.5MIMV
20 DO 60 IX*1/NX
DO 60 IY'1/NY
IF (THCK(IX/IY).EQ.O.O) GO TO 60
EOFCT1«CONST/THCK(IX/IY)
EQFCT2>EQFCT1/POROS
C1-CONC(1X/1Y)
CLKCN'0.0
SLEAK»(HK(IX/IV>-UT(IX/IY>>*VPRM(IX/IY>
IF (SLEAK.LT.0.0) CLKCN'CNRECH(I X/I V)
IF (SLEAK.GT.0.0) CLKCN-C1
CNREC-C1
RATE-R£C(IX,IY)«ARINV
IF (RATE.LT.0.0) CNREC«CNRECH(IX/IY)
VELOCITY...
FtOBC
F1090
FA100
G
G
G
G
G
G
G
G
G
F4120
F4130
F4140
F415C
F4160
F4170
F4180
F4190
F4200
F4210
F4220-
G 10
20
30
40
SO
60
70
80
90
100
G 110
G 120
G 130
G 140
G 1SO
G 160
G 170
G 180
G 190
G 200
G 210
G 220
G 230
G 240
G 250
G 26C
C ?70
G 280
G 290
G 300
G 310
G 320
G 330
G 340
G 350
G 360
G 370
G 380
G 390
G 400
G 410
G 420
G 430
G 440
G 4SO
G 460
G 47C
E-27
-------
FORTRAN IV program lifting—Continued
DIV«RATE*SLEAK»RECH(IX/IY)
If (S.EQ.0.0) 60 TO 30
DERH«
DIV«DIV*S*OERH
IF (S.LT.0.005) GO TO 30
...NOTE: ABOVE STATEMENT ASSUMES THAT S'0.005 SEPARATES CONFINED
FROM UNCONFINED CONDITIONS; THIS CRITERION SHOULD BE
CHANGED IF FIELD CONDITIONS ARE DIFFERENT.
DELCBEQFCT2*(C1*(D1V-POROS*DERH)-RATE*CNREC-SLEAK*CLKCN-RECH(IX«IY
1)*CNRECH< IX/IY)>
GO TO 40
30 DELC»EQFCT2*(C1*OIV-RATE*CNREC-SLEAK*CLKCN-RECH>
40 CNCNC(IX/IY)«CNCNC( IX/IY)*DELC
CONC. CHANGE DUE TO DISPERSION FOR 0.5*TIMV
-'-DISPERSION WITH TENSOR COEFFICIENTS
IF (BETA.EO.0.0) GO TO 50
X1-OISPUX/IY/1)«(CONC *(CONC(IX/IY*1)-C1>
Y2.-DISP(IX/IY-1,2)*(CONC(IX/IY-1)-C1>
XX1-DISPC1X/IY/S)*(CONC(IX»IY*1) + C.ONC(IX*1,IY*1)-CONC-CON
U(1X-1 ,IY«1)>
YY2*DISP(IX/IV-1/4)*(CONC(IX*1,1Y)*CONC(I X*1,IY-1 ) -CONC(I X-1/ I V)-C
50 CNCNC( IX/IY)-CNCNC(I X,IY ) »EQFCT1•(XI + X2»Y1 + Y2*XX1-XX2 + YY1 -YY2)
60 CONTINUE
*»*********«******»*»******»»*******»**»»**»*
IF (APC.GT.0.0) GO
IF =SUMC< IX/IY ) /APC
CONTINUE
--- CHECK NUMBER OF CELLS VOID OF PTS. ---
IF (NZERO.GT.O) WRITE (6/290) NZEROrlMOV
IF (NZERO.LE.NZCRIT ) GO TO 20
TEST«99.0
WRITE (6/3CO)
WRITE (6/320)
DO 100 IY*1/NY
WRITE (6/330) (NPCELL( IX/IY),IX = 1 /NX)
GO TO 20
GO TO 90
--- CHANGE CONCENTRATIONS AT NODES ---
00 130 IX«1/NX
00 130 IY*1,NY
IF (THCK(IX/IY).EQ.O.O) GO TO 120
CONC(IX/t Y)«CONC(IX/IV)*CNCNC( IX/IY)
G 480
G 490
G 500
G 510
G 520
G 530
G 540
G 550
G 560
G 570
G 580
G 590
G 600
G 610
G 620
G 630
G 640
G 650
G 660
G 670
G 680
G 690
G 700
G 710
G 720
G 730
G 740
G 750
G 760
G 770
G 780
G 790
G 800
G 810
G 820
G 830
G 840
G 850
G 860
G 37C
G 880
G 890
G 900
G 910
G 920
G 930
G 940
G 950
G 960
G 970
G 980
G 990
G100Q
G1010
G1020
G1030
G1040
G1050
G1060
G1Q70
G1080
G1090
E-28
-------
FORTRAN IV program toting—Continued
120
130
NPCELL(1X,IY)«0
SUMC«O.O
IF (CONC (1X,IY) .LE .0.0) GO TO 130
CNCPCT«CNCNC(IX,IY)/CONC(IX,1Y)
SUHC(IX/1Y)=CNCPCT
GO TO 130
IF (CONC(IX,IV).6T.O.O) WRITE (6,310)
CONC(IX,IY)«0.0
CONTINUE
140
ISO
160
170
1BO
190
200
210
220
230
240
2SO
260
270
I X, I Y ,CON C ( I X, 1 Y >
--- CHANGE CONCENTRATION OF PARTICLES ---
DO 180 IN«1,NP
IF (PAR-T <1,IN) .EO.0.0) GO TO 180
INX«ABS(PART(1,1N) )+0.5
INY»ABS(PART(2,IN))«0.5
--- UPDATE CONC. OF PTS. IN SINK/SOURCE CELLS ---
IF (REC( INX,INV).NE.O.O) GO TO 140
IF .LT.0.0) GO TO 170
PART(3,IN)«PARTC3,IN)«CNCNCUNX,INY>
GO TO 180
IF (CONCC INX,INY>. LE.0.0) GO TO 160
IF *PART<3,IN)*SUHC
CONTINUE
WRITE <6,2BO) T1M(N),TIMV,SUMTCH
•••••••••••••••••••••••••A***********************
--- COMPUTE MASS BALANCE FOR SOLUTE ---
CSTORM-0.0
STORM-0.0
DO 270 IX«1,NX
DO 270 IY«1,NV
IF (THCK(IX,IV).EQ.O.O> GO TO 270
SUMCd X,I Y)«0.0
--- COMPUTE MASS OF SOLUTE IN STORAGE ---
STORMBSTORM+CONC(IX,IV)*THCKUX,IY>*ARPOR
--- ACCOUNT FOR MASS PUMPED IN, OUT, RECHARGED,
IF (REC(IX,IY)) 200,210,190
CMSOUT-CMSOUT+REC( 1X,IY)*CNOLD(IX,IY)*TIMV
GO TO 210
CMSIN«CMS1N*REC(IX,IY)*CNRECH(IX,IY)*TIMV
IF CMSOUT*RECH ( IX, I Y > *CNOLD ( I X, I Y ) * T V A
GO TO 240
CMSIN»CMSIN+RECH(IX,IY)*CNRECH(IX,IY)*TVA
I DISCHARGED
••••••••*•••****•*•*•«*•*****<
—-ACCOUNT FOR BOUNDARY FLOW
IF (VPRH(IX,IY).EO.0.0) GO TO 270
FLW»VPRM
-------
1
c
c
c
c
c
c
c
c
~ — - — —
FORTRAN IV program lifting — Continued
C STORM* STORM-STORM I
SUMIO>FLMIN«FLMOT-CMS1N-CMSOUT
REGENERATE PARTICLES IF 'NZCRIT1 EXCEEDED
IF (TEST. GT. 98.0) CALL GENPT
TEST-0.0
••••••*•«•«•••*••*••»•******•**•*»*•»»»*••••»*•»•••*«**••*«•••••
RETURN
280 FORMAT (3H ,11HTIM(N) • , 1 G1 2 . 5, 1 OX , 1 1 HT IMV « ,1612. 5, 10X,
19HSUMTCH > ,G12.5)
290 FORMAT ( 1 H0,5 X,40HNUMB E R OF CELLS WITH ZERO PARTICLES » ,I4,5X,9
1HINOV • ,I4/)
300 FORMAT (1 HO,SX,44H*** NZCRIT EXCEEDED CALL GENPT • *•/)
310 FORMAT (IN ,5X, 37H* ••CONC.GT. 0. AND'. THCK . EO. 0 AT NODE * ,2I4,4X,7HC
10NC « ,610. 4, 4H •••)
320 FORMAT (1HO,2X,6HNPCELL/)
330 FORMAT (1H ,4X,20I3)
END
SUBROUTINE OUTPT
REAL •8TMRX,VPRN,HI , HR,HC,HK,WT,REC,RECH, TIM, AQPT, TITLE
REAL •8XDEL,VDEL,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINT,HMIN,PVR
COMMON /PRMI/ NTIM,NPMP,NPNT,NITP,N,NX,NY,NP,NREC,INT,NNX,NNY,NUMO
lBS,NMOV,INOVsNPMAX,ITMAX ,NZCRIT,IPRNT,NPTPND,NPNTMV,NPNTVL,NPNTD,N
2PNCHV,NPOELC
COMMON /PRMK/ NOD E I 0 ( 20 , 20) ,NPC ELL ( 20, 20) ,L I HBO ( 500) , I XOBS ( 5) , I YOB
1SC5)
COMMON /HE DA/ T HC K ( 20, 20 ) ,PERM ( 20,20) , TMU L ( 5, 50 ) ,TMOB S (50 ) , ANF CTR
COMMON /HEDB/ TMRX ( 20, 20 ,2 ) ,VPRM ( 20,20) ,H I ( 20, 2 0 > ,HR ( 20, 20) »HC (20,
120),HK(20,20),WT(20,20),REC(20,20),RECH(20,20),TIM(100),AOPT(20),T
2IT(.E(10) , XDEL,VDEL,S,AREA*SUMT,RHO,PARAN, TEST, TOL, PINT, HMIN, PVR
COMMON /BALM/ TOTLO
DIMENSION IH(20)
TINO-SUMT/86400.
TIMYsSUHT 7(86400.0*365. 2 5)
PRINT HEAD VALUES
WRITE (6,120)
WRITE (6,130) N
WRITE (6,140) SUMT
WRITE (6,150) TIMD
WRITE (6,160) TIMV
WRITE (6,170)
DO 10 IY*1,NY
10 WRITE (6,180) (HK( IX, I Y),IX»1 ,NX)
IF (N.EQ.O) GO TO 110
PRINT HEAD MAP
WRITE (6,120)
WRITE (6,130) N
WRITE (6,140) SUMT
WRITE (6,150) TIMD
WRITE (6,160) TIMY
WRITE (6,170)
00 30 IV«1,NY
DO 20 IX*1,NX
20 IH( IX) «HK( IX, I Y )«0.5
30 WRITE (6,190) ( IH( ID), 10-1 ,NX)
61720
61730
f • m / f\
9 1 7%U
61750
61760
61770
61780
61790
/• 4 onn
61800
61810
61820
61830
61840
61850
61860
G1870
G1880
G1890
G1900
61910
61920
61930-
H 10
H 20
H 30
H 40
H 50
H 60
H 70
H 80
H 90
H 100
H 110
H 120
H 130
H 140
Hi en
1 30
H 160
H 170
M ISO
H 190
H 200
H 210
H 220
H 230
H 240
H 250
H 260
H 270
u 9 bn
H £O(j
H 290
H 300
H 310
H 320
H 330
H 340
H 350
H 360
H 370
H 380
H 390
u tnn
E-30
-------
FORTRAN IV program luting—Continued
40
50
60
70
80
90
100
COMPUTE WATER BALANCE AND DRAWDOWN
QSTR'0.0
PUMP«0.0
TPUH-0.0
OIN-0.0
OOUT»0.0
QNET«0.0
DELQ'0.0
JCK«0
PCTERRsO.O
WRITE (6/290)
DO 80 IY«1/NY
DO 70 IX-1/NX
IH(IX>*0.0
IF (TMCK< IX,IV) .EG.0.0) GO TO 70
TPUMcREC<1X/IY)*RECH(IX,IY)«AREA+TPUM
IF (VPRH(IX,1Y>.EG.0.0) GO TO 60
DELO*VPRM(IX/IY)»AREA«(WT(1X/1Y)-HK(IX/[Y))
IF (DtLO.GT.0.0) GO TO (0
QOUT«QOUT + DELCI
GO TO SO
Q1N=UIN*OELO
QNET*QNET*DELQ
DDRU«HI(IX/IY)-HK(IX/IY)
IM(IX)=DORW*0.5
QSTR«QSTR«DORU*AR'EA*S
CONTINUE
PRINT DRAWDOWN MAP
WRITE (6/300) (1M(IX),IX«1/NX)
CONTINUE
PUMP*TPUM*SUKT
DELS=-abTR/SUMT
ERRHB-PUMP-TOTLO-O&TR
OEN*PUMP*TOTLU
IF (ABS(DEN).EO.ADS(ERRMB)) JCK=1
IF -(DEN.EG.0.0) GO TO 100
IF (JCK.E0.1) GO TO 90
PCTERR=ERRKB*20G.O/DEN
GO TO 100
IF COIN.EQ. 0.0) GO TO 100
PCTERR=100.0*QNET/blN
PRINT MASS BALANCE DATA FOR FLOJ MODIL-
WRITE (6/240)
WRITE
WRITE
WRITE
WRITE
(6
(6
(6
/250)
,230)
/260)
(6/270)
IF (JCK.
C
C
c
WRITE
WRITE
WRITE
IF (JC
4 A A A A 4
110 RETURN
120 FORMAT
130 FORMAT
140 FORMAT
EO.U)
(6/200)
(6
(6
K.
,210)
,220)
EQ.1)
PUMP
OSTR
TOTL&
E RRME
WRITE
(6/280)
PC TERR
01N/OOUT /QNET
TPUM
DELS
WHITE
(6/280)
PCTERR
( 1H1/2 JHHE AD
(1X,2ShNUMBE
(8X/16HT IME(
DI STRIOUTION - ROW)
K OF TIME
SECONDS)
STEPS > ,115)
• ,1012.5)
H 410
H 420
H 430
N 440
H 450
H 460
H 470
H 4&C
ri 490
K SOU
H 510
H 52G
H 53U
H 540
H 5SO
H 560
K 570
H 530
H 390
H 600
H 610
H 620
H 630
H 640
H 650
H 660
H 670
H 650
H 690
H 700
H 710
K 720
H 730
H 740
h 750
H 760
H 770
K 780
H 75C
H 8UO
S 610
H S2U
H 833
H 843
H 850
H 860
H 870
H 83G
H 890
H 900
H 910
H 920
H 930
H 94f
H 9Sf
H 960
H 970
H 980
H 990
H1000
H101D
H1020
E-31
-------
FORTRAN IV program, listing—Continued
150
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
FORMAT (BX,16HTIME(DAYS) * ,1£12.5>
FORMAT (8X,1oMTIME(YEARS) » ,1E12.5)
FORMAT <1H )
FORMAT (1HO,10F12.7/10F12.7)
FORMAT (1HO,20I4)
FORMAT <1HO,2X,33HRATE MASS BALANCE -- (IN
1 ,612.5/10x,8HflOUT * ,G12.5/1 Ox,8HQNET *
FORMAT (1H ,17X,8HTPUH * ,G12.5>
(1H ,17X,8HDELS - ,G12.5/)
(4X,29HUATER RELEASE FROM STORAGE
C.F.S.) //10X,8HQIN
,G12.S/)
FORMAT
FORMAT (4X,29HUATER RELEASE FROM STORAGE * «1E12.5)
FORMAT (1HO,2X,23HCUMULAT1YE MASS BALANCE//)
FORMAT (4X,29HCUMULATIVE NET PUMPAGE = /1E12.5)
FORMAT <4X,29HCUMULATIVE NET LEAK.ACE • ,1E12.5)
FORMAT (1HO»7X,25HMASS BALANCE RESIDUAL • ,G12.5>
FORMAT (1H ,7X,25HERROR (AS PERCENT) • ,G12.5/)
FORMAT (1M1/8HORAWOOWN)
FORMAT (3H ,2015)
END
SUBROUTINE CHMOT
REAL *8TMRX,VPRM,HI,HR,HC,HK,WT,REC,RECH,TIM,AOPT,TITLE
REAL •8XDEL»YDEL»S*AREA,SUMT,RHO,PARAM,TEST,TOL»PINT,HMIN,PYR
COMMON /PRMI/ NTIM,NPMP,NPNT,NITP,N,NX,NY,NP,NREC/INT/NNX«NNY,NUMO
1BS,NMOV,IMCV,NPMAX*ITMAX,NZCRIT,IPRNT,NPTPND,NPNTMV,NPNTVL«NPNTD,N
2PNCHV,NPDELC
COMMON /PRMK/ NODE I 0(20,20),NPCELL(20,20),LIHBO(500),IXOBS(5), I YOB
1S(5)
COMMON /HE DA/ THCK(20,20 ) ,PERM(20,20),TMUL<5,50),TM08S(50)»ANFCTR
COMMON /HEDB/ TMRX(20,20,2),VPRM(20,20),MI<20,20),HR(20,20) ,HC<20,
120)»HK(20,20),WT(20,20),REC(20,20),RECH(20,20),TIM(100),AOPT(20),T
2ITLE<10),XOEL,YOEL,S,AREA,SUMT,RHO,PARAM,TEST,TOL,PINTxHMIN,PYR
COMMON /CNNA/ PART(3,3200),CONC(20,20),TMCN(5,50),VX(20,20),VY<20,
120-),CONINT(20,20),CNRECH(20,20),POROS,SUMTCH,8ETA,T!MV,STORM,STORM
2I,CMSIN,CMSOUT,FLHIN,FLMOT,SUMIO,CELOIS,OLTRAT,CSTORM
DIMENSION IC(20>
A*****************************
TMFV»86400.0*365.25
TMYR-SUMT/TMFY
TCHD-SUMTCH/86400.0
TCHYR«SUMTCM/TMFY
IF (IPRNT.GT.O) GO TO 100
PRINT CONCENTRATIONS
WRITE (6,160)
WRITE (6,170) N —'
,GT.O) WRITE (6,180) TIM(N)6>
(6*190) SUMT t/ . •, _ «.
(6,450) SUMTCH . Vs' ' "' '
TCHD- -I' S />(J ~ «"'
TMYR— (_ - ^<"<
TCHYR . )Cj f.,j' - v.^-"1
I MOV - (.'
IF (N
WRITE
WRITE
WRITE
WRITE
WRITE
WRITE
UR ITE
DO 20
DO 10
10
20
(6,200)
(6,210)
(6,460)
(6,380)
(6,220)
IY«1,NY
IX=1,NX
IC(IX)»CONC
1,NX)
.*»»*»*•»•»*»«*•»*«••<
IF (N.EQ.Q) GO TO 150
IF (NPOELC.EQ.O) GO TO
50
PRINT CHANGES IN CONCENTRATION
WRITE (6,230)
H1030
H1040
H1050
Hi 060
H1070
Hioeo
H1090
H1100
H1110
H1120
H1130
H1140
H1150
H1160
H1170
H1180
H1190
H1200-
10
20
30
40
SO
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200
210
22C
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400
410
420
430
440
E-32
-------
FORTRAN IV program lifting— Continued
30
40
50
61
70
80
WRITE
WRITE
WRITE
WRITE
WRITE
WRITE
WRITE
WRITE
WRITE
00 40
DO 20
(6,170)
(6,180)
(6,190)
(6,450)
(6,200)
(6,210)
(6,460)
(6,380)
(6,220)
IY»1,NY
IXal ,NX
N
TIM(N)
SUMT
SUHTCH
TCHD
TMYR
TCHYR
I MOV
CN6«CONC(IX,IY)-CONINT(IX,IV>
IC(IX)»CN6
WRITE (6,240) < 1C ( I X) , 1 X = 1 ,NX )
DATA FOR SOLUTE ---
--- PRINT MASS BALANCE
RESIO»SUMIO-CSTORM
If (SUMIO.EQ.0.0) GO TO 60
RESID-SUMIO-CSTORM
ERR1*R£S1D*200.0/(SUMIO+CSTORM)
If (STORHI.EO.0.0) GO TO 70
ERR3»-100.0*RES1D/ ( STORM 1-SUHI 0)
WRITE (6,220)
(6,250)
(6,220)
(6,260)
(6,270)
FI.MIN
FLMOT
WRITE
WRITE
WRITE
WRITE
RECIN--CHSIN
RECOUT«-C«SOUT
WRITE (6,290) RECIN
(6,280)
(6,300)
(6,310)
(6,320)
(6,330)
WRITE
WRITE
WRITE
WRITE
WRITE
RECOUT
SUM 10
STORM1
STORM
CSTORM
IF (SUHIO.EQ.0.0) GO TO 80
WRITE (6,340)
WRITE (6,350) RESIO
WRITE (6,360) ERR1
IF (STORMI.EO.0.0) GO TO 90
WRITE (6,370)
WRITE (6,360) ERR3
«**4*«*»4!<**.ii
--- PRINT HYDROGRAPHS AFTER 50 STEPS OR
90 IF (MOO(1MOW,50).EO.O. AND.S.EQ.0.0) GO
IF (NOO(N,50).EO.O.AND.S.GT.O.O) GO TO
GO TO 150
10C WRITE (6,390) TITLE
IF (NUNOBS.LE.O) GO TO 150
WRITE (6,400) INT
IF (S.GT.0.0) WRITE (6,410)
IF (S.EQ.0.0) WRITE (6,420)
--- TABULATE HYDROGRAPH DATA ---
MOZ-0
IF (S.6T.O.O) SO TO 110
NTO-NMOV
IF (NMOV.GT.50) NTO»MOD ( IHOV, 50 >
GO TO 120
110 NTO-NTIM
IF (NTIM.GT.50) NTO>MOO(N,50)
120 IF (NTO.EO.O) NTO'SO
00 140 J«1,NUNOBS
END OF
TO 100
100
SIMULATION ---
450
460
480
490
SOD
S10
520
< 530
T S50
2 56C
! 57C
1 S80
~ 590
! 600
i 610
7 62C
T 63C
! 640
1 650
i 660
I 670
I 6«JO
I 690
I 700
I '10
I 7?0
I 730
1 740
I 750
I 760
T ?70
I 780
I 790
I 30C
I 310
1 320
i 330
1, 70
: VOO
I 910
94C
I
i
I
I
I 970
I 980
L 9VO
I'.CfJO
11010
M020
I10SO
11040
11050
E-33
-------
FORTRAN IV program lilting—Continued
C
c
C
c
TMYR-0.0
WRITE (6*430) J»IXOBS(J)/IY08S(J)
WRITE (6,4 40) MOZ«WT(IXOBS(J)/IYOBS(J))'CONINT( I XOBS( J ) • \ YOBS ( J) ) t
1THYR
DO 130 M«1,NTO
TMVR*TM08S(M)/TMFY
130 WRITE (6*440) M»TMWL/TMYR
140 CONTINUE
••»*»**•*********•*********•••*****»•******•»*******************
150 RETURN
••••••••••••••••••••••••••••••••••••••••••••••••a***************
160
170
180
190
200
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400
410
420
430
440
450
460
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
FORMAT
IT ION!)
FORMAT
FORMAT
FORMAT
ISTOREO
FORMAT
FORMAT
FORMAT
<1 Hi,13HCONCENTRATION/)
<1X,23HNUNBER OF TIME STEPS a ,115)
(8X«16HDELTA T • «1G12.5)
(8X,16HTIHE(SECONDS) * «1G12.5)
(3X«21HCHEM.TIME(DAVS) • *1E12.5)
(8X/16HTIME(YEARS) - ,1E12.5)
(1H )
<1H1,23HCHANGE IN CONCENTRATION/)
(1HO»20I5)
(1H »21HCHEMICAL MASS BALANCE)
(8X,25HMASS IN BOUNDARIES *1E12.5>
(8X,25HMASS OUT BOUNDARIES ,1E12.S)
(8X,25HMASS PUMPED OUT *1E12.5)
<8X«2SHMASS PUMPED IN »1E12.5)
(8X,25HINFLOW MINUS OUTFLOW «1E12.5)
(8X,25HINITIAL MASS STORED »1E12.5)
(8X«25HPRESENT MASS STORED ,1E12.S>
(8X»2SHCHANGE MASS STORED »1E12.5)
(1H «SX«S3HCOMPARE RESIDUAL WITH NET FLUX
AND MASS ACCUMULA
<8X,25HMASS BALANCE RESIDUAL •
(8X/25HERROR (AS PERCENT) =
(1H ,5X/55HCOMPARE INITIAL MASS
(1X,23H NO. MOVES COMPLETED * »
/1E12.S)
,1E12.5)
STORED WITH
CHANGE IN MASS
CONCENTRATION AT SELECTED 0
(1HO*5X*65HTIKE VERSUS HEAD AND
1BSERVATION POINTS//15X,19HPUMPING PERIOD NO. »I4////)
FORMAT (1HO»16X*19HTRANSIENT SOLUTION////)
FORMAT (1HO/15X«21HSTEAOY-STATE SOLUTION////)
FORMAT MHO,20X,22HOBS.WELL NO. X Y/17X.1HN,6X,40HHEAD
1 CONC.(NG/L) TIME (YEARS)//24X/I3»9X,12*3X,I2//)
FORMAT (1H *58X,I2,6X,F7.1,8X,F7.1,8X,F7.2)
FORMAT (1H »2X»21HCHEM.TIME(SECONDS> • »E12.5)
FORMAT (1H »2X«21HCHEM.TIME(YEAR5) • *E12.5)
END
(FT)
11070
11080
11090
11100
11110
11120
11130
ii no
11150
11160
11170
11180
11190
11200
11210
11220
11230
11240
11250
11260
IT270
11280
11290
11300
11310
11320
11330
11340
11350
11360
11370
1 1380
11390
11400
11410
11430
11440
11450
11460
11470
11480
11490
11500
11510
i1520
11530
11540
1 1550
11560-
E-3A
-------
Definition of Selected Program Variables
AAQ area of aquifer in model
ALNG BETA
ANFCTR anisotropy factor (ratio of T,, to T,,)
AOPT iteration parameters
AREA area of one cell in finite-difference grid
BETA longitudinal dispersivity of porous
medium
CELDIS maximum distance across one cell that
a particle is permitted to move in
one step (as fraction of width of
cell)
CLKCN concentration of leakage through con-
fining layer or streambcd
CMSIN mass of solute recharged into aquifer
CMSOUT mass of solute discharged from aquifer
CNCNC change in concentration due to disper-
sion and sources
CNCPCT change in concentration as percentage
of concentration at node
CNOLD concentration at node at end of pre-
vious time increment
CNREC concentration of well withdrawal or
injection
CNRECH concentration in fluid source
CONG concentration in aquifer at node
CONINT concentration in aquifer at start of
simulation
Cl CONG at node (IX.IY)
DALN longitudinal dispersion coefficient
DDRW drawdown
DELQ volumetric rate of leakage across a
confining layer or streambed
DELS rate of change in ground-water storage
DERH change in head with respect to time
DISP dispersion equation coefficients
DISTX distance particle moves in x-direction
during time increment
DISTY distance particle moves in y-direction
during time increment
DLTRAT ratio of transverse to longitudinal
dispersivity
DTRN transverse dispersion coefficient
FCTR multiplication or conversion factor
FLMIN solute mass entering modeled area
during time step
FLHOT solute mass leaving modeled area
during time step
GRDX hydraulic gradient in ^-direction
GRDY hydraulic gradient in y-direction
HC head from column computation
HI initial head in aquifer
HK computed head at end of time step
HMIN minimum iteration parameter
HR head from row computation in sub-
routine ITERAT; elsewhere HR
represents head from previous time
step
IMOV particle movement step number
INT pumping period number
IPRNT print control index for hydrographs
ITMAX maximum permitted number of
iterations
IXOBS z-coordinate of observation point
IYOBS {/-coordinate of observation point
KOUNT iteration number for ADIP
LIMBO array for temporary storage of
particles
N time step number
NCA number of aqutfer nodes m model
"•NCODES number of node.identification codes)
NITP number of iteration parameters'"
NMOV number of particle movements (or time
increments) required to complete
time step
NODEID node identification code
NP total number of active particles in grid
NPCELL number of particles in a cell during
time increment
NPMAX maximum number of available particles
NPMP number of pumping periods or simu-
lation periods
NPNT number of time steps between printouts
NPTPND initial number of particles per node
NREC number of pumping wells
NTIM number of time"stepa^>
NUMOBS number of observation wells
NX number of nodes in z-direction
NY number of nodes in y-direction
NZCRIT maximum number of cells that can be
void of particles
NZERO number of cells that are void of
particles at the end of a time
increment
PARAM iteration parameter for current
iteration
PART 1. x-coordinate of particle; 2. y-coordi-
nate of particle; 3. concentration of
particle. Also note that the signs of
coordinates are used as flags to store
information on original location of
particle.
PERM hydraulic conductivity (in L7"a)
PINT pumping period in years
POROS effective porosity
PUMP cumulative net pumpage
PYR total duration of pumping period
(in seconds)
QNET net water flux (in L'T ')
E-35
-------
Definition a/ »»leeted program variables—Continued
QSTR cumulative change in volume of water
in storage
REC point source or sink; negative for in-
jection, positive for withdrawal
(in 1ST')
RECH diffuse recharge or discharge; negative
for recharge, positive for discharge
(in L7--1)
RN range in concentration between regen-
erated particle and adjacent node
having lower concentration
RP range in concentration between regen-
erated particle and adjacent node
having higher concentration
S storage coefficient (or specific yield)
SLEAK rate of leakage through confining
layer or streambed
STORM change in total solute mass in storage
(by summation)
STORMI initial mass of solute in storage
SUMC summation of concentrations of all
particles in a cell
SUMIO change in total solute mass in storage
(from inflows—outflows)
SUMT total elapsed time (in seconds)
SUMTCH cumulative elapsed time during
particle moves (in seconds)
THCK saturated thickness of aquifer
TIM length of specific time step
(in seconds)
TIHD elapsed time in days
TIMY elapsed time in years
TIMV length of time increment for particle
movement (in seconds)
TIMX time step multiplier for transient flow
problems
TINIT size of initial time step for transient
flow problems (in seconds)
TITLE problem description
TMCN computed concentrations at observation
points
TMOBS elapsed times for observation point
records
TMRX transmissivity coefficients (harmonic
means on cell boundaries; forward
values are stored)
TMWL computed heads at observation points
TOL convergence criteria (ADIP)
TOTLQ cumulative net leakage through con-
fining layer or streambed
TRAN transverse dispersivity of porous
medium
VMAX maximum value of VX
VMAY maximum value of VY
VMGE magnitude of velocity vector
VMXBD maximum value of VXBDY
VMYBD maximum value of VYBDY
VPRM initially used to read transmissivily
values at nodes; then after line
B2270, VPRM equals leakance factor
for confining layer or streambed
(vertical hydraulic conductivity/
thickness). If VPRM^O.09, then the
program assumes that the node is a
constant-head boundary and is flag-
ged for subsequent special treat-
ment in calculating convective trans-
port.
VX velocity in x-direction at a node
VXBDY velocity in x-direction on a boundary
between nodes
VY velocity in y-direction at a node
VYBDY velocity in y-direction on a boundary
between nodes
WT initial water-table or potentiometric
elevation, or constant head in
stream or source bed
XDEL grid spacing in ^-direction
XOLD x-coordinate of particle at end of pre-
vious time increment
XVEL velocity of particle in x-direction
YDEL grid spacing in y-direction
YOLD ^-coordinate of particle at end of pre-
vious time increment
YVEL velocity of particle in y-direction
E-36
------- |