SJrEPA
United States
Environmental Protection
Agencv
Office of Mumcioai
^Dilution Control
Wasnmaton DC 20^60
Novemoer i3
Office of Water
Report to Congress
Municipal Wastewater
Lagoon Study
Volume 1
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VOLUME 1
TABLE OF CONTENTS
CHAPTER 1
CHAPTER 2
CHAPTER 3
EXECUTIVE SUMMARY ES-1
Study Authority and Objectives ES-1
Approach ES-1
Findings and Conclusions ES-2
Inventory and Waste Characterization of
Lagoons ES-2
Assessment of Potential Ground-water
Impacts ES-3
Risk Assessment ES-4
Alternatives to Prevent and Control
Ground-water Contamination ES-4
INTRODUCTION 1-1
METHODOLOGY AND LIMITATIONS 2-1
2.1 Approach 2-1
2.1.1 Lagoon Inventory and Characterization 2-1
2.1.2 Assessment of Potential Ground-water
Contamination 2-1
2.1.3 Selection of Target Exposure Point
Concentrations 2-3
2.1.4 Preventive and Corrective Measures 2-4
2.2 Limitations of Approach 2-5
2.2.1 Diversity of Lagoon Scenarios 2-5
2.2.2 Data Limitations 2-5
2.2.3 Use of Computer Modelling 2-6
2.2.4 Impact of Lagoon Seepage 2-6
2.2.5 Summary 2-6
Chapter 2 References 2-7
LAGOON DESIGN, INVENTORY AND CHARACTERIZATION 3-1
3.1 Types of Lagoons 3-1
3.1.1 Facultative Lagoons 3-1
3.1.2 Aerated Lagoons 3-1
3.1.3 Aerobic Lagoons 3-2
3.1.4 Anaerobic Laabdhs 3-2
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3.2 Regulations and Guidelines Related to
Lagoon Design, Construction and
Operation 3-2
3.3 Inventory of Lagoons 3-3
3.3.1 Domestic Lagoons 3-3
3.3.2 Domestic/Industrial Lagoons 3-6
3.4 General Uastewater Characteristics of
Lagoons 3-6
3.5 Nastewater Sampling of Individual Lagoons 3-9
3.5.1 Overview of Sampling Program 3-9
3.5.2 Lagoons Sampled 3-10
3.5.3 Sampling and Analytical Procedures 3-10
3.5.4 Results of Domestic Lagoon Sampling 3-13
3.5.5 Results of Domestic/Industrial Lagoon
Sampling 3-17
3.5.5.1 Domestic/Industrial Lagoon
Influent 3-17
3.5.5.2 Domestic/Industrial Lagoon
Effluent 3-22
3.5.5.3 Domestic/Industrial Lagoon
Sludge 3-22
3.5.6 Comparison of Results from Domestic
and Domestic/Industrial Lagoons 3-22
3.5.7 Findings and Conclusions 3-26
Chapter 3 References 3-30
CHAPTER 4 RESULTS OF ASSESSMENT OF POTENTIAL GROUND-
WATER IMPACTS 4-1
4.1 Model Output 4-1
4.2 Limitations of Computer Run Results 4-'
4.2.1 Computer Modelling and EPACMS ,-2
4.2.2 Input Data 4-2
4.2.3 Use of EPACMS Results 4-3
4.3 Discussion of Results: Dimensionless
Concentrations 4-4
4.3.1 Pollutants Undergoing neither
Hydrolysis nor Biodegradation 4-4
4.3.2 Pollutants Undergoing Hydrolysis
but not Biodegradation 4-4
4.3.3 Pollutants Undergoing Biodegrada-
tion but not Hydrolysis 4-7
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CHAPTER 5
CHAPTER 6
4.4 Discussion of Results: Lagoon Seepage
Concentrations
4.5 Interpretation of Results
4.6 Findings and Conclusions
ASSESSMENT OF HUMAN HEALTH RISK
5.1 Overview of Approach
5.1.1 Pollutant Release Rates from
Municipal Lagoons
5.1.2 Pollutant Fate and Transport in
the Environment
5.1.3 Distance to Exposed Populations
5.1.3.1 MEI Risk Exposure Distance
Distribution
5.1.3.2 Population Risk Exposure
_ , . Distance Distribution
b.l.4 Estimating Risks to Exposed
Populations
5.1.5 Aggregating Risks Across
Environmental Settings
5.2 Discussions of Quantitative Modelling
Results
5.2.1 Weighted National MEI Risks
5.2.2 Comparison of Risks from Domestic
and Domestic/Industrial Lagoons
5.2.3 Distribution of Risks Across Hydro-
geologic Settings
5.3 Qualitative Discussion of Population Risks
5.4 Findings and Conclusions
5.4.1 Magnitude and Distribution of Risks
5.4.2 Modelling Assumptions and Limitations
ALTERNATIVES TO PREVENT AND CONTROL GROUND-
WATER CONTAMINATION
6.1 Introduction
6.2 New Lagoon
6.2.1 Lagoon Siting
6.2.1.1. Soils, Hydrogeology
and Geology
6.2.1.2 Topography, Surface
Hydrology and Climate
4-7
4-9
4-13
5-1
5-1
5-2
5-3
5-3
5-3
5-4
5-4
5-4
5-6
5-6
5-6
5-7
5-7
5-9
5-9
5-10
6-1
6-1
6-3
6-3
6-3
6-4
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6.2.1.3 Distance to Ground or
Surface Water Supply
Wells or Intakes 6-4
6.2.2 Lagoon System Design 6-5
6.2.2.1 Selection of a Liner System 6-5
6.2.2.2 Liner Material Selection
and Design Considerations 6-9
6.2.3 Lagoon Construction 6-9
6.2.4 Costs 6-10
6.2.4.1 Capital Costs 6-10
6.2.4.2 0 & M Costs 6-11
6.3 Operations and Maintenance 6-11
6.4 Wastewater Pretreatment 6-13
6.5 Modification of an Existing Lagoon 6-14
6.5.1 Retrofitting 6-14
6.5.1.1 Liner Replacement 6-14
6.5.1.2 Liner Repair 6-15
6.5.1.3 Measures to Assure
Continuity of Operation
during Retrofitting/Repair 6-15
6.5.1.4 Costs 6-16
6.5.2 Improvement of O&M and Monitoring
Practices 6-16
6.5.3 Pretreatment 6-16
6.6 Lagoon Remediation 6-17
6.6.1 Site Investigation 6-17
6.6.2 Identification of Remedial
Alternatives 6-17
6.7 Findings and Conclusions 6-18
Chapter 6 References 6-19
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FIGURES
Figure Page
ES-1 Location of Municipal Lagoons by State ES-6
ES-2 Location of Domestic/Industrial Lagoons by State ES-7
2-1 National Assessment of Potential Ground-water
Contamination, Municipal Lagoon Study 2-2
3-1 Location of Municipal Lagoons by State 3-4
3-2 Location of Domestic/Industrial Lagoons by State 3-5
4-1 EPACMS Run No. 2 (CD) 4.5
4-2 EPACMS Run No. 2 (CLS) 4-8
5-1 National Aggregate Carcinogenic Risks 5-5
6-1 Schematic of a Compacted Soil Single Liner System
for a Lagoon 6-6
6-2 Schematic of a Flexible Membrane Single Liner System
for a Lagoon 6-7
6-3 Schematic of a Flexible Membrane/Compacted Soil
Double Liner System for a Lagoon 6-8
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TABLES
Table Page
3-1 Domestic Lagoon Distribution 3-7
3-2 Domestic/Industrial Lagoon Distribution 3-8
3-3 Domestic Lagoons Sampled 3-11
3-4 Domestic/Industrial Lagoons Sampled 3-12
3-5 Lagoon Sampling Points 3-14
3-6 Frequency of Occurrence by Sample Type: Domestic
Lagoons 3-16
3-7 Selected Sampling Results vs. Human Health-Based
Thresholds: Domestic Lagoons 3-18
3-8 Frequency of Occurrence by Sample Type: Domestic/
Industrial Lagoons 3-21
3-9 Selected Sampling Results vs. Human Health-Based
Thresholds: Domestic/Industrial Lagoons 3-23
3-10 Comparison of Influent Concentration Ranges for
Organic Pollutants 3-27
3-11 Comparison of Effluent Concentration Ranges for
Organic Pollutants 3-28
4-1 Model Results: Dimensionless Concentrations 4-6
4-2 Computed Target Lagoon Concentrations Based
on Human Health Thresholds 4-10
4-3 Number of Domestic Lagoons with Effluent or Waste-
water Concentrations Exceeding the Computed Target
Concentrations for a Given Hydrogeologic Category 4-11
4-4 Number of Domestic/Industrial Lagoons with Effluent
or Wastewater Concentrations Exceeding the Computed
Target Concentrations for a Given Hydrogeologic
Category 4-12
5-1 MEI Cancer Risks (Ground Water) from Municipal
Lagoons ' 5-8
6-1 Types of Preventive/Corrective Measures 6-2
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VOLUME 2
APPENDICES
APPENDIX 3.1 LAGOON DESIGN AND GROUND-WATER PROTECTION PRACTICES
Table 3.1-1: Wastewater Stabilization Lagoon Uses and
Sizing
Table 3.1-2: State Requirements for Ground-water Protec-
tion at Municipal Wastewater Lagoons
Table 3.1-3: Seepage Rates for Various Liner Materials
Table 3.1-4: Summary of State Ground-water Monitoring
Requirements for Municipal Wastewater
Lagoons
APPENDIX 3.2 LAGOON INVENTORY DATA
APPENDIX 3.3 CONVERSION OF LAGOON FLOW RATES TO AREAS
APPENDIX 3.4 WASTEWATER CHARACTERISTICS
Table 3.4-1: Typical Composition of Untreated Wastewater
Table 3.4-2: EPA's Toxic (Priority) Pollutants
Table 3.4-3: Common Consumer Products and Their House-
hold Sources
Table 3.4-4: Priority Pollutants in Household Wastes
APPENDIX 3.5 LAGOON SAMPLING PROGRAM
Lagoon Sampling and Analytical Procedures
Table 3.5-1: Summary of Domestic Lagoon Sampling Results
Table 3.5-2: Pollutant Frequency of Occurrence: Domes-
tic Lagoons
Lagoon Sampling Results: Nine Domestic Lagoons
Table 3.5-3: Summary of Domestic/Industrial Lagoon
Sampling Results
Table 3.5-4: Pollutant Frequency of Occurrence:
Domestic/Industrial Lagoons
Lagoon Sampling Results: 14 Domestic/Industrial Lagoons
APPENDIX 3.6 APPENDIX 3 REFERENCES
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APPENDIX 4.1 ASSESSMENT METHODOLOGY
4.1.1 Selection of Contaminants of Concern and Exposure
Point Threshold Concentrations
4.1.1.1 Domestic Lagoons
4.1.1.2 Domestic/Industrial Lagoons
Table 4.1-1: Pollutants of Concern (Domestic
Lagoons)
Table 4.1-2: Pollutants of Concern (Domestic/
Industrial Lagoons)
Table 4.1-3: Pollutants Selected for Computer Model-
ling
4.1.2 EPACMS Computer Model
4.1.2.1 Code Features and Applicability
4.1.2.2 Model Description
4.1.2.3 Model Assumptions
Figure 4.1-1: Schematic Description of Surface Im-
poundment and Hydrogeologic Regime
Figure 4.1-2: Schematic of Layered Analytical Solu-
tion for Transport in the Unsaturated
Zone
Figure 4.1-3: Schematic Description of Saturated Zone
Transport Model
4.1.3 Determination of Model Input Data
4.1.3.1 Hydrogeologic Parameters
4.1.3.2 Lagoon Seepage Rates
4.1.3.2.1 Theoretical Calculation of Seep-
age Rates
4.1.3.2.2 Effects of the Sludge Layer
4.1.3.2.3 -Selection of Lagoon Seepage Rates
for the National Assessment
4.1.3.3 Lagoon Area and Exposure Distance
4.1.3.4 Chemical Constants
Table 4.1-4: Summary of EPACMS Input Data (Saturated
Zone)
Table 4.1-5: DRASTIC Regions
Table 4.1-6: Hydrogeologic Categories and Settings
Table 4.1-7: Estimated Ground-water Velocity for the
Nine Hydrogeologic Categories
Table 4.1-8: Permeability of Various Liners and
Geologic Materials
Table 4.1-9: Summary of Measured Seepage Rates from
Municipal Lagoon Systems
Table 4.1-10: Estimated Seepage Rates and Hydraulic
Balances at 10 Lagoons (9 Domestic and
1 Domestic/Industrial)
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Table 4.1-11: Summary of State Seepage and Permeabi-
lity Limitations for Lagoon Systems
Table 4.1-12: Distance to Nearest Well
Table 4.1-13: Chemical Constants Used in EPACMS Runs
Table 4.1-14: Number of Lagoons per Hydrogeologic
Category ,
Figure 4.1-4: Lagoon Population with DRASTIC Ground-
water Regions
Figure 4.1-5: Schematic of Seepage Through a Lagoon
Liner
Figure 4.1-6: Seepage as a Function of Water Depth
and Liner Characteristics
4.1.4 Selection of Generic Modelling Scenarios
APPENDIX 4.2 DETERMINATION OF PROBABILITY DISTRIBUTIONS FOR LAGOON AREA
AND EXPOSURE DISTANCE
APPENDIX 4.3 SELECTION OF CHEMICAL CONSTANTS
APPENDIX 4.4 INPUT DATA FOR GENERIC RUNS
APPENDIX 4.5 RESULTS OF GENERIC RUNS: DIMENSIONLESS CONCENTRATIONS
APPENDIX 4.6 RESULTS OF GENERIC RUNS: TARGET LAGOON CONCENTRATIONS
APPENDIX 4.7 APPENDIX 4 REFERENCES
APPENDIX 5.1 MODEL LAGOON LEACHATE CONCENTRATIONS
APPENDIX 5.2 NINETIETH PERCENTILE HEALTH RISKS BY SETTING
APPENDIX 5.3 DESCRIPTION OF MAPPING SURVEY
APPENDIX 5.4 CALCULATION OF HEALTH RISKS FROM WELL CONCENTRATIONS
APPENDIX 5.5 DESCRIPTION OF COMPUTER RUNS
APPENDIX 5.6 DATA FROM MODEL OUTPUT
APPENDIX 6.1 LINER MATERIAL SELECTION AND DESIGN CONSIDERATIONS
Table 6.1-1: General Characteristics of Selected Earthen,
Asphalt and Cement Liners
Table 6.1-2: General Characteristics of Selected Synthe-
tic and Rubber Liners
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APPENDIX 6.2 LAGOON CONSTRUCTION
6.2.1 Subgrade Preparation
6.2.2 Liner Installation
APPENDIX 6.3 COSTS
Fact Sheets: Aerated, Facultative and Anaerobic Lagoons
Table 6.3-1: Development of Capital Costs
Table 6.3.2: Costs of Selected Flexible Membrane Liners
Table 6.3-3: Costs of Selected Earthen and Admixed Liners
Table 6.3.4: Ground-water Monitoring Costs
APPENDIX 6.4 PRETREATMENT
Table 6.4-1: Established Pretreatment Processes
APPENDIX 6.5 LAGOON REMEDIATION
Table 6.5-1: General Types of Response Alternatives
Applicable to Municipal Lagoons
Table 6.5-2: Remedial Technologies
Table 6.5-3: Common Ground-water Treatment Processes
APPENDIX 6.6 APPENDIX 6 REFERENCES
HAZW 5:61 TV
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ACKNOWLEDGEMENTS
This document was prepared under the guidance of Ms. Connie Bosnia and Mr.
Lam L1m of EPA's Office of Municipal Pollution Control and Mr. Walter G. Gilbert,
now of the Office of the Inspector General. Contractors for this effort Included
Dr. Timothy G. Shea, Mr. John W. Kubarewlcz, and Ms. Susan J. Tiffany of
Engineering-Science, Inc. of Fairfax, Virginia, and Mr. Myron Tiemens. Support-
Ing work was done by Brown and Caldwell Consulting Engineers of Pleasant Hill,
California. Review of the Report to Congress was provided by the following
members of the RCRA Lagoon Study Work Group:
George Denning WH-550
Tom O1Parrel1 WH-551
Ron Hoffer WH-550G
Dove Weltman LE-132S
James Plttman WH-565E
Jim BasilIco RD-681
Ron Benioff PM-220
John Gerba A-104
Doug Newman WH-556
J1m Patrick Region IV
Chuck Pycha Region V
M1ke Turvey Region VII
Jack Hofbunr Region VIII
Ms. Georgette Boddle, Mr. Peter E. Shanaghan, and Mr. Charles P. Vanderlyn
of EPA's Office of Municipal Pollution Control made significant contributions to
the preparation and submlttal of this Report to Congress.
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EXECUTIVE SUMMARY
STUDY AUTHORITY AND OBJECTIVES
This report presents the results of'the Municipal Uastewater Lagoon Study
performed by- the U.S. Environmental Protection .Agency (EPA) in response to
Section 3018 (c) of the Resource Conservation and Recovery Act (added by
Section 246 of the Hazardous and Solid Waste Amendments of 1984). The
objectives for the study are to determine:
(1) the number and size of municipal lagoons;
(2) the types and quantities of waste contained in such lagoons;
(3) the extent to which such waste has been or may be released from
such lagoons and contaminates ground water; and
(4) available alternatives for preventing or controlling such releases.
STUDY APPROACH
o The number and size of municipal lagoons were determined by compiling a
national municipal lagoon Inventory from EPA's 1984 Needs Survey data
base.
The inventory contains the following information:
(1) lagoon locations;
(2) number of lagoons nationwide and by State and size distribution
by design flow; and
(3) Identification of relative domestic and industrial flow
contributions to each lagoon.
o A literature search was conducted to compile information on alternatives
for preventing or controlling ground-water contamination from lagoons.
o A review of current lagoon design practices and State regulatory
requirements was conducted.
The report Includes a compilation of State standards and criteria
concerning design, construction, and ground-water monitoring.
o A limited lagoon sampling program was undertaken to assess the types and
quantities of wastes contained in municipal wastewater lagoons.
Twenty-one lagoons were sampled: Nine with domestic waste only and
12 with both domestic and industrial waste.
Sampling points were influent, mid-depth in the pond, accumulated
sludge at pond bottom and effluent.
Samples were analyzed for 126 priority pollutants and other selected
pollutants.
ES-1
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o The ground-water quality impacts of municipal lagoons were determined
using lagoon sampling data and computer modelling of ground-water quality.
- Seven pollutants (including six priority pollutants) were selected for
computer modelling. The EPACMS model was used In this study. EPACMS
is a two-dimensional composite numerical/analytical solution model
designed to evaluate the .migration of dissolved pollutants from a
surface impoundment to points of interest in an underlying aquifer.
Using generalized regional hydrogeologic characteristics the model
calculates the maximum allowable pollutant concentration in the lagoon
seepage based upon a human health based threshold at an exposure point
downgradient from the lagoon. The calculated maximum allowable
pollutant concentrations are compared to the measured pollutant
concentrations in the lagoon samples.
- Human health-based thresholds used as target exposure point
concentrations were selected from two sources: (1) Maximum Contaminant
Levels (MCLs) as promulgated by EPA under the Safe Drinking Water Act;
and (2) for those compounds without MCLs the risk specific dose (RSD)
based concentrations for the 10-6 incremental cancer risk. MCLs
represent currently acceptable concentrations of pollutants in
drinking water deemed to be health protective by the Agency. MCLs
reflect cost and technical feasibility of control measures as well as
health effects of the pollutants.
LIMITATIONS AND ASSUMPTIONS
o Limitations of the study approach include generalization of regional
hydrogeologic characteristics, limited wastewater characterization data,
absence of reliable ground-water mom'toring data, computer model
limitations, the unknown relationship between pollutant concentrations in
the lagoon effluent and those in lagoon seepage, and the lack of data on
degradation of pollutants in the aerated soil zone and In ground water.
- Assumptions for all computer model input data were conservative.
Predicted pollutant concentrations in ground water are probably higher
than actually exist.
- All computer simulations use generalized hydrogeologic data and
limited data on concentrations of pollutants found in lagoons, without
actual ground-water monitoring data for verification.
- The results and conclusions of this study should not be applied to
sewage sludge that is placed in sludge-only landfills (monofills) or
that is land applied. Sewage sludge that is used or disposed in this
manner is a distinctly different material than material that
accumulates in a wastewater treatment lagoon. Site characteristics
may also differ significantly between sludge monofills and lagoons.
EPA will be regulating use and disposal of sewage sludge including
monofilling under Section 405(d) of the Clean Water Act. Proposed
regulations for public comment will be issued in early 1988. In
subsequent rulemaking, the Agency may regulate sludge contained in
municipal wastewater lagoons under Section 405(d) of the Clean Water
Act.
ES-2
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SUMMARY OF FINDINGS
o There are 5,500 municipal wastewater treatment lagoons nationwide; most
are very small and handle only domestic wastes.
- 50 percent of lagoons treat flows less than 0.1 million' gallons per
day (M6D)
- 90 percent of lagoons treat flows less than 0.5 mgd.
- Less than 8 percent of lagoons receive significant industrial
discharges.
- Lagoons are used In all States except one, however one-third are in
the 12 midwestern States (see figure ES-1).
- Lagoons which treat a combination of domestic and industrial wastes
are used In a number of States, however, the greatest concentration of
such lagoons occur In the midwest (see figure ES-2).
o States have widely varying requirements for municipal wastewater
treatment lagoons"
- 18 States require ground-water monitoring wells for lagoons under
certain specific circumstances or based upon a case-by-case evaluation
of their need. Five additional States require monitoring under
specific conditions (e.g., unlined lagoon). Few municipal lagoons
have monitoring wells and those few wells are not properly located to
detect ground-water contamination. When required, monitoring is
usually conducted for conventional (i.e., non-priority) pollutants
only.
- 12 States require linings for all lagoons, 18 States require linings
as necessary to meet either State permeability criteria or
case-by-case demonstrations of need, 19 States have no specific lining
requirements, and one State does not allow lagoons. Most municipal
lagoons have linings of various types primarily formed from imported
clay or compacted clayey or other soils existing at the site.
o There were approximately 3 times as many priority pollutants in municipal
lagoons that treat 1noustrial wastes as compared to those that treaf
domestic waste onlyT
- 94 priority pollutants at concentrations up to 1,000 ppb were found in
domestic/Industrial lagoons
- 35 priority pollutants at concentrations up to 280 ppb were found in
domestic lagoons.
ES-3
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Seepage from domestic/industrial lagoons is more likely to contaminate
nearoy aquifers tnan seepage from similarly constructed and located
domestic only lagoons.
- Lagoons receiving only domestic wastes are unlikely to sufficiently
affect ground water to exceed present MCL's at exposure points.
However domestic/industrial lagoons may cause certain MCL's to be
exceeded.
- Domestic and domestic/industrial waste lagoons may sufficiently affect
ground water to exceed RSD-based concentrations.
o There are effective remedial measures for existing lagoons and
precautionary measures for new lagoons to prevent and controT
ground-water contamination from municipal wastewater treatment lagoons.
- EPA's Office of Research and Development has performed numerous
studies which document methods for preventing or controlling
ground-water contamination from municipal wastewater lagoons.
- Remedial measures for existing lagoons include:
o Clean up contaminated ground water and soils, if necessary
o Repair or replace liners
o Install monitoring wells
o Improve sampling and chemical analyses to include toxic pollutants
o Improve State requirements for lagoon sampling and monitoring
o Review pretreatment requirements and implement changes if needed
- Measures for new lagoons include:
o Site selection criteria
o Improve liners
o Proper monitoring well installation
o State requirements for lagoon sampling and monitoring
o Improve construction inspection procedures
o Consider pretreatment requirements as appropriate.
CONCLUSIONS
o The potential for ground-water contamination from municipal wastewater
lagoons is low. It appears, however, that some lagoons with industrial
discharges may be potential sources of ground-water contamination.
o Human health risks associated with ground-water contamination from
domestic lagoons are generally low and within an acceptable rangeT
Lagoons with significant industrial discharges pose a potential risk to
human health.
ES-4
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Existing State standards for lagoon design and construction and for
ground-water monitoring vary widely and some may be inadequate for
protection of ground water where lagoons receive significant industrlaT
discharges. States should review their standards and monitoring require-
ments for lagoons that receive significant industrial waste and which are
located In highly vulnerable hydrogeologic settings or in proximity to
drinking water wells.
ES-5
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FIGURE ES-]
LOCATION OF MUNICIPAL LAGOONS BY STATE
k$W* JfTTTl
h ..,; .»% .,«
A>i~~)l- -i^-tJiJ1 \ ' II ' 11 H'»-'"Wil'/l1
Xlr? w A-'V/v-l,v *:l'3i?l
/:'," ?. ^-%M«
pji • ir^^v.^
1 k i 'i i' / i'f
\\^A{fiY'^y^'<
I V.,
,./ ,V ,'I, ",^», "'/,('
i " i . / ' . I. -f h-l I, iln'i,/; . I
i! fll'l
' *«^ 6
LACUOllS
III lilt fill I to SlAlCS
AUCUSI ii
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FIGURE ES-2
LOCATION OF DOMESTIC/INDUSTRIAL LAGOONS BY STATE
OUnESIIC I IIIOUSI8IAL
LAGOONS
IN \Hl Dill l!l) SIAIES
jui T 21 I9b/
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CHAPTER 1
INTRODUCTION
Section 246 of the 1984 Amendments to the Resource Conservation and Recovery
Act (RCRA) adds section 3018(c) which requires that the U.S. Environmental Protec-
tion Agency (EPA) conduct a study and submit a report to Congress concerning waste-
water treatment lagoons at publicly owned treatment works and their effect on
ground-water quality. Uastewater treatment lagoons are frequently used by small
communities to provide a low-cost method for treating their wastewater. Based on
1984 Needs Survey data, 5,476 lagoons exist In the United States. Specifically,
Section 246 asks for:
o An Inventory of municipal lagoons (number and size);
o The types and quantities of wastes present In municipal lagoons;
o The extent to which wastes from lagoons may contaminate ground water; and
o Available alternatives for preventing or controlling such contamination.
EPA Initiated work on the study In early 1985, shortly after the passage of
the RCRA Amendments. A number of EPA offices and contractors were utilized to
assist 1n the development of the study approach and In the performance of the
study. This report presents the results of this three-year effort.
Chapter 2 briefly describes the methodology and limitations of the approach.
Chapter 3 Identifies the location of municipal lagoons and describes their waste
characteristics. An assessment of potential ground-water contamination from lagoons
1s presented In Chapter 4 followed by analysis of the potential health risks In
Chapter 5. Finally Chapter 6 describes available alternatives to prevent such
ground-water contamination. These Chapters give the reader a solid overview of the
Issues Involved Including summaries of the Important points discussed. Most of the
data summaries, computer printouts, and detailed methodology are presented 1n the
appendices for those who desire additional Information.
1-1
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CHAPTER 2
METHODOLOGY AND LIMITATIONS
2.1 APPROACH
The approach developed to meet each of the specific objectives of the study Is
briefly outlined In the following sections.
2.1.1 Lagoon Inventory and Waste Characterization
The Inventory of municipal lagoons was based on the 1984 Needs Survey data
developed by the EPA. Needs Survey data were reviewed and analyzed to Identify the
size, location, and lagoon type of the 5,476 lagoons In the Inventory.
A limited sampling program Identified types and amounts of EPA's 126 priority
toxic pollutants, plus a few additional selected pollutants, In the wastewaters
of some lagoons and provided data used for the national assessment of potential
ground-water contamination. Twenty-three lagoon systems nationwide were selected
for sampling and characterization. The first ten lagoons selected each have nearby
ground-water monitoring wells. The second group of 13 lagoons Includes those with
a significant contribution of wastes from Industrial sources, variations In their
sizes, and diversity In their geographic locations. Data from two of these 13
lagoons were obtained from Independent sources outside this study.
Samples taken from each lagoon were analyzed for priority toxic pollutants and
for selected non-conventional pollutants and pollutant parameters (barium, total
phenols, total organic carbon, ammonia nitrogen, oxidized nitrogen, and chloride).
The evaluation of laboratory analytical data from the lagoon samples Identified the
concentrations and frequency of occurrence of specific pollutants.
The sampling program was designed to facilitate the assessment of ground-water
contamination caused by municipal wastewater lagoons. Lagoons which receive
Industrial wastewater may also be significant sources of air pollutant emissions.
Since assessment of air emissions was not a goal of this study the sampling was not
conducted 1n a way to determine air emissions. Thus, data presented 1n this report
should not be used to assess air emissions from municipal wastewater lagoons.
2.1.2 Assessment of Potential Ground-water Contamination
The Impact of pollutants from municipal lagoons could be most effectively
assessed by direct field monitoring at selected lagoons. Such an approach was not
feasible, however, due to the absence of existing monitoring data, the great variety
of lagoon sizes and types, the site-specific hydrogeologlc settings, and the high
cost of full field monitoring activities. Instead, the assessment employed a
2-1
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FIGURE 2-1
NATIONAL ASSESSMENT OF POTENTIAL
GROUND-WATER CONTAMINATION
MUNICIPAL LAGOON STUDY
Compile regional
hyarogBolagic
paranutere
Lqgoon stapling
data
I
1. Establish threshold concentration
at the exposure point
Compile rangBB of ancfal
irput
I
prcbl
Step 2
ZI
from
4. ColoulotQ
conoantrotion bond on Input
from SUpe 1 end 3
I
5. Repeat Steps 3 and 4 to
ganarate a number of
solutions far source
oanpsntrations
&
ccnDentraticn with actual
concentration
Hanto Carlo Binulatlcn
by conputer
-------
combination of limited field monitoring and computer simulation. This approach,
shown by Figure 2-1, depends upon the use of an effective pollutant migration
simulation model and the development of realistic lagoon scenarios for Input to the
model.
Initially, the assessment focused on the selection of a computer model.
Several models were Investigated and two were selected for testing by simulation
runs. One of these two models, the sophisticated Sandla Waste Isolation and
Flow Transport (SWIFT) model, requires site-specific data Including ground-water
monitoring data from a large number of lagoons representing specific hydrogeologlc
settings. It was rejected because of the small number of lagoons sampled and the
lack of reliable data from the few ground-water monitoring wells for calibration or
verification.
The selected model, EPACMS, allows the user to choose a human health-based
threshold at an exposure point (ground-water monitoring well) downgradient from
a municipal lagoon and back-calculate the corresponding maximum allowable source
concentration in the lagoon seepage. Since site-specific situations are unavail-
able, the hydrogeologle and geochemlcal parameters used 1n the model calculations
are generated from the range of values known to exist for certain hydrogeologic
regions. The EPACMS program then generates repeated hypothetical input data and
back-calculates corresponding source concentrations. This approach fits the
municipal lagoon study because only limited site-specific data were available for
the generation of the national assessment.
>
A data base of realistic lagoon scenarios was generated for the assessment.
Hydrogeologle data were compiled using a methodology to systematically evaluate the
relative vulnerability of ground water associated with hydrogeologic settings
located throughout the United States (previously developed by cooperative agreement
between the National Water Well Association and the USEPA's Robert S. Kerr Environ-
mental Research Laboratory). This methodology, designated by the acronym DRASTIC,
is a standardized system for the evaluation of ground-water contamination potential
based on available geologic data (1). DRASTIC divides the entire nation into 15
ground-water regions and subdivides each region Into typical hydrogeologlc settings.
The vulnerability of each hydrogeologlc setting to ground-water contamination is
Indexed by key factors controlling the migration of pollutants from the land sur-
face to the ground-water table. Without site-specific data, selected DRASTIC
parameters are necessarily the key Inputs for the lagoon scenario data base. In
addition, the lagoons within the national Inventory were located within the appro-
priate DRASTIC subdivisions. These subdivisions (and lagoons) were then recombined
Into "hydrogeologlc categories" to form the basis of the national assessment.
Results of the assessment could then, If desired, be referenced to the relative
numbers of lagoons within each hydrogeologlc category.
2.1.3 Selection of Target Exposure Point Concentrations
Before conducting the computer modelling and subsequent analysis, human health-
based thresholds were determined for use as target exposure point concentrations.
Two sources were used to Identify these thresholds; (1) Maximum Contaminant Levels
(MCLs) and Maximum Contaminant Level Goals (MCLGs) as promulgated by EPA; and (2)
for those compounds without MCLs or MCLGs, existing Information on acceptable chronic
exposure (noncarcinogens) and(potent1al Incremental carcinogenic risk (carcinogens).
These sources are discussed below.
2-3
-------
Under the authority of the Safe Drinking Water Act (SDNA), the EPA regulates
drinking water contaminants that may cause adverse health effects In humans and are
known or anticipated to occur In drinking water. Drinking water regulations con-
sist of two components. The first component Involves the establishment of a non-
enforceable health goal called a maximum contaminant level goal (MCLG). The MCLG
Is set at a level at which no known or anticipated adverse health effects will
occur and which allows an adequate margin of safety. If the contaminant Is class-
ified as a known or probable human carcinogen, the MCLG 1s set at zero. For non-
carcinogens the MCLG Is derived from the Reference Dose (RfD) for exposure 1nges-
tlon (formerly called an acceptable dally intake). The RfD represents an estimate
of a daily exposure that would not increase the risk of an adverse health effect.
The RfD is adjusted for a 70-kilogram adult consuming 2 liters of water daily.
The MCLG is derived from this value by multiplying by the known or estimated
percentage exposure from a drinking water source.
The second component of the drinking water regulations 1s called the Maximum
Contaminant Level (MCLs). The MCL is an enforceable standard and is set as close
to the MCLG as Is technologically and economically feasible. For noncarcinogens,
the MCL most often will equal the MCLG. For carcinogens, the MCL is set within
the 10-4 to 10-7 excess cancer risk range for that contaminant. EPA proposes
and promulgates both MCLs and MCLGs concurrently. As of July 1987, approximately
30 contaminants are regulated under the SDWA. A total of 83 contaminants are to
be regulated by June 19, 1989.
For contaminants without MCLs or MCLGs, human health-based thresholds used 1n
this study were estimated on the basis of RfDs (noncarcinogens) and an excess life-
time cancer risk of 10-6 (Group A and B carcinogens) or 10-5 (Group C carcinogens),
based on the Risk Specific Dose (RSD) for Ingestlon as developed from established
carcinogenic potency factors. As for MCLs and MCLGs, the RSDs and RfDs are adjusted
for a 70-kilogram adult consuming 2 liters of water daily. Unlike the MCLs/MCLGs,
the resulting concentrations were not adjusted for the expected percentage exposure
via the drinking water route. These alternate human health-based thresholds were
developed for the pollutants found in the lagoon characterization program, and used
for the selection of specific chemicals for modelling.
2.1.4 Preventive and Corrective Measures
Information on corrective and preventive measures for controlling ground-water
contamination from municipal lagoons was gathered and compiled for review.
Information sources Included a computerized literature search, EPA publications and
personnel, commercial vendors and State regulatory agencies. Available corrective
and preventive measures were grouped into three major areas: (1) design/construc-
tion techniques for new lagoons; (2) retrofitting techniques for existing lagoons;
and (3) cleanup activities following discovery of soil/ground-water contamination
from existing lagoons. Specific technologies and regulatory requirements 1n each
area are described in this report and references are Identified for additional
Information. EPA's Office of Research and Development has performed numerous
studies which document methods for preventing or controlling ground-water contamin-
ation from municipal wastewater lagoons.
2-4
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2.2 LIMITATIONS OF APPROACH
The approach for this study was developed based on the maximum utilization
of the available Information and resources. The assessment presented In this
report provides a general Indication of the concentrations and types of pollutants
found In municipal lagoons and an estimate of the potential, on a national basis,
for ground-water contamination due to pollutant releases through seepage from the
lagoons. The limitations of the data available and the study approach Itself
prevent Identification of any Individual lagoons as posing a threat to ground-water
resources. Furthermore, because of the data limitations, several conservative
assumptions are made which very likely overstate the threat posed to ground water.
Nonetheless, the methodology used In this national assessment defines those sets of
circumstances that create the greatest potential for ground-water contamination
from municipal lagoons. The information In the report, although generalized, Is
useful 1n the review or development of regulations and guidance for the management,
planning, design and construction of municipal lagoons and for planning more detail-
ed studies of lagoons and their Impacts on ground-water resources. The findings
and conclusions of the report and the Interpretation of the study results must
recognize a number of specific limitations Inherent In the approach developed for
the study. These limitations, briefly discussed 1n the following sections, and
their likely Impact on the results of the study should be thoroughly understood
before drawing conclusions from the study results.
2.2.1 Diversity of Lagoon Scenarios
Results of the Needs Survey and limited sampling program demonstrate the large
diversity of lagoon types, settings, locations, and wastewater treated. This
diversity, the large number of lagoons identified and lack of existing ground-water
monitoring data prevent estimation of the actual number of lagoons posing a threat
to ground water.
2.2.2 Data Limitations
The migration of specific pollutants to the ground water depends on site and
pollutant-specific hydrogeologlc and chemical parameters. The current understand-
ing of many of these Individual parameters and their Interactive effects 1s limited;
therefore, substantial verification of data Is needed. Unfortunately, the amount
and quality of available lagoon characterization or monitoring data are severely
limited (23 lagoons with wastes characterized and without valid ground-water data
compared with 5,476 lagoons nationwide). Therefore, all computer simulations use
generalized hydrogeologlc data and limited data on concentrations of pollutants
found in lagoons, without actual ground-water monitoring data for verification.
Although the computer simulation results represent the best available information
at this time for a nationwide assessment, reliable lagoon and ground-water data are
still needed for verification of the modelling results.
2-5
-------
2.2.3 Use of Computer Modelling
Both the data Inputs and the capabilities of the computer model limit the
validity of the modelling results. This study attempts to match the data limita-
tions with the sophistication of the model. EPACMS, although designed for a
generalized approach, allows the Incorporation of chemical reactions and the biolo-
gical decay of specific pollutants. Nonetheless, physical constants for some of
these reactions are yet unknown. In addition, the model omits chemical transfor-
mations known to occur for specific pollutants Investigated In this study. There-
fore, the study results are conservative; actual concentrations of pollutants 1n
the ground water may be significantly lower than those estimated.
2.2.4 Impact of Lagoon Seepage
Presently, the technical basis Is limited for determining pollutant migration
from lagoon seepage. The rate of seepage and migration of the pollutants depends
on the nature of the lagoon bottom, underlying hydrogeology, and the specific
pollutants. Actual data for comparison of pollutant concentrations In lagoons with
concentrations 1n seepage Immediately beneath a lagoon do not now exist. There-
fore, seepage concentrations were likely overestimated for the study.
2.2.5 Summary
A number of limitations Inherent In the study approach must be recognized and
Incorporated Into the Interpretation of data. These Include the generalization of
regional hydrogeologlc characteristics, the limited characterization/monitoring
data, the diversity of lagoon scenarios, computer limitations, and the unknown Impact
of lagoon seepage. Although the results of the study represent the best available
information at this time, actual site-specific data are needed for verification of
these results. As conservative assumptions have been made throughout the study, the
actual concentrations of contaminants In ground water and the resulting human health
Impacts may be significantly less than those Indicated herein.
2-6
-------
REFERENCES
CHAPTER 2
1. National Water Well Association (NWWA), 1985. DRASTIC: A Standardized System
for Evaluating Ground Water Pollution Potential Using Hydrogeologlc Settings,
EPA/600/2-85/018, National Technical Information Service, Springfield, VA.
2-7
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CHAPTER 3
LAGOON DESIGN, INVENTORY AND CHARACTERIZATION
This chapter presents an Inventory of the nation's POTW wastewater lagoons,
Including a review of State regulations and guidelines for their design, con-
struction and operation, as well as a description of such lagoons' wastewater
characteristics.
3.1 TYPES OF LAGOONS
Lagoons are classified by dominant type of biological reaction (1). The four
principal types are:
o Facultative (aerobic-anaerobic)
o Aerated
o Aerobic
o Anaeroblc
Appendix 3.1 (Table 3.1-1) summarizes design criteria and other Information
on the four types of lagoons.
3.1.1 Facultative Lagoons
Facultative lagoons, the most common type, treat wastewater by anaerobic
fermentation In the lower layer and aerobic stabilization In the upper layer. The
key treatment mechanisms comprise oxygen production by photosynthetlc algae and
surface reaeratlon. Aerobic bacteria use the oxygen to stabilize the organic
material 1n the upper layer.
Facultative lagoons are used to treat raw municipal wastewater (usually from
small communities) and also to treat primary or secondary effluent (for small or
large cities). The facultative lagoon Is the easiest to operate and maintain.
Large land areas are required to maintain lagoon biochemical oxygen demand (6005)
loadings In a suitable range. The lagoon's facultative treatment capability for
raw wastewater usually does not exceed secondary treatment.
3.1.2 Aerated Lagoons
In an aerated lagoon, oxygen for breakdown of pollutants Is supplied mainly
through mechanical or diffused air aeration rather than by photosynthesis and
surface reaeratlon. Many aerated lagoons are modifications of overloaded faculta-
tive lagoons that require aerator Installation to supply additional oxygen for
proper treatment performance. 8005 and suspended solids (SS) removal In facultative
lagoons can be Increased with sufficient aeration and mixing. Aerated lagoons
require less land than facultative lagoons.
3-1
-------
3.1.3 Aerobic Lagoons
Aerobic lagoons, much shallower than either facultative or aerated lagoons,
maintain dissolved oxygen throughout their entire depth. Oxygen, provided by
photosynthesis and surface reaeratlon, 1s used by bacteria to stabilize the
pollutants. Mixing 1s often provided to expose all algae to sunlight and to pre-
vent anaerobic conditions at the bottom of the lagoon. Use of aerobic lagoons Is
limited to warm, sunny climates where a high degree of BOD5 removal Is desired but
land area Is limited. Because of shallow lagoon depths, the bottoms of aerobic
lagoons must be paved or covered to prevent weed growth.
3.1.4 Anaerobic Lagoons
Anaerobic lagoons receive such a heavy organic loading that formation of an
aerobic zone Is prevented. The principal biological reactions comprise add forma-
tion and methane fermentation. Use of anaerobic lagoons Is limited principally to
treatment of strong Industrial and agricultural wastes, or to pretreatment where an
Industry contributes wastewater to a municipal system.
3.2 REGULATIONS AND GUIDELINES RELATED TO LAGOON DESIGN,
CONSTRUCTION AND OPERATION
This section reviews State regulations and guidelines related to the design,
construction and operation of municipal wastewater lagoons with emphasis on those
practices pertaining to ground-water protection.
Originally, design criteria for wastewater lagoons were relatively simple and
were directed toward retention times, depth, number of ponds, and loadings. In a
state-of-the-art review of waste treatment lagoons In 1971, the Missouri Basin
Engineering Health Council stated that most health departments have more detailed
design criteria (2). Another publication, "Recommended Standards for Sewage Works,
Great Lakes-Upper Mississippi River Board of State Sanitary Engineers," presents
typical design criteria that are employed by engineers In the design of wastewater
lagoons (3). EPA's Design Manual for Municipal Wastewater Stabilization Ponds
(1983) (4) describes technological advances and presents Information for engineers
and municipal officials on lagoon planning, design, construction and operation.
A survey of State requirements for ground-water protection, conducted for
the U.S. Army Cold Regions Research and Engineering Laboratory In the late 1970s
(5), was updated as part of this study. Appendix 3.1 (Table 3.1-2) summarizes
requirements concerning lining, seepage or permeability limitations, and ground-
water monitoring. Of the 50 States, 12 require liners, one (Rhode Island) does not
allow lagoons, 18 evaluate the need for lining lagoons on a case-by-case basis, and
19 have no specific lining requirements. Ground-water conditions affect decisions
on providing liners and monitoring programs. Appendix 3.1 ( Table 3.1-3) presents
expected seepage rates for selected liner materials.
3-2
-------
Seepage limitations vary substantially among States. Some States have no
requirements and others specify stringent permeability limitations, as low as 10~6
to 10-7 centimeters per second.
• Appendix.3.1 (Table 3.1-4) summarizes the general ground-water monitoring re-
quirements for each of the 50 States and also presents specific monitoring Infor-
mation for each State. In all, 18 States have some form of monitoring requirements
that can be applied on a case-by-case basis or that are required as standard prac-
tice. (Five additional States have set monitoring requirements for specific situa-
tions such as unlined lagoons). The minimum number of wells required for each
site, the sampling frequency, and the pollutants to be monitored vary widely among
the States.
In addition to requirements for ground-water monitoring wells, States have
established standards for the location of water supply wells with respect to
potential sources of pollution such as municipal lagoons. These requirements
vary widely and are dependent on a number of variables (e.g., the establishment of
whether the well Is a public or private water supply). Wells Installed prior to
siting regulations are often "grandfathered" and remain operative until closed on
an individual basis.
As can be seen from the above discussion, State requirements for the design,
construction and operation of municipal lagoons vary widely. In addition to the
actual regulations and guidelines, it Is likely that enforcement activities are
similarly varied.
3.3 INVENTORY OF LAGOONS
The source of data for the USEPA lagoon Inventory was the 1984 Needs Survey
data base (6). The Inventory comprises 5,476 municipal lagoons (Appendix 3.2)
of which 5,043 contain domestic wastes (domestic lagoons) from residential,
commercial and Institutional sources; and 433 contain wastes from Industrial as
well as domestic sources (domestic/Industrial, lagoons). Lagoons treat waste from
about 13 million (8 percent) of the about 170 million persons nationwide served by
municipal wastewater treatment systems. Figure 3-1 shows the location of the
nation's 5,476 municipal lagoons, while Figure 3-2 shows the 433 domestic/indus-
trial lagoons.
3.3.1 Domestic Lagoons
Domestic lagoons serve about 10 million persons or six percent of those served
by municipal treatment systems. Of the 5,043 domestic lagoons in the nation,
approximately 60 percent (3015 lagoons) are designed for flows of 0.1 mgd or less
and 95 percent (4,791 lagoons) are designed for flows of less than or equal to 0.6
mgd. The distribution of design flow rates for the total population of domestic
lagoons Is presented In Table 3-1. The average flow rate for the entire domestic
lagoon population Is 0.19 mgd; only two lagoons are designed for flows exceeding 10
mgd. To place this Information In perspective, using a per capital generation rate
of 100 gallons per day, a flow rate of 0.1 mgd corresponds to a population of
1,000, while 0.2 mgd corresponds to 2,000 people. Therefore, most lagoons serve
small municipalities.
3-3
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FIGURE 3-1
LOCATION OF MUNICIPAL LAGOONS BY STATE
I.'Ifc0.nl.Ul rfculCCIIOM ACUCI
STORE! SYSTEM
LAGOONS
IN tut UUIIEO
AUCUSI 14 I38/
rnojicnou - «
»*•*< V Mitt
-------
V
U1
FIGURE 3-2
LOCATION OF DOMESTIC/INDUSTRIAL LAGOONS BY STATE
UlllKMntlllU MOItCIIQll ACUCI
SIOREI SrSIEM
OOntSIIC 1 IMOUSIAIAI.
LAGOONS
IN lnt UNI ltl< SIAICS
JULI 21 i >jb/
fflOj£CIIUN • AlHiHS (UUAL ANlA
-------
The above flow information, converted to lagoon areas, can be used to estimate
the mass flux of contaminants into the underlying ground-water system (See Appendix
3.3). This mass flux (gram/year) depends on: (1) the concentration of pollutants
In lagoon seepage (gram/cubic meter); (2) the rate of seepage through the lagoon
bottom (meter/year); and (3) the total area through which seepage occurs (square
meters). Estimated lagoon areas based on known flow rates and assumptions regarding
lagoon dimensions and residence times are presented in Table 3-1, which shows that
the expected size of almost 90 percent of the nation's domestic lagoons is less
than 15.5 acres.
3.3.2 Domestic/Industrial Lagoons
In the nation, 433 domestic/Industrial lagoon systems receive various types
and quantities of Industrial wastewater as well as domestic wastewater. Domestic/
Industrial lagoons serve about 3 million persons or two percent of those served by
municipal treatment systems. Table 3-2 summarizes the domestic/Industrial lagoon
population by flow category and percent Industrial flow based on the data presented
In Appendix 3.2. (Also Included 1n Table 3-2 is a compilation of estimated lagoon
areas, based on the conversion presented in Appendix 3.3). The design flow rate for
the domestic/industrial lagoons averages 1.1 mgd. Sixty-six percent (286) of the
domestic/industrial lagoons have flows of 0.5 mgd or less, and 97 percent (419) have
flows less than or equal to 5.0 mgd. Only seven lagoons are designed for flows
greater than 10 mgd. Of the 433 domestic/Industrial lagoons, almost half (214)
have Industrial contributions of 20 percent or less; one-quarter (107) have an
industrial content varying from 21 to 40 percent.
3.4 GENERAL WASTEWATER CHARACTERISTICS OF LAGOONS
The nature and composition of the wastewater treated 1n a municipal lagoon
system depend upon Its source(s). In general, municipal wastewater can be divided
into four components (7):
o Domestic (sanitary) wastewater, including discharge from commercial and
institutional facilities as well as residences;
o Industrial wastewater;
o Infiltration and Inflow, defined as extraneous water entering the sewer
system from the ground and stormwater from roof leaders, foundation drains
and similar sources; and
o Stormwater (If storm sewers are not separate from sanitary sewers).
Traditionally, the pollutants contained in raw and treated sewage are measured
using parameters such as biochemical oxygen demand (BODs), chemical oxygen demand
(COD), dissolved oxygen, solids, nitrogen, phosphorus and grease. Typical values
of these parameters are provided 1n Appendix 3.4 (Table 3.4-1). The Clean Water
Act Amendments of 1977 directed EPA to study and periodically update a list of
toxic pollutants that have since become known as "priority toxic pollutants." The
current list of 126 priority pollutants (volatile organic compounds, acid extract-
able organic compounds, pestlcldes/PCBs, base/neutral extractable compounds, metals,
and miscellaneous compounds) 1s presented in Appendix 3.4, Table 3.4-2.
3-6
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TABLE 3-1
DOMESTIC LAGOON DISTRIBUTION
Flow
CateyoryK
(mgd) a>t>
-^— — — — — — i
< 0.100
0.101 T 0.200
0.201 - 0.300
0.301 - 0.400
0.401 - 0.500
0.501 - 0.600
0.601 - 0.700
0.701 - 0.800
0.801 - 0.900
0.901 - 1.000
1.001 - 1.500
1.501 - 2.0UO
2.001 - 3.000
3.001 - 4.000
4.001 - 5.000
5.001 -10.000
> 10. 000
— — ^— — — — _ .
•— ••—^•^
Area
(ac
^^^^^^^^^H
5.23
10.42
15.60
20.78
25.96
31.14
36 33
41.51
46.69
51.87
77.78
103.69
155.51
207.33
259.15
— M^^^M^^M
— — ^— ^— .
Category
PAC \ '
— »— ^_^___
< 05.18
~ 10.36
- 15.55
- 20.73
- 25.91
- 31.09
- 36.27
• 41.46
- 46.64
- 51.82
- 77.73
• 103.64
- 155.46
- 207.28
- 259.10
- 518.20
> 518.20
^— — _>i^__
•— — — — —
Number of
Category
— ^ — —
3,015
978
423
166
126
83
39
45
20
34
60
18
18
8
4
4
2
— — — —
— — •— .
Lagoons
Cumu-
lative
— — ^— ^-^™
3,015
3,993
4,416
4,582
4,708
4,791
4,830
4,875
4,895
4.929
4,989
5,007
5,025
5,033
4,037
5,041
5,043
— •— ^— ^— «___
Percent of
Category
i
59.8
19.4
8.4
3.3
2.5
1.6
0.8
0.9
0.4
0.7
1.2
0.4
0.4
0.2
0.1 '
0.1
— — — — — _ _
Total Lagoons
Cumu-
lative
— — - — — — - .
59.8
78.0
87.6
90.9
93.4
' 95.0
95.8
96.7
97.1
97.7
98.9
99.3
99.6
99.8
99.9
99. '9+
100.0
b Based on present design flow.
c Average flow - 0.19 mgd.
Based on
6 feet.
median hydraulic residence time of 102.5 days and median depth of
3-7
-------
TABLE 3-2
DOMESTIC/INDUSTRIAL LAGOON DISTRIBUTION
cnu7!,u / ,. Njmber of Lagoons Iniiuct-ri^i
Lateyoi y Area Category By ' HV —
(mgd) *.b (acres)C.a Category Percent Category
^•10° 15.18 85 20 0-20
21- 40
41- 60
61- 80
81-100
• bUU b. 23-25.91 201 45 Q- 20
21- 40
41- 60
61- 80
81-100
v.-u* i.uuu «.»o-3i.B2 bb lb &I"70
21- 40
41- 60
61- 80
81-100
21- 40
41- 60
61- 80
81-100
a.uui-AU.UUO 25y. 15-518.20 1 2 Q7~20
21- 40
41- 60
61- 80
81-100
>iu.uuu >ai8.i>0 7 2 6. 20
21- 40
41- 60
61- 80
81-100
Total 433 log
Contribution6
kimoer of
Lagoons
34
31
9
3
8
108
46
27
15
5
12
8
6
6
17
7
3
8
3
1
1
0
2
3
0
0
0
4
433
Based on present design total flow.
£ Average flow * 1.1 myd.
Based on median hydraulic residence time of 102.5 days and median depth of 6
The small discontinuities between the area categories are due to the effects
e of rounding on the flow-to-area conversion process.
i»S£a nn narran* /4<*e4/in 4 .«4..»* _J .1 *i .
on
— - - — - - •-' •» •• • ™^ v**1**^!^!^
design Industrial flow.
3-8
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A 1980 study (8) Identifies eight different household sources of one or more
priority pollutants and the product categories associated with each source (Appendix
3.4, Table 3.4-3). A survey of production and use information for these 126 priority
pollutants found that the most frequently used products containing the priority
pollutants are household cleaning agents and cosmetics. These products are used on a
daily basis and contain solvents and heavy metals as their main ingredients. Also
high in frequency of use are deodorizers and disinfectants which contain naphthalene,
phenol and chlorophenols. Products that are used and wasted less frequently (I.e.,
once a week at most) include pesticides, laundry products, paint products, polishes
and preservatives. Appendix 3.4 (Table 3.4-4) presents priority pollutants poten-
tially present in each of the eight household waste sources. Based on these data,
23 priority pollutants (14 organlcs and 9 metals) are identified as being commonly
present In domestic wastewater.
Appendix 3.4 (Table 3.4-4) shows that domestic wastewater sources contribute
priority pollutants to municipal lagoons. The concentrations of these pollutants,
either in absolute terms or relative to the concentrations in industrial wastewater,
vary depending on the time of day, week, or year (e.g., paint use Increases on
weekends, pesticide use in the summer). While these concentrations are usually
small, they may be significant In some cases; this significance should be defined on
an individual, site-by-slte basis.
3.5 SAMPLING OF INDIVIDUAL LAGOONS
3.5.1 Overview of Sampling Program
The objectives of the lagoon sampling program were: (1) to Identify pollu-
tants of concern for computer modelling; and (2) to obtain data to assess ground-
water contamination. The sampling program was conducted in two phases. The first
phase Involved 10 lagoon systems, selected because of the presence of ground-water
monitoring wells. Data from the first phase were expected to provide Information
on ground-water contamination by lagoons. Additionally, the data were to be used
to verify results of the computer modelling.
Because few lagoons have ground-water monitoring wells already Installed, the
selection of lagoon systems for sampling was not random, thus introducing bias into
the sampling program. Additionally, conditions at some of the 10 sites were not
suitable for assessing the extent of contamination due to lagoon operations. For
example, one lagoon system (Laramie, WY) was designed as a percolation pond system,
and "upgradlent" wells at other lagoon systems were located so close to the lagoon
that they would likely be Influenced by lagoon seepage. Consequently, the results
of the initial round of sampling were more suited to lagoon wastewater characteriza-
tion than to an assessment of ground-water contamination.
Recognizing the above limitations, a second phase of sampling was conducted to
gather more data. The eleven lagoon systems sampled 1n this phase were selected
primarily on the basis of their industrial waste content and diversity of location.
Data from two additional lagoon systems, located in Everett, WA and Muskegon, MI,
were obtained from other sources for use In this study.
3-9
-------
3.5.2 Lagoons Sampled
Selected facilities fn the domestic and domestic/Industrial lagoon categories
were visited and sampled for priority pollutants (except dloxln), barium, total
phenols and for selected non-conventional pollutants (total organic carbon, ammonia
nitrogen, oxidized nitrogen and chloride). The total number of facilities sampled
was 21, nine of which received only domestic (Including commercial and Institutional)
wastewater; 12 received a mixture of domestic and Industrial wastewater. In addi-
tion, data were obtained from Independent sources for two domestic/Industrial
lagoon systems located In Everett, VIA and Muskegon, MI (which were not part of the
sampling program). The Initial phase of sampling, conducted In August-November
1985, Included nine domestic lagoons and one domestic/Industrial lagoon (Mandan,
NO). The remaining 11 domestic/Industrial lagoons were sampled In July and August
of 1986.
The nine domestic lagoons sampled as part of this program vary In size from 4
to 717 acres, with design flow rates of 0.19-5.0 mgd (actual flow rates were slight-
ly lower). One lagoon 1s unllned; others have liners constructed of bentonlte,
compacted clay, or compacted earth. Specific Information on each of the domestic
lagoons Is presented 1n Table 3-3.
The domestic/Industrial lagoons sampled as part of this program vary In size
from 8.5 to 368 acres, with design flow rates of 0.19-42.0 mgd. Three of the
lagoons were being operated at rates above their design flow. All 12 lagoons
sampled have some sort of liner; the most common 1s compacted earth. One lagoon
system (Mlnong, WI) has a synthetic Hner. Specific Information on the 14 domestic/
Industrial lagoons (Including those at Everett and Muskegon) 1s presented In Table
3-4.
3.5.3 Sampling and Analytical Procedures
Samples taken at the domestic sites Included Influent, lagoon wastewater,
effluent, sludge and ground water. Based on the observed chemical similarity of the
lagoon wastewater with the effluent, lagoon wastewater was not sampled at the domes-
tic/Industrial sites. Therefore, the three types of samples taken at domestic/In-
dustrial facilities were Influent, effluent and sludge. The types of samples taken
at each lagoon are listed In Table 3-5. All samples were taken on a single day, as
extended periods of sampling were not possible. Consequently, variations with time
1n wastewater characteristics could not be determined.
Influent sampling used automatic composite samplers (composites varied from 6
to 24 hours) for all pollutants except volatile organlcs, cyanide and total phenols,
for which grab samples were taken. Lagoon wastewater, effluent, sludge and ground-
water samples were all taken on a grab basis. Further details on the lagoon sampl-
ing procedures are presented In Appendix 3.5. The methods and the quality assur-
ance/quality control procedures employed by the laboratories are discussed In
Appendix 3.5, as are the analytical pollutant detection limits.
3-10
-------
TABLE 3-3
DOMESTIC LAGOONS SAMPLED
Site
Honeybrook, PA
Britton Village. MI
Pottervllle, MI
Stand ish. MI
Mi not. NO
McVille. NO
Laramie. WV
Lander. UY
Buffalo. UY
Lagoon Type/
Discharge Mode
Facultative with tertiary
aeration; seasonal /con-
trolled discharge
Facultative; seasonal/
controlled discharge
Aerated/Facultative in
series; seasonal/con-
trolled discharge
Facultative; seasonal/
controlled discharge
Facultative; seasonal/
controlled discharge
Facultative; seasonal/
controlled discharge
Aerated lagoon with perco-
lation beds and under-
drain collection system
Aerated; continuous
discharge
Aerated; continuous
Hic/*hai»nA
Flow (mgd)
uesign Actual
0.6 0.28
0.19 Q.Q7
0.45 <0.45
0.30 0.20
(0.46 with I/I)
NA 3.5
NA 0.06
(estimate)
5.0 4.2
NA 2.0
NA 1.3
Liner
Double bentonite
Compacted earth
Compacted clay
Compacted clay
Compacted clay
None
Bentonite
Bentonite
Bentonite
i
Total
Acreage
9.5
19.9
45.2
32.6
717
4
54.9
70
35
-------
TABLE 3-4
HONESTIC/INDUSTRIAL LAGOONS SAMPLED
Facility
Hebron. IL
Dexter. MO
Atkins, AK
Hattiesburg. HS
Alexandria, LA
U endive. NT
Scottsbluff. N£
Ninong. Ml
Kidgecrest, CA
Nandan. NU
Andrews SC
Pickens. SC
Everett. HA
Huskegon. HI
a
Total Flow (mud)
Design
0.19
0.45
" 0.75*
11.6
14.0
1.3
3.1
0.3
4.4
0.96*
1.6*
0.6'
31. U
42.0
Actual
0.26
0.30
0.25
9.0
9.5
0.93
3.9
0.09
4.25
1.5
0.91
0.26
12.5
33.0
Percent
Industrial Total
Flow Acreage Lining Type
77
78
88
40
5
2
15
11
55
•3
29
75
5
70
10.3
31.7
48.0
368.0
53.5
70.2
128.0
11.3
216.0
28.4
17.0
8.5
230.0
172.4
Compacted earth
Compacted earth
Compacted earth
Compacted earth
Clay
Compacted earth
Compacted earth
PVC/bentonite clay
Compacted earth0
Compacted earth
Compacted earth
Compacted earth
Compacted earth
Cement/clay
Identified Industries
Nnat packing1', zu,c plater
Oil filter manufacturer. Automotive
exhaust system manufacturer metal
plater
Pickling1*, metal plating
Poultry processor, resin manufacturer
Mood preserver1*, industrial laundry.
aluminum
Soft drink bottling plant, dairy.
railroad yard
Neat packing6. Industrial laundry
Neat packing
Military base (commercial).
evaporative cooler return
Creamery, meat packing, bottling
plant
Textiles'1, wire products'*
Helal plating1*, textiles
Netal plating1*, metal fabricators'*
Pulp and paper plant1*, chemical and
pharmaceutical manufacturers6
"Pretrealment provided.
cSome ponds sealed with bentonite and soda ash.
-------
For all analyses, except the extractable organics, analytical detection limits
were similar for all three laboratories, generally In the 1 to 10 parts per billion
(ppb) range. However, detection limits for extractable organics fell Into two
distinct categories. Samples from 12 lagoons (9 domestic and 3 domestic/Indus-
trial) were analyzed at detection limits of 10-200 ug/1 (liquid samples) and 10-250
ug/g (sludge samples). The remaining nine lagoons, however, were analyzed down to
limits of 0.1-1.8 ug/1 (wastewater) and 0.001-0.16 ug/g (sludge). Although the
Individual analytical detection limits for the first group (made up primarily of
domestic lagoons) were found to be near the lower end of the ranges above, the
difference In limits complicates comparison of extractable organics results for the
two types of lagoons.
3.5.4 Results of Domestic Lagoon Sampling Program
A summary of the analytical results for the domestic lagoon sampling program
1s presented In Appendix 3.5 (Tables 3.5-1 and 3.5-2). Results for Individual
lagoons are also presented 1n Appendix 3.5. Before examining these data, 1t should
be noted that the hydraulic residence times of the lagoon systems vary from three
to over 180 days and thus Influent values are only a "snapshot" of conditions at a
given facility on the day of sampling. Therefore, those values may not represent
typical Influent quality and must be Interpreted with care. In contrast, the
lagoon wastewater, effluent and sludge concentrations are likely to provide a better
representation of steady-state, long-term conditions, notwithstanding their grab-
sample basis. (This conclusion Is based on the assumption that the lagoons are
relatively well-mixed and that lagoon sludge has accumulated over a long period of
time).
Thirty-five of the 126 priority pollutants were detected at the nine domestic
lagoons. Of the organics, 11 volatiles, eight base/neutral extractables, one acid
extractable, one pesticide, one PCB, and total phenols (not a priority pollutant)
were present 1n at least one sample. Twelve of the priority pollutant metals, barium
and cyanide were also detected. Sludge concentrations are on a wet-weight basis;
percent total solids were between 7.2 and 21 percent. The number of pollutants
detected by category and the number of lagoons In which one or more pollutants from
each pollutant category were found are presented In Table 3-6. The number of
lagoons In which one or more pollutants from each pollutant category were found Is
also shown In Table 3-6.
Based on results for all domestic sample types, barium and the following 17
priority pollutants were detected In more than 10 percent of the samples obtained
from the domestic lagoons:
o Benzene
o Chloroform
o Tetrachloroethylene
o Toluene
o Trlchloroethylene
o Phenol
3-13
-------
TABLE 3-b
LAGOON SAMPLING PQINTS
Wastewater
51 te Domestic
Honey brook, PA • x
Britton Village. MI x
Potterville. MI x
Standish, MI x
Mi not. ND x
McVille. ND x
Laramie, WY x
Lander, WY x
Buffalo. WY x
Mandan, ND
Hebron. IL
Dexter. MD
Atkins. AK
Hattiesburg. MS
Alexandria, LA
Gl endive. NT
Scottsbluff, ME
Minong. WI
Ridgecrest, CA
Andrews. SC
Pickens. SC
Everett, HAa
Muskegon. MID
a..
Composition
Domestic/
Industrial
x
x
x
X
Lagoon
Influent
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Sa
Lagoon
Effluent
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
X
X
X
X
mples Collected
Lagoon Monitoring —
Wastewater Wells
x
x
x
x
x
x
x
x
x
x
x
x
X
X
X
X
X
X
X
X
X
X
X
X
Lagoon
SI udge
— ^»— ».— «.
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
bHni cfn!^ " ParJ °^ th1s Study: data obtai»ed from Reference 9.
Not sampled as part of this study; data obtained from References 10. 11 and 12.
-------
o Arsenic
o Cadmium
o Chromium
o Copper
o Lead
o Mercury
o Nickel
o Selenium
o Silver
o Thai 11 urn
o Z1nc
Of the 18 pollutants, all but two (nickel and selenium) were present In 10
percent or more of the Influent samples. Organic pollutant concentrations were as
high as 280 ug/1 (toluene) and metals were found at levels up to 228 ug/1 (zinc).
Only four of the volatile organics were found In lagoon effluent along with six of
the metals, at concentrations up to 9.6 ug/1 (toluene) and 117 ug/1 (zinc), respec-
tively.
Results for monitoring well samples Included one of the above organlcs
(phenol at 4.8 ug/1) and seven of the metals. The two metals with the highest
concentrations were zinc at 10,600 ug/1, followed by lead at 740 ug/1. Nickel,
found In ground water, was not detected In either Influent or effluent samples.
This observation can be tentatively attributed to either of two causes: (1) pre-
sence of these three metals In lagoon sludge, accumulated from wastewater received
1n the past; or (2) a non-lagoon source. Given the occurrence of nickel and other
metals In the sludge (the highest being copper at 2,100 ug/g, barium at 1,482 ug/g
and lead at 574 ug/g) and the frequency with which they were detected (10 of the
above 12 metals were found In over 10 percent of the sludge samples taken), the
former premise Is more likely. Nonetheless, It Is not possible to attribute defini-
tive levels of these metals to contamination from the lagoons sampled. Although
the data compiled as part of the domestic lagoon sampling program Indicate the
possibility of contamination of ground water, several limitations must be placed on
Interpretation of these data:
o Because the monitoring wells were often located close to the lagoon, wells
designated as "upgradlent" may actually be affected by lagoon seepage;
o At least one lagoon (McVllle, ND); was located downgradient of a landfill
or other "non-lagoon" source; and
o "nowngradlent" wells were located too close to the site In most cases for
the analytical results to represent ground-water quality at water supply
wells, usually located further downgradlent. On the other hand, they were
not necessarily located close enough to represent actual seepage concentra-
tions.
3-15
-------
TA6LC 3-6
FREQUENCY OF OCCURRENCE BY SAMPLE TYPE: DOMESTIC LAGOONS
Pollutant
Category
Volatile Organics (28)d
Acid Extractable Organics (ll)d
Base/Neutral Extractable
Organics (46)°
PCBs/Pesticides (25)d
Metals (13)d'e
Cyanide, Total Phenols (2)d>f
»
Iacj
Infl
9
3
3
0
9
9
Number of Lagoons with Detectable Concentrations
of One or More Pollutants3
loon .
uentb
(9)
(1)
(5)
(0)
(9)
(1)
Lagoon .
Effluentb'c
5
1
2
1
7
6
(6)
(1)
(2)
(1)
(6)
(2)
Lagoon.
Sludge0
3
0
1
1
8
0
(2)
(0)
(3)
(1)
(11)
(0)
Monitoring
we MS
6 (8)
2 (1)
3 (5)
0 (0)
9 (10)
4 (1)
jj Out of a total of 9 domestic lagoons.
* "*
c
d Includes lagoon wastewater.
e f ? ! T°Jal.nuraber of priority pollutants tested in a given category.
f Excludes barium which is not a priority pollutant. 9 ""gory.
Total phenols" is not a priority pollutant parameter.
(or
-------
An overview of the sampling data Indicates that metals tended to accumulate In
the sludge layer, and were more likely to be found In ground water than were the
volatile organic compounds. In contrast, volatile organlcs were detected more
often In the effluent and less often In ground water.
To provide a point of reference for the sampling results discussed In this
section, Table 3-7 presents health risk thresholds based on available Maximum
Contaminant Levels (MCLs), risk specific dose (RSD) and reference dose (RfD) applic-
able to the pollutants detected in the nine domestic lagoons. A description of
those three thresholds Is provided In Chapter 2 of this report. Table 3-7 also
presents the number of domestic lagoons In which effluent or lagoon wastewater
concentrations exceed the thresholds.
3.5.5 Results of Domestic/Industrial Lagoon Sampling
Analytical results for the domestic/Industrial lagoon sampling program are
presented 1n Appendix 3.5 (Tables 3.5-3 and 3.5-4). Results for Individual lagoons
are also presented In Appendix 3.5.
Ninety-four of the 126 priority pollutants, barium and total phenols were
detected based on the data collected from the 14 domestic/Industrial lagoon systems
Including Muskegon, MI and Everett, MA (References 9, 10, 11 and 12). The number
of priority pollutants detected by category and the number of lagoons In which one
or more pollutants from each pollutant category were found are shown In Table 3-8.
This table Indicates that volatlles are the only pollutants consistently detected
more often In lagoon Influent than other types of samples. This result Is logical
because volatlles tend to diffuse to the atmosphere during treatment. Almost all
other pollutants are observed In lagoon effluent and sludge with the same frequency
as In the Influent.
The Information presented In Table 3-8 and Appendix 3.5 Indicates that Indivi-
dual pollutants were detected with much greater frequency and at higher concentra-
tions In domestic/Industrial lagoons than In domestic lagoons. A discussion of
the maximum concentrations found In domestic/Industrial Influent, effluent and
sludge Is presented below. Ground-water monitoring data are not presented, as 11 of
the 14 domestic/Industrial lagoons Included 1n this study did not have ground-water
monitoring wells Installed.
3.5.5.1 Domest1c/1ndustrlal Lagoon I nfluent. In general, maximum volatile organlcs
concentrations were on tne order or lu to 1,000 ug/1 In lagoon Influents. Toluene
was the highest at 1,964 ug/1, followed by chloroform at 747 ug/1, and
1, 2-d1chloroethane at 730 ug/1 (one sample). Maximum concentrations of add-
extractable organlcs were consistently on the order of 100 ug/1, except for
pentachlorophenol (828 ug/1) and 2-chlorophenol (742 ug/1). Maximum concentrations
for base/neutral extractable organlcs were somewhat lower, on the order of 10-100
ug/1, with minimum detected concentrations often less than 1 ug/1.
Maximum metals concentrations generally ranged from 10 to 100 ug/1. However,
zinc concentrations, the highest observed, varied from a minimum detected value of
155 ug/1 to a maximum of 4,670 ug/1.
3-17
-------
TABLE 3-7
SELECTED SAMPLING RESULTS vs HUMAN HEALTH-BASED THRESHOLDS: DOMESTIC LAGOONS
Pollutant Category/
Pollutant
VOLATILES
Benzene
Ethyl benzene
Chloroform
Bromodichl oroinethane
Tet rachl oroethy 1 ene
Toluene
1,1-Dichloroethane
1.1,1-Trichloroethane
Tricnl oroethy 1 ene
Methylene Chloride
Human
MCLa
d
100f
.9
.9
—
200
5
.9
Health-Based Thresholds (ug/1)
Other Threshold6
~e
Jj bOO
0431)
. 1JIJ
14e
14
0686
0 500e
2 840e
2.50
No. of Domestic Laaoons
Lagoon
MCL
0
^
trriuentj
Other
-
0
4
0
2
0
0
-
n
i i
with E*
MCL
0
-
0
-
-
-
-
0
0
1
ind Water
Other
•
—
0
1
0
1
0
0
-
-
EXTRACTABLE ORGAN1CS
Phenol
01 ethyl Phthalate
B1s(2-ethylhexyl)
Phthalate
1,4-Di chlorobenzene
1,2-Dichlorobenzene
3,<
455,000e
3.85
3.150*
0
0
0
0
0
1
-------
VO
TABLE 3-7. Continued
SELECTED SAMPLING RESULTS vs HUNAN HEALTH-BASED THRESHOLDS: DONESTIC LAGOONS
Pollutant Cateyory/
Pollutant
PCBS/PESTICIDES
Lindane (gamma-BHC)
NETALS
MCL*
Antimony
Arsenic
Barium11
Beryllium
Cadmium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Silver
Thallium
Zinc
.9
50
1,000
A
«•'
10
58
50
2
.9
10
.1
^
isholds (uy/1)
iresholtib
-
14e
-
17.2e
-
"t
1.3001
"
350e
-
. £
14*
7.3006
No. of Domestic Laaoons
Layoon
NCL
1
0
0
0
0
-
0
0
-
0
0
"
Effluent-1
Other
0
_
0
_
—
0
*
^
0
-
-
0
0
with Exceedanc@«c
NCL
••^•^^
0
0
0
0
o
3
o
1
0
(iround Water
Other
0
0
0
0
—
0
1
OTHER
Cyanide
_9
750'
-------
TABLE 3-7. Continued
SELECTED SAMPLING RESULTS vs HUMAN HEALTH-BASED THRESHOLDS: DOMESTIC LAGOONS
Pollutant Category/
Pollutant
Non-Conventional
Pollutants
N02/h03-Nh
'teS:
Maximum Contaminant Level.
Human Health-Based Thresholds (u9/l)
HCL
Other Threshold
10.000
No. of Domestic Lagoons w1th'Exceedancesc
Lagoon tffluentjGround Water
MCL Other MCL ' Other
f **»wwi \**l WU|* n UIIU I) %»QI C I IIUyi7ll3 J UP CIIC XL
dOjt of a total of nine domestic lagoons.
•iilIJBJlCit!S*MCL n0tnava1!jJ,l? ?r other tnresho^s not applicable to the study,
fBased on a Reference Dose (RfD) for noncarcinogens.
Total trihalomethanes (THMs) cannot exceed 100 ug/1. If other THMs are
hMCLs and MCLGs will be promulgated for these pollutants by June 1989
^ot a priority pollutant.
Maximum Contaminant Level Goal (MCLG).
JIncludes lagoon wastewater and lagoon effluent.
imit
-------
TABLE 3-8
FREQUENCY Of OCCURRENCE BY SAMPLE TYPE: DOMESTIC/INDUSTRIAL UGOONS
Pollutant
Cateyory
————
Volatile Organics (28)(
Acid Extractable Oryanlcs (11)d
Base/Neutral Extractable Organics (46)d
PCBs/Pesticides (25)d
Metals (13)d'e
Cyanide, Total Phenols (2)d*f
Ojt of a total of 14 domestic/industrial layoons.
nu"ber of
Number of Lagoons with Detectable Concentrations
of One or More Pollutants9
Lagoon Influent5 Lagoon Effluent5'0 Lagoon Sludge5
14 (23)
13 (11)
12 (43)
1 (1)
13 (13)
9 (2)
•
10 (19)
10 (10)
13 (38)
2 (2)
13 (13)
9 (2)
— • — '•
11 (15)
9 (11)
10 (41)
0 (0)
13 (13)
9 (2)
""ected 1. one or .ore Ia9oo,,s.
..
Total phenols' is not a priority pollutant parser.
-------
3.5.5.2 Domestic/Industrial Lagoon Effluent. Most volatile organics were found
In lagoon effluent at concentrations below 35 ug/1, with the exception of 1,2-
dlchloroethane (164 ug/1), methylene chloride (280 ug/1), and chloroform (86 ug/1).
Compared with lagoon Influent, add extractable organics concentrations decreased
to less than 100 ug/1 for all but three compounds (4-nltrophenol; 2,4-dlnltrophenol
and pentachlorophenol). Base/neutral extractable organics concentrations did not
decrease as much, although fewer compounds were found at levels exceeding 100 ug/1.
Overall, metals concentrations appeared to be slightly lower In the effluent
than In the Influent, although some metals were found to have higher effluent
concentrations. One extremely high observed value, 5,103.6 ug/1 for nickel, Is
likely erroneous; the next highest value for nickel Is 30.1 ug/1 (Appendix 3.5).
Table 3-9 shows the number of domestic/Industrial lagoons for which human
health-based thresholds were found to be exceeded by pollutant concentrations In
lagoon wastewater and effluent.
3.5.5.3 Domestic/Industrial Lagoon Sludge. As expected, maximum sludge concentra-
tions for non-volatile organics were much greater than those for volatile organics
(by two to four orders of magnitude). The two exceptions were toluene, with a max-
imum concentration of 3,330 ug/kg, and chlorobenzene, at 3,700 ug/kg.
Maximum metals concentrations were also high, varying up to 1,034 ug/g
(1,034,000 ug/kg) for copper and 1,176 ug/g (1,176,000 ug/kg) for zinc. Other
metals with maximum sludge concentrations exceeding 100 ug/g (100,000 ug/kg) In-
cluded barium, chromium, lead and nickel.
3.5.6 Comparison of Results from Domestic and Domestic/Industrial Lagoons
A greater number of pollutants was detected In the domestic/Industrial
lagoons than In the domestic lagoons. In particular, 44 of the 46 base/neutral
extractable organics were detected In the domestic/Industrial systems versus only
eight In the domestic systems. This Indicates the Impact of Industrial contribu-
tions on raw wastewater quality. Additionally, all classes of compounds, both
organics and metals, were detected at higher levels In the domestic/Industrial
lagoons.
A comparison of Tables 3-7 and 3-9 shows that effluent from the domestic/Indus-
trial lagoons has a greater number of pollutants with concentrations exceeding the
applicable human health thresholds than effluent from domestic lagoons. Of the
pollutants for which MCLs were available (see Tables 3-7 and 3-9), one or more were
found In concentrations exceeding their respective MCLs In one domestic lagoon and
seven domestic/Industrial lagoons. For those pollutants without MCLs, one or more
exceeded the health thresholds calculated on the basis of RSDs or RfDs in two
domestic lagoons (four lagoons If the RSD-based threshold for chloroform 1s used
Instead of the MCL for total trihalomethanes) and 12 domestic/Industrial lagoons.
3-22
-------
TABLE 3-9
SELECTED SAMPLING RESULTS vs
HUKAN HEALTH-BASEO THRESHOtOS: OOHESTK/^NOUSTRIAL LAGOONS
Pollutant Category/
Pollutant
Human Health-Basec
Thresholds (u
-------
TABLE 3-9 (continued)
U..MAM ur.,Tu DELECTED SAMPLING KESULTS vs
HUMAN HEALTH-BASED THRESHOLDS: DOMESTIC/INDUSTRIAL LAGOONS
Pollutant Category/
Pollutant
iman Health-Based
Thresholds (uq/1)
MCL*
Other .
Threshold0
Lagoons with Exceedances
l\ annnn C^tfl..__«. \ C
(Lagoon Effluent)
EXTRACTABLE ORGANIC (Continued)
Base Neutral (Continued)
n-Nltrosodirnethylamlne
n-N1trosod1phenylam1ne
3,3'-uichlorobenz1d1ne
Dimethyl Phthalate
Fluoranthene
Dl-n-butyl Phthalate
01 ethyl Phthalate
B1s(2-ethylhexyl)
Phthalate
1,2-Dichlorobenzene -9
l,4-D1chlorobenzene 75
2,4-Dlnltrotoluene
Isophorone
Nitrobenzene
Bis (2-chloroethyl)
Ether
Hexachlorobenzene
Hexachlorobutadlene
Hexachloroethane
PCBs/PESTICIDES
Llndane (gamma BHC)
UTHER
Cyanide
4
.9
0.00135
7.113
0.0207
350.0006
214e
45,500e
455,000e
3.85
3.1506
0.113
210
17.56
0.0307
0.0210
0.452
2.50
1
2
1
0
0
0
0
5
4
0
0
3
5
0
2
750h
METALS
Antimony
Arsenic
Barium1
Beryl 1lum
Cadmium
Chromium
.9
5U
1,000
10
50
14e
17.2e
1
0
0
0
1
V
0
3-24
-------
TABLE 3-9 (continued)
UOOOKS
Pollutant Category/
Pollutant
METALS (Continued)
PULLUTAN
- N
jman Health-Baset
Thresholds (ua/li
MCL*
Other .
Threshold
10,000
, o* Uumestic/Industrial
Lagoons with Exceedances
(Lagoon Effluent^
Copper
Lead
Mercury
Nickel
Selenium
Silver
Thallium
Zinc
NON-CONVENTIONAL
.9
50
10
• w
!8
-
l,300h
350e
-e
7,300e
.
0
0
6
0
.
0
.
1
1
0
Notes:
^Maximum contaminant level.
and
" domest1e/t"''u«'-1«l '«9«««s (Includes U9oon «st.water
"* ava1"bl« » """• thresholds not 4ppl1c.ble to the
(RfD) for "oneare1no9ens
Not a priority pollutant.
these ponutints
3-25
-------
Table 3-10 presents a general comparison of influent concentration ranges for
the organic priority pollutants plus TOC detected In the domestic and domestic/Indus-
trial lagoon systems studied. This comparison shows that domestic/industrial raw
wastewater contains higher concentrations of these organic pollutants than the
domestic lagoons; maximum values of volatile organlcs In the domestic/Industrial
lagoons are approximately an order of magnitude higher, confirming the validity of
developing two data bases for the national assessment. The same trend appears to
hold true for extractable organlcs, although any comparison should take Into account
the difference in detection limits between the nine domestic lagoons and three of
the domestic/Industrial lagoons, and the remaining domestic/Industrial lagoons.
A comparison of lagoon effluent concentration ranges for the organic pollutants
1s shown in Table 3-11. These data Indicate higher effluent organic concentrations
for the domestic/Industrial lagoons than for the domestic lagoons.
3.5.7 Findings and Conclusions
o Based on the 1984 Needs Survey, the Nation has 5,476 municipal wastewater
treatment lagoons of which about one-third are in the 12 Midwestern States.
o About 57 percent of the municipal lagoons treat wastewater flows of less
than 0.1 million gallons per day (mgd), or a population equivalent of
roughly 1000 persons, and only 4 percent handle flows over 1.0 mgd.
o 18 States require ground-water monitoring wells for lagoons under certain
specific circumstances or based upon a case-by-case evaluation of their
need. Five additional States require monitoring under specific conditions
(e.g., unlined lagoon). Few municipal lagoons have monitoring wells and
those few wells are not properly located to detect ground-water contami-
nation.
o 12 States require linings for all lagoons, 18 States require linings as
necessary to meet either State permeability criteria or case-by-case
demonstration of need, 19 States have no specific lining requirements,
and one State does not allow lagoons. Most municipal lagoons have linings
of various types Including compacted earth or clayey soils existing at the
site.
\
o Seepage from lagoons, particularly those without linings, is difficult to
predict or measure , even with costly soils tests.
o Of the nine domestic lagoons sampled, eight have earthen, clay or synthetic
linings; all 12 domestic/Industrial lagoons sampled have similar linings.
o Of the 5,476 municipal lagoons, 5,043 treat only domestic wastewater; the
remainder treat combined domestic/Industrial wastes.
o Based on a survey of commonly used household products, of EPA's 126
priority toxic pollutants, 23 (14 organlcs and nine metals) from eight
household waste sources are commonly found in domestic wastewater.
3-26
-------
TABLE 3-10
COMPAQ ^CONCENTRATION
Pollutant Category
omestic/industrial Lagoons
Volatile Organics
Total Phenols3
Add Extractable
Organics
Base/Neutral
Extractable Organics
3.5 - 61
Not a priority pollutant parameter
- 828
3-27
-------
TABLE 3-11
COMPARISON OF EFFLUENT CONCENTRATION RANGES
FOR ORGANIC POLLUTANTS
_ Effluent Concentration Range fug/1
Pollutant Category Domestic Lagoons
Volatile Organics
-------
o 35 of the priority pollutants were detected at one or more of the nine
domestic lagoons sampled and 94 of the priority pollutants, generally
with higher concentrations, were detected at several of the 14 domestic/
Industrial lagoons Investigated. Priority pollutant concentrations, except
for volatile organic compounds, were generally found to be one or more
orders of magnitude greater In the sludge than In the effluent.
o The median effluent concentrations for the pollutants of concern were
very low for all of the lagoons sampled; few of the pollutants had median
values above their human health-based threshold concentrations and, In some
cases, the median concentrations were lower than analytical detection
limits.
o Of the pollutants for which MCLs were available, some were found In concen-
trations exceeding their respective MCLs 1n one domestic lagoon and seven
domestic/Industrial lagoons.
o Of those pollutants for which MCLs were not available, some exceeded the
non-MCL health thresholds In two domestic lagoons (four lagoons If the
RSD-based threshold for chloroform Is used Instead of the MCL for total
trfhalomethanes) and 12 domestic/Industrial lagoons.
o Samples were taken at ground-water monitoring wells for the nine domestic
- lagoons and for the few domestic/Industrial lagoons with ground-water
monitoring wells. No definitive conclusions can be reached as to the degree
of ground-water contamination actually caused by any of the lagoons sampled
because: (1) most of the domestic/Industrial lagoons lacked ground-water
monitoring wells; (2) lagoon seepage likely affected data for the upgradient
wells due to their proximity; and (3) the proximity of most down gradient
wells did not provide an adequate and reliable representation of actual
aquifer contamination at probable exposure points.
3-29
-------
CHAPTER 3 REFERENCES
1. Kumar, J. and Jedllcka, J.A., 1973. "Selecting and Installing Synthethlc Pond
Liners." Chemical Engineering. 80(3): 67-70.
2. Missouri Basin Engineering Health Council, 1971. Waste Treatment Lagoons
-State of the Art. Water Pollution Control Research Series.
3. Great Lakes—Upper Mississippi River Board of State Sanitary Engineers, 1978.
Recommended Standards for Sewage Works. Health Education Service.
4. U.S. Environmental Protection Agency, 1983. Design Manual, Municipal Waste-
water Stabilization Ponds. EPA-625/1-830-15.
5. Middlebrooks and Associates, 1978. Wastewater Stabilization Pond Linings.
Prepared for the U.S. Army Cold Regions Research and Engineering Laboratory.
Reprinted by EPA. MCO-54. November 1978.
6. USEPA. 1984 Needs Survey.
7. Metcalf & Eddy, Inc. 1979. Wastewater Engineering; Treatment/Disposal/ Reuse,
Second Edition. McGraw-Hill, New York, New York.
8. Hathaway S.W., 1980. Sources of Toxic Compounds in Household Wastewater. USEPA,
Office of Research and Development, Municipal Environmental Research Laboratory,
Cincinnati, Ohio.
9. Personal Communication. City of Everett, Washington, 1986.
10. Frykberg, W.R., C. Goodnight, and P.G. Meier, 1977. "Muskegon, Michigan Indus-
trial-Municipal Wastewater Storage Lagoons: Biota and Environment." EPA-600/
3-77-039.
11. Muskegon County Wastewater Management System, May 1977. Preliminary Survey of
Toxic Pollutants at the Muskegon Wastewater Management System.
12. Muskegon County Wastewater Management System, 1983. Fate of Organic Pollu-
tants In a Wastewater Land Treatment System Using Lagoon impoundment ana spray
Irrigation^
3-30
-------
CHAPTER 4
RESULTS OF ASSESSMENT OF POTENTIAL GROUND-WATER IMPACTS
As described In Chapter 2, the approach selected for the national assessment
requires three categories of basic Information: (1) lagoon waste characterization
data (Chapter 3); (2) selection of pollutants and their human health-based thres-
hold concentrations to serve as maximum concentration limits at the exposure
point; and (3) hydrogeologic, geochemlcal and other parameters required for the
EPACMS Monte Carlo simulation. Appendices 4.1. 4.2 and 4.3 contain detailed
discussions of the methodologies for Items (2) and (3).
4.1 MODEL OUTPUT
The Input data for each of the 63 scenarios (seven pollutants In nine hydro-
geologic categories) Is included as Appendix 4.4, and the results of the computer
runs are Included as Appendices 4.5 and 4.6. These results are presented in two
forms: dimension!ess concentrations and target lagoon seepage concentrations.
The initial output of EPACMS is in the form of a dimensionless concentration,
defined as:
CD a CM
^nr
where
CQ » dimensionless concentration
CH = concentration in the well (i.e., at the exposure point)
= concentration in lagoon seepage (i.e., at the source).
If either C|c or Cy Is defined, and CQ 1s calculated by the model for a given
set of input conditions (e.g., lagoon seepage rate, particle diameter, hydraulic
gradient, etc.), the above equation will produce values of Cy or CL$. respectively.
The values of CLS are based on maximum permissible well concentrations as defined
in Chapter 2 (i.e., human health-based threshold concentrations).
4.2 LIMITATIONS OF COMPUTER RUN RESULTS
Any interpretation of computer run results must recognize the limitations
inherent in the approach. These limitations can be divided into four types: (1)
the state-of-the-art of computer modelling in general and the EPACMS code in
particular ; (2) the assumptions concerning selection of input data applicable to
the wide variety of lagoons and hydrogeologic regimes found in the United States;
(3) operational constraints; and (4) use and interpretation of model output.
4-1
-------
4.2.1 Computer Modelling and EPACMS
In general, computer modelling to estimate environmental Impacts attempts to
enable prediction of the effects (e.g., pollutant concentrations) likely to occur
as a result of certain specified conditions. Because It Is difficult to fully char-
acterize the complex Interactions occurring 1n nature (e.g., degradation, metal
spedatlon, etc.), any model, no matter how complex, Is a simplification of the world
as It exists - a "best estimate." Therefore, whenever possible, modelling results
should be compared with actual monitoring data to verify the accuracy of the model,
its Input data or both.
Unfortunately, the verification process for surface media (air, surface water)
is simpler than that for ground water. Due to its great heterogeneity, the subsur-
face regime is extremely difficult to model, requiring the introduction of numerous
assumptions (e.g., homogeneous media, absence of faults or other geologic phenomena,
absence of confining layers, etc.). Once a model has been developed on the basis
of these or similar assumptions and results for a specific site have been obtained,
the verification process can be laborious due to the difficulty and expense encount-
ered in obtaining data adequate in both number and quality for the subsurface
regime.
In addition to the general problem of model verification, other issues include:
(1) the assumption of steady-state conditions for this application (the model is
not yet capable of addressing conditions of fully transient flow); (2) the exclusion
of aerobic blodegradatlon from the model; and (3) the developmental nature of por-
tions of the model.
The limitation of steady-state conditions has one major effect on this assess-
ment: it Is not possible to ascertain the time required, under a given set of
hydrogeologic conditions, for a particular pollutant to reach the exposure point(s).
That particular question may be suitable for further study at a later date.
The exclusion of aerobic blodegradatlon from EPACMS resulted from the diffi-
culty of modelling aerobic conditions (e.g., oxygen transfer) In the subsurface
environment. For those pollutants known to undergo aerobic blodegradation, this
exclusion will result In overestimatlon of a pollutant's concentration as It reaches
the saturated zone.
The third Issue, the model's developmental nature, is best illustrated by the
model's omission of metal spedatlon in the aqueous subsurface environment. These
processes can be quite Important under certain conditions, and their exclusion from
this assessment can result in the generation of conservative (I.e., high) values
of CQ for arsenic or any other metals specifically assessed. (A high value of CD
reflects a lower amount of dilution, transformation or degradation for a given pollu-
tant, and thus a higher concentration at the exposure point.) One computer program
for metal spedatlon, MINTEQ, 1s expected to be available soon.
4.2.2 Input Data
As presented In Appendix 4.1, several assumptions were made regarding numerous
site-specific variables, including lagoon characteristics, site hydrogeology, and
populations surrounding the lagoons. These assumptions Include:
4-2
-------
o Lagoon areas were estimated on the basis of flow data;
o The distance to the nearest exposure point was based on 220 (4 percent)
of the national total'of 5,476 lagoons;
o Lagoon seepage rates were estimated on the basis of State regulations,
mass balance considerations, and limited field data from other sources;
o Chemical constants, particularly hydrolysis and blodegradatlon, were not
available for all pollutants. Consequently the CQ values calculated by
the model are conservative (I.e., high) showing only the effects of di-
lution for certain pollutants (e.g., arsenic); and
o Kydrogeologlc parameters were compiled on the basis of expected regional
characteristics. Such a compilation over-simplifies a region's hydro-
geologic diversity.
The above limitations apply primarily to the saturated zone. The unsaturat-
ed zone, Included as an option 1n EPACMS, was not used In the study. Although
significant biological and chemical degradation can occur In the unsaturated
zone, rate constants for these reactions, particularly biodegradatlon, were not
available for most pollutants. Therefore, the unsaturated zone and Its effects
were omitted.
The necessary assumptions and estimates concerning Input data affect the
accuracy of the model. Since those assumptions are conservative, the Cn values
generated by the model are likely to be higher than Is actually the case, while the
resulting CLS concentrations are likely to be lower.
4.2.3 Use of EPACMS Results
Using the model output (a distribution of dimension!ess concentration,
CQ), for a given chemical and set of Input parameters, a target pollutant source
concentration can be determined If the maximum permissible well concentration, Cy,
Is known. This source concentration represents the concentration In the lagoon
seepage, not necessarily the lagoon wastewater (or lagoon effluent, assuming a
fully-mlxeinagoon). Therefore, a procedure must be developed to correlate the
calculated target seepage concentration for a pollutant with Its lagoon effluent
concentration.
The above exercise 1s difficult for a specific lagoon without actual data to
develop a correlation. With the wide variety of lagoons, liners, and sludge
'layers (especially the thickness and chemical/biological characteristics of the
sludge layers In the many lagoons), a generic relationship cannot be developed to
describe physical, chemical and biological attenuation across the sludge layer,
the lagoon liner or both. Therefore, this study assumes that lagoon effluent
resembles lagoon seepage, a conservative assumption.
4-3
-------
4.3 DISCUSSION OF RESULTS: DIMENSIONLESS CONCENTRATIONS
The results of EPACMS Run No. 2 are presented In Figure 4-1 (results for all
other runs, except nitrate, are presented In Appendix 4.5). This graph shows
the distribution of dimension! ess concentration (CD) values for hexachloro-
benzene In Hydrogeologlc Category 4.
The Interpretation of Figure 4-1 begins with the selection of a cumulative
frequency level of Interest. A cumulative frequency level of 85 percent provides
a reasonable representation of variation. Reading from the graph In Figure 4.1,
this value corresponds to a Cn of 0.43. This observation means that, In 85 per-
cent of the possible situations encountered In Hydrogeologlc Category 4, CQ
values will be less than or equal to 0.43. Using the relationship between CD, Cw
and CLS as defined In Section 4.1, this statement can be expressed algebraically
as:
C < 0.43
This relationship shows that hexachlorobenzene concentrations at typical exposure
points will be less than or equal to 43 percent of the lagoon seepage concentra-
tions in 85 percent of the situations encountered. CD values for hexachlorobenzene
and six other selected chemicals In the nine hydrogeologlc categories are presented
in Table 4-1. In general, these results fit within three pollutant groups, each
discussed below.
4.3.1 Pollutants Undergoing Neither Hydrolysis nor Biodegradation
Five pollutants (hexachlorobenzene; tetrachloroethylene; benzene; 2,4-dl-
nitrotoluene and arsenic) are included in this group. Because the model pre-
dicts steady-state, long-term conditions, retardation (as based on KQC and other
factors) does not affect the value of CD 1n the absence of other degradation
reactions (e.g., hydrolysis). Therefore, any attenuation that occurs can be
viewed as due to purely physical factors, which can be loosely described as
"dilution11.
The overall trend apparent from Table 4-1 regarding these five pollutants Is
that of Increasing dilution (i.e., lower CD) with Increasing velocity (see Appen-
dix 4.1, Table 4.1-7). For example, Hydrogeologlc Categories 3 and 4 have the
highest estimated velocities and the lowest Cn values. This trend Is modified
somewhat by other variables such as aquifer thickness and infiltration, both of
which affect the volume of ground water passing underneath and downgradient of
the lagoon. Changes in these variables thus change the degree of dilution of
the pollutants as they enter and are transported through the saturated zone. If
the model were run in a transient mode, differences in contaminant arrival times
due to velocity differences and retardation phenomena would also become apparent.
4.3.2 Pollutants Undergoing Hydrolysis but not Biodegradation
Only one pollutant, chloroform, belongs to this group. Table 4-1 shows that
results for chloroform follow the same pattern with respect to dilution as the
five pollutants above. Comparison of CD values for chloroform with CD values for
4-4
-------
I1BMS
o.o-
FIGURE 4-1
EPACMS RUN No. 2 ( CQ )
HEXACHLOROBENZENE - SATURATED ZONE ONLY
500 ITERATIONS - HYDROGEOLOGIC CATEGORY 4
CQ< 0.43
0.0 0.1
"~i—•—i—'—r
0.2 0.3 0.4
-T—i—|—i—,—
0.5 0.6 0.7
0.8
DIMENSIONLESS CONCENTRATION
JUNE 24, 1987
-------
TAULE 4-1
MODEL RESULTS: OlMENMONLESs' CONCLNTKAMUNS
I
Chemical
Chloroforn
Hexddilorobenzene
Tetrachloroethylene
Beiuene
2,4-Uinitrotoluene
Arsenic
Nitrate0
*•
1
0.70
0.73
0.73
0.73
0./3
0.73
2.59xlO'15
t Value at 851
2
0.77
0.82
0.82
0.82
0.82
0.82
2.09xlO~21
Cumulative
3
0.54
0.55
0.55
0.55
0.55
0.55
4.83xIO'U
Frequency Level
4
0.42
0.43
0.43
0.43
0.43
0.43
9.66xlO'13
for H/droyeolouic Catf
5
0.62
0.66
0.66
0.66
0.66
0.66
2.16X10'1'
—
6
~—
yones 1 through 'jd'h •
/ ti .
O.MO 0.76 0.73
0.87 0.84 0.75
0.87 0.84 0.75
0.8' 0.84 0.75
U.87 0.84 0.75
U-87 0.84 0.75
8.06xlO-4S 4.08xlO-50 3.47xUT13
9
0.75
0.80
0.80
O.tiO
0.80
0.80
3.97xlO"34
cu-e to l,.Us «,
„, SUl,sHM| d«,. .unto
,,,
„«,.
-------
the pollutants discussed 1n Section 4.3.1 shows a slight decrease 1n CD for
chloroform within a given hydrogeol ogl c category. (As expected, hydrolysis
Increases attenuation).
4.3.3 Pollutants Undergoing Blodegradatlon but not Hydrolysis
%
Only one pollutant, nitrate, belongs to this group. The blodegradation
rate constant, 3.2 x 10-6 second-1, corresponds to a half-life of 2.5 days
(0.0069 years). This rate Is quite rapid, and would be expected to result In
significant attenuation. That expectation was verified; In fact, the resulting
CD values were so low and covered such a wide range that they could not be dis-
played 1n graphical form (and thus no graphs are Included In Appendix 4.5).
Consequently the CD values corresponding to an 85% frequency of occurrence could
not be read as for the other pollutants; Instead, CD values for the 90* value
(explicitly calculated by the available statistics program) are shown.
The Interesting point to note for these nine runs was an approximate reorder-
ing of the hydrogeol ogle categories with respect to Increasing dilution.
For example, Categories 3 and 4, with the greatest degree of dilution due to
purely hydrogeol ogle factors (see Section 4.3.1) exhibited the highest CD
values for nitrate. This reversal Is due to the fact that blodegradation Is
modelled as a first-order reaction, dependent upon the Initial concentration of
the contaminant present In the aquifer. Therefore, the greater the degree of
dilution by hydraulic phenomena, the lower the Initial concentration (see Section
4.3.1), and thus the lower the degree of blodegradation.
4.4 DISCUSSION OF RESULTS: LAGOON SEEPAGE CONCENTRATIONS
The results of the computer runs as presented above were expressed In terms
of C0, a dimension! ess concentration. To determine target lagoon (seepage)
concentrations corresponding to a given maximum exposure point concentration,
the CD values must be transformed using the relationship between CD* Cu and CL$
discussed above. This transformation (where the values for CM are the human
health-based threshold concentrations presented In Tables 3-7 and 3-9 for the
seven chemicals being modelled), coupled with a rearrangement of the statistical
presentation, results In distributions such as that shown for hexachl orobenzene
In Figure 4-2.
The Interpretation of these results differs from that of Figure 4-1. To
find a target lagoon seepage concentration that will not result In exposure point
exceedances more than 85% of the time, It Is necessary to read the Ci_s value cor-
responding to 15 percent (I.e., 1.00-0.85 = 0.15). For example, the Ci$ corre-
sponding to 15% on Figure 4-2 Is 4.88 x 10-5 mg/l (4.88 x 10-? ug/1). This obser-
vation means that, of all possible situations encountered 1n Hydrogeol ogle Cate-
gory 4, only 15% will result In an exceedence of the exposure point threshold
(for hexachl orobenzene) of 2.1 x 10-2 ug/1, If the lagoon seepage concentration
Is less than or equal to 4.88 x 10-2 ug/1. This statement corresponds to an 85%
probability that the exposure point concentration will not be exceeded If:
CLS £4.88 x lO- ug/1.
4-7
-------
FIGURE 4-2
EPACMSRUNNo. 2(CLS)
HEXACHLOROBENZENE - SATURATED ZONE ONLY
500 ITERATIONS - HYDROGEOLOGIC CATEGORY 4
T 1 r
O.OE-4 0.5E-4 l.OE-4 1.5E-4 2.0E-4 2.5E-4
TARGET LAGOON SEEPAGE CONCENTRATION (mg/l)
r
3.0E-4
JUNE 23. 1987 |
-------
The corresponding C|_s values for other categories and pollutants are pre-
sented 1n Table 4-2. These values are determined using on the human health-based
thresholds discussed 1n Chapter 2.
\
Three of the seven pollutants modelled (benzene, arsenic and nitrate) had MCLs
available for use as exposure point concentrations (Cw). Three other pollutants
(hexachlorobenzene, tetrachloroethylene, and 2, 4-d1n1trotoluene) did not have
MCLs, and RSD-based concentrations are used as the exposure point values. The
seventh chemical (chloroform), Is part of a group of pollutants, tribalomethanes
(THMs), for which an MCL of 100 ug/1 has been established. (Thus, If other THMs
are present, the allowable chloroform concentration would be proportionally
reduced). Because this MCL Includes several pollutants, not just chloroform,
the RSD-based concentration specific to chloroform Is also presented.
Of the four modelled pollutants for which MCLs were available (Including
chloroform/THMs), none were found In domestic lagoons at levels exceeding the
computed target lagoon concentrations (based In a 10~6 Incremental cancer risk).
Two of the pollutants (arsenic and benzene) were found In concentrations above
target levels 1n domestic/Industrial lagoons; four of the 14 lagoons had concen-
trations of one or the other of these two pollutants In excess of the target
levels. Modelling results for the remaining three pollutants without MCLS and
chloroform were compared to lagoon concentrations on the basis of RSD-der1ved
exposure point concentrations. Two of these compounds (tetrachloroethylene and
chloroform) were found above target levels In domestic lagoons; while all four
were above the completed CL$ values In domestic/Industrial lagoons. Exceedances
of the RSD-based target levels for one or more pollutants were observed In four
domestic and nine domestic/Industrial lagoons.
Tables 4-3 and 4-4 show the variation with hydrogeologlc category of the
number of domestic and domestic/Industrial lagoons, respectively, with pollutant
concentrations above the target levels. This variation Is minimal for domestic
lagoons (Table 4-3) with only one pollutant (tetrachloroethylene) showing fewer
affected lagoons for locations with the characteristics of Hydrogeologlc Cate-
gories 3 and 4 (high ground-water velocity). For domestic/Industrial lagoons
(Table 4-4), benzene and arsenic target concentrations are exceeded In fewer
lagoons In the same two hydrogeologlc categories.
4.5 INTERPRETATION OF RESULTS
i
In this study, limited lagoon sampling data were compared with the results
of a computer modelling exercise to determine whether lagoon concentrations
exceeded target levels for seven pollutants 1n nine hydrogeologlc regimes.
(These target lagoon concentrations, generated by the computer model, were pre-
dicated on selected human health-based threshold concentrations at a down-
gradient exposure point). Interpretation and application of study results should
be made with care, for several reasons.
First, the results of the computer modelling exercise are likely to be con-
servative, given the numerous conservative assumptions required. Second, the
selection of lagoon effluent data to represent lagoon seepage concentrations Is
also a conservative assumption. Finally, the data obtained during the lagoon
sampling program are very limited and certainly do not represent a valid statls-
4-9
-------
««L KSUUS:
TABLE 4-2
TARGET LAGOON SLIHAGE CONCENTRATIONS BASED ON HUMAN
Chenical
•
lagoon St>epayi> Concentrations. Clf
»l) for llydroqcologlc CategorieslSt'hroti.fh 9 (..cf/if.l.
Chloroform0
MCLd ,43
Other Threshold6 6.14x10''
Hexachlorobenzcne
MCL
Other Threshold
Tetrachloroethylene
MCL
Other Threshold 9.26x10''
Benzene
MCL 6.jj5
Other Threshold
2.4-Uinltrotoluene
MCL
Other Threshold 1.55x10"'
Arsenic
"CI- 68.5
Other Threshold
"Liu'1
238
I.U2
161 125 IIP
6.94x10-' 5.3UX.O'' ^x.O'' "J,.,,,.. ^^
2.B8X10'2 2.56,10"2 3.82xlO'Z 4".88xlO'2
S.IB.IO" 2.4U10'2 2.bOx.O-2 2.aOxlO'2 2.63xlO'2
8.24x10'' 1.23
6.10 9.09
i.38xlO'! 2.05x10''
1.5' 1.02
H.63 7.58
,-1
/. 77x10'' 8.05x10'' 9.01x10'' 8.45x10''
5'75 5-« 6.67
6.25
61.0
90.9
2.63x10"' 1.71x10'' ,.30x10"' K35xl0-' i.5u,o'' 1.
»>6.0 75.8 57.5
59.5
66.7
62.5
- --• «•- " - «-»- — .
Contaminant Lovel (cnf orr ,-able standard).
,Cireio0!lcos).
-------
IAULE 4-3
Hydrogeologic Category
0
4
_e
U
2
0
0
4
0
2
0
0
4
0
1
0
U
4
0
U
0
0
4
0
2
0
0
4
0
2
0
0
4
U
2
0
0
4
0
2
0
0
4
0
2
0
U
U
Hexachlorobeiuene
MCL
Other Threshold
Tctrachloroethylene
MCL
Other Threshold
Beniene
MCL
Other Threshold
2.4-Dinltrotoluene
NIL
Other Threshold
Arsenic
MCL
Nitrate
MCL
*Fro» a sample population of nine domestic lagoons.
^Ihe computed target lagoon concentrat.on is based on human hea.th thresholds.
'Maximum Contaminant Level.
"Threshold ,s based on the Kisk Specific Dose for the HT* risk le¥cl.
Threshold «.ue not available (MCL) or not applicable (RSI,-,™*, threSllold).
0
hold 2
0
hold o
0
2
o"
U
0
2
0
0
0
2
0
0
0
2
0
U
0
2
0
U
0
2
0
0
0
2
0
0
0
2
0
0
-------
TABLE 4-4
NUNOEK OF DONESTIC/INOUSTHIAL
EXCEEDING THE COMPUTED TAKGtl
Hydroyeologic Category
Pollutant/Criteria
Chloroforn
HCLC
Threshold" .
Hexachlorobenzene
MCL
Threshold
Tetrachloroethylene
MCL
Threshold
Benzene
MCL
Threshold
2.4-Uinitrotoluene
MCL
Threshold
Arsenic
MCL
Threshold
Nitrate
MCL
Threshold
_•
5
2
3
0
3
2
3
4
1
0
3
2
2
4
0
0
3
2
0
0
3
2
3
0
3
2
3
0
3
2
3
4
1
0
3
2
3
4
I
0
3
2
3
4
1
aFron a sample population of 14 domestic/industrial layoor*.
bll,e canputed taryet layoon concentration is based on human health thresholds.
cMaximum Contaminant Level.
Threshold is based on the Risk Specific Dose for the IO'6 risk level.
threshold value not available (MCI) or not applicable (USD-based threshold)
-------
tlcal cross-section of the national lagoon population. Based on these three
factors, direct comparisons of model results with lagoon sampling data may not be
strictly valid.
Interpretation of the results and the above observations should be made with
care, taking Into account the following factors:
o There were no actual ground-water sampling data suitable for verifica-
tion of the model;
o The lagoon characterization data used for comparison with computer
modelling results were of a limited nature: only 23 of 5,476 lagoons
were represented; 21 of which were sampled on a short-term (I.e.,
one-day) basis;
o The nine hydrogeologlc regimes Investigated In this study represent
4,895 (89%) of the national total of 5,476 lagoons (Appendix 4.1, Table
4.1-14); and
o A conservative approach was taken In conducting model runs and Interpre-
ting model results. This approach Included (but was not limited to):
(1) exclusion of the unsaturated zone from consideration due to unavail-
ability of aerobic biological degradation parameters; (2) unavailability
of chemical and anaerobic blodegradatlon rate constants for some of the
pollutants, resulting In an overestimate of aerobic downgradlent concen-
trations; and (3) the assumption that lagoon seepage concentrations were
equal to lagoon liquid (effluent) concentrations.
Additionally, the results as shown represent steady-state conditions, and
thus provide no Information on the effects of retardation. For example, the
transport of hexachlorobenzene In ground water Is likely to be greatly retarded
and the compound may not reach an exposure point In appreciable concentrations
within the period of Interest. As a result of these and other considerations
d1cussed In more detail throughout this chapter and 1n Appendix 4.1, any Inter-
pretation of Tables 4-1 through 4-4 must be made with care, and must recognize
that the modelling results very likely overestimate the extent of potential
contamination. Therefore, the numbers presented In these tables should be
Interpreted only on a relative basis, within the context of this study.
4.6 FINDINGS AND CONCLUSIONS
o Of the four modelled pollutants for which MCLs were available (Including
chloroform) none were found In domestic lagoons at levels exceeding the
computed MCL-based target lagoon concentrations. Two of the four pollutants
(arsenic and benzene) were found In domestic/Industrial lagoons at concentra-
tions exceeding MCL-based target levels. These exceedances occurred In
four of the 14 domestic/Industrial lagoons for which characterization data
were available.
4-13
-------
Modelling results for the remaining three pollutants without MCLs (and
chloroform) were compared to lagoon concentrations on the basis of RSD-de-
rlved exposure point concentrations. Two of these pollutants (tetrachloroe-
thylene and chloroform) were found above target levels In at least one
domestic lagoon, while all four were above target levels In some of the
domestic/Industrial lagoons. Exceedances of target levels for at least
one of these four pollutants were observed in four domestic lagoons and
nine domestic/industrial lagoons.
Based on the sampling program and the modelling results, seepage from
domestic/industrial lagoons is more likely to threaten contamination of
nearby aquifers than seepage from similarly constructed and located domestic
lagoons.
Overall, lagoons receiving only domestic wastes appear unlikely to affect
ground water enough to exceed the available MCLs at exposure points of
interest.
4-14
-------
CHAPTER 5
ASSESSMENT OF HUMAN HEALTH RISK
An assessment of human health risks associated with ground-water contamina-
tion from municipal lagoons was conducted In order to better understand the
threats posed to existing populations on a regional and national basis. While
the national assessment described in Chapter 4 examines scenarios in which
municipal lagoons may pose a human health threat, this assessment of human
health risks focuses on the magnitude and geographic distribution of these
risks. The results of the risk assessment in this chapter can be used to
support the conclusions of the national assessment concerning the role of
preventive and corrective measures In reducing the potential health threat from
lagoons.
This assessment was conducted using an approach generally consistent with
that used to estimate protective (target) lagoon concentrations In Chapter 4.
The data used to characterize lagoons, environmental settings, the location of
potentially exposed populations, and pollutants were Identical to those used In
the national assessment, in order to ensure the comparability of the results
from the two types of assessment. Like the national assessment, this assessment
relies on several conservative assumptions and, therefore, generates upper-bound
estimates of risks. The results of this assessment provide an alternative
measure with which the threat posed by ground-water contamination from municipal
lagoons can be judged.
The following overview of the health assessment approach describes the
various technical components of the analysis and the sources of data. Next,
the chapter discusses the modelling results followed by conclusions concern-
Ing the magnitude and distribution of health risks attributable to municipal
lagoons. The chapter also presents the assumptions and limitations of the
health assessment risks. A more detailed discussion of the risk assessment
methodology Is presented In Appendix 5.
5.1 OVERVIEW OF APPROACH
This assessment of human health risks Is based upon an approach to modelling
similar to that described 1n Appendix 4.1 A risk modelling approach was chosen
for this analysis due to the scarcity of epldemlologlc Information on the
Incidence of either carcinogenic or noncarclnogenlc effects that could be
attributable to municipal lagoons. Accordingly, the analysis of the potential
threat to persons residing within the vicinity of municipal lagoons draws
extensively from both the data collection and modelling efforts begun In the
national assessment (Chapter 4).
5-1
-------
This health assessment examines cancer and noncancer health effects using
two different measures of risk: a quantitative estimation of risks to the maxi-
mally exposed individual (MEI risks) and a qualitative discussion of population
risks. These two measures provide different perspectives on the magnitude of the
potential threat to human health posed by lagoons. MEI risks quantify the level
of risk experienced by the person experiencing the highest level of exposure to
contaminated drinking water and therefore receiving the highest risk. This
measure of risk provides an indication of the maximum likelihood of contracting
the relevant human health effect; by definition, this level would not affect the
entire exposed population. Population risk can be used to estimate the total
number of carcinogenic or noncarcinogenic cases that can be expected nationally
or regionally from exposure to contaminated drinking water. Estimating popula-
tion risks requires information on the distribution of exposed populations resid-
ing near wastewater treatment lagoons.
This health assessment examines risk both on a regional and national basis in
order to highlight particularly vulnerable locations In the U.S., while developing
an overall estimate of the risks that can be expected nationwide. First, risks
are estimated for each of the pollutants of concern In each of the nine hydro-
geologic settings. After aggregating risks across pollutants in order to gene-
rate a total risk for each of the environmental settings, the environmental
setting risk results are weighted according to the frequency of occurrence of
municipal lagoons within each environmental setting and summed to provide a
national risk estimate. With this approach, it is possible to examine which
pollutants pose the greatest threats while examining the geographic variability
of risks.
In order to model risks from municipal lagoons, 1t is necessary to characte-
rize five components impacting risks: 1) pollutant release rates from lagoons,
2) pollutant fate and transport In the environment, 3) distances to exposed
populations, 4) health effects associated with the Ingestion of contaminated
ground water, and 5) frequency of occurrence of environmental settings. Each of
these factors is discussed briefly below.
5.1.1 Pollutant Release Rates from Municipal Lagoons
Municipal lagoons release pollutants Into ground water by seepage of leachate
containing dissolved pollutants through the bottom sludge layer and Into the
surflclal aquifer. In order to estimate the mass of each pollutant released to
an underlying aquifer, it Is necessary to quantify both the seepage rate of the
lagoon and the concentrations of pollutants In the leachate. The estimate of
seepage rates used here was Identical to the values used in the national assess-
ment and discussed In detail in Appendix 4.1.
Leachate concentrations from the lagoons were assumed to be equal to the
effluent or lagoon liquid phase concentrations of the pollutants being modelled.
As discussed in Chapter 3, data on lagoon effluent concentrations were collected
for 23 municipal lagoon systems. Both median and maximum effluent concentrations
reported In these data were modelled In order to characterize a range of represen-
tative lagoon seepage concentrations. In many cases, the median concentrations
5-2
-------
were based on analytical detection limits for all pollutants because concentra-
tions were not quantified. Appendix 5.1 provides the leachate concentrations of
the seven pollutants modelled In the assessment.
5.1.2 Pollutant Fate and Transport In the Environment
Fate and transport of pollutants released from municipal lagoons was modelled
using an analytical computer model, EPACMS, coupled with a Monte Carlo driver for
selecting the hydrogeologlc and exposure distance Input parameters described In
Appendix 4.1. This health assessment used the same hydrogeologlc and geochemlcal
parameters described In Appendix 4.1, ensuring the consistency of the assumptions
and limitations Inherent to the approaches presented here and in Chapter 4. The
modelling approach accounts for hydrolysis of organic pollutants where current
geochemlcal data Indicate this process to be significant for particular pollu-
tants (See Appendix 4.3). Anaerobic degradation of nitrate was also simulated;
the modelling approach did not account for any aerobic degradation processes.
Because the modelling assumes steady-state conditions, pollutant mobility Is only
considered to the extent that It affects the concentrations of degradable pollu-
tants.
Unlike the national assessment, which calculates protective lagoon leachate
concentrations based upon exposure point concentration Inputs to the ground-water
transport model, the health assessment employs leachate concentrations as model
Inputs In order to generate estimates of contaminant concentrations at these
potential exposure points.
5.1.3 Distance to Exposed Populations
The distance to a drinking water well Is a critical Input to the risk analy-
sis because of the dependence of ground-water contaminant concentrations on
distance from the pollutant source. Due to dispersion and degradation of contami-
nants In the aquifer, contaminant concentrations can decrease significantly as
the distance from the lagoon Increases. A mapping survey of 220 municipal waste-
water treatment lagoons was conducted In order to characterize the distance to
and numbers of potential receptors located within the vicinity of municipal
lagoons nationwide.
A continuous function fitting the MEI distance distribution was developed to
allow the distance to ground-water wells to be selected as a Monte Carlo Input.
This Monte Carlo modelling approach ensures that the estimated risks account for
the variation in distances between lagoons and the closest downgradlent drinking
water well nationwide. A brief description of how the MEI exposure distance and
population distance distributions were developed follows.
5.1.3.1 MEI Risk Exposure Distance Distribution. The MEI risk at a single
lagoon can be estimated by determining ground-water concentrations at the closest
well located downgradient from the lagoon and then calculating the risk to an
individual consuming the contaminated ground water. A national distribution
5-3
-------
representing the distance to the closest well for the entire lagoon population
was developed by combining the well distances estimated from 7.5-minute quadrangle
maps for each of the 220 lagoons included in the mapping survey into one distribu-
tion.
The closest well on each map was assumed to be the nearest private residence
downgradlent from the lagoon in areas not served by public water supplies, or the
nearest public well in locations served by public water. The dependence of the
populace in the area surrounding each lagoon on public water was determined
through the Federal Reporting Data System (FRDS), which was also used to locate
public water supply wells.
5.1.3.2 Population Risk Exposure Distance Distribution. Population risks are
discussed qualitatively in the health assessment based upon the survey informa-
tion on total potentially exposed populations. In order to develop a national
estimate of the population risks attributable to municipal lagoons, the total
number of people potentially exposed to contaminated ground water in the sample
of municipal lagoons was tabulated.
5.1.4 Estimating Risks to Exposed Populations
Once drinking water well concentrations are estimated with EPACMS, risks can
be calculated using standard ingestlon assumptions and health effects data (see
Appendix 4.1.1). Ingestlon rates are based on the assumption that an adult
weighting 70 kilograms Ingests 2 liters of contaminated water per day over a
70-year lifetime.
5.1.5 Aggregating Risks Across Environmental Settings
Once risks and hazards are calculated for each pollutant within each environ-
mental setting (hydrogeologlc category), the total carcinogenic risk Is calculated
for that setting by adding risks across carcinogens. Carcinogenic risks may be
summed together given the assumption of a non-threshold linear dose-response
curve. Because this assessment addressed only one noncarcinogen, nitrate/
nitrites, the noncarclnogenic hazard for this contaminant is equal to the total
noncarclnogenlc hazard.
Once the total carcinogenic risk and noncarcinogenic hazards have been
calculated for each environmental setting, a national risk and hazard estimate
is generated by weighting the Individual setting risks based upon their national
frequency of occurrence. As described in Appendix 4.1.3, the frequency of occur-
rence of lagoons In each setting was based upon a characterization of the United
States into hydrogeologlc regions using the DRASTIC methodology. Figure 4.1-4 in
Appendix 4.1.3 displays the numbers of lagoons found In each of the DRASTIC
regions; Table 4.1-14 (Appendix 4.1.4) presents the number of lagoons correspond-
ing to each of the nine environmental settings modelled.
5-4
-------
CANCER RISKS AGGREGATED WITHIN AND ACROSS CATEGORIES
1.0-
0.9:
0.6-
P0.4
0.(H
USING MEDIAN WELL CONC. USING MAXIMUM WELL CONC.
-5
-3
•|~rT~r
-2
f
o*
I
o
LOW RISK
CANCER RISKS (LOG10)
HIGH RISK
LEFT-HAND LINE IS MEDIAN RISK
Oirur.UAMn i IMP ic UAVIUMU nin/
-------
5.2 DISCUSSION OF QUANTITATIVE MODELLING RESULTS
5.2.1 Weighted National MEI Risks
Weighted national MEI risks were calculated using both median and maximum
lagoon effluent concentrations as estimates of the leachate concentration.
Because of several conservative assumptions described In Section 5.4.2, these
risk estimates are likely to overestimate actual risks. The Importance of leachate
concentration with respect to risk Is evident. The national distribution of
total carcinogenic risks associated with median lagoon effluent concentrations
ranged from 1.6 x 10-5 to 4.0 x 10-5, Whne risks associated with the maximum
concentrations ranged from 7.0 x 10~4 to 1.8 x 10-3. Figure 5-1 shows cancer risks
associated with median and maximum well concentrations versus cumulative prob-
ability of occurrence. The steep rise in the cumulative probability curves in
Figure 5-1 Indicates that there Is little variation In risks nationally from
lagoons (notwithstanding estimates of leachate concentration). Each point on the
curve represents the probability that a facility will result in risks to the
nearest exposed individual at or below the level on the X-axis. A risk of
4.0 x 10-5 means four persons 1n 100,000 will develop adverse health effects, in
this case cancer, from this exposure. Noncarcinogenic hazard, caused by nitrate/
nitrites, was negligible nationally, with ground-water concentrations never
exceeding one ten-thousandth of the level associated with the toxic health effect
methemogloblnenria (100 ug/1).
Each EPACMS run Included approximately 500 Iterations in which distance to
wells, environmental parameters, lagoon size, and other variables (See Appendix
4.4) were varied independently by the Monte Carlo simulator. Appendix 5.2 dis-
plays the ninetieth percentile risks associated with all seven constituents in
each of the nine hydrogeologlc settings for both median and maximum effluent
concentrations. (The ninetieth percentile risk 1s the risk associated with a
nine In ten chance of occurrence.) The constituents dominating the weighted
carcinogenic risks varied between the median and maximum effluent concentration
model runs were due primarily to differences In the relative magnitude of leachate
concentrations. The median concentration risks were dominated by two pollutants
found only In the domestic/Industrial lagoons, hexachlorobenzene and benzene,
with risks ranging from 3.0 x 10-7 to 4.5 x 10-5. The maximum leachate concen-
tration risks were dominated by three constituents found primarily in domestic/
Industrial lagoons: hexachlorobenzene, 2,4-dinitrotoluene, and chloroform, with
Individual risks ranging between 2.9 x 10-5 and 1.5 x 10-3.
The other potential pollutants of concern for carcinogenic risk, arsenic and
tetrachloroethylene, posed relatively Insignificant risks compared to the dominant
chemicals.
5.2.2 Comparison of Risks from Domestic and Domestic/Industrial Lagoons
The lagoon data survey did not provide sufficiently representative data to
allow health risks associated with domestic and domestic/industrial lagoons to be
quantified separately. Although the data characterizing the lagoons cannot be
5-6
-------
considered statistically representative of lagoons nationwide, a number of
observations can be made about the different risks that may be expected from
these two types of lagoons;. 1n general, risks from domestic lagoons are signifi-
cantly less than those from domestic/Industrial lagoons.
Because the pollutant concentrations in the domestic/Industrial lagoons were
significantly higher than those detected In the domestic lagoons, the maximum
concentration risk results correspond primarily to the risks associated with
domestic/Industrial lagoons. The pollutants dominating the maximum concentration
estimates (hexachlorobenzene, 2,4-dlnitrotoluene, and chloroform) were observed
solely 1n the domestic/Industrial lagoons and were not detected In the domestic
lagoons (with the exception that chloroform was detected In quantifiable concen-
trations once In the domestic lagoons; nonquantifiable trace values were detected
In 3 other lagoons). All of the maximum effluent concentrations modelled repre-
sent levels detected In the domestic/Industrial lagoons. In addition, the median
concentration risks were also dominated by two pollutants not detected in the
domestic lagoons: hexachlorobenzene and benzene.
The risks attributable to domestic lagoons correspond to the risks associated
with the four pollutants detected in them: arsenic, chloroform, nitrate/nitrite,
and tetrachloroethylene. Arsenic was detected in two of the nine lagoons at
equal concentrations of 11 mg/1, which is about eight times lower than the maximum
level modelled. Therefore, the risks from arsenic In domestic lagoons are likely
to be In the range of 1 x 10-6. Chloroform was quantified In one of the nine
domestic lagoons, at a concentration of 2.3 mg/1, more than 10 times lower than the
maximum level detected In the domestic/Industrial lagoons. The chloroform risks
from domestic lagoons, therefore, probably do not exceed 2 x 10~5. The nitrate/
nitrite levels in the ground water were extremely low and and do not represent a
health threat. Finally, tetrachloroethylene was detected In two of the nine
domestic lagoons at concentrations less than 1.5 mg/1, between one and two orders
of magnitude less than the levels detected In the domestic/industrial lagoons.
The risks from tetrachloroethylene at domestic lagoons are therefore unlikely to
exceed 5 x 10-6 based upon the lagoon survey data. Table 5-1 summarizes these
estimates of variation between domestic and domestic/Industrial lagoons.
5.2.3 Distribution of Risks Across Hydrogeologic Settings
EPACMS provides distributions of risk estimates corresponding to the Monte
Carlo Input values for each of nine separate hydrogeologic settings. The risk
estimates within each setting varied by-less than one.order of magnitude between
the 10th and 100th percentlle risks. In addition, the risk estimates varied
little across environmental settings. The 10th percentlle maximum aggregate
carcinogenic risks varied from 1 x 10-3 to 6.3 x 10-4, while the 100th percentlle
maximum aggregate cancer risks varied from 1.8 x 10-3 to 2.1 x 10-3 across the
nine hydrogeologic settings. The lack of variation In setting risks can be attri-
buted to interactions between the dominant hydrogeologic parameters, such as
hydraulic conductivity, depth of the saturated zone, and the slope of the ground-
water table. Because most lagoons are sited near rivers within flood-plain
areas, the hydrogeologic conditions are quite similar across the country.
5-7
-------
5.3 QUALITATIVE DISCUSSION OF POPULATION RISKS
The total risk.to exposed populations depends upon the location of all
residences and public water supply wells (rather than the closest well) within
the vicinity of municipal wastewater treatment lagoons. The mapping survey of
220 lagoons produced a distribution of potentially exposed populations within
2000 meters of wastewater treatment lagoons, and found that an average of 391
persons depend upon ground water within 2000 meters of wastewater treatment
lagoons nationally (Appendix 5.3, Table 5.3-1).
The magnitude of risks to these exposed Individuals depends upon their
distance from the lagoon. The mapping survey found that less than 8% of the
potentially exposed populations live within 500 meters of a lagoon; no public
water supply wells were observed within 130 meters of a lagoon. Because the
distribution of total exposed populations at lagoons 1s weighted to greater
distances and contaminant concentrations decrease with distance, the magnitude
of population risks attributable to municipal lagoons Is likely to be relatively
low. The risks to populations residing near domestic/Industrial lagoons are
likely to be much higher than those affecting populations near lagoons receiving
only domestic wastes.
TABLE 5-1
MEI CANCER RISKS (GROUND WATER) FROM MUNICIPAL LAGOONS
MEI Risk Associated With
Leachate Concentration
Risk-Dominating
Lagoon Type
All Lagoons
Median
1.6 x 10-5 to
4.0 x 10-5
Maximum
7.0 x 10-* to
1.8 x 10-3
Constituents3
Hexachl orobenzene,
benzene, chloroform,
2,4-d1n1trotoluene
Domestic only
Negligible
1.0 x 10-6 to
2.0 x 10-5
Chloroform, arsenic,
tetrachloroethylene
a Arsenic and tetrachl oroethyl ene were found In quantifiable concentrations In two
of the nine domestic lagoons sampled and chloroform In one of the nine lagoons.
5-8
-------
While the geographic areas used to select a random sample of lagoons for the
mapping survey were not selected statistically, the results are likely to be
quite representative of national trends. Generally, wastewater treatment lagoons
are located downstream of towns within close proximity to the point of effluent
discharge Into the river. This does not allow residences to be located between
the lagoon and the receiving stream, which often Intercepts the potentially
contaminated ground-water flow, thus preventing further subsurface migration of
contaminants. Additionally, people generally do not choose housing within a
close proximity to wastewater treatment facilities due to potentially objection-
able odors. These factors support the findings of the survey, which indicates
that approximately 25% of all wastewater treatment lagoons may have no exposed
populations within 2000 meters.
5.4 FINDINGS AND CONCLUSIONS
5.4.1 Magnitude and Distribution of Risks
This analysis has shown that the national risks associated with ground-water
contamination from municipal waste treatment lagoons are generally low and within
an acceptable risk range (10-* to 10-7). However, risks may exceed this range
for certain lagoons receiving both domestic and Industrial wastes in certain
hydrogeological settings in the country.
The risks to populations exposed to contaminated ground water from municipal
wastewater treatment lagoons will depend principally on the types of wastes
received by the facility. The analysis indicates that facility location has only
a slight Impact on risk levels. Based upon the lagoon sampling survey, lagoons
receiving only domestic wastes do not appear to pose unacceptable risks to popula-
tions, with maximum carcinogenic risks ranging from approximately 2 x 10-5 to 5 x
10-6. These risks correspond to three carcinogens which were detected in only a
few of the nine domestic lagoons sampled, and therefore may overstate the actual
risks from domestic lagoons. The most common pollutant Identified in domestic
lagoons, nitrate/nitrite, was shown to pose little or no threat to human health
based upon the modelling results.
Some lagoons receiving mixtures of domestic and industrial wastes may pose
more substantial risks to human health. Median carcinogenic risks for these
lagoons are approximately 10-5, with maximum risks ranging as high as 1.9 x
10-3, due primarily to hexachlorobenzene and 2,4-d1nitrotoluene. However, these
maximum risks may be rare occurrences. Because one of the primary factors affect-
Ing risk Is the concentration of pollutants In the leachate, the applicability of
these risk estimates to the nation Is limited by the representativeness of the
sample data. Lagoons that do not receive the riskdomlnating pollutants may pose
substantially lower risks to human health.
5-9
-------
5.4.2 Modelling Assumptions and Limitations
Several limitations and assumptions apply to the quantitative modelling
results described here. These Include limitations to the applicability of
the model and assumptions regarding model Inputs and data described previously
1n Chapter 2. In general, these assumptions will tend to overstate the actual
risks.
Although the health risks modelled here represent the best available informa-
tion, only a small number of municipal lagoons were sampled (0.2% of domestic
lagoons and 3% of domestic/industrial lagoons). Furthermore, assuming leachate
concentrations to be equal to effluent concentrations may overstate risks, as
physical processes that may reduce pollutant concentrations in the leachate, such
as adsorption and biodegradation in the sludge layer, were not considered.
Because of the low frequency of detection for many of the pollutants of
concern, the model employed detection limits as leachate concentrations when the
median value represented a non-detect. This may overstate the median risk
results, as the detection limit represents the upper-bound concentration in these
cases. Similarly, the maximum concentration values often represented outlying
data points, and may not be representative of most lagoons. Therefore, the
maximum lagoon risk estimates may also overstate risks.
r
EPACMS assumes steady-state conditions In estimating ground-water concen-
trations of contaminants at wells. Steady-state models do not account for
differences in breakthrough time at downgradient ground-water wells associated
with contaminants with different mobilities. (EPACMS does account for the addi-
tional opportunity for attenuation of degradable contaminants in the saturated
zone associated with the longer travel times of low mobility contaminants). Be-
cause it may take longer for lower mobility contaminants, such as 2,4-dinitro-
toluene, to reach a point of exposure than faster contaminants, such as benzene,
there may be no risk to existing populations from the a low-mobility contaminant
for many years. Accordingly, the risks to existing populations may be overstated
by these results.
United States Geological Survey (USGS) 7.5-m1nute series quadrangle maps
were used to located residential and public wells in the vicinity of lagoons.
Residences not served by a public water supply (as indicated in the FRDS data
base) were assumed to have private water wells. This information is the best
available for residences and ground-water usage, but the accuracy of the results
depends upon the date of the USGS maps and the FRDS data base.
The exposure survey assumed that populations located downgradient of rivers
large enough to Intercept the ground-water flow would not be exposed to contami-
nated ground water. Identification of situations in which ground-water flow 1s
likely to be Intercepted by surface water depended upon professional judgment
concerning the flowrate of the receiving stream and the likelihood that all of
the local ground-water flow would discharge Into the stream.
5-10
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Chapter 6
ALTERNATIVES TO PREVENT AND CONTROL GROUND-WATER CONTAMINATION
6.1 INTRODUCTION
The results of the assessment presented in Chapters 4 and 5 overrepresent
the potential ground-water contamination problem, due to the various conserva-
tive assumptions employed In the modelling approach. With this In mind, the
following discussion of appropriate preventive and corrective technologies is
directed primarily at those wastes, hydrogeologic settings, and lagoon designs
that are most likely to present a potential for contamination of underlying
ground water, with a resulting potential health risk to nearby populations. The
Installation, retrofitting, or decontamination of a lagoon should be specific to
that particular lagoon and Its wastes; measures which may be necessary for a
lagoon receiving industrial wastes may not be required for a purely domestic
lagoon.
Many of the measures discussed in this chapter can be Implemented at
several points during the useful life of a lagoon: (1) during design/construc-
tion of a new lagoon; (2) as part of retrofitting activities; or (3) as part of
cleanup activities following discovery of contamination of soil, ground water
or both. The types of preventive/corrective actions and their applicability to
these three cases are presented In Table 6-1 and discussed In more detail 1n
the following sections and Appendix 6.
In addition to the preventive/corrective measures discussed, States may
also have guidelines and standards for design, construction, and operation of
municipal lagoons. For example, the State of Wisconsin recently established
ground-water quality standards applicable to all "facilities, practices and
activities" which may affect ground-water quality and which are regulated under
specific statutes by various State agencies (1). Under the new regulations,
numerical standards were established for two sets of parameters (one set
protecting public health and the other protecting public welfare), enforceable
at various points adjacent to the pollutant source depending upon the type and
concentration of the pollutant. Should these standards be exceeded, the
Wisconsin Department of Natural Resources will assess the cause and significance
of the exceedance and specify the appropriate response action, which may range
from no action to site closure and treatment of contaminated ground water. Even
If a facility complies with State seepage limits and other requirements, It 1s
not excused from further regulatory action should the facility still leak.
Facility operators should therefore be encouraged to consider exceeding the
minimum State requirements.
Federal resources are also available to aid States In protecting public
water supply wells through EPA's Wellhead Protection Program. As part of this
program, EPA has established technical guidance to help States Identify and
delineate the areas around public wells needing protection through locally-
established mechanisms such as zoning or land use restrictions. Additionally,
federal grant money 1s available for program development In those States meeting
grant eligibility requirements.
6-1
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TABLE 6-1
TYPES OF PREVENTIVE/CORRECTIVE MEASURES
r!,
New Retrofitted Problem
Lagoon Lagoon Lagoon3
Use proper siting criteria x
Install single or double liner (natural or synthetic material) as
appropriate; choose compatible liner material x x xb
Install leak detection/collection system as appropriate x x xb
Practice construction QA/QC for new and retrofitted lagoons x x xb
Implement or change O&M, Inspection procedures x x XD
Require Industrial wastewater pretreatment to remove pollutants of concern
prior to entering the lagoon x x xb
Conduct ground-water monitoring x x x
Retrofit to minimize potential for future contamination x xb
Control the source of contamination via containment, treatment,
or removal of water, sludges and/or soils, Including full or
partial closure as appropriate x
Contain and/or treat contaminant plume x
aLagoons with know contamination.
bTh1s category may overlap with retrofitted lagoons In cases where contamination Is minor.
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6.2 NEW LAGOON
The design, Installation and operation of a new municipal lagoon can be
divided Into four major components:
o Siting
o Design and material selection
o Construction
o Operations and maintenance
Although proper performance of the first three components listed above Is
usually (If not always) necessary to ensure the Integrity of a lagoon system, 1t
may not be sufficient. Even the best-designed lagoons may leak If appropriate
quality assurance and control procedures are lacking during construction. The
potential for lagoon leakage can be further Increased If the necessary operations
and maintenance (O&M) procedures are not performed. However, If care Is taken to
Include all relevant site-specific considerations, lagoons can be designed and
constructed so as to minimize the potential for leakage.
6.2.1 Lagoon Siting.
The siting of municipal lagoons must first take Into account such practical
considerations as:
o Site-specific parameters related to ground-water contamination Including
soils, hydrogeology and geology;
o Land availability and costs;
o Proximity of receiving streams;
o Proximity of existing and anticipated residential or other aesthetically
sensitive areas;
o Proximity of water supply sources (surface water or ground water); and
o Proximity to existing and anticipated facilities (If the lagoon Is part
of a plant expansion).
6.2.1.1 Soils, Hydrogeology and Geology. Soils at the site must be tested to
determinetheirsuitabilityassubsurface material for the proposed lagoon
design. Both the subgrade and Impoundment structures such as dikes and berms
require soils of appropriate strength, permeability, volume change, plasticity
and comparability. Ideal soils will have low shrink/swell properties, low
organic content, and minimal amounts of carbonate or other soluble materials.
The availability of soils containing the required properties can be a major
6-3
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factor In determining the location of a surface Impoundment. Should appropriate
materials not be available locally, they must be transported to the site, usually
a costly proposition. On the other hand, the presence of Inappropriate or
"problem" soils can limit or prohibit the Installation of that lagoon at a parti-
cular site.
One of the most Important considerations In siting a lagoon Is the location
of the water table and underlying aqulfer(s). Depth to ground water and the
historical seasonal changes In aquifer levels must be defined to allow sufficient
distance between the saturated zone and the bottom of the lagoon. This minimum
separation distance Is often defined by State regulations; for example, the 1978
Recommended Standards for Sewage Works (2) require a minimum of 4 feet between
the bottom of a lagoon and the maximum ground-water elevation. This criterion
may not always be adequate, as seasonal and long-term fluctuations in water
table elevation may not always be determined to that accuracy.
The underlying geologic conditions must be determined to ensure siting on a
stable geologic foundation. Areas of karst geology or otherwise highly porous or
fractured materials should be avoided, as well as areas of potential subsidence
(e.g., collapsing soils, m1ned-out areas and sink holes) and geologically active
areas (e.g., volcanism and recent faults). These conditions could cause slow-
acting deformations resulting 1n liner breach or catastrophic failure as in the
case of a fault zone or sink hole. Ideally, the Impoundment should be sited in a
stable area of massive clay strata or clayey soil with low permeability.
6.2.1.2 Topography, Surface Hydrology and Climate. These three factors, topo-
graphy, surface hydrology andclimate, are usually of lesser Importance with
respect to ground-water contamination than site soils and hydrogeology. However,
they should still be taken Into account when siting a municipal lagoon.
In choosing a lagoon site the local terrain must be such that the potential
for a release caused by dike failure -is minimized. Sites within the 100-year
flood-plain or In areas of high relief are not recommended. Should a lagoon flood
or overtop Its dikes, pollutants would be released to unprotected (I.e.,
unllned) ground surfaces where they might Infiltrate Into the soil and ground
water. (The most significant impact of such a release would, of course, be on
local surface waters.) Consequently, the effects of climate must be considered.
Regions of excessive rainfall and flooding, frost penetration and extreme temper-
ature variations must be evaluated with care. Often, design and engineering
techniques can accomodate climate-sensitive parameters.
6.2.1.3 Distance to ground or surface water supply wells or intakes
The distance between a lagoon and a drinking water well or surface water
supply Intake has a large Impact on the human health risks associated with ground-
water contamination. Ideally, lagoons should not be located near drinking water
wells or surface water Intakes.
6-4
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6.2.2 Lagoon System Design
Lagoon design can be divided Into two major components: (1) sizing; and
(2)' selection of an appropriate Hner system. ' The sizing of a lagoon system
Is determined primarily by the type and degree of treatment necessary for the
given wastewater. An. additional consideration when sizing a lagoon Is the
effect of water column depth on the potential seepage rate (see Appendix 4.1.3).
In contrast, the selection of a liner system Is determined by the level of
protection required to prevent the lagoon's contents from entering the ground
water at a specific site. It Is related to lagoon operation only to the extent
that treatment operations determine the nature of any contamination that may
occur (I.e., the concentration and type of pollutants present In lagoon waste-
water). Other site-specific factors such as location (I.e., depth) and use of
ground water, proximity of withdrawal wells and soil type are also significant.
Liner material can be of three major types: (1) earthen, asphalt and cement
liners ("admixed", or mixed In-place, materials); (2) synthetic and rubber
liners; and (3) sealants (natural or chemical). The selection of a liner material
Is based on numerous factors that are site-specific (as discussed above) and
liner-specific (e.g., chemical resistance, ease of Installation and repair,
costs, and availability).
6.2.2.1 Selection of a Liner System. Lagoon Hner systems can be classified In-
to two general categories:
o Single (I.e., monolayer) Hner (Figures 6-1 and 6-2)
o Combination double (I.e., two-layer) liner, with a leak detection/collec-
tion system Installed between the two liners (Figure 6-3).
The selection of a liner system for a municipal lagoon Is based on the
degree of protection desired (or required, In the case of State regulations).
This decision must be based on several factors:
o The nature of the wastewater;
o Local hydrogeology, Including the presence of naturally occurring low
permeability strata at the site, depth to the water table, and the
hydraulic conductivity of the outcropping or subcropplng geologic unit;
o The use of underlying ground water and the proximity of any withdrawal
wells;
o Expected lagoon life and closure requirements; and
o Federal, State or local regulations regarding seepage rates, liner
materials, permeability, etc.
6-5
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ON
t
FIGURE 6-1
SCHEMATIC OF A COMPACTED SOIL
SINGLE LINER SYSTEM FOR A LAGOON
PROTECTIVE
SOIL OR COVER
(OPTIONAL)
mm i
H
UQUID
THICK LAYER
COMPACTED LOW PERMEABILITY SOIL
NATIVE SOIL FOUNDATION
minium
•LINER (COMPACTED
SOIL)
GW TABLE
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FIGURE 6-2
SCHEMATIC OF A FLEXIBLE MEMBRANE
SINGLE LINER SYSTEM FOR A LAGOON
PROTECTIVE
SOIL OR COVER
(OPTIONAL)
FLEXIBLE
MEMBRANE
LINER
NATIVE SOIL FOUNDATION
CW TABLE
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FIGURE 6-3
SCHEMATIC OF A FLEXIBLE MEMBRANE/
COMPACTED SOIL DOUBLE LINER SYSTEM
FOR A LAGOON
PROTECTIVE
SOIL OR COVER
(OPTIONAL)
FLEXIBLE
MEMBRANE
LINER
THICK LAYER
COMPACTED LOW PERMEABILITY SOIL
LEACHATE COLLECTION
AND REMOVAL SYSTEM
DRAINAGE MATERIAL
DRAIN PIPE (TYPICAL)
CW TABLE
NATIVE SOIL FOUNDATION
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The degree of protection provided for a given lagoon system must be decided
on a site-specific basis. Most municipal lagoons currently In existence are
constructed with a single liner, usually comprised of bentonlte or low-permeabi-
lity soil. In many cases, single liners (e.g., soil-bentonlte) may be adequate;
however, this may not necessarily be true for lagoons receiving large amounts of
Industrial wastes where Individual compounds may contribute to Hner degradation
or present a significant health risk due to their Inherent toxlclty. In such
cases, the Installation of a double liner with a leak detection/collection system
(Figure 6-3) may be warranted, especially If the lagoon 1s located In areas with
susceptible hydrogeology and nearby water supply wells.
6.2.2.2 Liner Material Selection and Design Considerations. As with liner sys-
tems, the selectionof a specificliner materialis very dependent on waste
characteristics and other site-specific parameters. Other factors to be consi-
dered Include: (1) chemical compatibility of the liner and waste; (2) liner
sensitivity to extreme temperatures and sunlight (ultraviolet radiation);
(3) liner permeability under expected site conditions; (4) liner strength, life
expectancy, ease of Installation and repair; and (5) relative cost. The two
major types of liners are earthen (e.g. clay), admixed (concrete and asphalt)
and synthetic (e.g. rubber). Appendix 6.1 discusses the selection of Hner
materials and related design considerations.
6.2.3 Lagoon Construction
Lagoon construction can be viewed as a two-step process: (1) subgrade
preparation; and (2) liner Installation. Construction procedures are critical
because Inadequate quality control during construction can compromise or Invali-
date a superior design. Therefore, all phases of construction should be super-
vised to ensure that the design specifications are met, and, 1f necessary,
revised after appropriate review when conditions at the site Indicate the need
for modification. A good quality control program will provide for sampling,
Inspection and monitoring of all phases of liner selection and Installation.
Documentation requirements for test results and all aspects of dally work should
ensure adherence to engineering design while allowing for any necessary
divergence from design specifications. For admixed liners, special attention
must be given to characterizing the properties of the soil or other material to
be used; while for synthetic liners, major areas of concern Include subgrade
preparation, seaming techniques, and sealing of penetrations through the liner.
Specific aspects of subgrade preparation and liner Installation are dis-
cussed 1n Appendix 6.2 for synthetic and admixed liners. Installation of
soil sealants, chemically absorbent liners, and spray-applied emulsions Is not
discussed as these methods do not provide an adequate hydraulic barrier when
used alone.
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6.2.4 Costs
The capital and 04M costs for a given municipal lagoon system depend on
several site-specific factors, Including:
o The facility's design capacity;
o The local cost of land;
o The need for a liner and, If so, the type; and
o The need for ground-water monitoring or other leak detection (and/or
collection) systems.
6.2.4.1 Capital Costs. While costs vary among different systems operating under
or In a wide variety of conditions, general cost Information 1s available In the
form of cost curves compiled by EPA (3). The cost curves compiled for aerated,
facultative, and anaerobic lagoons are presented In Appendix 6.3.
As an example, 1f the facility to be constructed Is designed to treat 0.1
mgd, the typical construction costs for a facultative lagoon system would
vary from $181,000 In a warm climate to $419,000 1n a cool climate. (June 1987
dollars; ENR Index of 4386.80). These costs Include excavating, grading and
other earthwork required for subgrade preparation, and service roads. The costs
of liner material, Installation and special subgrade preparation are excluded,
as are the costs of land and pumping facilities. The resulting total capital
costs, which Include piping, electrical, Instrumentation, site preparation,
engineering, supervision and contingency costs, are $235,000 and $530,000 for
warm and cool climates, respectively (June 1987 dollars). These total costs do
not Include auxiliary structures (e.g., offices, labs, etc.). A worksheet for
these calculations Is presented 1n Appendix 6.3 (Table 6.3-1).
If the lagoon is to be equipped with a liner, the capital costs for lagoon
construction will Increase significantly. For example, if the Installed cost of
a given synthetic liner is $8.00 per square yard, Including additional subgrade
preparation, and the area of the lagoon Is approximately five acres (correspond-
ing to a flow of 0.1 mgd, as derived In Chapter 3 and Appendix 3.3), then the
total Installed cost of the liner would be almost $200,000. Typical Installed
unit costs for selected synthetic, earthen and admixed liners are presented 1n
Appendix 6.3 (Tables 6.3-2 and 6.3-3). Factors affecting the cost of liner
Installation Include:
o Material costs;
o Suitability of local soils for use as subgrade, protective cover, or the
liner Itself;
6-10
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o Location of site (I.e. transportation costs);
o Labor availability (often dependent on time of year);
o Economies of scale, If present; and
o Weather conditions (especially for seaming of synthetic liners)
6.2.4.2 O&M Costs. Cost curves for annual O&M costs are also Included in Appen-
dix 6.3. For a facultative lagoon treating 0.1 mgd, the corresponding June 1987
O&M cost Is approximately $3,500 per year.
6.3 OPERATIONS AND MAINTENANCE
To ensure the Integrity and proper performance of a lagoon system through-
out Its active life, If Is necessary to Implement an effective operations and
maintenance (O&M) program. The major components of such a program Include routine
Inspections, monitoring and preventive maintenance.
Routine inspection procedures begin with Initial facility start-up and con-
tinue throughout final closure. The dike system should be Inspected after major
storm events or severe weather and the nature and extent of any problems should
be documented, along with any follow-up maintenance required. The scheduling of
routine inspections should be clearly outlined in the facility O&M manual.
If a leak is suspected or leak detection activities are required by regula-
tory authorities, there are several techniques available or under development for
detecting seepage from wastewater lagoons. Some of these techniques are designed
to Identify leaks as they occur; others (e.g., ground-water monitoring) detect
leaks only after they have occurred. The need for and selection of a particular
leak detection method is usually determined on a site-specific basis. One relia-
ble method of discovering a major leak Is that of liquid mass balance; however,
accurate measurements of Inflow, outflow, rainfall and evaporation must be kept.
Leachate collection systems can be a valuable tool in detecting the migration of
wastes past the liner. Lyslmeters, which sample the unsaturated zone beneath the
Impoundment, have also been successfully used to detect seepage. Several new
techniques are emerging to measure liner Integrity and detect leakage, Including
ground deformation monitoring, acoustic emission monitoring, and several types of
geophysical techniques. Innovative sensing systems are being designed to Improve
leak detection at planned Impoundment sites (4, 5, 6, 7 and 8).
If ground-water contamination Is suspected to have occurred, a ground-water
monitoring program can be instituted to measure any effect(s) the lagoon may have
on the underlying aquifer. Should this be necessary, care must be taken to
locate the monitoring wells so that at least one well Is upgradient and several
are downgradlent, spaced at appropriate Intervals to Intercept the flow of ground
water. Leachate contamination from waste Impoundments has been shown to move as
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a distinct plume within the ground-water flow. Placement of monitoring wells to
sample several sections of the aquifer Is usually necessary to Identify and
locate a contaminant plume. Other Innovative techniques that have been used to
locate contaminant plumes Include high frequency pulse, electromagnetics, resisti-
vity and seismic techniques.
The cost of ground-water monitoring can vary greatly, depending upon several
factors:
o Number of wells;
o Depth to ground water;
o Location of bedrock: If bedrock 1s shallow, equipment such as air,
specialized rotary, or rock coring drills will be necessary;
o Type of soil: Very sandy soil may cause cave-Ins or "heaving sands,"
where the sand rises In the hollow auger during drilling. If this
occurs, It may be necessary to employ mud rotary or other specialized
drilling techniques; and
o Degree of contamination: If severe ground water or soil contamination
1s encountered, It will be necessary to Implement a higher level of
personal protection (e.g., Tyvek suits, respirators, etc.). This Is
not likely to be necessary at municipal lagoon facilities.
Costs for a typical monitoring well system are presented In Appendix 6.3
(Table 6.3-4). These costs assume:
o Four monitoring wells (one upgradlent and three downgradient) with
4-Inch PVC pipe;
o A well depth of 40 feet (assumes a water table at 20-25 feet below
ground surface);
o Sllty soil (allows use of a hollow stem auger);
o Quarterly sampling of each well; and
o Analysis of well samples for priority pollutants; a fifth sample (field
blank or wash blank) Is Included for QA/QC purposes.
Based on the above assumptions, the total Installation costs (Including
supervision) for a four-well system are $15,000 (+20%). The total yearly
sampling and analysis costs are estimated at $43,000 Eased on quarterly sampling
(June 1987 dollars).
If occasional or periodic Increases In particular compounds 1n pond Influent
are expected (e.g., seasonal Industrial discharges), It may be advisable to moni-
tor pond Influent on a regular basis to detect the presence of these compounds.
If It Is determined that these compounds are present at levels high enough to
6-12
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Impair the lagoon system, either by Inhibition of biological action or by attack-
Ing the Integrity of the liner, It may be necessary to require dischargers to
pretreat their wastewater prior to release to the lagoon system.
Routine Inspection and monitoring will document any required maintenance and
repair due to weathering, animal or human Intruders, or structural failures.
Routine preventive maintenance will also keep spillways clear of debris, main-
tain embankment and dike slope vegetation and minimize erosion, and ensure sche-
duled fence repair and machinery upkeep.
All operations and maintenance procedures should be prescribed in a manual
and distributed to appropriate employees. Written records should be kept of all
O&M activities.
6.4 WASTEWATER PRETREATMENT
Certain compounds, when present In sufficiently high concentrations, can
often have deleterious effects on both lagoon performance and Integrity and can
contaminate groundwater If seepage occurs. Lagoon performance can be adversely
affected by compounds that: (1) Inhibit oxygen transfer (e.g., surfactants);
(2) Inhibit nutrient uptake (e.g., heavy metals); or (3) limit cell metabolism
(e.g., cyanide). These or other waste constituents can also compromise the
Integrity of a liner; for example, some synthetic liners are not resistant
to hydrocarbon solvents and petroleum oils (see Appendix 6.1, Table 6.1-1).
While It may not be likely that these compounds will be present 1n municipal
lagoons In concentrations high enough to cause liner degradation, laboratory
and field performance tests are advisable to confirm the compatibility of the
liner material with the expected waste (4, 9, 10, 11, 12, 13 and 14). This
Is especially true of lagoons with the potential to receive a high pro-
portion of Industrial wastewater.
In general, pretreatment requirements for a given Industry are specified for
selected chemicals by the locality (e.g., city or sewer authority) based on EPA's
Effluent Guidelines Limitations and/or local discharge requirements (whichever are
more stringent). The Industry Is then free to choose a treatment process or pro-
cesses to achieve pretreatment limitations. The particular type of treatment
process applied Is primarily a function of the type of waste (or Industry), the
concentration of pollutants In the waste, the desired level of treatment, and
treatment cost.
Where several Industrial plants discharge the same pollutant to a lagoon It
may be necessary to restrict the pollutant loading from each plant and not just
the pollutant concentration. A pollutant loading limitation Is based on the
appropriate local or categorical pretreatment standard and a dlschange volume
restriction. Pollutant loading limitations control the total amount of a pollu-
tant which Industrial plants can discharge. Such limitations Insure that lagoons
will not receive an excessive quantity of a pollutant.
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Pretreatment requirements offer the distinct advantage of controlling Indus-
trial pollutants which may contaminate groundwater at their source and of posing
the cost of groundwater pollution prevention on the Industries that discharge the
pollutants.
6.5 MODIFICATION OF AN EXISTING LAGOON
There are several circumstances under which It may be desirable to retrofit or
otherwise modify operation of a municipal lagoon system; the most obvious circum-
stances are the discovery of a leak or release. Other relevant situations Include
changes 1n applicable regulations, changes 1n wastewater composition, or changes
In operations philosophy.
If a lagoon system Is found to have the potential for leaks, or an added
degree of protection Is desired (or required), any of several measures can be
taken:
o The lagoon can be retrofitted with a lower permeability Hner(s);
o The existing liner can be repaired;
o Pretreatment by dischargers can be required If It Is determined that cer-
tain compounds present a significant risk to the potentially exposed
population; and
o O&M and monitoring practices can be Improved.
These options are discussed In the following sections.
6.5.1 Retrofitting
The most difficult design problem encountered In Hner application Is retro-
fitting of a liner In an existing lagoon. Effective design practices are essen-
tially the same as those used In new systems, but additional care must be exer-
cised In the evaluation of the existing structure and the required results.
Lining materials must be selected so that compatibility between old and new
sections Is obtained. Sealing around existing columns and footings should also
be considered (15).
6.5.1.1 Liner Replacement. Existing lagoons that are leaking, seeping excessi-
vely, or tnat nave liners found to be In a deteriorated condition can be retro-
fitted with new Hner systems If all supporting structures are sound. Liner
replacement usually requires a shutdown period to drain and prepare the lagoon
for the new liner.
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So11-benton1te and rigid liners with unacceptable cracks and Increased per-
meability properties must be removed and disposed prior to replacement. If the
degradation Is due to waste-liner Incompatibility, retrofitting with a synthetic
liner may be desired. Where the lagoon bottom has deformed and caused cracks or
other liner failure, grading and subsurface preparation will be required before
Uner replacement. A leachate detection/collection system may also be warranted
prior to liner Installation. If required by circumstances and/or regulatory
agencies, contaminated subsoils should be treated or disposed off site prior to
retrofit.
Synthetic liner replacement would similarly require draining the lagoon, re-
moving the old liner, resurfacing the subgrade and Installing the new liner. A
double liner system of clay overlaid by a flexible membrane may be required to
avoid a second failure. A leachate detection/collection system may also be
desired. As above, It may be necessary to treat or dispose of contaminated
subsoils.
6.5.1.2 Liner Repair. Of the admixed material liners, bentonite-soil liners can
be repaired with the greatest ease and effectiveness. Bentonlte-slurry additions
to a filled pond can often repair small holes In a soil or bentonite-llned pond.
Draining 1s required for repair of cement and asphalt mix liners which is not al-
ways effective. Placement of a soil layer over rigid materials may provide the
desired low permeability layer. See References 2, 8 and 10 for further discussion.
Synthetic liners can be repaired by patching If the leakage Is caused by a
small hole and it can be located and reached without damaging the rest of the
Uner. A soil overlayer may be desired for added protection and may provide
an hydraulic barrier sufficient to stop small leaks (2 and 8).
6.5.1.3 Measures to Assure Continuity of Operation During Retrofitting/Repair.
Except as noted above, In most cases a lagoon (or portion thereof) must be removed
from service during retrofitting/repair activities. If this shutdown Is properly
managed, the facility should be able to provide the level of treatment required
by permit, as long as the remaining plant capacity Is sufficient to handle
expected flows. Continued successful operation depends primarily on the ability
of plant personnel to define and take adequate measures to ensure that the design
capacity of the remaining unit operations Is not exceeded. Those remaining
facilities must be able to handle their expected Increased load during the repair
period. Whenever possible, retrofitting and repair work should be conducted
during periods of expected low flow to minimize the chance of capacity exceedance.
The overall success of any retrofit/repair activity depends on proper con-
struction sequencing. All temporary diversion facilities should be fully opera-
tional prior to the Initiation of work. The construction, Installation and opera-
tion of these facilities should be explicitly Included In the construction docu-
ments for the retrofit/repair work. Typical diversion facilities Include
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temporary pipe or channel connections, diversion valves and gates and pipe
plugs. In extreme cases, temporary lagoons may be constructed If required to
maintain design capacity. Due to variations In the construction and operation of
different facilities, the particular measures needed to ensure continued opera-
tion will be specific to each plant.
6.5.1.4 Costs. As for the construction of new lagoons, the costs for retrofitting
an existing lagoon are very site-specific. Costs of liner repair are highly
dependent on the size of the area requiring repair; unit costs for liner mater-
ials (as Installed) are presented In Appendix 6.3 (Tables 6.3-2 and 6.3-3).
Retrofitting an entire lagoon can require a variety of actions, ranging from
simple placement of a liner with no additional excavation or subgrade preparation
to removal and disposal of an old liner, recompactlon and other subgrade prepara-
tion, Installation of a new liner(s) and a leak detection/collection system, If
necessary. Additional costs will be Incurred through the need for temporary
diversion facilities to ensure continuity of operation. These costs are
site-specific and thus are not Included In this discussion.
6.5.2 Improvement of O&M and Monitoring Practices
All existing O&M practices should be reviewed and any Identified deficiencies
should be corrected. Common deficiencies Include:
o Infrequent and Inadequate Inspections;
o Inadequate preventive maintenance;
o Improperly sited monitoring wells;
o Improper Quality Assurance or Quality Control techniques used In sampling
and analysis; and
o Inadequate training of personnel In O&M procedures and emergency/safety
practices.
6.5.3 Pretreatment
Based on analyses, of lagoon Influent, It may be desirable to require pre-
treatment for specific waste dischargers to prevent damage (and subsequent
need for modification, repairs, or both) to the lagoon system (see Appendix
6.4, Table 6.4-1).
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6.6 LAGOON REMEDIATION
If contamination Is discovered at a municipal lagoon facility and 1t Is de-
termined that the contaminants present pose a significant risk to human health
and the environment, a site Investigation must be performed and the need for
remedial action assessed. Detailed guidance In the performance of both remedial
Investigations and feasibility studies has been prepared by USEPA for sites
covered by the Comprehensive Environmental Response, Compensation and Liability
Act, known as "Superfund" (15, 16 and 17). Although the guidance may not strictly
apply to municipal lagoons, It provides a framework for structuring site Investiga-
tion and selecting the best remedial alternative.
6.6.1 Site Investigation
The information to be obtained in a site investigation Includes (to the ex-
tent needed to accurately assess conditions at the site):
o Detailed hydrogeology of the site, Including the presence and location of
low permeability strata or bedrock, ground-water flow gradient, flow
velocity and the saturated thickness of the aquifer;
o Specific pollutants and their concentrations In wastewater, sediments,
soils, and ground water (and their subsequent behavior in these media);
o Potential migration/exposure pathways (i.e., Ingestion of contaminated
ground water);
o The location and number of potential receptors (i.e., residents rely-
ing on local wells for drinking water); and
o The presence of nearby surface waters which may receive overland flow or
exflltratlng ground water contaminated by the site.
The extent and level of detail of any site Investigation will vary depending
on the site and should be determined with the aid of appropriate regulatory auth-
orities. For example, If the aquifer Is not used and there are no potential re-
ceptors, less extensive sampling may be required than If water supply wells were
located 500 feet downgradient. Regulatory authorities will use this Information,
along with available health effects data, to set target cleanup levels for the
site.
6.6.2 Identification of Remedial Alternatives
Once the site Investigation Is complete, potentially applicable remedial
technologies and alternatives should be Identified for further assessment. Each
alternative Is subjected to a feasibility study, In which It Is evaluated and
compared with other alternatives on the basis of:
o Technical applicability;
o Impact on public health;
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o Institutional considerations (e.g., regulatory requirements);
o Environmental Impacts; and
o Costs.
Based on the feasibility study, one remedial alternative Is recommended for
Implementation. This alternative may be comprised of several technologies,
selected to address different aspects of a site (e.g., excavation and landfill of
soil, on-site treatment of contaminated ground water and long-term ground-water
monitoring). In some cases, remediation may be confined to source removal or
containment, along with necessary restrictions on land and ground-water use.
General types of response alternatives that are potentially applicable to
municipal lagoons are outlined In Appendix 6.5 (Table 6.5-1). Specific technolo-
gies that could be Implemented as part of these response actions are listed in
Appendix 6.5 (Table 6.5-2), along with their associated advantages and disadvant-
ages. A similar analysis of processes suitable for the treatment of contaminated
ground water Is provided In Appendix 6.5 (Table 6.5-3). For detailed information
on these technologies, the reader Is referred to References 7, 17 and 18.
6.7 FINDINGS AND CONCLUSIONS
o For new lagoons, adherence to proper siting criteria, sound design and
construction practices, Industrial pretreatment and pollutant loading
limitations , and finally a rigorous operations and maintenance program
together can minimize the potential for groundwater contamination. Wherever
seepage into an aquifer could occur, groundwater monitoring with properly
sited upgradient and downgradient wells is essential for assessing actual
contamination and, If necessary, determining the appropriate corrective
action.
o A ground-water monitoring program with properly sited upgradient and down-
gradient wells Is the basic prerequisite for defining measures to prevent
ground-water contamination for new lagoons or reduce such contamination
for existing lagoons.
o Available alternative measures that could be used to prevent ground-water
contamination from new lagoons or control contamination from existing lagoons
Include one or more of the following:
(1) Proper siting;
(2) Pretreatment of Industrial wastes;
(3) Installation of properly designed synthetic or soil linings In new
lagoons or retrofit and repair of such linings In existing lagoons;
(4) Changes in Inspection and maintenance procedures;
(5) Leak repair or collection and treatment of leachate; and
(6) Containment and treatment of the contaminant plume.
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CHAPTER 6 REFERENCES
1. State of Wisconsin. Cr. Register, 'October 1985, No. 358. Chapter NR140 -
Groundwater Quality (pp 679-695).
\
2. Great Lakes - Upper Mississippi River Board of State Sanitary Engineers, 1978.
Recommended Standards for Sewage Works. Health Education Service, Inc., Albany,
New York.
3. USEPA, 1980. Innovative and Alternative Technology Assessment Manual. USEPA,
Office of Water Programs, Washington, D.C.
4. USEPA, 1983. Lining of Waste Impoundment and Disposal Facilities. USEPA,
Office of Researcn and Development, Municipal Environmental Research Labora-
tory, Cincinnati, Ohio
5. EarthTech Research Corporation, 1983. "Evaluations of Time-Domain Reflecto-
met.ry and Acoustic Emission Techniques to Detect and Locate Leaks In Waste
Pond Liners." In: Land Disposal of Hazardous Waste, Proceedings of the Ninth
Annual Research Symposium.EPA/500/9-83/018.
6. Peters,, W.R. and D.W. Shultz of the Southwest Research Institute, 1983. "Pilot
Scale Verification of a Liner Leak Detection System." In: Land Disposal of
Hazardous Waste, Proceedings of the Ninth Annual Research Symposium. EPA/600/
9-83/018. "~~1
7. Shuckrow, A.J., A.P., Pajak, and C.J. Touhlll, 1982. Management of Hazar-
dous Waste Leachate. USEPA, Office of Solid Waste anHEmergency
Response, Washington, D.C.
8. USEPA, 1986. Criteria for Identifying Areas of Vulnerable Hydrogeology under
the Resource Conservation and Recovery Act. Statutory Interpretive Guidance""^"
Manual for Hazardous waste Land Treatment, Storage, Disposal Facilities -
interim Final. USEPA, Office of solid waste and Emergency Response. Washington.
inn
9. Geotechnlcs, Inc., 1980. Landfill and Surface Impoundment Performance Evalua-
tlon Manual. EPA/530/SW/89Hc"I USEPA, Office of Research and Develop ment,
Municipal Environmental Research Laboratory, Cincinnati, Ohio.
10. USEPA, 1985. Design, Construction and Evaluation of Clay Liners for Waste Manage-
ment Facll 1 ties. EPA/530/SW-86/007.USEPA,Office of Research and Development,
Washington, D.C.
11. Bass, J.M., 1985. Assessment of Synthetic Membrane Successes and Failures at
spo*
ancT Development, Cincinnati, Ohio.
of Sy
n CR
Waste Storage and Disposal sites. EPA/6UU/Z-85/1UO.USEPA, Office of Research
12. Mlddlebrooks, E.J., C.D. Perman, and I.S. Dunn, 1978. Wastewater Stabilization
Pond Linings. USEPA, Office of Water Program Operations, Washington, D.C.
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13. USEPA, 1984. Liner Materials Exposed to Hazardous and Toxic Wastes. EPA/600/
2-84/169. U.S. Environmental Protection Agency, Washington, D.C.
14^ Ghasseml, M., M. Haro, and L. Fargo, 1984. Assessment of Hazardous Waste
Surface Impoundment Technology; Case Studies ana perspectives or Experts?
EPA/600/2-84/173.USEPA, Office of Research and Development, Municipal En-
vfronmental Research Laboratory, Cincinnati, Ohio.
15. USEPA, 1986. Guidance Document for Cleanup of Surface Impoundment Sites. USEPA,
Office of Emergency and Remedial Response, Washington, D.C.
16. USEPA 1985. Guidance on Remedial Investigations under CERCLA. USEPA, Office of
Research and Development, Hazardous waste Engineering Laboratory, Cincinnati,
Ohio.
17. USEPA, 1985. Handbook -Remedial Action at Waste Disposal Sites (Revised).
EPA/625/6-85/006. USEPA, Office of Emergency and Remedial Response, Washington,
D.C. with the Office of Research and Development and Hazardous Waste Engineer-
Ing Research Laboratory, Cincinnati, Ohio.
18. Repa, E. and C. Kufs, 1985. Leachate Plume Management. EPA-540/2-85/004.
USEPA, Office of Solid Waste and Emergency Response and Office of Emergency
and Remedial Response, Washington, D.C., with Office of Research and Develop-
ment, Cincinnati, Ohio
19. USEPA, 1983. Design Manual, Municipal Wastewater Stabilization Ponds. EPA/
625/1-83/015. USEPA, Office of Research and Development, Cincinnati, Ohio.
6-20
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