PB88-185251
CORRECTIVE MEASURES FOR RELEASES TO
GROUND WATER FROM SOLID WASTE MANAGEMENT
UNITS
Alliance Technologies Corporation
Bedford, MA
Aug 85
U.S. DEPARTMENT OF COMMERCE
National Technical Information Service
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CORRECTIVE MEASURES FOR RELEASES TO
GROUND WATER FROM SOLID WASTE MANAGEMENT
UNITS
Alliance Technologies Corporation
Bedford, MA
Aug 85
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r,CA-TR-85-69-G
Prepared for
U.S. Environmental Protection Agency
Land Disposal Branch
Office of Solid Waste
401 M Street, SW
Washington, D.C. 20460
Contract No. 68-01-6871
Work Assignment No. 51
EPA Work Assignment Manager
George Dixon
CORRECTIVE MEASURES FOR RELEASES
TO GROUND WATER FROM
SOLID WASTE MANAGEMENT UNITS
Draft Final Report
• August 1985
Prepared by
Michelle M. Gosse
Lisa L. Farrell
Nancy Prominski
Mark Arienti
Donald Dwight
Eric Wood
Steven C. Konieczny
Neil M. Ram
CCA CORPORATION
GCA/TECHNOLOGY DIVISION
Bedford, Massachusetts U1730
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30277-101
REPORT DOCUMENTATION »• «TORT NO. z. i ,. R«,Bi.nt-, Acceiiion NO.
PAGE EPA/530-SW-88-020 Ps38 - 1 •« " O ^ 1 .^
4. Title and Subtitle
Corrective measures for releases to ground water from solid
waste management units
7. Author**)
M. Gosse, L. Farrell, etc.
9. Ptrforming Organuauon Name and Addra»
GCA Corp.
GCA/Tech. Division
Bedford, MA 01730
12. Sponsoring Organization Name end Addrma
U.S. Environmental Protection Agency
Office of Solid Waste
401 M Street
Washington, D.C 20460
1 Report Olti
8/85
«.
•• Performing Organization Rept. No.
10. Praioct/Teak/Work Unit No.
WA 51
11. Contrect(C) or Gr»nt(G) No.
(C168-01-6871
(C)
11. Typo o/ Rtport * Period Covered
Draft Final Report
14.
15. Supplementary Note*
1C. Abttreet (Limit: 200
HSWA of 1984 requires corrective measures for all releases of hazardous waste or
hazardous constituents from any solid waste management unit at a treatment, storage
or disposal facility seeking a RCRA permit, regardless of the time at which waste
was placed in such unit. In this report, ground-water control/treatment technologies
ahd hydrogeologic settings are identified and assessed.
17. Document Aiwlytit e. Detcrtptort
b. Identlfierv/Open-Cnded Termt
e. COSATI field/Croup
!«. Availability Statement ~~~~
RELEASED UNLIMITED
19. Security Cla» (This Report)
Unclassified
20. Security Clan (Thli Page)
Unclassified
21. No. of Pages
22. Price •
See Inttruetioni on fttverte
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
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DISCLAIMER
This Draft Final Report was furnished Co Che Environmental Protection
Agency by the CCA Corporation, GCA/Technology Division, Bedford, Massachusetts
01730, in fulfillment of Contract No. 68-01-6871, Work Assignment No. 51. The
opinions, findings, and conclusions expressed are those of the authors and not
necessarily those of the Environmental Protection Agency or the cooperating
agencies. Mention of company or product names is not to be considered as an
endorsement by the Environmental Protection Agency.
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CONTENTS
Figures iv
Tables v
1. Introduction 1-1
Background 1-1
Definition/Identification of Solid Waste
Management. Units -, 1-2
Identifying Releases to Ground Water 1-5
2. Overview of Corrective Measures for Releases to Ground Water 2-1
General 2-1
Hydrogeologic Approaches 2-4
Treatment Technologies 2-75
3. Case Studies 3-1
Introduction 3-1
Cilson Road Site, Nashua, NH 3-4
Mango lien Army Creek Landfill, New Castle, DE .... 3-11
Kocky Mount.iin Arson.! I, Denver, CO 3-15
Striugt'e I low Site, Riverside, CA 3-19
Gulf Coastal Plain Site % 3-23
Whitmoyer Laboratories, Myerstown, PA 3-26
4. Recommendations for Selecting and Implementing Corrective
Measures for Releases to Ground Water 4-1
Overview 4-1
Selection Process 4-2
Use of Summary Tables 4-5
Case Study Example 4-7
References 5-1
Appendices
A. Underground Injection Wells A-l
111
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FIGURES
Number
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
2.10
2.11
2.12
2.13
2.14
2.15
3.1
3.2
Plan of Circumferential Wall Placement
Plan of Upgradient Placement with Drain
Semicircular Grout Curtain Around Upgradient End of
Landfill
Block Displacement Method
Schematic of a Well Point Dewatering System r
Theoretical Representation of Hydrodynamic Isolation
Principle of Withdrawal Wells
Principle of Pressure Ridge System
Collector Drain System
Hydraulic Gradient Toward Interceptor System
Relative Location of a Permeable Treatment Bed
Cross Section of Landfill Treated by Chemical
Treatment of the Contaminated Ground Water by the
Bio reclamation Technique
Membrane Processes Using a Pressure Driving Force in
(a) Plane and (b) Tubular Designs
Worksheet for Screening Case Studies
Outline for Case Studies Write-Up
Pages
2-16
2-18
2-19
2-28
2-35
2-39
2-42
2-43
2-45
2-50
2-51
2-56
2-61
2-64
2-89
3-2
3-7
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TABLES
Number . Page
1.1 Causes of Direct Ground-Water Releases 1-10
1.2 Causes of Indirect Ground-Water Releases 1-11
2.1 Summary of Slurry Wall Configurations 2-20
2.2 Advantages/Disadvantages of Slurry Cut-Off Walls 2-23
2.3 Types of Grout 2-25
2.4 Advantages/Disadvantages of Grout Systems 2-31
2.5 Advantages/Disadvantages of Steel Sheet Piles 2-34
2.6 Advantages/Disadvantages of tlie Block Displacement Method . 2-38
2.7 Advantages/Disadvantages of Well Systems 2-48
2.8 Advantages/Disadvantages of Subsurface Drains 2-54
2.9 Advantages/Disadvantages of Crushed Limestone
Treatment Bed 2-58
2.10 Advantages/Disadvantages of Activated Carbon Treatment
Bed 2-59
2.11 Advantages/Disadvantages of Glauconitic Treatment Bed . . . 2-60
2.12 Advantages/Disadvantages of Bioreclamation Technique . . . 2-65
2.13 Summary of Hydrogeologic Ground-Water Control/Treatment . .
Technologies 2-66
2.14 State-of-the-Art Techniques for Treating Common
Ground-Water Contaminants 2-76
2.15 Operating Results and Characteristics of Carbon Adsorption
Systems for Influent Contaminants at g/1 Levels 2-77
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TABLES (continued)
Number Page
2.16 Operating Results and Characteristics of Carbon Adsorption
Systems for Influent Contaminants at tng/1 Levels 2-78
2.17 General Features of Construction and Operation of
Rapid Sand Filters 2-81
2.18 Treatment Applications of the Most Commonly Used Oxidants . 2-87
2.19 Calculated Henry's Law Constants at 20°C for
Organic Compounds 2-92
3.1 Types of Release(s) and Remedial Response(s) Implemented
at Selected Sites 3-5
4.1 Summary of Ground-Water Control/Treatment and Treatment
Technologies 4-6
4.2 Source Control Corrective Measures for Direct and Indirect
Releases to Ground Water 4-8
VI
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SECTION 1
INTRODUCTION
BACKGROUND
The 1984 amendments to the Hazardous and Solid Waste Act (HSWA) provide
the Agency with additional authorities for corrective action at facilities
seeking permits, and for facilities with interim status under
Section 3005(e). The amendments for corrective action address:
• Continuing releases at permitted facilities (Section 206);
• Corrective action beyond facility boundaries (Section 207);
• Financial responsibility for corrective action (Section 208); and
• Interim status corrective action orders (Section 233). *
The new authorization allows EPA to require corrective action in response to a
release of hazardous waste or hazardous constituents from any solid waste
management unit (SWMU) to the environment, regardless of when the waste was
placed in such unit. This authority addresses release to all media, including
ground water.
Subpart F of 40 CFR Part 264 requires cleanup of ground water at hazardous
waste land disposal facilities when hazardous constituents (identified in 40
CFR Part 261, Appendix VIII) are detected in ground-water monitoring wells.
As indicated above, Section 206 of the HSWA amendments (Section 3004(u) of the
Resource Conservation and Recovery Act (RCRA)) expand these "corrective
action" requirements to include ground-water releases from any SWMU.
Based on these 1984 amendments, the U.S. EPA, Office of Solid Waste (OSW),
Land Disposal Branch, must develop technical guidance for permit writers to
implement the "continuing releases" provision. Implementation of these new
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requirements will typically take place in three stages: (1) determining
whether there is a release at a facility that warrants further investigation,
(2) collecting additional information to define the nature and extent of the
release, and (3) selecting and performing the corrective measures. The
guidance provided in this document will identify mechanisms to correct
releases Co ground water. A draft document entitled "Phase I Corrective
Action Guidance: Information and Methodology for Identifying Releases from
Solid Waste Management Units" provides guidance on identifying releases to
ground water (Sobotka, 1985).
The remainder of this section, Section 1, identifies and defines the
various types of solid waste management units (SWMUs). It also discusses
releases to ground water from these units. Section 2 provides an overview of
corrective measures including ground-water treatment technologies and
mechanisms to intercept or divert ground-water flow. Section 3 discusses case
studies where releases to ground water from SWMUs have occurred and identifies
the corrective measures undertaken at the site to clean-up the contaminated
ground water. Finally, Section 4 provides recommendations for the application
of corrective measures to ground-water releases.
DEFINITION/IDENTIFICATION OF SOLID WASTE MANAGEMENT UNITS
Congress defined the term solid waste management unit (SWMU) to include
any unit at a facility "from which hazardous constituents might migrate,
irrespective of whether the units were intended for the management of solid
and/or hazardous wastes". SWMUs represent a broad category of waste
management units of which hazardous waste management units are a subset.
Under the new requirements, Subtitle D landfills and other units (at
facilities seeking a RCRA permit) which primarily handle non-hazardous solid
waste could be required to take corrective action if there is evidence of a
release of hazardous constituents from these units. The definition of SWMU
includes both active, or operating units, and inactive, or non-operating
units. This defintion also includes certain units that have previously been
exempted from 40 CFR Part 264 requirements, such as wastewater treatment tanks.
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The new requirements also extend to spills and other releases from SWMUs
that may occur during the normal operation of these units. However, spills
that cannot be linked Co SWMUs, such as those originating from production
areas or product storage tanks, are not covered under the continuing release
provision. These spills are illegal, however, under other RCRA provisions
(Sobotka, 1985).
The types of units included in the SWMU definition are in alphabetical
order:
• container storage areas;
• incinerators;
• injection wells*;
• landfills;
• land treatment units;
• surface impoundments;
• tanks (including 90-day accumulation tanks);
• transfer stations;
• underground injection wells*;
• waste handling areas;
• waste piles;
• waste recycling operations; and
• wastewater treatment tanks.
A container, as defined in 40 CFR Part 260.10, is any portable device in which
a material is stored, transported, treated, disposed of or otherwise handled.
A container storage area is the location where the container(s) resides.
Container storage areas typically consist of 55-gallon drums, but may very in
size. These areas usually include a spill containment system, typically a
diked area above a low permeable barrier that underlies the storage area, and
sometimes include a cover to shed precipitation.
Underground injection wells are not discussed in the body of this report;
their regulatory status and their potential cause of release to ground water
is discussed in Appendix A.
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An incinerator, as defined in 40 CFR Part 260.10, is an enclosed device
using controlled flame combustion, the primary purpose of which is to
thermally break down hazardous waste. Examples of incinerators are rotary
kiln, fluidized bed, and liquid injection incinerators.
A landfill, as defined in 40 CFR Part 260.10, is a disposal facility or
part of a facility where hazardous waste is placed in or on land and which is
not a land treatment facility, a surface impoundment, or an injection well.
This facility typically consists of wastes placed on a liner system to collect
liquids draining from waste and includes a similar liner system (cover) on top
of the waste to prevent incident precipitation from entering the waste.
A land treatment facility, as defined in 40 CFR Part 260.10, is a facility
or part of a facility at which hazardous waste is applied onto or incorporated
into the soil surface; such facilities are disposal facilities if the waste
will remain after closure. Land treatment involves degradation of organic
compounds through physiochemical biologic degradation. Nutrient and
biological seeding frequently occurs with aeration of the soil/waste mixture
by rototilling, plowing or harrowing.
A surface impoundment or impoundment, as defined in 40 CFR Part 260.10,
means a facility or part of a facility which is a natural topographic
depression, man-made excavation, or diked area formed primarily of earthern
materials (although it may be lined with man-made materials), which is
designed to hold an accumulation of liquid wastes or wastes containing free
liquids, and which is not an injection well. Examples of surface impoundments
are holding, storage, settling and aeration pits, ponds and lagoons.
A tank, as defined in 40 CFR Part 260.10, is a stationary device designed
to contain an accumulation of hazardous waste which is constructed primarily
on non-earthern materials (e.g., wood, concrete, steel, plastic) which provide
structural support.
A transfer facility, as defined in 40 CFR Part 260.10, is any
transportation related facility including loading docks, parking areas,
storage areas and other similar areas where shipments of hazardous waste are
held during the normal course of transportation.
Waste handling areas include container filling and emptying areas, and
transfer locations (e.g. from trucks to tanks) associated with all waste
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management facilities. Waste handling areas are usually associated with waste
transfer, such as solvent reclamation staging, incineration charging, or
transfer from tank truck to tank, or drum storage area to trucks.
A (waste) pile, as defined in 40 CFR Part 260.10, Ls any non-containerized
accumulation of solid, non-flowing hazardous waste that is used for treatment
or storage. This facility typically consists of wastes placed on a liner
system to collect liquids draining from the waste.
Waste recycling operations are areas where operations involving the
processing of waste materials for recovery are undertaken.
A wastewater treatment unit, as defined in 40 CFR Part 260.10, is a device
which: (1) is part of a wastewater treatment facility which is subject to
regulation under either Section 402 or Section 307(b) of the Clean Water Act;
(2) receives and treats or stores an influent wastewater which is a hazardous
waste as defined in 40 CFR Part 261.3, or generates and accumulates a
wastewater treatment sludge which is a hazardous waste as defined in
40 CFR Part 261.3, or treats or stores a wastewater treatment sludge which is
a hazardous waste as defined in 40 CFR Part 261.3; and (3) meets the
definition of tank in 40 CFR Part 260.10 (as previously discussed).
IDENTIFYING RELEASES TO GROUND WATER
A release to ground water has occurred when concentrations of hazardous
constituents (HCs), defined in 40 CFR Part 261, Appendix VIII, detected at
downgradient wells located at the point of compliance (POC) exceed either
background constituent levels, the maximum concentrations for parameters in
Table 1 of 40 CFR Part 264.94 or some Alternate Concentration Limit (ACL)
(Sobotka, 1985). The "Phase I Corrective Action Guidance: Information and
Methodology for Identifying Releases from Solid Waste Management Units", draft
report (Sobotka, 1985), provides guidance to facility owners or operators on
identifying releases to ground water.
All land-based SWMUs (landfills, surface impoundments, waste piles and
land treatment units) should be considered as having releases to ground
water. This is consistent with 40 CFR 264.70(a) which requires "regulated"
units (namely those indicated above) to comply with Subpart F. Other land
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based units and certain above ground units th.it contain or have contained
hazardous constituents should be considered to be releasing where the existing
monitoring system or inspection program is not capable ot detecting a release
or where there is a ground-water monitoring system in place and background
concentrations of hazardous constituents have been exceeded. Other land-based
SWMUs subject to ground-water monitoring include: container storage areas
without secondary containment; tank systems, including appurtenances (e.g.
pipes and valves), without full secondary containment and leak detection
systems and which are not fully above the ground; and waste handling areas
where discharges have occurred and have not been adequately cleaned up.
Categorical exemptions may be made for units that overlie Class III ground
waters since they are not considered as a potential source of drinking water
and are of limited beneficial use.
Specifically, "direct" ground-water releases from SWMUs occur primarily as
a result of poor design and operating practices. General categories which the
applicant should have addressed include but are not limited to:
• inadequate (JA/QC procedures uncd during construction and operation of
the SWHU;
• insufficient hydrogeologic investigations;
• improper luuiulation preparation prior to liner system installation;
• inadequate design of liner, leachate collection and leak detection
systems; and
• inadequate secondary containment and runon/runoff control systems.
Although the above design and operating practies should be considered for all
types of SWMUs, they are of particular importance to land-based SWMUs such as
landfills, surface impoundments, waste piles and land treatment units. During
and following liner system construction, strict QA/QC procedures should be
adhered to to ensure that no nonuniformitiea, damage or imperfections
( i in- I ml i up. i n.nle<|ii.il e liner M.MIIIIH) exixl i 11 I In* liner r;yM(etn (i.e., synthetic
.ind clay liners, leachate collection and leak detection systems) which could
result in failure and subsequent release of hazardous constituents.
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Additionally, prior to liner system installation, particularly for synthetic
liners, the foundation, or bedding layer should be smooth, uniform and free of
holes, cracks or pretruding debris which could result in increased hydraulic
conductivity. In designing liner, leachate collection and leak detection
systems these systems must be capable of withstanding waste loading, be
compatible with hazardous constituents, prevent migration of hazardous
constituents, and withstand physical, chemical and biological attack.
Inadequate design of any of these factors could result in hazardous
constituent release.
Hydrogeologic investigations should provide complete and detailed
information on subsurface characteristics, for example, fault locations, depth
to bedrock, water table and perched or confined aquifer locations, and
potential hazardous constituent transport pathways in the event of a release.
Hydrogeologic investigations are also essential to ensure that after
installation of a SWMU the facility will not fail (.structurally) as a result
of subsurface movement due to overburden pressures.
"Indirect" releases to ground water from SWMU3 occur as a result of
releases to soil and/or surface water that through, for example, percolation
make their way to ground water, thereby causing contamination. These releases
are due to unpermitted point source discharges, spills, leaks, or surface or
subsurface (unsaturated zone) run-off.
Certain unsound design and operating practices will allow waste to migrate
from the SWMU and possibly mix with run-off. Examples include surface
impoundments with insufficient freeboard that do not prevent periodic
overtopping, and leaking tanks or containers. In addition, precipitation
falling on exposed wastes can dissolve or transport hazardous constituents.
For example, at typical uncapped active or inactive waste piles and landfills
precipitation and leachate are likely to mix at the toe of the active face or
the low point of the trench floor. Design and operating practices which could
result in "indirect" releases to ground water from SWMUs are discussed below.
For further discussion'on indirect releases refer to the following draft
reports: "Corrective Measures for Releases to Surface Water", August 1985,
prepared by E.G. Jordan Co. under subcontract to GCA/Technology Division; and,
"Corrective Measures for Releases to Soil from Solid Waste Management Units",
August 1985, prepared by GCA/Technology Division.
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Container Storage Areas
Potential releases may occur due to failure to include a spill containment
structure; inappropriate separation of incident precipitation and spill
residue; accidental spills during operation; and corrosion of containers. The
presence of leaking containers or liquids increases the possibility of a
current or future release from these units. Leaking containers allow
uncontained run-off to mix with and transport hazardous waste. Uncontained
run-off may lead to either soil, ground water, or surface water contamination.
Incinerators
In addition to releases associated with waste handling tanks and container
storage facilities releases may occur as a result of residue quenching water
releases and stack emission control effluent.
Landfills and Waste Piles
Typical releases may be from inadequate control of run-on and incident
precipitation resulting in contaminated surface runoff from the facility, if
the water comes in contact with the waste and carries dissolved or suspended
waste solids. A failed leachate collection/removal system may also result in
indirect releases to ground water through indirect release to surface-water-
through seeps. In addition, a failed cover or liner system may result in
seeps.
Land Treatment Units
Releases occur primarily from run-on and incident precipitation.
Secondary releases that may affect stream water quality and subsequently
affect ground water include air blown solids, evaporation and recondensation
of volatiles or semivolatiles.
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Surface Impoundments
Surface impoundments with inadequate freeboard may result in overtoppin
because of wave action during storm events. Earth dikes which are not
structurally sound may result in releases through cracks and leaks. The lack
of either grass, rip rap (rock) or other protection on dikes may contribute to
future releases because of erosion resulting from exposure to wind and water.
Tanks
Release of hazardous constituents from tanks may occur as a result of
leaks or overflow. Leaks can occur due to cracks or structural failure.
Corrosion caused by waste/construction material or soils can contribute to
inadequate structural integrity of tanks. In addition, faulty valves or pipe
connections or open valves may result in release of hazardous constituents.
Operational failure may result in tank overflow. lack of a secondary
containment system further increases the risk of release to the environment.
Waste Handling Areas
Typical releases occur as a result of recurring spills (of limited
volume), and surface runoff flushing contaminated surfaces (soil, concrete,
spill containment structures).
Tables 1.1 and 1.2 summarize design and operating practices associated
with direct and indirect releases to ground water from SWMUs.
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TABLE 1.1 CAUSES OF DIRECT GROUND-WATER RELEASES*
Design Practices
Inadequate QA/QC procedures used during construction
Insufficient hydrogeologic investigations
Improper foundation preparation prior to liner system installation
Inadequate design of liner, leachate collection and leak detection systems
Operational Practices
Inadequate QA/QC procedures used during operation of SWMU
^Applicable to landfills, surface impoundments and waste piles.
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TABLE 1.2. CAUSES OF INDIRECT GROUND-WATER RELEASES*
Design and Operating Practices
Applicable SWMUs
Design Practices
Insufficient cover
Inadequate freeboard
(runon/runoff control)
Presence of liquids or 'waste
exposed to environment
Location of a SWMU near a
surface water body
Inadequate secondary containment
and runon/runoff control
Operational Practices
Operational failure, faulty piping
or other occurances resulting in
leaks and spills
Cracks or structural failure in
dike walls or tanks
Lack of protection from dike wall
erosion or tank corrosion
Repair, installation or replacement
of any primary or secondary
containment system while the unit
contains waste
Inadequate QA/QC procedures used
during operation of SWMU
Surface impoundments, waste piles,
landfills
Surface impoundments
Surface impoundments, waste piles,
landfills, land treatment units
Surface impoundments, waste piles,
landfills, land treatment units
Waste piles, landfills, land treatment
units, container storage areas, tanks,
waste handling areas
Tanks, container storage areas,
waste handling areas
Surface impoundments, landfills,
container storage areas, tanks
Surface impoundments, landfills,
tanks, container storage areas
All SWMUs
All SWMUs
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SECTION 2
OVERVIEW OF CORRECTIVE MEASURES FOR
RELEASES TO GROUND WATER
GENERAL
As previously indicated, the Hazardous and Solid Waste Act Amendments of
1984 require corrective measures for all releases of hazardous waste or
hazardous constituents from any solid waste managment unit (SWMU) at a
treatment, storage or disposal facility seeking a RCRA permit, regardless of
the time at which waste was placed in such unit.
Corrective measures for releases to ground water involve possible
upgradient diversion, downgradient diversion/interception, and
extraction/recharge of ground water for certain hydrologic configurations and
the assessment of treatment technologies to remove hazardous constituents or
to treat them in place. In this section, ground-water control/treatment
technologies and hydrogeologic settings are identified and assessed. From
these assessments and from the evaluation of case studies (Section 3) on
corrective measures implemented for clean-up of hazardous constituent releases
to ground water, the relative success or failure of each technology can be
determined for various hydrogeologic settings and waste types. Knowledge of
relative successes or failures provides the permit writer and the permit
applicant with guidance to determine the most appropriate corrective measures
for implementation at the site in question.
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However, prior co selection of a correccive measure or sec of corrective
measures, Che naCure and exCenC of release, and Che need for such meaures must
be adequately assessed. Only after Che need for correccive measures has been
defined can appropriaCe reliable, effeccive, and cosc-efficienc corrective
measures be selected. The assessment of need will address such factors as
source characterization, transport mechanisms, receptor identification and
risk assessment. Depending on the outcome of the needs assessment, corrective
measures including source control and/or offsite containment and recovery, and
control/treatment technologies may be implemented
Assessing Need for Corrective Measures
As stated previously a corrective measures for ground-water release is
required when concentrations of HCs measured at the point of compliance,
exceed either background constituent levels, the maximum concentration for
parameters in Table 1 of 40 CFR Part 264.94 or some Alternate Concentration
Limit. When corrective measures are required, an assessment should first be
made to define site conditions and the extent of containment release, to
identify the goal of corrective measures, to assist in the selection of
corrective measures, and to establish a time frame for implementation of
corrective measures. An assessment of the need for corrective measures should
include the following: source characterization; hazardous constituent
distribution; fate and transport mechanisms; hazard assessment; receptor
identification; and risk assessment. These assessment factors are discussed
below.
Source Characterization—
The first step in the assessment of need is source characterization.
Source characterization involves identifying volumes and concentrations of
hazardous constituents present, and the physical and chemical characteristics
of the hazardous constituents.
Identification of hazardous constituents may be a relatively simple matter
of reviewing records of the solid waste management unit (SMWU) or may require
tesc pics and borings, sampling of soil, sediments, ground water and surface
water, and chemical analysis. The identification process should include
estimaces of Che volume of each hazardous constiCuent and ics locacion boch
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onsite and offsite. Once identified, similar hazardous constituents should be
grouped by chemical type and similarity in metabolic or environmental fate.
The physical and chemical characteristics of concern include mobility,
bioaccumulation potential, degradation (persistence) and any special
characteristics (explosivity or flammability). Mobility of chemicals is
primarily related to the solubility, volatility, adsorbability, partition
coefficients, and density of the chemicals. Hazardous constituent mobility is
important in assessing the risk associated with a particular site. The
bioaccumulation and degradation potential also relate to the risk associated
with the chemicals released from a site.
Special characteristics of the chemicals must also be considered.
Chemicals may also react with soils thereby either increasing or decreasing
the physical properties of the soil, most notably permeability. The potential
for chemical interactions should also be considered. Chemical-to-chemical or
waste-to-waste interactions may affect mobility, reactivity, solubility, or
toxicity of the chemicals. The potential for wastes or reactive products to
interact with containment materials should also be considered.
Transport Mechanisms—
Hazardous constituents may be transported in ground waters intact, in a
dissolved state, as colloids or particulates, or adsorbed to sediment. The
method by which hazardous constituents are transported to and in ground waters
is important in evaluating the risk associated with a release. The transport
mechanism aids in identifying media contaminated or likely to be contaminated,
the fate of hazardous constituents in the environment and receptors likely to
be affected, and the effectiveness of corrective measures.
Receptor Identification—
Receptor identification is an important part of determining the need for
implementing corrective measures and the time frame within which
implementation should occur. Receptor identification will be related to
hazardous constituent characteristics and transport mechanisms. Receptors
should be identified by type, location, number of receptors and any special
characteristics.
The type of receptor most likely to be affected by releases to ground
water include drinking water supplies. Water supplies may be contaminated
directly by release of hazardous constituents to ground-water supply sources
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or indirectly when contaminated surface waters and soils contaminate
ground-water supplies. When water supplies are affected, applicable water
quality standards should be considered. When chemicals for which there are no
established standards are present, the toxicity of the chemicals must be
considered.
The distance between the source and the receptor affects the time until
exposure occurs and the effective concentration of hazardous constituents at
exposure. The persistence and fate of the chemicals during transport over
this distance affects the concentration of the chemicals at the receptor.
Additionally, the number of receptors or individuals and any sensitive
populations that may be present should be considered in establishing the need
for corrective measures.
Hazard and Risk Assessment—
The need for corrective measures should be based on the risk the release
presents to human health and the environment. The risk is determined based on
an exposure assessment and a hazard assessment. The exposure-assessment is a
function of the duration of exposure and concentration of chemicals over that
time. The hazard assessment evaluates toxic, chronic and carcinogenic/
mutagenic effects of the concentration of chemicals. Hazards may be assessed
by reference to ambient water quality criteria (AWQC), National Interim
Primary Drinking Water (NIPDW) regulations, state water quality standards and
health advisories, and Allowable Daily Intake (ADI) values. Where such
criteria are not available, the hazard of chemicals should be assessed based
on available scientific data.
HYDROGEOLOGIC APPROACHES
General Introduction
Ground-water contamination may result from the generation of leachate
which is defined under RCRA as "any liquid, including any suspended components
in the liquid, that has percolated through or drained from hazardous wastes"
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(Federal Register 45, 33075, May 19, 1980) or from a hazardous constituent
spill entering the saturated zone. Ground-water contamination may occur at a
wide variety of SWMUs such as landfills and surface impoundments.
Corrective measures include both: (1) control measures which temporarily
abate hazardous constituent release by interrupting constituent transport, and
(2) removal or treatment techniques which permanently remediate the release.
Such corrective measures include the following:
Control Measures
source control
upgradient ground-water
diversion
Removal/Treatment Techniques
source removal
downgradient ground-water interception
and treatment
extraction/recharge
in situ treatment
As per 40 CFR Part 264.100(b), if hazardous constituents from a regulated
unit exceed the ground-water protection standard established for the regulated
unit then the owner or operator must have a corrective action program designed
to bring the unit back into compliance with the standards. A corrective
action program to achieve compliance with the ground-water protection standard
must be achieved by removing the hazardous constituents or treating them in
place. That is, ground water can be protected by preventing the generation of
hazardous waste leachate, where feasible, and by removing such leachate from
the subsurface environment when it appears. Measures which only prevent the
migration of hazardous constituents in the ground water for some period of
time do not provide an adequate level of ground-water protection and must,
therefore, be supplemented with additional remedial measures.
Source control methods prevent or reduce the potential for hazardous
constituent release and thus, migration into the ground water. This might
include, for example, excavation of contaminated soil and reduction of surface
infiltration. Upgradient diversions or barriers are control meaures which
prevent ground water from contacting the waste mass or the hazardous
constituent plume by rerouting the ground-water flow pattern and adjusting the
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Level of Che water cable. These concrol measures, as seated in 40 CFR
Part 264.100(6) must be combined with other remedial meaures, such as
councerpumping, to constitute an adequate corrective action program.
Downgradient diversions/interceptions are barriers to intercept, prevent and
contain the flow of contaminated ground water and subsequently pump or direct
it to a discharge where it can be treated or disposed of under satisfactorily
controlled condtions (EPA, 1983). Extraction/recharge involves the extraction
and treatment of contaminated ground water and the subsequent recharge of the
treated ground water into the source aquifer. In situ treatment involves the
direct treatment of contaminated ground water in place. Although an emerging
technique, it is believed, as per 40 CFR Part 264.100(b), that the in situ
treatment of hazardous constituents is analogous to removal because it
provides long-term protection of human health and the environment.
Within each of these corrective measure approaches or strategies, several
technologies exist which may be either proven, imminent, or emerging; proven
being conventional and demonstrated, imminent being in a developmental stage,
and emerging being in a conceptual phase. Control technologies for the source
control strategy are only briefly discussed in this document since guidance is
being specifically directed toward corrective actions for releases to ground
water. The discussions on ground-water control and treatment technologies
identify technical considerations such as site applicability,
implementability, advantages and disadvantages, hazardous constituent
applicability, reliability, effectiveness, safety, cost, and hydrologic
parameters such as pump rate, placement and permeability. Institutional
issues are also addressed, where applicable. In viewing permit applications,
the permit writer must be aware of state laws so that institutional issues,
for example, the reinjection of treated ground water not being permitted in
certain states, can be addressed.
Environmental Considerations
Environmental issues resulting from the implementation of a
control/treatment technology also requires consideration. For the majority of
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che control/treatment technologies presented in this document the
environmental considerations arising from "pump and treatment" corrective
actions include: (1) subsidence, (2)decrease in well yield of adjacent well
fields, (3) drawdown of adjacent surface water bodies, and (4) induced
hazardous constituent migration to new pathways.
As ground water is withdrawn from a pumping well, the withdrawal rate
typically exceeds the recharge rate to the aquifer initially. In this case, a
cone of depression forms around the well in response to Darcy's law. The
potentiometric surface steepens around the well, forming the cone of
depression, and thereby increases the hydraulic gradient, in order Co satisfy
the stress imposed on the aquifer by Che pumping well. The cone of depression
will conCinue Co expand until a new equilibrium is reached when Che
ground-water withdrawal rate is balanced by recharge. The size of Che cone of
depression aC a given time is a function of Che pumping race and Che
permeability of Che aquifer. Expanding cones of depression and excessive
ground-water withdrawals are boCh potential causes of environmental problems
under Che circumstances described below.
In an aquifer chat contains more than one well screened within ic, it is
possible for the r.i«iii of influence of these wells to expand and intersect
when Chey are being pumped simultaneously. In confined aquifers, Che law of
superposition can be applied, and Che total drawdown effect in Che aquifer at
a point- is the sum of Che individual drawdown effects from each participating
well at chac poinC. This can lead Co a rapid, unexpecCed decline in Che
potentiometric surface.
Similarly, in unconfined conditions, cones of depression can inCersecC
surface water bodies such as streams or lakes. This can result in a decline
of Che waCer cable Co a point beneath the water body. In extreme cases, a
reversal in che hydraulic gradient can occur, which can ultimately cause
complete dewatering of che surface water body. In che case where the pumping
rate is adjusted to balance (or be less than) the recharge rate to the water
body, there are other potential problems which must be considered. For
example, if the aquifer is sufficiently permeable, any detrimental
constitutents in the water body might not be attenuated enroute to che well,
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and may therefore contaminate it. In a similar manner, if the cone of
depression reaches a source of hazardous constituents, induced migration of
the hazardous constituents within the capture zone of the well will cause them
to move toward the well.
In coastal areas, fresh ground water is in hydrodynamic equilibrium with
the denser sea water beneath it. The ground water discharges to the sea at an
outflow face above the fresh water-sea water interface. However, if
significant ground water withdrawals occur in coastal areas, a reversal of the
hydraulic gradient can occur, thereby causing an inland shift in the interface
such that sea water enters the wells. This process is known as sea water
intrusion. Likewise, in non-coastal areas where brackish or saline water is
located beneath a fresh ground-water supply, pumping of the ground water can
cause upconing of the interface and lead to saline water intrusion.
A final environmental concern due to ground water withdrawal is
subsidence. If ground water is displaced from the interstices of the
sediments at a rate greater than the recharge rate to the aquifer, then an
equal volume of land subsidence occurs due to aquifer consolidation. The
fine-grained sediments in the aquitards surrounding an aquifer will also
respond to the pumping by induced infiltration. Consequently, aquitard
consolidation also occurs. Clays and silts are more compressible than sands
and gravels and therefore, the majority of consolidation is primarily due to,
but not limited to, aquitard consolidation.
The ability to reverse this process by artificial recharge is quite
limited due to the inelasticity of the sediments. Further, since the
hydraulic conductivity of a typical aquitard can be several orders of
magnitude smaller than an aquifer, consolidation in the aquitard can proceed
quite slowly and even continue after pumping is terminated.
Subsidence is a function of aquifer thickness, the structure of the
aquifer sediments, aquifer compressibility, the vertical hydraulic
conductivity of the media, and the time and extent of the decline in the
potentiometric surface. For the case of many pumping wells in one aquifer,
the total subsidence is the sum of the consolidation caused by each individual
well. Subsidence can cause drastic changes in land surface elevation. The
differential setting that ultimately occurs can, for example, destroy wells,
foundations, buildings, bridges, and landscapes.
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Source Control Technologies
Releases to ground water may originate from a variety of solid waste
management units (SWMUa). When a release to ground water has occurred, part
of the corrective measures which may be employed will be directed at source
control. Source control corrective measures may be used to prevent additional
releases by containing hazardous constituents or by removing them from the
site.
Removal—
Preventing additional releases from a site can be accomplished by removing
all wastes and contaminated media. Removal may involve emptying and removal
of tanks, repacking and removal of drums, pumping surface impoundments, and
excavating contaminated soils and structures. Removed materials should be
transported to an approved facility for treatment or redisposal. The main
advantage of removal is that the source of releases is eliminated. A
significant disadvantage is the cost of excavation, transportation and
redisposal, and the potential risks posed by these activities.
Grading—
Grading refers to actions which are used to alter the topography and
runoff characteristics of a waste site. Grading includes excavation,
spreading, compaction, scarification, tracking, and contour furrowing. These
activities are accomplished with heavy earth-moving equipment (dozers,
loaders, scrapers, compactors). Grading has two primary purposes, slope
optimization and preparation for revegetation. Slope optimization may include
excavation, spreading, compaction and hauling in order to increase surface
runoff and decrease infiltration and ponding without increasing erosion. This
type of action is designed to prevent surface runoff from contacting waste.
Scarification, tracking and contour furrowing are all grading techniques
employed to roughen soils to facilitate revegetation. These methods slow
runoff thereby increasing infiltration and decreasing erosion potential.
Preparation for revegetation techniques are most commonly associated with
capping and diversion operations, as well as slope grading.
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Grading operations for slope optiraizacion and revegetation may be
incompatible with sites with steep topography. Local climatic conditions and
soil types will dictate the optimum slopes. Grading equipment and equipment
operators are readily available in most locations and grading techniques are
well established.
Surface Seals—
Caps, covers and surface seals refer to low permeable barriers which are
installed over waste disposal sites. Surface seals may be constructed from a
variety of low permeable materials including soils, admixtures (asphaltic
concrete, soil cement bentonite), and synthetic geomembranes. Clays and
synthetic geomembranes are the materials most often used. Seals reduce the
likelihood of releases from waste disposal sites by reducing surface water
infiltration and erosion. Surface seals also provide a media suitable for
revegetation. Seals are commonly used in conjunction with grading,
diversions, and revegetation.
Surface seals are most commonly used for closure operations at permitted
disposal sites (e.g., landfills, surface impoundments, waste piles, land
treatment units). They are also an appropriate corrective measure for use at
uncontrolled sites or where hazardous constituents are present in soils. The
main limitation of surface seals is the need for slope control and maintenance.
Diversion and Collection—
Ground water releases can also be controlled by the management of surface
waters. By routing surface runoff away from a site, thereby preventing
run-on, direct contact with waste and precipitation is reduced. Because the
majority of runoff is confined to channels, site erosion can also be reduced.
Diversion and collection includes dikes and berms, ditches, channels,
diversions; waterways, terraces and benches; and chutes and downpipes.
Diversion and collection systems are most applicable to landfills, surface
impoundments, and waste piles. They are typically used in conjunction with
grading, revegetation and surface sealing to prevent surface water runon, and
to reduce erosion. Preventing run-on has the effect of reducing infiltration
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of surface water into wastes, thereby reducing leachace generation. Reducing
erosion will minimize the likelihood of surface waters directly contacting
wastes and subsequently transporting hazardous constituents to soil and ground
water.
Revegetation—
Revegetation is typically used following grading and development of
diversion and collection systems. Revegetation stabilizes topsoil of covered
sites and areas disturbed by earth-moving activities. By binding together
soil particles and by reducing surface water flow velocities, revegetation
helps to control erosion. Vegetation may increase infiltration by retaining
water or may reduce infiltration due to increased evapotranspiration.
Vegetation may also treat contaminated soil and ground water through the
uptake and removal of hazardous constituents, nutrients, and water from the
soil.
Revegetation should include selection of plant species appropriate for
site conditions. Temporary erosion control measures such as mulching or
spraying surficial soils with binders may be required while vegetation is
becoming established. Maintenance will be required to repair erosion rills
until vegetation is established. Maintenance may also require periodic mowing
to control species development.
Site Management—
Permitted facilities usually have a number of structures designed to
reduce the potential for release of hazardous constituents to ground water.
These structures include dikes around surface impoundments, sediment traps,
diversion and collection channels, cover material and liners at landfills, and
concrete aprons and containment dikes at transfer stations and storage
facilities and around tanks. Although facility design may incorporate such
preventative measures, releases to ground water may occur as a result of:
• insufficient maintenance of facilities;
• inexperience and lack of training for employees; or
• exceeding the design capacity of the facility.
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Improved sice management may be an appropriate corrective measure for
preventing future releases from permitted facilities.
Ground-Water Control/Treatment Technologies
Ground-water control/treatment technologies can generally be classified
under four categories. These are:
• impermeable barriers;
• well systems;
• interceptor systems or subsurface drains; and
• in situ treatment.
Impermeable barriers, a form of passive ground-water control, can be used
to divert ground-water flow away from a waste disposal site or to prevent
contaminated ground water from migrating away from the site. Various methods
and materials can be used to construct impermeable ground-water barriers such
as bentonite slurry, cement or chemical grouts, or sheet piling, as discussed
in the following sections. However, before an impermeable barrier is selected
to control ground-water flow, it should be recognized that impeded
ground-water flow may cause an increase in upgradient hydraulic head, with
consequent associated effects on rates of vertical movement of water. The
probable effects of a locally heightened water table should be carefully
considered before deciding to apply this method of control. Additionally, to
meet the 40 CFR Part 264.100(b) corrective action requirements, impermeable
barriers must be used in conjunction with pumping and treatment measures.
Well systems encompass the most common techniques used for ground-water
pollution control/treatment. They enable the pumping of ground water for
subsequent treatment. Ground-water pumping, an active remedial measure, can be
specifically designed to manipulate the water table and, thus the subsurface
hydraulic gradient in the area of a disposal site through either withdrawal or
injection of water, or it can be designed to contain a contaminated
ground-water plume. Well systems include well points, deep wells and recharge
systems.
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Interceptor systems or subsurface drains are horizontal collector systems
used to intercept contaminated ground water in shallow aquifers or to lower
shallow ground-water tables. The most common example of a subsurface drain is
a leachate collection system used to collect leachate below liners of land
storage or disposal facilities. The results rendered from the use of
subsurface drains are very similar to those of well-point systems. There are
two types of interceptor systems used to manage ground-water pollution; these
are collector drains and interceptor trenches. Both systems are very similar
in terms of design, construction, and results rendered.
In situ treatment enables direct treatment of contaminated ground water by
introducing a reactant into the contaminated region to interact with the
hazardous constituent plume. The principal variations are permeable treatment
beds, chemical injection, and in situ biological treatment (bioreclamation).
The following subsection discusses, in detail, the technologies associated
with these four ground-water control/treatment categories. Technology
discussions include a generic description of the control/treatment technology
and associated system types, and provides guidance on technology applications,
data requirements and associated advantages and disadvantages.
Impermeable Barriers—
SLURRY CUT-OFF WALLS—Slurry cut-off walls (or simply, slurry walls) are
vertical, low permeable barriers used for capturing, diverting, or containing
contamination in ground water. Cut-off walls are gaining widespread
application in the area of hazardous waste management. However, as a
corrective measure, they do not remove hazardous constituents or eliminate
constituent problems, as required by 40 CFR Part 264.100(b). Thus, additional
remedial measures must be implemented at a site to meet the required
ground-water protection standard.
• Types of Cut-Off Walls - The type of cut-off wall is defined by the
material used to backfill the trench. There are basically three types of
slurry cut-off walls: soil-bentonite, cement-bentonite, and diaphragm.
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- Soil-bentottite cut-off waLLs—SoLl-bentonite (SB) walls are
composed of soil materials (often trench spoils) mixed with small amounts of
bentonite slurry from the trench. In general, SB walls can be expected to
have the lowest permeability, the widest range of waste compatibilities, and
the least cost (EPA, 1984). However, they also offer the least structural
strength and require the largest work area of any of the types of walls.
Soil-bentonite walls are usually used where low permeabilities are needed and
structural strength is not a problem.
Cement-bentonite cut-off walls—Cement-bentonite (CB) walls are
composed of a slurry of Portland Cement and bentonite which is left to set or
harden to form the final wall. CB walls can be constructed in more extreme
topographies than SB walls by allowing the wall to harden while continuing the
construction of the wall to higher or lower elevations. They also require
less work-area in terms of construction. CB walls are stronger than SB walls
but usually have at least an order of magnitude higher permeability than SB
walls (EPA, 1984).
Diaphragm Walls—Diaphragm walls are composed of pre-cast or
cast-in-place reinforced concrete panels (diaphragms). They are stucturally
the strongest of the three tupes of walls as well as the most costly. They
usually have about the same permeability as CB walls and because of a
similarity of materials about the same compatibility. However, because they
are more expensive tha SB walls and CB walls without offering more protection,
diaphragm walls are seldom used for ground-water pollution control.
• Applications - Slurry wails have many different applications. There
are a number of horizontal and vertical configurations of slurry walls and, at
different sites, slurry walls are used in conjunction with many different
remedial measures. The effectiveness of the slurry wall is determined, to a
large extent, by its configuration and associated remedial measures. There
are two types of vertical configurations of slurry walls:
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1. Keyed in walls; and
2. Hanging walls.
There are three types of horizontal configurations of slurry walls:
1. Circumferential wall placement;
2. Upgradient wall placement; and
3. Downgradient wall placement.
Four types of remedial measures are often used in conjunction with
slurry walls to imporve their effectiveness. These are ground-water pumping,
surface and subsurface collection, surface sealing, and grouting, sheet piling
of synthetic membrane installation. These measures and the above listed
configurations are discussed below.
Vertical Configurations—Slurry walls may either be keyed into a
low permeability layer beneath the aquifer (bedrock) or placed to intercept
only the upper portion of the aquifer. A keyed in wall is required if the
hazardous constituents are is apt to migrate vertically and horizontally
within the aquifer. The connection between the wall and the bedrock is very
important to the overall effectiveness of the wall. A suitable key in may be
difficult to attain if the bedrock is difficult to excavate or if the bedrock
is jointed or contains cracks.
Hanging slurry walls are not keyed into the bedrock. They are
exclusively used to control hazardous constituents which float on top of the
ground water (e.g. petroleum products, hydrocarbons). The depth of wall
placement will depend on the thickness of the hazardous constituent layer.
Horizontal Configurations—Different horizontal configurations
are used in different slurry wall applications. Circumferential wall
placement refers to placing a slurry wall completely around the wastes
contained within the site. This configuration is common practice. When used
in conjunction with surface water infiltration barriers (caps),
circumferential slurry walls can greatly reduce the amount of leachate
generated from a waste disposal site. Inward hydraulic gradients are often
maintained by the use of extraction wells inside the contained area. A
circumferential slurry wall is illustrated in Figure 2.1.
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Groundwater Flow
Slurry Wall
Extraction Wells
Figure 2.1. Plan of circumferential wall placement.
Source: EPA, 1984.
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Upgradient placement refers to the placement of a wall on the
upgradient side of the waste site. This configuration is used to divert
uncontarainated ground water around Che site to prevent clean water from
becoming contaminated. A high ground-water gradient is required for this
strategy to be effective. That is, unless the ground water can be diverted
around the site, and be drained to a lower elevation, it can flow around and
return to Che same elevation or rise Co Che surface Co overtop che wall (EPA,
1984). The use of a subsurface drainage system may be required Co promoCe
drainage around Che site. UpgradienC wall placement is illustrated in
Figure 2.2.
Downgradient wall placement refers to che placement of the wall
downgradient of Che waste aiCe. This configuration is only pracCical where
there is a relatively small amount of upgradient ground-water flowing through
che sice. In chis application, che slurry wall aces as a barrier Co conCain
contaminated ground water so that ic can be recovered for treatment or use.
In this case, compatibility of Che wall wich che hazardous constituent plume
is extremely important. Extraction wells will be employed Co withdraw the
contaminated ground water and Co limit the head build-up on Che wall.
Downgradient wall placement is illustrated in Figure 2.3.
Different combinations of verCical and horizontal wall. configuraCions
will be used in different applicaCions. Table 2.1 proides a summary of Che
effects of differenc combinaCions of configuraCions and indicates where they
can be used.
Slurry walls are often used in combination with other technologies to
form an effective remedial measure. Ground-water pumping is often required to
prevent head build up on a wall and to extract contaminated ground water that
is coming in contact with the wall. Surface or subsurface collection is often
required to promote drainage around a slurry wall and to improve the
effectiveness of che slurry wall. As seated previously, surface sealing
(capping) is ofcen used in conjunction with circumferential walls to decrease
the generation of hazardous constituents. CrouCing is often required to
promote the integrity of the bedrock key. Sheet piling and sychecic membrane
placemenC along a wall may increase Che structural stabiliCy of the wall and
decrease its permeability. Reference should be made to EPA 1984 for further
information on slurry cut-off walls.
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Figure 2.2. Plan of upgradient placement with drain.
Source: EPA, 1984.
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Groundwater Divide
Extraction Wall*
Slurry Wall
Figure 2.3. Plan of dovmgradienc placement.
Source: EPA, 1984.
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TABLE 2.1. SUMMARY OF SLURRY WALL CONFIGURATIONS
Vertical
Configuration
Horizontal Configuration
Circumferential Upgradient Oowngradient
Keyed-in
Most common and
expensive use
Most complete
containment
Vastly reduced
leachate
generation
Not common
Used to divert
ground wate
around site in
steep gradient
situations
Can reduce
leachate
generation
Compatibility
not critical
Used to capture
miscible or sinking
contaminants for
treatment or use
Inflow not
restricted, may
raise water table
Compatibility very
important
Hanging
Used for float-
ing contaminants
moving in more
than one direction
(such as on a
ground water
divide)
Very rare
May temporarily
lower water table
behind it
Can stagnat
leachate but not
halt flow
Used to capture
floating contamin-
ants for treatment
or use
Inflow not
restricted, may
raise water
table
Compatibility very
important
Source: EPA, 1984
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• Daca Requirements - In order Co design a slurry cut-off wall, a
number of sice specific characteristics should be known. The design should be
preceded by a hydrogeologic investigation of the site. Data obtained should
provide information on site soil, ground-water and aquifer characteristics to
assist in determining the suitability of the soil for use in slurry or
backfill and the expected lifetime and effectiveness of the wall.
Soil characteristics should include:
• texture - granular or cohesive;
• grain size distribution and gradation;
• moisture content;
• permeability; and
• soil pressure.
Ground-water characteristics should include:
• depth to water table;
• direction and rate of flow;
• pH;
• hardness; ~
• salt concentration;
• presence of other minerals and organics;
• water pressure; and
• hazardous constituent plume characteristics such as chemistry,
size and location.
Site soil characteristics assist in determining the suitability of
the soil for use in the slurry or the backfill and also in calculating the
expected lifetime and effectiveness of the wall. Ground-water characteristics
determine construction requirements such as additions and required strength
and also contribute to the wall lifetime determination.
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Aquifer characteristics should include:
• permeability and thickness of the water bearing strata;
• hydraulic gradient of the aquifer; and
• aquiclude characteristics such as depth, permeability, degree of
jointing, hardness and continuity.
Other information which should be provided includes the depth to
low-permeability stratum or bedrock to determine the optimal depth of the
wall; and the accessibility of suitable soil and bentonite in order that
potential cost and implementability can be determined.
Conceivably one of the most important characteristics of the slurry
wall that must be investigated before it is designed is its potential
compatibility with the hazardous constituents existing at the site. Many
types of constituents have been shown to degrade a slurry wall by increasing
its permeability. The types of constituents that are most incompatible with
slurry mixtures are concentrated organics and highly acidic constituents
(Anderson and Jones, 1983). The compatibility of the backfill used for wall
construction with the slurry must also be investigated.
• Advantages/Disadvantages - Slurry walls are gaining widespread use in
hazardous waste management. To date there is little information as to the
performance of slurry walls. However, investigations have indicated there is
a potential for structural and compatibility problems (Anderson and Jones,
1983). Slurry walls have a finite life and therefore, are not as effective as
other corrective measures. Slurry wall construction is a high technology
technique and thus, the cost for construction is relatively high compared to
other corrective measures. On the other hand, there is little operation and
maintenance required; therefore, low 0 .& M costs. Table 2.2 provides a list
of the advantages and disadvantages associated with slurry walls.
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TABLE 2.2. ADVANTAGES/DISADVANTAGES OF SLURRY CUT-OFF WALLS
Advantages
Disadvantages
1. Construction methods are simple3
Adjacent areas not affected by
ground water drawdown3
Bentonite (mineral) will not
deteriorate with age3
4. Leachate-resistant bentonites
are available3
5. Low maintenance requirements3
6. Eliminate risks due to strikes,
pump breakdowns, or power
failures'3
7. Eliminate headers and other above
ground obstructions'*
1. Cost of shipping bentonite
from west3
2. Some construction procedures
are patented and will require
a license3
3. In rocky ground, over-
excavation is necessary
because of boulders3
4. Bentonite deteriorates when
exposed to concentrated
organics and highly acidic
wastes
3Tolman, et al., 1978.
bRyan, 1980.
Source: Compiled by Knox, et al., 1984.
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GROUT CURTAINS—Grouting is the process of injecting a liquid, slurry, or
emulsion under pressure into the soil. The injected fluid moves away from the
point of injection to occupy the available pore spaces. This enables the
fluid to set or gel into the rock or soil voids, thereby greatly reducing the
permeability of and imparting increased bearing capacity to the grouted mass.
When properly carried out, this process can result in a curtain or wall that
can be a very effective ground-water barrier.
• Types of Grout - In general, grouts are classified as particulate or
chemical. Particulate grouts consist of water plus particulate material which
will solidify within the soil matrix. Chemical grouts usually consist of two
or more liquids which gel when they come in contact with each other.
Particulate grouts are generally comprised of either Portland Cement,
bentonite, or a mixture of the two. Their primary use is in sealing voids in
materials with rather high permeabilities. They are also often used as
"pregrouts" with a second injection of a chemical grout used to seal the fine
voids. Chemical grouts are a more recent development than particulate grouts
with the exception of silicate grout. Silicate-based grouts are the oldest
and most commonly used chemical grouts are presented in Table 2.3. Additional
information on grout products and their properties are provided in EPA 1982
and EPA 1983.
• Applications - Although grout curtains are useful under certain site
specific conditions, due to their relatively high cost they are generally not
the method of choice for ground-water control where a less expensive method,
such as slurry wall, is practical. Grouts are, however, the most practical
and efficient method for sealing fissures, solution channels, and other voids
in rock. They can also be very effective in ensuring a water-tight seal where
a slurry wall is keyed into bedrock or some other impermeable layer.
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TABLE 2.3. TYPES OF GROUT
Signiticant Characteristics
Portland Cement or
Particulace Grouts
Chemical Grouts
Sodium Silicate
Phenoplasts
Lignosulfonate
Derivatives
Aminoplasts
e.g., urea-
formaldehydes
Appropriate for higher permeability (larger grained)
soils
Least expensive of all grouts when used properly
Most widely used in grouting across the U.S.
(90 I of all grouting)
Most widely used chemical grout
At concentrations of 10-70X gives viscosity of
1.5 - 50 cP
Resistant to deterioration by freezing or thawing
Can reduce permeabilities in sands from 10~2 to
10~8 cm/s
Can be used in soils with up to 20Z silt and clay at
relatively low injection rates
Portland cement can be used to enhance water cutoff
Rarely used due to high cost
Should be used with caution in areas exposed to
drinking water supplies
Low viscosity
Can shrink (with impaired integrity) if excess
(chemically unbound) water remains after setting
unconfined compression strength of 50-200 psi in
stabilized soils
Rarely used due to high toxicity
Lignin can cause skin problems and hexavalent
chromium is highly toxic; both are contained in
these materials
Cannot be used in conjunction with Portland Cement:
pH's conflict
Ease of handling
Lose integrity over time in moist soils
Initial soil strengths of 50-200 psi
Rarely used due to high cost
Will gel with an acid or neutral salt
Gel time control is good
(continued)
2-25
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TABLE 2.3 (continued)
Significant Characteristics
Acrylamid Grouts
Rarely used due to toxicity
Should be used with great caution near to drinking
water supplies
Readily soluble in water
Manufacture in USA prohibited available as AV-100
from Japan
Can be used in finer soils than most grouts because
low viscosities are possible (1 cP)
Excellent gel time control due to constant viscosity
from time of catalysis to set/gel time
Unconfined compressive strengths of 50-200 psi in
stabilized soils
Gels are permanent below the water table or in soils
approaching 1002 humidity
Are vulnerable to freeze-thaw and wet-dry cycles,
particularly where dry periods predominate and will
fail mechanically
Due to ease of handling (low viscosity), enables
more efficient installation and is often
cost-competitive with other grouts
Kirk and Othmer, 1979; Sommerer and Kitchens, 1980.
Source: Compiled by EPA, 1983
2-26
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Theoretically, it is possible to place a grout curtain upgradient or
downgradient from or beneath a hazardous waste site. As with slurry walls,
the placement of a grout curtain upgradient of a waste site can redirect the
flow so that ground water no longer flows through the wastes that are creating
hazardous leachate. For a normal range of ground-water chemistries,-most
grouts could be expected to function well in this capacity. Figure 2.4
indicates the orientation of a grout curtain upgradient for a waste site.
Placement of a grout curtain downgradient from or beneath a hazardous
waste site, however, is not as accommodating. Problems could be expected when
attempting to grout in the presence of leachate or extreme ground-water
chemistry, for example, difficulty or impossibility in controlling the set
time and consequently emplacement of a curtain of reliable integrity.
Additionally, in order to grout a horizontal curtain or layer beneath a waste
site, injection holes most be drilled either directionally from the site
perimeter or down through the wastes. The first situation would be very
expensive and the second could be very dangerous. In either case it would be
very difficult to place an effective barrier and virtually impossible to
monitor its effectiveness.
Additionally, as with slurry cut-off walls, grout curtains only
provide a means of hazardous constituent control and therefore, require the
use of other remedial measures to be in accordance with 40 CFR Part
264.100(b). Other remedial measures may include ground-water pumping (well
systems), surface and subsurface collection/drainage systems, surface sealing,
slurry or sheet pile cut-off walls or synthetic membranes.
• Data Requirements - Prior to grout injection, a thorough
hydrogeologic study of the site must be completed.
Required site soil characteristics include:
• grain size distribution;
• moisture content;
• permeability;
2-27
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i
ro
Semicircular
Grout Curtain ~7
Grout Tubes
20ft.
Figure 2.4. Semicircular grout curtain around upgradient end of landfill,
Source: EPA, I978a.
-------
• porosity; and
• composition (chemistry).
These soil characteristics assist in determining soil groutabi lity, grout
pentration, rate of injection and grout material selection. Site soil is not
considered suitable for grouting if more than 20 percent of the soil passes
through a No. 200 sieve (Sommerer and Kitchens, 1980).
Ground-water characteristics should include:
• depth to water table;
• direction and rate of flow;
• pH;
• concentration of sulfides and calcium; and
• hazardous constituent plume characteristics such as chemistry,
size and location.
These ground-water characteristics are indicative of grout material selection
and thus, wall construction. Additionally, ground-water flow can adversely
affect the integrity of a grout curtain, particularly during construction.
Special consideration should be given to rate of flow and chemical composition
of the ground water (Sommerer and Kitchens, 1980). After grout material
selection, grout characteristics such as strength properties, viscosity and
gelation time assist in determining the grout curtain's potential performance
as a barrier to ground-water flow.
Other data requirements include: accessibility of grout equipment
and materials such that implementability and cost can be determined; and depth
to low permeability stratum or bedrock to determine optimal wall depth.
• Advantages and Disadvantages - The technology of grouting, as applied
to ground-water pollution control, is very recent. Its potential as a means
of stopping or rerouting ground-water flowing in porous rock is fairly high.
Grouts can be formulated to set within a few seconds so that even rapidly
flowing water can be shut off. Grout can also be used to control ground-water
2-29
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flow in soils, but in most cases, a more cost effective method is available.
Although its potential applicability to ground-water control is evident,
grouting procedures require specialized techniques and equipment. In addition
to these considerations, Table 2.4 provides a list of advantages and
disadvantages associated with grout systems.
SHEET PILE CUT-OFF WALLS—As with slurry walls and grout curtains, sheet
piling can be used to form a continuous ground-water barrier to control
ground-water contamination. However, it also requires additional remedial
measures to meet with the 40 CFR Part 264.100(b) regulations. Sheet piling
involves driving lengths of interlocking steel into the ground with a
pneumatic or steam driven pile driver to form a thin impermeable barrier to
flow. Sheet piles can be made of wood, precast concrete or steel. Wood is an
ineffective water barrier, however, and concrete is used primarily where great
strength is required; therefore, since steel is effective in terms of
ground-water cut-off and cost it receives primary emphasis for this
application (EPA, 1982).
• Applications - In terms of its application to ground-water pollution
control, sheet piling has seen minimal, if any, use. However, similar to
slurry walls (particularly) and grout curtains, sheet pile cut-off walls can
form barriers that will redirect ground-water flow around or below the
depostied wastes. Sheet piling is very applicable to controlling hazardous
leachate generation for locations where wastes are deposited in contact with a
permanent or seasonal water table.
Sheet piles are typically used in soils that are loosely packed and
predominantly sand and gravel. A penetration resistance of 4 to 10 blows/foot
for medium to fine - grained sand is recommended. Piling lifetime depends on
hazardous constituent characteristics and pile material. For steel piles, pH
is of particular importance. Ranges of pH from 5.8 to 7.8 enables a lifetime
of up to 40 years (depending on other hazardous constituent characteristics),
and pH as low as 2.3 can shorten the lifetime to 7 years or less (EPA, 1983).
Additionally, sheet piles should extend to bedrock or other impermeable strata
2-30
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TABLE 2.4. ADVANTAGES/DISADVANTAGES OF GROUT SYSTEMS
Advantages8
Disadvantages
1.
ro
I
When designed on basis of thorough preliminary
investigations, grouts can be very successful.
2. Grouts have been used for over 100 years in
construction and soil stabilization projects.
3. Many kinds of grout to suit a wide range of
soil types are available.
I. Grouting limited to granular types of soils
that have a pore size large enough to
accept grout fluids under pressure yet
small enough to prevent significant
pollutant migration before implementation
of grout program.''
2. Grouting in a highly layered soil profile
may result in incomplete formation of a
grout envelope.'*
3. Presence of high water table and rapidly
flowing ground water limits groutability
through:
a. extensive transport of contaminants;
b. rapid dilution of grouts."
4. Some grouting techniques are proprietary.8
5. Procedure requires careful planning and
pretesting. Methods of ensuring that all
voids in the wall have been effectively
grouted are not readily available.a
"Tolman, et al., 1978.
^Huibregtse and Kastraan, 1981.
Source: Compiled by Knox, et al., 1984.
-------
co be effective. However, steel piles should not be considered for use in
very rocky soils, even if enough force can be exerted to push the piles around
or through cobbles and boulders, because the damage to the piles would be
likely to render che wall ineffective.
• Data Requirements - After completion of a thorough hydrogeologic
investigation, site suitability for sheet pile use and potential pile lifetime
and pile placement can be determined.
Required soil characteristics include:
• grain size distribution; and
• compaction.
These characteristics are indicative of the soils' suitability for sheet pile
use.
Information on ground-water characteristics should include:
• depth to water table;
• pH; and
• hazardous constituent plume chemistry, size and location.
Pile lifetime and placement can be detemined from these ground-water
characteristics. Information should also include the depth to
low-permeability stratum or bedrock so that the optimal depth of the sheet
pile wall can be calculated.
• Advantages and Disadvantages - Construction of steel sheet piles as a
means of ground-water control can potentially be effective and economical in
specific cases. In general, however this is probably an over-elaborate
technique to achieve a relatively simple result. As the size of a project
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increases, sheec piling will become uneconomical because of high material and
shipping costs. In addition, pile driving requires a relatively uniform,
loose boulder-free soil for ease of construction. Other
advantages/disadvantages are listed in Table 2.5.
BLOCK DISPLACEMENT METHOD—Block displacement method is a control
technology, similar to the other impermeable barrier technologies in that it
requires the use of additional remedial measures to meet the 40 CFR Part
264.100(b) regulation, for placing a fixed underground physical barrier around
and beneath a fixed mass of earth (called a block) to confine and contain the
existing region of hazardous constituents and prevent further spread. The
bottom barrier is formed when fractures (or separations) extending from
horizontal notches at the base of the injection holes coalesce into a larger
separation beneath the mass block of earth. Continued pumping of slurry under
pressure produces a large uplift force against the bottom of the block and
results in vertical displacement proportional to the volume of slurry pumped.
A perimeter barrier around the block is constructed by conventional techniques
in conjunction with the bottom barrier either prior to or following bottom
barrier construction. The perimeter wall constructed prior to bottom
separation can be used to ensure a favorable horizontal stress field for
proper formation of the bottom separation. In geologic foramtions not
requiring control of horizontal stress, the perimeter may be constructed
following initial bottom separation or following the completion of block lift
(EPA, 1983).
Although in the developmental stage, the block displacement method can be
used to contain contaminated ground water, direct uncontaminated ground—water
flow around a (potentially) contaminated area, and lower the water table
inside the isolated area. A typical block displacement barrier is shown in
Figure 2.5. For further information on the block displacement method refer to
EPA 1983.
2-33
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TABLE 2.5. ADVANTAGES/DISADVANTAGES OF STEEL SHEET PILES
Advantages Disadvantages
1. Construction is not difficult; no excavation 1. The steel sheet piling initially is not
is necessary. watertight.
2. Contractors, equipment, and materials are 2. Driving piles through ground containing
available throughout the United States. boulders is difficult.
3. Construction can be economical. 3. Certain chemicals may attack the steel.
4. No maintenance required after construction.
5. Steel can be coated for protection from
corrosion to extend its service life.
Source: Tolman, et al., 1978.
-------
SLURRY
INJECTION
i »
PERIMETER
SEPARATION
PERIMETER
SURCHARGE
(WHEN
REQUIRED)
INJECTION
HOLES X
UPLIFT
/ PRESSURE \
H HMf Ht)
"-COALESCING
SEPARATIONS
a) CREATING THE BOTTOM SEPARATION
<_ PERIMETER
BARRIER
POSITIVE SEAL THROUGH
INJECTED BENTONITE
MIXTURE
b) CONFIGURATION OF FINAL BOTTOM AND PERIMETER BARRIERS
Figure 2.5 Block displacement method.
Source: EPA, 1983.
2-35
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o Applications—The block displacement method is of particular value in
strata where unweathered bedrock or other impermeable continuum is not
sufficiently near the surface for a perimeter barrier alone to act as an
isolator. The permeability of the bottom barrier depends both on the filter
cake that forms on the separation surfaces and on the permeability of the
entire barrier approaches that of the filter cake. Permeabilities of
_ Q
10 cm/sec are attainable with proper slurry design.
The effectiveness of the bottom barrier is based on the permeability
of the consolidated slurry material and the thickness of the barrier.
Effectiveness of the perimeter barrier is dependent on the perimeter
construction technique. In general, the perimeter should be designed with an
overall effectiveness compatible with the effectiveness of the bottom barrier
(EPA, 1983) These barriers should be compatible with in situ soil, ground
water and hazardous constituent plume conditions.
• Data Requirements—Upon completion of a thorough hydrogeologic
investigation, site soil and ground-water characteristics can be used to
determine the suitability of the soil for use in soil bentonite slurry and the
expected lifetime and effectiveness of the barrier, and construction
requirements such as additives and required strength, respectively.
Required soil characteristics include:
• discontinuities in soil strata in region of expected bottom
barrier construction;
• cohesive and consolidation states of individual strata;
• degree and orientation of soil stratification and bedding;
• absolute value and variation of soil permeability in individual
strata;
• proximity of weathered bedrocks or solution channels to expected
bottom barrier region;
• texture and grain size distribution;
2-36
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• moisture concent; and
• soil pressure.
Ground-water characteristics should include:
• depth of water table;
• direction and rate of flow;
• pH;
• hardness; and
• hazardous constituent plume characteristics such as chemistry,
size and location.
Additionally, the accessibility of suitable soil and bentonite should be
determined to indicate the potential cost and implementability of the block
displacement method.
• Advantages and Disadvantages - Advantages and disadvantages
associated with the block displacement method are presented in Table 2.6.
Well Systems—
WELL POINTS—A well point system is used to withdraw ground water in
shallow, unconfined aquifers. It consists of a number of closely-spaced,
shallow wells which are connected to a main header pipe and ultimately to a
centrally located centrifugal pump. Well point systems are only practical for
shallow aquifers because of the suction lift limits of the centrifugal pumps.
The primary design consideration for well point systems is the drawdown of the
system. The system should be designed so that the spacing of the wells and
the drawdown potential of the system are sufficient ot intercept the plume of
hazardous constituents. Spacing of the well points and drawdown potential
depend on site-specific conditions; particularly, the hydraulic conductivity
of the aquifer. A typical well point system is shown in Figure 2.6.
2-37
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TABLE 2.6. ADVANTAGES/DISADVANTAGES OF THE BLOCK DISPLACEMENT METHOD
Advantages
Disadvantages
1. Valuable when impermeable stratum
not sufficiently near surface.
2. Bentonite (mineral) will not
deteriorate with age.
3. Leachate - resistant bentonites
are available.
1. Bentonite deteriorates when
exposed to concentrated organics
and highly acidic waste.
2-38
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water-bearing
stratum
Figure 2.6. Schematic of a well point dewatering system.
Source: Johnson Division, 1975.
2-39
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DEEP WELL SYSTEMS—Deep well systems can be used Co withdraw water from
aquifers located at depths of up to several hundred meters. The construction
of these systems is similar to that of monitoring wells. The wells are built
to house a submersible pump and, therefore, are capable of extracting water
from great depths. As with well points, deep well systems must be designed so
that the drawdown and well spacing are sufficient to intercept the plume of
hazardous constituents.
RECHARGE SYSTEMS—Recharge systems that employ well systems are called
pressure ridge systems. These systems can be constructed similarly to either
well points or deep well systems. They function as the inverse of these
systems. Their purpose is to inject water into a ground-water system to form
an upconing of the water table which acts as a barrier to ground-water flow.
They can also be used in ground-water circulation systems to assist in
isolation and extraction of hazardous constituents in ground water. This
concept is discussed in subsequent paragraphs.
Another type of recharge system is a seepage .or recharge basin. This
system allows water to seep into the ground-water table by gravity flow.
These systems are often used in conjunction with downgradient pumping wells to
flush hazardous constituents from a specific area. They require continual
operation and maintenance to keep the porosities of the basin large.
• Applications - Well systems can be used in a number of applications
to control and treat ground-water pollution. In one general category of
applications, well systems can be used .to manage a plume by containment and/or
entraction. In another category they can be used to adjust the water table to
prevent ground-water pollution. The specific applications under each category
are discussed below.
Plume Management—The applications in this category include the
following:
• flushing of the ground water by using a series of
extraction and injection wells or seepage basins. The
ground water is pumped, treated and used to recharge the
aquifer; and
2-40
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• pumping of the plume without the use of recharged.
Extraction/Recharge Systems—The first application employs
both ground-water injection and withdrawal systems. The
system, as illustrated in Figure 2.7, is often referred to
as a hydrodynaraic isolation system. In this application,
wells are used to isolate and or extract hazardous
constituent plumes. The premise behind this concept lies
in the creation of a closed system within which a zone of
ground water is isolated and recirculated from recharge
wells to pumping wells. As a-result, the contaminated zone
is flushed and the water extracted. If the pumped water is
used for recharge, Che system should be incorporated into a
scheme where the captured ground water is treated before it
is returned into the ground. Further, information on this
application can be found in Ozbilgin and Powers, 1984.
A less costly alternative to using injection wells for a
source recharge would be to use seepage basins. However,
seepage basins require a high degree of maintenance to
ensure that porosity is not reduced. Therefore, the use of
seepage basins would not be practical where several basins
are required.
Pumping Without Recharge—Hazardous constituent plumes can
also be extracted by employing pumping well systems alone.
The principle of withdrawal systems is illustrated in
Figure 2.8. The design of this system is considerably less
complicated than the previously mentioned system because
recharge is not involved. However, larger volumes of water
may have to be pumped. Furthermore, the advantage of
ground-water replenishment is not gained. Consequently,
undesirable environmental impacts may occur if pumping
takes place in aquifers that are in use. This issue must
be considered in the selection of a suitable pumping
strategy.
Water Table Adjustment—Well systems can be used to adjust the
level of the water table to prevent future ground-water pollution. The
applications in this category include the following:
• lowering of the water table to prevent direct contact with
the plume; and
• upconing of the water table to act as a barrier to plume
movement.
2-41
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APPROXIMATE LIMITS
OF RECIRCULATION
STAGNATION
POINT
Figure 2.7. Theorecical representac ion of hydrodynatnic isolation
system.
Source: OzbiLgin and Powers, 1984.
2-42
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To Surface
Treatment Ł
and/or
Discharge
0
Original Water Table
Drawdown due to pumping
Note: System
also draws an
(excess) of non-
polluted water.
Source of Pollutant
-^777777777/7"
Figure 2.8. Principle of withdrawal wells.
Source: Knox et al., i984.
-------
W.-itiT/Tahle lowering—This nppLicacion involves pumping of
the ground wat«r to prewt>nt contamin.it ion of, or hazardous
constituent migration in, the underlying aquifer. By
lowering the water table below the hazardous constituent
plume, direct contact with the plume, is avoided. Lowering
•jf the water table may be accomplished by locating pumping
wells upgradient, downgradient or in both areas.
Raising of Water Table—In this application, water is
pumped into the ground water to form an upconing of the
water table. As a result, the hazardous constituent plume
can be diverted or isolated. This principle is illustrated
in Figure 2.9.
In addition to their ability to adjust the water table and contain a
plume, well systems (i.e., ground water pumping) can be utilized in
conjunction with the other ground-water controls, such as impermeable barriers
or subsurface drainage systems, to maximize their efficiency. Although well
systems, i.e. pumping, can be expensive compared to other control/treatment
technologies, it might be the most practical alternative under certain
circumstances, such as when (Doering and Benz, 1972):
• combinations of Cine and textured soils or upward hydraulic
gradients make subsurface drainage difficult; and
• ground-water conditions are stagnant e.g. hydraulic gradient is
nearly zero.
• Data Requirements - The design of any of the well systems must be
preceded by a hydrogcologic investigation of the waste disposal site. Data
should be provided on soil, ground water, and aquifer characteristics.
Soil characteristics should include:
• grain size distribution; and
• texture.
2-44
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Injcclton
of
fresh water
Source of Pollutant
Upconlng of water table
Original water table
Ground water flow
Figure 2.9. Principles of pressure ridge system.
Source: Knox et al., 1984.
-------
:"n.;;:e c IKI r.ac te r i.s c ic s 'lecermine whether site soil is suitable Co pumpinp.
Ground-water character Lsci.cs should include:
• depth to water table;
• potentioraetri.c surfaces-hydraulic gradient; and
• recharge quantity.
Ground-water characteristics assist in determining the effectivenss of
pumping. The effect of long-term pumping on local ground-water levels should
be considered (Soramerer and Kitchens, 1980).
Aquifer characteristics should include:
• permeability and thickness of water bearing strata;
• identification of ground-water tlow systems;
• transmissivity;
• storativity;
• effective porosity;
• specific yield;
• hydraulic gradient;
• depth;
• identification of recharge and discharge area;
• type - confined or unconfined;
• 'condition - homogeneous, leaky, isotropic; and
• extent - limited by barriers or surface water.
Aquifer characteristics, along with ground-water characteristics, determine
the effectiveness of pumping. Recharge of the aquifer may be necessary in
some cases to maintain water levels or to conform to state law. Therefore,
state regulations concerning the maintenance of existing water table levels
should be known. Data on the depth to impermeable strata should also be
2-46
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•i C'.iv iilml Co .'is.SL.st in (Jt: 11: cm in L n^ Clio t: I IMC C i veness of pumping. Additionally,
r.he hydrogeologic scady should indicate plume dimensions (width, length, depth
.ind general shape), the hydraulic gradient across the plume, and plume
chemistry (Lundy and Mahan, 1982). The above information, along with the
concepts of well hydraulics, can be used to establish the well number and
spacing, pumping or injection rate, and the necessary drawdown potential of
the system. Additional information on well systems, including empirical
formulas to calculate the important well system design parameters, is provided
in EPA 1982 and Knox, et al. 1984.
• Advantages and Disadvantages - The use of well systems is presently,
and will probably continue to be, the most utilized type of corrective measure
for release of hazardous constituents to ground water. Well systems are
presently the most proven and the most assured means of controlling subsurface
flows of hazardous constituents. Well systems are also understood somewhat
morp than other technologies used for corrective measures. However, due to
tho extent ot operation and maintenance of the system, the amounts of water
that may have to be pumped and the large scale construction that may be
involved, the cost of a well system by be considerably greater than o.her
technologies. Furthermore, implementation of this technology may require
extensive mathematical modeling of the ground-water movement which may not be
required in other measures. These and other advantages and disadvantages are
summarized in Table 2.7.
Subsurface Drains (Interceptor Systems)—
COLLECTOR DRAINS—Collector drains are commonly used below or near land
disposal facilities to intercept hazardous constituents leaking through the
liner. They are relatively simple in design anil consist of horizontal
perforated pipes placed in ttie ground in a grid configuration. These pipes
art connected to a main collector pipe which is connected to a sump. Ground
water is conveyed by collector pipes to he sump where it is pumped out for
2-47
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TABLE 2.7. ADVANTAGES/DISADVANTAGES OF WELL SYSTEMS
Advantages
Disadvantages
I. Efficient and effective means of
assuring ground water pollution
control.
2. Can be installed readily.
3. Previously installed monitoring
wells can somet Lines be employed
as part of well system.
4. Can sometimes include recharge
of aquifer as part of the
strategy.
5. High design flexibility.
6. Construction costs can be lower
than artificial barriers.
Source: Knox, et al., 1984.
1. Operation and maintenance costs
are high.
2. Require continued monitoring
after installation.
3. Withdrawal systems necessarily
remove clean (excess) water
along with polluted water.
4. Some systems may require the
use of sophisticated mathematical
models to evaluate their
effectiveness.
«
5. Withdrawal systems will usually
require surface treatment prior
to discharge.
6. Application to fine soils is
Iimited.
2-48
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subsequent treatment. Collector drains are installed perpendicular to
ground-water flow. A typical collector drain system is shown in Figure 2.10.
Construction of a collector drain system involves excavating trenches,
installing pipes, and backfilling with coarse gravel or sand to prevent
particles from clogging the system.
INTERCEPTOR TRENCHES—Interceptor trenches function similarly to collector
drains. They are constructed perpendicular to ground-water flow to intercept
hazardous constituents. Interceptor trenches can be either active or passive
systems. Active systems are either pumped by vertical removal wells or
drained by perforated, horizontal collector pipes. Active systems are usually
backfilled with coarse sand or gravel for wall stability. Passive systems are
open trenches used exclusively for collecting floating pollutants such as
petroleum products and hydrocarbons. Skimming pumps are installed for the
removal of hazardous constituents only. In trench systems, both pumping and
skimming operations must be continuous to prevent the collected hazardoous
constituents from seeping into the trench walls. It is recommended that
trench walls be lined with an impermeable materi.il to prevent such a
phenomenon from occurring. In any case, it is good practice to keep the water
level down to the bottom of the trench.
• Applications - Subsurface drains, a cont rol/1 reatraent strategy, h.is
two basic applications in the abatement of ground-water pollution; it either
functions as relief drains or interceptor drains. Relief drains are generally
installed in areas where the hydraulic gradient is relatively flat (i.e.
almost zero). They are often used to lower the water table beneath a site, or
to prevent hazardous constituents from migrating to deeper, underlying
aquifers. In this application, the drains are installed upgradient or
downgradient of the site or around the perimeter of the site so that their
areas of influence overlap. (Kufs et al. , 1983).
Interceptor drains are used for collection and removal of hazardous
constituents in ground water. They are installed downgradient of a pollutant
source in order to intercept the migrating plume. Figure 2.11 illustrates the
-ffttjcc of subsurface drains on a ground-water table that will be exhibited in
both die relief drain and interceptor drain applications.
2-49
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f
6
Profile
Figure 2.10. Collector drain system.
Source: Knox et al., 1984.
2-50
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original, water table _
hydraulic gradlen
Interceptor system
Figure 2.11. Hydraulic gradient toward interceptor system.
Source: Knox et al., 1984.
-------
In .1 prevencac ivii measure subsurface drains are installed beneach
and/or around disposal facilities to collect hazardous constituents. The
design of the drains in this application are similar to the interceptor drain
design. The only difference between the two systems is that the interceptor
drains are installed as an abatement measure after pollution has been
released. Therefore, the size and location of the drains are designed to
accomodate the size and location of the hazardous constituent plume.
Furthermore, subsurface drains which collect hazardous constituents are
usually installed in unsaturated media so that only hazardous constituents
(leachate) is collected. However, the theory behind these two approaches is
the same.
• Data Requirements - The data required to design a subsurface drainage
system is very similar to that required to design well systems. Essentially,
the design must be preceded by a hydrogeologic investigation of the area.
This investigation must generate data for the extent and location of
contamination and the dimensions of the area that is contaminated.
Furthermore, the investigation must render values for the hydrogeologic
characteristics of the aquifer. This information should include the following;
• permeability and thickness of water bearing strate;
• storativity (degree of confinement);
• effective porosity of the aquifer;
• regional hydraulic gradient;
• identfication of recharge ami discharge areas; and
• identification of aquifer boundaries, vertical leakage and
confining layers.
This information is essential to the determination of drain spacing, pipe
size, pumping rate at the sump and the drawdown potential of the system.
Formulas used to determine these parameters using the above listed data can be
found in EPA, 1982 and Knox, et. al., 1984.
2-52
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• Ad van cage s/1) i:sad van cages - Subsurface drains -ire a fairly common and
proven technology used for corrective and preventative mensures for hazardous
constituent releases. They are useful only to intercept shallow releases.
Subsurface drains are inexpensive relative to other ground-water
control/treatment technologies. Furthermore, a plan employing subsurface
drains would be relatively easy to implement due to the ease of installation
of the non-complex system design. Other advantages and disadvantages of the
system are identified in Table 2.8.
In Situ Treatment—
1'EKMKABLE TREATMKNT BEDS—Penneab le treatment beds use trenches filled
with a reactive permeable medium to act as an underground reactor.
Contaminated ground water or leachate entering the bed reacts to produce a
nonhazardous soluble product or a solid precipitation.
• Applications - Although in the more or less conceptual stage of
development, permeable treatment beds have the potential to physically and
chemically treat contaminated ground water in-place. Permeable treatment beds
are generally applicable for pollution control/treatment in relatively shallow
aquifers since a trench must be constructed down to the level of the bedrock
or an impermeable strata. These.beds are often only effective for a short
time because they lose their reactive capacity or they become plugged with
solids. Over-design of the system or replacement of the permeable medium can
Lengthen Llie time period over which permeable treatment is effective
Relatively few materials can be feasibly employed in permeable beds
to treat contaminated ground water. These materials include (EPA, 1983):
Limestone or Crushed Shell — Limestone neutralizes acidic
ground water and may remove heavy metals such as Cd, Fe, and
Cr. Dolomitic limestone (MgC03) is less effective at removing
heavy metals than calcium carbonate limestone. The particle
size of the limestone should match a mix of gravel size and sand
size. The larger sizes minimize settling of the bed and
channeling as the limestone dissolves. The small sizes maximize
contact. Extrapolated bench-scale data indicate that the
contact time needed to change I pH unit is 8 to 15 days.
2-53
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TABLE 2.8. ADVANTAGES/DISADVANTAGES OF SUBSURFACE DRAINS
Advantages
Disadvantages
Operation costs are relatively
cheap since flow to underdrains
is by gravity.
Provides a means ot collecting
leachate without the use of
impervious liners
Considerable flexibility is avail-
able for design ot underdrains;
spacing can be altered to some
extent by adjusting depth or
modifying envelope material.
Systems fairly reliable,
providing there is continuous
monitoring.
Construction methods are simple
and inexpensive.
Large wetted perimeter allows
for high rates of flow.
Produces much less fluid for
handling them well point systems.
Source: Knox, et al., 1984.
1. Not well suited to poorly
permeable soils.
2. In most instances it will not
be feasible to situate under-
drains beneath an existing site.
3. System requires continuous and
caretul monitoring to assure
adequate leachate collection.
4. Open systems may require safety
precautions to prevent tires or
explosions.
5. Operation and maintenance costs
are high.
6. Not useful for deep disposal
s ites.
2-54
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- Activated Carbon — Activated carbon removes non-polar organic
contaminants such as CCl^, PCBs, and benzene by adsorption.
Activated carbon, must be wetted and sieved prior to installation
to ensure effective surface solution contact.
Glauconitic Green Sand — This sand, actually a clay, is found
predominantly on the coastal plain of the Mid Atlantic states
and has a good capacity for adsorbing heavy metals. Bench-scale
studies indicate removal efficiencies of greater than 90 percent
for As, Cu, Hg, and Ni, and 60-89 percent for Al, Cd, Ca, Cr,
Co, Fe, Mg, Mn and Zn, for detention times on the order of
several days.
Zeolites and Synthetic Ion Exchange kesins — These materials
are also effective in removing solubilized heavy metals.
Disadvantages such as short lifetime, high costs, and
regeneration difficulties make these materials economically
unattractive for use in impermeable treatment beds.
With permeable treatment beds, plugging of the bed may divert
contaminated ground water and channeling through the bed may occur. Both
problems permit the passage of untreated ground water. Additionally, changing
the hydraulic loads and/or hazardous constituent levels may render the
detention inadequate to achieve the design removal level. Figure 2.12
illustrates the relative location of a permeable treatment bed to enable
ground-water treatment.
• Data Requirements - Prior to installation of a permeable treatment
bed hydrogeologic investigations should provide data on hazardous constituent
plume characteristics such as:
• depth to bedrock;
• plume cross-section;
• hazardous constituent (i.e., leachate) or ground-water velocity;
and
• hydraulic gradient.
2-53
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Permeable Treatment Bed
Figure 2.12. Relative location ot a permeable treatment bed.
Source: KPA, 1982.
2-56
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The above plume characceriseics as well as soil permeability are required in
order co determine the appropriate treatment bed design. Data should also
provide information on hazardous constituent composicion and reaction rate in
order that a reaction medium can be selected and a sufficient contact time be
determined.
• Advantages and Disadvantages - Advantages and disadvantages
associated with the use of limestone beds, activated carbon beds, and
glauconitic green sand beds are summarized in Tables 2.9, 2.10, and 2.11.
Zeolite and synthetic ion exchange resins, although very effective in the
removal of heavy metal constituents, could be used for removing hazardous
constituents in ground water but they are economically and practically
infeasible for permeable treatment beds because of problems such as short
life, high cost, and re-activation difficulties. Therefore, these materials
are not recommended for use except where engineering and economic evaluations
prove their desirability in specific cases.
CHEMICAL INJECTION—Chemical injection entails injecting chemicals into
the ground beneath the waste to neutralize, precipitate or destroy the
leachate constituents of concern (EPA, 1983).
• Applications - Chemical injection, also in Che conceptual stage, has
seen use in the treatment of hazardous constituent plumes containing cyanide
by sodium hypochlorite (EPA, 1983). The use of chemical injection requires
Chat the areal spread and depth of the hazardous constituent plume be well
characterized so that injection wells can be placed properly to intercept all
of the contaminated ground water. The use of this technique can, however,
displace hazardous constituents to adjacent areas due to Che added volume of
chemical solution. Also, hazardous compounds can be produced by the reaction
of injected chemical solution with hazardous constituents ocher Chan Che
creacment target. Refer to Knox, et al., 1984 for a detailed description of
specific chemical injection techniques. Figure 2.13 illustrates Che cross
section of a landfill being treated by chemical injection.
2-57
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TABLE 2.9. ADVANTAGES/DISADVANTAGES OF CRUSHED LIMESTONE TREATMENT BED
Advantages
Disadvantages
I. Can be used to neutralize a 1.
slightly acidic ground water
stream.
2. Applicable for the removal of 2.
certain heavy metals contained
in ground water.
3. Good potential for successful
control for chrornate anion
present in ground water flow.
4. Very cost effective to install
since limestone is inexpensive
and readily available.
Source: EPA, 1982.
Cementation or solidification
of the limestone bed may occur,
leading to plugging of the flow.
Not effective for the removal
of organic contaminants.
3. Solution-channelling through
bed may occur.
2-58
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TABLE 2.10. ADVANTAGES/DISADVANTAGES OF ACTIVATED CARBON TREATMENT BED
Advantages
Disadvantages
Very effective in the removal
of nonpolar organic compounds
from the ground water flow.
Readily available and easy to
handle and intall.
1. Plugging of the bed may occur.
2. Not very effective for the
removal of polar organic
compounds.
3. Presence of other chemicals in
the ground water may decrease the
effectiveness of bed absorption.
4. Desorption of the hazardous
absorbed materials to the clean
water flow may occur, resulting
in recontamination.
5. Removal and disposal of spent
activated carbon is difficult and
hazardous.
6. Cost ot the material is very high.
7. Competitive absorption with large
organic molecules may decrease
the removal effectiveness of the
bed.
8. Life of the bed may be vety short
in the presence of complex
organic compounds such as humic
compounds.
Source: EPA, 1982.
2-5V
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TABLE 2.11. ADVANTAGES/DISADVANTAGES OF GLAUCONITIC TREATMENT BED
Advantages
Disadvantages
1. Apparent high effectiveness in
the removal of many heavy metals.
2. Good residence time character-
istics for efficient treatment;
relatively little material
required for bed.
3. Abundant in New Jersey, Delaware,
and Maryland.
4. Good metal retention charac-
teristics.
5. Good permeability.
1. Saturation characteristics
unknown.
2. Area of application probably
limited by transportation
costs to Mid-Atlantic region.
3. May require land purchase
since it does not seem to be
commercially mined.
4. Reduction in permeability and
plugging of bed may occur after
a time.
5. May reduce pH.
b. Removal etficiencies of metals at
high concentrations unknown.
Source: EPA, 1982.
2-60
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to
I
4 Mclor** llOocr«tl
M«t«fing pump
ln|«chon pip* it pylU4
up end cn«ifticol it in|«ci««
ol t«cc«tti««
UNCONSOLIOATCO EARTH MATERIALS
Figure 2.13. Cross section of landtill created by chemical injection.
Source: EPA, 1983.
-------
• Daca Requirements - A site hydrogeoLogic investigation should be
conducted prior to chemical injection to provide data on the areal spread and
depth of the plume so Chat injection wells can be placed properly to intercept
all of the contaminated ground water.
• Advantages and Disadvantages - In situ chemical treatment is viable
only under particular hydrogeological and geochemical conditions. Other
aquifer restoration measures, such as withdrawal and treatment may be more
appropriate (Knox et al., 1984).
BIORECLAMATION—Bioreclaraation is based on the concept of utilizing
microbial organisms combined with aeration and addition of nutrients to
accelerate the biodegradation rate of the ground-water contaminants (if
contaminants are biodegradable).
• Applications - Bioreclamation has been previously demonstrated to be
an effective method of controlling ground-water contamination from underground
hydrocarbon spills. The method may also be applied to a clean-up operation of
ground-water contaminated by organic hazardous constituents from landfills.
The technique can be effectively used to clean-up underground hydrocarbon
plumes that contaminate the ground water. However, certain organic
substances, such as chlorinated solvents, cannot be very effectively treated.
Application of the bioreclamation method to treat contaminated ground
water from waste disposal sites may require slight modifications to the
currently employed method. Ground water contaminated with materials that
leached from a disposal site may contain a great variety of hazardous
substances besides hydrocarbon compounds. Therefore, when the bioreclamation
technique that was originally developed for the "in-situ" clean-up of ground
water contaminated with hydrocarbons is used, it is necessary to adjust
certain factors of the process to accommodate the removal of hazardous
constLtu«nts that may comprise a wide range of toxic materials (EPA, 1982),
It is recommended that the contaminated ground water be studied to
determine the chemical constituents to be removed. Once the hazardous
constituents are identified, appropriate bacteria can be chosen to accomplish
the desired degradation process.
2-62
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The general method of Creating contaminated ground water with the
bioreLaraation method is illustrated in Figure 2.14. First, wells are placed
at strategic locations with respect to the hazardous constituent plume. Then
the chosen microorganisms are injected into the ground water along with oxygen
and nutrients. Prior to the injection, the bacteria should be acclimated to
the hazardous constituents they are intended to treat. To promote raicrobial
action, a proper balance of oxygen and nutrients is maintained by continuous
pumping, makeup, and reinjection into the ground water (EPA, 1982).
Proper aeration can be obtained by purging oxygen into wells by the
use of diffusers attached to paint-sprayer-type compressors that can deliver
oxygen at a constant volumetric flow rate. The compressors are equipped with
pressure gages and relief valves to aid in determining that each diffuser is
operating properly (Raymond et al., 1976).
Refer Co Knox et al., 1984 for a detailed discussion of the
bioreclamation method.
• Data Requirements - In addition to a thorough hydrogeologic
investigation, the following information should be identified (EPA, 1982):
• chemical constituents of the contaminated ground water;
• type of bacteria most appropriate for the degradation of the
hazardous constituents;
• size of the contaminated ground-water plume;
• geological data on the site proposed for treatment, including
type of subsurface material and permeability; and
• volumetric flow rate of the ground-water flow and the level of
contamination.
• Advantages and Disadvantages - The advantages and disadvantages of
the bioreclamation method are summarized in Table 2.12.
A summary of the ground-water control and treatment technologies
previously discussed is presented in Table 2.13. Following this, a Permit
Writers' Checklist is provided indicating important points to consider when
reviewing a permit application.
2-63
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Oxygen
Figure 2.14. Treatment of the contaminated ground water with the biorectarnation technique.
Source: EPA, 1982.
-------
TABLE 2.12. ADVANTAGES/DISADVANTAGES OF THE BIORF.CLAMATION TECHNIQUE
Advantages
Disadvantages
1. Good for removal of hydrocarbons
and a limited amount of organic
material from contaminated ground
water.3
2. Environmentally sound.3
3. Fast, safe and economical.*1
4. Inexpensive materials used.3
5. Good for short-term treatment of
contaminated-ground water.3
6. Treatment moves with plume.''
1. Does not remove chlorinated
solvents or heavy metals.3
2. Introduction of nutrients
containing phosphate and nitrogen
may have adverse effects on the
surface water stream located near
the treatment site.3
3. Excessive breakdown of equipment
such as pumps, compressors, and
diffusers may occur, resulting in
higher maintenance and
operational cost.3
4. Long-term effectiveness ot this
method is unknown.3
5. Bacteria can plug the soil and
reduce circulation.'*
6. Residues can cause taste and odor
problems.&
7. Under certain conditions, such as
high concentrations ot pollutants,
it may be slower than physical
recovery methods.^
3EPA, 1982.
bKnox, et al., 1984.
2-65
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TABLE 2.13. SUMMARY OF HYDROGEOLOCIC GROUND-WATER
[CONTROL/TREATMENT TECHNOLOGIES
Control/I reaimcnl
technology
Control/Treatment Hydroguologic/Haiardou*
Strategy Constituent Applicability
Additional Rem
Measures
LIf ectiveuess/
ApplicabiI it y/Content. >
Slun y t'ul-Ott Ua I It
( sui l-t>enlonitt, cemenl-
bcntonil*. diaphragm)
- Vertical Com i
Prjvdn
(in ute but
no p*rluroance
LlAtrf )
Slurry nixturev inconpAt-
ible with concentr«tea
const Uuent*.
Cround-w«ter puaping (well
tytttmt), «urt«ce and sub»u
CI tect iven«fit
by wall com ig
lystcas) ; surface seal ing;
grouting; sheet pile cut-uti
wa 1 1 ; or synthetic nenbrane .
nigrates vertically and
dorUo.u-lly wittiin ihd
Keying tit a va 1 1 1 1 otorot-
|t dillicult it t ne b«oroch
i« dtlticv.lt to ekc^v^tc
or il it n jointcj ot
crackea.
- Horizontal
Used to control tloa
i.e. hytlro-carbont ,
products .
hcqu i r«;6 n tgli ^rourtu-wjt L-
Ltuwnyr jd iL-iil
divtrfcion/
int erct-pt ion
i'. i cumtvreni i
wall.
Uiil y ukeJ tor kBid I 1 s jjii-
titles ot upgi dJ Lent wdi •.-
I lowing tlirou^h the » it t,
wasiu/w^lI cofflpdlidi111)
iH very import ant.
Common practice.
(continued >
-------
TABLE 2.13 (continued)
Com rul'TreaiiMMtt Technology Cum rol /Treatment Hydrogeologtc/llatardous Addic ion A! Renedia I tl lect i vuness/
technology Si atu* Strategy const iluent Appl icabllily Measures Appli;«t>il*t y/Loonent b
emerging Upgr«dient All haiardous constituents Ground-water punping (well Not often uhi-4 clone uuc
eaical ) J i ver* ion general ly compaf ible . Used ay steal ); surface and tub- to con but practical ana
as iaparaejble barrier alone aurlace collection tinier- ellicicm lor sealing vuiu*
or lor tealing liiauret( ceptor ay at en*) ; turiace inroad*. Uround-wai er
solution channel a and other aealiag; Blurry or inect pile Mow can aaveratly attcct
eight teal tor keyed in a lurry aeobrane . curtain pa rticulaily during
cut-oil wall*. construction. Special
given to rate ot giouiio-
wat«r t low 4nd w^ste
conpji ibi I i ty .
Sheet Hile Cui-i>U Ualla laninent Upgradient l'»etul (or controlling Ground-water pumping (well Can not u«e in very rot:ky
diversion leachate general ion lor tyacent ); surface ana »uD- sol I b . pH ot the IciiCit^tc
locat ions where watte is surface collection I inter- is ot particular input i jnct
bowngr a a iem depotitedin contact with ceptor »yatcos ); aurtace inuetcruinin^pilt; lite.
diversion.' a permanent or seasonal sealing; grouting; slurry Cut-otl wall oust e^icua i>
intercept i on water table, 'typically cut -off wall; or tyntnetic inpe roe able st r^t a 01
used in unitora, loose, nembrane. ^eurock to be et tect i ve .
boulacr-trec soil. Costly.
kj blocit 1*1 splacenwiit Method Imminent Upgradient V«ryute(ul inntraiuir where Ground-water punping (wet 1 Placek a bot too ban ici lu
"^J Uowii^t-Jieiu futiiciently near the sur- ceptor aystens I : surlace beneath waste uite.
intt-'rccption ', e.g. slurry or sheet pile sheet pile Cut -ot I w«ll; or i totaled area.
cut -o If wjl 1 , grout curt a in) kynthetic oeobrane . El iect i venukk ul but t.»m
toactasanisolator* bjrritfrtkbaheiioniiit:
Slurry (bot too bar r ier ) perotc JD 1 1 1 1 y ol the
otter ia I incoapat iblewiih consuliojiedttluiry
concent rated organ ics and na t e ridl and t ho tiiti-'kiicbk
h igti I y jc i die coiikl Ituent s . ot Idc D*r r lor . f ei iat_l ci
anc bottoo Ddrrit-*rt ultnulu
b« compatible with u> nin
*° ' 1 i t * ouilUwa t f I , Jnd
li«ldr\JOub COIiklltuutil )•! HUM.'
(conl inued)
-------
TAULE 2.13 (continued)
•Joni r*>) •''( rcatment
lirchnolugy
»jnlrcl-1 recta
a; r-lt-^y
Hydrogeologic/Hazardous
Const iluenl Appl ic ah l I ity
Addi E iuna I
tt led ivi'
Ap;»l iLdbi 11 ( >
Lxt r*>: i ion.'
I
O^
a
Ucep Ucl I
Useful wh«te |jroond-w«tur
conditions Jtre tt«gnent
i.e., hydtaulic giid ient
nearly zero *nd, •!though
more costly, when coobin*-
tiont ot tine «nd textured
aoi It or upward ItyOraul tc
gradiuntii make iubiurlovea.eiti.
Lltect ol long-term
pumping on local giuiui
contiaereo.
Only practical tor »n<»lluw
aquile(» because ui :> jre suiticicnl lo
com,i ituent plua^,
l>e«( iyn kiiou Id be sucn
we I I bpac ing JIIQ ui au
potent iu| t>l »y>tdib j
kullicienl to inlcr^c
(cont inued)
-------
TABLE 2.13 (continued)
Irt' no logy Com lol/lieatcaent Hydrogcologic,Hazardous Ada it ional heaeoial Lllcitivcn.:.*,
scdt .1* Stirft ff.y Const ituent Appl ie j^i I it y Measures APP' it^^ 1111 y 1.00011: iti &
Injaci* waii.; tnio
w«Cer (or i*pcjning
tible to «cc at J b
- Seepjge or kcdurge Water seep* into grounJ- Used in conjunction with uown-
w«ter table by gravity (low. gradient pumping well*.
bUBil.'KFA.'L Uia:NS I'fi i*u^cn Only ipplu-abl« to lhallow bubiurtace dr«i
SYiTt.lS rdleaacs; usually ini;alled ba»ic applicati
col ItfCttid. either lunciion ^» t«U*:i
drains. Inekpen* i v«t
ireatiMnt technologies.
Itpgr^d i«nt Appl i cable tnfi ^ hydraulic Ground- vjter punping (we 1 1 Lowers water
diversion gradient i* Jlooit i*ro. iy»tea.»l. die site *nd
DowngraJient
a iver > ion.'
intercept ion
<1 i vor s inn/ hdz^rauuk <:>M
intercept ion l ruo ground
lypnally used brlow or near Installed pa rpuiiu icul J
.1 1 3 1 uf J i *[>*>» j I i jc 1 1 1 1 y i .• io yruuiiu -wjir t i I >>v .
intcrv ept Itfjchdtc leah tn^
through a I i iir r .
(com inu
-------
TABLE 2.13 (continued)
eontrol/Ireatrtenl i ethnology ilnnt ro I/Treat Bent Hyorogeu logic; Hazardous Add it tonal Henedial LI led i ve:i,r»*
I :;hnology St Jlus Si ralegy Const itu.:nt Aj.pl t:ar>i I icy Measures ApplicabiI 11>/».oo.:-.er.; *
Surface telling (e.g. «ynllie- Installed perpeno i.j l
tie membrane), to ground-w^ter lljw.
Cround-wdter p-oj-sJ out 01
backfilled trencritit by ver-
tical removal ue11. or
IN SITU TKLA7.V.M
In &itu tredtnh-ni Llleciively applied tJ
n.-o«tvj I tit hydrocarbon
t«t racl ion/ recharge cont «ni n«t «d jirounj water .
dm; to i ec 1 1 ouldt injt Haur J.iui coup I ituci>t »
procesbol 'jio- BUbl be h i adcgrab : < ; bu-
ruc lanat ion rec lanat ion incoopat tble wi i
e.g., chlorinated solvents.
Flottind h«urojui JO.T Punpin^ ana i»ijjrnifc ;:
• tituentfc (i.e.pet roleum cetfcei au«t be cJntIDLj
products, hydro-cjrbontJ «re to prevent collected \^
removed fraaopen irencnet tints Iron tetr(.int i:n.
by *kinning ^ucp&. trench wall*.
I'eriDcrfbltf 1 r«- Jtramt B.J J» i.mer t ui6 In » 1 1 u t n-^tnent Appl ic«h l« ( u »n« 1 low ut t en unly « I r« J i i v«. i . •
( I i me it one ,«ctiv«iea aquifer*. Blior I time because r-c:»
carbon, glaaconu ic green Downgradient lose their rcjct i vv --r-
• *nd( teol i te «nJ », <••.)- d i vert ion/ city or be coat v l^^^e-
thtfticion) intercept i on due wi tti «ol idt .
to placement of bed
:..-!«:rŁ i n0 I n k i tti Hat l rejted le^ch.,:,; Area! bpredtl «nj otpi
*sj ' trvatoenl containing cyaniae. hazaraouk contiiijcnt*
^ plutnc Oiu&t be Clur«J i*i-.
so tiiat injvvtion
we! Is <
placed to intcreep: -..
-------
PERMIT WRITERS' CHECKLIST
Sice Name/Location
1. Has applicant undertaken a hydrogeologic investigation of
the site in question? (yes or no)
2. Does hydrogeologic investigation include the following information (place
check beside data provided):
Site Soil Characteristics
• Type
• Texture (granular or cohesive)
• Grain size distribution and gradation
• Moisture content
• Permeability
• Soil pressure
• Porosity
• Composition
• Compaction
• Discontinuities in soil strate (e.g. faults)
• Cohesive and consolidation states of individual strata
• Degree and orientation of soil stratification and bedding
• Location and type of weathered bedrock or solution
channels
• Other (specify)
Ground-Water Characteristics
• Depth to water table
• Direction of flow
• Rate of flow
• pH
• Hardness
• Salt concentration
• Presence of minerals and organics
2-71
-------
• Concentration of suLfides and calcium
• Water pressure
• Recharge quantity
• Location of neighboring water bodies (e.g. streams)
• Other (specify)
Aquifer Characteristics
• Use of aquifer
• Permeability and thickness of water bearing strata
• Transmissivity
• Storativity
• Specific yield
• Depth
• Type (confined or unconfined)
• Condition (e.g. homogeneous, isotropic, leaky)
• Hydraulic gradient
• Effective porosity
• Identification of recharge and discharge areas
• Identification of aquifer boundaries (i.e. areal extent)
• Aquiclude characteristics (depth, permeability, degree
of jointing, hardness, continuity)
• Other (specifiy)
Hazardous Constituent Plume Characteristics
• Size.
• Location
• Shape
• Hydraulic gradient across plume
• Depth to plume
• Chemistry and concentration
• Velocity
• Other (specify)
2-72
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3. Indicate ground-water controI/treatment technology under consideration by
applicant (specify particular technology(s) beside appropriate category):
• Impermeable barrier
• Well system
• Interceptor system or subsurface drain
• In situ treatment
Control/treatment technology(s) strategy and location: (Check
strategy/location and indicate number of control/treatment units)
• Upgradient diversion
• Downgradient diversion/interception
• Surrounding site
• Extraction/recharge
• In situ treatment
(• Source control
5. Purpose of control/treatment technology: (check appropriate purposes)
• Control ground-water flow
• Treat ground water
• Isolate hazardous constituent plume
• Extract hazardous constituent plume
• Replenish ground water
• Adjust water table
• Control subsurface flow of hazardous constituents
• Neutralize, precipitate or destroy hazardous constituents
• Other (specify)
2-73
-------
b. Is conerol/treacmenc technology applicable Co sice Cerros of: (yes or no;
refer Co appropriate control/treatment cechnology discussions).
• Implementability
• Effectiveness
• Reliability
• Compatability of hazardous constituent (plume) with
technology
• Site's subsurface characteristics
7. Environmental concerns associated with this control/treatment technology:
(check where applicable)
• Subsidence
• Decrease in well yield of adjacent well field
• Drawdown of adjacent surface water bodies
• Induced hazardous constituent migration to new pathways
• Other (specify)
2-74
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TREATMENT TECHNOLOGIES
Several technologies are available to treat contaminated ground water
after being withdrawn from the subsurface. Treatment technologies are capable
of removing various percentages of certain hazardous constituents. In
selecting an appropriate treatment method, the following factors must be
considered: the type(s) of hazardous constituents to be removed; the amount
of water to be treated; the initial concentrationCs) of hazardous
constituents; and the desired final concentrations^) of hazardous
constituents. Table 2.14 lists several treatment techniques which are
available, and indicates the types of contaminants for which these techniques
can be used most effectively. Brief descriptions of the most commonly used
treatment technologies are given in the following subsections.
Carbon Adsorption
Carbon adsorption can be an effective process for the removal of dissolved
organic compounds from contaminated ground water. Compounds which are
effectively treated by carbon adsorption include chlorinated pesticides,
phenols, aliphatic chlorinated hydrocarbons, and aromatics (such as benzene,
toluene, and xylene) (Chillingworth, 1981). The efficiency of carbon
adsorption in removing various organic compounds is presented in Tables 2.15
and 2.16
Carbon adsorption can be designed for either column or batch applications
however, ground-water treatment generally utilizes carbon columns. In column
applications, adsorption involves the passage of contaminated water through a
bed of activated carbon which selectively adsorbs the hazardous constituent
(adsorbate) onto the carbon (adsorbent). When the activated carbon has been
utilized to its maximum adsorptive capacity (exhaustion), it is then removed
for disposal, destruction, or regeneration.
The carbon columns can be designed such that flow is downward (downflow)
through the bed, either under pressure or gravity flow (fixed bed), or the
flow can be upward (upflov) through a packed or expanded bed. For treating
contaminated ground water, a common adsorber configuration would be to place
2-75
-------
TABLE 2.14. STATE-OF-THK-AKT TECHNIQUES FOR TREATING COMMON
GROUND-WATER CONTAMINANTS
Candidate Treatment
Technologies
Air Stripping
Carbon Adsorption
Chemical Oxidation
Chemical Reduction
Distillation
Electrodialysis
Electrolysis
Evaporation
Filtration
Floccu lat ion
Hydrolysis
Ion Exchange
Liquid Ion Exchange
Neutra lization
Ozonat ion
Free i pi toe ion
Resin Adsorption
Reverse Osmosis
Sedimentation
Steam Stripping
Ultraf iltration
Common
Heavy "Metal"
Cations
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Types of
Ground-Water Contaminants
Heavy "Metal" Non-Metallic
Anions Toxic Anions
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Organics
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Source: Adapted from Arthur D. Little, Inc., 1977.
2-76
-------
TABLE 2.15. OPERATING RESULTS AND CHARACTERISTICS OF CARBON ADSORPTION SYSTEMS
FOR INFLUENT CONTAMINANTS AT pg/1 LEVELS
System
Number
1
2
3
4
5
6
7
8
Contaminants
Perchloroethylene
Trichloroethylene
Trichloroethane
Tetracl) loraethy lene
Trichloroethylene
Di-isopropylether
Trichloroethylene
Trichloroethylene
Di-isopropyl Methyl
Phosphonate .
Dicyclopentadiene
Chloroform
Trichloroethylene
DDT
DDE
DDD
Typical
Influent
Concentration
Pg/1
10
5
143
8.4
26.3
56
64
8-15
1,250
450
20
50
1
1
1
Typical
Effluent
Concentration Carbon Flow
Pg/1 Type GPM
<1 Virgin F-300 200
-------
TABLE 2.16. OPERATING RESULTS AND CHARACTERISTICS OF CARBON ADSORPTION SYSTEMS
FOR INFLUENT CONTAMINANTS AT rag/1 LEVELS
IS)
I
Typical
Influent
system Concentration
Number Contaminants mg/1
1
2
3
4
5
6
7
8
Methylene Chloride
1,1,1 Trichloroethane
Phenol
Orthochlorophenol
Phenol
Vinylidine Chloride
Ethyl Acrylate
Chloroform
Carbon Tetrachloride
Trichloroethylene
Perch loroe thy lene
Perchloroethylene
Trichloroethylene
Cis-1,2 Dichloroethylene
1,1,1 Trichloroethane
Dichloroisopropylether
Dich loroe thy let her
21
25
63
100
32-40
2-4
200
3.7
72.9
4.3
51.3
9
1
1
1
1
1.2
Typical Total
Effluent Contact
Concentration Carbon Flow Time in
raS/l Type CPM Minutes
.1 Reactivated 20 262
1
1 Reactivated 80 66
1
0.1 Reactivated 875 60
0.1
1 Reactivated 300 52
1 Reactivated 40 130
1
1
1
1 Virgin F-300 120 44
1
1
1 Reactivated 25 228
1 Reactivated 2,250 20
1
Carbon
Usage
(1 be/ 1,00':
gallons)
3.9
5.8
2 1
13.3
11.6
2.4
1.0
0.41
Source: Kaufmann, 1982.
-------
two downClow pressue adsorbers in series. The lead adsorber effects the
adsorption until it is exhausted. It is then taken off Line for regeneration,
and the flow is switched to the second column in series. Following
regeneration, Che fresh column is placed on-stream at the end of the sequence,
and the process is repeated.
Factors to consider in the design of a carbon adsorption system are carbon
exhaustion (usage) rate, contact time, hydraulic loading rate, and column
size. Carbon exhaustion rate is very important since it dictates how often
spent carbon must be replaced by new or regenerated carbon. It is defined as
the weight of carbon required for treating a specified volume of water to a
specific effluent quality, and it will depend on several factors includng the
effluent requirements and the type and concentration of the contaminant
(Troxler, 1983). Examples of carbon usage rates for removal of volatile
organics from ground water were previously given in Tables 2.15 and 2.16.
Tables 2.15 and 2.16 also present superficial contact times for several
ground water treatment applications. As is evident, Che contact times
required for treating hazardous constituent concentrations at the ug/1 level
are generally lower (12-160 minutes) than for those systems treating hazardous
constituent concentrations at the rag/1 level (20-202 minutes). Contact time
will also depend on the particular contaminant and the effluent requirements.
The hydraulic loading rate will depend on the contact time, the head loss
in the adsorber, Che dimensions of the adsorber, and the carbon particle
size. It can vary from less than 0.5'gpra/ft up to 8 gpm/ft3. Fifty percent
of the granular activaced carbon (GAC) columns evaluaCed in one study ucilized
hydraulic loading rates of less than 1.5 gpm/ft2 (Troxler, 1983).
Carbon column dimensions are also highly variable and depend on the two
previous parameters. Heights are typically 20 to 40 feet, and typical
diameters are less than 12 feet (Troxler, 1983).
The effectiveness of GAC in removing a variety of organics was presented
earlier in Tables 2.15 and 2.16. Adsorption efficiencies are affected by both
the characteristics of the hazardous constituent and the characteristics of
the aqueous waste streams in which they are contained.
2-79
-------
Characteristics of the hazardous constituent which affect adsorption
include polarity, molecular weight, solubility, and molecular structure. In
general, non-polar, high molecular weight organics with limited solubility are
preferentially adsorbed. Also, branched-chain compounds are generally more
adsorbable then straight-chain compounds.
Characteristics of the aqueous stream which affect adsorption efficiency
include: pH, temperature, suspended solids concentration, and oil and grease
concentration. The effect of pH will vary from compound to compound but, in
general, the compound will adsorb at the pH which imparts the least polarity
to the molecule. For example, phenol is a weak acid and will consequently be
adsorbed at low pH, while amines which are basic will be adsorbed more easily
at higher pH values. Because adsorption is an exothermic process, increased
adsorption will occur when temperatures are increased (Lyman, 1978;
Troxler, 1983).
For an aqueous stream to be treated by carbon adsorption, the suspended
solids concentration should generally be less than 50 ppm, and the
concentration of oil and grease should be less than 10 ppm. Consequently
pretreatraent, usually granular filtration, is often required to prevent
excessive headloss in the bed due to clogging by suspended solids or oil and
grease.
Granular Filtration
Granular filtration techniques can be used to remove suspended solids from
the aqueous phase. It is often employed as a pretreatraent technique
(intermediate process) or as a final polishing step. The two basic types of
filter systems are the rapid sand filter and the slow sand filter. Only rapid
sand filters, however, are appropriate for ground-water treatment
applications. Table 2.17 describes the general features of rapid sand filters.
The apparatus for the rapid sand filtration technique consists of a bed of
sand which is supported by an underdrain system that collects the filtrate.
As the filtration process proceeds, suspended particles become trapped on top
of and within the bed, which reduces the efficiency of the process.
Eventually, it becomes necessary to remove these solids from the filter media.
2-80
-------
TABLE 2.17. GENERAL FEATURES OF CONSTRUCTION AND OPERATION
OF RAPID SAND FILTERS
Rapid Sand FLLcers
Race of filtration
Size of bed
Depth of bed
Size of sand
Grain size distribu-
tion of sand in filter
Underdrainage system
Loss of head
Length of run between
cleanings
Penetration of
suspended matter
Method of cleaning
100 to 125 to 300 mgad
Small, 1/100 to 1/10 acre
18 in. of gravel; 30 in.
of sand, or less; not
reduced by washing
0.45 mm and higher; co-
efficient of nonuniformity
1.5 and lower, depending
on underdrainage system
Stratified with smallest
or lightest grains at top
and coarsest or heaviest
at bottom.
(1) Perforated pipe
laterals discharging into .
pipe mains; (2) porous
plates above inlet box;
(3) porous blocks with
included channels
1 ft inital to 8 or 9 ft
final
12 to 24 to 72 hr
Deep
Dislodging and removing
suspended matter by upward
flow or backwashing, which
fluidizes the bed.
Possible use of water or
air jets, or mechanical
rakes to improve scour
(continued)
2-81
-------
TABLE 2.17 (continued)
Rapid Sand Filters
Amount of wash water
used in cleaning sand
Preparatory treatment
of water
Supplementary treat-
ment of water
Cost of construction,
U.S.A
Cost of operation
Depreciation cost
I to 4 to 6* of water
filtered
Coagulation, flocculation,
and sedimentation
Chlorinat ion
Relatively low
Relatively high
Relatively high
125 mgad = 2 gpm per sq ft = 16 ft per hr = 125 m per day.
Source: Kair, et. al., 1968.
2-82
-------
Regeneration of che filtration media is accomplished by means of a
"back-washing technique. During this step, the underdrainage system doubles
as a water distribution system. Water rises into the filter bed in the
reverse direction of the original flow causing the filter bed to become
fluidized. Commonly used methods for scouring the filtering media include:
• High-Velocity Wash - Wash water is forced upward through the filter
bed at a velocity high enough to cause the filter bed to become
fluidized and turbulent.
• Surface Scour - Jets of water are directed into the fluidized bed
causing increased turbulence.
• Air Scour - Air is blown upward through the bed either before or
during fluidization of the bed.
• Mechanical Scour - The fluidized bed is stirred using a mechanical
apparatus.
During the scouring process che solids become dislodged from the sand and are
discharged in the spent wash cycle. The bed is then allowed to resettle. The
coarser, heavier grains tend to settle at the bottom while the finer, lighter
grains remain at the top. Thus, the bed becomes stratified.
Various modifications to the sand filtration unit may be employed. One
type of modification is the dual-media filtration unit which has a filter bed
consisting of a layer of anthracite underlain by a layer of sand. In
multimedia filtration, several layers of different materials are used for the
filtration media. Filter materials may include natural silica sand, crushed
anthracite, (hard) coal, crushed magnetite (ore), and garnet sands.
Filtration systems can consist of multiple compartment concrete or steel
units aligned horizontally or vertically. The flow through the filtration
units occurs by using the available head from the previous treatment unit, or
by pumping to a flow-split box and then using the effects of gravity to allow
flow to the filter cells. Pressure filters use pumping to increase the
available head.
2-83
-------
[on Exchange
Ion exchange is a reversible process in which an interchange of ions
occurs between a solution and an essentially insoluble solid in contact with
the solution. Both natural and synthetic substances can act as ion
exchangers. Natural ion exchange materials usually consist of clays or
zeolites (Skoog & West, 1979). Zeolites have been used effectively in the
removal of ammonia from wastewater (Metcalf & Eddy, 1972). Synthetic resins
are used more commonly because of their durability (EPA, 1982). Synthetic ion
exchange resins are composed of high molecular weight, polymeric materials
containing a large number of ionic functional groups per molecule (Skoog &
West, 1979).
Cation exchange resins exchange only positively charged hazardous
constituent species from contaminated ground water. The extent to which
removal of anions and/or cations occurs depends on the equilibrium that is
established between the ions in the aqueous phase and those in the solid phase
(EPA, 1982). The preference of one kind of exchangeable ion over another
depends on the nature and volume of the ion, the type of resin and its
saturation, and the ion in the contaminated ground water (EPA, 1982). As a
general rule, ions with a higher charge will form more stable salts with the
exchanger than those with a lower charge, and hence polyvalent species can
frequently be selectively removed from a solution of monovalent ions (species).
The ion exchange process may be operated using" a batch or continuous
technique (Metcalf & Eddy, 1972; EPA, 1982; EPA, 1980). In a batch process,
the ion exchange resin is stirred with the water to be treated until the
reaction is complete. The spent resin is removed by settling and is
subsequently regenerated and reused (Metcalf & Eddy, 1972). In a continuous
process, the exchange material is placed in a bed or packed column, and the
water to be treated is passed through it (Metcalf & Eddy, 1972). The
continous ion exchange process is operated in a cycle of four steps: service
(exhaustion), backwash, regeneration, and rinse (EPA, 1980). Initially, the
water to be treated is passed through the ion exchanger until the active sites
2-84
-------
Ln che exchanger ire partial ly or completely used up ("exhausted") by that ion
(hlJA, 1980). Uuring tlie backwash step, the bed is wasliod (generally with
water) in the reverse direction of che service cycle in order to expand and
resetcle the resin bed. The exchanger is Che "regenerated" by passing a
concentrated solution of the ion originally associated with it through the
resin bed. The rinse step removes the excess regeneration solution prior to
the next service step (EPA, 1980).
With the continuous process, three modes ot operation are possible:
cocurrent fixed bed, countercurrent fixed bed, and countercurrent continuous
(EPA, 1982). The fixed bed ion exchange technique is most often used to treat
contaminated ground water. Variations of the fixed bed exchange mode include
mixed beds and the use of exchange columns in a series. When a number of beds
are used in series, the upstream bed can be detached, regenerated, and
reattached at the downstream end (similar to a countercurrent stream) (EPA,
1982). A "staged" fixed bed technique is often employed to allow more
efficient use of the regenerant materials.
Ion exchange can be successfully used to remove cationic and anionic
metallic elements, halides, cyanides, nitrate, carboxylics, sulfonics, and
some phenols. However, there are limitations in the use of this technique for
ground-water treatment. Ion exchange is not suitable for removal of high
concentrations of exchangeable ions, because the resin material is rapidly
exhausted during the exchange process and costs for regeneration become
prohibitively high. The upper concentration limit for exchangeable ions for
efficient operations is about 2500 mg/1 expressed as calcium carbonate (or 0.5
equivalents/1). Another limitation of ion exchange is that pretreatment of
the ground water is often necessary because certain hazardous constituents
decrease ttie effectiveness o[ the resin. Also, certain organics (especially
aromatics) become irreversibly absorbed by the resin. Oxidants (such as
chromic or nitric acid) can also damage the resin. Pret'i Iter ing the ground
water and/or using scavenger exchange resins can alleviate these problems, at
an additional cost however.
2-35
-------
i ili.-ni i (.-.I I ' )x nl.i L" inn
Chemical oxidation is a ground-water treatment technology chat can be used
to remove ammonia, decrease the concentration of residual organics, and to
decrease the bacterial and viral content of ground water (Metcalf & Eddy,
1972). Additional applications include the conversion of organic and
inorganic substances into less harmful or into more desirable forms, the
removal of iron and manganese, and the removal of tastes and odors (Sundstrom
and Klei, 1979).
Oxidation-Reduction reactions (or "Redox" reactions) are those in which
the oxidation state of at least one reactant is raised while that of another
is lowered. The oxidation states of the reactants change as a result of
electron transfer. An oxidant is an electron acceptor and a reductant is a
substance which donates electrons.
Several oxidizing agents can be used in the treatment of contaminated
ground water. The more commonly used oxidants are listed in Table 2.18. The
extent of oxidation that occurs is affected by the dosage of the oxidant, the
pH of the reaction medium, the oxidation potential of the oxidant, and whether
or not stable intermediates are formed (EPA, 1980).
The first step of the chemical oxidation process usually involves
adjusting the pH of the solution Co be treated. Next, the oxidizing agent is
added. Mixing is utilized to contact the oxidizing agent and the ground
water. More concentrated solutions require cooling due to the heat that is
generated during mixing. Reaction times vary, but are generally not more than
a few minutes for most commercial-scale installations. Usually, additional
time is allowed to ensure complete mixing and oxidation. Upon completion of
the oxidation reaction, the oxidized solution is then generally subjected to
.mother form of treatment to precipitate nnd remove any insoluble oxidized
material, metals, or other residues. Th,; excess oxidizing agent (both reacted
.ind unreacted) may also have to be removed.
2-86
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I'ABLE .i.18. TKEATMKNT APPLICATIONS OF THt MOST COMMONLY USED OXIDANTa
Oxidant
Hazardous Constituent
Ozone
Air (atmospheric oxygen)
Chlorine gas
Chlorine gas and caustic
Chlorine dioxide
Sodium hypochlorite
Calcium hypochlorite
Potassium permanganate
Oxid.-mts that are present in
irac* quantities only
Permanganate
Hydrogen peroxide
Nitrous acid
Source: liPA, 1980.
Sulfites (S0§)
Sulfides (S=)
Ferrous iron (Fe"*"1") (very slow)
Sulfide
Mercaptans
Cyanide (CN~)
Cyanide
Uiquat
Paraquat pesticides
Cyanide
Lead
Cyanide
Cyanide (organic odors)
Lead
Phenol
Diquat
Paraquat pesticides
Organic sulfur components
Kotenone
Formaldehyde
Manganese
Phenol
Cyanide
Sulfur compounds
Lead
Benzidene
2-.S7
-------
The major disadvantage of chemical oxidation for ground-water treatment is
that it introduces new metal ions into the effluent. Depending on the levels
of these new ions, additional treatment techniques, such as filtration or
sedimentation, may often be necessary. For most chemical oxidations, there
will be a residue for disposal unless the concentration of the hazardous
constituent is so low that the oxidant products (if any) and the oxidized
constituents can be carried away with the effluent. The hazardous constituent
sludge which results from the oxidation treatment of cyanides when iron and
certain other transition metal ions are present (e.g., ferrocyanide) cannot be
easily treated with further oxidation.
Reverse Osmosis
Reverse Osmosis is a treatment technique used to remove dissolved organic
and inorganic materials, and to control amounts of soluble metals, TDS, and
TOC (Metcalf & Eddy, 1972; EPA, 1980).
The process of reverse osmosis involves filtering the contaminated ground
water through a semipermeable membrane at a pressure greater than the osmotic
pressure caused by the dissolved materials in the water. Operating pressures
generally range from atmospheric to 1500 psi (Metcalf & Eddy, 1972; EPA, 1980).
The semipermeable membrane can be either in the form of a sheet or tube
(Sundstrom and Klei, 1979). As shown in Figure 2.15, the ground-water
solution (termed the "feed") flows over the surface of the membrane, with the
treated water (termed the "concentrate") containing the removed materials
leaving the membrane (Sundstrom and Klei, 1979; KPA, 1980).
The amount of material which can be removed using the reverse osmosis
technique is dependent on the membrane type, operating pressure, and the
specific pollutant of concern (EPA, 1980). Multicharged cations and anions
are easily removed from the wastewater with this technique. However, most low
molecular weight dissolved organics are not removed or are only partially
removed with this method.
2-88
-------
Membrane Separation frocesses
Feed
Permeate
(a)
.'. .. -Concentrate
Membrane
Support
Reject
Feed
(b)
Permeate
Figure 2.15. Membrane processes using a pressure driving force in
(a) plane and (b) tubular designs.
Sources: Sundscrom and Klei, 1979.
2-89
-------
During iii/nm Lac Cu re , tiie semipermeabLe membrane is heac-Created in sucli a
way chat the rate at which water can be produced is fixed. Colloidal and
organic matter can clog the membrane surface, thus reducing the efficiency of
the process. Also, the low-solubility salts will precipitate on the membrane
and reduce the level of product water. Pretreatment techniques such as
activated carbon adsorption, chemical precipitation, and filtration, may need
to be used. Operating costs for membrane systems are a direct function of
the concentration of the impurity to be removed.
Air Stripping
Air stripping, when applied to the treatment of contaminated ground water,
is the process of driving volatile compounds from the aqueous to the gaseous
phase. Air stripping is most commonly achieved in a packed tower in which air
and water flow countercurrent to one another with the water flowing downward
over the packing as a thin flira, while the air flows upward carrying away the
volatile constituents.
Important factors to consider in the design of a stripping column
include: the type and size of packing, air-to-water ratio, pressure drop in
the column, and the height and diameter of the column. The packing material
used will depend on resistance to corrosion and ease of handling, and for
water treatment is usually plastic saddles or rings. The packing material
will influence both the head loss in the column and the mass transfer rate of
the contaminants. Once a packing material is selected and water flow rate is
known a number of air-to-water ratios, tower diameters and tower heights may
be used to achieve a given removal of a certain compound.
Models relating the above parameters to removal efficiency are presented
in several papers which should be consulted if further information is desired
(Hall et al., 1984; Roberts et al., 1985; Cross and Termaath, 1984;
Crittenden, 1984).
2-90
-------
Air stripping can he effective either as an alternative to carbon
adsorption or as a complementary process to adsorption. As an alternative, it
can be only 20 to 30 percent of the cost of adsorption, and still achieve
equivalent results (Shilling, 1985) for removal of volatile compounds. In
addition, many compounds which are difficult to remove by carbon adsorption
are effectively removed by air stripping. These include trihaloraethanes and
other halogenated methanes and ethanes. As a complementary process preceeding
adsorption, air stripping may decrease the organic loading on the carbon
adsorbent thereby decreasing the carbon requirements, and it may also remove
contaminants which would not be removed by adsorption (McCarty, 1979).
A disadvantage of air stripping is that the hazardous constituents which
are stripped from solution will be released into the air. In many cases this
may not present a problem since the concentration of hazardous constituents in
the water is in the ug/l range, and if a high air-to-water ratio is used, this
concentration will be lowered even further by dilution and dispersion. In
other cases, however, it may be necessary to control air emissions by
employing a vapor treatment process such as carbon adsorption or incineration.
Compounds susceptible to removal by air stripping include trihalomethanes,
chlorinated benzenes, some aromatic hydrocarbons, and even some pesticides.
In general, the amenability of an organic compound to be stripped from a
•
dilute aqueous solution can be determined by the equilibrium between the
concentration of the organic in the aqueous phase and the concentration in the
air. This relationship is quantified by the Henry's Law Constant. The higher
the value, the greater the potential for the compound to be air stripped.
McCarty (1979) has indicated that compounds with a Henry's Law Constant
-3 3
greater than I x 10 atm-m /raol should be amenable to air stripping. The
Henry's Law Constants for several compounds on the U.S. EPA priority pollutant
list are given in Table 2.19.
The effectiveness of removal for various compounds will depend on the
design of the column, but with proper design 90-100 percent removal of
compounds which are amenable to air stripping is possible.
2-31
-------
TABLE 2.19. CALCULATED HENRY'S LAW CONSTANTS AT 20°C FOR ORGANIC COMPOUNDS
H
Compound atm m-Vmol
Vinyl chloride 6.4
Dichlorofluoromethane 2.1
1,1-dichloroethylene 1.7 x 10~1
1,2-dichloroethylene 1.7 x 10~1
Trichlorofluoromethane l.l x 10~1
Methyl bromide 9.3 x 10~2
Toxaphene 6.3 x 10~2
Carbon tetrachloride 2.5 x 10~2
Tetrachloroechylene 2.3 x 10~2
ChloroeChane . 1.5 x 10~2.
beta-bHC l.l x 10~2
Trichloroethylene 1.0 x 10~2
Methyl chloride 8.0 x 10~3
PCtt (Aroclor 1260) 6.1 x 10~3
1,2-trans-dichloroethylene 5.7 x 10~3
Ethylbenzene 5.7 x 10~3
Toluene . 5.7 x 10~3
1,1-dichloroethane 5.1 x 10~3
Benzene 4.6 x 10~3
Chlorobenzene 4.0 x 10~3
1,1,1-trichloroethane 3.6 x 10~3
Chloroform 3.4 x 10~3
PCB (Aroclor 1248) 3.0 x 10~3
1,3-dichlorobenzene 2.7 x 10~3
Methylene chloride 2.5 x 10~3
Heptachlor 2.3 x 10~3
PCB (Aroclor 1254) 2.3 x 10~3
1,4-dichlorobenzene 2.1 x 10~3
Aldrin 2.1 x 10~3
1, 2-dichloropropane 2.0 x 10~3
1,2-dichloropropylene 2.0 x 10~3
Alpha-BHC 2.0 x 10~3
1,2-dichlorobenzene 1.7 x 10~3
Anthracene 1.4 x 10~3
1,2-dichloroethane 1.1 x 10~3
Hexachloroechane 1.1 x 10~3
1,1,2-trichloroethane 7.8 x L0~4
Bromoform 6.3 x 10~4
PCB (Aroclor 1242) 4.9 x 10~4
1,1,2,2-teCrachloroethane 4.2 x 10~4
Naphthlene 3.6 x 10~4
Fluorene 2.1 x 10~*
(continued)
2-92
-------
TABLE 2.19 (continued}
Compound
atm ro-Vmol
Acenaphchene
Phenenchrene
Bis(2-chioroi3opropyl) echer
AcroLein
2-nitrophenol
Acrylonitrile
Di-n-butyl phchalate
2,4-dichlorophenol
4,4'-DDT
2-chlorophenol .
Nitrobenzene
Isophorone
Peneachlorophenol
Dimethyl phchalate
Lindane
Phenol
Dieldrin
4,6-dinitro-o-cresol
1.9 x
1.3 x
1.1 x
9.7 x
7.6 x
6.3 x
6.3 x
4.2 x
3.4 x
2.1 x
1.1 x
4.2 x
2.1 x
4.2 x
3.2 x
2.7 x
1.7 x
1.7 x
-*
10
10-5
10-5
10-5
10-5
10-5
10-5
10-5
10-5
10~6
10-6
10-7
10-7
10-7
10-7
10-7
Source: EPA, 1978b.
2-93
-------
SECTION 3
CASE STUDIES
INTRODUCTION
GCA conducted a search for case studies which would demonstrate how to
select and implement corrective measures for releases to ground water from
SWMUs. Approximately 100 sites were reviewed to develop a list of sites for
potential case study analysis. Information was obtained from several data
sources including EPA Headquarters, EPA Regional offices, and literature
searches.
The site review focused on finding examples of sites where remedial
responses were either ongoing or completed. Site Selection Worksheets were
completed for sites which met this initial criteria. The worksheet (shown in
Figure 3.1) contained information*which was used to screen the sites for
potential case study evaluations.
The criteria used for final selection of case studies included:
• availability and completeness of site information and monitoring data;
• types of remedial measures implemented;
• types of wastes and hazardous constituents present at the facility;
• site characteristics;
• geographic locations; and
• waste management practices.
3-1
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WORKSHEET FOR SCREENING CASE STUDIES
SITE NAME
LOCATION
TYPE OF FACILITY
SIZE OF SITE/DISPOSAL AREA
YEARS OF OPERATION/DISCOVERY OF RELEASE (How & when release
discovered)
TYPES OF RELEASES
TYPE OF WASTE DISPOSED/HAZARDOUS CONSTITUENTS PRESENT
MEDIA CONTAMINATED
CLIMATE
TOPOGRAPHY
SOILS
Figure 3.1. Worksheet for Screening Case Studies
3-2
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GEOLOGY
HYDROLOGY (Ground Water & Surface Wacer)
RESPONSE ACTIONS (Including Designed and Implemented)
MONITORING DATA AVAILABLE
SUCCESS/FAILURE OF REMEDIATION (Removal Efriciency, Containment
Effectiveness)
Figure 3.1. (continued)
3-3
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In reviewing potential case studies, those case studies chat were designated
as being most representative of a variety of the above criteria and
constituents of each criterion were selected.
A list of the selected sites and a summary of the remedial responses at
these sites is presented in Table 3.1. Case studies were prepared using the
outline shown in Figure 3.2. These case studies are presented below.
CILSON ROAD SITE - NASHUA, NEW HAMPSHIRE
Facility Description
The 6-acre site was used as a sand and gravel borrow pit during the 1950s
and 1960s. By the late 1960s most of the sand had been removed. The
owner/operators began illegally disposing demolition debris, domestic refuse,
chemical wastes, and sludges to fill the excavation area. In 1979, after
reports of heavy odors heavy odors in a brook adjacent to the site and
subsequent detection of hazardous constituents in a nearby private well, a
court order was issued to restrain the owner/operators from further disposal
operations at the site. The site is currently on the list of EPA Superfund
sites.
Site Characteristics
Soils—
Soils at the site are stratified, unconsolidated glacial deposits
consisting primarily of two permeable, interfingering units. These two units
consist mostly of fine to medium sands or fine to coarse sands and gravels,
with total thicknesses ranging from 20 to 90 feet. The permeable sands overly
a thin sequence of glacial till having a maximum thickness of 12 feet. The
till is very dense and contains mixtures of unstratified silt, sand, and
gravel.
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TABLE 3.1. TYPES OF RELEASE(S) AND REMEDIAL ACTION(S) IMPLEMENTED AT SELECTED SITES
Sice Name/
Location
Type of
Facility
Hazardous Constituents Type(s) of
Present Release(e)
Remedial Action(s)
Cilson Road/
Nashua, NH
u>
I
Llangollen
Army Creek
Landfills/
New Castle, DE
Rocky
Mountain
Arsenal/
Denver, CO
Illegal dump site
(6 acre)
Landfill
( 50 acres)
Arsenal manufact-
uring chemical war-
fare products and
pesticides (unlined
waste lagoons,
storage areas, and
manufacturing plant
areas)
Metals and organics Ground water
(chloroform, methylene
chloride, ethylene
chloride, TCE, MEK
toluene, diethyl-
ether, acetone,
tetrahydrofurans)
Metals and organics
(Fe, Mn, Cr, Be,
Pb, Ni, Zn, As, TCE
chloroform, 1,2-
dichloroethane)
Ground water,
surface water
Pesticide residues,
toxic metals, solvents
Ground water
o Drums Removed
o Sludges disposed of
onsite in a double-
lined landfill
o Slurry wall
installed
o Constucting ground
water treatment-
reinjection system.
o 12 recovery wells
installed. Ground
water pumped without
treatment to nearby
stream
o Under consideration
are: grading, cap-
ping, barrier wall,
and recovery well
relocation.
o 3000 ft interceptor
trench installed
o Wastes from the
trench are collect-
ed and treated
(continued)
-------
TABLE 3.1 (continued)
Sice Name/
Location
Type of
Facility
Hazardous Constituents
Present
Type(s) of
Release(s)
Remedial Action(s)
Stringfellow/
Riverside, CA
LJ
I
Unknown Name/
Gulf Coastal
Plain
Whitmoyer
Laboratories
(Myerstown,PA)
Toxic industrial
disposal site
(surface impound-
ments, 17 acres)
Landfill
facility
(pond liner
punctured, leakage
occurred)
Wastewater genera-
ted by the manu-
facturing plant
treated with lime;
slurry disposal in
an unlined lagoon
, HN03, HC1,
50% DOT, TCE, Zn,
Hg, Cr, chloroform,
chlorobenzene
Ground water
Petrochemical
industrial organics
Ground water-
shallow aquifer
Arsenic
Soils,
ground water,
surface water
o Excavation
o Grout curtain
o Clay core barrier
and drain
o Neutralization and
grading
o Two interceptor
wells
o Submersible pump
ground-water
recovery system
o Ground-water model
developed
o Installation of re-
charge pit beneath
surficial clays
o Installation of
trench drain/jet
educator wel I
withdrawal system
o Ground-water treat-
ment and recovery
(counter-pumping)
o Excavation of
contaminated sludges
and soils
o Concrete storage
bins
-------
OUTLINE FOR CASE STUDIES WRITE-UP
I. FACILITY DESCRIPTION
A. TYPE OF SWMU/SYSTEM DESIGN (Including any leak
detection and/or monitoring system)
B. YEARS OF OPERATION
C. TYPE OF WASTES RECEIVED/DISPOSED
D. SIZE OF SITE/DISPOSAL AREA
E. ANY PREVIOUS OPERATIONS AT THE SITE/SITE BACKGROUND
F. REGULATORY & LEGAL STATUS (NPL, CERCLA, etc.)
II. SITE CHARACTERISTICS
A. CLIMATE
B. TOPOGRAPHY
C. SOILS
D. GEOLOGY
E. HYDROLOGY (Ground Water & Surface Water)
III. RELEASES
A. TYPES/CAUSES OF RELEASES
B. MECHANISMS FOR DETECTION (Include how & when release was
detected)
C. EXTENT OF CONTAMINATION & HAZARDOUS CONSTITUENTS PRESENT (Include
media contaminated, and area or volume of contamination)
IV. REMEDIAL ACTIONS
A. RESPONSE
1. IMPLEMENTED
2. UNDER CONSTRUCTION
3. DESIGNED/CONCEPTUALIZED
4. MONITORED/TESTED
B. SUCCESS/FAILURE OF REMEDIATION (Include summary of
results from available monitoring data)
Figure 3.2. Outline for Case Studies Write-Up
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Geology—
The predominant bedrock type in the site area is of the Merrimack
Formation (a metamorphic rock group of Silurian Age), which includes slates,
phyllites, and schists. The average depth to the bedrock is approximately 25
feet. Results of site geologic investigations indicated that the bedrock was
slightly weathered and moderately fractured including both horizontal and near
vertical joints up to 1/2-inch in width. Some of the fractures were partially
filled with sand and/or clayey silt. There is evidence that the fractured
rock beneath the site is somewhat permeable.
Hydrology—
The site is located less than 1000 feet from Lyle Reed Brook, a small
stream tributary to the Nashua River. Any surface discharge from the site
would likely flow into this brook which has a total drainage area of about 1.5
sq. miles. The flow from Lyle Reed Brook enters the Nashua River about seven
miles upstream from its confluence with the Merrimack River.
Ground water beneath the site occurs under unconfined or water-table
conditions in the permeable stratified sands and gravels. It probably also
occurs under semi-confined conditions in secondary fractures in the bedrock.
The principal direction of the ground water flow appears to be northwest
(toward Lyle Reed Brook). Regional flow is northwest toward Nashua River,
which is the ultimate sink for ground water leaving the disposal site. The
average depth to ground water is approximately 10 ft. Seasonal water table
fluctuations at the Gilson Road site are relatively small. Prior to
remediation (i.e. slurry wall and cap), the largest fluctuations occurred
within the gravel pit immediately to the west of the disposal area, probably
due to the effects from precipitation infiltrating through pervious deposits
underlying the base of the pit.
Releases
Types/Causes of Releases—
Demolition debris, domestic refuse, and chemical wastes in the form of
liquids and sludges were illegally disposed in a former gravel pit excavation
area (unlined). The pit extended into the bedrock, and hazardous constituents
were released to the ground water. The contaminated ground—water plume
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migrated in a northwesterly direction contaminating Lyle Reed Brook and some
private residential wells.
Mechanisms for Detection—
In the lace 1970s, after reports from nearby residents of heavy odors in
Lyle Reed Brook, an area investigation was conducted. Hazardous constituents
were subsequently discovered in the brook and in some nearby residential
wells. It was determined that the Gilson Road site was the source of this
contamination.
Extent of Contamination—
Extensive ground-water contamination exists at the site with the plume
extending over an area of 20 acres. Additional contamination exists in Lyle
Reed Brook (adjacent to the site). Major hazardous constituents present
include raethylene chloride, raethylethyIketone, toluene, benzene, chloroform,
tetrahydrofuran, acetone, manganese, nickel, zinc, barium, and arsenic.
Sampling and analysis has demonstrated that 800,000 gallons of ground water
are currently contaminated with organics. The total amount of organics
present in the ground water is estimated to be over 1-raillion gallons.
Remedial Actions
Response—
In 1980, the State of New Hampshire had approximately 1300 drums removed
from the site. The drums were transported to secure landfills in New York and
Ohio.
During 1981-1982, a ground-water interception and recirculation system
using surface trenches was installed to retard further plume migration. A
computer model was used to aid in the design of the interception-recirculation
system. Four 8-inch wells were installed near the leading edge of the plume,
depressing the water table. The wells formed overlapping cones of depression
within the water table, drawing back hazardous constituents from the stream
area as well as pumping out upgradient flow. The liquids were pumped back
into the ground through the recharge trench. Ground water moving toward the
system was diverted by mounding the area around the recharge trench.
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in lace 1982, a 3 ft Chick benconice-slurry wall was conscrucced Co a
maximum depth of approximately 110 ft (average depth to bedrock is 25 ft) in
order to key it into the bedrock. A 40 mil polyethylene (impermeable) surface
cap was used to cover the entire 20-acre site area. The purpose of the slurry
wall and cap was to contain the contaminated ground water while the treatment
plant was being built and during the operation of the treatment plant (i.e.,
until 99% of the hazardous constituents are removed).
In November 1985, construction of a ground-water recovery-treatment-
reinjection system will be completed. Treatment includes chemical
precipitation (to remove iron and manganese), pH adjustment, sand filtration,
air stripping (to remove volatile organics), and an activated sludge system
(to remove extractable organics).
The treatment system is designed such that 300 gpra will pass through all
phases of treatment except the activated sludge system. Prior to the
activated sludge treatment, the waste stream is split; 250 gpm of partially
treated ground water will be recirculated back into the ground (for dilution
purposes) and 50 gpm will pass through the sludge aeration system to remove
extractable organics. Sludge from the metals treatment system and the sludge
aeration system are landfilled onsite in two RCRA landfills with a double
liner and double leachate collection system. Treated ground water (i.e.,*
water that has passed through the entire treatment system including activated
sludge treatment) is reinjected outside the slurry wall to create a negative
hydraulic gradient. Ground-water flow is induced back up through the bedrock.
Success/Failure—
The ground-water interception-recirculation system was built with the
intent of preventing a major portion of the hazardous constituent plume from
reaching Lyle Reed Brook while the more permanent slurry wall was being
constructed. Recirculation is tending to homogenize the hazardous constituent
concentrations (i.e., eliminating areas of higher concentrations). Since the
start of the operation of the recirculation system, the constituent levels in
the brook dropped by more than an order of magnitude.
The purpose of the slurry wall and cap were to minimize the infiltration
of precipitation to the zone of contamination, to divert ground-water flow
around the site, and to slow the advance of the contaminated plume towards
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LyLe Reed Brook. The wall was expected Co leak somewhat due Co Che presence
of fraccures in Che bedrock. Also, some of Che chemicals in Che concaminaced
aquifer are suspected of being able Co degrade bentonite by removing water
from che mineral, thus altering Che composition of Che clay; lab tests do not
indicace that this is occurring at Che present time (U.S. EPA-MERL in
Cincinnati has recently been awarded a research contract to evaluate the
bentonite).
The slurry wall is considered to be a "controlled leakage facility". It
has been successful in slowing the hazardous constituent plume migration while
the treatment plant is being constructed. Some leakage has occurred.
However, it is expected that the wall will contain the majority of the
hazardous constituents during the treatment operations.
It is too soon to evaluate the effectiveness of the treatment facility.
However, the pilot Creatraent system was able to remove nearly 99 percent of
the highly volatile organic compounds by air stripping, and approximately 90
percent of heavy metals by chemical precipitation to metal hydroxides. It is
expected that the treatment facility will take 2 to 3 years (approximately 3
complete flushings of the contained area) to reduce Che contamination levels
in the contained area by 99 percent. The remaining one percent is considered
by the New Hampshire Water Supply and Pollution Control Commission, the State
of New Hampshire, and Che U.S. EPA to be acceptable (acceptable levels were
determined by using ACLS).
References: Porter, 1985; Versar, Inc., 1985; GHR Engineering et al., 1981;
Knox et al., 1984; Morrison, 1983.
LLANGOLLEN ARMY CREEK LANDFILL - NEW CASTEL, DELAWARE
Facility Description
During the period from 1960 to 1968, che sice was used as a landfill by
New Castle County for disposal of municipal and industrial wastes. The
approximately 47-acre disposal area was located in an abandoned quarry from
which 6 to 35 feet of sand and gravel had been removed. Excavation of the
area was continued until either the water table or a red-clay zone was
encountered. The average depth of che landfill was 25 feet.
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In 1970, New Castle County had Che Landfill covered with sandy material,
intending to use the property for a park. The site is currently on the list
of Superfund sices.
Site Characteristics
Soils—
The soils in the site area are predominantly sandy soil with some clay.
These soils are permeable.
Geology--
The bedrock underlying the site varies in thickness (the landfill was dug
through to the aquifer in some places) and is permeable. The landfill lies in
the Atlantic Coastal Plain and includes both saturated and unsaturated zones.
Hydrology—
Surface water in the vicinity of the site includes Army. Creek, which is
adjacent to the site and is currently being contaminated by discharge from
recovery wells. Army Creek discharges into the Delaware River located
approximately one mile downstream of the site.
Two ground-water aquifers underly the site and are separated by clay; the
Columbian and Potomac aquifers. Both aquifers are contaminated. The clay
layer separating the aquifers is thin or absent in some areas, thereby
allowing hazardous constituents to be passed to the lower aquifer. Pumping
from well fields lowered water levels and increased the rate of water movement
downward to the lower aquifer.
The Columbian aquifer varies in thickness is located at depths ranging
from 10 to 60 ft. The Columbian aquifer consists of surficial sands not thick
enough in the immediate area to be developed for water supply. The upper
Potomac aquifer, which is located below the Columbian aquifer and ranges in
thickness from 2 to 80 ft, is used as a drinking water supply. The maximum
depth to the upper Potomac aquifer is 140 ft. The Potomac aquifer overlies
Precambrian rocks and consists of silt and clay interbedded with quartz sand
and some gravel. The Potomac formation thickens to the southeast and forms
one of the most productive confined aquifers in the state. The upper
confining layer is thin or absent in areas near and beneath the landfill.
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Releases
Types/Causes of Releases—
The leachate from the landfill formed Army Creek and Army Pond. The
absence or removal of the red-clay layer in places permitted leachate to
migrate into the underlying aquifer. The leachate was not adequately diluted
or purified by filtration before it entered the aquifer. Contaminated
leachate spread extensively throughout the confined aquifer and began moving
toward major public water supply wells. The hazardous constituent plume did
reach some private wells in the area.
Mechanisms for Detection--
In 1972, residents of a nearby housing development (Llangollen Heights)
reported discoloration of their porcelain fixtures. Sampling and analysis
activities were subsequently conducted. A water quality problem was detected
in a nearby domestic well.
Currently, there are 58 monitoring wells in the site area to monitor the
hazardous constituent plume migration.
Extent of Contamination—
Both the upper and lower ground-water aquifers are contaminated. Surface
water adjacent to the site (Army Creek) is currently being contaminated from
ground-water pumping activities (recovery wells discharge to Army Creek, which
flows into the Delaware River).
Hazardous constituents present at the site include metals (iron,
manganese, chromium, beryllium, lead, nickel, zinc, and arsenic), and organic
compounds (chloroform, trichloroethylene, and 1,2-dichlorethane). Iron and
manganese are the most significant hazardous constituents present at the site.
Remedial Actions
Response—
In 1973, interim measures were undertaken at the Llangollen Army Creek
site. Pumping was reduced from the public water supply wells and a program of
recovery-well pumping between the landfill and the supply wells was
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initiated. The pumping system, which continues to operate at the present
time, has caused a local cone of depression, which has reduced hazardous
constituent movement toward the public water supply wells. Twelve recovery
wells have been installed at the site. Most of the recovery wells are
screened over 12 to 25 meter intervals and completed 25 to 43 inches below the
land surface. The recovery wells discharge into Army Creek (which flows to
the Delaware River).
In July 1984, a Consent Order was signed by the responsible party (the
County) to do the feasibility study at the site. Remedial measures currently
being evaluated include: covering the landfill with a synthetic surface cap,
isolating the leachate by installation of a barrier or drainage ditches,
removal of refuse and incinerating it or disposing of it at another site,
surface grading and runoff control, and relocation of the recovery wells.
Success/Failure—
Interim measures were taken to control migration of the hazardous
constituent plume. The feasibility study is being revised at this time
(expected completion is in October/November 1985). The hazardous constituent
plume is still migrating, but at a slower rate due to the effectiveness of the
interim measures implemented.
The direction of flow in the Potomac aquifer has been altered. In the
1960s, flow was to the south and east (after public water supply well fields
and industrial well fields were developed). Public water supply wells yield
water from depths of 45 to 60 meters (in the confined sand of the Potomac
aquifer).
The recovery well system reversed the direction of flow locally away from
the supply wells. Flow pattern indicates that water upgradient from the
landfill moves through and beneath the landfill where it encounters leachate
and is then partially discharged by the recovery wells downgradient from the
landfill. Part of the discharge from the recovery wells is uncontarainated
ground water from areas south and east of the landfill. Continued pumping for
water supply has permitted contaminants to move south of the recovery well
system.
References: Bendersky, 1985; Versar, Inc., 1985.
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ROCKY MOUNTAIN ARSENAL - NEAR DENVER, COLORADO
Facility Description
The Rocky Mountain Arsenal is an Army facility that, beginning in 1942,
was used to manufacture chemical warfare products needed by the U.S.
Military. After World War II, portions of the plant were leased to private
industry for the manufacture of insecticides and herbicides. During the
1950s, an additional plant was constructed by the Army for the purpose of
manufacturing nerve gas.
Liquid wastes from these chemical manufacturing processes were discharged
to several unlined surface impoundments resulting in extensive ground-water
contamination and some soil contamination. The site is currently listed as a
RCRA Superfund site.
Site Characteristics
Topography—-
The site is situated on the eastern edge of the broad valley of the South
Platte River, east of the foothills of the front range of the Rocky
Mountains. The topographic relief across the arsenal site is approximately
200--ft, with a northwest trending slope toward the South Platte River.
Soils—
The soil overburden consists of alluvial sands and gravels interbedded
with silt and clay layers. Wind blown sand and silt deposits overlie the
alluvium throughout much of the area. The thickness of the overburden ranges
from 0 to 100 feet. The overburden in the east and southeast portions of the
arsenal site predominantly consists of fine sediments of silty, clayey, fine
sands and fine sandy silts. Calcium carbonate cemented zones ranging from a
few inches to a few feet thick occur sporadically in the alluvium.
Ceo Logy—
The Rocky Mountain Arsenal site lies within the Colorado Piedmont section
of the Great Plains physiographic province. The bedrock immediately
underlying the site is of the Denver Formation and ranges in thickness from
250 to 400 feet. This Formation consists of deltaic shale, clay stone,
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sandscone, and occasional conglomerate. The bedrock materials are generally
impervious. Occasional thin beds of lignite occur. Fine grained sandscone
lenses formed by deltaic channel deposits grade laterally and vertically into
shale and claystone.
Hydrology—
The South Platte River is located approximately two miles west of the
Rocky Mountain Arsenal site. The general direction of the ground-water
movement is to the northwest toward South Platte River. Deviations from the
flow pattern occur in the ground water due to variations in the bedrock
surface and recharge from isolated ponds, lakes, and streams. Localized
direction of ground-water movement is influenced by channelized bedrock
surfaces and bedrock highs.
The saturated thickness of the aquifer ranges from 0 to 70 feet, but is
irregular and depends upon the configuration of the bedrock surface. The
saturated thickness of the bedrock decreases as the bedrock elevation rises.
The alluvial aquifer is recharged from the southeast and from infiltrating
precipitation within the arsenal site boundaries.
The thickness of the alluvial aquifer in the Northwest Boundary area
ranges from 0 to 25 ft. In the Irondale area, the bedrock is 50 to 60 ft
deep. Characteristics of the Northwest Boundary aquifer include:
transmissivity=210,228 gpd/ft, specific yield=0.085, hydraulic
conductivity=1144 ft/day.
Releases
Types/Causes of Releases—
Liquid wastes from the chemical manufacturing processes were disposed in
unlined surface impoundments. Hazardous constituents in the wastes included
disopropylmethyl phosphate (DIMP), dicyclopentadiene (DCPD), endrin, aldrin,
dieldrin, dibromochloropropane (Neraagen), organosulfur compounds, chlorides,
and various industrial waste solvents.
Hazardous constituents seeped out of the unlined disposal ponds,
infiltrated the underlying alluvial aquifer, and migrated downgradient toward
South Platte River. In 1956, an asphalt-lined pond was constructed to hold
wastes, but this disposal pond failed to contain the wastes and released
hazardous constituents to the underlying ground water aquifer.
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Mechanisms for Detection—
The area north of Che Arsensal is irrigated. Damage to crops irrigated
with shallow ground water was observed during 1950 to 1953. Severe crop
damage was reported during 1954, when ground water use was heavier than
normal. Several investigations have been conducted since 1954 to determine
the cause of the crop damage and to effect a solution. Crop and livestock
damages were again reported in 1973 and 1974. Subsequent sampling and
analytical data collected by the Colorado Dept. of Health indicated that
damages were being caused by ground water contaminated from the Arsenal.
Extent of Contamination—
The extent of ground-water contamination has been defined by 40 monitoring
wells installed in 1982. The plume enters the Rocky Mountain Arsenal from the
east-southeast and follows a northwest trending buried gully, before exiting
the arsenal by taking a northwesterly flow path. A main plume of contaminated
ground water extends beyond the northwestern boundary of the Arsenal and a
small secondary plume extends beyond the northern boundary of the Arsenal.
Hazardous constituents have also been found in several shallow bedrock wells
in or near the Arsenal. The areal extent, depth of penetration, and rate of
spreading of hazardous constituents in the bedrock have not yet been defined.
Remedial Actions
Response—
Interceptor trenches have been installed in three areas at the site.
Wastes from the trenches are collected and treated.
In the North Boundary area, a 6800 ft slurry wall barrier was constructed
with dewatering wells located on the southern side of the barrier and recharge
wells located on the northern side. The treatment system includes the use of
multimedia filters followed by granular carbon adsorbers.
In the Irondale area, a hydraulic barrier was constructed along a 1500 ft
line through the use of 30 dewatering wells and 14 reinjection wells. Ground
water is pumped to a treatment facility where it is filtered through cartridge
filters, adsorbed onto granular carbon, filtered through another set of
cartridge filters, and reinjected into the ground. It differs from the north
3-17
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boundary system in that all of the well waters are combined before treatment.
Also, the Irondale facility contains larger carbon beds, but less carbon
handling equipment.
A similar system of ground-water containment, followed by adsorption
treatment and subsequent reinjection of the purified water, has been
constructed at the northwest boundary. Three identical parallel treatment
trains are located at this boundary. Raw water (from a sump) is pumped
through pre-filters with replaceable filter cartridges for the purpose of
removing suspended solids (which could interfere with the flow characteristics
of the granular activated carbon in the pulse bed adsorber). Adsorbers are in
a pulsed bed design operated in the upflow mode similar to the North Boundary
and Irondale facilities. Each adsorber contains 1400 cubic feet of carbon
which provide a residence time of 21 minutes.
Following carbon treatment, flow from each of the three treatment trains
is manifolded together and passed through an on-line tubular post-filter
subsystem for removal of carbon fines. The filters are backwashed upon manual
or head loss initiation. The treated water is discharged into the treated
water sump.
Carbon slurry handling for the removal of spent carbon from and addition
of fresh carbon to the pulse bed adsorbers is carried out by a separate
subsystem (which includes fresh and spent carbon storage and dual blowcases
containing two pressure vessels for each type of carbon).
Success/Failure of Remediation—
The remedial actions implemented at the Rocky Mountain Arsenal site have
been successful in preventing contaminated water from exiting the site area.
The GAC treatment has decreased the concentrations of DIMP, DBCP, and DCPD to
levels below the detection limit. Multi-stage pulsed bed adsorbers, currently
employed at all 3 boundary control facilities, have reduced carbon exhaustion
rates by 50 percent compared to fixed bed single-stage treatment (originally
used at the North Boundary facility).
References: Watensky, 1985; Versar, Inc. 1985; Hager and Loven, 1985; Knox,
et al., 1984.
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STRINGFELLOW SITE - NEAR RIVERSIDE, CALIFORNIA
Facility Description
The Stringfellov site, located in the Pyrite Canyon (west of Riverside,
California), was operated as a licensed Class I toxic industrial waste
disposal site between 1956 and 1972. Approximately 32 million gallons of
wastes were disposed at the 17-acre site during its period of operation.
The liquid wastes were disposed in several unlined disposal ponds (at one
point there were 17 ponds). It was thought that the geology of the canyon
area in which the site was located would act as a natural barrier to
ground-water contamination. The liquid wastes were concentrated through solar
evaporation from the pond surfaces. For a limited period during the operation
of the facility, a fountain sprayer was used to enhance evaporation of the
wastes. A small concrete barrier (dam) was constructed such that it was keyed
into the bedrock at the downstream end of the site. Overflow from the ponds
flowed onto the surrounding ground uncontrolled. Fractures in the bedrock
formations may have caused releases to the ground water. The site is
currently an Enforcement case on the list of Superfund sites.
Site Characteristics
Climate—
The winters between 1977 and 1981 were characterized by abnormally heavy
rainfall. Also, heavy storms occurred in March 1969.
Topography—
The site is situated at the head of a small, narrow canyon located in the
Jurupa Hills.
Soils-
Alluvium underlies the site area, and ranges in thickness from 45 to
greater than 100 feet down the axis of the canyon with an average of about
70 feet. The residuum which lies directly below the alluvium is a weathered
portion of the basement complex and is 10 to 30 ft thick; lenses of saturated
permeable alluvium were discovered during excavation.
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Geology—
The basement complex underlying the alluvium is relatively impermeable and
is composed of granite and metamorphic rocks (i.e., two layers lie below the
alluvium layer; these are: decomposed or weathered granite and competent or
unweathered bedrock). Fractures are present within the basement complex and
may provide a means of transport of hazardous constituents to the ground water.
Hydrology—
The ancestral drainage of Pyrite Canyon has two separate branches: the
western and the eastern. The current surface drainage pattern corresponds to
the western branch. Both drainage patterns contain alluvium. The ancestral
eastern stream course passes to the east of the original concrete barrier
(dam) and continues down the eastern side of the canyon. The eastern branch
may account for the majority of the subsurface flow which currently exists in
the site area.
Ground water was discovered at shallow depth within the alluvial deposits
downstream of the Stringfellow disposal ponds. Ground-water flow is generally
in a southwesterly direction away from the disposal sice. Down canyon flow
gradients before remedial actions were implemented at the site varied from
0.04 to 0.1 m/m.
Releases
Types/Causes of Releases—
In March 1969 a major storm occurred which caused the waste pond to
overflow, inundating the site and causing the release of wastes from the
surface impoundment to a nearby creek (Pyrite Creek - normally dry), which
resulted in surface contamination of Pyrite Creek for several kilometers
downstream.
Additionally, fractures in the bedrock formations underlying the site
allowed the release of hazardous constituents to the ground-water beneath the
site. Ground-water releases are considered to be the most significant type of
hazardous constituent release at this site.
3-20
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Mechanisms for Detection—
A ground-water monitoring well was located at the mouth of Pyrite Canyon.
In 1972, samples from the monitoring well were analyzed. Elevated levels of
hexavalent chromium, nitrates, sulfates, and chlorides were indicated,
suggesting apparent permit violations. In 1974, the variance permit for
operating the facility was revoked by the riverside County Board of
Supervisors. Several site investigations have since been conducted in the
site area.
Extent of Contamination—
Hazardous constituents present in the ground water include heavy metals,
organic halides, and dissolved solids. Although the full extent of
contamination is still being investigated, the hazardous constituent plume is
known to cover.at least a one-mile radius extending downgradient from the site.
As an indication of the levels of organics present in the plume,
trichloroethylene has been found in onsite ground water at leves of 15,000
ppb. Analysis of samples collected from the area towards the edge of the
one-mile radius plume, have indicated trichloroethylene concentrates of 100
ppb. Other organics such as chlorobenzene, chloroform, and methylene chloride
have been found onsite at levels ranging from 700 to 1,700 ppb. Examples of
metal concentrations found onsite include: 5,000 ppra aluminum 40 ppra nickel,
and 900 ppm iron metals have not been detected in the raid-canyon area
(approximately 1,500-2,000 ft downgradient from the site).
Remedial Actions
Response—
Prior to construction of a barrier dam, contaminated materials were
excavated by traversing the canyon and cutting completely through to the
bedrock. Excavated material was placed in a containment area for
neutralization and capping. Ten parts of contaminated materials were mixed
with I part cement kiln dust (40% CaO) using a mechanical mixer. The mixture
was then graded. A six-inch layer of kiln dust, followed by a two-inch layer
of packed clay, was spread over the contaminated area to serve as a cap.
3-21
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A grouc curtain was conscrucced co seal che bedrock under Che entire
lengch of Che barrier dam. Holes were drilled on 3-fc cencers across 800 fc
of Che canyon in areas of inCerconnected fractures. A second offsec series of
grout holes were drilled. A chemical grout was injected via a curtain
grouting method using silica-based grout "injectoral". However, fractured
areas still remained under certain areas of the curtain.
A clay core barrier and drain was installed upon completion of the
grouting. A concrete base was installed at the deepest part of the canyon
where liquids would collect. The dimensions of the barrier were: 8 ft wide,
800 ft long, and 25-90 ft deep. The gravel drain, located immediately
upstream, is 3 ft t-hick with a pump located 3 ft from the base to expel
collected liquids.
Two interceptor wells were drilled 1800 ft downstream of the site (at what
was believed to be the limit of polluted ground water). An additional well
was installed 800 ft downstream at the clay barrier to extract more
concentrated pollutants before disposal. Wells were greater than 100 ft deep
with 6-inch internal diameters. The two southerly wells were able to produce
25 gpm, while the northerly well would only produce 2 gpm. The ability of
these wells to sustain these levels is currently being investigated. Two
8,000-gallon tanks were installed onsite for storage of extracted liquids.
Suecess/Failure—
Monitoring data collected to date does not yet indicate whether or not
migration of the hazardous constituent plume has been slowed. Data is not yet
available to determine the success or failure of Che remediation activites.
Determination of the migration rate is difficult because little data exists
from before remediation activities took place. Prior Co remediation
activities, only one monitoring well was in place. Presently, samples are
collected from approximately 50 monitoring wells.
References: Ullenberg, 1985; Versar, Inc., 1985.
3-22
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CULK COASTAL PLAIN SlTli
Facility Description
The Gulf Coastal Plain site is a landfill facility used primarily for the
disposal of hazardous chemical wastes. Wastewater from a lined
storage/evaporation pond was released to a shallow saturated zone when the
liner was punctured by construction equipment during a pond cleaning operation.
Site Characteristics
Topography--
The site is located in the Gulf Coastal Plain area. The average land
slope in the area is approximately 0.17 percent.
Soils—
The soil material at the site consists of a continuous layer of clay
nearly 15 feet in thickness, thinning somewhat in the northwest and southeast
portions of the site. The clay material is composed of tan to gray clay and
sandy clay with occasional discontinuous sand and clayey sand lenses.
Underlying the surficial clay, is a 20 to 40 ft thick sand layer
consisting of silty sand with numerous, thin clay lenses. Field permeability
tests indicate permeabilities in the range of 10 to 10 cm/sec. A tan,
brown and gray clay with thin sand lenses occurs beneath this sand layer.
This underlying clay layer ranges from 6 to 15 feet in thickness over the site.
Geology—
The Pleistocene Beaumont Formation, which is composed predominately of
clays interbedded with sand layers and lenses, outcrops in the vicinity of the
sice. These materials were deposited in Pleistocene Deltaic and Fluvial
environments and represent distributary channels, interdistributary lakes,
bays, and lagoons, as well as river channel and overbank deposits. The
Beaumont Formation is underlain by the Lissie Formation which consists of
layers of sand, clay, sandstone, and shale. The actual interface between
these formations has not been determined due to similarities in the Beaumont
Formation and the Upper Lissie Formation.
3-23
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Hydrology—
Ground water in the site area consists of fresh to slightly saline water
and is encountered at depths ranging from 250 to 500 ft. Artesian water in
the wells in the vicinity of the site rises to an elevation of 40 to 70 ft
below the ground surface. A shallow saturated zone, located in the silty sand
layer below the surficial clays, varies in depth from less than 25 ft to more
than 30 ft. Non-potable (too saline for use) ground water is contained in
this sand layer. Production of water in useable quantities is extremely
limited due to the relatively low formation permeabilities. Vertical movement
between the layers is limited by the retarding effects of the clays which
confine the water-bearing sands. Thus, the flow of contaminated water in the
uppermost saturated zone is .in a horizontal direction due to the presence of
the underlying confining layer.
Recharge to the fresh to slightly saline water zone occurs several miles
northwest of the site at the point where the water-bearing sands outcrop.
Recharge to the shallow sand occurs off-site to the northwest and southeast of
the site where the surficial clays are thinner. Ground-water flows to the
site from these areas and exits to the northeast and south.
Releases
Types/Causes of Releases—
The liner of a storage/evaporation pond was punctured by construction
equipment during a pond cleaning operation. Leakage of hazardous constituents
to the underlying shallow saturated zone subsequently occurred.
Mechanisms for Detection—
Several monitoring wells are located in the site area. Contamination was
detected in the shallow saturated zone by site monitoring wells following the
puncturing of the liner. Additional monitoring wells were added in both the
shallow saturated zone and underlying aquifers to define the extent of
contamination.
3-24
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Extent of Contamination—
Contamination is limited to the uppermost saturated zone in the
northeastern portion of the site. The plume remains within the site
boundary. Monitoring wells in the deeper aquifers have shown ;no evidence that
contamination has moved downward.
Remedial Actions
Response—
A submersible pump ground-water recovery system using submersible 29 wells
was designed and installed. The system was designed to establish a cone of
depression in order to contain and eventually remove ground water from the
contaminated zone to an evaporation pond.
The submersible pump ground-water recovery system was successful in
extracting the anticipated quantities of water. Ground-water contours were
altered in a positive fashion but a significant cone of depression that could
contain and expedite the removal of contaminated ground-water was not
developed. The low yield capacity of the wells was not sufficient to
continuously supply the submersible pumps. An engineering evaluation
determined that the system would be greatly improved if continuous drawdown at
the wells could be maintained.
A ground-water model was used to simulate the effects of various
alternatives for ground-water recovery systems. On the basis of the model
results, the system selected and constructed was a 500-ft long french drain
(form of collector drain) through the long axis of the hazardous constituent
plume with one submersible pump at the low end of the drain and five
strategically-located wells with jet educator pumps capable of pumping a
low-yield well continuously. The french drain consists of a 4-foot by 4-foot
gravel drain surrounded by filter cloth and is located at the bottom of the
upper sand layer and saturated zone. Jet educator wells were placed in
locations outside the zone of influence of the french drain to increase the
overall effectiveness of the recovery system. Recharge pits have been placed
ahead of the plume of contamination to provide for containment of the plume
and reversal of the ground-water flow direction back towards the recovery
system. Recharge water is presently being acquired from wells in the deeper
aquifers.
3-25
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A water creacmenc syscem is being completed co treac recovered ground
water and it is hoped that this treated water may be used for re-injection in
recharge pits in the future. Presently, treated ground water is pumped into
the site evaporation pond for disposal by evaporation.
Success/Failure of Remediation—
The french drain with eductor wells and recharge pits has produced a
higher recovery rate and a more dramatic cone of depression at a faster rate
due to a larger surface contact with the saturated zone than can be provided
by individual wells, a zone of high permeability which essentially forms a
long lateral well, and the allowance for continuous pumping. The actual
pumping rate has exceeded the predicted pumping rate by nearly 30 percent.
Monthly monitoring data is collected from the facility monitoring wells.
Current data shows that the plume has decreased in size and concentration due
to the operation of the system. In the three years that the recovery system
has been in operation, the areal extent of th plume of contamination has
decreased by approximately 50 percent. Results to this point in time indicate
that this combination recovery system can be used in various soils of
relatively low permeability; i.e., soils in the fine sand to silt ranges with
permeabilities too low to support continuous pumping with conventional
submersible pump recovery systems.
Reference: Underwood, 1985.
WHITMOYER LABORATORIES - MYERSTOWN, PENNSYLVANIA
Facility Description
Beginning in 1934 and continuing to the present, Whitraoyer Laboratories
operated a pharmaceutical manufacturing facility at the site. Wastewater
generated by the manufacturing processes was treated with lime and handled as
a slurry. The wastewater slurry was then disposed in an unlined lagoon.
3-26
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Sice Description
Climate—
The average annual precipitation in the site area is 44 inches. Average
annual snowfall is 35 inches. Average temperatures range from 30°F (July)
to 76°F (January) with an annual average of 53°F. The average windspeed
is 7.7 mph.
Soils—
Soils overlying the site consist of a 5 to 7 ft thick layer of alluvial
sand, silt, and gravels. These soils are fairly permeable, and allow for
rapid recharge to the bedrock aquifers.
Geology--
Bedrock underlying the plant site consists of limestones and dolomites
which strike east-northeast and exhibit a dip of 30 degrees to the southeast
[Ontelaunee Formation (dolomite) = 900 feet thick; underlying Annville
Formation (high calcium limestone) - 1500 ft north of the plant]
Hydrology—
The site lies adjacent to Tulpehocken Creek (37 miles upstream from its
confluence with the Schuylkill River, which in turn flows to Delaware Bay).
The drainage basin of Tulpehocken Creek covers 211 square miles and is 33.5
miles long. The average and minimum flows at the confluence of Schuylkill
River are 58 cfs and 56 cfs, respectively. The average annual flow for the
creek is approximately 200 cfs and the maximum flood flow was 9890 cfs (on
December 7, 1953). The creek flows east-northeast (following the strike of
the carbonate bedrock).
Ground water beneath the site is potable and is used by local residents
and fanners. There are some artesian wells near the site, but the static
water level in most wells lies near the ground-water table. The site lies
close to a ground-water divide in a system of limestone aquifers underlying
the Lebanon Valley.
3-27
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Releases
Types/Causes of Releases—
Improper waste disposal in an unlined surface impoundment (lagoon) caused
releases to ground-water underlying the site, soils onsite, and a nearby
stream (Tulpehocken Creek).
Mechanisms for Detection—
In July 1964, Whitmoyer Laboratories, Inc. became a subsidiary of Rohm and
Haas Company. Extensive arsenic contamination of the soils, ground-water, and
a nearby stream became apparent to Rohm and Haas Company officials during an
inspection of the facility.
Extent of Contamination—
Extensive ground-water, soils, and surface water contamination exists in
the site area. Hazardous constituents primarily include organically bound
arsenic compounds, calcium arsenate, and calcuim arsenite.
Remedial Actions
Response Actions—
Onsite treatment and disposal practices were discontinued in December
1964. Sludge was removed from the lagoon. Contaminated soils underlying the
lagoon were also removed. The contaminated soil and sludge materials were
deposited in an impervious concrete storage bin, which was filled to capacity
and then covered.
Four recovery wells were used to purge ground-water containing arsenic
compounds. The contaminated ground-water was treated by adding 2 parts
Fe2(SO^)-j to 1 part arsenic and adjusting the pH to neutral conditions
(by adding lime). Recovered water was handled in alternating batch mixing
tanks on a continuous feed treatment schedule and sent to the lagoons to
dissipate via slow percolation to the subsoil.
The plant reopened in the spring of 1965 on a no-discharge basis. Treated
wastes were trucked to a New Jersey holding area awaiting ocean dumping.
3-28
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In 1966, additional wells were installed. Production wells formed cones
of depression east of the plant to stop migration of ground-water. Production
rate is partially dependent on the purging rate. From 1968 to early 1971, the
purged water was discharged directly to Tulpehocken Creek.
It was decided that it would be too expensive to dredge Tulpehocken Creek,
and the hazardous constituent levels are declining through dilution.
Whitmoyer Laboratories currently supplies bottled water to area residents
whose wells remain affected.
Success/Failure of Remediation—
The first phase of remedial action cleanup and recovery involved the
removal of sludge and contaminated soils. The manufacturing processes were
halted until a process could be developed to remove arsenic from the
wastewater, thereby eleiminating the possiblity of new arsenic compounds being
added to the soils and subsequently to the ground and suface water.
The next phase, which involved removal of the arsenic hazardous
constituents from the ground-water, was also successful. The recycling and
treatment of the purged water did reduce the level of arsenic in the
ground-water, and succeeded in controlling its movement.
Little has been done to remove the hazardous constituents from the
sediments and surface water of Tulpehocken Creek, because of the costs
involved in dredging miles of creek bottoms and banks. Through dilution, the
arsenic levels in the creek water have been brought within the limits set by
the U.S. Department of Health, and monitoring has shown that the levels
continue to decline. Whitmoyer Laboratories supplies bottled water to those
area residents whose wells remain affected.
Finally, routine monitoring of the site is being performed to ensure that
the arsenic levels do not increase, either through the release of arsenic from
bottom muds, or via spills from the plant.
References: EPA, 1981.
3-29
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SECTION 4
RECOMMENDATIONS FOR SELECTING AND IMPLEMENTING
CORRECTIVE MEASURES FOR RELEASES TO GROUND WATER
OVERVIEW
As previously discussed in Section 2, before a suitable corrective measure
can be selected for remediation of contaminated ground water, the need for
such a corrective measure must be determined. A corrective measure for
ground-water release is required when concentrations of HCs, measured at the
point of compliance, exceed either background constituent levels, the maximum
concentration for parameters in Table 1 of 40 CFR Part 264.94, or an ACL.
After identifying a need, the most appropriate corrective measure(s) for the
site in question must be selected and subsequently implemented. Section 2
identified, hydrogeologic control/treatment technologies and specific
treatment technologies applicable to the remediation of contaminated ground
water so that the requirements of 40 CFR Part 264.100(b) are met. Table 2.13
indicates the proven, imminent and emerging control/treatment technologies
which may be used to treat, remove or control contaminated ground-water such
that the threat to human health or the environment is mitigated or
eliminated. Table 2.14 presents technologies applicable to the treatment of
contaminated ground water upon removal from the subsurface. These control and
treatment technologies are assessed according to their applicability in
certain hydrogeologic conditions, their compatibility with specific wastes,
their effectiveness in contaminated ground-water control, removal and
treatment and their technical, environmental and institutional suitability.
As is evident from Section 2, "Overview of Corrective measures for Releases to
Ground Water", there are many technologies that may be selected that are
capable of or potentially capable of treating or controlling ground-water
contamination. However, to ensure that the most appropriate technology(s) is
4-1
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selected for implementation at a site, available technologies must be assessed
according to their site applicability, waste compatibility, effectivenesss and
reliability.
SELECTION PROCESS
When a ground-water release has been detected, or suspected to have
occurred, as evidenced by a preliminary site assessment, and a corrective
measures deemed necessary, the most appropriate (technically, environmentally
etc.) corrective measure(s) must be selected. This requires that the
applicant perform a logical progression of decision making processes. These
are:
• adequate site/hydrogeologic investigation;
• screening;
• selection;
• recommedations;
• implementation; and
• monitoring.
This progression should also be followed by the permit writer to ensure that
the applicant has considered all available corrective measures and has
selected the one(s) most appropriate to the site in question.
Site Investigation
After a preliminary site assessment indicates that a release has occurred
and that the release is a potential hazard to human health and the
environment, a thorough site investigation is necessary to determine specific
site characteristics. The permit writer must examine the available data
submitted by the applicant and decide upon the adequacy of the site
investigation with respect to selecting an appropriate corrective measure for
remediation. The permit writer should identify any data gaps that may affect
the final selected action. The following must be properly characterized:
4-2
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• waste characteristics (type, toxicity, migration potential);
• extent of contamination (fate and transport, potential receptors,
concentration);
• ground water, surface water and soil characteristics (location, type,
flow rate, permeability, hydraulic gradient, pH);
• site location (proximity to local populations and ground-water
supplies, climate); and
• hydrogeology (bedrock location, fracturing, jointing, depth to water
table).
These parameters will determine the migration potential of hazardous
constituents and their potential environmental impact, and will greatly
influence the selection of an appropriate corrective measure and its final
engineering design. Many of the characteristics needed to be identified may
already be available through previous site investigations which should be used
as a base-line for any further investigation.
Section 2 ("Hydrogeologic Approaches" subsection) indicates the type of
site/hydrogeologic information that should be provided for the implementation
of the control/treatment technologies. Additionally, it provides a general
permit writers' checklist identifying the site soil, ground water, aquifer and
hazardous constituent plume characteristics which should be provided from a
site investigation. -
Screening
The initial step in the screening process is the development of general
response objectives to identify the goals and extent of the corrective measure
to be used. The site investigation should identify the possible receptors.
Corrective measures to mitigate or eliminate the threat posed to these
receptors can then be formulated.
4-3
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All potential remedial technologies should be gathered for consideration
and assessed according to their technical and environmental suitability to the
site in question. Applicable federal, state and local laws; technology
effectiveness, reliability, waste compatibility, site
applicability/effectiveness and relative cost; and potential environmental and
public health impacts due to the implementation of the corrective measure
should be considered in the screening process.
Selection
From the site investigation and the screening process a final decision
concerning the most applicable corrective measure must be made. The permit
writer must review all aspects of the applicant's report including the
completeness of the site investigation. As previously stated, much of the
site investigation material may be readily available from other reports
performed at the site; however, the permit writer must ensure that further
investigations have properly characterized all parameters that may affect the
release and corrective measure used.
From the technology screening, the applicant should arrive at the most
appropriate measure for remediation. The permit writer should be certain that
the measure is adequately focused on the risk posed by the contaminant
release; i.e., that the endangerraent or risk to human health and the
environment is mitigated/eliminated by the corrective action(s).
If the permit writer does not believe the applicant has properly addressed
the issues in the site investigation and screening process, then the applicant
should not implement the proposed corrective action plan. At this point the
permit writer may convey to the applicant any shortcomings evident in the site
investigation or thought process in obtaining the corrective measue.
The permit writer may also suggest to the applicant other measures that he
or she feels may be more applicable to the given situation. This could
possibly involve pilot studies to evaluate the overall performance and
effectiveness of a selected measure. These types of studies can be very
valuable in recommending and selecting the appropriate corrective measures for
site remediation.
4-4
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Conceptual Design
Once Che corrective tneasure(s) has been chosen, a detailed conceptual
design can be developed. Upon completion (and approval), implementation of
the corrective measure can proceed.
Some important activities must be carried out during the implementation of
the measure. These include field inspections to ensure quality control during
construction, and to ensure that design specifications for construction and
materials are being adhered to. Any alteration that occurs during
construction must be investigated by a certified engineer to determine if it
will affect the performance fo the corrective measure. These inspections
during implementation must include monitoring to determine that contaminated
ground water is being properly treated (i.e. to appropriate levels) or if
being removed, that it is being disposed of and/or transported in an
acceptable manner. These monitoring and inspection activities are very
important to ensure that the corrective measure(s) will perform as designed.
Monitoring
Upon completion of the corrective measure, a monitoring plan must be
initiated to ensure that the corrective measure has been properly installed
and is performing as specified. If failure or only partial success occurs,
then monitoring can be used to determine what further type of remediation may
be necessary.
Monitoring can be done in both the upgradient and downgradient ground
water through the use of monitoring wells to reveal if contamination is
continuing to migrate into the ground-water. Lysiraeters can also be used to
monitor the unsaturated zone for hazardous constituent concentration and
migration.
USE OF SUMMARY TABLES
Table 4.1, is presented to assist the permit writer in reviewing
applications for correcting releases to ground water. This table illustrates
the types of control/treatment and treatment (after removal from subsurface)
technologies applicable to remediation of contaminated ground water and the
4-5
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TABLE 4.1. SUMMARY OF GROUND-WATER CONTROL/TREATMENT
AND TREATMENT TECHNOLOGIES
Cone rol/TreatMnt
Strategies
Cont rul
Upgradteni
ground-
water
d i vert ion
Control/
Treatacni
Downgradicnt
grouna-wat er
diver* iun/
intercept i an
tit ract ion/
recharge
In-fe i tu
treatment.
Ia.p«rneabie
Slurry tut -Oil wall 1
X
X
Grout Curtain 1
<
Block Oibplacevent He t hod
X
[
Well
I
«A
c
I
a
X
X
X
r
K
5
L
X
11
I
S
i
X
X
X
Subaurtace
X
X
X
X
In Situ
1
C
H
41
m
•1
O.
X
X
Che.nica llnjection f
K
s
j
u
it
5
a
X
X
Air Stripping* |
K
[
rbon Adaorpt ion*
eaiical Ox i oat ion*
at i 1 lat ion
t> u o
X K X X
eiectrolyaia
Cvaporat ion
Fi Itrat ion*
Flocculat ion
XXIX
»
B
E
X
Ion Exchange* ]
I
I
j
X
t
X
X
Oronation 1
I
I
X
K
C
3
\
C
C
•*
•
t>
fiat
K
t
Sea latent at ion |
1 X
t X
M
C
o.
X
X
s
3
X
X
Not effective in •eet 1114 Hie
Part 264.IOOU) alone.
puBping and t re^imeni .
fart 264.1Uu(b) in mat it
provide* (or retnova 1 anu
treatment ot cont*iaiinjt«j
ground water .
Inc ludea 1 he reoova 1 oi con-
taoiinated ground water *nj
•ay include the treatment oi
•Cumrot/treatAcnl tcchnologiei. •• diicu««ed in Section 2 (Hydrogeologic Appro«chct •ubiection). «r« thoie techniques which can be applied directly 10
the cubaurface for containment, removal and/or [reatoent of contaminated ground water.
bTreala>ent lechnologiea, aa diacualed in Section ] (Treatment Ttchnologiea aubaeclion). are thole tecnnolofiee which can be applied to treat cunianinite
'Halt that the elfectiveneaa of control/treatment and treatment technologiea depend, on aeveral tactora. aa ditcuaaed in Section 1, particularly
hydrugeologic and haiardoua constituent characteriatica.
•Noat comonly used technologiea for the treatment ol contaminated ground water.
-------
rel.ati.ve Location and effectiveness of these technologies, as discussed in Che
body of this guidance document. Table 4.1 was developed from detailed
technology discussions provided in Section 2 and case studies, presented in
Section 3, indicating Che site applicability and success/failure of corrective
measures at Che sites studied. The usefulness of this table can be
illustrated by evaluating, in detail, one of Chese case studies.
Additionally, a Cable (Table 4.2) summarizing source control corrective
measures has been provided to further assist the permit writer in application
review.
CASE STUDY EXAMPLE
Consider the Gilson Road, Nashua, New Hampshire site. By reviewing the
technology discussions/data requirements provided in Section 2 and by
completing the Permit Writers' Checklist, as shown, the applicability of the
corrective measures implemented at this site can be assessed.
Site hydrogeologic information could be more extensive, however the
primary soil/ground-water/aquifer/hazardous constituent plume characteristics
have been addressed. As elaborated upon in the case study discussion, in 1980
source control remedial measures were undertaken. During 1981-82, a
ground-water interception and recirculation system using subsurface drains
(i.e., interceptor trenches) and well systems for extraction/recharge were
installed to retard plume migration. In late 1982, a bentonite-slurry wall
was constructed and keyed into Che bedrock and a cap was installed to cover
the entire site area so that contaminated ground water could be temporarily
contained until a recovery-treatment-reinjection plant/sysCem is constructed
(construction to be completed in November 1985). Treatment technologies
include chemical precipitation, pH adjustment, filtracion, air sCripping and
an activated sludge system.
As indicated on the subseq-ient completed Permit Writers' Checklist, for
the Cilson Road site, the slurry wall was a satisfactory temporary technology
for control of plume migration while the treatment facility was being
completed. However, due Co Che presence of bedrock fractures and Che
potential hazardous constituenc/slurry wall incompacibilicy
4-7
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TABLE 4.2. SOURCE CONTROL CORRECTIVE MEASURES FOR DIRECT AND INDIRECT
RELEASES TO GROUND WATER
Appr
3 § ! .
-* ••••«• U
§** « e
• c •
- ^ • e
• « C «
Facility Type/ 2 o S. *,
Nature of Release Response Strategy S 2 • Z J .-
- • •' s at M
Landfills/haste Piles
Failure ol liner/leachate Enhance capability ot XIX Dependent on eitcnt ot Likely to be costly and
collection ayste* reaulcing eyetea problems, original design. Kay require excavation
in the release ot leachate and aetouni ot overburden. 01 landfill, eecondjry
10 Around and surface watera containawoi mmy De n«eJ«
Applicable lor reducing
runon ao4 ml i Itrat ion.
Hay not affect aubiur-
fece water ewveawnt.
| ieleaie of contaminated Prevent aurlace water XXX Noveetent ol aurface water Surface water •anageocnt
CC runoft reiulting trots iroa contecting waste is an elfective nethoo ol erosion control ana a«in-
precipttat ton and/or reducing the voluae ol laming cover siateri*! ar
runon contactingwabte contaainatedwater. Bostelleccive when ubtd
in conjunction witn «acn
other.
precipitation ther
leachate.
ulting Erosion control X X Effective lu
naled alopes.
fro* site Run-on control X X Effective in reducing
threat of erosion.
washout ol landlill by Restore facility integrity XXX X Ettective if site hydro-
st reaae or tloodwaters and prevent tuture occur- ' geologic characteristics
(cont inued)
-------
TABLE 4.2 (continued)
Appropriate Corrective Actions
3 g I
Facility Type/ ooatlTtcZo
Nature of Reledtte Response Strategy SuS"*i.-««JS! Ei lect i v«n« •• Looranth
xoD^acuicoae
Surtace Impoundments
Overtopping ol dikes Reduce run-on XXX Effective if the cause 01 nanagemenl ol va»ici
resulting in release ol overtopping is eicessive suriace water* ou»( t
waste* and/or contaminated run-on. on the areas balance
runu" liquids in relation c
impoundment capac11 y.
Add freeboard to dikes X X Not likely to be cflec-
to increase impoundment live eicepl lor additional
capacity short-term storage.
Increase IreeboarJ by X X Likely to be etitctiv«
lowering impoundment only on a temporary
elevdt ion basis.
Seepage ol contaminated Kepair cracka in dikes XX X Dependent upon cause ut Seepage cuntiul aejbu
11 quids through conta inment cracks and qua 11 ty at me lutiu I inert ko I ia
dikes due to crack* or reoair work and nainten- bamor^
repair work and mainten- barrier* (stucll,
permeability ante. barrier; (temuni J.
reconat ruci tun
oeable «oi Is.
Cliainaie seepage due to X XX Variable depending on
(Ugh uermeabiIlly aattfriala technology caployeo ^nu
used in construction quality of inttallaiion.
Dike failure and wash-out ^placement ol dike and X X X To be etfectlve, replace-
due to overtopping, erosion. prevention ol reuccurences mem nust include an
or »lope failure evaluation ot the caused)
of dike failure and be
retlected in the design
ol new dikea.
(com inued)
-------
TABLE A.2 (continued)
Appr
Facility Type/
Nature of Release
Reaponhe Strategy
bflectivenei*
Tanks
I
»—•
o
Re lease ol liquid wattes
oi tank
overt low or
Uccooaission irreparable
tanka and replace with
new tanka
Repair C«nk
Improve facility »«n«gen«nt
and develop iccondary
Reauval ot waatea ana
cleaning tank will pre-
clude tuture releases.
Efiective repair will
likely require w«nte
removal, ttcpair nu*t
ttbtlity ot tank naterial,
repair Mterial «nd waste
lypei.
Baquirta comitoent by
facility operator to
reduce chance ot apilla.
Secondary contaiti*eni
lank removal will uvp«nu
on the ill* and naterial
of the t ank . alee I etay
be recyclable, cunciete
graded or diiponeu ul
ol t-aitc.
Site MiugeDe
lraining and
a 1 v
runot t
Prevent runon froa contact-
ing waiiv
Run-on control auic be
•anageaent to contine
Keep aite Iree of uncon-
caainaced w^ate
Secondary containment areas
should be etaintaiued tree
of hazardous constituents.
(com ioued)
-------
TABLE 4.2 (continued)
Appropriate Corrective Actiona
§
hi
c
~c B I
D 3 «t ti
Is""
Facility Typ«/ c -o o.
ature of Release keaponae Strategy ^un-l — «««> ti lect iveneti
Handling and Container
Replace or over pack leaking X XX tt tect ive in r«auc ing ht le*iie* ifjo »iura|te
container! threatoltuturerclea«e«. hdndlin^itcilttitftar
beet controlled oy
prevent u>^ re l«akck «n
by entur ing tri^t dilequ
second A i y con I J inment
Develop secondary contain- • XX Effective in confining
-">l r«le.«. 10 ih. i.c.l.iy.
Releate ot concaninated Prevent run-on (root con- X X X XX Surface water aanageo>ent
tun-on ^na/or precipitation tacting waste can prevent run-on, watte
BanageBcni ahould enture
that any precipitation or
do«t not leave the »»le.
Spillt ol waate during laprove handling procedurea I Pocua on eaployee training
handling operation* and awareneta and un appro-
priateneai ol eqmp«ent.
EMectiveneaa dirncult to
•eature.
Oevelop aecondary contain- X XX Effective in confining
Dent releaaes.
SOURCE: l.C. Juitlan. I98S
-------
PERMIT WRITERS' CHECKLIST
Site Name/Location Gilson Road New Hampshire Site
1. Has applicant undertaken a hydrogeologic investigation of
the site in question? (yes or no) yes
2. Does hydrogeologic investigation include the following information (place
check beside data provided):
Site Soil Characteristics
Type
Texture (granular or cohesive)
Grain size distribution and gradation
Moisture content
Permeability
Soil pressure
Porosity
Composition
Compaction
Discontinuities in soil strate (e.g. fault)
Cohesive and consolidation states of individual strata
Degree and orientation of soil stratification and bedding
Location and type of weathered bedrock or solution
channels
Other (specify)
Ground-Water Characteristics
• Depth to water table
• Direction of flow
• Rate of flow
• pH
• Hardness
• Salt concentration
• Presence of minerals and organics
4-12
-------
• Concentration of sulfides and calcium
• Water pressure
• Recharge quantity
• Location of neighboring water bodies (e.g. streams)
• Other (specify)
Aquifer Characteristics
• Use of aquifer
• Permeability and thickness of water bearing strata
• Transmissivity
• Storativity
• Specific yield
• Depth
• Type (confined or unconfined)
• Condition (e.g. homogeneous, isotropic, leaky)
• Hydraulic gradient
• Effective porosity
• Identification of recharge and discharge areas
• Identification of aquifer boundaries (i.e. areal extent)
• Aquiclude characteristics (depth, permeability, degree
of jointing, hardness, continuity)
• Other (specifiy)
Hazardous Constituent Plume Characteristics
• Size
• Location
• Shape
• Hydraulic gradient across plume
• Depth to plume
• Chemistry and concentration
• Velocity
• Other (specify)
4-13
-------
3. Indicate ground-water control/treatment cechnology under consideration by
applicant (specify particular technologyCs) beside appropriate category):
• Impermeable barrier X
• Well system X
• Interceptor system or subsurface drain X
• In situ treatment
4. Control/treatment technology(s) strategy and location: (check
strategy/location and indicate number of control/treatment units)
• Upgradient diversion
• Downgradient diversion/interception
• Surrounding site
• Extraction/recharge
• In situ treatment
(• Source control X )
5. Purpose of control/treatment technology: (check appropriate purpose(s))
• Control ground-water flow X
« Treat ground-water X
e Isolate hazardous constituent plume x
• Extract hazardous constituent plume X
• Replenish ground-water x
• Adjust water table
• Control subsurface flow of hazardous constituents X
Neutralize, precipitate or destroy hazardous constituents
Other (specify) Cap to minimize infiltration of precipitation
4-14
-------
6. Is control/treatment technology applicable to site terms of: (yes
refer Co appropriate control/treatment technology discussions).
• Implementability
• Effectiveness
• Reliability
• Compatability of hazardous constituent plume
with technology
• Site's subsurface characteristics
or no:
yes
yes
(as temporary measure)
yes
(as temporary measure
but additional measures
i.e., grouting could be
implemented)
7. Environmental concerns associated with this control/treatment technology:
(check where applicable)
Subsidence
Decrease in well yield of adjacent well fluid
Drawdown of adjacent surface water bodies
Induced hazardous constituent migration to new pathways
Other (specify)
4-15
-------
Che wall leaked and was expected to leak Co some degree. Although che
technologies implemented at this site were successful in minimizing hazardous
constituent migration, with the use of additional technologies, such as
grouting to seal the bedrock fractures, the effectiveness of corrective
measures at the site could be further improved. By referring to Table 4.1 it
is evident that the slurry wall, well system, and interceptor trench
corrective measures and treatment technologies implemented at the site for
remediation of contaminated ground water are appropriate. For further
verification refer to Tables 2.13 and 2.14 which discuss hydrogeologic and
hazardous constituent applicability of control/treatment and treatment
technologies, respectively.
4-16
-------
REFERENCES
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pp. 154-160. National Conference on Management of Uncontrolled Hazardous
Waste Sices, October 31 - November 2, 1983, Washington, D.C. @ 1983 by
Hazardous Materials Control Research Institute.
Arthur D. Little, Inc. Physical, Chemical and Biological Treatment Techniques
for Industrial Wastes. Volume I. Prepared for EPA Hazardous Waste
Management Division. 1977.
Baedecker, M. J., and M. A. Apgar. "Hydrocheraical Studies at a Landfill in
Delaware," National Academy Press. Washington, D.C. 1984.
Ball, W. P., et al. "Mass Transfer of Volatile Organic Compounds in Packed
Transfer Aeration," pp. 127-135. Journal of the Water Pollution Control
Federation. 1984.
Barto, R.L., T.S. death, R.L. Anderton, and J.M. Montogomery. "Stringfellow:
A Case History of Closure and Monitoring at a Hazardous Waste Disposal
Site." Fourth National Symposium and Exposition on Aquifer Restoration
and Ground Water Monitoring, May 23-25, 1984, Columbus, Ohio.
-------
Doering, E. J. and L. C. Benz. "Pumping an ArcesLan Source for Wacer Table
ConcroL." Journal of the Irrigation and Drainage Division, ASCE,
June 1972.
E.G. Jordan. "Corrective Measures for Releases to Surface Waters", Draft
Final Report. Prepared for the U.S. EPA Office of Solid Waste,
Washignton, D.C. under subcontract to GCA/Technology Division. August
1985. EPA Contract No. 68-01-6871.
EPA 1978a. "Guidance Manual for Minimizing Pollution from Waste Disposal
Sites". Cincinnati, Ohio. EPA-600/2-78-142.
EPA 1978b. "Innovative Alternative Technology Assessment Manual."
EPA-430/19-78-009.
EPA 1980. "Treatability Manual, Volume til: Technologies for Control/Removal
of Pollutants." July 1980. EPA-600/8-80-042c.
EPA 1981. "Remedial Actions at Hazardous Waste Sites: Survey and Case
Studies-Whitmoyer Laboratories." January 1981. EPA-430/9-81-05. SW-910.
EPA 1982. "Handbook for Remedial Action at Waste Disposal Sites." Prepared
for U.S. EPA Office of Research and Development, Cincinnati, Ohio.
June 1982. EPA-625/6-82-006.
EPA 1983. "Handbook for Evaluating Remedial Action Technology Plans."
Prepared for U.S. EPA, Office of Research and Devlopment, Cincinnati,
Ohio. August 1983. EPA-600/2-83-076.
EPA 1984. "Slurry Trench Construction for Pollution Migration Control."
Prepared for U.S. EPA, Office of Solid Waste and Emergency Response,
Washington, D.C. February 1984. EPA-540/2-84-001.
Fair, G. M., J. C. Geyer, and D. A. Okun. Water and Wastewater Engineering.
Volume 2: Water Purification and Wastewater Treatment and Disposal. John
Wiley and Sons, Inc., New York.1968.
CCA Corporation/Technology Division, "Corrective Measures for Releases to
Soils from Solid Waste Management Units," Draft Final Report. Prepared
for U.S. EPA, Office of Solid Waste, Land Disposal Branch, Washington,
D.C. August 1985. EPA Contract No. 68-01-6871.
GHR Engineering Corporation, Goldberg-Zoino & Associates, and Environmental
Resource Associates. "Final Report - Hazardous Waste Site Investigation,
Sylvester Site, Gilson Road, Nashua, New Hampshire," Volume I: Main
Text. Prepared for the U.S. EPA - Region I Laboratory, Lexington,
Massachusetts. July 1981.
5-2
-------
Gross, R.L., and S.G. Termaath, "Packed Tower Aeration Scrips
Trichloroechylene from Ground Water." Presented ac the 1984 Summer
National Meeting of the American Institute of Chemical Engineers, August
1984.
Hagar, D.G., and C.G. Loven. "Operating Experiences in the Containment and
Purification of Groundwater at the Rocky Mountain Arsenal". Third
National Conference and Exhibition on Management of Uncontrolled Hazardous
Waste Sites, Washington, D.C., November 29-December 1, 1982. @ 1982 by
Hazardous Materials Control Research Institute.
Hagar, D.G., C.E. Smith, C.G. Loven, and D.W. Thompson. "Groundwater "~~-
Decontamination at the Rocky Mountain Aresenal." Fourth National ~~"
Symposium and Exposition on Aquifer Restoration and Ground Water
Monitoring.May 23-25, Columbus, Ohio.@ 1984 by National Water Well
Association.
Huibregtse, K.R. and K.H. Kastman, "Development of a System to Protect Ground
Water Threatened by Hazardous Spills on Land". U.S. EPA, Cincinnati,
Ohio. May 1981. EPA-600/2-81-085.
Johnson Division, UOP, Inc. "Groundwater and Wells". Edward F. Johnson,
Inc., Saint Paul, Minnesota, 1975.
Kaufmann, H.G. "Granular Carbon Treatment of Contaminated Ground Water
Supplies". Second Annual Symposium on Aquifer Restoration and Ground
Water Monitoring. @ 1982 by the National Water Well Association.
Kirk and Othraer, Chemical Grouts, Vol. 5, pp. 368-874. John Wiley & Sons,
Inc., NY. 1979.
Knox R.C., L.W. Canter, D.F. Kincannon, E.L. Stover, C.H. Ward. "Draft
Report: State-Of-The-Art of Aquifer Restoration." National Center for
Ground Water Research, University of Oklahoma, Oklahoma State University,
and Rice University. June 1984.
Konikow, L.F., and D.W. Thompson, "Groundwater Contamination and Aquifer
Reclamation at the Rocky Mountain Arsenal, Colorado." Ground Water
•Contamination from Hazardous Wastes. Wood, et al., editors.
Prentice-Hall, Inc. 1984.
Kufs, C., et al., "Alternatives to Ground Water Pumping for Controlling
Hazardous Waste Leachates", pp 146-149. National Conference on Management
of Uncontrolled Hazardous Waste Sites. @ 1982 by Hazardous Materials
Control Research Institute.
.5-3
-------
Lundy, D.A. and T.S. Mahan, "Conceptual Designs and Cose Sens itivicies of
Fluid Recovery Systems for Containment of Plumes of Contaminated
Groundwater" pp. 136-140. National Conference on Management of
Uncontrolled Hazardous Waste Sites. <§ 1982 by Hazardous Materials Control
Research Institute.
Lytnan, W.J. "Applicability of Carbon Adsorption to the Treatment of Hazardous
Industrial Wastes." Carbon Adsorption Handbook. Published by Ann Arbor
Science Pi-blishors, Inc., Ann Arbor, Michigan. 1980.
McCarty, P.L.,^et al. "Volatile Organic Hazardous constituents Removal by Air
Stripping. American Water Well Association Seminar Proceedings:
Controlling Organics in Drinking Water. San Francisco.June 1979.
Me tea If & Eddy, Inc. Wastewater Engineering: Collection. Treatment, and
Disposal. McGraw-Hill Book Company, New York.1972.
Morrison, A. "Arresting a Toxic Plume". Civil Engineering August 1983.
Ozbilgin, M.M. and M.A. Powers. "Hydrodynamic Isolation in Hazardous Waste
Containment". Fourth National Symposium and Exposition on Aquifer
Restoration and Ground Water Monitoring. May 23-25. 1984. Columbus, Ohio.
@ 1984 by National Water Well Association.
Pendrell, D.J., and J.M. Zeltinger. "Contaminated Ground Water
Containment/Treatment System at the Northwest Boundary, Rocky Mountain
Arsenal, Colorado." National Symposium and Exposition on Aquifer
Restoration and Ground Water Monitoring"May 23-25, 1984, Columbus
Ohio.
-------
Sommerer, S. and J.F. Kitchens, "Engineering and Development Support of
General Decon Technology for the DARCOM Installation and Restoration
Program, Task 1. Literature Review on Groundwater Containment and
Diversion Barriers." Draft Report by Atlantic Research Corp. to U.S. Army
Hazardous Materials Agency Aberdeen Proving Ground. Contract No.
DAAK11-80-C-0026 (Oct. 1980).
Sundstrora, D.W., and H.E. Kiel. Wastewater Treatment. Prentice-Hall, Inc.,
Engleuood Cliffs, New Jersey. 1979.
Tewhey, J.D., J.E. Sevee, and R.L. Forcin. "Silresim: A Hazardous Waste Case
Study." Proceedings of the National Conference on Management of
Uncontrolled Hazardous Wastes Sites. October 31-Noveraber 2, 1983.
Washington, D.C. @ 1983 by Hazardous Materials Control Research Institute.
Tolraan, A.H. et al. "Guidance Manual for Minimizing Pollution from Waste
Disposal Sites." August 1978. U.S. EPA, Cincinnati, Ohio.
EPA-600/2-78-142.
Troxler, W.L., C.S. Parmele, and G.A. Barton. "Survey of Industrial
Applications of Aqueous Phase Activated Carbon Adsorption for Control of
Pollutant Compounds from Manufacture of Organic Compounds." Prepared by
IT Enviroscience for the U.S. EPA Office of Research and Development.
1983. EPA-600/2-83-034.
Ullenbang, B. U.S. EPA, IX. Telephone conversation with L. Farrell,
GCA/Technology Division, Re: Stringfellow Site. July 1985.
Underwood, E. U.S. Ecology, Inc. Telephone conversation with M. Arienti,
GCA/Technology Division, Re: Gulf Coastal Plain Site. May 1985.
Underwood, E. U.S. Ecology, Inc. Letter to M. Arienti, GCA/Technology
Division, RE: Area extent of plume at a waste management facility in a
Gulf Coastal Plain. May 2, 1985.
Underwood, E. U.S. Ecology, Inc. Telephone conversation with L. Farrell,
GCA/Technology Division, Re: Gulf Coastal Plan Site. July 1985.
Versar, Inc. "Site Selection Worksheets." Prepared for U.S. Environmental
Protection Agency, Hazardous Waste Engineering Research Laboratory,
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Watensky, L. U.S. EPA, Region VIII. Telephone Conversations with L. Farrell,
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July 1985.
5-5
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APPENDIX A
UNDERGROUND INJECTION: CLASS I AND IV WELLS
INTRODUCTION
Class I and IV underground injection wells are considered land-based
solid waste management units (SWMUs). Due to the unique operating conditions
and regulatory management of Class I and IV wells, it is worthwhile to discuss
Class I and IV wells separately.
DEFINITIONS OF CLASS I AND IV WELLS
Class I underground injection wells, commonly referred to as deep wells,
are defined as follows (40 CFR 144.6(a)):
I. Wells used by generators of hazardous waste or owners or operators
of hazardous waste management faculties to inject hazardous waste
beneath the lowermost formation containing, within one-quarter mile
of the well bore, an underground source of drinking water (USDW);
2. Other industrial and municipal disposal wells which inject fluids
beneath the lowermost formation containing, within one-quarter mile
of the well bore, an USDW.
Class IV underground injection wells are defined as follows
(40 CFR 144.6(d)):
I. Wells used by generators of hazardous waste or of radioactive waste,
by owners or operators of hazardous waste management facilities or
by owners or operators of radioactive waste disposal sites to
dispose of hazardous waste or radioactive waste into a formation
which within one-quarter mile of the well contains an USDW;
2. Wells used by generators of hazardous waste or of radioactive waste,
by owners or operators of hazardous waste management facilities, or
by owners or operators of radioactive waste disposal sites to
A-l
-------
dispose of hazardous waste or radioactive waste above a formation
which within one-quarter mile of the well contains an USDW; or
3. Wells used by generators of hazardous waste or owners or operators
of hazardous waste management facilities to dispose of hazardous
waste, which cannot be classified under item I of the definition of
a Class I well or under items 1 and 2 of the Class IV well
definition (see above definitions). Included but not limited to
this definition are wells used to dispose of hazardous waste into or
above a formation which contains an aquifer which has been exempted
pursuant to 40 CFR 146.04—criteria for exempted aquifers. In
general, an aquifer is exempted if it does not serve as a source of
drinking water and it cannot now and will not in the future serve as
a source of drinking water; or the total dissolved solids (TDS)
content of the ground water is between 3,000 and 10,000 mg/L and it
is not expected to supply a public water system.
Class I and IV wells are the only wells that inject hazardous waste. The
major difference between Class I and Class IV wells, as noted in the above
definitions, is the depth and loction of injection; Class IV wells having the
shallowest injection depth one-quarter mile above an USDW. The remaining
injection wells include oil and gas production and storage wells and enhanced
recovery wells (Class II), mineral mining wells (e.g., in situ production of
metals, sulfur mining and solution mining—Class III), and injection wells not
included in the definitions of Class I, II, III, or IV wells (Class V).
REGULATORY FRAMEWORK
Underground injection wells fall under the jurisdiction of the Federal
Safe Drinking Water Act (SDWA), Public Law 95-523, as amended. Part C of the
SDWA provides for the protection of USDWs through federal guidelines and
regulations and the administration of regulatory programs at the state level.
USDWs are defined as all aquifers containing water with less than 10,000 mg/L
total dissolved solids (TDS). The Federal Underground Injection Control (UIC)
Program appears at 40 CFR Parts 144 through 146. Part 144 contains permit
information and conditions, and financial responsibility. Part 145 contains
the State UIC Program requirements. Part 146 includes the UIC technical
regulations. Underground injection of hazardous waste is also regulated under
the Resource Conservation and Recovery Act of 1976 (RCRA). RCRA, however, is
only applicable when hazardous waste is being injected without a UIC permit or
in the absence of an authorized program. The National Pollutant Discharge
A-2
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li Li.mi.nac ion System (NPDKS) under Che Federal Clean Water Act (CWA) has little
authority over the actual injection of wastes underground, except where a
navigable body of water is receiving injected wastes.
Class IV wells have recently been banned and are required to be plugged
and abandoned six months after the UIC program becomes effective in a state,
40 CFR 144.23(c) (December 1984 for most states and June 1985 for the
remaining states). Section 405 of the Hazardous and Solid Waste Amendments of
1984 has reinforced the ban by prohibiting the disposal of hazardous waste by
underground injection into or above an USDW on May 8, 1935 (RCRA, Section
7010). Most states have already banned the use of Class IV wells, and when
Class IV wells are identified in those states they are shut down.
CURRENT STATUS
Data on Class I and limited data on Class IV wells have been compiled by
the EPA Office of Drinking Water in a report entitled "Report to Congress on
Injection of Hazardous Waste," signed and released May 1985 (herein referred
to as EPA/ODW, 1985). The banning of Class IV wells on the state and federal
levels has limited the use of Class IV wells and has, therefore, limited the
information available on Class IV injection practices. EPA is currently
focusing their effort on proper closure and monitoring of these wells to
detect and prevent any contamination to an USDW.
Although the Hazardous and Solid Waste Amendments of 1984 may place
future restrictions on the types of wastes available for injection and
location of new wells, the injection of hazardous waste into Class I wells
remains an active practice. As of March 18, 1985, 32 states had applied for
and received enforcement authority of the UIC program for Class I hazardous
waste wells. EPA has promulgated 25 programs in states that chose not to or
did not obtain delegation of the UIC program for Class I wells.
Active hazardous waste injection wells are found in 15 states. A
majority of the wells are located along the Gulf Coast and near the Great
Lakes with 66 percent of the wells concentrated in Louisiana and Texas. These
two regions have a history of underground injection in the area of oil and gas
production activities and, therefore, have abundant data on geologic
format ions. These regions also possess suitable geologic formations for
efficient injection.
A-3
-------
The EPA/ODW 1985 report revealed information on 34 Class IV wells located
in 12 states. Sixteen of these wells have been permanently plugged and
abandoned; II wells are in the closure process (i.e., abandoned but not yet
plugged). Four wells were active and under investigation as of March 1985;
and three wells, one of which is plugged, are designated CERCLA sites. The
EPA/ODW report identified 112 facilities which inject hazardous waste through
252 Class I wells. Ninety of these facilities were active and injected
hazardous waste into 195 wells during 1984 (only 181 wells were operating in
1983). The remaining 57 wells (out of 252) were inactive. Of the 195 active
wells, 152 operated continuously and 43 intermittently. Of the 57 inactive
wells, 41 were abandoned, 3 were shut-in or in the process of changing type of
operating, and 13 had a permit pending or were under construction.
GROUND WATER CONTAMINATION FROM UNDERGROUND INJECTION
Kive basic pathways have been identified in which injection practices can
cause fluids to migrate into an USDW (EPA/ODW, -1985):
1. Faulty wall construction (i.e., leaks in well casing);
•
2. Improperly plugged or completed wells in the zone of endangering
influence;
3. Faulty or fractured confining strata (i.e., due to improper
injection pressure used and injection into or below an inadequate
confining formation);
4. Lateral displacement (i.e., due to inproper injection pressures and
inadequate detection of faults and recharge areas); and
5. Direct injection (i.e., injection into or above USDWs which is
currently banned by EPA).
The technical requirements of the UIC regulations (40 CFR Part 146) are
designed to address the pathways of migration stated above. Proper
construction of Class I wells is required at 40 CFR 146.12. Mechanical
integrity tests (MITs) for Class I wells are required prior to initial
injection and every five years thereafter to confirm the integrity of the
well's construction (40 CFR Part 146.08). The use of MITs has proved to be an
A-4
-------
excellent device in identifying defects and preventing contamination before
any damage is done. The proper operation and continuous monitoring and
reporting of Che volume and the injection and annulus pressure, required at 40
CFR Part 146.13, provides information on the operation of wells. If detection
of fluid migration from the well occurs, corrective action is required (40 CFR
Part 144.55 and 146.07). In addition, financial requirements for Class I
wells (40 CFR 144 Subpart F) assure financial liability and responsibility for
those wells for present and future problems. Proper plugging and abandonment,
required by 40 CFR Part 146.10 and 144.23, reduces the possiblity of future
contamination from the well.
Due to the location of Class IV wells, it can be assumed in most cases
that hazardous waste or constituents will reach or have reached the uppermost
aquifer. This fact alone has provided grounds for the ban on use of Class IV
wells. However, the shallow depth of Class IV wells (maximum depth of 1,000
ft) does allow for the use of monitoring wells to determine and identify if
any release/migration of fluids from the well has occurred. Conversely, the
detection of fluid migration from Class I wells presents a problem. The
average depth of a Class I well ranges from 1,000 to 5,000 ft. Some wells are
documented with a depth of up to 7,000 ft. There are concerns about drilling
3 monitoring well this deep. The monitoring well could possibly serve as a
conduit for the rise of injected wastes into useable aquifers at some point in
the future. There is no current technology to properly locate a well for this
purpose because it may take hundreds to thousands of years to detect a release
from the injected zone. These monitoring wells are also difficult and
expensive to construct and operate. Presently, only a few deep aquifers
associated with Class I wells are being monitored. Some proponents of Class I
wells argue that if Class I wells are located in sound geologic areas and are
constructed and operated properly there should be few problems with
contamination of USOWs. Supporting data indicates that deep well injection
occurs in and below aquifers that contain very high volumes of TDS which are
too great to have any potential for human use now or in the future.
A-5
-------
Currently, few documented cases exist in which contamination of an UftttW
has occurred from underground injection practices. This may partly be the
rosult of the limited practice of underground injection. Enforcement
information collected by the Office of Drinking Water (EPA/ODW, 1985) revealed
that out of a reported 84 noncompliance incidents at 39 facilities,
administrative violations accounted for 50 percent (42 incidents) and
construction, design, or operational problems accounted for the remaining 50
percent. Of the 42 nonadminiatrative violations, legal action was only
required in 10 cases. Of all the violations only nine cases presented
significant problems which could have resulted in the contamination of USDWs.
Of these nine cases only three cases of USDW contamination have been
documented. Migration from the wells eventually causing USDW contamination
occurred from excessive injection pressures, the injection of incompatible
wastes, the injection of wastes with a lower pH than authorized, and
inadequate operator training. One of these sites is now a Superfund site and
is scheduled for remedial action. Current documented corrective measures
employed at these sites include plugging the wells, using recovery wells and
reinjecting into the permitted zones through new wells, and pumping out
contaminated water.
Preventative measures are currently being employed at some facilities
with Class I wells. Examples of these measures include pretreating the waste
prior to injection, avoiding the injection of incompatible waste streams,
installing automatic shutoff systems which stop injection when certain
monitored parameters reach specific levels, and installing special operating
techiques to prevent well blowouts. In addition, the implementation of proper
closure techniques to plug and abandon wells as well as proper monitoring
prior to and following closure remain the important techniques in detecting
releases and preventing contamination to USDWs.
A-6
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REFERENCES FOR APPENDIX A
"Ground-Water Protection Strategy for the Environmental Protection Agency,"
Final Draft. OGWP/EPA. May 1984.
Sobotka, Inc. "Phase I Corrective Action Guidance: Information and
Methodology for Identifying Releases from Solid Waste Management Units,"
Draft Report. April 19, 1985.
"Report to Congress on Injection of Hazardous Waste," Draft. ODW/EPA.
May 1985.
A-7
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