United States Office of Ground Water EPA/816-R-99-014p
Environmental and Drinking Water (4601) September 1999
Protection Agency
The Class v Underground Injection
Control Study
Volume 16
Aquifer Remediation Wells
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Table of Contents
Page
1. Summary 1
2. Introduction 2
3. Prevalence of Wells 4
3.1 States Where Relatively Large Numbers of Aquifer
Remediation Wells Exist 8
3.2 States That Reported No ARWs 8
4. Injectate Characteristics and Injection Practices 8
4.1 Injectate Characteristics 9
4.1.1 Remediation Agents 9
4.1.2 Treated Water 25
4.1.3 Freshwater 25
4.2 Well Characteristics and Operational Practices 30
4.2.1 Pump-and-Treat Systems 31
4.2.2 In Situ Bioremediation 31
4.2.3 In Situ Flushing 32
4.2.4 In Situ Chemical Treatment 32
4.2.5 Air Sparging 32
4.2.6 Steam Injection 40
4.2.7 Permeable Treatment Barrier Systems 40
4.2.8 Experimental Wells 42
5. Potential and Documented Damage to USDWs 42
5.1 Injectate Constituent Properties 50
5.2 Impacts on USDWs 51
6. Best Management Practices 53
6.1 Selection of Well Construction Materials 53
6.2 Compatibility with Site Conditions 54
6.3 Well Systems 54
6.3.1 Pump-and-Treat Systems 54
6.3.2 Air Sparging 55
6.3.3 Steam Injection 55
6.3.4 Permeable Treatment Barrier Systems 55
September 30, 1999
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Table of Contents (cont'd)
Page
7. Current Regulatory Requirements 55
7.1 Federal Programs 56
7.1.1 SDWA 56
7.1.2 CERCLA - Superfund Cleanups 57
7.1.3 RCRA Corrective Actions 58
7.1.4 Underground Storage Tank Program 58
7.2 State and Local Programs 59
ATTACHMENT A: State and Local Program Descriptions 60
REFERENCES 72
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AQUIFER REMEDIATION WELLS
The U.S. Environmental Protection Agency (USEPA) conducted a study of Class V underground
injection wells to develop background information the Agency can use to evaluate the risk that these wells
pose to underground sources of drinking water (USDWs) and to determine whether additional federal
regulation is warranted. The final report for this study, which is called the Class V Underground Injection
Control (UIC) Study, consists of 23 volumes and five supporting appendices. Volume 1 provides an
overview of the study methods, the USEPA UIC Program, and general findings. Volumes 2 through 23
present information summaries for each of the 23 categories of wells that were studied (Volume 21
covers 2 well categories). This volume, which is Volume 16, covers Class V aquifer remediation wells.
1. SUMMARY
Aquifer remediation wells (ARWs) are widely used around the country for beneficial uses
associated with the control of ground water contamination. These wells may be used for different specific
purposes, including to: (1) introduce remediation agents (i.e., chemicals or microorganisms) into
contaminated aquifers to neutralize the contamination; (2) increase ground water flow through the
contaminant zone in an aquifer to aid in contaminant removal; (3) form hydraulic barriers to contain
contaminant plumes; and (4) re-inject treated ground water for aquifer recharge after an onsite pump-
and-treat system.
For many reagents and nutrients injected into ARWs, the concentration in the injectate likely
exceeds MCLs or HALs because higher concentrations of such reagents and nutrients are needed for
them to serve their intended purposes. The data available about these wells are insufficient to establish
meaningful comparisons between concentrations of injected reagents or nutrients in ground water
monitoring wells, located downgradient from the ARW where they were injected, and the corresponding
MCLs or HALs. Based on the information reviewed, it appears that ground water monitoring activities
associated with remediation projects typically focus on the contaminants being remediated, rather than on
the reagents, nutrients, or other substances injected into the affected aquifer as part of the remedial
activity.
The injectate in ARWs is typically (i.e., in the case of the first three purposes mentioned above)
directed into a contaminated aquifer where constituents of concern exceed MCLs. On the other hand,
re-injection of treated ground water from an onsite pump-and-treat system may occur into a different
formation than that which is being remediated, with the objective of recharging the aquifer. In this last
case, the receiving formation may be a USDW and the injectate is monitored to ensure that constituents
of concern present in the injectate do not exceed MCLs.
One contamination incident associated with an ARW was reported in the state and USEPA
Regional survey conducted for this study. The incident occurred at the Hassayampa Landfill Superfund
Site in Arizona in 1998. A failure in an automatic cut-off valve in a pump-and-treat system, concurrent
with a failure in the treatment unit, resulted in the accidental injection of untreated ground water into a
September 30, 1999
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clean USDW. The extent of the impact on the USDW or to drinking water wells was not reported.
A majority of ARWs appear to be covered under Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA) Cleanups, Resource Conservation and Recovery Act
(RCRA) Corrective Actions, or Underground Storage Tank (UST) cleanup actions. As with any
remedial measure, they usually require the approval of the appropriate state and/or federal regulatory
agencies. There is some concern for voluntary cleanups that are not approved or completed according to
standards typical of cleanups with oversight. Limited information from the survey suggests that voluntary
cleanups do occur, but little is known about them based on the information available. Nevertheless, in
some USEPA Regions, voluntary cleanups are periodically the subject of inspections by state or federal
regulatory agencies (Micham, 1999a) and in Ohio, one of the states with the highest number of ARWs,
no contamination is known to have occurred as a result of the operation of an ARW (Cadmus, 1999).
The survey results indicated that there are 10,221 documented ARWs located in 39 states and
territories. A significant fraction (65 percent) of the total is concentrated in South Carolina (3,409),
Texas (1,177), Ohio (1,170), and Kansas (936). As part of this survey, state and USEPA Regional
officials estimated that a slightly higher number of wells, 10,756, actually exists. Taking into consideration
the fact that a significant number of additional wells were reported as "under construction" at the time of
survey (e.g., 2,170 wells in South Carolina alone), the actual total number of wells could be between
12,000 and 14,000. This also suggests a potential future increase in the number of ARWs.
Based on a review of relevant regulations for the states where ARWs are most prevalent and for
a limited set of additional states that constitute a broad geographical sample, it was established that
individual permits are required for these wells in at least Arizona, California, Kansas, Nevada, Ohio
(required for those wells expected to exceed MCLs), and South Carolina, which collectively have
approximately one-half of the documented wells. ARWs may be authorized by rule in New Hampshire
and Texas. At the federal level, ARWs are subject to the federal UIC standards, and, as indicated, may
be additionally regulated under CERCLA Cleanups, RCRA Corrective Actions, and the UST Program.
2. INTRODUCTION
Aquifer remediation can be defined as the implementation of remedial measures to correct
deficiencies, improve selected parameters (such as the quality of flow), or to prevent anticipated or
possible problems in permeable materials which contain or are capable of containing ground water. The
implementation of such measures historically has been in response to problems that have already
occurred. During the 1980s, the United States saw an increase in the incidence or, at a minimum, the
recognition of ground water contamination. The resulting aquifer remediation programs share certain
goals. The main goal is the abatement of contamination, followed by containment of the area of
contamination, and lastly, restoration of the aquifer (USEPA, 1987).
Under certain conditions, ground water remediation efforts may sometimes warrant the
subsurface injection of fluids. Injection wells may be used to achieve one or more of the goals of an
September 30, 1999
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aquifer remediation program. They may be used to introduce remediation agents (i.e., chemicals or
microorganisms) into contaminated aquifers to neutralize the contamination. Aquifer remediation injection
wells may also be used to aid in contaminant removal by increasing ground water flow through the
contaminant zone; to form hydraulic barriers to contain contaminant plumes; and to re-inject treated
ground water (USEPA, 1987).
The definition of Class V underground injection wells contained in the existing underground
injection control (UIC) regulations in 40 CFR 146.5(e) does not specifically mention ARWs. However,
all injection wells not included in Class I, n, m, or IV are defined as Class V wells. Class V ARWs are
distinguished from Class IV wells, which dispose of hazardous or radioactive waste into or above a
formation which contains a underground source of drinking water (USDW) within one-quarter mile (see
40 CFR ง144.6(d)). Although Class IV wells are generally prohibited, they are allowed if they are used
to inject contaminated ground water that has been treated and is being re-injected into the same formation
from which it was drawn, if approved by USEPA pursuant to the provisions for cleanup of releases under
CERCLA or RCRA (see 40 CFR ง144.13(c)). A well that meets this definition qualifies as a Class IV
well, not a Class V ARW.
In support of this study, USEPA conducted a survey of the state and regional staff that administer
the UIC programs to collect information on ARWs and other types of Class V wells (Cadmus, 1999).
The questionnaire used to gather data defined "ARWs" as wells that are "used to clean up, treat, or
prevent contamination of USDWs. Treated ground water (pump-and-treat), bioremediation agents, or
other recovery enhancement materials may be injected into the subsurface via Class V wells. These wells
may be associated with RCRA or CERCLA projects." As indicated earlier, ARWs may also be
associated with leaking UST site cleanups, voluntary cleanups, or with cleanups regulated under specific
state programs. While the UIC programs regulate the ARW itself, the cleanup level associated with the
remediation project is generally established by another regulatory program.
ARWs include relatively sophisticated designs in which holes are drilled and cased with metal or
plastic pipe. They also include simple systems designed to drain fluids to the subsurface. For example,
an improved sinkhole, defined as a surface depression altered to direct fluids into the opening (USEPA,
1987), qualifies as an injection well, as does an abandoned drinking water well that has been adapted to
convey fluids to the subsurface. If improved sinkholes or abandoned drinking water wells are used to
help clean up contaminated ground water, either by injecting solutions to neutralize contamination or to
return previously contaminated ground water that has been treated, they qualify as ARWs. Depending on
the system design, some infiltration systems1 may meet the definition of a Class V injection well.
According to available UIC guidance on this matter, each of the vertical pipes in such a system,
individually or in a series, should be considered an injection well subject to UIC authorities.
1 "Infiltration galleries" consisting of one or more vertical pipes leading to a horizontal,
perforated pipe laid within a trench, often backfilled with gravel or some other permeable material are
commonly used to return treated ground water at aquifer remediation sites.
September 30, 1999
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Conventional aquifer remediation technologies have been based on "pump-and-treat" systems.
In these systems, the contaminated water is extracted through a well or system of wells to the surface for
treatment. The treated water can be re-injected into the subsurface and a cyclical process of water
circulation can continue until the contamination level within the aquifer decreases to an acceptable level.
"Pump-and-treat" systems have been widely and successfully used for aquifer remediation at numerous
sites. However, these systems have been proven to be ineffective and/or considerably more expensive
than non-conventional systems under certain conditions, as discussed in Section 4.2.1.
Non-conventional (or alternative) remediation technologies are increasingly being used in stead of
conventional "pump-and-treat" systems. Since the early 1990s, innovative technologies have been widely
used in decontaminating soil and ground water aquifer at more than 66 percent of the sites with leaking
USTs (NRC, 1997). Innovative technologies that typically involve well injection include :
In situ bioremediation
in situ oxidation
in situ flushing
air sparging
steam injection
permeable active barrier systems.
3. PREVALENCE OF WELLS
For this study, data on the number of Class V ARWs were collected through a survey of state
and USEPA Regional UIC Programs. The survey methods are summarized in Section 4 of Volume 1 of
the Class V Study. Table 1 lists the numbers of Class V ARWs in each state, as determined from this
survey. The table includes the documented number and estimated number of wells in each state, along
with the source and basis for any estimate, when noted by the survey respondents. If a state is not listed
in Table 1, it means that the UIC Program responsible for that state indicated in its survey response that it
did not have any Class V ARWs.
A total of 33,872 documented ARWs were initially estimated nationwide by that survey.
However, one state - Wyoming - accounted for over two thirds of all the wells based on the survey's
data. As part of the preparation of this report, the Wyoming data, as well as the data for a number of
other states, were verified directly with the states or USEPA Regional UIC Programs. In the case of
Wyoming, the number reported in the survey has been revised to eliminate many non-ARWs incorrectly
assigned as ARWs (Lucht, 1999a). The data presented in Table 1 for Wyoming include one well
permitted as a water intrusion barrier well that is used to form a hydraulic barrier to contain a contaminant
plume, as discussed in Section 4.1.3. An additional apparent problem associated with the data obtained
in the survey on ARWs lies in the
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Table 1. Inventory of ARWs in the U.S.
State
Documented
Number of Wells
Estimated Number of Wells
Number
Source of Estimate and Methodology1
USEPA Region 1
ME
NH
RI
VT
13
64
18
Unknown
50-60
64
18
10
Best professional judgment.
N/A
N/A
Best professional judgment.
USEPA Region 2
NY
VI
30 per RCRA
permits (NYSDEC)
0
100 (NYSDEC)
50
1998 survey of permits for RCRA facilities.
Number of Superfund sites with a ground water component.
USEPA Region 3
DC
DE
MD
WV
25
4
8 facilities
46
25
4
>17
46
Total estimated number counts the documented number when
the estimate is NR.
N/A
4 facilities utilize infiltration galleries. One facility has 6
injection wells and another has five wells.
N/A
USEPA Region 4
AL
FL
GA
NC
sc
87*
25(1997UIC
inventory)
4-5 sites (Southwest
District DEP)
457
103*
3,409
87*
100-250
457
103*
3,409
N/A [5 experimental ARWs at the site of Utilities Board of
City of Bay Minette (ADEM, 1998)]
N/A
N/A
N/A [21 experimental ARWs (NCDENR, 1999)]
3,409 active wells at 189 sites; 2,170 wells under construction
at 145 sites (Devlin, 1999a).
USEPA Region 5
IL
150
150
Suspects that more wells exist in IL than documented. Total
estimated number counts the documented number when the
estimate is NR.
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State
IN
MI
MN
Documented
Number of Wells
5
107 (MI)
382 (Regional)
11
Estimated Number of Wells
Number
5
382
100
Source of Estimate and Methodology1
Total estimated number counts the documented number when
the estimate is NR.
USEPA Region 5 (Micham, 1999b). Total estimated number
counts the documented number when the estimate is NR.
Based on state records and discussion with state officials.
USEPA Region 5 (cont'd)
OH
WI
1,170
36
1,170
>36
Ohio EPA has conducted extensive outreach activities to
consultants and industry and believes that most of the ARWs
have been reported and inventoried. Some additional wells
may exist since other state agencies involved in remediation
(especially leaking underground storage tank remediation) do
not consistently advise owners/operators of the UIC
requirements.
Best professional judgment.
USEPA Region 6
LA
NM
OK
TX
17
83
284
1,177
17
83
284
1,177
N/A
83 active; 5 under construction; 224 temporarily abandoned;
and 2 permanently abandoned.
N/A
TXNRCC (Eyster, 1999a).
USEPA Region 7
IA
KS
NE
50
936
40
50
>936
40
N/A
KDHE Bureau of Water (Cochran, 1999).
N/A
USEPA Region 8
CO
SD
UT
94* sites
623
227
94* sites
623
>227
N/A [38 experimental ARWs at 3 sites (USGS, 1996;
SECOR, 1999; PEC, 1998)]
N/A
Some sites may have multiple wells. Inventory forms
received in FY1 998 are not reflected in the documented
number because of an anticipated change in data systems. An
additional 22 wells are under construction.
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State
WY
Documented
Number of Wells
11
Estimated Number of Wells
Number
12
Source of Estimate and Methodology1
22 existing wells; 1 1 active; the remaining wells were plugged
and abandoned (Lucht, 1999a). Includes one well permitted
as a water intrusion barrier well that is used to form a
hydraulic barrier to contain a contaminant plume.
USEPA Region 9
AZ
CA
NV
20
131
197
20
131
197
Suspects more wells exist in AZ than documented. Total
estimated number counts the documented number when the
estimate is NR.
N/A
N/A
USEPA Region 10
AK
ID
OR
WA
5
27
36
220*
>5
27
70
220*
Best professional judgement. Many more wells than those
documented are suspected to exist in AK (Williams, 1999).
N/A
Calvin Terada, USEPA Region 10, per telephone conversation
with state personnel.
1 experimental ARW at Fort Lewis Logistics Center, Fort
Lewis (Pierce County).
All USEPA Regions
All States
10,221*
10,756*
1 Unless otherwise noted, the best professional judgement is that of the state or USEPA Regional staff completing the survey
questionnaire.
N/A Not available
Unknown Questionnaire completed, but number of wells is unknown.
* Inventory includes experimental ARWs.
fact that, at least in some cases, monitoring wells installed and operated as part of an aquifer remediation
project may have been incorrectly reported as injection wells. For example, the number of ARWs
reported in Arkansas was 964, but upon verification, it was established that the state's UIC program
does not have any record of ARWs as part of its UIC program and that all the previously reported wells
were actually monitoring or recovery wells at RCRA sites (Allen, 1999). As shown, the revised total
number of documented ARWs nationwide is 10,221. However, as discussed in Section 3.1, the actual
number of ARWs in the U.S. is assumed to be much higher than the survey estimate. In addition, it is
estimated that the number of active ARWs may increase in the near future because new remediation
projects are being started at a faster pace than the existing projects are being closed.
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3.1 States Where Relatively Large Numbers of ARWs Exist
Approximately 65 percent of all the documented ARWs were reported in only four states,
including 3,409 wells in South Carolina, 1,177 wells in Texas, 1,170 wells in Ohio, and 936 wells in
Kansas. Eight other states (California, Georgia, Illinois, Nevada, Oklahoma, South Dakota, Utah, and
Washington) reported between 100 and 900 documented ARWs, with a total number equivalent to
approximately 22 percent of the national total. In one case, the survey respondents (South Carolina)
provided information about an additional 2,170 ARWs which were under construction (Devlin, 1999a).
In several states, the actual number of ARWs is expected to be considerably higher than the
reported number because a large number of wells are known to exist but are regulated by programs
different from the UIC program (e.g., wells associated with cleanup of leaking underground storage
tanks, Superfund cleanup, RCRA corrective actions, and voluntary cleanups). Some states reported the
number of sites where ARWs are known to exist, but did not specify the actual number of wells, which
can be expected to be much higher. For example, the state of Colorado reported 91 sites with ARWs.
According to the USEPA's 1987 Report to Congress on Class V Injection Wells (USEPA, 1987), of the
81 such wells that existed in Colorado, all of them were located at a single site (i.e., the Rocky Mountain
Arsenal). Based on this information, it is reasonable to assume that the actual number of ARWs in the
U.S. is higher than reported in the survey.
3.2 States That Reported No ARWs
According to the survey, seven states and a tribal program reported no ARWs (Cadmus, 1999).
Those states are located primarily in the eastern and southeastern part of the U.S. and include the
following: Connecticut, Massachusetts, New Jersey, Puerto Rico, Pennsylvania, Virginia, Kentucky,
Mississippi, and Hawaii. The same sources for uncertainty discussed in Section 3.1 may be applicable to
states that reported the complete absence of this type of well.
4. INJECTATE CHARACTERISTICS AND INJECTION
PRACTICES
This chapter provides an overview of the injectate and well characteristics of aquifer remediation
practices. Section 4.1 summarizes the characteristics of remediation reagents and re-injected treated
water that are injected into the ARWs. Section 4.2 discusses well systems and operational issues for
aquifer remediation technologies that have been commonly adopted. It is recognized that aquifer
remediation is an emerging field and innovative technologies are being developed rapidly. Information
regarding alternative aquifer remediation technologies may be obtained through other sources, such as the
Vendor Information System for Innovative Treatment Technologies (VISITT) database.2 It is not the
2 The VISITT database was developed by the USEPA Office of Solid Waste and Emergency
Response to promote the use of innovative treatment technologies in the cleanup of soil and ground water
contaminated by hazardous and petroleum waste. The database contains information on the technologies
September 30, 1999
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intention of this report to be inclusive of aquifer remediation technologies and systems.
4.1 Injectate Characteristics
The characteristics of the injectate associated with ARWs depends on the intended use of the
well. ARWs may be used for a variety of purposes, including:
introducing remediation agents (i.e., chemicals or microorganisms) into contaminated
aquifers to neutralize the contamination
aiding in contaminant removal by increasing ground water flow through the contaminant
zone
forming hydraulic barriers to contain contaminant plumes
re-injecting treated ground water.
Section 4.1.1 describes the various remediation agents associated with applications such as in situ
bioremediation, in situ flushing, in situ oxidation, air sparging, steam injection, and permeable reactive
systems. Section 4.1.2 presents information about re-injected treated ground water. Section 4.1.3
describes the use of freshwater injection to create a hydraulic barrier to prevent migration of a
contaminant plume. The information on remediation agents as described in Section 4.1.1 is based on a
limited review of published literature, papers released by the regulatory agencies, vendor literature, and
information provided by the reviewers of the draft of this document. In this section, information on
remediation agents is summarized in tabular form. In many cases, information regarding the empirical
experiments or applications of these remediation agents is also presented in the same tables in order to
provide the reader with a comprehensive view of such applications and thus minimize repetition of
information throughout the report. The injectate data for treated water presented in Section 4.1.2 was
obtained from various agencies. The reference to the hydraulic barrier application presented in Section
4.1.3 were obtained from the survey of state and USEPA Regional UIC Programs (Cadmus, 1999).
4.1.1 Remediation Agents
Bioremediation Agents
Bioremediation is a remediation technology that can take two forms: bioaugmentation and
biostimulation. Bioaugmentation involves introducing non-native soil microbes into the contaminated
aquifer. Biostimulation attempts to stimulate existing soil microorganisms with reagents to enhance their
natural capacity to degrade contaminants (Piotrowski, 1992).
designed to remediate ground water or nonaqueous phase liquids (NAPL) in situ, soil, sludge, solid-matrix
waste, natural sediments, and off-gas. The availability, performance, and cost of innovative technologies
are provided in the database. The information in the database is submitted voluntarily by technology
vendors to market their capabilities and enables federal, state, and private sector environmental
professionals to screen innovative technologies for application to specific sites (USEPA, 1997d).
September 30, 1999
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Bioaugmentation involves selecting bacterial strains to degrade specific contaminants. The
microbes selected for remediation can be enhanced prior to injection by enrichment culturing. Enrichment
culturing involves continually increasing the levels of contaminants that microbes are exposed to during
culturing (Sims et al., 1992). A few field studies have been conducted with recombinant bacteria
genetically engineered in the laboratory to degrade specific contaminants (USEPA, 1996c).
Biostimulation can be used more readily than bioaugmentation for larger contamination sites
because nutrients can be dispersed more easily than microbes throughout the contaminant zone
(Piotrowski, 1992). Nutrients injected to stimulate microorganisms may consist of inorganic phosphates,
nitrogen in the form of ammonia (NEy, and micronutrients (e.g., potassium, iron, sulfur, magnesium,
calcium, and sodium) (Scalzi, 1992). The types of reagents used to create aerobic and anaerobic
degradative environments are different. Oxygen, in the form of sparged air, hydrogen peroxide, or
oxygen releasing compounds (ORCs), is necessary to stimulate aerobic biodegradation. Air sparging can
create dissolved oxygen concentrations in the ground water as high as 8 to 10 mg/1. Hydrogen peroxide
can supply oxygen at concentrations as high as 1,000 mg/1 and not impair microbial degradation.
Anaerobic microorganisms can be stimulated with reagents such as methane gas, toluene, acetate, lactate,
and even molasses (NRC, 1994). Examples of bioremediation applications including the characteristics
of injected fluids are shown in Table 2. Several examples of proprietary nutrient compounds used to
stimulate microorganisms are shown in Table 3.
In Situ Flushing Agents
In situ flushing agents may be added to pump-and-treat injection well systems to enhance
contaminant removal. The types of agents that are introduced into the subsurface by injection include co-
solvents, surfactants, sugars, acids, and nutrients. These agents are cycled through an injection and
extraction system and enhance contaminant removal through various physical processes. Table 4
provides examples of flushing agents and contaminants that can be used to remediate ground water.
September 30, 1999 10
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Table 2. Examples of Bioremediation Applications
Remediation Agents
5.4 kg (dry weight) Methylosinus trichosporium OB3b
(strain of methanotrophic bacteria) suspended in 1,800 1
of ground water (5.4 x 109 cells/ ml), injected at 3.8 L/min.
for7.9hrs
Higgins' phosphate solution (at a concentration with a
molarity equal to 10 mM),
phenol red (as a tracer, at a concentration with a
molality equal to 20 (im)
5 tests with varying concentrations
Acetate: 84-1,000 mg/1 (electron donor)
Nitrate: 120-1,400 mg/1 (electron acceptor)
Toluene: 7 to 13. 4 mg/1
mixture of gaseous oxygen & hydrogen peroxide to
dissolved oxygen at cone, of 30-40 mg/1, to promote
cometabolism of toluene and contaminants by
microorganisms
l%-4% methane in air, pulsed injection
0.07% nitrous oxide and 0.007% tri-ethyl phosphate in
air, continuously injected
gaseous nutrient injection achieved better mass
transfer
than liquid nutrient injection
Pollutants
trichloroethene
(TCE) 425 ppb
carbon
tetrachloride (CC14)
TCE
(0.5 -1.2 mg/1)
TCE
PCE (tetrachloro-
ethylene)
Well type
single well at depth 27 m
single injection well
2 injection wells 10m apart
injection via a horizontal
well in the contaminated
aquifer
extraction via parallel
horizontal well in vadose
zone
Site & Scale
Chico Municipal
Airport, Chico, CA
Field test (40 days)
field demonstration,
Hanford, WA
35 days per test
410 day
demonstration project
at Edwards AFB, CA
22-meter sq.
treatment zone, 60-m.
wide ground water
plume
full scale
demonstration,
Savannah River Site,
GA
Reference
Duba, 1996
Hooker, 1994
McCarty, 1997
McCarty, 1998
Hazen, 1993
U.S. DOE, 1995
September 30, 1999
11
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Table 2. Examples of Bioremediation Applications (cont'd)
Remediation Agents
Methane research grade (99% purity) supplied in four
350-ft3 cylinders at levels between 1% and 1.8% v/v of
injected air flow
air, injection rate varied from 1.5 cfm to 5 cfm
vapor-phase nutrients (if needed)
injected to stimulate methanotrophs to degrade
methane and in doing so, produce an enzyme(MMO), a
non-specific oxidizer, which degrades TCE
Sodium benzoate
Sodium lactate
Methanol
reagents recirculated in ground water at 1 .5 gal/min. for
a total of about 250,000 gal. (equals 2 pore volumes)
during the pilot study
agents used to enhance anaerobic bacteria degradation
nutrient mix ratio: 100:10:1 (carbon: nitrogen:
phosphorus)
Ammonium chloride
Sodium dibasic phosphate
Sodium monobasic phosphate
substrate mix:
Sodium acetate (1,860 kg)
Sodium benzoate(2, 163 kg)
Added to both mixes
Sodium bromide (151 kg) or LOGO me/I
Pollutants
TCE
. 1 00-400 ppm
chlorinated VOC's
Well type
one 2-inch (diameter) air
injection well screened just
below ground water (39-41.5
feet)
one 4-inch (diameter) soil
venting well, screened in the
vadose zone and connected
to soil venting blowers (to
contain injected gasses and
remove vapors through
contaminated soil and water)
3- 8 ft. deep gravel filled
infiltration trenches
2- 240 ft. long horizontal
wells with 30 ft. screened
intervals (horizontal wells at
16 and 26 ft. depths
Site & Scale
CTMI test
Nov. 2, 1994 -Feb. 17,
1995
Pinellas Science,
Technology, and
Research Ctr., Largo
FL (former DOE site)
Pilot demonstration
area 45 ft. x 45 ft. x 30
ft.
Feb. -Jun. 1997
Gulf Coast
manufacturing site,
anaerobic in situ
bioremediation, 400
days
Reference
Sutfin & Ramey,
1997
Hightower, 1998
Sewell, 1998
Leethem, 1995
September 30, 1999
12
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Table 2. Examples of Bioremediation Applications (cont'd)
Remediation Agents
testing different methods to stimulate native anaerobic
bacteria
test lane: metal rods carrying electric current
generating hydrogen ions on the rods which microbes
use to degrade contaminants
several test lanes of various nutrients and additives
including yeast extract and vitamin B12
the nutrients (including yeast extract and vitamin B12)
were added in various concentrations and at different
depths.
Vitamin B12
Titanium citrate is added to reduce the central cobalt
atom in B12
both of these reagents are acceptable food additives
this biochemical system does not stimulate bacteria,
rather it causes in situ reductive dechlorination.
Vitamin B12
Titanium citrate is added to reduce the central cobalt
atom in B12
Pollutants
PCE
TCE
PCE
TCA
DNPALs
(dense non-
aqueous phase
liquids)
TCE
DNAPLs
Well type
patented in situ vertical
circulation column
patented in situ vertical
circulation column
Site & Scale
Fallen Naval Air
Station, Nevada. Test
site was a fire training
pit, test area is 20 ft.
deep, 25 ft. long and
has 5 treatment lanes
(each 10 ft. wide, and
separated by high
density polyethylene
sheet pile), ground
water is 8-10 ft. below
surface
series of in situ
column experiments
University of
Waterloo, Canada
series of in situ
column experiments
Reference
Civil Engineering,
1998
Lesage et al., 1996
Millar etal., 1997
Soreletal., 1998
September 30, 1999
13
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Table 2. Examples of Bioremediation Applications (cont'd)
Remediation Agents
Pollutants
Well type
Site & Scale
Reference
Molasses, injection of this carbohydrate solution
which is mostly sucrose, is degraded by heterotrophic
microorganisms. The degradation depletes the dissolved
oxygen in the ground water creating a reductive
environment
Carbon source (dilute molasses) periodically pumped
into the center of the contaminant plume
With in one month, strong reducing conditions existed
after heterotrophic microorganisms depleted soluble
oxygen in ground water
Reduction can occur:
by microbial processes involving species such
as Bacillus subtilis
by extra cellular reaction with by-products of
sulfate reduction such as H2S
Or by biotic oxidation of the organic
compounds including the soil organic matter
such as humic and fulvic acids
Hexavalent
Chromium
(<15ppm)
3 injection and 5 five
monitoring wells
Field demonstration
at a Midwest industrial
Nyer, 1996
September 30, 1999
14
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Table 3. Examples of Proprietary Nutrient Compounds for Bioremediation Applications
Manufacturer
Product Name
Nutrients
Contaminants
Source
Medina Agricultural
Products Co., Inc.
P.O. Box 390, Highway 90
West Hondo, Texas 78861
(830)426-3011
Medina Bio-D
One gallon weighs (10 Ibs.) & contains the following:
95, 367 mg Ammonia-N
95,367 mgNitrate-N
626,466 mg Organic-N
121,425 mgOrtho Phosphate
79,450 mg Potassium
136,200 mgHumic Material
Correspondence
with
manufacturer
Medina Agricultural
Products Co., Inc.
P.O. Box 390, Highway 90
West Hondo, Texas 78861
Medina Microbial
Activator
One gallon weighs 8.75 Ibs. & contains following:
4,782 mg Magnesium
l,392mg!ron(+2)
1,210 mg Zinc
2,361 mg Sulfate
14,710 mg Chloride
Correspondence
with
manufacturer
Homer & Co.
26197 Carmelo Street
Camel, CA 93923
(831)-620-0544
MaxBac
consists of a (resin coated) granule containing:
Ammonium nitrate
Phosphorus
trace inorganic nutrients
vitamins
the complete structure is referred to as a Prill and is
manufactured in two release profiles (3-4 months and
6-7 months) depending upon resin coating
concentrations used depends upon naturally
present soil nutrients(nitrate-nitrogen, ammonium-
nitrogen, & ortho-phosphate)
Organic wastes:
gasoline, diesel
fuel, crude oil,
pesticides,
creosote, and
pentachlorophenol
Manufacturer
literature
September 30, 1999
15
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Table 3. Examples of Proprietary Nutrient Compounds for Bioremediation Applications (cont'd)
Manufacturer
Ecology Technologies
International, Inc.
Product Name
FyreZyne
nontoxic by USEPA
recommended test for
marine vertebrate and
invertebrate forms, and non
toxic by ingestion or
inhalation in various
organisms.
Nutrients
FyreZyne (multifactoral aqueous liquid)
source of :
Bacterial growth agents
Extracellular enzymes
Bioemulsifiers/surfactants which are biodegradable
can be diluted 4, 5, and 6% for bioremediation
enhancing agent
Contaminants
Petroleum, partially
oxidized
contaminants
Source
Manufacturer
literature
September 30, 1999
16
-------
Table 4. Examples of Flushing Agents and Their
Application
Flushing Agents
Clean Water
Surfactants
Water/Surfactants
Co-solvents
Acids
Bases
Reductants/Oxidants
Contaminants Targeted
High solubility organics; soluble inorganic salts
Low solubility organics; petroleum products
Medium solubility organics
Hydrophobic contaminants
Basic organic contaminants, metals
Phenolics, metals
Metals
Source: RTDF, 1997
Nonaqueous phase liquids (NAPLs), which include dense nonaqueous phase liquids and light
nonaqueous phase liquids (LNAPLs), are not removed effectively with conventional pump-and-treat
remediation technologies. Injecting co-solvents (water plus a miscible organic solvent) into contaminated
ground water aids in dissolving both DNAPLs and LNAPLs. Co-solvents can be effective in remediating
NAPLs by increasing contaminant solubility in ground water. Once the co-solvent has begun to solubilize the
contaminant, ground water can be pumped to the surface for further treatment. Co-solvent remediation agents
can be used alone or in conjunction with surfactants. See Table 5 for examples of co-solvent applications.
Surfactants (surface- active-agents^ work in much the same manner as co-solvents. Surfactants
increase the solubility and/or mobility of NAPLs. However, unlike co-solvents, surfactants work by forming
microemulsions of surfactant micelles that surround contaminant molecules, as well as decreasing the interfacial
tension and capillary forces binding contaminants to porous aquifer materials. Thus, by increasing the solubility
of the NAPLs, surfactants enhance pump-and-treat technology and allow for extraction of the contaminant in
ground water. Most surfactants under investigation are used in detergents and food products. It is not
uncommon to investigate more than 100 surfactants before selecting a remediation agent for a project
(CffiMHill, 1997; Jafvert, 1996). This study did not identify documentation of actual full scale
demonstrations of this technology, but numerous pilot demonstrations are under way or have already been
completed. See Table 6 for examples of surfactant applications.
In situ flushing systems can also inject sugars, acids, and nutrients as remediation agents. The cycling
of reagents through the aquifer provides enhanced dispersal in the contaminant zone. Extracted ground water
can be analyzed and amended with additional reagents when necessary. For example, nutrient levels must be
monitored and amended to ensure optimal microbial activity to ensure degradation levels of contaminants. See
Table 7 for examples of in situ flushing application using sugars, acids and nutrients.
September 30, 1999
17
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Table 5. Examples of In Situ Flushing (Co-solvent Remediation) Applications
Remediation Agents
70% ethanol
12% n-pentanol
28% water
40, 000 L of mixture used over 15 days
either tert-butanol or isopropanol mixed with
n-hexanol
5,000-7,000 gallons of alcohol mixture
1,000 gallons of tert-butanol followed by
2,000 gallons of tert-butanol/hexanol mixture
followed by
4,000 gallons tert-butanol
Ethanol
washing solution:
alcohol = n-butanol
surfactant= Hostapur SAS 60ฎ
solvent = D-limonene and toluene
preliminary wash with polymer solution
Pollutants
NAPL
NAPL( 60 gallons)
SIAPLs:
1 decane
1 undecane
1 toluene
1,1,1 TCA
DNAPL
PCE
1 weathered refinery
)il wastes from the
1960s
1 chlorinated
DNAPLs:
. 1,1,2-TCA
naphtalene
Well type
one injection well
surrounded by four
recovery wells
Site & Scale
Hill AFB, Utah
Test 1 OPU 1
3 m. x 5 m. test cell 30 ft. deep
1994-1995
Hill AFB, UTAH
Cell 3, OPU1 test cell
3 m x m. x 30 ft. deep
summer 1996
Hill AFB, UTAH
Cell 3, OU-1
Dover AFB, Dover Delaware
Test Cell Dover 3
Pilot/Field Demonstration
Scheduled
Thouin San Pit, Quebec, Canada
4.3 m x 4.3 m test plot (0.075% of
contaminated site); 2 m thick silty sand
layer
Reference
Jafvert, 1996
Jafvert, 1996
RTDF, 1997
Roote, 1998
Marteletal., 1998
* Note: Some co-solvents are used in conjunction with surfactants.
September 30, 1999
18
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Table 6. Site Examples of In Situ Flushing (Surfactant Remediation) Applications
Remediation Agents
Triton X-100, 400 mg/1 at 3 gal/ min. for 30 days
Dowfax 8390, 60 mM, 540 gallons (3.8 wt %) at an
injection rate of 1 gal/min.
4.3 wt% Dowfax 8390
injected 2 PV* of water
then 10 PV of Dowfax solution
followed by 2 P V of water
3.6 wt % solution Dowfax 8390 and diphenyloxide
disulfonate mixture, same as Traverse City site
lOPVof surfactant, followed by SPVof water
Brij 97 (C18EO20) with n-pentanol as a cosurfactant
(makes a Winsor Type I single phase
microemulsion)
expect to use 2 PV of water, 5-7 PV surfactant/
cosurfactant, 2 PV of surfactant (alone), & 5 PV
water (PV = 2,500 gal.)
3% Brij 97, 2.5 % n-pentanol by weight in water, 9
PV of Bnj 97 & n-pentanol, then 1PV of Bnj 97 alone,
and finally 6.5 PV of water
produces a low viscosity oil-in-water
microemulsion on contact with NAPL
peristaltic pumps maintained a flow rate of 3.6 1/min
or 1 pore volume per day (1PV=5,500 1)
Pollutants
TCE at 1-5 mg/1
PCElOng/lJet
fuel
LNAPL
NAPL
NAPL
LNAPL (major
components)
l,3,5,tn-
methylbenzene
undecane
decane
Well type
3 injection wells 10 ft. apart
vertical circulation well, (two 5
ft. lengths of stainless steel
screen separated by 2 ft. of steel
casing)
single borehole well system
15 multilevel samplers, 3
extraction wells and 4 injection
wells. Injection and extraction
wells were screened from 4.9 m to
7.9 m below ground surface with
0.25 mm slotted stainless steel
casing.
Site & Scale
Picatinny Arsenal, NJ
test site (6 months)
Coast Guard Station,
Traverse City Michigan
Field Test, June 1995
Hill AFB, Utah
Cell6,OU-l
Hill AFB, Utah
OPUl,Cell6
test cell 3 m x 5 m. x 30 ft.
summer 1996
Hill AFB, Utah
OPUl,Cell8
test cell 3 m. x 5 m. x 30 ft.
summer 1996
Hill AFB, Utah, OU1
sand and gravel aquifer
material
2.8 m x 4.6 m test cell which
penetrated into the clay
aquitard 3.7 m.
sheet pile enclosed test cell
July-August 1996
Reference
Jafvert, 1996
Jafvert, 1996
Knox, 1997
RTDF, 1997
Jafvert, 1996
Jafvert, 1996
Rhue et al., 1998
September 30, 1999
19
-------
Table 6. Site Examples of In Situ Flushing (Surfactant Remediation) Applications (cont'd)
Remediation Agents
an Aerosol OT/ Tween series surfactant mixture,
with added CaCl2
8% Aerosol MA (Sodium dihexyl sulfosuccinate)
and 4% isopropyl co-solvent, injected 2.5 PV
4% Aerosol MA
H,500ppmNaCl
air (added to the solution to create a foam that
could control mobility)
simultaneously inject air and 3.5 PV of surfactant
solution
cannot use alcohol with this system because it
degrade foam
4 wt% Aerosol MA
Co-solvent 4 wt% isopropyl alcohol
2wt%l:lNaClandCaCl2
0.5 wt% NajCO;,
l.lwt%NaHC03
0.5wt%Na20(Si02)3.22
0.01 wt% Chloramine T plus 1,000 mg/1 xanthan
gum
Sorbitan monoleate (U.S. FDA food-grade
additive)
Pollutants
NAPL
DNAPL
1,1,1,TCA
TCE
PCE
DNAPL
TCE
DNAPLs
TCE
some PCBs and
other chlorinated
solvents
Hydraulic oil
LNAPL
DNAPL(TCE)
Well type
Site & Scale
Hill AFB, Utah
Cell5,OPUl,
test cell 3 m. x 5 m x 30 ft.
summer 1996
Hill AFB, Utah
OU2
Hill AFB, Utah
OU2
April 1997 work completed
DOE Gaseous Diffusion Site
Portsmouth, Ohio
Pilot/Field Demonstration
completed
Hialeah County, Florida
Pilot/Field Demonstration
former industrial site
completed
U.S. DOE Gaseous Diffusion
Plant, Paducah, Kentucky
pilot/field demonstration site
Reference
Jafvert, 1996
RTDF, 1997
RTDF, 1997
Roote, 1998
Roote, 1998
Roote, 1998
* PV = pore volume
September 30, 1999
20
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Table 7. Examples of In Situ Flushing (Sugars, Acids and Nutrients) Applications
Remediation Agents
(Sugars)
Cyclodextrin (beta cyclodextrin)
10 pore volumes of 10% cyclodextrin
Complexing sugar (macromolecular solubilization)
(Acids)
Citric Acid (originally used at the site)
Now a proprietary compound is used.
(Nutrients)
Nutrients (organic fertilizers) dissolved in treated site
ground water
Pollutants
1,1,1-TCA
o-xylene
decane
undecane
DNAPL (PCE)
Arsenic
PCP
PAHs
LNAPL (diesel fuel 5%PCP)
Site & Scale
Hill AFB,Layton Utah
OU-lCell4
Dover AFB, Dover, Delaware
scheduled Pilot/Field Demonstration
Gulf Power Co, Lynn Haven Florida
Full Scale/ Commercial site
Montana Pole & Treating, Butte Montana
Full-scale/Commercial
in progress
Reference
RTDF, 1997
Roote, 1998
Roote, 1998
Roote, 1998
September 30, 1999
21
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In Situ Chemical Treatment
In situ chemical treatment may be accomplished with reaction such as oxidation or reduction. In situ
oxidation involves the injection of reagents to stimulate degradative chemical reactions with the contaminants in
the ground water. For example, in one application, hydrogen peroxide (H2O2) is injected with ferrous sulfate
to produce hydroxyl radicals. The hydroxyl radicals then oxidize the organic compounds into carbon dioxide,
water, and chloride ions (in the case of chlorinated hydrocarbons). In another application, hydrogen peroxide
and potassium permanganate (KMnO4) were used at a DOE site in Kansas City to eliminate VOCs, SVOCs,
and PCBs in conjunction with soil mixing (Cline et al, 1997). Hydrogen peroxide has been used to treat
DNAPLs, although it has only been effective with tretrachloroethylene (PCE) and trichloroethylene (TCE).
Oxidation may also be fostered by introducing ORCs. Other in situ oxidants include ozone and chlorine,
which are injected into the ground water as a gas. Examples of in situ oxidation applications can be found in
Table 8.
Chemical reduction may also be used to remediate ground water contamination. For example,
chromium (VI), a toxic and mutagenic from of chromium, may be reduced to chromium (HI), which poses a
lesser health concern. Iron (II) and iron (0) are traditionally used as reductants and recently calcium
polysulfide was proven to be more effective (Sabatini, 1997; Slosky & Company, 1998).
Air Sparging
Air sparging uses wells to inject compressed air into the subsurface to volatilize dissolved contaminants
with vapor pressures less than 1 mm Hg (USEPA, 1994). This technology focuses on contaminants that can
be evaporated when exposed to increased air flow. Air sparging can also be used to stimulate aerobic
microorganisms present in the subsurface environment by providing oxygen, by injecting either air or pure
oxygen. Oxygen levels in the ground water can reach 8 to 10 mg/1 if air is injected and as high as 40 mg/1 if
pure oxygen is injected (Piotrowski 1992). This type of system, may also be referred to as forced air
injection, in situ aeration, or biosparging (depending, among other things, on the specific characteristics of the
application).
Steam Injection
Steam injection is sometimes used to remove organic contaminants from ground water and soil. Pilot
tests and full-scale applications have used steam injection to remove heavy fuel oils (No.2 diesel fuel to No.6
fuel oil, with vapor pressures >1.0 mm Hg) and to aid in vapor extraction and separate phase pumping
(Dablow et al., 1995). Steam is injected into the subsurface through injection wells to stimulate volatilization of
the contaminants. The high temperatures of the steam alter the phase of the contaminants into recoverable
forms (a vapor phase, a separate liquid phase, and a dissolved aqueous phase). Steam also physically
displaces the various phases of the contaminants and aids in surface recovery for further treatment. Steam
injection can be effective in cases where viscous forces cannot be used to remove volatile or
September 30, 1999 22
-------
Table 8. Examples of In Situ Chemical Treatment Applications
Remediation Agents
Hydrogen peroxide(H2O2) 4,200
gallons incrementally injected
Ferrous sulfate
solution of acidified ferrous sulfate
heptahydrate (FeSO4 7H2O)
5661bs.Fe+2
867 Ibs. HC1
1,628 Ibs. NaOH
Potassium permanganate (KMNO4)
Hydrous pyrolysis / oxidation
Chlorine dioxide (C1O2)
Treated 650 rrrYday of ground water
with oxidant concentration of
72mg/l
Used C1O2 because potassium
permanganate and hydrogen peroxide
didn't have enough oxidation
capability.
Pollutants
DNAPL (593 Ibs.)
TCE,PCE
Hexavalent Chromium
75,000-100,000 gallons
contaminated water
pure phase TCE
DNAPLs
dissolved organic
components
Petroleum concentrations as
high as l.Omg/1
Over 80 organic pollutants
Pollution not detected
below 40m. of water table
Well type
1 ,700 yd3 overlaying soil
excavated to a depth of
approx. 8ft.
series of injection wells
and trellises
injection well 480 mm
diameter, 200 m. deep.
generator produced
2kg/h of mixed gases
mainly of C1O2 with small
amounts of C12, O3 and
H202
gases dissolved into
circulating fresh water
and injected at 106 m
through a spray head.
Site & Scale
Full scale demonstration
Savannah River Site, Aiken, SC
(64,000 cubic foot site)
Perched aquifer 10- 12ft. Below
grade(aquifer with geology isolating it
from other aquifers or water)
Portsmouth Gaseous Diffusion Plant
DOE's Subsurface Contaminant
Focus Area (SCFA)
Commercial wood treatment facility
inCA
DOE's SCFA
Zibo, China
Pilot study (9 days)
Karst aquifer 75- 150m. below ground
surface
Water table at test site 26 m. below
land surface
Reference
Jerome, 1997
Cline et al., 1997
Environmental
Engineering, 1995
Jerome, 1997
Cline et al., 1997
Jerome, 1997
Zhuetal., 1998
September 30, 1999
23
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Table 8. Examples of In Situ Chemical Treatment Applications (cont'd)
Remediation Agents
Pollutants
Well type
Site & Scale
Reference
ORC (oxygen release compound)
proprietary formulation of
magnesium peroxide
ORC reacts with water to form a
suspension of magnesium hydroxide
magnesium hydroxide is common
Milk of Magnesia.
Regenesis Bioremediation Products,
San Juan Capistrano, CA
Manufacturer
literature
Chapman, 1997
Morin, 1997
Geo-Cleanse Process
proprietary method and equipment
which injects
hydrogen peroxide,
aqueous solution ferrous sulfate
trace quantities of metallic salts a
catalyst formulation
Geo-Cleanse, Ramsey, NJ
Common organics
including:
chlorinated hydrocarbons
(including ethenes, ethanes,
andDNAPLs)
BTEX
fuel oil
aromatic solvents
plasticizers
coal tar,
pesticides
PCB's
patented methodology
and equipment using
patented mixing heads
which deliver reagents
under pressure via
specially designed wells.
Manufacturer
literature
Vitamin B12
Titanium citrate is added to reduce
the central cobalt atom in B12
both of these reagents are acceptable
food additives
this biochemical system does not
stimulate bacteria, rather is causes in
situ reductive dechlorination.
PCE, TCA
DNPALs
>TCE,
DNAPLs
patented in situ vertical
circulation column
series of in situ column
experiments
Lesage et al.,
1996
Millar et al., 1997
Soreletal., 1998
September 30, 1999
24
-------
semi-volatile contaminants trapped in the subsurface (Davis, 1998a). Table 9 provides examples of
applications of this remediation technology.
Permeable Reactive Treatment Systems
In some cases, the dimensions of treatment barriers are such that they meet the definition of an
injection well. Permeable reactive treatment barriers are usually constructed downstream of a contaminant
plume and reactive zones can be located throughout a contaminant plume or downstream of it. Contaminants
become immobilized or degraded as ground water naturally flows through the wall or zone. Physical,
chemical, and/or biological processes can be involved in remediating the contaminants. These processes can
include: precipitation, sorption, oxidation/ reduction, fixation, or degradation. Treatment walls can be
constructed of various compounds such as: metal-based catalysts, chelating agents, nutrients, slurry, and
oxygen release compound (Vidic and Prohland, 1996). Examples of permeable treatment barrier systems can
be found in Table 10.
4.1.2 Treated water
As indicated earlier, pump-and-treat systems have been applied extensively and successfully to aquifer
remediation. Different onsite treatment technologies may be used as part of these systems, depending on the
characteristics of the contaminants of concern, as well as onsite characteristics. Obviously, the composition of
the re-injected treated ground water varies from site to site. As a result, a comprehensive discussion regarding
the characteristics of the re-injected treated water is beyond the scope of this document. As an example,
Table 11 presents data for the influent and effluent (i.e., the injectate) from the operation of an air stripping
system at the U.S. Department of the Army's Pueblo Depot Activity in Pueblo, Colorado (USDOD, 1998).
The data show that the concentrations of contaminants of concern found in the contaminated aquifer are
consistently reduced to levels below primary drinking water quality standards in the effluent of the treatment
system, which is then re-injected.
The South Carolina Department of Health & Environmental Control (SCDHEC) reported the results
of injectate monitoring at a site where ground water hydrocarbon contamination was being treated using a
pump-and-treat system that consisted of air strippers and activated carbon units. For all monitoring events
during the period between November 1997 and September 1998, the quality of the injectate was consistently
below the permit discharge limits (Devlin, 1999a). Table 12 summarizes the monitoring results; for simplicity,
the table presents the range of influent and effluent concentrations over the period indicated.
4.1.3 Freshwater
As discussed in Section 2, one of the purposes of ARW is the formation of hydraulic barriers to
contain contaminant plumes. This study did not identify documentation of hydraulic barrier applications
permitted as ARWs. However, an example of such an application was identified, although it was permitted as
a different type of well.
September 30, 1999 25
-------
Table 9. Examples of Steam Injection Applications
Remediation
Agents
steam 270 million
pounds, 171-182ฐC
air and/or steam is
injected through the
hollow kellys while
augers drill
steam
pressure at
wellheads varied
from 3,500-14,000
kg/nf with a steam
temp, of 120 ฐC
steam flowrates at
7,200 kg/h were
required during initial
heating
Once soil reached
100ฐC, the flowrate to
maintain the temp
was 3,600 kg/h
Pollutants
creosote
500-5,000 ppm
VOC'sbelowa
shallow water
table <2 ft. below
ground surface
diesel fuel
between 190,000
and 400,000 L
Well type
1 1 injection wells surrounding the
free-phase creosote (80-100 ft. deep)
recovery through 7 centrally located
extraction wells
dual auger 35 ft. long, with hollow
kelly bars with 5 ft. diameter augers,
48 wells drilled
Site & Scale
Southern California's
Edison's Visalia, CA Pole
Yard, field scale operation
field scale operation (3
month)
treatment of 2,000 cubic
yards of saturated soil and
ground water
Huntington Beach,
California
ruptured product delivery
pipeline polluted a sand lens
12- 13 meter deep
(interbedded fine to medium
sand, silt and minor clays ) as
well as a perched water to a
depth of 13 feet
Effectiveness
80,000 gallons
recovered or destroyed
since starting in May
1997
1,200 Ibs.VOC's
removed from soil and
ground water,
contaminant, levels
reduced 70-80 %
After 22 months,
approx. 1 1 3,000 L of
diesel fuel was removed
(98% recovery)
Reference
Davis, 1998b
Hightower, 1998
Dablowetal., 1995
September 30, 1999
26
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Table 10. Examples of Permeable Treatment Barrier Systems
Remediation Agents
ORC (oxygen release compound)
54 kg of sand and ORC mixture placed
in each treatment well, for a total of
378kg
ORC used to stimulate aerobic
biodegradation
treatment ratio of 3 pounds of
oxygen to 1 pound of GRO and
BTEX.
Total of approximately l,0001bs.
ORC used
Pollutants
BTEX
BTEX cone, of 48
mg/1
GRO cone, up to
170 mg/1
Reactive Wall Type
7 wells 20 cm. diameter P VC wire
wrapped treatment wells 0.6 meters on
center,
total depth of 6. 1 m. with 1.5m.
screen extending on both well ends.
treatment "fence" consisting of 15
borings spaced 10 feet apart
Each boring contained 90 Ibs. of 65%
solids ORC slurry. Each boring was 4
5/8 inches in diameter and to an
approx. depth of 10 ft. below the water
table
Site & Scale
former gasoline storage site
Ontario, Canada
southwestern Washington State
retail gasoline station
Reference
Chapman et al.,
1997
Morin, 1997
September 30, 1999
27
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Table 11. UIC Report - Pueblo Depot Activity, Pueblo, Colorado
(April through June, 1998)
Influent Concentrations
Analyte
1 , 1 -dichloroethene
1,2- dichloroethene (cis)
1,2- dichloroethene (trans)
Trichloroethene
Total Chromium
4/2/98
ND
0.033
ND
0.055
0.0081
4/14/98
0.00060
0.030
ND
0.050
0.013
5/5/98
0.00086
0.036
0.00036
0.056
0.0082
5/20/98
0.00077
0.034
0.00036
0.055
0.0074
6/03/98
0.00067
0.031
0.00033
0.048
0.0091
6/16/98
0.00053
0.027
0.00034
0.041
0.0085
MCL
0.007
0.070
0.0001
0.005
0.1
Effluent = Injectate Concentrations
Analyte
1 , 1 -dichloroethene
1,2- dichloroethene (cis)
1,2- dichloroethene (trans)
Trichloroethene
Total Chromium
4/2/98
ND
0.0034
ND
0.0026
0.0083
4/14/98
ND
0.0037
ND
0.0028
0.010
5/5/98
ND
0.0028
ND
0.0017
0.0082
5/20/98
ND
0.0028
ND
0.0018
0.0074
6/03/98
ND
0.0032
ND
0.0020
0.0090
6/16/98
ND
0.0038
ND
0.0025
0.0080
MCL
0.007
0.0070
0.001
0.005
0.1
All concentrations in mg/1.
ND: non detect
Source: U.S. DOD, 1998.
September 30, 1999
28
-------
Table 12. SCDHEC, UIC Permit #149M - SCRDI
Bluff Road Ground Water Treatment System
(System Effluent Report - November 97 through September, 1998)
Analyte
Acetone
Benzene
Carbon tetrachloride
Chlorobenzene
Chloroform
1 , 1 -Dichloroethane
1 ,2-Dichloroethane
1 , 1 -Dichloroethene
1,2-Dichloroethene (total)
1 .2-Dichloropropane
Ethylbenzene
Methylene chloride
1 ,1 ,2,2-Tetrachloroethane
Tetrachloroethene
Toluene
1,1,1 -Trichloroethane
1 ,1 ,2-Trichloroethane
Trichloroethene
Xylene (total)
Total VOCs
Iron
Permit Discharge
Limit
1.100
0.005
0.005
0.100
0.021
0.005
0.005
0.007
0.070
0.005
0.700
0.017
0.0006
0.005
2.000
0.200
0.002
0.005
10.000
_ *
Treatment system
influent
BDL - 0.073
BDL - 0.009
0.037-0.100
BDL - 0.004
0.310-0.760
0.120-0.270
0.017-0.035
0.068-0.240
0.182-0.360
BDL - 0.0022
0.0017 -BDL
BDL -0.01 8
0.033-0.072
0.040-0.094
BDL -0.011
0.023-0.062
BDL - 0.003
0.050-0.110
BDL - 0.005
0.943-2.103
0.914-2.710
Treatment system
effluent = Injectate
BDL
BDL
BDL
BDL
BDL -0.001
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL
BDL -0.001
BDL - 0.012
All concentrations in mg/1
BDL: below detection limit
* Secondary MCL for iron: 0.300 mg/1
Source: South Carolina Dept. of Health & Environmental Control, 1998.
September 30, 1999
29
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The Petrotonics Freshwater Injection System (PFIS) is used to prevent migration of a plume in
Wyoming. The parameter used to characterize the plume was total dissolved solids (TDS) and the plume was
caused by uranium tailings facilities. The PFIS is designed to inject freshwater through a buried perforated
pipe into the contaminated aquifer creating a freshwater hydraulic barrier. The Land Quality Division of the
Wyoming Department of Environmental Quality regulated the PFIS as a salt water intrusion barrier well
(Lucht, 1999b).
4.2 Well Characteristics and Operational Practices
The selection, design, construction, and operation of ARWs depend on a wide range of site specific
factors, the selected remedial techniques and reagents, and the well system designs. The site specific factors
include: for soil subsurface geology, hydraulic gradients, intrinsic permeability, soil composition; for water -
- EH, pH, suspended solids, and cation (calcium, magnesium, iron, sodium, and potassium) and anion (chloride,
sulfate, phosphate and nitrate) concentrations, and reactivity of certain naturally occurring constituents present
in the aquifer to the chemicals introduced; and for dissolved contaminant properties solubility and vapor
pressure (FRTR, 1997). As a result of the wide range of variables that affect the operation of ARWs, it is
extremely difficult to generalize the operational practices of the different types of ARWs.
ARWs can be used to inject remediation agents at various depths, pressures, phases and
temperatures. For example, bioremediation and in situ oxidation remediation inject reagents directly into the
contaminated aquifer. Remediation agents can also be injected below the contaminated aquifer, as can be the
case for air sparging.
Temperature can play an important role in the selection of well construction materials for several types
of ARWs. For example, in situ oxidation chemical reactions can generate significant amounts of heat that
requires using heat resistant well materials. A steam injection well system must also be resistant to heat and
pressure.
Clogging is a potential threat to the effectiveness or long term operation of most ARWs. For example,
specific cations can precipitate out of solution when exposed to elevated levels of oxygen. Iron precipitation
can lead to clogging of air sparging wells and the injection well apparatus. Practices used to prevent
precipitation include lowering aquifer pH with acids to keep cations in solution or injecting chelating agents to
bind iron. Well systems can also be clogged with excessive biomass, resulting from microbial growth due to
biostimulation (Dahab, 1992). Mcrobiocides can be used to diminish bacterial growth at the well head.
Colloid materials have been suggested as possible materials that may clog pump-and-treat systems.
In many applications, nutrients or reagents are not injected continuously, but rather periodically and
often the frequency of injection depends on the development of the remediation process. Therefore, in such
cases, the frequency of monitoring may be set to be the same as the frequency of nutrient/reagent injection.
Maximum permissible concentrations may be established at the downgradient monitoring wells and operation
of the injection system may be conditioned to meeting those maximum permissible concentrations. An
operational condition may be such that the nutrient/reagent addition program would be reevaluated and
appropriate adjustments made to the concentration of the injectate and/or to the frequency of injection if
September 30, 1999 30
-------
downgradient monitoring well data indicate that the maximum permissible concentrations have been exceeded
(USEPA, 1998b).
As stated earlier, the description of well systems used in aquifer remediation applications presented in
this volume is not intended to be all inclusive. Some system designs are shown as examples of the application
of conventional and innovative technologies. The omission of other alternative system and designs is not meant
to imply that they are not useful or valid systems.
4.2.1 Pump-and-Treat Systems
"Pump-and-treat" is by far the most common technology used in aquifer remediation. The treatment
system is composed of four elements: an extraction well or system of wells, a water pumping system, an above
ground treatment system, and injection wells. "Pump-and-treat" systems can be used for hydraulic
containment of contaminant plumes and/or for the removal of dissolved contaminants from ground water.
Wells that extract water create hydraulic containment or capture zones (low hydraulic points to which nearby
water will flow). Pressure ridges are formed by the water that is introduced to the subsurface from injection
wells, which also cause an increase in water flow/velocity to the extraction wells. The specific numbers of
injection and extraction wells are dependent upon the remediation site (USEPA, 1996a). As indicated earlier,
"pump-and-treat systems have been widely and successfully used for aquifer remediation at numerous sites.
However, pump-and-treat technology has been proven to be ineffective in removing contaminants that:
are immiscible in water
have diffused into micro pores or zones within the aquifer material not accessible to substantial
water flow
sorb to subsurface materials
exist in heterogeneous subsurface environments.
In addition, a pump-and-treat system requires substantial infrastructure and expenses for installation and
operation (NRC, 1997).
4.2.2 In Situ Bioremediation
The delivery of bioremediation agents most often occurs through injection wells, and well construction
depends upon the type of agent being used. Bioremediation systems can be pump-and-treat systems that
cycle added nutrients or can be in situ systems that inject dissolved agents or gases in to the subsurface.
Horizontal and vertical injection wells have been used in bioremediation systems. Soil conditions can greatly
affect the levels of nutrients added to a system. Soil composition needs to be taken into account for
remediation since calcium, aluminum, iron, and lead can sequester injected nutrients in significant quantities
(Scalzi, 1992).
Examples of bioremediation wells that inject methane gas and gaseous nutrients are shown in Figures
1- 3. These figures are for an in situ bioremediation project that used horizontal wells for reagent delivery.
The horizontal and vertical sections of these wells were composed of an outer casing of steel with a smaller
September 30, 1999 31
-------
diameter steel tube through which injection occurred. The well systems horizontal sections were composed of
perforated steel tubing for gas injection and vapor removal.
4.2.3 In Situ Flushing
Pump-and-treat systems sometimes add reagents to the injected water to enhance the efficiency of
contaminant removal. In situ flushing improves contaminant removal by increasing contaminant
solubilization/emulsion formation and/or chemical reactions in each pore volume extracted. The extraction rate
must be larger than the injection rate of the co-solvent/ surfactants to ensure recovery. Wells involved in situ
flushing can be vertical, angled, and/or horizontal (Roote, 1997). Figure 4 is an example of the in situ flushing
system.
4.2.4 In Situ Chemical Treatment
Injection of oxidative agents for in situ oxidation may require the use of metal as compared to PVC
piping due to the heat that can be generated from chemical reactions. An example of a well system used for in
situ oxidation is provided in Figure 5. This well system is composed of steel piping of two lengths, both with
stainless steel screens at the pipe bottoms allowing for injection of the hydrogen peroxide and ferrous sulfate
mixture. The wells are surrounded with grout and contain bentonite seals above each of the stainless steel
screens. This system injects the remediation agents under pressure.
4.2.5 Air Sparging
Air sparging systems (also known as forced air injection, in situ aeration, or biosparging) use wells that
inject pressurized air into the subsurface to volatilize contaminants that are dissolved in the aquifer. These
wells are usually constructed of PVC or stainless steel pipe with diameters of 1 to 5 inches. The screened
area of the well where air escapes ranges in length from 1 to 3 feet (screens of longer length do not transport
air more efficiently because air usually escapes from the upper portion of the screen). Grouting of the well is
essential to prevent leaks and maintain proper system function (USEPA, 1994). Figures 6 and 7 provide
examples of air sparging treatment systems.
Vertical injection wells are used for deeper contamination (>25 feet) and in water tables (>10 feet).
Horizontal wells can be used for sites that require numerous sparging or extraction wells and at a site with a
shallow water table (<25 feet) (USEPA, 1994). The depth of the injection well is usually deeper than the
contaminated aquifer to allow for percolation of air upward through the aquifer.
September 30, 1999 32
-------
Figure 1. In Situ Bioremediation Using Horizontal Wells:
Overall System Design
U.S. Department of Energy; Savannah River Site, South Carolina
Compressed
Natural Gas
X
HCI
Injection point for
air/methane
Source: U.S. DOE, 1995
September 30, 1999
33
-------
Figure 2. In Situ Bioremediation Using Horizontal Wells:
System Configuration
U.S. Department of Energy; Savannah River Site, South Carolina
Line
Abandoned
Veil 18c2 are paired wells targeting contaminated '=m^f f ^ew^r
sands. They are serniparaliel in the subsurface, one
in the uadose zone and one in the saturated zone.
i Legend
Horizontal Horizontal well
well surface plan view
borehole subsurface
profile
Veil #2
(all data taken from Reference 6)
r Cross-Sectional View of Veil 12
Surface
/N
loTt
Vater Table
75ft
120
Instated in Saturated zone
Screen Length = 205 ft.
Diameter = 4.5 in.
rCross -Sectional View of Veil #1i
Sufface
Vater Table
176ft
120 fti
Installed in Saturated
Screen Length =310 ft.
Diameter a 2.4 in.
Source: U.S. DOE, 1995
September 30, 1999
34
-------
Figure 3. In Situ Bio remediation Using Horizontal Wells:
Horizontal Wells Close-up
U.S. Department of Energy; Savannah River Site, South Carolina
Well#1
Well
Ground Surface
' -'2 3/8 in diameter steel tubing
Top of pocket assembly at 7 ft
Pup joints and subassembly
8 5/8 in diameter steel surface casing
p. Inflatable pocker assembly
15 in diameter borehole
^Top of whipstock at 121.8 ft
""85/8 in diameter steel surface casing
Perforated steel tubing for screen
kick-off
point
at 25 ft
End of screen at 459 ft ^ ^
Bottom of whipstock 121.2 ft
r8 5/8 in diameter steel
surf ace casing
-Cement "baskets" 14 6t 15 ft
-Centralizer
i of screen at 25.12 ft
"Vhipstock window at 14 ft
'1 in diameter borehole
Ground Surface
75ft
61/2 in diameter borhole
41/2 in diameter stainless
steel wirewrapped screen
(0.010 in screening)
Bull-nose plug
caged in at 205 ftj
Bottom of whipstock at 31.2 ft
263 ft'
Source: U.S. DOE, 1995
September 30, 1999
35
-------
Figure 4. An Example of an In Situ Flushing System
FLUSHING
SOLUTION
EFFLUENT DISCHARGE
[TO POTW OF? SI IRFAOF
WATER]
X'
OROUND
SURFACE J>"
SURFICIAL
SOILS
MuJified fruni U.S. EPA O391!l and U.S. DeparLnienl uf Eneryy (,\ 335).
Source: Roote, 1997
s
CT
a
-<
e
i
tz
33
O
o
t-J
O
LOW MtKMtABILI I V AfJUl I AKL1
September 30, 1999
36
-------
Figure 5. An Example of an In Situ Oxidation Treatment System:
Geo-Cleanse Patented Process Flow Diagram
PUMPS (TVP.)
MR MONITORING VENTS
. ...
MECHANICAL
CIRCULATION
.; .- QO .
"' ''ฐ '
^i/lv '*>/.*' *.tMrr
W"i-ปi_ .-*.' ป >H!?1.^.
GEO-CLEANSE PATENTED
PROCESS FLOW DIAGRAM
September 30, 1999
37
-------
Figure 6. Example of an Air Sparging System
Typical Sparging Weft
Concrete
M
tobnway and
Supplied by
Compressor
2" Dia PVC (Schedule 40)
Flush Joint Threaded Pipe
Cement/Bentonite Grout
Bentonite Pellets
Fine Silica Sand
Silica Sand (as appropriate)
Schedule 40 PVC Well
Screen with D.D2D" Slot Size
Bottom Cap
Drawing noffo scs/e
Note:
The in situ sparging system consists of 30 two-inch diameter air sparging wells within a 3-foot long screened section
installed into a depth of approximately 25 to 30 feet, two 300 scfm blowers housed within the ground water
treatment shed, and buried manifold connecting the blowers and sparging wells.
Sparging will be performed at an air flow rate of between 10 and 30 scfm and a pressure of 12 pounds per square inch
at each well.
Source: FRTR, 1995
September 30, 1999
38
-------
Figure 7. Typical Oxygen Enhanced Bioremediation System For Contaminated
Ground Water (Air Sparging/Nutrient Enhancement)
Air blower
Injection well
Nutrient pH
adjust|nent adjuatpient
5-*r* a-*
Extraction well
Contaminated
groundwater
Vadose
zone
Saturated
zone
Submersible
"^ pump I
Source: RTDF, 1997
September 30, 1999
39
-------
Dissolved minerals in the aquifer being remediated need to be assessed carefully. Dissolved iron can
become oxidized from the increased oxygen flow and precipitate as a consequence. Precipitation can become
a major problem, and eventually clog injection wells. Air sparging is an appropriate technology to be
considered in soil types that have permeabilities which allow circulation of injected air (USEPA, 1994).
4.2.6 Steam Injection
Key elements of an injection system to produce and inject steam include a steam generator,
distribution system to the wells, the extraction system, and the collers/condensers for the extracted fluids
(Davis 1998a). Steam injection wells are frequently composed of steel casing, rather than PVC and fiberglass
which are less resistant to temperature and pressure extremes. Well casing cementing also requires
modification for steam injection because conventional well cements will not remain stable under high
temperatures. Cements with 30 to 60 percent of quartz silica or silica by weight and sodium chloride are more
stable to temperature extremes. Figure 8 presents an example of a steam injection well.
Factors to be taken into account for steam injection systems include steam injection rate, pressure,
temperature, and quality.3 Soil fracture pressure can be estimated as 1.65 psi per meter of depth below the
surface of the ground.
Equally important is the placement of wells. Well placement, in terms of the distance between injection
wells and in overall system configuration, is crucial to system efficiency. A small contaminant area maybe be
surrounded by injection wells and have extraction wells in the center of the area. Larger areas of
contamination usually require a pattern of injection and extraction wells. Distances of 1.5 meters between
wells have been used in pilot studies and spacings up to 18 meters have been used in full scale operations
(Davis, 1998a). See Figure 9 for examples of steam injection well placement.
Injection rates are dependent upon the distance between injection wells, the sweep efficiency of
injected steam, and the heat losses to over- and under-burden. Continuous steam injection has proven
effective in contaminant removal in pilot and full-scale demonstrations (Davis, 1998a).
4.2.7 Permeable Treatment Barrier Systems
Permeable treatment barriers can be installed in several different ways. A trench can be dug
downstream from a contaminant plume and backfilled with reactive material. This method can be used for
shallow reactive barriers. However, if the length of the trench is greater than its depth, it is not considered a
well. For sites with contaminant plumes at greater depths, treatment
3The injection pressure of steam is dependent upon the depth of injection. It is recommended that
steam pressure be as high as possible without exceeding the soil overburden pressure such that fracturing
occurs.
September 30, 1999 40
-------
Figure 8. Steam Injection Well
4" Schedule 40
pipe
18" Casing
Steam infection/
Electrical Heating
Stainless steel
injection screen
for upper and
lower steam
Grout
Bentonite
Stainless steel
electrode heating
screen
Gawwwj not to scale
Approx. 1 45 ft 'various layers of
depth sand, gravel, and
anode material
Source: FRTR, 1995
Figure 9. Common Steam Injection Well Patterns
\ ฐ A ฐ
;vc\/ \
0 M C ^ J
' '. ," \ ^>
ir' n V o "V
FM: Soct
\ J ,*"*
id o !rJi
( u > < u
la ii n b---a.
S:ver ฃpct
h cot on Wo I
PioducfoniAfc)!
^vc apct ond acvcn soot wdl pat.crrc jscc 'ot s".comfloocing
Source: Davis, 1998a
September 30, 1999
41
-------
walls require reinforcement with slurry or steel sheet pilings (Vidic and Pohland, 1996). Figure 10 shows an
example of the well construction of permeable treatment barriers.
Permeable reactive zones, such as systems that inject ORC into wells in a contaminated area, can be
created with a matrix of multiple injection points. The injection wells are basically created with tools used to
inject well grout. An example of a reactive zone is presented in Figure 11; such a system may consist of 10
wells, each with a 6 inch diameter and packed with ORC through the contaminant zone. The dynamics of the
barrier are governed by the amount of oxygen placed in the wells, in the form of ORC, and the oxygen release
rate.
Based on information from the states of Texas (Eyster, 1999b) and South Carolina (Devlin, 1999b)
and from USEPA Region 5 (Micham, 1999c) (which together, according to the inventory, represent
approximately 60 percent of the total estimated number of wells nationwide), it appears that permeable
treatment systems are not typically regulated as Class V wells. Only in South Carolina have such systems
been permitted as Class V wells, and in both states and the region, such permitting is considered on a case-
by-case basis. Based on the federal UIC regulatory definition of "fluid" and "injection well," beyond the
dimensions of a treatment wall, the type and physical state of the material placed in the treatment wall and the
manner in which that material is placed are some of the factors that would be considered to determine if a
Class V permit should be issued (e.g., a treatment wall filled with metal shavings or other solids may not be
considered an injection well, while a slurry treatment barrier system or an treatment wall with ORC may be
considered injection wells, according to the information provided).
4.2.8 Experimental Wells
Several state UIC programs identified injection wells being used to test innovative aquifer remediation
technologies as experimental wells. Typically, these wells are initially permitted as experimental wells by the
USEPA Region or state and, once the technology is proven and if the system is to continue operating, the
wells are reclassified and the respective permits modified (Micham, 1999d). The wells involve experiments of
in situ bioremediation, in situ chemical treatment, and air sparging. Table 13 summarizes information on the
injectate and well characteristics as well as the operational practices of the experimental wells at seven sites.
Figure 12 provides the schematic diagram of an upgradient injection well system of a pilot test at Power
Engineering Company, located in Denver, Colorado.
5. POTENTIAL AND DOCUMENTED DAMAGE TO USDWS
The potential for damage of USDWs associated with ARWs depends on site-specific factors (i.e.,
hydrogeology, the nature of the injectate and remediation technology, the nature of the contaminants to be
remediated, the quality of well construction, and the operating conditions of the remediation system). The fact
that the purpose of ARWs is beneficial (i.e., to improve or protect the quality of an aquifer as a unit) and that
implementation of an aquifer remediation system, as with any remedial measure, usually requires the approval
of appropriate state and/or federal regulatory agencies, suggests that this type of Class V wells poses a low
potential for contamination of USDWs. However, as with any system injecting substances at concentrations
September 30, 1999 42
-------
Figure 10. Example of a Permeable Treatment Barrier Well Construction
Perneile subsurfsee 8tlil caneirt-baitomte
tneamemu.au s-kny ซdll
2V F
r
K
B 9A
Msnitjrina 0"oundwa:er Floui
OIA V/ell " ^^
i \
BLilding I Cemsnt-bentmits
I slurry uual
CBWBJT BENTOMTE
KEY WALL
SHEETS DRIVEN INTC
CB KEi' ฅl/ALL3 LEFT N
PLACE
TRENCH PjOTES USED A?
TaiPO^/SiFY CMDER
WALS DU1IN3 BACKFILL
SCALE IN FEET
KFYFD 18" l5Rฅ SHEET PILES
IR3N
MTHtA jKAVtL
MUNIIUKINU Wfc.L
4" XrtlN.
2MIM.
KE^'ED 18"INT3 SLURRY
1MITH SHFFTR
Design Plan for the Pemeable Barrier Installed at the Intersil Facility,
Sunnyvae, CA, Showing (a) Plan View of Funnel-and-Gate System and
(b) Sictbnal Viev/Throjgh the Gats
Source: Szerdy et si., 1996
September 30, 1999
43
-------
Figure 11. Example of a Permeable Treatment Zone
ORC OXYGEN BARR ER
~:j uissoiฅea-Phas
!:>:!: Hydrocarbon
ORC Socks in the Well
Source: Regenesis, Inc., Manufacturer Literature.
September 30, 1999
44
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Table 13. A Summary of the Well Characteristics and Operational Practices of
Experimental ARWs
Site & Scale
Remediation Agents
Pollutants
WeU type
Operational Practices
Reference
Stevens Point
Municipal Water
Dept, WI
ORC, consisting of a
proprietary of:
magnesium oxide (MgO)
magnesium dioxide (MgC
magnesium
hydroxide (Mg(OH)2)
sodium hypochlorite
(NaOCl) solution
manganese
2)
in situ
bioremediation
The system consists of 9 wells
situated around a municipal water
supply well in Stevens Point.
Phase I: 470 Ibs of 10 % mixture (as
O2) of ORC; injection rate 5.2
Ibs/day, 2 days/week for 24 weeks.
Phase II: 83 Ibs of 5.6% NaOCl
injected at a rate of 9.3 GPD, 2
days/week for 24 weeks.
Wells approved for 1-year operation
Wells subject to WI Admin. Code if
standard areexceeded.
Monitoring for disinfection
byproducts including total
trihalomethanes (TTHMs) and total
haloaceton acids (THMAs)
SPWSTD, 1998
UWSP, 1999
WDNR, 1998
City of Bay
Minette Utilities,
AL
sodium hypochlorite
(NaOCl) and water
bacteriological
contamination
in situ
bioremediation
Five wells around the City of Bay
Minette Utilities Board No. 5 drinking
water production well
Approx. 5,000 gallons of a 0.2%
solution of NaOCl injected into the
wells once a month
Monthly monitoring reports
submitted to Alabama Dept. of
Environmental Management
Concern for formation of
trihalomethanes (THMs)
City of Bay Minette, 1999
USEPA Region 8,1999
September 30, 1999
45
-------
Table 13. A Summary of the Well Characteristics and Operational Practices of
Experimental ARWs (cont'd)
Site & Scale
Remediation Agents
Pollutants
Well type
Operational Practices
Reference
Savannah River
Site, Aiken, SC
a gas mixture
consisting of air,
methane, nitrogen (as
nitrous oxide, N2O),
phosphorous (as
triethyl phosphate
(C2H5)3PO), and helium
TCE
air sparging
The well system consisted of 3 gas
sparge wells, a gas extraction well,
and 14 nested ground water
monitoring points at various points in
the saturated and unsaturated zones
The gas mixture injected into the
sparge wells consisted of 15 standard
ftVmin of air blended with 4%
methane, 0.07% N20,0.007-0.01%
(C2H5)3PO, and 1.0% helium injected
as a tracer gas. Injection took place 8
hours a day for six consecutive days
Brigmonetal., 1998
North Carolina
State University
In Situ
Bioremediation
Research Projects,
NC
nutrients and a NaCl
tracer
aromatic
hydrocarbons
in situ
bioremediation
Three experimental ARWs with a total
of 14 wells. Each well is approx. 17
feet deep, with 2-inch inner stainless
steel casing diameter and 24-inch
outer steel casing diameter; 6-inch
diameter concrete pad and 18-inch
bentonite seal
Each well is equipped with sampling
ports to sample injectate and ground
water quality
NCDENR, 1999
September 30, 1999
46
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Table 13. A Summary of the Well Characteristics and Operational Practices of
Experimental ARWs (cont'd)
Site & Scale
USGS
experimental
aquifer
remediation
study, Julesburg,
CO
SECOR
International Hudrofr;
Pilot Test, CO
Remediation Agents
denatured ethanol (EtOt
methanol
potassium bromide
(KBr) tracer
aqueous slurry
ctummsisting of sand,
guar (a food-grade
additive), a cross-link
breaker compound,
and borax
Pollutants
) nitrates
ground water
contaminants
Well type
in situ
bioremediation
(denitrification)
air stripping;
soil vapor
extraction
system
Operational Practices
The USGS proposed to install 10 to
12 injection wells around a former
drinking water production well.
Denatured EtOH in water was injected
at a concentration of 40 mg/1 (as
EtOH). A total of 2,000 gallons of
denatured EtOH was anticipated to be
injected over the course of the study.
The maximum injectate concentration
of MeOH from the denatured ethanol
was 5 mg/1 and the maximum
concentration of EtOH was 70 mg/1
(USGS1996a). The KBr tracer was
injected periodically at a
concentration of 25 mg/1 and it was
anticipated that a total of 5 kilograms
of KBr would be injected over the
course of the study
two shallow wells and two deep wells
are proposed for a hydraulic
fracturing pilot test
Reference
USGS, 1996a
Rubin, 1999
September 30, 1999
47
-------
Table 13. A Summary of the Well Characteristics and Operational Practices of
Experimental ARWs (cont'd)
Site & Scale
Power
Engineering
Company (PEC)
aquifer
remediation pilot
test, CO
Remediation Agents
calcium polysulfide
Pollutants
chromium (VI)
Well type
in situ reduction
reaction
Operational Practices
PEC proposed to inject 520 GPD of
calcium polysulfide into shallow
aquifer upgradient of facility through
10 pairs of 1-inch PVC wells at one
location. Injection rate of 0. 12 GPM
per well would achieve a 1%
concentration of polysulfide in the
aquifer. (Initial proposal of an
injection rate of 0. 1 8 GPM resulting in
a 3% concentration of polysufide was
rejected because of potential impact
to nearby river.)
Reference
Slosky & Company, 1998
USEPA Region 8, 1999
September 30, 1999
48
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Figure 12. Schematic Diagram of the Upgradient Injection Well System
Power Engineering Company Pilot Test, Denver, CO
Celtvary
Wanffald
UHtMIUAL
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above MCLs into the subsurface, the potential for damage to USDWs exists, especially in instances involving
voluntary cleanups that have not been adequately reviewed and approved by experts. Nevertheless, in some
USEPA Regions, voluntary cleanups are periodically the subject of inspections by state regulatory agencies
(Micham, 1999a). In addition, it is noted that improper plugging upon completion of cleanup would pose
potential risk to the ground water aquifer (Micham, 1999a).
For example, a failure in the treatment train of a pump-and-treat aquifer remediation system may
potentially lead to the injection of untreated ground water back into the contaminated aquifer, or to a different
formation, which may be a clean aquifer. This latter case was reported in an incident that occurred in Arizona,
which is described in Section 5.2. Proper design and operation of the system would prevent the occurrence of
such an incident and proper monitoring could ensure early detection and correction. In the event of an
incident, the potential for damage of USDWs depends on the site-specific factors mentioned above, as well as
on the magnitude of the incident itself (i.e., amount of contaminants injected, duration of the incident).
The purpose of injecting any reagent or nutrient into an ARW is precisely its participation in a physico-
chemical or a biological reaction within the affected aquifer. However, a variety of problems may occur,
which may interfere with that purpose. Such problems include short-circuiting through preferential paths (e.g.,
cracks and faults), which would prevent proper mixing. As a result, a reagent would not react or be
consumed completely, but rather, it would potentially be transported beyond the limits of the original
contaminant plume at concentrations that may exceed MCLs or SMCLs. Additionally, chemical precipitation
of soluble salts or excessive bacterial growth may lead to a loss of effective soil porosity, which would also
affect proper mixing and reduce the effectiveness of reactions. Furthermore, unexpected physico-chemical
and/or biological reactions between the injected reagents or nutrients and the existing contaminants or naturally
occurring constituents present in the aquifer may result in the generation of compounds not previously present,
which could potentially damage a USDW if they were not contained. These issues must be taken into
consideration during the design, implementation, and monitoring of any in situ aquifer remediation project.
Lastly, it is possible for injected steam to change the chemistry of the formation such that the potential
mobilization of previously immobile constituents could occur. This phenomenon has not yet been documented
to have occurred in full-scale ARW, but it has been observed in experimental ARWs.
5.1 Injectate Constituent Properties
The primary constituent properties of concern when assessing the potential for Class V ARWs to
adversely affect USDWs are toxicity, persistence, and mobility. The toxicity of a constituent is the potential of
that contaminant to cause adverse health effects if consumed by humans. Appendix D to the Class V Study
provides information on the health effects associated with contaminants found above drinking water standards
or health advisory limits in the injectate of ARWs and other Class V wells.
Persistence is the ability of a chemical to remain unchanged in composition, chemical state, and
physical state over time. Appendix E to the Class V Study presents published half-lives of common
constituents in fluids released in ARWs and other Class V wells. All of the values reported in Appendix E to
the Class V Study are for ground water. Caution is advised in interpreting these values because ambient
September 30, 1999 50
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conditions have a significant impact on the persistence of both inorganic and organic compounds. Appendix E
to the Class V Study also provides a discussion of mobility of certain constituents found in the injectate of
ARWs and other Class V wells.
As presented in Section 4.1 of this volume, a wide variety of constituents may be present in the
injectate of ARWs. It is fair to say that most reagents are not toxic (e.g., bioremediation nutrients), although
there are exceptions (e.g., certain organic compounds used as substrates in in-situ bioremediation and certain
co-solvents used as in-situ flushing agents). The instances when a constituent is present in the injectate of an
ARW at a concentration that may exceed the respective MCL or HAL are related to either the injection of
treated water, as in a pump-and-treat system, or to the injection of certain biological or chemical agents.
The universe of constituents that may be present in the injectate of pump-and-treat systems in the
United States is as extensive as the universe of constituents present in contaminated aquifers. Therefore, a
detailed discussion on the properties of those constituents is beyond the scope of this document. When the
contaminated aquifer receives the injectate (which is typical), the concentration of the constituents of concern
in the injectate will typically be lower, and at most equal (e.g., in the event of a system failure), to the
concentration in the untreated ground water. For the contaminants present in the injectate that are also present
in the untreated (pumped) ground water, the persistence and mobility characteristics of the contaminants
following injection is generally expected to be similar to those prior to pumping.
Reagents injected into remediation wells are generally mobile but not persistent. They are mobile by
design, because contact with the ground water to be treated is required for the system to be effective.4
Chemical reagents are generally not persistent in the ground water environment at a remediation site because
they react with the contaminants as part of the treatment process. Biological reagents (microbes) are
persistent as long as their food source (the contaminants) is available, but die and decay as the contaminant
concentrations are reduced.
5.2 Impacts on USDWs
ARWs that inject reagents or nutrients are operated as part of a specific aquifer remediation
technology. The conditions of the operation of such a system, including injectate properties, are generally
designed specifically to address a particular type of aquifer contamination (e.g., heavy metals, chlorinated
organic compounds). Overall, ARWs appear to be unlikely to contribute to ground water contamination. The
fact that, in general, aquifer remediation projects involve the operation of monitoring wells implies that
contamination incidents would be detected relatively quickly if they occur. Information related to
contamination incidents associated with the operation of ARWs is very limited (Cadmus, 1999). Only one
contamination incident in Arizona and two potential contamination incidents were reported, one in Kentucky
and one in Colorado, as described below.
4 Some reagents are more less mobile than others, of course. Mobility is taken into account in
system design in that the density of the injection well network will generally be greater for less mobile
reagents to ensure contact with all of the ground water to be treated.
September 30, 1999 51
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Some state regulators perceive that, in general, ARWs appear to be operating properly, based on
ground water monitoring results. In Ohio, even though the remediation systems that these wells are a part of
are not necessarily successful in remediating the subject aquifers, no contamination is known to have occurred
as a result of the operation of an ARW (Ohio regulator as reported in Cadmus, 1999).
Contamination Incident at the Hassayampa Landfill Superfund Site, Arizona. The Arizona
Department of Environmental Quality (ADEQ) reported an incident associated with an aquifer remediation
system (Cadmus, 1999). The Hassayampa Landfill Site is an unlined solid waste landfill site where hazardous
wastes were disposed of. Hazardous constituents leaked and impacted the underlying aquifer (Unit A). The
contaminants included chlorinated organics such as 1,1-dichloroethane (1,1-DCA); 1,1-dicholorethelyne (1,1-
DCE); 1,2-dichlorothelyne (1,2-DCE); 1,1,1-trichloroethane (1,1,1-TCA); and trichloroethelyne (TCE). A
pump-and-treat system using air stripping technology was set up. In March 1998, after several months of
operation of the treatment system, the air stripping unit failed (i.e., blower failure). However, the injection
system was not cut off, leading to the injection of untreated water into a deeper aquifer (Unit B), which was a
clean drinking water aquifer, over a period of almost ten hours. The estimated volume of contaminated water
that was injected into Unit B was approximately 4,275 gallons. ADEQ required monitoring of Unit B over a
four month period and re-design of the appropriate parts of the air stripping system to prevent further incidents
of contamination. The requested monitoring did not take place and ADEQ collected samples six months after
the incident occurred. The analyses of those samples did not detect any of the hazardous constituents that had
leaked from the landfill (Victor, 1999).
Potential Contamination During Surfactant Demonstration Project, Kentucky. A proposed
surfactant demonstration project to facilitate removal of TCE from ground water at the DOE's Paducah
Gaseous Diffusion Plant in Kentucky apparently resulted in migration of the surfactant, as reported by the
state's Division of Waste Management, Federal Facility Oversight Unit. During the demonstration, the
contractor was unable to recover all of the surfactant, some of which may have either moved down gradient or
was bound up in the matrix . Documentation of this case was not available. According to the Federal Facility
Oversight, potential causes for the failure of the demonstration included inadequate pumping rate and poor
preliminary geologic assessment prior to the demonstration. Nevertheless, after this incident, state regulators
remained interested in the application of surfactants to enhance the performance of pump-and-treat systems
(USEPA, 1995a).
Potential Impact of Sulfides at Power Engineering Company (PEC), Colorado, Pilot Test.
Calcium polysulfide was used as injectate for experimental in situ remediation of a shallow aquifer
contaminated with hexavalent chromium at the PEC facility. Both the ground water plume and the injection
zone were located near the South Platte River and the plume flowed in the direction of the river. USEPA
Region 8, the authorizing agency for this project, expressed concern that the injection of calcium polysulfide
could result in formation and migration of bisulfide ions (HS") and hydrogen sulfide (H2S) that are toxic to fish,
and are more toxic than the hexavalent chromium being remediated (USEPA Region 8, 1999). USEPA
Region 8 restricted injection to upgradient wells and made this a pilot study because of lack of adequate data
regarding persistence of reaction and dissociation products, particularly sulfides, after injection. At the PEC
site, the downgradient wells were very near to the South Platte River, and USEPA Region 8 wanted to
prevent sulfides from entering that stream and affecting the fish. USEPA Region 8 indicated that recent
September 30, 1999 52
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monitoring data from the PEC site show that sulfide was detected at several of the downgradient wells. The
injection rate of calcium polysulfide was reduced upon the detection of sulfides and since then sulfides have not
been detected. An additional problem was posed by the distribution of calcium polysulfide in the ground
water plume after injection. The injectate being denser than the ground water, it migrated to the bottom of the
plume and did not treat the chromium (VI) within the shallow portion of the plume. To address this problem,
the injectate is being diluted to reduce the density difference between the injectate and the ground water.
6. BEST MANAGEMENT PRACTICES
Best management practices that are applicable to ground water wells in general (e.g., selection of well
construction materials) obviously are also relevant to ARWs. Additionally, there are some BMPs that are
specific to the different types of ARWs.
6.1 Selection of Well Construction Materials
Materials used for ARWs are similar to those for water wells (Miller, 1996a). Possible choices of
well construction materials include:
fiber reinforces plastic (FRP);
fiberglass reinforced epoxy (FRE);
high density polyethylene (HDPE);
high temperature polyethylene (HTPE);
polyvinyl chloride (PVC);
stainless steel; and
porous polyethylene well screen.
Well materials must be compatible with the contaminants being removed and the remediation
technology being employed. Well materials have been shown to be reactive with specific types of
contaminants and ground water conditions. Stainless steel can be susceptible to leaching dissolved metals
under anoxic conditions. Creosote wastes pumped under pressure can weaken and cause PVC to fail, thus
creosote manufacturers recommend using steel. At a Superfund site in Texas, NAPLs caused a dedicated
PVC bailer to fuse with the PVC well casing material inside a monitoring well. This caused permanent damage
to the well and resulted in its abandonment. The use of an alkaline polymer surfactant (APS) at a creosote
contaminated waste site in Laramie Wyoming caused the complete destruction of PVC piping (McCaulou et
al., 1995).
Structural integrity of the well systems can be affected by the presence of NAPLs and high
concentrations of dissolved organic compounds in ground water (McCaulou et al., 1996). McCaulou and
Huling (1999) observed incompatibility between DNAPLs and bentonite. It was found the intrinsic
permeability of water hydrated bentonite was 46 to 2,640 times greater to DNAPLs, thus developing
desiccation cracks that detriment the well system. A chemical compatibility table for 73 chemicals and 28
commonly used materials was compiled based on laboratory tests and literature review (McCaulou et al., 1996).
September 30, 1999 53
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Many manufacturers recommend compatibility testing of well materials and equipment before
installation in a remediation system. However, even short-term testing may not indicate problems that would
only become evident over the extended duration of a remediation project (McCaulou et al., 1995).
Monitoring of well apparatus and equipment is thus highly appropriate to ensure minimizing system failures.
6.2 Compatibility with Site Conditions
An important consideration is the compatibility of aquifer remediation reagents with soil formation
minerals and contaminants - beyond the primary contaminants of concern - present in the ground water. A
potential reaction could result in the formation of complexes that may significantly reduce injection rates and
potentially impact contaminant removal rates. Aquifer clogging or plugging may occur as a result of changes in
aquifer characteristics due to an increase in iron precipitation or biomass accumulation caused by oxygen
injections (Miller, 1996b).
An additional site specific consideration is the compatibility of the site lithology and soil heterogeneity
with the mass transfer mechanisms associated with a particular aquifer remediation system. For example, air
sparging would be ineffective if applied at a site where a low-permeability layer overlies the aquifer. Similarly,
heterogeneous soils may cause channeling (preferential movement of a fluid - liquid or gas - through high
conductivity layers and potentially away from the area of contamination) (Miller, 1996a). When low
permeability clay lenses are present in an aquifer, the injected fluids often bypass these low permeability areas
and, therefore, do not contact the contaminants contained within them (USEPA, 1997a).
A report on state regulators' perspectives and experiences with the use of surfactant injection for
ground water remediation (USEPA, 1995a) presents some recommendations from a California regulator
regarding the most important technical considerations associated with ARWs. The considerations included the
following: (1) certainty of hydrogeologic control (for both surfactants and tracers) and (2) an understanding of
the interaction of the surfactant with the contaminant and the media. The monitoring system in place must be
able to address those two issues (USEPA, 1995a). Although these considerations specifically address the use
of surfactants, they are relevant, and may be extrapolated, to the operation of aquifer remediation injection
wells in general. The operation of monitoring wells is critical to establish whether the system is performing as
planned, without exceeding ground water quality standards beyond the area of contamination as a direct result
of the operation of the aquifer remediation injection well.
6.3 Well Systems
The following sections discuss some specific design, construction, and implementation issues and best
management practices of individual well systems.
6.3.1 Pump-and-Treat
In addition to site characterization, design and operation of a pump-and-treat system are key
components of the effective remediation of the system. As with any wells system, mathematical models are
developed to capture the hydrogeologic characteristics of the site and provide insights to the flow patterns of
September 30, 1999 54
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alternative treatment approaches. Optimization programming may be used to improve the system design
(USEPA, 1996a). Construction of extraction wells and injection wells may be carried out with subsequent
phases. Based on the monitoring results, the siting of subsequent wells could reflect the effectiveness of
contaminant removal. The contaminant removal and re-injection rates may be maximized by operating the
extraction and injection wells with an adaptive manner. It has been found that pulsed pumping can increase the
contaminant concentration in pumped ground water and, therefore, could be used to improve contaminant removal.
6.3.2 Air Sparging
A basic objective of the design of an air sparging system is to ensure that the aeration of the
contaminated soils occurs with little or no uncaptured volatization. The blower, vent wells, and piping can be
designed after making decisions about the required air flow system, air flow rates, and well spacing (USEPA,
1995b). In any case, the system must be carefully monitored to prevent possible health or safety violations,
which can include ground water mounding, vapor migration, or increased mixing which in turn increases mass
transfer of contaminants to ground water and vapor phases (Miller, 1996b).
6.3.3 Steam Injection
Injection pressure must be lower for shallow treatment zones than for deeper ones. High pressure can
cause fractures which allow steam to escape to the surface, or gravity can cause steam override, both of which
decrease efficiency. Special care must be taken in choosing materials to construct the steam injection well,
due to both the high pressures and temperature involved. Also, the water is generally treated to prevent scale
buildup in the generator. (Davis, 1998a).
6.3.4 Permeable Treatment Barrier Systems
Treatability studies and other field research can help determine the effectiveness of treatment walls.
Specifically, it is important to determine the reactive media to be used and the reaction zone size. Even with
the proper medium, the type of contaminant being treated may affect design choices. For example, radioactive
contaminants can accumulate on the surface of the reactive medium, resulting in the need to replace the
treatment wall.
Prolonging the life of the reactive medium is important to the success of this technology, and although
some techniques have been developed, there are still concerns that gradual loss of media reactivity will
decrease the effectiveness of the barrier. Barriers at depths of 10 - 30 m are currently not cost-efficient. To
increase the effectiveness of this technology, other technologies such as in situ soil washing are used in
combination with it (Vidic and Pohland, 1996).
7. CURRENT REGULATORY REQUIREMENTS
Several federal, state, and local programs exist that either directly manage or regulate Class V ARWs.
On the federal level, management and regulation of these wells fall primarily under the underground injection
control program authorized by the Safe Drinking Water Act (SDWA). Some states and localities have used
September 30, 1999 55
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these authorities, as well as their own authorities, to extend the controls in their areas to address endemic
concerns associated with ARWs.
Aquifer remediation injection wells potentially are subject to at least three categories of regulation.
First, a state's underground injection control program (or in direct implementation states the federal UIC
program) may have jurisdiction over such wells. In some states without UIC programs, the state's program
for ground water protection or pollution elimination program requirements may apply to remediation wells.
Finally, remediation wells are affected by federal and state remediation requirements, arising out of either
Superfund programs or corrective action programs under RCRA, the UST program, or other environmental
remediation programs. In the case of remediation programs, however, the regulatory requirements typically
address the selection of aquifer remediation as a cleanup alternative and establish the degree of required
cleanup in soil and/or groundwater, while deferring regulation of the injection wells used in the remediation to
other programs. In the case of voluntary cleanup programs, some concern exists because they may not be
approved or completed according to standards typical of cleanups overseen by a state or federal agency.
Nevertheless, in some USEPA Regions, voluntary cleanups are periodically the subject of inspections by state
regulatory agencies (Micham, 1999d).
7.1 Federal Programs
7.1.1 SDWA
Class V wells are regulated under the authority of Part C of SDWA. Congress enacted the SDWA to
ensure protection of the quality of drinking water in the United States, and Part C specifically mandates the
regulation of underground injection of fluids through wells. USEPA has promulgated a series of UIC
regulations under this authority. USEPA directly implements these regulations for Class V wells in 19 states or
territories (Alaska, American Samoa, Arizona, California, Colorado, Hawaii, Indiana, Iowa, Kentucky,
Michigan, Minnesota, Montana, New York, Pennsylvania, South Dakota, Tennessee, Virginia, Virgin Islands,
and Washington, DC). USEPA also directly implements all Class V UIC programs on Tribal lands. In all
other states, which are called Primacy States, state agencies implement the Class V UIC program, with
primary enforcement responsibility.
ARWs currently are not subject to any specific regulations tailored just for them, but rather are subject
to the UIC regulations that exist for all Class V wells. Under 40 CFR 144.12(a), owners or operators of all
injection wells, including ARWs, are prohibited from engaging in any injection activity that allows the
movement of fluids containing any contaminant into USDWs, "if the presence of that contaminant may cause a
violation of any primary drinking water regulation ... or may otherwise adversely affect the health of persons."
Owners or operators of Class V wells are required to submit basic inventory information under 40
CFR 144.26. When the owner or operator submits inventory information and is operating the well such that a
USDW is not endangered, the operation of the Class V well is authorized by rule. Moreover, under section
144.27, USEPA may require owners or operators of any Class V well, in USEPA-administered programs, to
submit additional information deemed necessary to protect USDWs. Owners or operators who fail to submit
the information required under sections 144.26 and 144.27 are prohibited from using their wells.
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Sections 144.12(c) and (d) prescribe mandatory and discretionary actions to be taken by the UIC
Program Director if a Class V well is not in compliance with section 144.12(a). Specifically, the Director must
choose between requiring the injector to apply for an individual permit, ordering such action as closure of the
well to prevent endangerment, or taking an enforcement action. Because ARWs (like other kinds of Class V
wells) are authorized by rule, they do not have to obtain a permit unless required to do so by the UIC Program
Director under 40 CFR 144.25. Authorization by rule terminates upon the effective date of a permit issued or
upon proper closure of the well.
Separate from the UIC program, the SOW A Amendments of 1996 establish a requirement for source
water assessments. USEPA published guidance describing how the states should carry out a source water
assessment program within the state's boundaries. The final guidance, entitled Source Water Assessment and
Programs Guidance (USEPA 816-R-97-009), was released in August 1997.
State staff must conduct source water assessments that are comprised of three steps. First, state staff
must delineate the boundaries of the assessment areas in the state from which one or more public drinking
water systems receive supplies of drinking water. In delineating these areas, state staff must use "all
reasonably available hydrogeologic information on the sources of the supply of drinking water in the state and
the water flow, recharge, and discharge and any other reliable information as the state deems necessary to
adequately determine such areas." Second, the state staff must identify contaminants of concern, and for those
contaminants, they must inventory significant potential sources of contamination in delineated source water
protection areas. Class V wells, including ARWs, should be considered as part of this source inventory, if
present in a given area. Third, the state staff must "determine the susceptibility of the public water systems in
the delineated area to such contaminants." State staff should complete all of these steps by May 2003
according to the final guidance.5
7.1.2 CERCLA - Superfund Cleanups
According to the Comprehensive Environmental Response, Compensation, and Liability Act
(CERCLA or Superfund), all remedial alternatives proposed for a Superfund site cleanup must be evaluated
using the nine criteria established in 40 CFR 300.430 (e)(3)(iii). The nine criteria for evaluation are the following:
Overall protection of human health and the environment;
Compliance with applicable or relevant and appropriate requirements (ARARs) in other
federal statutes or regulations;
Long-term effectiveness and permanence;
Reduction of toxicity, mobility, or volume through treatment;
Short-term effectiveness;
Implementability;
Cost;
State acceptance; and
Community acceptance.
5 May 2003 is the deadline including an 18-month extension.
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Under Superfund, requirements for evaluating the effectiveness of a remedy are site-specific and must
demonstrate that cleanup levels are achieved. This is generally consistent with RCRA requirements.
The purpose of the federal UIC program is to protect USDWs by prohibiting injections that may affect
water quality in USDWs. On a site-specific basis, a contaminated aquifer at a Superfund site may not serve as
USDW; under those circumstances, the UIC requirements may not apply to wells at a Superfund site
(USEPA, 1996b).
7.1.3 RCRA Corrective Actions
RCRA regulations relevant to corrective actions are addressed in 40 CFR 264.90-101. RCRA
requires that a ground water monitoring program be implemented to demonstrate the effectiveness of the
corrective action. RCRA corrective action measures may be terminated when ground water monitoring data
demonstrate that the contaminant levels are below the ground water protection standard.
Overall, the monitoring program must provide for the determination of the quality of background water
that has not been affected by leakage from a regulated unit. Additionally, that monitoring program must yield
ground water samples that represent the quality of ground water at the point of compliance, as established in
40 CFR 264.95. RCRA requires that ground water monitoring data be collected from background wells and
wells at the compliance point(s) and that the data be maintained in the facility operating record. Reporting
frequency is established by the Regional Administrator on a site-specific basis.
Under RCRA, the concentration limits in the ground water for hazardous constituents to be achieved
through corrective action are established in the permit (40 CFR 264.94(a)). RCRA allows the EPA Regional
Administrator to establish alternate concentration limits, provided that such limits are protective of human
health and the environment.
7.1.4 Underground Storage Tank (UST) Program
In the event of a release from a UST system, an implementing agency under the UST program (40
CFR 280.60) may require owners and operators to develop and submit a corrective action plan for
responding to contaminated soils and ground water. The implementing agency will ensure that the plan will
adequately protect human health, safety, and the environment. The factors that the implementing agency must
take into consideration, as appropriate, are as follows:
The physical and chemical characteristics of the regulated substance, including its toxicity,
persistence, and potential for migration;
The hydrogeologic characteristics of the facility and the surrounding area;
The proximity, quality, and current and future uses of nearby surface water and ground water;
The potential effects of residual contamination on nearby surface water and ground water;
An exposure assessment; and
Any information assembled in compliance with the UST program.
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40 CFR 280.66(c) establishes that owners and operators must monitor, evaluate, and report the
results of implementing the plan.
7.2 State and Local Programs
ARWs are found in many states, although based on the inventory presented in Section 3, a significant
portion of such wells are located in Kansas, Ohio, South Carolina, and Texas, which combined account for
approximately 65 percent of all documented ARWs. Selected state programs relevant to Class V wells were
reviewed in these four states, as well as five other states where substantial numbers of ARWs are found
(Arizona, California, Colorado, Nevada, and New Hampshire) to provide a geographical sample of
regulations for this type of well. Altogether, these nine states have a total of 7,198 documented ARWs, which
corresponds to approximately 70 percent of the documented well inventory for the nation based on a survey
conducted by the USEPA of the state and regional staff that administer the UIC programs (Cadmus, 1999).
In three of the nine states, Arizona, California, and Colorado, the USEPA Region directly implements
the UIC Class V program in the state. All three states, however, also have enacted state requirements that
can be used to regulate some ARWs. Arizona's Department of Environmental Quality issues Aquifer
Protection Permits under the state's aquifer protection program. This permitting authority does not cover
remedial actions for releases of hazardous substances, but does cover remediation of ground water
contaminated by petroleum. California's Water Quality Control Act creates Regional Water Quality Control
Boards that can prescribe requirements for discharges to ground water. Control boards issue site-specific
orders addressing sites using reinjection of treated ground water in a remedial action. Colorado's State
Engineer has authority to issue permits for well construction.
Of the six states that were reviewed with primacy for the UIC Class V program, individual permits are
also required for ARWs in Arizona, Kansas, Nevada, Ohio (required for those wells expected to exceed
MCLs), and South Carolina. ARWs may be authorized by rule in New Hampshire and Texas, although such
authorization is prohibited if the well causes or allows the movement of fluid that would contaminate a USDW.
In summary, individual permits are required for at least half of the documented ARWs.
No state has a direct regulatory prohibition on injection technologies for treating contaminated
aquifers. Until recently, a few states prohibited the use of injectants, either through bans on new Class V
injection wells or prohibition of injectants that did not meet ground water quality criteria. Currently, exceptions
are made for Class V remediation wells, and the states that prohibit injection of fluids that do not meet ground
water quality standards allow the use of site-specific criteria for contaminated aquifers (USEPA, 1996b).
However, in some cases, local regulations may prohibit any type of injection well (e.g., Merced County, California).
Attachment A of this volume presents a more detailed overview of the state programs relevant to
ARWs for the nine states summarized above.
September 30, 1999 59
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ATTACHMENT A
STATE AND LOCAL PROGRAM DESCRIPTIONS
This attachment presents an overview of the selected state programs relevant to ARWs for the four
states (Kansas, Ohio, South Carolina, and Texas) where, based on the inventory presented in this volume, a
significant portion of such wells are located. (The four states combined account for approximately 65 percent
of all documented ARWs). The overview also includes regulations from other states (Arizona, California,
Colorado, Nevada, and New Hampshire) selected to provide a geographical sample of regulations for this
type of well. Altogether, these nine states have a total of 7,198 documented ARWs, which correspond to
approximately 70 percent of the documented well inventory for the nation based on a survey conducted by the
USEPA of the state and regional staff that administer the UIC programs (Cadmus, 1999). The overview also
includes some examples of local programs.
Arizona
USEPA Region 6 directly implements the UIC program for Class V injection wells in Arizona. The
state has not enacted regulations pertaining to underground injection wells. The state has enacted a ground
water protection statute, however, that could address ARWs. Under the Arizona Revised Statutes (Title 49,
Chapter 2, Article 3 - Aquifer Protection Permits) any facility that "discharges" is required to obtain an Aquifer
Protection Permit (APP) from the Arizona Department of Environmental Quality (ADEQ) (ง49-241 .A). An
injection well is considered a discharging facility and is required to obtain an APP, unless ADEQ determines
that it will be "designed, constructed, and operated so that there will be no migration of pollutants directly to
the aquifer or to the vadose zone" (ง49-24l.B).
The APP requirements do not cover all remedial activities. Under the authority of ง49-250 of the
statute, the APP rules provide that they do not apply to activities conducted pursuant to a remedial action
order issued or a plan approved pursuant to งง49-281 through 49-287 and Rules 18-7-101 through 18-7-
110. Sections 49-281 through 49-287 and associated rules pertain to remedial actions for the release or
threat of release of hazardous substances. Under 49-282.06. A.4, ground water remedial actions may include
controlled migration, physical containment, and plume remediation. An injection well used to remediate
ground water that is not affected by hazardous substances (e.g., petroleum as defined in ง49-1001 is not a
hazardous substance in Arizona, except to the extent that certain constituents of petroleum are subject to 49-
283.02) is subject to the APP requirements. An injection well used to remediate hazardous substances is
subject to the remedial action requirements, which include preparation of a remedial investigation and feasibility
study and a remedial action plan.
The aquifer protection statute provides that an applicant for an APP permit may be required to
provide information on the design, operations, pollutant control measures, hydrogeological characterization,
baseline data, pollutant characteristics, and closure strategy. Operators must demonstrate that the facility will
be designed, constructed, and operated as to ensure greatest degree of discharge reduction and aquifer water
quality will not be reduced or standards violated. By rule, presumptive best available demonstrated control
technology, processes, operating methods or other alternatives, in order to achieve discharge reduction and
water quality standards, are established by ADEQ (ง49-243).
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An APP may require monitoring, recordkeeping and reporting, contingency plan, discharge limitations,
compliance schedule, and closure guidelines. The operator may need to furnish information, such as past
performance, and technical and financial competence, relevant to its capability to comply with the permit terms
and conditions. A facility must demonstrate financial assurance or competence before approval to operate is
granted. Each owner of an injection well to whom an individual permit is issued must register the permit with
ADEQ each year (ง49-243).
ADEQ designates a point or points of compliance for each facility receiving a permit. The statute
defines the point of compliance as the point at which compliance with aquifer water quality standards shall be
determined and is a vertical plane down gradient of the facility that extends through the uppermost aquifer
underlying that facility. If an aquifer is not or reasonably will not foreseeable be a USDW, monitoring for
compliance may be established in another aquifer. Monitoring and reporting requirements also may apply for a
facility managing pollutants that are determined not to migrate (ง49-244).
Permitting
The Arizona Aquifer Protection Permit Rules (Chapter 19, sub-chapter 9, October 1997) define an
injection well as "a well which receives a discharge through pressure injection or gravity flow." Any facility
that discharges is required to obtain an individual APP from ADEQ, unless the facility is subject to a general
permit. Permit applications must include specified information. This includes topographic maps, facility site
plans and designs, characteristics of past as well as proposed discharge, and best available demonstrated
control technology, processes, operating methods, or other alternatives to be employed in the facility. In order
to obtain an individual permit, a hydrogeologic study must be performed. This study must include a description
of the geology and hydrology of the area; documentation of existing quality of water in the aquifers underlying
the site; any expected changes in the water quality and ground water as a result of the discharge; and the
proposed location of each point of compliance (Rl 8-9-108).
Well Construction Standards
No injection wells may be constructed unless an APP has been completed and approved. Wells are
required to be constructed in such as manner as not to impair future or foreseeable use of aquifers. Specific
construction standards are determined on a case-by-case basis.
Operating Requirements
All wells must be operated in such a manner that they do not violate any rules under Title 49 of the
Arizona Revised Statutes, including Article 2, relating to water quality standards, and Article 3, relating to
APPs. Water quality standards must be met in order to preserve and protect the quality of waters in all
aquifers for all present and reasonably foreseeable future uses.
Monitoring Requirements
Monitoring generally will be required for ARWs to ensure compliance with APP conditions.
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Monitoring may include both injectate monitoring and monitoring of the injection site. The permit establishes,
on a case-by-case basis, alert levels, discharge limitations, monitoring, reporting, and contingency plan
requirements. Alert level is defined as a numeric value, expressed either as a concentration of a pollutant or a
physical or chemical property of a pollutant, which serves as an early warning indicating a potential violation of
any permit condition. If an alert level or discharge limitation is exceeded, an individual permit requires the
facility to notify ADEQ and implement the contingency plan (Rl 8-9-110).
Financial Assurance
An individual permit requires that a owner have and maintain the technical and financial capability
necessary to fully carry out the terms and conditions of the permit. The owner must maintain a bond, insurance
policy, or trust fund for the duration of the permit (R-18-9-117).
Plugging and Abandonment
Temporary cessation, closure, and post-closure requirements are specified on a case-by-case basis.
The facilities are required to notify ADEQ before any cessation of operations occurs. A closure plan is
required for facilities that cease activity without intending to resume. The plan describes the quantities and
characteristics of the materials to be removed from the facility; the destination and placement of material to be
removed; quantities and characteristics of the material to remain; the methods to treat and control the
discharge of pollutants from the facility; and limitations on future water uses created as a result of operations or
closure activities. A post-closure monitoring and maintenance plan is also required. This plan specifies
duration, procedures, and inspections for post-closure monitoring (R-18-9-116).
California
USEPA Region 9 directly implements the UIC program for Class V injection wells in California. The
California Water Quality Control Act (WQCA), however, established broad requirements for the
coordination and control of water quality in the state, set up a State Water Quality Control Board, and divided
the state into nine regions, with a Regional Water Quality Control Board that is delegated responsibilities and
authorities to coordinate and advance water quality in each region (Chapter 4 Article 2 WQCA). A Regional
Water Quality Control Board can prescribe requirements for discharges (waste discharge requirements or
WDRs) into the waters of the state (13263 WQCA). These WDRs can apply to injection wells (13263.5 and
13264(b)(3) WQCA). In addition, the WQCA specifies that no provision of the Act or ruling of the State
Board or a Regional Board is a limitation on the power of a city or county to adopt and enforce additional
regulations imposing further conditions, restrictions, or limitations with respect to the disposal of waste or any
other activity which might degrade the quality of the waters of the state (13002 WQCA). In some cases,
however, actions taken by regulatory agencies to protect or restore the environment are exempted from
otherwise applicable regulatory standards by California law.
Permitting
The WQCA provides that any person operating, or proposing to operate, an injection well (as defined
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in ง13051 WQCA) must file a report of the discharge, containing the information required by the appropriate
Regional Board, with that agency (13260(a)(3) WQCA). Furthermore, the Regional Board, after any
necessary hearing, may prescribe requirements concerning the nature of any proposed discharge, existing
discharge, or material change in an existing discharge to implement any relevant regional water quality control
plans. The requirements also must take into account the beneficial uses to be protected, the water quality
objectives reasonably required for that purpose, other waste discharges, and the factors that the WQCA
requires the Regional Boards to take into account in developing water quality objectives, which are specified in
ง13241 of the WQCA ((13263(a) WQCA). However, a Regional Board may waive the requirements in
13260(a) and 13253(a) as to a specific discharge or a specific type of discharge where the waiver is not
against the public interest (13269(a) WQCA).
Two examples of the requirements imposed by Regional Water Quality Control Boards on remedial
wells are the following. The California Central Valley Region in Order No. 96-138 and the North Coast
Region in Order No. 96-022 have both issued site-specific WDRs to sites using re-injection of treated ground
water in a remedial action. These WDRs have required geologic well logs, an engineering installation report,
certifications of proper installation, and have included maximum contaminant levels for the injectate and site-
specific monitoring and reporting programs. The Central Valley Board cited as authority the State Water
Resources Control Board Resolution No. 92-49, which provides that dischargers shall cleanup and abate the
effects of discharges in a manner that promotes attainment of background water quality or the highest water
quality that is economically and technically feasible. The Central Valley Board also cited its own Water
Quality Control Plan, which contains beneficial use designations and water quality objectives for all waters of
the Basin. The Board noted that the action to adopt waste discharge requirements for the facility is exempt
from the provisions of the California Water Quality Act, under California Code of Regulations 14, งง15308
and 15269. Section 15308 provides that actions by regulatory agencies for protection of the environment may
be exempted from certain regulatory processes, although relaxation of standards allowing environmental
degradation is not included in the exemption. Section 15269 provides that specific actions necessary to
prevent or mitigate an emergency are exempt from the requirements of the California Environmental Quality
Act.
The North Coast Regional Board cited CERCLA and the Department of Defense
Installation/Restoration Program as authority for the ground water cleanup system. It also cited the Board's
own Water Quality Control Plan for the Basin. Under the Public Resources Code, Section 21000 et seq. It
specified that the discharger was required to protect the environment to the greatest degree possible. Finally,
it noted that the discharge was exempt from the requirements of Chapter 15, Division 3, Title 23 of the
California Code of Regulations, pursuant to Section 251 l(b) because the Board had issued waste discharge
requirements, the discharge complied with the Basin Plan, and the wastewater does not need to be managed
as a hazardous waste. Section 2511 (d) provides that actions taken by or at the direction of public agencies
to cleanup or abate conditions of pollution or nuisance arising from unintentional or unauthorized releases of
waste or pollutants to the environment are exempt from certain Water Code requirements.
California counties also may enact requirements for ARWs. In some cases, they may prohibit certain
categories of wells entirely. For example, Merced County prohibits the construction of "recharge/injection
wells," defined in part as wells constructed to "introduce water, nutrients, and/or microbes for the purpose of
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subsurface contamination treatment" (Merced County Code 9.28.060.B and 9.28.020 S).
Colorado
USEPA Region 8 directly implements the UIC program for Class V injection wells in Colorado.
However, the State Engineer issues permits to construct wells. The Water Well Construction Rules (2
Colorado Code 402-2) apply to well construction contractors and drillers and to the construction of water
wells, test holes, dewatering wells, monitoring and observation wells, and well plugging and sealing
(abandonment). The rule specifies that excavations that do not penetrate through a confining layer between
aquifers recognized by the State Engineer may be designed, constructed, used, and plugged and sealed by
authorized individuals, as specified in the rule, who are not a licensed well construction contractor. Wells
constructed for sampling, measuring and test pumping for scientific, engineering, and regulatory purposes that
do not penetrate a confining layer may be constructed by an authorized individual.
Kansas
Kansas is a UIC Primacy State for Class V wells. It has incorporated the federal UIC regulations by
reference in Kansas Administrative Regulations (KAR) Article 28-46. ARWs also must meet the well
construction requirements for the state's water wells (KAR 28-30).
Permitting
ARWs are required to obtain a site-specific operating permit developed by the Department of Health
and Environment (KDHE) Bureau of Water.
Siting and Construction
Siting is dependant on location of the contaminant plume and is reviewed by KBER. Construction
logs are reviewed by KDHE. Remediation projects also must be approved by the Bureau of Environmental
Remediation (KBER).
Operating Requirements
Injectates are approved on a site-by-site basis. The permit requirements may include limits on
injection volume and pressure, injectate monitoring, and ground water monitoring to evaluate the migration of
contaminants. Requirements are determined in conjunction with the Bureau of Environmental Remediation or
Bureau of Waste Management.
Nevada
Nevada is a UIC Primacy State for Class V wells and the Division of Environmental Protection (DEP)
administers the UIC program. Aquifer remediation injection wells must satisfy Nevada's UIC program
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requirements, although the statute does not specifically define ARWs as Class V wells (445 A.849 NRS).
Nevada Revised Statutes (NRS) งง 445A.300 - 445A.730 and regulations under the Nevada
Administrative Code (NAC) งง 445A.810 - 445A.925 establish the state's basic underground injection
control program. The injection of fluids through a well into any waters of the state, including underground
waters, is prohibited without a permit issued by DEP, (445A.465 NRS), although the statute allows both
general and individual permits (445A.475 NRS and 445A.480 NRS). Furthermore, injection of a fluid that
degrades the physical, chemical, or biological quality of the aquifer into which it is injected is prohibited, unless
the DEP exempts the aquifer and the federal USEPA does not disapprove the exemption within 45 days after
notice of it (445A.850 NRS).
Regulations, particularly Chapter 445A NAC, "Underground Injection Control," define and elaborate
these statutory requirements. First, they provide that any federal, state, county, or municipal law or regulation
that provides greater protection to the public welfare, safety, health, and to the ground water prevails within
the jurisdiction of that governmental entity over the Chapter 445A requirements (445 A. 843 NAC).
Permits
The UIC regulations specify detailed information that must be provided in support of permit
applications, including proposed well location, description of geology, construction plans, proposed operating
data on rates and pressures of injection, analysis of injectate, analysis of fluid in the receiving formation,
proposed injection procedures, and corrective action plan (445A.867 NAC). The DEP may, however,
modify the permit application information required for a Class V well.
Siting and Construction
The state specifies, among other siting requirements, that the well must be sited in such a way that it
injects into a formation that is separated from any USDW by a confining zone that is free of known open faults
or fractures within the area of review. It must be cased from the finished surface to the top of the zone for
injection and cemented to prevent movement of fluids into or between USDW (445A.908 NAC).
Operating Requirements
Monitoring frequency for injection pressure, pressure of the annular space, rate of flow, and volume of
injected fluid is specified by the permit for Class V wells. Analysis of injected fluid must be conducted with
sufficient frequency to yield representative data. Mechanical integrity testing is required at once each 5 years,
by a specified method (445A913.5 NAC and 445A.916 - 445A.920 NAC).
Financial Responsibility
Class V wells may be required to provide a bond in favor of the state either equal to the estimated cost
of plugging and abandonment of each well or, if approved by DEP, a sum not less than $50,000 to cover all
injection wells of the permit applicant in the state (445 A. 871 NAC). However, if adequate proof of financial
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responsibility is presented, the bonding requirements may be waived or reduced.
Plugging and Abandonment
A plugging and abandonment plan and cost estimate must be prepared for each well, and reviewed
annually. Before abandonment, a well must be plugged with cement in a manner that will not allow the
movement of fluids into or between USDW (445A.923 NAC).
New Hampshire
New Hampshire is a UIC Primacy State for Class V wells. Part Env-Ws 410 of the New Hampshire
Administrative Code (NHAC) establishes the state's ground water protection program, which includes
underground injection registration. The state has established a policy that, unless due to a natural condition or
specifically exempted, all ground waters of the state shall be suitable for use as drinking water without
treatment, and that ground water shall not contain any regulated contaminant at a concentration greater than
the ambient ground water standards in Env-.Ws 410.05 (Env-Ws 410.03 NHAC). However, the rules
contain a specific exemption for a discharge from a ground water treatment system operating under and in
accordance with a ground water management permit (Env-Ws 410.08(a)(7)c.(l) NHAC).
Permitting
A ground water discharge permit is required to be obtained by certain categories of discharges.
However, a ground water treatment system operating under and in accordance with a ground water
management permit is considered to have a permit by rule and to be exempt from the requirements of Env-Ws
410.08 (Env-Ws 410.08(a)(7)c.(6)NHAC).
To obtain a ground water management permit, an applicant must submit the following (Env-Ws
410.18 NHAC):
A site investigation report that defines the nature, extent, and magnitude of contamination and
identifies threats to human health and the environment. The report must meet the requirements
of Env-Ws 410.22. The report must be reviewed and approved by the Department of
Environmental Services (DES).
A remedial action plan, prepared in accordance with Env-Ws 410.23 to remedy ground water
contamination and restore ground water quality to meet ground water quality criteria of Env-
Ws 410.03. The plan must be approved by DES.
Detailed permit application materials, including maps, site plans locating 16 specifically listed
types of features, including ground water contours, monitoring wells, and drinking water wells.
All monitoring results for the past 5 years.
Lists of reports on land use history, water quality, and hydrogeology associated with the site.
A detailed proposal for a water quality monitoring program.
Test pit data, specified in detail.
Well construction details.
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The requirements for the site investigation report (Env-Ws 410.22 NHAC) and the remedial action
plan (Env-Ws 410.23 NHAC) are specified in substantial detail. The latter requires a description of the
operational details of the remedial action, a plan of the design and construction details of the remedial system,
and delineation of the ground water management, among other requirements.
Every well that injects a fluid other than wastewater is required to register the underground injection
with DES. Inventory information must be supplied in the application for registration.
Ohio
Ohio is a UIC Primacy State for Class V wells. Regulations establishing the underground injection
control program are found in Chapter 3745-34 of the Ohio Administrative Code (OAC).
Permitting
Class V injection well definitions do not explicitly address ARWs (3745-34-04 OAC). However, any
underground injection, except as authorized by permit or rule, is prohibited. The construction of any well
required to have a permit is prohibited until the permit is issued (3745-34-06 OAC).
Injection into Class V injection wells is authorized by rule (3745-34-13 OAC).
However, a drilling permit and an operating permit are required for injection into a Class V injection well of
sewage, industrial wastes, or other wastes, as defined in ง 6111.01 of the Ohio Revised Code, into or above a
USDW (3745-34-13 OAC and 3745-34-14 OAC). Therefore, if the injectate is anticipated to exceed
primary drinking water standards, MCLs or Health Advisories, permits to install and operate the well will be require
Wells required to obtain an individual permit or an area permit fromOhio must submit detailed
information, including location, formation into which the well is drilled, depth of well, nature of the injectate,
and a topographical map showing the facility, other wells in the area, and treatment areas (3475-34-16(E) OAC).
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Siting and Construction
There are no specific regulatory requirements for the siting and construction of wells permitted by rule.
Wells required to obtain an individual permit must submit siting information and construction records.
Operating Requirements
There are no specific operating or monitoring requirements for wells permitted by rule. Injectate must
meet drinking water standards at the point of injection, unless a permit allows otherwise. Permitted wells will
have monthly and quarterly monitoring and reporting requirements (3745-34-26 (J) OAC).
Mechanical Integrity Testing
Not specified by statute or regulation.
Financial Responsibility
Not specified by statute or regulation.
Plugging and Abandonment
Under general standards for all wells, Ohio requires plugging and abandonment.
South Carolina
South Carolina is a UIC Primacy State for Class V wells. The state's underground injection control
program is implemented by the Department of Health and Environmental Control (DHEC). The UIC
regulations, found in Chapter 61 of the state regulations (SCR), divide Class V wells into two groups, with
ARWs, defined as "corrective action wells used to inject ground water associated with aquifer remediation,"
found in group (A). ((R61-87.10E.(l)(i)) The same requirements apply to ARWs as are applied to other
Class V(A) wells.
Permitting
ARWs, as Class V(A) wells, are prohibited except as authorized by permit (R61-87.10.E.(2)). The
permit application must include:
A description of the activities to be conducted.
The name, address, and location of the facility.
The names and other information pertaining to the owner and operator.
A description of the business, and proposed operating data, including average and maximum
daily rate and volume of fluid to be injected.
Average and maximum injection pressure, and source and an analysis of the chemical,
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physical, biological, and radiological characteristics of the injected fluid.
Drawings of the surface and subsurface construction of the well (R61-87.13.G(2)).
The movement of fluids containing wastes or contaminants into USDWs as a result of injection is prohibited if
the waste or contaminant may cause a violation of any drinking water standard or otherwise adversely affect
the health of persons (R61-87.5).
Siting and Construction
Siting and operating criteria and standards for Class V(A) wells require logs and tests, which will be
specified by DHEC in the permit, to identify and describe USDWs and the injection formation. Construction
standards are the same as those applied to drinking water wells.
Injection may not commence until construction is complete, the permittee has submitted notice of
completion to DHEC, and DHEC has inspected the well and found it in compliance
(R61-87.13U).
Operating Requirements
DHEC will establish maximum injection volumes and pressures and such other permit conditions as
necessary to assure that fractures are not initiated in the confining zone adjacent to a USDW and to assure
compliance with operating requirements (R61-87.13V). Operating requirements for Class V(A) wells are not
distinguished in the state regulations from operating standards for Class n and m wells (R61-87.14). Injection
pressure at the wellhead may not exceed a maximum calculated to ensure that injection does not initiate new
fracturing or propagate existing fractures in the confining zone adjacent to the USDW
Monitoring requirements will be specified in the permit. Monitoring requirements for Class V(A) wells
are the same as those for Class HI wells, and may include installation of monitoring wells in the injection zone
and adjacent zones as necessary to detect the dispersion and migration of injection fluids within and from the
injection zone. Monitoring of the fluid levels and water quality in the injection and monitor wells at specified
intervals and submission of monitoring results will be specified in the permit. However, reporting of monitoring
results to DHEC is required at least quarterly (R61-87.14.G and 1(1)).
Mechanical Integrity
Prior to granting approval for operation, DHEC will require a satisfactory demonstration of mechanical
integrity. Tests will be performed at least every 5 years (R61-87.14.G).
Plugging and Abandonment
A plugging and abandonment plan must be prepared and approved by DHEC (R61-87.12.B and
.15).
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Texas
Texas is a UIC Primacy State for Class V wells. The Injection Well Act (Chapter 27 of the Texas
Water Code) and Title 3 of the Natural Resources Code provide statutory authority for the underground
injection control program. Regulations establishing the underground injection control program are found in
Title 30, Chapter 331 of the Texas Administrative Code (TAG).
Permitting
Underground injection is prohibited, unless authorized by permit or rule (331.7 TAG). By rule,
injection into a Class V well is authorized, although the Texas Natural Resources Control Commission
(TNRCC) may require the owner or operator of a well authorized by rule to apply for and obtain an injection
well permit (331.9 TAG). No permit or authorization by rule is allowed where an injection well causes or
allows the movement of fluid that would result in the pollution of a USDW. A permit or authorization by rule
must include terms and conditions reasonably necessary to protect fresh water from pollution (331.5 TAG).
ARWs are not specifically defined as Class V wells, but the regulations state that Class V wells inject non-
hazardous fluids into or above formations that contain USDWs, and that the Class V wells are not limited to
listed categories (331.11 (a)(4) TAC).
Siting and Construction
All Class V wells are required to be completed in accordance with explicit specifications in the rules,
unless otherwise authorized by the TNRCC. These specifications are:
A form provided either by the Water Well Drillers Board or the TNRCC must be completed;
The annular space between the borehole and the casing must be filled from ground level to a
depth of not less than 10 feet below the land surface or well head with cement slurry. Special
requirements are imposed in areas of shallow unconfmed ground water aquifers and in areas of
confined ground water aquifers with artesian head.
In all wells where plastic casing is used, a concrete slab or sealing block must be placed above
the cement slurry around the well at the ground surface; and the rules include additional
specifications concerning the slab;
In wells where steel casing is used, a slab or block will be required above the cement slurry,
except when a pit-less adaptor is used, and the rules contain additional requirements
concerning the adaptor;
All wells must be completed so that aquifers or zones containing waters that differ significantly
in chemical quality are not allowed to commingle through the borehole-casing annulus or the
gravel pack and cause degradation of any aquifer zone;
The well casing must be capped or completed in a manner that will prevent pollutants from
entering the well; and
When undesirable water is encountered in a Class V well, the undesirable water must be
sealed off and confined to the zone(s) of origin (331.132 TAC).
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Operating Requirements
None specified. Chapter 331, Subpart H, " Standards for Class V Wells" addresses only construction
and closure standards (331.131 to 331.133 TAC).
Mechanical Integrity Testing
Injection may be prohibited for Class V wells that lack mechanical integrity. The TNRCC may require
a demonstration of mechanical integrity at any time if there is reason to believe mechanical integrity is lacking.
The TNRCC may allow plugging of the well or require the permittee to perform additional construction,
operation, monitoring, reporting, and corrective actions which are necessary to prevent the movement of fluid
into or between USDW caused by the lack of mechanical integrity. Injection may resume on written
notification from the TNRCC that mechanical integrity has been demonstrated (331.4 TAC).
Financial Responsibility
Chapter 27 of the Texas Water Code, "Injection Wells," enacts financial responsibility requirements
for persons to whom an injection well permit is issued. A performance bond or other form of financial security
may be required to ensure that an abandoned well is properly plugged (ง 27.073). Detailed financial
responsibility requirements also are contained in Chapter 331, Subchapter I of the state's UIC regulations
(331.141 to 331.144 TAC). A permittee is required to secure and maintain a performance bond or other
equivalent form of financial assurance or guarantee to ensure the closing, plugging, abandonment, and post-
closure care of the injection operation. However, the requirement, unless incorporated into a permit, applies
specifically only to Class I and Class IE wells (331.142 TAC).
Plugging and Abandonment
Plugging and abandonment of a well authorized by rule is required to be accomplished in accordance
with ง331.46 TAC (331.9 TAC). In addition, closure standards specific to Class V wells provide that closure
is to be accomplished by removing all of the removable casing and filling the entire well with cement to land
surface. Alternatively, if (1) the use of the well to be permanently discontinued, and (2) the well does not
contain undesirable water, the well may be filled with fine sand, clay, or heavy mud followed by a cement plug
extending from the land surface to a depth of not less than 10 feet. If the use of a well that does contain
undesirable water
is to be permanently discontinued, either the zone(s) containing undesirable water or the fresh water zone(s)
must be isolated with cement plugs and the remainder of the well boring filled with sand, clay, or heavy mud to
form a base for a cement plug extending from the land surface to a depth of not less than 10 feet (331.133 TAC).
September 30, 1999 71
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REFERENCES
Allen, Robert. 1999. Water Division, Department of Pollution Control, Arkansas. Telephone communication
with Jia Li, ICF Inc. April 26, 1999.
Alabama Department of Environmental Management (ADEM). 1998. Class V Underground Injection
Control Permit No. ALSI9902355, issued by the Alabama Department of Environmental Management to the
Utilities Board of the City of Bay Minette, Alabama. September 9, 1998.
Arizona Department of Environmental Quality (ADEQ). 1998. Best Available Demonstrated Control
Technology (BADCT) Guidance Document for Domestic and Municipal Wastewater Treatment, Draft.
Water Quality Division, Aquifer Protection Program.
Agency for Toxic Substances and Disease Registry (ATSDR). 1999. Public Health Statements. Atlanta,
GA: Agency for Toxic Substances and Disease Registry, Division of Toxicology. Available:
http://www.atsdr.cdc.gov/ToxProfiles [April, 1999]
Borden, R.C., R.T. Goin, C-M. Kao, C.G. Rosal. 1996. Enhanced Bioremediation of BTEX Using
Immobilized Nutrients: Field Demonstration and Monitoring (Project Summary). U.S. Environmental
Protection Agency, National Exposure Research Laboratory, EPA/600/SR-96/145. December 1996.
Brigmon, RL. et. al. 1998. Evaluation of Methanothrophic Bacteria during Injection of Gaseous nutrients for
In Situ Trichloroethylene Bioremediation in a Sanitary Landfill, 1998. Westinghouse Savannah River
Company Report WSRC-MS-98-00854, 1998. Published at WSRC Internet site
http://www.srs.gov/general/sci-tech/fulltext/ms9800854/ms9800854.html
California Regional Water Quality Control Board (CRWQCB). 1999. Waste Discharge Requirements for
Coast Wood Preserving Inc. CRWQCB North Coast Region. Order No.99 ID No. IB235004224.
The Cadmus Group. 1999. State-by-State Notebooks Compiling Results from the Class V Underground
Injection Control Study. February 1, 1999.
Chapman, S.W., B.T. Byerley, DJ.A. Smyth, D.M. Mackay. 1997. A Pilot Test of Passive Oxygen Release
for Enhancement of In Situ Bioremediation of BTEX-Contaminated Ground Water, Ground Water
Monitoring and Remediation (Spring 1997), p.93-105.
CH2MHILL (No date). Technology Practices Manual for Surfactants and Cosolvents, [Online]. Available
at: http://www.clu-in.com/aatdf/toc.htm [1997, February].
Chapman, S.W., B.T.Byerley, DJ.A. Smyth, D.M. Mackay. 1997. A Pilot Test of Passive Oxygen Release
for Enhancement of In Situ Bioremediation of BTEX-Contaminated Ground Water, Ground Water
Monitoring and Remediation (GWMR), Spring 1997, p.93-105.
September 30, 1999 72
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Civil Engineering. 1998. Air Force Tests Bioremediation Bugs. 63(3): 10-11.
City of Bay Mnette Utilities Board. 1999. Letter from Mr. Harry Still, Jr., General Manager of Utilities
Board of the City of Bay Minette, Alabama, to Mr. Scott Hughes, Alabama Department of Environmental
Management, Groundwater Division, Re: UIC Permit Number ALSI 99902355 Monthly Monitoring Report.
February 26, 1999.
Cline, S.R., O.R. West, R.L. Siegrist, W.L. Hoi den. 1997. Performance of in situ chemical oxidation field
demonstrations at DOE sites, in the proceedings of the ASCE Geoenvironmental Conference, Special
Publication No. 71, Minneapolis MN. October 5, 1997.
Cochran, M. 1999. Regional/state comments on the draft of the Aquifer Remediation Wells Information
Summary dated May 14, 1999. KS Department of Health & Environment.
Dablow, J., R. Hicks, D. Cacciatore. 1995. Steam Injection and Enhanced Bioremediation of Heavy Fuel
Oil Contamination. Applied Bioremediation of Petroleum Hydrocarbons, Conference Title: 3 International In
Situ and on Site Bioreclamation Symposium, April 24-27, 1995. Bioremediation. 3(6): 115-121.
Dahab, M.F., P.Y. Lee. 1992. Nitrate Reduction by In-Situ Bio-denitrification in Ground water.
Wat.Sci.Tech. 26(7-8): 1493-1502.
Davis, E.L. 1998a. Steam Injection for Soil and Aquifer Remediation. (Ground Water Issue). U.S.
Environmental Protection Agency, Office of Research and Development, Office of Solid Waste and
Emergency Response. EPA/540/S97/505. January 1998.
Davis, E.L. 1998b. Dynamic Underground Stripping for Creosote Removal, [Online]. U.S. Environmental
Protection Agency, Solid Waste and Emergency Response. Ground Water Currents, Issue No.28.
EPA/542/N98/006. Available: http://clu-in.com/gwc/gwccurre.htm [1998, July 1].
Devlin, Rob. 1999a. Ground Water Protection Division, South Carolina Department of Health &
Environmental Control (SCDHEC). Telephone communication with Jia Li, ICF Incorporated. April 21,
1999.
Devlin, Rob. 1999b. Ground Water Protection Division, SCDHEC. Telephone communication with Jia Li,
ICF Consulting. August 2, 1999.
Duba, A.G., K.J. Jackson, M.C. Jovanovich, R.B. Knapp, R.T. Taylor. 1996. TCE Remediation Using In
Situ, Resting-State Bioaugmentation. Environ. Sci. Technol. 30(6): 1982-1989. June 1996.
Environmental Engineering World. 1995. In Situ Process Converts Toxic Cr+6 to Non-tox Cr+3. 1(2): 38-39.
Eyster, Richard. 1999a. Texas Natural Resource Conservation Commission (TNRCC). Telephone
conversation with Jia Li, ICF Inc. April 28, 1999.
September 30, 1999 73
-------
Eyster, Richard. 1999b. TNRCC. Telephone communication with Jia Li, ICF Consulting. August 3, 1999.
Federal Remediation Technologies Roundtable (FRTR). 1997. Remediation Technologies Screening Matrix
and Reference Guide, Version 3.0. Available: http://www.frtr.gov
FRTR, 1995. Remediation Case Studies: Ground water Treatment. U.S. Environmental Protection Agency.
EPA/542/R95/003.
Hazen, T.C., B.B. Looney, M. Enzien, M.M. Franck, C.B. Fliermans, C.A. Eddy. 1993. In Situ
Bioremediation Via Horizontal Wells. Conference Title: Symposium on engineering hydrology, San Francisco,
CA, July 25-30, 1993, p. 862-867.
Hightower, M. 1998. In Situ Steam Stripping and Bioremediation Used in Shallow Media at Pinellas. U.S.
Environmental Protection Agency, Solid Waste and Emergency Response. Ground Water Currents, Issue
No.28. EPA/542/N98/006. Available: http://clu-in.com/gwc/gwccurre.htm [1998, July 1].
Hooker, B.S., R.S. Skeen, M.J. Truex, B.M. Peyton. 1994. A demonstration of in-situ bioremediation of
CCLJ at the Hartford Site. Conference title: 33. Hartford symposium on health and the environment:
symposium on it-situ remediation-scientific basis for current and future technologies, Nov. 7-11, 1994, p.
281-292.
Howard, P.H., R.S. Boethling, W.F. Jarvis, W.M. Meylan, E.M. Michalenko. 1991. Handbook of
Environmental Degradation Rates. Lewis Publishers.
Interstate Technology and Regulatory Cooperation (ITRC). 1998. Technical and Regulatory Requirements
for Enhanced In Situ Bioremediation of Chlorinated Solvents in Groundwater. ITRC Work Group, In Situ
Bioremediation Work Team. December 23, 1998.
Jafvert, C. 1996. Surfactants/Cosolvents (Technology Evaluation Report). Ground-Water Remediation
Technologies Analysis Center. TE-96-02. December 1996.
Jerome, K. 1997. In Situ Oxidation Destruction of DNAPL. Ground Water Currents, No.25. U.S.
Environmental Protection Agency, Solid Waste and Emergency Response. EPA/542/N97/004. Available:
http://www.clu-in.com/gwc/gwcl.htm#August 1997 [1997 September].
Knox, R.C., D.A. Sabatini, J.H. Harwell, R.E. Brown, C.C. West, F. Blaha, C. Griffin. 1997. Surfactant
remediation field demonstration using a vertical circulation well. Ground Water. 30(6): 948-953.
Leethem, J.T., R.E. Beeman, M.D. Lee, A.A Biehle, D.E. Ellis, S. Shoemaker. 1995. Anaerobic In Situ
Bioremediation: Injected Nutrient and Substrate Fate and Transport. Applied Bioremediation of Petroleum
Hydrocarbons, Conference Title: 3 International In Situ and on Site Bioreclamation Symposium, April 24-27,
1995, Bioremediation. 3(6): 271-280.
September 30, 1999 74
-------
Lesage, S., S. Brown, K. Millar. 1996. Vitamin B12-Catalyzed Dechlorination of Perchloroethylene Present
as Residual DNAPL. GWMR. 16(4): 76-85.
Lucht, Robert. 1999a. Water Division, Department of Environmental Quality, Wyoming. Telephone
conversation with Jia Li, ICF Inc. April 23, 1999.
Lucht, Robert. 1999b. Water Division, Department of Environmental Quality, Wyoming. Telephone
conversation with Alejandro Fernandez, ICF Inc. September 22, 1999.
Martel, R, PJ. Gelinas, L. Saumure. 1998. Aquifer Washing by Micellar Solutions: 3 Field Test at the
Thouin Sand Pit (L'Assomption, Quebec, Canada). J. of Contam. Hydrology. 30:33-48.
McCarty, P.L. 1997. Biodegradation of TCE through Toluene Injection. Ground Water Currents. No.25.
U.S. Environmental Protection Agency, Solid Waste and Emergency Response. EPA/542/N97/004.
Available: http://www.clu-in.com/gwc/gwcl.htm#August 1997 [1997, September].
McCarty, P.L., M.N. Goltz, GD. Hopkins, M.E. Dolan, J.P. Allan, B.T. Kawakami, T.J. Carrothers. 1998.
Full-Scale Evaluation of In Situ Cometabolic Degradation of Trichloroethylene in Ground water through
Toluene Injection. Environ. Sci. Technol. 32(1):88-100.
McCaulou, D.R., D.G Jewett, S.G Huling. 1995. Nonaqueous Phase Liquids Compatibility with Materials
Used in Well Construction, Sampling, and Remediation. U.S. Environmental Protection Agency, Office of
Research and Development, Office of Solid Waste and Emergency Response. EPA/540/S95/503. July
1995.
McCaulou, D.R., D.G. Jewett, S.G. Huling. 1996. Compatibility of NAPLs and Other Organic Compounds
with Materials Used in Well Construction, Sampling, and Remediation. GWMR. Fall 1996.
McCaulou, D.R, S.G. Huling. 1999. Compatibility of Bentonite andDNAPLs. GWMR. Spring 1999. Page
78-86.
Micham, Ross. 1999a. Responses to Peer Review. Change for Class V UIC Study, Aquifer Remediation
Wells: Information Summary dated May 16, 1999. USEPA Region 5 UIC Program.
Micham, R. 1999b. Telephone conversation with Jia Li, ICF Inc. April 26, 1999. USEPA Region 5 UIC
Program.
Micham, R. 1999c. Telephone communication with Jia Li, ICF Consulting. July 29, 1999. USEPA Region 5
UIC Program.
Micham, R. 1999d. Responses to Peer Review. Change for Class V UIC Study, Experimental Technology
Wells: Information Summary dated May 16, 1999. USEPA Region 5 UIC Program.
September 30, 1999 75
-------
Millar, K., S. Lesage. 1997. Bio-compatibility of the Vitamin B12-catalyzed Reductive Dechlorination of
Tetrachloroethylene. The Fourth International In Situ and On-Site Bioremediation Symposium. New Orleans.
April 28-Mayl, 1997.
Miller, R.R. 1996a. Horizontal Wells. Ground-Water Remediation Technologies Analysis Center.
Technology Overview Report TO-96-02. October 1996.
Miller, R.R. 1996b. Air Sparging. Ground-Water Remediation Technologies Analysis Center. Technology
Overview Report TO-96-04. October 1996.
Morin, T.C. 1997. Field Results on the Use of Solid-Phase Oxygen Supplementation Compounds to
Accelerate Intrinsic Biodegradation of GRO and BTEX in a High K Aquifer. Kennedy/ Jenks Consultants.
Proceedings of the Petroleum Hydrocarbons and Organic Chemicals in Ground WaterPrevention,
Detection, and Remediation Conference: Nov. 12-14, 1997, Houston, TX. pp. 683-691. Series: Ground
water management, Ground Water Publishing Co. 1997.
National Research Council (NRC). 1980. Drinking Water and Health. Volume 3. Washington, DC:
National Academy Press. 3: 278-279.
NRC. 1994. Alternatives for Ground Water Cleanup. National Academy Press, Washington, D.C.
NRC. 1997. Innovations in Ground Water and Soil Cleanup: From Concept to Commercialization. National
Academy Press. Washington, D.C.
North Carolina Department of Environment and Natural Resources (NCDENR). 1999. Application for
Permit to Construct and Use a Well for Injection (Class 5). Submitted to the NCDENR Underground
Injection Program by Dr. Robert C. Borden, North Carolina State University, June 1, 1998.
Nyer, E.K., S. Suthersan. 1996. In Situ Reactive Zones. GWMR. 16(3): 70-75.
Piotrowski, M.R 1992. In Situ Aquifer Treatments. Environmental Protection. 3(4):34, 36-38, 49.
Puls, R.W., R.M. Powell. July 1997. Permeable Reactive Subsurface Barriers for the Interception and
Remediation of Chlorinated Hydrocarbon and Chromium(VT) Plumes in Ground Water. U.S. Environmental
Protection Agency, National Risk Management Research Laboratory, EPA/600/F-97/008.
Remediation Technologies Development Forum (RTDF). 1997. Summary of the Remediation Technologies
Development Forum In Situ Flushing Action Team Meeting. RTDF In Situ Flushing Action Team. Hill Air
Force Base, Utah. May 8-9, 1997., Available: http://www.rtdf.org/public/flushing/minutes/Isf0597.htm [1998,
August 10].
RTDF Permeable Reactive Barriers Action Team, 1998a. LEAP Permeable Barrier Demonstration Facility,
Portland, OR. Available at http://rtdf.org/PRBSUMMS /Leapnm. htm [Sept.2, 1998)]
September 30, 1999 76
-------
RTDF Permeable Reactive Barriers Action Tea, 1998b. Nickel Rim Mine Site, Sudbury, Ontario Canada.
Available at http://rtdf.org/PRBSUMMS/Sudbury.htm (Sept.2, 1998)
RTDF Permeable Reactive Barriers Action Team, 1998c. Summary of the Remediation Technologies
Development Forum, Steering Committee Conference Call, 11:30A.M.-1:OOP.M. June 1. Available: http.www.rtd
Rhue, R.D., M.D. Annable, P.S.C. Rao. 1998. Lab and Field Evaluation of Single-Phase Microemulsions
for Enhanced In-Situ Remediation of Contaminated Aquifers. Available: http://www.ruf.rice.
edu/~aatdf/pages/spme.htm [1998, September 2].
Roote, D.S. 1997. In Situ Flushing (Technology Overview Report). Ground-Water Remediation
Technologies Analysis Center, TO-97-02.
Roote, D.S. 1998. Featured Technology Summary Report In Situ Flushing August 7, 1998 (Information
Report). Ground-Water Remediation Technologies Analysis Center. TI-98-01.
Sabatini, D.A., R.C. Knox, J.H. Harwell. August 1996. Surfactant-Enhanced DNAPL Remediation:
Surfactant Selection, Hydraulic Efficiency, and Economic Factors (Environmental Research Brief). U.S.
Environmental Protection Agency, National Risk Management Research Laboratory, EPA/600/S-96/002.
Sabatini, D.A., R.C. Knox, E.E. Tucker, R.W. Puls. 1997. Innovative Measures for Subsurface Chromium
Remediation: Source Zone, Concentrated Plume, and Dilute Plume. EPA Environmental Research Brief.
EPA/600/S-97/005. September 1997.
Scalzi, M. 1992. Bioremediation can produce predictable, reproducible results. Soil & Ground water
Cleanup. Available: http://www.sgcleanup.com/bio/biorem.html [1998, Sept. 15 ]
SECOR International Incorporated, 1999. Letter from Mr. Scott D. Andrews, P.E., Project Manager,
SECOR International Incorporated, to Mr. Bob Becker, USEPA Region 8, Underground Injection Control
Program, Re: Notification of Initiation of Hydrofracture Test Activities, Material Testing Laboratory Project,
CDOT Headquarters, Denver, Colorado, March 19, 1999.
Sewell, G.W., M.F. DeFlaun, N.H. Baek, E. Lutz, B. Weesner, B. Mahaffey. 1998. Performance
Evaluation of an In Situ Anaerobic Biotreatment System for Chlorinated Solvents. U.S. Environmental
Protection Agency, National Risk Management Research Laboratory, EPA/600/A98/041.
Sims, J.L., J.M. Suflita, H.H. Russell. 1992. In-Situ Bioremediation of Contaminated Ground Water (Ground
Water Issue). U.S. Environmental Protection Agency, Office of Research and Development, Office of Solid
Waste and Emergency Response, EPA/540/S92/003. February 1992.
Slosky & Company. 1998. Letter from Michael J. Galloway, P.G., Senior Hydrologist, Slosky & Company,
September 30, 1999 11
-------
Inc., to Ms. Valois Shea-Albin, USEPA Region 8, Underground Injection Control, Re: Class V Underground
Injection on Behalf of Power Engineering Company, Denver, Colorado, December 15, 1998.
Sorel, M., J.A. Cherry, S. Lesage. 1998. In Situ Vertical Circulation Column: Contaminant System for
Small-Scale DNAPL Field Experiments. GWMR. Winter 1998.
Stevens Point Water and Sewage Treatment Department (SPWSTD). 1998. Letter from Mr. Gregory R.
Disher, Administrator, Stevens Point Water and Sewage Treatment Department, to Mr. Richard Roth,
Wisconsin Department of Natural Resources, Bureau of Drinking Water and Groundwater, Re: University of
Wisconsin Stevens Point Proposal for Groundwater Manganese Remediation Testing, June 10, 1998.
Sutfm, J.A., D. Ramey. 1997. In Situ Biological Treatment of TCE-Impacted Soil and Ground water:
Demonstration Results. Environmental Progress. 16(4):287-296.
U. S. Department of Defense (USDOD). 1998. Letter to Mr. Ron Zbyd, USEPA, Region 8, from Phillip M.
Mayer, Acting Director, Environmental Management, Pueblo Chemical Depot, Department of the Army.
Subject: Quarterly Underground Injection Control Report for the Landfill Area - Ground Water Remediation
System, Pueblo Depot Activity, Pueblo, Colorado (EPA File #CO5000-03986). August 4, 1998.
U.S. Department of Energy (USDOE). 1995. Office of Environmental Management, Office of Technology
Development. In Situ Bioremediation Using Horizontal Wells. Innovative Technology Summary Report.
Available: http://www.em.doe.gov/plumesfa/intech /isbuhw /index.html.
U.S. Environmental Protection Agency (USEPA). 1984. National Secondary Drinking Water Regulations.
Publication No. EPA 570/9-76-000.
USEPA. 1986. Quality Criteria for Water. Washington, DC: Office of Water. EPA 440/5-86-001.
USEPA. 1987. Office of Water. September 1987. Report to Congress: Class V Injection Wells. EPA
570/987/006.
USEPA. 1998. National secondary drinking water regulations. 40 CFR ง143.
USEPA. 1992. Integrated Risk Information System (IRIS) Background Document 4: USEPA Regulatory
Action Summaries. Cincinnati, OH: Office of Research and Development. January 1992.
USEPA. 1994. Office of Solid Waste And Emergency Response. How To Evaluate Alternative Cleanup
Technologies At Underground Storage Tank Sites. EPA 510/B94/003. March 1994.
USEPA. 1995. Ecological Restoration: A Tool To Manage Stream Quality. Washington, DC: Office of
Water. EPA 841/F-95-007. Available at: http://www.epa.gov/OWOW/NPS/Ecology/
September 30, 1999 78
-------
USEPA. 1995a. Office of Solid Waste and Emergency Response, Technology Innovation Office. Surfactant
Injection for Ground Water Remediation: State Regulators' Perspectives and Experiences. EPA 542-R-95-
011. December 1995.
USEPA. 1995b. Manual: Bioventing Principles and Practice. USEPA, Office of Research and
Development. Washington, D.C. September 1995.
USEPA. 1996. Drinking Water Regulations and Health Advisories. Office of Water. EPA 822-B-96-002.
USEPA. 1996a. Office of Research and Development, National Risk Research Laboratory. Pump and Treat
Ground-Water Remediation: A Guide for Decision Makers and Practitioners. EPA 625/R95/005. July 1996.
USEPA. 1996b. Technology Innovation Office. State Policy and Regulatory Barriers to In Situ Ground
Water Remediation. EPA/542/R-96/001. March 1996.
USEPA. 1996c. Office of Solid Waste and Emergency Response, Technology Innovation Office. Summary
of the August 1996 Meeting of the Bioremediation Action Committee. Available at: http://www.clu-
in.com/bac.htm [1998, September 2].
USEPA. 1997a. Office of Research and Development, Office of Solid Waste and Emergency Response.
How Heat Can Enhance In-Situ Soil and Aquifer Remediation: Important Chemical Properties and Guidance
on Choosing the Appropriate Technique. EPA/540/S-97/502. April 1997.
USEPA. 1997b. Technology Innovative Office. Vendor Information System for Innovative Treatment
Technologies. VISITT Database. Version 6.0. Available: http://www.clu-in.com/ [December 1997]
USEPA. 1998. National Secondary Drinking Water Regulations. 40CFRง143.
USEPA, Region 8, 1998b. Situation Statement, UIC Class V Injection Well, Ground Water Remediation
Injection Well, Rule Authorization, Mustang-Shadow Mountain Gas Station (EPA File #CO5000-03793).
June 9, 1998.
USEPA. 1999. Drinking Water Regulations and Health Advisories. Publication No. EPA-822-b-96-002.
October 1996. Available at: http://www.epa.gov/OST/Tools/dwstds.html (1999).
USEPA. 1999. Integrated Risk Information System (IRIS). Cincinnati, OH: Office of Research and
Development, National Center for Environmental Assessment. Available:
http://www.epa.gov/ngispgm3/iris/index.html [April, 1999]
USEPA. 1999a. Integrated Risk Information System (IRIS). Cincinnati, OH: Office of Research and
Development, National Center for Environmental Assessment. Available:
http://www.epa.gov/ngispgm3/iris/index.html [March, 1999]
September 30, 1999 79
-------
USEPA. 1999b. National Primary Drinking water Regulations Technical Fact Sheets. Washington, D.C.:
Office of Water, Office of Ground Water and Drinking Water. Available at:
http://www.epa.gov/OGWDW/hfacts.html [March, 1999].
USEPA Region 8. 1999. State/Regional comments on the May 16 draft of the Experimental Technology
Wells report.
U.S. Geological Survey (USGS). 1996a. Letter from Mr. Peter B. McMahon, Ph.D., Hydrologist, USGS
Water Resources Division, Colorado District, to Mr. Ronald Zdyb, U.S. Environmental Protection Agency.
July 28, 1996.
University of Wisconsin, Stevens Point (UWSP). 1999. Personal Communication between Professor Byron
Shaw, University of Wisconsin at Stevens Point, and Mr. Michael Browning, ICF Inc. March 23, 1999.
Victor, W.R. 1998. Errol L. Montgomery & Associates, Inc. Assessment of Potential Impact of Blower
Failure Groundwater Remediation system Hassayampa Landfill EPA Superfund Site. A letter addressed to
Nadia Hollan (SFD-7-11), Remedial Project Manager, USEPA. March 23, 1998.
Vidic, R.D., F.G. Pohland. 1996. Treatment Walls (Technology Evaluation Report). Ground-Water
Remediation Technologies Analysis Center. TE-96-01. October 1996.
Williams, Jonathan. 1999. USEPA Region 10. Telephone conversation with Jia Li, ICF Consulting. August
3, 1999.
Wisconsin Department of Natural Resources (WDNR). 1998. Letter from Mr. William T. Rock, P.E., Chief,
Private Water Systems Section, Wisconsin Department of Natural Resources, Bureau of Drinking Water and
Groundwater, to Mr. Gregory R. Disher, Administrator, Stevens Point Water and Sewage Treatment
Department, Subject: Approval for underground injection of Oxygen Releasing Compound and sodium
hypochlorite for the purpose of performing in-situ manganese reduction demonstration testing in the area of the
Stevens Point Municipal Wellfield, June 30, 1998.
Zhu, H.K., L. Guanghe, L. Zhaochang. 1998. In Situ Remediation Of Petroleum Compounds In Ground
water Aquifer With Chlorine Dioxide. Water. Res. 32(5): 1471-1480.
September 30, 1999 80
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