United States Office of Ground Water EPA/816-R-99-014t
Environmental and Drinking Water (4601) September 1999
Protection Agency
The Class V Underground Injection
Control Study
Volume 20
Salt Water Intrusion Barrier Wells
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Table of Contents
Page
1. Summary 1
2. Introduction 2
3. Prevalence of Wells 4
4. Injectate Characteristics and Injection Practices 6
4.1 Injectate Characteristics 6
4.2 Well Characteristics 10
4.3 Operational Practices 14
5. Potential and Documented Damage to USDWs 14
5.1 Injectate Constituent Properties 14
5.2 Observed Impacts 15
6. Best Management Practices 15
6.1 Siting and Evaluation of Salt Water Intrusion Barrier Wells 15
6.2 Alternatives to Salt Water Intrusion Barrier Wells 15
6.2.1 Change in Pumping Patterns 15
6.2.2 Extraction Barrier 16
6.2.3 Subsurface Barriers 16
7. Current Regulatory Requirements 16
7.1 Federal Programs 16
7.1.1 SDWA 16
7.1.2 Other Federal Rules and Programs 18
7.2 State and Local Programs 20
Attachment A: State and Local Program Descriptions 22
References 28
September 30, 1999
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SALT WATER INTRUSION BARRIER 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 20, covers Class V salt water intrusion barrier wells.
1. SUMMARY
Salt water intrusion barrier wells are used to inject water into a fresh water aquifer to
prevent the intrusion of salt water. Control of salt water intrusion through the use of these wells
may be achieved by creating and maintaining a "fresh water ridge." This fresh water ridge may
be achieved with a line of injection wells paralleling the coast. Another method used to control
salt water intrusion is through the use of an injection-extraction system. Such a system may be
used to inject fresh water inland, while salt water intruded into the aquifer is being extracted
along the coast.
Waters of varying qualities are injected to create salt water intrusion barriers, including
untreated surface water, treated drinking water, and mixtures of treated municipal wastewater
and ground or surface water. Injectate typically meets primary and secondary drinking water
standards. Ground water monitoring and lexicological, chemical, and epidemiological studies
have found no measurable adverse effects on either ground water quality or the health of the
population ingesting the water, when the injectate was treated wastewater effluent.
Salt water intrusion barrier wells are drilled to various depths depending on the depth of
the aquifer being protected. They inject into fresh ground water aquifers used as drinking water
supplies that are in hydraulic connection with an extensive salt water body, such as a sea, a salt
lake, or an ocean.
No contamination incidents associated with the operation of salt water intrusion barrier
wells have been reported.
Because protection of drinking water supplies is the major goal of a salt water intrusion
barrier well and the injectate typically meets drinking water standards, salt water intrusion
barrier wells are unlikely to receive spills or illicit discharges of potentially harmful substances.
According to the state and USEPA Regional survey conducted for this study, there are
315 salt water intrusion barrier wells documented in the United States. The number of salt water
intrusion barrier wells in the nation is estimated to be greater than 609, but unlikely to be higher
than 700. All documented salt water intrusion barrier wells are located in California (308),
September 30, 1999
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Florida (1), and Washington (6). In addition, as many as 200 salt water intrusion barrier wells
are believed to exist in New York. There also may be some wells in New Jersey, which
indicated in its survey response that it has salt water intrusion barrier wells but did not provide
any numbers.
The statutory and regulatory requirements differ significantly among California, Florida,
Washington, and New York. In California and New York, USEPA Regions 9 and 2,
respectively, directly implement the UIC program for Class V injection wells. However, both
states have additional jurisdiction over salt water intrusion barrier wells through state regional
water quality control boards in California and state pollutant discharge elimination system
permits in New York. In contrast, Florida and Washington are UIC Primacy States for Class V
wells. Both of these states require individual permits for the operation of salt water intrusion
barrier wells.
2. INTRODUCTION
Salt water intrusion is a problem in some areas of the United States. It is a man-made
problem caused by excessive drainage of low lying coastal areas or, in some cases, the over
pumping of fresh ground water from aquifers that are in hydraulic connection with an extensive
salt water body, such as a sea, a salt lake, or an ocean.1 Other causes of salt water intrusion
include the destruction of natural barriers that separate fresh and salt water (e.g., construction of
salt water canals), which would enable salt water to advance inland and percolate into a fresh
water aquifer, and commercial and urban development of recharge areas, which reduces the
permeable land surface. The extent of intrusion depends on several factors, such as climatic
conditions, the aquifer properties, changes in seaward natural flow, barometric changes, tidal
effects, and human activities such as discharge and recharge wells (Kashef, 1986).
Figure 1 illustrates the situation that occurs when fresh water is withdrawn from an
unconfmed coastal ground water basin. The figure shows: (a) the natural equilibrium between
fresh and sea water; and (b) salt water intrusion into an aquifer resulting from ground water
withdrawal.
1 Most of this summary discusses salt water intrusion in coastal areas, which is generally defined
as a lateral movement of water. In non-coastal areas, most of the water quality deterioration is a result of
vertical migration (Bloetscher, 1999). Vertical migration only occurs as a result of some type of
withdrawal, generally pumping, and the solutions are very different to those employed to detain the salt
water intrusion that results from the lateral movement of water (Bloetscher, 1999).
September 30, 1999
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Figure 1. Hydrological Conditions in an
Unconfined Coastal Ground Water Basin
Extraction Field
in Basin p
Hydrological Conditions in an Unconfined Coastal Ground
Water Basin:
A-Not subject to Sea-water Intrusion
B--Subject to Sea-water Intrusion
Source: based on Atkinson, 1986
One method used to control salt water intrusion is artificial recharge. In this context,
artificial recharge refers to the injection of water into a low water quality or contaminated
aquifer with no intent to withdraw the injected water. The injected water then produces a
hydraulic
barrier that has the effect of a physical barrier to sea water intrusion. The hydraulic barrier is
created by raising the piezometric head of the fresh water aquifer and preventing the salt water
from moving inland. Hydraulic barriers are created with either recharge basins or recharge
wells.
"Salt water intrusion wells used to inject water into a fresh water aquifer to prevent the
intrusion of salt water into the fresh water" are considered Class V injection wells, according to
the existing UIC regulations in 40 CFR 146.5(e)(7). For the purpose of this study, salt water
intrusion barrier wells include those wells that inject mixtures of treated wastewater and ground
or surface water. Wells that inject treated wastewater only are addressed separately in the
sewage treatment effluent well summary, which is Volume 7 of the Class V UIC Study. In
addition, aquifer recharge and aquifer storage and recovery (ASR) wells, whose primary
objective is to replenish the water in an aquifer but may have salt water intrusion control as a
secondary objective, are addressed separately in Volume 21 of the Class V UIC Study.
September 30, 1999
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3. PREVALENCE OF WELLS
An estimated two-thirds of the continental United States is underlain by saline waters that
can intrude into fresh water supplies as a result of excessive drainage or over pumping. Thus,
salinity and salt water intrusion problems are not limited to coastal areas (Fairchild, 1985). Salt
water intrusion problems have been reported in almost every state in the continental United
States (Fairchild, 1985). Only three states, Colorado, Kentucky, and Tennessee, have not
reported any current or expected future salt water intrusion problems.
Fairchild (1985) reviewed areas that were both suitable for aquifer recharge and in need
of salt water intrusion prevention. Areas prone to salt water intrusion and areas with favorable
conditions for injection well operation were mapped separately and then overlaid. The
overlapping areas indicated that aquifer recharge has widespread applicability to solving both
ground water demand and salt water intrusion problems in coastal areas and the Central Plains
states. Coastal areas, which are more densely developed, tend to use injection wells. Because
the Central Plains states have more available open land, they tend to use recharge basins and
infiltration areas rather than injection wells. As open land area for recharge basins becomes
more scarce, however, injection of wastewater or surface water may become a more desirable
management option for creating salt water intrusion barriers (Fairchild, 1985).
For this study, data on the number of Class V salt water intrusion barrier wells 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 UIC Study. Table 1 lists the numbers
of Class V salt water intrusion barrier wells 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 salt water intrusion barrier wells.
As shown in Table 1, there are currently a total of 315 salt water intrusion barrier wells
known to exist in the United States (i.e., documented wells). However, the actual number of salt
water intrusion barrier wells in the United States is estimated to be greater than 609. These
estimates do not include any wells in New Jersey, which indicated in its survey response that it
has salt water intrusion barrier wells but did not provide any numbers.
September 30, 1999
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Table 1. Inventory of Salt Water Intrusion Barrier Wells in the United States
State
Documented
Number of Wells
Estimated Number of Wells
Number
Source of Estimate and Methodology1
USEPA Region 1 - None
USEPA Region 2
NJ
NR
NR
N/A
NY
200
Best professional judgement, based on the
fact that salt water intrusion is a
significant problem on Long Island.
USEPA Region 3 - None
USEPA Region 4
FL
1 (testing phase)
>1
Best professional judgement.
USEPA Region 5 - None
USEPA Region 6 - None
USEPA Region 7 - None
USEPA Region 8 - None
USEPA Region 9
CA
308
308
Inventory submitted by injectors.
USEPA Region 10
WA
50 to 100
Best professional judgement.
All USEPA Regions
All States
315
>609
N/A
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.
NR Although USEPA Regional, state and/or territorial officials reported the presence of the well type, the
number of wells was not reported, or the questionnaire was not returned.
September 30, 1999
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4. INJECTATE CHARACTERISTICS AND INJECTION
PRACTICES
4.1 Injectate Characteristics
Varying levels of water quality are injected to create salt water intrusion barriers,
including untreated surface water, treated surface water, and mixtures of treated wastewaters and
ground water or surface water. (For further discussion on sewage treatment effluent wells,
which inject only sewage treatment effluent rather than mixtures of such wastewaters and other
waters, refer to Volume 7 of the Class V UIC Study.)
Because protection of drinking water supplies is the major goal of a salt water intrusion
barrier well, injectate is usually monitored, and injectate constituent concentrations typically
meet primary and secondary drinking water standards (Crook et al., 1991). Two salt water
intrusion barrier projects in California provide examples of the quality of water being injected
into this type of Class V well. Injectate data for both projects are presented in Table 2, along
with available drinking water standards for the purpose of comparison. These data represent 97
percent of the documented salt water intrusion barrier wells in the United States. A brief
description of these projects follows.
The Los Angeles County Department of Public Works in California operates the West
Coast, the Dominguez Gap, and the Alamitos Barrier Project systems. These systems include
229 injection wells that protect 15 miles of coastal Los Angeles County from salt water
encroachment. The Los Angeles Metropolitan Water District (MWD) provides a treated blend
of drinking and surface water imported from the California Aqueduct and the Colorado River.
Secondary effluent is pumped from the City of Los Angeles Hyperion Treatment Plant to the
West Basin Municipal Water District Water Recycling and Barrier Treatment Facility and
subject to further advanced treatment prior to being blended with the MWD water and
discharged through the salt water barrier intrusion system as injectate. During 1998, Los
Angeles County injected approximately 8,287 million gallons of water into the wells. As seen in
Table 2, analyses of the injected water show that it meets all primary and secondary drinking
water standards.
Operated by the Orange County Water District (OCWD) in California, the Talbert Barrier
Project is a series of 23 multi-point injection wells (81 injection points) that inject into four
coastal aquifers (Talbert, Alpha, Beta, and Lambda aquifers). The source of injectate for the 23
wells is tertiary-treated wastewater effluent mixed with other water. As of 1991, OCWD was
accepting up to 15 million gallons per day of secondary-treated municipal wastewater from the
County Sanitation District of Orange County's Fountain Valley plant for advanced treatment at
Water Factory 21 in the City of Fountain Valley. To produce high quality reclaimed water,
Water Factory 21 utilizes lime clarification for removal of suspended solids, heavy metals, and
dissolved minerals; carbonation for pH control; mixed-media filtration for removal of suspended
solids; adsorption with granular activated carbon for removal of dissolved organics; reverse
September 30, 1999
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Table 2. Water Quality Data for Two Salt Water Intrusion Barrier Projects in California
Constituents
Drinking Water Standard"
(mg/1, unless otherwise
indicated)
Health Advisory Level
(mg/1, unless otherwise
indicated)
Constituent Concentration
(mg/1, unless otherwise indicated)
Los Angeles County, CA1
Orange County, CA2
Volatile Organic Compounds
Bromoform
Chloroform
Dibromochloromethane
Dibromodichloromethane
Dichloroacetic Acid
Dichloromethane
Total Trihalomethanes
Trichloroacetic Acid
0.1 (F);0.08(P)
0.1 (F);0.08(P)
N/A
N/A
0.06 (P)
0.005 (F)
0.08 (P)
0.06 (P)
0.4 (D,C)
0.6 (D,C)
N/A
N/A
D
0.5 (F,C)
N/A
0.3 (D,N)
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Table 2. Water Quality Data for Two Salt Water Intrusion Barrier Projects in California
(continued)
Constituents
Mercury
Nickel
Nitrate (as N)
Nitrite (as N)
Nitrate plus Nitrite (as N)
Selenium
Silver
Zinc
Drinking Water Standard"
(mg/1, unless otherwise
indicated)
0.002 (F)
0. 1 (F)b
10 (F)
1(F)
10 (F)
0.05 (F)
Secondary MCL: 0.1 (F)
L
Secondary MCL: 5 (F)
Health Advisory Level
(mg/1, unless otherwise
indicated)
0.002 (F,N)
0.1 (F,N)
N/A
N/A
N/A
N/A
0.1 (D,N)
2 (D,N)
Constituent Concentration
(mg/1, unless otherwise indicated)
Los Angeles County, CA1
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Table 2. Water Quality Data for Two Salt Water Intrusion Barrier Projects in California
(continued)
Constituents
Drinking Water Standard"
(mg/1, unless otherwise
indicated)
Health Advisory Level
(mg/1, unless otherwise
indicated)
Constituent Concentration
(mg/1, unless otherwise indicated)
Los Angeles County, CA1
Orange County, CA2
Additional Parameters
Calcium
Magnesium
Potassium
Sodium
Total Organic Carbon
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
D
N/A
36-67
14-24
2.7-3.9
45 - 103
2.09-3.12
Not reported
Not reported
Not reported
29.2 - 62.3
1.14-3.23
Data Sources:
1 Metropolitan Water District, 1997 and West Basin Municipal Water District, 1997
2 Orange County Water District, 1996
a Primary maximum contaminant level (MCL), unless otherwise noted.
b Being remanded.
c Constituent concentrations in blended water from the Los Angeles Metropolitan Water District and reclaimed water.
Regulatory Status:
D: Draft
F: Final
L: Listed
P: Proposed
R: Under Review
T: Tentative (not officially proposed)
Health Advisory:
C: 104 cancer risk
N: Noncancer lifetime
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osmosis for demineralization; and chlorination for biological control and disinfection. This
reclaimed water is then blended with ground water from deep wells for injection into the
seawater barrier system. During 1996, OCWD injected 1,320 million gallons of water into its
wells. Analyses of the injectate water show that it meets all primary and secondary drinking
water standards (Table 2).
4.2 Well Characteristics
As stated earlier, salt water intrusion wells are used to inject water into fresh water
aquifers to prevent the intrusion of salt water into the fresh water. Control of salt water intrusion
through the use of these wells may be achieved by creating and maintaining a "fresh water ridge."
This fresh water ridge may be achieved with a line of injection wells paralleling the coast. Figure
2 illustrates the use of injection wells to create a fresh water ridge to control salt water intrusion.
Figure 2. Use of Injection Wells to Create a Fresh Water Ridge
to Control Salt Water Intrusion
Extraction Field in Basin
INJECTION WELL
1 Ground Surface ,
_sz
IN AN UNCONFINED GROUNDWATER BASIN
INJECTION WELL
I A CONFINED GROUNDWATER BASIN
Source: USEPA, 1987
September 30, 1999
10
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Although the design and construction of salt water intrusion barrier wells depend on site-
specific conditions, the components of most salt water intrusion barrier wells are very similar.
These include: (1) the well casing; (2) the well screen (except in rock and other open hole wells);
(3) sand/gravel pack around the screen (except in rock and other open hole wells); (4)
grout/cement around the casing; and (5) a pump.
Figure 3 shows a typical salt water intrusion barrier well. This design was used to
construct two wells that will be part of the proposed Salinity Barrier System at the City of
Hollywood Wastewater Treatment Plant in Broward County, Florida. The salt water intrusion
barrier wells were constructed with twelve-inch outside diameter schedule 80 polyvinyl chloride
(PVC) casing extending to a depth of approximately 136 feet below land surface.
Figure 3. Design of a Typical Salt Water Intrusion Barrier Well
FEET BELOW OPEN HOLE Off
LAND SURFACE CONSTRUCTION
SCREENED
CONSTRUCTION
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September 30, 1999
11
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Figure 4 shows the design of the salt water intrusion barrier wells being used in the
Talbert Barrier Project, which is operated by OCWD in California.
Figure 4. Design of Salt Water Intrusion Barrier Wells
Used in the Talbert Barrier Project
V)
I
o.
ui
a
200
'VAULT
TYPICAL INJECTION OR
OBSERVATION WELL
GROUT SEAL
GRAVEL PACK
PERFORATED WELL
CASING
Source: California Regional Water Quality Control Board, Santa Ana Region, 1991
September 30, 1999
12
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Another method used to control salt water intrusion through the use of injection wells is
the use of an injection-extraction system. Such a system may be used to inject fresh water inland,
while salt water intruded into the aquifer is being extracted along the coast. An illustration of an
injection-extraction system is shown in Figure 5.
Figure 5. Use of an Injection-Extraction System to Control Salt Water Intrusion
EXTRACTION WELL
INJECTION WELL
Extraction Field
in Basin
\ AN UNCONFINED GROUNDWATER BASIN
EXTRACTION WELL
INJECTION WELL
Extraction Field in Basin
Sea Leve
Fresh Witer -^ Confined Ajuifer
I A CONFINED GROUNDWATER BASIN
Source: USEPA, 1987
September 30, 1999
13
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4.3 Operational Practices
Injecting high-quality water reduces the frequency of well clogging, increases the
operating life of the well, and reduces cleaning costs. In addition, chlorination of the injected
water helps to protect the well casing, prevents potential leaks, and reduces nearfield biofouling
of the formations (Bloetscher, 1999). However, even when using high-quality water, clogging is
inevitable.
When there is clogging and the injection head has increased above acceptable levels
(approximately every three years when using high-quality injectate water), redevelopment of the
injection wells is necessary (Bruington, 1968). Redevelopment of a well involves the removal of
finer material from the natural formations surrounding the perforated sections of the casing.
Periodic redevelopment of the well is used to restore its efficiency and specific capacity.
Thorough initial development of the injection wells will delay the need for redevelopment and
increase the initial specific capacity of the well, making it more efficient (Bruington, 1968).
Supply line pressure must be closely monitored and carefully controlled to prevent
injection head fluctuations that could disrupt the well's gravel pack or even damage the injection
well itself (Bruington, 1968). Injection wells should be supplied with pressure either individually
or in small groups. This will prevent the complete collapse of the pressure ridge barrier in cases
of shut down due to accidents, malfunctions, or strikes (Bruington, 1968).
Observation wells should be installed along the line of the injection barrier to monitor
ground water levels. This allows operators to make an accurate, informed determination
regarding the amount of water that should be injected to prevent salt water intrusion (Atkinson et
al., 1986).
Abandoned salt water intrusion barrier wells should be thoroughly plugged to prevent the
infiltration of contaminated surface waters into bodies of ground water. Wells are typically
plugged with cement slurries; the exact composition of the slurry should be tailored to the specific
geology of the well site (Atkinson et al., 1986).
5. POTENTIAL AND DOCUMENTED DAMAGE TO USDWs
5.1 Injectate Constituent Properties
The primary constituent properties of concern when assessing the potential for Class V
salt water intrusion barrier wells to adversely affect USDWs are toxicity, persistence, and
mobility. Appendices D and E of the Class V UIC Study provide information on these properties
for constituents found above drinking water standards or health advisory levels in injectate of
various types of Class V wells. As discussed in Section 3.1, water injected into salt water
intrusion barrier wells is typically treated to meet primary and secondary drinking water
standards. Thus, no further discussion of injectate constituent properties is provided here.
September 30, 1999 14
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5.2 Observed Impacts
Based on information obtained from state and USEPA Regional offices, there are no
documented contamination incidents associated with the use of salt water intrusion barrier wells.
Ground water monitoring and lexicological, chemical, and epidemiological studies have found no
measurable adverse effects on either ground water quality or the health of the population
ingesting the water, when the injectate was treated wastewater effluent (Crook et al., 1991; Mills,
1991). Salt water intrusion barrier wells protect drinking water supplies from salt water
contamination and augment the amount of fresh water available from a USDW.
6. BEST MANAGEMENT PRACTICES
6.1 Siting and Evaluation of Salt Water Intrusion Barrier Wells
Prior to establishing a salt water intrusion barrier, detailed hydrogeologic data should be
collected and all sources of salt water intrusion should be identified. Once that is complete, an
inventory of water supplies, water usage, existing pumping patterns, and surface development
should be made. With these data in hand, intensive computer modeling should be conducted to
determine the magnitude and extent of the salt water intrusion problem. Computer modeling is
required for a successful salinity project to address technical issues and also to obtain information
needed in the permitting process (Walker, 1999). Furthermore, computer modeling might be used
to determine the siting and characteristics of the proposed salt water intrusion barrier wells and to
evaluate the effects of the proposed recharge and monitoring programs on the USDW.
When using injection wells to control salt water intrusion, the hydraulic barrier injection
point should be located near the toe of the salt water intrusion. Otherwise, the buoyancy effects
that exert pressure on the salt front are not realized and salt water will continue to migrate inland
(Bloetscher, 1999).
6.2 Alternatives to Salt Water Intrusion Barrier Wells
Control measures, other than salt water intrusion barrier wells, used to control salt water
intrusion include: change in pumping patterns; use of extraction barriers; and use of subsurface
barriers. These control measures are discussed briefly below.
6.2.1 Change in Pumping Patterns
A change in pumping patterns can be achieved by reducing pumping and relocating
withdrawal wells to eliminate areas of intense pumping. Due to the difference in density between
salt water and fresh water, these two methods will maintain the fresh water at a desirable
piezometric head. According to the Department of Water Resources in California, water
conservation is the best method to reduce pumping patterns. In other areas, like Florida, projects
have been conducted to determine the most efficient arrangement of wells and rates of pumping to
avoid salt water intrusion (Atkinson et al., 1986).
September 30, 1999 15
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6.2.2 Extraction Barrier
This control program is a line of wells that are constructed adjacent to the coast and
pumped to form a trough at the ground water level. The extraction barrier causes the sea water's
piezometric head to be lower than the fresh water piezometric head, which protects the fresh
water aquifer. The water pumped is brackish and normally is discharged into the sea (Todd,
1980).
6.2.3 Subsurface Barriers
Subsurface barriers are vertical walls that are placed inland to restrict the movement of sea
water. There are three types of subsurface barrier walls: slurry walls, grout cutoffs, and steel
sheet piles. Slurry wall construction involves pumping a slurry made of water and bentonite clay
into a trench. Grout cutoffs are constructed by injecting a liquid, slurry, or emulsion under
pressure into the soil. The injected fluid will occupy the pore spaces and will solidify to form an
impermeable wall. Sheet piling involves driving lengths of steel that connect together into the
ground to form a thin impermeable barrier to flow. These three types of barriers must be
connected to an underlying impermeable geologic zone (Atkinson et al., 1986).
7. CURRENT REGULATORY REQUIREMENTS
Several federal, state, and local programs exist that either directly manage or regulate
Class V salt water intrusion barrier wells. On the federal level, management and regulation of
these wells falls primarily under the UIC program authorized by the Safe Drinking Water Act
(SDWA). Some states and localities have used these authorities, as well as their own authorities,
to extend the controls in their areas to address concerns associated with salt water intrusion
barrier wells.
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.
Salt water intrusion barrier wells 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.
September 30, 1999 16
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Under 40 CFR 144.12(a), owners or operators of all injection wells, including salt water intrusion
barrier wells, 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.
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 salt water intrusion barrier wells (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 SDWA 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 salt water intrusion barrier wells, 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.2
2 May 2003 is the deadline including an 18-month extension.
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7.1.2 Other Federal Rules and Programs
As stated earlier, salt water intrusion barrier wells are used to protect USDWs from salt
water contamination. Thus, salt water intrusion barrier well injectate is typically treated to
drinking water standards, which are established under Section 1412 of the SDWA. This section
requires USEPA to establish National Primary Drinking Water Regulations (NPDWRs) for a
contaminant if (1) the contaminant may have an adverse public health effect; (2) it is known or
likely to occur in public water systems with a frequency and at levels of public health concern;
and (3) if regulation of such contaminant presents a meaningful opportunity for health risk
reduction. A brief description of these regulations follows.
Total Trihalomethane Rule
In November 1979, USEPA set an interim MCL for total trihalomethanes (TTHMs) of
0.10 mg/1 as an annual average (44 FR 68624). Compliance is defined on the basis of a running
average of quarterly averages of all samples. The value for each sample is the sum of the
measured concentrations of chloroform, bromodichloromethane, dibromochloromethane, and
bromoform. The interim TTHM standard only applies to community water systems using surface
water and/or ground water serving at least 10,000 people that add a disinfectant to the drinking
water during any part of the treatment process.
Surface Water Treatment Rule
In June 29, 1989, USEPA promulgated the final Surface Water Treatment Rule (SWTR)
(54 FR 27486). Under the SWTR, USEPA set maximum contaminant level goals (MCLGs) of
zero for Giardia lamblia, viruses, and Legionella; and promulgated NPDWRs for all public water
systems using surface water sources or ground water sources under the direct influence of surface
water. The SWTR includes treatment technique requirements for filtered and unfiltered systems
that are intended to protect against the adverse health effects of exposure to Giardia lamblia,
viruses, and Legionella, as well as many other pathogenic organisms. The rule became effective
in June 1993.
Total Coliform Rule
In June 29, 1989, USEPA also promulgated the Total Coliform Rule, which applies to all
public water systems (54 FR 27544). This regulation sets compliance with a MCL for total
coliforms. If a system exceeds the MCL, it must notify the public using mandatory language
developed by the USEPA.
Interim Enhanced Surface Water Treatment
On December 16, 1998, USEPA finalized the Interim Enhanced Surface Water Treatment
Rule (IESWTR) (63 FR 69478). The purposes of the IESWTR are to: (1) improve control of
microbial pathogens, including specifically protozoan Cryptosporidium, in drinking water; and
(2) address risk trade-offs with disinfection products. The IESWTR applies to public water
September 30, 1999 18
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systems that use surface or ground water under the direct influence of surface water and serve
10,000 or more people. The regulation became effective on February 16, 1999.
Stage 1 Disinfection Byproducts Rule
In December 16, 1998, USEPA finalized: (1) maximum residual disinfectant level goals
(MRDLGs) for chlorine, chloramines, and chlorine dioxide; (2) MCLGs for four trihalomethanes
(chloroform, bromodichloromethane, dibromochloromethane, and bromoform), two haloacetic
acids (dichloroacetic acid and trichloroacetic acid), bromate, and chlorite; and (3) NPDWRs for
three disinfectants (chlorine, chloramines, and chlorine dioxide), two groups of organic
disinfection byproducts (TTHMs—a sum of chloroform, bromodichloromethane,
dibromochloromethane, and bromoform—and haloacetic acids—a sum of dichloroacetic acid,
trichloroacetic acid, monochloroacetic acid, and mono-and dibromoacetic acids), and two
inorganic disinfection byproducts (chlorite and bromate) (63 FR 69389). The NPDWRs consist
of maximum residual disinfectant levels or MCLs or treatment techniques for these disinfectants
and their byproducts. The NPDWRs also include monitoring, reporting, and public notification
requirements for these compounds.
The Stage 1 Disinfection Byproducts Rule applies to public water systems that are
community water systems and nontransient, noncommunity water systems that treat their water
with a chemical disinfectant for either primary or residual treatment. In addition, certain
requirements for chlorine dioxide apply to transient noncommunity water systems.
Radon Rule
On July 18, 1991, USEPA proposed a MCLG, a MCL, monitoring, reporting, and public
notification requirements for radon and a number of other radionuclides in public water supplies
(systems serving 25 or more individuals or with 15 or more connections) (56 FR 33050).
USEPA proposed to regulate radon at 300 pCi/1.
On August 6, 1996, Congress passed amendments to the SDWA. Section 1412(b)(13)(A)
of the SDWA, as amended, directs USEPA to withdraw the proposed national primary drinking
water regulation for radon. Thus, as directed by Congress, on August 6, 1997 (62 FR 42221),
USEPA withdrew the 1991 proposed MCLG, MCL, monitoring, reporting, and public notification
requirements for radon.
USEPA expects to publish a final MCLG and national primary drinking water regulation
for radon by August, 2000.
Ground Water Rule
Currently, USEPA is developing a Ground Water Rule that will specify appropriate use of
disinfection and encourage the use of alternative approaches, including best management
practices and control of contamination at its source. The rule will be designed to protect against
pathogenic bacteria and viruses in source water, against growth of opportunistic pathogenic
bacteria in ground water distribution systems, and to mitigate against any failure in the engineered
September 30, 1999 19
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systems, such as cross-connections or sewage infiltration into distribution systems. The Ground
Water Rule will apply to systems using only ground water, which are not regulated under the
1989 SWTR.
USEPA expects to publish the Final Ground Water Rule by November 2000. The
statutory deadline, under the SDWA (Section 1412(b)(8)), for the Ground Water Rule is May
2002.
7.2 State and Local Programs
As discussed in Section 3, the four states for which documented or estimated numbers of
salt water intrusion barrier wells were provided by the states or USEPA Regional offices are:
California, Florida, New York, and Washington. California, New York, and Washington each
contain a significant number, while Florida is testing a single well. The statutory and regulatory
requirements differ significantly among these states, as described in Attachment A of this volume
and summarized below.
In California, USEPA Region 9 directly implements the UIC program for Class V
injection wells. Salt water intrusion barrier wells in the state are authorized by rule in accordance
with the existing federal requirements. However, the state has additional jurisdiction over salt
water intrusion barrier wells through state regional water quality control boards. If treated
wastewater is planned to be used for artificial recharge, regional water quality control boards
issue site-specific discharge requirements. In addition, the Department of Health Services must
review and approve the application. In these instances, the injectate must meet drinking water
standards at the point of injection. County water districts and/or county health departments may
supplement the requirements. If potable water is planned to be used for aquifer recharge, the
projects are reviewed and regulated by local health departments.
Florida is a UIC Primacy State for Class V wells. In this state, owners or operators of salt
water intrusion barrier wells are required to obtain a Construction/Clearance Permit from the
Department of Environmental Protection before receiving permission to construct. In order to use
the well, the applicant is required to submit information needed to demonstrate that well operation
will not adversely affect a USDW. Once such a demonstration is made, the Department will issue
an authorization to use the well subject to certain operating and reporting requirements, including
the requirement to meet drinking water standards at the point of injection. Injection of fluids that
exceed the drinking water standards is allowed only if it is not into a USDW and if it is controlled
in accordance with a site-specific operating permit.
In New York, USEPA Region 2 directly implements the UIC program for Class V
injection wells. However, the state has promulgated additional regulations in the state's Code of
Rules and Regulations to establish water quality standards, effluent limitations, and monitoring
requirements; and create a state pollutant discharge elimination system requiring permits for
discharges into the waters of the state. The Environmental Conservation Law (§17-0105) defines
"pollutant" to include water, waters of the state to include ground water, and point source to
include a well.
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Washington is a UIC Primacy State for Class V wells. In this state, an individual permit is
required to operate a salt water intrusion barrier well. In addition, Washington has set standards
for direct ground water recharge projects using reclaimed water. These rules primarily address
the standards and treatment requirements for the reclaimed water, when injected into potable and
non-potable ground water.
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ATTACHMENT A
STATE AND LOCAL PROGRAM DESCRIPTIONS
This attachment does not describe every state's program controls; instead, it focuses on
the four states where salt water intrusion barrier wells are known or believed to exist: California,
Florida, New York, and Washington. Altogether, these four states have a total of 315
documented and more than 409 estimated salt water intrusion barrier wells. These estimates
represent approximately 99 percent and 67 percent of the documented and estimated salt water
intrusion barrier wells, respectively.
California
USEPA Region 9 directly implements the UIC program for Class V injection wells in
California. The California Water Quality Control Act (WQCA), however, establishes broad
requirements for the coordination and control of water quality in the state, sets up a State Water
Quality Control Board, and divides the state into nine regions, with a Regional Water Quality
Control Board (RWQCB) that is delegated responsibilities and authorities to coordinate and
advance water quality in each region (Chapter 4 Article 2 WQCA). A RWQCB 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).
Permitting
Although the RWQCBs do not permit injection wells, the WQCA provides that any
person operating, or proposing to operate, an injection well (as defined in §13051 WQCA) must
file a report of the discharge, containing the information required by the Regional Board, with the
appropriate Regional Board (13260(a)(3) WQCA). Furthermore, the RWQCB, 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 §13241 of the WQCA (13263(a)
WQCA). However, a RWQCB 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).
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).
September 30, 1999 22
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Siting and Construction Requirements
Construction standards from Bulletin 74-90 of the Department of Water Resources
generally apply. In addition, RWQCBs have jurisdiction over injection barrier wells. The Santa
Ana RWQCB has jurisdiction over the Orange County Seawater Intrusion Barrier Project. The
Los Angeles RWQCB has jurisdiction over the Los Angeles County injection barriers (Alamitos
Barrier, Dominguez Gap, and West Coast Basin barriers). Requirements established by the
RWQCBs pertain to injection wells injecting reclaimed water. No such requirements pertain to
injection wells injecting solely potable water.
The following requirements are established by Order No. 91-121 issued by the Santa Ana
RWQCB for the Orange County Project, whose seawater barrier consists of 23 specially designed
multiple casing wells. The limitations in the Order are intended to maintain ground water quality
in the underlying ground water subbasin and to protect beneficial use of the ground water
subbasin. The Order requires the county to adopt an ordinance or resolution that prevents
construction of new domestic water supply wells within 2,000 feet of the injection wells.
Operating Requirements
Order No. 91-121, which applies only to the Orange County Project, requires compliance
with a Monitoring and Reporting Program and submission and approval of a draft operating plan
and a final operating plan. It requires monitoring of domestic water supply wells in the vicinity of
the injection barrier, and provision of an alternate safe water supply if necessary if a domestic
water supply well is adversely affected by the discharges.
The RWQCB discharge specifications in Order No. 91-121 include 4-sample average and
daily maximum concentration limits for specified constituents; pH limits for the injection water; a
requirement that the injection water shall not cause taste, odor, foam or color in the ground water;
a requirement that neither the treatment nor injection shall cause a nuisance or pollution as
defined by the California Code; prohibition of injection of any substance in concentrations toxic
to human, animal, plant, or aquatic life; prohibition of injection of saline wastes; a requirement
that the injection water at all times must meet all the California primary drinking water standards;
a requirement that all reclaimed water injected shall at all times be adequately disinfected,
oxidized, coagulated, clarified, filtered wastewater meeting the requirements specified in the
California Wastewater Reclamation Criteria; a requirement that all reclaimed water injected shall
receive organics removal treatment such that the total organic carbon concentration does not
exceed 2.0 mg/1; a requirement that total nitrogen concentration shall not exceed 10 mg/1; and a
limit on the amount of water injected in the Talbert Barrier project shall not exceed 25 million
gallons per day (mgd), of which the maximum amount of reclaimed water shall not exceed 18
mgd based on the quarterly average flow. Monthly and quarterly monitoring of the results of all
weekly analyses, results of monthly analyses, and total flow of all injection water by source must
be collected and reported to the RWQCB (Order No. 91-121).
September 30, 1999 23
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Monitoring Requirements
Not specified by statute or regulations.
Plugging and Abandonment
A closure plan must be submitted to the RWQCB and financial assurance for closure must
be provided.
Florida
Florida is a UIC Primacy State for Class V wells. Chapter 62-528 of the Florida
Administrative Code (FAC), effective June 24, 1997, establishes the state's UIC program, and
Part V of Chapter 62-528 (62-528.600 to 62-528.900) addresses criteria and standards for Class V
wells. Class V wells are grouped for purposes of permitting into 8 categories. Group 2 includes
salt water intrusion barrier wells.
Permitting
Underground injection through a Group 2 Class V well is prohibited except as authorized
by permit. Owners and operators are required to obtain a Construction/Clearance Permit before
receiving permission to construct. The applicant is required to submit detailed information,
including well location and depth, description of the injection system and of the proposed
injectate, and any proposed pretreatment. When site-specific conditions indicate a threat to a
USDW, additional information must be submitted. If a Group 2 well applicant demonstrates that
the operation of the well will not adversely impact a USDW, the Department will issue a non-
renewable and non-expiring authorization to use the well. The authorization will contain
operating and reporting requirements. The fluids injected must meet the primary and secondary
drinking water quality standards in Chapter 62-500 FAC. A Group 2 well that does not inject
fluids meeting the primary and secondary drinking water requirements must obtain an operating
permit. Finally, all Class V wells are required to obtain a plugging and abandonment permit.
Siting and Construction Requirements
Specific construction standards for Class V wells have not been enacted by Florida,
because of the variety of Class V wells and their uses. Instead, the state requires the well to be
designed and constructed for its intended use, in accordance with good engineering practices, and
approves the design and construction through a permit. The state can apply any of the criteria for
Class I wells to the permitting of Class V wells if it determines that without such criteria the Class
V well may cause or allow fluids to migrate into a USDW and cause a violation of the state's
primary or secondary drinking water standards, which are contained in Chapter 62-550 of the
FAC. However, if the injectate meets the primary and secondary drinking water quality standards
and the minimum criteria contained in Rule 62-520-400 of the FAC, Class I injection well
permitting standards will not be required.
September 30, 1999 24
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Class V wells are required to be constructed so that their intended use does not violate the
water quality standards in Chapter 62-520 FAC at the point of discharge, provided that the
drinking water standards of 40 CFR Part 142 (1994) are met at the point of discharge.
Operating Requirements
All Class V wells are required to be used or operated in such a manner that they do not
present a hazard to a USDW. Pretreatment of injectate must be performed, if necessary to ensure
the fluid does not violate the applicable water quality standards in 62-520 FAC.
Monitoring Requirements
Monitoring generally will be required for Group 2 wells, unless the wells inject fluids that
meet the primary and secondary drinking water standards in 62-550 FAC and the minimum
criteria in Rule 62-520, and that have been processed through a permitted drinking water
treatment facility. Monitoring frequency will be based on well location and the nature of the
injectant and will be addressed in the permit. The Department will determine the frequency of
monitoring based on the location of the well, the nature of the injected fluid, and, where
applicable, water quality criteria for the receiving waters.
Plugging and Abandonment
The proposed plugging method will be approved as a condition of the permit.
New York
USEPA Region 2 directly implements the UIC program for Class V injection wells in
New York. Under the state's Environmental Conservation Law, however, the Department of
Environmental Conservation, Division of Water Resources (DWR) has promulgated regulations
in the state Code Rules and Regulations, Title 6, Chapter X, Parts 703, 750, 754, and 756. These
regulations establish water quality standards and effluent limitations, create a State Pollutant
Discharge Elimination System (SPDES) requiring permits for discharges into the waters of the
state, specify that such discharges must comply with the standards in Part 703, and provide for
monitoring in Part 756.
Permitting
New York's SPDES prohibits the discharge of any pollutant into the waters of the state
without an SPDES permit. The Environmental Conservation Law (§17-0105) defines "pollutant"
to include water, waters of the state to include ground water; and point source to include a well.
Applications for a SPDES permit must be submitted on a required form, describe the
proposed discharge, supply such other information as the DWR requests, and are subject to public
notice. SPDES permits must ensure compliance with effluent limitations and standards, and will
include schedules of compliance, monitoring requirements, and records and reports of activities
(Parts 751-756).
September 30, 1999 25
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Siting and Construction Requirements
New York law requires all well drillers on Long Island to be licensed (Chapter 338).
Operating Requirements
Effluent limits (Part 703) in the SPDES permit must be met. Monitoring and reporting
requirements in the SPDES permit must be met.
Monitoring Requirements
Not specified by statute or regulations.
Plugging and Abandonment
Not specified by statute or regulations.
Washington
Washington is a UIC Primacy State for Class V wells. Chapter 173-218 of the
Washington Administrative Code (WAC) establishes the UIC program. Under the program, the
policy of the Department of Ecology is to maintain the highest possible standards to prevent the
injection of fluids that may endanger ground waters which are available for beneficial uses or
which may contain fewer than 10,000 mg/1 total dissolved solids. Consistent with that policy, all
new Class V injection wells that inject industrial, municipal, or commercial waste fluids into or
above a USDW are prohibited (172-218-090(1) WAC). Existing wells must obtain a permit to
operate.
Permitting
A permit must specify conditions necessary to prevent and control injection of fluids into
the waters of the state, including all known, available, and reasonable methods of prevention,
control, and treatment; applicable requirements in 40 CFR Parts 124, 144, 146; and any
conditions necessary to preserve and protect a USDW. Any injection well that causes or allows
the movement of fluid into a USDW that may result in a violation of any primary drinking water
standard under 40 CFR Part 141 or that may otherwise adversely affect the beneficial use of a
USDW is prohibited (173-218-100 WAC).
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Siting and Construction Requirements
The state has promulgated minimum standards for construction and maintenance of wells
(173-160-010 through -560 WAC). However, injection wells regulated under Chapter 173-218
are specifically exempted from these constructions standards (173-160-010(3)(e) WAC).
Operating Requirements
The water quality standards for ground waters establish an antidegradation policy. The
injectate must meet the state's ground water standards at the point of compliance (173-200-030
WAC).
Monitoring Requirements
Not specified by statute or regulations.
Plugging and Abandonment
All wells not in use must be securely capped so that no contamination can enter the well
(173-160-085 WAC).
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Injection Control Study: Salt Water Intrusion Barrier Wells Information Summary. Florida
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California Regional Water Quality Control Board, Santa Ana Region. 1991. Order No. 91-121:
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D.C. EPA 570/9-87-006. September 1987.
USEPA. 1997. Source Water Assessment and Programs Guidance. Office of Water.
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