United States Office of Ground Water EPA/816-Z-99-003
Environmental and Drinking Water (4601) July 1999
Protection Agency
The Class V Underground Injection
Control Study
Volume 1: Study Approach
and General Findings
PUBLIC COMMENT DRAFT
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Table of Contents
Page
1. Executive Summary 1
2. Background 11
2.1 Class V Wells 11
2.2 Safe Drinking Water Act 14
2.3 UIC Regulations 14
2.4 1987 Report to Congress on Class V Wells 14
2.5 Actions Since the 1987 Report to Congress 15
3. Study Approach 16
4. Information Collection 17
4.1 Literature Review 17
4.2 State and EPA Regional Data Collection 18
4.2.1 Data Collection Methods 18
4.2.2 Information Obtained 18
4.3 Requests to the Public for Information 21
4.4 Peer Review 22
5. Inventory Models 23
5.1 Storm Water Drainage Wells '. 23
5.2 Large-Capacity Septic Systems 24
6. Well-Specific Summaries 24
6.1 Agricultural Drainage Wells 24
6.2 Storm Water Drainage Wells 27
6.3 Carwash Wells 29
6.4 Large-Capacity Septic Systems 30
6.5 Food Processing Wells 32
6.6 Sewage Treatment Effluent Wells 34
6.7 Laundromat Wells 36
6.8 Spent Brine Return Flow Wells 37
6.9 Mine Backfill Wells 38
6,10 Aquaculture Waste Disposal Wells 40
6.11 Solution Mining Wells 42
6.12 In-Situ Fossil Fuel Recovery Wells 43
6.13 Special Drainage Wells 44
6.14 Experimental Wells 46
6.15 Aquifer Remediation Wells 48
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Table of Contents (cont'd)
Page
6.16 Geothermal Electric Power Wells 49
6.17 Geothermal Direct Heat Wells 51
6.18 Heat Pump/Air Conditioning Return Flow Wells 52
6.19 Salt Water Intrusion Barrier Wells 54
6.20 Aquifer Recharge Wells 55
6.21 Aquifer Storage and Recovery Wells 57
6.22 Noncontact Cooling Water Wells 58
6.23 Subsidence Control Wells 59
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STUDY APPROACH AND GENERAL FINDINGS
1. EXECUTIVE SUMMARY
Class V underground injection wells are typically shallow waste disposal wells or other
devices used to release fluids underground. These wells generally inject either directly into
underground sources of drinking water (USDWs) or into the shallow subsurface that overlies
those resources. Class V wells have a variety of designs and uses and include disposal
mechanisms such as large-capacity septic systems, storm water and agricultural drainage systems.
The U.S. Environmental Protection Agency (EPA) addresses Class V injection wells
through the federal underground injection control (UIC) program under the authority of the Safe
Drinking Water Act. This program includes the basic requirement that Class V injection wells
cannot endanger USDWs and gives UIC program staff the authority to take whatever actions are
needed to ensure that underground drinking water supplies are in fact protected. Many States
have primary responsibility for implementing the program and/or control Class V wells under
their own authorities.
This report presents the results of a study of 23 categories of Class V wells. The study
was conducted to develop background information for EPA to use in evaluating the risk that
these wells pose to underground drinking water supplies and if additional federal regulation is
warranted. Information collected on these wells included: inventory, injectate constituents,
contamination incidents, and current State regulations.
EPA estimates that more than 500,000 Class V wells within these 23 different categories
currently exist in the U.S. The two largest categories by far are storm water drainage wells
(approximately 125,000) and large-capacity septic systems (approximately 290,000), which
together comprise almost 83 percent of the national total. In contrast, some categories are very
small, including in-situ fossil fuel recovery wells, which are not presently known to exist, and
spent brine return flow wells, aquaculture waste disposal wells, and geothermal direct heat wells,
which have about 100 or less each. In general, there are significant uncertainties associated with
these data. States maintain relatively accurate numbers for mine backfill, geothermal, aquifer
recharge, aquifer storage and recovery, and aquifer remediation wells. For other well types,
however, EPA and the States suspect that their inventories underestimate the true numbers of
wells.
Class V wells are located in virtually every State, especially in unsewered areas where the
population is likely to depend on ground water. This is particularly true for stormwater drainage
wells, large-capacity septic systems, and aquifer remediation wells, which likely exist in every
State, as well as heat pump/air conditioning return flow wells which exist in 46 States. The
following potentially exist in seven or fewer States: spent brine return flow wells, aquaculture
waste disposal wells, solution mining wells, geothermal power wells, salt water intrusion barrier
wells, and subsidence control wells. All of the others are potentially in 11 to 32 States.
Public Comment Draft
July 12, 1999 1
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Sampling data that can be used to characterize the chemical composition of the fluids
released are sparse for most well types, but the information available provides evidence that
many of the wells release fluids with one or more chemicals in concentrations above drinking
water maximum contaminant levels (MCLs) or health advisory levels (HALs). Nitrate along
with several metals and other inorganics are particularly prevalent, with organic pollutants
generally being less of a concern for most wells. Biological contaminants (coliform bacteria and
other microorganisms) are also a concern for some well types, such as agricultural drainage
wells, large-capacity septic systems, food processing wells, sewage treatment effluent wells if
treatment systems do not function properly, possibly aquaculture waste disposal wells, and lake-
level control wells (included within the "special drainage well" category).
Class V wells are typically shallow, injecting into or above USDWs, but they may also
inject below USDWs. Many Class V wells release fluids into USDWs. For example, salt water
intrusion barrier wells, aquifer recharge, and aquifer storage and recovery wells generally release
fluids directly into USDWs for the purpose of preserving drinking water supplies, and as such,
are typically held to high standards for injectate quality. Several Class V wells inject above
USDWs. Large-capacity septic systems and other kinds of Class V wells that are designed as
septic systems (including many food processing wells and some carwash wells and aquaculture
waste disposal wells) release fluids into the shallow soil above ground water. Class V wells may
also inject below the lowermost USDW, such as spent brine return flow wells.
There are no or few cases of contamination linked to most of the well types studied,
although this may be due to the fact that EPA and State UIC programs generally have limited
resources to search for such cases. Wells with the most contamination cases are, predictably, the
most prevalent wells, including storm water wells, large-capacity septic systems, and agricultural
drainage wells. Each of these well types, plus several others, are also vulnerable to spills or
illicit discharges. For example, storm water wells can be located conveniently along roads and in
parking lots where spills of oil, gasoline and other contaminants can occur.
Regulatory authority over Class V wells varies widely among States. Regulatory
schemes, which are very State- and well-specific, include general authority to protect USDWs
using discretionary authority; permit-by-rule, meaning an entire class of wells is deemed
permitted as long as they comply with standards and requirements found in the regulations; an
identical or general permit, based on State technical regulations, is issued for each well within a
given category; and authority to issue site-specific permits, inspect, and take enforcement action.
State UIC programs are generally resource-constrained. This means the States are often not able
to implement UIC programs as vigorously as they would like. The lack of resources typically
manifests itself in a State program that is more reactive than proactive.
An overview of the Class V injection wells included in this study is provided in the table
at the end of this section. These wells, which are described in detail in separate volumes that
make up the body of this report, are extremely diverse in their purpose, their design and
operation, their number and location, the nature of the fluids they inject, their potential to
contaminate USDWs, and the way they are currently regulated by the States. They include
Public Comment Draft
July 12, 1999 2
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relatively simple designs that drain storm water runoff or excess water from agricultural fields,
large-capacity septic systems used to dispose of sanitary sewage, wells used to dispose of
wastewater from certain commercial and industrial establishments, wells used to inject water for
the purpose of storage or recharging an aquifer, wells used to test new technologies, and wells
used to inject fluids for the purpose of remediating a contaminated aquifer or protecting a
freshwater aquifer from the intrusion of saltwater.
Public Comment Draft
July 12, 1999
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Overview of Class V Wells Included in This Study
Well Type
Agricultural
Drainage
Wells
Storm Water
Drainage
Wells
Carwash Wells
Inventory
Documented
> 1,069
-115,000
± 4,65 1
Estimated
>2,914
-125,500
±7,192
Number of
States
Potentially
with Wells
21
probably 50
25
Injectate Constituents
> MCLs or HALs
Nitrate, Boron, Sulfate,
Coliforms, Cyanazine,
Atrazine, Alachlor,
Adlicarb, Carbofuran, 1,2-
Dichloropropane,
Dibromochloro-propane,
Chloride, and TDS
Arsenic, Cadmium,
Chromium, Nickel,
Nitrate, Zinc, Aldrin,
Benzene, Chloroform,
Endrin, Methyl tert-butyl
ether, Phenol, Toluene,
Chloride, Iron,
Manganese, and TSS
Antimony, Arsenic,
Beryllium, Cadmium,
Lead, Thallium,
Methylene chloride,
Tetrachloroethene,
Aluminum, Iron, and
Manganese
Contamination Potential
Five contamination incidents
documented. In addition,
general studies in agricultural
areas have linked nitrate
contamination in ground
water to agricultural drainage
well use. Wells may be
vulnerable to spills from
manure lagoons, direct
discharges from septic tanks,
and accidental releases of
materials used in farming
operations (e.g., motor oils,
pesticides).
Presence of these wells near
highways, parking lots, and
loading facilities increases
likelihood/vulnerability to
accidental spills and
purposeful illicit discharges.
Fifteen contamination
incidents documented.
Possibility of contamination
due to self-service nature of
facilities. Easy for someone to
use degreasers or other
chemicals or change oil over
drains. Two documented
contamination incidents.
State Regulations in States With
the Most Wells
Individual permit: ID (>18 deep) and TX
Permit by rule: ID (for wells <18 feet deep)
IA: all wells that existed before 2/18/98 must
close or get a permit by 12/31/01; new wells
prohibited but may be permitted under strict
conditions
Ban new wells, rule authorize existing wells:
MNandOH
Authorized by rule: IL, IN, MI, MN, OH, WI
(existing only), MT, WY, ND, SD, UT, CO, ID
(< 18 ft. deep), OR, WA, KS, TO, RI
Individual permit/registration system: AZ, CA,
HI, ID (> 18 ft. deep), AL, FL, TX, NH, MD,
NE.NY
Banned: NC, GA, WI (new)
Permit by rule: WV
Report discharge: CA
Individual permits: AL, MS, NY, WA, and NH
Ban: IA
Public Comment Draft
July 12, 1999
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Overview of Class V Wells Included in This Study
Well Type
Inventory
Documented
Estimated
Number of
States
Potentially
with Wells
Injectate Constituents
> MCLs or HALs
Contamination Potential
State Regulations in States With
the Most Wells
Large-
Capacity
Septic Systems
(LCSS)
94,000
(112,000 is
more likely)
~ 290,000
(95%
prediction
interval of
250,000 to
330,000)
50
Fecal Coliform, Nitrate
(as N), Total nitrogen
species (as N),
formaldehyde (from RV
toilets), Aluminum, Iron,
Manganese, and Sodium
Vulnerable because any
materials spilled/dumped
down drains enter the well.
Twenty-seven documented
contamination incidents.
No consistent State regulation of LCSSs. State
regulations vary from stringent siting,
construction, and operation requirements (e.g.,
MA, MN) to general construction permitting
(e.g.,NJ,IA)
Food
Processing
Wells
182
1,471
29
Nitrate, Nitrite, Total
Coliform, Ammonia,
Odor, Turbidity, and
Chloride
High potential for contami-
nation due to little State
oversight and type/nature of
facilities. Moderate potential
for receiving spills of strong
cleaning chemicals due to
location of floor drains and
chemical storage and use
practices. One documented
contamination incident.
Authorized by rule: AL, TO, WV, IA, and WI
Individual permits: AK, ME, and NY
Varies by county/region: CA
Banned: OR
Sewage
Treatment
Effluent Wells
1,702
±1,755
19
Nitrate
Potential for impacts to
ground and surface water
quality from nutrients. Low
vulnerability because most
wells appear to have
discharge limits and
monitoring requirements; any
injectate that does not meet
the permit conditions is likely
to be detected by the
monitoring program. Three
contamination incidents.
Permit by rule: ID, TX
Aquifer Protection Program Permit: AZ
Ground Water Discharge Permit: MA, NH, WI
Individual permit: CA, FL, HI, WV
Public Comment Draft
July 12, 1999
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Overview of Class V Wells Included in This Study
Well Type
Laundromat
Wells
Spent Brine
Return Flow
Wells
Mine Backfill
Wells
Aquaculture
Waste
Disposal Wells
Inventory
Documented
<700
95
4,987
55
Estimated
>3,495
>95
±7,817
<106
Number of
States
Potentially
with Wells
26
3
22
6
Injectate Constituents
> MCLs or HALs
IDS and pH
Barium, Boron, Chloride,
Copper, Iron, Manganese,
IDS, and pH
Antimony, Arsenic,
Barium, Beryllium,
Boron, Cadmium,
Chromium, Fluoride,
Lead, Mercury,
Molybdenum, Nickel,
Selenium, Silver,
Thallium, Zinc,
Aluminum, Copper, Iron,
Manganese, TDS Sulfate,
and pH
Nitrate, Turbidity, and
Chloride
Contamination Potential
Wells may be susceptible to
uncontrolled laundering of
contaminated articles due to
unsupervised nature of coin-
op laundromats. No reported
contamination incidents.
Unlikely to receive accidental
spills or discharges. No
contamination incidents
reported.
Contamination potential
depends on site-specific
conditions and practices. No
contamination incidents
reported.
Potential exists for operators
to dispose of liquid wastes
(e.g. waste or spent
aquaculture chemicals) via
aquaculture injection wells.
No contamination incidents
reported.
State Regulations in States With
the Most Wells
Permit by rule: IA, MS, and WV
Individual permits: AL and NY
Individual permits: AR, MI
Authorized by rule: ID, WV, and ND
(sometimes general or individual permits are
required)
General permits: WY
Individual permits: OH
Authorized by rule: ID (for wells <18 feet deep)
Individual permit: HI, MD, ID (for wells 2 18
feet deep)
General permit: WY
Public Comment Draft
July 12, 1999
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Overview of Class V Wells Included in This Study
Well Type
Solution
Mining Wells
In-Situ Fossil
Fuel Recovery
Wells
Special
Drainage
Wells
Inventory
Documented
2,694
0
-2,193
Estimated
2,694
0
>3,282
Number of
States
Potentially
with Wells
2
0
15
Injectate Constituents
> MCLs or HALs
Sulfate, Molybdenum,
Radium, Selenium,
Arsenic, Lead, Uranium,
TDS, Chloride,
Manganese, Aluminum,
Iron, Sulfate, and Zinc
Ammonium nitrate
Coliform, Turbidity,
Nitrogen-total ammonia,
Arsenic, Cadmium,
Cyanide, Lead,
Molybdenum, Nickel,
Nitrate, Radium 226, Iron,
Manganese, TDS, Sulfate,
Penta-chlorophenpl, Fecal
Coliform, Iron,
Manganese, pH, and
Color
Contamination Potential
Not likely to receive
accidental spills or illicit
discharges. No
contamination incidents
reported.
Most recovery operations, in
the last 20 years, seem to
have caused some ground
water contamination (number
of cases unknown). Problems
are due to recovery operations
not necessarily injection.
Injection wells, deemed
unlikely to receive accidental
spills or illicit discharges.
Depends on the well type and
site characteristics. Two
contamination incidents, both
involving lake level control
wells, reported.
,
State Regulations in States With
the Most Wells
Individual permit: AZ, NM
Mining permits: CO, WY
Individual permits: WY
Permit by rule: IA, IN, OH
Area permits: FL (single family swimming
pools only)
Individual permits: AK, FL, OR
Public Comment Draft
July 12, 1999
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Overview of Class V Wells Included in This Study
Well Type
Experimental
Wells
Aquifer
Remediation
Wells
Geothermal
Electric Power
Wells
Inventory
Documented
445'
10,182
234
Estimated
None
provided
10,713
234
Number of
States
Potentially
with Wells
16
50
4
Injectate Constituents
> MCLs or HALs
Nitrates, Chloride,
Sulfides, pH, Sulfates,
and Copper.
Experimental aquifer
remediation wells
sometimes inject reagents
at concentrations above
MCLs.
Sometimes inject reagents
at concentrations above
MCLs, though no data to
show levels
Antimony, Arsenic,
Cadmium, Lead,
Mercury, Strontium,
Sulfate, Zinc, IDS
Manganese, pH, Sulfate,
and Chloride
Contamination Potential
Experimental solution mining
and aquifer remediation wells
not likely to be vulnerable
because injectate quality
controlled by the conditions
of the operations being
conducted. Tracer study
wells not likely to be
vulnerable to spills and illicit
discharges. Experimental
ATES and ASR systems
inject treated water, and are
not very vulnerable to spills
or illicit discharges. One
contamination incident
reported.
Concern for unapproved
voluntary cleanups. One
contamination incident
reported.
Generally not vulnerable, in
some cases due to Best
Management Practices
(BMPs). No contamination
incidents reported.
State Regulations in States With
the Most Wells
Permit by rule: ID, TX.
Individual permit: AL, FL, NC, SC, WA.
Permit by rule, Well Construction Permit: CO
Aquifer Protection Program Permit: AZ
General or individual permit: NV.
Permit by rule or individual permit: IL, TN,
WV.
Discharge to ground water permit: WI
Authorized by rule: NH, TX
Individual permit: AZ, CA, KS, NV, OH, SC
Individual permits: CA, HI, NV, UT
1 Of the 445 documented wells, 389 are associated with tracer injection, 39 are associated with aquifer remediation, 6 are associated with
solution mining, and 11 are other various types (e.g., compressed air storage, food processing, aquifer storage, and air injection for landfill gas
control).
Public Comment Draft
July 12, 1999
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Overview of Class V Wells Included in This Study
Well Type
Geothermal
Direct Heat
Wells
Heat Pump/Air
Condition
Return Flow
Wells
Salt Water
Intrusion
Barrier Wells
Aquifer
Recharge
Wells
Aquifer
Storage and
Recovery
Wells
Noncontact
Cooling Water
Wells
Inventory
Documented
31
27,921
317
1,136
374
<5,215
Estimated
48
>32,804
(but likely
<35,000)
>611 (but
likely
<700)
>1,633
(but likely
<2,000)
>383 (but
likely
<500)
<7,800
Number of
States
Potentially
with Wells
11
46
7
22
13
32
Injectate Constituents
> MCLs or HALs
Arsenic, Boron, Sulfate,
Fluoride, Chloride, Iron,
Manganese, and TDS
Lead, Copper, Chloride,
and TDS
A few constituents
reported at levels above
the MCLs (typically meets
MCLs)
A few constituents
reported at levels above
the MCLs (typically meets
MCLs)
A few constituents
reported at levels above
the MCLs (typically meets
MCLs)
Injectate expected to meet
MCLs/HALs because
contains no additives/not
chemically altered
Contamination Potential
Unlikely to receive accidental
spills or illicit discharges. No
contamination incidents
reported.
Low contamination potential
because the wells are part of
closed systems and are
generally maintained on
private property. Four
contamination incidents
reported.
Unlikely to receive accidental
spills or illicit discharges. No
contamination incidents
reported.
Unlikely to receive accidental
spills or illicit discharges. No
contamination incidents
reported.
Unlikely to receive accidental
spills or illicit discharges. No
contamination incidents
reported.
Low probability of pipe leaks
that could result in accidental
releases. No contamination
incidents reported.
State Regulations in States With
the Most Wells
Permit by rule: ID (<1 8 ft deep)
Individual permits: CA, NM, NV, UT, OR, ID (
>1 8 ft deep)
Authorized by rule: ID (<18 feet deep), IL, KS,
ME, ND (most wells), OH, SC, TX, WV
Individual permit: AZ, DE, FL, ID (a 18 feet
deep), MD (some wells), MN, MT (for large
wells), NV, NY, NC, OR (unless individually
exempted), VT, Wl
Permit by rule: CA
Individual permits: WA
Permit by rule: CA, ID (<18 feet deep), OK, TX
Individual permits: FL, ID (>18 feet deep), NV,
SC, WA
Permit by rule: CA, TX, ID (<18 feet deep)
Individual permits: CO, FL, WA, ID (>18 feet
deep)
Permit by rule: TN and WV
Individual permit: AK and WA
Public Comment Draft
July 12, 1999
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Overview of Class V Wells Included in This Study
Well Type
Subsidence
Control Weils
Inventory
Documented
87
Estimated
>131 (but
likely
<200)
Number of
States
Potentially
with Wells
3
Injectate Constituents
> MCLs or HALs
Injectate data not
available; reasonable to
assume injectate in NY,
WV, LA exceeds MCLs
for some parameters.
Contamination Potential
Cannot be assessed due to
lack of access to details on
well design, construction, and
operation. No contamination
incidents reported.
State Regulations in States With
the Most Wells
Authorized by rule: LA, WV
Individual permits: 'WI
Public Comment Draft
July 12, 1999
10
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2. BACKGROUND
The U.S. Environmental Protection Agency (EPA) regulates five classes of underground
injection wells, called Class I through V wells, under the authority of the Safe Drinking Water
Act and through a series of underground injection control (UIC) regulations. While
implementing this program, EPA has studied Class V injection wells and pursued new
rulemaking activities arid non-regulatory approaches to improve the management of Class V
wells.
2.1 Class V Wells
As defined by EPA, an injection well is any hole that is deeper than it is wide and is used
to emplace fluids underground. This includes sophisticated designs in which holes are drilled
and cased with metal or plastic pipe. However, it also includes simple designs to drain fluids to
the subsurface. For example, natural surface depressions associated with a conduit to the
subsurface for fluid discharge (called "improved sinkholes") qualify as injection wells.
Likewise, both large-capacity septic systems and those at commercial or industrial sites qualify as
wells, as do abandoned drinking water wells that have been adapted to convey fluids
underground. Injection wells, however, do not include surface impoundments, ditches, or
trenches that are wider than they are deep.
In order to define Class V wells, you must first define the other classes of injection wells,
all of which are regulated to protect underground sources of drinking water (USDWs). USDWs
are aquifers or portions of aquifers that currently are, or could in the future be, used as drinking
water sources. Injection wells are classified based primarily on the type of fluids disposed in the
well, and EPA requirements for each well class are designed to ensure USDWs are not
threatened by the well operations. Class I wells are used to inject hazardous and non-hazardous
waste beneath the lowermost formation containing a USDW within one-quarter mile of the well.
Class II wells are used to inject fluids associated with oil and natural gas recovery and storage of
liquid hydrocarbons. Class III wells are used in connection with the solution mining of minerals.
Class IV wells, which are generally prohibited, are used to inject hazardous or radioactive wastes
into a formation which within one-quarter mile of a well bore contains a USDW. Class V wells
are defined as any well not included in Classes I through IV.
Class V injection wells are generally shallow waste disposal wells, septic systems, storm
water and agricultural drainage systems, or other devices used to release fluids either directly into
USDWs or into the shallow subsurface that overlies USDWs. In order to qualify as a Class V
well, the fluids released cannot be a hazardous waste as defined under the Resource Conservation
and Recovery Act (RCRA). Frequently, Class V wells are designed as no more than shallow
holes or septic tank and leachfield combinations intended for sanitary waste disposal. This study
focuses on the following 23 categories of Class V wells2:
2Three other categories of Class V wells - motor vehicle waste disposal wells, large-capacity
cesspools, and industrial wells — were proposed to be subject to additional UIC regulation (63 FR 40586,
Public Comment Draft
July 12, 1999 11
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Categories of Class V Wells
1. Agricultural Drainage Wells include all wells receiving agricultural runoff. This includes improved sinkholes,
abandoned drinking water wells, and underground drain tiles and cisterns receiving agricultural runoff, excess
irrigation water, and flood water. Those drain tiles that discharge to a ditch are exempted from UIC regulation.
2. Storm Water Drainage Wells are shallow injection wells designed for the disposal of rain water and melted
snow. These wells typically drain paved areas such as streets and parking lots, or roofs. Improved sinkholes and
abandoned drinking water wells are considered storm water drainage wells when they receive storm water runoff.
3. Wells Used to Drain Fluids from Carwashes Where No Engine or Undercarriage Washing is Performed
(called "carwash wells" in the remainder of this report). This includes floor drains in bays of coin-operated,
manual carwashes where people use hand-held hoses to wash only the exterior of cars, trucks, and other vehicles.
These kinds of carwashes are sometimes referred to as "wand washes," as opposed to "tunnel washes" or "rollover
washes" where automatic washing equipment is used.
4. Large-Capacity Septic Systems are septic tanks and fluid distribution systems, such as leachfields or wells, used
to dispose of sanitary waste only (not industrial waste, motor vehicle waste fluids, or other kinds of commercial
waste that does not qualify as "sanitary waste"). These kinds of systems are typically used by multiple dwellings,
business establishments, or communities for the disposal of sanitary waste. Individual or single family septic
systems and non-residential systems having the capacity to serve fewer than 20 persons a day are not included.
5. Food Processing Wells are any type of system that accepts food processing wastewater and releases it into or
above USDWs. This includes systems used to dispose of wastewaters generated from the preparing, packaging,
or processing of food products (e.g., slaughterhouses, seafood or poultry processing facilities, etc.), not septic
systems used solely for the disposal of sanitary waste.
6. Sewage Treatment Effluent Wells are used to inject treated effluent from publicly owned treatment works or
treated effluent from privately owned treatment facilities receiving solely sanitary waste. A well that receives
effluent from a privately owned treatment facility that receives industrial waste (as opposed to solely sanitary
waste) qualifies as an industrial well, not a sewage treatment effluent well. Also, a well that injectsmunicipal
waste beneath the lowermost USDW in an area qualifies as a Class I well rather than a Class V well.
7. Wells Used to Inject Fluids from Laundromats Where No Onsite Dry Cleaning is Performed or Where No
Organic Solvents are Used for Laundering (called "laundromat wells" in the remainder of this report). This
includes drains that lead to drywells (open holes) or septic systems at coin-operated laundromats that do not have
onsite drycleaning services.
8. Spent Brine Return Flow Wells are used to dispose of brines from which minerals, halogens, and other
compounds have been extracted. These wells are commonly associated with manufacturing facilities that produce
specialty chemicals such as boron, bromine, magnesia, or their derivatives.
9. Mine Backfill Wells are used to place slurries of sand, gravel, cement, mill tailings or refuse, fly ash, or other
solids into underground mines. These wells can serve a variety of purposes, including subsidence prevention,
filling dangerous mine openings, disposing of wastes from mine operations, and fire control.
10. Aquaculture Waste Disposal Wells dispose of water used for the cultivation of marine and freshwater animals
and plants under controlled conditions.
11. Solution Mining Wells are used to extract desired minerals from mines that have already been conventionally
mined. Leaching solutions (called "lixiviants") are injected through solution mining wells into an underground
ore deposit, metals are leached from the ore, and the resulting "pregnant" solution is pumped to the surface for
subsequent recovery from the solution. Wells used to inject lixiviant into ore bodies that have not been
conventionally mined beforehand are considered Class HI solution mining wells, not Class V.
July 29, 1998) and are not included within the scope of this draft report.
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Categories of Class V Wells (continued)
12. In-Situ Fossil Fuel Recovery Wells are used for recovery of lignite, coal, tar sands, and oil shale. The wells
inject water, air, oxygen, solvents, combustibles, or explosives into underground or oil shale beds to liberate fossil
fuels. Underground coal gasification and in-situ oil shale retorting are two processes that use in-situ fossil fuel
recovery wells.
13. Special Drainage Wells include a variety of wells such as potable water tank overflow, construction dewatering,
swimming pool drainage, and mine dewatering wells. These wells receive fluids that cannot be classified as
agricultural, storm water, or industrial drainage.
14. Experimental Wells are used to test new technologies. Wells are not classified as experimental if the technology
can be considered under an established well subclass. For example, a well used for bioremediation should be
classified as an aquifer remediation well.
15. Aquifer Remediation Wells are used to clean up, treat, or prevent contamination of ground water. Treated
ground water (from pump and treat systems), bioremediation agents, or other contaminant recovery enhancement
materials may be injected into the subsurface via these wells. These wells may be associated with RCRA or
Superfund cleanup projects.
16. Geothermal Electric Power Wells dispose of spent (meaning cooled) geothermal fluids following the extraction
of heat for the production of electric power.
17. Geothermal Direct Heat Wells dispose of spent (cooled) geothermal fluids following the extraction of heat used
directly, without conversion to electric power, to heat homes or provide heat to commercial or industrial
activities.
18. Heat Pump/Air Condition Return Flow Wells reinject ground water that has been passed through a heat
exchanger in order to heat or cool buildings. A heat pump takes thermal energy from the ground water and
transfers it to the space being heated. When cooling is required, the heat pump removes heat from a building and
transfers it to the ground water.
19. Salt Water Intrusion Barrier Wells are used to inject fluids to prevent the intrusion of salt water into an aquifer.
These wells may have secondary purposes, such as to recharge an aquifer with fresh water to be used later.
20. Aquifer Recharge Wells are used to inject fluids to recharge an aquifer. These wells may have secondary
purposes, such as salt water intrusion prevention, subsidence control, or aquifer storage and recovery.
21. Aquifer Storage and Recovery Wells are used to inject water for later recovery and use. These wells may have
secondary purposes, such as aquifer recharge.
22. Noncontact Cooling Water Wells. Noncontact cooling water is water used in a cooling system designed to
maintain constant separation of the water with process chemicals. Wells that inject contact cooling water or
noncontact cooling water that contains additives (e.g., corrosion inhibitors, biocides) or is contaminated compared
to the original source water are considered industrial wells.
23. Subsidence Control Wells inject fluids to control land sinking, or subsidence, caused by ground water
withdrawal and other activities (but not oil and gas production).
EPA estimates that more than 501,000 Class V wells within the above categories
currently exist in the United States. These wells are located in virtually every State, especially in
unsewered areas where the population is likely to depend on ground water.
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2.2 Safe Drinking Water Act
The Safe Drinking Water Act (SDWA or the Act) is designed to protect the quality of
drinking water in the United States. Part C of the Act specifically mandates the regulation of
underground injection of fluids through wells.
Section 1421 of the Act requires EPA to propose and promulgate regulations specifying
minimum requirements for State programs to prevent underground injection that endangers
drinking water sources. EPA promulgated administrative and permitting regulations, now in 40
CFR Part 144 and 146, on May 19,1980 (45 FR 33290), and technical requirements in 40 CFR
Part 146 on June 24,1980 (45 FR 42472). These regulations have since been amended on
several occasions.
Section 1422 of the Act provides that States may apply to EPA for primary responsibility
to administer the UIC program (those States receiving such authority are referred to as "Primacy
States"). Where States do not seek this responsibility or fail to demonstrate that they meet EPA's
minimum requirements, EPA is required to prescribe, by regulation, a UIC program for such
States. These direct implementation (DI) programs were established in two phases, on May 11,
1984 (49 FR 20138) and November 15,1984 (49 FR 45308).
2.3 UIC Regulations
Under the EPA UIC Program, Class V wells are currently authorized by rule, meaning
they do not have to obtain an individual permit unless required to do so. 'Under 40 CFR
144.12(a), owners or operators of all injection 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 human health. Sections 144.12(c) and (d) specify actions to be
taken by the UIC Program Director if a well is not in compliance with section 144.12(a).
Owners or operators of Class V wells are also required to submit basic inventory and
assessment information under 40 CFR 144.26. In addition, Class V wells are subject to the
general program requirements of section 144.25, under which the UIC Program Director may
require a permit, if necessary, to protect USDWs. Moreover, under section 144.27, EPA may
require owners or operators of any Class V well, in EPA-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.
2.4 1987 Report to Congress on Class V Wells
In accordance with the 1986 Amendments to the SDWA, EPA summarized information
on Class V wells in a Report to Congress entitled Class V Injection Wells - Current Inventory;
Effects on Ground Water; and Technical Recommendations, September 1987 (EPA Document
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Number 570/9-87-006). That report presents a national overview of Class V injection practices
and State recommendations for Class V design, construction, installation, and siting
requirements. These State recommendations, however, did not give EPA a clear mandate on
what, if any, additional measures were needed to control Class V wells on the national level. For
any given type of well, the recommendations varied broadly and were rarely made by more than
two or three States. For example, the recommendations for large-capacity septic systems ranged
from further studies (three States) to Statewide ground water monitoring (one State).
2.5 Actions Since the 1987 Report to Congress
On December 30,1993, the Sierra Club filed a complaint against EPA in the United
States District Court for the District of Columbia alleging that EPA failed to comply with section
1421 of the SDWA regarding publication of proposed and final regulations for Class V injection
wells. The complaint alleged that EPA's current regulations regarding Class V wells do not meet
the SDWA's statutory requirements to "prevent underground injection which endangers drinking
water sources."
On August 31,1994, EPA entered into a consent decree with the Sierra Club requiring
that by no later than August 15,1995, the EPA Administrator sign a notice to be published in the
Federal Register proposing regulatory action that fully discharges the Administrator's
rulemaking obligation under section 1421 of the SDWA with respect to Class V injection wells.
The consent decree further required that a final rule on Class V wells be signed by November 15,
1996. Accordingly, on August 15,1995, the Administrator signed a notice of proposed
rulemaking intended to fulfill this obligation (60 FR 44652, August 28, 1995). In this notice,
EPA proposed not to adopt additional federal regulations for any types of Class V injection well.
Instead, the Agency proposed to address the risks posed by certain wells using existing
authorities and a Class V management strategy designed to (1) speed up the closure of potentially
endangering wells; and (2) promote the use of best management practices to ensure that other
Class V wells of concern do not endanger USDWs.
EPA received many comments that supported the Agency's proposal to not impose more
regulations for Class V wells. However, EPA also received a number of comments that raised
concerns about the proposal. In particular, several commenters questioned whether a UIC
program without additional requirements for relatively high-risk well types, including Class V
motor vehicle waste disposal wells, industrial waste disposal wells, and large-capacity cesspools,
could prevent endangerment to drinking water sources as required by the SDWA. The Sierra
Club alleged that the proposal failed to carry out statutory requirements.
Based on these and other comments, EPA decided to reconsider the 1995 proposed
approach. Because this reconsideration would extend the time necessary to complete the
rulemaking for Class V wells, EPA and the Sierra Club entered into a modified consent decree
on January 28,1997 that extended the dates for rulemaking that had been in the 1994 decree.
The modified decree requires three actions.
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• First, by no later than July 17,1998, the EPA Administrator was required to sign a
notice to be published in the Federal Register proposing regulatory action that
fully discharges the Administrator's rulemaking obligation under section 1421 of
the SDWA with respect to those types of Class V injection wells presently
determined to be high risk. According to the consent decree, the Administrator
must sign a final rulemaking for high-risk Class V wells by no later than August
31,1999.
• Second, by no later than September 30,1999, EPA must complete a study of all
Class V wells not included in the rulemaking on high-risk Class V injection wells.
Based on this study, EPA may find that some of these other types of Class V wells
also pose a high risk.
• Third, by no later than April 30,2001, the EPA Administrator must sign a notice
to be published in the Federal Register proposing to discharge the Administrator's
rulemaking obligations under section 1421 of the SDWA with respect to all Class
V injection wells not included in the first rulemaking for Class V injection wells
identified as high risk. That proposal will supersede the 1995 proposal with
respect to all remaining Class V wells. The Administrator must sign a final
rulemaking for these remaining Class V wells by no later than May 31, 2002.
On July 29,1998 (63 FR 40586), in response to the first action required under the
modified consent decree, EPA proposed revisions to the Class V UIC regulations that would add
new requirements for the following three types of wells that, based on available information, are
believed to pose a high risk to USDWs: motor vehicle waste disposal wells, large-capacity
cesspools, and industrial wells. All remaining Class V wells, which make up the 23 categories
defined above, are required by the modified consent decree to be studied further to determine
whether they warrant additional UIC regulation. This study, known as the Class V study, is the
subject of the remainder of this report.
3. STUDY APPROACH
EPA initiated the Class V study by convening a workgroup of EPA and State UIC
representatives to help design the research effort. Workgroup members met during the spring
and summer of 1997 to develop a method for collecting information. Based on these meetings,
EPA concluded that State programs have information useful to the, study, but that additional
information should be collected from other sources as well. EPA also recognized that very little
inventory information (i.e., data on the numbers of existing Class V wells in different locations)
was available from the States for some types of wells.
As a result of this initial scoping, the final Class V study design had two components: (1)
an information collection effort for the 23 Class V well categories; and (2) inventory models to
estimate the number of storm water drainage wells and large-capacity septic systems, two types
of wells that were believed to be quite prevalent but for which adequate inventory information
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was particularly lacking. These two components are described below in Sections 4 and 5,
respectively. The workgroup continued to meet throughout both of these efforts to provide
feedback as the study progressed.
The information developed from this research has been compiled into the following
products.
• A 24-volume final report:
> Volume 1 (this volume) provides general information on the study
approach and results;
»• Volumes 2-24 provide a well-specific information summary for each of
the 23 categories of wells that were studied; and
* Five appendices, as follows:
Appendix A provides the Class V Study Information Collection
Request.
Appendix B presents the questionnaires that were used in general
information collection effort.
Appendix C outlines the methods and information used to select
census tracts to visit for the purpose of developing the inventory
models, presents the results from those census tract visits, and
summarizes the inventory model development and results.
Appendix D presents the drinking water standards and other
criteria used in the well-specific summaries to compare to data on
the quality of fluids released by the 23 well types; and
Appendix E presents information on the ground water persistence
and mobility of various chemicals possibly released by Class V
wells.
• A set of 58 binders that contain all of the information collected on Class V wells
in each State and on several Indian lands.
4. INFORMATION COLLECTION
The information collection consisted of four activities: a literature review, State and EPA
Regional data collection, requests to the public for data, and peer review. Each of these efforts is
described in turn below.
4.1 Literature Review
EPA started the search by locating available references from the Ground Water Protection
Council's (GWPC's) Injection Well Bibliography. To supplement this bibliography, EPA used a
list of key words to search the Boston Library Consortium, individual libraries, ten scientific
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databases, the World Wide Web, the Library of Congress, and libraries linked to the Library of
Congress. EPA also sought available information through targeted phone calls to trade
associations, research institutes, universities, and other sources.
4.2 State and EPA Regional Data Collection
4.2.1 Data Collection Methods
EPA prepared an Information Collection Request (ICR) that outlined the methodology,
identified the information to be collected, and calculated the burden associated with responding
to a Class V survey. OMB approved the ICR (OMB # 240-0194) on July 31,1998.
The first step in the collection process was to ask EPA Regional representatives to
identify the best UIC contact for each State in the Region. The scope of this search included all
50 States, the District of Columbia, Guam, the Commonwealth of Puerto Rico, the Northern
Mariana Islands, the Virgin Islands, American Samoa, and the Trust Territory of the Pacific
Islands. It also included Indian lands in EPA Regions 5, 8, 9, and 10.
Next, EPA called each contact person to explain the study, obtain some preliminary
information about the data the contact had available, and describe an information request letter
that the contact would soon receive. This letter requested information on the types of wells in
each State and appropriate contacts for those wells.
EPA then sent well-specific questionnaires to the contacts identified in responses to this
letter. EPA distributed nearly 700 questionnaires to EPA Regional, State, and local respondents.
Because some States were unable to complete the questionnaires due to resource constraints and
other States (particularly DI States) had very limited information to share, EPA supplemented the
information from the questionnaires through follow-up telephone interviews and on-site file
searches in ten primacy States (Massachusetts, Maryland, West Virginia, Florida, Illinois,
Minnesota, Kansas, Wyoming, Oregon, and Washington); two DI States (California and
Colorado); and two Regional Offices with DI States (Region 3: Pennsylvania, Virginia, and the
District of Columbia; and Region 8: Colorado). In some cases, EPA also completed summaries
using information from other sources such as State Internet Web sites or studies and reports.
4.2.2 Information Obtained
EPA received information on all but a few UIC programs. American Samoa was the only
program to report that no Class V wells exist. Altogether, EPA received and completed by
telephone approximately 475 questionnaires, conducted scores of telephone conversations, and
received a large volume of written and e-mail correspondence. All of the information obtained is
included in the set of 58 State binders.
While EPA collected a significant amount of information, the study also discovered
where States are lacking data. The following sections summarize the information collected arid
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limitations of that information in four categories: inventory data, injectate quality data,
contamination incidents, and regulatory authority and implementation.
Inventory Data
Two generalizations can be made about the inventory information that was obtained:
• States generally maintain accurate inventories for mining, geothermal, aquifer
recharge, aquifer storage and recovery, and aquifer remediation wells. Because
these wells often require State approval before construction, States believe that
they have kept accurate records of these wells.
• For other well types, States and EPA Regions suspect that their inventories
underestimate the true number of wells. For example, inventories of agricultural
drainage wells may be inaccurate because these wells are often located on private
property to which UIC inspectors have limited access. The survey responses
indicate that agricultural drainage and storm water drainage wells are often
constructed and used by individuals who may not be aware of Class V regulations
and, thus, have never been reported. Furthermore, local agencies often have
jurisdiction over these well types, so they may not be accounted for in a State's
inventory.
In addition, there are significant uncertainties associated with the inventory data:
• In some cases, different sources provided different numbers, both for documented
and estimated number of wells. In particular, documented numbers of wells
reported in survey responses sometimes differed from the numbers reported in
computer database printouts provided by the same State staff. These differences
occasionally could not be reconciled.
• Estimated numbers were often provided as a range, or as "more than" or "less
than" the documented number.
• • In some State databases, different subclasses of wells could not be distinguished.
For example, most States do not distinguish between carwash wells, laundromat
wells, food processing wells, or non-contact cooling water wells, grouping them
instead into a general industrial well category. Also, some States do not
distinguish between aquifer storage and recovery wells and aquifer recharge wells
in their current inventories.
• State classification of some well types differs from the classification used in this
study. This was commonly the case for experimental wells.
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• Although a number of studies that discuss the likely existence of agricultural
drainage wells in various areas were found, EPA was unable to get much
documentation of the number or location of this type of well. State and local
officials often either did not know of the existence of agricultural drainage wells
or simply reported that there were none because they were banned or being phased
out in the State.
• Most States use different criteria than in the federal UIC regulations for
distinguishing between small and large-capacity septic systems (most States use a
flow threshold rather EPA's 20 persons-a-day definition).
Injectate Quality-Data
The injectate quality data obtained during the study vary widely. They range from a one-
time sample at one well to multiple samples at multiple wells in multiple States. The data
include results from routine and special monitoring, studies, permit applications, journal articles,
and reports.
There is little injectate data available for well types perceived to pose low risks to
USDWs, such as heat pump/air conditioning return flow wells. State injectate sampling data for
agricultural and storm water drainage wells were also difficult to find since many of these wells
are located on private property. However, many studies on these well types have been conducted
and EPA more often found injectate data in the literature.
Contamination Incidents
Contamination incidents are often handled by an office other than the UIC program
office, such as separate State enforcement and compliance offices. The study was less successful
in tapping these other offices for information. As a separate issue, States were often reluctant to
disclose contamination incidents, especially when enforcement action was pending.
Furthermore, very little documentation is available that directly links contamination problems to
Class V wells, although wells are often suspected of contributing to contamination.
• Regulatory Authority and Implementation
Regulatory authority over Class V wells varies widely among States. Four typical
regulatory schemes are as follows:
• General authority to protect USDWs. The State UIC Program Director has
discretionary authority to take actions necessary to protect USDWs.
• Permit-by-rule. An entire class of wells is deemed permitted as long as they
comply with standards and requirements found in the regulations.
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• General permit. An identical permit, based on State technical regulations, is
issued for each well in a specified class of wells.
• Authority to issue site-specific permits, inspect, and take enforcement action.
This authority may be linked to technical standards in the regulations and/or may
give the State UIC Program Director discretion to include standards necessary to
protect USDWs.
Where States have technical standards, they may contain requirements for siting or
setbacks, construction, mechanical integrity testing, injection pressure or flow, injectate quality,
monitoring, best management practices, reporting, financial responsibility, and closure and post-
closure care.
State UIC programs are generally resource-constrained. This means the States are often
not able to implement UIC programs as vigorously as they would like. This lack of resources
typically manifests itself in a State program that is more reactive than proactive. For example:
• States do not make wide use of discretionary authority, except when problems are
evident;
• Sampling and inspections are often problem- or complaint-driven with few States
conducting routine inspections; and
• States are often unable to confirm that abandoned wells are properly plugged so
that contaminants cannot enter them.
4.3 Requests to the Public for Information
EPA sought information from the public for the Class V study. One avenue for obtaining
information was the National Drinking Water Advisory Council (NDWAC). The Class V study
was an agenda topic during a NDWAC workgroup meeting held on January 7-8,1999 in Denver,
Colorado (see 63 FR 66168, December 1,1998). Issues relevant to the study also were discussed
in another NDWAC workgroup meeting on March 25-26,1999 in Washington, DC. In both of
these meetings, members of the public were allowed to make statements. To obtain additional
information on issues raised during these NDWAC discussions, EPA accompanied State UIC
program staff on site visits of facilities with Class V wells in New Hampshire and Maine.
EPA also requested information through two' notices in the Federal Register.
• 64 FR 1008, January 7,1999, Call for Peer Reviewers and Data on Aquaculture
Injection Wells, Mining Wells, Sewage Treatment Effluent Wells, and Other
Class V Injection Wells Including Certain Industrial Wells; and
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64 FR 1007, January 7,1999, Call for Peer Reviewers and Data on Aquifer
Storage and Recovery Wells, Aquifer Recharge Wells, Saline Intrusion Barrier
Wells, Subsidence Control Wells, and Aquifer Remediation Injection Wells.
EPA staff made presentations about the status of the study at semiannual meetings of the
GWPC, including a March 1998 meeting in Annapolis, MD, a September 1998 meeting in
Sacramento, CA, and a March 1999 meeting in Washington, DC. During each of these
presentations, the meeting participants were requested to provide available information and to
identify additional information sources.
EPA also maintained an Internet Web site for the Class V study (http://www.epa.gov/
OGWDW/uic/cl5study.html). The Web site included definitions of the well types, successive
drafts of well-specific information summaries, and other information about the study. It also
included a form that anyone could submit on-line to provide information about Class V wells.
The Web site, which was frequently visited, was advertised in the Federal Register notices listed
above, at the GWPC meetings, and in other forums.
Finally, the July 28,1998 proposed rule on Class V motor vehicle waste disposal wells,
industrial wells, and large-capacity septic systems introduced the study and gave the pubic an
opportunity to comment on the need to regulate those and all other kinds of Class V wells.
Indeed, several comments were submitted providing information useful to the Class V study,
including additional information on Class V food processing waste disposal wells and other types
of Class V wells in Tennessee. EPA followed up on these comments by conducting, along with
State UIC Program staff, site visits to a number of food processing facilities in Tennessee that
own or operate Class V wells.
4.4 Peer Review
EPA coordinated peer reviews of draft information summaries for each of the 23 types of
wells studied in order to ensure technical accuracy and completeness of the documents. These
reviews ranged from a formal peer review process in which recognized technical experts for
selected well types were sought, to an informal process hi which drafts of the well-specific
information summaries were distributed to teams of State, EPA Regional, and EPA Headquarters
reviewers.
During these processes, reviewers were supplied with the draft information summary and
a charge that asked general and specific questions to help guide the review. Some of the reviews
included a conference call as an opportunity for the reviewers to discuss and share thoughts on
the document. EPA incorporated the comments received into the information summaries. Upon
completion of the review process, EPA also developed a table explaining how EPA used the
comments.
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5. INVENTORY MODELS
Although the general information collection effort did include storm water drainage
wells and large-capacity septic systems, the participants in the Class V study workgroup meetings
told EPA that very little inventory data on these wells were available from the States. In general,
States believe that their inventories of these well types are inaccurate and would not provide a
realistic national estimate. As a result, EPA determined that it would be necessary to construct
statistical inventory models to provide national estimates of the numbers of storm water drainage
wells and large-capacity septic systems.
The inventory models predict the number of storm water drainage wells and large-
capacity septic systems nationally based on geologic, demographic, and other characteristics.
There is little theory ~ and virtually no empirical research - regarding the factors affecting the
number and location of these wells. Therefore, EPA selected and visited a sample of 99 census
tracts across the nation to collect information on the numbers of wells and a variety of factors
that might influence the wells' prevalence. EPA then analyzed the data collected from these
visits to develop mathematical models that can be used to estimate the numbers of storm water
drainage wells and large-capacity septic systems in other locations based on certain
characteristics known to exist in those areas. Appendix C describes the development and results
of the inventory models in more detail.
5.1 Storm Water Drainage Wells
Storm water drainage wells were located in 22 of 99 census tracts surveyed. Such wells
were primarily found along streets, but were also common in parking lots and residential areas.
A few storm water drainage wells were also found in other areas, such as along bike paths or in
recreational vehicle parks.
The estimate of the number of storm water drainage wells in the nation is the combination
two estimates: a model estimate for wells in non-urbanized areas, and State estimates of the
number of wells in urbanized areas. This approach is necessary because of the sampling strategy.
Urbanized areas were excluded from the sample based on the assumption that very few storm
water drainage wells would be found in urbanized areas. While a few cities make extensive use
of these wells, EPA could not adequately represent all urbanized areas in the sample to account
for these wells because of the relatively small size of the sample. Therefore, EPA relied on State
and other estimates gathered as part of the general data collection effort to account for the wells
in urbanized areas, and used the sample to build a model of the number of wells in non-urbanized
areas.
The estimate for the total number of storm water drainage wells hi the country is
approximately 125,500. This represents the sum of the number of documented and estimated
wells in urbanized areas (35,000 and 26,500, respectively) and the model's estimate for non-
urbanized areas (64,000).
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5.2 Large-Capacity Septic Systems
Large-capacity septic systems were found in sewered and unsewered areas and were used
in a wide variety of circumstances. They were found in 88 out of 99 of the census tracts visited.
The largest percentage of systems were located at churches, but many were also found in
commercial areas, restaurants, campgrounds, public buildings, motels, residential areas,
industrial areas, schools, recreational areas, and a few in other areas such as farms and ranger
stations.
The model assumes that the number of large-capacity septic systems in a census tract is a
linear function of the number of households on septic systems in the tract, the tract's housing
density, and the percentage of soil in the tract that is poorly drained. Using an equation with
these variables, the model predicts approximately 290,000 large-capacity septic systems
nationwide. The 95 percent prediction interval is 250,000 to 330,000.
6. WELL-SPECIFIC SUMMARIES
This section presents information summaries for each of the 23 categories of Class V
wells addressed in the study. Volumes 2 through 24 of this report provide more detail on each of
these well categories in the same order in which they appear below. Although each summary
below is tailored to the particular issues relevant to the different wells, they all address the
following basic topics in the following sequence: (1) well purpose and fluids released; (2) the
extent to which the fluids released exceed drinking water standards at the point of injection; (3)
generalizations about the characteristics of the underground zone receiving fluids from the wells;
(4) contamination incidents or studies, if any; (5) vulnerability of the wells to spills or illicit
discharges; (6) prevalence of the wells; and (7) existing State and federal controls. If any other
factors are key in summarizing information on a given well type, they are woven into appropriate
places within this general outline.
6.1 Agricultural Drainage Wells
Agricultural drainage wells (ADWs) are used in many places throughout the country to
drain excess surface and subsurface water from agricultural fields, including irrigation tailwaters
and natural drainage resulting from precipitation, snowmelt, floodwaters, etc. ADWs may also
receive animal yard runoff, feedlot runoff, dairy runoff, or runoff from any other agricultural
operation. In some cases, these fluids are released into ADWs in order to recharge aquifers that
are used as sources of irrigation water.
The water that drains into ADWs may contain high levels of naturally occurring minerals
or may be contaminated with fertilizers, pesticides, or bacteria and other microorganisms.
Available sampling data show that the primary constituent in ADW injectate that is likely to
exceed health-based standards is nitrate. The data also indicate that boron, sulfate, coliforms,
and certain pesticides (cyanazine, atrazine, alachlor, aldicarb, carbofuran, 1,2-dichloropropane,
and dibromochloropropane) in agricultural drainage have exceeded primary, or health-based,
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maximum contaminant levels (MCLs) or health advisory levels (HALs). Total dissolved solids
(TDS) and chloride in some ADWs also have been measured above secondary MCLs, which are
designed to protect against adverse aesthetic effects such as objectionable taste and odor.
Concerns about high concentrations of contaminants entering ADWs are compounded by'
the fact that the point of injection for most ADWs is within a permeable coarse-grained unit,
karst, or a fractured unit. Such hydrogeologic settings usually allow contaminants to migrate
readily without significant attenuation.
A number of studies and incidents have shown that ADWs have in fact contributed to or
caused ground water contamination. For example, several studies document nitrate
contamination of ground water in agricultural areas. Some of these studies clearly link the nitrate
contamination to ADW use, with the Class V survey results going so far as to suggest that one-
third of the drinking water supply wells in Humboldt and Pocahontas Counties in Iowa have been
contaminated by nitrate from ADWs. Other studies, however, do not clearly distinguish nitrate
contamination from ADWs versus more general sources of nonpoint source pollution associated
with agriculture. In addition to these nitrate studies, there are two known contamination
incidents in Iowa (in 1977 and 1997) involving direct discharges from septic tanks to ADWs. In
one of these incidents, the ADW was also contaminated by runoff from the field application of
hog manure. Other contamination incidents include ground water and drinking water
contamination linked to 15 drainage wells in Minidoka County, Idaho in 1979, and a community
supply well in Dane, Wisconsin being contaminated around 1988 by atrazine draining into an
ADW.
A further concern associated with ADWs is the potential for some wells to be vulnerable
to spills or illicit discharges. The close proximity of ADWs to large earthen lagoons for storing
manure at large-scale confined animal feeding operations is a particular issue that has been
recognized for some wells in Iowa, although the growth of such operations nationwide may also
make it an issue in other locations. The two cases cited above involving septic tank discharges to
ADWs in Iowa may also illustrate a practice that is not uncommon in other States. Investigations
after one of those incidents estimated that as many as 30 percent of the rural septic tanks in one
Iowa town were directly connected to ADWs. Separately, some ADWs may occasionally receive
accidental releases of materials during farming operations, such as spills of motor oils used in
equipment or bulk releases of pesticides during storage or handling. Moreover, if not carefully
managed, the land application of manure in areas drained by ADWs can cause contamination, as
illustrated by one or the incidents reported in Iowa.
According to the State and EPA Regional survey conducted for this study, there are at
least 1,069 documented ADWs and more than 2,914 ADWs estimated to exist in the U.S.
Although believed to exist in at least 20 States, more than 95 percent of the documented wells are
in just five States: Idaho (303), Iowa (290), Ohio (>200), Texas (135), and Minnesota (92). In
truth, there may be thousands more ADWs than these results suggest, recognizing the significant
uncertainties in the current inventory. For example, it is likely that more ADWs exist than have
been counted because such wells occur on rural private property that is not accessible to UIC
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inspection, some ADWs are hard to find or not even known to exist because they consist of tile
drainage lines entirely below ground, and ADWs have been grouped with storm water drainage
wells in some State inventories. In general, the construction of new ADWs has been decreasing
since the 1950s. This is a trend that is expected to continue as more and more States are
beginning to ban new ADWs and phase existing ones out.
States with the majority of known ADWs are developing and implementing regulatory
programs to address these wells. Specifically:
• In Idaho, wells >18 feet deep are individually permitted, while shallower wells are
permitted by rule.
• In Iowa, all ADWs that existed before February 18,1998 must close or get a
permit by December 31,2001. New wells in Iowa are generally prohibited,
although they may be permitted under strict conditions.
• Ohio authorizes all ADWs by rule.
• All of the known ADWs in Texas have received individual permits.
• Minnesota bans new ADWs and requires existing ADWs to close when found, but
acknowledges that some continue to exist.
The regulatory picture in several other States with few or no ADWs in the current inventory is
similar. For example, Georgia, North Carolina, and North Dakota have banned new ADWs and
require existing ADWs to close when they are found. Oregon, Washington, and Wisconsin also
have a ban, but recognize that some ADWs continue to exist.
These regulatory programs in the States are supplemented somewhat by non-regulatory
programs and guidance at the federal level. Namely, under the authority of the Clean Water Act,
the U.S. Department of Agriculture and EPA released a draft Unified National Strategy for
Animal Feeding Operations on September 11,1998. Once finalized, the goal of this strategy will
be for owners and operators of animal feeding operations to take actions to minimize surface and
ground water pollution from confinement facilities and land application of manure. In addition,
under the Coastal Zone Act Reauthorization Amendments, 29 coastal States are required to
develop and implement Coastal Nonpoint Pollution Control Programs addressing nonpoint
pollution from agriculture and other sources. Although these programs are aimed primarily
toward surface water protection, they also will benefit ground water by emphasizing contaminant
source reduction and conservation measures such as nutrient, integrated pest, and irrigation
management. To support the development and implementation of these programs, EPA issued
Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal
Waters. Much of this guidance is relevant to Class V ADWs because it presents techniques for
minimizing seepage to ground water.
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6.2 Storm Water Drainage Wells
Storm water drainage wells are used extensively throughout the country to remove storm
water or urban runoff (e.g., precipitation and snowmelt) from impervious surfaces such as
roadways, roofs, and paved surfaces to prevent flooding, infiltration into basements, etc. The
primary types of storm water drainage wells are bored wells, dug wells, and improved sinkholes.
Subsurface disposal of storm water is prevalent in places where there is not enough space, or site
characteristics do not allow, retention basins, where there is not a suitable surface water to
receive the runoff, or where near-surface geologic conditions provide an attractive drainage zone.
The runoff that enters storm water drainage wells may be contaminated with sediments,
nutrients, metals, salts, fertilizers, pesticides, or microorganisms. Storm water sampling data
indicate that the concentration of arsenic, cadmium, chromium, nickel, nitrate, zinc, and certain
organics (e.g., aldrin, benzene, chloroform, endrin, methyl tert-butyl ether, phenol, and toluene)
in storm water runoff have exceeded primary MCLs or HALs. Available sampling data show
that suspended sediment, the principal pollutant in storm water drainage (i.e., present in the
largest amount), often exceeds secondary MCLs. Chloride, iron, and manganese concentrations
above secondary MCLs also have been measured in some runoff entering storm water drainage
wells.
In general, the point of injection for most storm water drainage wells is into sandy, porous
soils, a permeable coarse-grained unit, karst, or a fractured unit because these types of formations
can readily accept large volumes of fluids. Such hydrogeologic characteristics usually allow
contaminants to migrate readily into ground water without significant attenuation.
Contamination related to storm water drainage wells has been reported to various degrees
in Ohio, Kansas, Wisconsin, California, Washington, Arizona, Oklahoma, Tennessee, New York,
Indiana, Florida, Kentucky, and Maryland. Several studies, however, do not clearly distinguish
contamination from storm water drainage wells versus more general, nonpoint source pollution.
The following three examples demonstrate cases in which storm water drainage wells have
contributed to or caused ground water contamination.
• In 1989, a commercial petroleum facility in Fairborn, Ohio accidentally released
21,000 gallons of fuel oil that overflowed a dyked area and entered two storm
water drainage wells.
• In 1980, organic solvent contamination was discovered in drinking water supply
wells for Lakewood, Washington following the disposal of organic waste solvents
and sludge in leach pits and storm water drainage wells at McChord Air Force
Base.
• In 1998, the Oak Grove, Kentucky water plant (a ground water system) was shut
down due to a sharp increase in raw turbidity following a severe storm event.
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As illustrated by some of these incidents, storm water drainage wells are generally
vulnerable to spills or illicit discharges of hazardous substances, as they are often located in close
proximity to roadways, parking lots, and commercial/industrial loading facilities where such
substances are handled and potentially released. Public commenters on the July 28,1998
proposed revisions to the Class V UIC regulations cited cases in which citizens have been
observed draining used motor oil into storm water drainage wells.
Based on the survey and inventory model described above, there are approximately
115,000 documented storm water drainage wells and approximately 125,500 storm water
drainage wells estimated to exist in the U.S. About 50 percent of the documented wells are in
seven western States: Arizona (14,857), California (3,743/30,000 estimated), Washington
(22,688/700,000 estimated), Oregon (4,148/20,000 estimated), Idaho (5,359/7,575 estimated),
Montana (4,000/5,000 estimated), and Utah (2,940). Six other States contain the majority of the
remaining wells: New York (Ml30,000 estimated), Ohio (3,036/30,000 estimated), Florida
(4,430), Michigan (1,301), Maryland (1,678), and Hawaii (2,622). There is considerable
uncertainty regarding the exact number of storm water drainage wells for several reasons, as
discussed hi Sections 4.2.2 and 5.1 above. In general, the construction of new storm water
drainage wells is expected to increase. Many States are permitting new wells and the increased
regulation of surface discharge under the National Pollutant Discharge Elimination System
(NPDES) may lead to increased underground injection.
Some States with the majority of storm water drainage wells have developed and are
implementing regulatory programs to address these wells. Examples include the following:
• In Idaho, wells <, 18 feet deep are authorized by rule, while deeper wells are
individually permitted.
• In Arizona, California, Hawaii, Florida, Maryland, and New York, storm water
drainage wells are individually permitted.
Other States with large numbers of storm water drainage wells, however, are essentially
implementing only the minimum federal UIC requirements. In particular, Washington, Oregon,
Montana, Utah, Ohio, and Michigan authorize storm water drainage wells by rule.
The regulatory structure in other States with fewer or no storm water drainage wells hi the
current inventory is also mixed. For example, Indiana, Illinois, Minnesota, Wyoming, North
Dakota, South Dakota, Colorado, Kansas, Tennessee, and Rhode Island also authorize storm
water drainage wells by rule. Alabama, Texas, New Hampshire, and Nebraska have a permit and
registration system for storm water drainage wells. Georgia and North Carolina ban new and
existing wells, while Wisconsin bans only new storm water drainage wells.
These regulatory programs in the States are augmented to a degree by non-regulatory
programs and guidance at the federal level. The Federal Highway Administration's (FHWA's)
highway runoff water quality standards indirectly reference storm water. Although these are non-
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enforceable recommendations only, FHWA has issued guidance that discusses best management
practices (BMPs), such as wet and dry detention basins, infiltration trenches and basins, and dry
wells, for controlling storm water runoff and infiltration into ground water. The Coastal Zone
Management Act and Coastal Nonpoint Pollution Control Program, described above in Section
6.1 for agricultural drainage wells, also indirectly reference storm water in nonpoint pollution
regulations; however, storm water discharges controlled under the NPDES program are exempt
from the coastal nonpoint pollution control program.
6.3 Carwash Wells
Wells used to dispose of used washwater at coin-operated, manual carwashes where
people use hand-held hoses to wash only the exterior of vehicles (sometimes called "wand
washes") are the only carwash wells within the scope of this draft report.3 Even though the term
"carwash" is used, the category includes wells that receive used washwater at facilities designed
for washing all kinds of vehicles, including cars, vans, trucks, buses, boats on trailers, etc.
The cleaning solutions used at these carwashes generally consist of soap solutions,
rinsewater, and wax, and should not contain significant amounts of degreasing agents or solvents
such as methylene chloride or trichloroethylene (because these wells, as defined, are not
supposed to be receiving engine or undercarriage washwater, which is more likely to contain
such substances). As a result, the spent washwater disposed in a carwash well as defined in this
report primarily contains detergents, road salts, sediments, and incidental contaminants that may
be washed from a vehicle's exterior, comparable to typical storm water runoff. There is also
concern that de-icing agents may be rinsed from cars and enter ground*water. The limited data
available on the quality of fluids entering carwash wells indicate that the concentrations of
antimony, arsenic, beryllium, cadmium, lead, and thallium in the injectate typically exceed
primary MCLs and HALs. Some samples show that methylene chloride and tetrachloroethene
also have exceeded primary MCLs or HALs, indicating that degreasers may in fact be working
their way into the washwater at some facilities. The concentrations of aluminum, iron, and
manganese in the injectate exceed secondary MCLs.
It is not a typical practice to locate carwash wells in injection zones with specific geologic
characteristics (they do not tend to be located in areas with karst, fractured bedrock, or any other
particular kind of subsurface feature). Rather, the wells are usually relatively shallow and
located wherever the need for carwash drainage exists.
Two possible contamination incidents involving carwash wells were reported in Hawaii
in the early 1990s. The nature and extent of contamination are unknown, but both wells were
closed.
3Class V wells used to inject fluids from carwashes where engine or undercarriage washing is
performed were classified as industrial wells in the July 28, 1998 proposed revisions to the Class V UIC
regulations.
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Although there are few reported contamination incidents associated with carwash wells,
there is concern over the potential for such wells to be vulnerable to spills or illicit discharges.
There is a high possibility of contaminants entering these wells due to the self-service nature of
the facilities. Because the facilities are usually unsupervised (meaning an attendant is not onsite),
individuals may in fact wash their engines or undercarriages using degreasers, wash the exterior
of their vehicles with chemicals other than common soap solutions, or may pour used oil,
antifreeze, or other hazardous materials down these drains.
The inventory results for these wells is very uncertain because most responses to the State
and EPA Regional survey conducted for this study did not distinguish carwash wells from other
kinds of commercial or industrial wells. These survey results suggest that there are up to 4,651
documented carwash wells and approximately 7,192 carwash wells estimated to exist in the U.S.
Although the wells are documented in 14 States, 92 percent are located in Washington, New
York, West Virginia, and Alabama. Many States estimate that more than the documented
number of wells exist, although these estimates are typically based only on best professional
judgment and the true number of wells is unknown. As sewer system hookups become
increasingly available to carwash owners, it is expected that the number of Class V carwash wells
will decrease.. Many States close carwash wells when they find them.
Although West Virginia permits carwash wells by rule (in accordance with the existing
federal UIC program), other States with the majority of documented and estimated carwash wells
are developing and implementing more extensive regulatory programs to address these wells.
Specifically:
• Alabama, Mississippi, New York, Washington, and New Hampshire issue
individual permits.
• Iowa bans carwash wells.
• California requires reporting of discharges from carwash wells.
6.4 Large-Capacity Septic Systems
. Large-capacity septic systems (LCSSs) are an on-site method for partially treating and
disposing of sanitary wastewater. Only those septic systems having the capacity to serve 20 or
more persons-per-day are included within the scope of the UIC regulations.
LCSSs do not utilize a single design but instead are designed for each site according to
the appropriate State and/or local regulations. Many conventional LCSSs consist of a gravity
fed, underground septic tank or tanks, an effluent distribution system, and a soil absorption
system. LCSSs may also include grease traps, several small septic tanks, a septic tank draining
into a well, connections to one large soil absorption system, or a set of multiple absorption
systems that can be used on a rotating basis.
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LCSSs are used by a wide variety of establishments, including residential (multi-unit
housing) and non-residential (commercial, institutional, and recreational) facilities. The
characteristics of the sanitary wastewater from these establishments vary in terms of biological
loadings and flow (e.g., daily, seasonal). Generally, the injectate from a LCSS is characterized
by high biological oxygen demand and chemical oxygen demand, nitrate, trace metals and other
inorganics, limited trace organics, and biological pathogens.
Even with a fully functioning system, data indicate LCSS effluent may contain arsenic,
fecal coliform, nitrate (as N), total nitrogen species (as N), and formaldehyde (in septic systems
serving recreational vehicles) at concentrations above primary MCLs or HALs. The
concentrations of aluminum, iron, manganese, and sodium may exceed secondary MCLs.
The effect of these constituents on USDWs depends in part on the characteristics of the
injection zone. It is difficult to generalize about the injection zone for LCSSs because these
systems have been constructed nationwide. Typically, LCSSs are located in well-drained soils,
even systems located in areas with karst or fractured bedrock. The injectate from LCSSs receives
partial treatment from the system (i.e., settling and biodegradation in the septic tank). However,
additional treatment occurs as the wastewater travels through the soil media below the fluid
distribution system, which is most commonly a leachfield. Dissolved organic matter, pathogens,
and some inorganic constituents can be attenuated in unsaturated soils below the soil absorption
system.
The likelihood of ground water contamination resulting from these systems may be
minimized by following BMPs relating to siting, design, construction and installation, and
operation and maintenance. Careful siting and design of the system are important because
understanding site limitations can prevent future system failure. The construction and
installation of the septic system should be conducted by professionals. These individuals should
not damage the soil and should not undertake construction during periods of high moisture, both
of which are likely to contribute to early system failure. Further, an LCSS needs to be properly
operated and maintained by conducting inspections and performing maintenance as appropriate,
"resting" the soil absorption field, pumping the septic tank as necessary, and limiting system
loading (e.g., water conservation, limiting chemical use or addition). Owners or operators of
LCSSs who follow such BMPs are likely to maximize the life of their system and lower the
likelihood that their system would contaminate a USDW.
Nevertheless, contamination incidents caused by LCSSs have occurred. For example, in
Racine, MO during 1992, two drinking water wells were contaminated by sewage, causing 28
cases of Hepatitis A at a nearby church and school. In Coconino County, AZ during 1989, failure
of the leaching field (due to excessive flow) at a resort area resulted in approximately 900 cases
of gastroenteritis. In Richmond Heights, FL during 1974, a drinking water well was
contaminated by sewage from a nursery school, resulted in approximately 1,200 cases of
gastrointestinal distress. In addition, 24 other instances have been identified where LCSSs failed
and ground water contamination may have resulted. While there are surely other examples of
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LCSS failure across the U.S. beyond these known incidents, the prevalence of contamination
cases appears low relatively to the prevalence of these systems.
LCSSs are vulnerable to spills because any materials spilled or dumped down drains
connected to septic systems will eventually enter the system. Examples of the materials that may
enter LCSSs include household cleaning products (e.g., cleaning solvents) that were accidentally
spilled as well as chemicals dumped illicitly (e.g., waste oil). Once in the LCSS, these materials
are not necessarily treated by the system and may be released to ground waters that may serve as
USDWs. USDWs may also be vulnerable due to the large numbers of LCSS operating
nationwide. While the incremental effect associated with spills at each LCSS may be small,
aggregating each of these spills may provide evidence of a broader contamination problem for
USDWs.
According to anecdotal evidence, the LCSS is believed to be a frequently used onsite
wastewater disposal option. Yet, until this study constructed the inventory model to estimate
total numbers of LCSSs nationwide, no quantitative information on system prevalence was
available. As discussed in Section 5.2, the inventory model estimated that 290,000 LCSSs exist
nationwide (with a 95 percent prediction interval of 250,000 to 330,000).
In the future, the total number of systems is expected to increase as the population
increases. EPA found that construction and use of LCSSs will continue in areas where
geological conditions are favorable and sewerage is not readily available or economically
feasible. In addition, these systems will continue to be constructed because using LCSSs is an
accepted and economically attractive practice. While some States are now encouraging owners
of large systems to connect to municipal sewers (when such connections become available), there
do not seem to be any States planning to ban LCSS entirely.
There are no consistent State definitions or regulations of LCSSs. While the 20 persons-
per-day criterion is used to define systems subject to federal UIC regulation, States generally
characterize large systems using flow definitions that range from 2,000 to 20,000 gallons-per-day
(gpd). Regulation of LCSSs is also highly variable across States. Some States have stringent
requirements for large systems. For example, Massachusetts and Minnesota both use 10,000 gpd
as the cutoff for large systems and have strict requirements for siting, construction, and
operation. Other States only require general construction permitting. For example, New Jersey
and Iowa both use a 2,000 gpd threshold for large systems but only require that such systems
meet required construction standards. In addition, LCSSs may be regulated by local regulations
that focus on enforcing State and/or County building and health ordinances.
6.5 Food Processing Wells
Food processing wells are septic systems used to dispose of food preparation-related
wastewater and equipment or facility wash down water. This group of wells also includes food
processing wastewater drywells, which allow wastewater to enter the soil untreated. These
systems usually inject process wastewater that may contain high levels of organic substances
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(e.g., food waste), cleaning compound residues, and various inert substances. Food processing
wells are typically found at small, family-owned facilities located in unsewered, rural areas.
The wastewater entering the soil via food processing wells can contain very high
biochemical oxygen demand (BOD) levels due to the organic fluids (e.g., blood from cows) and
food residues (e.g., shellfish meat and fluids) entering the wastewater stream. In addition, the
injectate may contain high levels of nitrogen, nitrate, nitrite, total coliform, fecal coliform,
dissolved solids, ammonia, and chlorides. Very little food processing well injectate sampling has
been performed, so it is difficult to ascertain what constituents typically exceed MCLs or HALs.
However, based on observations during site visits and assumptions described in studies of similar
wastewater treatment systems, it appears likely that the concentrations of nitrate, nitrite, total
coliform, and ammonia exceed primary MCLs or HALs. It is also possible that due to the high
organic content of the injectate, the secondary MCLs for odor, turbidity, and chloride may be
exceeded.
Food processing wells typically inject above USDWs and into a variety of different
geological formations, terrains, and soils (except sandy soils). As with sanitary septic systems,
for food processing wells to work properly it is necessary that the injection zone consist of
moderately permeable soils. Site visits in Tennessee revealed that food processing facilities were
being allowed to inject slaughterhouse wastewater, via septic systems, into fractured geologic
units and karst terrains that had very little top soil.
Only one USDW contamination incident has been identified that is clearly linked to a
food processing well. In Maine, in 1998, a lobster processing/holding facility discharged large
volumes of seawater into its combined food processing well and sanitary septic system. As a
result, the chloride concentration in a nearby private drinking water well exceeded the secondary
MCL. Other incidents may have occurred in rural areas, but gone unreported because there were
no nearby ground water users or because individuals using water from private drinking water
wells did not notice any discernable differences in the taste or appearance of their drinking water.
Food processing wells may be vulnerable to receiving spills that occur at the facility.
Some food processing facilities use strong cleaning compounds to clean or disinfect equipment
and, based on observations from site visits, some facilities may not always store these chemicals
in storage areas away from floor drains that are connected to food processing wells. Therefore,
there is the potential that spills may result in the release of cleaning/disinfecting chemicals into
the food processing well injection zone. Food processing wells may also be used for illicit
discharges due to limited oversight and the relatively primitive food processing techniques used
at some facilities. For example, during one visit to a custom slaughterhouse facility, employees
were observed draining the blood from a cow and allowing it to flow directly into the well; the
facility owner had previously stated that all blood was collected and sent for secondary
processing.
According to the State and EPA Regional survey conducted for this study, there are at
least 182 documented food processing wells and more than 1,471 estimated to exist in the U.S.
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Of the 182 documented wells 75% ± 10% are found in Maine and the remainder are found in
Tennessee, Alaska, and Wisconsin. Of the 1,471 estimated wells: 33% are found in New York;
25% in Oregon; 17% in Iowa; 15% in West Virginia; 10% in Alabama; and 7% in Iowa. These
numbers are considered very uncertain because the estimates are often based on professional
judgment only and because there is no way to distinguish food processing wells from other kinds
of commercial/industrial wells in many State inventories. Considering all available information,
it appears that the total is no more than 2,500 wells. In general, the number of food processing
wells is decreasing because many States are actively encouraging individuals not to install
injection wells for this purpose and the areas served by sewers are expanding. Additionally, there
are some States that are closing all food processing wells as they are found.
States such as Tennessee, Alabama, West Virginia, Iowa, and Wisconsin, which have
significant numbers of food processing wells, authorized these wells by rule. For the most part,
these States require that applicants provide basic information for inventory purposes and may
require some additional information to demonstrate that USDW contamination is unlikely. In
Alaska, Maine, and New York, individual permits are required prior to installation and operation.
In Oregon, food processing wells are banned, and in California, regulation of food processing
wells varies by region. Depending on the type of food being processed, food processing facilities
must comply with regulations put forth by the Federal Meat Inspection Act, the Federal Poultry
Inspection Act, or the Federal Drug and Cosmetic Act.
6.6 Sewage Treatment Effluent Wells
Sewage treatment effluent (STE) wells are used in many places throughout the country to
dispose of treated sanitary waste from municipal wastewater treatment plants or treated effluent
from a privately owned treatment works that receives only sanitary waste. For the purpose of this
study, injection wells that are used to dispose of industrial waste (not sanitary waste) from
industrial wastewater treatment facilities are not STE wells. In addition to wastewater effluent
disposal, STE wells are commonly used where injection will aid in aquifer recharge or
subsidence control, or prevent saltwater intrusion.
The effluent that is injected into STE wells is generally subjected to secondary or tertiary
treatment in a municipal wastewater treatment plant. Secondary treated effluent may contain
fecal coliform and nitrates at concentrations above primary MCLs. Available sampling data for
STE well injectate, however, do not indicate any exceedances of MCLs or HALs.
Nearly 50 percent of the documented STE wells are located in Florida, and most of these
wells inject into aquifers that have extremely poor water quality and that are not likely to be used
as a source of drinking water (e.g., in the Florida Keys). Approximately 15 percent of the
documented STE wells are in California and are situated along the Southern California sea coast
where they are used to inject treated effluent as a saltwater intrusion barrier. STE wells in other
states (e.g., Arizona) are used to inject treated effluent for aquifer recharge systems. No data are
available concerning the characteristics of injection zones for other States where STE wells are
currently operated.
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Several studies and incidents have shown that STE wells may have contributed to or
caused ground water or surface water contamination. One study showed nitrate contamination of
onsite ground water at an STE site in New Hampshire where both primary treated effluent and
septage were released into a leach field. Two STE wells on the Island of Maui, Hawaii were
thought to be causing surface water contamination through migration of nitrates in the injectate
to surface water bodies. One of these wells has been shut down and the other is the subject of an
ongoing enforcement action by EPA. The U.S. Geological Survey is conducting a long-term
study of the operation of STE wells in the Florida Keys to assess whether migration of nitrates
from injectate is contributing to surface water contamination.
STE wells are not vulnerable to spills or illicit discharges. The injectate is treated
wastewater, and the wastewater treatment plants that generate the injectate are generally subject
to effluent quality standards and monitoring, reporting, and record keeping requirements.
Incidents where injectate failed to meet injectate quality standards would generally be detected,
and corrective action would be taken by the wastewater treatment plant operator. Moreover, STE
injectate is piped to the well from the wastewater treatment plant, so contamination in route is
unlikely, and the types and quantities of hazardous materials that would be present at a
wastewater treatment plants is limited. Spills of hazardous materials (e.g., chlorine) into the
wastewater treatment plant system are unlikely and would also generally be detected by the
wastewater treatment plant effluent monitoring system.
According to the State and EPA Regional survey conducted for this study, there are 1,702
documented STE wells and more than 1,755 STE wells estimated to exist in the U.S. More than
97 percent of the documented wells are in five States: Arizona (79), California (278), Florida
(830), Hawaii (378), and Massachusetts (105). New York did not report any documented STE
wells in the State, but reported that there may be as many as 50 undocumented wells.
Considering that STE wells are associated with wastewater treatment plants, which are generally
required to have permits, the inventory is considered to be relatively complete as compared to
inventories for other injection well categories. Nevertheless, there may be somewhat more STE
wells than these results suggest. For example, New Hampshire did not report any STE wells
operating in the State; however, two wells were identified as the result of field investigations.
Maine initially identified more than 100 STE wells operating in the State, but Further
investigation revealed that these injection wells are not injecting treated municipal effluent, and
are actually septic systems, not STE wells.
States with the majority of STE wells have developed and implemented regulatory
programs to permit these wells. Specifically:
• In Florida, STE injectate is required to meet primary MCLs and STE wells are
required to have individual permits.
• In Hawaii, regulations have established ground water protection zones where the
construction of STE wells is prohibited. Such wells in Hawaii are required to
obtain individual permits.
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• Arizona requires STE wells to obtain ground water protection permits, and
requires the well operators to demonstrate that MCLs will not be exceeded at the
facility property boundary. Arizona also has published BMPs for the operation of
wastewater treatment plants (and their associated STE wells).
• California requires STE wells to obtain individual permits.
• Massachusetts requires STE wells to obtain ground water discharge permits.
The regulatory picture in several other States with few STE wells in the current inventory
is varied. States either permit STE wells by rule (e.g., Texas, Idaho), require them to obtain
ground water protection permits (e.g., New Hampshire, Wisconsin), or require them to obtain
individual permits (e.g., West Virginia). Some States (e.g., New Hampshire) establish ground
water compliance zones (generally at the site boundary) while others (e.g., Idaho) require
injectate to meet MCLs at the point of injection. Some States have published BMPs, like
Arizona.
These regulatory programs in the States are supplemented by regulatory standards and
guidelines that apply to operation of municipal wastewater treatment plants under the authority of
the Clean Water Act and associated State regulations. BMPs for wastewater treatment plants
have also been established by EPA under the Clean Water Act. These BMPs are equally
appropriate for treatment plants that discharge to surface water and those that discharge (inject)
into ground water.
6.7 Laundromat Wells
Wells used to inject fluids from laundromats where no onsite dry cleaning is performed or
where no organic solvents are used for laundering are classified as "laundromat wells" for the
purpose of this study. These wells are located throughout the U.S. and can be found at coin-
operated laundromats.
The characteristics of the fluids drained into these wells are similar to those of graywater
from households washing machines. The limited data that are available from coin-operated
washers indicate that none of the primary MCLs are exceeded by laundromat washwater.
However, the injectate exceeds the secondary MCLs for pH and TDS.
It is not a typical practice to locate laundromat wells in injection zones with specific
geologic characteristics (like carwash wells, laundromat wells do not tend to be located in areas
with karst, fractured bedrock, or any other particular kind of subsurface feature). Rather, the
wells are usually located wherever the need for laundromat drainage exists.
Although there are no reported contamination incidents associated with laundromat wells,
some wells may to be vulnerable to spills or illicit discharges. The unsupervised nature of coin-
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operated laundromats may make Class V wells at those facilities susceptible to contamination
due to laundering of contaminated articles. For instance, an individual may wash articles, such as
solvent-soaked or oily rags, that may result in increased contaminant concentrations in the wash
water. In addition, it reasonable to expect that any sinks or floor drains at the facility, which also
may receive minor spills, would be hooked into same plumbing system that collects and transfers
wash water to the injection well.
As for carwash wells, the inventory results for laundromat wells is very uncertain because
most responses to the State and EPA Regional survey conducted for this study did not distinguish
laundromat wells from other kinds of commercial or industrial wells. These results suggest that
there are less than 700 documented laundromat wells and more than 3,495 estimated laundromat
wells in the U.S. The wells are documented in 12 States, although 81 percent are thought to exist
hi New York, Mississippi, and Iowa. Although many other States also estimate numbers of
wells much higher than the numbers documented, most are unsure of the exact number of wells.
As sewer system hookups become increasingly available to laundromat owners, it is expected
that the number of Class V laundromat wells will decrease.
States with the majority of documented or estimated laundromat wells are implementing
various kinds of regulatory programs to address these wells. Alabama and New York issue
individual permits. However, in Iowa, Mississippi, and West Virginia, the wells are permitted by
rule, even though individual permits are sometimes required in West Virginia.
6.8 Spent Brine Return Flow Wells
Naturally occurring surface and underground brines are used as the source for commercial
production of a variety of mineral commodities, including common salt, magnesium compounds,
calcium chloride, iodine, bromine, and sodium sulfate. When underground brines serve as the
raw material for production of mineral commodities, the brine is extracted from the subsurface
through production wells, the target compounds or elements are extracted, and the resulting
"spent brine" is returned to the subsurface through spent brine return flow wells.
The chemical characteristics of the injected spent brine are determined primarily by the
characteristics of the brine that is withdrawn for processing and the nature of the extraction
process used. As a result, spent brine characteristics can vary substantially from facility to
facility, although in some cases the brine characteristics are similar when several facilities
withdraw brine from a common formation, as is the case in Arkansas. In Arkansas, available
data indicate that concentrations of barium and boron in spent brine routinely exceed primary
MCLs or HALs. Data available for Michigan facilities indicate that chloride, copper, iron,
manganese, TDS, and pH levels frequently exceed secondary MCLs. It is not clear from
available data whether concentrations of some other constituents, including some heavy metals,
are present at concentrations above health-based levels.
Spent brine return flow wells inject spent brine into the same formation from which it
was withdrawn, which in all current cases is below the lowermost USDW. (These wells are
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included in Class V rather than Class I or II due to a clarification of well classifications issued in
1981 (46 FR 43156, August 27,1981)). In fact, most spent brine return flow wells were initially
drilled as production wells and subsequently converted to injection wells. The chemical
composition of the spent brine is generally similar to that of the produced brine except that the
concentration of target elements (e.g., magnesium) has been reduced and the concentration of
other elements (e.g., calcium) may have been increased through substitution. Thus, the MCL
exceedances observed for the spent brine are also typical for the produced brine and the receiving
formation.
No contamination incidents associated with spent brine return flow wells are reported. In
addition, spent brine return flow wells are not likely to receive accidental spills or illicit
discharges. Corrosion of some well materials by the brine is a common problem, however.
Therefore, injection is through corrosion-resistant tubing and well integrity is monitored on an
ongoing basis.
According to the State and EPA Regional survey conducted for this study, there are 95
documented spent brine return flow wells that are regulated as Class V injection wells in
Arkansas (74) and Michigan (21). Several other States, including New York, Tennessee,
California, and Oklahoma, indicate that spent brine wells exist, but they are regulated as Class II
or III wells. Also, Kentucky indicates that spent brine wells are present in the State but did not
provide any information on how many.
The specific features of well construction and operation vary somewhat with the site and
when the well was constructed, but in general the wells are built according to regulatory or
permit requirements that have many features in common with Class I and Class II injection wells.
Arkansas has placed jurisdiction over spent brine return flow wells in its Oil and Gas
Commission, which applies Class IIUIC permitting requirements as well as a special set of
construction and operating standards. For wells in Michigan, individual UIC permits are issued
by EPA Region 5.
6.9 Mine Backfill Wells
Mine backfill wells are used in many mining regions throughout the country to inject a
mixture of water and sand, mill tailings, or other materials (e.g., coal combustion ash, coal
cleaning wastes, acid mine drainage treatment sludge, flue gas desulrurization sludge) into mined
out portions of underground mines. On occasion, injection also occurs into the rubble disposal
areas at surface mining sites. Mine shafts and pipelines in an underground mine, as well as more
"conventional" drilled wells, used to place slurries and solids in underground mines are
considered mine backfill injection wells. Such wells may be used to provide subsidence control,
enhanced ventilation control, fire control, reduced surface disposal of mine waste, enhanced
recovery of minerals, mitigation of acid mine drainage, and improved safety.
The physical characteristics and chemical composition of the materials that are injected
into backfill wells vary widely depending on the source of the backfill material, the method of
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injection, and any additives (e.g., cement) that may be included. Data on injectate characteristics
for mine backfill wells indicate that concentrations of antimony, arsenic, barium, beryllium,
boron, cadmium, chromium, fluoride, lead, mercury, molybdenum, nickel, selenium, silver,
thallium, sulfate, and zinc frequently exceed primary MCLs or HALs. Concentrations of
aluminum, copper, iron, manganese, TDS, sulfate, and pH frequently exceed secondary MCLs.
In addition, available data from leaching tests (e.g., EPA Method 1311--TCLP) also indicate
exceedances for many of these same constituents, although the exceedances are generally less
frequent and of lesser magnitude.
At sites where water is present hi the injection zone (the previously mined ore body), the
mine water may already exceed MCLs or HALs prior to injection either as a result of mining
activity or natural conditions. At some sites, the objective of injection is to improve the already
poor quality of the mine water by reducing the availability of oxygen in the mine workings and/or
neutralizing the acid content of the water.
No incidents of contamination of a USD W have been identified that are directly
attributable to injection into mine backfill wells. Although ground water contamination is not
uncommon at mining sites, it is generally difficult to identify the specific causes, which may
include mining, processing, waste management, injection, or other activities. The chance that
backfill injection will contribute to ground water contamination is highly dependent on site
conditions, including mine mineralogy, site hydrogeology, backfill characteristics, and injection
practices. Some studies of the effects of backfill injection on mine water quality show that
concentrations of some cations and anions can increase in mine water following injection,
whereas concentrations of trace metals generally are relatively unaffected or decline over tune.
Other studies (at other sites) show an increase in selected metal concentrations.
The vulnerability of mine backfill wells to receiving spills or illicit discharges also
depends on site-specific conditions and practices. For example, if coal ash is hauled to a mine
site, slurried with water, and then injected, the likelihood of contamination of the injected
material resulting from a spill or illicit discharge is relatively low. On the other hand, if mill
tailings are collected in a tailings pond along with site runoff and other facility wastes prior to
injection, then the likelihood of contamination of the backfill material by spills would be higher.
In some cases, injection (dumping) into abandoned mine shafts has occurred.
According to the State and EPA Regional survey conducted for this study, there are at
least 4,987 documented mine backfill wells and more than 7,817 wells estimated to exist in the
U.S. A total of 17 states report having mine backfill wells. More than 90 percent of the
documented wells reported are in four states: West Virginia (328), Ohio (3,570), North Dakota
(200), and Idaho (575). In truth, there may be thousands more due to the broad classification of
this well type and the fact that some State inventories may count these wells as subsidence
control wells. Also, the number of active wells at any given time varies widely due to their
generally short life span, most often less than one day. The number of mine backfill wells has
the potential to grow in the future due to the growing movement to decrease surface disposal and
control ground subsidence.
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State regulations pertaining to mine backfill wells vary significantly in their breadth and
stringency. Some States impose few restrictions while others require permitting, or impose
requirements by contract rather than regulation. Some of these approaches include permit by rule
(e.g., West Virginia, Idaho, North Dakota), general or area permits (e.g., Wyoming), and
individual permits (e.g., Ohio). In addition, federal requirement for planning and approval of
mining activities include mine backfill activities. These requirements apply in States that have
not obtained primacy under the Surface Mining Control and Reclamation Act and to activities on
federal and Indian lands.
6.10 Aquaculrure Waste Disposal Wells
Aquaculture is commonly defined as the active cultivation of marine and freshwater
aquatic organisms under controlled conditions. While some aquaculture facilities use holding
structures in natural, open water bodies and rely on natural water circulation for water
replenishment, many facilities use closed systems (e.g., tanks or ponds) and accumulate
wastewater and sludge that must be removed. At dozens of such facilities in Hawaii and several
other States, this wastewater and sludge is disposed via underground injection.
All injected aquaculture wastewater includes fecal and other excretory wastes and
uneaten aquaculture food. The primary chemical and physical constituents of these wastewaters
are therefore nitrogen- and phosphorus-based nutrients and suspended and dissolved solids.
Injected aquaculture wastewater may also contain bacteria that are pathogenic to humans, and
chemical additives used in aquaculture. Such additives may include: antibiotics to control
diseases; pesticides to control parasites, algae, and other pests; hormones' to induce spawning;
anesthetics to immobilize fish during transport and handling; and pigments, vitamins, and
minerals to promote rapid growth and desired qualities in the cultivated organisms. The
incidence and concentrations of human pathogenic bacteria and chemical additives hi injectate is
not known. Information on aquaculture wastewater quality industry-wide is very limited, and
wastewater properties are believed to vary greatly among different aquaculture operations.
Available sampling data for aquaculture injectate indicate that nitrate and turbidity levels
frequently exceed primary MCLs or HALs . The secondary MCL for chloride is also exceeded in
the wastewater from seawater-based operations hi Hawaii (these wastes are injected to saline
aquifers).
The injection zone for aquaculture wastewater must be of relatively high porosity, as
aquaculture wastewaters typically have significant suspended solids content. As noted above,
seawater-based aquaculture operations in Hawaii inject wastewater into brackish or saline
aquifers that flow seaward. Little information is available regarding other aquifers receiving
aquaculture injectate.
No contamination incidents related to aquaculture wastewater disposal have been
reported. However, available information about some aquaculture injection wells suggest that
USDW contamination could occur. In Idaho, an aquaculture well is known to inject wastewater
directly into an aquifer, but the quality of the aquifer, its status as a USDW, and the resulting
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impacts are unknown. The one subsurface disposal system (actually a leaching field) known to
be in use by an aquaculture operation in Maryland is situated above a Type 1 (high quality)
aquifer.
Aquaculture wells generally are not vulnerable to spills or illicit discharges. Most are
located within private facilities and are not accessible to the public for unsupervised waste
disposal. However, the potential exists for operators to dispose of harmful liquid wastes (e.g.,
waste aquaculture chemicals, or spent tank water with higher concentrations of chemicals used
for temporary treatment of cultivated organisms) via aquaculture injection wells. No such cases
have been reported.
According to the State and EPA Regional survey conducted for this study, a total of 55
documented Class V aquaculture waste disposal wells exist in the U.S. The great majority occur
in Hawaii (51 wells, or 93 percent). The remaining wells are in Wyoming (2 wells), Idaho (1
well), and Maryland (1 well). In addition to these documented wells, as many as 50 additional
wells are estimated to exist in California, and one well described in a technical publication in
New York fits the definition of a Class V well (but is not reported as such by New York State).
Thus, the true number of aquaculture waste disposal wells in the U.S. is likely to approach 100.
Given that the value of U.S. aquaculture production has grown by 5 to 10 percent per year over
the past decade, and that the aquaculture industry remains the fastest growing segment of U.S.
agriculture, it is likely that the number of Class V aquaculture waste disposal wells will increase.
Programs to manage Class V aquaculture waste disposal wells vary between the four
States with documented wells:
• In Hawaii, aquaculture injection wells are authorized by individual permit. Class
V wells are grouped for purposes of permitting into six subclasses. Aquaculture
wells may fall into two of the subclasses, depending on the character of the
injectate and the water in the receiving formation.
• In Wyoming, aquaculture wells are covered under a general permit. The permit
specifies certain construction and operating requirements (e.g., pretreatment of
waste water).
• In Idaho, wells greater than 18 feet deep are individually permitted, while
shallower wells are authorized by rule.
• In Maryland, individual permits are required for any discharge of pollutants to
ground water, for any industrial discharge of wastewater to a well or septic
system, for any septic system with 5,000 gpd or greater capacity, or for any well
that injects fluid into a USDW.
Inconsistent or unclear permit requirements exist in the other two States thought to have
aquaculture injection wells. In California, regional authorities issue permits for all Class V
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wells, but this is not done consistently across the State. Thus, the aquaculture facilities thought
to operate injection wells are not required to obtain permits for these wells. In New York,
several State regulations could apply to the construction and operation of aquaculture injection
wells, but it is not clear whether the facility thought to operate injection wells is subject to any
permit requirement.
6.11 Solution Mining Wells
Solution mining wells are used to inject a fluid (lixiviant) into underground mines to
dissolve mineral values from the ore. The resulting "pregnant" solution is then brought to the
surface, through separate wells, for subsequent recovery of the dissolved mineral that is being
produced. Solution mining wells that are regulated under the federal definition of Class V
injection wells are used in the recovery of copper, uranium, and potentially other minerals, from
mines that have already been conventionally mined, through the injection of solutions of sodium
bicarbonate or sulfuric acid in ground water or recirculated mine water. When solution raining
techniques are used to extract minerals from ore bodies that have not been conventionally mined,
the injection wells are classified as Class III injection wells under federal regulation. Class III
solution mining wells are much more common than Class V wells, which are active in only two
States.
The characteristics of the injected solution are highly dependent on those of the ore body
being mined because a variety of metals present in the ore body are incorporated into the solution
as it goes through repeated cycles of injection, extraction, and reinjection. Data on the
composition of solution mining fluids indicate that the concentrations of sulfate, molybdenum,
radium, selenium, arsenic, lead, and uranium exceed primary MCLs or HALs. Concentrations of
IDS, chloride, manganese, aluminum, iron, sulfate, and zinc have been measured above the
secondary MCLs. Exactly which constituents exceed the standard depends on site-specific
factors.
In many cases, the injection zone, or mined ore body, has already been altered by
previous mining and often by ground water pumping as well. In the case of uranium mining, for
example, the formation is a water-bearing sandstone. As part of solution mining operations,
ground water flow is normally modified to create a drawdown, or zone of depression, so that the
injected lixiviant is retained in the leaching zone for subsequent recovery.
No ground water contamination incidents have been identified that are directly
attributable to Class V solution mining injection wells. However, the fluids injected into these
wells inherently contain a variety of metals at concentrations above MCLs or HALs, and
contamination resulting from a combination of mining-related activities has been reported at
several sites. Elevated concentrations of metals have been observed in ground water in the
vicinity of solution mining operations, but complex hydrogeology and other mining and mining-
related activities make it difficult to attribute the cause to a specific activity, such as solution
mining injection wells. At sites were solution mining injection wells are used, the likelihood that
ground water contamination will result is dependent primarily on overall mining operations
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rather than the specific construction and operational practices of the injection wells. Specifically,
the chance of migration of the solubilized metals from the injection zone depends on the
effectiveness of measures like ground water pumping and monitoring that are used to ensure that
the leaching solution is contained within the in situ leaching zone.
The vulnerability of these wells to receive spills or illicit discharges is unclear pending
receipt of additional information on how the lixiviant solutions are handled in surface facilities.
The State and EPA Regional survey results indicate that there are 2,694 documented
solution mining wells hi the U.S. (no more were estimated, indicating that there is substantial
confidence in this documented number). Eight of these wells are associated with a uranium mine
in New Mexico and the remaining wells occur at two copper mines in Arizona. Wells at one
solution mining operation in Potash, Utah that meet the federal Class V definition are not
included hi this report because they are regulated by the State as Class III wells. Another
solution mining well in Colorado that is permitted as an experimental well is covered under the
experimental well category. The prevalence of Class V solution mining wells in the future
depends on a wide range of factors such as commodity prices and the development of lower cost
mining and beneficiation processes.
Both Arizona and New Mexico control solution mining through the use of individual
permits, although in Arizona, which is a DI State, the State uses an Aquifer Protection Permit
rather than a UIC permit. Both States have operating and monitoring requirements. Arizona also
places requirements on construction and maintenance practices, and financial assurance must be
demonstrated.
6.12 In-Situ Fossil Fuel Recovery Wells
In-situ fossil fuel recovery wells are used to facilitate in-situ conversion, through partial
combustion, of a hydrocarbon resource into a gaseous or liquid form that can be extracted
through production wells. Specifically, in-situ fossil fuel recovery wells are used to initiate and
then maintain and control combustion through injection of water, air, oxygen, steam, or ignition
agents. There are three types of processes that may use in-situ fossil fuel recovery wells: in-situ
combustion of tar sand deposits, underground coal gasification (UCG), and in-situ oil shale
retorting. In-situ combustion of tar sand deposits has not been employed in the U.S.
Most of the injected materials are gases (e.g., air, oxygen) that are not likely to show
exceedanees of MCLs or HALs. No data have been identified that describe the quality of water
that has been injected into in-situ fossil fuel recovery wells. When ignition agents such as
ammonium nitrate are injected, exceedanees of MCLs or HALs would be expected, but has not
been documented.
In-situ fossil fuel recovery wells inject into a hydrocarbon-containing unit, which is often
a steeply inclined coal seam or oil shale deposit that is not practical to mine with conventional
methods. Although injected gases generally do not introduce contaminants into the subsurface,
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injection may alter the characteristics of a USDW, if the gases are allowed to contact a USDW,
by changing the USD W's temperature or increasing the level of gas saturation.
Contamination of ground water resulting from in-situ fossil fuel recovery operations is
well documented, to the extent that most, if not all, in-situ fossil fuel recovery operations
initiated in the last 20 years appear to have caused some ground water contamination. The
ground water is not contaminated with the injected materials, however. Rather, it is
contaminated with combustion byproducts, such as benzene. At some sites, water containing
benzene and other combustion byproducts, such as phenols, has migrated via fractures or other
means from the reaction zone into nearby ground water.
These contamination problems are associated with routine in-situ fossil fuel recovery
operations, rather than rare spills or accidents. Overall, in-situ fossil fuel recovery wells are not
likely to receive spills or illicit discharges.
According to the State and EPA Regional survey conducted for this study, there are no
documented nor estimated active in-situ fossil fuel recovery wells in the U.S. The inventory of
these wells is anticipated to remain at zero for the foreseeable future due to depressed oil prices.
State UIC regulations in Wyoming and State mining regulations in both Wyoming and
Colorado establish permitting and operating requirements for in-situ fossil fuel recovery wells.
In both States, mining plans are required that must address siting, construction, operation,
monitoring, and closure of production and injection wells. Colorado's mining regulations do not
include specific requirements for mechanical integrity testing, plugging and abandonment, or
financial assurance. Requirements in Wyoming are both extensive and more specific.
6.13 Special Drainage Wells
Special drainage wells are used throughout the country to inject drainage fluids from
sources other than direct precipitation. This is a "catch-all" category, including all drainage wells
that are not agricultural, industrial, or storm water drainage wells. The specific types of wells
that fit into this category are:
, • Pump Control Valve Discharge and Potable Water Tank Overflow Discharge Wells;
• Landslide Control Wells;
• Swimming Pool Drainage Wells;
• Dewatering Wells; and
• Lake Level Control Wells.
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Pump control valve discharges and potable water tank overflows may be drained to the
subsurface on occasion, usually when an emergency overflow or bypass procedure takes place.
Landslide control wells are used to dewater the subsurface in landslide-prone areas. Swimming
pool drainage wells are used to drain swimming pool water to the subsurface for seasonal
maintenance or special repairs. Dewatering wells are used at construction sites to lower the
water table and keep foundation excavation pits dry. Dewatering wells may also be used at
mining sites, where they are known as "connector wells," to drain water from an upper aquifer
into a lower one to facilitate mining activities. Lake level control wells are used to drain lakes to
prevent their overflow.
Injectate characteristics vary among the types of special drainage wells. The injectate
from pump control valve discharge and potable water tank overflows is expected to meet all
drinking water standards due to the potable nature of the water. The quality of injectate in
landslide control wells depends on the quality of the ground water that is being drained to a
deeper level in the subsurface. The limited amount of available data indicates that swimming
pool drainage well injectate contains coliforms. In addition, the recommended chemical
composition of swimming pool water includes TDS levels above the secondary MCL. Data
show that dewatering well injectate typically contains the following constituents above primary
MCLs or HALs: turbidity, nitrogen-total ammonia, arsenic, cadmium, cyanide, lead,
molybdenum, nickel, nitrate, and radium 226. Additionally, the following constituents in
dewatering well injectate are typically detected above secondary MCLs: iron, manganese, TDS,
and sulfate. Finally, water quality data from Florida indicate that lake level control well injectate
exceeds primary MCLs or HALs for turbidity, nitrogen-total ammonia, arsenic,
pentachlorophenol, and fecal coliforms, as well as secondary MCLs for iron, manganese, pH, and
color.
Because special drainage wells do not tend to be located in areas with specific geologic
characteristics (they are typically located wherever the need for a certain type of drainage exists),
generalizations about the injection zone characteristics are very limited. In Florida, where
swimming pool drainage wells, lake level control wells, and mine dewatering wells are prevalent,
the injection zone is typically karst. Swimming pool water is often injected into aquifers from
which the pool water was initially withdrawn, and the injected water quality is usually not
significantly degraded from that in the receiving aquifer. In some cases, swimming pool drainage
wells inject into saline aquifers. Landslide control wells and dewatering wells inject into deeper
aquifers that can accept volumes of fluid from upper aquifers.
No contamination incidents have been reported for pump control valve discharge and
potable water tank overflow discharge wells, landslide control wells, or swimming pool drainage
wells. However, a 1984 study expressed concern over water quality received by the Floridian
aquifer when dewatering wells were operated at several phosphate mining sites. Lake level
control wells also have been associated with two documented contamination incidents. The first
occurred in 1993 when private drinking water wells in Lake Orienta, Altamonte Springs, Florida,
were contaminated. In 1998, private wells in Lake Johio, Orange County, Florida, were
contaminated by fluids released into lake level control wells.
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In general, special drainage wells are not highly vulnerable to spills or illicit discharges.
The extent of the potential contamination caused by dewatering or landslide control wells is
highly dependent upon the characteristics of the construction or mining site or potential landslide
location that is being dewatered. Pump control valves and potable water tanks and swimming
pools are not especially vulnerable to spills or illicit discharges. Some lakes, however, may be
vulnerable to spills or illicit discharges.
According to the State and EPA Regional survey conducted for this study, there are
approximately 2,193 documented special drainage wells and more than 3,282 special drainage
wells estimated to exist in the U.S. The wells are documented in 13 States, although 97 percent
are located in Florida (1,032) and Indiana (1,102). The trends in constructing and operating
special drainage wells indicate that these numbers are likely to decrease in the future. An
alternative type of landslide control well may replace the type that injects water deeper into the
subsurface. This alternative moves water to the ground surface or to surface water bodies.
Swimming pool drainage wells, which are mainly located in Florida, are associated with older
pools and are no longer constructed. Many of the mine dewatering wells associated with
phosphate mining in Florida have been closed. The number of lake level control wells is
unlikely to decrease because these wells are essential in some communities, particularly in
Florida, to aid in flood prevention.
Special drainage wells are rule authorized in Idaho, Indiana, and Ohio. However, the
other States with the majority of special drainage wells are implementing more specific
regulatory programs to address these wells. Specifically, individual permits are issued in Alaska,
Florida, and Oregon, and general permits for single family swimming pools are issued in Florida.
6.14 Experimental Wells
Experimental technology injection wells have been reported in 16 States and are used to
test new or unproven technologies. New or unproven technologies have been applied in Class V
wells associated with solution mining, aquifer thermal energy storage (ATES) systems, chemical
tracer studies, aquifer remediation experiments, experimental aquifer storage and recovery (ASR)
systems, and other unidentified experimental purposes. The existence or use of these
technologies vary widely from State to State because, in some instances, different definitions for
experimental wells are used by different States. These definitions may not necessarily
correspond to the EPA definition of an experimental well.
Given the wide range of injection well applications that have been classified as
experimental by one or more States or EPA Regions, many different types of substances are
injected into these wells. Examples of these substances include: (1) dilute sulfuric acid or
sodium bicarbonate (for solution mining wells); (2) heated water (for ATES systems); (3) organic
dyes, inert gases, short half-life radionuclides, rare earth metals, radioisotopes, and inorganic or
organic compounds (for tracer studies); (4) sodium hypochlorite and calcium polysulfide
(reagents for aquifer remediation wells); (5) nitrous oxides, triethyl phosphate, ethanol, and
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methanol (nutrients for aquifer remediation wells); and (6) water treated to drinking water
standards (for ASR systems).
In certain situations, the injectate for specific well types has not met the primary MCLs,
secondary MCLs, and/or HALs. This is not unexpected, considering that certain experimental
well types are designed to introduce reagents into ground water formations. The injectate for the
aquifer remediation injection wells and solution mining wells, for example, would not be
expected to meet primary or secondary MCLs given the purpose of the injection activity.
Injectate for experimental aquifer remediation wells has exceeded the primary MCLs for nitrates
and sulfides, and the secondary MCLs for chloride and pH. Injectate for experimental solution
mining wells has exceeded primary MCLs for sulfates, copper, and other metals (for sulfuric acid
injection for solution mining of copper and dilute sodium bicarbonate injection for solution
mining of nahcolite), and the secondary MCL for pH.
The injection zone characteristics for experimental technology injection wells vary widely
depending upon the purpose of the well. For instance, wells used for aquifer remediation
generally inject into contaminated aquifers, sometimes including aquifers that serve as drinking
water supplies. Experimental solution mining wells inject into mineral formations, while
experimental ASR wells inject into municipal ground water supply systems. Lastly,
experimental ATES wells inject heated water that is being returned to the same aquifer from
which it was withdrawn.
While no contamination incidents were reported for experimental technology injection
wells, several reports mentioned that the concentration of constituents in'ground water receiving
fluids from some ASR wells and ATES wells were higher than background levels.
Experimental solution mining wells and aquifer remediation wells are somewhat
vulnerable to receiving spills or other unintended discharges, because reagents are injected, and
there is the potential for spills or malfunction from reagent handling systems. Other kinds of
experimental wells are less vulnerable to illicit discharges because injectate quality is controlled
by the conditions of the experiment being conducted. For example, experimental ATES and
ASR systems inject treated water. Tracer study wells are less vulnerable to spills and illicit
discharges because the tracers are used in small quantities.
' According to the State and EPA Regional survey conducted for this study, 16 States have
a total of 445 experimental technology injection wells: Massachusetts, West Virginia, Alabama,
Florida, Mississippi, North Carolina, South Carolina, Tennessee, Illinois, Wisconsin, Texas,
Colorado, Arizona, Nevada, Idaho, and Washington. Most of these experimental wells exist in
South Carolina (207 wells or 47%), Nevada (179 wells or 40%), and North Carolina (21 wells or
5%). Most of the experimental wells in South Carolina and Nevada are tracer study wells being
operated at U.S. Department of Energy facilities. The States of Massachusetts, Florida, and
Mississippi reported that their number of experimental wells is unknown. None of the States
provided an estimated number of experimental wells.
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While the experimental technology wells in South Carolina, North Carolina, Alabama,
Florida, and Washington are individually permitted by the State, the wells in Nevada are
permitted by general permit or by individual permit. Idaho and Texas permit the wells by rule,
while the wells in Illinois, Tennessee, and West Virginia are permitted by rule or by individual
permit. Other unique permitting conditions, by State, include:
• Colorado, in which the wells are permitted by rule but must have a well construction
permit;
• Arizona, in which the wells must have an aquifer protection program permit; and
• Wisconsin, in which the wells must have a discharge to ground water permit, and
must satisfy the conditions stipulated by the Clean Water Act and the National
Pollutant Discharge Elimination System.
Experimental solution mining wells in Colorado and Arizona were permitted as Class V
experimental wells during startup. However, the permits for these wells were converted to Class
III well permits once the solution mining wells are put into full production.
6.15 Aquifer Remediation Wells
Aquifer remediation wells 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 on-site pump-and-treat system.
For many reagents and nutrients injected into aquifer remediation wells, 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 purpose. The data available about these
wells are insufficient to establish meaningful comparisons between concentrations of injected
reagents or nutrients in ground water monitoring wells 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 of concern for remediation, rather
than on the reagents, nutrients, or other substances injected into the affected aquifer as part of the
remedial activity.
The injectate in aquifer remediation wells 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 a 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.
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One contamination incident associated with an aquifer remediation well was reported in
the State and EPA 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 clean USDW. The extent of the impact on
the USDW or to drinking water wells was not reported.
A majority of aquifer remediation wells appear to be covered under Superfund, RCRA, or
Underground Storage Tank (UST) cleanup actions and, as with any remedial measure, they
usually require the approval of the appropriate State and/or Federal regulatory agencies. There is
greater concern for voluntary cleanups that are not approved or completed according to standards
typical of cleanups overseen by a state or federal agency. Limited information from the survey
suggests that voluntary cleanups do occur, but nothing more is known about them based on the
information available.
The survey results indicated that there are 10,182 documented aquifer remediation wells
located in 41 States. A significant fraction (66 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 EPA regional officials estimated that a slightly higher number of wells, 10,713, 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 aquifer remediation wells.
Based on a review of relevant regulations for the States where aquifer remediation wells
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. Aquifer
remediation wells may be authorized by rule in New Hampshire and Texas. At the federal level,
aquifer remediation wells are subject to the federal UIC standards, and may be additionally
regulated under Superfund (CERCLA) Cleanups, RCRA Corrective Actions, and the UST
Program.
6.16 Geothermal Electric Power Wells
Several dozen power plants located in four western states use geothermal energy to
produce electricity. At these power plants, hot (>100°C (200°F)) geothermal fluids that are
produced from subsurface hydrothermal systems serve as the energy source. Following the
recovery of heat energy from the produced fluids, the liquid fraction (if any) is reinjected into the
same hydrothermal system through one or more electric power geothermal injection wells.
The temperature and chemical characteristics of geothermal fluids vary substantially from
field to field. For example, TDS concentrations are about 1,000 mg/L at The Geysers (in
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northern California) but about 250,000 mg/L at the Salton Sea geothermal field (in southern
California). Despite these variations, however, concentrations of some metals (e.g., antimony,
arsenic, cadmium, lead, mercury, strontium, zinc) and other constituents in the produced and
injected geothermal fluids routinely exceed primary MCLs or HALs at one or more geothermal
fields. The specific constituents that exceed the standards and the magnitude of the exceedances
varies from site to site, with substantial variations observed within some fields. Sulfate, chloride,
manganese, iron, pH, and TDS also frequently exceed secondary MCLs.
At some geothermal power plants, other fluids associated with power plant operation,
such as condensate and cooling tower blowdown, are injected along with the geothermal fluids.
In a few situations, supplemental water from additional sources, such as surface waters, storm
waters, and wastewater treatment effluent, is also injected. Concentrations of metals and other
constituents in these supplemental water sources are typically lower than in the geothermal
fluids. An exception is biological constituents (e.g., coliforms) that are sometimes present in
injected surface water and treated wastewater at concentrations above drinking water standards.
The Geysers geothermal field is the principle example of injection of surface waters and
treatment plant effluent along with geothermal fluids.
Geothermal fluids used for electric power generation are normally injected into the same
subsurface hydrothermal system from which they were produced. In fact, a majority of
geothermal injection wells were drilled as production wells and subsequently converted to
injection wells. Both production and injection wells are carefully engineered because power
production depends on the wells and drilling costs are substantial, frequently exceeding $1
million per well.
Despite this care, well failures have occurred during both drilling and operation, due to
the high pressures and temperatures encountered, exposure of well equipment to the corrosive
geothermal fluids, and seismic activity that sometimes bends or breaks well casings. However,
no documented contamination of USDWs attributable to such well failures has been identified.
Changes in ground water quality were observed after a blowout while drilling a geothermal well
in Hawaii, but it is uncertain whether these changes were related to the blowout. In some cases,
well failures have occurred at sites where no USDW is present.
. In general, electric power geothermal injection wells are not vulnerable to receiving spills
or illicit discharges because geothermal fluids are handled in closed piping systems that are
managed as an integral part of the power plant system. At some facilities, contaminants could be
added to the injectate as a result of leaks or spills of lubricants, fuels, or chemicals at the power
plant site. For example, at sites that collect and inject storm water, such as the power plants at
The Geysers, injectate could include fuel, transformer oil, lubricants, or chemicals that leak or
spill on the site. To help prevent injectate contamination from such sources, potential sources of
leaks and spills are covered and/or are bermed separately from other parts of the facility. In
addition, oil/water separators are provided for some plant areas (e.g., the electric switch yard) to
provide further assurance that leaked or spilled oil is not injected.
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According to the State and EPA Regional survey conducted for this study, four states --
California, Utah, Hawaii, and Nevada - have a total of 234 electric power geothermal injection
wells, with most of the wells reported in California (174, or 74 percent) and Nevada (53, or 23
percent). The number of geothermal power injection wells is not expected to increase
substantially in the foreseeable future because gas-fired power plants can generally produce
power at a lower cost than geothermal plants. However, if marketing of geothermal power as a
"green" energy source is successful as the utility industry is deregulated, a modest increase in the
number of geothermal power plants and associated injection wells may occur. Additional
geothermal power plants are currently being considered in California and have been proposed in
the past in Oregon.
Individual permits are required for electric power geothermal injection wells in all four
States that have this type of Class V injection well. The permits are issued by State agencies,
Bureau of Land Management, and/or the EPA Regional Office, depending on the State and
whether the well is located on State, federal, or private land. In general, the permits are similar to
those issued for Class II injection wells. They establish requirements and oversight for design
and construction, operating conditions, monitoring and mechanical integrity testing, financial
responsibility, and plugging and abandonment.
6.17 Geothermal Direct Heat Wells
Geothermal fluids are used to heat individual homes and/or communities or to provide
heat to greenhouses, aquaculture, and other commercial and industrial processes in several
(primarily western) States. Following use of geothermal fluids for such heating application,
some facilities use geothermal direct heat return flow wells to return these geothermal fluids to
the subsurface.
The temperature and chemical characteristics of geothermal fluids used for heating vary
substantially from site to site. At some sites, the geothermal fluids are of drinking water quality
and, in fact, are used as drinking water and not reinjected. More commonly, concentrations of
some constituents exceed MCLs or HALs. Available data indicate that arsenic, boron, sulfate,
and fluoride frequently exceed primary MCLs or HALs and that TDS, chloride, iron, manganese,
and sulfate exceed secondary MCLs. TDS concentrations are generally <10,000 ppm except hi
the comparatively rare situations where high temperature geothermal fluids used for power
production are also used for heating.
When geothermal fluids used for heating are reinjected into the subsurface following use
(rather than discharged to surface water or used for drinking, irrigation, or livestock watering),
they typically are reinjected into the same hydrothermal formation from which they were
produced. In addition, the composition of the geothermal fluids normally does not change
appreciably as a result of use for heating, although traces of pump lubricating oil may be added in
some cases.
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No documented cases of USDW contamination by geothermal direct heat return flow
wells have been reported. In addition, the wells typically are not vulnerable to receiving
accidental spills or other illicit discharges because the geothermal fluids are handled in closed
piping systems. Typically, the geothermal fluids are produced from a well, passed through a heat
exchanger, and injected down another well.
The survey results indicate that there are at least 31 documented geothermal direct heat
return flow wells and another 17 more wells estimated to exist. Although these wells exist in as
many as 11 States, more than 80 percent of the documented wells are in only five States: Oregon
(8), Nevada (7), Utah (4), New Mexico (4) and Idaho (3). All of the 17 estimated wells are in
Oregon, but Alaska also indicated the presence of these wells without providing an estimated
number.
Individual permits are required for geothermal direct heat return flow wells in all five of
the states that have most of these wells. In Idaho, an individual permit is not required if the well
is <18 feet deep, but all of the geothermal direct heat return flow wells are substantially deeper
than 18 feet. Individual permit requirements, which also apply in California, are similar in many
respects to those for Class II wells. Further, for wells located on federal land, Bureau of Land
Management approval of well drilling, testing, and abandonment is also required by regulations
promulgated under the Geothermal Steam Act of 1970.
6.18 Heat Pump/Air Conditioning Return Flow Wells
Heat pump/air conditioning (HAC) systems heat or cool buildings by taking advantage of
the relatively constant temperature of underground hydrogeologic formations. They extract heat
energy from ground water for use in heating buildings, and use ground water as a heat sink when
cooling buildings. Two types of HAC systems are in wide use: closed-loop systems and open-
loop systems. Closed-loop systems circulate water entirely within a system of closed pipes,
involve no subsurface injection of wastewater, and are therefore not subject to oversight and
regulation by the UIC program. Open-loop HAC systems withdraw ground water, pass it through
the HAC heat exchanger, and then discharge the water. Many open-loop HACs return used
ground water to the subsurface via injection wells. These "return flow wells" are classified as
Class V wells under the UIC program, and are the focus of this study.
Since water is not consumed by HAC systems, the quantity of return flow water
(injectate) is the same as that withdrawn. The quality of HAC injectate also usually reflects the
characteristics of the source ground water. However, HAC injectate may differ from source
water in several ways. HAC injectate is generally roughly 10° F cooler or warmer than the
source water (depending on whether the HAC is in heat or cooling mode). In some cases, the
temperature drop can cause salts and other dissolved solids to precipitate into suspension, or the
temperature increase can cause suspended solids to dissolve into solution. HAC injectate can also
contain: metals leached from the pipes and pumps; bacteria (where oxygen, nutrients, and a
source of bacteria are present); precipitated ferric iron solids (where dissolved iron is present in
source water, and the HAC system introduces oxygen); and chemical additives (sometimes used
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for disinfection or corrosion prevention). In addition, some HAC systems return water into an
aquifer other than that from which the source water is withdrawn (so-called "dual-aquifer
systems"). Very little data on injectate properties were available for this study. However, the
available data indicate that HAC injectate has in some cases exceeded the primary MCLs or
HALs for lead and copper and the secondary MCLs for chloride and IDS. These exceedances
are believed to be isolated cases and must be considered anecdotal, as the quality of HAC
injectate industry-wide is unknown.
HAC systems most commonly re-inject groundwater into the same formation from which
it is withdrawn. The aquifer used must be relatively porous in order to provide adequate ground
water flow to source wells and from return wells. Dual-aquifer systems may be installed where a
formation other than that from which source water is withdrawn is more readily accessible for
return flow discharge, and is capable of handling HAC return flow. Dual-aquifer systems that
withdraw from contaminated aquifers and re-inject into USDWs can contaminate the receiving
USDWs. As a result, several States prohibit dual-aquifer HAC systems, or require that HAC
source aquifers be of higher quality than return aquifers.
A few USDW contamination incidents have been reported for HAC return flow wells. In
1996, a well in New York was found to have contaminated a USDW with chloride and TDS
above the secondary MCLs, attributed to leaking well casings and inter-aquifer contamination.
In Minnesota, a water sample from a well in 1984 indicated high levels of lead, while another
sample taken from a different well in 1985 showed high levels of lead and copper (all above the
primary MCLs or HALs). This was attributed to leaching of metals from the HAC system pipes
and pumps. In North Carolina, well samples have been reported to contain high levels of iron
and coliform, attributed to poor HAC well construction and operation allowing introduction of
oxygen and contaminants.
HAC return flow wells are generally part of systems that are completely closed above
ground, and are generally located on private property. Therefore, the likelihood of USDW
contamination by spills or illicit discharges at HAC return flow wells is very low.
According to the State and EPA Regional survey conducted for this study, there are
27,921 documented HAC return flow wells in 34 States4. The estimated number of wells
existing in the U.S. is more than 32,804 wells (but probably not more than 35,000), in over 40
States. Approximately 88 percent of all documented wells are in four States: Texas (12,828
wells, or 46 percent), Virginia (7,769, or 28 percent), Florida (3,101, or 11 percent), and
Tennessee (1,000, or 4 percent). Another 30 States collectively account for the remaining 11
percent of the total documented U.S. inventory, with each State having less than 3 percent of the
total. However, many States do not have accurate well counts and well definitions used by some
States differ from EPA definitions.
4 This number includes some closed-loop systems, as not all States use the same definitions as
EPA for "open-loop" and "closed-loop" systems.
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Nearly all of the States with HAC return flow wells have statutory and regulatory
requirements at the State level, some of which regulate the size, design, and/or additives used in
these systems. The States that authorize HAC return flow wells by rule are: Idaho (for wells less
than 18 feet deep), Illinois, Kansas, Nebraska, North Dakota (most wells), Ohio, South Carolina,
Texas, and West Virginia. Other States issue individual permits, including Arizona, Delaware,
Florida, Idaho (for wells greater than 18 feet deep), Maryland (some wells), Minnesota, Montana
(for large wells), Nevada, New York, North Carolina, Oregon (unless individually exempted),
Vermont, and Wisconsin.
In addition to these regulatory controls, a number of relatively straight-forward BMPs are
available that can virtually ensure that HAC wells do not contaminate USDWs. Judging by the
very low incidence of recorded USDW contamination relative to the number of wells.
6.19 Salt Water Intrusion Barrier Wells
Salt water intrusion barrier wells are used to inject water into a fresh water aquifer to
prevent the intrusion of salt water into 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. 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 saltwater intrusion barriers, including
untreated surface water, treated drinking water, and treated municipal wastewater. Injectate,
which often consists of a blend of water from several sources, typically meets primary and
secondary drinking water standards. Ground water monitoring and epidemiological studies have
shown no evidence of problems when the injectate was tertiary-treated wastewater effluent.
However, it should be noted that, in some instances, constituents have been measured at
concentrations slightly above MCLs.
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.
•*N
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 saltwater intrusion
barrier well and its injectate typically meets drinking water standards, salt water intrusion barrier
wells are unlikely to receive spills or illicit discharges.
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According to the State and EPA Regional survey conducted for this study, there are 317
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 611, but unlikely to be higher
than 700. These estimates include two "atypical" saltwater intrusion barrier wells located in
Colorado and Wyoming. Approximately 99 percent of the documented salt water intrusion
barrier wells are located in California (308), Florida (1), and Washington (6).
These States have used SDWA authority, as well as their own authorities, to address
regional or local concerns associated with salt water intrusion barrier wells. Specifically:
• In California, salt water intrusion barrier wells are permitted by rule. However, 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. The
injectate must meet drinking water MCLs 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 health departments.
• In Florida, 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 actually 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 MCLs at the point of
injection. Injection of fluids that exceed the MCLs is allowed only if it
is not into a USDW and if it is controlled in accordance with a
site-specific operating permit.
• In Washington, 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.
6.20 Aquifer Recharge Wells
Aquifer recharge wells have the primary objective of replenishing water in an aquifer.
These wells, however, may have secondary objectives, such as storage of water for subsequent
recovery, prevention of salt water intrusion into fresh water aquifers, and subsidence control.
Aquifer recharge wells are found in areas of the U.S. that have high population density and
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proximity to intensive agriculture; dependence and increasing demand on ground water for
drinking water and agriculture; and/or limited ground water availability.
As for saltwater intrusion barrier wells and aquifer storage and recovery wells, various
types of water quality are injected into aquifer recharge wells, including treated drinking water,
surface water (treated or untreated), surface runoff, and ground water (treated or untreated).
Injectate typically meets primary and secondary drinking water standards. Studies specifically
designed to monitor health effects have found no evidence of problems when the injectate was
tertiary-treated wastewater effluent. However, it should be noted that, in some instances,
constituents have been measured at concentrations slightly above drinking water standards.
Aquifer recharge wells are drilled to various depths depending on the depth of the
receiving aquifer. They may inject into confined, semi-confined, or unconfined aquifers.
Typically, the injection zone is a drinking water aquifer that has been partially dewatered due to
overpumping.
No contamination incidents associated with the operation of aquifer recharge wells have
been reported.
Because replenishment of drinking water supplies is the major goal of an aquifer recharge
well and its injectate typically meets drinking water standards, aquifer recharge wells are unlikely
to receive spills or illicit discharges.
The survey results indicate that there are 1,136 aquifer recharge wells documented in the
United States, although this total includes some aquifer storage and recovery wells (in California
and Idaho) that are not distinguished from aquifer recharge wells in the available inventory. The
estimated number of aquifer recharge wells in the nation is greater than 1,633, but unlikely to be
higher than 2,000. Approximately 89 percent of the documented aquifer recharge wells are
located in California (281), Florida (404), Idaho (48), Nevada (110), Oklahoma (44), South
Carolina (55), Texas (66), and Washington (6).
Some States and localities have used SDWA authority, as well as their own authorities, to
extend the controls in their areas and address regional or local concerns associated with aquifer
recharge wells. The same regulatory program in California and Florida described above for
saltwater intrusion barrier wells is applied to aquifer recharge wells in those States. The
regulatory programs in the other States where the majority of aquifer recharge wells exist are as
follows:
• In Idaho, construction and operation of shallow injection wells (< 18 feet) is
authorized by rule, as long as inventory information is provided and use of the well
does not result in endangerment of a drinking water source or cause a violation of
water quality standards that would affect beneficial use. Construction and use of deep
injection wells (>18 feet) may be authorized by individual permit.
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• In Nevada, construction and operation of an aquifer recharge well is prohibited except
as authorized by permit by the State Engineer. The State Engineer must determine
that the project is hydrologically feasible and that it will not cause harm to users of
land or other water within the area of hydrological effect of the project. 'The permit
specifies the capacity and plan of operation of the recharge project, any required
monitoring, and any other conditions believed necessary to protect ground water.
• In Oklahoma, construction and operation of Class V wells is authorized by rule. The
State has incorporated by reference into the Oklahoma Administrative Code those
parts of 40 CFR Part 124, and 144 to 148 that apply to the UIC Program.
• In South Carolina, aquifer recharge wells are prohibited except as authorized by
permit. Injection may not commence until construction is complete, the permittee has
submitted notice of completion to the Department of Health and Environmental
Control (DHEC), and DHEC has inspected the well and found it in compliance.
DHEC will establish maximum injection volumes and pressures and other such
permit conditions as necessary to assure that fractures are not initiated in the
confining zone adjacent to the USDW and to assure compliance with operating
requirements. The movement of injected fluids containing contaminants into USDWs
is prohibited if the contaminant may cause a violation of any drinking water standard
or otherwise adversely affect health.
• In Texas, underground injection is prohibited, unless authorized by permit or rule. By
rule, injection into an aquifer recharge 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. 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.
• In Washington, an individual permit is required to operate an aquifer recharge 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.
6.21 Aquifer Storage and Recovery Wells
Aquifer storage and recovery (ASR) wells are dual-purpose injection/recovery wells used
to store water in a suitable aquifer for later recovery through the same well. ASR wells are
usually found in areas of the United States characterized by high seasonal fluctuations in water
demand and availability, as well as in areas with large projected population increases. They are
also found in areas that have no freshwater drinking water supplies, or in coastal areas where salt
water intrusion into freshwater aquifers is an issue.
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ASR well injectate consists of potable drinking water (from a drinking water plant),
untreated ground water, untreated surface water, reclaimed water, and partially treated surface
water. Water injected into an ASR well is usually treated to meet, or already meets, primary and
secondary drinking water standards. The use of "good" quality water is necessary to avoid
clogging of the well and to ensure that the quality of the ground water to be recovered is adequate
for subsequent use. In addition, most regulatory agencies require the injectate in ASR wells to
meet drinking water standards in order to prevent degradation of ambient ground water quality.
However, it should be noted that, in some instances, constituents have been measured at
concentrations slightly above drinking water standards.
ASR wells, like saltwater intrusion barrier and aquifer recharge wells, are drilled to
various depths depending on the depth of the receiving aquifer. They may inject into confined,
semi-confined, or unconfmed aquifers, although most ASR wells inject into semi-confined
aquifers that have been partially dewatered due to overpumping.
No contamination incidents associated with the operation of ASR wells have been
reported.
Because storage of drinking water is the major goal of an ASR well and its injectate
typically meets drinking water standards, ASR wells are unlikely to receive spills or illicit
discharges.
According to the State and EPA Regional survey conducted for this study, there are
Approximately 374 ASR wells documented in the U.S., although this total includes some aquifer
recharge wells (in California and Idaho) that are not distinguished from ASR wells in the
available inventory. The estimated number of ASR wells in the nation is greater than 383, but
unlikely to be higher than 500. This estimate does not include 200 wells proposed to be built in
Florida as part of the new "Everglades Project." Approximately 94 percent of the documented
ASR wells are located in California (200), Colorado (7), Florida (>89), Idaho (48), and
Washington (6).
The regulatory programs described in the above sections on saltwater intrusion barrier
wells and aquifer recharge wells in California, Florida, Idaho, and Washington also are applied to
ASR wells in those States. In Colorado, an individual permit is required to operate an ASR well.
In addition, Colorado has promulgated permitting, siting, and construction requirements under
"artificial" recharge rules that apply to extraction of waters recharged via an injection well.
6.22 Noncontact Cooling Water Wells
For the purpose of this study, "noncontact cooling water wells" are limited only to wells
used to inject noncontact cooling water that contains no additives and has not been chemically
altered. Wells that inject contact cooling water or noncontact cooling water that contains
additives (e.g., corrosion inhibitors, biocides) or is contaminated compared to the original source
water are considered "industrial wells."
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EPA defines noncontact cooling water (in 40 CFR §418.21 governing fertilizer
manufacturing) as "water which is used in a cooling system designed so as to maintain constant
separation of the cooling medium from all contact with process chemicals...provided, that all
reasonable measures have been taken to prevent, reduce, eliminate and control to the maximum
extent feasible...contamination...." No sampling data were obtained during the course of this
study that can be used to characterize the quality of fluids injected into noncontact cooling water
wells. However, given the very narrow way that such wells and noncontact cooling water are
defined, it is reasonable to expect that the quality of the fluids should not threaten USDWs.
Available information suggests that these wells are commonly used in situations in which
cooling water is withdrawn from an aquifer and then injected back into the same formation (so-
called "cooling water return flow wells" as defined in 40 CFR §146.5(e)(3)). In these situations,
the quality of the fluids injected should be the same as the quality of the fluids in the receiving
formation, except for a change in temperature.
No contamination incidents associated with noncontact cooling water wells, as defined
for the purpose of this study, have been reported. In addition, there is a low probability that such
wells could be contaminated by spills or illicit discharges. The only scenario in which
noncontact cooling water wells could be contaminated would involve pipe leaks that allow
process chemicals or other contaminants to commingle with the cooling water. Illicit discharges
into these wells appear extremely unlikely, since noncontact cooling water systems are operated
as closed systems that are virtually inaccessible for "midnight dumping." No incidents of this or
any other kind were uncovered during the course of this study.
As for some of the other well categories discussed above, the inventory results for
noncontact cooling water wells is very uncertain because most responses to the State and EPA
Regional survey did not distinguish these wells from other kinds of commercial or industrial
wells. The survey results suggest that there are <7,800 noncontact cooling water wells in the
nation, but the true number is expected to be far less because this number includes some carwash
wells, laundromat wells, and food processing waste disposal wells. The survey results also
indicate that noncontact cooling water wells may exist in as many as 22 States, although most
appear to be concentrated in Alaska (212), Washington (<3,900), and Tennessee (<1,000).
. Of these States that have the vast majority of noncontact cooling water wells, Alaska and
Washington require the wells to be individually permitted. Tennessee currently permits them by
rule, following a program like the minimum federal requirements established in EPA's existing
UIC regulations.
6.23 Subsidence Control Wells
Subsidence control wells are injection wells whose primary objective is to reduce or
eliminate the loss of surface elevation due to removal of ground water providing subsurface
support. These wells also may be used to control land subsidence caused by man-induced
activities other than ground water withdrawal (e.g., mining, discussed in section 6.9, and
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construction), but are not related to oil and gas production activities (such wells associated with
oil and gas production activities qualify as Class II injection wells). Land subsidence control
through the use of subsidence control wells is achieved by injecting water into an aquifer to
maintain fluid pressure and avoid compaction.
Sources of injectate hi subsidence control wells include untreated surface water, coal
preparation plant wastes, saline water, and surface water treated to drinking water standards. No
data on injectate constituents or concentrations associated with subsidence control wells are
available. However, it is reasonable to assume that injectate in some subsidence control wells
exceeds MCLs for some parameters.
None of the known, active subsidence control wells inject into USDWs. Some wells
inject into mined out areas in order to control subsidence associated with mining activities, some
inject beneath construction zones to minimize damage from settlement caused by construction,
and some inject into a salt dome cavity that is used for the storage of oil at the Strategic
Petroleum Reserve.
No contamination incidents associated with the operation of subsidence control wells
have been reported.
Details on the design, construction, and operation of subsidence control wells are not
available. Thus, it is not possible to determine if subsidence control wells are vulnerable to
receiving spills or illicit discharges.
According to the State and EPA Regional survey conducted for this study, there are 87
subsidence control wells documented in the United States. The estimated number of subsidence
control wells in the nation is greater than 131, but unlikely to be higher than 200 (also see
Section 6.9). All documented subsidence control wells are located in Louisiana (8), West
Virginia (73), and Wisconsin (6). In addition, no wells were reported in Alaska and
Pennsylvania, but officials responsible for the UIC Program hi those States did not rule out the
possibility that some exist.
Subsidence control wells located in Louisiana and West Virginia are authorized by rule.
Such wells in Wisconsin are individually permitted by the Department of Natural Resources.
Public Comment Draft
July 12. 1999 60
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