United States Office of Ground Water EPA/816-R-99-014s
Environmental and Drinking Water (4601) September 1999
Protection Agency
The Class v Underground Injection
Control Study
Volume 19
Heat Pump and Air Conditioning Return
Flow Wells
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Table of Contents
Page
1. Summary 1
2. Introduction 3
3. Prevalence of Wells 4
4. Wastewater Characteristics and Injection Practices 8
4.1 Injectate Characteristics 8
4.2 Well Characteristics 10
4.2.1 Well Types 10
4.2.2 Well Design 12
4.3 Operational Practices 12
5. Potential and Documented Damage to USDWs 14
5.1 Potential Injectate Impacts to USDWs 14
5.1.1 Thermal Alteration 14
5.1.2 Mineral Precipitation Due to Changes in Water Pressure
or Oxygen Levels 15
5.1.3 Chemical Contamination 15
5.1.4 Water Quantity 17
5.2 Observed Impacts 17
6. Best Management Practices 18
6.1 Well Design and Siting 19
6.1.1 Alternative Technological Design 19
6.1.2 Pre-Construction Practices 19
6.1.3 Siting Issues 20
6.1.4 Design Features 20
6.2 Heat Pump Injection Well Construction 21
6.3 Heat Pump Injection Well Operation, Maintenance, and Monitoring 22
7. Current Regulatory Requirements 24
7.1 Federal Programs 24
7.2 State and Local Programs 25
Attachment A: State and Local Program Descriptions 27
References 58
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HEAT PUMP AND AIR CONDITIONING
RETURN FLOW WELLS
The U.S. Environmental Protection Agency (USEPA) conducted a study of Class V
underground injection wells to develop background information the Agency can use to evaluate
the risk that these wells pose to underground sources of drinking water (USDWs) and to
determine whether additional federal regulation is warranted. The final report for this study,
which is called the Class V Underground Injection Control (UIC) Study, consists of 23 volumes
and five supporting appendices. Volume 1 provides an overview of the study methods, the
USEPA UIC Program, and general findings. Volumes 2 through 23 present information
summaries for each of the 23 categories of wells that were studied (Volume 21 covers 2 well
categories). This volume, which is Volume 19, covers Class V heat pump and air conditioning
return flow wells.
1. SUMMARY
Ground-source 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 ground-source HAC systems are generally
used: 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 from a source well, 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.
Because water is not consumed by HAC systems, the quantity of return flow water
(injectate) is generally 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 4 to 10 degrees Fahrenheit cooler or
warmer than the source water (depending on whether the HAC is in heating 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 for disinfection or corrosion prevention). 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 drinking water maximum contaminant levels (MCLs) for
lead and copper and the secondary MCLs for chloride and total dissolved solids (TDS).
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HAC systems most commonly re-inject ground water into the same formation from which
it is withdrawn. The aquifer used is relatively porous in order to provide adequate ground water
flow to source wells and from return wells. Dual-aquifer systems may be feasible where another
formation (a different formation 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. The incident was 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 standards). 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. As the quality of HAC injectate industry-wide is unknown, it is not
clear whether these known contamination cases are isolated cases, or indicative of a wider
problem with this type of well.
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 USEPA Regional survey conducted for this study, there are
27,921 documented HAC return flow wells in 34 states.1 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
the USEPA definitions.
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. Of the states in which the largest numbers of HAC wells are found, USEPA
directly implements the UIC program for all Class V injection wells (including HAC return flow
wells) in Arizona, Michigan, Minnesota, New York, Pennsylvania, Tennessee, and Virginia. The
other states with many HAC return flow wells are UIC Primacy States for Class V wells, and
1 This number includes some closed-loop systems, as not all states use the same definitions as
USEPA for "open-loop" and "closed-loop" systems.
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authorize the wells by rule (Illinois, Kansas, Nebraska, North Dakota, Ohio, South Carolina,
Texas, West Virginia, and Wyoming) or issue individual permits (Delaware, Florida, Maryland,
Missouri, Nevada, North Carolina, Oregon, Vermont, and Washington). In Wisconsin, which is
also a Primacy State for Class V wells, discharge to a shallow absorption system located in
unsaturated soils is allowed under a general permit, but discharge directly into a saturated soil or
aquifer is prohibited.
A number of relatively straight-forward best management practices 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), it appears that HAC owners
and operators are aware of and generally apply best management practices.
2. INTRODUCTION
At depths below the influence of atmospheric temperatures, and in areas not affected by
geothermal heating or the cooling effect of seasonal glacial and snow mass melting, subsurface
hydrogeologic formations typically maintain fairly constant temperatures year round. These
relatively uniform ground temperatures in the United States range from approximately 42 degrees
Fahrenheit (6 degrees Celsius) near the Canadian border to 77 degrees Fahrenheit (25 degrees
Celsius) in southern Florida (Oklahoma State University, 1988). Ground-source HAC systems
withdraw ground water at this temperature and either extract the heat energy from the water for
use in heating buildings, or use the water as a heat sink to carry off excess heat when cooling
buildings. Water is not consumed in the process; once the ground water has passed through the
heat exchange process it is discharged, commonly through re-injection into the ground. By
making use of the natural heat energy or heat removal capacity of ground water, heat pumps
require less fossil fuel or electrical energy to heat or cool buildings, and are therefore regarded as
an energy efficient technology.
There are two main types of ground-source HAC systems: closed-loop and open-loop
systems. Closed-loop systems (also known as ground-coupled heat pumps) are, as the name
implies, completely closed systems in which fluids (e.g., water, or propylene glycol and water)
are circulated continuously through a loop of pipes that pass underground and through the heat
exchanger of the HAC system. Because the circulating fluids do not have contact with the
outside environment, closed-loop HAC systems are not considered to involve Class V wells
(USEPA, 1997), and are outside the scope of this study. All references to HAC systems in the
remainder of this study refer to open-loop HAC systems, unless otherwise specified.
Open-loop HAC systems (also known as ground water heat pumps) withdraw water from
an underlying aquifer, pass it one or more times through the heat pump(s), and then discharge the
water. Common means of water disposal are: surface discharge, generally to existing bodies of
water such as ponds and streams; and re-injection to the subsurface via an injection well separate
from the withdrawal well. Injection wells used for subsurface disposal (or return) of water from
HAC systems are classified as Class V underground injection wells (USEPA, 1997). Thus, the
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focus of this study is the injection wells associated with open-loop HAC systems that dispose of
water via underground injection. These are commonly referred to as HAC return flow wells.
According to the UIC regulations in 40 CFR 146.5(e)(l), Class V wells include "air
conditioning return flow wells used to return to the supply aquifer the water used for heating or
cooling in a heat pump." In some cases, water is withdrawn from the supply aquifer, circulated
through the HAC system, and reinjected into a different aquifer.
As currently defined in the UIC regulations (40 CFR 144.3), a "well means a bored,
drilled or driven shaft, or a dug hole, whose depth is greater than the largest surface dimension."
Therefore, any hole that is deeper than it is wide or long qualifies as a well. In the case of HAC
return flow wells, this includes holes drilled and cased with pipe, as well as "infiltration galleries"
consisting of one or more vertical pipes leading to an array of horizontal, perforated pipes laid
below the ground surface, designed to release wastewater underground. As described in more
detail below, this design is used for disposal of water by some HAC systems. Each of the vertical
pipes in an infiltration gallery system (exclusive of the network of horizontal subsurface piping),
individually or in a series, is considered an injection well subject to UIC authorities (Elder and
Lowrance, 1992).
3. PREVALENCE OF WELLS
For this study, data on the number of Class V HAC return flow wells were collected
through a survey of state and USEPA Regional UIC Programs. The survey methods are
summarized in Section 4 of Volume 1 of the Class V Study. Table 1 lists the number of Class V
HAC return flow wells in each state, as determined from this survey. The table includes the
documented number and estimated number of wells in each state, along with the source and basis
for any estimate, when noted by the survey respondents. If a state is not listed in Table 1, it
means that the UIC Program responsible for that state indicated in its survey response that it did
not have any Class V HAC return flow wells.
Inventory data quality and quantity is not consistent across all states. In some cases, the
difference between the number of documented wells and the estimated number of actual wells
(documented and undocumented wells) may be great and estimates can only be made using best
professional judgement. In addition, it is apparent that some state definitions for closed-loop
(non-Class V) and open-loop HAC systems are different than those used by USEPA. Industry-
approved definitions, such as those provided by the International Ground Source Heat Pump
Association or the American Society of Heating, Refrigerating and Air-Conditioning Engineers
(see ASHRAE, 1995), are not used uniformly by state and federal agencies. The definition of
closed-loop wells used by some states actually encompasses open-loop wells as defined by
USEPA (and as defined in this study). In such cases, the wells in the state's closed-loop HAC
well inventory were included in the open-loop HAC return flow wells inventory presented here.
As presented in Table 1, almost 28,000 Class V HAC return flow wells are documented in
the U.S., based on data from state, USEPA, and other sources. The estimated number of wells
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Table 1. Inventory of Heat Pump/AC Return Wells in the U.S.
State
Documented
Number of Wells
Estimated Number of Wells
Number
Source of Estimate and Methodology1
USEPA Region 1
MA
NH
RI
VT
2
2
1
NR
2
2
1
25
N/A
N/A
N/A
Best professional judgement (estimated that some operators
may not know that a permit is required).
USEPA Region 2
NY
18
500
Best professional judgement, based on conversations with
installation contractors and State of New York staff.
USEPA Region 3
DE
MD
PA
VA
WV
526
0
34
7,769
2
526
815
>34
> 7,769
> 1,000
N/A
Onsite review of water appropriations permits.
N/A
N/A
N/A
USEPA Region 4
AL
FL
MS
NC
sc
TN
11
3,101
NR
85
467
1,000
>11
NR
184
170
900-1,300
1,000
Best professional judgement and discussions with regulated
community; State of Alabama officials believe that more
wells exist but cannot form an accurate estimate.
N/A
N/A
Best professional judgement based on assumption by state
officials that approximately half of the state's HAC wells are
documented.
Best professional judgement based on determination by state
officials that 55 percent of well drillers submit required
documentation.
N/A
USEPA Region 5
IL
MI
0
832
<59
NR
Estimated 59 wells are believed to be mostly closed-loop
systems.
Documented number is based on a 1988 study.
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Table 1. Inventory of Heat Pump/AC Return Wells in the U.S. (cont'd)
State
MN
OH
WI
Documented
Number of Wells
6
5
3
Estimated Number of Wells
Number
39
50 - 500
75
Source of Estimate and Methodology1
Estimated number is based on a 1981 study; state staff could
not confirm the estimate. State staff suspect that some of
these wells may no longer be active.
Best professional judgement, based on a January 1997 site
visit by USEPA to Ohio EPA.
Best professional judgement; WDNR estimated one HAC
well with drain field discharge in each of the 72 counties in
the state in addition to the three documented systems.
USEPA Region 6
AR
LA
OK
TX
20
10
1
12,828
20
NR
1
12,828
N/A
State officials indicate that more HAC wells may exist in LA
than reported, but did not give an estimate.
N/A
Based on UIC database. Authorizations listed for 748 of the
total number of wells.
USEPA Region 7
IA
KS
MO
NE
17
457
472
104
100
> 1,000
>472
104
Best professional judgement and discussions with heat pump
installers.
Best professional judgement. State officials believe that some
documented wells may be inactive or misclassified.
However, there may be significant numbers of undocumented
wells in Wichita, Hutchinson, and Garden City. It is
suspected that several thousand wells exist in total.
Heat pump wells serving single family residences, or serving
up to eight family residences and injecting/withdrawing less
than 600,000 BTU/hr, are not required to obtain operating
permits and are not documented.
N/A
USEPA Region 8
CO
MT
ND
3
1
10
3
>1
50
N/A
USEPA Region 8 Montana Operations Office believes some
HAC wells may exist, but neither the state nor the USEPA
Region tracks information on this well type.
Best professional judgement. Only commercial and industrial
wells are documented; thus, there are incomplete records on
private and residential heat pump injection wells.
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Table 1. Inventory of Heat Pump/AC Return Wells in the U.S. (cont'd)
State
UT
WY
Documented
Number of Wells
11
3
Estimated Number of Wells
Number
>H
3
Source of Estimate and Methodology1
Inventory forms received in FY 1998 are not reflected in the
documented number because of an anticipated change in data
systems. Additionally, 3 wells are under construction and 2
wells are temporarily abandoned.
Information provided by Lucht, 1999.
USEPA Region 9
AZ
CA
NV
0
9
0
< 50 systems
9
40-50
Drilling permit requests, best professional judgement (note:
each system may contain >1 well).
N/A
Best professional judgement.
USEPA Region 10
AK
ID
OR
WA
13
0
14
81
NR
NR
50
81
USEPA Region 10 suspects that more wells may exist in AK
than documented, but did not give an estimate.
219 wells are documented in ID, but these are believed to be
all closed-loop wells.
Best professional judgement, based on review of personal and
state departmental files.
N/A
All USEPA Regions
All States
27,918
>32,801
Total estimated number counts the documented number when
the estimate is NR.
Unless otherwise noted, the best professional judgement is that of the state or USEPA Regional staff completing the survey
questionnaire.
N/A Not available.
NR Although USEPA Regional, state and/or territorial officials reported the presence of the well type, the number
of wells was not reported, or the questionnaire was not returned.
is nearly 33,000 (the total estimated number uses the documented number when an estimate was
not reported for a given state). USEPA Regions 3, 4, and 6 have the greatest number of
documented wells, with each USEPA Region having thousands of wells. Within these USEPA
Regions, several states have 1,000 or more documented wells, including Texas (12,828), Virginia
(7,769), Florida (3,101), and Tennessee (1,000). West Virginia, South Carolina, and Kansas are
estimated to have greater than one thousand wells each, but are documented to have only two,
467, and 457 wells, respectively. USEPA Regions 1, 2, 8, 9, and 10 each has approximately one
hundred or fewer documented HAC return flow wells.
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Data for Illinois indicate that an estimated 59 HAC wells exist in that state, but these are
believed to include both open-loop and closed-loop systems, with the majority being closed-loop
systems by USEPA's definition. Because the available information does not allow distinction
between open- and closed-loop systems, all 59 systems were included in the estimated U.S.
inventory in Table 1.
4. WASTEWATER CHARACTERISTICS AND INJECTION
PRACTICES
4.1 Injectate Characteristics
The injectate from HAC systems generally reflects the characteristics of the source ground
water. Data from individual facilities therefore tends to be rather site-specific. In the following
paragraphs, the general constituents and physical properties of HAC injectate is examined.
Open-loop HAC systems utilizing subsurface disposal to the original source aquifer - if
properly constructed and operated are considered by some industry experts to function
essentially as closed-loop systems (Knape, 1984). In these open-loop systems, water is
withdrawn from the HAC supply well, pumped through the heat exchanger, and returned to the
same aquifer from which it was withdrawn without being exposed to outside sources of
contamination. The chemical and physical properties of the HAC return flow (injectate) are
therefore essentially identical to those of the water from the supply well, with the exception of a
change in temperature, generally of less than 10° Fahrenheit. Well-designed HAC systems that
return water to the same aquifer from which it is withdrawn (hereafter referred to as single-
aquifer HAC systems) therefore have minimal impacts on this aquifer. Where the aquifer in use
is a USDW, return flow (injectate) does not degrade the quality of the USDW. Where the aquifer
in use is not a USDW, the system poses no threat to USDWs.
In such systems, temperature changes and associated changes in the physical properties of
the return flow water are the main issues associated with HAC return flow. The temperature
difference between supply and return water is usually on the order of 4-10 degrees Fahrenheit.
HAC systems typically cause a 4-8 degrees Fahrenheit decrease in water temperature while
operating in the heating cycle, and an 8-10 degrees Fahrenheit increase in water temperature
while operating in the cooling cycle (Rawlings, 1999). In some cases, slight temperature
changes can result in precipitation of salts and solids from the water, or the dissolution of salts or
solids into the water. The greatest temperature change usually occurs within the HAC system
heat exchangers, sometimes resulting in the precipitation of salts and the formation of scale on the
inner walls of the heat exchanger. Thus where water is withdrawn from and returned to the same
aquifer the dissolved solids and suspended solids content of the return flow water can differ from
those of the water in the aquifer. This effect is usually minimal, however, and has no implications
for human health.
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The injectate from HAC wells may contain other types of contaminants. A greater
potential for contamination of USDWs exists where HAC systems withdraw water from and re-
inject the water into different aquifers (hereafter referred to as dual-aquifer systems). Dual-
aquifer systems pose a threat to USDWs when the source aquifer is contaminated, and return
water is re-injected into a USDW. In such cases, return flow water (injectate) properties will
reflect the characteristics of the supply aquifer, and could contain both chemical and
microbiological contaminants. The greater potential for USDW contamination by dual-aquifer
HAC systems is well recognized, and many states and jurisdictions prohibit, or have much more
complex permitting requirements for, dual-aquifer systems. However, inventory data do not
distinguish between single-aquifer and dual-aquifer systems, and the prevalence of dual-aquifer
systems can not be determined. No data on injectate properties in dual-aquifer HAC systems are
available.
Closed-loop HAC systems commonly circulate a solution of water and various additives
(e.g., propylene glycol) to prevent corrosion, to fight microbial cultivation, and/or to depress the
freezing point of the solution. Similar additives may also be used in some open-loop systems,
although the prevalence of additive use or types of additives used could not be determined from
the data available for this report. In the inventory of HAC wells conducted for this report, state
and USEPA Regional officials were asked whether additives were allowed or used in Class V
HAC return flow wells. For the majority of states, officials indicated that additives are either not
allowed or not used in open-loop HAC systems. However, for several states the use of additives
is less clear. The States of Arizona, Louisiana, Michigan, Nevada, and Texas allow the use of
additives in open-loop HAC systems under some circumstances, although data are not available
indicating whether additives are actually used in such systems in these states. No specific cases
of additive use in open-loop HAC systems were identified during this study and no data are
available regarding additive concentrations in injectate. While few, if any, system manufacturers
and industry participants recommend using chemical additives in open-loop systems (Rawlings,
1999), it is possible that additives are occasionally used in open-loop systems. The question of
additive use in open-loop HAC systems remains as a gap in the understanding of the potential
impact of these systems on USDWs.
Constituents leached into the water from the pipes or pumps of the HAC system itself are
also potential contaminants in HAC return flow wells. Based on empirical evidence, metals may
be introduced to HAC return flow water in this way, potentially contaminating the receiving
aquifer. However, the prevalence of this phenomenon is unknown. It is only reported once in the
HAC return flow well inventory (see Section 5.2 for details), and the extent to which HAC return
flow is monitored for heavy metals is not known. Significant leaching of toxic metals from HAC
systems into return flow water would require specific conditions, including relatively acidic or
corrosive water, and a HAC system design in which relatively large surfaces containing toxic
metals are in contact with water.
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4.2 Well Characteristics
4.2.1 Well Types
HAC systems vary in terms of well arrangement and disposal method. Two types of
subsurface systems are used to return used water: horizontal drains and vertical injection wells.
Horizontal drains are generally designed as typical leaching fields, where vertical pipes direct
water underground for discharge through a network of horizontal, perforated pipes. The
horizontal pipes are installed in trenches on top of beds of gravel or other highly porous material,
and are covered with more gravel, and then 1-2 feet of original soil from the site. Return flow
water percolates from the pipes, down through the bed of porous material, and into the underlying
strata and aquifer. This type of system functions well in sandy or highly porous soil.
Most HAC systems that re-inject return flow water to the subsurface use vertical injection
wells. There are two types of vertical injection well systems: standing column wells and two-well
systems with separate source and return flow (recharge) wells. Standing column wells,
sometimes called turbulent wells, are used for both supply and discharge of water. Ground water
is pumped to the surface by a submersible pump located at the bottom of the well. Water is
circulated through the heat exchanger of the HAC system and returned to the top of the well
(Orio, 1994). This design is generally used for domestic systems. In a two-well system, supply
and return flow wells are installed separately. The recharge water in two-well systems can be
returned either to the same or to a different aquifer from which it was withdrawn.
Figures 1 and 2 show standard configurations for HAC return flow wells, installed in
consolidated and unconsolidated formations, respectively. Figure 3 shows the design of a typical
two-well system using a single aquifer.
Figure 1. A HAC Return Flow Well in a Consolidated Formation
PVC pin
Cimtm (2' tiib on turfieil
Source: Knape, 1984.
10
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Figure 2. A HAC Return Flow Well in
PVC pip*
Ground level rrr.
I I I I
.. i,,.!.. r.i
WaU screen*
an Unconsolidated Formation
Cement (T slab on surfece)
S:]fev'Vr::^»A'£S£,';r!y:^i-^''.-',-iJ^
Source: Knape, 1984.
Figure 3. Typical Two-Well System
Ground
Supply wtll lni«ett(w»
Ctmtnt jltb
WtH«r»«ni
Source: Knape, 1984.
11
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4.2.2 Well Design
HAC supply and recharge wells are generally similar in design and construction to drinking
water wells and other types of wells (see USEPA, 1975, for water well design and construction
details). However, air, cable tool, and reverse circulation drilling methods are preferable to rotary
drilling for injection wells because they use less damaging drilling fluids (i.e., air or clean water
rather than mud) and as a result pose less of a threat to the performance of the completed injection
well (Kavanaugh and Rafferty, 1997).
The depth of the HAC return flow well and the acceptance rate of the receiving aquifer are
important factors in well design. Depths of HAC return flow wells are dictated by the
hydrogeology of each site. HAC return flow well depths (based on the HAC return flow well
inventory) include: from 200 to 400 feet in Texas; as deep as 1500 to 2000 in New York; and from
200 to 2000 feet in Nevada. Installing both the supply and return flow wells of single-aquifer
systems, and the return flow wells of dual-aquifer systems, in an aquifer with relatively high
porosity and water flow rates will ensure sufficient infiltration. For well design recommendations
related to water acceptance capacity, see Section 6.1.4.
For the single-aquifer two-well system, it is important to prevent recharge water from
causing thermal degradation of supply waters. The spacing between the supply and return flow
wells is a critical factor affecting the effectiveness of heat exchange of the heat pump (see Section
6.1.3 for important parameters to consider when evaluating spacing needs). If these wells are too
close together, the potential exists for return flow water to move through the aquifer and be
withdrawn again by the supply well before the temperature of this water has an opportunity to
return to the natural temperature of the aquifer. This can reduce the efficiency of the HAC system.
A dual-aquifer system may be feasible where two aquifers, one with sufficient supply
capacity and one with sufficient porosity to accept the return flow, are available. The distance
between the two wells is less important for dual-aquifer systems. However, in dual-aquifer HAC
systems, water withdrawn from the supply aquifer is not replaced. As is the case with any system
involving relatively high rates of water withdrawal from an aquifer, this has the potential to result
in land subsidence and, in coastal areas, salt water intrusion into the supply aquifer. While these
issues are related to water withdrawal, not underground injection, and no cases involving HAC
return flow wells have been identified, they are nevertheless factors often considered in the
planning of HAC systems, and in contemplating possible regulation of such systems. These
problems are largely avoided with single-aquifer HAC systems.
4.3 Operational Practices
During operation, the typical water consumption of a residential HAC system can be from 3
to 12 gallons per minute (gpm), or 4,320 to 17,280 gallons per day (gpd) (PA DEP, 1996). Others
have noted that since HAC systems do not typically run 24 hours per day in fact, annual average
run time may be only 35 to 40 percent, and continuous operation only occurs during rare extreme
weather periods actual water usage is probably as low as 1 to 3 gpm per nominal ton of capacity
12
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(Kavanaugh, 1998; Rawlings, 1999). The actual water flow requirement is a function of many
variables, including ground water temperature, loop supply and return temperatures, heat exchanger
performance, pump performance, and building peak block load (Kavanaugh and Rafferty, 1997).
HAC system return flow wells most commonly operate by gravity flow. Where the
receiving aquifer can not accept water at the peak return flow rate, storage tanks may be installed to
even out the return flow at a rate that can be absorbed by the return flow well. Where the return
flow well can not accept the overall average return water flow rate, pumps are used to re-inject
return flow water under pressure.
Return flow water from HAC systems is always warmer (when HAC system is in the
cooling mode) or cooler (when the HAC system is in the heating mode) than the supply water.
When re-injected, this return flow creates a thermal plume or a volume of water within the
aquifer surrounding the discharge point that is either warmer or cooler than the natural aquifer
temperature. If this thermal plume extends to the intake point of the supply well (in a single-aquifer
system), the efficiency of the HAC system will be reduced. Some HAC systems take advantage of
the thermal storage capacity of an underlying aquifer by reversing supply and return wells in winter
and summer. In this way, cooler water from the cool plume created in the aquifer during winter
(HAC system heat mode) is withdrawn during the summer (HAC system cooling mode), increasing
the cooling efficiency of the HAC system in summer. Well roles are again reversed in winter, so
that warmer water is supplied to the HAC system while it is in heating mode.
Under standard industry practice, HAC water systems are carefully and sufficiently sealed
and generally do not allow the entrainment of air. Air bubbles can, however, become lodged in the
open spaces of an aquifer and the pressure of recharge water can prevent the upward movement of
bubbles to the water table. These bubbles could have the same effect as clay particles and reduce
the flow rate of recharge water into the aquifer. An experiment conducted by the U.S. Geological
Survey showed that air entrainment can reduce the capacity of the return flow well by as much as
fifty percent (Snyder and Lee, 1980).
It should also be noted that 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 illicit discharges is very low. However, it is possible that
some facilities may operate without proper registration and permits. For example, State of
Minnesota officials reported that a single well was being operated illegally without a permit "for
some time" before state officials discovered it. Upon inspection, a state sanitarian discovered a
leak in the injection well. The leak was later corrected and it is not known whether any USDW
contamination occurred.
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5. POTENTIAL AND DOCUMENTED DAMAGE TO USDWs
5.1 Potential Injectate Impacts to USDWs
5.1.1 Thermal Alteration
The 1987 Class V UIC Report to Congress (USEPA, 1987) stated that one of the most
serious threats to USDWs associated with HAC systems is thermal degradation. The increase in the
temperature of return flow water (in the cooling cycle) can cause the dissolution of suspended
solids into the water, increasing the concentration of total dissolved solids in the return flow and in
the aquifer where the return flow is re-injected. As previously noted, the decrease in temperature of
return flow water during the heating cycle can cause certain salts and metals to precipitate from the
ground water, increasing the suspended solids content.
The magnitude and significance of thermal alteration of the ground water is determined by
many factors, including the number of aquifers used (i.e., a single- vs. dual-aquifer system), the
distance between the supply and injection wells, the recharge volume and temperature, the water
chemistry, viscosity, permeability and porosity, and other ground water characteristics. Both
Knape (1984) and USEPA (1997) have stated that the temperature change of water in HAC systems
is generally less than ten degrees Fahrenheit. USEPA (1997) indicated that returning water to the
same aquifer year-round may essentially negate the effects of thermal degradation due to the
seasonal alternation of HAC return flow between cooler and warmer water.
Thermal degradation to aquifers may not be evident until several years after the system goes
into operation and may be observed only at distances relatively close to the HAC return flow well.
Andrews (1978), using a single-aquifer mathematical model to estimate temperature change over 10
years of operation, indicated that the change in aquifer water temperature will be less than 1 degree
centigrade at a distance greater than 40 meters from the HAC return flow well. According to
another study, a single-aquifer, 20-ton HAC system will not produce any noticeable thermal effects
at distances greater than 100 feet from the return well (Williams and Sveter, 1987).
A temperature change in an aquifer may alter its ability to transmit fluid (Knape, 1984). If
the ground water temperature were to decrease due to cold water injection during a HAC system
heating cycle, the viscosity of the ground water can be increased, and the aquifer can transmit fluid
less easily. Knape (1984), however, notes no significant hazard to aquifers due to the potential
change in aquifer transmissivity. No data have been identified relating to HAC return flow well
impacts on aquifer transmissivity.
Knape (1984) also states that the solubility of most common salts, such as calcium or
magnesium, is generally more dependent on the degree of acidity of the solution rather than the
temperature. While the precipitation of salts may result in pore clogging in the receiving aquifer,
this is likely to be restricted to areas near the outlet of the return flow well. Pore clogging therefore
could conceivably affect performance of the HAC system, but is not likely to have a significant
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effect on the aquifer as a whole. No data on pore clogging from salt precipitation have been
identified during the course of this study.
Armitage et al. (1980) list several studies on thermal degradation of aquifers, and indicate
that none have shown serious adverse effects to the aquifer.
5.1.2 Mineral Precipitation Due to Changes in Water Pressure or Oxygen Levels
In addition to differences in temperature, return flow water is different from supply water in
that the pressure and dissolved oxygen levels may be altered by the HAC system. Changes in water
pressure and oxygen levels may potentially lead to metal precipitation and iron oxide development
(USEPA, 1997). Williams and Sveter (1987) indicate that "pressure changes can alter the
equilibrium of dissolved constituents and result in precipitation," and they identify calcium and iron
precipitation to be a major problem in HAC systems in Texas. Armitage et al. (1980) state that
calcium carbonate can precipitate when the injectate contains high levels of calcium, bicarbonate,
and carbonate and is injected into a carbon dioxide deficient aquifer.
Although air leaks are generally not tolerated in a well-designed HAC system (Rawlings,
1999), some poorly-designed or constructed HAC systems allow entrainment of or exposure to air,
increasing the oxygen level in the water. When oxygen-rich ground water is injected into a
reducing aquifer, the precipitation of ferric hydroxide is likely. Increased oxygen levels also aid in
the growth of oxygen-dependent bacteria, which oxidize ferrous iron and contribute to the
precipitation of ferric hydroxide (Snyder and Lee, 1980).
HAC injection wells do not change the pH-Eh conditions of return flow water, but in dual-
aquifer systems the compatibility of the pH-Eh equilibrium between two aquifers is a significant
consideration. If this equilibrium is radically different in the two aquifers, solids precipitation and
clay colloid dispersion is likely, and the result can be a significant reduction in aquifer permeability
in areas affected by the return flow plume (Armitage et al., 1980).
5.1.3 Chemical Contamination
Construction and operation of any type of borehole/well system can potentially lead to the
contamination or cross-contamination of aquifers, particularly if such systems are poorly designed,
built, or managed. This is not a problem specific to HAC injection wells, but experience has shown
that poor well design, construction, and/or management can result in USDW contamination by
HAC well systems.
Potential sources of contamination during the drilling of HAC wells include contaminants
present in or on surface soils, hydraulic fluids or fuels from the drilling rig, residual drilling fluid
constituents (if used), materials encountered during drilling (e.g., accidental puncture of sewage
lines, encountering buried wastes, etc.), and airborne pollutants that could migrate down the hole
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(PA DEP, 1996). If significant amounts of water are spilled on the ground during drilling, surface
contaminants can infiltrate the ground and contaminate the underlying ground water, depending on
the depth to ground water and local hydrogeologic conditions (USEPA, 1997).
USDWs can also be contaminated by dual-aquifer HAC systems, when water in the source
aquifer is contaminated or non-potable, and the return flow is injected into a clean USDW. In any
inter-aquifer contamination case of this kind, the properties of the return flow water will reflect the
properties of the supply aquifer. While undocumented inter-aquifer contamination incidents may
have occurred, broad statements cannot be made at this time given the available information. The
specific contaminants, the concentrations of these contaminants, and the significance of inter-
aquifer contamination are specific to the properties of the aquifer from which the contamination
emanates, and the particulars of each case.
As with other types of wells, unintended inter-aquifer transfer of water can occur when
HAC wells are poorly built, and allow seepage of water from contaminated or non-potable aquifers
into or out of the system. This problem is generally due to lack of training, care, or expertise on the
part of the driller or well installation contractor, and this same problem exists for all types of wells,
not just HAC wells. The problem can occur in both single- and dual-aquifer systems, even when
the intended supply and return flow aquifers are uncontaminated, if wells with porous or leaky
liners pass through aquifers with contaminated or non-potable water. Where well liners are
permeable or HAC systems are inadequately sealed, both the withdrawal and injection processes
associated with HAC systems can cause unintended transfer of water between aquifers, including
the transfer of contaminated or non-potable water to USDWs. This can happen in two ways for
HAC systems: (1) when water from a contaminated aquifer seeps into an HAC system designed to
withdraw water from a clean aquifer and re-inject it into a USDW; and (2) when water seeps out of
an HAC system using contaminated or non-potable aquifer, and the seepage reaches a USDW.
Contaminants reaching the USDW in such cases will reflect the characteristics of the contaminated
or non-potable aquifer involved. Section 5.2 details the lone documented incident of this type of
contamination from a well in New York.
The inter-aquifer contamination scenario is most likely to occur when the HAC supply well
is located near sources of contamination such as areas of heavy commercial fertilizer or pesticide
use, landfills, livestock pens, underground fuel or chemical storage tanks, or septic systems
(USEPA, 1997). Clearly, inter-aquifer contamination can also occur if the supply well taps saline
coastal aquifers, or other aquifers with naturally high dissolved solids (salts) content.
USDWs may also be contaminated by chemical additives used to maintain HAC well
function. The environment found in the HAC pipes can encourage the growth of several types of
bacteria, including Crenothrix and Leptothrix, which oxidize ferrous iron and lead, increasing ferric
hydroxide precipitation (Snyder and Lee, 1980). Additives may be used to control the growth of
these biological organisms, and to prevent them from clogging the pipes and pumps. Chlorine, for
example, is a relatively common additive used in many types of water wells infested with bacteria.
Chlorine and other chemical additives can enter the USDW with the return flow water. Data
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regarding the prevalence of additive use, types of additives used, and concentrations of these
additives in open-loop HAC injectate are not available.
Finally, USDWs can potentially be contaminated by materials leached from the pipes and
pumps of the HAC system itself. This is particularly a concern where the supply water is acidic or
corrosive, and HAC water contacts large surfaces of toxic metals or other materials. For example,
excessive flows can lead to significant copper leaching from the heat exchanger. Only two
documented contamination incidents due to metal leaching have been reported. In Minnesota, two
wells were found to exceed the MCL for lead and one of these wells was found to exceed the MCL
for copper, and this contamination was attributed to metal leaching (see Section 5.2 for details of
these incidents).
5.1.4 Water Quantity
HAC systems can affect the quantity of water in USDWs. Gravity alone is often not
sufficient to cause return flow water to flow into recharge wells at sufficient rates (e.g., in aquifers
with low permeabilities) (USEPA, 1987). In fact, most aquifers will not accept 100 percent of their
yields without pressurizing the return flow. If the injected return flow from single-aquifer HAC
systems is not pressurized to ensure sufficient infiltration rates (and excess water is discharged to
the surface or used in another way), then the quantity of water in the aquifer may be reduced (for
injection pressure calculations and requirements, see Kavanaugh and Rafferty, 1997). However, a
single-aquifer HAC system that effectively returns used water to the aquifer via underground
injection will minimize future drawdown problems and will maintain the ground water resource
relatively well over the long term (Kavanaugh and Rafferty, 1997). Clearly, dual-aquifer HAC
systems can also affect the water supply in the source aquifer because the source aquifer is not
being replenished.
Important considerations relating to water removal from USDWs include aquifer drawdown
and well interference, land subsidence, and salt water intrusion. Aquifer drawdown and well
interference can take place in areas where yields are low, use of ground water is high, or where
supply wells are close to each other (PA DEP, 1996). The results are lower water levels in wells
and smaller yields. In some cases, water levels may drop below pump intake levels and result in
"dry wells." Land subsidence may result from changes in water quantity and ground water flow,
although other factors include the composition of the underlying carbonate rock and the surface
water drainage (PA DEP, 1996). In coastal areas, salt water intrusion may occur when fresh-water
aquifers are drawn down by excessive pumping.
5.2 Observed Impacts
Relative to the number of HAC wells that exist in the U.S., the number of documented cases
where USDWs have been negatively affected by HAC return flow wells is small. The few
incidents uncovered during the Class V well survey conducted for this study are described in this
section. (For information on the health effects associated with contaminants found above drinking
water standards and health advisory levels, see Appendix D of the Class V UIC Study. For half-
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lives and mobility information for certain constituents found in injectate of HAC return flow wells
and other Class V wells, see Appendix E of the Class V UIC Study).
Samples from a HAC return flow well in Albany, New York, indicated that an underlying
USDW was being contaminated by contaminants in the return flow water. Indications are that this
was caused by seepage of water from a non-potable water supply into the HAC water system, due
to poor design and failure to extend HAC well casings to an adequate depth. Water samples from
the return flow well contained over 14,000 mg/1 of TDS and 9,000 mg/1 chlorides (Kushwara,
1998). Secondary drinking water MCLs of 500 mg/1 and 250 mg/1 have been established for TDS
and chloride, respectively. Due to high levels of TDS and chloride, the Albany well has since been
closed (Lynes, 1998).
There are two cases documented in Minnesota. In 1985, water from a HAC return flow well
owned by the Itasca-Mantrap Co-op was observed to contain 0.61 mg/1 of lead and 1.8 mg/1 of
copper (Englund, 1985). The maximum contaminant level goal for lead has been established at 0
and the MCL is dictated by treatment techniques, with an action level of 0.015 mg/1 (USEPA,
1998). The MCL for copper is also dictated by treatment techniques, and the action level is 1.3
mg/1 (USEPA, 1998). A Minnesota Pollution Control Agency official stated in a July 7, 1992,
memo to the Minnesota Department of Health that the lead in Itasca-Mantrap injection well
samples was probably "coming from the heat pump system, related plumbing, or wells" and
suggested that further samples be taken (Convery, 1992). In addition, it was recommended that the
heat pump system be treated for coliform bacteria which was discovered in the injection well
(O'Brien, 1992).
Separately, a sample taken in 1984 from a HAC return flow well in Maplewood, Minnesota
revealed a level of 0.061 mg/1 of lead in the water (Englund, 1984). There is no further information
reported on the current status of this well, remedial steps taken to halt the contamination, or specific
causes of contamination.
Additionally, officials in North Carolina have reported that iron and coliform have been
observed in HAC return flow wells at levels higher than those found in the supply aquifer. Data on
actual concentrations, however, were not provided by state officials. State officials presume that
most of the problems resulted from poor well construction or operation. These problems were
reportedly resolved by simple measures such as disinfection of the well or replacement of the
fixtures containing rusty components. No additional information is available. It is possible that
impacts may have occurred to the receiving aquifer.
6. BEST MANAGEMENT PRACTICES
The primary concerns associated with HAC return flow wells are impacts on ground water
quality and ground water quantity (see Section 5), geologic impacts (e.g., sinkholes, land
subsidence), and degradation of the integrity and long-term functionality of the HAC system itself.
A variety of best management practices (BMPs) can be used to minimize the risk of environmental
impacts and HAC system degradation and/or failure. These BMPs, described below, are grouped
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into the following categories: (1) well design and siting; (2) well construction; and (3) well
operation, maintenance, and monitoring. The following discussion is neither exhaustive nor
represents a USEPA preference for the stated BMPs. Each state or USEPA Region may require
certain BMPs to be installed and maintained based on that state's or USEPA Region's priorities and
site-specific considerations.
6.1 Well Design and Siting
Careful pre-construction HAC well design and siting practices can minimize potential
damage to the aquifer(s). The type of system employed and the location and arrangement of wells
are important considerations that can significantly affect a system's potential for affecting USDWs.
6.1.1 Alternative Technological Design
The advantages of open-loop HAC systems compared to closed-loop HAC systems are that
they are lower in cost, water well contractors are widely available, and the technology has been used
for decades (Kavanaugh and Rafferty, 1997). However, all potential environmental or
maintenance/operational problems associated with open-loop HAC systems can be avoided through
the use of the closed-loop HAC system (Armitage et al., 1980). In fact, in 1987, Tennessee and Utah
recommended using only closed-loop systems (USEPA, 1987). The selection of the type of system
will depend on many factors, including the availability of ground water, soil type, size of lot (i.e.,
available ground area), and energy requirements (PA DEP, 1996). Many existing open-loop systems
can also be converted to closed-loop systems.
6.1.2 Pre-Construction Practices
Several pre-construction BMPs are available to minimize the impacts of HAC return flow
wells. During the design and siting phase, a broad assessment can be conducted to determine the
effect of the proposed well on the surrounding area. This will provide baseline data which can be
used later (during monitoring) to evaluate changes in the aquifer that may result from the well. This
assessment can be conducted for HAC systems using any type of subsurface disposal (e.g., vertical
injection wells and horizontal drains) and might include the following information (PA DEP, 1996)2:
the proposed well spacing, water use, and withdrawal amounts;
the effect on aquifer quantity and quality (relevant parameters might include temperature, pH,
specific conductance, total dissolved solids, and bacterial levels);
changes relative to adjacent land and water use;
the stability of bedrock and the effect of increased ground water movement;
the precautions that will be taken to prevent aquifer drawdown and well interference;
future changes in water use; and
water use plans.
2 For an alternative discussion on complete pre-construction site surveys, see Caneta Research
(1995).
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6.1.3 Siting Issues
USEPA (1997) recommends that source wells be sited away from sources of pollution or
contamination, including areas of heavy commercial fertilizer or pesticide application, landfills,
livestock pens, underground storage tanks, and septic systems (see Section 5.1.3). If installation of
the system near such an area is unavoidable, the well must be placed upgradient from the pollution
source. Another attribute for a potential well area is adequate surface drainage away from the well.
If a well is located in a low-lying area, standing water may accumulate and could seep down along
the borehole and, if contaminated, affect the underlying ground water (USEPA, 1997).
Thermal alteration of the aquifer can cause environmental problems and can lead to HAC
system performance problems (see Section 5.1.1). The spacing of the source and return flow wells is
essential for single-aquifer systems, since inadequate separation of these two wells will not allow the
return flow water to reach the natural temperature of the aquifer before it flows through the aquifer to
the supply well withdrawal point. PA DEP (1996) recommends that wells generally be more than
100 feet (horizontal distance) apart. A different model seeking to determine the optimal distance
between supply and return flow wells in single-aquifer HAC systems suggests that a distance of 50 to
75 feet is typically adequate to prevent thermal contamination (Clyde and Madabhushi, 1983). It is
apparent that optimal spacing varies depending on many case-specific factors. Specifically,
evaluation of the well supply and recharge capacities, ground water flow velocity, relative well heads
(water levels) in supply and return flow wells, aquifer transmissibility, aquifer thickness, duration of
heat pump operation, natural ground water gradient, natural ground water temperature, and effective
porosity will aid in the determination of the appropriate distance between supply and return wells.3
Ideally, wells are sited so that the advancement of the aquifer's thermal front will follow the
natural flow of the aquifer. The thermal plume moves more rapidly and temperatures in the aquifer
change more rapidly when supply wells are located downgradient from injection wells. Therefore, in
areas with significant ground water flow, many recommend that the supply well be located
upgradient from the return flow well, and the wells positioned so that the ground water flow is
parallel to the line joining the two wells (Clyde and Madabhushi, 1983; USEPA, 1987).
6.1.4 Design Features
Perhaps the single most important BMP for HAC systems is to restrict these systems to a
single-aquifer design. This design can generally ensure that ground water quality and quantity in the
utilized aquifer is maintained (PA DEP, 1996). Dual-aquifer design is already not accepted in many
jurisdictions unless the supply and return aquifers are chemically compatible (USEPA, 1987).
When designing a HAC system, the well contractor must consider the acceptance rate of the
3 For a simple calculation to determine typical well spacing, see Orio (1994). For a matrix of
recommended spacing distances under various thermal and hydraulic parameters, see Kazmann and
Whitehead (1980).
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receiving aquifer. By designing the return flow wells to handle twice the needed water flow rate of
the HAC system, the potential for clogging and capacity loss will be greatly minimized. Water
acceptance capacity of return flow wells can be maximized by increasing well screen diameter and
length.
Clyde and Madabhushi (1983) note that in dense communities where surface area limits the
spacing of wells (and supply and return flow wells are located in closer proximity than is optimal),
wells should be designed so that water can be pumped from the top of the aquifer and re-injected to
the bottom of the aquifer. This design reduces the risk of intra-aquifer thermal alteration. For
housing subdivisions and other dense communities with limited well sites, Armitage et al. (1980)
recommend implementing a cluster well concept (i.e., several houses with individual heat pump units
being supplied by the same supply and recharge well).4
6.2 Heat Pump Injection Well Construction
PA DEP (1996) lists the acceptable methods of well drilling to include rotary, cable tool, and
auger. However, as discussed earlier in Section 4.2.2, Kavanaugh and Rafferty (1997) recommend
that the conventional rotary method be avoided in favor of methods using less damaging drilling
fluids, such as the air rotary drilling, cable tool, and reverse circulation methods.
When a driller constructs a well, one of the primary concerns is the prevention of aquifer
contamination. Well construction could result in both downward and upward migration of
contamination. Extensive drilling data can and should be recorded for all wells, including well
location, depth, diameter, materials, dates of work, and a geologic log (PA DEP, 1996).
To prevent surface contamination from reaching the aquifer, PA DEP (1996) recommends that
casing be used (see USEPA, 1975, for further details). Installing the casing through the overburden
of unconsolidated material and into solid material will act to prevent the collapse of the hole.
Kavanaugh and Rafferty (1997) recommend that the casing should be at least two nominal sizes
larger than the outside diameter of the pump bowl assembly (which includes the impellers, or the
rotary parts of the pump, and their housing). Strong casing material will protect the well during
construction and over the anticipated life of the well.
PA DEP (1996) also notes that grout should be placed in the entire annular space between the
surface casing and the drill hole to prevent the seepage of water down along the outside of the casing
and to minimize the potential for the entry of surface or subsurface pollutants into the well water.
The grout, which can be either bentonite- or cement-based, can be placed by gravity or by pumping.
Rawlings (1999), however, recommends that only the pumping method be used because gravity
placement can cause bridging (e.g., if a fluid, such as water or a water/drilling mud solution, is
present in the annulus and is then lost over time) and the remaining open space can become a
4 For further discussion on the design of the F£AC system, as well as quantitative methods to
estimate system requirements (e.g., size, ground water flow), see Kavanaugh and Rafferty (1997).
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pathway for the upward or downward flow of contaminants along the casing. For wells deeper than
30 feet, where the annular space cannot be seen to the bottom, the well should be grouted from the
bottom to the surface using a tremie pipe (i.e., a pipe that is lowered into the borehole, through which
the grout material is delivered until the annular space is filled to the surface). For wells penetrating
more than one aquifer, other grouting methods, such as sleeves, packers, and other devices, can be
employed to prevent inter-aquifer flow and the spread of contamination (USEPA, 1997).
The most commonly used material for well piping is polyvinyl chloride (PVC), because it is
economical, durable, and corrosion-resistant (PA DEP, 1996). The heat pump exchanger and water-
side piping are typically made of copper or cupro-nickel. This is a solution to many corrosion
problems, unless the water contains hydrogen sulfide or ammonia (Caneta Research, 1995). Most
manufacturers use lead-free solder (Rawlings, 1999).
Careful design and construction of the return flow well (i.e., sufficient diameter and depth)
will aid in the acceptance of the maximum discharge from the HAC return flow system and prevent
clogging due to the precipitation of minerals. Kavanaugh and Rafferty (1997) recommend that the
screen lengths for injection wells be doubled compared to those used in production wells for the same
flow. An extended pumping test (e.g., 12-24 hours) is recommended to help determine the hydraulic
characteristics of the injection well. The installation of a back valve can help to prevent pressure
differences that could result in the precipitation of minerals. Installing a blind flange allows for the
emergency surface discharge of water, should this become necessary.
These construction-phase BMPs seek to both minimize environmental impacts and ensure
long-term HAC well function. Practices that prevent surface contamination from reaching the
underground aquifer are sensible ways to prevent aquifer quality damage. The use of certain
construction materials and the estimation of the optimum well size, while primarily seeking to
preserve well functionality and integrity, also act to protect the aquifer by minimizing changes in
water quality.
6.3 Heat Pump Injection Well Operation, Maintenance, and Monitoring
The avoidance and the containment (if necessary) of ground water contamination is a top
priority. In the event that water does become contaminated, backlashing the injection well is a
technique that can recover contaminated water. Backlashing is made possible by installing pumps in
both the supply and injection wells (Knape, 1984; Williams and Sveter, 1987). The contaminated
water withdrawn during backlashing can be disposed of by a method other than subsurface injection.
Backlashing also acts to reduce clogging due to sediment. The use of surface-mounted
separators to remove solids prior to re-injection further limits clogging (Williams and Sveter, 1987).
However, separators can present a chronic maintenance problem under high-volume flows. Rawlings
(1999) notes that although the volume of water typically used and needed by a residence, for
example, may be relatively small, the volume of water required for the HAC system to operate will be
considerably larger and thus a larger-than-anticipated burden will be placed on the separators.
Separators can be an effective means of sediment removal, but it is important to evaluate their
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potential maintenance requirements using the expected flow rate required for the HAC system rather
than the typical water usage associated with a given type of facility (i.e., commercial or residential).
The reversal of well flows (roles) between heating and cooling seasons can be used to
alleviate well plugging due to mineral precipitation in those wells where it is a problem. USEPA
(1997) discusses several preventative operational practices that can be used to limit mineral
precipitation before it begins. First, most precipitation can be avoided by ensuring that return flow
waters do not free-fall back into the return well, as free-fall results in the entrainment of oxygen into
the return flow water, which in turn can cause the precipitation of solids. Free-fall can be limited
through the use of a simple dip tube or avoided outright by discharging the return flow below the
standing water level, greatly reducing turbulence and air entrainment (Kavanaugh and Rafferty,
1997). Second, any other means of aeration of the return flow water should be avoided. If a surface
reservoir or tank is used to store water before it is returned to the ground, for example, it can be a
"diaphragm" type tank, or one that does not allow venting to the atmosphere.
As discussed earlier in Section 5.1.3, additives may currently be used in some HAC systems
to control the growth of biological organisms. Although disinfection (e.g., chlorination) is sometimes
prescribed to remedy this problem (Knape, 1984; Williams and Sveter, 1987; USEPA, 1997; see
USEPA, 1975 for disinfection details), the use of chlorine or other chemical additives (for any
purpose) is not universally recommended due to potential water quality impacts (see PA DEP, 1996).
While other additives such as antifreeze are used in closed-loop systems, they should not be used in
open-loop HAC systems. In addition to the environmental problems these practices might pose, the
use of chemical additives many change the legal classification of the return flow well (PA DEP,
1996). If the use of chemical additives is judged necessary, for whatever reason, it is best to carefully
analyze the site-specific conditions and solicit expert opinions before they are used.
In addition to water quality considerations, BMPs can act to minimize impacts on water
quantity. As noted earlier in Section 5.1.4, gravity alone is sometimes not sufficient to return water
to the return flow well. The use of pumps to pressurize the return flow will ensure sufficient
infiltration rates. Alternatively, the temporary storage of used water can help to slow the return flow
rates and prevent spillage of excess water out on the ground (USEPA, 1987). Furthermore, the
volume of water withdrawn from the source well is dependent on the recharge capacity of the aquifer.
To avoid legal issues and prevent water quantity problems, hydrogeological investigations can be
conducted by qualified professionals to assess recharge capacity and use limits prior to the
construction of a new HAC system (USEPA, 1997).
Continual system monitoring is an integral part of sound HAC well management. The use of
monitoring wells is especially important for very large systems (e.g., hundreds of wells) and for
systems that are very close to large municipal water supplies (PA DEP, 1996). Several states
specifically recommend that volumes and temperatures of return flow (injected) waters be monitored,
and that periodic analyses of the receiving aquifer be conducted to monitor changes in aquifer
temperature and chemistry (USEPA, 1987). Maintenance of these and other data by county and state
agencies will allow for more accurate assessment of well number, density, and overall impact that
HAC return flow wells have on USDWs. A complete monitoring program includes a baseline
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analysis of the injectate and ground water prior to injecting, a monitoring schedule (sampling
frequency), parameters to be measured, location of sampling point(s), and a discussion of the
technical basis for selecting the sampling point(s).
7. CURRENT REGULATORY REQUIREMENTS
Several federal, state, and local programs exist that either directly manage or regulate Class V
HAC return flow wells. On the federal level, management and regulation of these wells falls
primarily under the UIC program authorized by the Safe Drinking Water Act (SDWA). Some states
and localities have used these authorities, as well as their own authorities, to extend the controls in
their areas to address concerns associated with HAC return flow wells.
7.1 Federal Programs
Class V wells are regulated under the authority of Part C of SDWA. Congress enacted the
SDWA to ensure protection of the quality of drinking water in the United States, and Part C
specifically mandates the regulation of underground injection of fluids through wells. USEPA has
promulgated a series of UIC regulations under this authority. USEPA directly implements these
regulations for Class V wells in 19 states or territories (Alaska, American Samoa, Arizona,
California, Colorado, Hawaii, Indiana, Iowa, Kentucky, Michigan, Minnesota, Montana, New York,
Pennsylvania, South Dakota, Tennessee, Virginia, Virgin Islands, and Washington, DC). USEPA
also directly implements all Class V UIC programs on Tribal lands. In all other states, which are
called Primacy States, state agencies implement the Class V UIC program, with primary enforcement
responsibility.
HAC return flow wells currently are not subject to any specific regulations tailored just for
them, but rather are subject to the UIC regulations that exist for all Class V wells. Under 40 CFR
144.12(a), owners or operators of all injection wells, including HAC return flow wells, are prohibited
from engaging in any injection activity that allows the movement of fluids containing any
contaminant into USDWs, "if the presence of that contaminant may cause a violation of any primary
drinking water regulation ... or may otherwise adversely affect the health of persons."
Owners or operators of Class V wells are required to submit basic inventory information
under 40 CFR 144.26. When the owner or operator submits inventory information and is operating
the well such that a USDW is not endangered, the operation of the Class V well is authorized by rule.
Moreover, under section 144.27, USEPA may require owners or operators of any Class V well, in
USEPA-administered programs, to submit additional information deemed necessary to protect
USDWs. Owners or operators who fail to submit the information required under sections 144.26 and
144.27 are prohibited from using their wells.
Sections 144.12(c) and (d) prescribe mandatory and discretionary actions to be taken by the
UIC Program Director if a Class V well is not in compliance with section 144.12(a). Specifically, the
Director must choose between requiring the injector to apply for an individual permit, ordering such
action as closure of the well to prevent endangerment, or taking an enforcement action. Because
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HAC return flow wells (like other kinds of Class V wells) are authorized by rule, they do not have to
obtain a permit unless required to do so by the UIC Program Director under 40 CFR 144.25.
Authorization by rule terminates upon the effective date of a permit issued or upon proper closure of
the well.
Separate from the UIC program, the SDWA Amendments of 1996 establish a requirement for
source water assessments. USEPA published guidance describing how the states should carry out a
source water assessment program within the state's boundaries. The final guidance, entitled Source
Water Assessment and Programs Guidance (USEPA 816-R-97-009), was released in August 1997.
State staff must conduct source water assessments that are comprised of three steps. First,
state staff must delineate the boundaries of the assessment areas in the state from which one or more
public drinking water systems receive supplies of drinking water. In delineating these areas, state
staff must use "all reasonably available hydrogeologic information on the sources of the supply of
drinking water in the state and the water flow, recharge, and discharge and any other reliable
information as the state deems necessary to adequately determine such areas." Second, the state staff
must identify contaminants of concern, and for those contaminants, they must inventory significant
potential sources of contamination in delineated source water protection areas. Class V wells,
including HAC return flow wells, should be considered as part of this source inventory, if present in a
given area. Third, the state staff must "determine the susceptibility of the public water systems in the
delineated area to such contaminants." State staff should complete all of these steps by May 2003
according to the final guidance.5
7.2 State and Local Programs
As discussed in Section 3 and shown in Table 1 above, the nearly 28,000 documented HAC
wells in the U.S. are distributed across 34 states. While only four states have 1,000 or more
documented wells each (i.e., Texas, Virginia, Florida, and Tennessee), many other states are
documented or estimated to have dozens or hundreds of wells. Attachment A to this volume
describes how the twenty-six states containing nearly all of the HAC return flow wells
(approximately 99 percent of the documented and estimated HAC wells) currently address these
wells. In brief:
USEPA directly implements and authorizes by rule the federal UIC program for all Class V
injection wells in several states, including: Arizona, Michigan, Minnesota, New York,
Pennsylvania, Tennessee, and Virginia.
The other states with many HAC return flow wells are UIC Primacy States for Class V wells
and may authorize by rule or issue individual permits.
' May 2003 is the deadline including an 18-month extension.
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Those that authorize by rule in accordance with the minimum federal
requirements include: Illinois, Kansas, Nebraska, North Dakota, Ohio,
South Carolina, Texas, West Virginia, Wisconsin, and Wyoming.
Those that issue individual permits include: Delaware, Florida,
Maryland, Missouri, Nevada, North Carolina, Oregon, Vermont, and
Washington.
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ATTACHMENT A
STATE AND LOCAL PROGRAM DESCRIPTIONS
This attachment describes the statutory and regulatory requirements and guidance applied to
HAC return flow wells in those states in which the largest numbers of such wells are found. In
several states, this category of well is permitted by rule or is permitted through a general permit that
does not apply a detailed set of siting, construction, operating, or monitoring requirements or
guidance.
For some of those states that do have specific programs for Class V HAC systems, state
definitions for "open-loop" and "closed-loop" HAC systems differ somewhat from the definitions
used by USEPA. The state and local program descriptions include information about "closed-loop"
HAC systems if: (1) "closed-loop" system (as defined by the state) requirements or guidance seems
to apply to "open-loop" systems (as defined by USEPA), (2) "open-loop" requirements or guidance
could not be found, or (3) such information is relevant for comparison purposes.
Arizona
USEPA Region 9 directly implements the UIC program for Class V injection wells in
Arizona. The state has not enacted regulations pertaining to underground injection wells. The state
has enacted a ground water protection statute, however, that could address HAC return flow wells.
Under the Arizona Revised Statutes (Title 49, Chapter 2, Article 3 - Aquifer Protection Permits) any
facility that "discharges" is required to obtain an Aquifer Protection Permit (APP) from the Arizona
Department of Environmental Quality (ADEQ) (§49-241. A). An injection well is considered a
discharging facility and is required to obtain an APP, unless ADEQ determines that it will be
"designed, constructed, and operated so that there will be no migration of pollutants directly to the
aquifer or to the vadose zone" (§49-241.B).
The aquifer protection statute provides that an applicant for an APP may be required to
provide information on the design, operations, pollutant control measures, hydrogeological
characterization, baseline data, pollutant characteristics, and closure strategy. Operators must
demonstrate that the facility will be designed, constructed, and operated as to ensure greatest degree
of discharge reduction and aquifer water quality will not be reduced or standards violated. By rule,
presumptive best available demonstrated control technology, processes, operating methods or other
alternatives, in order to achieve discharge reduction and water quality standards, are established by
ADEQ (§49-243).
An APP may require monitoring, recordkeeping and reporting, a contingency plan, discharge
limitations, a compliance schedule, and closure guidelines. The operator may need to furnish
information, such as past performance, and technical and financial competence, relevant to its ability
to comply with the permit terms and conditions. A facility must demonstrate financial assurance or
competence before approval to operate is granted. Each owner of an injection well to whom an
individual permit is issued must register the permit with ADEQ each year (§49-243).
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ADEQ designates a point or points of compliance for each facility receiving a permit. The
statute defines the point of compliance as the point at which compliance with aquifer water quality
standards shall be determined and is a vertical plane downgradient of the facility that extends through
the uppermost aquifer underlying that facility. If an aquifer is not or reasonably will not foreseeably
be a USDW, monitoring for compliance may be established in another aquifer. Monitoring and
reporting requirements also may apply for a facility managing pollutants that are determined not to
migrate (§49-244).
Permitting
The Arizona Aquifer Protection Permit Rules (Chapter 19, sub-chapter 9, October 1997)
define an injection well as "a well which receives a discharge through pressure injection or gravity
flow." Any facility that discharges is required to obtain an individual APP from ADEQ, unless the
facility is subject to a general permit. Permit applications must include specified information,
including topographic maps, facility site plans and designs, characteristics of past as well as proposed
discharge, and best available demonstrated control technology, processes, operating methods, or other
alternatives to be employed in the facility. In order to obtain an individual permit, a hydrogeologic
study must be performed. This study must include a description of the geology and hydrology of the
area; documentation of existing water quality in the aquifers underlying the site; any expected
changes in the water quality and ground water as a result of the discharge; and the proposed location
of each point of compliance (Rl 8-9-108).
Well Construction Standards
The construction of HAC return flow wells greater than 100 feet in depth is regulated by the
Arizona Department of Water Resources, Ground Water Management Support Section. In general,
all water wells drilled must be at least 100 feet (preferably uphill) from septic tanks or sewage
disposal areas, landfills, hazardous waste facilities, hazardous material storage areas, or petroleum
storage areas and tanks, unless authorized in writing by the Director. In addition, wells must be
properly capped, and have a proper surface seal (consisting of a steel casing extending from one foot
above ground level to a depth of 20 feet surrounded by cement grout. Also, any drilling fluids and
cuttings must be contained in a manner which prevents discharge into any surface water (AAC R12-
15-801 through 822).
No injection wells may be constructed unless an APP has been completed and approved.
Wells are required to be constructed in such as manner as not to impair future or foreseeable use of
aquifers. Specific construction standards are determined on a case-by-case basis.
Operating Requirements
Each APP has specific operating requirements. All wells must be operated in such a manner
that they do not violate any rules under Title 49 of the Arizona Revised Statutes, including Article 2,
relating to water quality standards, and Article 3, relating to APPs. Water quality standards must be
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met in order to preserve and protect the water quality in all aquifers for all present and reasonably
foreseeable future uses.
Monitoring Requirements
Monitoring of both injectate and the injection site generally will be required for HAC return
flow wells. The permit establishes, on a case-by-case basis, alert levels, discharge limitations,
monitoring, reporting, and contingency plan requirements. Alert level is defined as a numeric value,
expressed either as a concentration of a pollutant or a physical or chemical property of a pollutant,
which serves as an early warning indicating a potential violation of any permit condition. If an alert
level or discharge limitation is exceeded, an individual permit requires the facility to notify ADEQ
and implement the contingency plan (Rl 8-9-110).
Plugging and Abandonment
Temporary cessation, closure, and post-closure requirements are specified on a case-by-case
basis in an APP. The facilities are required to notify ADEQ before any cessation of operations
occurs. A closure plan is required for facilities that cease activity without intending to resume. The
plan describes the quantities and characteristics of the materials to be removed from the facility; the
destination and placement of material to be removed; quantities and characteristics of the material to
remain; the methods to treat and control the discharge of pollutants from the facility; and limitations
on future water uses created as a result of operations or closure activities. A post-closure monitoring
and maintenance plan is also required. This plan specifies duration, procedures, and inspections for
post-closure monitoring (R-18-9-116). Additional specific abandonment requirements are found at
R12-15-816.
Financial Responsibility
An individual APP requires that a owner have and maintain the technical and financial
capability necessary to fully carry out the terms and conditions of the permit. The owner must
maintain a bond, insurance policy, or trust fund for the duration of the permit (R-18-9-117).
Delaware
Delaware is a UIC Primacy State for Class V wells. The Delaware Regulations Governing
Underground Injection Control (Parts 122, 124, and 146) set forth the detailed
requirements of the state's UIC program. The state's UIC regulations are generally equivalent in
substance to the federal UIC requirements.
Permitting
Delaware requires permits for the construction, use, operation, or modification of any
Class V well, with certain exceptions. These exceptions include air conditioning return flow wells
(Delaware UIC Regulations, Section 122.23).
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Siting and Construction
Section 6023 of the Delaware Environmental Protection Act (7 Delaware Code Chapter 60)
stipulates that well drillers and septic tank installers must be licensed by the Secretary. New HAC
return flow wells must meet construction and siting requirements. These construction requirements
are specified in "Delaware Regulations Governing the Construction and Use of Wells." The states's
construction requirements for HAC return wells specifically address siting, casing, screens, grouting,
caps, well disinfection, well maintenance and repair, and abandonment. Closed-loop heat pump wells
are not considered injection wells, and construction requirements are therefore different for open-loop
and closed-loop systems (Sections 5.04 and 5.05 respectively). Inspections generally are performed
during or immediately following construction.
Siting requirements consist primarily of set-backs from existing or potential contamination
sources. For example, heat pump recharge wells must be at least 50 feet from any potential or
existing contamination sources such as septic tanks, tile fields, and manure pits.
Operating Requirements
A heat pump recharge well is required to re-inject water into its source aquifer; injectate must
not include any additives; and wells must be properly capped.
Florida
Florida is a UIC Primacy State for Class V wells. Chapter 62-528 of the Florida
Administrative Code (FAC), effective June 24, 1997, establishes the UIC program, and Part V (62-
528.600 to 62-528.900) addresses criteria and standards for Class V wells. Florida groups Class V
wells into eight categories, with wells associated with thermal energy exchange processes, including
air conditioning return flow wells, placed in Group 1. Such wells may be part of an open-loop or
closed-loop system, with or without additives (62-528.600(2)(a) FAC). Florida's rules provide
different requirements for open- and closed-loop systems and for systems with and without additives.
Permitting
Underground injection through a Class V well is prohibited except as authorized by permit by
the Department of Environmental Protection (DEP). Owners and operators are required to obtain a
Construction/Clearance Permit before receiving permission to construct. The applicant is required to
submit detailed information, including well location and depth, description of the injection system
and of the proposed injectate, and any proposed pretreatment. When site-specific conditions indicate
a threat to a USDW, additional information must be submitted. Finally, all Class V wells are required
to obtain a plugging and abandonment permit.
Closed-loop ground water heat pumps are authorized through a general permit (62-528.705
FAC). However, operators of air conditioning return flow wells serving single family units are not
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required to obtain a Class V permit or general permit prior to construction. Only inventory
information must be submitted for such wells (62-528.630 FAC). All other ground water heat pumps
are considered open-loop and require an individual permit. Ground-coupled (i.e., closed-loop) heat
pumps are not regulated under the UIC program because there is no discharge of fluids. Such wells
must satisfy the conditions in Rule 62-528.630 (3) through (6), which provide that the well may not
cause or allow movement of fluid containing any contaminant into a USDW, and that the DEP may
take actions to address violations of primary drinking water standards or other threats to health from
the well.
Siting and Construction
Specific construction standards for Class V wells have not been enacted by Florida, because
of the variety of Class V wells and their uses. Instead, the state requires the well to be designed and
constructed for its intended use, in accordance with good engineering practices, and approves the
design and construction through a permit. The state can apply any of the criteria for Class I wells to
the permitting of Class V wells, if it determine that without such criteria the Class V well may cause
or allow fluids to migrate into a USDW and cause a violation of the state's primary or secondary
drinking water standards, which are contained in Chapter 62-550 of the FAC. However, if the
injectate meets the primary and secondary drinking water quality standards and the minimum criteria
contained in Rule 62-520-400 of the FAC, Class I injection well permitting standards will not be
required.
Class V wells are required to be constructed so that their intended use does not violate the
water quality standards in Chapter 62-520 FAC at the point of discharge, provided that the drinking
water standards of 40 CFR Part 142 (1994) are met at the point of discharge. These standard Class V
siting and construction requirements apply to HAC return flow wells. Construction of such wells
must be certified upon completion. Siting is established on a case-by-case basis.
Operating Requirements
All Class V wells are required to be used or operated in such a manner that they do not
present a hazard to a USDW. Pretreatment of injectate must be performed, if necessary to ensure the
fluid does not violate the applicable water quality standards in 62-520 FAC (62-528.610 FAC).
Monitoring Requirements
Injectate monitoring generally will be required for open-loop systems or those using additives
(62-528.615(l)(a)l FAC). Monitoring is not required for air conditioning return flow wells receiving
a general permit under Rules 62-528.705 or -528.710 FAC. The Department determines the
frequency of monitoring based on the location of the well, the nature of the injected fluid, and, where
applicable, the requirements of Chapters 62-600 and 62-601, FAC. The monitoring parameters and
frequency shall be addressed in the permit or authorization to use a Class V well (62-528.615 FAC).
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Plugging and Abandonment
The Department will order a Class V well plugged and abandoned when it no longer performs
its intended purpose, or when it is determined that the presence of the well may cause or allow a
violation of a primary or secondary drinking water standard, or may otherwise adversely affect the
health of persons. A plugging and abandonment plan shall be submitted to the Department with the
construction permit application. Prior to abandonment, the well shall be plugged with cement in a
manner that will not allow movement of fluids between USDWs. The proposed method of plugging
and type of cement shall be approved by the Department as a condition of the permit (62-528.625
FAC). Plugging must be performed by a licensed water well contractor.
Illinois
Illinois is a UIC Primacy State for Class V wells. The Illinois Environmental Protection
Agency (IEPA), Bureau of Land has promulgated rules establishing a Class V UIC program (35
Illinois Administrative Code (IAC) 704) that are intended to be identical in substance to USEPA rules
in 40 CFR 144. The state regulations address permitting, construction requirements, operating
requirements, monitoring and reporting, plugging and abandonment, financial responsibility, and
mechanical integrity that closely parallel the federal requirements.
Permitting
Any underground injection, except into a well authorized by permit or rule, is prohibited. The
construction of any well required to have a permit is prohibited until the permit has been issued
(704.121 IAC). Class V wells will be inventoried and assessed and regulatory action will be
established at a later date (704.102 IAC). Injection into Class V wells is authorized by rule until
requirements under future regulations become applicable (704.146 IAC).
Operating Requirements
Owners or operators of wells authorized by rule must submit inventory information to IEPA
(704.148 IAC). In addition, IEPA may require submission of other information deemed necessary
(704.149 IAC).
Kansas
Kansas is a UIC Primacy State for Class V wells. The state has incorporated by reference the
federal UIC regulations (40 CFR 124, 40 CFR 144, 40 CFR 145) in Kansas Administrative
Regulations (KAR) 28-46. In addition, the Kansas Department of Health and Environment (KDHE)
has a ground water non-endangerment regulation (KAR 28-46-27), which it uses to prevent
construction of industrial wells.
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Permitting
Class V wells are authorized by rule, with the exception of aquifer remediation wells, which
are permitted. Class V injection wells are authorized to operate until regulations concerning that
class of injection wells are adopted, provided the requirements of 40 CFR 144.12 are satisfied (KAR
28-46-26). When conditions require that a permit be issued for a Class V well, the permit shall be
effective for a term of no more than 10 years (KAR 28-46-10(a)). KDHE does not consider closed-
loop systems to be Class V wells.
Siting and Construction
Wells that inject into USDWs must meet the construction and siting requirements specified in
the state's water well construction requirements at KAR 28-30-6, which address casing, grouting, and
set-backs from known sources of contamination, buildings, and property lines. In particular, the
casing-borehole annulus must be grouted from the surface to a minimum of 20 feet or five feet into
the first clay or shale layer, if one is present, whichever is greater; wells must be cased from the
surface to the top of the producing zone of the aquifer; and wells must be located at least 50 feet from
a pollution source (e.g., septic tanks; sewer lines; seepage pits; fuel, fertilizer or pesticide storage
areas; feed lots; or barn yards).
Operating Requirements
The state has incorporated the federal UIC regulations by reference. General operating,
monitoring, and reporting requirements for injection wells are found at KAR 28-46-30, although
these requirements explicitly do not apply to Class V wells. Inventory and assessment requirements
for Class V wells are addressed at KAR 28-46-38.
Plugging and Abandonment
The state has incorporated the federal UIC regulations by reference (see KAR 28-46-34). In
addition, KAR 28-30-7 sets forth specific requirements for plugging of abandoned wells, as well as
cased and uncased test holes, although these requirements do not apply explicitly or exclusively to
Class V wells. Heat pump holes drilled for closed-loop heat pump systems are required to be plugged
by filling the entire hole with an approved grouting material from the bottom of the hole to the
bottom of the horizontal trench, using a grout tremie pipe or similar method approved by the
department (KAR 28-30-7(d)(3)).
Maryland
Maryland is a UIC Primacy State for Class V wells. Maryland has incorporated the federal
UIC regulations (42 CFR 124, 40 CFR 144, 40 CFR 145) by reference.
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Permitting
Permits are not required under the state UIC regulations for Class V wells (COMAR
26.08.07.01.B). However, a well construction permit is required for any well that injects water into a
formation from which ground water may be produced. Such wells must meet construction
requirements for casing, screens, and grouting. Construction permits are generally issued by local
health departments in conjunction with the Maryland Department of Environment (MDE). HAC
return flow wells are covered by the construction requirements.
Owners and operators of closed-loop systems are not required to obtain water appropriations
permits.
Siting and Construction
Heat pump wells must meet the state's water well construction requirements. Wells must be
sited in appropriate hydrogeologic settings, cased and grouted, and properly maintained. The casing
must meet nationally recognized standards; the required minimum length depends upon the
hydrogeologic setting. Grouting requirements depend upon the hydrogeologic setting and the flow
rate (COMAR 26.04.04).
Operating Requirements
Residential permit holders must return water to the same aquifer from which it is withdrawn.
Commercial permit holders may re-inject or discharge to a surface water body. MDE generally does
not inspect HAC return flow wells unless there is a complaint.
Michigan
USEPA Region 5 directly implements the UIC program for Class V injection wells in
Michigan. Class V owners and operators contact the USEPA Region 5 UIC program directly to
report inventory or are referred to the USEPA Regional UIC program by state, city, or county staff or
consultants. The USEPA Region retains all records regarding well location, injectate information,
and regulatory requirements. Michigan does not plan to seek primacy in the near future.
Michigan's Natural Resources and Environmental Protection Act (NREPA) (1994 P.A. 451,
Part 31) defines "waters of the state" to include ground waters (§3101) and provides that a person
may not discharge directly or indirectly into the waters of the state a substance that is or may become
injurious to the public health, safety or welfare, or to domestic, commercial, industrial, agricultural,
recreational or other uses that are being made or may be made of such waters (§3109(l)(a) and (b)).
Discharge of waste is prohibited without a permit from the Department of Environmental Quality
(DEQ)(§3112(1)).
The Department of Natural Resources, Water Resources Commission has promulgated rules
under the authority of Part 31 NREPA that provide for the non-degradation of ground water quality in
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usable aquifers, define the requirements for hydrogeological study before permitting a discharge into
ground waters, and establish ground water monitoring requirements for ground water discharges (Part
22 Rules 323.2201 - 323.2211). The Water Resources Commission also has promulgated
requirements for wastewater discharge permits (Part 21 Rules 323.2101- 323.2192). According to
these rules, a "point source discharge" includes a well from which wastewater is discharged (R
323.2104(vi)). Waste and wastewater are defined broadly under the rules to include liquid waste
discharges from industrial and commercial processes (R 323.2104(q) and (r)). An open-loop HAC
well with additives may be required to satisfy the state's ground water protection requirements.
Minnesota
USEPA Region 5 directly implements the UIC program for Class V injection wells in
Minnesota. However, the state has promulgated regulations for HAC return flow wells implemented
by the Minnesota Pollution Control Agency.
The state adheres to a non-degradation policy for ground water. The Minnesota Department
of Health (MDH) has adopted stringent construction requirements for all wells in the state, including
a very broad definition of "well." Under that definition, a well is a drilled, dug, or bored excavation
that ends below the water table. Both MDH and MFC A have banned injection directly into the
saturated zone (Minnesota Rules, 7060.0600).
Permitting
Prior to 1981, heat pump return flow wells were prohibited in Minnesota except through a
variance from Part 4725.2050. In 1981, the Minnesota Legislature authorized MDH to issue a
maximum of 210 permits for ground water thermal exchange device (i.e., heat pump) return flow
wells. Minnesota Statutes, Chapter 1031, Section 621, and Minnesota Rules, Part 4725.1831
authorize the issuance of permits for the re-injection of water by a properly constructed well into the
same aquifer from which the water was drawn for the operation of a ground water thermal exchange
device. Other more general water use permit requirements and penalties also apply to permit
recipients. To date, only seven of the possible 210 permits have been issued.
Minnesota Rules, Part 4725.1833 addresses permit requirements for vertical heat exchanger
construction.
Siting and Construction
Chapter 1031 of the Minnesota Statutes contains a number of requirements regarding well
construction. A person may not drill construct, repair, or seal a well unless the person has a well
contractor's license (also addressed in Minnesota Rules 4725.0475). Other requirements set forth in
Chapter 1031 and Part 4725 of the regulations address set-backs from sources of contamination, well
sealing, casing, permit fees, and acceptable construction materials (e.g., screens, fluids, and grouts).
Section 1031.641 of the statute and Part 4725.7050 of the Minnesota Rules set forth specific
construction and siting requirements for vertical heat exchangers.
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Withdrawal and re-injection for a ground water thermal exchange device must be
accomplished by a closed system in which the waters drawn for thermal exchange do not have
contact or commingle with water from other sources or with polluting material or substances (Chapter
1031.621).
In addition, the Minnesota Water Well Construction Code (Minnesota Rules, Chapter 4725)
sets out construction, siting, maintenance, and abandonment requirements for wells. For example, it
prohibits wells completed in more than one aquifer, requires grouting in the casing-borehole annulus,
and requires that steel casing meet ASTM or API specifications. It also contains setback
requirements from surface water bodies and contamination sources. HAC return flow wells must
meet these requirements. Newly permitted wells are inspected to ensure compliance with
construction standards.
Minnesota has a separate construction permit program for vertical closed-loop systems.
Operating Requirements
Part 4725.2050 of the Water Well Construction Code prohibits the use of a well or a boring
for disposal of surface water, ground water, or any other liquid, gas, or chemical. However, heat
pump return flow wells are specifically exempted from this prohibition. Also, given the definition of
the term "well," this prohibition does not apply to injection into the unsaturated zone (such as with
infiltration galleries, dry wells, or grainfields) or to injection into naturally occurring depressions
(such as sinkholes).
Additives are prohibited in HAC return flow well injectate.
Missouri
Missouri is a UIC Primacy State for Class V wells. The Missouri Department of Natural
Resources (DNR) regulates Class V wells by permit. Construction permit applications must be
submitted to DNR at least 180 days prior to well construction. Operating permit applications must be
submitted to DNR 30 days before the well receives wastewater.
Permitting
Operators of heat pump wells serving single family residences, or serving up to an eight-
family residence with a combined injection/withdrawal rate of less than 600,000 BTU/hr, are not
required to obtain operating permits (10 CSR 20-6.070(1)(A)). The Clean Water Commission
requires an operating permit for systems greater than 600,000 BTU/hr. An operating permit is valid
for a period of up to five years (10 CSR 20-6.070).
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Siting and Construction
Vertical heat pumps must be located at least 300 feet from storage areas for chemicals and
pesticides, landfills, lagoons, or above ground storage tanks. They must also be at least 100 feet from
manure storage areas, cesspools, unplugged abandoned wells, and subsurface disposal fields. They
must be at least 50 feet from existing operating wells, septic tanks, buried sewers, pits, or sumps.
Variances from siting requirements may be obtained with Department permission (10 CSR 23-5.040).
Open-loop systems must meet construction standards in 10 CSR 23-3, Chapters 1, 2, and 3
concerning casing, casing depth, well seal, borehole, grouting, and reporting (10 CSR 23-5.060).
Steel well casing may be used. The annular space must be sealed so that it does not leak. Casing
materials used will vary based on the stress the pipe is subjected to during construction and the
corrosiveness of the ground water. 10 CSR 23-3.030 also sets forth recommended amounts of grout
depending on borehole diameter and the type of grout used.
The depth of the injection well may not exceed the depth of the supply well. Water must be
returned to the aquifer from which it was taken. A water well installation permit is required to drill
and construct an open-loop system (10 CSR 23-5.060).
Return wells for open-loop systems used for non-domestic purposes will be approved on a
case-by-case basis. System approval takes into account water quality and quantity, geology,
hydrology, and water usage in the area (10 CSR 23-5.060). Regulations also require the installation
of monitoring wells to ensure compliance with water quality regulations. Submission of reports is
required on a set schedule (10 CSR 20-6.070(4)).
Construction requirements differ for closed- and open-loop systems. Open-loop systems must
be constructed in accordance with 10 CSR 23 Chapters 1, 2, and 3. Closed-loop systems must be
constructed in accordance with standards set in 10 CSR 23-5.050.
Operating Requirements
Only large systems (greater than 600,000 BTU/hr) that require permits have operating
requirements. Such operating requirements are specified in the permit.
Monitoring Requirements
If a permit is required, an annual report must be submitted. The annual report must include
the volume of water injected and withdrawn, temperature records for every monitoring well, and
copies of any water quality analyses performed (10 CSR 20-6.070(10)).
The maximum, minimum, and average water temperature, and the maximum, minimum, and
average injection and withdrawal rates must be measured and recorded monthly. Total dissolved
solids must also be measured and recorded monthly (10 CSR 20-6.070(8)-(9)).
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Plugging and Abandonment
Open-loop heat pump wells must be plugged as set forth in 10 CSR 23-3.110, and a
registration report form submitted as if it were a water supply well.
When the Division determines that a heat pump well is improperly constructed, it must be
brought into compliance with the rules or plugged. To plug an improperly constructed heat pump
well, the following specifications must be met:
Remove all pipes from hole;
Clean out well bore of loose material;
Plug well full-length with approved grout; and
Submit registration report form and fee (10 CSR 23-5.080).
Nebraska
Nebraska is a UIC Primacy State for Class V wells and has promulgated regulations for all
Class V wells. The construction and operation of Class V wells, except for large capacity septic
systems, is currently authorized by rule by the Nebraska Department of Environmental Quality
(DEQ) under the Nebraska Administrative Code (NAC Title 122)
Permitting
While Class V wells are currently authorized by rule in accordance with 122 NAC 5, if DEQ
learns at any time that a Class V well may cause a violation of primary drinking water regulations or
the Nebraska Ground Water Protection Standards or may otherwise be adversely affecting the health
of persons, DEQ will require the owner or operator to obtain an individual or area UIC permit (NAC
Title 122, Chapter 4). Permit applications may require a $5,000 fee (NAC Title 122, Chapter 38).
Once granted, the permit is effective for a fixed term not to exceed ten years (NAC Title 122, Chapter
23). DEQ may also order the owner or operator to take such actions (including, where required,
closure of the injection well) as may be necessary to prevent the violation, or take enforcement action
against the owner or operator (NAC Title 122, Chapter 4).
The Director may require any Class V injection well authorized by rule to apply for and
obtain an individual or area UIC permit for one of the following reasons: The injection well is not in
compliance with one or more requirements; the well is not or no longer is within the category of wells
and types of well operations authorized by Title 122, Chapter 7; the protection of USDWs required
that the injection operation be regulated by requirements, such as for corrective action, monitoring
and reporting, or operation, or the well may cause a violation of primary drinking water standards or
the Nebraska Ground Water Protection Standards (NAC Title 122, Chapter 7).
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Siting and Construction
All Class V well operators must submit an Application for Injection to DEQ. Open-loop
systems must be constructed in accordance with the construction standards for Domestic Water
Wells, described in NAC Title 178, Chapter 12.
Water wells must be constructed to prevent the introduction of microbiological, chemical, or
radiological substances into the aquifers penetrated by the wells. Water wells must have a well
casing, an annular space filled with grout, a well screen, and a gravel pack (NAC Title 178, Chapter
12). A water well, by definition, is any excavation that is drilled, cored, bored, washed, driven, dug,
jetted, or otherwise constructed for the purpose of exploring for ground water, monitoring ground
water, utilizing the geothermal properties of the ground, or extracting water from or injecting water
into the aquifer.
Water wells constructed as a source of water for a ground water heat pump system shall be
constructed in accordance with NAC Title 178, Chapter 12, Section 004, Domestic Water Wells.
Operating Requirements
The person authorized by rule shall retain all records concerning the nature and composition
of injected fluids until five years after completion of any required plugging and abandonment
procedures. The person authorized by rule also shall report any noncompliance which may endanger
health or cause pollution of the environment, orally within 24 hours of becoming aware of the
circumstances, and in writing within five days (NAC Title 122, Chapter 7).
At least 90 days advance notice is required before conversion or abandonment of a Class V
well (NAC Title 122, Chapter 7).
Mechanical Integrity Testing
The owner or operator of a Class V well must be able to demonstrate its mechanical integrity
as defined in Chapter 16 of Title 122 (NAC Title 122, Chapter 7). In conducting and evaluating the
tests of mechanical integrity, the owner or operator and Director shall apply methods and standards
generally accepted in the industry. When the owner or operator reports the results of the mechanical
integrity tests to the Director, he shall include a description of the test(s) and method(s) used (NAC
Title 122, Chapter 16).
Plugging and Abandonment
Class V wells must be plugged and abandoned in accordance with the Regulations Governing
Water Well Construction, Pump Installation, and Water Well Decommissioning Standards
promulgated by the Nebraska Department of Health and Human Services, Regulation, and Licensure
at NAC Title 178, Chapter 12 (NAC Title 122, Chapter 36).
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Financial Responsibility
Permittees shall maintain financial responsibility (as prescribed by NAC Title 122, Chapter
37) to close, plug, and abandon the wells and to restore the affected resources in a manner that has
been approved by the Director. The permittee must show evidence of financial responsibility to the
Director by the submission of a surety bond or other adequate assurance acceptable to the Director in
an amount set by the Director (NAC Title 122, Chapter 9).
Nevada
Nevada is a UIC Primacy State for Class V wells and its Division of Environmental
Protection (DEP) administers the UIC program. Nevada Revised Statutes (NRS) §§ 445A.300 -
445A.730 and regulations under the Nevada Administrative Code (NAC) §§ 445A.810 - 445A.925
establish the state's basic UIC program. The injection of fluids through a well into any waters of the
state, including underground waters, is prohibited without a permit issued by DEP (445A.465 NRS),
although the statute allows both general and individual permits (445A.475 NRS and 445A.480 NRS).
Furthermore, injection of a fluid that degrades the physical, chemical, or biological quality of the
aquifer into which it is injected is prohibited, unless the DEP exempts the aquifer and USEPA does
not disapprove the exemption within 45 days (445A.850 NRS).
Permitting
General permits are issued, among others, for a closed-loop well used to inject fluids for
heating or cooling by a heat pump (445 A.869 NAC). Operators of open-loop systems are required to
obtain individual permits. The UIC regulations specify detailed information that must be provided in
support of permit applications, including proposed well location, description of geology, construction
plans, proposed operating data on rates and pressures of injection, analysis of injectate, analysis of
fluid in the receiving formation, proposed injection procedures, and corrective action plan (445A.867
NAC). The DEP may, however, modify the permit application information required for a Class V
well for good cause and upon determination that additional or less information will ensure that the
proposed injection well will not degrade a USDW (445A.891 NAC).
Siting and Construction
The state specifies, among other siting requirements, that the well must be sited in such a way
that it injects into a formation that is separated from any USDW by a confining zone that is free of
known open faults or fractures within the area of review. It must be cased from the finished surface
to the top of the zone for injection and cemented to prevent movement of fluids into or between
USDWs (445A.908 NAC).
Operating Requirements
Under an individual permit, monitoring frequency for injection pressure, pressure of the
annular space, rate of flow, and volume of injected fluid are specified by the permit (445A.913
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NAC). Analysis of injected fluid must be conducted with sufficient frequency to yield representative
data.
Mechanical Integrity Testing
If required by the state, mechanical integrity testing must be conducted at least once every
five years for the life of the well, or more frequently if conditions of operation warrant, by a specified
method (445A.916 NAC). Methods of testing are listed in 445A.917 - 445A.919 NAC.
Plugging and Abandonment
For an individually permitted well, a plugging and abandonment plan and cost estimate must
be prepared, included with the permit application, and reviewed annually. Before abandonment, a
well must be plugged with cement in a manner that will not allow the movement of fluids into or
between USDWs (445A.923 NAC). If the Director determines that a well is abandoned, he may
order it to be plugged (445A.924 NAC).
New York
USEPA Region 2 directly implements the UIC program for Class V injection wells in New
York. However, under the State of New York's Environmental Conservation Law, the Department of
Environmental Conservation, Division of Water Resources (DWR) has promulgated regulations in
the State Code Rules and Regulations, Title 6, Chapter X, Parts 703, 750, 754, and 756. These
regulations establish water quality standards and effluent limitations, create a state pollutant
discharge elimination system requiring permits for discharges into the waters of the state, specify that
such discharges must comply with the standards in Part 703, and provide for monitoring in Part 756.
Permitting
Applications for a State of New York Pollution Discharge Elimination System (SPDES)
permit must be submitted on a required form, describe the proposed discharge, and supply such other
information as the DWR requests. These applications are subject to public notice. SPDES permits
must ensure compliance with effluent limitations and standards, and will include schedules of
compliance, monitoring requirements, and records and reports of activities (Parts 751 - 756).
With regard to HAC return flow wells, only open-loop systems require a permit. Closed-loop
systems do not require a permit if no chemicals are added to the water and the heat added is not
significant enough to be considered a pollutant and if the discharge is from a single household and is
less than 1,000 gallons per day.
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Operating Requirements
Effluent limits (Part 703) and monitoring and reporting requirements in the SPDES permit
must be met. For HAC return flow wells, injectate may not exceed MCLs, and no additives are
allowed. Siting and construction requirements also may apply to HAC return flow wells.
North Carolina
North Carolina is a UIC Primacy State for Class V wells. The state's requirements for HAC
return flow wells are found primarily at North Carolina Administrative Code, Title ISA, Department
of Environment, Health, and Natural Resources, Division of Water Quality, Subchapter 2C, Section
.0200, Well Construction Standards, Criteria and Standards Applicable to Injection Wells.
Permitting
Closed-loop heat pump systems that re-circulate potable water are authorized by rule
(.021 l(u)(2) NCAC). Operators of closed-loop heat pump systems that use additives in their cooling
fluids and operators of open-loop systems are required to obtain an individual permit for construction
and operation. Such wells may only be approved by the Director if the temperature of the injection
fluid is not in excess of 30 degrees Fahrenheit above or below the naturally occurring temperature of
the receiving ground water (.0209(e)(3)(A) NCAC).
State staff will not issue a permit for the injection of wastes or any substance of a composition
and concentration such that, if it were discharged to the land or waters of the state, it would create a
threat to human health or would otherwise render those waters unsuitable for their intended best
usage unless specifically provided for by statute or rules (.0211 (a) NCAC).
In addition to identification information, a permit application must include the following
(.021 l(a) - (c), and (d)(l) NCAC):
Description of the proposed injection activities;
Detailed map showing wells, boundaries, buildings, existing or abandoned wells; existing
sources of known or potential ground water contamination, and surface water bodies within
the area of review;
Chemical, physical, biological, and radiological characteristics of the proposed injectate;
Proposed average and maximum daily rate and quantity of fluid to be injected;
Detailed plans of the construction of the system;
Listing of all permits and approvals; and
Other information as required by the Department.
Permits are issued for a period not to exceed five years from the date of issuance. The permit
may be modified, revoked and reissued, or terminated by the Director in whole or in part for actions
which adversely impact human health or the environment (.021 l(j)(l) NCAC).
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Siting and Construction
Class V wells may not be located in an area generally subject to flooding. The minimum
horizontal separation for HAC return flow wells between the well and potential sources of ground
water contamination are specified by rule (.0213 (a)(4) NCAC). The methods and materials used in
construction shall not threaten the physical and mechanical integrity of the well during its lifetime
(i.e., it shall be designed and constructed to operate for the projected life of the well) and shall be
compatible with the proposed injection activities (.0213 (c)(l)(C) NCAC).
Operating Requirements
An individually permitted well must be inspected by the Department following construction
before injection can commence. The Department must approve the proposed operating procedures,
and there must be a satisfactory demonstration of mechanical integrity. The Department may
establish maximum injection volumes and pressures (.021 l(h) NCAC). The permittee must at all
times properly operate and maintain all facilities and systems of treatment and control (and related
appurtenances) which are installed or used by the permittee to achieve compliance with permit
conditions (.021 l(k) NCAC).
Injection wells and effluent return water must comply with the state's drinking water
standards so as not to contaminate or degrade the aquifer of injection. Monitoring requirements may
be specified by the Department as necessary generally on a site-specific basis to demonstrate
adequate protection of USDWs (.0213(f) NCAC). Generally, influent and effluent water samples are
taken to insure no contamination is occurring to the injected aquifer.
Mechanical Integrity
Mechanical integrity testing is required, using specified procedures (.0207 NCAC).
Plugging and Abandonment
Procedures for temporary and permanent abandonment are specified. When a drilled well is
permanently abandoned, it is required to be completely filled with cement grout (.0214 NCAC).
Financial Responsibility
Individual permittees must maintain financial responsibility in the form of performance bonds
or other equivalent forms of financial assurance, to close, plug, and abandon the injection operation
(.0208 NCAC).
North Dakota
North Dakota is a UIC Primacy State for Class V wells. The state has promulgated specific
UIC regulations, found at Chapter 33-25-01 of the North Dakota Administrative Code (NDAC).
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Permitting
Most Class V wells are authorized by rule, although the Department of Health may require
owners and operators to obtain a permit in some circumstances. The Director of the Division of
Water Supplies and Pollution Control at the North Dakota Department of Health may require Class V
well operators to obtain a permit if the injection well is not in compliance with appropriate rules, the
injection well is no longer within the category of wells authorized by rule, or if protection of a
USDW requires that the injection operation be regulated. In addition, owner/operators may request a
permit, rather than rule authorization.
Class V permits when issued are effective for a term not to exceed ten years. Permit
applications must include the location of the proposed facility, with references to the nearest lines of
governmental section (NDAC 33-25-01-06(3); NDAC 43-02-07-06).
Siting and Construction
All wells must be constructed by a certified water or monitoring well contractor. All
facilities, all fluids, and all additives must be approved by the State Geologist prior to installation
(North Dakota Century Code 33-18; NDAC 43-02-07-10).
Operating Requirements
North Dakota's UIC regulations specify that the owner or operator of a proposed Class V
injection well must demonstrate that the construction, operation, maintenance, plugging, and
abandonment of the proposed well will not allow movement of fluid to a USDW which could cause
an adverse health effect or a violation of MCLs (NDAC 33-25-01-04).
All rule authorized well operators must submit inventory information to the Director.
Inventory information shall include the name of the owner/operator; number of wells and location by
township, section, range; nature and volume of injected fluids; construction features including well
depth, screened interval, and casing size and type; and other requested information (NDCC 33-25-01-
16).
Plugging and Abandonment
None specified by statute or regulations (NDAC plugging and abandonment regulations refer
only to closed-loop systems).
Financial Responsibility
Permittees must maintain financial responsibility and resources to properly close, plug, and
abandon the UIC operation. Evidence of financial responsibility must be submitted to the Director in
the form of a surety bond or other adequate assurances, such as financial statements (NDAC 43-02-
07-09; NDAC 33-25-01-10(4)).
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Ohio
Ohio is a UIC Primacy State for Class V wells. The State of Ohio UIC program requirements
are found primarily in the Ohio Administrative Code (OAC), Chapter 3745-34, Rules 3745-34-01
through 3745-34-62.
Permitting
All Class V wells are authorized by rule, unless they inject sewage, industrial wastes, or other
wastes into or above a USDW. In such cases, individual drilling and operating permits are required
(OAC 3745-34-14(A)), although in practice very few wells are permitted. In addition, owners and
operators of Class V wells are required to submit inventory information to Ohio EPA, including the
name and location of the facility, legal contact, ownership of the facility, and the nature, type, and
status of the injection well (OAC 3745-34-13(B)). No HAC return flow wells are currently permitted
by the Ohio UIC program.
If at any time the Director learns that a Class V well may cause a violation of any drinking
water standard or otherwise adversely affect the health of persons, the injector will be required to
obtain an individual permit; take whatever action (up to and including closure of the well) that may
be necessary to prevent the violation; or be subject to enforcement action (OAC 3745-34-07).
Siting and Construction
OAC 3745-34 sets forth construction, siting, and operating requirements for permitted Class
V wells, although the requirements often do not apply since most types of Class V wells are not
permitted. There are no construction or siting requirements specific to HAC return flow wells.
Oregon
Oregon is a UIC Primacy State for Class V wells. The UIC program is administered by the
Department of Environmental Quality (DEQ). Under the State of Oregon's Administrative Rules
(OAR) pertaining to underground injection, a "waste disposal well" is defined as any bored, drilled,
driven or dug hole, whose depth is greater than its largest surface dimension, which is used or is
intended to be used for disposal of sewage, industrial, agricultural, or other wastes and includes drain
holes, drywells, cesspools and seepage pits, along with other underground injection wells (340-044-
0005(22) OAR). Construction and operation of a waste disposal well without a water pollution
control facility (WPCF) permit is prohibited.
OAR 632-020-0005 sets forth specific regulations addressing construction, operation,
maintenance, and abandonment of wells in a manner that safeguards the life, health, property, and
welfare of the people of the state. Specific topics addressed include drilling, redrilling, and
deepening; alteration of casing; permits; completion and abandonment; plugging methods and
procedures; well spacing; disposal of wastes; and construction of injection wells.
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Certain categories of wells are prohibited entirely, including wells used for underground
injection activities that allow the movement of fluids into a USDW if such fluids may cause a
violation of any primary drinking water regulation or otherwise create a public health hazard or have
the potential to cause significant degradation of public waters. The Department of Water Resources
issues permits for HAC return flow wells.
Permitting
Any underground injection activity that may cause, or tend to cause, pollution of ground water
must be approved by the DEQ, in addition to any other permits or approvals required by other
federal, state, or local agencies (340-044-0055 OAR). Permits are not to be issued for construction,
maintenance, or use of waste disposal wells where any other treatment or disposal method which
affords better protection of public health or water resources is reasonably available or possible (340-
044-0030 OAR). A waste disposal well, unless absolutely prohibited, must have a WPCF permit
(340-044-0035 OAR, 340-045-0015 OAR).
Wells that re-inject air conditioning or heat pump transfer water to the same aquifer or one of
equivalent quality may be exempted from the permit requirement on a case-by-case basis.
Siting and Construction
Permits for construction or use of waste disposal wells include minimum conditions relating
to their location, construction, and use (340-044-0035 OAR). In general, injection wells must be
constructed in conformance with OAR 690-200-0005 to 690-225-0110 (Well Construction and
Maintenance, Well Driller Licensing, Well Construction Standards, Abandonment of Wells). Wells
must be constructed in a manner that protects ground water from contamination, waste, loss of
artesian pressure, and substantial thermal alteration (OAR 690-230-0030). Special standards (OAR
690-230-005 to 690-230-0140) are applied by rule on an ad hoc basis. Permit conditions are on an ad
hoc basis.
Operating Requirements
Procedures required to inject effluent into an injection well must not cause failure of the well
casing and/or seal materials or other components of well structure, including movement,
displacement, or fracturing of overburden (OAR 690-230-0100). An injection plan must be filed with
the Director. In addition, adequate wellhead protection equipment to ensure public safety and the
protection of ground water resources must be installed on any well when the temperature of the fluid
being withdrawn from the well bore exceeds 150 degrees F (OAR 690-230-0070).
Plugging and Abandonment
Upon discontinuance of use or abandonment a waste disposal well is required to be rendered
completely inoperable by plugging and sealing the hole. All portions of the well which are
surrounded by "solid wall" formation must be plugged and filled with cement grout or concrete. The
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top portion of the well must be effectively sealed with cement grout or concrete to a depth of at least
18 feet below the surface of the ground, or if this method of sealing is not effective, in a manner
approved by the DEQ.
Pennsylvania
USEPA Region 3 directly implements the UIC program for Class V injection wells in
Pennsylvania. The Bureau of Water Quality Management in the Pennsylvania Department of
Environmental Protection has developed policies on wastewater discharges to ground water. No state
policies are available on HAC wells.
South Carolina
South Carolina is a UIC Primacy State for Class V wells. The Department of Health and
Environmental Control (DHEC) oversees the Class V UIC program. Rules addressing the UIC
program are found at Chapter 61, section R61-87.1 et seq. of the South Carolina Department of
Health and Environmental Control (DHEC) regulations.
South Carolina's regulations divide Class V wells into two groups: (A) and (B). Class V(A)
wells include storm water drainage, recharge, and industrial wells; DHEC issues individual permits
for these well types. Class V(B) wells include all injection wells used to return to the supply aquifer
the water which has passed through a non-contact system, including HAC return flow wells. These
well types are authorized by rule. Closed-loop systems are not regulated by the UIC program.
Permitting
The injection of any fluids to the subsurface or ground waters of the state by means of an
injection well is prohibited except as authorized by a Department permit or rule (R61-87.4). DHES
issues individual permits for Class V(A) wells (R61-87.13.A). Permits are issued for a period not to
exceed ten years from the date of issuance for a Class V(A) well (R61-87.13.W). The permit may be
modified, revoked and reissued, or terminated for cause (R61-87.13.Y).
Class V(B) wells are authorized by rule and do not require a permit. However, no person may
construct, use or operate a well of this class for injection in violation of R61-87.5 (R61-87.1 l.F).
Siting and Construction
Minimum standards for construction and abandonment of injection wells are those stated for
all wells in the South Carolina Well Standards and Regulations (R.61-71). Injection may not
commence until construction is complete, the permittee has submitted notice of completion of
construction to the Department, and the Department has inspected or otherwise reviewed the injection
well and finds it in compliance with these regulations (R61-87.13.U).
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Operating Requirements
Operating requirements are not specified for wells permitted by rule. For individually
permitted wells, the Department may establish maximum injection volumes and pressures and such
other permit conditions as necessary to assure that fractures are not initiated in the confining zone
adjacent to a USDW; that injected fluids do not migrate into USDWs; that formation fluids are not
displaced into any USDW; and to assure compliance with operating requirements (R61-87.13.V).
Monitoring Requirements
Monitoring requirements are not specified for wells permitted by rule. For individually
permitted wells an appropriate number of monitoring wells shall be installed in the injection zone and
any USDWs that could be affected by the injection operation (R61-87.14.G). Permittees are required
to retain copies of records of all monitoring information, including all calibration and maintenance
records, all original strip chart recordings for continuous monitoring instrumentation, and copies of
all reports required by the permit, for a period of at least three years from the date of the sample,
measurement, report, or application (R61-87.13.CC). The permittee shall report any monitoring or
other information which indicates that any contaminant may endanger a USDW and any
noncompliance with a permit condition or malfunction of the injection system which may cause fluid
migration into or between USDWs (R61-87.13.EE).
Mechanical Integrity Testing
Mechanical integrity testing is not specified for wells permitted by rule. For individually
permitted wells, prior to granting approval for the operation of any injection well the Department will
require a satisfactory demonstration of mechanical integrity (R61-87.13.U). Permittees must
demonstrate mechanical integrity at least once every five years during the life of the well (R61-
87.14.G.3.C).
Plugging and Abandonment
Plugging and abandonment requirements are not specified for wells permitted by rule. For
individually permitted wells, prior to plugging or abandonment the permittee must provide 180 days
advance notice, and submit a plugging and abandonment plan to the Department that demonstrates
technical adequacy. The well to be abandoned must be in a state of static equilibrium with the mud
weight equalized top to bottom. Prior to final approval to abandon an injection well, the permittee
shall demonstrate to the satisfaction of the Department that the well has been plugged in a manner
that will not allow the movement of fluids either into or between USDWs (R61-87.15).
Tennessee
USEPA Region 4 directly implements the UIC program for Class V injection wells in
Tennessee. The state generally authorizes the use of Class V wells under the authority of state
statutes at Section 69-3-105 of the Tennessee Administrative Code, and state regulations at 1200-4-6
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TCA. The state largely runs its UIC Class V well program with support and oversight from USEPA
Region 4.
Texas
Texas is a UIC Primacy State for Class V wells. The Injection Well Act (Chapter 27 of the
Texas Water Code) and Title 3 of the Natural Resources Code provide statutory authority for the UIC
program. Regulations establishing the UIC program are found in Title 30, Chapter 331 of the Texas
Administrative Code (TAC).
Permitting
Underground injection is prohibited, unless authorized by permit or rule (331.7 TAC).
Injection into a Class V well is authorized by rule, although the Texas Natural Resources Control
Commission (TNRCC) may require the owner or operator of a well authorized by rule to apply for
and obtain an injection well permit (331.9 TAC). No permit or authorization by rule is allowed
where an injection well causes or allows the movement of fluid that would result in the pollution of a
USDW. A permit or authorization by rule must include terms and conditions reasonably necessary to
protect fresh water from pollution (331.5 TAC).
Siting and Construction
All Class V wells are required to be completed in accordance with explicit specifications in
the rules, unless otherwise authorized by the TNRCC. These specifications are listed below:
A form provided either by the Water Well Drillers Board or the TNRCC must be completed.
The annular space between the borehole and the casing must be filled from ground level to a
depth of not less than 10 feet below the land surface or well head with cement slurry. Special
requirements are imposed in areas of shallow unconfined ground water aquifers and in areas
of confined ground water aquifers with artesian head.
In all wells where plastic casing is used, a concrete slab or sealing block must be placed above
the cement slurry around the well at the ground surface (the rules include additional
specifications concerning the slab).
In wells where steel casing is used, a slab or block will be required above the cement slurry,
except when a pitless adaptor is used (the rules contain additional requirements concerning
the adaptor).
All wells must be completed so that aquifers or zones containing waters that differ
significantly in chemical quality are not allowed to commingle through the borehole-casing
annulus or the gravel pack and degrade any aquifer zone.
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The well casing must be capped or completed in a manner that will prevent pollutants from
entering the well.
When undesirable water is encountered in a Class V well, the undesirable water must be
sealed off and confined to the zone(s) of origin (331.132 TAG).
Operating Requirements
None specified. Chapter 331, Subpart H, " Standards for Class V Wells" addresses only
construction and closure standards (331.131 to 331.133 TAG).
Mechanical Integrity Testing
Injection may be prohibited for Class V wells that lack mechanical integrity. The TNRCC
may require a demonstration of mechanical integrity at any time if there is reason to believe
mechanical integrity is lacking. The TNRCC may allow plugging of the well or require the permittee
to perform additional construction, operation, monitoring, reporting, and corrective actions which are
necessary to prevent the movement of fluid into or between USDWs caused by the lack of
mechanical integrity. Injection may resume on written notification from the TNRCC that mechanical
integrity has been demonstrated (331.4 TAG).
Plugging and Abandonment
Plugging and abandonment of a well authorized by rule is required to be accomplished in
accordance with §331.46 TAG (331.9 TAG). In addition, closure standards specific to Class V wells
provide that closure is to be accomplished by removing all of the removable casing and filling the
entire well with cement to land surface. Alternatively, if the use of the well to be permanently
discontinued, and if the well does not contain undesirable water, the well may be filled with fine
sand, clay, or heavy mud followed by a cement plug extending from the land surface to a depth of not
less than 10 feet. If the use of a well that contains undesirable water is to be permanently
discontinued, either the zone(s) containing undesirable water or the fresh water zone(s) must be
isolated with cement plugs and the remainder of the wellbore filled with sand, clay, or heavy mud to
form a base for a cement plug extending from the land surface to a depth of not less than 10 feet
(331.133 TAG).
Financial Responsibility
Chapter 27 of the Texas Water Code, "Injection Wells," provides TNRCC with the authority
to implement financial responsibility requirements for persons to whom an injection well permit is
issued (§ 27.073). Detailed financial responsibility requirements are contained in Chapter 331,
Subchapter I of the state's UIC regulations (331.141 to 331.144 TAG). Permittees are required to
secure and maintain a performance bond or other equivalent form of financial assurance or guarantee
to ensure the closing, plugging, abandonment, and post-closure care of the injection operation.
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However, this requirement, unless incorporated into a permit, applies specifically only to Class I and
Class III wells (331.142 TAC).
Vermont
Vermont is a UIC Primacy State for Class V wells. The State of Vermont Agency of Natural
Resources, Department of Environmental Conservation (DEC) implements Vermont's UIC program.
Title 10, Chapter 47 of Vermont's statutes ("Water Pollution Control") establishes the state's water
quality policy and requires a permit to inject any potentially hazardous discharge. Chapter 11 of
Vermont's Water Pollution Control Regulations6 incorporate many elements of 40 CFR 146,
including the definition of Class V wells (see Appendix II to that Chapter).
Permitting
The state requires individual permits for all discharges. Permits require compliance with
drinking water standards at a drinking water supply or property line. HAC return flow wells,
however, are authorized by rule (13 UIC 25(a)(l)). In addition, if a discharge is regulated by another
permit, no UIC permit is required.
If at any time the Secretary learns that a Class V well may cause a violation of any drinking
water standard or otherwise adversely affect the health of persons, he or she will require the injector
to obtain an individual permit; order the injector to take whatever action (up to and including closure
of the well) may be necessary to prevent the violation; or take enforcement action (13 UIC 24(c) and
(d)).
Permits are issued for a maximum of five years (13 UIC 25(h)).
Siting and Construction
To qualify for authorization by rule, ground water heat pump return wells must be constructed
such that the water is not exposed to the atmosphere or any substance other than the interior of the
well; flow is less than 25,000 gpd; water is withdrawn from and discharged to the same aquifer; the
return water does not cascade down the well, but is instead injected below the water level; and return
water does not cause a violation of drinking water standards (13 UIC 25(a)(l)). Return water also
must be unaltered (13 UIC 25(a)(l)).
Operating Requirements
No owner or operator of an injection well may construct, operate, maintain, convert, plug,
abandon, or conduct any other injection activity in a manner that allows the movement of fluid
6 While the numbering of the relevant portion of the state regulations apparently has been
changed from Subchapter 13 to Chapter 11, we were working from a set of regulations printed before this
change was instituted. Thus, citations of the state regulations given below are still shown as "13 UIC(x)."
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containing any contaminant into USDWs, if the presence of that contaminant may cause a violation
of any drinking water standard or may otherwise adversely affect the health of persons (13 UIC
24(a)).
All owners or operators of Class V injection wells must submit inventory information (e.g.,
facility name and location, name and address of legal contact, ownership of facility, nature, type, and
operating status of injection wells) to the Secretary unless the discharge is already authorized by the
Secretary under other authorities. Owners or operators of existing but unauthorized Class V injection
wells must submit inventory information no later than 45 days after notice by the Secretary (13 UIC
25(b)).
Monitoring Requirements
State regulations stipulate that all permits shall specify requirements concerning the proper
use, maintenance, and installation of monitoring equipment or methods; required monitoring,
including type, intervals, and frequency sufficient to yield data that are representative of the
monitored activity including, when appropriate, continuous monitoring; and applicable reporting
requirements based on the impact of the regulated activity (13 UIC 16; see also Sections 146.13,
146.23, and 146.33 in Appendix II of the state UIC rule (adopted from the federal UIC regulations)).
Virginia
USEPA Region 3 directly implements the UIC program for Class V injection wells in
Virginia. While there are no specific state regulations for injection wells other than septic systems,
the state does regulate ground water quality through an anti-degradation policy. The state requires
that ground water quality be maintained per the numerical standards set forth in 9 VAC 25-260-210.
The state's general ground water quality policy is set forth at 9 VAC 25-260-5 et seq.
Specifically, 9 VAC 25-260-200 states that if the concentration of any constituent in ground water is
less than the limit set forth by ground water standards, the natural quality for the constituent shall be
maintained; natural quality shall also be maintained for all constituents, including temperature, not set
forth in ground water standards. If the concentration of any constituent in ground water exceeds the
limit in the standard for that constituent, no addition of that constituent to the naturally occurring
concentration shall be made. Variance to this policy shall not be made unless it has been
affirmatively demonstrated that a change is justifiable to provide necessary economic or social
development, that the degree of waste treatment necessary to preserve the existing quality cannot be
economically or socially justified, and that the present and anticipated uses of such water will be
preserved and protected.
Permitting
Ground water withdrawal permits are required where water is withdrawn from an aquifer in a
ground water management zone (9 VAC 25-610-40). However, operators of heat pumps that inject
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water into the same aquifer from which the water was withdrawn are not required to obtain a ground
water withdrawal permit (9 VAC 25-610-50).
Washington
Washington is a UIC Primacy State for Class V wells. Chapter 173-218 of the Washington
Administrative Code (WAC) establishes the UIC program. Under the program, the policy of the
Department of Ecology is to maintain the highest possible standards to prevent the injection of fluids
that may endanger ground waters which are available for beneficial uses or which may contain fewer
than 10,000 mg/1 TDS. Consistent with that policy, all new Class V injection wells that inject
industrial, municipal, or commercial waste fluids into or above a USDW are prohibited (172-218-
090(1) WAC). Operators of existing wells must obtain a permit to operate.
Permitting
A permit must specify conditions necessary to prevent and control injection of fluids into the
waters of the state, including all known, available, and reasonable methods of prevention, control,
and treatment; applicable requirements in 40 CFR Parts 124, 144, 146; and any conditions necessary
to preserve and protect USDWs. Any injection well that causes or allows the movement of fluid into
a USDW that may result in a violation of any primary drinking water standard under 40 CFR Part 141
or that may otherwise adversely affect the beneficial use of a USDW is prohibited (173-218-100
WAC).
Siting and Construction
WAC 173-160-010(3)(e) specifically excludes injection wells regulated at chapter 173-218
WAC from the requirements of WAC 173-160-010 through -560.
Operating Requirements
The water quality standards for ground waters establish an antidegradation policy. The
injectate must meet the state ground water standards at the point of compliance (173-200-030 WAC).
Plugging and Abandonment
WAC 173-160-010(3)(e) specifically excludes injection wells regulated at chapter 173-218
WAC from the requirements of WAC 173-160-010 through -560.
West Virginia
West Virginia is a UIC Primacy State for Class V wells. Regulations establishing the UIC
program are found in Title 47-13 of the West Virginia Code of State Regulations. The state does not
identify a separate category of Class V industrial wells, but does specify that Class V includes
injection wells not included in Classes 1, 2, 3, or 4 (47-13-4.5. WVAC).
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Permitting
Class V injection wells are authorized by rule, unless the Office of Water Resources within
the Division of Environmental Protection requires an individual permit (47-13-12.4.a and 47-13-13.2
WVAC). Injection is authorized initially for five years under the permit by rule provisions.
Operating Requirements
Owners or operators of Class V wells are required to submit inventory information describing
the well, including its construction features, the nature and volume of injected fluids, alternative
means of disposal, the environmental and economic consequences of well disposal and its
alternatives, operation status, and location and ownership information (47-13-12.2 WVAC).
Rule-authorized wells must meet the requirements for monitoring and recordkeeping
(requiring retention of records pursuant to 47-13-13.6.b. WVAC concerning the nature and
composition of injected fluids until three years after completion of plugging and abandonment);
immediate reporting of information indicating that any contaminant may cause an endangerment to
USDWs or any malfunction of the injection system that might cause fluid migration into or between
USDWs; and prior notice of abandonment.
The rules enact a general prohibition against any underground injection activity that causes or
allows the movement of fluid containing any contaminant into a USDW, if the presence of that
contaminant may cause a violation of any primary drinking water regulations under 40 CFR Part 142
or promulgated under the West Virginia Code or may adversely affect the health of persons. If at any
time a Class V well may cause a violation of the primary drinking water rules, the operator may be
required to obtain a permit or take such other action, including closure, that will prevent the violation
(47-13-13.1 WVAC). Inventory requirements for Class V wells include information regarding
pollutant loads and schedules for attaining compliance with water quality standards (47-13-13.2.d.l
WVAC).
If required for protection of a USDW, the injection operation may be required to satisfy
requirements (e.g., corrective action, monitoring and reporting, or operation) that are not contained in
theUIC rules (47-13-13.2.C.1.C. WVAC).
Mechanical Integrity
Operators of permitted Class V well are required to demonstrate that the well has mechanical
integrity (47-13-13.7.h WVAC).
Plugging and Abandonment
Class V well operators required to obtain individual permits must ensure that the plugging and
abandonment of the well will not allow the movement of fluids either into a USDW or from one
USDW to another. A plan for plugging and abandonment must be submitted (47-13-13.7.f WVAC).
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Financial Responsibility
Class V well operators required to obtain individual permits must demonstrate financial
responsibility for plugging and abandonment (47-13-13.7.g WVAC).
Wisconsin
Wisconsin is a UIC Primacy State for Class V wells. The Wisconsin Department of Natural
Resources (DNR) oversees the Class V UIC program. Wisconsin Admin. Code S. NR 812.05
stipulates that the use of any well, drillhole, or water system for the underground placement of any
substance is prohibited unless it is approved by DNR for purposes of remediation or to construct,
rehabilitate, or operate a well.
Permitting, Siting, and Construction
Operators must notify DNR of their intent to construct a well. If DNR authorizes the well by
rule, DNR issues a letter of approval, which may contain siting, design, or monitoring requirements.
DNR generally requires that well casings meet ASTM standards and be grouted. In addition, a HAC
return flow well must be sited at least 50 feet from the nearest water supply well. Well construction
reports must be submitted to DNR for review and approval.
Operating Requirements
Use of additives in open-loop systems is prohibited. In addition, DNR may impose operating
requirements in the letter of approval sent to operators prior to well construction.
DNR has the authority to conduct inspections of HAC return flow wells. In practice,
inspections are conducted every one to five years for vertical wells, and on a complaint-driven basis
for horizontal wells.
Monitoring Requirements
Operators must report to DNR results of monitoring requirements specified in either the letter
of approval or established under a general WPDES permit.
Wyoming
Wyoming is a Primacy State for UIC Class V wells. The Wyoming Department of
Environmental Quality, Water Quality Division, oversees the Class V UIC Program. Wyoming
Statute 35-1 l-301(a)(i) & (ii) provides that no person, except when authorized by a permit, may
discharge any pollution or wastes into the waters of the state or alter the physical, chemical,
radiological, biological, or bacteriological properties of any waters of the state. All ground water
within Wyoming, including water in the vadose zone, is considered water of the state. Because
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altering the physical properties of the waters of the state is considered to include altering the
temperature of the water, all HAC return flow wells, regardless of whether they are open- or closed-
loop systems, are required to have a permit.
Permitting
On April 14, 1998, the Water Quality Division promulgated Chapter 16, Wyoming Water
Quality Rules and Regulations (WWQR&R). HAC return flow wells are designated type 5A2
systems (16 WWQR&R Appendix A). Type 5A2 systems are not required to have an individual
permit (16 WWQR&R Section6(a)). Such wells are required to be covered by a general permit
within six months of the date when a general permit is issued (16 WWQR&R Section 4(b) and (7)).
To date, the general permit has not been issued and these systems are temporarily authorized by rule
(16 WWQR&R Section 4(c) and (8)). A separate permit to construct is not required for Class V
wells (16 WWQR&R Section 5(a)(v)).
Prior to the promulgation of Chapter 16, operators of HAC return flow wells were required to
obtain individual permits under Chapter 9 of WWQR&R. Under that requirement a total of seven
open-loop systems were permitted, with stringent monitoring requirements. Of these four have been
plugged and abandoned.
Siting and Construction
The Class V UIC rules include construction requirements. All wells must meet the design
standards in Chapter 11, WWQR&R, Parts B and G. They must be constructed to allow the use of
testing devices and to provide for metering of the injectate volume (16 WWQR&R SectionlO). The
requirements in 11 WWQR&R Part G include requirements for well location, sealing the annular
space, surface construction, casing, sealing strata, and plugging and abandonment.
Operating Requirements
Chapter 16 WWQR&R Section 10(c ) requires that all heating and cooling facilities
(including type 5A2 wells) shall include: (I) Provisions for the use of non-toxic circulating medium in
closed-loop systems or an operating system which cannot be made to operate with fluid leaking; (ii)
Provisions for operations without the use of corrosion inhibitors, biocides, or other toxic additives in
open-loop systems; (iii) Provisions to control the total dissolved solids of waters injected into open-
loop systems to the class of use standard; (iv) Provisions for automatic shutdown of the system in the
event of a fluid loss from a closed-loop system or any loss of product to an open-loop system; (v)
Provisions to ensure that injected water does not come to the surface or flood any subsurface
structure in the immediate vicinity of the injection system; and (vi) Provisions to insure that known
ground water contamination is not spread by the direct injection of contaminated water or by
movement of contamination from one zone to another caused indirectly by the injection.
Chapter 16 WWQR&R Section 9 (e) provides that no heating and cooling facility, including
type 5A2 wells, shall be constructed so as to directly receive any waste other than cooling water. No
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corrosion inhibitors, scale inhibitors, antifreeze agents, salts or refrigerants shall be added to the
water prior to injection.
Plugging and Abandonment
Chapter 16 WWQR&R Section 12 establishes abandonment standards for all Class V wells,
including HAC return flow wells. Section 12(a) through (c) applies to air conditioner return flow
wells and provides that Class V facilities may be abandoned in place if the following conditions are
met and if it can be demonstrated to the satisfaction of the administrator that: (1) no hazardous waste
has ever been discharged through the facility; (2) no radioactive waste has ever been discharged
through the facility; (3) all piping allowing for the discharge has either been removed or the ends of
the piping have been plugged in such a way that the plug is permanent and will not allow for a
discharge; and (4) all accumulated sludges are removed from any septic tanks, holding tanks, lift
stations, or other waste handling structures prior to abandonment. Facilities which cannot
demonstrate compliance with these requirements may be abandoned in place if: (1) tests are run on
sludges accumulated in the septic tanks, holding tanks, lift stations, or other waste handling structures
and show that none of these materials contain characteristic hazardous waste or radioactive waste; (2)
monitoring of the ground water in the immediate area of the facility shows that there are no toxic
materials (substances) present in the ground water at levels higher than class of use standards and
which are present as a result of the injection; or (3) some other method acceptable to the
administrator. Facilities which cannot make the demonstrations required under either approach must
be excavated to the point where contamination is no longer visible in the soil. At that point, samples
shall be taken of the soil for all hazardous constituents which may have been discharged through the
system. Materials excavated shall be removed from the site for disposal under approval of the Solid
and Hazardous Waste Management Division.
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