SHALLOW INJECTION
WELL PRACTICES
CLASS V
WELL
FACTS
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OFFICE OF
DRINKING WATER
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INTRODUCTION
The subsurface environment has been utilized for cen-
turies to dispose of liquid wastes with the philosophy
that the waste was out of sight and out of mind. The
recent realization that subsurface waste disposal could
contaminate ground water prompted the development
of an Underground Injection Control (UIC) program as
part of the Safe Drinking Water Act (SDWA) of 1 974. This
program was designed to prevent contamination of Un-
derground Sources of Drinking Water (USDW) by injec-
tion wells. A well, as defined in Title 40 of the Code of
Federal Regulations is either a dug hole or a bored, drilled
or driven shaft whose depth is greater than its largest
surface dimension. Injection is defined as the subsur-
face emplacement of fluids in a well where a fluid is any
material that flows or moves whether it is semisolid, liq-
uid, sludge or gas. No injection is authorized without
approval from the appropriate regulatory agency. In
states with primacy for implementing the UIC program,
this would be a state agency. In states that have not
received primacy, the regulatory agency is the USEPA.
As part of the UIC program, injection wells were divided
into five main classes.
INJECTION WELL
CLASSIFICATION
Class 1: Wells used to inject hazardous wastes or
dispose of industrial and municipal flu-
ids beneath the lowermost USDW.
Class 11: Wells used to inject fluids associated with
the production of oil and natural gas or
fluids/compounds used for enhanced
hydrocarbon recovery. These wells nor-
mally inject below the lowermost USDW
except in cases where the USDW is hy-
drocarbon producing.
Class 111: Wells which inject fluids for the extrac-
tion of minerals.
Class IV: Wells which dispose of hazardous or ra-
dioactive wastes into or above a USDW
(BANNED).
Class V: Wells not included in the other classes,
generally inject nonhazardous fluid
into or above a USDW.
If a well does not fit into one of the first four Classes
and meets the definition of an injection well, it is consid-
ered a Class V well. It should be noted that not all Class
V wells are used for disposal. Examples of Class V prac-
tices which are not disposal related include: Aquifer Re-
charge, Fossil Fuel Recovery and Mineral Recovery.
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CLASS V -
SIMPLE TO COMPLEX
Class V injection practices recognized by the USEPA
include 30 individual types of wells which range in com-
plexity from simple cesspools which are barely deeper
than they are wide to sophisticated geothermal reinjec-
tion wells which may be thousands of feet deep. Table 1
illustrates the abundance, potential for ground water
contamination and potential contaminants for the 30
different types of Class V wells.
As can be seen in Table 1, the Class V injection well
category is very large and diverse. Class V injection prac-
tices can be divided into two general categories, "high-
tech" and "low-tech". "Low-tech" wells generally have
simple casing designs and surface equipment and inject
into shallow formations by gravity flow or low volume
pumps. In contrast, "high-tech" wells typically have mul-
tiple casing strings, sophisticated well head equipment
to control and measure pressure and inject high volumes
of fluid into deep saline formations that are separated
from aquifers by an impermeable confining layer.
CLASS V INJECTION SYSTEMS
AND YOUR DRINKING WATER
The majority of Class V injection is into or above the
USDW. USDW is defined as an aquifer or its portion which
supplies any public water system or contains a sufficient
quantity of ground water to supply a public water sys-
tem, contains less than 10,000 mg/L total dissolved sol-
ids and is not an exempted aquifer.
Potential for contaminating ground water is quite var-
ied and depends on:
1. Where injection occurs relative to the aquifer.
2. Well construction, design, and operation.
3. Injectate quality.
4. Volumes of waste injected.
Wells injecting below the lowermost USDW have the
least potential for contaminating ground water. Class V
injection directly into USDW is potentially more harmful
to the water quality than discharges above the water
table. This is because some contaminants are removed
from the waste by attenuation, adsorption and degrada-
tion in the unsaturated zone.
Based on inventories conducted by the states, it is
estimated that there are hundreds of thousands or more
Class V wells in the United States and its Territories and
Possessions. There are seven main categories of Class V
injection wells which contain the 30 individual well types.
Most Class V wells belong to two main categories: drain-
age wells and sewage related wells.
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PUBLIC AWARENESS: THE
KEY TO PROTECTING
DRINKING WATER
The large number of Class V wells releasing a wide
variety of contaminants pose a significant threat to
ground water supplies. Almost half of the U.S. popula-
tion receives their drinking water from underground
sources. Therefore, it is imperative that these supplies
be adequately protected. The threat to ground water
from Class V practices can be significantly reduced by
utilizing the best management practices available at the
local or regional level. One example of a regional prac-
tice would be the optimal application of pesticides and
fertilizers to reduce the amount of chemicals that would
reach ground water through agricultural drainage wells.
An example of a local management practice would be a
public awareness program to educate people on the det-
rimental effects of disposing of household chemicals into
a septic system. Household chemicals, when discharged
into a septic system, can directly contaminate ground
water and can reduce the effectiveness of the septic sys-
tem to remove other potentially harmful contaminants.
Some types of Class V wells may require stricter regu-
lation than those currently in place. The UIC program
addresses only a part of the overall threat to underground
sources of drinking water. At the local level, a UIC pro-
gram integrated with careful planning and the utilization
of best management practices available and other ground
water protection initiatives can significantly reduce the
threat to our drinking water supplies.
For additional information you can contact the USEPA
Safe Drinking Water Hot Line: 1 -800-426-4791.
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Table 1
Class V Wells
Ground Water Estimated States With
Contamination POTENTIAL Number of * High Numbers
NAME OF WELL TYPE AND DESCRIPTION Potential CONTAMINANTS Wells Of Wells (Reported)
DRAINAGE WELLS (a.k.a. DRY WELLS)
Agricultural Drainage Wells — receive irrigation tailwaters, other field
drainage, animal yard, feedlot, or dairy runoff, etc.
High
Pesticides*, nutrients*, pathogens, metals transported by
sediments, salts.
1338
Idaho, Iowa, Texas, NY
Storm Water Drainage Wells — receive storm water runoff from paved
areas, including parking lots, streets, residential subdivisions, building
roofs, highways, etc.
Moderate
Heavy metals (Cu, Pb, Zn) organics, high levels of coliform
bacteria. Contaminants from streets, roofs, landscaped ar-
eas, Herbicides, Pesticides.
90,333
Arizona, NY, Indiana, Florida,
Utah, Washington
Improved Sinkholes — receive storm water runoff from developments
located in karst topographic areas.
High-Moderate
Variable: pesticides, nutrients, coliform bacteria
479
Michigan, Kentucky, Missouri
Industrial Drainage Wells — wells located in industrial areas which
primarily receive storm water runoff but are susceptible to spills, leaks, or
other chemical discharges.
High-Moderate
Usually organic solvents, acids, pesticides, and various other
industrial waste constituents. Similar to storm drainage wells
but usually higher concentrations.
3,799
New York, Washington, Utah
Special Drainage Wells — used for disposing water from sources other
than direct precipitation. Four types were reported: landslide control drain-
age wells (Montana), potable water tank overflow drainage wells
(Idaho),swimming pool drainage wells (Florida), and lake level control
drainage wells (Florida).
Moderate-Low
Chlorinated and treated water, pH imbalance, algaecides,
fungicides, muriatic acid.
1,555
Florida
GEOTHERMAL REINJECTION WELLS
Electric Power Reinjection Wells — reinject geothermal fluids used to
generate electric power — deep wells.
Moderate
pH imbalance, minerals and metals In solution. (As,Bo,Se),
sulfates
89
California, Nevada
Direct Heat Reinjection Wells — reinject geothermal fluids used to gener-
ate heat for large buildings or developments — deep wells.
Moderate
Hot geothermal brines with TDS between 2,000 to
325,000 mg/l. Co,, CaSO„ Sr, and Ba, As.
21
Nevada, Oregon
Heat Pump/Air Conditioning Return Flow Wells — reinject groundwater
used to heat or cool a building in a heat pump system — shallow wells.
Low
Potable water with temperatures ranging from 90° to 110° F.,
may have scale or corrosion inhibitors.
10,006
Texas, Virginia, Florida
Groundwater Aquaculture Return Flow Wells — reinject groundwater or
geothermal fluids used to support aquaculture. Non-geothermal aqualcul-
ture disposal wells are also included in this category (e.g. Marine aquari-
ums in Hawaii use relatively cool sea water).
Moderate
Used geothermal waters which may be highly mineralized &
include traces of arsenic, boron, fluoride, dissolved & sus-
pended solids, animal detritus, perished animals and
bacteria.
25
Hawaii
DOMESTIC WATESWATER DISPOSAL WELLS
Untreated Sewage Waste Disposal Wells — receive raw sewage wastes
from pumping trucks or other vehicles which collect such wastes from
single or multiple sources. (No treatment)
High
Soluble organic & inorganic compounds including household
chemicals. Raw sewage with 99.9% water and .03% sus-
pended solid. May contain pathogenic bacteria & viruses, ni-
trates, ammonia.
980
Illinois
Cesspools — including multiple dwelling, community, or regional cess-
pools, or other devices that receive wastes and which must have an open
bottom and sometimes have perforated sides. Must serve greater than 20
persons per day if receiving solely sanitary wastes. (Settling of solids)
High
Soluble organic & inorganic compounds including household
chemicals. Raw sewage with 99.9% water and .03% sus-
pended solid. May contain pathogenic bacteria & viruses, ni-
trates, ammonia.
6,622
Oregon
Septic Systems (Undifferentiated disposal method) — used to inject the
waste or effluent from a multiple dwelling, business establishment, com-
munity, or regional business establishment septic tank. Must serve
greater than 20 persons per day if receiving solely sanitary wastes.
(Primary Treatment)
High-Low
Varies with type of system; fluids typically 99.9% water (by
weight) and .03 suspended solids; major constituents include
nitrates, chlorides, sulfates, sodium, calcium, and fecal coli-
form.
26,700
Florida, Michigan,
California, Puerto Rico
Septic Systems (Well Disposal Method) — examples of wells include
actual wells, seepage pits, cavitettes, etc. The largest surface dimension
is less than or equal to the depth dimension. Must serve greater than 20
persons per day if receiving solely sanitary wastes. (Less treatment per
sqaure area that 5W32)
High-Low
Varies with type of system; fluids typically 99.9% water (by
weight) and .03 suspended solids; major constituents include
nitrates, chlorides, sulfates, sodium, calcium, and fecal coli-
form.
4,435
Michigan, Maryland, Kentucky
Septic Systems (Drainfield Disposal Method) — examples of drainfields
include drain or tile lines, and trenches. Must serve more than 20 persons
per day if receiving solely sanitary wastes. (More treatment per square
area than 5W31)
High-Low
Varies with type of system; fluids typically 99.9% water (by
weight) and .03 suspended solids; major constituents include
nitrates, chlorides, sulfates, sodium, calcium, and fecal coli-
form.
3,764
Waska, California, South Carolina
Domestic Wastewater Treatment Plant Effluent Disposal Wells—dispose
of treated sewage or domestic effluent from small package plants up to
large municipal treatment plants (Secondary or further treatment)
High-Low
Lower levels of organics and bacteria than other septic
systems and cesspools.
1,099
Florida, Hawaii
MINERAL AND FOSSIL FUEL RECOVERY RELATED WELLS
Mining, Sand, or Other Backfill Wells — used to inject a mixture of water
and sand, mill tailings, and other solids into mined out portions of
subsurface mines whether what is injected is a radioactive waste or not.
Also includes special wells used to control mine fires and acid mine
drainage wells.
Moderate
Acidic waters
6,500
Missouri, Pennsylvania, Idaho
Solution Mining Wells — used for in-situ solution mining in conventional
mines, such as stopes leaching.
Moderate-Low
2-4% sulfuric acid. pH less than 2 for copper & ferric cyanide
solution for gold or silver.
2,025
Arizona, New Mexico
In-Situ Fossil Fuel Recovery Wells — used for in-situ recovery of coal,
lignite, oil shale, and tar sands.
Moderate
Steam, air, solvents, igniting agents.
66
Wyoming, Colorado
Spent-Brine Return Flow Wells — used to reinject spent brine into the
same formation from which it was withdrawn after extraction of halogens
or their salts.
Low
Variable
121
Arkansas, Michigan
INDUSTRIAUCOMMERCIAL/UTILITY DISPOSAL WELLS
Cooling Water Return Flow Wells—Used to inject water which was used
in a cooling process, both open and closed loop processes.
Low-Moderate
Anti-sealing additives, thermal pollution, potential for
industrial spills reaching ground water.
289
Idaho, Michigan, Florida
Industrial Process Water and Waste Disposal Wells—used to dispose of
a wide variety of wastes and wastewaters from industrial, commercial, or
utility processes. Industries include refineries, chemical plants, smelters,
pharmaceutical plants, laundromats and dry cleaners, tanneries, car-
washes, laboratories, etc. Industry and waste stream must be specified.
(e.g. Petroleum Storage Facility — storage tank condensation water;
Electric Power Generation Plant — mixed waste stream of laboratory
drainage, fireside water, and boiler blowdown; Car Wash — Mixed waste
stream of detergent, oil and grease, and paved area washdown; Electro-
plating Industry — spent solvent wastes; etc.)
High
Potentially any fluid disposed by various industries, sus-
pended solids, alkalinity, sulfate volatile organic compounds.
1,938
Ohio, New York, Alaska
Automobile Service Station Disposal Wells—repair bay drains connected
to a disposal Well. Suspected of disposal of dangerous or toxic wastes.
High
Heavy metals, solvents, cleaners, used oil and fluids, deter-
gents, organic compounds.
98
Michigan, New Jersey, Alaska
RECHARGE WELLS
Aquifer Recharge Wells — used to recharge depleted aquifers and may
inject fluids from a variety of sources such as lakes, streams, domestic
wastewater teatment plants, other aquifers, etc.
High-Low
Variable: water is generally of good quality.
3,551
New York, Florida
Saline Water Intrusion Barrier Wells—used to inject water into fresh water
aquifers to prevent intrusion of salt water into fresh water aquifers.
Low
Varies: advanced treated sewage, surface urban and agricul-
tural runoff, and imported surface waters.
164
California
Subsidence Control Wells — used to inject fluids into a non-oil or gas
producing zone to reduce or eliminate subsidence associated with over-
draft of fresh water and not used for the purpose of oil or natural gas
production.
Low
No specific type of injected fluid noted, similar to aquifer
recharge wells.
4
Wisconsin
MISCELLANEOUS WELLS
Radioactive Waste Disposal Wells — all radioactive waste disposal wells
other than class IV wells.
Unknown
Low-level radioactive wastes.
122
Washington
Experimental Technology Wells—wells used in experimental or unproven
technologies such as pilot scale in-situ solution mining wells in previously
unmined areas.
Low-Moderate
Varies depending on project
225
Wyoming, Arizona
Aquifer Remediation Related Wells — wells used to prevent, control or
remediate aquifer pollution, including but not limited to Superfund sites.
Unknown
Nutrients used in Biodegradation of organics, oil/grease, phe-
nols, toluene.
353
Colorado, Michigan, New Mexico
Abandoned Drinking Water Wells — used for disposal of waste.
Moderate
Potentially any kind of fluid, particularly brackish or saline
water, ha7arrlniis dipmicals and sewage.
3,050
Minnesota, Texas
Other Wells —any other unspecified Class V wells. Well type/purpose and
injected fluids must be specified.
Unknown
Variable
37
Florida, North Dakota
Inventory based on 1987 Class V Report to Congress
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