The Underground Injection Control Program (UIC) protects
ground water quality by regulating the disposal of fluids into the
subsurface. Most UIC wells or injection wells are simple devices that allow
fluids into the shallow subsurface under the force of gravity. For example,
in Washington State (Washington) thousands of UIC wells, mainly dry wells, are located
along parking lots and roads to manage stormwater runoff. The potential for
ground water contamination from UIC wells can occur and is dependent on the
well construction and location, the volume and quality of the fluids
injected and the hydrogeologic setting.
The UIC Program, authorized by the Safe Drinking Water Act, is
Title 40 Code of Federal Regulations (CFR) part 144. Washington
Department of Ecology was delegated authority by the Environmental
Protection Agency (EPA) in 1984 to administer the program (RCW
43-21A.445). State regulation
Chapter 173-218 WAC (Underground Injection Control Program) is used to
administer the program.
Injection wells are man-made or improved holes in the
ground, deeper than they are wide at the ground surface, or an improved
sinkhole or a sub-surface fluid distribution system. They are used to
release or dispose of fluids underground. Examples include sumps,
drywells, drainfields and infiltration trenches that contain perforated
pipe. A fluid
is any flowing matter, regardless of whether it is in a semisolid, liquid,
sludge, or gaseous state. The fluid may be injected for a beneficial use
(e.g. ground water recharge or at an aquifer remediation site) or
potentially harmful (e.g. misuse of a septic system by accepting fluids
other then sanitary waste).
EPA groups injection wells
into five classes, depending on the type of waste to be disposed in
- Class 1: receives industrial, commercial, or municipal waste
fluids injected beneath the lowermost formation containing an
underground source of drinking water (USDW) within 1/4 mile of where the
well was drilled. Class 1 wells are prohibited in Washington.
- Class 2: receives fluids that are brought to the surface as part of
oil or natural gas exploration, recovery or production.
- Class 3:
used for mineral extraction. 2 basic types: solution mining and in-situ
leaching for minerals. Class 3 wells are prohibited in Washington.
- Class 4: receives radioactive or hazardous waste injected into or
above underground sources of drinking water. Class 4 wells are
prohibited in Washington except for Class IV wells used at an approved
Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA) or Resource Conservation
and Recovery Act (RCRA) facility that reinjects treated ground
water into the same formation.
- Class 5: all other injection
practices not included in the other classes. Class 5 injection wells,
the most common injection well in our state, are generally shallow wells
used to discharge fluids into or above a
ground water aquifer. In many cases, these aquifers are shallow,
unconfined or surficial. Large on-site septic systems, serving 20 people
or more per day or having a capacity of 3,500 gallons per day, are
considered Class 5 wells.
- Class 6: wells
used for injection of carbon dioxide (CO2) into underground subsurface
rock formations for long-term storage, or geologic sequestration.
Geologic sequestration refers to a suite of technologies that may be
deployed to reduce CO2 emissions to the atmosphere to help mitigate
There are two main requirements of the program:
- A non-endangerment
performance standard must be met, prohibiting injection that allows the
movement of fluids containing any contaminant into ground water. In
Washington, all ground water is considered a potential source of
All well owners must provide inventory
information by registering their wells with Ecology (or with
EPA, Region 10, if the wells are located on tribal land).
For more information visit the registration form page at
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Last updated December 2012
Copyright © Washington State Department of Ecology. See http://www.ecy.wa.gov/copyright.htm