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EPA standards is constructed with specifications similar to those for a Class I well. In 1980,
Congress added Section 1425 to the SDWA that controls underground injection, relieving Class II
well programs from having to meet the technical requirements in the UIC regulations. Instead, they
can make a demonstration that the state has an
…effective program (including adequate record-keeping and reporting) to prevent underground injec-
tion which endangers drinking water sources.
Most of the oil and gas injection wells are located in the Southwest, with Texas having the largest
number (53,000) and California, Oklahoma, and Kansas having about 25,000, 22,000 and 15,000
wells, respectively (U.S. EPA, 2002a). More than 700 million gallons of liquids are injected annu-
ally into Class II wells (U.S. EPA, 2002b).

17.4.3.3 Mining Wells (Class III)
A number of minerals are mined by using injection wells. The technology involves the injection
of a fluid, called lixiviant, which contacts an ore containing minerals that dissolve in the fluid. The
lixiviant fluid, nearly saturated with components of the ore, is pumped to the surface where the
mineral is removed from the fluid. In situ leaching of uranium is the practice of injecting a fluid
to leach out the uranium salts and pumping it back to the surface where the uranium is extracted.
About 80% of the uranium extracted in the United States is produced using this technique (U.S.
EPA, 2002b).
The EPA protects drinking water from contamination from mining wells by implementing reg-
ulations that set minimum standards. These regulations require mining well operators to:

● Case and cement their wells to prevent the migration of fluids into an underground drink-
ing water source
● Never inject fluid between the outermost casing and the well bore
● Test the well casing for leaks at least once in every 5 years

17.4.3.4 Shallow Hazardous and Radioactive Injection Wells (Class IV)

Class IV wells are defined in 40 CFR 146.5(d) as:
Wells used by generators of hazardous waste or of radioactive waste, by owners or operators of haz-
ardous waste management facilities, or by owners or operators of radioactive waste disposal sites to dis-
pose of hazardous waste or radioactive waste into a formation which within one quarter mile of the well
contains an underground source of drinking water.

A second category includes wells that:
…dispose of hazardous waste or radioactive waste above a formation which within one quarter mile of
the well contains an underground source of drinking water.
Class IV wells are prohibited unless the injection wells are used to inject contaminated groundwa-
ter that has been treated and is being injected into the same formation from which it was drawn.
These wells are authorized by rule for the life of the well if the EPA or a state, pursuant to provi-
sions in CERCLA or RCRA, approves emplacement of fluids.

17.4.3.5 Shallow Injection Wells (Class V)

Class V wells are a diverse grouping and are considered a ‘catch-all’ category; wells not included
in the previous four classes that inject nonhazardous fluids into or above formations that contain
USDW fall into Class V. This category came about after all the easily definable wells were placed