Frequently Asked Questions about the UIC Program | Region 10 | US EPA

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Frequently Asked Questions about the UIC Program

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For additional information, mail or call Thor Cutler, 206-553-1673

Q: What does "UIC" mean and what's the purpose of the UIC program?
A: "UIC" stands for "Underground Injection Control." This is a program authorized by the Safe Drinking Water Act to protect ground water, a.k.a. underground sources of drinking water (USDWs), by regulating the disposal of waste fluids through underground injection wells.

Q: Where does the UIC program get its authority?
A: The UIC program is authorized by the Part C of the Safe Drinking Water Act (SDWA), PL 93-523 and Amendments. The UIC program also implements portions of the Resource Conservation and Recovery Act (RCRA), PL 94-580 and Amendments, with respect to the underground disposal of hazardous wastes. Regulations are published in Title 40 of the Code of Federal Regulations, primarily in Parts 144-146.

Part 144

Park 145

Part 146

Q: What's an USDW?
A: USDWs are defined broadly to include all fresh water aquifers unless they have been specifically exempted from protection. A USDW may be in current use as a source of drinking water, but that is not necessary. A USDW is simply any aquifer which is currently being used as a drinking water source or which is of sufficient volume and adequate quality to be a source for a public water system (25 or more connections.)

Q: What's an injection well?
A: Injection wells are defined broadly to include: boreholes, sumps, dry wells, drainfields, and other subsurface disposal devices used to put fluids into the ground.

Q: Is underground injection really necessary? Can't it simply be banned?
A: If properly situated, constructed, and operated, injection wells are by far the best way to dispose of some waste fluids. Also, not all injection wells are used for waste fluid disposal. Other common uses of injection wells include aquifer recharge, ground water clean-up, petroleum and natural gas storage, mineral production, and enhanced recovery of petroleum. The injection of hazardous waste above or into USDWs has been banned since 1985.

Q: How are all the different types of injection wells regulated?
A: All injection well owners/operators are required to operate and (eventually) close their injection wells in a manner which will prevent ground water contamination above a primary drinking water standard or other accepted human health-based limits. So the performance standard is the same for all types of injection wells. Compliance with this "non-endangerment" performance standard is ensured by EPA or a delegated state agency through the issuance of permits for some types of injection wells. However, most injection wells are authorized by rule.

Q: What does "authorized by rule" mean?
A: "Authorized by Rule" basically means that an injection well may be operated without a permit as long as two primary conditions are met. First, the injection well must be inventoried, i.e., a form must be submitted to the UIC program, which provides the UIC program with information about the injection well, for example, address of the owner/operator, physical location of the injection well, type of fluid disposed, and number of injection wells used. Second, the injection well must be constructed, installed, operated, maintained, and/or closed in a manner that protects ground water quality. If these two primary criteria can be met by the owner/operator of an injection well, an UIC permit is not needed for that injection activity.

Q: Which kinds of injection wells are authorized by rule and which ones require a permit?
A: The UIC regulations define five different classes of injection wells. Class I, II, and III wells all require permits, Class IV wells are banned, and Class V wells are authorized by rule.

Q: What are Class I wells?
A: Class I wells discharge below the deepest underground source of drinking water (USDW.) They are subdivided into industrial and municipal based on their ownership and into hazardous and non-hazardous based on the nature of the injected waste. Region 10 currently regulates a few Class I non-hazardous industrial waste wells on the North Slope of Alaska. Click here to obtain copies of current and proposed Class I permits.

Q: What are Class II wells?
A Class II wells inject fluids directly associated with oil and gas production wells. Generally, when oil or gas is produced, a lot of water comes up with the petroleum products. This "formation water" is normally saline and contaminated by the petroleum. These fluids can be disposed of in a Class II injection well along with non-hazardous waste fluids from any on-site gas plant. Wells injecting petroleum products underground for storage are also considered Class II wells. Class II wells also include enhanced recovery wells. These wells, often called "waterflood" wells, increase the production of petroleum by injecting water or other fluids into the petrolem bearing formation. There are about 800 Class II wells in Region 10, mostly located on Alaska's North Slope.

Q: What are Class III wells?
A: Class III wells inject for the extraction of minerals. These wells include sulfer mining by the Frasch process, in situ production of uranium and other metals, and solution mining of salts or potash. There are no known Class III wells in Region 10.

Q: What are Class IV wells?
A: Class IV wells inject hazardous waste fluids (as defined by the Resource Conservation and Recovery Act, RCRA, into or above a USDW. Class IV wells have been banned nationwide since 1985

Q: What are Class V wells?
A: Any injection wells which do not fit into Classes I through IV are, by default, Class V injection wells. As documented in EPA's 1987 Report to Congress, there are dozens of different types of Class V injection wells. They are described in this this table prepared by our partners in Oregon. Mostly, across the U.S. and within EPA Region 10, these wells are relatively shallow and simply constructed devices which inject under the force of gravity. The potential for Class V injection wells to pollute ground water varies markedly, depending upon factors such as the volume and quality of the injected fluid, the type(s) of soil and other geologic materials within the unsaturated zone, depth to ground water, and climate.

Q: What are the most common types of Class V injection wells in the Pacific Northwest and Alaska?
A: Urban stormwater runoff wells and sanitary wastewater disposal wells (multi-family and large commercial septic systems) are by far the most common. Less common but still significant numbers of Class V wells are used to inject vehicle maintenance waste fluids, other commercial/industrial wastewater streams and, in some areas, agricultural drainage.

Q: How big a threat to ground water quality do those sorts of shallow injection wells really pose?
A: The degree of risk to underlying ground water varies from quite high to very low, depending upon factors such as the hydrogeologic setting, well construction and operation, volume and quality of commonly injected fluids, likelihood of accidental injection, etc. For example, an injection well receiving untreated urban runoff from a commercial area and injecting it directly into an aquifer could be expected to routinely violate the non-endangerment performance standard. Further, a nearby product spill might lead to severe ground water contamination.

Q: Why does EPA regulate injection wells instead of state or local agencies?
A: Many state and local agencies do regulate different types of injection wells, either through implementation of the federal UIC program with EPA grant assistance or under some different regulatory authority. In order to implement the UIC program, state primacy agencies must have regulations at least as stringent as the federal ones, and they may be more restrictive.

Q: Which States in Region 10 have UIC program primacy, and which ones depend upon EPA to implement the UIC program?
A: Idaho, Oregon, and Washington have obtained full UIC program primacy. Alaska has UIC program primacy for the regulation of Class II injection wells. EPA has direct UIC program implementation responsibility for all classes of injection wells on Indian Lands, and for all but Class II injection wells in Alaska. Click for a list of UIC program contacts for the Region.

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