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X. Underground Injection

Source: EPA 1994 Toxics Release Inventory
Public Data Release, Appendix A:
Questions and Answers


Q71 What is an underground injection of toxic chemicals?

A Underground injection is the release of toxic chemicals below the surface of the earth. Such releases may be directed to different types of wells. Class I wells are technologically sophisticated wells that inject hazardous and non-hazardous waste into deep subsurface, isolated rock formations that are separated from the lower most underground sources of drinking water by layers of impermeable clay and rock. Generally, the largest number of facilities that practice underground injection inject waste into Class I wells. When constructed and operated in compliance with program requirements, these wells are expressly designed to prevent the movement of disposed and leachate fluids into protected aquifers. Other facilities may be injecting waste into Class V wells, which may be of concern because they may be directly discharging into aquifers protected by the Underground Injection Control program and are a high priority for inspection and enforcement follow-up. EPA bans injection of hazardous waste into or above aquifers used as sources of drinking water.

Q72 How are the TRI data used by the Safe Drinking Water Act's Underground Injection Control (UIC) Program?

A EPA and the implementing states verify the accuracy of TRIreported underground injection operations to determine if these operations are properly authorized and in compliance with the program's requirements.

Q73 Why is there such disparity from state to state in the underground injection data reported to TRI?

A Underground injection is a practice that varies widely across geographical areas of the United States. Underground injection control reporting to TRI will range from little or no data to showing millions of pounds injected annually. This is due to several factors: (1) whether a particular area's geology and hydrology is suitable for injection; (2) industry disposal, injection, and reporting practices; and (3) state laws and regulations governing underground injection control practices.

Where an area is geologically suitable for injection, there is usually a high degree of subsurface disposal activity and generally a high degree of reporting for that area. Conversely, in areas not geologically suitable for injection, there is little subsurface disposal activity and, therefore, there will be little or no reporting for that area. Industrial complexes engaged in subsurface disposal are generally located in geographically suitable locations such as the Gulf Coast, Midwest Region, Midcontinent Region, etc. The states in these geographic regions are where one may expect to find the highest TRI reporting levels. Some states have either banned underground injection or have never implemented an underground injection control program. These states will have little to no TRI reporting for underground injection.

Q74 How could a release of a toxic chemical into an underground injection well affect an area's groundwater resources?

A Underground injection of toxic chemicals may, depending on the type of well and well management practices, pose a threat of contamination to underground sources of drinking water. For this reason, each facility in the TRI database that reports a discharge to an underground injection well is checked to verify that it is permitted for such discharges. If it is not properly authorized, the facility would then be subject to state or EPA enforcement action. If the facility is properly permitted, the operation would be subject to a compliance review on a prescribed schedule.

Q75 Does EPA have any estimation of what percentage of the TRI releases to underground injection wells are going to Class I wells (deep underground injection of industrial or municipal wastes)?

A The current TRI Form R does not differentiate the underground injection releases by well type. Other UIC volume data reported by the states and the Regions indicate that the majority of TRI releases are to Class I industrial (nonhazardous) and Class I hazardous injection wells.

Q76 How are Class I injection wells monitored to ensure against any toxic releases to the environment?

A All permitted Class I wells are rigorously monitored to prevent any loss of fluids injected in the receiving geologic formations. Class I wells must be properly sited and adequately cased and cemented to protect underground sources of drinking water and isolate the injection zone; the well casing, tubing, and annular seal must be tested for mechanical integrity; a test for any fluid movement along the borehole must be run at least every five years; and the operator must identify all wells within a specified distance from the injection well bore to assure that all abandoned wells are properly plugged so that there is no potential for fluid movement by these paths.

Q77 What is the difference between a hazardous and nonhazardous Class I Injection well permit?

A All Class I Injection wells, hazardous and nonhazardous, must have an approved UIC permit to operate in the U.S. The basic difference between the two well permits is the physical, chemical, and biological makeup of the waste to be injected. Both well permits establish the necessary criteria and standards for the safe operation of these wells, in addition to protecting underground sources of drinking water from contamination. Hazardous and nonhazardous Class I injection well permits similarly address siting, construction, operation, reporting, testing, and monitoring requirements. However, the hazardous UIC well permit addresses these requirements more stringently because of the hazardous nature of corrosive and toxic wastes. There is more frequent well testing and monitoring. Additionally, since a 1988 UIC rulemaking, all Class I hazardous waste injection wells disposing a RCRA-banned hazardous waste must either complement the well permit with a rigorous technical demonstration referred to as a "No-migration Demonstration" or treat the waste to Agency-approved safe levels before disposal.

It should be noted that some state UIC programs (Primacy) require the same stringent requirements for the granting of nonhazardous UIC well permits as for hazardous well permits.

Q78 Have any Class I wells released fluids to underground sources of drinking water (USDWs), and, if so, were these wells adequately repaired?

A Instances of contamination of underground sources of drinking water by Class I wells have been rare. EPA and the states have identified only two cases where hazardous injected waste contaminated underground sources of drinking water (USDWs) and one case where a Class I well was suspected of causing contamination. All three cases occurred prior to the implementation of a state or Federal UIC program. EPA also identified eight cases where leakage from Class I hazardous wells entered non-USDW formations. These leaks were minor in nature and immediately adjacent to the well bore. All of these cases were addressed by either repairing the wells or properly plugging and abandoning operations.

Q79 What happens to abandoned operations?

A Prior to abandoning a Class I, II, or III well, the well owner or operator is required to plug the well with cement to prevent the movement of fluids either into or between underground sources of drinking water. The regulations concerning the plugging and abandoning of Class I-III wells can be found at 40 CFR 146.10.

In addition, the owner or operator of a Class I hazardous well must comply with much more stringent closure plan requirements. These owners or operators must submit a detailed closure plan as part of their permit applications and demonstrate financial responsibility (i.e., that they will be able to pay all costs associated with the closing of the well). The regulations concerning the closing of a Class I hazardous well can be found at 40 CFR 146.71.

Source: USEPA 1994 Toxics Release Inventory Public Data Release (EPA 745-R-96-002, June 1996).

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