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associated with gas storage wells warranted that these wells be studied further before subjecting <br />them to regulation equivalent to other Class II wells. <br />Class III, which includes special process wells (including those used for solution mining) <br />are classified separately from other wells because of their atypical injection practices. Special <br />process wells serve a variety of purposes, including the extraction of minerals or other materials <br />from the earth. Individual domestic injection wells used to generate heat and/or electricity, <br />although special process wells, have been included in Class V. The Agency chose to consider <br />these systems under Class V due to the limited impact on underground sources of drinking water <br />anticipated from these wells. It should be noted that domestic syst ems utilizing a closed loop in <br />conjunction with heat exchangers are not injection wells and consequently, are not covered under <br />these regulations. <br />In the course of public review, a number of commenters urged that Class III wells be <br />subcategorized In response, the Agency commissioned a study to provide information on this <br />issue.' Based on this study it does not appear that either current operating and construction <br />practice for existing State regulations governing such wells differentiate sufficiently to warrant <br />subcategorizing Class III wells. Consequently, the final regulations do not establish <br />subcategories for Class III wells. <br />As stated earlier, Class IV wells injecting into a USDW are banned; decisions concerning <br />Class IV wells injecting above an USDW are being reserved. In order to afford some level of <br />protection before the final promulgation of regultions for Class IV wells and implementation of <br />State UIC programs, all injectors of hazardous waste must obtain "interim Status" under the <br />RCRA hazardous waste management program. The Agency decided to reserve final decisions <br />concerning Class IV wells which inject above USDW's for several reasons. Commenters pointed <br />out that injection wells which overlie deep or remote drinking water supplies would have little or <br />no potential for contaminating the aquifer and thereby endangering health. Moreover, portions of <br />some aquifers may be so deep or so remote that they may never serve as drinking water sources, <br />or may not be subject to contamination from injection practices. <br />A further reason for the proposed approach is that regulations under RCRA and SDWA overlap <br />at several points. Facilities under Class I and Class IV overlap the class of facilities designated <br />under RCRA as hazardous waste management facilities. It is, therefore, appropriate that <br />technical standards under RCRA and UIC be consistent, to the extent allowable under the <br />governing statutes, for facilities capable of causing a similar degree of risk. <br />EPA anticipates issuance of permitting standards for HWM facilities until fall 1980. <br />Adoption of UIC standards now for class IV wells could prove misleading to the States and the <br />public, because EPA might decide this fall to revise the standards to reflect policy decisions <br />9 Development of Procedures for Subclassification of Class III Injection Wells, Geraghty <br />and Miller, April 30, 1980. <br />Page 6 of 20