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Permit to document the naturally-occurring concentrations of the listed constituents in the <br />A2 sandstone at the location of the injection well. <br />3. The Final Permit requires the permittee to collect composite samples of stored A2 <br />sandstone groundwater samples collected from both storage tanks. The samples will be <br />analyzed for "Total Coliforms; Total Metals for arsenic, barium, cadmium, chromium, <br />lead, mercury, selenium, and silver; Volatile Organic Compounds; Semi-volatile Organic <br />Compounds; and Total Petroleum Hydrocarbons. The analytical results will be submitted <br />to the EPA for review and approval before EPA authorizes reinjection of the stored <br />groundwater back into the A2 sandstone. This requirement was added in response to <br />concerns that the stored groundwater may be contaminated after being pumped to the <br />surface during the aquifer-pump test and before reinjection. <br />4. The Final Permit establishes a Maximum Allowable Injection Pressure of zero at the well <br />head. This requirement is included as a response to concerns that injection under <br />pressure could result in A2 sandstone groundwater moving across a confinement zone <br />into another underground source of drinking water. <br />5. The Final Permit includes new mechanical integrity test requirements appropriate for <br />PVC-cased wells with no injection tubing. This requirement was changed because of the <br />concern that the mechanical integrity test procedure in the Draft Permit does not work on <br />wells with PVC casing and no injection tubing inside the well casing. Because the <br />Maximum Allowable Injection Pressure is zero, the requirements for mechanical integrity <br />tests on the injection well are no longer linked to the injection pressure. <br />Response to Comments <br />1. Comments related to the administrative procedures for the Draft Permit. The EPA <br />received requests for an extension of the public comment period for the first Draft Permit to <br />provide time for interested parties to submit information about closure procedures used for <br />historic exploratory boreholes drilled at the Centennial Project site. There was also a concern <br />that errors in the permit number in the first Draft Permit were potentially confusing to the public. <br />Commenters also expressed concern that the public hearing for the first Draft Permit was held in <br />a location that was too far away from the residents who lived near the proposed site for the <br />injection activity. <br />EPA Response: <br />In response to the comments regarding potential public confusion, the EPA issued a <br />second Draft Permit with the corrected permit number and offered a second public comment <br />period. The EPA wanted to ensure that there was proper clarity on the Administrative Record <br />and ample opportunity for the public to comment on this UIC Class V permitting action. EPA <br />held a second public hearing for the second Draft Permit in Nunn, Colorado, closer to the site of <br />the proposed injection activity. <br />Page 3 of 24