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<br />There are, however, fractures and dissolution features which may allow some vertical fluid <br />movement. The best description of the Mahogany zone may be that of an aquatazd which limits <br />the vertical movement of fluids. The fact that there could be some vertical fluid movement was <br />the basis of the requirement that there be 150 feet of the saline zone cap rock above the cavity. <br />EPA has reviewed this comment and the information associated with the discussion in the <br />SOB and has determined that no changes to the Permit are necessary in response to this <br />comment. <br />Comment 14: The Financial Assurety should cover the costs of eround-water quality <br />remediation as well as the costs of closinz, plugeine, and abandonine the wells. <br />Response; Although the operator of the Yankee Gulch project is required to carry out any <br />measures necessary to prevent endangerment ofUSDWs (See 40 CFR 144.12 and 40 CFR <br />144.51(d)), including any cleanup and monitoring prescribed by the Director (See 40 CFR <br />146.10(d)), establishing a bond for such activities is beyond the scope of the existing UIC <br />regulations. Establishment of a bond for remediation-focused corrective action would have to be <br />based on the assumption that some type of failure would occur and that it would be possible now <br />to establish a basis for the size of the bond. Thus, establishment of a bond to cover an unknown <br />and unplanned type of excursion is not feasible or warranted. However, the purpose behind the <br />construction, operating and monitoring measures in the Permit is to prevent well failure and <br />unauthorized fluid movement. 40 CFR 144.52 (a)(7) requires the operator to demonstrate and <br />maintain financial responsibility and resources to close, plug and abandon the UIC operation in a <br />manner prescribed by the Director. EPA does not believe that the financial assurance requirement <br />requires bonding to cover hypothetical future well failures or excursions from a cavity. As <br />explained in Comment 17, however, the Duector does have the authority to require the operator <br />to use their resources to undertake clean-up of certain excursions or failures to ensure protection <br />of USDWs. <br />The ezistence of this authority to require aquifer clean-ups as appropriate to protect <br />non-contaminated USDWs does not require that the Permittee's bond today cover the <br />highly speculative cost of any such cleanups. No changes will be made to the bonding <br />requirements in the Permit as a result of this comment. EPA will, however, track the <br />monitoring results, especially the NIIT related monitoring. If there are failures that result <br />in excursions that could affect USDWs, modifications to the plugging abandonment plan <br />may be required (also see response to Comment 17). <br />Comment 15: I am concerned that the Drag SOB for this project sienificantly misrepresents the <br />existine water quality of the Upper and Lower aciuifers and the hydro-geologic conditions at this <br />site. (SOB. Pages 5-8) <br />Response: Site-specific ground-water quality data that were collected by American Soda during <br />its experimental Class V operations indicate that the location of potential USDWs is limited to the <br />Uinta Formation portion of the Upper Aquifer. Concerns regarding potential limitations of the <br />ground-water data collected during the test phase were the underlying reason for the requirement <br />31 <br />