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<br />provides for 25 monitoring completions, including g lower aquifer completions, 12 upper aquifer <br />completions and 4 alluvial aquifer completions. The monitoring well locations are shown in <br />Figure 1 of the Water Monitoring Plan, which was added to the Permit at the suggestion of <br />commeutors. <br />Water level and water quality monitoring will occur on a monthly basis, except for the <br />water level monitoring of the Dissolution Surface which will occur weekly. The head changes in <br />the zone adjacent to the Dissolution Surface will be monitored weekly with atransducer/surface <br />recorder system during commercial mining. The Apri122°d plan called for monitoring the <br />Dissolution Surface at 3 different locations. This has not changed in the revised plan incorporated <br />into the Permit. EPA believes that the proposed Dissolution Surface monitoring locations and <br />frequency are adequate for initial mining activities. EPA does not believe that continuous <br />water level monitoring of the Dissolution Surface is needed at this time. <br />In addition to the existing monitoring wells, EPA is allowing the operator to install <br />multiple completion monitoring wells. The Water Monitoring Plan presently calls for three such <br />completions. These wells must be completed in a manner that will ensure isolation of each zone. <br />However, if zone isolation cannot be demonstrated, the operator will have to install separate wells <br />for each zone. These monitoring data will be evaluated at the end of the first year of operation to <br />determine if changes to the monitoring plan related to the well completion design are warranted. <br />EPA acknowledges that the specifics of the operators draft monitoring plan were not <br />clearly articulated in the Draft Permit. The status of aU of the actions provided for in the draft <br />Water Monitoring Plan was not clearly articulated. Provisions for modifying the monitoring plan <br />and having these changes covered were also unclear. To avoid potential confusion regarding <br />actual ground-water monitoring requirements of the Permit and to provide a mechanism <br />for modifying the Water Monitoring Plan, the revised Water Monitoring Plan dated <br />December 23, 1999, has been incorporated into the Final Permit as Appendix L Key <br />elements of the monitoring plan are also summarized separately in Section D. 1. of the <br />Permit. <br />With the exception of domestic wells, the revised Water Monitoring Plan now calls for <br />monthly monitoring during the baseline period. The water quality monitoring requirements do not <br />include monitoring for total organic carbon. However, the Plan does require process water <br />monitoring for BETX, dissolved organic carbon, methane and oil and grease. EPA believes that <br />this monitoring will detect break down of the oil shale sufficiently to allow decisions to be made <br />regarding modifications to the ground-water monitoring requirements. With regards to the <br />suggestion that additional monitoring wells are needed at the Parachute site, this facility is not <br />included within the scope of this UIC Permit. Thus, EPA has no authority to requve monitoring <br />of any wells at that site. <br />EPA agrees with commentors that subsidence is an important issue and includes <br />subsidence monitoring requirements in the Permit. With an extraction ratio as low as 12 percent, <br />however, the Yankee Gulch Project is expected to have faz fewer subsidence effects than room- <br />and-pillar mining operations. The applicant has performed substantial site operational simulations, <br />21 <br />