1999-11-24_PERMIT FILE - M1999051

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mining interval up through the Dissolution Surface will be conducted at baseline and every six months. These logging results will be included in annual reports. Increases in the temperature, which indicate a casing or cavity leak, will be reported to the DMG the next business day following verification. 7.c) The baseline water characterization plan, as part of the Surface Water and Ground Water Monitoring Plan,contemplates data collection until sufficient data have been collected to statistically characterize baseline conditions. This characterization will be conducted prior to injecting heated and pressurized mining solutions. 7.d)Horizontal gradients in the various aquifers are well established in the Piceance Basin. The average hydraulic gradient of the Upper and Lower Aquifers from the upper reaches of Stake Springs Draw to the lower reaches of Yellow Creek is 67 and 57 feet per mile (ft/mi)respectively. Closer to the Rock School Lease,the hydraulic gradient is 53 ft/mi in the Upper Aquifer and 26 ft/mi in the Lower Aquifer. The direction of flow near the Rock School lease is 42 degrees east of north for the upper aquifer and 52 degrees east of north for the lower aquifer. Documentation of these gradients is presented in Attachment 6—Letter dated September 20, 1999, to Roger Day from Jerry Daub. Te) The proper method of analyses are identified in Tables 2 and 3 in the Surface Water and Ground Water Monitoring Plan. 8. Proposed surface and subsurface subsidence monitoring and reporting are presented in the Monitoring Plan included with this document as Attachment 4. Comments from the DMG in a letter dated September 27, 1999, included a request to show on a map the locations of subsidence monuments. Surface subsidence reference monuments will be located outside of the potential zone of influence and will consist of existing USGS Section markers and other monuments yet to be established. Surface subsidence monuments within the potential zone of influence will consist of the actual production and monitoring well heads. These facilities are shown on the Revised Figure C-1 included as Attachment 1. Other monuments will be added,and their locations on specific maps will be provided to the DMG in a Technical Revision at least 60 days before start-up of solution mining. Surface and subsurface subsidence monitoring information will be included in the annual report for routine data or reported to the DMG within five business days if surface subsidence is detected or if subsurface subsidence is detected which could harm the USDW bedrock aquifers Pre-operational baseline logging of each production well will include gamma, casing integrity, and cement bond. This logging will conform to practices generally accepted in the profession and commonly interpreted using standard techniques. When production reaches 75,000 tons in any cavity, gamma logging for the production well for that cavity will be repeated and compared to baseline conditions. If any wells are plugged and abandoned before producing 75,000 tons, gamma logging will be done and compared to baseline if mining recovery the cavity for that well exceeded 50,000 tons. 5 DMG 11-23-99 Response AmenAlia,Inc.