2011-06-02_APPLICATION CORRESPONDENCE - C2010089 (19)

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• • • Murari P. Shrestha, P.E. August 25, 2010 Page 4 water supply wells on the New Horizon North and Cyprus Block properties will have very little impact on neighboring wells. The amount of water level change projected by this analysis (maximum of 0.85 feet or 1.29% of the available drawdown in neighboring wells) will not be noticeable in the operation of nearby wells. Water levels in this and other bedrock aquifers fluctuate naturally, and this water level change is well within the range of natural water level fluctuations. Wells can tolerate the natural water level changes, and they can tolerate this very small additional water level drawdown. It is important to note that the pumping amount is in line with the water use at a typical residence. Therefore, the water level interference resulting from the wells at the mine sites is not expected to be any greater than the water level interference resulting from a new home. Analysis of Impact to Neighboring Wells Resulting from Mine Dewatering All of the nearby production wells investigated produce from geologic formations below the coal or from alluvial material close to the San Miguel River. There are no nearby production wells that produce from the coal or from the overburden material above the coal. Although water level changes may occur in the coal and in the overburden material above the coal, there is no potential for impacts to neighboring wells. Alluvial wells located close to the San Miguel River are effectively located in a separate hydrogeologic system and in material of significantly greater transmissivity. Water level changes in the alluvium will not result from the mining operations, and therefore alluvial wells will not be impacted by the mine dewatering. Stream Depletions and Potential Impacts to Surface Water Rights Analysis of Lagged Stream Depletions Resulting from Well Pumping To determine the timing, location and amount of lagged stream depletions resulting from the new water supply wells at New Horizon North and the Cyprus Block mine locations, we completed Glover lagged stream depletion analyses using the Integrated Decision Support System's Alluvial Water Accounting System (IDS AWAS) software. We used the same aquifer characteristics for the Brushy Basin Formation as described above, which is appropriate given that ground water flow from streams to wells is through the Brushy Basin Formation. The points of depletion for the water supply wells at each mine property were determined based on outcrop mapping for the Brushy Basin Formation, which was provided by Western Fuels. The Brushy Basin may not be the only productive formation below the properties, but will likely be the target formation for water supply wells. Using this unit to determine the points of depletion is conservative because it is the shallowest productive unit beneath the mine areas and results in the shortest possible travel path for lagged depletions. Return flows resulting from the operation of the wells will return through septic systems and lawn irrigation return flows, which will deliver the water through shallower geologic material than the Brushy Basin Formation. Therefore, the timing of return flow accretions will be different than the timing of pumping depletions. Western Fuels provided hydrogeologic characteristics for the coal seam and the overburden material from the hydrologic analyses presented in the existing mine permit documents. Based on the provided information, a transmissivity of 160 gpd/ft and a storage coefficient of 0.000082 were determined for the return flow analysis. The www.bbawater.com Bishop- BrogdenAssociates, inc.