2008-03-05_REVISION - M1997054 (24)

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Based on the results reported in these geotechnical testing summaries, in conjunction with existing geologic records of the area in and around the granite quarry, dewatering is unexpected at this time. Thus, anticipated impacts to adjacent groundwater systems are expected to be negligible. The operator does acknowledge that granitic fractures may exist within the quarry that contain subsurface water, and they propose that should such a fracture be unearthed immediate action to ensure the absence of injury to any adjacent water user will be taken. CONCLUSIONS AND RECOMMENDATIONS The effects of the dewatering operation at the Parkdale Aggregate Mine should not result in adverse impacts to existing structures, including wells. The maximum drawdown at any existing well due to the mining operation is expected to be less than half a foot principally due to the presence of the constant head boundary of the Arkansas River. COLLECTION OF MONITORING DATA The analytical approach discussed herein was made necessary by the lack of existing monitoring well data in area. This approach does however present a very conservative estimate of the potential maximum drawdown anticipated during mining operations. Prior to commencement of dewatering operations, the operator may need to install monitoring wells to collect pre-mining ground water data, as required by the DRW. The wells should be located throughout the permit area, spaced at regular intervals as needed. The monitoring should continue throughout the duration of mining. The collection of this data would allow for more detailed analysis of impacts during and post-mining and evaluation of potential mitigation measures should they become necessary. The collection of monitoring data would also allow the comparison of actual drawdown surrounding the pit and the modeled results presented herein. It is expected that the predicted effects would exceed the actual effects due to the conservative nature of the modeled parameters. However, if the actual effects are greater than those predicted mitigation measures may be required. MITIGATION OF IMPACTS DURING MINING The largest impacts on the surrounding hydrologic balance will be confined to the areas to the west and northwest of the site. Though we do not expect any adverse impacts to existing structures, the operator should be prepared to instigate mitigation measures should they become necessary. Possible mitigation measures include: • Providing substitute supplies of water to wells adversely impacted by the dewatering operation; • Deepening of existing wells or lowering of existing pumps therein; ' • Placement of recharge trenches bordering the site to help alleviate impacts to the surrounding ground water table, and Parkdale Aggregate Mine I Conclusions and Recommendations •