2021-09-09_REVISION - M2004044 (10)

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new well in roughly the same location in 2018. MW-11 will not be reinstalled as the area of the well is adjacent to the river and Todd Creek has monitoring wells that they monitor as part of their alluvial wellfield. For the wells around the East and West Mine areas, monthly water monitoring would continue to be appropriate. If sufficient data is collected during the life of the mining operation, and a demonstration can be made that impacts to the groundwater system have been minimized, Al can Apply to the Division would consider approval of a Technical Revision to revise the water level monitoring frequency at a later date. The Monitoring Plan will now consist of 16 monitoring wells. Monitoring data will be used to identify potential changes in alluvial groundwater flow or elevation associated with mining and reclamation activities. Baseline data collected from the monitoring program will provide a range of relative water levels associated with pre-mining groundwater conditions. Experience at other sand and gravel mine sites in similar geologic settings shows that groundwater levels tend to fluctuate between two to four feet each year; levels are highest in the summer and lowest in the winter and early spring. Al will meet with the nearby well owners and enter into a monitoring and mitigation agreement with them. The details of the Mitigation Plan are provided below. • If, during mining, the relative seasonal groundwater elevation at any of the domestic wells or monitoring wells differs from the baseline conditions by more than two feet, and the condition was not observed during baseline monitoring, or if Aggregate Industries receives a complaint from any well owner within 600 feet from the site boundary, then Aggregate Industries will notify the DRMS and then evaluate the cause and take action within 30 days. • After the DRMS has been notified. Aggregate Industries will review the available data and information and submit a report to the DRMS within 30 days. The evaluation will include discussions with any well owner who has contacted Aggregate Industries regarding a concern, and a review of baseline data from the well and vicinity to evaluate potential changes due to seasonal variations, climate, mining, or other factors. The report will identify the extent of potential or actual impacts associated with the groundwater changes. If the extent of groundwater changes due to mining or reclamation activities is determined to be a significant factor creating potential or actual adverse impacts, the mining-associated impacts will be addressed to the satisfaction of the DRMS. Aggregate Industries will begin to implement one or more mitigation measures. • Mitigation measures may include, but are not limited to: • Cleaning a well to improve efficiency. • Providing an alternative source of water or purchasing additional water to support historic well use water quantity and quality. If needed, water quality parameters will be checked in affected wells to ensure alternative sources support the historic use. • Modifying a well to operate under lower groundwater conditions. This could include deepening existing wells or lowering the pumps. All work would be done at Aggregate Industries' expense except for replacing equipment that was non- functional prior to mining. • If existing wells cannot be retrofitted or repaired, replacing the impacted well with a new replacement well. Aggregate Industries—Tucson South Amendment—MLRB 112 Permit Application Exhibit G-8