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Stiles Mining Resource <br /> Groundwater Monitoring and Mitigation Plan <br /> December 2022 <br /> Page 7 <br /> ■ Continue quarterly monitoring until two (2)consecutive quarters of groundwater <br /> monitoring indicate results are at or below site-specific groundwater quality benchmark <br /> value(s). <br /> ■ Conduct a statistical trend analysis to determine: 1) if exceedances are statistically <br /> significant increases over background; and/or 2)if a new site-specific groundwater <br /> quality benchmark is appropriate(to be submitted to DRMS as a Technical Revision). <br /> ■ Discuss options available with down-gradient adjacent well owner(s)within 600-feet to <br /> reach a mutually agreed upon solution to replace the water sourced from the impacted <br /> well with an appropriate alternate water source for equivalent use(e.g., install new well, <br /> water tap connection, etc.). <br /> 4.0 GROUNDWATER QUANTITY MONITORING <br /> ASCI will pump groundwater to facilitate dry mining at the Site which will affect groundwater <br /> levels within the alluvial aquifer GWBU.As a result,ASCI will monitor groundwater levels at the <br /> Site boundaries to observe any affects from pumping and to identify potential adverse off-site <br /> impacts to nearby wells completed within the alluvial aquifer.According to the Colorado Division <br /> of Water Resources (DWR) Colorado's Decision Support System (CDSS) Well Permit Viewer, <br /> the transmissivity of water flow through the alluvial aquifer in this area generally ranges between <br /> 80,000 to 100,000 gallons per day per foot(gpd/ft). All nearby alluvial aquifer wells identified are <br /> anticipated to be hydraulically up-gradient or cross-gradient relative to any area being mined at <br /> the Site. Five (5) off-site wells have been identified on adjacent properties within 600 feet of the <br /> permit boundary (Well Permit Numbers: 55498-MH, 55499-MH, 103102, 299707, and 283674). <br /> The location of these wells are shown on Figure 2. <br /> 4.1 MONITORING WELL NETWORK <br /> A monitoring well network of seven (7) wells will be used to observe groundwater levels in the <br /> alluvial aquifer GWBU at the Site boundaries.The network will consist of the six(6)groundwater <br /> quality monitoring wells(MW-1 through MW-6)and a seventh well(MW-7)completed along the <br /> eastern Site boundary. The location of these wells are shown on Figure 2. <br /> 4.2 GROUNDWATER MEASUREMENT FREQUENCY AND SCHEDULE <br /> Beginning in March 2022, ASCI will collect monthly groundwater elevation readings from <br /> monitoring wells MW-1 through MW-7 to establish baseline groundwater level conditions at the <br /> Site prior to commencing mining operations (Pre-Operational Groundwater Level Monitoring). <br /> ASCI will continue to collect monthly groundwater elevation readings (i.e., current groundwater <br /> level monitoring schedule)for a minimum of four(4)consecutive quarters after mining operations <br /> begin(Post-Operational Groundwater Level Monitoring). Any change to the current groundwater <br /> level monitoring schedule(i.e., reduction in measurement frequency)will be submitted to DRMS <br /> via Technical Revision for approval prior to implementing. <br />