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Colorado Mined Land Reclamation Board <br /> Page 5 <br /> March 2, 2018 <br /> Department of Public Health and Environment(CDPHE) should one be required. LRM further commits <br /> to submitting an application to the WQCD for stormwater coverage in accordance with Colorado <br /> Discharge Permit System General Permit for Stormwater Discharge Associated with Construction <br /> Activities. LRM will develop an operations Stormwater Management Plan(SWMP) for the facilities <br /> associated with sand and gravel mining and ancillary batch plant operations. The SWMP will be kept on <br /> site so the Division can review it during an inspection. The Division finds that the proposed plan meets <br /> the requirements of Rule 3.1.6(1),which requires disturbances to the prevailing hydrologic balance of the <br /> affected land and of the surrounding area and the quality of the water in the surface water system both <br /> during and after the mining operations and during reclamation shall be minimized. <br /> Concerns have been raised regarding the mines potential impact to the groundwater quality. In <br /> accordance with Rule 3.1.7, operations that may affect groundwater quality shall comply with all state- <br /> wide groundwater quality standards established by the Water Quality Control Commission(WQCC). <br /> Given this, LRM has submitted a groundwater sampling and analysis plan. The Division required and <br /> LRM agreed to collect baseline water quality data sufficient to characterize existing groundwater quality. <br /> The WQCC Basic Standards for Groundwater Regulation 41 table values were used to establish the <br /> analyte list and analytical detection limits of the monitoring plan. LRM shall not expose groundwater or <br /> initiate dewatering operations until they have collected the required baseline water quality data. During <br /> the life of the operation, LRM will continue to monitor water quality and shall submit the results of water <br /> quality monitoring with their annual report. Through these measures, LRM will be required to comply <br /> with the applicable WQCC standards. The groundwater monitoring plan complies with Rule 3.1.7(7). <br /> b. Concerns regarding the impact of the mining operation dewatering on surrounding <br /> groundwater levels. (19) <br /> LRM modeled the potential impacts of the groundwater levels at the mine and the surrounding area <br /> during the proposed mining and reclamation operation. During mining of the five phases, drawdown of <br /> the alluvial aquifer was predicted to occur. The largest off-site drawdowns are anticipated during the <br /> mining phase north of the Little Cache La Poudre Ditch. No wells are known to exist in this area. On the <br /> south side of the mine,three wells are predicted to be impacted by dewatering operations. The Applicant <br /> has committed to monitoring water levels withinl4 monitoring wells installed at the site and several <br /> adjacent neighbors wells during the life of the mine. LRM commits to mitigating impacts to affected <br /> wells and has proposed a trigger level where mitigation measures may be initiated if necessary. <br /> Similarly, LRM has predicted slight groundwater mounding up-gradient of the permits west boundary and <br /> near the water management pond. The most significant predicted mounding is due to reinjection into the <br /> water management pond. If groundwater level monitoring shows mounding, LRM will take action to <br /> determine the cause of the change, initiate mitigation measures and will explore long-term solutions. <br /> As mining and reclamation proceed, LRM will install a perimeter drain along the outer perimeter of the <br /> excavation that will serve to dewater the toe of the highwall to maintain stability. Once the gravel pit <br />