Laserfiche WebLink
Mining and Reclamation Permit Amend.-M-1988-112 <br /> Groundwater Management Plan Battle Mountain Resources,Inc. <br /> Other than through the alluvial window, groundwater movement between the various <br /> hydrologic units is assumed to be relatively minor, primarily due to the large contrasts in <br /> hydraulic conductivity between the backfill and the Precambrian and Santa Fe units. <br /> 5.0 CURRENT GROUNDWATER MANAGEMENT <br /> A GWMP was prescribed under TR-26 to the Colorado Mined Land Reclamation Permit <br /> M88-112 (BMRI, 1999a) to prevent discharge of impacted groundwater from the West <br /> Pit. Additionally, DP CO-0045675 was issued by the CDPHE-WQCD under the <br /> Colorado Discharge Permit System (CDPS) to prescribe effluent limitations, monitoring <br /> and reporting requirements related to discharge from the West Pit into the Rito Seco. <br /> The GWMP requires extraction of groundwater from the West Pit in order to reverse the <br /> hydraulic gradient between the West Pit and the Rito Seco. Currently, groundwater is <br /> extracted from the West Pit at rates of up to 200 gpm. Groundwater extraction is <br /> maintained at a rate sufficient to lower the potentiometric surface across the West Pit to <br /> an elevation of below 8,582 ft amsl (CSPS NGVD29) that effectively reverses the <br /> hydraulic gradient such that groundwater flows into, instead of out of, the West Pit, as <br /> prescribed in DP CO-0045675. <br /> The GWMP also includes a groundwater capture system to address a plume of affected <br /> groundwater within the Rito Seco alluvial aquifer downgradient of the West Pit that <br /> flows along the naturally occurring hydraulic gradient and that may flow into the Rito <br /> Seco. That system consists of two groundwater capture wells (M-32 and M-33) located <br /> downgradient of the plume of affected groundwater. Those wells are pumped at a rate <br /> sufficient to maintain water levels within the wells at an elevation of 8,540 ft amsl (CSPS <br /> NGVD29) as prescribed in DP CO-0045675. <br /> Additionally, monthly visual inspections are conducted in the area of the historical seeps <br /> that were initially identified in 1998. In the event that seepage is observed, CDPHE- <br /> WQCD must be notified according to the requirements of DP CO-0045675. <br /> TR-26, TR-32 and DP CO-0045675 also require collection of groundwater samples from <br /> select site monitoring wells to evaluate water quality changes within the affected aquifers <br /> and from the Rito Seco at location RS-2 to evaluate changes in surface water quality. The <br /> water quality data are provided in quarterly reports to the CDPHE-WQCD. Quarterly <br /> time series charts of select constituents are provided to the Colorado Division of <br /> Reclamation, Mining and Safety, as specified in the TR-26 final performance monitoring <br /> program and in the groundwater monitoring program specified in TR-32. <br /> Verification that the groundwater extraction achieves the required hydraulic reversal is <br /> demonstrated by potentiometric surface maps developed from water level elevation <br /> measurements of site monitoring wells. The water level data and potentiometric surface <br /> maps are provided in quarterly reports to the CDPHE-WQCD. The water management <br /> plan implemented under TR-26 has maintained a hydraulic gradient reversal between the <br /> West Pit and the Rito Seco since February 2000. <br /> April 2025 8 Engineering Analytics,Inc. <br />