2005-11-16_REVISION - M2004078 - Laserfiche WebLink

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Recharge Site Trigger to Begin Operation RS-A Groundwater dewatering at North Silt Pond RS-B Mine Progression half way through Pond 1 or reported impacts to alluvial irrigation wells. RS-C and RS-D Groundwater dewatering at South Silt Pond After mining years one and two, it is anticipated that the north and south silt ponds will provide adequate recharge to the local alluvial aquifer. However, the Recharge Sitgs may require activation if adverse impact to local groundwater levels is observed. The recharge sites are shown relative to the local groundwater table on Figure 3. Recharge sites will be designed for a typical recharge rate of 1,000 gpm with a maximum of 2,000 gpm which is consistent with the groundwater model completed for the site. The active mining area will be dewatered using perimeter trenches that gravity drain to a sump collection area at the bottom of the aggregate deposit. The dewatedng water produced from this site is not expected to pick up significant sediment load for two reasons:1) the natural aggregate formation is an unusually clean deposit (i.e. <2 percent passing the 200 sieve typical); and 2) the dewatering Uenches and sump will be constructed on bedrock that is erosion resistant claystone. This dewatering volume will be pumped either directly to recharge sites or to a settling pond. The dewatering volume that is pumped directly to recharge sites will recharge the natural groundwater table along the perimeter of the active mine to reduce the potential local drawdown of the aquifer and subsequent impacts to local well users. The proposed method of returning the dewatering volume to the natural aquifer is via clear water ponds. These ponds will recharge into the upper portion of the sand and gravel deposit (above the naturel groundwater table). The recharge water will filter down through the unsaturated sand and gravel media and subsequently to the natural groundwater table below. The dewatering volume pumped to settling ponds will either recharge the aquifer at these locations, be pumped to one of the recharge sites or be discharged off-site as surface water return to the dver. Water discharged off-site as surface water must meet monitoring and water quality standards determined by the Colorado Department of Public Health and Environment Water Quality Control Division, per conditions established in a Colorado Discharge Permit System (CDPS) permit. The gravel and asphalt plant operations will employ Best Management Practices including chemical, concrete and fuel management methods, stormwater management, equipment mainteriance, spill containment and reporting requirements, and sediment control. Any and all spills or other incidents will be reported to Division of Minerals and Geology and other appropriate agencies including the Colorado Department of Public Health and Environment, and the local emergency service agencies. 4.0 GROUNDWATER MONITORING PROGRAM The approach to the monitoring program is to include a broad scope of analytes with higher sampling frequency at the beginning of the project (and prior to mining to the extent possible) to estimate background conditions and then to decrease the frequency and number of analytes as the program progresses if the initial program indicates little to no degradation of the groundwater quality. Following is a proposed schedule for sample collection and groundwater quality parameters based on the proposed mining of the south and north silt ponds in Mining Years 1 and 2, respectively. A minimum of five quarters of monitoring will be required prior to disturbance of groundwater on the north silt pond per DMG requirements. November 2005 Groundwater Sampling and Analysis Plan 2 Lupton Lakes Project