GENERAL41305 - Laserfiche WebLink

Home Browse Search

-35- Two monitor wells are located above the first panel to be subsided. Water levels in these wells will be monitored monthly, and quality samples will be drawn twice per year. These wells are designed to assist in evaluating the hydrologic impacts subsidence may have upon the Barren Member. WECC has been monitoring two wells that overlie the first panel to be mined since 1980. In addition, 4-8 additional wells were be installed in 1985. These wells are used to monitor any effects to lenticular sands of the Barren Member caused by subsidence. The applicant proposed to monitor springs in the five year permit area and springs C-22 and C-23 three times annually. The applicant also proposed to monitor spring C-14 twice yearly for water quality. Since the springs in the mine plan area are an important indicator of both bedrock and colluvial aquifers, and since the impact upon ground water will first be manifested as reduced spring flows, the Division required that an expanded spring monitoring plan be implemented. This spring monitoring plan is to determine the effects of mining on spring flows and quality within the mine plan and adjacent areas to aid in predicting affects in subsequently permitted areas. The monitoring of springs in the northern half of the Dry Fork watershed is to provide adequate baseline data. The baseline data can then be compared with monitoring data acquired during mining in this area. The applicant states that there will be "no uncontrolled mine water discharge after mining is complete, which might otherwise degrade surface streams or ground water." Entries to the Mt. Gunnison Mine No. 1 lie downdip from the recharge areas of the aquifers to be encountered. As such, it is likely that some mine drainage will result after mine shutdown. Since the applicant states that no uncontrolled drainage will occur after completion of mining, specific plans foc sealing of mine openings after mining were presented in the application and found to be in cort~liance by the Division. Waste-Rock Piles No ground water contamination is expected from either the upper or lower waste rock piles. Both piles are designed to handle the worst case condition, that is to handle toxic, acidic, alkaline, and/or combustible waste rock. (See Geo-Hydro Report dated March, 1981). Monitoring wells would be installed below the upper pile to assess any i~acts on the ground water. The location of these monitoring wells has been provided in the application. Ground Water Effects from Proposed Permanent Lower Waste Pile Two rock underdrains will be installed in the lower waste pile. The drains run roughly normal to the ground surface and will intercept leachate. The drains will increase the stability of the pile by avoiding saturation; this will be done by draining the perched aquifer that will form as a result of water percolating through the pile. A