Laserfiche WebLink
<br />De-watering will occur in portions of the coal seam that contain <br />water and in the lower portions of the Barren Member; it will reach <br />a maximum at the furthest extent of mining. Shallow surface <br />aquifers located close to the coal outcrop will experience <br />depletion by the second mechanism of mine inflow, mentioned above <br />in areas of shallow overburden. It is also anticipated that mine <br />inflows will be encountered as mining progresses under creeks due <br />to flow through fractures. <br />The Mt. Gunnison Mine has submitted calculations for projected mine <br />inflows and resultant surface water depletions for the 5 year and <br />life of mine areas. These projections were based on actual <br />observations and data collected from the mining operation. They <br />are worst case assumptions and actual inflows will probably be <br />less. The calculations are for inflows from areas of low <br />overburden and flows from fracture zones under streams. <br />Maximum worst case inflows for the 5 year mine plan are expected to <br />be 184 gpm (for projected life of mine inflow see CHIS section. <br />The projection is for worst case depletion and is calculated for <br />maximum flows during spring snowmelt; it will be less in dry years <br />and during non-snowmelt periods. Water monitoring data collected <br />by the mine does not support the worst case scenarios. Presently, <br />no undermined springs or monitoring wells have shown any observable <br />impact due to mining. To date the only drainage that has been <br />mined under is Sylvester Gulch. The inflows presently associated <br />with this area averaged 20 gpm for water year 1985. The maximum <br />inflows expected during the 5 year mine plan is 99 gpm. Water <br />quality of mine inflows average between 500 and 700 conductivity. <br />The low EC's of the mine inflows indicate close connection between <br />surface flows of Sylvester Gulch and mine inflows. <br />The applicant anticipates no degradation of ground water quality <br />during mining. The applicant will treat any effluent as necessary <br />to meet water quality standards prior to discharge and there will <br />be no uncontrolled mine water discharge after mining is complete <br />which might otherwise degrade surface streams or ground water. The <br />mine operation plans indicate that mine discharges may occur when <br />WECC's water rights are not in priority, but again, that all <br />discharges will be appropriately treated. The operation plan <br />further indicates most water used for dust control will be absorbed <br />on the coal and carried from the mine thereby minimizing the <br />quantity to be treated. Any discharge will be delivered and <br />treated in the sedimentation ponds and discharge as specified in <br />the NPDES permit. In order to assess the quantity, quality, and <br />source of mine inflows, and in order to verify the impacts of the <br />mine workings on the hydrologic balance within the mine plan <br />adjacent areas, the Division is requiring the following stipulation <br />to the permit to be continued. <br />43 <br />