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Surface Water <br />The probable hydrologic consequences of coal mining at the Yoast mine in <br />regard to surface water include contributions of sediment to streams from <br />storm runoff, and impacts to stream water quantity and quality during and <br />after mining. Potentially affected streams and drainages include Annand <br />Draw, Grassy Creek, and Sage Creek. The most significant impact of <br />mining on surface water will be the effect of spoil spring discharges from <br />the reclaimed mine on surface water quality. Seneca Coal Company's <br />predictions of the magnitude of these impacts is discussed below. <br />Sediment Loading <br />All runoff from areas disturbed during the life of mine will pass through <br />one of five sedimentation ponds prior to leaving the permit area. <br />Discharges from the ponds will be required to meet NPDES effluent <br />limits, and should, therefore, not contribute additional suspended solids to <br />stream flows near the permit area. <br />Since drainage channel reconstruction and revegetation is complete at the <br />mine, more runoff from the mine area will occur than during mining, when <br />pits were in place and maximum disturbance had not yet occurred. <br />However, sediment loads in the increased runoff should be no larger than <br />those coming from the permit area during mining, which was treated <br />effectively by the existing sediment ponds. <br />Quantity of Surface Flows <br />The largest peak flow recorded in Annand Draw during baseline data <br />collection was 0.585 cfs. The presence of a sediment pond in Annand <br />Draw will attenuate peak flows in that drainage during mining. After <br />mining, flows in Annand Draw will increase due to establishment of spoil <br />springs and additional runoff from the reclaimed area. Spoil springs are <br />projected to add approximately 0.073 cfs of base flow to Annand Draw. <br />Spoil springs in Annand Draw and the Pond 11 drainage will add year- <br />round base flow to Grassy Creek. These spoil spring contributions are <br />projected to increase mean flows during irrigation season (June 1- <br />September 30) in Grassy Creek from 0.25 to 0.37 cubic feet per second <br />downstream from the Yoast Mine. <br />Spoil springs are projected to add approximately 0.159 cfs of base flow to <br />Sage Creek during irrigation season (June 1 - September 30). These spoil <br />spring contributions are projected to increase mean flows during the <br />irrigation season in Sage Creek from 0.259 to 0.418 cfs. <br />Yoast Mine 27 December 15, 2010