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<br />The mining and reclamation activities will act to change stream channel <br />geomorphologies. Drainage densities and channel frequencies will be reduced, <br />however, Peabody has designed and located post-mining drainage channels to <br />minimize the erosive results of the lowered frequencies. <br />During mining operations and until adequate vegetation is established runoff <br />and erosion rates within the disturbed area will be higher than pre-mining <br />rates. The applicant has calculated runoff and erosion/sediment yield rates <br />from disturbed areas in designing Sediment Pond 006 (see Section XXI). <br />Sediment leaving the site will be controlled by effluent limits placed upon <br />the discharge at Pond 006 by Colorado Department of Health as part of the <br />applicant's NPDES permit. Baseline flows in Hubberson Gulch exhibit TSS <br />levels from 5 mg/1 to 606 mg/1 with an average of 100 mgl. The total <br />suspended solids increase to Hubberson Gulch is expected to be minimal from <br />mining. Once vegetation is successfully established, the erosion rates are <br />expected to return to the pre-mining level of approximately 140 tons/m i2/yr. <br />Sediment Pond 006 will act to control flood flows from the disturbed area. <br />The pond will regulate flood discharges minimizing the impact of the floods. <br />The pond is not expected to significantly reduce the quantity of runoff water <br />available in Dry Creek. The mine area makes up only a small portion of the <br />Dry Creek watershed (0.9%). <br />Surface water quality will be affected by mining. Runoff from disturbed areas <br />will exhibit increases in total dissolved solids. Baseline water quality is <br />of a calcium-magnesium sulfate type. Magnesium and sulfate levels may show an <br />increase in disturbed area runoff, however, these parameters are elevated in <br />baseline waters and the water type will not undergo a change. TDS levels in <br />Hubberson Gulch range between 385 mg/1 and 1632.2 mg/1. It is expected, based <br />upon the applicant's measurements in Little Grassy Creek, a stream draining <br />their Seneca II Mine, that TDS levels may double in Hubberson Gulch during <br />mining and reclamation. The waters of Hubberson Gulch are not actively <br />utilized for irrigation due to elevated salinities. The water will be usable <br />for livestock watering and by wildlife. <br />Flow from several springs discharging to the surface water system will be <br />interupted by mining activities. These springs help to classify Dry Creek as <br />an intermittent stream. It is believed that post-mining the backfilled pits <br />will develop significant head to discharge to the surface water system. This <br />discharge will be greater than the current combined spring discharge. <br />The major impact of mining will be the development and subsequent discharge to <br />the surface system of spoils aquifer waters. As each successive pit is <br />reclaimed, a spoils aquifer will begin to develop. The water necessary to <br />recharge this aquifer will be derived from precipitation, overland flow, and <br />discharge from the Williams Fork formation overburden and the Wadge coal. <br />-38- <br />