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parameters will decrease with time as the readily dissolvable elements are leached until an equilibrium level is reached. Further discussion of this is found under the Surface Water Effects of the Probable Hydrologic Consequences section. Surface Water Effects The majority of runoff from disturbed aeeas during the mine life will be diverted to Sediment Ponds 005 and 006, prior to release off site. Effluent from Ponds 005 and 006 flows to unnamed ephemeral gulches, and ultimately Dry Creek. Runoff from the south extension area will flow into Hubberson Gulch, and ultimately Dry Creek. Effects of mining on Dry Creek will involve changes in quantity and quality, which are further described below. A negligible acreage affected by the extreme eastern extension of the south area pits and the neck pits between the north and south mining areas will drain to Sediment Ponds 009 and 015, and eventually to Sage Creek. Measurable effects on Sage Creek water quality or quantity are not projected, due to the small disturbance acreage and the fact that there will be no spoil water flow to the Sage Creek watershed. The mining and reclamation activities will act to change stream channel geomorphology. Drainage densities and channel frequencies will be reduced; however, Seneca Coal Company has designed and located post-mining drainage channels to minimize the erosive results of the lowered frequencies. During mining operations and until adequate vegetation is established, runoff and erosion rates within the disturbed azea will be higher than pre-mining rates. Seneca Coal Company calculated runoff and erosion sediment yield rates from disturbed areas when designing all sediment ponds. (Tab 13). Sediment leaving the site will be controlled to meet effluent limits placed upon sediment pond dischazges in Seneca Coal Company's Colorado Discharge Permit System permit. Baseline flows in Hubberson Gulch exhibit TSS levels from 5 mg/1 to 606 mg/1 with an average of 100 mg/1. The total suspended solids increase to Hubberson Gulch that can be attributed to mining is expected to be minimal. Once vegetation is successfully reestablished, the erosion rates aze expected to return to the pre-mining level of approximately 140 tons/mi'-/yr. Sediment ponds will act to control flood flows from the disturbed azea. The ponds will regulate flood discharges, minimizing the impact of the floods. The ponds aze not expected to significantly reduce the quantity of runoff water available in Dry Creek. The mine area makes up only a small portion of the Dry Creek watershed (0.9 %). Seneca II-W Findings Document 30 November 3, 1999