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• 2.05.6 (3)(b) RESPONSE continued percent increase in the annual dissolved solids load at gage site S-4 on Hayden Gulch. A 3 percent increase ("worst case") in the annual dissolved solids loading at gage site S-4 would be difficult to detect, considering the natural fluctuations in dis- solved solids (770-1690 mg/1) occuring at that station. Specific dissolved solids, as iron and manganese, may discharge at levels (maximum of 7.0 and 4.0 mg/1, respectively) exceeding that typical to the drainage during the period of active mining. Post-mining levels will approximate pre-mining levels. - - The contribution of suspended sedunent to Hayden Gulch from - the permit area may be noticably decreased. Measurements at ~, the upper gage site (S-3) indicate suspended solid levels aver- aging 79 mgll and ranging from 2-543 mg/1. Permit require- . ments will restrict discharges from the detention ponds to a maximum of 45 mg/1 suspended solids. Aquatic organisms in Hayden and Dowden Gulch should not be significantly impacted by the mining operation. Minor habitat changes may result from the retardation of peak flow events by the detention ponds. Ground water The impact of the mining on the ground water will be negligible, except for the temporary disruption of a few local springs/seeps. The Twenty Mile sandstone will be hydrologically isolated from the mined area. (See Section 2.04.7, Part (vi) of this section, and Exhibit BB, Exhibits Volume II) . The minerals in the upper part of the Williams Fork Formation, which contains the coal seams, have low permeabilities. (See • Section 2.04.7 and Part (vi) of this section.)