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_12_ The applicant resampled exposed strata at Pit 4, and submitted the sample analyses in a response dated April 24, 1984. Channel samples were taken separately for the overburden above the No. 2 Rider, for each inturburden zone, and for the underburden stratum below the No. 5 Rider. Samples were taken from each interval at the north end and at the south end of the Pit 4 highwall. The acid zone was determined to be a shale immediately below the lower most seam. Since the material will not be excavated, there is no potential for adverse impacts on plant growth or water quality. The data for the overburden and interburden zones does not identify any potential]y inhibitory strata. The proposed operation is in compliance with the requirements of this section. V. Surface Water Hydrology - Rules 2.04.5, 2.04.7, 2.05.3(4), 2.05.6(3) and 4.05 The surface water information within the permit application is found in Section II-F. Further information can be found in the response to adequacy issues submitted during March and April, 1984. A description of surface water occurrences and mining impacts within the permit and adjacent area can be found in Section IX. - "Probable Hydrologic Consequences of Mining and Cumulative Hydrologic Impact Study" of this document. Sediment control at Grassy Gap Mine is achieved by routing disturbed drainage through diversion ditches to sediment ponds. At Pit No. 2 a small slide (approximately 1 acre) area has been exempted from passing through the sediment pond. The slide and a small affected area above the slide has been revegetated and mulched and a diversion has been constructed above the disturbance. Sediment Pond 4 - Sediment Storage Capacity The sediment yield from Pit 4 into the pond was calculated using data taken from a paper on highway construction in Pennsylvania. This data is inappropriate for the Grassy Gap area due to the extreme climatologic difference and the excess compaction used in highway construction. Sediment yields calculated using the USLE give sediment volumes of 2.0 acre feet/year. The dewatering device level allows for 2.5 acre feet of sediment storage. It is expected that sediment levels will reach the invert level if some sediment clean-out is not effected. For this reason the following stipulation is needed.