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representative particle-size distribution of soils in the area, <br />sedimentology information, etc. The curve numbers and average slope <br />were taken from Table 13-3 on page 20 in Tab 13 for HRD-A2ME5 and <br />HRD-G1, respectively. <br />The SEDCAD+ computer program was also utilized to calculate the <br />sediment flowing to each porous rock check dam using the DEPOSITS <br />portion of the program. The Revised Universal Soil Loss Equation <br />(RUBLE? was used to determine the sediment loading. Input consists <br />of particle size distribution, "k" factor, length and slope <br />factors, and CP factor. The particle size distribution for this <br />analysis was based on sieve and hydrometer analysis of various soil <br />types in the Seneca II-W permit area. Please refer to the output <br />for the exact distribution. The specific gravity and the submerged <br />bulk specific gravity of the soil are estimated to be 2.50 and <br />1.25, respectively. The "k" and CP factor values were taken from <br />information in the Seneca II Mine permit. Please refer to volume 5, <br />Attachment 7-6-7, pages 7-6-7-5 and 7-6-7-6. The values for <br />gravel/disturbed roads listed in the appropriate tables were used <br />in this analysis for the porous rock check dams. <br />Summarv <br />The results of the SEDCAD+ computer analysis indicate thar_ the trap <br />efficiency for the porous rock check dams along both haul roads <br />would be approximately 92~. Seneca Coal Company believes that <br />installing several of the porous rock check dams/straw bale <br />barriers in both haul road ditches will result in a reduction in <br />silt reaching both ME-5 and G-2 culverts, minimize the silt flowing <br />through the culverts, and help eliminate a majority of the problems <br />that currently exist at both of these locations. <br /> <br />13-6A-2 Revised 06/08/95 <br />