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r\'r n'rmh,•r l`J!li CYC."C-.S~'(lunen/ 1"irld DCN)p2ClI'[I/1011 - lt.IIRC J • 9 <br />3.0 RESULTS <br />• 3.1 Sl?DCAD+ MODELING <br />l he lullawing table summarizes the model inputs and results for the 10-year, 24-hour storm event for the Block <br />North and Block South reclaimed areas at Mine 3: <br />CYCC, MINE 3, SEDIMENT YIELD DEMONSTRATION <br />INPUTS AND RESULTS <br /> <br />Arca <br />Size <br />(ac) <br />Tc <br />(hrs) <br />CN Runoff <br />Volume <br />(ac-ft) Peak <br />Q <br />(c(s) <br />K Slope <br />Length <br />(ft) Avg. <br />Slope <br />(%) <br />CP Sediment <br />Yield <br />(tons/ac) <br />Block North Pre-h4ine 1 0.033 77 0.03 0.38 0.29 2082 6.0 0.08 0 2 <br />Block North Post-Mine I 0.063 80 0.04 0.50 0.30 52.2 6.0 0.03 OA <br />Block South Pre-Mine I 0.018 77 0.03 0.038 0.29 208.2 20 0.09 I.0 <br />Block South Post-Mine I 0.059 74 0.02 0.28 0.28 55.2 20 0.04 0.I <br />As shown by the SEDCAD+ modeling results, the total sediment contributions calculated for representative <br />areas within CYCC Mine 3 Block North and Block South are less than comparable unmined areas with <br />vegetative cover approximating that of the approved Combined Reference Area. These results are derived using <br />vegetative information provided from [he three approved reference areas for comparison and modeling surface <br />• roughness characteristics on the reclamation as provided by contour furrows and seedbed preparation practices <br />typtcaliy utilized on the reclaimed areas. The time of concentration values presented for the post-mmmg areas <br />represent the smn of the time of concentration and travel times for [he subwatershed exhibiting the longest <br />hydraulic Flow path within the modeled watershed. The SEDCAD+ computer printouts are included in <br />Appendix B <br />3.2 FIELD INSPECTION SUMMARY <br />Field inspections of Mine 3 Blocks North and South have been carried out tltrouglt the annual Rill attd Gully <br />and Permanent Gully Surveys and through summer vegetation sampling, years 1995 - 1997. Over that time, <br />tltorouglt inspections of the areas have been completed. These two areas show no sign of significant erosion. <br />Contour furrows are still evident and continue to be stabilizing structures. <br />Block North has three permanent drainageways, Pl, P2, and P3, which direct the majority of the runoff to the <br />Mine 3 North pond (M3N). The majority of the runoff from Block South is directed through three permanent <br />drainageways, H1, H2, and H3, [o the Mine 3 South pond (M3S). M3N and M3S will remain as a permanent <br />impomtdments. The permanent drainageways are stable with minimal down-cutting. The overall watersheds in <br />bout blocks are stable with adequate vegetative cover attd litter to reduce runoff velocities. All areas of bout <br />blocks record adequate litter component which adds to [he overall stability. In conclusion, no significant or <br />persistent erosional features are evident within these two blocks and the findings of the field inspections are <br />consistent with the results predicted by the Sedcad+ modeling. <br />• <br />is\bondcel\mine3\sedh~edmine3 doc <br />