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C~ <br />• <br />I <br />Pond 9 <br />Interim Drainage Check <br />The original or operational design of pond 9 provided for the collection of run-off from a portion <br />of the Roadside Refuse Disposal Area "RSRDA" and the drainage area below the south <br />diversion ditch, ref. Exhibit 6B. Interim drainage is defined as that period of time after <br />reclamation that Pond 9 will remain in place. This period could range from three to ten years. <br />During the interim period, Pond 9 will receive run-off from the RSRDA upper diversion ditch and <br />the lower bench of the RSRDA. <br />During the interim period, Pond 9 will collect run-off from Drainage Area D, ref. Appendix 14-6 <br />page 14-6-1 i. Drainage Area D, which is the drainage area for the RSRDA upper diversion <br />ditch, encompasses 72 acres broken down as follows: <br />Curve Number 64 67.6 Acres B Soil Group, Sage-grass 20% cover <br />Curve Number 86 4.4 Acres B Soil Group, fallow bare soil <br />The lower bench of the RSRDA contributes another 3.0 acres of fallow bare soil to the drainage <br />area of Pond 9. Therefore the drainage area and run-off volume for Pond 9 is: <br />10-year evenU <br />Area Acres Curve Number direct run-off Run-off Acre Feet <br />Upland 67.6 <br />Disturbed 7.4 <br />64 <br />86 <br />Total Required Water Capacity -Acre Feet <br />Pond 9 Actual Water Capacity -Acre-Feet <br />1.4/0.01 0.07 <br />1.4/0.43 0.26 <br />0.33 <br />0.66 <br />The actual water capacity of Pond 9 is listed in the yearly impoundment inspection report dated <br />April 8, 2002. <br />Pond 9 has an emergency spillway comprised of a half 30-inch diameter culvert. The rated <br />capacity of this emergency spillway is 23 cfs, ref. appendix 13-2 page RSS-18. The RSRDA <br />upper diversion ditch has a 100-year design flow of 8.8 cfs. Therefore, the existing emergency <br />spillway is considered adequate to handle the 25-year event. <br />Sediment volume will not be considered for this analysis. Pond 9 has a design sediment <br />capacity of 0.33 acre-feet, ref. appendix 13-2 page RSS-15. The sediment will be cleaned from <br />Pond 9 when the sediment accumulation approaches 60% of the design volume. <br />The calculations and inforr~al~gOERb~6~j on this page were prepared by me or under my <br />direct supervision during~#~~htf~ q~~~~~002, and the information presented is true and <br />correct to the best of m~r~dge anQc~D. <br />*~~9 ms's *e ~~ <br />s8 a ~ <br />mimes E. Stovet~E. <br />RSA `84ed Profe~S~ AI Engineer <br />~: Pof j~~l c~~~c4~ o. 19230 <br />Append 13-2 •, RSS-15i <br />6/02 <br />