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l~ As shown in the Espey, Huston d Associates report (page c-34a and appendix R of the permit applicat ion> the Nothern No. 1 Sedimentation Pond is designed to contain the 10 year-24 hour storm. Also the spillway was designed to safely pass the 25 year-24 hour event. The amount the 12 inch gated spillway o. the Northern No. 1 Sedimentation Pond must be opened to allow - automatic deuatering with an average retention time of 24 hours i<_ ir~c hes <see attached calculations>. RFF IC ^ICPO L RRFR P I~~! Rs shown in the Espey, Huston d Rssociates repc•rt (pages 13-1i ar~d 13-52 of the mine permit application) the Refuse L,~•~posal Sedimentatioi~ • Pond is designed to contain the 10 Year-24 hc•1•r storm. Also th~r spillway was designed t0 safely pass the 25 yezr-~' hour event. The Refuse Disposal Rrea pond has an open 6 incl. :ron outlet pi; This pond was evidently designed to autorr~etie: :, dewater with average retention time of 24 hours. The quantity cf flow required maintain an average retention time of 24 hours is 0.64 cubic feet second (see attached calculations). The max imu rn flow through the inch iron pipe using the Hazin-Williams Formula was found to be [ cubic feet per second <see attached calculations). Therefore provic an average retention time of approximately 28 hours. Rs shown in Rppend ix D-2A3 d 4, Modification No. 2 of the per r~,:. application and the Panorama Resource Services report of August !, ISL. the Sedimentation Pond R was constructed to contain in excess of a IC year-24 hour event. Rlso the spillway was designed to pass safely try 25 year-24 hour event. The amount the 12 inch gated spillway on the Rienau No. 2 Sedimentation Pend A rnU St be opened to allou for automatic deuatering with an average • retention period of 24 hours is 1.5 inches <See attached calculations).