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most conservative parameter for Total Suspended Solids (35 mg/1) . 2 <br /> This is very conservative because run-off from the small areas <br /> which are the subject� of this request for technical revision would <br /> occur only during storm events and snowmelt, when alternate <br /> effluent limits apply to the pond discharge. <br /> As indicated by the calculations at Attachment B, outfall 016, <br /> which has an average outflow of 300 to 600 gpm has an allowable <br /> solids of 23 .19 to 46. 38 tons per year, assuming the most stringent <br /> effluent limit of 35 mg/1 TSS. <br /> In comparison, as indicated by the table at Attachment A, the total <br /> potential sediment load from all areas combined is 12.4 tons per <br /> year. Further, berms will contain the run-off from most of these <br /> areas, preventing even this contribution of sediment. <br /> Mid-Continent believes this demonstrates that sedimentation ponds <br /> are not necessary as drainage from these small areas would <br /> contribute no greater sediment load to waters of the state (i.e. <br /> Coal Creek and tributaries) than is allowable for a point source <br /> subject to effluent limitations. <br /> Further, the disturbance created by construction of sedimentation <br /> ponds and ditches, particularly given the topography and location <br /> of these areas, would would in fact contribute additional sediment. <br /> MONITORING <br /> The Division requests a commitment by Mid-Continent to monitoring <br /> of run-off from areas for which small area exemptions are granted. <br /> The purpose of the sampling would be to compare suspended solids <br /> which may be contributed to surface waters by run-off from these <br /> areas to discharge of solids from a point source subject to <br /> effluent limits. <br /> When f lows are suf f icl ently concentrated and sustained to allow for <br /> collection of a sample, Mid-Continent will collect a grab sample of <br /> run-off flow leaving the area. During precipitation events <br /> discharge from a sediment pond which receives stormwater run-off is <br /> subject only to a settleable solids (not TSS) limit, and during <br /> 2 The CDES permit for outfalls at Coal Basin establishes 35 <br /> mg/1 as a 130 day average but allows a daily TSS of 70 <br /> mg/l; for surface water runoff discharge an alternate <br /> standard applies, namely Settleable Solids, where the <br /> effluent limit is 0.5 ml/l; during snowmelt greater than <br /> a 10-year/;4-hour event, the permit allows exemption from <br /> TSS and settleable solids limitations. <br /> 6 <br />