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RENEWAL OF <br /> CONS71?UCY70N DE WATERING <br /> OPERATIONS IN COLORADO <br /> GENERAL PERMIT FOR DISCHARGE <br /> RATTONALE <br /> COLORADO DISCHARGE PERMIT NUMBER: COG-070000 <br /> Update <br /> This is the second renewal of the general permit for Construction Dewatering Operations which was originally issued <br /> November 2, 1983. <br /> The General Permit system for regulating discharges from the construction operations has worked well for the State. <br /> The most significant changes in the second renewal are as follows: <br /> A. The Division has reasonable concerns with construction dewatering sues near areas with potential groundwater <br /> pollutants contributed by leaking underground storage tanks, landfall areas, surface ground contamination from <br /> gasoline and diesel spills, chemical dumping areas, etc. Groundwater characteristics and movement may change <br /> because of excavation and groundwater pumping activities. In some cases the construction dewatering areas may <br /> indicate a potential problem with groundwater pollutants entering into the sue after excavation as a result of pumping. <br /> Additional monitoring should aid in evaluating possible changes in groundwater conditions during the Pumping <br /> activity, insuring that the conditions of the general permit are valid, and also indicate if a situation exists where an <br /> individual permit should be issued This requirement will be imposed where the potential for problems exist. <br /> B. Additional monitoring may be requested to ensure that the antidegradation presumption is overcome by site specific <br /> reasons specified in Section 3.1.8(1)(c)(i)(ii)(iii)of The Basic Standards and Methodologies for Surface Water, as <br /> further explained in Pan L C.7.B of the permit. <br /> C. The addition of phosphorus (as P)monitoring for facilities which discharge into drainage basins that have phosphorus <br /> monitoring and reporting requirements and for drainage basins that may latter become areas for phosphorus <br /> monitoring, as further explained in Pan L C.7.G, of the permit- <br /> D. The daily maximwn suspended solids limitation of 60 mg/1 shall no longer apply. The suspended solids limitation of 30 <br /> mg/l,- 30-Day Average and, 45 mg/4- 7-Day Average, shall apply as per the State E 7uent Regulations Section <br /> 10.1.4.(1). The definitions of 30 day and 7 day averages eliminate the need for a daily maximum. <br /> Reauthorization <br /> Pan LA.1 of the permit specifies that authorization to discharge under this general permit will expire on September 30, <br /> 1998, thus facilities wishing continual coverage under this permit must reapply by April 1, 1998. <br /> Robert Cribbs <br /> January 11, 1993 _ <br />