CC PACKET 01161996 - Laserfiche WebLink

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01/02/96 17: 17 ^0612 937 5522 WESTWOOD PRO SN'S L0014 Page 12 DRAFT—Silver Lake Center EAW January 2, 1996 detention and will meet RCWD permitting requirements. The efficacy of the water quality basins was modeled using the Pondnet model(Walker,1989). The results predict a 26 percent reduction In phosphorus runoff from the 54 acre tributary watershed(a small portion of the drainage area is outside the subject property). The ultimate project conditions Include the addition of a fourth water quality basin In the southwestern portion of the site. This would allow virtually the entire 54-acre watershed to be pre- treated prior to discharge from the subject property. The Inclusion of the fourth basin will result in further stormwater discharge rete reductions and will provide a 45 percent total reduction In phosphorus discharge relative to existing conditions. Both the Interim and ultimate Implementation of the project will provide positive benefits for the quality and quantity of stormwater runoff and provide a positive impact on the water quality of Silver Lake. As shown In Appendix .the.RCWD has reviewed a draft concept of the storm water management plan for the project and concurs with the Intent of the project proposer. The Intent of the developer Is to work closely with regulatory authorities to maximize the practical Implementation of stormwater BMPs. b. Identify the route(s)and receiving water bodies for runoff from the site. Estimate the impact of the runoff on the quality of the receiving waters.(If the runoff may affect a lake consult"EAW Guidelines"about whether a nutrient budget analysis is needed.) As described above,the majority of pre-redevelopment runoff is conveyed directly to a trunk storm sewer In Sliver Lake Road via three main storm sewers,and ultimately to Silver Lake. None of the runoff Is pretreated prior to discharge to the sewer system. Phase 1 runoff,Including the proposed Cub Foods,two lots,and all of the parking area associated with these new uses,will drain to three newly constructed stormwater ponds. Additionally,runoff from the existing bank will be rerouted to a stormwater pond prior to discharging to the storm sewer system. In the ultimate development scenario,most of the,site runoff from Phase 1 will continue to drain toward the three stormwater ponds In the northern portion of the site. Phase 2+development will drain to a fourth stormwater pond which will be constructed In the southwestern portion of the site. See item 18(a)for runoff impact summary. 19. Water duality-Wastewaters a. Describe sources,quantities,and composition(except for normal domestic sewage)of all sanitary and industrial wastewaters produced or treated at the site. Only normal domestic SOWaga wastewater production Is expected. Because the proposed project will Include retail development,a fastfood restaurant,and a Gas Statlon/Convenience Store/Car Wash,production of Industrial wastewater Isnot anticipated. The only non-domestic wastewater expected to be produced following site redevelopment is assoclated with the proposed Gas/Convenience/Cer Wash. As shown below,the car wash is a:expected to generate 3,014 gallons of wastewater per day. All wastewater from this facility would drain through grit chambers to collect sediment in accordance with Village standards. sanitary wastewater production has been estimated based on the methods outlined In the Service Availability Charge(SAC)Procedures Manual(Metropolitan Council Environmental Services,1996). One SAC unit equals 274 gallons of maximum potential dally wastewater flow volume. The volume 00 Is determined by assigning one SAC unit per 3, 0 91 of retail/grocery,3,000 9.1.of convenience store,or 8 restaurant seats. In addition;the proposed car wash at the gas station would add an Westwood Professional Services,Inc. ��'