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Mr. Jay Kennedy <br />March 19, 1996 <br />Page 2 <br />Table 1. Summary of Flood Elevations <br />Condition Sennett Lake Legion Pond Owasso <br />Lake <br />Roseville Surface Water Management Plan <br />Maximum 100-year Flood Elevation 892.25 891.03 888.60 <br />Minimum Building Elevation 892..8 891.0 889.0 <br />XP-SWM Mode! of 100-year Event <br />Maximum Existing Flood Elevation 892.3 890.8 888.9 <br />With 24" Pipe and Pump 892.2 890.8 889.0 <br />With 42" Pipe and Pump 892.1 890.8 888.9 <br />XP-SWM Model of 10-year Event <br />Maximum Existing Flood Elevation 891..8 888.3 887.8 <br />Without the Pump Operating 892.1 888.6 887.7 <br />With 24" Pipe and Pump 891.6 888.4 887.8 <br />With 24" Pipe and No Pump 891.8 888.3 887.8 <br />With 42" Pipe and Pump 890.9 888.4 887.8 <br />Owasso Lakes highest flood elevation is a 10-day snowmelt event. Bennett Lake and Legion Pond <br />highest flood elevations are in a Flood Evaluation Storm (SCS Type II, typical of Minnesota). <br />For the 10-year and 100-year events the pump is assumed to be operational. The pump was <br />modeled as turning on when the water in Bennett Lake reaches Elevation 888.0. The discharge of <br />the pump was taken as 10,000 gpm (22.3 cfs). The 24-inch pipe alone cannot conduct the 10-year <br />or 100-year discharges from Bennett Lake. <br />Based on topographic maps and the Surface Water Management Plan Bennett Lake is assumed to <br />overflow at Elevation 891.6. For the existing conditions, a 10-year event will result in water <br />overflowing Victoria Street from Frog Pond to Legion Pond.. With the installation of a 24-inch pipe <br />and assuming the pump is operated, Victoria Street will not overtop in a 10-year event. If the <br />existing pump is not operated during a 10-year event (with a 24-inch pipe is installed), Victoria <br />Street will again be inundated. <br />It has been a pleasure to work with you. If you have any question about this study please do not <br />hesitate to call either myself (832-2755) or Denny Palmer ;832-2814). If you have any further <br />work, you would like done, we would be happy to discuss it with you. <br />I hereby certify that this Study was prepared by me or under <br />my direct supervision and. that I am a duly Registered <br />Professional Engineer under the laws of the State of Minnesota. <br />Craig T~omeen <br />Date: March 18, 1996 Reg. No. 24398 <br />362406\35873-1 <br />