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<br />.. <br /> <br />;"'~~~ <br />'~ ~~, <br /> <br />~1~ 20 2001 <br /> <br />t <br /> <br />3535 Vadnais Center Drive, SI. Paul, MN 55110-5196 651,490,2000 651,490.2150 FAX <br /> <br />architecture <br /> <br />engineering <br /> <br />environmental <br /> <br />transportation <br /> <br />February 12,2001 <br /> <br />RE: Roseville, Minnesota <br />Cleveland Lift Station Review <br />SEH No. AROSEVO 10 . <br /> <br /> <br />Ms. Debra M. Bloom, P.E. <br />Assistant Public Works Director <br />2660 Civic Center Drive <br />Roseville, MN 55113 <br /> <br />Dear Debra: <br /> <br />As you requested, we have reviewed the Cleveland Avenue Lift Station to determine if upgrades to <br />the station will be necessary in light of the proposed development within the service area. Our <br />findings for both existing and proposed conditions are summarized below. <br /> <br />Existing Conditions <br />The Cleveland A venue Lift Station is a prefabricated duplex flooded suction lift station with a <br />precast concrete wet well. The station is equipped with two 4" Fairbanks Morse pumps connected <br />to 15 H.P. motors. The pumps are rated for initial conditions of 300 gpm against a total dynamic <br />head of 52 feet. The station was constructed in 1986. The force main is a 6" cast iron pipe that <br />was constructed in 1962. <br /> <br />Currently, the station appears to be functioning adequately for the existing development. Recent <br />pumping records provided by City maintenance staff were reviewed to determine the station's <br />ability to accommodate existing flows. Under dry weather conditions, the highest hourly flow rate <br />was approximately 65 gpm. Test pumping records indicated that Pump 1 pumps at about 263 gpm, <br />and Pump 2 pumps at about 268 gpm. Pump-down times ranged from 2.2 minutes to 5.0 minutes. <br />The minimum time between starts of the same motor was approximately 24.3 minutes. These <br />values are all within acceptable operating ranges. <br /> <br />However, during recent wet weather conditions, flows at the lift station have exceeded the rated <br />pump capacity of 300 gpm. For example, a 4" rainfall occurred on September 2, 2000, and the <br />station pumped continually for nearly 10 hours to keep up with the flow. During this event, both <br />pumps pumped simultaneously for periods of time ranging from 20 minutes to 1.8 hours. The <br />discharge when both pumps were pumping was estimated to be 322 gpm. No property damage due <br />to backups was reported. According to maintenance staff, wet weather flows were not a problem at <br />this station prior to the summer of 2000. <br /> <br />Short Elliott Hendrickson Inc. <br /> <br />Offices located throughout the Upper Midwest <br />~ help you plan, design, and achieve. <br /> <br />Equal Opportunity Employer <br />