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gpm, or 4.5 gpm per service connection. Since a 2-inch forcemain is adequate for 45 gpm, it is <br />proposed that the design capacity for Lift Station No. 2 equal or exceed 45 gpm. <br />The original lift station design capacities are shown on Table 1. Testing performed in 1993 showed <br />that the capacity of Lift Station No. 2 was down to 22 gpm, and that Lift Station No. 4 was down to <br />12 gpm pumping alone, and 0 gpm with Lift Station No. 2 running. Lift Station No. 3 was not <br />tested due to lack of inflow. The capacities stated in Table 1 are with one of the twin pumps <br />running. <br />TABLE 1 <br />19S0 Lift Station Design Conditions <br />Lift <br />Station <br />Number <br />1 <br />Pumping <br />Capacity <br />(gpml <br />45-60 <br />15 <br />Pumping <br />Headm. <br />90 - 120 <br />8 <br />Motor <br />Size <br />fhol <br />5 <br />1.5 <br />Forcemain <br />Diameter <br />finches! <br />4 (to MCES forcemain) <br />2 fto Wayzata) <br />It is believed that the following factors are responsible for the reduced capacity, alarm history, and <br />high run times on the Femdale area lift stations: <br />• Deposits and encrustation in the 2-inch forcemain, which severely restrict pumping rates. <br />• Inflow and infiltration of groundwater, which cause pumps to run continuously at times. <br />With multiple pumps running, pumping rates are severely reduced by the increased <br />pumping head. <br />• Normal pump wear may also be a factor. <br />The proposed hydraulic improvements are: <br />1. <br />2. <br />3. <br />4. <br />5. <br />Clean the encrustation and deposits from the 2-inch forcemain. The City has recently <br />received quotes from specialty contractors for this work. <br />Eliminate public property I & I by sealing structures, leaking joints, and raising manhole <br />tops. The City has recently received quotes from specialty contractors for this work. <br />Point excavate to re-route the 2-inch forcemain from Lift Stations No. 3 and 4 into Lift <br />Station No. 2. This will allow Lift Stations No. 3 and 4 to pump without fighting the <br />increased pumping head when Lift Station No. 2 is running. <br />Provide pumps in Lift Station Nos. 3 and 4 that are capable of 15 to 20 gpm with both <br />stations pumping. The use of semi-positive displacement pumps is recommended, as there <br />would be little flow variation with variations in pumping head. <br />Lift Station No. 2 would pump the combined flow from Lift Stations No. 3 and 4, and from <br />the small gravity collection system that flows into Lift Station No. 2 Increase the pumping <br />l3999l0T\word\report3\Utter reportdoc