03-16-1978 Council Minutes - Laserfiche WebLink

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� � ' Page 48 � r. ;�,r. �rad `,an ';�st, '�yur Ci�y of Orono t��rch 1 , 1978 Pace T�ro Long Lake Station (one pump and one standby pump) 1600 gpm peak or .65 mgd average 99 feet of total dynamic head 16" rorce�r�ain velocity = 2.6 feet per second 20" Forcerr,ain velocity = 4 feet per second ropulation Equivalent served by Lift Station 950 Orono 400 hiedi na-t�iorni nasi de 4250 Long Lake J . The desiyn of the pumps include consirierations for a ?_0-year life base on current flows and population projections. l�le have used engineering practices and ooerating experience to size the punps at 100 horsepoti•�er and to pump against approximately 100 feet of total dynamic head. l�Je know from experience that pumps in excess of 100 horsepawer and heads greater than 100 feet involve costly operation and maintenance. The forcemains are directly related to the pump sizing and are designed to minimize head loss and still provide adequate scouring velocity at the design flows. The total dynamic head of approximately 100 feet in tne forceTain system is higher than average. The Cor�nission owns and operates 59 lift stations in which one-third of the facilities have heads of 50 feet or less, one-third have heads between 50 and 90 feet and the remaining third are considered high head lift stations with heads greater than 90 feet. . _In the design of the lift stations, space has been allocated for the addition of a third pump. If it becomes necessary to install a third ' pump in the future to provide a two-pump system with one pump as standby the capacity of the Orono Station will be increased to 2800 gpm (about a 17 percent increase) and the Long Lake Station will be increased to 1900 gpm (about a l9 percent increase). The 16, 18 and 20-inch forcemain system as proposed for the Orono-Long Lake Interceptor represent a higher head than normal pumping situation, but are considered to provide the nost cost effective arrangement for the design needs. Enclosed is a map delineating the Orono-Long Lake Interceptor Service ' Area as defined by the Metropolitan Council in the approval of tne Preliminary Engineering Report.