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Mr. Brad Van Nest, Mayor City of Orono • March 1, 1978 Page Two Long Lake Station (one pump and one standby pump) 1600 gpm peak or .65 mgd average 99 feet of total dynamic head 16" Forcemain velocity = 2.6 feet per second 20" Forcemain velocity = 4 feet per second Population Equivalent served by Lift Station 950 Orono 400 Medina -Morningside 4250 Long Lake The design of the pumps include consideration's for a 20 -year life base on current flows and population projections. We have used engineering practices and operating experience to size the pumps at 100 horsepower and to pump against approximately 100 feet of total dynamic head. We know from experience that pumps in excess of 100 horsepower 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 i::)oroximately 100 feet in the forcemain system is higher than average. The Commission 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 19 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 most 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 the Preliminary Engineering Report.