2003-065 Council Resolution - Laserfiche WebLink

Home Search

Jim Studenski, P.E. City of Lino Lakes, Minnesota Century Farms Lift Station May 7, 2003 Page 3 Recommended Modifications to Century Farms North Subdivision Development Plans It is recommended that the 140 -foot forcemain, as shown on the existing development plans, be removed and replaced with an extended 15 -inch gravity sanitary sewer. The extended 15 -inch sanitary sewer would extend to the new Manhole No. 16 location as shown on Exhibit "A ". Replacing the longer forcemain with an extended gravity sewer and a short forcemain section has the following benefits: • One short 8 -inch forcemain can be provided in Phase 1 of the lift station construction to serve both the short (2003 to 2007) and long term (Ultimate) service conditions. No future modifications to the 8 -inch forcemain (from the valve MH only) will be necessary when the Ultimate Developed area is on -line. For the short term, the velocities in the forcemain will be below 2 -feet per second. This is not of a concern since the forcemain is so short. • Reduce the pumping head required, thereby reducing pumping costs and energy usage for both the short and long term conditions. Phase I- Recommended Immediate Needs for Century Farms Lift Station To provide a smooth transition from the Short Term Service Conditions to the Ultimate Service Conditions, it is recommended that the initial construction of the Century Farms Lift Station include the following amenities (See Exhibit "A "): 1. Furnish and install a 10 foot diameter precast concrete structure for containing a duplex submersible pump system, while providing room for a third pump to be installed sometime in the future. Depth of the structure will be approximately 32 -feet deep. 2. For the short term conditions install a 6 -foot diameter precast concrete barrel section inside the 10 -foot structure. The 6 -foot structure will make it feasible to maintain a minimum pump cycle time of 6 starts per hour. 3. Furnish and install a 10 -foot diameter precast concrete valve manhole. The valve manhole will contain two 4 -inch to 6 -inch discharge pipes (with check and plug valves) leading from the lift station. The two discharge pipes will be connected together into a new 8 -inch forcemain that will discharge into the extended gravity system via Manhole No. 16. Provide a blinded tee connection inside the valve manhole for the future connection of a third discharge line leading from a third new submersible pump. 4. Furnish and install two (2) submersible pumps, each having a minimum peak capacity of 180 gpm (at approx. 20.5 feet of head). Each selected pump shall have the capability of having its impeller replaced with a larger one to increase the pumping capacity of the system (without getting a new pump). 5. To more efficiently pump the low sanitary flows during the development of the Century Farms Subdivision, one of the submersible pumps will most likely be a variable speed submersible pump.