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HomeMy WebLinkAbout2003-065 Council Resolution• CITY OF LINO LAKES RESOLUTION NO. 03-65 RESOLUTION ACCEPTING THE FEASIBILITY STUDY FOR LIFT STATION, CENTURY FARM NORTH. WHEREAS, the City Engineer has prepared a feasibility study for lift station, Century Farms North, and, WHEREAS, the developer will pay for the feasibility study; NOW, THEREFORE, BE IT RESOLVED BY THE CITY COUNCIL OF THE CITY OF LINO LAKES, MINNESOTA: 1. Such feasibility study, a copy of which is hereto and made part hereof, is hereby accepted. Adopted by the Lino Lakes City Council this 12th day of May, 2003. Ann J. BI, fr, City Clerk • John J erge , May r AGENDA ITEM 7Biv STAFF ORIGINATOR: James E. Studenski, City Engineer COUNCIL MEETING DATE: May 12, 2003 TOPIC: Resolution No. 03 - 65, Accepting Feasibility Study for Lift Station, Century Farm North Vote Required: Simple Majority BACKGROUND: As the City utility service areas expand, the City must install infrastructure to allow for future growth. The area of the Century Farm North subdivision will require a sanitary sewer lift station to service the development and the surrounding area. A feasibility study has been completed for this service area. A copy of the study is attached. OPTIONS: 1. Return to staff for further review. 2. Adopt Resolution Number 03 - 65, accepting the feasibility study for lift station, Century Farm North. 3. Not adopt Resolution Number 03 — 65. RECOMMENDATION: Option No. 2 - Staff recommends that Resolution Number 03 - 65 be adopted. TKDA ENGINEERS • ARCHITECTS • PLANNERS May 7, 2003 Mr. James E. Studenski, P.E. City Engineer 600 Town Center Parkway Lino Lakes, Minnesota 55014 Re: Preliminary Design Investigation Century Farms Lift Station City of Lino Lakes, Minnesota TKDA Commission No. 12793 -01 Dear Mr. Studenski: 1500 Piper Jaffrey Plaza 444 Cedar Street Saint Paul, MN 55101 -2140 (651) 292-4400 (651) 292 -0083 Fax www.tkda.com The future lift station for Century Farms was analyzed for two conditions. The first being the Immediate to Short Term Conditions; from now to 2007 when the 249 housing units of Century Farm's Development are connected to the new lift station. The second condition is for the Ultimate Service Area Condition. A maximum of 1,595 housing units can be served by the New Century Farm's Lift Station (sometime after 2020). The maximum number of housing units that can be developed for this case is limited by the capacity of the existing 15 -inch sanitary sewer located south of the proposed lift station. Immediate to Short Term Service Area Condition (2003 to 2007) Service Area Service area includes the Century Farms North Subdivision in which 249 housing units are planned to be developed on approximately 100 acres by the end of 2007. Average and Peak Design Flows The following average and peak design flows were calculated using the "Ten State Standards for Wastewater Facilities ": Average Daily Flow ( *) = 47 gpm Peaking Factor = 3.8 Peak Design Flow = 180 gpm ( *) Average Daily Flow Rates were calculated by applying 274 gpd to each housing unit. An Employee Owned Company Promoting Affirmative Action and Equal Opportunity Jim Studenski, P.E. City of Lino Lakes, Minnesota Century Farms Lift Station • May 7, 2003 Page 2 • • Ultimate Service Area Condition (sometime after 2020) 2020 Service Area and Densities The 2020 service area is assumed to include the following housing units and densities: • 63 existing units on approximately 86 acres located east of 4th Avenue North • 415 medium density units (5 units per acre) on approximately 84 acres located west of 4th Avenue North • 420 low density units (2 units per acre) on approximately 210 acres located west of 4th Avenue North • 140 low density units (2 units per acre) on approximately 70 acres located east of 4th Avenue North • 249 existing units from the Century Farms North Subdivision on 100 acres 2020 Service Area = 1,287 housing units on approximately 550 acres Ultimate Service Area and Densities (after 2020) The Ultimate Service Area is assumed to include the 1,287 housing units from the 2020 conditions, plus the following additional housing units and densities: • 310 low density units (2 units per acre) on approximately 155 acres located directly north of the Century Farms North Subdivision Ultimate Service Area = Approximately 1,597 housing units (round to 1,595) on about 705 acres Ultimate Average and Peak Design Flows Average Daily Flow (1) = 304 gpm Peaking Factor = 3.3 Peak Design Flow (2) = 1,000 gpm (2.23 cfs) Notes: (1) Average Daily Flow Rates were calculated by applying 274 gpd to each housing unit. (2) The Ultimate developable service area served by the Century Farms Lift Station is limited by the capacity of the existing 15 -inch (2.5 cfs capacity) sanitary mainline located downstream of the proposed lift station. 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. Jim Studenski, P.E. City of Lino Lakes, Minnesota Century Farms Lift Station • May 7, 2003 Page 4 • Note: The type of power supply (e.g., 3 -phase or single - phase, voltage requirements) required for this lift station is important and should be addressed immediately during the final design of the lift station. Projected Future Lift Station Modifications As housing development progresses past the 2007 service conditions, the Century Farm Lift Station will require the following general modifications: 1. As the number of housing units in the service area approaches 400 to 500, increase the pumping capacity of the lift station. This may be accomplished by replacing the existing pump impellers with larger ones. The amount of increased pumping capacity depends upon the specific pump type that is originally selected. 2. As the number of housing units approaches the Ultimate Service Conditions, increase the pumping capacity of the lift station to a peak capacity of 1,000 gpm. This will be accomplished by adding a third submersible pump creating a tri-plex system. The other two pumps may also have to be modified so that if any one of the three pumps fail, the two remaining pumps can maintain a peak capacity of 1,000 gpm. Other lift station modifications for the Ultimate Service Condition include: • Setup a temporary bypass prior to beginning the lift station modification work. • With the addition of the third pump, replace the existing pump controls and floats with new systems. • Remove the existing 6 -foot diameter barrel section from the bottom of the 10 -foot diameter lift station structure. • Add a third discharge pipe from the lift station to the 10 foot diameter valve manhole. • Add a new third set of check and plug valves inside the existing valve manhole. Inside the valve manhole connect the 3rd discharge pipe to the existing 8 -inch forcemain. If you have any questions, or wish to discuss this analysis further, please feel free to contact me. Sincerely, Aaron D. Hass, P.E. Project Engineer ADH:art Enclosures: Exhibit "A" cc: Scott Brink, P.E., TKDA, with enclosure Bob Stark, P.E., TKDA, with enclosure Paul Blum, P.E., TKDA, with enclosure • 1 • NOTE NEW 8" FM IS FOR 2 & ULTIMATE SERVICE PPEA CONDITIONS MN VIOL 0 0 MO NU NEW DUPLEX SUBMERSIBLE UFT STATION (10' DIA. STRUCTURE- PROVIDING ROOM FOR A THIRD PUMP). TOP OF STRUCT. EL= 900.5* SEWER 874.1 NEW LOCATION FOR MH 16 EL 893.5* (2) 4" TO 6" DIA. DISCHARGE PIPING FROM UFT STATION TO VALVE MANHOLE. D 15" GRAVITY SEWER TO NEW MH 16 LOCATION LEGEND REMOVE FORCEMAIN FROM CENTURY FARMS DEVELOPMENT PLANS N DA1E: 5/6/03 SCALE 1%40' EXHIBIT "A. PRASE 1- CENTURY FARMS LIFT STATION UNO LAKES MINNESOTA COMM. NO. 12793-01