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5. Anderson Erickson lift station and drainfieldBO L—rC:>" 8L. M F== N IAC , f Consulting Engineers & Surveyors " 12224 Nicollet Avenue • Burnsville, MN 55337 Phone (952) 890-0509 • Fax (952) 890-8065 www.bolton-menk.com MEMORANDUM Date: 3/21/16 To: Seth Peterson, P.E. Ryan Goodman, P.E. From: Morgan Salo, E.I.T. Subject: A/E Lift Station and Drain field Scandia, MN r ---j Ce The Anderson/Erickson drain field was designed to treat up to 6,700 gallons per day. The report that analyzed the existing system states that the drain field is only being operated with half of the designed infiltration area with flows exceeding 7,500 gallons per day during the peak summer months, starting in 2006. The report indicates that it is likely that flows are exceeding 10,000 gallons per day. The lift station contains two — 5 HP grinder pumps designed to deliver 50 gallons per minute. Based on drawdown testing, pump no. 1 can produce 60 gpm and pump no. 2 can produce 59 gpm. Analysis of historic pump run data show is shown in Table 1 below. Table 1: Historic Pump Run Times Year Peak Day Flow (gal/day) 2013 9,867 2014 11,588 2015 5,134 Typically, the highest flows occurred between April and July for each year, with peak flows exceeding the design capacity of 6,700 gallons per day of the system. Peak flows for each year were determined by first finding the peak day flow for the entire year. The peak flow was then determined by taking the seven day average of the previous three days, the peak day, and the three days after the peak. 2013 and 2014 have peak flows that exceed the design capacity of the system. Generally, the flows in 2014 were higher than any other year. Flows commonly Anderson Erickson Drain field Evaluation DESIGNING FOR A BETTER TOMORROW Bolton & Menk is an equal opportunity employer. 0 Page 2 exceeded 10,000 gpd from January through May. The rest of the year saw flows ranging from 5,500 gpd to 9,894 gpd. The flows in 2015 were typically low. The peak flow occurred on July 7 with a total flow of 9,870 gpd. The 7 day average was calculated to be 5,134 gpd. For a majority of the year, the flows were approximately 50% of the design capacity of the system. Using the historic flows, an estimate of how many houses can be connected to the system can be determined. Septic systems are designed based on volume of water per person per bedroom in a house. The design standard for Minnesota is 150 gpd/bedroom. This assumes that there are two people per bedroom. Using this criteria, and assuming each house has four bedrooms, the total flow from each house would be 600 gpd into the system. Using the 2013 and 2014 flows, the peak flows exceed the design capacity by 32% and 42%, respectively, allowing no more houses to be added onto the system. However, using 2015 peak flows, another three, four bedroom, houses can be added onto the system before the system exceeds the design capacity of 6,700 gallons per day. Anderson Erickson Drain field Evaluation DESIGNING FOR A BETTER TOMORROW Bolton & Menk is an equal opportunity employer. Consulting Engineers & Surveyors " 12224 Nicollet Avenue • Burnsville, MN 55337 Phone (952) 890-0509 • Fax (952) 890-8065 www.bolton-menk.com Table 3: 2013 A/E Flow Month Avg. (gal/day) Peak (gal/day) January 3260 5300 February 3913 5300 March 3723 5300 April 7611 12066 May 4651 8784 June 4636 6116 July 5004 8985 August 4134 5591 September 3763 5591 October 3267 4416 November 6866 7944 December 7072 9564 Average/Max 4825 12066 Table 4: 2014 A/E Flow Month Avg. (gal/day) Peak (gal/day) January 7643 18762 February 7605 10320 March 8270 15042 April 9180 19128 May 5565 11784 June 5276 9894 July 5457 8619 August 3518 5502 September 2488 4956 October 2284 4248 November 2507 5502 December 3431 9540 Average/Max 5269 19128 Anderson Erickson Drain field Evaluation DESIGNING FOR A BETTER TOMORROW Bolton & Menk is an equal opportunity employer. Table 5: 2015 A/E Flow Month Avg. Peak (gal/day) (gal/day) January 2097 3330 February 2633 3660 March 2478 3282 April 2549 3660 May 2377 3306 June 2523 3306 July 3643 9870 August 2502 3660 September 2610 3755 October 2227 2928 November 2568 5856 December 2662 3536 Average/Max 2572 9870 Anderson Erickson Drain field Evaluation DESIGNING FOR A BETTER TOMORROW Bolton & Menk is an equal opportunity employer.