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. . . URS Worksession Item 2A MEMORANDUM Thresher Square 700 Third Street South Minneapolis, rvIN 55415 Phone: (6]2) 370-0700 Fax: (612) 370-1378 To: Ms. Michelle Wolfe/ City of Arden Hills Copy: Frank Ticknor/URS Tom Moore/AH File: 31809733 From: Greg Brown Arden Hills City Engineer Date: July 18, 2005 Subject: Lift Station #7 Issues Background The City completed the reconstruction of Lift Station #7 during the spring of2004 which included the installation of a new wet well and two submersible pumps, Lift Station #7 tributary area includes the residents along Sandeen Road and the Presbyterian Homes senior care facility. The lift station is located on an easement within Presbyterian Homes' property, Over the past few years City staff noticed the appearanee of rags and clothing in the sanitary sewage handled at Lift Station #7, These materials are illegal to dump in the public sewer and cause the pumps to clog ultimately requiring City staff to physieally remove and dispose ofthe material. This situation has been discussed with Presbyterian Homes numerous times over the past several years, Earlier this spring, City staff, URS and Presbyterian Homes' plant engineer conducted a series of meetings to determine a solution to the problem, Presbyterian Homes indieated that most of the problem is out of their control since it is being caused by residents who are not supervised, Presbyterian Homes has informed their staff that dumping cloth and/or rag materials into the sewer is illegal and has agreed to evaluate the paper products that are utilized in the faeility to see if any ehanges can be made to limit the introduction of industrial strength paper towels etc, from being dumped in the sewer. It is clear however that the complete elimination of this problem is not within the power of the staff and management of Presbyterian Homes, A number of options were considered to deal with the problem during the series of meetings; the following is a summary of the proposed solution, Proposed Solution The proposed solution to the problem is to replace the two standard pumps with two "chopper" pumps which grind up the material being discharged, The chopper pumps are submersihle pumps and are compatible with the existing lift station infrastructure, These pumps should essentially eliminate the type of clogging which has occurred over the past several years as the materials would be shredded and pumped down-stream. The two standard pumps could be salvaged and utilized as a part of the rehabilitation of Lift Station # I or # I] in the future, Presbyterian Homes has purchased two chopper pumps which are anticipated to be installed in late July, 2005,