Agenda - Public Works Committee - 04/18/2018

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Civil Engineer IV Linton explained that construction of the infiltration basin is necessary to fulfill the City obligations incurred with LRRWMO approval of project in The COR since 2015 and to provide capacity for future development to occur. He stated that the City has collected infiltration mitigation funds from all developments in The COR since 2015 and those funds will pay approximately 1/4 of the cost of the project. He noted that the City will pay for the remainder of the project now and will be reimbursed as future development occurs. He recommended that the Committee recommend that the City Council authorize preparation of a Feasibility Study for The COR Infiltration Basin Improvement, Improvement Project #18-09. Councilmember Kuzma referenced the remaining balance that would be owed, apart from the funds that have been paid from developers and asked where those remaining funds would come from. City Engineer Westby replied that the funds would come from the storm water fund and confirmed there are sufficient funds. Councilmember Johns asked for details on future development and how those funds would be paid to the City. Civil Engineer IV Linton replied that The COR is unique because of the wellhead protection area and therefore most of the future developers will pay into the infiltration mitigation fund. He noted that a certain area of The COR (outside of the wellhead protection area) would provide developers with the choice of whether to do their own stormwater management or to pay into the infiltration mitigation fund. Chairperson Riley asked for details on how this basin will look. Civil Engineer IV Linton stated that the basin will be about four feet deep. He stated that a requirement of the basin is that all water must infiltrate within 48 hours. He noted that selected plantings must be resistant to short-term flooding. Councilmember Johns asked if there would be landscaping. City Engineer Westby stated that a landscaping plan has not been developed yet but costs for vegetation are included in the estimate, including minimal landscaping. He replied that it will likely look more like a natural prairie area. Chairperson Riley asked if staff is being smart with the calculations for future developers to ensure that the cost would cover long-term maintenance duties. City Engineer Westby replied that the long-term maintenance would be covered through the storm water maintenance program. He stated that staff will work with PSD on the acquisition of easements and/or land, as needed. He stated that thus far, PSD has stated they would prefer to deed the triangular piece of their property to the City. He noted that if this progresses forward, staff would bring back an agreement with PSD with the plans. Public Works Committee / March 20, 2018 Page 3 of 9