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EN HILLS <br /> MEMORANDUM <br /> DATE: December 20, 2010 <br /> TO: Honorable Mayor and City Council Members <br /> Patrick Klaers, City Administrator ,yam <br /> FROM: Terry Maurer, Public Works Director 1� p <br /> Kris Giga, Civil Engineer <br /> SUBJECT: Valentine Park Drainage Review <br /> Background <br /> In February 2009, WSB prepared the Valentine Park Drainage Analysis in anticipation of a <br /> future park improvement project. Valentine Park historically has been periodically inundated <br /> when Valentine Lake's water level rises in spring snow melt or after large rainfall events. The <br /> WSB analysis was undertaken to better understand the options available for investment in the <br /> park given the periodic flooding from Valentine Lake. When the analysis was presented to the <br /> City, neighborhood concerns regarding its conclusions led to the City Council directing staff to <br /> have another consultant review the analysis and render a professional opinion regarding its <br /> conclusions. <br /> Discussion <br /> Staff solicited quotes and Bolton& Menk, Inc. (BMI)was retained to perform the review of the <br /> February 2009 WSB drainage analysis. BMI's letter dated November 2, 2010 summarizing their <br /> findings is attached. The summary of BMI's findings is that the inputs into the drainage model <br /> are accurate, and the conclusions in the WSB report appear to be appropriate. They do question <br /> the Normal Water Level (NWL) in the WSB report of 875.5 versus the Ordinary High Water <br /> Level (OHWL) they received from the DNR of 878.8. BMI also suggests the drainage model be <br /> rerun after a determination is made regarding which is the appropriate elevation so the City will <br /> have an accurate representation of a storm event. <br /> Staff also had Roseville's surveyor determine the lowest opening on the homes adjacent to the <br /> park. The lowest opening was determined to be a walk-out patio door at elevation 8839. BMI's <br /> review determined that the DNR's highest recorded lake level is 881.1. Industry standards would <br /> have the lowest opening elevation a minimum of 2' above the highest flood elevation. The above <br /> information indicates that there is 2.8' between the highest flood elevation and the lowest <br /> City Council Meeting = - <br /> 11Metro-inetlardenhillslAdmin\CouncillAgendas&Packet Information12010112-20-10 WorksessionTacket Information112- <br /> 20 ValentineParkDrainageReview.doe <br /> Page 1 of 2 <br />