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City of Arden Hills <br /> November 2,2010 <br /> Page 3 <br /> Valentine — 62007100 <br /> 679.75 <br /> 6 $76.5 <br /> � 4,J <br /> Ui <br /> 877.25 <br /> 676 <br /> 2001 2002 200 2004 2005 2006 2007 2008 2009 2010 <br /> Figure L -Valentine Lake Water Level Graph(Jan 2000—Nov 2010) <br /> We understand that based on data that the City has collected on lowest structure opening for the <br /> residences adjacent to Valentine Park, the lowest opening recorded was 883.92,effectively three feet - <br /> above the 100-yr high water level(HWL)of Valentine Lake. The state minimum for lowest opening <br /> above HWL's is two feet. We believe that the current standard of three feet of free board provides an <br /> acceptable level of safety for residences adjacent to water bodies within the City. <br /> The tail water condition at the Snelling Avenue culvert that was identified in the drainage report as a <br /> "...contributing factor to the flooding in the park"may be mitigated,in part,with the installation of a tidal <br /> valve on the culvert outlet within Valentine Lake. If this approach is considered,the City will need to <br /> coordinate with,and obtain approvals from,the Mn/DNR and the Rice Creek Watershed District prior to <br /> installation. Although, if the average lake surface elevation is 878.7,no amount of mitigation with water <br /> quality and volume control BMPs in the Valentine Park sub-watershed areas will address the localized <br /> flooding in the park. This observation is based solely on the recorded OHWL of Valentine Lake and the <br /> ground surface elevation of Valentine Park. A tidal valve may represent a cost effective solution that <br /> would isolate the tail water effect created by the current OIIWL of Valentine Lake while still allowing the <br /> Valentine Park sub-watersheds to discharge through the culvert. <br /> PROPOSED STORMWATER SYSTEM LAYOUT <br /> The stormwater system layout identified in Option#1 appears to have been configured in the appropriate <br /> manner given the space constraints and park programming identified during the public meeting and <br /> recommended by the Park,Trails,and Recreation Committee. <br /> F:1_CiviHARDMT1 6 1 206451T]6.120645 Report Review_FINAL.docx <br />