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City of Mounds View Page 9 <br />Ardan Avenue Drainage Subdistrict Analysis 000435-07129-0 <br />4.5 LOW POINT AT THE KNOLLWOOD DRIVE AND ARDAN AVENUE INTERSECTION <br />Existing Flood Protection Characteristics: <br />ƒOverland area to street low point (Node 21) = 9.1 acres <br />ƒSurveyed critical flow path elevation (circled in blue above) = 909.77 feet to rear yard of 8261 <br />Knollwood Drive <br />ƒSurveyed lowest opening elevation = 909.96 feet (8261 Knollwood Drive Garage Floor) <br />ƒFlood protection between critical flow path and lowest opening elevations = 0.19 feet <br />ƒExisting downstream conveyance restriction = 18” storm sewer, between Nodes 21 and 22 <br />Proposed Improvements to Increase Flood Protection: <br />ƒUpsize existing storm sewer between Nodes 21 and 22 from 18” to 21” <br />Storm sewer conveyance capacity between Nodes 21 and 22 is increased from 5 to 7 cfs <br />Flood Protection Recommendation: <br />ƒIt appears that a berm (top of berm elevation = 911.32) has been constructed along the rear lot lines <br />of 8261 and 8241 Knollwood Drive and the low openings for these homes are 911.0 (Egress Window) <br />and 909.96 (Garage Floor), respectively. It is recommended that with the installation of the Ardan <br />Avenue trunk storm sewer improvements, this berm be lowered/removed to provide adequate flood <br />protection to the adjacent homes.