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City of Mounds View Page 10 <br />Ardan Avenue Drainage Subdistrict Analysis 000435-07129-0 <br />4.6 LOW POINTS ON LAPORT DRIVE AND REDOAK DRIVE,SOUTH OF ARDAN AVENUE <br />Existing Flood Protection Characteristics: <br />ƒOverland area to street low point (Nodes 28 and 29) = 2.6 acres (Laport Drive), 6.0 (Redoak Drive) <br />ƒSurveyed critical flow path elevation (circled in blue above) = 908.75 feet (Laport Drive), 906.43 <br />(Redoak Drive) <br />ƒSurveyed lowest opening elevation = 909.63 feet (8200 Redoak Drive Garage Floor) <br />ƒFlood protection between critical flow path and lowest opening elevations = 0.88 feet <br />ƒExisting downstream conveyance restriction = 18” storm sewer, between Nodes 29 to 31 <br />Proposed Improvements to Increase Flood Protection: <br />ƒUpsize existing storm sewer between Nodes 29 and 30A from 18” to 21” <br />Storm sewer conveyance capacity from Node 29 to the proposed trunk storm sewer in Ardan <br />Avenue is increased from 6 to 10 cfs <br />ƒAbandon 18” storm sewer between Nodes 30A and 31 and construct new storm sewer in Ardan Avenue <br />Storm sewer conveyance capacity from Node 30A is increased from 8 to 21 cfs <br />Flood Protection Recommendation: <br />ƒThe existing beehive catch basin rim elevation in the rear of 8200 Redoak Drive is 3.5 feet above the <br />ground in this area. Presumably the rim elevation of this structure was raised to prevent storm sewer <br />flows from surcharging out of this structure and flooding the rear yard areas. It is recommended that <br />with the installation of the Ardan Avenue trunk storm sewer improvements, this rim elevation be <br />lowered to match the adjacent ground elevation.