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Pamela Sheldon <br /> June 6, 1997 <br /> Page 2 <br /> We suggest the public works department make a preliminary investigation to determine if a curb <br /> cut <br /> will remain as the primary means to drain Eastwood Road in the future. Another option may be to <br /> install catch basins and storm sewers which discharge to the ditch. A review of the submitted survey <br /> data indicates that it may be difficult to construct catch basins due to the low elevation of Eastwood <br /> Road and high elevation of the Highway 10 ditch. <br /> If the curb cut remains,the existing swale needs to be relocated to drain around the pond if the city <br /> wishes to maintain a direct discharge to the highway ditch. Another option is to work with the <br /> developer and have the pond expanded to provide water quality improvements for both their site and <br /> the madway. If Eastwood Road does drain into the pond,the developee s engineer must include this <br /> additional drainage area in their hydrologic calculations. <br /> Site Grading Plan <br /> Upon review of the plan,we do act have the ditch,parking lot,and pipe slopes. A quick check of the <br /> site indicates that the parking lot has a flat slope which does not provide good drainage.If a surface <br /> elevation of 910.8 is at the northern most end of the site and the pond discharge is at 908.0,the slope <br /> in the parking lot is 0.49 percent(3.8 feet!570 feet). This is a relatively flat slope and may cause <br /> drainage problems such as standing water and ice patches in the parking lot. A final grading plan <br /> should show how this site drains. <br /> III Pend Grading Plan <br /> The developerprovided a rough outline of the pond but did not provide fins?contours. Due to it's <br /> location near pedestrian traffic,a safe pond she r1 d be designed by the developer and reviewed by the <br /> Cry. 'The City needs to verify that the pond meets retention pond standards for safety and function. <br /> At a minimum the pond.should include 10 to 1 side slopes in the first foot of retention volume(or <br /> be fenced), have a water depth of at least four feet, and discharge at an elevation that will be high <br /> enough to drain to the highway ditch. <br /> Hydrologic c icniatiens <br /> A summary of the hydrologic calculations were provided but this information contained no detailed <br /> data. We would like to review all of the hydrologic calculations,fru-furling input data,that was used <br /> to determine the highwarer elevamien.(s)and sediment pond size. <br /> RJKlrjkIJ'TD <br /> SAMA M!D <br />