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December 22, 2008 Item No. 7B <br />Page 2 <br />Bonestroo has completed the new 2008 Drainage Report in accordance with Resolution <br />7361. A copy of the 2008 Drainage Report is included with this Staff Report, along with <br />select pages from the 1989 Drainage Report for comparison. Complete hard copies of the <br />bound 2008 Drainage Report, which includes the entire 1989 Drainage Report as an <br />appendix, are on file at City Hall and are available for review if desired. <br />Findings of the 2008 Ardan Avenue Drainage Subdistrict Analysis <br />The overall findings of the 2008 Ardan Avenue Drainage Subdistrict Analysis include the <br />following: <br />x The East Detention Pond proposed in the 1989 Drainage Report is not <br />necessary <br />x The Sherwood Road trunk storm sewer proposed in the 1989 Drainage Report <br />is not necessary <br />x Alternate improvements are possible to the storm sewer system. Features of <br />the alternate improvements include: <br />- Lower cost than the improvements proposed in the 1989 Drainage Report <br />- Less physical impact than the improvements in the 1989 Drainage Report <br />- Increased efficiency in comparison to the existing storm sewer system <br />- Flood protection characteristics of each street low point will be improved <br />through either a reduction in drainage area being conveyed at that location <br />or an increase in the storm sewer pipe size and capacity <br />x Isolated rear yard land locked areas do exist within the analysis area. <br />- Further investigation would be necessary to determine the extent of the <br />existing conditions and what options are available to address the situation. <br />Impact on the 2009-2010 Street and Utility Improvement Project <br />The 2008 Ardan Avenue Drainage Subdistrict Analysis also identified the impact of the <br />storm sewer system improvements on the 2009-2010 Street and Utility Improvement <br />Project. The impacts are summarized as follows: <br />x No new trunk storm sewer needs to be installed along Sherwood Road <br />x No new regional pond needs to be constructed <br />x A segment of existing storm sewer on Red Oak Drive south of Ardan Avenue <br />needs to be replaced with new, larger diameter pipe <br />x A future trunk storm sewer will be required on Ardan Avenue. The limits of the <br />permanent street improvements performed to Red Oak Drive on the north side <br />of Ardan Avenue should be located to allow the future pipe.