Laserfiche WebLink
City of Arden Hills - Indian Oaks Area Downstream Drainage Review <br />March 12, 2018 <br />Page 4 <br /> <br /> <br />Building a legacy – your legacy. <br />Equal Opportunity Employer | wsbeng.com <br /> <br />Figure 3. Colleen Wetland and Trail Crossing <br /> <br /> <br /> <br />IV. DOWNSTREAM DRAINAGE IMPROVEMENTS <br /> <br />A 15”, 18”, and 21”/24” combination discharge pipe from the IOC Wetland and Ponding Area was <br />analyzed and considered in evaluating the necessary downstream improvements. The 2-, 10-, and 100- <br />year NOAA Atlas-14 storm events were analyzed. The proposed improvements necessary to increase <br />peak discharge rates from the IOC Wetland to provide additional protection are described below. <br />Attachment A shows the location of the proposed improvements for the 18” and 21”/24” discharge pipe <br />options. A summary table of the analysis results is provided in Attachment B showing the highwater <br />levels and peak discharge rates at key locations. This table also lists the critical elevations where flooding <br />of adjacent properties would potentially occur. <br /> <br />15” Option <br />The following summarizes the proposed 15” discharge pipe improvements: <br />- Install 15” HDPE pipe from Indian Oaks Court to Colleen Avenue. Connect to the existing <br />manhole in Colleen Avenue. <br />- Re-establish the emergency overflow (EOF) between the Ponding Area and Colleen Avenue and <br />EOF north of the Colleen Avenue sag to 1’ below the adjacent house low opening. <br /> <br />The 15” discharge pipe option results in a 100-year high water level elevation in the IOC Wetland and <br />Ponding Area of 962.52 and 961.71, respectively. The 15” option provides similar discharge results to <br />existing and does not warrant additional downstream improvements. <br /> <br />18” Option <br />The following summarizes the proposed 18” discharge pipe improvements: