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City of Arden Hills - Indian Oaks Area Downstream Drainage Review <br />March 12, 2018 <br />Page 5 <br /> <br /> <br />Building a legacy – your legacy. <br />Equal Opportunity Employer | wsbeng.com <br /> <br />- 18” RCP outfall with outlet control structure from IOC Wetland <br />- 18” HDPE pipe from Indian Oaks Court to Colleen Avenue <br />- 18” RCP along Colleen Avenue <br />- Install Additional Inlet at Colleen Avenue Sag for revised sewer configuration and to improve <br />roadway ponding. <br />- Directional drill 12” DR-17 HDPE parallel to existing 15” RCP. Directional drilling new storm sewer <br />will minimize disturbance to adjacent properties and avoid excavation conflicts with utilities and <br />timber retaining wall. See Figure 4 (below). <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 />- Provide additional riprap at storm sewer outfall to Colleen Wetland. <br />- Raise bituminous trail grade adjacent to the Colleen Wetland to 932.80 at EOF (Approximately <br />200ft of trail improvements). <br />- Outlet control structure with 27” discharge pipe for Colleen Wetland rate control and 18” culvert <br />- Pavement removal/replacement and other associated work. <br /> <br />The 18” discharge pipe option results in a 100-year high water level elevation in the IOC Wetland and <br />Ponding Area of 962.20 and 959.47, respectively. <br /> <br />Figure 4. Colleen Avenue Sag Improvements <br /> <br /> <br /> <br />21”/24” Option <br />The following summarizes the proposed 21”/24” discharge pipe improvements: <br />- 21” RCP outfall with outlet control structure from IOC Wetland