10-25-2010 Council Packet - Laserfiche WebLink

Home Browse Search

City of Orono Project No: 000139-10047-0 Old Crystal Bay Road Reconstruction Page 11 CITY OF ORONO – OLD CRYSTAL BAY ROAD RECONSTRUCTION 5.0 Storm Sewer Improvements The existing street consists mainly of a rural section served by drainage ditches, culverts, and a minimal amount of storm sewer. The existing stormwater system generally outlets runoff at three points: to the wetland north of CSAH 6, to the wetland just north of City Hall, and to the east to a ditch and existing storm sewer along the north side of CSAH 112. The latter two outlet points ultimately outlet to the Stone Bay regional pond between Kelley Parkway and CSAH 112. Under the proposed improvements, most of the roadway will be reconstructed with an urban street section with curb and gutter and storm sewer. The northerly 600’ is proposed to remain a rural section with ditches to convey stormwater. The outlet points and drainage areas will generally remain the same. The proposed storm sewer improvements are shown in Figure 4. The Minnehaha Creek Watershed District (MCWD) requires stormwater treatment to be incorporated into a project if there is a proposed net increase in hardcover. Given that the proposed improvements to Old Crystal Bay Road consist of adding turn lanes and/or roundabouts, there will be a small increase in hardcover (less than 1 acre). Therefore, we must include Best Management Practices (BMPs) to address potential water resource impacts as a result of the proposed improvements. Proposed BMPs will limit the amount of impervious surface, promote on-site filtration, control flow rates, and limit sediment and pollutant discharge from the site. Proposed locations for BMPs are shown in Figure 4. Potential BMPs are listed below. RURAL SECTION A series of ditches and culverts will convey runoff from the road north to the existing culvert under CSAH 6. BMPs such as filtration basins/rain gardens can be incorporated into the ditches to minimize runoff rates and sediment discharge. The BMPs can be constructed adjacent to the roadway within the existing right-of-way. URBAN SECTION There is a high point in the road approximately 1400’ south of CSAH 6. Runoff to the north of the high point up to the northernmost Orono Middle School/High School driveway (approximately 600’ of roadway) will be routed through proposed storm sewer into the existing storm sewer in the Orono Middle School parking lot. It will then be routed to the existing pond just north of the Middle School parking lot. The size of the pond may need to be expanded to accommodate this additional runoff. Runoff to the south of the high point will be collected in storm sewer and routed south to CSAH 112 and then east to an existing 24” – 30” storm sewer pipe that runs parallel to CSAH 112. The 24” portion of this pipe is not large enough to convey the additional runoff, so it will be upsized to 30” pipe. This pipe then outlets into the Stone Bay regional pond between Kelley Parkway and CSAH 112. The pond has been sized to treat this runoff from Old Crystal Bay Road. We have identified the area in the northeast Item #10 - CC Agenda - 10/25/2010 Old Crystal Bay Road Reconstruction Feasability Study [Page 14 of 42]