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LANDFORM <br />MINNEAPOLIS- PHOENIX <br />¥ <br />MEMORANDUM 650 BUTLER NORTH BUILDING <br />510 FIRST AVENUE NORTH, MINNEAPOLIS. MN <br />55403 <br />OFFICE: 612 2529070 <br />FAX 612 252 9077 <br />DATE April 17. 2002 <br />Michael Gaffron, City of Orono <br />FROM Steve Johnston <br />copy Terry Dahlstrom, DahlsL'om Development LLC <br />Regional Pond Feasibility - Orono Village <br />Feasibility Report <br />for <br />Orono Village Regional Pond <br />The Orono \MIlagc project will require construction of a regional pond that would scr\'c the site <br />and other developed and undeveloped properties north of US Highway 12 and east of Old <br />Cr>’stal Bay Road. This 104-acre area, as determined by topographic information obtained by <br />Landform and the City of Orono, is comprised of a large amount of woods, wetlands, open <br />fields, 1-2 acre residential lots, city oflioes, .school district facilities, public works facilities, and <br />two existing MN/DOT treatments ponds. The proposed regional pond will provide NURP <br />standard treatment of storm water as well as runoff rate control for the 100-yr storm event. <br />The regional pond w ill be constructed within MN/POT right-of-way in essentially the same <br />location as the existing ponds. Preliminary correspondence inu cates that MN/DOT would be <br />receptive to allowing construction s ithin the right-of-way if the City initiates the request. <br />Preliminary hydrologic studies have shown that the pond volume necessary to meet NURP <br />criteria is approximately 8.2 acre-feet. The current Orono Village concept pond has a volume <br />of approximately 8.5 acre-feet. Furthermore, the runoff rate for the existing drainage basin is <br />approximately 33.5 cfs through a 24” culvert under Highway 12. The new pond will be <br />limited to this discharge rate under fully develop«'d conditions within the watershed. To detain <br />this runoll rmd not flood the Orono Village project it will be necessary to lower the normal <br />water level of the pond. This can be accomplished by jacking a new 24” culvert under <br />Highway 12 approximately three feet lower than the existing cuKert. The new pipe will act as <br />the primary pond outlet with the existing culvert providing for emergency overflow purposes. <br />Page 1 ^2789