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<br />05/:31/94 <br /> <br />15:55 FAX 612 441 5665 <br /> <br />JOHN OLIVER ASSO <br /> <br />~001 <br /> <br />e <br /> <br />Civil ElIginftrbag <br />Land Sl.tn'eying <br />und P'411njllg <br /> <br />John Oliver & Associatesl Inc. <br /> <br />SID Dodge AWlmue, m RMr, MN SSJ3D <br />(61%) 441-~07~ . F4.JC 441-$66$ <br /> <br />May 31, 1994 <br /> <br />Steve Rohlf <br />city of Elk Ri~er <br />13065 orono parkway <br />Elk River, .MN 55330 <br /> <br />Re: EAW for Lakoduk site <br /> <br />Dear Mr. Rohlf, <br />Per your request we have conducted a preliminary analysis to determine what <br />potential impacts the proposed development might have on the water quality of <br />Lake orono. <br /> <br />The sedimentation ponds proposed should remove most of the particulate matter <br />above 5 microns in size. Nurp ponds typically remove approximately 90% of 5 <br />micron sized particles for ponds with surface areas of o. 8~ residential areas and <br />1. 7% commercial areas respectively. The ponds as designed represent 2.43% of t.he <br />total residential area. The commercial area ponds are not yet designed but will <br />be meeting this criteria. <br /> <br />other common stormwater pollutants have the following reductions at the 90\ <br />removal. <br /> <br />e <br /> <br />Lead and copper: 77% removal <br /> <br />COD, BOD, <br />soluble and <br />total phosphorus, <br />Nitrates and zinc: 54% removal <br /> <br />Organic Nitrogen: 36' <br /> <br />This information comes from Stomwa't.er Wet Detention pond Design for water <br />Quality Benefits, 1994, Robert pitt Pb..o, Lewis ~lishers. <br /> <br />We also examined the relative impact to the lake in ter.m.s of i't.s total watershed. <br />please see the attached analysis. ~he total increase in total phosphorus is <br />slightly more than 0.04% but with a slightly decreased residence time in the lake <br />due to the increased volume of runoff proposed to reach the lake. The result is <br />no significant increase in chlorophyll-A which of course is an indicator of <br />nutrients reaching the lake. <br /> <br />Based on this info:r:mation we feel that we can say that there will be no <br />significant impact to the water quality of Lake orono. <br /> <br />Sincerely, <br /> <br />th~ <br /> <br /> <br />U: Tony Emmerich <br /> <br />e <br /> <br />file: 6719-05 <br /> <br />i <br />