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john Oliver & Associates, Inc. <br /> Civil Engineering <br /> •Land Surveying 580 Dodge Avenue, Elk River,MN 55330 <br /> Land Planning (612)441-2072 • Fax:441-5665 <br /> April 27, 1993 <br /> Steve Rohlf <br /> Building and Zoning Administrator <br /> City of Elk River <br /> something address <br /> Elk River, MN 55330 <br /> Re: Environmental Assessment Worksheet (EAW) for Elk Park Center <br /> We have prepared the following responses to the comments received for the above referenced project. If you <br /> have any questions concerning these responses feel free to give us a call. <br /> Minnesota Department of Natural Resources,Thomas Balcolm <br /> Mr. Balcolm comments on item 11b,That there is a significant mixed oak forest within one mile of the project <br /> that should be mentioned in the EAW. At the time of writing the mixed oak forest to which he has referred <br /> had been partially clear cut and partially developed. <br /> . Mr.Balcolm stated concern over the release of untreated water into a natural wetland system from the proposed <br /> project. As a result of his comment and concerns by the city engineer a system of skimmer and sedimentation <br /> basins will be created. This system will completely retain a 2" rainfall on the site. These sedimentation ponds <br /> will incorporate skimmers in the design. <br /> He also raises concerns over the volume of runoff going to the wetland. He states that a rise of 5.5 feet in the <br /> wetland area is unacceptable. The EAW did not state the impact for the creation of this site correctly. The <br /> impact of the entire tributary area to the site after full development is 5.5 feet for a one hundred year storm. <br /> After discussions with the City Engineer sedimentation/water quality ponds will be used throughout the site to <br /> retain the first 2" of runoff. The impact from the subject project itself for a 100 year storm is 1.5 feet. The <br /> following table provides an estimate of the impacts created from the proposed development. <br /> STORM EVENT IMPACT <br /> (year) (ft) <br /> 1 0 <br /> 2 0 <br /> 5 0.06 <br /> 10 034 <br /> 100 0.85 <br /> In addition the City Engineer is looking at providing an outlet from this wetland to mitigate the impact of the <br /> runoff to this wetland from a fully developed tributary area. <br /> Erosion control shall be implemented according to the MPCA Best Management Practices manual. The city <br /> will require that such practices be followed. <br /> • <br />