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Howard R, Green Company <br />CONSULTING ENGINEERS <br /> <br />July 16, 1997 <br />File: 800720J-0240 <br /> <br />CONS[tTINIi £iliINEEII~ <br /> <br />Mr. Steve Rohlf <br />Building & Zoning Administrator <br />City of Elk River <br />13065 Orono Parkway <br />P.O. Box 490 <br />Elk River, MN 55330 <br /> <br />RE: <br /> <br />TILLER CORPORATION MINERAL EXTRACTION AND HOT-MIX ASPHALT PLANT <br />PERMIT APPLICATION <br /> <br />Dear Mr. Rohlf: <br /> <br />As you requested, we have reviewed the package of information submitted by Tiller Corporation <br />concerning their request for a mineral extraction and hot-mix asphalt plant permit. As you are <br />aware, the property in question is approximately 130 acres of land located in the northwest <br />quadrant of 221st Avenue and TH 169. There is a small portion of the property in question that is <br />south of 221st Avenue. Much like the plant along Proctor Avenue, the proposal is to operate both <br />sides of the road utilizing a culvert conveyor system under 221 st Avenue. The application indicates <br />that it will take approximately 20 to 25 years to complete mining the entire site. <br /> <br />We have reviewed this permit application from two standpoints, one being drainage and the other <br />being transportation considerations. With regard to these two issues, we would offer the following <br />comments: <br /> <br />1. DRAINAGE <br /> <br />The permit indicates that during the mining operation, surface water drainage will be <br />directed to Iow areas within the property. No surface water drainage is expected to be <br />directed off-site. Sedimentation would occur in these temporary ponding areas. The permit <br />application indicates the ponds could be readily cleaned by on-site equipment. Erosion will <br />be minimized by seeding and mulching side slopes as appropriate. <br /> <br />The reclamation plan for the site indicates a lowest finished elevation of approximately 956 <br />in the northeast quadrant of 221st and TH 169. The Highway 169 intersection elevation is <br />approximately 1,010. This would indicate that the finished mine elevation will be <br />approximately 50 feet below TH 169. It appears that the only reasonable long-term <br />drainage scenario for this site would be an on-site retention basin preceded by <br />appropriately sized sedimentation basins for quality control. 'This type of drainage pond <br />with no outlet would have to be appropriately sized for the worst storm event that might be <br /> <br />1326 Energy Park Drive · St. Paul, MN 55108 · 612/644-4389 fax 612/644-9446 toll free 800/888-2923 <br /> <br /> <br />