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EM <br /> 8300 Norman Center Drive 555 West 27th Strwt <br /> Minneapolis,MN 55437-1026 Hibbing,MN 55746 <br /> Phone:(612)832-2600 Phone:(218)262-3465 <br /> Engineering Company Far (612)832-2601 Fax. (218)262-3460 <br /> March 12, 1996 <br /> Mayor and City Council <br /> City of St. Anthony <br /> 3301 Silver Lake Road <br /> St. Anthony, Minnesota 55418-1699 <br /> Re: Drainage District 6 Stormwater Modeling <br /> Dear Mayor and City Council: <br /> This letter will outline the scope of work necessary to evaluate whether there is value in partial <br /> implementation of the storm drainage system recommended in the July 1992 report, Stormwater <br /> Management Analysis, District 6 Drainage Basin. It is my understanding that the City Council wishes <br /> to better estimate the costs and benefits associated with development of a stormwater storage basin in <br /> the trailer park south of 27th Avenue N.E. and east of Stinson Boulevard. Because a partial <br /> implementation scenario was not modeled in 1992, additional analysis will be necessary to establish <br /> O these costs and benefits. The scope of work which is necessary is described below. <br /> • Define Scope of Improvements: To development the storage basin will require acquisition of <br /> right-of-way and excavation of the storage basin, improvements to the storm sewer system on <br /> Wilson Street including special connections to existing storm sewers in the alley south of 27th <br /> Avenue N.E., and possible adjustments to existing sanitary sewer and water systems. <br /> — Stormwater Storage Basin: Alternative grading plans will be considered to determine an <br /> upper and lower limit of property requirements for developing storage. The alternative <br /> stormwater storage designs will be described, and construction costs for storage will be <br /> estimated. <br /> — Storm Sewer Improvements: The primary advantage to constructing this pond will be <br /> reduced flooding along St. Anthony Boulevard and in the area of Pahl Avenue and Wilson <br /> Street. In order to achieve these benefits, upgrading the storm sewer system in Wilson <br /> Avenue will be necessary. The preliminary layout of this improvement, including the pond <br /> inlet, pond outlet, and special connections to nearby existing storm sewers will be <br /> determined. Cost will be estimated for the proposed storm sewer improvements. <br /> — Utility Improvements: Barr will evaluate whether utility adjustments will be necessary in <br /> order to upgrade the storm sewer in Wilson Street. It is possible that the new storm sewer <br /> will interfere with existing sanitary sewer and water facilities and modifications to the <br /> sewer and water facilities will be necessary to accommodate the storm sewer. The cost for <br /> these utility adjustments will be estimated. <br /> • Determine Benefits of Improvements: The runoff models which were used to develop the 1992 <br /> recommendations will be used as the basis for a model of the proposed improvements. The <br /> O Barr computer hydrograph runoff program will be used to determine design flow and the timing <br /> of flows within the storm sewer system. The SWAMP model will be used to evaluate storm <br /> sewer system performance because downstream flood levels have significant impact on the <br />