8A, TH 10 Local Access Interchange

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L TC)f'J E: f'J I< ~ Consulfin En ineers & Surveyors 12224 Nicollet Avenue · -Burnsville, MN 55337-1649 Phone (952) 890-0509. FAX (952)890-8065 I ~c:- MEMORANDUM Date: June 25, 2008 To: Kristine Giga, P "E. - Civil Engineer Greg Hoag - Public Works Director City of Arden HiHs Christopher S. Chromy, P.E., P.T.O.E~' Bolton & Menk, Inc. -. .. Highway 10 Local Access Interchange Explanation of Interchange Bridge Width BMl Project No. T42,,22335 From: RE: Per your request, J have reviewed the bridge deck width proposed for the current Local Access Interchange concept as well as the design of the frontage road to the Scherer Brothers property. My findings are sumlnarized below: Bridge Deck Width The bridge deck width in the proposed Local Access Interchange concept includes necessary turn lanes and thru lanes to accommodate anticipated traffic volunles in the year 2030, including full build out of the TCAAP development. This includes two through lanes in each direction, a single left turn lane to the northbound TH 10 entrance ralnp, and two left turn lanes to the southbound TH 10 entrance ranlp. In addition, roadway shoulders are included on the right side for both directions of travel to accommodate disabled vehicles, motorists yielding to emergency vehicles, snow storage and removal, and more advanced bicyclists. AlTIulti-use trail is also proposed to accommodate pedestrians and less advanced bicyclists. The bridge deck width fOf this interchange concept is approximately 130 feet and is needed to provide the necessary lanes, shoulders, and traiL The tight dialnond interchange design being used on the west side ofTH J 0 does result in additional width on the bridge. Since the west ramp intersection on this interchange concept is pulled in "tight" to the lnainline, there is less space for left turn storage and results in the left turn lanes being side-by-side on the bridge. This results in a wider bridge deck of approxinlately 12~, or one Jane "vidth. Conceptual design includes conservative decision-making relative to project costs and impacts. During preliminary and final design, the roadway geon1etry and bridge deck width win be finalized based on nlore defined traffic needs, cost-effectiveness, and service life expectancy. Bridges typically have a service life of 50 years or more and are planned for accordingly. The need for two \vestbound thru lanes, two westbound left tU1l1 lanes, and shoulder width should be evaluated during preliminary design. MANKATO, MN · FAIRMON!, MN · SLEEPY EYE, MN · BURNSVILLE~ MN · CHASKA, MN WILlMAR, MN. RAMSE't MN · AMES, fA www.bolfon-menk.com An Equal Opportunity Employer