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• Bc> LT4N- <br />Consulting Engineers & Surveyors <br />" 12224 NlcolletAvenue • Burnsville, MN 55337 <br />Phone (952) 890-0509 • Fax (952) 890-8065 <br />www.bolton-menk.com <br />MEMORANDUM <br />Date: August 13, 2009 <br />To: Kristine Giga, P.E., Civil Engineer <br />Michelle Olson, Parks and Recreation Manager <br />From: Travis Winter, P.E., LEED® AP <br />Subject: CP Rail Bridge Trail <br />City of Arden Hills <br />Project No.: T16.100325 <br />As requested we have updated the probable costs for constructing the CP Rail Bridge Trail. With our field <br />topography completed at the site some additional characteristics have been revealed that will make this <br />crossing more challenging. <br />The initial cost estimate for the project was based on the information available which included GIS 2' <br />contours and NWI wetland indications. No record drawings for the bridge were available. Now that the <br />topographic survey has been completed, we have identified a probable wetland located just north of the <br />bridge crossing, which was not shown on the NWI map. Our survey also revealed a very shallow bury <br />depth of the existing bridge abutment — that is, ANY excavation adjacent to this abutment will need to be <br />mitigated with a structural retaining wall. The combination of these influences makes for a more complex <br />design. <br />What we're now faced with is a deeper cut under the bridge (--7'-S'), necessary to avoid impacting the <br />wetland to the north, but also a corresponding taller wall, necessary to mitigate the deeper cut. In <br />addition, temporary shoring will likely be needed to allow the permanent wall to be built. Based on this <br />design, we estimate the project costs will be $340,000. This is quite a bit more than the original estimate <br />of $221,000 that assumed a much shallower cut. <br />Please contact me at your convenience to discuss these project developments. <br />F:1_Civil\ARDHIT 161003251Correslmemo_081309.doc <br />DESIGNING FOR A BETTER TOMORROW <br />Bolton & Menk is an equal opportunity employer <br />