THE CONCRETE BRIDGE MAGAZINE

FALL 2018

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

Issue link: http://www.aspiremagazinebyengineers.com/i/1027820

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The 6670-ft-long replacement bridge crossing the St. Croix River between Minnesota and Wisconsin includes a seven-span, 3365-ft-long extradosed main unit over the river and a dual seven-span, 1715-ft-long approach bridge with a 960-ft-long off-ramp and a 630-ft-long on-ramp. These structures were constructed with a combination of precast and cast-in-place concrete construction. The extradosed bridge, which is a hybrid between a concrete segmental box-girder and a cable-stayed bridge, has four 600-ft main spans and a total length of 3365 ft between expansion joints. The out-to-out dimension of the bridge deck is 98 ft 6 in. The approach b r i d g e i s l o c a t e d o n a 3 - d e g re e horizontal curve (1910 ft radius) with a 6% superelevation and includes a 1000- ft vertical curve before the alignment transitions to a tangent 1.74% upward grade from Minnesota to Wisconsin. The distance between the bridge deck and the water line varies from approximately 100 to 150 ft. The bridge was opened to traffic in 2017, although construction continues. When completed, the St. Croix Crossing will be the second extradosed bridge built in the United States and the longest in North America. Project Approval Process The St. Croix Crossing project has a long history. Talk of a new bridge began in 1951, with advocates for new construction arguing that the existing Stillwater Lift Bridge was hindering economic growth and causing traffic delays. However, the St. Croix River is protected by its designation as a National Wild and Scenic River, and, for decades, conservationists and some local community members opposed the construction of a new bridge because of its potential environmental impact and fiscal costs. To address these concerns and comply with federal environmental regulations, a new bridge project would need to include mitigation strategies to protect all of the following: • Historic properties • Threatened and endangered species profile ST. CROIX RIVER CROSSING / OAK PARK HEIGHTS, MINNESOTA, AND ST. JOSEPH, WISCONSIN BRIDGE DESIGN ENGINEER: HDR, Minneapolis, Minn., and COWI North America Ltd., North Vancouver, BC PRIME CONTRACTOR: Lunda Ames Joint Venture (Lunda Construction Company, Black River Falls, Wisc., and Ames Construction Company, Burnsville, Minn.) OTHER CONSULTANTS: Bridgescape, LLC, Columbia, Md.; Illumination Arts, Bloomfield, N.J.; M-P Consultants, St. Louis Park, Minn.; Prime Engineering, Baltimore, Md.; Rani Engineering, Minneapolis, Minn.; RWDI, Guelph, ON; Weidlinger Associates, New York, N.Y. ST. CROIX RIVER CROSSING by Craig Lenning, HDR, and Don Bergman, COWI North America Ltd. A view of the St. Croix River Crossing looking toward the Wisconsin shore. The unique shapes of the rounded, "reed- like" split piers and the cantilevered pedestrian overlook are visible at the pier in the foreground. Photo: HDR. 16 | ASPIRE Fall 2018 P R O J E C T

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