The City of Detroit, in collaboration with several public and non-profit organizations, is undertaking the Link Detroit project to strengthen connectivity between key destinations through on- and off-road non-motorized greenways and bike lanes, bridge replacements and streetscape improvements. Wade Trim designed bridge improvements within the Dequindre Cut Greenway Phase 2 that links to other multimodal connection points in and around Eastern Market. Bob Breen, PE, Senior Bridge Engineer, presented the project at the Michigan Infrastructure Conference in Plymouth as part of a joint session with SmithGroupJJR entitled, “From Roadways to Greenways – Reconnecting the Motor City”. The Conference was sponsored by the Michigan associations of the American Council of Engineering Companies, American Society of Civil Engineers, and Urban Land Institute.

Four bridges constructed in the 1920’s over the Grand Trunk Railroad, now the Dequindre Cut Greenway, had become structurally deficient and in extremely poor condition. Wade Trim designed the replacement of three of these bridges (Wilkins, Division and Adelaide) and the removal and site restoration for the fourth bridge (Alfred) for the City of Detroit Department of Public Works. The bridges are two-span, precast concrete arch structures with wing walls that tie into existing cast-in-place concrete retaining walls. Wide sidewalks were incorporated into all the bridges to help pedestrians and other non-motorized users access Eastern Market, the Midtown Loop Phase IV pathway, the Dequindre Cut and Hamtramck Connector. Bike paths were added at the Wilkins Street bridge and room for future bike paths was incorporated into the other bridges.

Typical of urban infrastructure improvements, special care was needed to work near existing utilities and buildings. The bridge replacements are supported on steel H-piles that extend 130 feet to bear on hardpan. With the tight constraints of existing adjacent buildings, a two-stage piling operation was used to minimize vibrations on the buildings. Vibration monitoring was conducted to measure effects to the existing buildings to prevent damage. In addition, with the tight right-of-way at each bridge, precast retaining walls were used instead of conventional concrete footings that would have interfered with building foundations.

Context sensitivity is important to the City and project stakeholders. Care was taken to visually blend the improvements with adjacent buildings and structures as well as other projects in the area. Concrete bridge and wall railings match the 1928 concrete rails while meeting AASHTO requirements. A pedestrian fence design similar to existing bridge fencing along the Midtown Loop was incorporated into all four locations to create a similar look. Lighting on and under the bridges will provide security at the bridges and pathway. The streetlight fixtures mounted at each bridge corner match the lights of the Eastern Market improvement project. Wade Trim coordinated with SmithGroupJJR to achieve a unified look for separate bridge and pathway projects. The Division and Adelaide bridges are open to traffic and the Wilkins bridge is anticipated to open in July 2015.

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Bridge replacements within the Dequindre Cut Greenway Phase 2 section will strengthen connectivity between downtown Detroit destinations including the RiverWalk, Eastern Market, Midtown Loop and Hamtramck Connector. (Click on map to enlarge)