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Portage Lake Lift Bridge Rehabilitation

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The Portage Lake Lift Bridge (built 1959), which connects the cities of Houghton and Hancock, is the heaviest and widest double-deck bridge in the world and only one of its kind in the state of Michigan. The lift span, which can be raised up to 100-ft., features an upper and lower deck. The upper deck carries four lanes of US Highway 41 and M-26. The lower deck originally carried railroad traffic and currently is used for permit vehicles in the summer and as part of the statewide snowmobile trail system in the winter. It is the only bridge in the region connecting Copper Island in the north with the rest of the Keweenaw Peninsula to the south. In an effort to preserve and maintain this vital crossing, the Michigan Department of Transportation (MDOT) asked Modjeski and Masters (M&M) to lead the structural, electrical and mechanical rehabilitation of the massive lift span.

The project focused primarily on the replacement of the wire ropes which connect the lift span to the counterweight. To successfully accomplish this, M&M performed work during winter months when the bridge could be left in the fully lowered position, with traffic maintained on the upper deck. This also helped to accommodate snow mobile traffic which commonly uses the lower deck during the same season. M&M also implemented homeland security recommendations, provide structural repairs to the operator’s house, and design upgrades to the barrier gates. Implementing the repairs and retrofits with minimal disruption to traffic was very important as this is the only connector for emergency services on each side of the lake.

Bridge Geometry
Main Span 269 feet
Total Length 1,310 feet
Lanes on Structure four lanes, multiple sidewalks