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Steel Shots: Rehabilitating the Heaviest Double-Deck Lift Bridge
Posted by Tasha Weiss on October 18, 2013 at 4:21 PM.


The steel Portage Lake Lift Bridge, which connects the Michigan cities of Houghton and Hancock, is the heaviest and widest double-deck bridge in the world and the only one of its kind in the state. Photo: Martin Hogan
portage-lake-lift-bridge-2.jpgBridge engineering firm Modjeski and Masters has been selected by the Michigan Department of Transportation (MDOT) for the rehabilitation design of the Portage Lake Lift Bridge, a 269-ft-long, 54-ft-wide steel lift bridge. The lift span, which can be raised up to 100 ft, features an upper and lower deck capable of carrying a total of eight lanes of US Highway 41 and M-26. Photo at left (click to enlarge): Nathan Holth


As part of the agreement, Modjeski and Masters will lead the steel replacement design as well as the electrical and mechanical design of the rehabilitation.


The project will focus primarily on the replacement of the wire ropes, a critical hoisting mechanism. To successfully accomplish this, Modjeski and Masters engineers proposed that replacement take place during winter months when the bridge can be left in the fully lowered position, with traffic maintained on the upper deck. This would also help to accommodate snowmobile traffic, which commonly uses the lower deck during the same season. The engineering team will also implement homeland security recommendations, provide structural repairs to the operator’s house, and design upgrades to the barrier gates.


Preservation of this historic structure is a high priority. The Portage Lake Lift Bridge was completed in 1959 and is the fourth bridge crossing to be built at the site. The bridge replaces two steel swing bridges before it, and supercedes the original 1875 wooden swing bridge.
“The Portage Lake Lift is no doubt an iconic structure due to its sheer size, but also its history of connecting the two communities,” says Kevin Johns, P.E., project manager and movable bridge business unit leader with Modjeski and Masters. “We’re very grateful to continue our long-term relationship with MDOT, and are thrilled to help with the rehabilitation of this monumental bridge.”


The rehabilitation design will be finished by the end of next summer and construction will take place during the first half of 2015.

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