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US-31 / Island Lake Outlet

MDOT Historic Bridge US-31 / Island Lake Outlet aerial

County: Charlevoix

City/Township: Charlevoix

Location: US-31 / Island Lake Outlet

Year Built: 1949

About this Bridge:
The double-leaf bascule bridge spans Island Lake Outlet, also known as the Pine River Channel. The channel, which was dredged in 1870, connects Lake Michigan to Lake Charlevoix via Round Lake, a popular harbor. The bridge carries US-31 (Bridge Street) in downtown Charlevoix.
The 44-foot steel-mesh roadway is flanked by six-foot sidewalks, which are cantilevered beyond the outer girders of the bascule. The metal-lattice replacement railings are somewhat more ornate than the original standard highway department metal panels, but are not a serious infringement on the integrity of the bridge's design. When closed, the bridge has an overhead clearance of 17 feet. Electric motors open the 45-foot leaves, providing a 90-foot channel. The machinery and casings that move the leaves weigh some 50 tons. The equipment is controlled from an operator's house at the bridge's southeast corner, with transformers in a vault on the east bank. Barriers rise from pockets in the pavement to stop vehicles from reaching the rising leaves. Gates and flashing signals also warn motorists that the bridge is opening. Facted concrete piers support the bascule leaves. The piers also support 40'-10" rolled-steel-beam approach spans with concrete roadways. The abutments are supported by thousands of cyprus pilings, while the bascule piers rest on steel piles.

This location has served as an important crossing for the area since at least 1869, when the first of a series of five bridges was erected here. The current bascule replaced a swing truss span built by the city in 1901. The new structure was designed by the state highway department bridge division, led by George M. Foster, and by prominent Chicago consulting engineers Haslett and Erdal, founded in 1936 as the successor to the Scherzer Rolling Lift Bridge Company, a pioneer in bascule design. Plans for the bridge were prepared in the early 1940s, but the project was delayed by World War II. In January 1947, the state highway department announced that it would open bids for erecting the bridge on 6 February. Five bids were submitted. The lowest, $697,981, was from contractors L.W. Lamb Company of Holland, Michigan, and the Luedtke Engineering Company of Frankfort, Michigan, who were awarded the contract for erecting the superstructure and substructure and building the detour roadway. The state purchased the fabricated steel from the Mt. Vernon Bridge Company of Mt. Vernon, Ohio, for $270,433. Work on the approaches was anticipated to cost an additional $46,500. The electrical contractor was Lake Shore Engineering Company of Iron Mountain, Michigan.

Luedtke Engineering's pile driver arrived in late May 1947, and preliminary work was soon underway. N.F. Kinney, project engineer for the state highway department, oversaw the project with district bridge engineer H.J. Conroy from Cadillac. In August, an old 123-foot swing-truss spans was towed across Lake Michigan from Sturgeon Bay, Wisconsin, for use as a detour. The north end of the truss was fixed to the river bank; the south end, floating on a pontoon could move to open the Pine River Channel for navigation.

By November, work was progressing on the north pier, and the coffer dam for the south pier was being set in place. The north pier was ready to receive its pair of steel bascule racks by March 1948, but the company had problems, however, casting the bronze-alloy trunnions. After two failed attempts, a set finally met the specification in September.

In the meantime, construction continued on the approaches and retaining walls. The assembled bascule girders arrived from Mt. Vernon in Octover, and workers rushed to install them before the onset of winter. The south leaf was assembled by early November, and attention then shifted to the north leaf. Bad weather and a labor shortage, compounded by the opening of deer hunting season, slowed progress towards the end of the month.

By January, 73 tons of concrete had been poured for the south counterweight, and crews were welding the steel-mesh deck on the south leaf. Work on the north counterweight followed. During the rest of the winter and into the spring, machinery was installed and other details were finished. The highway department approved plans for the transformer house, to the southeast of the bridge, in April.

The bridge was opened to traffic on 27 June, but it was not until 30 July that the structure was officially dedicated as a memorial to 22 local men who died during World War II. State Highway Commissioner Charles Ziegler used oversized wooden sheers to formally cut the ribbon to the bridge.