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The US 31–Island Lake Outlet Bridge is a double-leaf bascule bridge in downtown Charlevoix, Michigan, that carries U.S. Route 31 (US 31, Bridge Street) across Island Lake Outlet (also known as the Pine River Channel). It is the fifth bridge to cross the channel there with the first being a pedestrian-only structure that was built in the nineteenth century. The bridge was planned in 1940, but World War II delayed the acceptance of bids until 1947. Construction finished in 1949 and the bridge opened to traffic in late June of that year. The bridge is part of the National Highway System.〔 ==History== Island Lake Outlet, also known as the Pine River Channel, was dredged in 1870 to connect Lake Michigan to Lake Charlevoix through Round Lake.〔 A total of five bridges have crossed the channel at this location; the first was a small footbridge built in 1869.〔〔(【引用サイトリンク】url= http://www.charlevoix.org/Play/memorial-bridge.html )〕 The current bridge replaced a swing truss bridge built by the city of Charlevoix in 1901. The US 31–Island Lake Outlet Bridge was designed by the bridge division of the Michigan State Highway Department, led by George M. Foster, and by consulting engineers Haslett and Erdal. Plans were prepared in 1940, but World War II delayed the project. In January 1947, the department announced that it would accept bids beginning February 6 for the bridge's construction. Five bids were received and the contract was awarded to the lowest bidder ($697,981) submitted by L.W. Lamb Company of Holland, Michigan, and the Luedtke Engineering Company of Frankfort, Michigan.〔 Construction was overseen by N. F. Kinney from the state highway department and H. J. Conroy (a district bridge engineer). Fabricated steel was purchased at a cost of $270,433 from the Mt. Vernon Bridge Company of Mt. Vernon, Ohio. In late May 1947, Luedtke Engineering arrived on site with their pile driver and construction commenced. Electrical work was contracted to Lake Shore Engineering Company from Iron Mountain, Michigan. In August, a was towed from Sturgeon Bay, Wisconsin, to carry traffic while the new bridge was under construction. The temporary bridge was fixed to the north bank and mounted to a pontoon on the south end to permit navigation of the channel.〔 By November, construction of the north pier was underway and the south pier coffer dam was being installed. By March 1948, the north pier was ready to have its two steel bascule racks installed. However, the bronze-alloy trunnions were difficult to cast and were not satisfactory until the third attempt in September. In October, bascule girders arrived, manufactured by Mt. Vernon Bridge Company. Assembly of the south leaf was completed by early November, but the north leaf was delayed by poor weather and an insufficient number of laborers worsened by the start of deer hunting season.〔 By January 1949, the south counterweight had been poured and welding of the mesh road surface of the south leaf was underway, followed by work on the north side. Into spring, machinery was installed and finishing details completed. Plans for the transformer structure were approved in April and the bridge opened for traffic on June 27, 1949. On July 30, it was dedicated in memory of twenty-two locals who died fighting in World War II. The ribbon-cutting ceremony was performed by State Highway Commissioner Charles Ziegler.〔 The bridge originally had standard metal panels along the sidewalks.〔 In the early 1990s, they were replaced with new railings, but these were replaced again with metal lattice railings in the mid-1990s through the efforts of Edith Gilbert.〔〔(【引用サイトリンク】url=http://www.chxhistory.com/2007news/2007-08.htm )〕 The bridge is listed on an inventory of historic bridges maintained by the Michigan Department of Transportation.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「US 31–Island Lake Outlet Bridge」の詳細全文を読む スポンサード リンク
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