Hardy Bridge is a Warren through truss, three-span, two-lane bridge in the western United States. It crosses the Missouri River and is located at milepost 6 on Old U.S. Route 91, about southwest of Cascade, Montana, which is southwest of Great Falls.
Constructed in 1931, it was one of many similar bridges built during a great expansion of bridges and roadways in the state of Montana. It was added to the National Register of Historic Places on January 4, 2010.
Hardy Bridge is named for the unincorporated small community of Hardy, which is about downstream from the bridge below the Pine Island Rapids. The bridge is located on a northwest-southeast axis in the Adel Mountains Volcanic Field, a spectacularly eroded 75-million-year-old volcanic field; the approximate elevation of the river is above sea level.
Description The toll-free bridge is long and is wide. Two lanes of traffic (with a curb but no shoulder) are carried by the bridge. The two longest of its three spans are 198 feet (60.4 m) in length. The trusses are riveted steel, and the deck is cast-in-place concrete (with no membranes or weathering protection). The bridge has an overhead clearance of . The bridge also spans the BNSF Railway tracks on its northwestern approaches, where the clearance is .
The trusses are the defining feature of the bridge. Two through-trusses with eight panels on each side and one through-truss with six panels on each side form the body of the bridge. The arc of the truss consists of steel beams connected to one another by "batten plates" (single-piece, flat, cast steel plates). The chords (the vertical and sloping beams) fit within a flange (a U-shaped, single-piece, cast steel plate) which is battened to the arc of the truss. The portal braces (the criss-crossing small beams that form a box hanging from the "roof" of the truss) are fastened to the truss with gusset plates. The horizontal struts at the top of each portal brace is made of "laced" steel (beams with holes in it), since the struts are in tension (being pulled apart) rather than compression (crushed from the ends). This allows them to be lighter and save weight. The sway braces (criss-crossing beams perpendicular to the portal braces) are attached to the truss with gusset plates, and bolted to one another at midpoint. In the deck, the 19 long floor I-beams are held together by five "stringer" I-beams. The deck itself is a single concrete slab, cast in place."Montana's Historic Steel Truss Bridges-Hardy Bridge." NPS Form 10-900 (rev. 01/2009). National Register of Historic Places. National Park Service. U.S. Department of the Interior, 2009, p. 3. Online at Montana Memory Project. Accessed 2013-01-23.
Three reinforced concrete piers support the bridge. The piers at either end are on land, while the central pier is in the river. The central pier has a base that is solid concrete. The approach span in the southeast is supported by a reinforced concrete T-beam, and the deck is supported by concrete girders.
The bridge carried about 100 vehicles per day in 2002, of which about 3 percent were heavy trucks. No increase in traffic is expected between 2010 and 2026.
The last inspection was in September 2010. At that time, state bridge inspectors found the deck to be in fair condition. The superstructure and substructure were both in satisfactory condition, with only minor deterioration. With no appreciable river traffic in this area, there were no pier protections. There was only minimal scouring of the riverbed around the piers, and minor bank erosion around the approaches.
History
Early highways In the summer of 1860, U.S. Army Lieutenant John Mullan and his party of scouts, surveyors, and trail blazers finished construction on the Mullan Road, the first route to connect Fort Benton, Montana, with Fort Walla Walla, Washington. North of Helena, the Mullan Road passed through Prickly Pear Canyon in the northwestern tip of the Big Belt Mountains. After it exited the canyon, the road went north across the prairie rather than follow the Missouri River through the Adel Mountains Volcanic Field.The Mullan Road exited Mullan Pass and passed roughly due east until it reached Prickly Pear Creek (also known as Big Prickly Pear Creek) in what is northeast Helena near Lake Helena (which did not exist at the time; it was created in 1907 after Hauser Dam was completed). The Mullan Road then passed north through the Helena Valley along what is roughly Interstate 15 today. The road reached Little Prickly Pear Creek as it began its passage through the Big Belt Mountains (which Mullan called "Medicine Rocks") via the Prickly Pear Canyon. Near what is now Exit 228 on Interstate 15, the Mullan Road passed north across rolling prairie to the Sun River. It roughly followed the path of U.S. Route 287 to Montana Highway 200, then Montana Highway 200 east along the Sun River to what is now Great Falls, Montana. From there it roughly followed what is now U.S. Route 87 to its terminus at Fort Benton, Montana. See: Mullan, p. 52-53; Fletcher, et al., p. 50-51. In 1865, the Montana Territorial Legislature gave the Little Prickly Pear Wagon Road Company the right to build a toll road along the path of the Mullan Road through Prickly Pear Canyon, and from there along the Missouri River through the river's canyon in the Adel Mountains Volcanic Field to Great Falls and then Fort Benton. The following year, Helena businessmen James King and Warren Gillette purchase the road from the Little Prickly Pear Wagon Road Company. They made $40,000 in improvements (a huge sum at the time), and traffic on the new "Benton Road" boomed.Fletcher, et al., p. 51.
The Montana Central Railway, which began operation between Great Falls and Helena in November 1887, largely followed the path of the Benton Road through both the Adel and Big Belt mountains. James J. Hill, primary stockholder and president of the St. Paul, Minneapolis & Manitoba Railway (StPM&M), established the Montana Central Railway on January 25, 1886. Few railroads served Montana at that time. But Butte, Montana, was a booming mining town that needed to get its metals to market; Helena was competing to be the state capitol (and would win that fight in 1875); and coal companies in Canada were eager to get their fuel to Montana's smelters. Hill had already decided to build the StPM&M across the northern tier of Montana, and it made sense to build a north-south railroad through central Montana to connect Great Falls with Helena and Butte. Because the Benton Road already laid out a route, surveyors and engineers began grading the line between Helena and Great Falls in the winter of 1885-1886 (even before the company had been incorporated). By the end of 1886, they had surveyed a route from Helena to Butte.Hidy, Hidy, and Scott, p. 57. Construction on the Great Northern's northern Montana line began in late 1886, and on October 16, 1887, the link between Devils Lake, North Dakota; Fort Assinniboine (near the present-day city of Havre); and Great Falls was complete.Hidy, Hidy, and Scott, p. 57-60. Service to Helena began in November 1887, and service to Butte followed on November 10, 1888.Hidy, Hidy, and Scott, p. 60; "St. Paul Minneapolis and Manitoba," Railway News, November 30, 1889, p. 966.
Shortly after the railroad was completed, Cascade County constructed an unpaved county road alongside the Montana Central Railway. This county road crossed the railway tracks in numerous places,Official Automobile Blue Book, p. 529-530. At Hardy, Cascade County constructed a timber bridge across the Missouri River.
U.S. Route 91 upgrade With the development of the Ford Model T in 1908, automobiles became affordable for the average American citizen. But few paved roads or highways existed, as long-distance overland travel was done by railroad and local transportation was horse-drawn. In the early 1910s, the National Park Service conceived of building a paved highway between Yellowstone National Park and Glacier National Park as a means of encouraging tourism in both parks. It helped establish "citizens associations" in both parks to lobby for state and federal funds for road construction. At first, the lack of a national transportation policy hindered these efforts. Later, World War I diverted funds and material to war use.Baranowski and Furlough, p. 168-169. In 1919, however, the first Geysers-to-Glaciers Highway opened.Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1919, p. 140. Accessed 2013-01-23. This two-lane highway followed what is now US 89 W from the Yellowstone border to Livingston, and then followed U.S. Route 191/Interstate 90 west through Bozeman to Three Forks. It then went north along what is now U.S. Route 287/Interstate 15 until it reached Exit 228, at which point it continued to follow the old Mullan Road route along U.S. Route 287 and Montana Highway 200 to Great Falls. From Great Falls, it continued north on what is now Interstate 15 to Shelby, then went west along current U.S. Route 2 from Shelby to Cut Bank. At that point, it went north along the Glacier National Park border, following current MT 213 from Cut Bank to the Canada–U.S. border.National Park Service, p. 21-23. Accessed 2013-01-23. In 1920, a shorter eastern route known as the Yellowstone-Glacier Beeline Highway opened. The "Y-G Beeline" continued to follow U.S. Route 89 from Livington, until it reached Great Falls. It rejoined the Geysers-to-Glaciers Highway thereafter.
Beginning in 1924, the American Association of State Highway Officials (AASHO) began an effort to number America's "auto trails" such as the Geysers-to-Glaciers Highway. A numbering system was proposed in 1925, and the Secretary of Agriculture (who had supervision over federal highway naming at the time) approved the system on November 18, 1925.Weingroff, Richard F. "U.S. 11 - Rouses Point, New York, to New Orleans, Louisiana." Highway History. Federal Highway Administration. April 7, 2011. Accessed 2013-01-23. The Geysers-to-Glaciers Highway from Great Falls to Helena was now the northern terminus of U.S. Route 91—a transnational highway that extended into Idaho, Utah, Arizona, Nevada, and California, and terminated at Long Beach, California.
The state of Montana's roads and bridges were considered abysmal in the early 1920s, even by the low standards of the day. Throughout the decade, the state began a program of road improvements and bridge building that constructed more than 400 masonry, iron, or steel bridges in the state by 1930.Axline, p. 81-82. As a cost-saving measure, the State Highway Commission (now the Montana Department of Transportation) had already adopted a uniform riveted steel Warren through truss design in 1915. Throughout the 1920s, both steel and timber bridges were constructed. Almost 1,000 timber bridges, designed to bridge small creeks or coulees, were built. Roughly an additional 170 bridges were made of masonry, iron, or steel.
With the onset of the Great Depression in October 1929, the State Highway Commission needed to cut back on the expense of the more advanced bridges. It simplified the design of its steel truss and steel girder bridges, so they would cost less and take less time to build (reducing labor costs).Axline, p. 82, 85. Construction of these types of bridges was limited, however, by access to aggregate and water for cement, a lack of contractors capable of building such bridges, and a small skilled workforce trained in building with cement and steel.Axline, p. 85.
Bridge construction