It's a dam history walk!
The 1,768 foot long and 56 foot tall Gillespie Dam was built in 1921 by agriculturalist Frank A. Gillespie to supply water to his Paloma Ranch and aid thousands of acres of new farmland along the Gila River between Arlington and Gila Bend. At the time, it was the largest privately financed concrete irrigation diversion dam in Arizona. The concrete dam was the last of four dams built at this site. The others were made of earth, stone, or wood, and were washed out by floods on the Gila River.
The current dam was breached in 1993, which was one of the largest dam failures in Arizona History. Another site associated with the construction of the dam and bridge is the Gillespie Dam Construction Camp. The site contains remnants of the machinery and structures used to build the dam, including an innovative pulley system for delivering concrete during construction.
On January 9, 1993 after heavy rains and winter runoff caused flooding on the Gila River estimated to be 200,000 cubic feet per second a 180-foot section of the dam failed. The dam was never repaired, nor was the remaining structure dismantled. An earthen levee was built to direct river flow to a pond where the necessary irrigation water is now pumped into adjacent canals.
Historic Gillespie Dam Bridge
The historic Gillespie Dam Bridge spans the Gila River on Old US 80 Highway, between the communities of Arlington and Gila Bend. Opened in 1927, the bridge is a unique and elegant reminder of Arizona's rich past and America's transportation history. The bridge is listed on both the Arizona State and National Register of Historic Places. During the winter of 2011, the bridge underwent a $7.3 million rehabilitation effort by the Maricopa County Department of Transportation.
Shortly after Arizona’s statehood in 1912, a major east-west transportation route was established between Clifton and Yuma. Several bridge and ford crossings of the Gila River were attempted in the early years and proved unreliable due to frequent washouts during rain and flooding.
In 1921, the highway route was realigned to ford the Gila River just below the newly constructed Gillespie Dam. Heading south towards Gila Bend, the new route was known as the Phoenix-Yuma highway. The following year, the Arizona Highway Department built a concrete apron on the downstream side of the Gillespie Dam to help automobiles to cross the Gila River. This crossing point also proved to be unreliable, as high water often made passage difficult. Between 1922 and 1926, large trucks, tractors, and horse teams were frequently used to pull automobiles across the apron of the dam.
The Arizona Highway Department set about designing an all-weather bridge structure in 1925 to span the Gila River. Construction of the Gillspie Dam Bridge began in February 1926 and later that same year, the American Association of State Highway Officials adopted our present day highway numbering system, when the new Gillespie Dam Bridge opened to traffic on August 1, 1927. It was officially designated part of the early southern transcontinental US 80 Highway.
The new bridge and US 80 Highway through the Arlington Valley became part of the National “Ocean-to-Ocean” Highway and carried US 80 transcontinental traffic from 1927 until 1956, when the route shifted east to Rainbow Valley and the Arlington Valley stretch was decommissioned. The old highway and the bridge were transferred from the state of Arizona to Maricopa County.
Lee Moor Construction of El Paso, Texas built the nine-span steel truss bridge for a cost of $320,000. The 1,662-foot-long Gillespie Dam Bridge was unique for its time and one of the longest bridges and the largest steel structure in the state. All of Arizona's major bridges before this were built using reinforced concrete arches which proved to be no match for swollen, flooding rivers. The new design produced a more durable and flexible bridge that could better withstand the force of flood waters.
Bridge design elements include a connected series of rigid through trusses weighing 2.3 million pounds. The bridge has a total of nine steel truss spans - five 200-foot-long trusses centered over the river channel, flanked by two 160-foot long trusses at each end. Each steel truss features a camelback web configuration with a built-up box beam for the upper and lower steel members. The trusses are supported by solid concrete abutments and pier columns placed on bedrock at a depth of 25 feet, with the deepest pair extending 43 feet below the riverbed.
The bridge and dam area today is largely open to the public, with only a small fenced area near where the electric pumps deliver river water to the canal system. The dam and apron can be climbed, and a narrow walkway crosses the diversion channel gates to the concrete apron. There are abundant species of birds and excellent fishing opportunities.
On the west side of the river, on the hill above the dam, an impressive display of petroglyphs can be found at the base of the cliffs. Access may be easiest by driving a quarter mile west of the bridge, parking in the dirt pull-out and following the use paths that lead down to the numerous panels.
Source: Most of the text above was taken from the interpretive signage placed at the bridge during the 2011/2012 bridge rehabilitation project. Unfortunately, at the time of this writing, vandals had removed those signs and no information is currently available on site.
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