Maricopa County
Gillespie Dam
Gillespie Dam is a failed dam across the Gila River near Arlington, Arizona. The dam is located on the outskirts of the Valley and at the end of the Robbins Butte/Gillespie Dam Trail. Old Highway 80 crosses the Gila River just below the dam on an iconic, steel truss bridge. Both sites are easily accessible by pavement and dirt roads.
Frank Gillespie was a local farmer and rancher. In 1921, he financed the construction of the dam to replace an older structure along the river. The dam was used by Gillespie and other local farmers to help control water used for irrigation of their crops.
The technical aspects of the dam are impressive. The dam itself is a concrete gravity dam that stands only 20 feet tall. It uses many large arches across the front of the dam for support, and a large, flat slab on the back to hold the water in place. The dam spans an impressive 1,700 feet entirely across the Gila River channel.
Damming the Gila River was useful to more than just Gillespie and other farmers. The Arizona Highway Department used Gillespie Dam to its advantage as well. In 1926, ahead of the creation of the U.S. Highway System, the state funded the creation of a steel truss bridge across the Gila River just south of the dam. The bridge cost $320,000 to complete. It opened to the public in August of 1927 and with it, established US-80 on the map in Arizona. At one point, Gillespie Bridge was the longest highway bridge in Arizona. In 1956, the highway was decommissioned and US-80 turned into Old Highway 80, nothing more than a county highway.
Fast forward to winter of 1993. A large amount of winter rain meant that Valley rivers were flowing at high capacity. The Gila River is fed by both the Agua Fria River which extends north of the valley, as well as the Salt River, which extends east of the Valley. On January 9th, under high stress from the large amount of water, Gillespie Dam failed. A 120 foot section near the east bank of the river broke loose and fell into the river. The Gillespie Highway Bridge survived unscathed and is still used today.
No attempt was ever made to repair Gillespie Dam. It sits today as it did in 1993, with considerably less water. Improvements have been made to the river bottom however. Just below the dam, an earthen embankment diverts water from the Gila River (which still flows year round) into nearby canals. The canals transport river water further south towards Gila Bend where it is used for agriculture. Today, Gillespie Dam serves as a local attraction for fishing and for the curious traveler to pull over and inspect the unique sight. A large amount of water remains today and has created a wetland on both sides of the dam. Visitors can park at a small pullout and view the bridge and walk out on the embankment to see the collapsed dam. The bridge and dam sit about 40 miles southwest of Phoenix. Access is via I-10, MC-85 and Old Highway 80 (paved) or via Robbins Butte/Gillespie Dam Trail from MC-85 (unpaved).
Sources:
"Gillespie Dam." Wikipedia. Wikimedia Foundation, n.d. Web. 15 Jan. 2016. <https://en.wikipedia.org/wiki/Gillespie_Dam>.
Leatherman, Benjamin. "Gillespie Dam: The Public Works Project That's Now Home to Wildlife." Phoenix New Times. N.p., 25 June 2012. Web. 15 Jan. 2016. <http://www.phoenixnewtimes.com/arts/gillespie-dam-the-public-works-project-thats-now-home-to-wildlife-6554661>.