SR 79 Bridge - Triumph Over the Gila River

The Gila River has always been a formidable obstacle for Arizona bridges crossing it.

To give you an idea of the challenges it posed, this ADOT bloghas this description: "Before Coolidge Dam was built and before the canal system began siphoning the river's water supply, [the] Gila River…ranged from 150 to 1,200 feet wide and from two to 40 feet deep. It could pump 6,070 cubic feet of water per second into the Colorado River."

All that water made for unpredictable flooding, which could and did destroy many bridges that crossed the Gila River, like the Antelope Bridgenear Tacna. Flooding also necessitated constant repairs on other crossings such as the bridge over the Gila River in Florence.

The historic inventory document for this bridge says in 1885, the Arizona Territory replaced a wooden bridge over the river with one of wood and metal. However, that structure was repeatedly damaged. Replacing it was the first project of the newly established Arizona Territorial Engineer, J.B. Girand. According to ADOT's historic inventory description, Girand designed a concrete and metal structure that was completed in 1910.

However, the bridge didn't last long. The historic inventory description says "Despite the new bridge's immense weight, parts of it were carried away with almost every Gila River flood. For example, just before Christmas 1914, the river washed away approaches on both sides of the bridge. Although repairs were quickly completed, they had to be done again in 1915 when another flood destroyed about 1,200 feet of embankment on the south end."

In the 1950s, the Arizona Highway Department decided to replace the entire bridge again. The new structure, measuring just over 1,500 feet long, was completed in 1957 and was in use for more than 60 years on a stretch of State Route 79 in Florence.

In 2023, after that structure reached the end of its useful life, the bridge was replaced using a unique method that literally slid segments into place. With the new construction technique, the new bridge piers were built while the existing bridge was still in use. The new bridge halves were slid into their permanent positions over two weekends.

The new bridge has a single lane in each direction with eight-foot-wide shoulders. It also includes a protected pedestrian walkway on the west side.

Despite having to be replaced at least four times, the SR 79 bridge over the Gila River in Florence was and is one of the most important river crossings in Arizona.

Back To ADOT Blog