Ashfork-Bainbridge Steel Dam

The Bainbridge Dam is a marvel of engineering and worth the effort to go see.

The Ashfork Bainbridge Steel Dam, the first large steel dam in the world, and one of only three ever built in the United States, was constructed in 1898 by the Atchison, Topeka and Santa Fe Railway (ATSF) to supply water for railway operations near Ash Fork, Arizona. It is named for the town of Ash Fork, and for Francis H. Bainbridge, a civil engineer and graduate of Rensselaer Polytechnic Institute (RPI), a member of the Rensselaer Society of Engineers, and an engineer for ATSF. The dam has been listed on the National Register of Historic Places since 1976.

Steel dams use relatively thin steel plates in contact with the water surface, with a framework of steel behind them transmitting the load to the ground. The plates are slanted upwards in the direction of water flow, so that the weight of the water puts compressive forces on the girders holding the plates up. This transmits force to the ground without the bending moment that a vertical wall of plates would engender. It was believed that these dams could be constructed faster and more cheaply than masonry dams.

The dam was fabricated by the Wisconsin Bridge and Iron Company and shipped to the site in pieces for erection. Construction of the dam began in 1897 and was completed March 5, 1898, at a total cost of US$63,519 (equivalent to $2.3 million today).

The structure gets its scalloped appearance from 24 curved 3⁄8-inch (9.5 mm) steel plates that slope downstream. Loose and rigid plates are alternated to compensate for a temperature range from 104 °F (40 °C) to −4 °F (−20 °C). The central steel section is 184 feet (56 m) long, 46 feet (14 m) high, and weighs about 460,000 pounds (210,000 kg). No spillway was provided; instead, the dam was designed to withstand overtopping of six feet (1.8 m) of water pouring directly over its crest.

It holds about 36,000,000 US gallons (140,000,000 L) of water when full.

The dam is an Arizona Historic Civil Engineering Landmark. A professional journal wrote in 1902 that Ash Fork Dam “has so many novel features of an experimental character that it is specially interesting and instructive to the engineering profession.”

In a survey in 1955, George Lamb said “it appears to be in as good condition as if it was just built.” It is still in use, unlike the other two steel dams in the United States.

The Kaibab National Forest (part of the United States Forest Service holdings) is now the owner of the dam, after acquiring it through a land exchange.

It was added to the National Register of Historic Places in 1976 with a structure ID of #76000373.

The quickest route to the dams is to take I-40 to take the County Line Road exit and go up past the cinder pit, there is a gate to the right, please close this, go up the hill and go right through the gate. Park at the top of the hill, enjoy the view as it’s amazing and look for the trail going off to the right.