Arrowrock Dam, Arch dam in Elmore County, United States.
Arrowrock Dam is a concrete arch dam crossing the Boise River in Elmore and Boise counties, Idaho, listed on the National Register of Historic Places and recognized as a Historic Civil Engineering Landmark. The dam holds back a large reservoir that has long supplied water for irrigation across the surrounding agricultural areas.
Construction began in the early 1910s as part of a federal reclamation program aimed at bringing water to dry western lands, and the dam was finished in 1915. At the time it was completed, it was the tallest arch dam ever built.
The dam sits in a dry high desert landscape where farming would be nearly impossible without water storage. The reservoir it holds back has shaped the way people in the surrounding valleys grow food and manage their land.
The dam is reached by rural roads outside Boise, and conditions on those roads can change quickly with rain or snow, so dry weather is the best time to visit. Sturdy footwear is a good idea since the ground around the viewing area is uneven.
During construction, temperature sensors were embedded directly into the concrete to track how the material cured, which was an early and forward-looking approach to monitoring a large structure. The workers' camp built on site also had running water and electric lighting, which was far from standard on remote construction sites at that time.
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