Dam Failure Case Study: Walnut Grove Dam (Arizona, 1890)

Walnut Grove Dam was constructed at a site approximately 20 miles northeast of Wickenburg, Arizona. Gold had been discovered in the area and a New York Investor Wells H. Bates wanted a dam built in order to supply water for hydraulic mining. He acquired the mining rights and then hired William P. Blake a renowned geologist to design and construct the dam. However, he was fired shortly after beginning work. He was replaced by EN Robinson a civil engineer from San Francisco. Robinson was unable to salvage any of the construction that Blake had begun and no design documents were available, so he largely started over. It is unclear exactly why, but he was then replaced by one of the New York Investors brothers who had no engineering or construction experience. Managing a dam construction project from over 2,000 miles away presented many challenges. During the construction, there were frequent complaints about low pay, poor oversite and quality control, an untrained workforce, and high construction and design costs. Work was being done on the spillway when on February 16th 1890 it began to rain. It would rain on and off until February 22nd. This rain-on-snow flood event caused the dam to overtop, leading to failure on February 22, 1890.