The Walnut Grove Dam was built north of Wickenburg, Arizona, United States, along the Hassayampa River. Its failure in 1890 killed over 100 people. Its construction from 1886 to 1888 was chiefly on the impetus of the Bates family, whose mismanagement of the project was considerable. Intended to be used for gold mining, the dam failed before it could be put to use.
Construction
Gold was discovered along the tributaries of the Hassayampa River in 1863 by Pauline Weaver and Joseph R. Walker, prompting an Arizona gold rush. The river is subject to considerable seasonal change, including vast flash floods. In the words of one prospector, the river was a place "where at times an ocean steamer might be floated, and where at other seasons ... the fish must carry canteens."
Into this environment came two brothers, Wells & DeWitt Bates, who filed 63 placer gold mining claims in 1881 along the Hassayampa. Just a mile from Rich Hill, Arizona (the site of the Weaver/Walker gold rush), the Bates brothers purchased the Marcus mine, hoping to strike it rich. They intended to follow the example of the California gold rush, and use hydraulic mining. But the ephemeral nature of the Hassayampa made such operations difficult year round. To solve this, the brothers resolved to build a dam. Efforts to procure land and capital for the dam were in earnest by 1883. Wells Bates spent a portion of 1883 in the area, making legal arrangements related to building a dam, including claiming all the water in the Hassayampa. The brothers established the Walnut Grove Water Storage Company for the purpose of creating a dam.
A site some north of Wickenburg was chosen for the dam, mostly for gold mining, but also for general purpose irrigation. William P. Blake was the initial designer, but was fired shortly after beginning work in 1886. Blake (a prominent geologist and grand-nephew of Eli Whitney) seems to have been on the project only so that his reputation might attract investors. While he had considerable mining experience, Blake lacked civil engineering or dam building experience. Blake accompanied Wells Bates to the dam site in February 1886, where further rights to build a dam were secured, and it was determined a considerable amount of gold could be retrieved. Blake returned to New York, but was back on site by August 1886. He and two of his sons oversaw the digging of a quarry for dam fill, the construction of roads, a sawmill, an office, and quarters for workers, and the building of the initial part of the dam. Wells Bates, and Charles Henry Dillingham, visited the dam in Christmas 1886. Christmas was described as pleasant by all involved, including Blake who noted they had had a "fatted turkey". But it seems Dillingham was annoyed by a conversation he had witnessed the day before between Blake and another local prospector. So Dillingham returned on January 15, 1887, and fired Blake. Blake was very bitter, feeling that he had done the most difficult work for very little pay, but acquiesced on January 30. Blake was replaced by the firm of Nagle and Leonard, of San Francisco. The position of Chief Engineer, formerly Blake's, went to N.E. Robinson.
Robinson proved a more able engineer than Blake. He revamped the dam's design, rebuilt the leaky core of the dam, and called for a large spillway wide by deep. Crucially, Robinson's design for the spillway put the outflow about a half mile away from the dam itself. But Robinson's design also grew much higher, to tall, more than Blake's. Robinson seems to have been the most competent of the many engineers who were cycled through the project. But Robinson soon discovered that the Bates brothers were more interested in selling stock than building an actually sturdy dam. Despite Robinson's quality work, he was fired for unknown reasons just four months after being hired. The final design was done by Walter Gillette Bates, a Bates brothers' nephew. Walter had no experience, having previously been a professor.