Congressional Hearing on Church Rock Dam Break (1979)

On October 22, 1979, Congress members listened to testimony about the difficulties faced by Diné (Navajo people) living on the land that was contaminated by the Church Rock Uranium mine spill. The Church Rock mine was the country's largest underground uranium mine, used for nuclear power plants. When a dam at the plant collapsed, it caused the largest spill of radioactive material in U.S. history. Although located on privately-owned land, the mine was near Diné reservation land. As part of this hearing, the Army Corps of Engineers reported about how and why the dam broke.

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The Army Corps of Engineers has also reviewed the Church Rock site materials since the accident, and its conclusions support the questions raised by Dr. Tschantz. The corps report made a number of points:

One. A zone of tailings against the upstream face of the dam was incorporated in the company's dam design to help buttress the structure in light of its likely settlement problems. This design aspect was not met.

Two. The cracking of the dam which appeared in 1977 and subsequent cracking identified by the company in 1978 were not reported by the company to the State regulatory agencies. The Army Corps report notes that: "Since this information was of utmost significance and paramount in the evaluation of the safety of the structure at the time when cracking was first observed, not only the owner of the structure, but also the State Engineer Office should have been contacted and informed of these conditions."

Three. The design of the dam did not incorporate all the necessary protective measures recommended by the company's engineering consultant. Had the dam been constructed in accordance with the approved design and had recommended materials been used in construction, according to the corps, "it is possible that the failure would not have occurred."