80th Anniversary of the Fort Peck Dam Construction Slide

Beginning at about 1:15 PM on September 22, 1938, the upstream slope of the dam experienced a large failure as the construction work had progressed to within 20 feet of the final dam crest elevation. One hundred eighty men were working in the area. Thirty four men were injured. Eight men lost their lives, six of whom were never found and are buried somewhere in the dam.
As a result of this slope failure, the original design Board of Consultants was expanded to assess the cause of the failure, and review options for completing the dam construction including repairs in the failure area. There were many lessons learned. The failure as well as other performance factors during first filling of the reservoir altered the U.S. Army Corps of Engineers (USACE) design and construction practices significantly. The failure also imparted important lessons to the U.S. community of practice for dams and levees.
This paper is written in two parts. Part I covers the background of the project through the reconstruction of dam in the area where the slide occurred and the early performance of the dam following first filling of the reservoir. Part I concludes with the controversies that the expanded board of Consultants encountered in preparing a report on the cause of failure, and in completing their review of the redesign of the section of the dam requiring repair. Part II explores the broader Technology and Human Factors that influenced the design and post failure investigation. This part begins with a discussion of the differences of opinions about technical matters that were revealed in the project literature. It presents a summary of the state of the practice at the time of design and construction, and briefly traces technology advances during the next 40 years following the slide. This includes a discussion of evolution of technology related to the shear strength of shales, and the liquefaction of sands.