After damage by record-high runoff and flooding in 2011, more than $42.9 million in repairs to Fort Peck Dam have been approved by the U.S. Army Corps of Engineers.
The work is part of $234 million that will be spent on more than 100 projects along the Missouri River to stabilize the Corp’s system of dams and levees from Fort Peck to the Missouri River’s junction with the Mississippi River.
The work is needed in the wake of record-setting 2011 floods that punctured levees, flooded homes and towns and required the Corps' dams to release more than double the amount of water ever released previously.
The flooding was caused by near-record snowpack on the High Plains and northern Rocky Mountains that remained on the ground later than normal and then quickly melted off into already-saturated ground. Heavy rains in the lower Yellowstone River basin also boosted the Missouri River's already-bloated flow. Almost one-third of the homes in Minot, N.D., were damaged by flooding.
The flooding caused more than $2 billion in damage and five fatalities and prompted the Federal Emergency Management Administration to issue disaster declarations in each state along the Missouri and Souris rivers.
All of the work identified as high priority after the flooding, such as repairing 15 levees along the lower Missouri River, is expected to be completed by March 2013. The majority of work at the Corps’ six dams is expected to be completed by the end of 2014.
Six contracts were awarded last year to repair damage at Fort Peck Dam. The most expensive contract — more than $33.8 million — was awarded to ASI Constructors Inc. of West Pueblo, Colo., for the rehabilitation of the dam’s plunge pool. That work is not expected to be completed until December 2015.
To repair the plunge pool, a coffer dam will be built to dry out the area, then roller-compacted concrete will be installed and anchored.
“We allowed three years for that work,” said John Daggett, Fort Peck project manager. “Part of the job is to cut those bank walls back and stabilize those.”
The second-most-expensive repair on Fort Peck’s list is $6.62 million that will be spent on rehabilitating the dam’s huge spillway gates. That contract was awarded to J.F. Brennan Co. Inc., a marine construction company from La Crosse, Wis. The gate repair is scheduled for completion in December 2014.
The 800-foot-wide spillway can release up to 275,000 cubic feet per second of water through its 16 steel gates. Each gate is 40 feet wide and 25 feet tall.
Next on the list of expenses is $1.69 million to repair drains on the 5,000-foot-long spillway channel. That work was awarded to DRL Corp., based in Oxford, Mass.
Contracts for the remaining projects, and the amounts, are: install 17 relief well outfall pipes that alleviate pressure on the downstream toe of the dam, Prudent Technologies Inc., $122,748; rehabilitation of the emergency spillway, American Contracting LLC, $646,243; under-seepage control, Lakeside Excavation, $6,900. All of these repairs are scheduled for completion in December.
At the height of the work, an estimated 80 workers would be employed at the various projects.
Fort Peck Dam was completed in 1940 and is the largest hydraulically filled dam in the United States. On June 15, 2011, the reservoir reached a record elevation of 2,252.3 feet above sea level. That month also marked the reservoir’s largest releases of water — 65,900 cfs.