Some Dam Repairs Done, Close To It

While the flood of 2011 is still a topic of conversation, necessary repair work at Fort Peck Dam is ongoing. Even though several repair projects have been completed, the U. S. Army Corps of Engineers continues work on the Fort Peck spillway.

Operations Project Manager John Daggett explained that the high discharge through the dam caused erosion and wear on the spillway when they were releasing 52,000 cubic feet per second (cfs) out of the spillway. The spillway was originally designed to release 230,000 cfs, but the bottom of the spillway did not have a stilling basin. Consequently the 2011 discharge caused a lot of erosion. The interim repair is designed to allow about 80,000 cfs discharge without damage to the bottom of the spillway.

That massive amount of water rarely finds its way down the spillway, so not only was it a unique site to see, but the heavy waters caused unusual wear and tear. The spillway ran for over four months. Downstream dams along the Missouri River are also undergoing flood repairs.

Since then work to repair the dam and spillway has been taking place. The projects, costing around $45 million, are coming closer to completion. Daggett explained that several projects are complete, or near completion. The plunge pool repair and gate repair at the spillway will continue into the next year.

As the oldest dam managed by the U. S. Army Corps of Engineers on the Missouri River, a few interesting challenges arose during the repair work. The current work includes repairing welds on the 16 gates and repainting them with a special protective vinyl paint. The plunge pool repair involves excavating the side slopes and reinforcing the bottom of it with roller compacted concrete.

"The original steel used on the gates is similar to steel found on WWII Liberty ships," Daggett said. "One problem is trying to adapt to modern welding criteria for the 75 plus year old gates, since they didn't have the standards we have now."

Because of the age and type of steel used, special techniques are needed to complete the work. Daggett explained if the work isn't done correctly it could lead to cracking or make the gates worse than they were before. J.F. Brennan, Marine Contractors, out of La Crosse, Wisconsin, are performing the work on the spillway gates. Currently they are planning to be finished with the work by spring of next year.

Around 100 trucks a day have been making their way toward the end of the spillway. A haul road was built for the project to carry gravel and special concrete aggregate to the end of the spillway. The Roller Compacted Concrete (RCC) is placed more like asphalt. It is spread with small dozers and then roller compacted.

Leading RCC experts will be involved in looking at a test section this month to be sure that the design and materials will work. The banks of the plunge pool are being excavated and sloped back to curtail erosion. Work on the plunge pool is being done by ASI Constructors, of Pueblo, Colorado.

Much of the materials needed to finish the project should be hauled to the site by the end of July. Several other projects continue around Fort Peck Project, which include paving Flat Lake Road and repairing other Project roads.