Lower Monumental Dam Gate Replacement

  • February
  • LM #3 11-02-10 026
  • LM #3 11-02-10 059
  • LM #3 11-02-10 102
  • LM 11-2010 004
  • LM 11-2010 091

Vancouver, Washington

The US Army Corps of Engineers, which owns and operates eight dams in the Northwest, began the process of replacing navigation lock gates on three of the dams in 2010. One of these dams was The Lower Monumental Dam located on the lower Snake River, near Kahlotus, Washington. The Army Corps of Engineers closed the lock on December 10, 2010 and began a 14 week project to replace the existing 41 year old gate.

The dimensions of the new gate were 88 feet wide, 84 feet high, 16 feet deep, weighing 1,482,000 pounds. Due to the enormous size of the gate, it had to be fabricated in three sections which entailed a “Bottom”, “Middle” and “Top” section. Each section was 88 feet wide, 16 feet deep and the Bottom section was 29 feet high, the Middle section 23 feet high and the Top section 31 feet high. The Bottom section weighed 550,000 pounds, the Middle Section 392,000 pounds and the Top section 540,000 pounds. Upon arrival at the dam, the three sections would be assembled and welded together on site.

OXBO was hired by the fabrication company and the prime contractor to move the gates in two phases. The first phase involved moving the three gate sections from inside the fabrication facility to an outside assembly area. The second phase involved moving the gates from the assembly area onto the barge for transport to the dam. At the assembly area, the three gate sections were mated together and dimensionally checked to make sure the gate was fabricated within the tolerances allowed by the US Army Corps of Engineers. By using our self-propelled hydraulic power dollies, we were able to place all three pieces within 1/32 inch level and 1/32 inch square of each other. By setting the pieces within such tight tolerances, it helped make this phase of the project a success and expedited the second phase of the project which was loading the pieces on the barge.

The self-propelled hydraulic power dollies were used again to move the gate sections from the assembly area to the barge. Due to the limited length of the barge, a prime mover or winch truck could not assist with loading the gates. The power dollies eliminated the need for any other type of towing or stopping apparatus, therefore providing one of the only options for loading the gates. The gates were safely loaded on the barge and transported to the Lower Monumental Dam for assembly and installation. According to the US Army Corps of Engineers, the new gate will extend the life of the navigation lock by 50 years.

OXBO has state of the art equipment and a highly trained team of employees” said Dave Williams of Thompson Metal Fab, Inc.


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