The Dalles Dam Mitre Gate Replacement
Vancouver, Washington / The Dalles, Oregon
The locks at The Dalles Dam were closed on December 10, 2010 in order for the US Army Corps of Engineers to replace the aging downstream lock gates. This project was time sensitive as the Columbia River had to be shut down to all barge traffic in order to complete the necessary replacement of the gates. The river was scheduled to be closed for 14 weeks so it was imperative that all parties involved kept to the tight time schedule that had been allotted.
Our services were retained by the fabrication company hired to build the replacement gates and by the prime contractor hired to install the gates. At the fabrication facility, the scope of work consisted of two phases. The first phase of the project was to test weigh one of the gate sections to determine the crane capacity needed to off-load the gates at the dam. The second phase of the project was to move the two identical gates from inside the fabrication facility to an outside staging area.
The prime contractor’s scope of work also consisted of two phases. The first phase of the project was to move the two gates from the staging area, load them on a barge and secure them for transport to the dam. The second phase of the project was a collaborative effort between our company and the crane company to move one of the gate sections from a vertical to a horizontal position in a temporary staging area at the dam.
Each gate measured 54 feet wide, 106 feet long and weighed 1,000,000 pounds each. On this project, we used our remote controlled hydraulic power dollies to move the gates. This allowed us to safely lift, steer and drive the gates without the need of a prime mover or winch truck. This was especially beneficial due to the limited space in the fabrication facility, staging area and on the barge. The trip from the staging area to the barge ramp consisted of two 90 degree corners and a 5% downhill grade. The transport dollies were equipped with proportional air brakes which kept the load safely in control on the downhill grade.
Challenges of the project
One of the challenges of this project was the size of the barge used to transport the gates to the dam. The barge was over 300 feet long, but only 56 feet wide which was approximately 2 feet wider than the load. The placement of the gates on the barge had to be precise as there was no margin for error once the loading began. Once the gates were loaded and placed on 48 inch temporary supports, all equipment removal had to be done from underneath the load as there was insufficient space on each side of the load.
At the dam, one of the gates had to be off-loaded and stored in a temporary horizontal position so the barge could be released and the crane could assist with installing the other gate. This proved to be a challenge since the crane did not have the capacity to safely lay down the gate. We worked with the engineers to solve this issue by using our self-propelled equipment to eliminate the weight and reach issues of the crane. While the crane held the gate in a vertical position, a hinge and pin set-up was connected to the bottom of the gate and then attached to our transport equipment. In an orchestrated effort, the crane operator released cable line from the top of the gate while we used our self-propelled dollies to move the bottom of the gate until it rested in a horizontal position. When it was time to install this gate, the process was reversed until the gate stood in a vertical position which allowed the crane to take back full control. Both gates were successfully installed and the Columbia River was reopened to navigational traffic once again.
The downstream gate replacement has been a successful project for the navigation industry, taxpayers and the Corps,” said Lt. Col. David A. Caldwell of the US Army Corps of Engineers. “This was a complex project and it went very well, thanks to the efforts, coordination and communication of our great staff, partners and stakeholders.”