PROJECT DETAIL

Bull Run Dam

January , 2010

In 1929 the City of Portland built Bull Run Dam 1 on Federally protected and restricted land, the Bull Run Watershed. This complex, Bull Run Dam 1 and 2 is a significant source of potable water for the City of Portland and the surrounding area. Due to its location of Federally protected land and fact that we are working in potable water great care has been taken during the project, from complete decontamination of all diving gear and related equipment that enters the water, to complete containment for all mechanical equipment on site. Access to the site is extremely limited, there is no thru access across the top of the dam, all of the equipment had to be staged on top of the dam. The water level has fluctuated over 40 feet during the project,making access to the water extremely difficult.

The dam has seven slide gates mounted to the face of the dam inside a trashrack enclosure. These gates, located at various levels allow the operators the control the flow of water as well as the level (temperature) of the water as it moves through the system. During the project the existing trashracks as well as the supporting beams were found to be severely rusted. They are all being replaced with new galvanized beams and panels. One existing gate, #6 had severely eroded concrete behind the frame where it mounts to the dam wall allowing water to pass even when the gate was closed. Part of the project was the complete removal of the gate, drilling out of the original anchor bolts, repair to the concrete and reattachment of the gate to the dam. This entire process was carried out inside of the trashrack enclosure Tracks were mounted to the underside of the enclosure and the gate was moved to the outside edge where it lifted and set on deck for cleaning and storage while the concrete repairs were being made. The gate was reinstalled and secured with new anchors.

The existing materials were all the original installation, the nuts which secured the stem to the gate were severely corroded and had to be cut off. All of the existing stems were removed and disposed of as well as all of the stem guides and the actuators mounted on the surface. New stems guides were mounted to the face of the dam. New stems were attached to the guides. As stated above, all of the work was carried out inside of the trashrack structure, all of the parts and pieces had to be lowered into the water then cross hauled under the overhead structure and lowered into place. Once installed through the operator floor the stems were attached to new operators and connected to the gate itself. All gates were fully function tested for proper operation.

Part of the project also involved repairs to the spillway. Rolling scaffolding was raised and lowered on the curved spillway surface as needed to access the area to be repaired.