Monday, July 26, 2010
The in-water work period for the decommissioning of Powerdale Dam started on July 1, and crews are wasting no time taking out the 1923-built concrete diversion dam. With a window of now until Aug. 31 to work in the river, crews are moving as quickly as possible to isolate the dam from the river, pound it out with hydraulic hammers, remove many tons of material and restore the river to a natural grade.
This week workers from Weekly Bros. Inc. — the prime contractor PacifiCorp chose for the roughly $2.4 million project – were busy creating side canals to reroute the Hood River around the 200-foot-long dam. On the west side of the river, the steel flume that once channeled water into the dam’s pipeline was moved into place and is now being utilized to divert about half the river’s flow around the large pool just below the dam. On the east side, workers are removing the Oregon Department of Fish and Wildlife facility that was used to trap, count and regulate fish passing upstream. Soon in its place will be a second diversion for the remainder of the river to flow around.
Above and below the dam, temporary cofferdams will be used to cut it off from the flow of the river. Crews will then go to work on the concrete structure with hydraulic hammers and heavy equipment. No explosives will be used in the project. They will bury much of the concrete and will eventually remove the cofferdams and work to reestablish the area to as close of a natural set of rapids as they can.
Fish passage during the project has been routed to the dam’s old fish ladder, which was blocked off after the ODFW facility was built in the late 1990s. A project manager explained that once the center of the dam is removed and the river can flow through, fish will have free-flowing passage up and downstream for the remainder of the project.
Public access to the dam site and to the lower Powerdale substation site just outside of downtown Hood River has been restricted for several months now. Although the river is still open (excluding a buffer up and down stream from projects), access via the two popular parking areas is closed for the duration of the project.