Owners of the 366.82-MW Pelton Round Butte hydroelectric project say they will need three months to come up with a new schedule for completing a 273-foot-tall underwater intake tower and fish collection station that fell apart during construction.
Licensees Portland General Electric and the Confederated Tribes of the Warm Springs Reservation of Oregon said they think it will take 90 days to develop a new schedule for completing the tower, a selective water withdrawal facility designed to restore fish passage to the Deschutes River Basin. A PGE spokesman said at least four months would be required just to resume construction from the point the incident occurred.
In an April 21 letter to the Federal Energy Regulatory Commission, the licensees asked for a 90-day abeyance of the schedule for completing the tower. They said they would use the additional time to develop a new schedule for finishing the tower and a plan for downstream fish passage while the tower is completed. Action by FERC is pending.
The incident occurred April 11, while a vertical flow conduit was being floated into position as part of the final assembly of the $108 million tower. Half of the conduit sank to the bottom of Lake Billy Chinook, above Round Butte Dam, part of the Pelton Round Butte project. The other half of the conduit, supported by flotation devices, floated to the water's surface and was not damaged.
?Segments of the conduit separated for whatever reason before the conduit could be connected to a fish collection facility,? PGE spokesman Steven Corson said, adding that the portion that sank fell in several pieces.
The licensees said they initiated a root cause analysis to determine the cause of what they are calling a ?structural failure.? As part of the probe, parts of the conduit that sank will be retrieved and analyzed.
The parties engaged in consultations with fish agencies and others to determine steps that should be taken to provide downstream fish passage while the tower is completed. The PGE spokesman said fish migrating downstream will be trapped and transported by truck to an area below the dam, where they will be released to continue migration.
PGE and the Confederated Tribes said the incident did not create any threat to the safety or stability of the project (No. 2030). There were no injuries. However, the licensees said, loss of a portion of the vertical flow conduit has made it impossible to finish construction of the tower in a timely manner. At one time the tower was to be completed by May. (HNN 9/2/08)
CH2M Hill, EES Consulting, and ENSR/AECOM Technology Corp. designed the tower in collaboration with PGE Engineering. The utility said Barnard Construction Co., Dix Corp., and Thompson Metal Fab were involved in its construction.
When complete, the underwater tower is to draw water from the warmer surface layer and from the cooler bottom layer of Lake Billy Chinook. It is designed to modify currents and temperatures to mimic natural conditions and attract migrating fish into the collection facility. At the fish collection station at the top of the tower, fish will be sorted, with salmon and steelhead transported by truck past the dams.
