While investigations are continuing to identify the extent and cause of a 65-foot-long crack across a Wanapum Dam spillway pier monolith, fishery experts, engineers and others are scurrying to assure passage for fast-approaching salmon spawners.
The Grant County Public Utility District hydro project was rendered impassable for adult salmon and steelhead when, following the Feb. 27 discovery of the crack, the reservoir upstream of Wanapum was drawn down by roughly 26 feet to reduce pressure on the fractured spillway structure.
The current reservoir level of 541-545 feet elevation, the lowest it has ever been since the dam went into operation in 1964, doesn’t allow water to pour into the fish ladders that were built to allow upstream passage.
The lowered reservoir also leaves a considerable fall from the top of the ladder for fish, should they be able to ascend it.
Likely remedies for both issues are nearly in place. Workers are currently installing pumps in the dam’s two fish ladders and will install weirs and flumes to help migrating fish navigate to the top of the ladders and then to the reservoir behind the dam.
Work on the fish ladders is expected to be completed by April 15, which is the start of the spring chinook salmon run. At the request of agencies and stakeholders, Grant PUD now plans to initially trap fish at Priest Rapids Dam and haul them in trucks before releasing them above Wanapum or Rock Island dams during the first few weeks of the fish run while the effectiveness of the ladder modifications are evaluated.
Access to the “left bank” fish ladder, where more than 80 percent of the fish pass, is expected to be completed by this weekend or Monday, Grant PUD fishery biologist Russell Langshaw told the Technical Management Team Wednesday. TMT is made up of federal, state and tribal fishery and hydro experts. The panel meets to discuss options for improving hydro operations in the Columbia and Snake river systems to improve survival for salmon and steelhead.
Those stocks include wild fish that are listed under the Endangered Species Act, such as Upper Columbia spring Chinook salmond and steelhead that must get up and over Wanapum to reach spawning grounds. ESA listed bull trout also pass up and down. Also passing the dam are summer and fall Chinook, sockeye and coho salmon, fish stocks that are not ESA listed, as well as lamprey.
“Corkscrew” slides are expected to be completed at Wanapum’s two fish ladders within the next three or four weeks. The slides are intended to provide a safer descent for fish from the top of the fish ladder down to the lowered reservoir.
At the request of agencies and stakeholders, Grant PUD now plans to initially trap fish at Priest Rapids Dam – the next hydropower project downstream on the Mid-Columbia -- and haul them in trucks upstream before releasing them above Wanapum or Rock Island dams.
Fish collected at the Priest Rapids adult trap would be hauled “at least around Wanapum in the near term,” Langshaw said. That involves a road trip of about a half hour one way. Grant PUD to start has identified four available trucks, each likely to carry from 75 to 100 spawners, though Langshaw said some have suggested as many as twice that number could be carried. Potentially as many as 10 tanker trucks could be employed.
Travel time would be roughly doubled if fish are transported to above the Chelan County PUD’s Rock Island Dam, the next dam upstream of Wanapum. Ladders are an issue too at Rock Island because of the lowered Wanapum Reservoir.
Chelan County PUD is taking steps to ensure passage of juvenile and adult spring Chinook salmon can occur at Rock Island Dam.
Engineers working for Chelan PUD have made adjustments to the release pipe for the Rock Island juvenile fish bypass system that monitors smolts heading to the ocean. The PUD will be able to use its standard river flow and special spill gates for juvenile salmon and steelhead migration.
Meanwhile work has begun extensions to the left and right bank fish ladders for adult salmon heading upstream. The juvenile bypass was expected to be ready by April 1 and the adult fish ladders by April 15 for the returning Chinook.
Chelan PUD was able to take advantage of a March 22-23 drawdown to assess needed modifications for the fish ladders and the juvenile fish bypass at Rock Island Dam.
Coordination with Mid-Columbia PUDs, Bonneville Power Administration, the Bureau of Reclamation and the Army Corps of Engineers means that river flows will be modified in early April to allow Chelan PUD to do some critical work on the fish ladder extensions.
“We will start modifying two entrances for the right bank (Chelan County side) fish ladder, with planned extensions of 84 feet each that allows fish to access the permanent ladder under low tailwater conditions,” said Keith Truscott, PUD Natural Resource director.
“Once the right bank ladder modifications are complete, efforts will turn to modifying the entrance to the left bank (Douglas County side).” Truscott said “With these modifications, and anticipating the usual high flows of spring runoff to help raise the tailwater levels during the peak of the spring Chinook migration, as well as guaranteed flows of 45,000 cubic feet per second through October 2014, we feel that we can adequately handle the record returns expected this year.”
Last year was a stellar year. A total of 13,725 spring Chinook; 71,083 summer Chinook and 263,924 fall Chinook were counted passing Priest Rapids on their way upstream. The fall Chinook total compares to a recent 10-year average of 40,496 adult fish; and the recent four-year average of 98,100.
The sockeye count at Priest Rapids was 163,078 in 2013.
The numbers could be even larger this spring, summer and fall. The predicted sockeye return to the mouth of the Columbia is nearly double last year’s actual return. The upriver bright fall chinook return is expected to approach 1 million, which would be a record.
A drilling team has completed six investigative holes into the Wanapum Dam spillway pier monolith No. 4 as part of the forensic examination of the fracture.
Drilling will resume after a larger platform is constructed on the monolith to support the workers and their equipment. Windy weather has created delays in the drilling process, according to a Monday press release from Grant. All work on the monolith, which is only accessible by boat or crane, must stop in wind gusts that are more than 35 miles per hour. The platform construction and drilling is expected to take about three to four weeks without significant wind delays. The drilling will help determine the geometry of the fracture and how far it reaches into the monolith.
Grant PUD has accelerated plans for boat launch improvements during the reservoir drawdown, which decreases cost and environmental impacts by doing work in the dry. New estimates show that the utility will save nearly $1 million for improvements to the Kittitas Boat Launch and Frenchman Coulee recreation sites near Vantage after competitive bids were submitted last week.
Completing the work during the reservoir drawdown reduces estimated costs by approximately 50 percent. Grant PUD is also looking into the possibility of performing similar work in other locations, pending approval from regulatory agencies.
The Wanapum shoreline remains closed during the low-reservoir conditions because of safety hazards and to protect culturally sensitive sites. Grant PUD expresses its appreciation for the public’s patience and understanding.
For additional information, visit: http://www.grantpud.org/your-pud/media-room/wanapum-dam-spillway-response.
Meanwhile, the PUD also is working on ways to provide for recreational access to the Rock Island reservoir during the coming summer months. Right now, only Wenatchee Confluence State Park boat ramp is available for public use on the Columbia River between Rock Island and Rocky Reach dams. The PUD is looking at what modifications may be possible this season to ensure that one or more of the ramps can remain open.
“What we don’t know right now is how the situation will look in August and September,” said Truscott. “We have the benefit of a decent runoff this year, so our river levels and the river flow should be sufficient through July if we are able to keep the headwater behind Rock Island Dam at or above 609 feet (above sea level).
“Our engineers are working on detailed analysis that will be complete in the next two to four weeks and it will tell us more. We also are working closely with Grant PUD to see if the Wanapum reservoir level will change. There are a lot of moving pieces at the moment.”
Chelan PUD encourages its customer-owners and visitors to follow updates about its response to the Wanapum Dam situation by going to chelanpud.org and clicking on “Wanapum Drawdown Response” in the upper right hand corner of the District’s home page. Real-time data on reservoir levels and river flows are being maintained there and Rock Island public boat ramp closures also are being posted.