It would appear to be business as usual for spawning salmon, even though Grant Public Utility District and its contractors continue to work to repair and reinforce the damaged 800-foot-long Wanapum Dam spillway on the mid-Columbia River in central Washington.
On Feb. 24, a worker at Wanapum Dam noticed that part of the dam’s spillway deck had shifted slightly. When divers were called in to inspect the area on Feb. 27, they discovered a fracture below the water line on Wanapum’s spillway pier monolith No. 4. The dam has 12 such piers and spillways that allow the passing of excess water.
The fracture – a two-inch opening -- ran in a horizontal direction across the 65-foot width of the monolith, which raised fears of potential structural failures.
To relieve pressure on the pier, the elevation of the reservoir backed up by Wanapum was dropped by 26 feet. While the problem was evaluated and since repairs have begun, the reservoir has been operated at an elevation of from 541 to 545 feet, well below the normal minimum operating level – 562 feet. The dam’s federal license calls for operations between 562 and 571.5 feet, according to Grant PUD spokesman Chuck Allen.
The drawdown has created a variety of problems. It fouled up operation of fish ladders both at Wanapum and 36 miles upstream at Rock Island Dam just before spring chinook salmon where expected arrive. The lowered reservoir level took away the Wanapum fish ladder water supply, so pumps were installed to feed the passage device. And the top of the ladder was reconfigured and a fish “slide” installed to ease what was now a considerable descent into the reservoir upstream.
Because of Wanapum’s lowered pool elevation, work has been done to extend Rock Island’s ladders into the reservoir to assure access for migrating fish. Rock Island is the next dam upstream of Wanapum.
The fish ladder renovations were largely complete by mid-April, just in time for the arrival of the first spring fish.
Rock Island is the next dam upstream from Wanapum. Wanapum, and Priest Rapids downstream on the mid-Columbia, are owned by Grant PUD. Rock Island is owned by Chelan County PUD.
The fish passage modifications to both of the dam’s ladders proved almost immediately to be effective, according to Grant PUD. That allowed the suspension of a stop-gap “trap and haul” operation in May. That plan was in place just in case adequate fish passage was not restored. It aimed to trap fish at Priest Rapids and haul them upstream for release above Wanapum.
The spring season went smoothly with more than 23,500 spring Chinook adults have migrated upstream successfully to be counted as they passed over Rock Island’s fish ladders. That compares to a 10-year average count of 14,700 adults, according to data compiled by the Fish Passage Center. The overall upriver spring Chinook return to the mouth of Columbia – fish bound for the mid and upper Columbia and the Snake River -- proved to be well above the 10-year average.
Since the end of the spring run, the fish slide at Wanapum fish ladder exits has been further enhanced with the installation of spiral flumes that are expected to ease the trip down to the reservoir above the dam.
Those modifications were completed last week, just in time for the summer Chinook migration and what are expected to be mammoth sockeye and fall Chinook runs.
Federal, state and tribal fisheries experts have predicted that the sockeye return to the mouth of the Columbia will total 347,100 adults. That preseason forecast is 63,400 Wenatchee stock and 272,500 Okanogan stock that are heading upstream of Wanapum, as well as 1,200 returning to the Snake River. The forecast is nearly twice (178 percent) the 2004-2013 average return of 194,600 fish.
Through Thursday, a total of 224,262 sockeye had been counted passing over the lower Columbia’s Bonneville Dam. Bonneville is located 146 miles upstream from the mouth of the Columbia. Priest Rapids is at river mile 397.1.
A total of 78,415 sockeye had been counted at McNary Dam as of Thursday. The count Thursday alone was 19,847. McNary is 146 miles upstream of Bonneville. The fish must swim another 105 miles to get to Priest Rapids.
As of Monday, more than 13,000 sockeye had been counted passing Priest Rapids Dam, according to data posted by the FPC.
And still to come is a record fall Chinook run, including nearly 1 million upriver fall chinook bound for the Columbia and Snake. Most of those fish will be forging upriver from August-October.
Meanwhile, Wanapum repairs are under way, aiming for a return to normalcy before next summer.
Various types of drilling are ongoing as crews prepare for repairs that can be implemented once they are approved by the Federal Energy Regulatory Commission, which licenses the dam’s operations.
The drilling work is the most time-intensive phase of the repair process, according to Grant PUD. Holes are being drilled throughout the spillway in anticipation of high strength cables (known as tendons) being installed from the top of the dam into the bedrock below. Repairs will also likely include additional reinforcing anchor bars in the upstream and downstream sides of the spillway.
Thousands of pages of technical data outlining repair plans require the FERC approval prior to being implemented. All repairs will occur over the summer allowing the utility to increase the river elevation in the fourth quarter of 2014. Costs are still on track at the $61 million estimate.
“It won’t happen until Oct. 1, and maybe later,” Allen said of a return to the minimum operations level, 562 feet. Once the reservoir is lifted to that “intermediate” level, evaluations will be conducted, and work will continue to shore up both Pier 4 and the rest of the spillway piers.
Allen says that, unless problems arise, the repair work is expected to be complete by the end of March. That would allow the full range of operations, from 562 to 571.4, by the start of next year’s recreation season.
“That would be the goal,” Allen said. Public use of the river-reservoir is now shut down.
Excavation and pile-driving work is near completion on both the Vantage and Frenchman Coulee boat launches. The improved sites will be available to the public by the 2015 Memorial Day weekend. Current low-river conditions have allowed the utility to expedite these projects at a decreased cost to customers, Grant PUD says.
The 38-mile stretch of shoreline from above Wanapum Dam to below Rock Island Dam will continue to be closed as a precaution for public safety and to protect culturally-sensitive sites. The shoreline will remain closed until repairs to Wanapum Dam are in place. While there may be some portions of the shoreline that appear safe, the velocity of water moving through the narrow river channel, and sandy banks creates hazardous conditions for the public. Recreation sites below Wanapum Dam continue to provide recreation opportunities throughout the summer months.
Wanapum Dam remains stable and is operating at approximately 50 percent capacity. The river elevation above the dam has been reduced by approximately 25 feet while repairs occur.
For additional information, visit: http://www.grantpud.org/your-pud/media-room/wanapum-dam-spillway-response
The Washington Department of Fish and Wildlife has extended the closure of four water access sites along the Columbia River behind Wanapum Dam through Oct. 31, while work continues to repair a fractured spillway.
WDFW officials closed the sites and access to the beach in March, after Grant County Public Utility District drew Wanapum Reservoir down.
Jim Brown, WDFW regional director for north-central Washington, said the extended closure is necessary to protect public safety, fish habitat, and archeological and cultural resources.
"For their own safety, we're asking people to stay off the beaches and any other areas that were under water before the drawdown," Brown said. "Repair work on the spillway is coming along well, and Grant County PUD expects it will be able to raise the water level in a few more months."
The closures affect the Yo Yo, Old Vantage Highway, Sunland Estates and Frenchman Coulee water access sites.
WDFW also has closed the lower ends of roads that lead into the reservoir at the Colockum and L.T. Murray wildlife areas in Kittitas and Chelan counties, and at the Columbia Basin Wildlife Area in Grant County.
The upland portions of the wildlife areas above the ordinary high-water level remain open to the public, Brown said. Closures will be enforced by WDFW law enforcement officers in cooperation with local sheriff's offices, he said.
Grant County PUD has also closed 38 miles of shorelines it owns stretching from above Wanapum Dam to below Rock Island Dam in response to the extreme low water level.
Columbia Basin Bulletin
The Columbia Basin Bulletin e-mail newsletter is produced by Intermountain Communications of Bend, Oregon and supported with Bonneville Power Administration fish and wildlife funds through the Northwest Power and Conservation Council's Columbia Basin Fish and Wildlife Program.
Articles republished by The Dalles Chronicle with permission.