VANCOUVER, Wash. (AP) — There's no turning back now.
After a dozen years of planning, the White Salmon River, dammed 3.3 miles upstream from its confluence with the Columbia River since 1913, is on its way to becoming a free-flowing river again.
Northwestern Lake, the 92-acre reservoir behind Condit Dam, dropped 10 feet last week and another 10 feet Monday, exposing more of its sediment-covered bottom. The lake was closed to all boat traffic on Monday, and white-water rafters who put in at Husum and BZ Corners have been using a new takeout point upstream from the reservoir.
On Monday, engineers began dewatering the area immediately below the 125-foot dam to allow workers and equipment to begin drilling into the dam's 90-foot-thick base. To maintain the required minimum flow of 15 cubic feet per second for fish in the river below, water will be diverted around a plunge pool at the foot of the dam and released downstream. Fish in the pool, mainly trout and steelhead at this time of year, will be caught and released downstream.
Drilling equipment, a generator, a ventilator fan and an air compressor have been lowered by cable from a yarder erected on the river's east bank at the top of the dam.
Garth Wilson of the construction management company Kleinfelder is overseeing the logistics of dam removal for PacifiCorp. He's been on site for a month and oversees a crew of about a dozen. JR Merit Industrial Contractors of Vancouver is the general contractor on the project.
The first task for the contractor, Wilson said, will be to assess the quality of the concrete in the dam. That will tell crews in charge of drilling and blasting how far into the dam they can safely go.
The plan is for crews to drill in eight-foot increments. They'll drill a hole, pack the drill hole with dynamite, blast away the concrete, then drill in another eight feet and blast again. The tunnel created will tilt slightly upward. At the end, they plan to leave a 25-foot plug, which will be exploded on the day the actual breaching occurs.
"The plug will stay in place as short a time as possible," Wilson said.
Those who expected to see the entire dam blasted to smithereens in one gigantic explosion will be disappointed.
"It wouldn't be practical to do it all at once," Wilson said. "The force of the explosion would be too great."
The actual breaching of Condit is scheduled for mid- to late October, after all wild fall chinook entering the lower river have been captured, transported and released above the dam.
On that day, explosives will blast out the concrete plug in the tunnel and the impounded waters of Northwestern Lake will flow through a 12-foot by 18-foot hole at the dam's base. The water will race down a steep-sided slot canyon to the river's mouth and beyond. At an initial rate of 10,000 cubic feet per second, the reservoir is expected to drain in about six hours.
Also flushed downstream will be an estimated 2.7 million cubic yards of sediment that has accumulated behind the dam over a period of 98 years. The sediment plume will enter the Columbia and travel all the way to Bonneville Dam. It's expected to temporarily obliterate nearly all life in the river on its way.
Actual demolition of the dam, using concrete cutters, won't happen until next April or May. The concrete rubble will be buried along the route of the flow line, which carries most of the river's flow one mile to a concrete powerhouse through a wood-stave pipe that also will be dismantled.
Condit Dam, owned by Portland-based utility PacifiCorp, will become the second-highest dam ever breached in the United States
Glines Canyon Dam on the Olympic Peninsula's Elwha River, at 210 feet, will be the highest U.S. dam removed when it is breached in September.
Removal of Condit Dam will open up 14 miles of habitat on the White Salmon to threatened Lower Columbia chinook salmon. Mid-Columbia steelhead will regain access to 33 miles of habitat on the river and its tributaries.
PacifiCorp made the decision to take out the dam rather than install expensive fish passage structures, which would have been required as a condition of federal relicensing. In 1999, the utility signed a settlement agreement with conservation groups, state agencies and the Yakama Tribe detailing the process it would use to remove the dam. All parties to the settlement agreed not to challenge it in court.
Skamania and Klickitat counties and cabin owners at Northwestern Lake were not parties to the settlement, and they fought the project for 10 years. But in November, the counties reached a settlement with PacifiCorp in which they agreed not to oppose dam removal and the utility agreed to pay them $675,00 to offset the impacts, including the effects on owners of cabins nestled in the woods above the reservoir.
A few of those cabins now post for-sale signs. But Chris Balmes, a Tualatin Realtor and former Northwestern Lake cabin owner who has two current listings near the lake, said she thinks when the dam comes out, it will be a good for property values.
"It's been on the back burner for so many years," she said. "It's been such an unknown. I think the cabin values will actually go up when people can actually see where the river's going to be. The unknown has been the biggest concern."
Fly-fishing may replace bank fishing and kayaks may replace rowboats, but the area will still be a relaxing getaway, she said. "It will change from one beautiful area to another. It will have different appeal to different buyers and owners."
Condit's hydroelectric water right will be transferred to Klickitat County, and PacifiCorp will agree to protect the structural integrity of Northwestern Lake Bridge. In return, the counties agreed to control noxious weeds in the project area after decommissioning and to work with the utility to protect public safety during demolition.
The breaching of the dam, originally planned for 2006, has been delayed repeatedly, and the cost has nearly doubled over time, from $17 million to an estimated $32 million.
Garth Wilson has worked in construction for 50 years. During that time, he's overseen the construction of dams in British Columbia, Greece, The Philippines, Indonesia and the U.S. Condit is the first dam he's taken out.
"A lot of projects I've worked on have involved demolition," he said. "Demolition is not anything new, but demolition of a major dam, that's something unusual."
On Monday, the small park next to Northwestern Lake was quiet as the water level receded. Two men played chess at a picnic table. Kerry and Jon Warszynski of Hood River played with their dogs along the shore.
Already, someone had stolen the Powerhouse Road sign out on State Highway 141 as a trophy.
Ross Chubb and his wife Penny of Vancouver paid a visit to the dam, though they didn't get past the construction managers in their hard hats and safety vests. They have a vacation house up north, near Trout Lake.
"This river just happens to run through my property," Ross Chubb said. "I fish the lake a lot. I know this river all the way to the Columbia."
How was he feeling about the prospect of a free-flowing White Salmon River?
"I've been waiting for this for 45 years," he said.
Information from: The Columbian
Copyright 2011 The Associated Press.