Northwest Newspaper Hydropower Articles

SWIFT POWER CANAL FORTIFIED FOR WINTER

By Thomas Ryll
The Columbian

The road is patched, the powerhouse is nearly cleaned up and now heavy equipment is readying the Swift power canal for its next battle: winter. A five-week, $658,000 "emergency winterization" project will smooth the steep, shattered gash in the canal's earth-fill dam and construct a sediment-retaining structure.

At the same time, work aimed at putting the powerhouse back in business after the canal's spectacular April 21 failure is also under way at a slower pace.

"We're in a process where it will be pushing two years before we're back producing power if everything goes well," said Dave Andrew, Cowlitz County Public Utility District spokesman.The consulting engineering firm CH2M Hill is studying the cause of the dam's breach. In a preliminary May report, failure was attributed to the collapse of ancient lava tubes beneath the structure, just east of the community of Cougar. That in turn, the report said, led to formation of a sinkhole and the resulting 300-foot-long breach, which washed out a section of state Highway 503 and ruined much of the dam's 70-megawatt powerhouse.

Hill's final report, expected this month, will be submitted to a panel of three engineers named at the request of the Federal Energy Regulatory Commission. The engineers have viewed the site at least twice and will issue the formal report on the cause of the breach.

The Cowlitz PUD also is seeking a consulting engineering firm to conduct a feasibility and design analysis for a reconstruction project, answering such questions as whether the canal can be safely repaired and whether it would make economic sense.

This week, two dozen engineers from a dozen companies interested in the study visited the Swift site, photographing the ravaged powerhouse and prodding equipment at the nearby substation.

Few if any wanted to pass up the chance.

"It's a 'non-mandatory site visit,' but most of them showed up today," said Ron Worthington, Cowlitz PUD customer service director and a member of the entourage.

More pressing is the earthmoving work being done by Vancouver contractor J.R. Merit to forestall additional damage by winter's rain and snow. Excavators are plucking huge boulders and buckets of smaller material from the blown-out section of the canal, reducing the steepness of the opening "so it doesn't come down on its own," said Worthington.

Meanwhile, a small dam-like berm is being built inside the drained power canal. Captured water rain and inflow from streams that feed the canal will flow through a 9-foot-diameter steel culvert to the powerhouse intake structure. From there the water will flow to the powerhouse. The purpose is not to produce power, since that equipment was damaged or destroyed, but to shunt the runoff past the gaping hole in the canal. The repaired section of Highway 503 runs past the hole, and there were concerns that the runoff, if left uncaptured, could overwhelm culverts and again threaten the highway.

But it would be nothing like the events of April 21, when millions of gallons of water blasted out of the 3.2-mile-long canal feeding the powerhouse. The first minutes of the breach were captured on 68 digital-camera images, the only known photographs of the event, by a hydro operator who was among the first people on the scene. One of those pictures keeps the memory of April 21 fresh, at least for Worthington: he displays the most spectacular image on his computer at work.

Columbian
Vancouver, WA
October 4, 2002

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