Explosion will breach Condit Dam on Wednesday

Nearby roads, waterways airspace will be closed much of day

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The day has arrived.

After more than a decade of planning and legal wrangling, the 125-foot-tall Condit Dam is set to breached with a dynamite blast that will send the White Salmon River rushing through a hole at its base Wednesday. The noon breaching will drain Northwestern Lake, the reservoir behind Condit Dam.

Nearby roads, waterways and airspace will be closed for much of the day.

Portland-based utility PacifiCorp, which owns the hydroelectric dam, has made careful preparations. Northwestern Lake has already been partially drained, and crews have been gradually blasting and drilling through the dam’s base for months. All that’s holding back the river now — and an estimated 2.7 million cubic yards of accumulated sediment — is a concrete plug that will be blown out by 700 pounds of dynamite.

The Condit Dam has blocked migrating salmon and steelhead from the White Salmon River 3.3 miles from its confluence with the Columbia River at the Skamania-Klickitat county line since 1913. The breaching will open several miles of fish habitat in the upper river and will eventually open the lower river to white-water rafters and kayakers. Though Wednesday’s blast will send the river through a hole in the base of the dam, the removal of the structure itself isn’t scheduled to happen until next spring.

The Columbian will cover the historic breaching of the Condit Dam from multiple angles. Look for updates throughout the day on http://www.columbian.com and http://www.twitter.com/thecolumbian and full coverage in Thursday’s Columbian.