It’s Not Your Usual Grout Work Engineer Navigates Tunnels Within Dam To Make Repairs

Engineer Heather Weir pulls on a yellow rainsuit heavy enough to weather a hurricane before stepping into an elevator for a journey to the center of Dworshak Dam.

Weir heads up the U.S. Army Corps of Engineers’ contract to seal cracks in the bedrock beneath the massive concrete dam straddling the Clearwater River’s North Fork.

The corps hopes the $1.3 million contract will draw tight a curtain of grout in the bedrock beneath the dam’s south shoulder.

Weir carries a three-dimensional map, a now-unneeded guide to the maze of tunnels or galleries within.

“It’s easy to get turned around down here,” Weir said. Five weeks of navigating to keep track of crews drilling holes and preparing to inject grout have given her a working familiarity with the high concrete dam.

Everett Wright, the corps’ Walla Walla District dam safety chief, is prowling the galleries, too. The work qualifies as preventative maintenance, he said, intended to head off a problem before it occurs.

“With something like this, we want to get it in and scheduled for funding so we can take care of it,” Wright said.

The project means drilling 42 to 69 holes, 3 inches in diameter and 130 feet through several feet of concrete and deep into the bedrock beneath the dam. The work could be done as early as February, or until March 31.

Corps engineers designed the drilling pattern to intercept the cracks in the bedrock that have opened since Dworshak was built.

Grout also may have washed out of old cracks during those 25 years.

The gallery was included in Dworshak in the early 1970s to channel water trickling through.