Dam near Carson will be removed this summer

Enrollees from Company 944, Camp Hemlock, near Carson, stand atop the newly finished Trout Creek Dam in 1936. (Files/The Columbian)

A long-standing obstacle for trout in Trout Creek will be removed this summer, with Skamania County's decision to drop its appeal of a Forest Service plan to tear down Hemlock Dam north of Carson.

The 26-foot-high Hemlock Dam was built in 1935, originally as a hydroelectric dam powering a nearby Civilian Conservation Corps encampment and later as a water source for the Forest Service's old Wind River Nursery. The old fish ladder doesn't meet modern environmental standards — scarcely 50 steelhead a year manage to cross it — and the Forest Service prefers to spend $2 million removing it rather than even more money retrofitting it with modern fish passage.

"There will be pretty significant improvement of habitat quality in the area of the reservoir and downstream," said Bengt Coffin, a hydrologist for the Mount Adams Ranger District. "Silt and sand covers the reservoir. It's not great habitat for steelhead."

He said it's poor habitat downstream, too. Because the dam has cut off the normal resupply of gravel, the creek has been scoured down to bedrock in the two miles between the dam and the creek's confluence with Wind River.

Before removing the dam, the Forest Service will scoop between 35,000 and 65,000 cubic yards of silt that has accumulated on the back side of the 160-foot-wide dam.

Biologists expect the dam removal will clear the way for hundreds of steelhead to repopulate the upper reaches of a creek that historically produced a major share of the wild fish in the entire Wind River drainage.

"It's going to increase fish significantly in the Wind River watershed," said Emily Platt, executive director of the environmental group Gifford Pinchot Task Force. "There is definitely high-quality habitat behind the dam."

However, local residents had grown accustomed to the recreational lake behind the dam.

Skamania County appealed the state Department of Ecology's water-quality certification for dam-removal to the Pollution Control Hearings Board. The county dropped that appeal last month. In return, the Department of Ecology agreed to expedite a decision to allow the county to irrigate an extra 10 acres it now owns at the old nursery site.

Coffin said the concrete dam will be removed chunk by chunk with a jackhammer-type tool mounted on an excavator working on the downstream side.

Erik Robinson: 360-735-4551, or erik.robinson@columbian.com.