Demolition Pops Cork in the Sandy River

By Libby Tucker

With a loud blast, a plume of smoke and scattered concrete, contractors on Tuesday began demolition of the Marmot Dam, long considered a cork in the Sandy River.

The blast came off like a champagne toast for conservation and fish advocates who have worked for decades to free the river for salmon and steelhead passage.

“It’s the culmination of 10 years’ work putting together this wild fish sanctuary,” Phil Wallin, president of Western Rivers Conservancy, a non-profit river advocacy in Portland, said. “The dam is the cork in the bottle.”

The dam’s removal, scheduled for completion in October, will free 100 miles of upstream habitat for fish spawning and migration.

But the celebration was bittersweet for general contractor Natt McDougall Co., which built the dam in 1989. The demolition marks the first time owner Natt McDougall has torn down a project that he built, he said.

“We worked hard to build it, so tearing it apart, psychologically it’s very difficult,” McDougall said. But, he said, “it’s what PGE decided was the right thing to do.”

PGE will spend $17 million to decommission its Bull Run hydropower project, which includes the Marmot Dam, the Little Sandy Dam, Roslyn Lake reservoir, and the Bull Run powerhouse.

The Bull Run power plant, located 25 miles east of Portland, is one of PGE’s smallest generators, producing 22 megawatts of electricity each year.

Retrofitting the dams to comply with federal regulations to protect endangered species would cost more than PGE could earn from the electricity generated by the hydropower plant, Peggy Fowler, the company’s CEO, said

“You always have to weigh the environmental impact” of hydropower projects, Fowler said. “It’s important to keep as many (dams) as we can in a way that’s cost effective.”

The 47-foot-high Marmot Dam is the largest dam to be removed in the Northwest in 40 years, and it is the first of eight dams slated for removal in the next five years. As such, the project ushers in the end of an era in energy development in which hydropower projects provided cheap and plentiful energy.

“There are a number of projects going through this issue,” John Esler, project manager of the Bull Run decommissioning for PGE, said. “You bite the bullet when you can’t figure out how to make it work.”

Marmot dam goes boom

Preparation for Tuesday’s demolition began in May when the U.S. Army Corps of Engineers approved the permits necessary to begin the work. Contractors first installed a temporary coffer dam, a mound of dirt and rock that diverts the river’s flow around the spillway, to isolate the concrete dam and free up dry space for the contractor to work.

With access to the concrete face, contractor Superior Blasting Inc. drilled 68 holes in which to place about 4,000 pounds of ammonium nitrate explosives. The blast cracked the dam’s face and turned the top 8 feet to concrete rubble.

Tuesday’s explosion was the first of four blasts to loosen concrete for demolition.

Once the dust cleared, a parade of excavators rigged with hydraulic hammers rolled slowly into the construction area, and immediately began breaking the concrete and scooping up the remains of the dam, which was littered with steel rebar.

“For some people it might be a challenge – downsizing the chunks of concrete so efficiently,” Dennis Snyder, owner of Clackamas- based Dennis Snyder Contractors and a spectator at Tuesday’s event, said. “But this is a knowledgeable company that’s been around a long time. It fits the project.”

Once the dam is removed, winter rains will increase the river’s flow by up to 10 feet, washing downstream the temporary dam and 800,000 yards of material that had built up behind the dam since the original structure was built in 1913.

PGE will continue to monitor the river sediment until the channel returns to its original flow, Esler said.

The exact effect the project will have on salmon and steelhead that use the river is uncertain, but fish biologists involved in the project expect fish populations in the Sandy River to increase in the long term.

“We’ll get more returning adult salmon back to the river,” Dan Shively, fish biologist with the National Forest Service in the Mt. Hood National Forest, said. “All of these fish can make it back to their spawning ground more easily.”

(c) 2007 Daily Journal of Commerce (Portland, OR). Provided by ProQuest Information and Learning. All rights Reserved.