Cascades Dam Removal Lets River Flow Free in Yosemite

The Modesto Bee - January 12, 2004

A Geology textbooks describe how rivers constantly shift over
millions of years.

In Yosemite National Park, it took crews only two months to change the course of the Merced River, demolishing the obsolete Cascades Diversion Dam that had diverted water for the better part of a century.

Yosemite watchdog groups say they'd never seen that part of the river flow naturally in their lifetime.

"It looks like it's natural," said George Whitmore, chairman of the Sierra Club's Yosemite Committee. "What an improvement."

Said project manager Mike Pieper, "That's the whole intent -- to make it look like we were never here."

Crews began attacking the dam in November, as the Merced's water headed toward its lowest ebb. They built a ramp to get jackhammers into the river bed, close to the 184-foot-long dam constructed of concrete walls filled with boulders and overlaid with redwood slabs.

The dam, which sat near the intersection of El Portal and New Big Oak Flat roads, was built in late 1916 and 1917 to provide electricity for the Yosemite Valley's budding tourism business. It served the valley for nearly 70 years, until age rendered it useless in the 1980s. A massive flood damaged it further in 1997.

The dam cost $200,000 to build, Pieper said. It cost $2.8 million to demolish. Crews removed the dam under the prescription of the Yosemite Valley Plan.

More than 20 years in the making, the plan aims to restore parts of Yosemite Valley -- the park's most popular area with millions of visitors a year -- to a more pastoral state.

"It's nice to see a project that focused on the river and has succeeded so well," said Greg Adair of the Friends of the Yosemite Valley, a group dedicated to resisting development in the park and making it more accessible to visitors.

"We're delighted," he said, adding there is similar work to do in the park.

"This is one good thing about the Yosemite Valley Plan," Whitmore said.

Rep. George Radanovich, R-Mariposa, is at odds with the Sierra Club about the number of campsites in the valley that should be restored after the 1997 flood washed many away. While that argument continues, "I haven't heard anybody criticize this," Whitmore said of the dam removal.

Pieper has dedicated 2 1/2 years to the project. Just as much research as concrete-pulverizing went into removing the dam.

Pieper had to search a water resources library at the University of California at Berkeley to find maps, drawings and photographs of what the area looked like before the dam was built. The National Park Service used them as a blueprint to restore the area, planting trees and rebuilding river banks eroded by water constricted by the dam.

Crews worked around the sensitive vegetation in the area, including the only grove of tanbark oaks in Mariposa County.

While much of the demolition and rehabilitation was completed by Dec. 22, there's still work to do. It includes rebuilding El Portal Road, which was rerouted around the project area, over the next year.