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Dam draining a possibility
September 14, 2005, 12:00 AM By Heather Murtagh
Practical, reasonably-priced solutions for draining and restoring Yosemite's Hetch Hetchy Valley were revealed in a study released yesterday in Sacramento.

The study, released by the Sonora-based nonprofit Restore Hetch Hetchy, states by diverting water from the Tuolumne River and a tributary into existing pipelines, 95 percent of the water and 73 percent of the energy that would be lost if the dam was removed could be retained.

The plan calls for dam removal, valley restoration, water filtration and replacement of water and energy supplies costing in total about $1 billion.

The changes would not interfere the repairs being made to the rest of the San Francisco water supply system.

After the 1906 earthquake and fire, San Francisco claimed Hetch Hetchy Valley was the only good damsite to provide water to the city and the San Francisco Peninsula. The O'Shaughnessy Dam was built as a result of the Raker Act passed by Congress in 1913.

State's water

Hetch Hetchy currently stores less than 1 percent of the state's water, and the Don Pedro and Calaveras dams could be enlarged to make up for it, according to the group. The O'Shaughnessy Dam also creates 500 million kilowatt hours of electricity, less than two tenths of 1 percent of California's electricity supply. Removal of the O'Shaughnessy dam would take five years. During that time ecological restoration would begin. The valley would appear restored within 10 years.

The study also suggests San Francisco begin a filtration program immediately to increase the quality of water sent to the Bay Area.

San Francisco will continue to receive water from the Tuolumne River, however the points of diversion and storage will change.

The first suggestion to replace the water lost due to the removal of the reservoir is to divert the water from the Tuolumne River below Hetch Hetchy into the existing Canyon Tunnel. This would bring most of the water stored in Hetch Hetchy to the Bay Area creating a small short fall in some dry years. All of the water within Hetch Hetchy could be store in Don Pedro if it were raised less than 30 feet.

To replace the energy lost, the study suggests energy conservation, the use of a new low polluting natural gas combined cycle power plant and use of solar and wind energy.

Since funding is needed to provide the changes some congressional action is required. Some funding will need to be provided at the state level. The San Francisco Board of Supervisors and maybe even the voters may be asked to approve the removal of the dam.

Art Jensen, general manager of the Bay Area Water Supply and Conservation Agency, had not had a chance to look over the plan yet, but said it was a long time coming.

BAWSCA oversees the interests in Alameda, Santa Clara and San Mateo counties that purchase water on a wholesale basis from the San Francisco regional water system. While there is not a statement about the study, BAWSCA did release a statement in July about Hetch Hetchy. Within the statement it said BAWSCA will oppose a proposal to drain Hetch Hetchy unless five requirements are met.


The requirements are: 1. No delay in building the earthquake-vulnerable Hetch Hetchy system caused by a program to drain the reservoir or destroy the dam. 2. No change in the quality of water delivered to San Francisco's customers. 3. No increase in the cost of water for San Francisco's customers. 4. No change in physical facilities or institutional arrangements should reduce water supplies or expose existing and future water customers to more frequent or severe water shortages. 5. No modifications to the existing water system or its operation until all replacement facilities are funded, built and operational, and all institutional arrangements are in place, and fully funded.

For more information on Restore Hetch Hetchy visit For more information on BAWSCA visit

Heather Murtagh can be reached by e-mail: or by phone: (650) 344-5200 ext. 105. What do you think of this story? Send a letter to the editor: <

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