Water Tunnel in Danger

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Hetch Hetchy Water System - Which Supplies 2.6 million Bay Area Residences and Businesses - is at Risk of a "Catastrophic Collapse"

Mountain Tunnel, a key part of the Hetch Hetchy water system - which supplies 2.6 million Bay Area residences and businesses - is at risk of a "catastrophic collapse" and will cost more than $100 million to repair or up to $630 million to replace, according to the San Francisco Public Utilities Commission.

City officials have known for 25 years that significant work is needed on the 19-mile-long tunnel just outside Yosemite National Park in a steep, hard-to-access wilderness area. They considered making it part of the puc's decade-old, $4.6 billion water system improvement program, which is now more than 80 percent complete. But ultimately, the 89-year-old connector was left out of the rebuild, which focused on upgrading Bay Area water facilities that could fail in an earthquake.

PUC officials say that the program gave priority to infrastructure on the three major Bay Area fault lines whose failure could shut off the water supply, such as the Calaveras Dam near Fremont - and that the tunnel, as well as other "upcountry" projects, didn't pose enough of a seismic risk to be included.

Now, the PUC is grappling with whether to shore up the Mountain Tunnel, which would require shutting it down for two months at a time for up to 10 years, or go the far more expensive but arguably more reliable route of building a new tunnel. The issue has taken on more urgency since the January release of a report that laid out the options and recommended building a new tunnel.

A major project

Whichever fix the agency chooses, said Steve Ritchie, the commission's assistant general manager for enterprise, it's going to be an expensive, complex project - far bigger than most of the individual components of the water system improvement program.

Concern outside S.F.

The potential for catastrophe, however, has raised alarms at the Bay Area Water Supply and Conservation Agency, which represents the PUC's 1.7 million residential customers and 30,000 business customers outside the city of San Francisco. The costs of any improvements would be borne by water ratepayers as well as the commission's hydropower customers, because the tunnel is used for both purposes.

Source: SFGate

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