Bridge’s Quake Monitors Will Give Instant Reading on Shaking

Efforts to protect the Bay Area’s biggest bridges against a massive earthquake took a small step forward on Thursday when state officials demonstrated strong-motion monitoring devices on a new suspension bridge across the Carquinez Strait northeast of San Francisco.

In the event of an earthquake, the 130 instruments would convey to state authorities an immediate assessment of the intensity of shaking along the $500-million bridge, which will carry westbound traffic from Sacramento toward San Francisco.

With the Carquinez suspension bridge -- due to open to traffic Nov. 10 -- Caltrans will have finished two of its five Bay Area projects designed to modernize the bridges and protect them against earthquakes up to the magnitude 8 range.

The improvements range from building totally new, more secure, spans to strengthening and stiffening others.

The Golden Gate bridge is also being retrofitted, under the control of a separate local authority, at a cost of $392 million.

Estimated costs of the bridge projects have risen sharply, with inflation, redesign and changes since the early 1990s.

Dan McElhinney, toll bridge construction manager for Caltrans, put the total cost of the projects, including the Golden Gate, at about $6.6 billion. He said there were firm completion dates for all the Caltrans projects outstanding.

However, Mary Curry, spokeswoman for the Golden Gate Bridge Highway and Transportation district, said funding had not yet been secured for the final $160-million portion of the Golden Gate retrofitting, so that date is uncertain.

Caltrans finished retrofitting the San Mateo-Hayward Bridge in 2000.

The Carquinez suspension bridge opening next month will be the first of its type completed in California since the Vincent Thomas Bridge in San Pedro in 1963, McElhinney said.

The new east span of the San Francisco-Oakland Bay Bridge is about 30% complete. It is to be finished in 2009, at an estimated cost of $2.6 billion.

The west span and existing approaches of the Bay Bridge, costing $670 million to retrofit, are scheduled to be finished next summer.

The retrofitting of the Richmond-San Rafael Bridge, now 60% complete, is due to be finished in late 2005 at a cost of about $90 million.

Completion of a new span of the Benicia-Martinez bridge is scheduled for 2007, at a cost of $700 million. That figure, however, includes the recent upgrading of the existing span.

Curry said the Golden Gate retrofitting project has been separated into three phases.

Phase 1, work on the North Viaduct, was completed in 2002 at a cost of $71 million.

Phase 2, work on the South Approach Viaduct, South Anchorage and Fort Point Arch, is costing $161 million and will be finished in 2005.

Phase 3, the as-yet-unfunded $160-million portion, will be the retrofitting of the North Anchorage, the Main Span and the Main Towers.

That part of the work on the Golden Gate is estimated to take 3 1/2 years to complete, once funding is secured.

The bridge retrofitting and reconstruction projects were undertaken after the 1989 magnitude 7.1 Loma Prieta earthquake south of San Francisco Bay, when a short span of the eastern side of the Bay Bridge collapsed.