The question of whether a tunnel through San Pedro Mountain is geologically feasible has been put to rest by the findings of the first phase of the independent tunnel study, officials reported this week.
Meanwhile, the focus of the proposed tunnel is shifting away from a wider single-bore tunnel with a "splitter wall" dividing traffic toward two separate, narrower tunnels.
At a July 31 meeting in Oakland, a consultant presented the results of completed engineering and geotechnical studies that confirm a tunnel bypassing Highway 1 at Devil's Slide can be built, according to representatives who were at the meeting.
"It's unanimously accepted that a tunnel is feasible from geotechnical and engineering standpoints," said Tim Manzagol, a member of the Citizens Advisory Committee who attended the meeting.
The meeting, held at the California Department of Transportation's East Bay headquarters, was attended by representatives of Woodward-Clyde, the firm doing the tunnel study, its subcontractors, more than a dozen CalTrans officials, the three-person Technical Review Committee, San Mateo County officials, and members of the Citizens Advisory Committee. Its purpose was to review the findings of the study to date.
Core samples taken to determine the type of rock in the path of the proposed 4,000-foot-long tunnel revealed that most of it is rated, in geological terms, three and four. Rock rated one is too hard to cut, two is ideal, three is stable and four is less stable, but is easier to excavate and, as a result, less expensive to drill through.
According to Manzagol and others at the meeting, the nature of the rock in San Pedro Mountain may make it more cost-effective to build two smaller tunnel bores of between 26 and 29 feet wide instead of one single bore of between 50 and 53 feet wide, which would be more difficult to structurally support. Cost estimates have yet to be prepared for either option, however.
The tunnel study consultants also reported that a perfectly straight alignment of the proposed tunnel could take advantage of the prevailing coastal winds and air circulation, resulting in the need to run only large air-circulating fans in the heaviest of traffic and emergencies. That could potentially cut down annual operating costs.
Allowing bicyclists and pedestrians inside the tunnel would necessitate running the fans continuously, but those at the meeting were reportedly united in their sentiment, including CalTrans representatives, that bikers and hikers do not belong in the tunnel.
"(Federal Highway Administration tunnel expert) Tony Caserta made it very clear it is not an acceptible option," said one person who attended the meeting.
The consultant also revealed that the current alignment of Highway 1 would not need to be closed during construction of the tunnel except for 15-minute periods during the final phase of construction when the tunnel approaches are linked to the existing road.
Those in attendance said the discussion of the proposed tunnel touched on high-tech features that could be used, including sensors that would monitor the light outside the tunnel and keep it a constant 10 percent darker inside the tunnel so drivers' eyes are not shocked by sudden changes from light to dark and vice versa. Another feature would automatically shut down the tunnel if a truck carrying hazardous materials not authorized to enter the tunnel tried to do so.
The next phase of the study _ determining how much a tunnel and its various components would cost _ will be the most important in determining whether a tunnel or the bypass is a better buy, though perhaps more to locals than the federal government. Sources said that John Schultz, a representative of the Federal Highways Administration, told those at the meeting that the cost of a tunnel would not be an issue if it falls within 10 percent either way of the estimated bypass cost. His comments, however, did not address funding issues.
Woodward-Clyde representatives promised that their estimates for the tunnel would be accurate within 10 percent, but informally they are suggesting they may be accurate within 3 or 4 percent.
The desire by tunnel proponents to have the cost of the 4.5-mile Martini Creek Bypass updated to include new requirements was also discussed at the meeting. It was suggested that Woodward-Clyde update the bypass cost estimates, but CalTrans Project Manager Dennis Bosler objected to that. CalTrans will do the update itself, but James Roberts, CalTrans' representative on the Technical Review Committee, suggested the agency hire an outside consultant to verify its estimates. Bosler reportedly said that was a reasonable suggestion and could be accommodated within the time frame of the study, Manzagol said.
Last week, CalTrans was strongly criticized for refusing to attend a public meeting scheduled to bring the public up to date on the progress of the study. At the meeting in Oakland, however, agency officials were reportedly somewhat apologetic over the decision by their boss, District Director Joe Browne, not to allow the agency to attend.
There are tentative plans to hold another version of that meeting on Oct. 7, this time with attendance by CalTrans and Woodward-Clyde.
"I thought it was very informative," summed up Manzagol of the Oakland meeting, adding that he was initially not going to be allowed to speak, but was offered an opportunity to make some comments.