Tunnel study changes suggested

Consultant proposes innovative, cost-saving ventilation system

Half Moon Bay Review, June 5, 1996

By Eric Rice

The independence of the study of a tunnel bypassing Devil's Slide will be tested this week. The consultant preparing the study has asked the California Department of Transporation for permission to modify four of the six proposed tunnel proposals to be studied.

Woodward-Clyde Consultants, the Oakland firm doing the project, has proposed changing the design of the tunnels planned for study to incorporate an innovative ventilation system that could cut standard ventilation costs by possibly one-third, according to S. Gordon Marsh, project manager for Woodward-Clyde.

On Tuesday, Marsh offered the public a glimpse into the tunnel study at a progress report before the San Mateo County Board of Supervisors. The consultant began work on the study last month. It is expected to be delivered to the board sometime in mid- or late October, just prior to a countywide vote on whether the tunnel should be the preferred permanent repair for Highway 1 at Devil's Slide.

Marsh announced that Woodward-Clyde is asking CalTrans to allow it to modify the proposed tunnel sections that will be studied. The proposed change would incorporate a wall separating the two opposing lanes of traffic. That would enable the use of two jet fans _ one on each side _ to ventilate carbon dioxide from the tunnel.

Marsh told supervisors that the feature is an innovative and unique proposal that CalTrans would not necessarily be out of line in rejecting.

"That would be their decision," Marsh said.

After the meeting Marsh said such a feature could cut the cost for ventilation by a third. The change could be important since ongoing ventilation costs are a significant added cost of operating a tunnel, as opposed to the overland Martini Creek Bypass.

Dennis Bosler, CalTrans District 4 project manager, attended Tuesday's meeting. Afterward he said the suggested modifications had not been fully studied, but "it seems like a good idea."

The study has been dogged by questions of whether it will be free of influence from CalTrans given the highway agency's continued oversight of it, but Marsh said they "are certainly open to our suggestions." He also stressed that Woodward-Clyde has its own international panel of tunnel experts reviewing the study.

"They are going to be looking over our shoulders and are not going to let us get away with anything," Marsh said.

He suggested that it might be preferable for reasons of air quality and safety to keep bicycles and pedestrians out of the tunnel. Tunnel supporters have argued likewise, also pointing out the potential dollar savings in building a narrower tunnel that does not have bike and pedestrian lanes.

The narrowest width of the tunnels to be studied without the lanes is 52 feet, six inches, compared with 71 feet, six inches with the lanes, Marsh said.

Marsh reported that Woodward-Clyde has chosen a preferred alignment for the tunnel that is several hundred feet shorter than the 4,500-foot-long tunnel that has been previously discussed. The new alignment is just east of the old one and runs about 4,000 feet. Marsh described it as "short, straight and cheap."

The "guts" of the tunnel will include a ventilation system, signs in Pacifica and on the Coastside in case it needs to be closed, surveillance cameras and a drainage system to remove gasoline that might be spilled. The tunnel's surveillance system would be tied back to CalTrans' control centers in Oakland and at the Caldicott Tunnel. An emergency response agreement is being drafted with the Pacifica Fire Department in the event of a fire, Marsh said.

If a tunnel is built, the north end would have to connect to a 100-foot-long bridge across a portion of Shamrock Ranch that is likely to be problematic and costly, Marsh said, because of access problems for construction equipment and the need to not disturb red-legged frog habitat.

When Woodward-Clyde has completed the study it will present it to CalTrans, but it will not make a recommendation of which tunnel would be best to build, or compare it to the bypass. All the tunnels that will be presented in the study, Marsh said, will be buildable, though their pricetags will vary.

The delivery date for the study continues to be a concern since it will be so close to the countywide tunnel vote.

In a related matter, the county Elections Office reported that it has begun checking some of the 34,000 signatures submitted to put the tunnel initiative to a vote. A spokeswoman for the office said they are not disqualifying many signatures, but added that the verification process will not be completed until Friday or early next week.

Half Moon Bay Review