Tunnel advocates, however, denied it would cost that much, reasserting previous estimates by geologists and a tunnel-building firm that it would cost $50-$70 million.
CalTrans spokesman Greg Bayol said Tuesday that the agency recently undertook a new study of the cost of a tunnel in response to questions raised during the review of noise impacts from the proposed Martini Creek Bypass. The report will not be made public for about two weeks until CalTrans publishes its completed noise study, but Bayol said work on the new estimate is complete and discussed it in a telephone interview.
He said the study's findings confirm CalTrans' previous claim that a tunnel would cost more than the 4.5-mile Martini Creek Bypass.
"It would he considerably more expensive," Bayol said
The new estimate was prepared by an engineer in CalTrans Sacramento "structure squad" to give the agency an up-to-date idea of how much a tunnel would cost. It is based on a 4,600-foot-long single-bore tunnel, the same the Sierra Club and several geologists have proposed, Bayol said.
In arriving at the $120 million estimate, Bayol said cost factors including current excavation costs, equipment providers and the design of a ventilation system were examined. He said a "best-case scenario" was used in guessing what kind of rock might be encountered.
The actual cost to build the tunnel would be $105 million in today's dollars, but delays needed for design and environmental studies, plus inflation, would add $15 million to the total, Bayol said.
Peter Markle, spokesman for the Federal Highway Administration in Sacramento, said he had not yet seen or reviewed the new estimate. But he said the FHA and CalTrans are trying to reach a consensus on what the minimum safe width for a tunnel would be, and that that figure would play a significant role in the cost estimate.
The most recent CalTrans' estimate to build a single-bore tunnel was in July 1993 when it was estimated to cost $77.5 million. That figure was based solely on a 1974 CalTrans study, which was updated for inflation, but did not include any new information.
CalTrans estimates the 4.5-mile Martini Creek Bypass would cost $73 million, but opponents believe it would cost $100 million or more.
Tunnel advocates rejected the new estimate as far too high. Sierra Club spokeswoman Olive Mayer said the estimate is "absolutely false" and accused CalTrans of being "deceitful, dishonest."
Mayer said she was told earlier this month by Tony Caserta, the Federal Highway Administration's tunnel expert in Washington D.C., that previous estimates of $50 to $70 million are "satisfactory and realistic."
In March, Shank/Balfour Beatty, a San Francisco tunnel-building firm, estimated the same tunnel would cost only $60.35 million.
On Tuesday, Mike Shank said his estimate did not include possible costs for acquisition of right of way, but said $120 million is "wholly unrealistic."
"I've seen how CalTrans makes its estimates," he said. "They allow a lot of dollars for engineering."
CalTrans' estimate would translate to about $25,000 per foot of tunnel. Shank claimed a more realistic estimate might be $10,000 or $11,000.
"It's kind of like the fox guarding the henhouse," Shank said. "What is their estimate worth if they don't want to build it?"
CalTrans' latest estimate is certain to fuel the war of words being waged between bypass supporters and tunnel supporters. The Pacifica City Council and Pacifica Chamber of Commerce have scheduled a public forum on June 27 to debate the tunnel issue.
Tunnel supporters have previously accused CalTrans of using inflated figures and worst-case scenarios in past tunnel estimates.
By contrast, Half Moon Bay resident Ed Stoehr, a member of the Coastside Committee for the Bypass, said the estimate reinforces the feasibility of the bypass.
"Obviously, the higher (a tunnel) gets, the less likely it's going to happen," Stoehr said Tueday.
Bayol anticipated the response from tunnel supporters. He said the engineer who drew up the new estimate was completely unaware of the debate raging over a permanent repair of Devil's Slide.
"People beg us for information and then when you provide it they call you a liar," he fumed.