THE ADVANTAGES OF A TUNNEL SOLUTION TO THE DEVIL'S SLIDE PROBLEM
WHY LOOK AT A TUNNEL NOW?
We need a permanent solution to the Devil's Slide problem that all sides can accept so that we never again have to suffer the personal and economic pain of this winter's closure. A tunnel has become that solution. It is safer than the bypass and appears to cost less to build. There is growing support for the tunnel among residents north and south of Devil's Slide. Most importantly, the Sierra Club, the Committee for Green Foothills and others who have sued Caltrans have agreed to drop their pending lawsuits if Caltrans commits to building the tunnel. This action alone could greatly speed the process of getting a permanent fix.
A tunnel is the one solution that resolves the Devil's Slide problem for everyone.
The following information is based on facts and opinions from a panel of independent engineers and geologists with specific expertise in highway construction, tunneling, and landslide evaluation. These experts are working with San Mateo County Supervisors Ted Lempert and Ruben Barrales to find a solution to the Devil's Slide problem.
COST: WILL SAVE TAXPAYERS' MONEY
Caltrans considered a four-lane tunnel alternative in the 1970s, but by 1985 they dismissed it based solely on a very high cost estimate -- not on feasibility. Today, state law restricts Highway 1 to two lanes, and so the cost of the required two-lane tunnel will be significantly less than the four-lane tunnel Caltrans briefly looked at. The panel of engineers and geologists are therefore recommending a tunnel less than one mile long, compared to a 4.5-mile-long bypass. The width of the tunnel will be 46 ft., with two 12-ft. lanes, plus approximately 10-ft.-wide shoulders for emergency vehicles, and room for a center barrier.
Geologist Douglas Hamilton (a member of the panel) states:
"Vehicular tunnels of comparable size and length have been constructed recently at costs ranging between $25 and $65 million. Thus, in addition to the obvious functional and environmental superiority of a tunnel, a tunnel may well be the least expensive to construct and it certainly would be the least expensive to maintain."
A licensed engineer specializing in tunnel design, agrees:
"I would expect construction costs for the tunnel to be in the $50 to $60 million range."
In contrast, Caltrans estimates the bypass will cost at least $73 million. One factor likely to increase that cost is ensuring the bridges of the the bypass meet new earthquake engineering standards.
CONSTRUCTION TIME: NO DELAY
It appears that the tunnel will take about the same amount of time to build as the bypass -- approximately 2 1/2 years.
MAINTENANCE: CHEAPER AND EASIER
Commenting on the tunnel, geotechnical consultant and panel member Tim Manzagol states:
"I believe that the long-term maintenance would be less, public safety would be greater, and environmental and visual impacts substantially less for the tunnel option."
Geologist Hamilton says the bypass will have significant maintenance costs because of the steep cuts and fills along the route. (Fills are loose earth material deposited and compacted to fill in a gap.) He believes the tunnel's maintenance costs will be much lower in comparison, and these lower maintenance costs will tend to offset the operational costs for the tunnel.
SAFETY: STRAIGHT, FLAT, AND CLEAR
Tunnels are commonly used around the world as safe and direct routes through mountains. The panel experts agree that a tunnel is safer than the bypass. The nearly 1-mile tunnel is straight and virtually level, whereas the bypass has more than 4 miles of steep curves, at 6.5% grades, in potentially unstable terrain. The 6.5% grade is the steepest grade allowed by federal regulations. The bypass has three bridges, and the drop-off from one of them is 250 feet -- as high as a 25-story building. The steep bypass route is often shrouded in fog, which would create hazardous driving conditions, especially with the cliff drop-offs. Moreover, according to the panel, the tunnel would be much safer than the bypass during an earthquake because ground motion is greater on the surface. The bypass also could be a trouble spot in an earthquake because of the bridges, and the potential for failures in the large cuts and fills.
ENVIRONMENTAL ISSUES AND STUDIES: LESS IMPACT, FAST REVIEW
The environmental studies on the bypass must, under law, be reviewed and updated, in part to make sure the bypass complies with all new requirements. One concern is the Monterey Bay Marine Sanctuary. Erosion along the bypass route, from the cuts and fills that Caltrans agrees are too steep to support revegetation, will send silt into local creeks that run into the ocean sanctuary. This could be a problem for the bypass, and further delay construction.
The tunnel, however, does not impact the Marine Sanctuary, Montara Mountain, or McNee Ranch State Park. Contrary to some statements, neither the tunnel nor its approach roads are within the property of the State Park. Because it has no negative environmental impact, the tunnel can be approved quickly.
The excavated material will be used to build the approaches to the tunnel. Rocks will not have to be transported and dumped elsewhere.
FUNDING: IT CAN HAPPEN
Legislation can make funding available, and our elected officials will find the cost savings of the tunnel very appealing. If they hear that there is broad public support behind the tunnel, they can make this legislation happen.
Sponsored by Citizens for the Tunnel
For more information, please leave a message at (415) 737-1981.