Arthur Keller, a Palo Alto planning commissioner, favors trenches.
Using a technique known as "cut and cover" and starting at surface level, a trench is dug, tracks laid inside, other equipment installed, and then the trench is covered. Keller believes the trenches could either be dug under Alma Street or under the current railroad right of way.
If several cities buy into the idea, the trench could start as far south as Mary Avenue in Sunnyvale, he said.
"One advantage is you don't have to put in the grade separations," said Keller, who has enjoyed high-speed rail in France and Japan.
He shuns tunneling.
"I don't see why you would want to do that. The cost is prohibitive," Keller said. "Think of the cost of tunneling for BART. This is worse than BART in terms of tunneling costs."
Like other community leaders, Keller views air rights as key to funding the undergrounding. He is likewise concerned about the possible increased disruption to traffic as more — and faster — trains run through Palo Alto.
"As Caltrain increases the number of trains going by ... it decreases the time for the cross traffic going along East Meadow. It's especially problematic, going to Paly on Churchill," Keller said. "You could have three trains going by at one time. You could be waiting there 10 minutes — or at least it feels like 10 minutes."
A project to electrify the Caltrain system aims to double the number of passenger trains per hour, from six to 12, according to Bob Doty, Caltrain's director of rail transportation.
There would be challenges to trenching, of course. Keller acknowledged the Oregon Expressway underpass would have to be reconstructed, and underground public utilities would need to be re-routed.
Also, either Alma or the current railroad right of way would be torn up during construction. If its the right of way, then the train system would have to be relocated — yet still be operational, Keller acknowledged.
That conflict between train and auto traffic flow — and the everyday life of residents — is one reason some cities and agencies are now preferring tunneling to trenching, civil engineers say.
Historically, tunneling has been more costly than other methods, said Victor Romero, principal for Jacobs Associates in San Francisco, a civil-engineering consulting firm.
But the costs of buying property and loss of business during construction of trenches and other qualitative downsides have started to add up.
"These [tunneling] projects initially have higher capital construction costs than above-ground or cut-and-cover, but in the long term there's the biggest benefit," he said.
Costs aside, however, trenching is possible, even at key junctions such as San Francisquito Creek, Romero said. There, the trench would likely go under the creek.
Trenches can also be stacked on top of one another and can go down to depths of 80 or 90 feet, he said.
Keller believes trenches could work, even if the construction phase could be difficult.
"It's like living through three years of hell for decades and decades after of peace and quiet," he said.
"It's unifying ... and in terms of the benefit of not having to get rid of homes for the right of way, you're doing something nice for the city."