Deep tunnels and covered trenches have been dropped as alternatives for the Palo Alto/Midpeninsula portion of the state's high-speed-line under the latest plan from the California High Speed Rail Authority, officials disclosed Thursday.
The agency dropped the tunnel and cut-and-cover alternatives despite heavy lobbying on their behalf by Palo Alto, Menlo Park, Atherton, Mountain View and other Midpeninsula cities.
A short tunnel under San Francisquito Creek is a possibility, the report indicates -- which would facilitate flood-control planning and possibly remove threats to the root system of the landmark El Palo Alto redwood tree.
The authority board heard a presentation on design options for the San Francisco-to-San Jose segment of the line at its meeting Thursday in San Francisco.
A new staff report lists just two design options for the Peninsula segment: one relies on at-grade and aerial structures and another includes tunnels at several portions of the segment. Tunneling is still an option for a stretch in San Francisco, in the Burlingame/Millbrae area and in Santa Clara.
But in Palo Alto, where city leaders and residents have long clamored for an underground tunnel, deep tunnels and covered trenches now appear to be off the table. The only design options recommended by staff engineers are a at-grade trains, aerial viaducts and open trenches, according to a staff summary made public at the meeting.
According to the Supplemental Alternative Analysis, the covered-trench alternative in the Palo Alto area is "impracticable due to major constructability issues" and presents significant ventilation and life safety problems.
A deep tunnel would "result in critical risks due to ground conditions, have major constructability issues, lengthy construction schedule and substantial cost features," the report said.
"Partially or completely covered trench or short-tunnel sections may be constructed to ameliorate either narrow right of way or environmental concerns" on the Peninsula segment, the report states.
"The San Francisquito Creek in Palo Alto could be a location where a short tunnel underneath the creek would be necessary in order to not interfere with the creek's water flow," it states.
It says that in other sections, trenching would be designed "to not preclude future decking or coverage.
"This would allow cities to cover sections of the trench if they found it desirable and if it were acceptable by Caltrain and the Authority."
Covered sections of less than 600 feet could be added later "without requiring sophisticated fire/life safety systems," it said.
The new analysis also recommends a horizontal four-track configuration for the new rail system, with Caltrain operating on the outside two tracks and high-speed trains on the inside tracks. Earlier this year, the rail authority's engineers considered designs that stack two tracks over two tracks. Since then, they had determined that such a system would require considerable right-of-way acquisitions at locations where the horizontal tracks transition into stacked tracks.
Bob Doty, director of the Peninsula Rail Program, said the horizontal four-track alignment also gives the Caltrain and high-speed-rail systems more flexibility and more options for sharing stations and tracks. The Peninsula Rail Program, a partnership of the rail authority and Caltrain, is responsible for deigning the San Francisco-to-San Jose segment for the high-speed-rail system, which would ultimately stretch to Los Angeles.
The authority's board of directors approved the Supplemental Alternatives Analysis unanimously with little discussion. The board also heard from dozens of speakers, including union members and business leaders who said they support the controversial project, and elected officials and residents who criticized it.
Menlo Park Mayor Rich Cline thanked the board for improving its communications with local leaders and said he supports trenches over freeways. Burligname Vice Mayor Terry Nagel asked the board to keep the locally popular covered-trench option on the table.
"We would like the below-grade options to be carried forward, including a trench that would be covered adjacent to homes and busineses," Nagel said. "We would then have something we can sell to our constituents instead of just doing damage control."
Doty said the new analysis doesn't eliminate options so much as "focus" them. He also indicated that the system's design could still change as engineering work continues.
"If these don't work, we may have to go to something else," Doty said.