The controversial $40-billion bullet train would whisk passengers at speeds up to 125 mph along the Caltrain corridor and travel to Los Angeles. Service is expected to begin late next decade.
The rail authority is proposing three track alignment options: raised tracks on either open aerial structures similar to freeway overpasses or on filled-in berms, typically about 20 feet above street level; adding two tracks next to the existing Caltrain railroad; or underground tracks through either a tunnel or open trench. At no point would the tracks cross a road at street level.
The authority plans to select a track alignment in early 2011, and construction is expected to start in late 2012. That would give planners, city officials and residents a year and a half to study - and debate -the configurations proposed Wednesday.
Many cities favor underground tracks but fear they would be too expensive. High-speed rail project manager Dominic Spaethling said the authority is studying the options and does not yet favor any one particular alignment.
In most scenarios, the railroad would feature four side-by-side tracks, with two for electrified Caltrains and a pair for bullet trains.
The expansion may result in the use of eminent domain, although Spaethling said the authority might consider stacking tracks, two-by-two, in tight areas such as Millbrae, San Mateo and Redwood City.
Among the highlights of the newly released report, the state said it is now considering Mountain View, in addition to Palo Alto and Redwood City, for the region's fourth high-speed rail station. Stops have already been cemented in San Francisco, San Jose and Millbrae.
Also, for several cities that want the railroad "out of sight, out of mind," the authority said it would study tunneling or trenching in communities such as Burlingame, Palo Alto, Menlo Park and Atherton.
Two of those cities, Menlo Park and Atherton, went as far as to sue the rail authority last summer, and Palo Alto filed a legal brief in support of their lawsuit earlier this year. A Sacramento judge next week is expected to issue a disposition in the suit against the rail authority.
" Other cities and areas where tunneling or trenching are set to be studied include San Francisco, Millbrae, northern San Mateo, southern San Carlos, northern Redwood City, Mountain View, northern Sunnyvale, Santa Clara and San Jose.
Some cities received only one proposal and would not have their track elevations altered. Instead, planners will likely just add two tracks to the sides of their existing stretch of Caltrain railroad. These sections include the stretches between the Bayshore and South San Francisco Caltrain stations, most of San Bruno, from southern San Mateo to northern San Carlos, and from southern Sunnyvale to northern Santa Clara.
Conversely, the rail authority said it would absolutely need to build elevated rail bridges or send its trains underground in northern San Mateo and near the Redwood City and San Jose Diridon Caltrain stations. The trains would need to run underground in most of northeastern San Francisco, as well.
Finally, the rail authority released six proposals for the start and stop points for the Bay Area portion of the high-speed rail line. The authority said the San Jose stop would either be at the Diridon Station or adjacent to it, and proposed four areas for the San Francisco stations at or just south of the Transbay Terminal.
Spaethling said in many areas the authority would also study whether to raise or lower roadways to accommodate high-speed trains traveling beneath or over them.
The proposals put to rest any hopes residents had that the tracks would travel along an alternative path, such as Interstate 280 or Highway 101.