Traffic backs up on Valley Boulevard in Alhambra. A tunnel could eventually connect the 710 to the 605, the 210 or the 2. (Gary Friedman / Los Angeles Times)
The preliminary survey examines five proposed underground areas for the final phase of the freeway and presents the challenges of each. Public hearings will be held before the report is finalized.A long-awaited geological study for a proposal to complete the 710 Freeway as a tunnel under either the San Gabriel Valley or northeast Los Angeles found that such a project would be scientifically feasible.
The findings mark a small step in what even supporters say is a long road for the tunnel idea, which was proposed by transportation officials and some politicians after residents fought for decades against completing the 710 as an above-ground freeway.
The tunnel has also generated opposition, and building it would be significantly more expensive than a regular freeway.
The 710 ends in Alhambra, just north of the 10 Freeway. Planners originally envisioned that it would go through South Pasadena and Pasadena to link with the 210 Freeway.
Transportation officials began studying areas in five directions from the end of the freeway in January of last year.
Those zones stretch east to the 605 Freeway, north to the 210 Freeway, and west to the 2 Freeway.
The study, which is still in draft form, will not be finalized until early 2010, after a series of public meetings are held, said officials with the California Department of Transportation.
Abdi Saghafi, the Caltrans project manager for the 710 corridor, said the study did not favor one particular zone over another, but rather presented issues, challenges and conditions of each.
It was based on the assumption that the tunnel would be about 200 feet below ground and about 50 feet in diameter.
The study researched issues such as faults and seismic activity, groundwater conditions and the presence of hazardous materials, among others.
Some of the findings for each zone, according to the study, are:
Zone 1 (Northeast L.A.): There is one Superfund site in the northwest portion of the zone which could be a source of contaminated soil and groundwater in the tunnel.
There is also a possibility of encountering naturally occurring gases such as methane and hydrogen sulfide.
There are no active faults in the zone.
Zone 2 (Northeast L.A.): The active Raymond fault crosses the zone and there is also the potential of encountering naturally occurring gases.
Some soil and groundwater contamination could result in hazardous materials being encountered.
Zone 3 (South Pasadena/Pasadena): The Raymond and San Rafael faults are groundwater barriers in this area, and there is one active and two potentially active faults in the area.
There are two places with minor soil contamination in the northern limits of the zone.
Zone 4 (San Marino/Pasadena): Active faults that cross the zone are the Raymond and Alhambra Wash faults.
There is one Superfund site in the southwestern end of the zone.
There are also six other sites with various levels of soil contamination.
Zone 5 (Alhambra/San Gabriel/Temple City): The active Alhambra Wash fault is in this zone and so are the perennial Rio Hondo and San Gabriel rivers.
There is one Superfund site in the south-central portion of the zone and seven other sites with various levels of soil and groundwater contamination.
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