Inside Seven
Current Issue: September 2014
The Study began in April 2008 with a funded budget $11.5 million from the Los Angeles Metropolitan Transportation Authority (Metro), Caltrans and a federal House Resolution sponsored by California Congressman Adam Schiff, District 29.

Caltrans Completes the State Route 710 Tunnel Technical Study
by  Maria Raptis
Issue Date: 05/2010

Nearly five decades of progress and setbacks has not deterred District 7 from finding a regional transportation solution.

[Click on photos to read captions.]

After 46 years of working toward the closure of the State Route 710 gap in Los Angeles County, Caltrans reached a milestone last month when the department released a final geotechnical feasibility report that examines extending the freeway by constructing a tunnel.

The State Route 710 Tunnel Technical Study, led by District 7, confirmed the geotechnical feasibility of building a below-ground tunnel to complete Route 710 in all five of the studied zones which encompassed Alhambra, Glendale, La Cañada-Flintridge, Los Angeles, Monterey Park, San Marino, South Pasadena and Pasadena.

District 7 and its funding partner, the Los Angeles County Metropolitan Transportation Authority (Metro) presented the Final Geotechnical Report containing the Study findings to its Steering and Technical Advisory committee members at a meeting on March 30 in South Pasadena.

The 14,000-page final report consists of several volumes of research, exploration data and technical analysis on conditions found while drilling (boring) at depths of more than 250 feet. It includes revisions requested by committee members and citizens during the draft process prior to a final report. The final report also documents a vigorous public outreach effort including all public comments received from committee members, elected officials, stakeholders and the general public.

“Caltrans is very pleased with the accomplished work and final product. We delivered a solid report,” said Abdi Saghafi, Caltrans project manager. “The amount of data collected and the geographical area undertaken were unprecedented as compared to similar studies.”

The Study, a joint effort by Caltrans and Metro that began in April 2008, examined soil, rock, sand, and sub-surface conditions in areas where a bored tunnel might be bored to extend SR-710 from the northern terminus near the San Bernardino Freeway (I-10) to an undetermined point. The Study also documented the groundwater and seismic conditions within the five selected study zones. The Study was conducted in a route-neutral manner, meaning that all reasonable and practicable alternatives for completing the route were considered. Each city and community within the Study’s five zones was asked to appoint two representatives to participate on both the Steering Committee and the Technical Advisory Committees.

“Public involvement was an important component of the Study,” said Deborah Harris, Chief, Public Affairs and Media Relations for Caltrans District 7. “It allowed for dialogue between Caltrans and citizens on a one-to-one basis and it was important that the technical subject matter was presented in easy terms.”

The $1 million public outreach portion of the Study allowed for funding of 29 briefings to elected officials, 31 community meetings and presentations to community groups, neighborhood canvassing and staffing a full-time Study Information Office and a public domain website, among many other components. Information on the Study’s public outreach was translated in Spanish, Mandarin and Armenian. Many of the questions and comments from the public were related to traffic studies, air quality, cost comparisons, right of way mitigation and design alternatives. These elements are part of the next steps in the process -- an environmental impact report, or EIR.

“Today, extending the route continues to be a necessary step to complete the Los Angeles County freeway system,” said Mike Miles, District 7 Director. “Doing so will provide connectivity to several routes, a key component to relieving congestion in a heavily travelled corridor, improving mobility for all motorists, and enhancing safety.”

On April 22, the Metro Board of Directors delayed its discussion regarding the next steps until its May meeting.

The Final Geotechnical Report is available on the Caltrans District 7 website and on DVD at 22 public libraries within the five Study zones.
A 13-page Executive Summary based on the Study is available in English, Spanish and Mandarin on this website, along with the list of libraries.

This chart shows the five zones identified for the Study.  The final report concluded that from a geotechnical perspective, it is feasible to tunnel in all five zones, that each zone presents unique geotechnical conditions; that technology exists to address these conditions; and that tunneling has successfully been implemented in California and around the world.  A core sample of soil and rock pulled during the exploration program that included boring up to 500 feet. The final report has volumes of research, exploration data, charts, graphs and technical analysis on conditions found while drilling (boring) at depths of more than 250 feet.  It also documents a vigorous public outreach effort and collected public comments.   The geotechnical study’s exploration program also included non-invasive seismic reflection and surface wave testing on surface streets in some of the zones.