The SR 710 Study is the culmination of a long history of efforts to address north-south mobility in the western San Gabriel Valley and east and northeast Los Angeles. The history of the planning efforts dates back to 1933 when Legislative Route 167, later renamed SR 7, was defined to run from San Pedro east to Long Beach and north to the vicinity of Monterey Park. The majority of this route has been constructed and incorporated into the Interstate Highway System as Interstate 710 (I-710). In 1959, the proposed northern limits of SR 7 were extended to the planned Foothill Freeway (now I-210). Over the years, planning efforts continued to address community and agency concerns, eventually leading to the issuance of a Record of Decision (ROD) in 1998 by the Federal Highway Administration (FHWA) for a surface freeway. After litigation initiated by some of the affected communities, FHWA rescinded the ROD in 2003, citing changes in project circumstances such as funding uncertainty and the opening of the Metro Gold line to Pasadena, and requiring a more thorough evaluation of the feasibility of a bored tunnel.
In 2006, Metro and Caltrans conducted two tunnel feasibility assessments, the Route 710 Tunnel Technical Feasibility Assessment Report and the SR-710 Tunnel Technical Study, to evaluate the feasibility of constructing a tunnel to complete the planned SR 710 freeway route that would lessen the potential impacts associated with a surface route. The studies found that a tunnel would be a viable solution and would warrant more detailed evaluation. In November 2008, Measure R (a half-cent sales tax dedicated to transportation projects in Los Angeles County) was approved by a two-thirds majority of County voters. Included in the Measure R plan is the commitment of $780 million to improve the connection between the SR 710 and I-210 freeways.
In March 2011, Caltrans published a Notice of Intent (NOI) under the National Environmental Policy Act (NEPA) and a Notice of Preparation (NOP) under the California Environmental Quality Act (CEQA) to initiate the environmental review process for the “Interstate 710 North Gap Closure” project. The environmental review process began with the “SR-710 Conversations” outreach effort, led by Metro, including 21 pre-scoping and scoping meetings throughout the study area in March and April of 2011. Metro also initiated the “State Route 710 Gap Closure Transit Profile Study” to gather transit service and patronage data and to assess current and future transit travel markets within the study area.