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Department of Public Works

  • Sound Wall Project on I-210

    What are sound walls?

    Simply put, sound walls are noise barriers constructed of a solid material. They are normally built between freeway and residential property to reduce traffic noise.

    Who is responsible for building and maintaining sound walls?
    Traditionally, Caltrans has been the agency responsible for both construction and maintenance of sound wall projects in California. Due to the increasing backlog of projects, legislation has been passed to transfer the responsibility of building retrofit sound walls to the local transportation agency. In Los Angeles County, MTA has inherited a long list of sound wall projects that need to be completed, totaling nearly $1 billion. Sound walls areas still required to be built and approved using Caltrans specifications and will be maintained by Caltrans.

    When are sound walls considered for a community?
    Sound walls are considered under the following circumstances:

    • Type 1 – As part of new highway construction or major reconstruction
    • Retrofit – Along existing freeways when noise levels exceed 67 decibels
    • Private Sound Walls – Developers of property located adjacent to an existing freeway are responsible for mitigation of sound using privately funded sound walls.

    What are the criteria for approving a sound wall?
    The noise impact evaluation criteria for this project are in agreement with the Metro Soundwalls Implementation Policy. The Metro Soundwalls Program follows State of California Soundwall program guidelines contained in the Streets and Highways Code Sections 215.5 and 215.6. Sound walls are only warranted in a community if they are able to meet the following criteria:

    • Residential property developed prior to construction of the freeway or prior to implementation of a freeway capacity-enhancing project
    • Hourly noise levels at the location exceed the 67 decibel threshold
    • Proposed sound wall results in a minimum 5 decibel noise reduction
    • Cost Versus Benefit Requirement (The project cost may not exceed $77,000 per residential unit).

    How is the Cost Versus Benefit Requirement calculated?
    The cost effectiveness of noise abatement is determined by the number of living units immediately adjacent to the freeway, built before the construction of the freeway, which will benefit by a 5 dB or more noise reduction. According to Metro Soundwall Implementation Policy, projects costing no more than $77,000 per benefited (receive a minimum 5 dB noise reduction) residential unit are considered cost effective. All living units adjacent to the freeway which receive a 5 dB or greater noise reduction are counted and multiplied by $77,000 to determine the cost effectiveness of each barrier. If the construction cost of the sound wall exceeds the Cost Versus Benefit Requirement total, then the sound wall does not meet Metro’s criteria and cannot be constructed.

    How does sound travel?
    Sound waves are able to bend around objects and transmit through solid materials. Therefore, it is impossible to completely eliminate the noise generated by freeway traffic. In addition, even when traffic volumes are the same, there are many other factors that affect noise levels including: changes in terrain, curves in the freeway and changes in elevation between above and below ground.

    How does a sound wall work?
    Sound walls reduce the level of freeway noise that enters a community by either absorbing the sound, reflecting it back across the highway, or forcing it to take a longer path over and around the barrier. To protect a community, a sound wall must be tall enough and long enough to block the view of a highway.

    How will MTA deliver the Post-1989 Retrofit Sound Wall Projects?
    On January 27, 2000, MTA’s Board adopted the Los Angeles County Sound Wall Implementation Policy. Given the substantial cost to implement these retrofit sound walls, this policy document incorporated a phase-in strategy to ensure a fair and rational implementation process. Towards that end, existing state criteria were augmented to include dividing the projects into two phases:

    Phase I – Includes those projects on freeway segments where High Occupancy Vehicle (HOV) or carpool lanes were built without warranted sound walls
    Phase II – Contains qualified sound wall segments on freeways without carpool lanes.

    What funding is currently available for the sound wall project along the I-210 freeway?
    Currently, Metro has no funds to build the sound walls along the study corridor. However, the City has obtained funding via a federal grant (SAFETEA-LU) in the amount of $540,000 with a local match of $135,000 for the preliminary engineering of soundwalls. An additional $900,000 in federal funding has been committed for construction of this project, with a local match of $225,000.

    What is the status of sound walls along the I-210 freeway in the City of Pasadena?
    The City of Pasadena recently completed a sound study to identify potential locations for new or replacement sound walls along the segment of the I-210 between Arroyo and Orange Grove. The study was conducted to identify areas where existing traffic noise levels are 67 decibels (dBA) or higher, and locations for the potential construction of sound walls to abate noise generated by traffic along I- 210. The 67dBA level is equivalent to standing next to a busy street intersection.

    The City of Pasadena held a public information meeting on Thursday, November 18, 2010, at the Rose Bowl, to present the results of the noise study to local residents. Eleven sound walls in six systems were identified as meeting the Metro’s criteria of a 67 dBA threshold and providing a 5 dBA noise reduction (shown in Column 5 of the project matrix). Once Metro’s Cost Versus Benefit Requirement is factored in, only five sound walls in three systems were eligible (shown in Column 6 of the project matrix). However, only one 10’ wall, approximately 700’ long, along the east side of Pasadena Avenue north of Orange Grove Boulevard, meets all of Metro’s criteria and is within the project’s construction budget of $1,125,000. Please see the attached displays for graphical depictions of the project area and potential sound walls.

    What are the next steps in sound wall construction in the study corridor?
    The Department of Public Works will recommend that the City Council approve the construction of the Pasadena Avenue sound wall. Design will begin shortly thereafter and the wall is tentatively scheduled to begin construction in late 2011.

    If you would like further information about the sound wall project, please contact:

    Dan Rix, City Engineer
    (626) 744-4267 (Office)
    (626) 744-3823 (Fax)
    drix@cityofpasadena.net

    Sean Singletary, Project Manager
    (626) 744-4273 (Office)
    (626) 744-3823 (Fax)
    ssingletary@cityofpasadena.net

    Sound Wall Related Files