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Program Description

With the passage of SB-45, the California Street and Highway Code was amended to transfer the programming and funding responsibilities of the Post 1989 Soundwall Retrofit Program to Regional Transportation Planning Agencies. In Los Angeles County, Metro assumed this responsibility. The eligibility determination as well as design and construction responsibilities for the program remained with Caltrans. Metro inherited a backlog of soundwall projects totaling nearly $1 billion without any corresponding funding from the state.

In January 2000, Metro Board adopted the Soundwall Implementation Policy ; this policy contains a process for prioritizing, funding and constructing the Post 1989 Soundwall Retrofit Program. The soundwalls will be prioritized and delivered in two phases:

  1. Phase I will contain all soundwall projects along freeway segments where HOV lanes were constructed without soundwalls.
  2. Phase II will contain all other soundwalls including soundwalls identified prior to the adoption of this policy.


Metro is currently seeking funds for implementation of remaining soundwalls in Phase 1 and 2. The order of priority of implementation of soundwalls will be Phase 1: Priority 2, Packages 12 to 14; Phase 1: Priority 3: and ultimately Phase 2 soundwalls.

The design and construction cost of soundwalls are estimated at $10 million per mile on the freeway shoulder and $20 million per mile if placed on a structure (2017 estimates). Currently, over $2 billion is needed to design and construct the soundwalls on the existing Post 1989 Soundwall Retrofit List.

There is a possibility that the soundwalls currently on the Post 1989 Soundwall Retrofit List may be constructed out of order as new highway improvement projects are developed (i.e. corridor highway projects, ExpressLanes) as such eligible soundwalls within the limits of those projects will be included in those projects.

Soundwall Criteria

In order for a wall to be considered for funding, it must first pass preliminary field tests. The criteria for the test is summarized below:

  • The location is along residential property, parks, churches or other sensitive receptors that exist prior to the construction of a highway or proposed improvements of a highway.
  • The hourly noise levels at the location exceeds a 67-decibel threshold.
  • The soundwall will result in a minimum five-decibel noise reduction.
  • The soundwall cost is below "reasonable allowance" as calculated using established Caltrans criteria, which is currently $107,000 per benefitted dwelling.

Once a project is deemed eligible and becomes funded, then it goes through the preliminary engineering stage which includes: Noise Barrier Scope Summary Reports (NBSSR) including a Noise Study Report, environmental studies and Right of Way Assessments. Following approval of the preliminary engineering phase, the project then advances through final design and construction.