Background
The I-5 Ship Canal Bridge Noise Study evaluates freeway traffic noise in neighborhoods surrounding the I-5 Ship Canal Bridge. Freeway noise from the Ship Canal Bridge reaches surrounding neighborhoods by reverberating or reflecting off the bridge decks, and directly from the car tires as they travel over the pavement.
As you might imagine, reducing multiple types of freeway noise is a unique challenge. WSDOT has been evaluating new and innovative noise-reducing elements to determine the best approach. We have identified three potential options for reducing noise in this area:
- For reverberant and/or reflective noise: Noise-absorptive materials on the ceiling above the I-5 express lanes.
- For direct noise: Street-level noise walls near the bridge approaches.
- To reduce noise at the source: Replacement or rehabilitation of the pavement.
Traffic noise is a major concern for many residents in our heavily traveled urban areas. Residents want solutions that reduce freeway traffic noise in their neighborhoods. WSDOT identified the I-5 Ship Canal area as one of the top ten priorities for reducing traffic noise in the state.
The project extends from E Roanoke Street, across the Ship Canal Bridge to approximately NE 45th Street. From east to west, the project limits extend from about 12th Ave NE to near Sunnyside Ave N.
The Eastlake, Roanoke Park, University District, and Wallingford neighborhoods will benefit from this project.
The project received $5 million in funding from the 2005 Transportation Partnership Account for the 2005-2007 and 2007-2009 bienniums to study noise reducing elements in the area and test ceiling panels (Phase 1). Phases 2 and 3 have been identified and will require additional funding and analysis.
WSDOT is considering:
- Structural capacity: The I-5 Ship Canal Bridge was strengthened in the late 1990s as part of a seismic retrofit project. This work enhanced the strength of both the concrete approaches and portions of the steel truss. Additional analysis would be required before installing any noise-reducing elements on the steel truss portion of the structure.
- Cost: Implementing multiple noise-reducing elements is expensive and could require significant structural work on the bridge structure itself.
- Maintenance and inspection: Any noise-reducing element installed on the Ship Canal Bridge must allow access for ongoing and emergency inspection and maintenance activities.
- Wildlife: WSDOT would likely incorporate netting or other bird deterrents into the design of any noise-reducing ceiling treatment implemented on the bridge.
Noise and How WSDOT Addresses Highway Noise
Existing noise levels in the neighborhoods surrounding the I-5 Ship Canal Bridge range from 66 – 87 decibels (dBA). At 66 dBA, most people find it difficult to have a conversation outside.
WSDOT considers two scenarios for reducing noise in neighborhoods:
- Scenario 1: WSDOT considers noise reduction projects in neighborhoods that will experience an increase in traffic noise after the completion of a state highway project, such as a road widening project. The cost of implementing noise-reducing elements is added to the scope and budget of the highway project to reduce the overall effect of increased traffic noise on the surrounding community.
- Scenario 2: Noise reduction projects are also considered for neighborhoods developed prior to May 14, 1976, when federal noise standards were issued, if the neighborhoods are adjacent to major freeways currently experiencing a high level (66 decibels or higher) of noise. Neighborhoods developed after this date were eligible for noise reduction projects when constructed (Scenario 1). The qualifying neighborhoods are prioritized statewide to receive traffic noise reduction as funding allows. The Ship Canal Bridge Noise Study is among the top ten highest priority projects on the list and was awarded funds as part of this statewide noise program.
Neighborhoods are ranked on a number of factors including:
- The cost of the proposed noise reducing element.
- The level of noise from the freeway reaching their homes.
- The amount of anticipated noise reduction for surrounding neighbors.
- The number of people that could benefit from a noise reduction project.
Only neighborhoods developed prior to May 14, 1976 can be considered for placement on the statewide noise reduction priority list. This is because federal guidelines provide noise relief for areas that existed before the policy was implemented. When I-5 was originally constructed, the increase in traffic noise was not addressed. Since the completion of I-5, new roadway improvement projects now include evaluation of noise reducing elements, so these areas are not considered for the noise reduction priority list.
Options for Reducing Noise from Ship Canal Bridge Traffic
What is a ceiling panel?
Ceiling treatments may include a variety of absorptive noise-reducing technologies, e.g., ceiling panels or blankets. These are lightweight materials that are used to absorb noise in a variety of environments, including classrooms and theaters. Since WSDOT has not used ceiling treatments before, we would likely install a test section on the ceiling of the lower deck (express lanes) of the I-5 Ship Canal Bridge. Lining the ceiling of the lower deck could significantly reduce noise for surrounding communities because vehicles traveling at higher speeds produce more noise, and the noise reverberates between the two decks of the Ship Canal Bridge.
A street-level noise wall is a reflective or absorptive barrier constructed of concrete, wood, earth or other material that is built between a neighborhood and a freeway to reduce traffic noise. WSDOT generally uses concrete due to physical and financial constraints. These barriers vary in height and appearance depending on the location of their installation. Noise walls near the Ship Canal Bridge would be constructed at street-level rather than on the bridge itself. This would reduce noise for the neighborhood directly adjacent to the bridge approaches.
Pavement rehabilitation could include a number of new and innovative methods for designing pavements to reduce noise at the source by making the pavement smoother and quieter. WSDOT is currently testing different types of pavement in Washington state, and may consider using an innovative pavement application to address noise on the Ship Canal Bridge. For more information about current pavement testing, please visit: www.wsdot.wa.gov/Projects/QuieterPavement.
Estimated noise reduction will vary depending on the proximity of residences to the I-5 Ship Canal Bridge. Residents closest to the locations of the noise-reducing treatment would experience the highest benefit. Neighbors further away could notice a reduction in noise even with just a 3 dBA reduction.
Freeway noise sometimes masks other noises in the neighborhood. Noise-reducing elements such as ceiling treatment, noise walls, and pavement rehabilitation, would be implemented to reduce freeway noise. Once these elements are implemented, other noises in your neighborhood that are not coming from the freeway could become more noticeable, such as noise from local street traffic.
Since some of the technologies proposed as part of this project are new and innovative for use on freeways, WSDOT will monitor noise levels after implementation of a noise-reducing element to test the noise reducing quality. WSDOT will also monitor the condition (wear and tear) of the treatment over time and evaluate its maintenance requirements and qualities.
WSDOT will work with the community to ensure the bridge’s aesthetic value and historical character are maintained. Please visit the Washington State Department of Archaeology and Historic Preservation Web site for more information.
Public Involvement
How is the public involved in this project?
In response to community input, WSDOT currently closes the I-5 express lanes on the Ship Canal Bridge from 11 p.m. to 5 a.m. on weekdays and 11 p.m. to 7 a.m. on weekends. This minimizes the amount of freeway noise the neighborhoods near the Ship Canal Bridge experience during the nighttime.
WSDOT will keep residents informed through mailings, e-mail updates, and community meetings. Please visit our project Web site for the most current information: www.wsdot.wa.gov/Projects/I5/ShipCanalBridge.
WSDOT would like the public to be involved in this project. Feedback from the community is critical during the design of this project to ensure all reasonable requests are included in the project plans. Residents will have the opportunity to provide input via e-mail, phone, and during community meetings.
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