Background
Through the I-5 Ship Canal Noise Study, WSDOT is studying and testing ways to reduce noise in the area near the I-5 Ship Canal Bridge. The study area is between E. Hamlin Street in the south, to approximately NE 43rd Street in the north. Existing noise levels in the neighborhoods surrounding the bridge range from 66 to 87 decibels. For reference, a train passing by at 50 feet away is approximately 70 decibels and a jackhammer at 50 feet is approximately 90 decibels.
What is the project timeline?
- 2004: Preliminary analysis of potential noise-reducing technologies in the I-5 Ship Canal Bridge area.
- 2005: Legislature allocated funding to study potential solutions.
- 2006 – 2007: Examined feasibility of noise-reducing technologies identified in 2004 and continued research and analysis.
- 2008: Convened panel of national acoustics experts to evaluate and recommend feasible solutions.
- 2009: Design a test section of a noise reduction technology on the bridge.
- 2010 – 2011: Advertise contract, procure materials, install and monitor the test section.
Why is the study needed?
Highway traffic noise can interfere with sleep, work and other daily activities during the day and night, and is a concern for many residents living along state highways. Traffic noise from the I-5 Ship Canal Bridge is a problem for residents and businesses near the bridge. Located in a heavily traveled urban area, traffic noise from the bridge reaches the densely populated Seattle neighborhoods of Eastlake, Roanoke Park, University District and Wallingford. Due to the large number of affected residents, high noise levels, and the close proximity of communities to the highway, we identified the area near the I-5 Ship Canal Bridge as a priority for reducing traffic noise.
How does traffic noise reach neighborhoods from the I-5 Ship Canal Bridge?
As shown in the graphic below, there are two ways traffic noise reaches neighborhoods. Noise can travel directly to the neighborhoods from vehicles moving across the bridge, and noise can also reflect and reverberate within the bridge structures before reaching the neighborhoods.
What technologies have been evaluated as part of the study?
Reducing noise from multiple sources is a unique challenge, and this is the first time the state has pursued noise reduction on a double-deck bridge structure. We have been evaluating new and innovative noise-reducing technologies to determine the best approach for this unique situation. In coordination with national acoustics experts, we identified these potential options for reducing noise in this area:
- To reduce reverberant and reflective noise: Install noise-absorptive materials on the ceiling above the I-5 express lanes.
- To reduce noise near the source: Modify existing bridge barriers to block and/or absorb noise.
- To reduce noise at the source: Replace or rehabilitate the pavement.
The acoustic experts also recommended pursuing a system of noise technologies in one section of the bridge to determine the effectiveness of implementing multiple solutions.
Which noise-reducing technology is WSDOT pursuing with the allocated funding?
Based on expert recommendations and available funding, we are moving forward to install a test section of noise-absorptive treatment on the outer edges of the ceiling above the I-5 express lanes on the south concrete approach. We plan to begin installation in 2010.
What is a ceiling treatment?
A ceiling treatment is a noise-reducing technology that is made of a lightweight material, such as a rigid panel or soft blanket. These materials are installed on ceilings to absorb noise in a variety of environments, including classrooms and theaters. Since ceiling treatments are not typically used for transportation facilities, we will install a test section on the ceiling above the lower deck of the I-5 Ship Canal Bridge and monitor it for at least one year to evaluate its effectiveness.
 |
Example of one type
of noise-absorptive
ceiling treatment,
provided by Sound Seal. |
How was the location of the test section identified?
The bridge consists of a steel truss section in the middle and concrete approaches on both the north and south sides. The results of our structural analysis show that we would need to modify the north approach and steel truss portions of the bridge in order to accommodate the ceiling treatment, while the south concrete approach would not require any modifications. For this reason, we are proceeding with a test section on a portion of the south concrete approach. The test section will be approximately 500 feet long and is proposed between E. Gwinn Place and E. Allison Street.
How will WSDOT determine if the noise-absorptive ceiling treatment is effective?
Installing a noise-absorptive ceiling treatment is a new and innovative method for state transportation agencies working to reduce highway traffic noise. We will monitor noise levels before and after installing the test section to measure the noise-reducing capabilities of the ceiling panels. We will also monitor the wear and tear of the treatment over time and evaluate its maintenance requirements and qualities. This monitoring will help us understand how the noise-absorptive material works and determine if it should be used in future projects.
Why not invest in noise walls on the bridge?
We have traditionally used noise walls to reduce highway traffic noise in nearby neighborhoods. However, the I-5 Ship Canal Bridge would require significant structural modifications to support the weight of new noise walls. Since structural upgrades to the bridge are not currently needed, we determined that it would be neither cost effective nor feasible to build noise walls on the bridge at this time.
What other noise reduction technologies could be pursued if more funding becomes available in the future?
Other technologies that could be pursued if additional funding were allocated for the study include:
- Installing a ceiling treatment on other portions of the bridge to address the reflected and reverberant noise from the bridge—this would be contingent on the results of the test section.
- Modifying the existing barriers on the bridge to add noise reduction capabilities to structures already in place.
- Constructing new noise walls at ground level in the area near the bridge approaches.
- Rehabilitating the pavement to reduce noise at the source by making the pavement smoother and quieter—this would be contingent on the results of the statewide study on quieter pavement that we are currently conducting.
These options were not pursued in the initial phase of the study because they would require additional funding and/or structural modifications to the bridge.
Other than this study, what else has WSDOT done to reduce noise in this area?
In response to community input, we currently close the I-5 express lanes on the bridge from 11 p.m. to 5 a.m. on weekdays and 11 p.m. to 7 a.m. on weekends. This reduces the amount of highway traffic noise residents near the bridge experience during the night. The Legislature allocated the funding for this study to help find additional solutions for neighbors living by this busy stretch of highway.
How can I provide input regarding this study?
Your opinions and participation in the study are important to us, and we welcome your involvement. Residents and other interested parties can provide input via e-mail, phone at 206-819-7230, and during community meetings. Sign up to receive updates.
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