The City of Bellevue is the first jurisdiction to apply a local noise code to light rail operations and was faced with a challenge in how to apply its regulations to this particular operation. In addition to operational noise, construction noise needed to be addressed. View Mitigation Map (Jan. 2018)
Construction Noise
Bellevue’s Noise Control Code (Noise Code) regulates and establishes permissible noise levels based on the type of land use (e.g. residential, business or commercial). The code also sets daytime noise levels in residential areas at a maximum of 55 dBA (decibel level) and nighttime (between 10 p.m. and 7 a.m.) at a maximum of 45 decibels.Construction noise is allowed between 7 a.m. and 6 p.m., Monday through Friday and 9 a.m. to 6 p.m. on Saturday. Construction noise is prohibited beyond these hours, on Sunday, and on certain holidays, unless otherwise allowed by a city-approved permit. The Noise Code does contain exemption provisions.
For the East Link light rail project, the City has approved the following Expanded Exempt Work Hours Permits
- South Bellevue (Permit 15-124380 LY)
- East Channel Bridge to the south end of the South Bellevue light station. Work is anticipated to occur in 10 to 12-hour shifts (during 24-hour period) for a 39 months. Maximum noise level is 77 dBA
- North of the South Bellevue station to the “Wye” at 112th Avenue SE. Work is anticipated to occur from 7 a.m. to 10 p.m. on weekdays and from 7 a.m. to 9 p.m. on weekends for 34 months. Maximum noise level is 80 dBA.
- Note: A supplemental permit (17-114040 LY) was issued to allow for the installation of pre-cast tub girders for the light rail guideway to occur within the South Bellevue Station site. This permit covers the anticipated operations from January 2018 through January 2019.
- View Sound Transit graphic of Expanded Work Hours Permit by construction zones.
- Central Bellevue (Permit 17-102696)
- Long span aerial guideway over I-405 from NE 6th Street to 116th Ave NE. Work anticipated to occur in 10- to 12-hour shifts, varying in times with 24-hour days and up to 24 months. Maximum noise level is 78 dBA
- Across NE 8th Street along BNSF railroad. Work is anticipated to occur in 10- to 12-hour shifts varying in time within 24-hour day and for approximately one (1) month. Maximum noise level is 58 dBA.
- BelRed (Permit 16-145773 LY)
- Elevated guideway over Kelsey Creek. Construction in the area of 124th Ave NE to 130th Ave NE for 24 months. Work anticipated to occur in 10- to 12-hour shifts. Maximum noise level is 58 dBA.
- Tunnel (Permit 15-122917 LY)
- To complete downtown Bellevue tunnel on a continuous 24-hour cycle using sequential excavation method for 52 months.
Operational Noise
The East Link light rail facility is a permitted use under Bellevue’s land use code and its construction (including the guideway system and supporting infrastructure) is governed by the Design and Mitigation Permit (D&M Permit) process. A D&M permit has been issued for:
- Spring District/120th Street Station D&M Permit (issued Oct. 2016)
- South Bellevue E320 D&M Permit (issued Jan. 2016)
- BelRed E340 D&M Permit (issued April 2015)
Noise from the operation of light rail is expected from a number of components of the system:
- Light rail vehicle operation noise: The noise of a train travelling by a location including wheel/rail interface, train-mounted warning devices, and track cross overs.
- Stationary noise: The noise of the safety systems associated with the train including pedestrian-audible warning systems at stations, station public address systems, electrical transformers, and traction power substations.
The City’s Noise Code anticipates regulating noise from stationary noise generators but includes exemptions for safety features.
Because the City’s code does not take into account how to deal with ambient noise levels above the allowed threshold, and additionally is fashioned to deal with stationary noise sources, the City engaged a consultant to assist the City in determining how to apply the code to Sound Transit’s operational noise, and determine the appropriate mitigation. The City’s consultant primarily reviewed studies conducted by Sound Transit to ensure that industry best practices were followed in developing the noise models, interpreting the outcomes and fashioning mitigation.
These studies concluded the level of ambient nighttime noise in South Bellevue exceeds what the City’s code allows. Ambient noise is the level of typical existing noise from all sources. In the South Bellevue area ambient noise is due to everyday traffic noise from I-405, I-90 and 112th Avenue NE. The city’s consultant reviewed Sound Transit’s reports and proposed additional mitigation, such as extensions in length and height of sound walls, maintenance of rails and train vehicles, and nighttime reduction of any audible warnings (such as bells or announcement). This additional mitigation is designed to ensure that East Link’s operational noise does not increase the ambient noise levels in residential areas and is addressed in the E320 D&M Permit.
Additionally, the city is requiring monitoring of the light rail system to ensure operating sound levels are consistent with projections made through the environmental and permit review process. This monitoring ensures that these sounds do not become louder over time because of lack of maintenance.