1. Sound Transit
Capitol Hill Station
Major Public Project Noise Variance
February 11, 2010
6:30 p.m. – 8:30 p.m.
SCCC

2. University Link
• 3.15-mile light rail extension
– Capitol Hill Station
– UW Station
• Schedule
– Construction: 6.5 years
– Open for Service: 2016
• Adds 70,000 daily riders,
114,000 system wide (2030)

3. Expanding light rail
• 16 miles and13 stations in service
• 36 additional miles funded

4. Capitol Hill Station
• Underground station with 3
entrances
• Staging area - station and
tunnel excavation at site
• Ridership: 14,000 daily
boardings
• Travel time:
– 3 minutes to downtown
Seattle (University St.)
– 3 minutes to UW Station

5. Capitol Hill Site Noise Variance
• Sound Transit has applied for variance from City of
Seattle
• Noise variance establishes noise limits for contractor
work between 10pm - 7am weekdays, 10pm - 9am
weekends, holidays
• Variance would allow up to 26 months of nighttime
activity
• Daytime construction activities will comply with City’s
construction noise limits.

6. Previous Outreach on Noise Variance
• June 17, 2009:
– Initial nighttime construction plans
and noise predictions
• October 8, 2009:
– Updated noise measurements
– Proposed mitigation measures
– Noise variance application and
process
– Added trucking restrictions on 10th
• Jan 14, 2010:
– Review of nighttime work
– Status update on variance
– Wall height on 10th Ave. increased

7. Why Work at Night?
• Continuous tunneling
has lower risk
• Certain activities are
required for tunnel
worker safety
• Maximizes project
safety, efficiency,
duration and cost

8. Construction Schedule
Nighttime
construction
activity

9. What Goes on at
Night?
Type of Equipment:
• Tunnel ventilation fans, pumps,
air compressors
• Generator
• Vehicles
– hauling and delivery trucks
– muck haul trucks
– front-end loaders, backhoe
– loaders, excavators
• No high impact equipment
(jackhammers, concrete saws,
etc.) will be allowed at night

10. Existing Nighttime Noise
Hourly nighttime average (midnight – 5 AM)
63 dba
54 dba
63 dba
53 dba
54 dba

11. Nighttime Noise Limits with Variance
6 dba increase from existing
69 dba
60 dba
69 dba
59 dba
60 dba

12. Noise Mitigation Requirements - Walls
• Surround the site on all
sides
• 8 to 24 feet high, plywood
construction
• Help contain noise, dust,
and debris
KEY
8’ wall
12’ wall
16’ wall
24’ wall

13. Noise Mitigation Requirements - Equipment
Stationary equipment (compressors, generators) enclosed in noise reducing material

14. Noise Mitigation Requirements - Trucking
• Nighttime truck operations
– No tonal back up alarms
– Engine idle limit of 5
minutes
– No compression brakes
– Muck haul bins lined with
noise dampening material
– Haul trucks prohibited on
10th Ave during night hours

15. Monitoring and Responding to Complaints
• Continuous sound monitoring stations
• 24 - hour construction hotline: 1-888-298-2395
• Independent response by City noise abatement
specialist
• City, ST and contractor will investigate, determine how
to prevent future incidents, and respond back to caller
• City review of variance after 1 year

16. Next Steps
• Comments from tonight’s meeting are recorded and
considered in the review of the application
• City will decide whether to approve the noise variance
within 60 days after public comment is received
• Contractor will prepare a detailed noise management
plan to comply with variance conditions
• Tunnel construction activities begin – late 2010