As a massive tunnel boring machine begins its path beneath Volunteer Park — and some of the most expensive residential real estate along Sound Transit’s light rail U-Link route — the Montlake resident who has surveyed, mapped, measured and documented the noise and vibrations that more than 60 households in the area say they feel and hear has a message for his neighbors up the Hill.
“If I were on the other side of Volunteer Park,” Montlake resident Jeff Parke told CHS, “I would say, ‘Wow there may be something about about the trains or tunnels that creates amplification.”
But, according to federal environment impact reports completed to win approval of the project, Capitol Hill’s real “Montlake Murmur” are of worry isn’t Volunteer Park. The only questions are will predictions of possible noise and vibrations on Broadway come true? And, will anybody notice?
In recent weeks, Parke has been a leading voice among neighbors who are complaining to Sound Transit about noise and vibrations in Montlake that many say are keeping them up at night and causing them stress as they worry about damage to their homes and a possible future where light rail tunnel noise is a permanent part of life around the Boyer Basin.
Sound Transit says the noise and vibration is a surprise. Kind of.
“We’ve been surprised by the impacts in the Boyer Basin and Shelby/Hamlin neighborhoods because we finished two one-mile tunnels under Beacon Hill with no noise or vibration issues and more recently wrapped up our first tunnel between Capitol Hill and downtown with no noise and vibration issues,” Sound Transit spokesperson Bruce Gray said. “All of that work has been in very similar soil conditions.”
Measurements from Interlaken from the Pacific Northwest Seismic Network
But Sound Transit is also telling residents of the area impacted by the noise and vibrations that, yeah, we said that might happen.
In email, Gray pointed CHS to the final 2006 Environmental Impact Statement for the project:
…the EIS finished in 2006 did note some potential for impacts from ground borne noise and vibration at a couple locations along U-Link, including the Boyer and Shelby/Hamlin areas, so this hasn’t been a complete surprise
An EIS is a detailed report on predicted impacts to the environment required of federally funded projects. Here is some of the language Sound Transit used in the approved report:
Finally, ground-borne vibration from construction activities can sometimes also produce ground-borne noise. Ground-borne noise is a rumbling sound caused by the vibration of room surfaces. The relationship between the level of ground-borne vibration and the noise it may produce depends on the frequency content of the vibration source, stiffness of the soil, and the acoustical properties of the receiving room. Typical human perception of ground-borne noise occurs at approximately 75 VdB, which equates to an interior noise level of approximately 40 dBA for average soil conditions. Construction activities in stiffer clayey soils or rock has the potential to produce noise levels of 45 dBA with vibration levels of 65 VdB. Ground-borne noise may be noticeable at times at locations where the tunnel depth is less than 100 feet; however, the actual level of ground-borne noise will depend on the frequency of vibration, geological strata between the vibration source and receiver, and acoustical conditions of the receiving structure.
The EIS also detailed where on the route (the full map is embedded below) engineers predicted the noise and vibrations could occur. Sounds like they nailed it in Montlake:
Construction for all Segment B route tunnels, vent shafts/TPSS, and stations would involve the vibration-causing factors and impacts described above. Locations in Segment B where tunnel vibration could be an issue because of tunnel depth include the University of Washington Station on Montlake Boulevard; residences along E Hamlin in the Montlake Neighborhood; within 300 feet north and south of Boyer Avenue; and near the Capitol Hill Station along Broadways Avenue between E Thomas Street and E Howell Street. Vibration is also likely to be noticeable near the cut-and-cover construction area along Eastlake Avenue.
In Montlake, some homes directly above the tunnel route in the problem area aren’t affected by the problems at all while homes nowhere near it have some of the worst vibrations.
So, are you ready for a little rattle and roll, Broadway? According to the EIS, the area around Volunteer Park probably doesn’t have much to worry about when it comes to the irritations the Boyer Basin is facing. But for homes, apartments and businesses along a short stretch of Broadway leading to the station, the Montlake Murmur may be coming for you once the first tunnel passes beneath and reaches the station construction area in coming months.
Despite the predictions, Sound Transit is scrambling to find a solution in Montlake. CHS reported on the noise and vibration issues from underground tunnel construction in November. In a notice mailed to the community last week, Sound Transit said some of its more significant noise mitigation efforts that have been delayed will finally be put into place:
The first delivery on our special order of rubber pads will arrive on Monday, 12/19. The contractor plans to stop TBM operations for two days and focus on the pad installation in order to get the mitigation complete as soon as possible. Work on the cross-passage will not interfere with the pad installation, so it will continue through the holidays as planned.
Once the pads are in place, ST’s vibration consultants will be conducting another round of vibration and noise monitoring to evaluate the effectiveness of the pads. The analysis takes some time and we do not expect to have a final report until the second or third week of January.
TBM supply trains continue to operate at reduced speeds. As with any operation that involves human beings, there is some margin of error in adherence to standards. We are working with our contractor and the locomotive operators to stress the importance of operating at reduced speed, and to improve consistency among the operators.
Some of you have been asking questions about the extent of sound transit’s program to monitor the noise and vibration levels in the neighborhoods originating from the tunnel mining operations by ST. I’d like to reassure you that we take the problem seriously, have collected sufficient data to help us understand the impact, and develop several means of reducing construction vibration.
ST’s vibration specialists, Wilson Ihrig & Associates, measured the vibration in both indoor and outdoor settings in both Shelby Hamlin and Boyer neighborhoods on different occasions and have compared their findings to independent seismic readings provided by Jeff Parke and USGS. The seismic data from Dr. Parke’s location is generally consistent with ST consultants’ measurements and is reviewed regularly by ST’s construction management team. Sound Transit is confident we have identified the source and magnitude of the problem.
Parke tells CHS that he believes Sound Transit should be given the benefit of the doubt and hopes the agency’s contractors are successful in stemming the problems with the supply train and tracks that officials believe are causing the issues. But he is also frustrated with the bureaucracy that seems to have a difficult quickly translating its public messages to changing the way its contractors execute the plan.
Parke said one example of this disconnect were the messages around a decision to slow the supply trains running in the under-construction tunnel in an effort to cut down the noise and vibrations. Parke said his measurements showed no such slow-down in the weeks following the Montlake community meeting. In fact, he said, his recordings showed that the trains actually went faster.
“I think they’re all nice human beings working in this bureaucratic [messed] up network,” Parke said of the situation.
The frustration has lead the analytic Parke to try to create an unemotional set of evidence to push Sound Transit to do more for him and his neighbors. In a survey he ran to collect feedback from residents in the area, more than 60 respondents reporting hearing or feeling vibrations “from the ground below” on their property:
Of 82 validated survey participants, 77% hear or feel vibrations coming from the ground below them. Of those, 94% are certain these subterranean vibrations emanate from the Sound Transit construction trains traveling back and forth 90 feet or more below their homes or businesses.
Here are some breakout answer from where the problem seems to be focused in the Boyer Basin:
What are they hearing and feeling? Here are a few verbatims:
Regardless of how much noise and shaking is going on in Montlake, the survey shows a perception problem in the neighborhood. If this week’s work to reduce the complaints doesn’t cure it, however, it’s unlikely Sound Transit will do more than look into other possible solutions. Construction noise, after all, is part of the plan. Here’s another passage from the Environmental Impact Statement for the project:
Construction noise and vibration may affect residences, University of Washington research facilities, andother uses of property along the corridor, particularly in station areas. No exceedance of any state or local noise control ordinance is projected at any of the staging areas or construction sites as long as mitigation suchas noise walls and/or other measures are implemented.
While we haven’t heard from the state yet, the City of Seattle’s DPD says it has received complaints but won’t be acting on them. “We have conveyed that the noise generated by the underground trains on the tracks is not addressed under Seattle noise regulations,” a representative told CHS in November.
For some in the city, the situation falls into a long line of Montlake community complaining — from the original 520 bridge to today’s light rail tunneling. Parke said maybe it’s true. “I live here because I love this neighborhood,” he said. “Maybe we are a little more persnickety.”
“This is ruining the lives of people at the surface,” Parke said. “There has to be a better solution.”