On Wednesday night, about 40 members of the community showed up at the John Stanford School to meet with State Senator Jamie Pedersen, State Speaker Frank Chopp, and representatives of WSDOT about the possibility of erecting a wall alongside I-5 to mitigate highway noise in Wallingford, similar to the one in place north of 52nd along 5th Ave NE.
This past summer, WSDOT ran a study to evaluate the feasibility and reasonability of the project. “Feasible”, in this case, means specifically that the “noise wall has to reduce noise levels by at least 5 dBA for at least 51% of the first row homes and it must be constructible.” “Reasonable” means that the wall must be “cost effective and desired by the community”. “Cost effective” means something arcane and far more difficult to understand than you would think.
As part of the study, sound sensors were placed in a number of yards on the two streets closest to I-5 (see the red dots in the image at right). Readings from these sensors were then combined with simultaneously collected traffic data from I-5 to build a model of how traffic generates noise. This model, once validated, was then used to extrapolate what traffic would be like in the 2020’s, to determine whether there was a legitimate (legal) problem.
The conclusion: yes, indeed, most houses along that strip will experience noise levels in excess of the 66 dBA FHA threshold for acceptability. Further, constructing the wall running along I-5 down 5th Ave NE from 45th Street to just south of 42nd Street would reduce noise levels for houses within that narrow strip by 5 – 10 dB. So, it’s “feasible”. The wall would terminate on the south end where the grade drops off and the bridge deck rises, at which point more wall becomes unfeasible.
Construction of the wall (which would come in three segments, see red and green shaded area in the second map) would ring in at about $11,000,000 (and likely wouldn’t happen until 2020 or so.) This isn’t in any budget, but Pedersen and Chopp were there to ask the residents whether they should go to bat to find a way to get it funded as part of upcoming transportation bills.
It’s worth noting, before those of you further away get your hopes up, that sound walls have a very short range impact: we were told that only houses within 200 – 300 ft of the wall itself would see…errrr…hear much of a difference. That amounts to about 23 houses in WSDOT’s model. In other words, that would be about $500,000 spend per house to reduce their noise.
Seems pricey to me. Pedersen’s response, when I asked about this, was that a) our tax dollars are being spent on other people’s noise walls elsewhere and b) we’re carrying the burden of the I-5, something that everyone else benefits from.
Still seems like a lot of money for a little benefit.
That said, there’s a genuine problem for folks close to the highway (and not so close to the highway, while we’re talking about it), and it would be lovely if that could be addressed.
In the past, WSDOT has experimented with other solutions: sound baffles hung from the ceiling of the express lanes on the bridge, for one. This was promising, because the bridge is the “dominant noise source in the neighborhood,” because of how the noise is reflected off the roof. Dampening it should help. But, that was attempted a few years back and didn’t have a significant impact.
Another strategy that’s been tried is “quiet pavement”. Most of the noise we hear isn’t from car engines, it’s from the tire – pavement interface (so no, the rise of electric and hybrids won’t help). A special pavement, full of voids to absorb sound, was tested in various spots around the region (520 in Bellevue, I-5 Lynnwood, 405). I’ve driven on it: it really is remarkably quiet. But, unfortunately, it doesn’t last: with our weather conditions, it needs to be resurfaced after only three years or so, as opposed to typical pavement that lasts 15 years.
Some have called for restricting the hours that the express lane is open (presently, it stays open until 11 pm at night). This got pushback from the city, which notes that, especially when there are Mariners games and the like, the lanes are necessary in the evenings to keep traffic flowing quickly across the bridge.
Finally, one gentleman with a couple buildings in the affected areas, says he’s had remarkable success by installing triple-paned windows. Not only are they energy efficient, but they have a huge impact on inside noise (“nirvana” was how he described it). Perhaps money could be offered to impacted residents to subsidize the installation of triple-paned windows. Not only would it cost less then $500,000 per house, the reduction in dB would larger and mitigation could be offered to houses further than the 200 – 300 ft that the sound wall would impact.
Of course, as my neighbor Lesli noted, nobody wants to be locked inside their house, sealed off from our wonderful yards and gardens, just to escape the roaring din. And, it’s not clear that transportation dollars could be legally allocated in that way. There was some back-and-forth between the officials at the meeting on this, but consensus seemed to be that Federal dollars couldn’t be used in this way, at least.
So, what’s going to happen? Pedersen and Chopp want to gather feedback from the neighborhood (and specifically from the people that would be impacted) to find out whether the wall (or the subsidy alternative) is something that people would be interested in and that they would like their representatives (Pedersen and Chopp) to pursue funding for it. They recruited three folks from the neighborhood to work with them on building a survey to be sent out, and that should happen in the next month or so.
To be continued.
As a side note, I chatted with Mike Ruby a bit about the health impact of living near the highway. As someone who is raising a child just a block and a half away, I’ve always been worried about studies showing negative health impacts of living near major roadways. According to Mike, though, the Pacific Northwest has less of a reason to be concerned about this than other areas: the major source of harm is from particulates kicked up by tires, rather than spat out by engines, and our frequent rain keeps those particles down and washes them away. Dry areas of the country like California have more reason for concern, in this view.