As described in my previous blog and numerous media accounts, a noxious odor reminiscent of either a bathroom or pulp mill hit Seattle, Bainbridge Island, and parts of the Kitsap Peninsula on Wednesday morning.
The coverage of this unfortunate phenomenon has gone national including the NY Post and the Charlotte North Carolina NBC affiliate who suggested that BOTH our city and the Seahawk's game play stank. They will regret saying that.
But this mysterious odoriferous phenomenon is back and has expanded its range. Today, many residents of Bainbridge Island were greeted by the now familiar stench. Biking home this evening I was hit by it in north Seattle. And most importantly, large number of Victoria residents were disturbed by the sulfurous smell, as did some residents of Lopez Island.
A major contributor to the regional smell problem has been very light winds and an extraordinarily strong and very low level inversion, which caps pollutants near the surface. Here are plots of temperature with height in Seattle on Wednesday morning and this morning (Friday). Very strong inversion and a very shallow layer of cold, polluted air near the surface. Unusual persistence of an extraordinarily shallow air layer capped by an inversion.
There has been an animated debate of where the smell is coming from. One idea was that the heavy rains resulted in soggy fields with decaying organic matter, leading to the smells. But a careful examination of the location of the smell reports indicated few on the eastside (e.g,, Redmond, Duvall, etc.) where it should have been worst. Cross that out.
Another idea was that low tide exposed smelly tide flats. This is attractive, since many of the locations getting hit are in the vicinity of water. However, the tides have not been unusually low, nor has low tide extended over a particularly long period. Perhaps a contributor, but it doesn't explain the extended length of the smell.
Another suggestion was that we were smelling the effluent from the Tacoma or Port Townsend pulp mills. Perhaps a contributor, but it unlikely that two point sources could have could have produced the smell over such an extended area.
Perhaps the most outrageous suggestion, made by a reporter from a Tacoma newspaper was that Big Bertha, the broken tunnel boring machine under Seattle, hit a huge pocket of decaying matter, and that the smell ascended from the chamber being drilled to replace the broken sections of Bertha. This Tacoma reporter noted that the access hole to Bertha looks like a giant toilet (see image, it does).
My conclusion, and one supported by my friends at the Puget Sound Clean Air Agency, is that there is no one cause. The very strong inversion, shallow cold air layer, and weak winds were ideal for maintaining pollutants near the ground. There are many sources of bathroom and and sulfurous smells that all contribute: gases released from drains and waste pipes, exposed tide flats, rotting garbage (and Seattle's new composting law ensures there is plenty of that), industrial waste and pulp mills, and many more. I often get major smell from the nearby Mathews Beach sewer pump station and it spread over thousands of feet. Reports and my experience suggests the smell is intermittent and localized, suggesting local sources.
In some ways, the low inversion was like an odor microscope, making apparent smells that normally are diffused deep in the atmosphere.
In some ways, the low inversion was like an odor microscope, making apparent smells that normally are diffused deep in the atmosphere.
Panther fans can tease us about the smells, but tomorrow a weak front will clean the air, the inversion will lift, and Seahawks will rise ascendant.
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