Friday, May 11, 2007

What's That Noise? It's the Sound of Clean Water

If you've been surprised by loud vacuuming sounds during the past week, it's because the City of Tacoma crews are cleaning the storm drain systems in the downtown area. The process involves sending pressurized water through the storm drains to remove sediment buildup in the pipes, after which a vactor truck pumps out the water and sediment, redirecting the mixture through the wastewater system for treatment.

Admittedly, this effort to stop sometimes century-old contaminated sediment from leaching into the Thea Foss Waterway is loud and annoying, but it's also necessary--and quite temporary. In an effort to get through the cleaning as quickly as possible and make the resulting noise and blocked lane inconveniences as painless as possible, crews are working long days and weekends to get the work completed by the end of September.

The efforts have already proven effective, as crews have seen results in the form of eliminating several sources of mercury and lead contamination linked to likely decades-old sediment. This surface water system cleaning is mandated by the Washington State Department of Ecology as part of ongoing efforts to keep contaminants out of the recently cleaned up Thea Foss Waterway, part of the Commencement Bay Superfund site.

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