Tuesday, March 29, 2011

What is that down there?

This is a stormwater treatment vault ten feet down, under the parking lot at a Skagit County, Washington shopping center. The black cartridges are stormwater filters. Inside each cartridge is…leaves! They’re not just ordinary leaves – they’re leaves collected and composted by the city of Portland, Oregon. The stable leaf compost has been pelletized and heated, placed into these cartridges, and re-named “leaf media.” All the stormwater from the shopping center flows into this large underground vault, and through these cartridges, where sediments and other contaminants are removed, before the water is discharged into a stormwater piping system, and into a nearby waterway called Gages Slough.

What exactly is collected in the cartridges, and what happens to it? Whatever is on the surface of the parking lot ends up here. If the parking lot is spick and span (my dream come true) nothing will end up here. If our cars drip mud, oil, grease, bits of metal, copper shavings, and we throw out pop cans, cigarettes, and other litter into the parking lot, the cartridges will fill up with all of this, and they will require frequent cleaning. Then what? The solids in the cartridges get disposed of like street sweeping waste, according to the solid waste rules of the local jurisdiction. The cartridges get filled with new leaves and re-used. There are an estimated 60,000 of these cartridge systems installed throughout Washington and Oregon.

Thanks to City of Burlington for the photo, Contech Construction Products for building these vaults, and Enviro Northwest for servicing these systems. This is not an endorsement.

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