Wednesday, October 21, 2015

Giving runoff pollution a…swirly?

By Caitlin Morris
Orange cat: Pollution
Brown cat: WSDOT

Caring for the environment is about to take a page from the old high school prank book. On Friday, Oct. 23, crews will begin installing a new storm water drainage system along northbound I-405 in Bothell that literally swirls debris and pollutants away from water headed to the Sammamish River. Contrary to pranking lore, this time the bully (runoff pollution) is head-first in swirling water.

Here's how it works. Storm water and water runoff is channeled toward an underground vault. First the water full of litter, oil and sediment enters a swirl chamber—not a medieval torture device or a bully's name for a bathroom stall—but rather, a large container that gently swirls the polluted water. With the help of the swirling movement and gravity, highway grit sinks to the bottom of the chamber and the floating pollutants (think leaves and trash) rise to the top.

The water is then channeled through a layered labyrinth-like system of walls that first block the heavy debris below, allowing the water to flow upward to another chamber. The water is then directed below, blocking the floating debris above. A little confusing? See the diagram below. The company that produces the 19' by 13' vault also made an animated video that demonstrates the water filtration process.

The Vortechs® vault uses a swirling chamber to efficiently clean storm water.

Closure today; swirly tomorrow
In order to install the new drainage vault, we need to close the new braided ramps that lead to SR 522 (in both directions) coming from northbound I-405 and NE 160th Street in Bothell. The ramps will close at 9 p.m. Friday, Oct. 23 and will be open to traffic at noon on Sunday, Oct. 25. So plan ahead if you're headed to the Pygmy Goat Show at the Evergreen State Fairgrounds, Woodinville for a winetasting or the Haunted Trails in Kenmore. A detour will be in place, but anticipate waiting a little longer to get to your destination.

Even though the Vortechs® vault will be completely underground, when you cruise to northbound I-405 or SR 522 on the Bothell Braids on a rainy day, you can rest assured that we and the vault are protecting the Sammamish River one swirly at a time.


Unknown said...

How often will it need to be maintained?

WSDOT said...

Thanks for the question! The required time in between maintenance is a year. Since it's a new system, in the next few months we'll be monitoring the vault closely to see if we need to clear it out more frequently.

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