By Bill Lucia
Route Fifty
SEATTLE — Brake dust, remnants of auto exhaust, the zinc in vehicle tires. These are just a few of the substances commonly found in the toxin-laden residue on city streets.
“When it rains, all of that ends up in the waterways,” Shelly Basketfield, a program manager at Seattle Public Utilities, said during a recent interview at the agency’s headquarters. “It’s nasty stuff.” In a city known for abundant rainfall, and where the surrounding waters are home to species like salmon, orca whales and harbor seals, the road grime presents a problem.
In recent years, Seattle Public Utilities has turned to street sweeping as a solution, a partial one at least, to reduce the amount of street contaminants that mix with rainfall and flow into creeks, lakes, the Duwamish River, which is a Superfund site, and Puget Sound.
During this time, the utility has collected performance data that seems to show street sweeping can not only help keep pollutants out of stormwater, but also that it may be a more cost-effective way of doing so than building some types of infrastructure.
In about two-thirds of Seattle, the rainwater that hits city streets goes down storm drains and through pipes that feed directly into bodies of water. About 13 billion gallons of this discharged water is released in an average year, according to Seattle Public Utilities.
The other approximately one-third of the city is served by a system where stormwater and sewage flow through the same pipes to treatment plants. But during heavy rains, this system can overflow and dump into waterways. SPU says these overflows totalled 154 million gallons in 2012.
Next week, the Seattle City Council will begin considering financing for a 15-year, $600 million plan intended to keep the sewer overflows and polluted runoff in check. The plan calls for expanding the street-sweeping program to help achieve this goal.
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