Trading gray cities for green

As any Northwestern knows from experience, a good rain has a cleansing effect.

But that cleansing results in impacts downstream, literally.

Every acre of land in our cities covered by impervious surfaces — roads, parking lots, sidewalks and roofs — catches and channels about a million gallons of runoff each year into the rivers, lakes and marine waters of Western Washington, while only 3,000 gallons reaches the ground to replenish groundwater, according to a new report by The Nature Conservancy, “Outside Our Doors.” Carried away with that runoff is a toxic mix of pollutants that includes the oil and gas that leak from vehicles, zinc and lead from roofing materials, hydrocarbons from vehicle exhaust and copper from brake pads.

Three-quarters of the toxic chemicals that reach Snohomish County’s Possession Sound, Puget Sound and other marine waters, are carried there by stormwater runoff.

Easier this week, a summit organized by The Nature Conservancy and other partners, brought together more than 200 representatives from nonprofits, government agencies, business and universities to discuss ways to advance “green infrastructure” that slows the path of water, collecting and filtering pollutants.

During the next 25 years, the region is expected to add as many as 2 million residents. As Snohomish County and the rest of the region grow we have the opportunity to begin replacing our “gray infrastructure” with improvements that integrate our cities and neighborhoods into natural solutions that along with treating runoff, offer the benefits of a cleaner air, a reduction in traffic noise, parklike settings, improved health for residents and the creation and support of “green-collar” jobs.

And the things that add liveability to our neighborhoods, also make them more valuable. Something as simple as the presence of trees on a residential property can add as much as $9,000 to a home’s value, according to a recent study by the U.S. Forest Service.

Some of these solutions already have a foothold in the region, including residential rain gardens and roof gardens, swales, street tree programs, tree canopy ordinances and building materials, such as porous concrete, that allow rainwater to seep into the ground beneath rather than flow directly into stormwater channels.

Rain gardens, which can collect rainwater from roofs, driveways, patios and sidewalks, are an affordable method for treating runoff and have been shown to help solve problems with wet or flooded basements. The Snohomish County Conservation District offers advice on installing rain gardens, and the City of Everett has a program that offers residents up to a $2,500 rebate.

The intent of the summit, said Jessie Israel with The Nature Conservancy and Aaron Clark with Stewardship Partners, is to look beyond government regulations that support these efforts. The summit seeks to forge partnerships with businesses, including builders and the region’s major employers, to look for opportunities to use green infrastructure concepts. While government regulations have their place, voluntary measures by builders and others can be quicker to implement, especially when cost and other benefits can be demonstrated.

Cleaning the rainwater that flows into our rivers and lakes, sounds and bays and improving the habitat for herring to salmon to orca is reason enough to shift the balance of our city landscapes from gray to green. But doing so provides added benefits in more liveable cities and neighborhoods.