Last January, someone jet skied on Iowa Street beneath the I-5 Freeway overpass. "Lake Iowa," as it was nicknamed by members of the Public Works Department, was created by a combination of heavy rains and a paved-over floodplain, and was stewing with oil, gas, grease and other pollutants.
Stormwater is the main source of water pollution in Western Washington, but businesses and homeowners can incorporate technologies like porous concrete and rain gardens to filter out pollutants.
"The point is to allow the earth to behave as it did before it was developed," said Katie Skipper, communications director of the Department of Ecology.
Most precipitation falls onto trees and evaporates back into the atmosphere. The rain that reaches the ground is absorbed by vegetation or becomes groundwater, helping to refill underground aquifers. But when roads, roofs and driveways replace forest, all of the water that would evaporate or be absorbed flows straight into a lake or bay, picking up pollutants along the way.
One inch of rain on a one-acre parking lot could fill 450 bathtubs. All of that water washes 150,000 pounds of untreated toxic chemicals into Puget Sound every day, according to Puget Sound Partnership, a state-founded organization. Industrial or sewage treatment plant discharges, pesticides, herbicides, vehicle exhaust and fluid leaks are among the sources of toxic chemicals.
In an effort to curb stormwater runoff and pollution, the city of Bellingham is requiring business and homeowners to maintain a certain percentage of permeable surfaces during development. Brothers Bob and Rick Wilson were required to make half of their new Toyota dealership permeable. They paved porous asphalt on the sales lot and porous concrete, which is more durable because it’s reinforced with epoxy, on the well-traveled areas.
The dealership is the largest application of porous pavement in all of Whatcom and Skagit Counties, Rick Wilson said. But unless it rains, it’s hard to tell.
Low Impact Development is often invisible. A closer inspection of a normal-looking parking lot reveals what looks like a mass of packaging peanuts. Bob Wilson said laying the porous concrete and asphalt was like spreading Styrofoam.
"It was a tremendous project to lay, not at all like laying normal cement," he said. "If it gets compacted at all, it’s ruined."
The lot had to be paved in sections, and took three weeks to dry.
Beneath the concrete’s surface lies a four-foot layer of gravel and sand. Bacteria live in this layer, separating and breaking down pollutants from stormwater. The gradual slope of the lot sends water slowly trickling into Whatcom Creek.
Porous pavement can be expensive, said Freeman "Fritz" Anthony, an engineer for the city of Bellingham. Anthony helped design a half-mile stretch of porous bike lanes and sidewalks along Northshore Drive, a heavily-traveled road that hugs the north shore of Lake Whatcom. Porous concrete costs $65 per square yard versus $15 per square yard of traditional asphalt. Time-consuming application and a 3 to 4 foot layer of sand and gravel beneath it contribute to higher costs, Anthony said.
However, a cost analysis by the U.S. Environmental Protection Agency found that installing rain gardens costs 15 to 80 percent less than curbs, gutters and piping.
Rain gardens are either found in naturally low-lying areas or are dug as pits to capture runoff from roofs and driveways before it gets into drains or streams. They contain mulch and a variety of native shrubs, herbs, grasses and small trees. Water is absorbed by the plants or seeps down to replenish groundwater. Because native plants are used, rain gardens don’t require any extra watering in the summer.
Rain gardens have been popular not only with business owners, but also with homeowners interested in what they can do to reduce stormwater runoff, said Colleen Mitchell, a project engineer for 2020 Engineering.
This sustainable civil engineering firm in Bellingham has seen an influx of rain gardens, which are an attractive landscape feature that people may spend money on anyway, Mitchell said.
The city of Bellingham is doing what it can to incorporate these technologies with the $4 million it pulls in each year from the stormwater utility fee that’s tacked onto people’s water bills. The Lake Whatcom watershed is a priority with projects similar to the Northshore Drive installation of porous bike lanes and sidewalks, said Bill Reilly, stormwater manager for the city. Eventually the projects will expand out, but this will take years, he said.
Although the city’s priorities lie in the watershed, there have been projects popping up all over. The new Bellingham Art and Children’s Museum opening this spring will include a porous concrete courtyard and alley, rain gardens and a 3,000 square-foot planted roof. These installations are expected to reduce runoff by 64 percent. City Hall has a rain garden in the parking lot. Matthei Place, a recent development of low- to moderate-income housing in Fairhaven, included rain gardens and a porous concrete parking lot.
The cost of stormwater runoff in the Puget Sound region over the next decade will total $1 billion, according to a 2006 study by the University of Washington. The study included degraded water quality, landslides, flooding, shellfish harvest closures, habitat losses and repairs.
It’s not only revenue that will be lost through inaction. Currently there are 40 species in Puget Sound, including orcas, otters, steelhead and salmon that are listed as threatened, at risk or endangered, according to Puget Sound Partnership.
Water will always follow the path of least resistance, but people don’t have to. By making roads and driveways of porous pavement and channeling runoff to enter rain gardens, we are giving the earth the opportunity to function as it once did.
Tuli Alexander studies environmental journalism. She has been published in The Western Front and Pasadena City College’s Inscape Magazine.