Natural drainage_Flickr_kuow949In response to the sluggish economy, Seattle Public Utilities is paring down its budgets and programs, and has identified three stormwater-related projects that could be eliminated: the “Swale on Yale,” protections for Venema Creek, and an expanded street sweeping program. While these projects require some expenditure now, they represent opportunities and investments that can pay dividends in the near future.

All three projects promise to make the city cleaner and more livable. The two capital improvements would create engineering, construction, and landscape jobs. They would also help Seattle comply with numerous regulatory obligations, from the federal Clean Water Act to salmon recovery projects required by the Endangered Species Act. And they would better prepare Seattle for climate changes that are expected to include an increase in heavy rainstorms.

Times are undeniably tough economically, but Seattle should not forget the importance of investing in stormwater projects that will benefit the city over the coming years and decades.

All three projects include the construction of natural drainage systems, also called low-impact development (LID). The idea behind LID is to replace conventional “gray” drainage infrastructure of downspouts, ditches, and gutters that speeds polluted rainwater to our streams and lakes with a “green” system that helps runoff evaporate or soak into the earth, filtering and cleaning the water.

Local and national studies have concluded that LID is the smart investment financially, most often costing less upfront than traditional stormwater systems, and also providing better environmental protection, increased property values, and benefits to human health.

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  • Green drainage systems will increasingly be required under state and federal rules. The state Department of Ecology recently released a draft of proposed stormwater rules that require the more widespread use of a suite of LID technologies including swales, rain gardens, and green roofs. The US Environmental Protection Agency is updating national stormwater treatment rules and will likely put an emphasis on LID as well. And the city is already working on plans to spend $500 million to satisfy EPA requirements to address combined-sewer overflows (CSOs), a problem caused by poor conventional stormwater infrastructure that sends raw sewage spewing into local waterways.

    The natural drainage projects from Seattle Public Utilities that are at risk of being eliminated offer a cost-effective alternative to some of the expensive, gray methods of dealing with stormwater and CSO problem—and they could help put the city out in front of the coming state and federal regulations.

    Lake Union_Flickr_kenkilfedder1. The Swale on Yale

    The Swale on Yale proposes to construct swales stretching four blocks long and 10 feet wide that would treat 188 million gallons of dirty rainwater each year. Swales are essentially broad, shallow, planted ditches that help clean and absorb stormwater runoff. Polluted runoff currently flows straight off the streets, parking lots, and rooftops on the west side of Capitol Hill into Lake Union. The stormwater carries with it oil and grease, sediment, pesticides, heavy metals, and other toxic pollutants into potential habitat for juvenile Chinook salmon and other salmonids.

    The swales proposed here, sited along Yale and Pontius avenues in the South Lake Union neighborhood, would not require expensive retrofits of developed roadways and landscapes. Instead, they would take advantage of a planned redevelopment in which a private partnership would help defray the costs to the city.

    The swales would be built while the area is being torn up for construction by Vulcan, Inc., which is replacing one-storey warehouses with multi-storey mixed-use buildings. The natural drainage techniques proposed for the Swale on Yale use well-understood technology, but represent a unique, large-scale application of swales in an ultra-urban setting. The project would cost $2.8 million in the coming biennium, and $8.8 million total, with $1 million potentially coming from a state Department of Ecology grant. City Investors, a Vulcan affiliate, would spend an additional $1.2 million on the project, and would also help with some of the maintenance.

    2. Venema Creek

    The second project under threat of elimination is the construction of natural drainages in the watershed that feeds Venema Creek in northwest Seattle. Swales built along the downhill side of 10 residential blocks would capture stormwater draining from 85 acres in the Broadview neighborhood.

    Currently, the rainwater gushes from roofs and roads into ditches that in turn dump the water into Venema and Piper’s creeks. The runoff fouls the streams with dirt and pollutants, and erodes the creek banks. It buries the eggs of Coho and chum salmon that return in the fall and winter to spawn in the streams, an annual homecoming that attracts hundreds of spectators to Carkeek Park. The Venema Creek project would capture and clean nearly all of the polluted stormwater that drains into the creek, according to interviews with Tracy Tackett and Bruce Bachen with SPU.

    The project would cost about $6.36 million, partially offset by a potential $1 million grant from the state Department of Ecology.

    In addition to the environmental benefits for the creek and its inhabitants, the project will provide some protection against flooding, as well as a rare research opportunity. It is currently not known precisely how much retrofitting with natural drainages is needed for effective restoration. The Venema Creek project could help answer this question because there is already a monitoring station in place that has produced important baseline data on existing pollution levels and water flows.

    “There is no more important kind of project to do,” said Curtis Hinman, a stormwater expert and professor with Washington State University Extension in Tacoma, in a recent interview. The chance to take baseline data and observe a stream as upland area is being restored: “It’s pretty rare.”

    An $850,000 grant from the US EPA would help pay for research to measure the effects of the green infrastructure on Pipers Creek.

    Seattle has been on the leading edge of innovative, customized st
    ormwater fixes, but the projects can run counter to the cookie-cutter solutions favored by many regulatory agencies. With additional data demonstrating their success, the city can make a stronger case for projects that are more effective and less expensive in the long run, including using natural drainages as a cheaper solution to the conventional drainage systems of combined-sewer overflows.

    Street sweeper_Flickr_marymactavish3. Street sweeping expansion

    The third project at risk is an improvement of the city’s street sweeping program through the purchase of better equipment and, in some neighborhoods, increasing the amount of sweeping to once every two weeks.

    Water-quality experts agree that the most effective and cheapest way to solve stormwater pollution is to keep the harmful contaminants out of the water in the first place. Because many of the pollutants dissolve in water or bind to dirt, they are difficult and expensive to remove once they reach the drainage system.

    Street sweeping could remove between 2,200 and 3,100 pounds of dirt, motor oil, and other waste per acre of street swept annually, according to a recently-completed pilot project in Seattle.14 It would cost $1.4 million to purchase equipment and a sweeping truck, and about $1 million annually to run the stormwater-focused street-sweeping program, though it would also save the general fund $500,000 in yearly sweeping costs currently spent by the Department of Transportation.

    On Tuesday, the Seattle City Council’s Seattle Public Utilities and Neighborhoods Committee will take a vote on these cuts. Let’s hope they put their money behind green infrastructure investments that will pay future dividends.


    Natural drainage photo courtesy of Flickr user kuow949, Lake Union photocourtesy of Flickr user kenkilfedder,and street sweeper photo courtesy of Flickr user marymactavish. All are used under the Creative Commons license.