Seattle’s 84-year-old Aurora Bridge is built with steel downspouts that dump 3.2 million gallons of untreated rainwater directly into the ship canal between Lake Union and Puget Sound every year, something that bridge designers in the 1930s probably never considered to be a problem.
The CoU Project, named for the Fremont neighborhood that calls itself the Center of the Universe, is tackling the bridge runoff in its design of the Fremont Office Building at 34th Street and Troll Avenue. Situated in the shadow of the Aurora Bridge and two of its downspouts, the project broke ground this spring and is scheduled for completion next year.
Early in their planning discussions, the developer Stephen C. Grey & Associates and the civil engineering firm KPFF decided to catch the water from the downspouts and filter it. Their design includes a stepped system of six bioretention cells, or rain gardens, in the public right of way along Troll Avenue beneath the Aurora Bridge. The roadway’s 15-degree incline poses an engineering challenge, but KPFF designed a system that diverts outflow from the cell above to the cell below. This way, each cell receives enough water to keep the gardens’ plants healthy without irrigation while also filtering rainwater. The last cell sends the filtered water into the ship canal.
Water runoff from hard surfaces is the largest contributor to pollution in Puget Sound. This isn’t just rain we’re talking about. As it drains from pavement to the sound, the water becomes contaminated with motor oil, gasoline and a variety of heavy metals.
Striking research by Professor Jenifer McIntyre at Washington State University (WSU) has demonstrated that untreated stormwater runoff from State Route 520 can kill salmon in just a few hours. Salmon are considered an indicator species because their sensitivity to environmental toxins shows how the toxins might affect the health of other species, including humans. Filtering the stormwater through a mixture of sand and compost absorbs the toxins and allows the fish to survive.
The biorentention cells in Fremont will accomplish the same thing in a remarkable example of public/private partnership that has come up with a creative solution despite potential obstacles. The developer and the engineers needed to get cooperation from both the Washington State Department of Transportation and Seattle Public Utilities (SPU) even though they will receive no financial benefit by keeping vast quantities of untreated water out of Lake Union.
“Very few private developers are willing to do this sort of thing,” says Jeremy Febus, KPFF’s civil engineer in charge of the CoU Project. “It’s a big undertaking.”
The COU project will divert about 6,000 gallons of runoff per year, or the equivalent of 16 gallons a day. This isn’t a staggering amount, but Mark Grey, principal and property manager at Stephen C. Grey & Associates, believes it is only the beginning. He says his company has in the pipeline projects that will filter more water and he hopes other developers will be inspired to jump on board to address the issue on a regional level.
The Seattle 2030 District, a public-private collaborative working to create a groundbreaking high-performance building district in downtown Seattle, has developed guidelines to encourage developers to take action on stormwater management, which is becoming a greater issue as climate change leads to more days per year of substantial rainfall. Heavy storms overwhelm existing water-treatment systems, causing untreated water to overflow into local waterways.
District guidelines require newly constructed buildings to keep stormwater discharge 50 percent below the current district average in their designs. Existing buildings must implement retrofits to achieve the 50 percent reduction by 2030. Although the guidelines only affect buildings within the district — 11 neighborhoods in and around downtown Seattle — other communities are taking action as well and coming up with their own site-specific solutions to stormwater management.
The Sheraton Seattle downtown is finishing the design on a project that will divert rainwater from its roof to a storage tank for filtering, sanitizing and ultimate use in the hotel’s laundry operation. The Sheraton is working with Seattle-based Herrera Environmental Consultants on the filtration and pumping system design and is evaluating bids to find a certified mechanical contractor to complete the work. The goal is to install the system by this fall.
Rodney Schauf, director of engineering at the Sheraton, believes Starwood Hotels — Sheraton’s parent company — may follow suit with similar efforts to reuse stormwater in its properties nationwide. The result is attractive from financial and environmental standpoints, as it allows the hotel to buy less water from the city.
Seattle’s little wing Office Building on Sixth Avenue houses the administrative offices of the EMP Museum and demonstrates that creating a green infrastructure doesn’t necessarily cost more money than more established methods and can actually save money. Vulcan Inc., the property owner, is one local developer taking a lead in implementing environmental consideration into its designs.
The Little Wing design includes a sloping green roof that filters rainwater and also keeps the building cooler in the summer. Runoff from the roof is filtered and either stored in a 9,000-gallon tank for later use or distributed immediately into the building to supply the sewage system.
Theoretically, the system can save up to 89,000 gallons of water per year; actual data show results closer to 60,000 gallons. Installing the green roof and outdoor storage tank for about $180,000 eliminated the need for an underground detention tank and a secondary storm/sewer discharge connection below the street, which would have cost about $250,000.
The Little Wing building is also Salmon-Safe certified, which means it has met a list of performance requirements that aim to minimize the impact of urban development on the environment and enhance salmon habitat. Standards cover stormwater management, water use, water quality protection and more. Vulcan’s aim is to certify all its properties as salmon safe.
Over in north Bothell, Clearwater Commons, a small, eco-friendly residential development, has a goal of achieving zero discharge. All stormwater is infiltrated on site. The houses stand on pin foundations so rainwater that isn’t sent to cisterns flows underneath the buildings and soaks into the ground, making the houses look more like cabins in the country than suburban homes a quarter-mile from a main road.
None of the houses have basements or garages. The “road” running down the center of the development is made from drivable grass — square bricks with greenery growing between them and sand underneath — and is intended primarily as a pedestrian path with access for emergency vehicles. Residents park their cars in a lot at the front of the development, much of which is covered in permeable pavement.
Permeable pavement absorbs rainfall that would otherwise flow into storm drains, but it suffers from certain drawbacks, such as not being durable enough to be used on heavily traveled roads. Collaboration among the Boeing Company, WSU and the Washington Stormwater Center led to a pilot project using discarded carbon-fiber composites from aircraft production to develop a stronger alternative to existing permeable pavement. Initial testing suggests the material absorbs water efficiently and does a good job of filtering toxic chemicals. More research is needed before such a product reaches the market.
Meanwhile, projects like Little Wing and the Sheraton that reuse roof runoff have the double benefit of helping Puget Sound while saving on water bills — the green roof of Audi Seattle’s new showroom in the University District recycles water that’s used to wash cars — but local regulations make such recycling impossible in many cases.
The CoU Project, for example, is prohibited from recycling the Aurora Bridge runoff for use inside the building because the runoff falls onto public property and cannot be diverted to private use without first going through the municipal water system. SPU maintains ownership of stormwater that empties onto publicly owned land, including rights of way in front of private buildings.
While some business owners are resistant to change and may not be eager to invest in new technologies to address stormwater management, tighter regulations may force them into action. As stricter national regulations based on the Clean Water Act trickle down to states and cities, local businesses will not have a choice whether to control stormwater discharge. Rather, they will have to decide just how to do so.
The Sheraton’s Schauf offers this advice to building owners: “Start out with an open mind and get creative about what can be done. There are ways that aren’t expensive that both save costs and limit the impact on the environment.”