Sustainable Infrastructure as Interpreted by Seattle

The Emerald City’s green-tinted take on strategies for integrated capital investment

Urbanist Article

Seattle is looking for ways to not only improve city services as it invests in its capital infrastructure, but also to coordinate that investment to provide new value. The goal is to get the most out of every dollar in ways that make the city more sustainable.

Seattle spends more than $650 million a yearin capital dollars to build, renew and repair our infrastructure. Yet the priorities for how, where and why this money is spent are divided up between numerous city departments, each with its own mission, strategies, priorities and funding streams. An interdepartmental team at the City of Seattleis suggesting that some percentage of that capital spending might be more effective and even more sustainable if it were directed toward integrated outcomes — outcomes that not only address expected levels of service, but also explicitly add value to the community, the environment and the economy.

To test this idea, Seattle has launched the Sustainable Infrastructure Initiative, an experiment in which we have selected a handful of upcoming capital projects that might benefit from a more integrated approach. One example is the 73-acre Seattle Center, which is considering major renovations. lmpervious surfaces blanket this former World's Fair site including both rooftops and walkways with virtually no auto or truck traffic. Thus, when it rains, almost all of this 73-acre site produces fairly clean stormwater flows. Unfortunately, these flows are then sent to a combined sewer overflow facility — a huge pipe where both sewage and stormwater runoff are held for later treatment at the wastewater treatment plant. Meanwhile, just a few blocks to the east of that same combined sewer overflow (CSO) pipe, highly polluted runoff from the streets of Seattle's Capitol Hill flows into nearby Lake Union with no water-quality treatment. This begs the question: Can we use the clean Seattle Center stormwater for water features, toilet flushing, cooling or irrigation, and route the polluted Capitol Hill water into the CSO facility? Early results suggest the answer is yes; there may be opportunities for significant reductions in water use at the Seattle Center, and valuable water quality treatment savings if we use this strategy.

To assess this and the other selected projects, members of the Seattle city staff are conducting “triple bottom Iine" (community, economy, environment) analyses of alternative solutions. These “dollars to dollars” comparisons will address not only near-term capital costs, but also long-term operations and maintenance.

Other projects under consideration for an integrated approach:

> Every year, oceangoing vessels unloading at Port of Seattle docks release 50,000 tons of greenhouse gases and smog-causing chemicals just while tied to the clock. Plugging these ships into Seattle City Lights hydroelectric energy supply could remove nearly all of these pollutants from our atmosphere. However, upgrading the electrical infrastructure necessary to deliver this much power to the docks could require multimillion-dollar improvements to a local substation and feeder lines. Meanwhile,in neighborhoods adjacent to these docks, new development following normal conservation practices may cause greater demand for electricity from this same substation. Can we create suitable incentives for enhanced energy efficiency beyond current requirements and delay these expensive substation investments? Can we stop tons of greenhouse gases, slow down smog-causing releases and enhance energy conservation for new development while saving money, too?

> Areas of historic Underground Seattle have the potential to store hundreds of thousand of gallons of rooftop runoff before it is released to our combined sewer, which overflows to Elliott Bay during big storms. Can these “areaways" serve as cisterns for water features and irrigation, or will substandard soils and frail, century-old construction limit our ability to use this strategy to create water features and urban amenities while protecting water quality?

> A former transit park-and-ride lot is being sold to the City of Seattle for a future park. On the edge of the park is a stormwater line that drains hundreds of acres of residential stormwater into Thornton Creek, a local salmon stream. Can we integrate a stormwater facility into the design of the park so that the use of the park is enlivened by water and new wetland habitat while also improving the water quality in this important salmon stream?

> Some areas of north Seattle were developed without sidewalks. One particular stretch of street has significant multifamily growth and elder housing on a street that is little used by cars. Each new development provides sidewalks, but only along their right-of-way frontage. The city has a design for a traditional curb-and-gutter street, but that would cost millions to implement and is unlikely to attract transportation funding. Can we re-imagine mobility strategies for this area that would fit with an overall vision of sustainability, but keep the costs to a reasonable level? For example, can we build permeable sidewalks that infiltrate their stormwater without the need for expensive gutters and drains? Can we create cost-effective vegetated swales that not only treat and store stormwater, but also protect pedestrians and bicyclists from traffic?

> To meet water-quality and safety standards, Seattle is putting covers over water-supply reservoirs in the city. These covers may be built strong enough to support two or three feet of soil. Is there a new use for this new landscape that ought to be considered? What about urban agriculture or other neighborhood strategies to create local food for local residents?

We are in the middle of this experiment. We have much to learn before we can claim any success. It is likely that some percentage of the integrated alternatives we evaluate will not pencil out. Yet for the alternatives that do, we believe Seattle will have increased value for each dollar spent. If we can successfully make this approach part of our everyday capital processes, we believe we will be making our city more sustainable. And that would be a win.

The 73-acre Seattle Center produces relatively clean stormwater that could be removed from sewer flows in the Denny Way Combined Sewer Overflow facility, potentially allowing the much more polluted runoff from Seattle’s Capital Hill to receive treatment.

Steve Moddemeyer is a senior strategic advisor in the Department of Planning and Development for the City of Seattle.