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March 11, 2004
Rendering by Miller/Hull Partnership
The project team for the $18.4 million park, library and community center at Northgate expects 0.5 percent of its budget will go toward achieving LEED silver status.
Whether to pursue LEED certification is a complex issue when designers consider seemingly conflicting factors of environmental responsibility, lean construction budgets and lifecycle building costs.
Conventional wisdom seems to support the hypothesis that LEED certification can add significant costs to a project. For some types of projects and clients, however, this may not be the case.
In 1998, voters in Seattle approved the $196.4 million “Libraries for All” bond measure that funded new and improved libraries, and in 1999 and 2000, voters approved funding for additional community centers and parks.
Shortly thereafter, the Seattle Public Library and Seattle Parks and Recreation began discussing co-locating some projects and redeveloping sites in the Northgate neighborhood. These discussions led to an $18.4 million project that included a 10,000-square-foot library, a 20,000-square-foot community center and a 1.7-acre park.
The projects were funded before Seattle adopted its current standards for LEED-certified buildings, however the library and parks department decided to voluntarily pursue LEED as long as the budget could support it. Designers needed to calculate how much more it would cost to achieve LEED certification or LEED silver building ratings.
On the Northgate project, the design team was led by the Miller/Hull Partnership. AHBL Inc. provided civil and structural engineering services. Other consultants included Site Workshop and PAE Consulting Engineers.
Weighing credits and cost
LEED checklist for Northgate
The Miller/Hull team developed a matrix for evaluating the relative merits of a LEED credit against the additional cost of achieving that credit.
For each potential credit, the matrix identified additional costs for design fees, documentation and construction. The additional costs were then totaled, added to the construction estimate, and compared to the budget.
Because many sustainable features were already included in the schematic design, some credits added no additional cost. The evaluation concluded that LEED silver certification may be achievable without exceeding available funding, which also included additional city funding sources designed to support sustainability. It also helped that one of the projects was a park, which gave the design team access to sustainable features that are more difficult to achieve on dense urban sites.
In order to achieve basic LEED certification, a project must achieve a minimum of 26 credits on a 69-point scale, (a silver project must achieve 32 credits). Nearly 40 percent of potential LEED credits can be realized through careful site selection and design.
Several important factors contribute to the high number of possible LEED credits related to site. Chief among these factors is the general project location. Redevelopment of an urban site can meet several sustainable goals: avoid inappropriate sites; locate within a half-mile of two or more bus lines; reduce the development footprint; and provide native or adapted vegetation on 50 percent of the remaining open space.
The Northgate project also earns LEED credits by providing preferred parking for car pools and van pools, reducing the number of parking stalls from the current site, and reducing light pollution. Sustainable features also include the reuse of rainwater for irrigation.
Two more goals for sustainable sites are simply met by meeting stringent Seattle stormwater codes.
The drainage design will reduce the stormwater runoff from the site and provide water quality treatment. Stormwater treatment will be enhanced through a rainwater garden located between the park and the community center.
Runoff captured from the parking lot will be released into the rain garden where typical pollutants will be removed by filtering through terrestrial plantings and amended soils. The filtered water will then be collected through an underground pipe and released into a detention pipe.
Collaboration among city departments will be the basis for a LEED credit for project innovation.
Under a separate project, the Seattle Department of Transportation plans to install street medians, sidewalks and street trees in the first phase of improvements for Fifth Avenue Northeast.
Seattle Public Utilities calculated that 5,000 cubic feet of detention will be required to provide runoff control for the redeveloped right-of-way.
The library and parks department agreed to provide an additional 5,000 cubic feet of detention for off-site stormwater on their site to handle the Fifth Avenue Northeast runoff. The cooperation of city departments led to a solution that exceeded minimal LEED stormwater criteria, and should qualify for an innovation credit.
The bottom line
When all of these solutions were totaled, basic LEED certification will cost less than 0.4 percent of the entire project budget. Silver certification will cost about 0.5 percent of the entire project budget. The clients feel confident they can pursue a LEED rating with the available funding.
David Kunselman, the library's project manager for the Northgate project, said he is pleased with the direction.
“The community wants an alternative to its image of asphalt parking lots and lack of green space,” he said. “The library and parks want to create a sustainable project, and we have a competent design team that is working hard to achieve that. We expect to be able to deliver an environmentally sound project to a community that desperately wants one.”
Several of these solutions (like reuse of rainwater for irrigation) would also positively affect the lifecycle operational costs for these facilities.
With creative design and cooperative, thoughtful clients, some projects can achieve LEED certification without significantly increasing project costs.
Doreen Gavin is principal and civil engineer at AHBL responsible for civil design of the Northgate library project and other sustainable projects.