Case studies to Identify and evaluate sustainable design measures for two light rail extension projects are presented. By incorporating some of these measures, the transit agency contributes to the greater resilience of the communities in which it operates and the region as a whole.
Sound Transit, the regional transit agency serving Washington State’s Puget Sound region, is developing strategies to build a sustainable transit system that contributes to resiliency of the region and local communities in which Sound Transit operates. In 2011, Sound Transit established a sustainability plan that committed the agency to reducing its environmental footprint and contains a section on climate change adaptation, including the setting of an initiative to “ensure climate impacts are addressed in risk management, safety and security plans.” Sound Transit recently completed an assessment of agency resiliency to climate change impacts, one of seven climate change adaptation pilot projects from the Federal Transit Administration (FTA). The assessment identified potential climate change-related impacts to existing and future Sound Transit services, including flooding, sea level rise, and heat stress on agency facilities. These issues relate to how climate change can affect Sound Transit capital facilities and its ability to provide services and operations. This paper describes the former aspect of resilience; by incorporating sustainable design features into its capital projects, Sound Transit can contribute to not only its own resilience as an agency, but also to the greater resilience of the communities in which it operates and the region as a whole.
Sound Transit’s design criteria manual establishes requirements for sustainability-related design approaches in project development, including a sustainability checklist to be used for all capital projects. The checklist, which is modeled after the LEED rating system, provides a basis for identifying and evaluating sustainable features to be considered for inclusion in projects. Sound Transit has been gradually incorporating this into its project planning and design processes. Parsons Brinckerhoff (now part of WSP | Parsons Brinckerhoff) has recently led the evaluation of sustainable design elements in two Link light rail extension projects: East Link Final Design and Lynnwood Link Extension EIS and Preliminary Engineering. For East Link, the introduction of new sustainable design elements has been limited due to the late stage of project development (final design). The Lynnwood Link project provides an opportunity to introduce these measures at an earlier stage in project development. These evaluation efforts are described below. WSP | Parsons Brinckerhoff is helping Sound Transit to incorporate sustainability at an even earlier stage with the recent start of development of a new system expansion plan.
WSP | Parsons Brinckerhoff is conducting final design to extend light rail from Seattle to the eastern suburbs of Mercer Island and Bellevue across Lake Washington. The project, which will involve constructing light rail on a floating bridge for the first time, includes two new stations as well as retrofitting two existing roadway tunnels to accommodate light rail. The contract calls for the design team to identify and evaluate potential sustainability measures, work with Sound Transit staff to select which measures to incorporate into the design, and then complete a checklist and sustainability report to document the process and reasons for including or not including measures.
WSP | Parsons Brinckerhoff facilitated multiple workshops with Sound Transit and the design team staff, as well as representatives from the other partner public agencies. The attendees first agreed upon a set of general sustainability goals and then used the sustainability checklist from the Sound Transit design criteria manual to identify a range of potential concepts for evaluation. The design team then conducted a high-level qualitative assessment of cost and construction implications for these measures. Based on the results of this initial assessment, a more detailed total cost of ownership (TCO) analysis was conducted for the most promising measures. Those measures and the key findings are listed below:
- Solar panels on station roofs, estimated to provide between 2 percent and 12 percent of the annual electricity needs of the station, depending on the system size;
- LED lighting in tunnels with cost savings estimated at more than $200,000 over 25 years for using LED fixtures instead of florescent fixtures (LED lighting is being incorporated into a Sound Transit tunnel project currently under construction);
- Green roofs on stations that reduce stormwater runoff and serve as a visible example of Sound Transit’s commitment to sustainability (due to stations’ adjacency to an interstate freeway); and
- Rainwater harvesting that would provide a total of 166,000 gallons annually for landscaping irrigation.
While the TCO analysis indicated that photovoltaic panels would increase the station construction cost, the ideal south-facing orientation of the station roof and unimpeded solar exposure, combined with high visibility to motorists using an adjacent freeway, made this measure appealing to Sound Transit staff. The final design team is now in the process of incorporating solar panels into the station design for one of the stations.
Phase 3 of this 8-mile extension of light rail between North Seattle and the city of Lynnwood in neighboring Snohomish County includes completing preliminary engineering (PE) and environmental analysis for Sound Transit’s identified preferred alternative. The consultant team is currently evaluating five sustainable design measures for potential inclusion. The evaluation process is similar to the evaluation conducted for East Link, but takes place in an earlier phase of project development, which may influence the outcome of potential inclusion in the project. Based on guidance from Sound Transit, WSP | Parsons Brinckerhoff, in partnership with Parametrix as North Corridor Transit Partners, LLC, developed a new total cost of ownership (TCO) tool to analyze baseline and alternative scenarios for three out of five potential sustainable design measures. A high-level evaluation was conducted for the remaining two measures. Those measures and preliminary findings include:
- Solar panels atop a station parking garage and station canopy that could generate up to 40 percent of the station’s annual energy demand (see Figure 1);
- A green roof atop a station parking garage that requires significant financial investment above the current open air (no roof) PE design but reduces stormwater detention and water quality treatment facility needs (see Figure 2);
- Pervious pavement for parking and pedestrian areas that reduces downstream stormwater management systems and recharge ground-water;
- Collection and reuse of rain water from a station parking garage roof for irrigation of station landscape areas; and
- Potential locations and system configuration criteria for use of wall systems that support plant life, allowing site water movement while providing required long-term structural function.
Sound Transit will refine the evaluation findings to better meet the scale of the project and ability to invest in such features. This information will then be presented to decision-makers in order to determine how to move forward with investing in green infrastructure design in the Lynnwood Link Extension Project.
As indicated previously, the FTA-sponsored risk reduction project identified resiliency issues in terms of how climate change can affect Sound Transit capital facilities and its ability to provide services and operations. However, the sustainable design efforts described in this paper present another aspect of resilience; by incorporating some of these measures, Sound Transit can contribute to not only its own resilience as an agency, but also to the greater resilience of the communities in which it operates and the region as a whole. For example, the incorporation of solar panels in its projects will reduce the reliance of the grid in general on other sources of energy, including gas, coal, and even hydro-power (which, while considered a carbon-free energy source, is likely to become less reliable in the future due to the region’s decreasing mountain snowpack). The use of green stormwater infrastructure measures such as pervious paving can help recharge groundwater and underground aquifers while reducing the need for costly detention and treatment facilities.
Going forward, WSP | Parsons Brinckerhoff is helping Sound Transit incorporate sustainability considerations earlier in the project development process. As part of the recent update of the Sound Transit long-range plan, WSP | Parsons Brinckerhoff staff researched and developed an issue paper with recommendations on the most appropriate actions to be undertaken during Sound Transit’s early planning efforts. The paper reported on research and interviews conducted regarding incorporation of sustainability by peer agencies into system planning and project development. Key recommendations included a specific focus on potential funding mechanisms for incorporating sustainable design into infrastructure projects. WSP | Parsons Brinckerhoff has recently begun a project with Sound Transit to help in the development of a new system expansion plan, and will be implementing some of the recommendations from the issue paper as the plan develops.