Barbara Deutsch, Landscape Architecture Foundation (LAF) and Jose Alminana, FASLA, and Tom Amoroso, Affiliate ASLA, of Andropogon Associates discussed how to quantify the ecosystem services provided by sustainable landscapes using the Sustainable Sites Initiative (SITES) prerequisites and credits and other tools and calculators (see earlier post) in a session at the 2010 GreenBuild.
SITES and LAF’s Landscape Performance Series
According to Barbara Deutsch, LAF’s Landscape Performance Series aims to make “landscape performance as well understood as building performance” among design professionals and also complement SITES. To quantify all the benefits of SITES projects, landscape architects must use a “collaborative, integrated, systems-based approach,” design for natural processes and use natural resources, collect performance data, and continually measure benefits over time. (see earlier post)
She implied the usual landscape architecture project brief, which often just lists a “set of features,” is pretty useless. “We actually need solutions so we need to communicate the benefits of these features.” For landscape architects, Deutsch said it’s important to just start “defining and quantifying benefits now. If we are going to start investing in sustainability, we need to show value, a return on investment.”
Quantifying Benefits in the Design and Development Phase of a SITES Pilot Project
Jose Alminana and Tom Amoroso of Andropogon, a Philadelphia-based landscape architecture firm, discussed a case study that demonstrate how to both apply SITES prerequisites and credits to projects in the design and development phase, and quantify the value of ecosystem services. Alminana said “any landscape can provide ecosystem services. It’s about putting a price tag on the value nature provides.”
Shoemaker Green, a 3.5-acre open space used often used for athletic events on the campus of University of Pennsylvania, was highlighted as an example of how to start quantifying benefits early in the design and development phase. The project, a SITES pilot project, is a hub for urban redevelopment and part of new UPenn leadership’s plans for preserving its network of open space and redeveloping underperforming areas.
Andropogon’s design is also expected to earn the project some 80 percent of SITES credits, said Alminana. SITES prerequisites 1.5 and 1.6, which relate to sustainably siting, were easily met because the project designers are redeveloping a brownfield site that already serves an existing community. “The site is next to existing transportation networks and amenities. This project is in a dense area with links to pedestrian paths and open spaces,” said Amoroso.
To meet prerequisite 2.1, which asks project designers to “complete a pre-design site assessment,” Andropogon did in-depth studies of the site’s existing soils, vegetation, hydrology, and materials. On soils, Amoroso found that the existing site soils were “urban fill soils,” but the reference soils were “alluvial, common to floodplain areas.” Other studies were done by testing “soil borings, percolation rates, and levels of organic matter.” Soils are important for vegetation and water.
To determine water management capabilities on site, the team studied the hydrology and modeled the “aspect” in 3-D to determine the slope and path of water and the sun across the site, which will help determine which plants can be used. An inventory of existing materials was also conducted to determine how unearthed materials can be reused in the site to ensure the site has “zero-waste.”
In the “pre-design assessment,” the team said they would win credits for 2.3, “engaging users and other stakeholders in site design” because the team has set up regular meetings with user groups, a project steering committee, and clients. “We brought in a general contractor for pre-construction support,” to help streamline the design review process.
Moving into the actual design, the project team is expecting to earn credits by preserving open space networks, reducing potable water use by 75 percent (credit 3.2), and addressing stormwater management on site (credit 3.5). To store stormwater on site, Andropogon used a system of ”silva cells” and tree trenches, porous pavers, and raingardens to deal with the first inch of rainwater and a cistern as a water storage depot. Finally, for major flood events, there is infrastrucuture to direct water to the combined sewer system.
Alminana said the site “can deal with runoff from adjacent buildings and store up to 87,000 gallons per year,” which translates into real economic value for the university given Philadelphia now has high stormwater run-off fees calculated based on impervious surface areas. Amoroso added that “previously, 70 percent of the site was impervious. We will flip this to 70 percent pervious.”
The project can accrue credits for its soil management plan (credit 4.3), preservation and restoration of moved trees (credit 4.6), and use of recycled materials (credit 5.5). The team plans to mimize excavation, but where it’s inevitable, reuse broken up asphalt in the site structure and achieve zero-waste. This means lots of avoided expense taking materials to landfill, as well as avoided CO2 emissions.
Unfortunately, because urban soils don’t work with a lot of the sustainable vegetation and water systems, new soils will need to be trucked in though, perhaps adding to the project’s carbon footprint. While sustainable soils, water, and plants are crucial to any restorative landscape, project estimates for C02 emissions should be included in the mix of what’s tracked.
Calculating Gains in Construction Efficiency and Learning from Monitoring and Evaluation Results
The Salvation Army community center in central Philadelphia was used to explain how SITES construction credits work. The 11-acre site was redeveloped on a brownfield and now includes an integrated water management system. “For 2-year storm events, we calculated we reduced run-off by 99 percent, and for 100-year storm events, reduced run-off by 79 percent.”
The project would win all the credits for using recycled content (5.5) because reused concrete was integrated into the site. To achieve zero-waste, Alminana said you first need to create a plan for dealing with the materials in the beginning. “We focused on material sorting, upcycling and material placement in the site, and then backfill and grading and planting soil mixes.”
He said this approach worked, but it was “hard to quantify this benefit.” They eventually calculated they saved $300,000 in truck hauling fees. However, avoided CO2 emissions from material transportation wasn’t calculated.
Lastly, Alminana discussed Thomas Jefferson University’s Luebert Plaza, which is “basically a green roof over a parking lot,” in the context of SITES credit 9.1, which calls for “monitoring performance of sustainable design practices.” In this case, they found the soils weren’t working as planned. The plaza had to be watered twice a day to keep the grasses alive.
“We had to use soils that dry quickly so they don’t soak up too much water and put strain on the green roof structure. As a result, the root systems didn’t need to grow all the way down and the soil wasn’t balanced.” Tests showed that the there was too much bacteria and not enough fungi. The project team came up with a “customized organic composting tea” that “favors this species,” which helped reduce irrigation by 40 percent, eliminate chemical fertilizers, increase root growth, and limit compaction. Soils are key to the functioning of the site. ”This demonstrates that beauty isn’t skin deep, but, in fact, you need to dig below the surface.”
Learn more at the Sustainable Sites Initiative.