Why do practicing designers often forget the power of learning? Aside from being creative problem-solvers, designers are innately visceral tinkerers, so why have we strayed from the passion, the craft of observation and experimentation, that originally led many of us to our profession?
As a relative newcomer to the field with a growing body of work, I was beginning to be haunted by my own answers to these questions. So when the opportunity presented itself to examine whether a project was indeed performing as it was designed, Andropogon Associates and our client, the University of Pennsylvania, seized the moment and launched a five-year monitoring project that, in addition to measuring transpiration and various other metrics, might illuminate the way forward for designers equally interested in tracking performance.
One Large Bathtub
At first glance, Shoemaker Green appears like any college green: a central lawn adorned by shade trees, undergraduates playing Frisbee, and freshmen hurrying to class. But despite its familiarity above ground, the green space is a heavy-duty piece of living machinery, outfitted with gadgets to track its every vital.
In its first year, this college green in Philly has managed 100% of stormwater due to its strategically designed rain gardens and other living features. Photo: Barrett Doherty
A stormwater schematic shows Shoemaker Green’s ability to capture all roof runoff and air-conditioning condensate, up to 90,000 gallons of water a year. Courtesy of Andropogon Associates.
The 2.75-acre parcel on Penn’s urban campus in West Philadelphia is a SITES pilot project and a part of the Penn Connects Master Plan. As a landscape architecture firm specializing in ecological planning and design, Andropogon was commissioned to revive the property, one of the most underused spaces on campus.
What previously housed aging tennis courts, concrete walkways, and only a few trees is now the “front door” to the surrounding historic athletic structures and the recently completed Penn Park. Through a variety of strategies and technologies, Shoemaker Green not only has provided vibrant social spaces but also—and, perhaps, more importantly—has become a living laboratory of green infrastructure, brought benefits to the City of Philadelphia’s ecosystem services, and spurred the development of sustainable design and maintenance policies for the entire campus.
Despite its vibrant condition today, the project began with an abundance of both literal and figurative quandaries. Below the tennis courts were roadbeds, a piped stream, and row-home foundations. Since infiltration rates ranged from a half-inch to thousands of inches per hour, infiltration was not recommended. Even within these limitations, the site was required by the City to treat one inch of stormwater for water quality concerns, and additional capacity was requested by the client in order to manage runoff from potential future renovations of adjacent buildings.
Before: The site housed tennis courts, walkways, and London planetrees. The planetrees were preserved and impervious surfaces reduced by 49% by leaving the tennis courts and adding soil and vegetation above.
After: Shoemaker now features an extensive green with a stormwater sand-storage bed below, an extension of Smith Walk, a rain garden (pictured), tree trenches, a restored war memorial, and various seating areas. Photo: Barrett Doherty
Adding to the complexity of the program, Penn required that the site not only provide niches for passive recreation, but also support large gatherings, such as graduation events and the Penn Relays, which are attended by more than 100,000 people each year.
The resulting design was one large bathtub, where evapotranspiration and irrigation reuse became critical. A sand storage bed, rain garden, and 20,000-gallon cistern along with tree trenches, planting beds, and various other conveyance systems route nearly every drop of water on the site—including air-conditioning condensate—through a matrix of plants and soil and to the cistern for irrigation. Then, it’s either a gracious exit to the atmosphere or a less glamorous one to the combined stormwater system, which overflows to the Schuylkill River less than a half-mile away during heavy rain.
Feedback Loops
A five-year monitoring plan was established with the University’s Earth and Environmental Science Department to measure the design’s performance. The goal of the monitoring was to not only test the assumptions the green infrastructure’s performance within an urban setting, but also to provide feedback for the facility managers to improve landscape performance across the campus. (A grant was secured to purchase the monitoring equipment.)
Monitoring the water, soil, and micro- and macrofauna has proven to be a wonderful and necessary feedback loop for the performance of the designed system. Without this knowledge and ability to tweak the systems based on data findings—especially in the first few years of the life of the project—the effort to design the systems for maximum performance might have been lost.
Major findings include the discovery of just how undervalued plants and soils are in stormwater management. From May 2013 to June 2014, data shows that no stormwater left the system for the combined sewer, even during a 3.16-inch storm in June 2013 and 11 unusually wet months within the 14-month monitoring period. Transpiration measurements of the vegetation show that native floodplain species and uncompacted turf are veritable workhorses, transpiring anywhere from three to ten gallons of water per day during the growing season. Increased residence time within the vegetated areas also allows more opportunity for transpiration and evaporation, especially in higher-temperature microclimates. We also analyzed stormwater for the prevalence of pollutants, and results show significantly decreased levels as water moves through the system.
In addition to managing stormwater, Shoemaker Green includes an extension of Smith Walk, an important corridor linking the historic part of the campus to the athletic precinct. Photo: Barrett Doherty
Despite this success, analysis of the data indicates that during the summer and winter of 2013, stormwater was not efficiently managed and came very close to overflowing to the sewer system on 14 separate occasions. This can be partly attributed to the winterization of the cistern due to the use of deicing salts and the dormant vegetation. Currently, the designers are devising a plan to increase the efficiency of the system during the winter months in order to prevent a possible future overflow; ideas include adding storage capacity in the lawn for the winter months and adding real-time electrical conductivity sensors.
Beyond the abiotic, the living inhabitants on the site also provide important feedback. Sand-based soils were a no-brainer to resist compaction given the foot traffic, and so a compost tea program was developed to build organic matter within the mostly inorganic, engineered soil. Data indicates that beneficial microorganisms are proliferating and that the soils are developing organic matter to the desired levels with the help of the compost tea program and a turf management plan, which has become a part of the campus’s standard maintenance regime.
Wildlife that is visible without a microscope also makes use of the site. The migratory yellow warbler, rarely found in urban settings, has been spotted gleaning insects in the grasses and sedges of the rain garden. Following this project, habitat creation has been integrated into Penn’s new Ecological Landscape Plan.
Custom granite benches with black locust inlays were designed to allow for social interaction and individual use. Granite cobbles near the benches deter skateboarders and bikers. Photo: Barrett Doherty
The social impacts of the site are currently being studied through surveys and behavior mapping. From surveys, most of the respondents value stormwater management amenities but were not aware of the contributions of Shoemaker. The extensive use of the space, as observed through the seasons, and the perceived value of the space indicate an opportunity for education that can encourage an appreciation for urban ecological systems. Strategies are being devised to enrich the users’ experiences through environmental education.
Exceeding Multiple Goals
Data indicates that this relatively small urban landscape is capable of exceeding environmental goals and has the capacity to fulfill the multiple aesthetic and social roles a public space demands.
There is still much more to learn from ongoing monitoring, but clearly, we must adapt our communication and collaboration channels between maintenance, monitoring, and design to demand more out of our landscapes. Monitoring built work does not have to be costly—it mostly requires a desire for the feedback. We must push ourselves to continually ask questions and seek answers—not just design and walk away.
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Emily McCoy, ASLA, PLA, is the director of integrative research at Andropogon Associates in Philadelphia.
