Tapping the Potential of Rainwater
Elmhurst College (Ill.) shares many traits with colleges throughout the country - a private liberal arts college with a religious affiliation; founded over a century ago; located within a quiet residential neighborhood; roughly 38 acres in size; hosts students from many states and countries; and comprised of about 2,400 traditional undergraduates and 230 graduate students.
Elmhurst College also shares a desire to grow, which is where the viewpoint - tapping the potential of rainwater - begins. After completing an updated master plan that identified of dozen new buildings for curriculum and on-campus housing needs, the college had to tackle the impending question: how do we fit all of the proposed development onto a campus that is completely landlocked along with required stormwater detention per the City of Elmhurst?
During design discussions for West Hall, a paradigm shift occurred that forever changed the way the college looks at development - use ecology as the basis for site design decisions. This simple statement not only revolutionized the way West Hall, the first building to be built per the updated master plan, evolved from start to finish, it also changed the way faculty and students interact with the building. Not just seen as a residence hall, the project became a portal for curriculum enhancement, urban wildlife habitat, and sustainable educator.
The site for West Hall was comprised almost entirely of asphalt parking lots, so one goal was to not lose any parking and fit a 170-bed residence hall in the same area. Fitting all the pieces together was the easy part, where to put stormwater runoff was the challenge. With ecology as the basis of design, replacing old asphalt with new asphalt was not an environmentally wise choice, especially since the college sends most of their stormwater runoff to Salt Creek, a local tributary of the DesPlaines River. Runoff from parking lots contains oil, grease, and detergents, and is a temperature lethal to native flora and fauna, which has rendered Salt Creek virtually lifeless. Unfortunately, conventional stormwater management of this type is a common occurrence on too many campuses.
A free resource that falls from the sky, rain is often treated as a waste product to be quickly dispatched somewhere else. By sending rain somewhere else, we have inadvertently degraded a valuable global resource: the Gulf of Mexico. Believe it or not, if you reside within a watershed that eventually feeds the gulf, rain that falls on your roof, parking lot, and even landscape, turns into urban runoff - water polluted by phosphorous, nitrogen, and other deadly water borne detergents - that have contributed to the Gulf of Mexico Dead Zone, an 8,000 square-mile area equivalent to New Jersey. This nitrogen tide stimulates the growth of algae to the point that floating mats of vegetation prevent sunlight from entering the water, which retards the growth of aquatic vegetation and thus depletes oxygen, suffocating and killing the entire marine ecosystem.
So, back to Elmhurst College, what initially seemed like a simple assignment - design and build a new residence hall - quickly turned into a project that codified ecological principles with infrastructure and city ordinances. Instead of conventional rainwater management that uses invaluable land area for water detention, the project uses numerous techniques such as permeable pavements, rain gardens, bioswales, and recycling to make the site more permeable, re-instating historical-based hydrology patterns to cleanse and infiltrate water.
Starting with the largest impermeable surface and contributor to urban runoff on the site - the parking lot - the team proposed that it become both parking surface and detention facility. This was accomplished by building the parking lot out of permeable interlocking concrete pavers (PICP), not asphalt. PICP are individual concrete bricks with a small notch in the corner that allows a significant amount of rain to filter between them. When built over open-graded rock that both supports and infiltrates - the rock has a 40 percent void ratio area within its own volume - the project met city stormwater ordinance requirements and Elmhurst College aesthetic values.
The interesting aspect is that the lot has an eight-foot deep hole, filled with three-inch rock below it, to create the required detention. As rain migrates down through the rock, it will infiltrate through the soil, evaporate back up through the pavers, or migrate laterally within the stone. And yes, providing an eight-foot deep hole, backfilled with rock may sound like an expensive design solution for detention but it is much cheaper than purchasing adjacent residential properties, tearing down homes, and digging a hole in the ground for conventional detention. The other solution would have been the elimination of invaluable parking stalls in lieu of a large hole in the ground next to the building. By placing the hole under the parking lot, the college was able to do double duty with one item and they now have a parking garden
At the Illinois Institute of Technology (IIT) in Chicago, PICP has been proposed for three blocks of streetscape renovation. The deciding factor to use PICP over asphalt at IIT was a life cycle analysis of the two products. When projected out over a 50-year time period, PICP will cost nearly a tenth of the amount to maintain than asphalt. When presented with the life analysis data, the facility manager at IIT did not hesitate to use PICP.
Rain gardens along the perimeter of West Hall and bioswales in the parking garden are another integral part of the ecology-based design philosophy at West Hall. As rain comes off the roof, rain gardens collect water from downspouts and infiltrate it back into the ground through large catchments of open-graded aggregate wrapped in filter fabric. Bioswales in the parking garden work under the same principal, overflow from the PICP will migrate into soils underlain with open graded aggregate in order to encourage infiltration.
At Lewis University (Ill.), bioswales play an integral role in the stormwater management system within new parking lots. Because the parking lots will be constructed with asphalt, the bioswales have been designed to infiltrate the "first flush" of runoff, quite often the most polluted water and most damaging to local waterways.
Another important aspect of the ecology-based paradigm shift is the landscape itself. Instead of a default landscape of Kentucky bluegrass lawn, which is not from Kentucky, and ornamental foundation plants, both of which require an inordinate amount of energy and irrigation to keep alive, Elmhurst College chose native prairie and woodland gardens as their primary landscape motif. Once established, the native gardens will provide invaluable wildlife habitat in an urban setting, will slowly rebuild carbon organics to support the infinitesimal amount of soil microorganisms that create microrhizal affiliations (there are a billion or more microorganisms in a teaspoon of prairie soil), will provide a seasonal display of grasses and forbs, and will reduce the amount of airborne pollen that instigates hay fever and asthma since every plant in a prairie is pollinated by an insect. All by planting native prairie and woodland gardens around West Hall.
Elmhurst College has taken full advantage of the educational benefits of these sustainable design features as well, especially in their science programs. For example, chemistry students will collect water samples from a monitoring station at the parking garden. Using state-of-the-art equipment, students will analyze the temperature, pH, clarity, quantity, and quality of water samples from the PICP sub base as compared to runoff from asphalt. This data will provide an assessment as to the efficacy of the BMPs.
Biology students will use the site as a living lab. They will measure growth rates, seed dispersion patterns, and pollination techniques of various insects within the native gardens. There has even been a suggestion that literature courses incorporate nature writings with supplemental visits to West Hall's native gardens.
Elmhurst College is also making the green aspects an "environmental showcase" for students, visitors and the community. Numerous signs remind campus visitors that the school is contributing to a better environment. Year after year, incoming students will be exposed to the idea that rainwater management is important, leaving them with a greater appreciation for its real world benefits.
To help finance these and other green efforts, there are grants to offset cost premiums. West Hall was partially funded by a DuPage County Stormwater Management Division Grant for its green infrastructure efforts. Also, keep in mind that LEED certified projects are designed to qualify for tax rebates and zoning allowances.
So, it all began with rain, a free resource that falls from the sky. As discussed, an ecology-based design philosophy can provide educational benefits and, more importantly, can provide environmental benefits that go beyond the property lines of the campus. It will provide clean water for local waterways and global ecosystems. As more campuses like Elmhurst College, IIT, and Lewis University promote and invest in these sustainable solutions, they will become more mainstream, more cost effective, and more often the first consideration rather than conventional mitigation methods.
Jay Womack, ASLA, LEED AP, is director of sustainable design for Wight & Company, an architecture, engineering and construction firm based in Darien, Ill. He can be reached at firstname.lastname@example.org.