Integrating Stormwater Into the Landscape

April 14, 2004
Rain falls on a rooftop, slides down a gutter, and flows out to a curbside. Following the slope of the street, the water joins rivulets from other roofs and gushes into a storm drain. As it journeys, it sweeps dirt, oil, and trash from the street, into the storm drain, and on through pipes until it is flushed out into a nearby creek or lake. Meanwhile, the business owner is paying his utility bill, including a hefty fee for irrigation water and air-conditioner electricity. During this brief rainstorm, this scenario is repeated on thousands of streets. What if we could change even a tiny portion–keep the stormwater on-site or give the business owner a break on his utility bills? What if we could extend this to each office building and home in the community? Proponents of green building concepts say that this scenario is within our reach. By using sustainable development, a community can change stormwater management from “end of the pipe” structures to onsite handling. The cost often is cheaper, and the result is a greener, cleaner environment. Several factors are driving this paradigm shift in stormwater management. Meeting National Pollutant Discharge Elimination System (NPDES) Phase II regulations has forced many communities to research different ways of directing stormwater flow. Loss of usable land and declining-quality water make people consider how to use these valuable resources in better ways. Budget crunches on state and municipal levels reduce the amount of funding available for many projects. So, if a group of technologies and methodologies can help meet NPDES regs and increase water quality without sacrificing land for detention ponds and treatment plants, people are more than willing to consider them. Sustainable development comes under several names and methods. The US Green Building Council (USGBC) has introduced standards that measure environmental soundness. As a national group of leaders from several industries, USGBC compiled the LEED (Leadership in Energy and Environmental Design) Green Building Rating System. This rating and certification system outlines specific parameters that must be met for sustainable development; buildings receive points in several categories. In the stormwater area, certified LEED buildings must limit the amount of pollutants and manage the rate and quantity of runoff.Techniques used to meet the LEED standards include incorporating green roofs and rain gardens, building swales and wetlands, paving parking lots with pervious asphalts, and reusing stormwater for irrigation. Viewing stormwater as a resource rather than a nuisance to get offsite as soon as possible requires a new perspective. These concepts can be used in new design and construction and in retrofitting or infilling developed areas.Beginnings of InnovationBruce Ferguson, director of the School of Environmental Design at the University of Georgia, points to a classic project where stormwater management was integrated into the design: Village Homes, built in Davis, CA, during the 1970s and ’80s. The level land was carefully graded into swales behind each home. Also included were weirs, check dams, and bike trails along the swales. Homeowners planted trees and other vegetation and built small pools, creating a riparian ecosystem that supports birds, mammals, and butterflies. “It was very innovative for its time,” Ferguson says. “We would be able to do even more today.” The new urbanist ideas to revalue cities are more challenging than projects like Village Homes. Denser populations and the need for multiple-use areas call for stronger interdisplinary planning. “We’re down to looking for multiple uses for every square inch,” Ferguson notes.Ferguson believes that site design incorporating stormwater management is improving, much of it driven by NPDES regulations. Governmental permitting agencies are becoming more open to sustainable development ideas. Research and new technologies also strengthen this field and will continue to do so.Main Street, AnchorageCreekside Town Center in Anchorage, AK, is designed to feel like “small town USA.” The 64 square blocks will replace a trailer park with a mix of residential, retail, and commercial properties. Sidewalks and bike paths encourage movement without dependence on cars. Recreation areas, a library, a daycare center, a community center, and schools increase the feel of a small town in the middle of a city. Residential units number about 1,200, from single-family homes to condominiums and apartments. Retail and business space encompasses about 190,000 square feet. Chester Creek, which had been damaged by the original development, will be restored. Nine parks and a park strip provide recreational areas, vegetation buffer zones, floodplain, and wildlife habitat. Street design includes landscaped medians and pockets.The Creekside Town Center is a joint project between Venture Development Group, the Cook Inlet Housing Authority, and the City of Anchorage and receives funding from a state grant. The time frame for build-out is seven to ten years. The city eventually hopes to design and build seven centers similar to Creekside. Collaboration in Denver
Landscape Architect Bill Wenk of Wenk Associates in Denver, CO, says the most successful stormwater projects seem to come from a collaboration of civil engineers and landscape architects. The engineers ensure that the design criteria are met, and the landscape architects provide what is often a more creative view. When the two disciplines collaborate, they draw from the strengths of each. “I know construction processes and materials as well as engineering principles, and engineers respect that, which speeds up the process,” he notes.Wenk also believes “change happens very slowly,” but as sustainable projects are completed, people see the results and the push to integrate stormwater management as part of a multifunctional agenda grows. He recalls a 20-year-old project in Aurora, CO; the plan was to channelize a stream in concrete, but the neighborhood protested, so other options were considered. Wenk Associates proposed a softer, ecologically friendly approach incorporating what have now become more conventional ideas: widening and deepening the channel, vegetating the slopes, and installing check dams that stabilize the streambed. The new plan met engineering criteria, and the neighborhood was happy with the final result.Because of upstream development, Goldsmith Gulch in Denver lacked flood capacity for downstream areas and threatened a community park it passed through. The neighbors were concerned that flood-control improvements would threaten the park’s open-space qualities. Wenk Associates worked with the local neighborhoods and constituents to develop concepts for improvements that would enhance open-space qualities and participated in site walks to aid neighbors in visualizing the proposed improvements. The channel was reconstructed, and contoured boulder drop structures were put in to slow the flow of water, creating better habitat, improving water quality, and controlling bank erosion. As a result, the neighborhood has been pleased with the improvements. Another example, Denver’s Creekfront, transformed an underutilized, concrete-lined stream channel into a more natural-looking city open space. Cherry Creek along Speer Boulevard is a major tributary in Denver, providing flood control in the city. Wenk Associates stabilized the streambed, retaining soft bottoms, vegetation, and flood-control requirements while providing a new multiuse resource in the heart of downtown. To provide recreational use, parts of the concrete walls were removed and small parks and plazas were installed, allowing for access to the bottom of the creek. Bike trails were built along the creek, integrated with the primary engineering function of unimpeded conveyance of floodwaters. Drop structures, constructed as part of the project, work to stabilize the channel bottom and protect the channel walls. At the same time, they provide a series of informal pedestrian seating areas that are oriented to the stream. Urbanization in the Shop Creek drainage basin had caused severe channel erosion in Cherry Creek State Park, which surrounds the Cherry Creek Reservoir. Sedimentation and phosphorous pollution had become significant problems in the reservoir. The solution developed by Wenk Associates and the project engineer was a radical departure from standard landscape architectural and engineering approaches to stream channel stabilization. Soil cement drop structures were designed and the channel was shaped to preserve its original alignment. Extensive wetland areas were created, providing new areas of habitat and removing 50% phosphorous. This sustainable, more natural solution was less expensive than typical channelization. Since the completion of the project, water-quality goals have been met and a diverse ecology has developed. The project has received national and state engineering and landscape architectural design awards for its innovative response to the broad range of engineering, aesthetic, and ecological issues it addressed.
Wenk Associates also participated in the design of the redevelopment of a vacant 1960s-era shopping center in Brooklyn Park, MN, just north of Minneapolis. The city saw the potential of Shingle Creek, a channelized stream located behind the center, to serve as the recreation and open-space focus of redevelopment. The new area will be a mixed-use town center, with office, retail, and housing units. The design concept focuses on maximizing the natural and recreation potential of the creek while enhancing habitat and improving water quality. Porous Is BetterPorous or permeable pavements have been around since the 1970s. The asphalt composition is the same as that of regular pavement, except that most aggregate fines have been removed, leaving larger open spaces for water to pass through more freely. An underlying stone bed allows for infiltration. The stones are uniform in size to permit water percolation to the soil layer. A geotextile layer under the stone prevents soil particles from migrating upward into the stone and plugging the holes. The stone layer can provide stormwater storage as well as recharge groundwater resources. Porous pavement areas can even provide infiltration for adjacent impervious areas. A typical ratio is 5:1 impervious area to pervious (5 acres to 1 acre). The porous design also has good pollutant-removal properties for such pollutants as total suspended solids, oils, and metals. Studies have shown that porous pavements hold up as well or better than conventional asphalt in most environments in low-traffic areas, such as parking lots, and the cost is comparable to that of conventional asphalt.A project at the University of California at Berkeley is incorporating porous pavement and other techniques to meet numeric stormwater-quality criteria required by the state’s Regional Water Quality Control Board. University Village at Albany is a 20-acre redevelopment project that will provide 500 housing units for graduate students. The site and landscape plan has been developed with an integrated stormwater management system that includes pervious concrete parking, infiltration areas, and vegetated swales. Construction is beginning this fall. The designer-builder for the project is J.R. Roberts, the architects are Christiani-Johnson and Sam Davis, and the engineering firm is BKF.Tom Richman, principal of Catalyst, the landscape architect for the project, agrees that sustainable building techniques are increasingly accepted: “It’s the present, it’s the future, it’s become the industry standard.”  He adds, “This project is a very good example of institutional commitment by UC Berkeley, a strong design-build process to get the details right, and a design effort that integrates stormwater management from the beginning. It achieves its numeric goals while improving livability at fairly high densities.” Green Is the RoofIn the Maryland Stormwater Design Manual, adopted in 2000, green roofs are one of the encouraged innovative stormwater management practices. Building roofs are often ignored or just accepted as impervious areas, but the Maryland Environmental Design Program is campaigning for more green roofs.Green roofs are a multilayered system with a waterproof membrane, insulation, gravel and soil layers, and plants–usually succulents or herbaceous ones that require little maintenance. Structural loads are about 15 to 50 pounds per square foot. Green roofs provide stormwater management, energy efficiency, and ecology benefits. Advantages of green roofs include reduction of utility costs, both summer and winter; extended roof life by two to three times; reduction of stormwater runoff and noise; and an aesthetically pleasing environment. The State of Maryland has demonstrated its belief in green building concepts in the choice of the headquarters for the Maryland Department of the Environment (MDE). Stewart Comstock of MDE describes that an old Montgomery Ward catalog warehouse was retrofitted as a green building. Seventy-five percent of the construction and deconstruction waste was recycled, as were old window frames, conduits, elevator shafts, and trash chutes. Low-energy facilities, such as those with low-wattage lighting, high-efficiency mechanical and electrical systems, and low-water-use bathroom fixtures, add to the environmentally friendly atmosphere. Old glass was used in parking lot paving, and recycled materials were used for drywall and flooring. The crowning achievement, literally, is a green roof garden. Sustainable Design Problems
The biggest problem in any stormwater management program is maintenance, according to Comstock. He says that challenge is especially true for in-ground best management practices. Nonstructural methods have the advantage of not needing as intensive of maintenance. “They more closely mimic natural processes,” Comstock says. Bill Wenk says that another problem is encouraging municipalities to take measured risks to engage in sustainable development plans. The liability of pollution or flood makes many government employees think twice before giving these designs a green light. It should be the other way around, he says, because the sustainable development techniques cost less in infrastructure. Pressure is increasing as the public becomes more educated about these possibilities. The principal barrier to sustainable development, in Bruce Ferguson’s opinion, is lack of knowledge on the part of municipal and technical people who limit the techniques used. They feel a strong duty to protect public health and safety, and in their minds, these projects are untested: “If I can’t verify it, it doesn’t count.” While some municipalities remain committed to conventional techniques, emerging generations of engineers and designers are more familiar, and comfortable, with sustainable techniques, and new laws–community, state, and federal–help push along these initiatives. Awareness of the scarcity of clean water and usable land causes the public to rethink building and community design.

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