Stormwater runoff contains harmful contaminants and is one of the leading sources of water pollution in the United States. The conventional remediation for this has been to capture runoff from large storm events in underground vaults or detention ponds and then release it at a controlled rate. This costly option, however, provides no direct return on investment to the property owner, does not replenish local aquifers, and in many cases cannot meet water quality goals.
In the early 1990s, a new concept called low impact development (LID) offered an alternative to traditional stormwater management practices for construction projects of all sizes. LID is a comprehensive land planning and engineering design approach to managing stormwater runoff that emphasizes conservation and the use of onsite natural features to protect water quality.
The use of LID began to gain broader acceptance in 2007 with the passage of the Energy Independence and Security Act (EISA), which required construction on federal development and redevelopment projects larger than 5,000 square feet to meet predevelopment hydrology conditions — the combination of stormwater runoff, infiltration, and evapotranspiration rates and volumes that typically existed on a site before construction. Under EISA’s new Section 438, agencies can comply using a variety of LID practices — green infrastructure — such as reducing impervious surfaces or using vegetative practices, porous pavements, cisterns, and green roofs.
Examples of how Wight & Company has helped its clients “repurpose” stormwater into attractive rain gardens.
Rainwater harvesting: Naper Settlement
Today, more and more local county and municipal stormwater regulations are incorporating — and rewarding — LID best management practices (BMPs). For example, as of this year the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) has begun to allow LID practices to satisfy a portion of stormwater requirements. The six collar counties around Chicago have enacted or are considering implementing LID water quality control requirements. Last year, the Philadelphia Water Department and state environmental officials signed an agreement that will transform at least one-third of the impervious areas served by its combined sewer system into “greened acres” — spaces that use green infrastructure such as roadside planting strips, rain gardens, trees and tree boxes, porous pavement, cisterns, and other features to infiltrate or otherwise collect the first inch of runoff from any storm. This plan is expected to reduce Philadelphia’s annual sewer overflows by nearly 8 billion gallons per year — at a cost billions less than the more traditional approach of building underground storage tunnels.
In the early 1990s, a new concept called low impact development (LID) offered an alternative to traditional stormwater management practices for construction projects of all sizes.
These regulatory trends give civil engineers, architects, construction managers, and property owners new and plentiful opportunities to integrate LID BMPs into more projects. With some creativity and imagination, an LID solution also can do more than reduce stormwater runoff volume and flow rates. The following examples show how Wight & Company has helped its clients “repurpose” stormwater into attractive rain gardens, the source for historical rainwater harvesting, and tools for education.
Disconnecting with rain gardens
One of the most cost-effective LID strategies is “disconnection,” which decouples roof downspouts, roadways, and other impervious areas from stormwater conveyance systems. This is usually accomplished by collecting and managing stormwater onsite or dispersing it into the landscape, which can be especially challenging on projects with spacious parking lots or in congested urban environments.
For example, the disconnection strategy for the expansive parking lot at the new Kane County Branch Court and Conference Center in St. Charles, Ill., was to retrofit its sewer inlets to become rain gardens. The entire site was designed to drain to these rain gardens, which had curb cuts to capture the runoff. Runnels were cut across the width of sidewalks for the same purpose, and were covered by grates to maintain a level surface for pedestrians. Decorative landscape blocks were added for erosion control.
The Metropolitan Water Reclamation District of Greater Chicago has begun to allow LID practices to satisfy a portion of stormwater requirements
Small rain gardens the size of planter boxes also were a key element in engineering the project landscaping for a two-plus mile stretch of Cermak Road and Blue Island Avenue, which will become the greenest street in the city of Chicago. Along with bioswale parkways, these infiltration planters divert, clean, and reuse stormwater, while a landscaped plaza with a zero-depth waterworks feature further slows its flow and removes impurities. The project’s goal is to collect and purify as much as 80 percent of the area’s average annual rainfall before it hits city sewers.
Rainwater harvesting: Naper Settlement
Since 1939, the Naper Settlement has educated visitors on the heritage of Naperville, Ill., in a museum setting that recreates living conditions in a 19th century village. Until recently, the 12-acre site had large asphalt walking paths, compacted soils, and buildings that sent roof runoff directly onto the ground. As a result, the water flow during rain events or snow melting caused pooling, erosion, and collection of pollutants before entering the DuPage Watershed.
As part of its master plan to incorporate BMPs into all future developments, the Naper Settlement completed a roadways and stormwater management plan last year that paid homage to the village’s past. The early settlers, for example, harvested rain using cisterns and barrels for later use as drinking water and to irrigate their kitchen gardens. At the site’s 1883 Martin-Mitchell Mansion, a 3,400-gallon cistern was constructed near the location of the home’s original cistern. At the original Barn and Maintenance Shop, a cistern was added to collect overflow from a rain garden, which is being used to irrigate a nearby garden.
Rain from the rooftops is now treated and cleansed primarily through rain gardens or infiltration zones around the perimeter of each building. The Naper Settlement also replaced its 42,000 square feet of asphalt pathway and parking space with environmentally friendly permeable, interlocking concrete pavers. All told, the site’s BMPs included eight rain gardens, seven infiltration zones, two cisterns, a bioswale, and a rain barrel.
Grants from county, state, and federal funding sources, including the U.S. and Illinois Environmental Protection Agencies, supported more than 85 percent of the total $2.3 million project cost. Earlier this year, Napier Settlement and the Naperville Heritage Society received a Sustainable Development Award from The Conservation Foundation.
Just as clean stormwater replenishes the earth, the use of stormwater BMPs can be a springboard for nourishing the mind. Many of our projects, especially those involving schools or nature centers, feature BMPs for using stormwater solutions to help educate students and the community about the importance of sustainability practices in everyday life.
For example, Northbrook School District 28 is planning additions and renovations to Greenbriar School, which was built in the 1950s and with little thought given to stormwater management. By implementing BMPs such as permeable pavers, rain gardens, green roofs, and a dry-bottom detention basin with native plantings, the school district hopes not only to stop polluting a nearby river but also to educate its students and community about how everyone can help prevent nonpoint source pollution. This initiative will include:
- teaching at the school about the purpose and benefits of the BMPs;
- recruiting students throughout the district who are interested in environmental stewardship to learn about the BMPs, collect and disperse seeds, and help maintain the native areas;
- using Greenbriar as a case study to give the district’s 1,700 students a yearly lesson about the importance of watersheds and ways to reduce nonpoint source pollution at home; and
- placing permanent interpretive signs in prominent locations with stories to explain bioswales, rain gardens, permeable pavers, native plants, green roofs, and pollinators.
Elmhurst College also is involving students in its sustainable design features, especially in its science programs. For example, chemistry students will collect water samples from a monitoring station at a parking lot rain garden. Using state-of-the-art equipment, students will analyze the temperature, pH, clarity, quantity, and quality of water samples from the permeable, interlocking concrete pavement subbase as compared with runoff from asphalt to assess the efficacy of the BMPs.
For a streetscape project, Wight is taking roof runoff from an adjacent high school and redirecting it to a plaza where students can watch its movement across cement embedded with recycled glass. Rainwater will flow through runnels to the plaza, and an overhead runnel that will spill water into the plaza from almost 16 feet above the ground. The interactive educational feature includes seating blocks decorated with mosaics by local artists and students that depict life in the neighborhood and the importance of rain in their culture.
A different mindset
For years, stormwater was viewed as a waste product that needed to be disposed or dispersed. But that attitude is now hopelessly outdated. Rain gardens, cisterns, water-recycling features, and other LID techniques are prominent elements in many sustainable building projects. They foster an appreciation of water’s intrinsic value and serve to educate and remind all of us to do our part in preserving this vital resource for future generations.
Tom Powers, P.E., CFM, LEED AP, CPESC, is a project manager who specializes in design and construction engineering services for public projects with Darien, Ill.-based Wight & Company (www.wightco.com), a sustainable design and construction firm with more than 60 LEED Accredited Professionals on staff.
American Concrete Pipe Association
A tour of a state-of-the-art concrete pipe manufacturing facility is available to educate your engineering staffs on pipe manufacturing, which will help make proper decisions when specifying drainage pipe. Many plant tours also feature a demonstration of proper methods of post installation inspection of all types of pipe used for gravity pipe installations. Methods include the proper technique for laser video post installation inspection.
To receive assistance, simply call the American Concrete Pipe Association contact information below and ask for a member in your area. Design information and software can also be found at www.concrete-pipe.org