Home  Sustainable Land Development Today March 2007
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Effective Stormwater Management Using Low Impact Development |
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Written by Bill Lites
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Thursday, 01 March 2007 |
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The New American Home in Florida serves as a test laboratory for innovative techniques.
During the peak of the housing boom, more than one million new homes were built in Florida annually. Extensive land development has, and continues to significantly alter the environment’s natural ability to absorb and treat rain water. This rainfall or stormwater must be “handled” in the design of new developments. Before the housing expansion even begins, the majority of water would absorb into the land or evaporate into the air and a very small percentage would run off into larger bodies of water. Unfortunately, alterations from development have reduced the amount of water absorbed into the land and increased the amount of water and pollutants that run off.
Even though there are stormwater regulations in place today, more efficient stormwater management systems are needed to better protect the environment. High nutrient runoff still gets into our surface waters, and wetlands and downstream wetlands experience drastic changes in their natural hydro-periods. In light of these concerns, a movement known as “Low Impact Development” (LID) has built momentum among development stakeholders. Proponents of this concept support the creation of systems that treat water where it falls. The components of LID are complicated and diverse – but provide a viable solution to improved stormwater management and water quality treatment. (Historically, Florida has been a leader in implementing stormwater management techniques and by implementing LID, water quantity and quality issues can be improved.)
In the absence of LID techniques, stormwater in developments is generally treated using one or a series of large centralized ponds. However, there are significant infrastructure costs associated with current water management designs – including complex and extensive sub surface piping, extensive site grading and filling, and “lost” land. The current standard approach focuses on detaining water from major storm events, but often increases volume discharge and reduces groundwater recharge compared to pre-development levels. In response to these issues, LID systems were developed to improve onsite stormwater treatment, increase aquifer recharge by reducing runoff and retaining water for irrigation.
An Oasis in the City
As LID concepts have grown in popularity, developers have begun incorporating the systems in home designs. Examples are the LID systems implemented in The New American Home®(TNAH), the test house featured at the International Builders’ Show, which was held in Orlando in February 2007.
This three-story, 5,283-square-foot contemporary Craftsman home by builder Carmen Dominquez, was designed to create an environmentally friendly oasis in the heart of historic downtown Orlando. Certified as a “Green Home” by the Florida Green Building Coalition, the home features Florida’s first operational, residential “green” roof and a multifaceted stormwater management system. With a stormwater management system designed by Dyer, Riddle, Mills & Precourt (DRMP) and landscape architecture by Glatting Jackson Kercher Anglin (Glatting Jackson), the home was truly a collaborative effort.
Managing Stormwater…From the Lawn to the Roof
TNAH is designed in an upside-down arrangement – housing two bedrooms, one bathroom and a mudroom on the first level, a master suite with a built-in coffee bar and a balcony occupying the second floor, and the main living area, including the kitchen and family room, on the third story. By utilizing such a design, TNAH takes advantage of the sweeping lake views in the area most often occupied. The home also includes pest defense, ten foot ceilings on the third level, Honeywell touch screen temperature controls and other technological advancements. Solar panels line the roof, providing alternative energy for the home. The outside of TNAH features exposed timber brackets and stucco as well as clapboard siding – combining a traditional look with contemporary appeal.
In a similar upside-down design and by utilizing LID principles, DRMP and Glatting Jackson designed the test home’s stormwater management system and “green” roof to treat rainwater where it falls. The site was extremely narrow – only 47’ wide with 5’ side and rear setbacks – limiting the size of a water basin. DRMP created an innovative stormwater design that directed the runoff into a pollutant-reducing concealed pond known as a bioswale, which is located along the south edge of the property. The home’s bioswale transports the stormwater to a 7,000-gallon cistern located under the garage, where it is retained for later use. This stored water is pumped to the green roof and other landscaping for irrigation. The driveway is made of porous concrete that allows additional stormwater to absorb directly into the ground thus recharging the surficial aquifer similar to the predevelopment condition.
The home’s green roof is impressive in its unique design. Working in partnership with the University of Central Florida’s Stormwater Academy, Glatting Jackson designed the roof to include drought-tolerant plants, which grow in recycled tire material. The roof’s stormwater design is one of the most innovative aspects of TNAH. The roof is lined with a pollution-control fabric that filters waste material from the water before it drains into the cistern. Recycled gravel also is used on the roof and throughout the home’s landscaping to collect contaminants and recharge the aquifer.
The home’s landscaping also incorporates LID elements. The landscape plants are either native to Florida or are drought tolerant. In addition, a portion of the lot was landscaped with artificial turf, which is water permeable. These two factors significantly reduce water consumption and maintenance such as mowing, fertilizing, or insect control. The bioswale was designed with an accordion-style grade to increase surface area for additional stormwater treatment, to increase soil moisture variability, and to provide a more attractive appearance. The green roof and the bioswale also hold water to allow for more evapotranspiration thereby reducing the amount of water to be treated or discharged. The combination of the cistern, the green roof, innovative landscape architecture, and the on-lot bioswale enable the following stormwater benefits: there is a reduction in the potable water required for irrigation, the local aquifer is replenished with the home’s runoff, the site requires less treatment due to evapotranspiration, and the stormwater discharge volumes are reduced.
Benefits and Apprehension
The successful design and implementation of an LID stormwater management system in an aesthetically pleasing home begs the question: “How can we apply this example to general community planning?” Pollution reduction will become an increasingly critical issue for developers … particularly in areas of high growth or in watersheds with currently degraded water quality.
Developers who implement a community-wide stormwater management system, using LID techniques, will reap multiple benefits. First, more land will be available to develop. Traditionally, about 15 to 20 percent of developed land is designated for stormwater management. However, by treating the water where it falls, developers can design smaller stormwater bioswales into the landscaping plan in medians, side lots, and utility easements and leave more land for other purposes.
In addition, LID practices can help developers overcome project delays caused by water quality and usage issues. LID can help improve water quality treatment for water sheds that are becoming polluted due to development. By creating a series of small bioswales within a development and reducing the role of large neighborhood-wide stormwater ponds, developments can retain more water on site for groundwater recharge, provide better treatment, and keep water volume discharges in line with pre-development levels. Developers who can demonstrate that their projects will not adversely affect water basins will likely acquire stormwater permits more easily. In addition, in places like Florida, developers may soon face difficulties obtaining consumptive-use permits (CUP) due to concerns over water consumption and aquifer level reductions. LID eases these concerns thanks to the native or drought tolerant landscaping and aquifer recharge
As with any new approach to development, there is some apprehension. Due to LID’s additional complexity and untested nature, some engineers, developers, and regulators are resistant to change
Concerns have been raised regarding mosquitoes in the bioswales or gutters, but experts contend that, in most cases, the stormwater will percolate so quickly that the mosquitoes will lack the time to breed. One legitimate concern is that homeowners will not properly maintain the stormwater management systems. But this issue can be addressed with proper education about the system’s operation and benefits to the consumer and the environment. Another concern among developers about LID is that the homes will be unattractive and unappealing to homebuyers. But TNAH is just one example of how LID can be ecologically friendly and aesthetically pleasing.
LID does not only apply to new home construction. Current homes can be retrofitted to include some of the features of TNAH. Building bioswales in yards, adding cisterns to homes, installing new permeable driveways, and using native or drought tolerant landscaping could be costly, but the reduction of contaminants and volume discharge and fresh water use would be significant.
Eco-Friendly” Living
TNAH is intended to be a test laboratory for new ideas and concepts that can be implemented by developers, architects, engineers and planners throughout the country. One important lesson to learn from this year’s test home is this: innovative LID stormwater management systems can be designed without detracting from a home’s overall appearance.
Although LID systems are complicated, many communities have found them to be a viable solution to water management problems. As developers across the country look for better ways to handle water-related issues, community-wide stormwater LID systems may be an appropriate first step. LDT |
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