Greening the Site: Design Options for Sustainability

A discussion of current trends in site sustainability techniques to improve the health of urban forests and stormwater quality, and provide design solutions if there is no room for trees
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Sponsored by Deep Root Partners, L.P., greenscreen®, IRONSMITH, SOIL RETENTION
Angela D. Dye, FASLA, LEED AP

Installation of plantable pavement at a boat ramp

Photo: SOIL RETENTION

Installing an engineered concrete grid system or the familiar open grid concrete block allows more permeable area and potentially up to 60 percent plantable area. Common applications of this type of pavement in the landscape are for fire lanes, parking spaces within parking areas, and service vehicle delivery areas. Most masonry units of this type are upwards of 2½ to 4 inches in thickness to handle the heavy vehicle weight. One alternate but similar product comes in a 2-foot by 2-foot flexible but permeable mat of 5,000 psi concrete, 1½ inches thick. Placed over a compacted 80/20 sand and organic mix, 1½ inch to 3 inches thick, the shallow thickness allows for turf root growth and moisture containment under the paving system, yet can achieve loading of up to 29,000 rear axle vehicle weight (GAW), or an F-64 fire truck. At 45 pounds per mat, the material can be handled by one person, and is flexible enough to bend and conform to irregular surfaces. The product can be placed using alternate fills, such as angular rock, decomposed granite or crusher fines, and even artificial turf, if natural turf or groundcover is not an appropriate material due to water conservation requirements. Common applications are for fire lanes and parking lots, but installations also include bioswales, driveways and boat ramps. Stormwater retention can be achieved through gradation of the soil section. Turf can be planted on a sand base over the mats as sod, or planted with seed, plugs or sprigs. Irrigation spray heads can be integrated into the grid system. Parking space edge markers and end bars can be anchored to delineate parking spaces.

Fire truck washing station in Oceanside, California

Photo: SOIL RETENTION

A 2006 study was conducted by GMU Geotechnical (and as reported in Stormwater Journal 2007) at a fire station in Oceanside, California, where daily truck washing was contributing to unacceptable runoff volumes and contaminating water quality. To test for deflection and endurance of this type of plantable grid pavement, four different weights of fire trucks were driven on a concrete grid with seed and gravel infill over an 8-inch base material. The infiltration factor in addition to the weight-bearing feature were the primary reasons for selecting this type of pavement, which demonstrated it could handle daily vehicle traffic and washing while maintaining turf grass growth.

Green Walls Increase Biomass in a Unique Way

Where trees don't fit, another design option can help provide the green. Vertical screen systems that support vines and other climbing plants add vegetation in narrow and otherwise inhospitable areas where even shrubs and groundcover are restricted in space. According to James Sable, Executive Vice President at greenscreen®, "the Integrated Design approach to building and site development is providing an opportunity to include vertical landscape design elements as an important contribution to energy use efficiencies, green infrastructure, security, and habitat reestablishment. Those using green facade elements in their designs are not just applying this technology once, they're doing it again and again, with great success and interesting variations." The cooling and shading effects of vegetation help reduce cooling needs, and offer shade and privacy in narrow or confined spaces.

Green wall at U.S. Census Headquarters parking structure, Suitland, Maryland

Image: James Sable

Placing a screen panel system, also known as a green wall, on to, and adding vines that grow up the side of an existing or new building can help reduce energy needs. Applications of this simple, and ancient, technology can help reduce the heat island effect by shading pavements and walls that would otherwise release heat and raise nighttime temperatures. By shading the pavement, or roofs of parking structures and buildings, surfaces don't absorb as much heat or reradiate it at night. Using vegetation is essential, as it keeps metal screens from absorbing heat, and provides the perceptual and actual cooling to keep transit riders cool while waiting on platforms or at bus stops when the sun is low and hot in late afternoon summers.

A range of possibilities for use of this type of cooling approach has sparked the interest of the federal government, where energy conservation to save both the planet and public funds has become imperative. The installment of vertical green walls on new and existing buildings is planned, thanks in part to new initiatives encouraged by President Obama and the U.S. Department of Energy. The U.S. Census Headquarters Building (LEED® Silver rating) in Suitland, Maryland in the Washington, DC Metro area has green wall technology on a 75,000-square-foot façade of two parking structures.

Other unique applications of this type of screen panel system include the AirTran offices and hangar at Hartsfield Airport in Atlanta where an arc of freestanding vertical screen creates an outdoor area and controls views; at the Baptist Hospital in Louisville, Kentucky, where a third floor vertical green wall planted with flowering vines improves the patient experience by creating a quiet zone, and offers therapeutic value to patients and their families; and La Madera Community Garden in east Los Angeles where twining vines of beans, peas, and grapes can be seen growing on freestanding panels.

Green walls for privacy and access at AirTran in Atlanta, Georgia

Photo: greenscreen®

 

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Originally published in GreenSource
Originally published in November 2010

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