Sep 10, 2007

Building Green Involves Thinking “Blue”

 

Green building projects have become prevalent across the country, but an Illinois contracting firm is now incorporating a “blue” approach into its conservation-oriented development projects.

 

Leonard W. Besinger and Associates Inc. has broken ground on its green and blue project, a 114-acre subdivision that will include 28 homes in McHenry County, Ill. The Wildwood community of luxury residences marks the first U.S. installation of a porous (permeable) pavement system for all hard surfaces in a single-family subdivision. Crews will install more than one mile of porous pavement throughout the development space.

 

“We’re applying both blue and green conservation measures at Wildwood,” said Besinger. “The blue aspect involves conserving and purifying onsite water. This is an increasingly important issue now gaining worldwide attention. The green aspect pertains to the native plants and trees on the property.”

 

All hard surfaces within Wildwood — roadways, walkways, driveways, private patios, etc. — will be constructed using porous pavement. The Wildwood Conservation Association and its Architectural Control Committee will manage the property and review residents’ proposed and completed landscaping and construction projects to ensure that the all-porous rule is upheld.

 

Project engineer Bruce Shrake said that the existence of high-quality wetlands on the land to be developed and the need to continue storm water flow into them makes retention volume-lowering porous pavement an ideal fit. “I’ve been engineering for 31 years, and this is probably the most sensitive plan I’ve ever done,” he said. “It was truly the only way to develop this area of land.”

 

Managing Storm Water at Wildwood

The system being installed at Wildwood is comprised of numerous components, and, according to project contributor Charles Taylor of Advanced Pavement Technology, gravity will keep it working.

 

The top layer consists of 3.5-in. concrete porous pavers made up of impervious segmental units that have porous joints and voids filled with small, fractured-limestone aggregate. Taylor reported that the layers will provide a total suspended soil removal rate of more than 90 percent.

 

Storm water runoff flows through 14 in. worth of filtration layers before it enters
perforated pipes and underground soils. “[It] will treat and provide a total maximum daily load that will meet National Pollutant Discharge Elimination System Phase II rule requirements,” Taylor said. “In addition, the sub-base aggregates will utilize the void areas as a detention area or, in some cases, a retention area for this treated water.”

 

The special-made pavers and overall system allow for controlled, onsite storm water drainage in addition to the filtered recharge of the groundwater and aquifer. Besinger and his colleagues nearly eliminated the need for roadside swales in Wildwood. “Instead of knocking down all the trees, we went to a 23-ft roadway, and the trees are right up against the road,” Besinger said. “We saved some 33 ft of right of way, and it’s just land, not swales.”

 

In addition, four of the subdivision’s six ponds will act as retention basins. The system promotes groundwater recharge, and most water is returned via the swales to the wetlands. Specially engineered bridges and causeways supported by retaining walls will convey traffic over the wetlands to minimize potential harmful effects.

 

 

Why Porous?

Shrake said Wildwood’s pavement system choice came down not just to its appealing look but also to meeting environmentally-driven construction goals. “If we did a normal road, we would have had to put ditches in and taken out trees all throughout,” he said.

 

In fact, Shrake had originally developed a traditional design for Wildwood in 2001. However, he and Besinger scrapped the plans and took an entirely different approach when Shrake learned about the benefits of porous pavement at a seminar. McHenry County officials carefully considered the new design proposal and eventually gave Wildwood’s all-porous construction plan the green light.

 

Looking Ahead

“This system is a long-term, low maintenance and durable poststructural best management practice and supports low-impact development (LID) methods,” Taylor said. “This system will reduce runoff, provide treatment of first-flush pollutants, provide underground storage and promote groundwater recharge. In addition, this site will conserve and improve land usage, negate the need for additional surface retention ponds and provide more land for sale as construction sites.”

 

Other conservation efforts being made at Wildwood include planting trees native to the region, winding roads around the 3,500 trees that exceed 8 in. to avoid removal, dedicating more than half of each three-acre home site as a no-build conservation area and enforcing protective covenants to maintain the development’s natural resources.

 

“The combination of all these elements will help to protect the integrity of the ecosystem, and I believe that Wildwood will be a model for conservation in future residential development,” Besinger said. “And I believe that permeable pavement will become a standard for roadways in the future.”

About the author

<i>Caitlin Cunningham is managing editor for</i> Storm Water Solutions.<i> Cunningham can be reached at 847.391.1025 or by e-mail at [email protected].</i>

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