Low-impact development is new approach to an old problem
- October 27, 2010
In the 1970s, detention ponds were state of the art. The newly passed Clean Water Act charged localities with protecting streams from heavy rains that raced off roads, roofs and other man-made surfaces.
The idea behind the ponds was to blunt storm-water runoff so it wouldn’t erode soil and pollute waterways. For three decades detention basins, which temporarily store water that slowly drains to another location, seemed the best tool on hand.
Fast forward to today. “The science has been continually evolving,” says Randy Bartlett, deputy director of public works for Fairfax County. Now developers, lawmakers and municipalities understand how efficiently green space absorbs and filters water. The knowledge has given birth to a new generation of storm-water management known as “low-impact development,” or LID.
One of the biggest differences between LID and the traditional basins (also known as best management practices or BMP) is that LID makes water design priority one. “On a lot of development, they worry about transportation — how are they going to get people to and from the site — and they focus on architecture, and storm drainage is an afterthought,” says Bartlett, “The idea of LID is that we need to look at storm water as a resource upfront.”
LID begins with an inventory of a site. Natural hydrologic features — mature vegetation, naturally porous soil, etc. — are valued as free ways to meet government-mandated limits on water volume and nutrient levels. Buildings are positioned or clustered to preserve these natural assets. Then the remainder of the site is designed to minimize runoff. Developers using LID draw from a buffet of options including pervious concrete, vegetated swales (channels used in place of paved gutters) and bioretention gardens.
The public benefits of LID include replenished groundwater supply, improved regional water quality, pollution abatement, and habitat preservation/creation. On-site benefits include increased property value and lot yield.
In 2007 the EPA released a cost-comparison of more than a dozen LID projects nationwide, including a new retail development in Fredericksburg. In nearly every case, LID cost less than conventional best management practices, due to the need for less infrastructure, such as detention ponds and pavement. Savings ranged from 15 to 80 percent depending on LID techniques employed.
And that’s just in capital investment. “We save about $400 a year in storm-water fees,” says Michael Rolband, founder and president of Gainesville-based Wetland Studies and Solutions Inc.
And there are public relations benefits. In 2005 the construction consulting company moved into an LID headquarters that it designed. “It’s the right thing to do,” says Rolband, who notes that interest in LID is on the rise among clients.
“A few developers are very creative and come in using these new, different practices,” notes Bartlett, though for the most part, LID in Fairfax is driven by the county’s educational efforts. It’s not hard to explain, says Bartlett. People get it. “It’s about using the whole site, and understanding that a forest on-site can do far more than a constructed feature.”