Low-impact development and all that encompasses can be easily summed up in two words: water quality. At least that's the goal. For the Green-minded builder, techniques are evolving to help him or her reach it. In King County, where an effort is under way to protect Puget Sound from stormwater runoff and the pollution that accompanies it, LID is required for new subdivisions-to the extent that 10 percent of the impervious area of a development has to go through one or more Best Management Practices, says Rebecca Cushman, project engineer with Triad Associates.

NAVIGATING LID

Triad is a consulting firm that works with builder-developers in Washington. The majority of its clients seeks Triad's services for help in the planning and permitting process and in navigating the differing rules and regulations regarding LID in county and city jurisdictions, says David Manning, Triad's marketing director.

Just as rules and regulations differ from one jurisdiction to another, so do attitudes toward implementing and encouraging LID. "That can make it difficult to do LID,
Manning says. "That's why HBAs have lobbyists-or hire people like us who have deep relationships with jurisdictions.

Kirkland is one jurisdiction that Manning describes as "very progressive
in allowing builders to try a new LID technique and then watch it to see how well it works.

"Bottom line,
Manning sums up, "it's all coming down to clean water.

LID is one pathway to clean water. A builder who does everything he can to reduce his impact is Chris Chase, whose Mukilteo, Wash., firm, Cottage Werks, makes building small the first priority.

Chase, who primarily does infill, looks for nontraditional lots (he calls them lots with "wrinkles
) and designs and builds the house for the site. He likes to bring mulch in to reduce soil erosion on the site and reduce runoff, which has the added benefit of providing a stable working surface. When it comes to landscaping, Chase says he thinks in terms of preventative design, to manage and control water on the site.

RUNOFF REDUCTION METHODS

Chase also likes pavers, which he says "provide a huge economic advantage overall. The surfaces hold up better; they don't crack like concrete eventually will do, and they don't break down like asphalt. We lay a gravel bed under them and get better compaction and settling over all. We're saving money there.

The homeowners Chase works with are losing their affection for sod and turning to what he calls "natural-style yards.
That plays directly into a key LID tenet: keeping the native vegetation and soils on site. "That's what has adapted to this environment,
says Linda Lyshall of the Puget Sound Action Team. "If it's left alone, it will naturally deal with stormwater.

When a site is fully developed, stormwater runoff can be up to 20 to 30 times what it would be on undeveloped land. One way to keep that runoff and its attendant pollution out of Puget Sound is to keep the water in the watershed, where it belongs. That can be done through rain gardens (shallow landscaped areas composed of amended soils and moisture-tolerant plants that provide a temporary holding area for rainwater to give it more opportunity to infiltrate the ground), wetlands or Green roofs.

Use of pervious materials, which also allow water to infiltrate the soil and trap pollutants, for roads, driveways and patios, is another way for builders to keep their footprint on the land small. "We're finding that works really well,
Lyshall says. "It surpasses all expectations.
Permeable paving surfaces at a King County office building infiltrated nearly 100 percent of stormwater runoff over a six-year period and showed no detectable levels of copper or zinc in samples taken from those surfaces.

Mulch, or compost, is now an accepted Best Management Practice to prevent erosion under the U.S. EPA's National Pollutant Discharge Elimination System, which requires all point sources discharging pollutants into U.S. waters to obtain a permit. That's a boon for composters such as Cedar Grove Composting-and for builders, too.

Jami Burke, soil consultant with Cedar Grove, says that by 2009, all of the municipalities in King and Snohomish counties will have post-construction soil regulations in place for soil quality and depth. "What we're trying to prevent,
Burke says, "is the typical construction site where topsoil is scraped from the surface and the site continues to be compacted over construction.
The recommendation is to "rip,
or break up, the subsoil and then bring in compost to amend the soil at the end of project to a depth of 12 to 18 inches.

FUTURE TREND

Builders can also use a compost "sock
as a site wrap to protect the native soil from compaction. The sock is photodegradable, which Burke says makes it a good choice for construction, if a site is under development for a year or more.

"There are a lot of places where a silt fence (a commonly used BMP for managing erosion on a site) can be replaced with a compost filter sock,
Burke says. "The compost can be blown into place onsite without any trenching.

Jurisdictions are looking at incentives to encourage more builders to use LID techniques, Cushman says. For example, use of LID techniques can provide developers with more buildable lots by reducing size requirements for stormwater ponds and providing incentives such as density bonuses. More information on low-impact development can be found at psat.wa.gov/LID.