By Matthew Power. These days, paving a driveway or a street in a new community costs about $15 per square yard. What's more, that impervious surface amplifies the volume of rainwater that has to be carried away in storm gutters, drains, and culverts. Exceed a certain volume and the runoff has to be treated by your local jurisdiction, which makes for unhappy officials and hikes in impact fees.

The NAHB Research Center recently challenged the conventional pave-and-drain method of site development, at a place called Kensington Estates, in Pierce County, Wash. Research Center experts redesigned the site using new technologies and techniques intended to reduce environmental impact. The results: big savings on storm drainage, erosion control, and site prep and utilities, with only slightly higher costs for road construction.

Neil Weinstein, executive director of the nonprofit Low Impact Development Center in Beltsville, Md., has worked closely with the NAHB. His group encourages the use of development techniques that go lighter on the earth.

"We have a number of pilot projects throughout the country," Weinstein says. "We usually start with conservation techniques and work from there."

Many of the techniques, he says, are quite easy to adopt and can end up saving builders money -- even paving, which is traditionally one of the biggest site costs. "It has a lot to do with grading, which can be done a lot less intensively."

Take a look at this quick guide to some of the basics of low-impact development (LID). With thoughtful planning, you may save money on your next development, at the same time winning support from municipalities reluctant to deal with more polluted stormwater runoff.

Photo: Harry Whitver

Preserve Open Space

Because natural biofilters are so important to LID, keeping large "green" areas intact is a critical first step in sustaining densely developed areas nearby. Trees provide a buffer for noise pollution, while grasses and wetlands offer natural building blocks for the creation of bioretention ponds that can naturally treat stormwater runoff. As an added bonus, wildlife habitats can be preserved without pavement causing a major disruption of local migratory patterns.

Photo: Harry Whitver

Direct the Flow

Control rainwater runoff from the house with gutters, downspouts, and grading. Also, choose roofing and flashing materials that are less likely to add to pollution. Direct runoff away from driveways and toward planted retention areas. Separate sidewalks from main streets with depressed grass swales, and grade walkways so that runoff flows into the swales (not the street). The swales should direct water to a nearby bioretention area or pond.

Photo: Harry Whitver

Catch and Release

Rain barrel water catchment isnt just for graywater systems. The barrels have earned the respect of municipal planners in Canadian cities--and more recently Boston--because new systems capture high-volume runoff from housing rooftops and slowly release it back into the ground, filtering out grit and running other pollutants through natural rain gardens for further filtering. One Toronto-based company, RiverSides, sells 150-gallon barrels that are scaled and designed for residential use.

Photo: Harry Whitver

Make It Porous

For pervious drives and walkways to work, soil and gravel layers must be prepared to allow water time to settle and give harmful materials such as oil and antifreeze a chance to be filtered out before they can enter groundwater. In warm regions, use porous pavers or porous asphalt. In colder climates, salt and sand may clog gaps between porous pavers, so plan accordingly.

Photo: Harry Whitver

Shrink Flatwork

As a first, important step, design narrow walkways and driveways to the minimum acceptable width. Use the minimum parking-space-to-unit ratio. Also, seek relaxed setbacks on the street side to keep driveway length to a minimum. Consider the use of shared driveways when possible. Put sidewalks on only one side of the street. Consider using the "two-track" type of driveway (with pavers only under the vehicles wheels) for best water penetration.