Washington's Kitsap County and all four of its cities are rapidly embracing cleaner storm water systems, commonly called low-impact development.

City and county authorities have revised their development codes and trained their engineering staffs to encourage low-impact development, said Art Castle, executive director of the Home Builders Association of Kitsap County. Now, local officials are pushing to get public and private engineers to incorporate low-impact development into their projects.

"Kitsap County is the low-impact-development capital of Washington state," Castle declared Tuesday at a meeting of the Kitsap Regional Coordinating Council. "No other county has this level of involvement."

Castle has been working for two years with city and county engineers to develop a kind of "cookbook" of low-impact recipes that developers can use in their project — one that's expected to be endorsed by the Washington Department of Ecology, which provided him a grant to come up with the guide.

In about a month, the guidelines will be ready for adoption by the county and cities, Castle said.

Several projects incorporating low-impact development techniques are under way in the county. Bremerton's Blueberry Park on Sylvan Way, now under development, was designed as a model of low-impact development, as are sidewalks on Poulsbo's Caldart Avenue and the future Silverdale Community Center on Randall Way.

Old-fashioned notions of building big storm water ponds encircled by chain-link fencing are going out of style, Castle said. Developers are realizing that the ponds are taking up valuable land that could be used for houses. Such storm water systems also require expensive piping.

On the other hand, low-impact development is about letting rainwater soak into the ground, as it would in a natural system. "Pervious pavement" consists of special concrete and asphalt mixes that allow water to drain straight through. "Bioswales" infiltrate water flowing through wide grassy ditches. "Rain gardens" temporarily store water in underground beds of gravel. And "green roofs" use natural vegetation to increase evapotranspiration and reduce the runoff rate.

Because Kitsap County receives 80 percent of its drinking water from groundwater wells, replenishing underground supplies must be a long-range goal, said Dave Tucker of Kitsap County Public Works.

"We have traditionally thought of storm water as a waste stream; we try to get rid of it," Tucker said. "We need to think of storm water as a resource."

Storm water is considered the major pollution problem for Puget Sound, because water flowing over the ground picks up oil and other chemicals and delivers pollutants to streams, wetlands and estuaries. Water that soaks directly into the ground is far cleaner, while small amounts of pollutants become trapped in gravel or soil.

Engineers who aren't yet comfortable with low-impact development have been slow to use it, said Phil Williams, Bremerton's Public Works director. But the city's experience has been favorable, and that increases confidence.

The city laid 500 feet of pervious asphalt on Schley Boulevard going into the new the East Park development near Manette. Crews tore up and pulverized the old concrete street to create a base that stores water beneath the pavement.