With a fluttering splash, the salmon vanished into the muddy roar of Pipers Creek. It was Nov. 6, 2006, the third rainiest day in Seattle's history, and this urban creek swelled with water pouring off roofs, driveways, parking lots and streets.

The water - storm water - is the next frontier of environmental cleanup and a key to saving Puget Sound. Storm water pounds stream and river habitats with frequent and intense floods. It carries filth and chemicals that threaten fish, streams and the Sound itself. And as governments gear up to stop it, builders and developers face more expenses and regulations, which they say can increase the price of a new home by $10,000 or more.

At the same time, the state Department of Ecology has put out rules requiring urban areas to have their own storm water management programs. Developers are worried the new regulations will ultimately cost too much in money, time and exposure to liability.

"I can see hours and hours and hours of doing it and then follow-up," says Kevin Russell, co-owner of Clawson Construction and Pacific Northwest Log Homes in Port Angeles. "Your whole day is going to be spent running around and checking things; heaven forbid you have to mitigate it." Add to that factors beyond the control of the developer, such as runoff from a neighboring property, and the fines could be punitive, he says.

And regulating new development can only do so much. Ultimately, governments and homeowners have to halt storm water pollution from existing buildings and streets.

Since the advent of the Clean Water Act in the 1970s, governments and industries have made progress cleaning up sewage and industrial emissions. Yet Puget Sound is deteriorating. Various fish and marine bird populations are declining. Chinook salmon in the Sound carry so much mercury and polychlorinated biphenyl (PCB) that the Washington Department of Health recommends that people limit how much of the fish they eat.

By 2020, 1.4 million more people are expected to make the Puget Sound region their home. That will mean more homes, cars, pavement - and more storm water. Storm water can be more complicated than pollution from sewage or industry, says Curtis Hinman,

a watershed ecologist with Washington State University Extension.

"Storm water is coming from everywhere you have development," Hinman says. "It's coming from many thousands or millions of individual actions daily across the landscape. We're starting to realize how much damage storm water can do."

Many of the actions that lead to storm water pollution are ordinary. Fertilize a lawn, drive a car, even let your cat roam outside, and you add to the pollution coming downstream.

Pipers Creek surges under dripping willows and big-leaf maples, providing park-goers with a scenic view of a salmon creek in action. Volunteers release chum into the creek each spring, and a few hundred return each year, along with a few Coho that are probably strays from other runs.

The creek used to be the outlet to a peat bog more than half a square mile in size, while most of the other twoand- a-half square miles of watershed was forest.

Not anymore. Now the creek is surrounded by Seattle neighborhoods, tiled with roofs and pavement. Builders compressed the soil, scraped off the duff, and built over the peat bog. The landscape no longer absorbs water, but sheds it.

While the volume of water used to stay consistent in all but the most ferocious storms, now the creek swells with every rain, sometimes threatening the survival of the fish. The surging water scours the creek, pushing aside the gravel where the fish bury their eggs. Or it can coat the eggs with a suffocating layer of silt.