EurekAlert: “A simple column of common soil can reverse the toxic effects of urban runoff that otherwise quickly kills young coho salmon and their insect prey, according to new research by Washington State University, NOAA Fisheries and the U.S. Fish and Wildlife Service. The affordable and remarkably effective treatment offers new promise for controlling toxic pollutants that collect on paved surfaces and wash off as stormwater into rivers, streams and the ocean. Polluted stormwater has been identified as a risk factor for many threatened and endangered salmon and steelhead and has caused die-offs of coho salmon in the Pacific Northwest. The research builds on increasingly common building practices that promote natural infiltration of stormwater into the ground. It indicates that a “bioretention” system that first filters runoff through a basic soil mixture removes toxics lethal to aquatic life. Such systems are increasingly found in Washington State’s Puget Sound area as people build “rain gardens” that trap runoff before it gets to a creek or stream. The research published in the journal Chemosphere examined the toxic effects of runoff collected from a major Seattle highway during storms. The untreated runoff killed all juvenile salmon exposed to it within 12 hours. But all fish survived in runoff filtered through the soil column of sand, compost and bark. The soil filtration also prevented reproductive damage to tiny insects salmon eat.”