PACIIFIC PALISADES, CA - AUGUST 07: Signs warn the public to stay out of the water in an area harboring high bacteria levels near a drain at Will Rogers State Beach on August 7, 2007 in Pacific Palisades, northwest of Los Angeles, California. Pollution at the nation?s 3,500 ocean, lake, and bay beaches caused more than 25,000 closing or swimming advisory days last year, 28 percent more than in 2005 and the highest number in the 17 years that records have been kept, according to the newly-released federal ?Testing the Waters? report by the National Resources Defense Council (NRDC). 10,000 of the closings, twice that of the year before, came from storm run-off and another 1,300 days were attributed to sewage spills. Fecal contamination from undetermined sources made up the rest of the closings. The vast pavement of large urban areas, such as the Los Angels Basin, adds to the problem by preventing run-off water from penetrating and percolating through the soil which acts as a natural filter before the water reaches the coast. At greatest risk of diarrhea and vomiting from exposure to the waterborne parasites are beach-going 5- to 12-year old children.