The county’s Department of Environmental Health (DEH) is still uncertain of the source of the solid sewage debris that began washing up on the western shore of Fiesta Island last week. “There’s no way to know where it came from,” said Mark McPherson, chief of land and water quality with DEH. “If it was dumped from a vehicle, those tanks usually hold anywhere between 1,000 and 5,000 gallons. But there’s no way to even know if it was dumped from a vehicle. Right now we have no smoking gun, so to speak. We can’t attribute to any point or actual discharge locations.” DEH was notified about the contamination on Monday, Sept. 17 and began posting signs around the boat launches and swimming areas. San Diego Bayfair organizers were concerned that the sewage would force the county to shut down the thunderboat races, but health officials felt the contamination levels would safe for the race to continue. Warning signs did stay up at beaches, including the western shore of Fiesta Island, which is the best spectator spot for the three days of races. “With the wind action out there, it pushes the material in to the shore area, and that’s where they’re collecting,” McPherson said. McPherson said city crews are cleaning up the organic waste that has washed up on the beaches since the discovery. “Any liquid material that’s in the bay, there’s no way to clean it up and it becomes part of the bay. But the solid material, the city has been going out and raking the beaches every morning and collecting the material and taking it to the landfill,” he said. As for finding the person responsible for releasing the sewage in Mission Bay, McPherson implied that the chances are slim. “I would assume that if a septic truck was sitting at the bay pumping sewage into it, with all the media attention on the bay being closed because of illegal sewage and someone saw it, I would guess that they would give us a call,” he said. “We haven’t had that call.”