Wednesday, April 9, 2008 | Last year, when scientists were studying the effects of San Diego’s sewage on the offshore marine environment where it is discharged, they noticed something unusual.
The scientists were working to determine whether dumping treated sewage off the Point Loma coast was having a negative impact on the fish and other creatures living nearby. San Diego Mayor Jerry Sanders sought the analysis to determine whether it was necessary to upgrade the city’s sewage treatment or to simply seek a waiver of federal standards. The scientists concluded that the underwater environment wasn’t being impacted by the sewage — with one caveat. Some fish in the area were contaminated with detectable levels of PCBs, a family of toxic cancer-causing chemicals, and scientists weren’t sure why.
Two potential sources were identified: The sewage outfall, a pipe that delivers waste 4.5 miles offshore, or a federally approved dump site for dredged sediment located to the pipe’s south, about five miles offshore.
The results from testing around the dump site, known as LA-5, have raised concerns among at least one scientist that contaminated sediment dredged to make room for shipping traffic in San Diego Bay may have been dispersed throughout the ocean. While regulators and environmental groups have focused on a proposed cleanup of contaminated sediment in the bay, toxic chemicals found farther out on the coastal shelf have received little attention.
Ed Parnell, a marine ecologist at Scripps Institution of Oceanography, said the presence of PCBs off-shore raises concerns that polluted sediment from San Diego Bay has been shifted around instead of cleaned up. The bay contains higher levels of contamination than the areas around the dump site and sewage outfall, Parnell said. But some fish around the dump site are contaminated, he said.
“You’re fast-tracking pollutants in the bay into the marine food web out there,” Parnell said. “That’s something we might want to rethink. … It’s a highway for pollutants from the bay to get out on the coastal shelf. You’re doing that at the expense of toxifying the coastal shelf.”
PCBs, polychlorinated biphenyls, are a family of chemicals used as coolants and lubricants in electrical equipment until their 1977 ban. They got into the environment when being manufactured and used, as well as from leaks or equipment fires. The chemicals do not break down in the environment and raise health concerns at concentrations as low as 22 parts per billion, the equivalent of 22 drops of PCBs diluted in an Olympic-sized swimming pool.
Even at low levels, the chemicals can be absorbed by worms or other creatures living in contaminated sediment. The pollutants work their way up the food chain, as those contaminated organisms get eaten by larger fish, which concentrate the cancer-causing chemicals in their livers, ultimately posing a threat to humans who eat the fish.
Parnell and other scientists who analyzed data collected by the city of San Diego as part of its water-quality testing around the sewage outfall noticed that rockfish caught around the dump site showed elevated levels of PCBs in their livers.
PCB levels in treated sewage are relatively low today, said Rick Gersberg, a San Diego State environmental health professor who contributed to the data analysis funded by the city of San Diego. But that does not mean the dump site is the source, he said.
“One cannot really define the source,” Gersberg said. “Who knows what is dumped into sewage?”
San Diego Bay has a variety of pollutants blanketing a wide swath of its seafloor, a toxic mix of PCBs and heavy metals currently the subject of a years-long cleanup effort targeting shipbuilding companies and the Navy.
The federal agencies that monitor and permit disposal at the dump site say they do not believe those pollutants from the bay are being transferred to the ocean, pointing to stringent biological testing that takes place before any dredging project is allowed.
When a local agency such as the Unified Port of San Diego wants to dredge the bay, it must take multiple borings of the target area. Those borings are analyzed to determine how concentrated contaminants are. If concerns are raised, dredged material cannot be disposed in the ocean and must be taken to a landfill. If the sediment is clean and sandy, it can be used to replenish beaches. If it is clean and full of gravel, it can be dumped at LA-5, an area about a mile wide and 660 feet deep, located along a gently sloping stretch of ocean bottom located deep enough that currents do not shift material around.
While extensive analyses are done before dredging projects take place, Robert Smith, an engineer with the U.S. Army Corps of Engineers’ Rancho Bernardo office, said no oversight happens while dredge projects are underway to ensure that what’s been permitted actually occurs.
“Who’s to say what happens with some of these dredge projects?” Smith said. “We’re not always watching.”
The U.S. Environmental Protection Agency has infrequently monitored conditions around the off-shore dump site. Allan Ota, an oceanographer with the EPA’s dredging and sediment management team in San Francisco, said the agency is conducting monitoring this spring, the first time it has done so recently. The EPA is required by law to maintain an effective monitoring program.
“The reality for us is that our budget is pretty limited and we don’t have regular money for doing monitoring work,” Ota said.
Extensive biological testing has not always been in place, and PCB pollution around the dump site could be decades old, the result of sediment unloaded before today’s strict regulations existed.
Brian Ross, a fisheries biologist with the EPA’s dredging and sediment management team, said sediment testing was improved in 1991, when modern standards for analyzing potential contaminants were adopted.
“There may have been things that slipped through the cracks, or (were dumped) back before we knew as much,” Ross said.
Even so, sediment dumped before 1991 has likely been buried beneath dredge material deposited in the years since, he said. The Navy dumped 7 million cubic yards of sediment in the late 1990s when it dredged to make room for a nuclear aircraft carrier (that’s enough sediment to fill 2,800 Olympic-sized pools). “If there was legacy stuff, it should be pretty well-covered,” Ross said.
Rockfish, which are long-lived, could show levels of PCBs because of chronic low-level exposure to contaminants over a period of decades, Ross said, or because of high-level exposure 20 years ago.
“We do look for it,” Ross said. “There shouldn’t be anything bad from the last couple of decades.”
Parnell, the Scripps professor, has continued his research into the dump site since last year’s study and is preparing to release a report detailing his findings. It is currently undergoing review, he said, and is expected within about a month.
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