Sludge Dumping in Sea Extended by 90-Day Study

Sewage sludge may continue to be dumped on the ocean floor off the Palos Verdes Peninsula, in defiance of the federal Clean Water Act and the objections of environmental groups, under a 90-day arrangement approved Monday by state water quality officials.

The sludge comes from sewage treatment plants operated by the Los Angeles County Sanitation Districts. Relatively small amounts of the sludge, or concentrated sewage, are involved, but the waste is considered sufficiently harmful that Congress decided in the 1970s to forbid its discharge into the ocean.

The sanitation agency, which disposes of nearly all local sewage that does not originate in the city of Los Angeles, has buried most of its sludge in landfills or converted it to garden fertilizer for many years. But the agency still pipes a thinned form of residual sludge, known as centrate, into the sea and missed a July 1 federal deadline to halt the practice.

At a hearing Monday, the state Regional Water Quality Control Board delayed a vote that would have permitted the county to dump centrate at sea for two more years.

Time for More Study

Instead, the board promised county sanitation officials that no penalties would be imposed for 90 days while the problem is studied further. At the end of 90 days, the board is expected to reconsider the county’s argument that a grace period of two years is needed before the discharges can be stopped.

Sludge derived from sewage has been blamed for widespread damage to undersea life, with some of the most serious problems found off Los Angeles on the floor of Santa Monica Bay. Scientists have found a large area of the bay where the sea floor is covered with a thick blanket of toxic black sludge, bubbling with methane gas and nearly devoid of marine life.

The Santa Monica Bay sludge field resulted from 30 years of heavy dumping by the city of Los Angeles from the Hyperion sewage treatment plant near Playa del Rey. The city stopped piping sludge out to sea in November under pressure from the federal government and the courts.

Charles W. Carry, chief engineer for the county sanitation districts, said Monday that the volume of centrate discharged off Palos Verdes is a mere fraction of the thick sludge formerly discharged from Hyperion or the county’s own treatment plant in Carson.

When raw sewage arrives at the treatment plant, it is 90% liquid, mostly water, and about 10% solids. The solids are removed through settling, then distilled for 15 days in huge pressure tanks, and finally are spun in centrifuges to remove even more of the moisture. The thick cake batter-like material, or sludge, that emerges from the centrifuges is buried or allowed to decompose into fertilizer. The liquid is drained off and piped out to sea through an ocean outfall pipe off White’s Point on the Palos Verdes Peninsula.

Centrate is the finely screened solid material left in the waste water. Carry said Monday that chlorine is added before centrate is piped to sea to minimize any threat to marine life.

Environmental activists Monday disputed Carry’s assertions and said they have observed a marked increase in the sewage sludge detected off Palos Verdes, with an accompanying drop in the acreage of kelp beds.

Rimmon Fay, a marine scientist and frequent critic of ocean sewage dumping, said that since January his attempts to trawl the sea floor off Palos Verdes for samples of marine life have been thwarted by a thick layer of sludge. Last year, he said, “we could trawl anywhere we wanted, even right off the mouth of the outfall.”

“We don’t really know where the recently appeared sludge field is coming from,” said Don May of Heal the Bay, an environmental group which advocated Monday that the county be fined $25,000 a day for not meeting the July 1 deadline. “We assume that it must be coming from the centrate, but we don’t really know.”