As the San Diego spill reminded people, the nation's shorelines have long been the dumping ground for urban sewage. Each day, billions of gallons of sewage are poured into the sea, with varying levels of treatment to kill the bacteria that can make humans ill.
Compared to the daily deluge of sewage from Los Angeles and Orange counties alone--643 million gallons of partially treated effluent--the San Diego spill from a ruptured, 29-year-old concrete pipeline near Point Loma is pint-sized.
But the spill, spewing 180 million gallons a day just offshore, has thrust ocean dumping into the public spotlight for the first time since a spate of sewage accidents contaminated Los Angeles-area beaches in the late 1980s and George Bush's 1988 presidential campaign attack on Michael S. Dukakis for pollution in Boston Harbor.
While the amount of sewage spilled in San Diego is small in comparison to the amount discharged routinely in U.S. waters every day, environmentalists say such flagrant incidents sharpen the public's concern over marine pollution.
"(The) perception on this is it's comparable to what happened with the Exxon Valdez," said Suzanne Iudicello, an attorney with the Center for Marine Conservation in Washington, D.C. "We have a highly visible spill in a highly visible place and it's got everybody's attention.
Opinions differed Thursday on how marine life would be affected by the San Diego spill. David Skelly, a coastal engineer at Scripps Institution of Oceanography, called the spill "an environmental disaster," but others said most environmental effects would be short term.
John Grant, a marine biologist with the California Department of Fish and Game, said: "A year from now, two years from now, you won't know this happened. But that isn't the (immediate) issue. We're talking about 50 tons a day of solid waste falling into the ocean in 35 feet of water."
Grant said there will be "significant impacts" in the immediate vicinity of the sewage plume, and that fish and young kelp plants could be hurt.
Ecologist Alan Mearns with the National Oceanic and Atmospheric Administration predicted that the area will quickly recover once the spill is stopped.
"As soon as they button up the spill there will be some contamination, particularly bacteria for a few days, but it will clean up pretty quick--particularly this time of year if more storms come through the area," Mearns said.
Mearns, who is on a National Academy of Sciences panel examining waste-water management in coastal urban areas, spent 10 years in Southern California leading a team looking at sewage discharges.
"The main problem is that the (San Diego) discharge is closer to shore," he said. The rupture in the sewage line is 3,150 feet from shore at a depth of 35 feet. Normally, the line extends 2.2 miles to sea and discharges effluent at a depth of 220 feet.
The shallow depth and proximity to shore means that beaches are likely to be off limits for some time after the spill is stopped. Another problem, Mearns said, is that the effluent is flowing into the ocean in one large plume instead of seeping out of the pipe through a matrix of small holes, known as diffusers, which allow the waste to dilute and mix more readily with the water.
Even when sewage pipelines do not rupture, the effluent pumped into oceans from sewage treatment plants is far from pure.
Some treatment plants, including San Diego's, provide only limited processing of the effluent before discharging it. The limited treatment--known as advanced primary treatment--amounts to holding the sewage in tanks until about 75% of the solids settle to the bottom. The bottom sediment or sludge can be disposed of on land, but the rest--mostly water still contaminated with raw sewage--is discharged to sea.
Despite a federal Clean Water Act requirement of more complete "secondary treatment" since 1972, loopholes in the law and official waivers have allowed some sanitation districts to escape the full requirement.
In secondary treatment, microorganisms called activated sludge are introduced into the sewage to digest and decompose the waste that does not settle. Secondary treatment eliminates another 10% to 15% of the suspended solid waste that remains after primary treatment.
After more than a decade of federal litigation, the city of Los Angeles is in the process of upgrading its huge Hyperion sewage facility near Los Angeles International Airport to full secondary treatment.
The city had fought the government's order that the massive outpouring of waste into Santa Monica Bay be cleaned up to meet federal standards. In 1987, the city agreed to pay a $625,000 penalty for missing a 1977 deadline for complying with the full secondary treatment requirement. It was one of many fines paid by the city and at the time the largest collected for Clean Water Act violations.