High-pressure barriers, built in the 1960s to hold the ocean at bay, have failed to halt the flow of seawater into South Bay water basins.
In addition, huge pools of saltwater trapped inside the barriers have continued to move inland, closing dozens of drinking-water wells from Manhattan Beach to central Torrance and threatening several others in Carson that were once thought safe.
These developments, detailed in new studies, have prompted water officials to conclude that the two barriers, stretching 13 miles along Santa Monica Bay and Los Angeles Harbor, must be reinforced and expensive cleanups begun if South Bay ground water is to remain potable.
"We're talking about something that could end up costing on the order of $50 million over a period of years," said John G. Joham, general manager of the Central and West Basin Water Replenishment District.
A third barrier, at Alamitos Bay in Long Beach, is perhaps 95% effective and has virtually removed the threat of chloride contamination to that city's drinking water, county and city officials say.
"The Long Beach area is pretty well protected," said James A. Rancilio, the engineer who directs barrier operations for Los Angeles County. "I don't think they will ever have this saltwater problem in Long Beach."
However, if left unchecked, the South Bay saltwater migration could eventually taint not only the entire West Coast Basin, but the Central Basin to the north and east, according to the replenishment district, which imports water for both. The South Bay's one million residents get about 15% of their water from wells, and another two million people in the Southeast and Long Beach areas get nearly half their water from the Central Basin. The rest is imported at about twice the price of well water.
Representatives of the county Flood Control District and the replenishment district met Thursday to review possible solutions to the South Bay problem.
Officials say that a new, unreleased report and a second one also due this year provide technical information that will allow them to draft a comprehensive plan to stop saltwater intrusion and begin to purge the salt from ground water supplies.
"Everybody's itching to get going on this," Joham said. Because it has taken years to complete the reports, there is a sense of urgency in adopting a plan, he said.
Municipal and private water companies, which rely on ground water supplies and would be asked to pass along the high cost of cleanups to their customers, say they are anxiously awaiting the proposal.
"The most important thing is to try not to lose the entire basin," said Robert O'Cain, Torrance municipal water superintendent. "That would be disastrous. The basin is still quite a supply of water, and in times of drought we rely very heavily on it."
At least 20% of the storage capacity of the West Coast Basin, which underlies the South Bay, is already inundated by water too salty to drink, studies show. Since 1950, about 45 South Bay wells have been closed because of high chloride levels, including one this year about three miles from the coast near the Torrance Civic Center.
The leading edge of the massive wedge of saltwater is only about 1,000 feet--or two to three years--away from two other Torrance wells that provide about 10% of the city's water.
May Last 10 Years
O'Cain estimates it will cost $1.3 million to construct replacement wells and storage facilities a mile east at Western Avenue. Even then, he said, the new wells would be lost in about a decade if the saline wedge continues to move at its current pace.
Water officials have known for many years that the saltwater trapped inside the barriers was moving progressively inland.
It has been pulled by the pumping of inland wells, which lowers the water table and leaves a vacuum that the seawater fills. And, in an ironic twist not fully anticipated, the trapped saltwater also has been pushed inland by the powerful streams of freshwater injected into aquifers by the barriers themselves.
Steady Move Inland
A 1986 replenishment district report said a saltwater wedge that stretches from Los Angeles International Airport to the Palos Verdes Peninsula had moved a mile east since completion of the West Coast Barrier 15 years before. The wedge continues to move inland at a rate of up to 400 feet a year, the report said.
Water officials also have known that leaks were occurring in the coastal barriers, which were designed to be 100% effective, said the county's Rancilio.
But it was only recently, as consultants pulled together years of data on the leaks, that the extent of the problem became clear, he said.
Studies now indicate that the nine-mile-long barrier along Santa Monica Bay is only about 90% effective overall, leaking most in the Hermosa Beach, Redondo Beach and Torrance areas, Rancilio said.