LOS BANOS, Calif. — More than two decades after toxic farm drainage emptying into a small wildlife refuge stilled the chatter of migrating waterfowl with death and deformity, the federal government is on the verge of deciding what to do with vast amounts of tainted irrigation water still produced by San Joaquin Valley croplands.
The selenium-spiked flows that poisoned ponds at Kesterson National Wildlife Refuge were shut down long ago. But the irrigation didn't stop, and the drainage continues to build up in the shallow groundwater table that underlies part of the valley's west side, stunting crops.
The U.S. Bureau of Reclamation is under court order to do something about the drainage problem. But its proposed solutions -- which involve treating the tainted water and taking a huge chunk of farmland out of production -- have raised alarms that they could wreak more environmental havoc while costing federal taxpayers a potentially enormous sum.
"There is no good answer to how to do this," said Joseph Skorupa, a U.S. Fish and Wildlife Service biologist who spent 16 years working on Central Valley selenium issues.
Nobody was thinking of selenium when growers persuaded Congress in 1960 to extend the federal Central Valley Project, the nation's biggest water supply system, to the San Joaquin Valley's west side.
But they knew there were problems with drainage, caused partly by insoluble clay beneath the groundwater. So the expansion's congressional authorization included a clause that the government would also build a drainage system.
In the 1970s, a master drain was partly constructed, ending in 1,200 acres of ponds at Kesterson Reservoir, where the farm water evaporated in the scorching summer sun.
Fish and Wildlife officials at the nearby refuge welcomed the drainage, which seemed like a blessing in a region where most of the vast historic wetlands had been filled or plowed under. Some 10 million to 20 million waterfowl winter or pass through the Central Valley every year looking for places to rest and nest.
But within two years of the drain's 1981 start-up, it was evident that something was terribly wrong.
The Kesterson ponds had become a death trap. Federal biologists discovered chick embryos were missing eyes and parts of their beaks. Others had only stubs where their wings and legs should have been growing.
Researchers testing the water and bird carcasses discovered toxic concentrations of selenium, which had washed by the ton into valley soils from the neighboring coast range.
Essential to human and animal life in minute amounts, selenium had reached dangerous levels in the irrigation drainage, which leached the chemical from the soil and carried it into the aquatic food chain.
The Kesterson drain was shut down in 1985. The ponds were covered with dirt. The old reservoir is now a field of brown grass guarded by a locked metal gate and red, white and blue U.S. government "No trespassing" signs.
But the drainage problem didn't go away. Landowners went to court, and in 2000 they won a U.S. Court of Appeals decision that the federal government had to provide drainage.
Now, the Bureau of Reclamation's proposal to create at least 1,270 acres of evaporation ponds as part of the drainage treatment has again raised the specter of Kesterson.
"My God," said Ed Imhoff, a retired U.S. Interior Department official who in 1990 headed a state and federal task force on valley drainage. "Why would we be replicating something that caused all the deaths and deformities at Kesterson? Why would we do that?"
Most selenium in the drainage would be removed by high-tech filtration and microbes before the resulting brine was piped to the ponds. But the water would still contain selenium at 10 parts per billion -- twice the U.S. Environmental Protection Agency's standard for aquatic life and five times a state standard used in some Central Valley wetlands.
Moreover, some scientists warn that the microbial treatment could convert the selenium into a more toxic form.
A March assessment by the U.S. Fish and Wildlife Service concluded that the proposed project carried an "incredible amount of risk and uncertainty" and predicted that several thousand birds could die from selenium poisoning each year.
Bureau of Reclamation officials acknowledge there will be bird losses and plan to create wetlands as compensation. Agency engineers say that though they initially experienced problems with a treatment pilot project, recent tests have yielded good results.
"It's not perfect. We're not getting all the selenium out. But we're getting most of it out," said Scott Irvine, an environmental engineer.