A dozen wild bird eggs plucked from nests on the west side of the San Joaquin Valley show how easily things can go awry when trying to clean up the region's tainted farm drainage.
The eggs, collected last year in fields that are part of a treatment project, contained the same lethal levels of selenium that poisoned migrating waterfowl more than two decades ago at the Kesterson National Wildlife Refuge near Los Banos.
The 2005 egg contamination was the worst detected in five years of monitoring at the project, which recycles selenium-laced agricultural drain water by using it to irrigate crops.
The results, reported to the U.S. Bureau of Reclamation this summer, come at a time when the agency is considering greatly expanding such reuse areas as part of a massive proposed drainage program on the valley's west side.
The high selenium levels reinforce the concerns of the U.S. Fish and Wildlife Service, which has warned that the bureau's drainage plans could endanger thousands of Central Valley waterfowl.
"They have to be extremely careful; that water is so potent, they can't make any mistakes," said U.S. Fish and Wildlife biologist Joseph Skorupa. "If they make a mistake, they'll have dead birds."
The tainted eggs come from the Grasslands project, which has otherwise been a success in reducing the flow of selenium-spiked water into the San Joaquin River, where it could do environmental damage. The project takes drainage from fields south of Los Banos and uses it to irrigate crops that can tolerate the soil salts that accumulate in drain water.
A naturally occurring trace element, selenium is washed out of valley soils by irrigation. In drain water, it can build to levels toxic to wildlife, a problem that first came to light in the early 1980s at Kesterson, when widespread birth defects were found in birds that foraged in refuge ponds filled with farm drainage.
In the case of the 3,500-acre Grasslands reuse project, coordinator Joe McGahan said it is unclear why selenium levels suddenly jumped last year in eggs taken from the nests of black-necked stilts, a shorebird that is among several dozen species that frequent the site.
"We had no reason to think in 2004 it was going to go up like that," he said.
McGahan added that the monitoring found no deformed or dead bird embryos.
But Skorupa, an expert on selenium contamination in the Central Valley, said that was only because a relatively small number of eggs were tested.
"We would have expected them to find deformed embryos if they had checked every egg" in the sampled nests, Skorupa said.
This year Grasslands managers have taken steps to reduce bird exposure to selenium.
They have created nearby habitat to lure waterfowl away from the reuse area and regraded drainage channels to make them less attractive to foraging birds.
They have also tried to drive the birds away by shooting firecracker shells. But McGahan acknowledged the limits of such efforts.
"You can't haze and prevent birds from nesting," he said. "It's not practical. But you can do the best you can to try to scare off as many birds as possible."
The acreage devoted to such reuse areas could grow significantly under proposals in the final stages of review by the reclamation bureau.
The agency is under court order in a long-standing lawsuit to solve the drainage problem on about 379,000 acres of west-side farmland with a high water table. The bureau, which supplies the area with federal irrigation water, was supposed to have made a final decision this summer on how to proceed. But negotiations to settle the case have left the matter up in the air.
In documents released this year, the reclamation bureau outlined a variety of options, favoring a complex solution that would cost nearly $1 billion. It revolves around taking most of the poorly drained land out of irrigation and converting it to dryland farming or fallowing it, a step that could cost federal taxpayers more than $700 million.
The proposal also calls for treating drainage from land remaining in irrigation through a combination of 7,500 acres of reuse areas, high-tech filtration and nearly 1,300 acres of selenium-spiked evaporation ponds.
But it's likely that either a settlement or the agency's final decision would retire less land than the Los Angeles-size chunk the bureau has proposed. Most of the acreage lies in the huge, politically powerful Westlands Water District, which opposes extensive land retirement.
The less land taken out of irrigation, the more drainage treatment will be required -- and the more evaporation ponds and reuse areas will need to be built.
That has raised alarms at the fish and wildlife agency, which in a report earlier this year said the "service remains very concerned with the potential for adverse environmental effects of installing over 3,200 acres of highly toxic evaporation ponds and up to 19,000 acres of drain water reuse" -- the maximum created under any of the treatment options.
Michael Delamore, an official in the bureau's Fresno office, said new reuse areas constructed under the reclamation proposal would not have the open drain-water channels that are the presumed source of contamination at the Grasslands project.
"You have to identify what happened, what resulted in this exposure that led to these high [selenium] levels and address that component," Delamore said. "And if indeed it is the open ditch irrigation system, we've already addressed it. If it's something else, then we'd have to address it."
Conveying the tainted drain water in pipes -- as is planned -- will be an improvement, said Terry Young, a senior scientific consultant for Environmental Defense, an environmental group familiar with the Grasslands project.
But she warned that it would not eliminate potential dangers.
"The bottom line is: If you lose control of one of these systems, you can have a disaster worse than Kesterson within a period of a very few months, if not days."