Selenium Levels in Delta Bring Alert to Water Users

Wildly fluctuating test results have indicated alarmingly high levels of selenium in waters of the Sacramento-San Joaquin Delta, it was disclosed Thursday.

Although state officials said they do not believe the levels to be a public health threat, they nevertheless are warning municipal water users of the California Water Project to monitor water supplies used for drinking closely.

One official, Larry Mullnix of the state Department of Water Resources, said he doubted that the selenium-tainted water would raise health concerns in Southern California because the water would be thoroughly diluted before it reached the Southland in the long California Aqueduct.

Mullnix said department officials are skeptical of initial water tests in the delta region that show a range of selenium readings for drinking water from relatively safe levels to measurements far in excess of safety levels.

Even so, Mullnix said, the department would rather err on the side of caution and issue the warnings to municipal users of the California Water Project rather than do nothing and face possible serious consequences for failing to issue the alert.

Selenium is a trace element found naturally in the environment. In small amounts, it is a requirement for good health in humans, but can be lethal in heavy concentrations.

Heavy concentrations were found in the Kesterson National Wildlife Refuge a few years ago and were blamed for causing death and deformities in birds and other wildlife. A federal cleanup operation, estimated to cost $26 million, is under way at Kesterson Reservoir in Merced County.

The first phase of the enormous project, which started last month, involves draining contaminated water from the reservoir into the San Joaquin River, which flows into the delta, the main collecting pool for the state Water Project. The selenium-tainted water first is diluted before being pumped into the San Joaquin.

Mullnix said the source of the selenium measured in the water tests has not been determined. “It does not look like this is related to Kesterson,” he said. “It could have come from some drainage districts between Kesterson and the delta.”

He said the tests that produced the “alarming data” were taken Feb. 10 at three sites at or near the delta: at the Harvey O. Banks pumping plant; at the federal Delta Mendota Canal pumps; and at Vernalis on the San Joaquin River south of Stockton.

Water tainted by selenium to a level of 10 parts per billion is safe for drinking, according to the Environmental Protection Agency. But, Mullnix said, tests at the Vernalis site show selenium at 21 ppb; at 18 ppb at the Banks pumping station; and at 12 ppb at the Delta Mendota pumps.

Results of the tests were received by the Water Resources Department on Wednesday and Mullnix said samples were reanalyzed by laboratory technicians. On the second test, the results fell easily below the federal safety standard for drinking water.

He said the lab people were unable to explain the wild variation in results.

Results of separate tests taken at the same sites on Feb. 19 and Feb. 22, he said, again showed selenium levels well below the danger level. Additionally, tests are now being taken daily instead of weekly.

“We don’t know what we have,” Mullnix said. “We think everything is OK but we are not taking any chances. We don’t think there is a public health threat.”

Officials said that alerting municipal water users to the possible threat is required under previous law and under Proposition 65, the anti-toxics and clean water initiative enacted in 1986.

The alerts will apply to state Water Project supplies provided to all or parts of San Joaquin, Alameda, Santa Clara, Contra Costa and possibly Stanislaus counties, Mullnix said. The Metropolitan Water District of Southern California also was alerted, although Mullnix stressed that the chances of the Southland receiving tainted water are virtually nil.