Report Disputes Water District on Nitrate Pollution

OXNARD — A new study of Oxnard well-water contamination suggests that hazardous nitrate levels may be caused partly by low-quality river water filtered into underground basins by the United Water Conservation District--and not by the city’s pumping practices.

The finding contradicts an October report by United, which concluded that the high nitrate levels that shut down all 10 Oxnard wells were caused by excessive pumping by the city, farm fertilizers and leaking septic tanks.

“It is apparent that outside influences, not Oxnard pumping, have affected the water quality in these wells,” concluded the new report by Stetson Engineers Inc. of West Covina.

Stetson’s engineers recommend a follow-up study of the possible correlation between operations at the United spreading grounds in Saticoy and El Rio, and the water quality in wells nearby.

The report suggests that nitrate contamination--which at extreme levels can kill infants and sicken the elderly--may be spreading in underground basins downhill from the settling ponds toward Oxnard and the city’s wells several miles away.

“Personally, I think this report is very significant,” said Richard Eccles, water quality manager in Oxnard. “It’s truthful; it’s accurate.”

Because Oxnard officials disputed some of United’s findings last fall, city officials hired Stetson in December to conduct an independent analysis of United’s report. The water district agreed to pay 50% of the study’s cost.

However, United officials said Tuesday that they strongly disagree with some key findings, especially the implication that United’s spreading grounds may be part of the problem.

“I disagree wholeheartedly with that,” said Steve Bachman, ground-water program manager for United. “We have plenty of documentation to show that is not correct.”

United already regularly tests wells down-gradient from the spreading ponds for nitrates and has never found high levels, Bachman said. In fact, the same set of wells produces half of Oxnard’s water supply and meets all drinking-water standards, he said.

In addition, Bachman said concentrations of nitrates in the water pumped from the Santa Clara River to the holding ponds--about 2% of it reclaimed sewage water--have never approached levels that would make it undrinkable.

“Our source water has been tested for years and years, and it is always low in nitrates,” he said. “Our average on river water is about 6 or 7 [milligrams per liter] in nitrates, compared to the drinking water standard, which is 45.”

Oxnard shut down its wells, located miles from the spreading ponds in the city’s downtown area, in 1995 after nitrate levels reached 55 to 60 milligrams per liter.

Eccles said the shutdown translates into a huge taxpayer expense because water from city wells is cheaper than if bought from United, and only a fraction of the cost of high-quality water imported from Northern California, which the city uses for about half its water supply.

“It means that water rates could go up,” he said. “We have a large amount of money invested in these wells, and they are unusable now unless we blend them with real high-quality water.”

Eccles said 1995 was the first time in at least three decades that nitrate levels had exceeded state standards. He theorized that nitrates are higher in recent years because United’s opening of the Freeman Diversion Dam in 1991 drastically increased the amount of river water diverted to holding ponds and into aquifers.

“If you look at the whole picture, they really started diverting a lot of water in ’91 or ‘92, and it took a lot of time for that water to move to our wells,” he said.

United diverts about 60,000 acre-feet of water each year from the river into the Freeman dam, and about three-fourths of that is used to refill underground basins.

The recharge program has been hailed as a breakthrough in halting underground seawater intrusion and replenishing basins historically over-pumped by agricultural users.

And United officials said Tuesday that despite Stetson’s suggestion that the recharge water is causing contamination, the program is a huge success. Volumes of data show that the program is also benign, he said.

Yet Stetson said in its report that United repeatedly failed to provide raw data--instead of summary reports--that Stetson requested to properly analyze the quality of water used in United’s recharge program. The years-long averaging done in United’s report masked the true extent of nitrate concentrations in river water that would filter through sandy soil into the Oxnard Aquifer, the report added.

Bachman countered that United, in background documents supporting its fall report, provided Stetson with plenty of data to support United’s conclusions.

“We have a half-million data points in our database, and to give them everything would have been an overwhelming amount of data,” he said. “And we thought that was way outside their scope [of their study].”

Even before Stetson recommended a follow-up study, Bachman said United had already begun an expanded monitoring program by increasing testing at two dozen existing water wells and by installing six new ones in El Rio.

There are holes in United’s knowledge, Bachman said.

“We are going to get a better look at how the nitrates are moving,” he said. “And we are going to identify the source of the nitrates.”