Study Says Runoff, Old Wells Taint Aquifers : Oxnard Plain: In addition to contamination from the ocean, scientists find more sources of salt in underground reservoirs.

Underground water reservoirs that supply farms and cities on the Oxnard Plain are being polluted with salty water from agricultural runoff and leaky wells in addition to seawater intrusion, a new federal study has found.

Abandoned oil and water wells and runoff from one of the county’s richest agricultural areas were cited as sources of saltwater contamination for the first time Wednesday in an interim report on a four-year study of ground-water problems.

The team of eight U. S. Geological Survey scientists also found that seawater, while no longer believed entirely responsible for high salt levels in the underground reservoirs, continues to intrude into the freshwater supplies despite a 10-year, multimillion-dollar program to combat the problem.

“Seawater is not being held back; it’s a continuing problem and it’s getting worse,” said John Izbicki, one of the federal hydrologists who presented the findings in Santa Paula on Wednesday.

Izbicki said that regardless of whether the salt comes from seawater, wells or runoff, the reason for the movement of the salty water into freshwater aquifers remains the same as it has been for the last 50 years--overpumping.

“The ultimate cause is the increasing pumpage of ground water,” Izbicki said. “All of the issues of regional water quality problems are tied together.”

Lynn Maulhardt, president of the United Water Conservation District, which funded the $1-million study, said the district will not wait until the report is finished in two years before acting on the new findings.

“We will begin working on an interim solution,” he said. “But we’re not going to go around spending a lot of money in a shotgun approach just to make a lot of people happy, either.”

United has been criticized by Ojai real estate agent Carla Bard, a former member of the state Water Quality Control Board, and other environmentalists who have contended that the district has not moved fast enough to combat seawater intrusion.

“I’m just not satisfied that what they are doing will take effect soon enough,” Bard said.

The preliminary findings were issued after the scientists completed two years of work on the project. The scientists drilled 83 wells at various depths to determine where and at what concentrations seawater had breached the freshwater aquifers.

Based on differences in the chemical makeup of the water, they determined that seawater had only entered about two-thirds of the 23-square-mile area that was believed to have been contaminated with seawater.

Nevertheless, because of the other sources of salt in the ground water, the area of contamination was just as extensive as previously believed.

Scientists say the reservoirs beneath the Oxnard Plain are separated into two parts, known as the upper and lower aquifer systems.

The upper system is made up of a salty layer of poor-quality water, known as the “perched zone,” that dips to about 90 feet below sea level and two freshwater aquifers reaching to about 400 feet below sea level. They are called the Oxnard and the Mugu aquifers.

The lower level is made up of the Hueneme and Fox Canyon aquifers, two valuable freshwater supplies for county farmers and residents. The Hueneme reaches about 800 feet below sea level, and the Fox Canyon extends about 1,200 feet below sea level. Beneath them is the Pico Formation, an expanse of shale, sand and extremely poor-quality water.

Through faulty casings on the abandoned wells, the poor-quality water from the Pico Formation moves into the Hueneme and Fox Canyon aquifers, scientists said. Salty water from the perched zone is also sucked into the Oxnard and Mugu aquifers.

United General Manager Frederick Gientke said the district is already looking for ways to find all the abandoned wells in the area to determine what needs to be done to cap them to prevent leakage.

“It won’t be easy because some of them have been plowed over and now have buildings over the top of them,” he said.

Gientke also said the district’s projects to stop the intrusion of seawater and lower the concentrations of salt water have not been given enough time to work.

He said the underground basins have yet to see the full effect of the Freeman Diversion dam, which opened last February. The district also set up a pipeline to supply some farmers with water from the lower aquifer system to relieve pressure on the upper aquifers, which have been the areas of heaviest contamination.

The district is also studying whether it can store additional water during storms in a former gravel basin. In addition, it is investigating whether a series of wells near the coast could serve as a barrier to continued seawater encroachment.

“It took 50 years for seawater to move in and we cannot expect it to move out in 50 hours,” Gientke said.