Rockwell Says Wells Only Show Normal Radioactivity : Water: Samples at the Santa Susana lab find naturally occurring radiation, the company says. EPA officials are skeptical.

Water samples taken from new monitoring wells at Rockwell International’s Santa Susana Field Laboratory west of Chatsworth show only naturally occurring levels of radioactivity, a company official said Wednesday.

The data from the wells make up “the best report we’ve had” since controversy erupted last spring over environmental problems at Santa Susana, said Steve Lafflam, manager of environmental affairs for Rockwell’s Rocketdyne division, which operates the research complex in the Simi Hills. “I think it really confirms everything that we’ve been trying to put out to the public all along.”

In a press release accompanying the data, Rockwell said the tests confirmed that nuclear operations at Santa Susana “have in no way impacted ground water.” But an official with the U.S. Environmental Protection Agency said he was unsure the data support that conclusion.

The radioactivity measurements were the first taken of water from 18 monitoring wells that were drilled last summer in an area of the field lab where Rockwell has done nuclear work for the U.S. Department of Energy.

The private lab retained by Rockwell noted that cobalt-60 and certain other man-made radioactive substances were not found in the well water. However, the lab reported that it did detect low levels of radioactive tritium in some wells at concentrations of up to 699 picocuries per liter. A picocurie is a unit of radiation measurement.

Although such levels “aren’t significant” in terms of health risk, according to Gregg Dempsey, chief of the field studies branch for the EPA’s Office of Radiation Programs in Las Vegas, the levels appeared to be higher than the background radiation that is normal for the area, he said.

Dempsey stressed that he had not yet received the report, but said that if the tritium numbers Rockwell cited are accurate it’s “not quite the case” that they represent naturally occurring amounts.

Rockwell officials said they will continue sampling the wells on a quarterly basis to obtain additional radioactivity data.

Chemical solvents were detected in separate tests of water from the 18 wells late last year. Based on direction of ground-water flow, state water quality officials said they believe some of the contamination may have seeped off the site.

Rockwell is working with environmental officials to devise a plan for drilling off-site wells to determine if contaminants have migrated off the property. Officials have said there are no drinking wells in the immediate area.