The U. S. Environmental Protection Agency said Tuesday that soil and ground water tests show the Santa Susana Field Laboratory west of Chatsworth presents "no public health risk from radiation at this time."
The agency gave that assessment in releasing a report on soil and water sampling done last July at the Rockwell International nuclear research site in the Simi Hills.
"From the levels of contamination detected and their location, it is doubtful that contamination has spread off-site," the report said.
But EPA officials were backpedaling slightly by the end of the day and predicting that there will be more tests, in part because they failed to test one area of known contamination.
The main findings in the report--the discovery of low levels of radioactive tritium in a ground water sample and cesium-137 in soil samples--had been disclosed by EPA officials in September.
But the report revealed for the first time that the July tests were limited to only six soil and water samples on the entire 290 acres at Santa Susana that have been used for nuclear work.
The author of the report, Gregg Dempsey, chief of field studies for the EPA's radiation programs office in Las Vegas, acknowledged that the sampling was limited. He said the agency was under a "pretty heavy time constraint" to get data on potential hot spots to see "if there was an immediate problem."
But one of these areas, called the radioactive materials disposal facility, was not sampled due to a communication mix-up and will probably have to be checked on a follow-up visit, another EPA official said late Tuesday.
And Dempsey said he has proposed to EPA regional officials in San Francisco that they fund a more complete study, involving more tests of soil, water and vegetation samples.
"I don't think we're going to find anything in any of these other areas," he said, but "you have to be thorough."
Rockwell officials refused to answer questions. But in a prepared statement, they said the report confirmed their contentions that "only very minor amounts of low-level contamination are present in the soil and water . . . and that there is no evidence of it migrating off-site."
The cesium-137 was found in soil near Building 64, where contaminated soil was being cleaned up at the time of the EPA visit. Dempsey said the cesium levels were far above amounts deposited by fallout from atomic weapons tests, but far below hazard level.