Some levels of radioactive chemicals found on a portion of the Santa Susana Field Laboratory site were as much as 1,000 times higher than standards, according to federal data released on Monday.
Acting as an independent monitor, officials with the U.S. Environmental Protection Agency conducted radiological surveys on a portion of the land known as Area IV, where a partial meltdown of a nuclear reactor occurred in 1959.
That portion is currently overseen by the Department of Energy.