Last summer, the Center for Investigative Reporting began looking into reports of radioactive contamination at the former Treasure Island Naval Station. Along the way, a source told CIR that cesium-137 had been found at the site – yet that alleged finding from 2007 was not in official U.S. Navy cleanup reports reviewed by CIR.
In 2012, the Navy told state regulators there had been no findings of cesium contamination beyond release limits established for the cleanup of Treasure Island. We set out to determine whether significant cesium-137 contamination was present on the island. Part of the reporting involved soil testing by certified laboratories. Here are the steps we undertook:
- CIR reporters reviewed military archives and other documents to research the history of radiation use at Treasure Island. Documents reviewed included detailed drawings, maps and inventory lists describing the use of cesium, plutonium and barium, among other radioactive material at classrooms used to train sailors in nuclear warfare.
- The reporters discovered that the elevated radiation levels, and the radioactive material use depicted in the archives, occurred on the same block on the former base. The classroom buildings had been declared clean in 2008 and cleared for future development by the Navy, as well as by state regulators.
- Reporters were trained by a certified health physicist to operate radiation survey instruments. Using a Ludlum Model 44-10 sodium iodide detector, as well as a Ludlum Model 44-9 Pancake Geiger-Mueller Detector, they spent 45 hours surveying the block in question.
- Once a suspect area was identified, the reporters, protected with disposable gloves and shoe covers, unearthed 12 half-pound soil samples and took them to a certified radiology lab. The samples were examined using a high-purity germanium detector set for high-resolution gamma spectroscopy.
- The analysis produced a finding of elevated levels of cesium-137 in three samples taken near the former classroom.
- Reporters returned to the island, taking additional samples from the suspect location. Those samples, along with the original sample, were tested at two certified radiation laboratories.
- Soil tests by Eberline Services of Richmond showed cesium-137 concentrations as high as 0.180 picocuries per gram.
- The sample showing the highest radiation level was retested by New World Environmental, a certified radiation laboratory in Livermore. That test showed a greater radiation concentration of 0.315 picocuries per gram. A picocurie, or one-trillionth of a curie, is a standard measure of the intensity of radioactivity in a sample of material.
- Both of the results exceeded the Navy’s threshold for releasing land for development at Treasure Island, which is 0.113 picocuries per gram.