At 1205 on February 2, 2005, the licensee called the Brea office to report that one of their
moisture density gauges had been run over by construction equipment at 1145 that morning. The
gauge was damaged to the extent that they were unable to retract the source rod back into the shielded position (
CPN, model 3, # M22054410 - 10 mCi
Cs-137 and 50 mCi Am:Be). The incident happened at a construction site located at 3208 Quarter Horse Drive in Yorba Linda at the water reservoir.
The outer gauge casing was in pieces, the rod handle was broken and the source rod was extended into the ground. The maximum dose rate with the source rod extended into the ground was 2 mrem/hr at contact measured with a Bicron microrem instrument. The dose rate when the source rod was extracted from the ground was approximately 30 mrem/hr at one foot from the rod tip. The Cs-137 end of the gauge source rod was placed in a lead pig, which was taped into place to keep the Cs-137 source shielded. The unit remains were placed in a plastic bag which was then placed into the transportation case. The device was transported to the local CPN service representative - Maurer Technical Services. Maurer Technical Services stated the sources appeared to be intact, and they took a wipe for a leak test. The wipe was sent out for counting. Alpha and beta surveys at the accident scene did not detect any contamination. Two wipes of the source housings were collected, which were counted in the Brea office on a Ludlum 3030 alpha-beta counter the next day. No contamination was detected on these two wipes.
The incident apparently occurred when the construction equipment, a front end loader, changed direction to avoid a truck, and there wasn't time for the
gauge operator, who was in a safe location about 15 feet from the
gauge, to signal the front end loader to stop.