UPDATE Aug. 20:
A small camera lowered Monday into a hole discovered Thursday in the Hanford SX Tank Farm found it was only three feet deep.
“It’s believed the cause of the hole is poor soil compaction and water drainage around a rock in the ground,” said contractor Washington River Protection Solutions.
A planned inspection of the interior of a nearby tank was canceled and work resumed at the tank farm, with the exception of a 20-foot area around the hole.
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Video inspections are planned out of an abundance of caution after a small, unexplained hole in the ground was discovered near an underground tank storing radioactive waste at the Hanford nuclear reservation.
Work was being done Thursday to compact earth in preparation to add an asphalt covering over the soil at the SX-Tank Farm in the center of the Hanford nuclear reservation.
The farm has 15 single-shell tanks, each with a 1-million gallon capacity. The asphalt covering will keep precipitation from driving any waste that has previously leaked or been spilled deeper into the ground.
A worker noticed a hole up to 2 feet in diameter about 6 feet from one of the tanks as the worker prepared to make a second pass to compact the soil there.
Workers left the tank farm. It was the appropriate action when faced with an uncertain condition, said Jerry Holloway, spokesman for contractor Washington River Protection Solutions.
Employees were preparing for work in another part of the tank farm Friday morning when one or more of them called a stop to work out of concern that the hole could be a sign of a problem with the integrity of a nearby tank. Workers may stop work if they have a safety concern.
Surveys have not detected radiation or chemical contamination at the hole.
Plans are being made for a video inspection inside the nearby tank and to see if a small camera can be lowered in the hole in the ground to see how deep it is or determine other information.
Holes sometimes appear at the Hanford Site unexpectedly and do not necessarily indicate a problem. For instance, wood buried in the ground may rot away and soil may fall in, or a pipe may be removed from the ground and the soil may subside later if it has not been compacted.