The final state investigation into a Sept. 7 explosion at the Wacker Polysilicon plant in Charleston, Tenn. recommended no enforcement action be taken against the company. The incident resulted in a plant worker, a firefighter, four deputies and seven local residents being treated by local hospitals. The explosion also closed some area roads and led Bradley County Emergency Management Agency to urge residents to shelter in place and turn off HVAC units.
The Tennessee Department of Environment and Conservation investigation released today ruled the blast sent 1,784 pounds of hydrochloric acid into the air and was caused by a “sudden and unavoidable failure of process equipment.” The investigation also determined there were no hydrochloric acid readings that exceeded exposure guidance levels. The threshold for reportable quantity is 5,000 pounds, according to the report.
“Because the event meets the definition of a malfunction, and it is unlikely that public health or the environment were impacted due to the excess [hydrochloric acid] and [Trichlorosilane] emissions, it is recommended that no enforcement action be taken for the excess emissions resulting from the event,” according to the report.
Investigators determined the explosion was caused by a mechanical failure in the company’s hydrogen recovery building. The failure occurred when a new piston part of an upgraded compressor design broke, resulting in the explosion.
A Tennessee Occupational Safety and Health Administration investigation into the same incident determined there were five serious violations and two “other-than-serious” violations that resulted in more than $25,000 in fines. A separate TOSHA investigation into an unrelated chemical spill that sent five workers to area hospitals a week prior to the explosion found two serious violations resulting in more than $20,000 in fines.