In an open letter to the president and CEO of Tesoro Corporation, the U.S. Chemical Safety Board (CSB) requests that Tesoro cooperate with the agency's investigation of the sulfuric acid release at the company's Martinez, Calif., refinery on Feb. 12.
Tesoro allowed three federal investigators into the facility on Feb. 13, but had refused entry to CSB staff since then, the San Francisco Chronicle reported. According to CSB, Tesoro Corporation's refinery management, in consultation with legal counsel, refused to permit CSB to return to the site, refused to preserve the site, prohibited CSB from conducting certain interviews, and indicated an unwillingness to comply with document requests.
"The action taken by Tesoro in preventing lawfully authorized CSB investigators from performing their official duties calls into question why Tesoro has taken this unprecedented action," the letter reads. "It creates a real concern that Tesoro may be trying to withhold other facts and issues from the agency."
The Chronicle reported that on Friday, Feb. 28, Tesoro agreed to let CSB inspectors back into the refinery. But CSB Managing Director Daniel M. Horowitz told the Chronicle that the company had already modified the accident site.
Two workers suffered first- and second-degree chemical burns as a result of the chemical release. CSB lists several findings already determined by its investigation team:
A mechanical integrity failure occurred on equipment connected to a 100,000-gallon process vessel containing flammable hydrocarbons and concentrated sulfuric acid, which caused the workers to be sprayed with acid
Operators being sprayed by acid during routine sampling activities is a common occurrence
At the time of the chemical release, operators did not have access to face shields and acid suit jackets required by procedure for sampling
Approximately five gallons a minute of sulfuric acid was leaking until isolated
For further details, read the full letter.