A significant portion of Shell's Martinez refinery lost power on Monday afternoon, leading to a loud flaring operation that sent flames and black smoke into the sky, prompting an hours-long health advisory.
To relieve pressure the facility pushed close to 39,000 pounds of gas, which included hydrogen sulfide, to its flares, the company said in a preliminary report sent to Contra Costa County officials on Thursday.
As gas was pushed through the refinery's flaring system, nearby residents and first responders could hear it, according to Randy Sawyer, the county's chief environmental health and hazardous materials officer
"It was a high pressure system with a lot of gas going through at one time that the whole thing rumbled," Sawyer said in an interview. "People could hear it off-site."
The outage began at 1:15pm on Monday, according to Shell. One of the three main electrical substations that feeds power to the refinery "tripped", the company's 72-hour report said.