Chevron has explained what caused the strong hydrogen sulfide odor that drew complaints across Richmond last week. We reported on the odor and the 130 complaints when it happened.
The Grandview Independent obtained Chevron's 72-hour report to Contra Costa Health. It says a section of the flare system had been shut down and isolated for scheduled maintenance, and hydrocarbon gas containing hydrogen sulfide and ammonia leaked into it. Chevron said the release likely exceeded the 100-pound-per-day reportable amount. Flaring also passed the 500,000 standard cubic feet daily threshold on Oct. 22 and 23, the paper reported.
"The immediate issue has been resolved, and we are committed to working with the Air District and County Hazardous Materials officials," Chevron said, according to Richmond Confidential.
How high levels got
Richmond Confidential reported that levels stayed above the state's 30 parts-per-billion one-hour benchmark for six hours, from about 5 p.m. Thursday to 1 a.m. Friday. The peak was over 200 ppb at 7th Street and Hensley. The Grandview Independent said the Castro Street monitor peaked at about 491 ppb and portable monitors read as high as 4 parts per million on site. Levels were back to normal by 4 a.m.
Questions about the alert
The county's Level 1 alert didn't go out until 12:19 a.m. Friday. Contra Costa Supervisor John Gioia raised concerns about what Richmond Confidential described as a four-hour gap. County health officials said a Level 1 alert was appropriate because levels didn't reach 300 ppb over eight hours. The Air District started getting complaints at 6:09 p.m. Chevron owes the county a 30-day follow-up report.