A minor oil spill in San Pablo Bay at the Phillips 66 oil refinery this week was most likely caused by a corroded pipeline, a revelation prompting a new set of concerns as the energy company pushes to expand the number of oil tankers that unload crude at the Rodeo facility's marine terminal.
The Monday morning spill, which is the subject of three investigations, released an estimated 25 to 50 gallons of gas oil from a "pinhole leak" on an inactive pipe along the refinery's causeway, according to an email the company sent Contra Costa County health officials and obtained by KQED.
"The cause of the leak is still under investigation, but is believed to have been due to localized corrosion," wrote Morgan Walker, the refinery's health and safety manager.
That disclosure reignited outrage from environmental groups opposed to Phillips' proposal to raise the daily average of oil unloaded at the marine terminal from about 51,000 barrels to 130,000.
The company's request to expand came months after a spill in September 2016 at the same facility that was believed to have been the source of noxious fumes that sickened dozens of people in Vallejo.
"This latest accident shows how little concern oil companies have for safety," said Hollin Kretzmann at the Center for Biological Diversity. "We've got to be concerned about a repeat of this and the next accident could be bigger and much more damaging to our bay and nearby communities."
A corrosive pipeline indicates the marine terminal's infrastructure is getting old and could allow future spills, according to Sejal Choksi-Chugh, executive director of San Francisco Baykeeper.
"The refinery cannot keep contaminating the Bay and our communities with oil," Choksi-Chugh said. "And if they do, they cannot expect their proposal to more than double the amount of oil that they bring into the Bay Area to go unchallenged by the public and the responsible agencies."
Phillips 66 has said the extra tanker deliveries would replace crude oil currently delivered by pipeline.
A spokesman for the company has not responded to several requests for comment about the recent spill.
The refinery's letter to county health officials stresses that the spill was stopped and contained quickly and that there were no odor complaints or impacts to boating.
Randy Sawyer, the county's chief environmental health and hazardous materials officer, wants to know what the refinery is doing to avoid a repeat.
"What I have asked them is what are they're doing to ensure the integrity of the rest of the line before they start that line back up," Sawyer said.
The leak is under investigation by the U.S. Coast Guard, the California Department of Fish and Wildlife's Office of Spill Prevention and the Bay Area Air Quality Management District.