Smoke from a prescribed burn on Angel Island hit Contra Costa County far harder than forecast on Wednesday, Sept. 23, pushing the air quality index above 400 along the Richmond coast.

The Bay Area Air Quality Management District (BAAQMD) is now reconsidering how it approves prescribed burns, as first reported by KQED. Contra Costa County Supervisor John Gioia, who also sits on the Air District's board of directors, plans to raise the permit review process at the board's Oct. 7 meeting in San Francisco.

As we reported Sept. 24, the Contra Costa County Fire Protection District had warned residents that smoke from the burn could drift into the area. What followed was far worse than predicted.

Fire crews began burning at 10 a.m. Sept. 23 on Angel Island State Park, the second attempt at a planned 260-acre prescribed burn funded through Proposition 4, the 2024 Climate Bond. A first attempt beginning Sept. 8 was called off the following day after covering 62 acres, following discussions with the Air District and smoke complaints.

Winds shifted by early afternoon on Sept. 23, sending thick smoke plumes into San Francisco and western Contra Costa County. Air quality app notifications in Richmond glowed purple and showed an avatar wearing a respiratory mask. The view of Angel Island from Miller/Knox Regional Shoreline was completely blocked by smoke, according to KQED.

The burn ended around 2:15 p.m. after crews treated another 85 acres, bringing the September total to 147 of the planned 260 acres, according to the California Department of Parks and Recreation. Smoke lingered over western Contra Costa County into the evening.

Andrea Polidori, the Air District's deputy executive officer of science, said forecasters did not anticipate how much fine particulate matter would settle at ground level.

"What was difficult to forecast and predict was the ground concentration of fine particulate matter from the smoke, and so the impact was more than we predicted," Polidori told KQED.

Polidori apologized for the community impact and said the agency would reassess its process.

The Air District said it received one complaint of a person with asthma needing medical care because of the smoke. Western Contra Costa County already has elevated asthma rates due to chronic air pollution from industrial sources, according to the Air District.

Air District spokesperson Kristina Chu told the San Francisco Chronicle that the forecast had predicted smoke would rise and disperse, but "actual weather and air quality conditions developed differently than forecast, resulting in more smoke impacts to nearby communities than we expected."

Gioia posted on X around 2:05 p.m. Sept. 23 that the Air District had ended the burn and that there would be no more burning on Angel Island for the rest of the year. He has asked the district's executive officer to review its policies for approving controlled burns.

@supejohngioia: "I've been in contact w/ @AirDistrict about ending the burn due to smoke impacts in SF and East Bay. I've been told by Air District that the burn (fire ignition) has ended and smoldering may continue and there will be no more burning on Angel Island this year."

The California Department of Parks and Recreation said Sept. 25 that no additional burning is planned for the foreseeable future. State Parks spokesperson Ryan Forbes defended prescribed burns as safer than wildfires because crews control the timing, and noted that only one landing craft in the Bay can move fire trucks onto Angel Island.

A 2008 wildfire burned nearly half the island. Stanford University researchers have found that annual prescribed burns can reduce wildfire smoke exposure by as much as 25% in California's worst fire years.

The Air District board meets Oct. 7 at 10 a.m. at the district's San Francisco office. The specific agenda for that meeting has not been posted.