Smoke from an 85-acre prescribed burn on Angel Island Wednesday may be visible through roughly Saturday, Sept. 26.

The Contra Costa County Fire Protection District, which covers Walnut Creek, issued a smoke advisory on Tuesday, Sept. 22, warning that smoke from the island could drift into the district.

California State Parks, working with CAL FIRE and the Marin County Fire Department, completed the second phase of a prescribed burn on the largest island in San Francisco Bay, according to the agency's Angel Island State Park page. The burn had been planned for as early as Wednesday, according to a State Parks release distributed via the Contra Costa Herald.

The key message for residents: do not call 911 to report the smoke. California State Parks said the calls could overwhelm emergency dispatchers.

The Wednesday burn picked up where a Sept. 8 operation left off. That first session cleared 62 acres before project partners paused the work after discussions with the Bay Area Air Quality Management District about conditions. Combined, the two burns have treated 147 acres of a planned 260-acre fuel-reduction project supported by Proposition 4, the 2024 climate bond.

Division Chief Graham Groneman of the Marin County Fire Department said officials time the burns to minimize smoke impact. "We work closely with the Air Quality Management District, and we really look for those small windows that have the greatest ability to disperse the smoke in the least impactful manner," Groneman said.

Division Chief Sean Jerry of the CAL FIRE Sonoma-Lake-Napa Unit said the fuels reduction work has reduced the chance of a catastrophic fire on the island.

Smoke from the burns is visible from 9 a.m. to 6 p.m. on burn days and can linger up to three days after ignitions, according to California State Parks. The agency's Angel Island page confirmed burning was completed for the week as of 6 p.m. Wednesday, with firefighter teams remaining on site to monitor the burn area.

Officials urge anyone who smells smoke to limit time spent in smoky areas.

Several trails on Angel Island are closed for one to three days during and after burn operations, including the Ida Trail, Sunset Trail, the fire road and Perimeter Road. Access to the summit of Mt. Livermore is also restricted on some burn days. The park itself remains open.

No dates have been announced for the remaining roughly 113 acres of the project. Burn status updates are available on the Angel Island State Park webpage and the Watch Duty app.