Crews Make Progress On 1,000-Acre Sierra Fire

OCEANSIDE, CA — The Sierra Fire burning on Camp Pendleton Marine Corps Base that has been sending unhealthy air to Southwest Riverside County and beyond was 20 percent contained Thursday morning with updated burn area of 1,000 acres.

The large wildland blaze prompted the South Coast Air Quality Management District to issue an advisory Wednesday night warning that smoke and ash were causing unhealthy air quality in Southwest Riverside County and as far northeast as the San Gorgonio Pass Area.

The agency advised that air quality Thursday will depend on fire containment and weather conditions.

The weeklong controlled burns at the base were canceled, base officials announced Thursday morning. It's still unclear whether the blaze was ignited as part of the burns or possibly by live munitions' training that had been ongoing at the base this week.

The controlled burns were taking place on the base as part of Wildland Fire School. The annual training event brings numerous federal and local firefighting agencies together to gain experience tackling wildland fires.

However, shortly before 4 p.m. Wednesday, Camp Pendleton Fire Department announced the brush fire.

"The cause of the fire is unknown at this time," a base official told Patch at the time. The cause of the fire remains under investigation.

Base officials released a map outlining the fire's location, which showed it burning on the southeast side of the military installation.

Camp Pendleton Fire Department crews battled the blaze overnight, and more personnel were expected to arrive Thursday morning, base officials said.

There were no immediate reports of injuries.

#SierraFire UPDATE as of 5:10 p.m.

CPFD and neighboring fire departments are working to contain a fire of unknown size east of the 33 Area. The Evacuation Control Center is located at Paige Fieldhouse, as indicated by the “here” icon.

The cause of the fire is unknown. pic.twitter.com/1kQ8tCsAqS
— Camp Pendleton (@MCIWPendletonCA) June 10, 2021

The blaze was initially reported at 1,000 acres, but officials downsized it late Wednesday night to 925 acres and then pushed the figure back up Thursday morning.

Base evacuations were ordered Wednesday afternoon, including at Lake O'Neill Camp Ground, and the Wounded Warrior Battalion, but they were lifted at 8 p.m.

Base road closures were also announced, but as of 7:25 p.m. Basilone Road was reopened, including the Vandergrift Boulevard intersection.

San Diego County-based North County Fire Protection District tweeted just before 4:30 p.m. that residents in its service area were not immediately threatened by the brusher, and Cal Fire/Riverside County Fire Department made no announcements about its residents being in danger, including Santa Rosa Plateau residents.

An unrelated controlled burn was also planned Wednesday along the Santa Rosa Plateau west of Murrieta, and officials advised residents and motorists not to be alarmed by the smoke.

Roughly 60 acres were slated to be torched by Cal Fire/Riverside County Fire Department crews in the area of Tenaja and Forest Boundary roads.

The operation was planned between 7 a.m. and noon