A wildfire burning on the south side of Vandenberg Air Force Base near Lompoc has more than doubled in size since the weekend and now covers 10,542 acres, Air Force officials said Tuesday.

The Canyon fire was 20% contained, and 633 firefighters from federal, state and local fire agencies were battling the blaze.

The fire was “very active” Monday, growing by about 6,000 acres on the north and west sides, Air Force officials said in a statement. The South Base portion of the military facility was closed Tuesday to everyone but “emergency personnel,” and officials said the fire was “significant and unpredictable.”


Cultural sites related to the Chumash people and wildlife habitats are potentially threatened by the fire, and there are watershed concerns, military officials said. A team of resources advisers is working with fire crews to identify what is being threatened.

At a Tuesday afternoon news conference, Vandenberg Fire Department Assistant Chief Wayne Seda said no facilities or buildings had been damaged although a number were threatened by the fire. Also, railway service through the sprawling base had been halted, and Union Pacific personnel were conducting an assessment of the route.

Seda said four firefighters had suffered minor injuries while battling the blaze, two on Sunday and two on Monday.

There have been power outages in several buildings on the base, officials said.


The 30th Security Forces Squadron based at Vandenberg set up road blocks along West Ocean Avenue, and base officials were asking military personnel to stay clear of West Ocean between Vandenberg’s north and south bases.

The Canyon fire broke out Saturday in a remote canyon at the southern end of the military base and quickly spread. Its cause remains under investigation.

Over the weekend, the blaze forced officials to postpone the launch of an Atlas V rocket, which was schedule to take off Sunday and carry a commercial satellite.

Seda said Tuesday that the rocket was not in danger, although “it’s a concern.” He said crews were making preparations to defend it and other “critical assets” should “the fire come to them.”


Smoke will continue to impact the Central Coast, according to the National Weather Service. An expected increase in onshore flow on Tuesday will send the smoke across interior areas. Smoke could reach portions of the Ventura County coast by Wednesday, forecasters said. If the fire continues into the weekend, an offshore flow could help blow the smoke out to sea, according to the weather service.

Meanwhile, the cost of fighting the 189-square-mile Soberanes fire burning near Big Sur has passed $200 million, making it the costliest to fight in U.S. history, according to federal data.

As of Tuesday morning, it has cost $208.4 million to fight the Soberanes fire, according to the National Interagency Coordination Center. The cost, which is not adjusted for inflation, surpasses the previous high set by the 2002 Biscuit Complex fire in Oregon and California. According to the Government Accountability Office, that fire cost more than $150 million to fight.

The tallies include only the cost of firefighters suppressing and containing the fire, not property value and rehabilitation, said Jessica Gardetto, a spokeswoman for the National Interagency Coordination Center.


Other significant fire costs include the 2013 Rim fire in the Stanislaus National Forest, which cost about $127 million to fight, and the 2007 Zaca fire in the Los Padres National Forest, which cost about $122 million, Gardetto said.

The Soberanes fire, officials said, has been so expensive in large part because it has been burning for so long. The blaze, which was started by an illegal campfire, ignited on July 22.

The wildfire, burning in steep and difficult terrain, was 71% contained as of Tuesday. More than 2,000 firefighters were battling the blaze.

Dennis Godfrey, a spokesman for the interagency team battling the Soberanes fire, said crews have had “great success” over the last few days performing burnout operations and expanding containment lines.


But on Monday night, with winds between 34 and 40 mph, a hot ember in what was thought to be a “contained, cool dry area” on the eastern side of the fire was blown across a containment line and burned about 150 acres, forcing more evacuations, Godfrey said.

“We did not anticipate the high winds last night,” he said.

hailey.branson@latimes.com

Twitter: @haileybranson


UPDATES:

2:40 p.m.: This article has been updated with details from an afternoon news conference.

12:54 a.m.: This article has been updated with information about the Soberanes fire.

This article was originally published at 10:50 a.m.