A firefighter sprays down a hot spot while battling the 12,000-acre Canyon Fire burning on Vandenberg Air Force Base. Containment has reached 70 percent in the 5-day-old wildfire. (U.S. Air Force photo)

Favorable weather finally aided crews battling a 12,353-acre wildfire at Vandenberg Air Force Base.

As of Wednesday night, the Canyon Fire was 70 percent contained, VAFB officials said, adding that firefighters “made considerable progress over the course of the day establishing new containment lines and reinforcing existing lines.”

“Favorable weather throughout the day and a marine layer that lasted until late morning dampened temperatures and kept the fire activity to moderate levels, which allowed fire teams to work aggressively against the fire,” VAFB officials said.

Dramatic large columns of smoke rising from the canyons on South Base and visible around the Lompoc Valley and beyond for several days this week gave way Wednesday to wispy smoke mixed with marine layer, another sign of firefighting success.

But the fifth day of the fire brought tragedy for the 1,140 firefighters involved in the battle.

A water tender traveling west on Highway 246 at Purisima Road crashed at the roundabout, killing Ventura County firefighter Ryan Osler and injuring a colleague.

Now that firefighters have surrounded nearly three-fourths of the fire, evacuation warnings have been lifted for nearby La Salle and Miguelito canyons. Those warnings were called off at 8 p.m. Wednesday, according to Santa Barbara County Fire Capt. Dave Zaniboni.

The good news about the firefighting progress was tempered by Thursday’s weather forecast of northwest winds of up to 45 mph. On Friday, the winds are expected to switch direction to offshore.

Progress on containment also meant VAFB began assessing damage and developing a recovery plan.

Vandenberg officials have remained tight-lipped about potential damage, despite reports circulating in local communities. The cause of the fire remains under investigation, authorities say.

The Union Pacific railroad tracks through the 99,000-acre military base experienced minimal damage so train service can resume, VAFB officials said.

The fire started around 5:30 p.m. Saturday on South Base, which is home to several aerospace launch pads and support facilities.

Federal officials estimate the Canyon Fire will be contained Sept. 30.

Since the fire’s start, four firefighters have been injured, officials said, declining to give additional details.

The cost of the firefighting effort reportedly has climbed to $4.6 million, federal sources said.

Noozhawk North County editor Janene Scully can be reached at jscully@noozhawk.com. Follow Noozhawk on Twitter: @noozhawk, @NoozhawkNews and @NoozhawkBiz. Connect with Noozhawk on Facebook.