Fire crews make progress against California blaze

Officials said yesterday a massive wildfire burning near Yosemite National Park grew overnight, but they were still making progress in containing it.

The Rim Fire remained 20% contained last night but officials said the fire grew to about 280sq miles, (725sq km) up from about 252sq miles the previous day, but back-burning by crews was responsible for at least part of that increase.

California fire spokes- man Daniel Berlant said crews were hoping cooler temperatures and higher humidity over the coming days could allow them to gain the upper hand.

The fire is threatening thousands of structures, the main reservoir serving San Francisco, and historic giant sequoias.

As flames lapped at the edge of the main reservoir, fears that the inferno could disrupt water or power to the city diminished.

“It looks great out there. No concerns,” Glen Stratton, an operations section chief on the blaze, said of the Hetch Hetchy Reservoir.

Nearly 3,700 firefighters battled the fire, the biggest wildfire on record in California’s Sierra Nevada. Crews remained confident they could protect hydroelectric transmission lines and other utility facilities at the reservoir, the chief source of San Francisco’s drinking water.

Utility officials monitored the basin’s clarity and used a massive new $4.6bn (€3.43bn) gravity- operated pipeline system to move water quickly to reservoirs closer to the city. So far the ash that has been raining onto the reservoir has not sunk as far as the intake valves, which are about halfway down the 300ft O’Shaughnessy Dam.

Utility officials said the ash is non-toxic but that the city will begin filtering water for customers if problems are detected.

Power generation was shut down last week so firefighters would not be imperilled by live wires.

It has been at least 17 years since fire ravaged the northernmost stretch of Yosemite that now is under siege.

Park officials cleared brush and set sprinklers on two groves of giant sequoias that were less than 10 miles (16km) away from the fire’s front lines.

While sequoias have a chemical in their bark to help them resist fire, they can be damaged when flames move through slowly with intense heat.