San Francisco officials are scrambling to send more water to the metropolitan area as the massive Rim fire near Yosemite rains ash down on a key reservoir.
On Monday, utility officials monitored the clarity of the Hetch Hetchy Reservoir and used a massive new $4.6-billion, gravity-operated pipeline system to move water quickly to reservoirs closer to the city, the Associated Press reported.
The reservoir serves as San Francisco's chief source of water and officials there hoped to make the transfer before the water became tainted by falling ash.
Hetch Hetchy supplies water to 2.6-million people in the San Francisco Bay area, 150 miles away.
The Rim fire has so far charred a swath of nearly 161,000 acres — including about 21,000 acres inside Yosemite National Park. It has destroyed at least 23 structures and threatens two groves of giant sequoias and historical structures in the famed park.
Containment on Monday reached 20% — up from 7% Sunday.
The most hopeful sign that conditions were improving Monday was written in the sky.
For the last week, each afternoon has brought a towering plume of smoke rising over the flames. Inside the plume are lightning and hail, and when the plume collapses, it sends wind pushing the fire in all directions. Fire officials call from noon to 5 p.m. the burning hours.
On Monday, the weather changed slightly — an inversion layer kept the smoke thick and low just a little longer — but it was enough to chop the plume down to half its size.
About 25 miles away, the tourist magnet of Yosemite Valley remained safe, surrounded by its famed granite walls.
The fire is burning hotter and faster than any in modern Sierra Nevada history, firefighters say.
"The fire will burn until the snow flies," Tom Medema, a Yosemite National Park interpretive ranger, said Monday. "But today, we finally had a chance to box it in."
Temperatures in the Yosemite Valley region were expected to remain in the mid-90s this week. Officials at Yosemite said campgrounds have been packed and that the popular Yosemite Valley and much of the park are free of smoke.
Times staff writer Robert J. Lopez in Los Angeles contributed to this report. Marcum reported from Groveland, Schaefer and Serna from Los Angeles.
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