The massive Rim Fire burning in and around Yosemite National Park has reached the area surrounding the Hetch Hetchy Reservoir, which provides drinking water to San Francisco residents, city utility officials said Tuesday.
The blaze, which has blackened nearly 180,000 acres, is not expected to affect the quality of Hetch Hetchy water because of the rocky terrain and limited brush along the reservoir, according to the San Francisco Public Utilities Commission.
Since before the Rim Fire began Aug. 17, the SFPUC had been transferring water from the full Hetch Hetchy Reservoir to other reservoirs closer to San Francisco. It's now increasing that amount from 275 million gallons to 302 million gallons a day as a precaution.
SFPUC officials say the water's turbidity, or cloudiness, is well below state-mandated levels despite some ash falling onto the reservoir's surface.
SFPUC crews also repaired a hydroelectric turbine unit at the Kirkwood Powerhouse that was damaged by the fire last week and are working to re-energize transmission lines.
The lines need to be inspected further before power delivery can resume, SFPUC officials said this morning.
The commission has spent about $600,000 on supplemental power supplies from outside sources since last week because of the fire-related disruption.
All of the SFPUC's 2.6 million water and electric customers continue to be fully supplied and can find updates about the fire at www.sfwater.org/RimFire, according to the commission.
Gov. Jerry Brown on Friday declared a state of emergency for San Francisco because of the threat to the water and power infrastructure.
The Rim Fire has burned 179,481 acres and was 20 percent contained as of Tuesday morning, according to the U.S. Forest Service.
Meanwhile, forestry experts say unnaturally long intervals between wildfires and years of drought primed the Sierra Nevada for the explosive conflagration.
The fire is the biggest in the Sierra's recorded history and one of the largest on record in California.
While containment increased Tuesday, the number of destroyed structures rose to 101 and some 4,500 structures remained threatened. The types of lost buildings were not specified. Firefighters were making stands at Tuolumne City and other mountain communities.
The blaze was just 40 acres when it was discovered near a road in Stanislaus National Forest, but firefighters had no chance of stopping it in the early days.
Fueled by thick forest floor vegetation in steep river canyons, it exploded to 10,000 acres 36 hours later, then to 54,000 acres and 105,620 acres within the next two days. On its 11th day it had surpassed 179,400 acres, becoming the seventh-largest California wildfire in records dating to 1932.