TUOLUMNE COUNTY (CBS/AP/BCN) – The massive Rim Fire burning in and around Yosemite National Park has reached the area surrounding the Hetch Hetchy Reservoir, which provides water to San Francisco residents, city utility officials said Tuesday.

Meanwhile, firefighters have reported more progress Tuesday in fighting the massive wildfire,

The blaze, which has blackened nearly 180,000 acres, was not expected to affect the quality of the 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 on Aug. 17, the SFPUC has been transferring water from the full Hetch Hetchy Reservoir to other reservoirs closer to San Francisco, and is 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 were 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 city’s water and power infrastructure.

On the fire lines, crews gained some ground Tuesday against the huge wildfire burning forest lands in the western Sierra Nevada, including parts of Yosemite National Park.

The 11-day-old Rim Fire has burned 179,481 acres, or about 280 square miles, and was 20 percent contained as of Tuesday morning, according to the U.S. Forest Service.

The portion of the fire in Yosemite doubled to about 64 square miles but remained in back country, and the main attractions in the nearly 1,200-square-mile park remained open.

California fire spokesman Daniel Berlant says the next couple of days will be key. The National Weather Service says an expected increase in humidity Tuesday afternoon could help suppress flames.

The fire is now the seventh-largest California wildfire in records dating to 1932. It is was threatening about 4,500 structures and has destroyed at least 23.

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