The blaze, which has blackened nearly 180,000 acres, is 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.
About 87 percent of the city of Mountain View's water supply is purchased from SFPUC, according to the city's website.
Mountain View firefighters have joined the fight against the Rim Fire, deploying Engine 7 and a strike team on Aug. 23, according to the department's Facebook page. The crew has been working 24-hours shifts and was teamed with other local firefighters, including ones from Palo Alto and Sunnyvale.
On Tuesday, the Mountain View crew and the Santa Clara County strike team were assigned to structure protection in Cold Springs on Highway 108, the department reported.
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 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 city's water and power infrastructure.
The Rim Fire has burned 179,481 acres and was 20 percent contained as of Tuesday morning, Aug. 27, according to the U.S. Forest Service.