Firefighters staunch Rim fire growth rate, now 20 percent contained Started on August 17, 2013, the fast-moving Rim fire has already charred more than 100,000 acres in central California, near Yosemite National Park.. Hundreds of people were forced to evacuate their homes, and roads in the area were closed. UPI/NASA Visible Earth YOSEMITE NATIONAL PARK, Calif., Aug. 26 (UPI) -- Firefighters in California said Monday the massive Rim fire raging in Stanislaus National Forest was 20 percent contained. Thousands of people face mandatory or advisory evacuation orders for the fire, currently the largest wildfire burning in the United States, officials said. In Tuolumne City, firefighters dug trenches, cleared brush and set backfires during the weekend in an attempt to steer the massive blaze away from the 1,600 homes there, the Los Angeles Times reported Monday. Residents are under voluntary evacuation orders. Residents of Ponderosa Hills were also advised to leave. Parts of Groveland were evacuated Friday. The fire had devoured more than 265 square miles as of Monday and was only one ridge line away from Tuolumne City, a foothill community about 60 miles northeast of Modesto, USA Today reported. More than 3,400 firefighters from across the state and as far away as Florida were battling the fire, which started Aug. 17 east of Groveland. The fire has burned some Yosemite acreage, but is still about 20 miles from the most-visited area of the park, the Yosemite Valley, which was not immediately threatened, officials said. California Gov. Jerry Brown declared a state of emergency for San Francisco and San Francisco County Friday after the fire -- whose flames were leaping across treetops, creating a "crown fire" -- damaged the Bay Area power infrastructure and threatened the Hetch Hetchy reservoir, San Francisco's main water source, serving 2.6 million customers, or 85 percent of the city's water supply. The fire had destroyed 23 structures so far. President Obama was updated on the fire Sunday during a phone call with the governor. The White House said the president "expressed his gratitude for the brave men and women working tirelessly to combat this devastating fire" and reiterated his commitment to providing needed federal resources to support the ongoing state and local response.