TUOLUMNE CITY, California (AP) — Fire officials say crews are finally gaining ground on a massive wildfire burning near Yosemite National Park and they expect no water or power disruptions from ash raining on the main reservoir that supplies San Francisco.

Glen Stratton, an operations chief on the fire suppression team, said late Monday that while the blaze continues to grow in size, containment numbers are up, as is optimism that crews are making progress.

The fire, which began Aug. 17, is 20 percent contained.

Flames have charred nearly 252 square miles (161,280 acres) of brush and timber and about 34 square miles (88 sq. kilometers) of that is inside the park.

Stratton says while flames reached the edge of the Hetch Hetchy Reservoir, crews are confident they will be able to protect the infrastructure.