| SAN FRANCISCO
SAN FRANCISCO Aug 28 A wildfire in Yosemite
National Park that ranks as one of the largest California blazes
on record was set to force the closure on Wednesday of a key
route to the premiere outdoor destination and possibly block
some visitors from reaching the park over the Labor Day weekend.
This comes a day after the so-called Rim Fire burned deeper
into the park and reached the shores of a key reservoir that
serves as the primary water supply for San Francisco some 200
miles (320 km) to the west.
The blaze has charred nearly 184,500 acres (about 75,000
hectares) - an area larger than the land mass of Chicago - since
it erupted on Aug. 17.
It ranks as the biggest California wildfire since October
2007, and the sixth-largest in state history, according to the
records of Cal Fire, a state government site.
The fire is burning mainly in the Stanislaus National Forest
west of Yosemite, but it has scorched more than 40,000 acres of
The Rim Fire last week forced the closure of a stretch of
Highway 120 that leads to the west side of the 750,000-acre
(300,000-hectare) Yosemite National Park and is the main
entrance from the San Francisco Bay area.
On Wednesday at noon local time, the second of four access
routes to the park was set to close when Tioga Road shuts down
to allow fire crews to build containment lines along the road
before the blaze approaches, said Yosemite spokesman Tom Medema.
"That will limit the access for visitors to and from the
east side of the park, quite possibly over Labor Day weekend,
which will have a significant economic impact on the area and an
inconvenience for visitors," he said.
Some 4 million people visit Yosemite each year, most of them
during the peak months of June through August.
Cooler temperatures, higher humidity and calmer winds
expected overnight into Wednesday would likely help firefighters
burn containment lines around the Rim Fire, said Alison
Hesterly, spokeswoman for the California Department of Forestry
and Fire Protection.
But later on Wednesday, temperatures were expected to be hot
and dry, reaching a maximum of 94 Fahrenheit (34 Celsius) in the
area with a minimum of 15 percent humidity, she said. "If we
reach the maximum temperature and the minimum humidity, we're
expecting continued erratic fire behavior," she added.
On Tuesday, a firefighting force of some 4,100 personnel,
backed by teams of bulldozers and water-dropping helicopters,
continued to make headway in their drive to encircle and
suppress the flames.
Containment lines have been established around 20 percent of
the fire's perimeter, nearly triple Sunday's figure, though the
overall area of the blaze continued to grow as much of the
firefighting effort focused on structure protection.
After advancing on the Hetch Hetchy Reservoir for several
days, the flames reached the shores of the artificial lake on
Tuesday, officials said. But the San Francisco Public Utilities
Commission said in a statement there was "little risk for direct
impacts" on the reservoir because of the rocky terrain and lack
of brush surrounding it.
Officials said ash had drifted onto the surface of the Hetch
Hetchy Reservoir, but testing of samples showed water quality
If the water should become fouled by too much ash and soot
and require filtration, it can be diverted through a treatment
plant near San Francisco before being delivered to customers,
officials from the Public Utilities Commission said.
Firefighters hacking through dense, dry brush and trees to
create clearings in the rugged terrain on Tuesday rushed to
improve buffer zones around some 4,500 homes threatened by the
blaze on its northwestern flank on Tuesday, said Cal Fire
spokesman Daniel Berlant.
Most of those dwellings have been ordered evacuated or were
under advisories urging residents to leave voluntarily or be
ready to flee at a moment's notice. The fire has already
destroyed dozens of homes and cabins, Berlant said, but no
serious injuries have been reported.
The cause of the blaze remained under investigation.
(Editing by Alex Dobuzinskis and Lisa Shumaker)