| OROVILLE, Calif.
OROVILLE, Calif. Feb 14 Tens of thousands of
Northern California residents remained in shelters on Tuesday as
engineers worked to shore up a crumbling overflow channel and
drain the rain-swollen reservoir at the United States' tallest
dam before new storms sweep the region.
Evacuation orders for some 188,000 residents remained in
effect as the risk to those living in the Feather River valley
below the Lake Oroville Dam, 65 miles (105 km) north of
Sacramento, was being reviewed, officials said.
“We're doing everything we can to get this dam in shape that
they can return and they can live safely without fear. It’s very
difficult," California Governor Jerry Brown told reporters
during a news conference on Monday evening.
Brown on Monday sent a letter to President Donald Trump
requesting he issue an emergency declaration, which would open
up federal assistance for the affected communities.
Residents below the dam were ordered from their homes on
Sunday when an emergency spillway that acts as an automatic
overflow channel appeared on the brink of collapse from severe
erosion during what is on track to be Northern California's
wettest winter on record after years of drought.
The earth-filled dam is just upstream and east of Oroville,
a town of about 16,000 people. At 770 feet (230 meters) high,
the structure, built between 1962 and 1968, is the tallest U.S.
dam, exceeding the Hoover Dam by more than 40 feet (12 meters).
Authorities said they had averted the immediate danger of a
catastrophic failure that could unleash a wall of water three
stories tall on towns below.
On Monday afternoon, crews dropped large bags filled with
rocks into a gap at the top of the emergency spillway to rebuild
the eroded hillside.
The main spillway, a separate channel, is also damaged
because part of its concrete lining fell apart last week. Both
spillways are to the side of the dam itself, which has not been
compromised, engineers said.
The situation grew less dire later on Sunday as water levels
dropped, leaving the weakened unpaved emergency spillway largely
intact. By Monday, the level of the lake fell enough so that
water was no longer pouring over the hill.
Erosion caused by the hole in the side of the main concrete
spillway appeared to have abated by Monday, and it was back to
more or less normal operations, officials said.
On Monday, water could be seen gushing from the main
spillway as dam operators for the California Department of Water
Resources continued controlled releases through the chute into
channels that route the water away from populated areas.
The aim is to lower the reservoir's overall water level by
50 feet - and prevent further spillover down the emergency
hillside channel - before more rain arrives in the coming days
and snow-melt runoff begins in the spring, acting state water
resources director Bill Croyle told reporters. He said he hoped
to achieve that goal within two weeks.
Another storm was forecast to arrive as early as Wednesday
or Thursday, though officials said they expected much of that
precipitation to fall as snow rather than rain.
(Additional reporting by Brendan O'Brien in Milwaukee; Editing
by Christian Schmollinger)