Oroville Dam spillways weather latest storm as inflow of water slows
California got just what it needed Tuesday – a break in the relentless shower of rainstorms – but thousands of residents still were dealing with the threat of street flooding, overtopped levees and evacuations. Many of the state’s major reservoirs remained at or near capacity, and the risk of high waters persisted in much of the state even as patches of blue appeared in the sky.
The Sacramento area experienced localized street flooding from overflowing creeks, as did San Jose. The Modesto region braced for problems as heavy releases flowed from the New Don Pedro Dam spillway for the first time since 1997. Work crews patched a breached levee that prompted the evacuation of 500 residents near Manteca in San Joaquin County. And a flash flood warning was issued for Lyon County, Nev., east of Carson City, where a storm water detention basin was overflowing.
Still, as a whole California’s major levees were holding well, and urban centers appeared to be navigating the aftermath of the storms without serious problems. The Sacramento and American rivers were expected to crest at around 12 feet below flood stage in downtown Sacramento. And the two-week crisis at Oroville Dam continued to ease.
Despite the breather, Jay Lund, the head of UC Davis’ Center for Watershed Sciences, said Californians can expect to stay on guard for flooding for several more weeks. In some cases, particularly in the areas downstream of New Don Pedro, the highest water flows might lag Monday’s rainstorm by a day or two.
“We’ll certainly have a few days to dump out as much as they can from these full-to-the-top reservoirs, and get ready for the next one,” Lund said. “I think it’s going to go that way until April.”
There were still plenty of issues to deal with Tuesday. In Sacramento County, Dry Creek overflowed its banks, flooding streets in Rio Linda and prompting a voluntary evacuation that was called off by early afternoon as the waters receded. The sun poking through an overcast sky was a welcome sight for residents.
“Otherwise, we’d be canoeing right now,” said Amy Sequra, who wore a pair of heavy rubber boots as she walked around her home at Sixth and K streets in Rio Linda. Sequra’s place had avoided floodwaters, but farther along Sixth Street, driveways were blocked by sandbags and the road was bathed in 6 inches of water.
The flooding was far worse in San Jose, where Coyote Creek overflowed its banks and 186 residents were rescued by boat from a low-lying residential area. Water pouring out of Anderson Reservoir in Morgan Hill was expected to reach levels not recorded since the reservoir was built in the 1950s. Some animals at the city zoo were moved to higher ground, and a section of northbound Highway 101 was closed due to flooding.
The source of the latest misery was a Monday storm that created havoc throughout the state. Sacramento absorbed 1.69 inches of rain, breaking a century-old record for Feb. 20. But meteorologists said the pause in the wet weather, which should last several days, could be just enough to allow the region to escape serious troubles.
“The flooding concerns could be potentially a lot worse, but since we’ve had these breaks between these storms it has let some of these rivers and other waterways recede a little before our next system comes through,” said Hannah Chandler, a meteorologist with the National Weather Service in Sacramento.
She said the next storm will strike the valley on Saturday. It’s likely to be lighter than Monday’s, with less than an inch of rain falling in the Sacramento area.
Still, any rain that falls on the saturated soils could cause problems. Some of the most pressing trouble spots are south of the Sacramento-San Joaquin Delta. New Don Pedro Dam in Tuolumne County opened its spillway gates Monday for the first time since the great flood of January 1997. Although the water releases weren’t as high as originally expected, they will put stress on downstream levees leading into the Modesto area in the days to come.
“Just the continued pressure on those levees is of some concern,” said Alan Haynes of the federal government’s California Nevada River Forecast Center.
Releases from the New Don Pedro spillway were reduced slightly overnight, but flows in the Tuolumne River channel downstream are above flood stage and poised to spill into farmland, parkland and trailer parks that line the channel. The reservoir, which can hold just over 2 million acre-feet of water, was 98 percent full Tuesday. The Turlock Irrigation District, which manages the dam, will continue releases from the spillway for at least the next four days, said Calvin Curtin, a district spokesman.
At the San Joaquin River Club, a community of 800 in the Tracy area, resident volunteers were continuing foot patrols on the levee that shields the development from the San Joaquin River. The clubhouse kitchen was transformed into an emergency action center. Close to 1,000 sandbags were filled. They hadn’t been needed Tuesday afternoon, but the surge of water from New Don Pedro hadn’t hit yet.
“Our levees are good, until they aren’t,” said Dan Diviney, a resident who chairs the community’s emergency action committee.
At Oroville Dam, where fears of a failure of the emergency spillway Feb. 12 sparked the temporary evacuation of 188,000 downstream residents, the Department of Water Resources said it was making progress on shoring up the emergency spillway while keeping water levels stable in the reservoir.
Although inflows from Monday’s rains spiked at about 91,000 cubic feet of water per second overnight – about triple the amount from a couple of days earlier – Lake Oroville had plenty of empty space to absorb the water.
Monday night “was a good night overall,” said Butte County Sheriff Kory Honea. “We weathered the storm.”
The lake level rose about 2 feet early Tuesday, to just under 852 feet, and was expected to rise to about 855 feet in the next day or so, said DWR acting director Bill Croyle. That would be slightly above the 850 feet considered appropriate by U.S. Army Corps of Engineers flood-safety regulations.
Oroville Dam’s battered main spillway, where a giant crater opened up Feb. 7, was continuing to pump water out at 60,000 cfs, producing a spectacular shower of thundering white water at the base of the dam.
At some point Croyle said he’d like to halt the outflows altogether to assess damage to the main spillway and accelerate efforts to remove debris clogging the channel below. The debris has raised water levels and made it impossible to restart the dam’s hydroelectric power plant, which is capable of pushing out an additional 14,000 cfs. That could be crucial in reducing water levels during the long spring season, when snowmelt from the Sierra will take on greater significance.
Meanwhile, an independent board of five engineering consultants set up to review the state’s handling of the dam’s malfunctions was in its formative stages Tuesday. DWR created the panel under orders from the Federal Energy Regulatory Commission, which licenses Oroville Dam. The group is charged with advising the state on how to deal with operations at the crippled facility for the rest of the rainy season. The board also will review a separate forensic analysis, to be undertaken by independent third parties “with no previous involvement in assessing the spillway structure,” according to the order issued by FERC.
The Bee’s Bill Lindelof and Jessica Hice contributed to this report.