The Corcoran levee is being raised – again.
The fear is it won’t be high enough as runoff from record breaking snowpack above several rivers that feed into the old Tulare Lake gets underway.
Before repair work got started the levee stood at 188 feet.
That’s four feet shorter than when it was last raised in 2017, after sinking several feet from its prior height.
The problem is subsidence, the land is sinking. And it’s taking the levee with it.
When California dries out and farmers can’t get enough water from river and state supplies, they turn to groundwater.
Around Corcoran, farmers have pumped the ground so hard it is collapsing – subsiding – over a large area.
The massive area of subsidence has been documented in satellite photos. It even has a name: “the Corcoran bowl.”
Because the subsidence covers such a large area, it’s hard to see the damage. Bridges, homes and roads haven’t crumbled into sinkholes. Buildings aren’t tilting sideways. Nothing so dramatic.
But the land is quietly and irrevocably sinking.
In this epic water year, the cost is coming due.
Piling up dirt – and debt
Flood water is already lapping at the west and south sections of the Corcoran levee. At the height of flooding last month, water briefly washed up against the levee’s short eastern arm, which wraps around two state prisons.
With heavy runoff anticipated to roll down the Sierra Nevadas over the next month, the Cross Creek Flood Control District is scrambling to build up the 14.5 mile levee
The district only has about $1 million for a job that is estimated will cost $17 million to $21 million. Even so, it is pushing forward with construction.
When asked if Kings County is helping pay for the levee work, Finance Director Erik Gonzalez said it’s still up in the air.
“…funding for the Corcoran levee project has still not been settled,” he wrote in an email. “On our end, the County is hoping to work with CalOES and FEMA to ensure that the project qualifies for reimbursement by these two organizations and have requested that assistance from CalOES.”
So far, no word back.
The Cross Creek district and City of Corcoran sent an urgent plea for funding to the California Department of Corrections and Rehabilitation on April 25, noting the importance of the levee to the two state prisons.
“…we are in a more desperate situation seeking funding support for the remaining Corcoran Levee reinforcement work, and hope that you can be of assistance,” wrote Cross Creek General Manager Dustin Fuller and Corcoran City Manager Greg Gatzka.
“Finding flood protective measure funding is proving to be extremely elusive,” Fuller and Gatzka added.
The prisons gave them dirt, but it’s unclear if any money was forthcoming.
Fuller directed questions to Gatzka. And Gatzka did not return multiple phone calls.
Been there, done that
Six years ago, the mountains were also heavy with snow. Flood water wasn’t at the door but the Cross Creek district looked at its elevation maps back in March 2017 and realized it had a problem.
The levee, which had stood at 195 feet in 1983, had sunk.
It was down to 188 feet, not high enough for a potentially huge flood.
So, Cross Creek scrambled through March and April of 2017 to rebuild the levee to 192 feet. It cost $10 million, which the district didn’t have.
Contractors were issued IOUs just to get the work done.
In the end, the mostly farmworker residents of Corcoran voted to add an extra $250, on average, to their property taxes for three years to make good on those IOUs.
The Department of Corrections also paid a share of the tax burden, which was divvied up considering the protective benefit each property received from the levee based on proximity and property value.
Corrections’ share in 2017 was close to $6 million.
Now, here they all are again. Another epic snow year, a sunken levee and a big bill to pay.
Merging flood zones
No matter how high it’s rebuilt, though, the Corcoran levee may not keep the town dry.
That’s because groundwater pumping has caused the land to sink southeast of Corcoran.
The extreme topographical changes were documented in a 2017 engineering report commissioned for the High Speed Rail project, which runs along Corcoran’s eastern edge next to Highway 43.
The report noted existing and future anticipated subsidence would cause three flood zones to merge, putting the rail line in the path of potentially catastrophic flooding.
The Tulare Lake, Deer Creek and Tule River flood zones will merge, according to the report by Amec Foster Wheeler Environment and Infrastructure Inc.
“The resulting flood depth along the HSR (High Speed Rail) Alignment could potentially be more than 16 ft, and the length of the HSR Alignment within the modified flood zone could potentially be more than 20 miles.”
Those water depths and distances are based on an Army Corps of Engineers estimate of a 100-year flood volume in the lake of 1.65 million acre feet, according to the report.
The report states that because of rapid subsidence around Corcoran, “…it does not seem prudent to consider this risk to be negligible.”
New lake bottom?
Areas around Tulare Lake that had not flooded before were swamped this year after the March 10 storm drenched the region and washed down an unusually large amount of low-elevation snow.
Some farmers blamed the giant J.G. Boswell Company, which owns most of the Tulare Lake bed and its levees. They alleged the company held water off the lake bottom in order to plant tomatoes and purposely pushed it onto neighbors south and east of Corcoran.
Others say there was just such a rush of water down the Tule River and Cross creek that breaks were bound to happen.
What’s clear is the “new” southeast area that flooded appears to be following scenarios predicted in the 2017 Amec Foster engineering report.
Under those scenarios, subsidence will cause the old Tulare Lake footprint to morph from mostly egg-shaped to more of a lopsided mushroom, with greater amounts of water at the top of the lake that will spread out to the east and south.
People are already seeing that happen on the ground.
Several years ago, water managers had to install lift stations to pump water from the Angiola water district southeast of Corcoran up and into canals that cross the lake bed. That water used to run by gravity.
And if there hadn’t been pumps moving water from Deer Creek up into the lake bed earlier this spring, it would have flooded farms and towns including Allensworth and Alpaugh, said Jack Mitchell, manager of the Deer Creek Stormwater District.
Elevation maps completed for the district bear out what the Amec Foster report predicted six years ago. The area around Angiola has sunk 24 feet in the eight years since Deer Creek had its previous surveys done, Mitchell said.
“There’s a new lake bottom,” he said.
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