An intense atmospheric river storm continued to put pressure on taut levees in Monterey and Santa Cruz counties Tuesday as authorities considered emergency measures to prevent further catastrophic flooding from hitting the already flooded area.
“The real question today is how do you manually break a section to relieve pressure,” said Zach Friend, a Santa Cruz County supervisor whose district includes Watsonville, which is now threatened by the rising Pajaro River.
Just a few days ago, a levee breach along the river triggered massive flooding in the city of Pájaro, prompting dozens of water rescues and evacuation orders covering hundreds of residents. County and state officials have been working to stabilize the roughly 350-foot gap by placing rocks and cobbles to prevent it from widening, but there is no deadline yet to fix it.
“When these systems come in, and the system is already very wet, the flows don’t really slow down for quite some time,” Monterey County water resources engineer Shaunna Murray said during a news conference.
The challenge is added to the fact that water flowing through a space under Highway 1, between a levee and the highway embankment, is “out of the river channel” and “erodes the levee from the river side.” the floodplain rather than the river side,” said Mark Strudley, executive director of the Pajaro Regional Flood Management Agency.
Possible solutions include cutting Highway 1 to relieve pressure on the river, he said.
Major utilities, including a sewage and water irrigation pipeline, run through the levee and are threatened by erosion.
But its location makes it a tricky solution: The only way to access the gap is through a small open area that straddles the north and south lanes of Highway 1.
And because the rails cross a shallow bridge, an excavator cannot be used to repair the erosion. Also, it would not be good to throw rocks or sand through the opening between the rails, because that could damage utility lines.
“If the water continues to erode through the levee in such a way that it re-enters the river system … it could overwhelm the river system downstream of Highway 1,” where a wastewater treatment plant for Watsonville is located, Strudley said.
If water overflows or seeps through the levee, “we can destroy parts of the plant and we may end up releasing raw sewage into the floodplain, into the river and eventually into Monterey Bay.”
Officials have three options to deal with the situation, Strudley said.
“One thing you can do is open up the levee downstream from that point, a little bit downstream, but upstream from the wastewater treatment plant, to allow the water to come back into the floodplain,” he said.
The second option “is actually opening up Highway 1. Basically going through Highway 1 and the low point, which is south of the river, and letting the water run out of the floodplain.”
The last option, he said, is to do nothing, which might be enough because the storm didn’t hit as hard as expected. A decision is likely to be made on Tuesday afternoon.
Times staff writer Hayley Smith contributed to this report.
