The Tehama County Board of Supervisors this week tabled an urgency ordinance that would have limited new well permits in areas at risk of land subsidence, where the ground surface sinks.
The move followed studies showing sinking ground in parts of the county, a phenomenon linked to declining groundwater levels due to drought and agricultural use.
The ordinance proposed pausing new well permits in high-risk areas unless a study could show that a well would not hinder the region’s sustainable groundwater management goals.
Public Works Deputy Director Justin Jenson, speaking at the meeting, said small annual drops in the county’s ground level are adding up.
“Our threshold for total subsidence is 0.5 feet. We are roughly halfway there over the last five years," Jenson said. “The threshold is the thing that you want to avoid at all costs.”
The ordinance noted that subsidence in the county could result in less water storage capacity, due to underground spaces closing that would otherwise store groundwater.
“You should be serious about groundwater decline as a whole, about fixing these problems. Because they're real,” Jenson said.
Jenson said that InSAR satellite imaging shows the sinking is getting worse, even in wet years. Besides reducing the capacity for water storage, a sinking ground can impact infrastructure.
“Imagine a scenario where a road has a 2.5-inch difference of elevation in it," Jenson said. "Do you think that could cause damage? It can.”
He warned that if the county didn’t solve the problem, then state regulators would.
According to data presented at the meeting, groundwater has steadily declined in the area since 2007. Last year, the Red Bluff sub-basin gained about 44,800 acre-feet in groundwater, Jenson said, but the area still has 425,000 acre-feet in cumulative loss of water compared with historical levels.
The meeting attracted a long line of residents for public comment. Many of those who spoke said they were caught off-guard by the ordinance and a previous press release describing the county’s land subsidence.
Supervisors will meet in February to discuss the ordinance again.
