Butte County directs staff to begin CEQA and pursue Prop 218 vote to fund Five‑Mile Basin sediment project

Butte County supervisors on Jan. 28 directed public‑works staff to begin the environmental review required under CEQA and concurrently pursue a Proposition 218 election to fund removal of long‑accumulated sediment from the Five‑Mile Basin, a flood‑control structure that serves Chico and surrounding areas.

Director of Public Works Joshua Pack told the board staff estimates about 67,000 cubic yards of sediment have accumulated in the basin since its construction in the mid‑1960s. "Breaking it down, if you have a regulation size football field and you filled it with 2 feet of sediment or gravel, that's the approximate amount of 67,000 cubic yards," Pack said. Hydraulic modeling shows the loss of freeboard ranging from roughly a half‑foot to as much as 1½ feet for large storms, reducing the basin's designed margin of safety during 50‑ and 100‑year events.

The presentation separated long‑term sediment removal from short‑term, post‑fire risks. Pack said post‑Park Fire conditions and watershed changes increase the near‑term risk of debris and sediment flows; state and Cal Fire analyses modeled conservative, worst‑case impacts for 2‑ and 10‑year storms. Pack outlined short‑term mitigations already under way — increased monitoring, vegetation removal where approved, staging equipment and partnering with contractors to remove debris ahead of storms — but said those measures do not substitute for a long‑term sediment project.

Pack estimated preliminary construction costs of about $5.4 million, but warned that CEQA, permitting, mitigation and unexpected site conditions could push total project costs above $7–8 million. He said many environmental permits will be required because native riparian habitat has developed in the basin, and most permit processes require a completed environmental document before work can proceed.

To fund the work, staff proposed using County Service Area 24 (CSA 24), which covers roughly 15,200 parcels largely in Chico, as a per‑parcel assessment mechanism. "Based on 2024 dollars our estimate's about $500" per parcel to raise roughly $7.5 million if collected up front, Pack said; phased collection over several years could lower annual assessments. The assessment approach would require a Prop 218 majority election of affected property owners.

Supervisors debated tradeoffs between starting CEQA immediately and completing the CSA election first. Several members urged an expedited timeline, citing recent storms and the unpredictable nature of weather. The board reached consensus to direct staff to initiate CEQA and simultaneously pursue the Prop 218 election, and to return with a CSA budget amendment and follow‑up reporting. Supervisors also asked staff to pursue state and federal advocacy to seek grant support and to identify contingency funding — including existing CSA fund balance, ARPA or reserves — if the election fails.

Pack cautioned the board that CEQA and permitting are the critical path: "My estimate is at least 3 to 5 years to go through these processes to get the approval to complete the construction," he said.

Next steps: staff will prepare a budget amendment for CSA 24 reflecting initial CEQA costs, begin the CEQA scoping and funding‑strategy work, and return to the board with a timeline and a proposed Prop 218 election schedule. The board also asked staff to draft letters to state legislators and congressional representatives describing the county's needs.