Butte supervisors authorize targeted emergency work at 5 Mile Basin to reduce flood risk

The Butte County Board of Supervisors on Aug. 12 directed county staff to pursue a consultant-recommended, targeted treatment at 5 Mile Basin intended to redirect stormflows away from the Big Chico Creek diversion and reduce near-term flood risk.

The decision, made by board consensus rather than a roll-call vote, follows presentations by Joshua Pack, director of public works, and months of coordination with federal and state agencies and members of the public. Pack recommended a three-tiered set of options and said his consultant favored a focused plan (Alternative 3) that would create flow paths, repair scour holes and remove selected vegetation to push water toward Lindo Channel and Sycamore Creek rather than concentrating flows at the Big Chico structure.

Pack said the county has submitted permit applications to regional regulators, including the California Department of Fish and Wildlife and the U.S. Army Corps of Engineers, and that the Army Corps initially resisted treating the work as an emergency action. He said county staff and federal and state legislative offices — including Congressman Doug LaMalfa’s and Assemblyman Kevin Kiley’s offices — have been engaged to help expedite reviews.

Why it matters: The basin, built by the Army Corps in the 1960s and maintained by the county, is heavily silted and, after recent wildfire and winter storms, has redirected flows in ways that created two scour holes and increased pressure on levees and diversion structures upstream of Chico. Pack warned that a repeat of recent atmospheric river events could produce more serious damage if the basin is not relieved.

What the county will do: Pack described three options: routine annual maintenance (Alternative 1), a full sediment-removal restoration back to the 1960s design (Alternative 2, estimated in excess of $4 million), and a targeted approach (Alternative 3, estimated about $500,000). The board instructed staff to pursue Alternative 3 now, using a job-order contract (JOC) already in place, and to continue pursuing funding and permit approvals for a longer-term solution. Board members also asked staff to continue annual maintenance after the targeted work to prevent re-growth from recreating the same problem.

Funding and risk: Pack said the county had earlier appropriated roughly $2 million in CSA 24 (County Service Area 24) funds to the basin and that Alternative 3 would be funded from that CSA account. He warned CSA 24 is not unlimited. He also warned that moving forward without all permits would carry regulatory risk, including notices of violation, fines or other enforcement actions from agencies, but characterized Alternative 3 as more aligned with regulatory expectations than a full, unpermitted restoration.

Public comment: Dozens of residents who live downstream and adjacent to vulnerable levees described repeated property damage, eroded levees and debris-clogged channels. Speakers including Les Harringer and Daniel Adamas urged a larger removal; others asked that the city of Chico take long-term management responsibility for infrastructure inside its limits. Supervisors said they would pursue a longer-term governance and funding discussion — including potential CSA annexation or state/federal grants — while starting the targeted work for this coming fall.

Next steps: Pack said crews are ready to begin work, and he requested board authorization to allow the JOC to proceed promptly; the board gave a consensus direction to proceed with Alternative 3, continue permit and funding outreach, provide public notice of any start date, and to return material and modeling results to the board as they become available.