US businesses and the city of Oroville are suing the California Department of Water Resources (DWR) for “decades of mismanagement” of the Oroville Dam.
The claimants allege the spillway failures at the dam last year were caused by “decades of mismanagement” and “intentional lack of maintenance”.
The complaint documents also allege there was an attitude of “patch and pray”, despite cracks appearing in the concrete shortly after construction, which were quickly deemed normal.
Lead lawyer Niall McCarthy of law firm Cotchett, Pitre & McCarthy said: “Local businesses were hammered by the state’s recklessness. Their losses continue to grow. It is time to correct this injustice.”
In February last year 180,000 Californian residents were evacuated when an emergency spillway, a chute cut into the hillside designed to carry excess water flows from the dam, began to fail.
Oroville Dam’s main spillway had crumbled in the previous few days, leading to engineers shutting the water off and allowing water levels in the dam to rise.
Last week the Los Angeles Times reported that costs for repairing the Oroville Dam had risen to $870M (£611M), far higher than the £351M figure reported in October.
In January, a report from the Independent Forensic Team investigating the crisis revealed that a graduate engineer with no previous experience had been given sole design responsibility for the Oroville Dam spillway.
The concrete chute had knowingly been built on weak rock and the report blamed “systematic failures” within the DWR.
A spokesperson for DWR said it could not comment on pending litigation.