Crews work to contain and remove oily debris from the Yuba River near Englebright Lake on Feb. 22 following the New Colgate Powerhouse penstock failure. Yuba Water Agency reported that 17 bins of material had been removed in recent days as cleanup efforts continue. Photos courtesy of Yuba Water Agency

YUBA COUNTY, CA (MPG) - Cleanup and environmental monitoring efforts continued this week after a Feb. 13 rupture of a large penstock pipe at Yuba Water Agency’s New Colgate Powerhouse near Dobbins triggered a mudslide, damaged infrastructure and sent debris into the Yuba River.

Yuba County officials proclaimed a local emergency Feb. 19, citing disaster conditions caused by the failure and damage to power infrastructure and nearby waterways. The declaration allows the county to seek state and federal disaster assistance if needed. The Yuba County Board of Supervisors is scheduled to consider ratification of the proclamation Feb. 24.

The rupture occurred shortly before 3 p.m. Feb. 13 while crews were testing the system after months of maintenance. The 14-foot-diameter penstock connects to a five-mile tunnel that carries water from New Bullards Bar Reservoir. It delivers high-pressure water to Pelton wheel turbines capable of producing up to 350 megawatts at peak output.

The sudden water release caused hillside erosion and significant damage to facilities below the pipe. Mud, sediment and man-made debris, including oil, entered the Yuba River. The incident damaged generation and distribution equipment and knocked out electricity to about 15,000 households. PG&E rerouted service and restored most power within hours, though some foothill communities experienced longer outages.

Several workers required rescue after access roads were damaged. One worker remains hospitalized in stable condition. Officials have reported no fatalities.

Yuba Water Agency officials said investigators continue to determine the cause of the rupture. General Manager Willie Whittlesey said it could take weeks or months to understand the extent of the damage and longer to complete repairs.

“The reality is, it’s going to take weeks to months to fully understand the extent of the damage to the hillside and to our facilities and then months to years for recovery,” Whittlesey said.

An aerial view shows the New Colgate Powerhouse and surrounding hillside following the Feb. 13 penstock rupture near Dobbins. Yuba County has proclaimed a local emergency to support environmental monitoring and cleanup efforts, officials said. Photos courtesy of Yuba Water Agency

Environmental impacts remain under review. Fisheries scientists with the South Yuba River Citizens League reported that juvenile salmon and steelhead were stranded and likely died after river conditions changed rapidly following the incident. State and local agencies continue monitoring water quality and ecological effects.

Initial independent laboratory tests of water samples collected downstream of New Colgate Powerhouse and at Englebright Lake showed no detections of polychlorinated biphenyls, petroleum hydrocarbons or volatile organic compounds, according to Yuba Water Agency. Those substances are commonly associated with petroleum-based and industrial materials.

“We’re encouraged by these initial results, which suggest that any oil that washed into the river is likely limited to oily debris on the surface,” Whittlesey said. He added that monitoring remains ongoing.

The agency has collected daily samples since the morning after the incident and is developing a long-term monitoring plan in coordination with state and federal agencies. Sampling includes control sites upstream of the incident and sites within the affected area.

Cleanup crews have removed more than 100 cubic yards of oily debris from the river corridor and lake shoreline. Several large oil and debris booms have been installed to contain material in the upper stretch of Englebright Lake. Barges are operating on the lake as crews continue removal efforts. Officials said crews expect to remove several hundred cubic yards of material per day as work continues.

Englebright Lake remains closed to recreation. Officials have urged the public to avoid the stretch of the Yuba River between New Colgate Powerhouse and Englebright Lake during response operations.

Access to the powerhouse area remains restricted. Lake Francis Road is closed beyond the last residence while geotechnical experts assess hillside stability and develop stabilization measures. Washed-out roads have complicated full damage assessments and repair planning.

The county’s emergency proclamation states there is no identified risk of downstream flooding. However, officials cited public safety concerns related to debris and potential hazardous materials in the waterway, requiring coordination among multiple agencies.

Yuba Water Agency has posted updates and a video message from agency leadership on its website as response efforts continue. Officials have not released a timeline for repairs or when the Colgate facility might return to service.