County investigates cause of widespread townsite power outage on May 8

A high-magnitude fault on both transformers feeding the Los Alamos townsite left much of the community in the dark Thursday night, and county utility crews are still trying to explain why the failure spread so widely.

The outage began at 9:32 p.m. on May 8, when the electric substation on Los Alamos National Laboratory property lost both transformer feeds serving the townsite. County crews were dispatched by 9:40 p.m. after reports of a possible transformer blowing near Trinity Drive and Timber Ridge, and residents soon reported what looked like sparking or explosions in that area.

The blackout stretched across a broad swath of town, from the far east ends of North Mesa and Barranca Mesa west toward the outer edge of Quemazon, then back east toward commercial and county buildings beyond the Los Alamos Airport. Elk Ridge on East Jemez Road stayed energized because it is served by LANL’s electric distribution system, underscoring how dependent the rest of the townsite is on a limited set of high-voltage feed points.

County staff say the root cause remains under investigation. Electric distribution personnel are collecting data for review by the Los Alamos County consulting engineer, while crews continued patrolling lines, found melted jumpers near Trinity and Canyon View Apartments, then discovered twisted wires and an underground cable issue near the Aquatic Center. Additional damaged underground cable was later found on Cheyenne Street.

The county says the outage produced 5,785 meter failures in its automated portal, a scale that shows how many homes and businesses were swept into the event at once. Even with the Department of Public Utilities keeping line crews on standby around the clock, the response expanded to bring in additional lineworkers because the incident was not a routine local interruption.

Restoration was completed by 8 a.m. on May 9, but the county’s utility materials point to a deeper reliability problem. Los Alamos County has two substation sources of electric power, yet the townsite switch station is supplied by a Los Alamos National Laboratory substation, leaving the townsite vulnerable when a fault hits that corridor.

County officials say the nearly completed Los Alamos Switch Station on LANL property is the department’s highest-priority electric project because it should substantially improve redundancy and reduce the impact of future outages. The latest event echoes earlier disruptions, including the Oct. 22, 2021 townsite outage tied to a LANL substation and a Nov. 4, 2024 outage that affected about 1,300 customers on electric circuit 13, including Western Area, neighborhoods off Trinity Drive down to Oppenheimer, and Pajarito Mountain.