The strangest fact in the Eaton Fire record is that the circuit blamed for the ignition was not carrying power. It had been taken out of service. Understanding why that matters starts with understanding what was actually standing on that ridge.
Three towers, three different loads
Witnesses kept saying "the towers", which was not precise enough to investigate. Three transmission towers stand on a narrow spur ridge running northeast to southwest above Eaton Wash, and because they are referenced constantly in interviews, videos and photographs, the investigation team spent dedicated time on January 11, 2025 giving each a clear reference description. They labelled them by position rather than by SCE's numbering, so that a resident pointing out a window could be matched to a structure.
Tower #1 is the tallest and sits at the southwest end of the group. The equipment section of the report describes it as supporting the Mesa-Vincent #2 circuit on the east side and the Eagle Rock-Mesa circuit on the west. Each circuit has three cross arms, each cross arm carries two conductors, for a total of twelve conductors at 220kV. The conductors extend both north and south from the tower. Its base forms a square, it carries a guard or shield line at the top with a small coax line wrapped around it, and a small sign on top reads "6".
Tower #2 is the second tallest, northeast of Tower #1, and supports the Mesa-Vincent #1 circuit on the uphill east side and the Goodrich-Gould circuits on the downhill west side. Again twelve conductors, again 220kV, again a square base.
Tower #3 is the odd one. It is the shortest, sits north of Tower #2, and is rectangular rather than square. It supports only three conductors, for the Mesa-Sylmar circuit, and the report notes in parentheses that the circuit is idle. Those conductors are on one side of the tower only and do not continue to the other side. The report adds a detail that matters: the leads appear to ground the conductor to the tower's steel frame.
Where the finding lands
The supplemental report signed July 22, 2026 is specific about the hardware. The arcing events occurred at the southwest conductor paddle of the out of service Southern California Edison Mesa-Sylmar circuit tower. A conductor paddle is the fitting where a conductor terminates and attaches to the tower structure. That is not a general statement that something on a tower failed. It is a location on a component.
The physical evidence pointing there was found early. On January 12, 2025, a CAL FIRE battalion chief located a beaded metallic like substance in the origin area on the interior frame in the southwest corner of Tower 3, near the attached grounding cable. It was photographed in place, collected into a clear plastic container as evidence item #2, secured in a locked compartment of a department vehicle and transferred into the evidence chain three days later. Two further metallic like objects with beaded end appearances were logged as items #3 and #4.
Beading on metal is one of the classic artefacts of electrical arcing. It is the reason the search of the origin area was conducted with magnets first and then metal detectors, and the reason an aluminium coloured item that was not attracted to a magnet was flagged separately with a green flag for collection.
What the released documents do not explain
We will not pretend to more than the record supports. The released reports state where the arcing happened and what it ejected. They do not publish the electrical explanation of how an out of service circuit came to arc.
The reason is visible in the documents themselves. The supplemental report references attachment #10.23, the Eaton Fire Electrical Investigation Report, and attachment #10.24, the Metallurgy and Failure Analysis Report, both delivered in final form by CAL FIRE Assistant Chief Brian Hawkins on July 22, 2026. Those attachments were not released. Neither were the names of the retained electrical engineer and metallurgist, which are redacted throughout. Anyone publishing a confident mechanism today is filling that gap with something other than these documents.
The condition of the Mesa-Sylmar hardware elsewhere
There is one passage in the initial report that speaks to the state of this circuit's equipment, and it comes from a site visit rather than a laboratory.
On February 20, 2025, SCE facilitated tours of the Eagle Rock and Gould substations for the CPUC, LACoFD and CAL FIRE, and on the same day a tour of transmission towers near La Canada Flintridge. The lead investigator records observing three SCE transmission towers at that location, and identifies the tower of interest as the last tower of the out of service Mesa-Sylmar circuits.
What they saw there is documented plainly. The centre conductor was dangling free from the bridge section of the tower. It appeared that the remaining two conductors were not bolted down to the tower bridge. SCE photo evidence later showed that one conductor was hanging loosely from a bolt, and the other was wedged into a corner section of the bridge with birdcaging on the end holding it in place. Birdcaging is the splaying apart of the individual strands of a stranded conductor.
Then the exchange the report chose to record: CPUC attendees, the SCE lineman, and an SCE lawyer discussed the maintenance of that tower and whether the abnormalities seen with the conductors were new. The lineman said that they were not new and were like this last year, and he was also unsure why they were not corrected when it was inspected.
That observation is at a different tower from the origin, and the reports do not connect it to the ignition. It is recorded here because it is in the primary document, it is attributed to a named role rather than an anonymous source, and it is the kind of detail that disappears from secondary coverage.
Why the distinction between the circuits matters
The practical significance of the finding sitting on the idle circuit rather than a live one is about detection. A fault on an energized transmission line announces itself: protective equipment sees it and operates, and the event lands in the utility's electrical data with a timestamp. That is exactly what happened five miles away on the Eagle Rock to Gould 220kV line at approximately 1811 hours, where a protection device detected the fault, opened to isolate it, attempted an automatic reclose because an earlier attempt to disable that function was unsuccessful, found the fault had not cleared, and locked the line out.
An idle circuit has no comparable story to tell about itself. SCE initially reported no line faults on the lines until more than an hour after the reported start time of the fire. The event that the investigation ultimately attributes the fire to was captured not by the grid, but by a homeowner's camera pointed at a mountain because of a fire in 1993.