The Corral Fire ignited on June 1, 2024, in the southeast portion of Lawrence Livermore National Laboratory’s (LLNL’s) Site 300, a 7,000-acre experimental test site near Tracy, California. Fueled by high winds averaging 32.7 mph (with gusts up to 43.1 mph), the fire rapidly spread across almost 15,000 acres, damaging infrastructure, disrupting operations, and damaging offsite properties. The fire significantly damaged the Superfund cleanup infrastructure at Site 300, as detailed in LLNL’s July 2024 slide presentation made to Tri-Valley CAREs.
Thanks to Tri-Valley CAREs’ Freedom of Information Act (FOIA) request, we now have the first publicly released report identifying the cause of the fire. This is a major step forward in the public’s understanding of what happened that day at Site 300. However, what the public still does not know is significant. This high-explosives testing facility, where blasts have dispersed over 100 hazardous constituents (including significant quantities of depleted uranium) around outdoor firing tables, uses only minimal air monitoring technologies (despite the U.S. EPA Region 9’s suggestion that LLNL increase the air monitoring at the site boundary). Thus, it is not known if the Corral Fire smoke contained radionuclides or other hazard constituents. Additionally, Public safety risks have long been a concern because the site stores significant quantities of high explosives, and the lab has not reported on whether the fire threatened any of those storage areas and put the public at risk.
The causation analysis did disclose many important new pieces of information. For example, over 21 power faults were recorded as the fire jumped Corral Hollow Road, two firefighters sustained injuries, and asbestos was released from a burned building awning, heightening health concerns.
Figure 1: Map of Site 300, showing the location of Pole 8009 and Substation 846, where the fire originated due to electrical failure.
What We Learned from the Report
The root cause analysis, conducted by LLNL, concludes that the fire started due to an electrical failure at high-voltage pole 8009. Here’s what the report reveals:
- The fire ignited near pole 8009 when an aluminum hand tie failed, allowing two power lines to come into contact.
- The electrical arcing produced sparks, which ignited the surrounding dry grassland.
- High winds (gusting up to 43.1 mph) worsened the fire’s spread, quickly pushing it across Site 300 and into offsite land.
- LLNL had previously begun replacing these aluminum hand ties with stronger steel alternatives, but pole 8009 had not yet been updated.
LLNL prioritized replacing hand ties only after observed failures (e.g., a 2023 storm where a hand tie melted). Since no prior wind-related hand tie failures had occurred, upgrading Pole 8009 was not deemed urgent.
For the first time, we have official documentation that this was not an accident of nature—it was an entirely preventable equipment failure.
Figure 2: Map of the Corral Fire’s affected areas
What LLNL Fails to Address: A Critical Review
While the lab acknowledges its failed infrastructure sparked the fire, the report raises more questions than it answers. Here are the biggest gaps in the lab’s explanation—and the hard questions LLNL must answer:
1. Why Was This Weakness in its Infrastructure Allowed to Persist Despite Well Known Wind and Wildfire Risk?
The report acknowledges that LLNL has been replacing outdated aluminum hand ties with stronger steel versions since 2014—yet pole 8009 was still using a known weaker material when the fire ignited. Why wasn’t this replacement prioritized in high-wind areas like Site 300? If LLNL knew that steel hand ties are 8-18 times stronger, why were weak aluminum ties still present at a site prone to extreme wind events?
2. Why Didn’t LLNL Implement More Aggressive Wind Safety Measures?
The lab’s own report suggests that no additional controls were in place to mitigate high wind risks—despite feeder 8 being located on the highest ridgeline at Site 300, where wind speeds are often extreme. The report even lists several safety measures that could have helped but were never implemented. Why didn’t LLNL turn off reclosers during extreme wind conditions? Why wasn’t feeder 8 relocated or put underground, given its known vulnerability? Why hasn’t LLNL implemented Public Safety Power Shutoffs, as California utilities have done to prevent wildfires?
These are standard wildfire prevention strategies used by utilities across California—so why is Livermore Lab failing to meet basic fire safety standards?
3. Did LLNL Underestimate the Risk of Electrical Failure?
The report suggests that this is the first recorded instance of a hand tie failure in high wind at Site 300. But that does not mean the risk should have been ignored. In fact, the lab previously experienced a hand tie failure in 2023, though in that case it was due to a different cause. Did LLNL conduct any risk analysis on these failures before the fire? What criteria did LLNL use to decide which poles would be replaced first? Why did it take a catastrophic fire for LLNL to acknowledge this as a serious vulnerability?
The fact that this issue had never been documented before does not mean it was unforeseeable—especially given that California has experienced devastating wildfires caused by similar electrical failures.
4. Why Was the Public Kept in the Dark?
LLNL did not release this report voluntarily. Only through Tri-Valley CAREs’ FOIA request was this information made public. This raises serious concerns about transparency from the Lab towards residents of Tracy. Why did LLNL not disclose the fire’s cause sooner? How many other reports about fire risks at Site 300 have been withheld from public view? Why should the community trust LLNL to conduct objective investigations into its own failures? Given that Site 300 contains hazardous materials and conducts high-explosives testing, the public deserves immediate access to any report that affects community safety. Instead, LLNL only released this after legal action—undermining its credibility.
5. What the Report Says vs. What It Doesn’t Prove
The report confirms that prescribed burns were conducted from May 28-31, 2024, covering 1,911 acres, with the last burn occurring just 24 hours before the Corral Fire ignited 2,900 feet away. LLNL dismisses any connection, but without thorough heat measurements, ember modeling, or independent verification, their conclusion could lack credibility. Did residual embers smolder in high winds? Was post-burn monitoring sufficient? Could the burns have lowered the ignition threshold of nearby vegetation? These unanswered questions demand scrutiny, especially given California’s history of wildfires linked to controlled burns. Given the proximity and timing, further clarity on how LLNL ruled out any connection would help build public trust in their findings.
Accountability and Next Steps
There is no indication that LLNL planned to post this report on its public website or otherwise make the cause of the fire public. Without Tri-Valley CAREs’ intervention, there would have been no possibility for public input, questions or scrutiny into how LLNL can prevent future fires or how it responded to the Corral Fire.
With the information now provided, albeit 9 months later, what might the he lab must act now to:
- Accelerate the replacement of outdated electrical fastenings to prevent similar failures.
- Improve fire mitigation measures, such as reconsidering prescribed burns and increasing vegetation management.
- Consider wind-resistant upgrades (e.g., underground lines, automatic recloser shutoffs).
- Enhance public transparency by proactively sharing safety-related reports on its webiste rather than requiring FOIA requests.
Figure 3: Infrastructure Damage
Why This Matters
If LLNL is willing to hide the fire’s cause until forced to release documents under FOIA, how can we trust them to objectively investigate all possible contributing factors?
The Corral Fire is not just an isolated incident—it highlights the ongoing risks posed by Site 300’s operations and the importance of independent oversight. As a community advocacy group, Tri-Valley CAREs remains committed to ensuring that LLNL prioritizes safety and environmental responsibility. The victory for transparency is a reminder of the power of public pressure. We will continue to demand accountability, stronger safety measures, and full disclosure of hazards that could impact our communities.
Get Involved
If you’re concerned about wildfire risks, environmental health, or Site 300’s operations, join us in advocating for stronger safeguards and public accountability.
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