On Wednesday, May 18, at approximately 7:50 a.m. a large tree fell and snapped the power transmission lines that supply electricity to SLAC. The resulting site-wide power outage lasted over three days. Most staff, users and students were required to leave the site for safety and security reasons. While no one was hurt, the incident provided opportunities for learning and improving our preparation and response for emergencies.

Evacuate High Hazard Areas

Steps were taken to secure high hazard buildings and areas. Once an initial evacuation was completed, specially trained teams went through the site to make sure no immediate hazards were present due to the power outage and no staff remained in high-hazard areas. High-hazard areas include those where the oxygen supply is deficient (ODH), chemicals are stored and where injuries might be caused due to machines and equipment restarting when power returns. People found in these areas were asked to evacuate.

Power Up Critical Systems

After ensuring that people were not at risk, getting power to critical systems became paramount. Though most emergency and back-up generators performed adequately, the power outage exposed some deficiencies in the system. Additional portable generators were brought on site to fill in gaps where power was needed. Plans are now in the works to provide permanent solutions for areas where there was insufficient back-up power.

Once power was restored to the master substation, high-hazard and/or sensitive areas - like ODH areas and the computer building - were brought back on-line in stages. This was done to prevent unforeseen hazards from the sudden return of power to building systems and equipment. As power was restored, buildings were checked for oxygen deficiency, chemical, electrical and other hazards. Once cleared of these hazards, occupancy by regular staff was not allowed to resume until SLAC Security had performed a building sweep. Security staff turned off coffee pots, space heaters and other heat-generating equipment that could cause a fire if left unattended after power returned.

Areas for Improvement

From debriefing the teams who restored power to the site, the following areas for improvement were developed:

• Evacuate high-hazard buildings and areas
• Keep an updated hard copy of emergency contact numbers
• Ensure that critical systems have reliable back-up power
• Medical Department
• Communications systems
• Critical scientific equipment
• Fire and life safety systems
• Make sure non-essential staff remain off site

Basic Steps can Prevent Problems Turn off coffee pots, space heaters, soldering irons and other heat producing equipment. If employees are aware of heat producing equipment that was not turned off, they should notify their supervisor.