Approximately 5 to 10 gallons of water containing "dilute sulfuric acid" were released onto the ground and asphalt where the tower's containment system failed. At SLAC, water is circulated to cool the heat generated by the accelerator and pumped into one of seven cooling towers, then exposed to air and re-circulated, Lyon explained.

Chemicals are added to the water, using industry standard processes, to prevent contamination caused by the growth of algae or mold. The acidity of the water that leaked out was comparable to lime juice, and no injuries, exposure or off-site contamination were reported, Lyon said.

The leak was discovered about 2 a.m. on Tuesday by a SLAC technician during a routine daily inspection of the cooling tower. A hazardous incident team from the Palo Alto Fire Department initially responded and contained the spill. The fire department left the scene later that morning, Lyon said.

About five SLAC workers were evacuated from the accelerator's main control center, the only building near the cooling tower. The accelerator was shut down until about 8 a.m., but Lyon described the impact on operations as "negligible."

The contamination site remained sealed off until 6:30 a.m. today, when an outside contractor finished cleaning up the spill and the vicinity. SLAC workers are repairing the leak and investigating the cause, which Lyon said could take another day or two.

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