Fire crews said 250 gallons of aqueous ammonia leaked into a secondary containment unit around 10:45 a.m. at the Santa Teresa Water Treatment Plant on Graystone Lane. It was not immediately clear what caused the leak.
The spill caused a shelter in place order for a time as emergency officials assessed the situation. The shelter applied to people Graystone Lane at Via Santa Teresa; Rosalind Lane; Skuse Court; and Carriage Hill Drive. It was lifted around 2:30 p.m.
No injuries were reported and it didn't appear that anyone outside the plant ever reported smelling ammonia.
Fire officials said the spill did not impact drinking water.
"We don't think there's been any involvement in the water treatment part," fire Capt. Steve Forman said. Forman said he expected the clean up to take awhile.
The treatment plant is located at 7011 Graystone Lane in San Jose.