The hydrants were opened in Pleasant Hill, Pacheco, Martinez, Lafayette and Walnut Creek between 11 p.m. Friday and 1:15 a.m. Saturday, sending a large amount of water gushing into the streets, according to the Contra Costa County Fire Protection District.
Fire officials said each of the opened hydrants was an unnecessary call for service that made it harder for firefighters to respond to legitimate emergencies. In addition, the flowing water poses a threat to traffic and to nearby property, and could damage the hydrants.
"This is not a harmless prank," said Fire Prevention Captain Randy Champion.
"I can not emphasize enough how this type of criminal activity was dangerous and irresponsible," Champion said.
The district is asking for the public's help in identifying those responsible. Anyone with information is asked to contact local police, the Fire District's Fire Investigation Unit at (925) 942-9140 or the arson tip line at (866) 502-7766. Callers can remain anonymous.