At Tuesday’s board of supervisors meeting, Public Works director, John Diodati said the contaminated water event was rare and unusual. “For over the last 50 years, we’ve treated Lopez water for the five cities and this is the first boil notice,” said Diodati. … On April 30th, a boil water notice was issued because water samples from the Lopez Lake water distribution system showed a presence of E. coli. A second round of tests displayed higher levels of coliform bacteria, not E. coli. The notice was lifted after the drinking water supply was tested and confirmed safe. Testing to find the cause of the contaminated water is expected to take 30 days to complete. Starting on May 7, the Five Cities water supply will be treated with free chlorine — a stronger water disinfectant — until May 28.