The Greenlawn Water District issued a "boil water" alert Thursday after E. coli bacteria were detected in a sample taken from one of its 18 wells.
"That well was immediately taken offline and chlorine was added," said district engineer Dennis Kelleher.
Thursday's test of all 18 wells was prompted by a discovery of total coliform bacteria at one of the district's 20 testing locations Wednesday, during routine checks, Kelleher said. E. coli and total coliform bacteria were then found in one well sample.
The presence of E. coli indicates possible contamination of the water supply by human or animal waste. Consuming E. coli-contaminated water can cause diarrhea, cramps, nausea and headaches. Total coliform bacteria is a category including those found in the soil, in water influenced by surface water and in human or animal waste.
"We are required, when bacteria is detected, to take the next step and check all of our wells for bacteria," Kelleher said.
The 20 testing locations are at various places, such as homes and firehouses.
The alert advises residents to boil water as a safety precaution either before drinking it or using it in food preparation. The alert says emergency chlorination of the water supply had begun and that additional water samples are being tested.
Kelleher said the alert will remain in effect until further notice.