The Oak Bluffs water district has violated state drinking water standards for the second time in five months, although this time the contamination did not trigger an emergency boil-water order, as happened last September.

A town notice published in today’s Gazette states the water department took 24 water samples on Dec. 28, three of which showed the presence of coliform bacteria: one at the Farm Neck well, one at the town standpipe and one at town hall. Department of Environmental Protection regulations permit a maximum of one sample per month showing elevated coliform levels.

Samples taken on Dec. 30 at the three wells were clean.

“This is not an emergency. If it had been, you would have been notified immediately. Total coliform bacteria are generally not harmful themselves. Coliforms are bacteria which are naturally present in the environment and are used as an indicator that other, potentially-harmful, bacteria may be present,” the notice states.

Nevertheless, people with specific health concerns are warned to consult their doctor; coliform bacteria poses a risk to people with compromised immune systems, some elderly and infants.

On Sept. 25 the town water district issued a boil-water order that forced nearly all town residents to use boiled or bottled water for most of their needs for nearly a week.

Oak Bluffs water district superintendent Thomas Degnan said this week that the cause of the problem remains unknown, but he said some water samples may have been drawn from older pipes where bacteria often gathers. This would not necessarily indicate a system-wide contamination problem.

Mr. Degnan said the water district plans to ask the DEP for permission to change some testing locations.