Bacteria detected in Oak Bluffs water no cause for alarm, official says

Upper Lagoon Pond in Oak Bluffs is a water source for the town. — File photo by Ralph Stewart

Monthly testing done last week on water pumped by the Oak Bluffs Water District (OBWD) tested positive for bacteria.

Speaking to The Times on Monday morning, OBWD superintendent Kevin Johnson said there is no cause for alarm.

“We had an issue where we did our routine sampling and three locations came up positive for total coliform (TC) bacteria,” he said. “A TC positive can be because of iron bacteria, which is not harmful. We don’t have any E. coli. The water is perfectly safe to drink.”

Escherichia coli is a coliform bacteria that is associated with septic systems and runoff from agricultural fields. Most strains of E. coli are harmless, but some can cause illness. Other types of coliform bacteria are ubiquitous in the natural world. Iron bacteria are found in water-supply systems because they feed on dissolving ferrous iron (i.e. rust). They are not harmful to human health, but can clog filters and other equipment.

Mr. Johnson said routine testing on Nov. 1 revealed an elevated bacteria level, but did not specify the bacteria. Subsequent re-sampling showed positive for TC and negative for E. coli. It takes 24 hours to get test results.

According to the Department of Environmental Protection (EPA) website, “Total coliforms are a group of related bacteria that are (with few exceptions) not harmful to humans…. EPA considers total coliforms a useful indicator of other pathogens for drinking water.”

Mr. Johnson said the bacteria level triggered a “Level 1 assessment” which prompts the OBWD to formulate an action plan with the DEP, which includes flushing the system. Flushing was done Thursday, Friday, Saturday, and Sunday.

The action plan also called for putting chlorine back in OBWD water, beginning on Friday.

Since late September, the OBWD has been supplying the Edgartown Water Department while its water tower is shut down for painting and maintenance. Edgartown provided similar reciprocity when the Oak Bluffs water tower was offline for maintenance in 2014. Because Edgartown does not chlorinate town water, OBWD suspended chlorination, as well as fluoridation, until the repairs are complete. Mr. Johnson said the Edgartown repairs should be done by the end of the month.  

Mr. Johnson speculated that the reason for the elevated bacteria level was an Internet connection failure. “Edgartown wasn’t seeing our tank and was pumping into our system; because of the water moving back and forth, it could have suspended some iron bacteria. When you have a change in flows, you can sometimes get bacteria suspended in the water column.”

Mr. Johnson said more samples will be taken this week and sent to the Wampanoag Environmental Laboratory.

“The bottom line is this is not a public health issue,” he said.