Why Natick's E. Coli Problem Doesn't Threaten Nearby Communities

FRAMINGHAM, MA — On Wednesday evening, Natick officials were surprised to learn the town's water supply was possibly contaminated with E. coli bacteria. A boil-water advisory was put in place, ordering residents (and pets) across town to avoid ingesting water without cooking it first, even for tasks like brushing teeth.

The discovery might raise alarm bells for residents in nearby communities like Wayland and Framingham because bacteria knows no borders.

But wastewater managers in both communities say Natick's E. coli discovery won't spill over into neighboring water supplies. It is true that bordering communities share water pipe connections, but those connections are always closed, except in water emergencies, according to officials. There's a similar connection between Wayland and Natick that stays closed at all times unless there's an emergency.

The three communities also get their water from different sources.

Wayland's drinking water comes from the Sudbury, Assabet and Concord River basins. Framingham is one of more than 40 communities in the Boston area that gets its water through the Massachusetts Water Resources Authority (MWRA), which draws from the Quabbin and Wachusett reservoirs. Framingham's drinking water is treated at the MWRA John J. Carroll wastewater plant in Marlborough.

RELATED: Wayland DPW: Natick E. Coli Contamination Won't Cross Town Line

Natick's water comes from 11 wells spread across the town and Dover. The main wells are Springvale, Evergreen and Elm Bank. Natick does use the MWRA's sewer treatment system.

On the other side of Natick, there are a number of homes in Wellesley that get drinking water from Natick's wells, and so have had to obey the boil-water advisory.

Natick has not determined how E. coli got into the drinking water system, but there are a number of ways it can happen.

According to Framingham DPW spokeswoman Allyssa Jewell, some reasons include animal excrement, excessive stormwater runoff or snow melt, a water treatment error or possibly a sampling error. Natick officials have also said a broken pipe somewhere in the system could be a culprit.

The good news is that all three communities frequently test drinking water at multiple sites to find contamination. Framingham tests at 18 locations each week, plus the city's water storage tanks.

In response to the positive tests, Natick has taken the water sources that tested positive offline, and has boosted treating water. The town expects to get a second round of tests back by Saturday, and the boil-water advisory will be in place until then.