Water Testing Results

Water Testing Results

The Wellesley Water Division has confirmed elevated levels of PFAS6 in the drinking water during initial monitoring starting in April 2021.  Even though the level is above the MCL, a PFAS6 MCL violation has not yet occurred, as violations are based on three months of testing, and we are waiting for the results of the June 2021 sampling.  Instead, we are required to provide you with these materials to make you aware of the elevated levels so you can make informed decisions about your drinking water while we continue to monitor the water supply.

Even though the reported levels are above the MCL, we are not currently in violation of the MassDEP PFAS6 MCL standard.  However, as it is likely that the next set of test results will also exceed the MCL putting us in violation of the standard, we are providing you with these materials to make you aware of the elevated levels so you can make informed decisions about your drinking water while we continue to monitor the water supply.

Water Testing Results for Quarter 1

Sample Location by Entry Point to Distribution SystemMonitoring PeriodSample Collection DatePFAS6 Result (ng/L)Average (ng/L)*MCL (ng/L)
Wellesley Avenue Water Treatment PlantQuarter 1 Initial

Quarter 1 Confirmation
4/21/2021


5/3/2021
10.4


tbd
N/A20
Rosemary/Longfellow Water Treatment PlantQuarter 1 Initial

Quarter 1 Confirmation
4/21/2021


5/3/2021
10.9


tbd
N/A20
Morses Pond Water Treatment PlantQuarter 1 Initial

Quarter 1 Confirmation
4/21/2021


5/3/2021
45.1


tbd
N/A
20

Purchased Water by Entry Point to Distribution SystemMonitoring PeriodSample Collection DatePFAS6 Result (ng/L)Average (ng/L)*MCL (ng/L)
Hegarty Pumping Station (Massachusetts Water Resources Authority - MWRA)**RoutineJanuary 20210020

*Average = (Initial Result + Confirmation Result) divided by 2.

**MWRA conducts sampling as required for their water supply, Wellesley is not responsible for sampling this water source.  

Note: Morses Pond is off-line and no water being pumped into the drinking water system.

Note: The location where elevated levels PFAS6 were reported (Morses Pond) is one of 4 active entrance points (or sources) that supply drinking water to our system. PFAS6 levels were reported below the 20 ng/L MCL at these other locations.

MCL = Maximum Contaminant Level

ng/L = nanograms per liter, equal to parts per trillion (ppt)

The location where elevated levels of PFAS6 was reported is the Morses Pond Wellfield, one of the three entrance points (POE) that supplies drinking water to our system.  PFAS6 levels were reported below the 20 ng/L MCL at the other two POE locations.

 Mass. DEP Drinking Water PFAS Analysis Reports

  • Massachusetts DEP Drinking Water PFAS Analysis Reports links to original scanned images can be found here when available.

Mass DEP Notice of Noncompliance

  • Mass DEP PFAS Notice of Noncompliance can be found here if applicable (not applicable as of 5/4/2021).
  • Mass DEP PFAS Violation Response and Compliance Schedule Approval (CSA) Form can be found here if applicable (not applicable as of 5/4/2021).

Where Does My Drinking Water Come From?

Wellesley’s local water supplies consist of ten wells located within the Town. Four wells tap into the Waban Brook alluvial aquifer and six wells tap into the Rosemary Brook alluvial aquifer. The water pumped from the ten wells is treated at our three corrosion control and iron/manganese removal facilities. 

Wellesley operates three water treatment facilities. The primary purpose of these facilities is to provide the regulatory approved treatment technique (TT) for corrosion control under the Safe Drinking Water Act’s Lead and Copper Rule. These facilities provide the same treatment processes to all of our wells.  The well water is oxidized and its pH is adjusted prior to filtration. The filter process removes the naturally occurring iron and manganese minerals in the raw water. The filtration units consist of anthracite, green sand and garnet sand. After filtration, the water cascades through a tray aerator, which removes naturally occurring carbon dioxide from the water. This aeration process removes the acidity from the water. The water is fluoridated and finally the water is disinfected with hypochlorite and detained in large holding tanks prior to being pumped into the distribution system.

Does my home get water from a particular supply well? No. We cannot say with any certainty that a particular household received water from a particular well, regardless of proximity of the well. Because water in our distribution system is a blend of water from our wells and the MWRA.  This causes levels of PFAS to fluctuate throughout the water distribution system, it cannot be said for certain from where a particular address receives its water. As a matter of public health and regulatory requirements, the Town's outreach and response is based upon the results of all samples taken at our water supply well fields.