Water Testing Results

Water Testing Results

The Wellesley Water Division has confirmed elevated levels of PFAS6 in the drinking water during the period of April 2021 to July 2021.  The exceedance was from our Morses Pond water treatment plant which is now offline.  Water for all Wellesley residents and businesses is currently being supplied by the Town’s two other water treatment plants and the Massachusetts Water Resources Authority (MWRA).  Below are testing results and additional information about our water supply to help you make informed decisions about your drinking water while we continue to monitor the water supply.

Water Testing Results

Sample Location by Entry Point to Distribution System
Monitoring Period
Sample Collection Date
PFAS6 Result (ng/L)
Average (ng/L)
MCL (ng/L)
Wellesley Avenue Water Treatment PlantQuarter 1 Initial
Quarter 1 Confirmation
Quarterly 1 Monthly
Quarter 2 Monthly
4/21/2021
5/3/2021
6/16/2021
7/29/2021
10.4
12.9
8.3
9.5

Q1 10.5




20



Rosemary/Longfellow Water Treatment PlantQuarter 1 Initial
Quarter 1 Confirmation
Quarter 1 Monthly
Quarter 2  Monthly
4/21/2021
5/3/2021
6/16/2021
7/29/2021
10.9
14.5
11.1
12.8

Q1 12.2




20



Morses Pond Water Treatment PlantQuarter 1 Initial
Quarter 1 Confirmation
Quarter 1 Monthly
Quarter 2 Monthly
4/21/2021
5/3/2021
Off-line
Off-line
45.1
52.6
Not Required
Not Required

Q1 32.6*




20



Purchased Water by Entry Point to Distribution SystemMonitoring Period
Sample Collection Date
PFAS6 Result (ng/L)Average (ng/L)*MCL (ng/L)
Hegarty Pumping Station (Massachusetts Water Resources Authority - MWRA)**RoutineJanuary 2021
April 2021
0
0
0
0
20

*Quarterly Average calculation per MADEP requirements.

**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 Notice of Noncompliance

  • Mass DEP PFAS Notice of Noncompliance 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.