Acton water officials set tentative PFAS treatment dates, warn of possible discoloration and water-use restrictions

Acton Water District leaders told the Acton Select Board on Oct. 6 that two large PFAS treatment systems are entering the final commissioning phase and that the town should expect short-term impacts to water quality and supply while the systems are tested and conditioned.

"The PFAS levels in our water supply have not exceeded the Massachusetts drinking water standard since the 2023," Acton Water Commissioner Erica Lynn said at the meeting, adding that the district has taken steps since discovery to reduce exposure.

District Manager Matthew Mostoller said the South Acton plant — which typically supplies about 60 to 80% of the community’s water demand — and the Centre Acton plant will enter the final media-conditioning phase within weeks of each other. "As of this afternoon ... we're anticipating our Centre Acton plant receiving media starting on October 27 and we anticipate receiving media at our South Acton plant beginning on November 5," Mostoller said.

Why it matters: the South Acton plant supplies a majority of Acton’s water, and both new systems must be taken offline for conditioning and proof testing before they can be declared operational. Conditioning the granular activated carbon (GAC) media and completing regulator-required startup testing can increase short-term PFAS concentrations and cause water discoloration, Mostoller said.

Mostoller listed the district’s planned steps to get both systems into service while protecting public health: increase pumping from other local treatment plants and bedrock wells; pause the town’s fall hydrant-flushing program (which uses several million gallons); ask customers to reduce discretionary outdoor water use; activate emergency interconnects with Littleton and Concord if needed; and push the state for expedited approval to bring two bedrock wells at 549 Main Street online. "We are also reaching out to our neighbours in Littleton and Concord to activate emergency interconnects that we have," Mostoller said.

Officials warned residents that these actions may produce visible changes. "We may see some discolored water throughout town and we may see our PFAS concentrations go higher than they've been over the past two years," Mostoller said. He added that customers who receive water almost directly from Concord or Littleton may notice different taste, odor or feel because that water will not have mixed with Acton water bound for other neighborhoods.

Timing and uncertainty: Mostoller told the board that conditioning times for the filter media are unpredictable. "On the short end, we've done it in five days. On the long end, it's taken over a month," he said. He said the district was pushing state regulators to approve activation of the bedrock wells at the 549 Main Street property and that if regulators did not act, the district could declare a water-supply emergency to bring those wells online sooner. The district collected bacteria samples from the wells on Oct. 6, a step Mostoller said is "one of the final steps before we get that approval."

Customer communications: Select Board members pressed the district on how residents would be notified if water discoloration or other changes occurred. Mostoller said the district will use multiple communication tools — email to bill addresses, the town website, social media and possibly the town’s reverse 911 system for widespread impacts — and will refine messaging as schedules firm up.

Costs and demand management: The district confirmed that purchasing water from neighboring systems will incur added cost: "we will be paying for that water," Mostoller said. He also said that the district planned to impose a Level 4 water-use restriction if necessary; under the district’s definitions that level allows only public safety and critical food/fiber production uses.

Board reaction and next steps: Select Board members thanked the water officials and pressed for clear notification procedures for residents who may wish to delay laundry or otherwise prepare for temporary discoloration. The district emphasized the schedule remained fluid because construction projects frequently have multiple delays; it said the district’s optimistic target for completing both plants was by the end of calendar year 2025, with a more conservative expectation extending into late 2025 if setbacks occur.

The district asked residents to reduce discretionary water use and said it would provide further public updates as commissioning plans firm up and sampling results are returned to the state.