Cumberland County, Maine: drinking water report. Cumberland County is Maine's most populous county, with about 310,000 residents including the city of…
Cumberland County is Maine's most populous county, with about 310,000 residents including the city of Portland. The Portland Water District draws from Sebago Lake, one of the cleanest large lakes in the United States – so clean that the system qualifies for a federal filtration waiver, meaning the water goes through disinfection but not full filtration. Most of Greater Portland drinks Sebago Lake water, while some outlying communities use groundwater wells.
Sebago Lake's water quality is exceptional by national standards. According to the Portland Water District's 2024 annual report, the lake's clarity and low nutrient levels have allowed the district to maintain its filtration waiver for over 30 years – one of only a handful of surface water systems in the country to do so. However, development pressure around the lake's watershed threatens that status over time.
The PFAS picture is different. Maine has been aggressive about PFAS testing statewide, and the EPA's UCMR5 data shows detections in some Cumberland County systems. The former Portland International Jetport has used AFFF firefighting foam, creating a localized PFAS source. According to the Maine Department of Environmental Protection, three wells in the South Portland area near the jetport have shown PFAS levels above Maine's MCL of 20 ppt (for the sum of six PFAS compounds).
If you are on the Portland Water District's Sebago Lake supply, your baseline water quality is among the best in the country. But if you are near the Jetport or on a private well in the southern part of the county, PFAS testing is worth pursuing.
Check your water for the latest data on your system. For PFAS near the Jetport area, reverse osmosis is the most effective household solution. Our water filter guide details which systems carry the relevant certifications. Pull your detailed report for trends, and visit our Maine page for statewide context.