PFAS and Maine DEP

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PFAS Wastewater Effluent Testing | PFAS Fish and Surface Water Testing | Overview of Maine's PFAS Soil and Groundwater Evaluation of Sludge and Septage Sites | The Process to Evaluate Licensed Sludge Sites | The Process to Evaluate Licensed Septage Sites | Status of Investigation of Licensed Sludge and Septage Sites | PFAS Landfill Leachate Testing | PFAS Investigation at Remediation Sites in Maine

PFAS Investigation Map

PFAS Wastewater Effluent Testing

DEP has completed a study, pursuant to Public Law 2021, Chapter 641, to evaluate the wastewater effluent and groundwater from certain municipal and private wastewater treatment facilities. Municipal discharges included the discharge of treated wastewater from municipal or quasi-municipal public sewer systems, and private discharges included the discharge of treated wastewater from industrial and commercial sources. Samples were generally collected monthly over a period of 10 months.

Wastewater Effluent Monitoring for PFAS Report (November 2023)

PFAS Fish and Surface Water Testing

Since 2014, DEP has collected fish samples for PFAS analysis from lakes, rivers, and streams as part of the Surface Water Ambient Toxics (SWAT) monitoring program. DEP coordinates sampling with the Maine Center for Disease Control and Prevention (Maine CDC) to inform the process of setting fish consumption advisories. DEP typically collects ten fish per sample location and processes the skinless fillets in two composite samples, each with five fish. In certain circumstances, DEP may collect additional samples and samples from more than one species. Currently, perfluorooctane sulfonate (PFOS) is the only kind of PFAS that is considered for fish consumption advisories.

Maine CDC’s current fish tissue action level for PFOS is 3.5 nanograms per gram (ng/g) wet weight, which is equivalent to parts per billion (ppb). The fish tissue action level is the concentration of PFOS in fish tissue above which Maine CDC begins to consider the need for a consumption advisory. In determining whether a PFOS-specific advisory needs to be issued, Maine CDC will evaluate whether the concentrations of PFOS in fish tissue warrant an advisory that is more restrictive than the current statewide mercury advisory or any other waterbody-specific advisories. The fish data provided on the PFAS Investigation Map focus on PFOS. SWAT reports are available with data for PFOS and other kinds of PFAS from when the DEP started sampling fish for PFAS in 2014 to the most recent reporting year.

Water samples for PFAS analysis have also been collected from lakes, rivers, streams, and other water features as part of the SWAT monitoring program and other site evaluations. The PFAS Investigation Map provides data tables with concentrations of PFOS and other kinds PFAS in milligrams per liter (mg/L), which is equivalent to parts per million (ppm). Maine has not established any standards for PFAS in surface water.

Overview of Maine's PFAS Soil and Groundwater Evaluation of Sludge and Septage Sites

DEP Staff sampling soils for PFASPublic Law 2021, Chapter 478, An Act To Investigate PFAS Substance Contamination of Land and Groundwater became effective on October 18, 2021. This law requires the DEP to develop and implement a program to evaluate soil and groundwater for PFAS at locations licensed to land apply sludge or septage prior to 2019.

DEP began its initial statewide evaluation into the presence of PFAS in soil and groundwater at licensed sludge/septage land application sites in November 2021. Sites were identified based on gathering, reviewing, and evaluating decades of licensing information. Each site typically includes multiple fields (i.e., agricultural land, pasture, or other land) and may also cross district, town, and county boundaries. Some sites may have different owners than when a license was first issued, requiring DEP’s evaluation to include identifying land use changes and practices. As an example, a site that was an active farm back in 1986 may now include several small farms, a subdivision, and a school. Moreover, some sites may have been used by multiple generators (different sources of sludge or septage), which was land applied in the same location.

The initial evaluation process for each site includes sampling soils at licensed land application sites as well as nearby private drinking water wells (groundwater) determined to be at risk for PFAS impacts from these sites. The initial sampling locations are selected by DEP scientists based on several site-specific factors including land application records, hydrogeology, and proximity to licensed sites.

Once DEP staff have completed the initial evaluation, DEP scientists review the data and make a determination as to whether an expanded investigation is necessary, referred to as a “step-out investigation”. Where concentrations of PFAS in groundwater exceed Maine’s interim drinking water standard surrounding a land application site, the radius of investigation may be expanded. Not all sites will require step-out sampling. Step-out sampling may take a few extra weeks or in some cases may take years for larger sites that have many fields contributing to potential contamination.

DEP Staff sampling water after treatmentIn locations where it is determined that private drinking water wells exceed Maine’s interim drinking water standard for the sum of 6 PFAS (PFOA, PFOS, PFNA, PFHxS, PFHpA, and PFDA), and contamination is likely due to the land application of sludge or septage, DEP will work with homeowners to ensure that they have clean water to drink. In these circumstances, DEP will provide homeowners with bottled water until a filtration system can be installed and determined to be effective.

Any questions about risks of exposure to PFAS that may impact human health should be directed to the Maine CDC at 1-866-292-3474.

The Process to Evaluate Licensed Sludge Sites

In October 2021, DEP prioritized all licensed sludge land application sites statewide into four Tiers (I, II, III, and IV) to designate an approximate schedule for sampling. Initial sampling evaluations are mostly complete at Tier I and II sites and are now beginning at Tier III sites. It is anticipated that Tier III sampling evaluations will extend through 2024.

Breakdown of Tiers for the evaluation of soil and groundwater for PFAS from the land application of sludge
Tier I Sites where 10,000 cubic yards or more of sludge was land applied, where homes are within 1/2 mile, and where PFAS is likely to be present in the sludge based on an evaluation of known sources or contributors of wastewater at a given treatment facility. 60 sites
Tier II Sites where between 5,000 and 10,000 cubic yards of sludge were land applied, where homes are within 1/2 mile, and where PFAS is likely to be present in the sludge based on an evaluation of known sources or contributors of wastewater at a given treatment facility. In cases where homes are over 1/2 mile away, a site may be downgraded to Tier III depending on distance and other hydrogeological factors. Likewise, a site may be elevated to Tier I if results from a Tier II site with similar source contributions show a greater than anticipated impact to the soil and water being tested.
46 sites
Tier III Sites where under 5,000 cubic yards of sludge were land applied, where homes are within 1/2 mile, and where PFAS is likely to be present in the sludge based on an evaluation of known sources or contributors of wastewater at a given treatment facility. Likewise, a site may be elevated to Tier I or II if results from a Tier III site with similar source contributions show a greater than anticipated impact to the soil and water being tested.
Estimated over 400 sites*
Tier IV Sites where information gathered to date indicates that no sludge was land applied. Additional research and time will be needed to verify this information. Once identified, these sites may be placed in another Tier as appropriate using the above criteria. Estimated over 500 sites*

* The number of sites are estimated as staff continue to review project files. In some cases, project files reveal duplication of sites or alternatively that similarly named sites may actually be multiple sites. A “site” is determined by license number and project information. For context, the number of sites has changed from an initial estimation of 700 to a current estimation of over 1,000.

The Tier list below identifies communities, not specific locations, where the PFAS investigation will be taking place. This is to protect individual landowner and homeowner privacy. For a closer approximation of where the investigation is or will be taking place, please visit Maine DEP PFAS Investigation Map (Formerly the “Septage and Sludge Map”). Please direct any feedback to

This list will be updated as it is anticipated to change.

Communities with Tier I-III Sites – as of February 2024

Inquiries about the soil and groundwater evaluation should be directed to David Madore, Deputy Commissioner and Communications Director, 207-287-5842. You can also contact the Department directly by e-mail at:

The Process to Evaluate Licensed Septage Sites

Septage land application sites are being evaluated separately from sludge sites and are not part of the Tiered system. This is because septage application sites are both licensed and managed differently, with several that are currently active. Evaluation of these sites began during the Summer of 2022.

Initial investigations into the septage land application sites began in the communities identified in the table below. A majority of the septage land application sites are being investigated by contractors that the DEP has determined to be qualified to conduct the work. Additional counties and communities will be added to the investigation as more contracts are put into place. Similar to the sludge site investigation, the initial evaluation process for each septage land application site includes a file review and historical research, followed by sampling of soils and at-risk drinking water wells (groundwater) for PFAS. It is anticipated that the septage investigation will be completed during the 2024 field season with the majority of sites completed by the end of 2023.

County Communities Who is doing the work
2022 Field Season
Aroostook Benedicta, Blaine, Cary Plt, Castle Hill, Cross Lake Twp, Crystal, Dyer Brook, Eagle Lake, Easton, Fort Fairfield, Frenchville, Grand Isle, Haynesville, Houlton, Island Falls, Monticello, Nashville Plt, New Canada, Presque Isle, St. Agatha, St. John, Sherman, Stockholm, TD R2, T16 R9, Wallagrass, Washburn DEP staff
Penobscot Patten, Stacyville
Washington Danforth
Cumberland Baldwin, Bridgton, Casco, Gorham, Gray, Harrison, Naples, Raymond Campbell Environmental Group
Oxford Andover, Bethel, Brownfield, Fryeburg, Lovell
York Parsonsfield
Androscoggin Livermore Falls Haley Ward
Kennebec Albion, Belgrade, Canaan, Chelsea, Readfield, Vassalboro, West Gardiner, Windsor
Sagadahoc Bowdoinham, Phippsburg
Knox North Haven, Owl's Head, Thomaston, Union, Warren, Washington Fessenden Geotechnical (FGT) and John Turner Consulting (JTC)
Lincoln Bristol, Damariscotta, Newcastle, Nobleboro, Squirrel Island, Westport Island, Wiscasset
Waldo Belfast, Frankfort, Freedom, Islesboro, Palermo, Searsmont, Swanville
2023 Field Season
Franklin Carrabassett, Coplin Plt, Freeman Twp, Industry, Kingfield, New Sharon, Rangeley, Salem Twp

Campbell Environmental Group

Penobscot Brownville, Charleston, Enfield, Garland, Lincoln, Milo, Winn
Hancock Deer Isle, Gouldsboro, Orland, Stonington
Washington Addison Calais, Cherryfield, Edmund Twp, Eastport, East Machias Indian Twp, Lubec, Machias, Marion, Meddybemps
Cumberland Peaks Island Haley Ward
Kennebec Albion, China
Oxford Upton
Waldo Searsport, Unity
York Kennebunk
Somerset Athens, Bingham, Cornville, Long Pond Twp, Norridgewock
Piscataquis Abbott, Atkinson, Dover-Foxcroft, Greenville, Sangerville, Shirley, T5 R10 WELS, T6 R11
Penobscot Bradford, Detroit, Garland, Glenburn, Hermon, LaGrange, Newburgh, Plymouth

Status of Investigation of Licensed Sludge and Septage Sites

Preliminary Private Drinking Water Well Information by Town as of March 4, 2024

DEP has completed the initial evaluation of Tier I and II sludge application sites and will begin initial evaluations of Tier III sites by August 2023. This means that DEP will be able to shift the focus to the evaluation of Tier III sites while simultaneously continuing to conduct step-out sampling in Tier I and II sites, as warranted (see PFAS Tiered Community List), as well as continued filtration system monitoring and maintenance.

DEP expects to finalize the investigation of septage land application sites in 2024, completing the majority of sites during 2023.

Please visit the DEP’s interactive map (opens in new tab) to see where water or soil samples have been collected at or near sludge or septage land application sites. Use the Search Box to find specific communities or addresses.

After the initial evaluations are complete at both tiered sludge and septage investigation sites, some communities will require additional step-out sampling. These are communities where PFAS sampling results showed that PFAS contamination is likely to extend beyond the already sampled areas, or where additional information is needed to adequately evaluate the fate and transport of PFAS in the environment as the contaminants relate to sludge or septage land application sites. DEP staff review each site’s results to determine where step-out sampling is necessary. Information about where step-out sampling is occurring is available on the current PFAS Tiered Community List.

In contrast to step-out sampling, many Tiered sludge and septage investigation communities will observe DEP staff and their consultants conducting sampling after the initial sampling has been completed. This is because in locations where groundwater results have been found to exceed the state’s interim drinking water standard of 20 parts per trillion for the sum of 6 PFAS and where filtration systems were installed, ongoing maintenance and monitoring are required. To ensure a filtration system is operating properly, routine sampling is required and at this time the DEP is overseeing the ongoing monitoring and maintenance of these systems. While this monitoring timeframe will vary depending on the sample results and system, all filtration systems will need ongoing monitoring to ensure they are working effectively. The DEP plans to oversee this process until such time as funding is no longer available.

PFAS Landfill Leachate Testing

On September 1, 2021, the DEP sent a letter to solid waste landfills that manage leachate (contaminated liquid that drains from a landfill) requiring that leachate be tested for PFAS, beginning October 18, 2021, as required by Public Law 2021, Chapter 478. Five rounds of sampling are required in total: each round collected during the fall and spring beginning fall 2021 and ending fall 2023. Data collected must be sent to the Department for review and evaluation. In 2024, DEP will present the data to the legislature along with recommendations.

Landfill Leachate Sampling Results for 6 PFAS (PFOA, PFOS, PFNA, PFHxS, PFHpA, and PFDA):

Fall/Winter 2021

Spring/Summer 2022

Fall/Winter 2022

Spring/Summer 2023

Fall/Winter 2023

PFAS Investigation at Remediation Sites in Maine

In addition to sludge and septage land application sites, PFAS contamination is also being investigated at remediation (or cleanup) sites in Maine. Investigation at these sites typically occurs to assess whether a hazardous substance is present at a concentration that poses a risk to public health or the environment. In these cases, the DEP works toward removing or mitigating those identified threats. While PFAS compounds have not yet been listed as hazardous substances under the United States Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), PFAS generally may be considered a “pollutant or contaminant” under the statute’s provisions. This means that at many CERCLA sites, PFAS may be evaluated as part of the investigation and remedial activity associated with those sites. It should be noted that the EPA has proposed listing two specific PFAS, PFOA and PFAS, as hazardous substances under CERCLA, but this rule has not yet been finalized or adopted.

In 2021, the Maine legislature changed the definition of hazardous substance under the state’s Uncontrolled Sites Law to include PFAS under 38 M.R.S. § 1362 (1)(H). This change clarifies that a hazardous substance in Maine means any substance that is listed as a hazardous substance or meets the criteria for a “pollutant or contaminant” under CERCLA. This is important as it provides the state with the authority to designate a state site with PFAS contamination as an uncontrolled site. DEP submitted a status report to the legislature on the designation of uncontrolled hazardous substance sites for PFAS in January 2023.

Specific remediation programs at DEP that have investigated PFAS at contaminated sites include the following programs Uncontrolled Sites, Municipal Landfill Closure and Remediation, VRAP, and Brownfields. In addition, several Federal facilities and Superfund sites are also undergoing investigation and remediation of PFAS.