Mahopac Assessment Area

Protecting Mahopac's Drinking Water and Investigating Sources of PFOA and PFOS

As part of New York State's Emerging Contaminant Sampling Initiative to investigate groundwater for emerging contaminants at new and legacy State Superfund and Brownfield Cleanup Program sites, the New York State Department of Environmental Conservation (DEC) has identified per- and polyfluoroalkyl substance (PFAS) contamination in groundwater and private water supply wells in an area of interest around the Mahopac Business District Wells site, a State Superfund site in Putnam County. Specifically, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) were detected at concentrations above New York State maximum contaminant levels (MCLs) for public drinking water (10 parts per trillion).

The Mahopac Business District Wells site is a State Superfund site (DEC Site No. 340013) impacted by releases of dry-cleaning chemicals prior to 1980. The contaminants of concern at that time were volatile organic compounds (VOCs) such as tetrachloroethene (PCE), trichloroethene (TCE), and cis-1,2-dichloroethene (cis-1,2-DCE) in the soil, groundwater, and sewer sediment. In the early 2000s, the VOC contamination was removed to reduce exposure and prevent the migration of those contaminants off-site. DEC continues to monitor the site to ensure that the dry-cleaning impacts are controlled.

Emerging Contaminant Sampling

In 2020, as part of New York State's Emerging Contaminant Sampling Initiative to evaluate and address emerging contaminants in drinking water, DEC began sampling on-site groundwater with the New York State Department of Health (DOH) to determine if PFAS or other contaminants may be present.

Although New York State does not regulate PFAS in private wells, the maximum contaminant levels for PFOA and PFOS (10 parts per trillion) for public drinking water are used as guidelines to recommend actions to reduce exposures for people with private drinking water wells. The 2020 sampling detected concentrations of PFOA and PFOS in groundwater monitoring wells near Routes 6/6N and Cherry Lane at levels above 10 parts per trillion. A survey of the area revealed that many properties rely on private wells for their drinking water. In response, sampling was expanded by DEC and DOH to evaluate nearby potentially affected properties' water supply wells.

Sampling of private wells at nearby properties has been conducted in phases in the area of interest shown on the following map. Most sampled wells had levels of PFOA and/or PFOS above 10 parts per trillion.

DEC initially provided bottled water to properties where results were above 10 parts per trillion and also offered installation of point-of-entry treatment (POET) systems. At properties where DEC's offer was accepted, POET systems were installed to filter out PFAS and provide clean drinking water on a longer-term basis. DEC will maintain these systems for as long as necessary to prevent potential exposure to contamination. More information about POET systems is found in the POET System Homeowner's Guide (PDF, 88 KB).

Additional information about private wells, including information about PFAS in private wells and steps people can take if they are concerned about PFAS or other contaminants in drinking water, can be found here:

• General Private Well Website (leaves DEC website)
• PFAS in Private Wells (leaves DEC website)
• In-Home Filtration Options (leaves DEC website)

Next Steps in the Area of Interest

The efforts of DEC and DOH to engage the public for participation in the private well sampling initiative are ongoing. To speak with DEC and DOH representatives and supporting consultants, and obtain information and resources related to this community issue, please join us for our upcoming Availability Session. Additional information about this event can be found in the Latest News box above.

The area of interest includes a 1/2-mile radius around the Mahopac Business District Wells site. Property owners who have not participated in prior private well sampling events are being canvassed again by DEC's environmental engineering consultant who is in the area to discuss the effort and leaving information about the program.

If you live in the Mahopac area of interest and wish to participate in the program, please email [email protected] to reach DEC's environmental engineering consultant who will review and provide a response to your inquiry.

Source Investigation

A review of private well sampling data indicates that PFAS in groundwater in the area of interest may not be directly connected to the sources of dry-cleaning chemical releases from the Mahopac Business District Wells site. DEC is conducting a thorough investigation into the source of PFAS that has impacted groundwater and private water supplies in the area of interest.

This source investigation includes a review of private well PFAS data and potential PFAS sources, implementation of a subsurface investigation to collect soil and groundwater samples near potential PFAS sources, and surface water, sediment, and fish tissue sampling to evaluate impacts to Lake Mahopac. The subsurface investigation and Lake Mahopac sampling activities will begin in fall 2022.

Collection of private well data is ongoing. Based on data collected to date, relatively uniform PFAS concentrations have been detected throughout the area; groundwater results for site monitoring wells suggest that there may be more than one source. Potential sources could include a combination of industrial and domestic wastewater discharges.

Per- and Polyfluoroalkyl Substances (PFAS)

PFAS are a group of manufactured chemical compounds that have been used in industry and consumer products since 1950s and are receiving increasing attention. PFAS are widely used, long-lasting chemicals that break down slowly over time. These compounds have been used in a range of products, including cosmetics; water, grease, and oil-resistant products; and some fire-fighting foams.

PFAS Exposure

People can be exposed to PFAS through air, water or soil contaminated from fire-fighting foam, industrial sources, food, and PFAS-containing consumer products. Some of these compounds remain in the environment and in the human body for many years, but levels go down once exposures have ended. PFAS has also been detected in public drinking water supplies and in private wells near where these chemicals were manufactured, used, or disposed of in New York State and the U.S. People are exposed to PFAS in water mainly through drinking and foods prepared with that water. Household uses, such as cleaning, washing, and bathing, do not result in significant exposure.

PFAS in Drinking Water

If you live in the area of interest and would like to have your private well sampled for PFAS, please contact the DEC hotline provided in the letter you received in the mail. If you did not receive a letter, your well is not in an area of concern. Sampling will be coordinated with you and based on your schedule. Typically, drinking water samples will be collected from your kitchen tap in two small bottles and submitted to a certified laboratory for PFAS analysis. Results will be received in approximately 1 month.

Health Risks Associated with PFAS

The available information on the health risks associated with PFAS, like many chemicals, comes mostly from studies of high-level exposure in laboratory animals. Less is known about the chances of human health effects occurring from lower levels of exposure, such as from drinking water. High dose studies in animals indicate that exposure to water with PFAS can cause a wide range of health effects with the most consistent findings being effects on the liver, immune system, and impaired fetal growth and development. The United States Environmental Protection Agency considers PFOA and PFOS as having suggestive evidence for causing cancer based on studies of animals exposed to high levels of this chemical over their lifetimes.

Biomonitoring projects which test people's blood, such as The National Health and Nutrition Examination Survey (NHANES), show that human exposure to PFAS is widespread. Nearly all people in the United States have some PFAS in their body. DOH continues working with other federal agencies and researchers across the country to learn more about the complex relationship between PFAS exposure and health. Read more about New York State PFAS, Exposure and Health Projects.

Public Involvement and Document Access Information

Community Update Letters and Other Documents

This link provides access to Community Update Letters and other documents related to PFAS in drinking water:

Additional information regarding the Mahopac Assessment Area may be obtained by:

1. Telephone: Contacting DEC's Albany Office at 518-402-9575.
2. Online: Accessing the DECinfo Locator: an interactive map that lets you access DEC documents and public data about the environmental quality of specific sites in New York State. Also, information on the state superfund program (Site Number 340013) at the Environmental Site Remediation Database Search.
3. Electronic Mail: Sign up to receive updates by email: Also, to receive copies of related correspondence by email, including future Community Update Letters, area residents can provide their contact information via an online form (link leaves DEC webpage).
4. Other Ways to Engage: Area residents can participate in the source investigation by completing the online questionnaire (link leaves DEC webpage).

Additional Information regarding PFAS may be obtained at the following links:

Per- and Polyfluoroalkyl Substances (PFAS) - NYS Dept. of Environmental Conservation
New York's Public Water Systems (ny.gov)
Public Water Systems and NYS Drinking Water Standards for PFAS and Other Emerging Contaminants
PFAS and Private Wells (ny.gov)
In-home Water Filtration Options for Household Drinking Water (ny.gov)
New York State Multi-site PFAS Health Study (ny.gov)
PFAS in Food Packaging - NYS Dept. of Environmental Conservation

Project Management Contact Information

Access our HOTLINE LINK with any questions/comments/concerns and a DEC representative will follow up shortly after.

For questions related to the site, surface water, groundwater and drinking water sampling, and PFAS source evaluation:

Jasmine Stefansky
NYSDEC; Division of Environmental Remediation
625 Broadway
Albany, NY 12233-7017
(518) 402-9575; [email protected]

Jeffrey Dyber
NYSDEC; Division of Environmental Remediation
625 Broadway
Albany, NY 12233-7017
(518) 402-9621; [email protected]

To determine if your property is located within the area of interest, and therefore eligible for sampling, contact DEC's environmental engineering consultant at the Mahopac PFAS Information e-mail:

[email protected]

For questions related to the provision of an alternate water supply (i.e., bottled water, POET systems, or public water supply connections):

David Chiusano
NYSDEC; Division of Environmental Remediation
625 Broadway
Albany, NY 12233-7017
(518) 402-9813; [email protected]

For health-related questions:

Stephen Lawrence
NYSDOH
Empire State Plaza, Corning Tower, Rm 1787
Albany, NY 12237
(518) 402-0450; [email protected]

Contact for this Page

Division of Environmental Remediation
625 Broadway
Albany, NY 12233

Phone: 518-402-9764

[email protected]

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