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On October 2, 2020, MassDEP published final regulations establishing a drinking water standard, or a Maximum Contaminant Level (MCL), for the sum of six per- and polyfluoroalkyl substances (PFAS). The MCL is 20 parts per trillion (ppt) for what the regulations call PFAS6, or the sum of six PFAS compounds: perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluoroheptanoic acid (PFHpA), and perfluorodecanoic acid (PFDA).
Additional MassDEP regulations for testing of PFAS in the environment are likely in the future as scientific studies are conducted and the understanding of these chemicals increases. The Town of Nantucket has been and will perform all testing as required by MassDEP. The Town also performed testing as recommended by our professional and licensed consultants to address specific situations.
The Town of Nantucket, Nantucket Memorial Airport and Wannacomet Water Company along with MassDEP are working together to coordinate PFAS related activities.
MassDEP and UMass conducted free PFAS testing for a limited number of private wells, focusing on Massachusetts towns where 60% or more of residents are served by private wells. Nantucket was included in this sampling and testing program performed in 2021.
MassDEP selected the wells that were sampled based on priority factors including geographic distribution throughout the town, proximity to potential sources of PFAS, and available funding.
Fourty-one private wells were sampled. Testing results have been posted by MassDEP
https://www.mass.gov/info-details/per-and-polyfluoroalkyl-substances-pfas-in-private-well-drinking-water-supplies-faq (scroll down the webpage to “PFAS Testing in Private Wells” for map and results.
The public water supply on the Island is provided by seven (7) groundwater sources located in two systems, Wannacomet Water Company and Siasconset Water Department. The Wannacomet Water Company and Sconset Water Department well sampling results have been below the Maximum Contaminant Level (MCL) Massachusetts Department of Environmental Protection (MassDEP) set as safe for PFAS in drinking water, with most wells showing no PFAS.
The majority of the Town's public water supply is provided by the Wannacomet Water Company that is served by five wells (Well 12, 13, 14, 15, and 16) located in Nantucket's Sole Source Aquifer. Two wells (Well 15 and 16) pump groundwater from a shallow aquifer at about 75 feet, while the remaining three wells (Well 12, 13, 14) pump groundwater from a deeper aquifer at about 150 feet with a confining unit separating the two. The wells are located in the center of the Island in the proximity of the intersection between Milestone Road and Polpis Road. Wells 12, 15, and 16 are manifolded together at the Wyers Valley Pumping Station. Wells 13 and 14 enter the distribution system individually. The groundwater does not require any physical or chemical treatment before pumping to distribution.
The Siasconset Water Department serves a much smaller distribution area on the east side of the Island with two wells (Wells 6 and 7). Well 7 is the primary well while Well 6 acts as the backup well. The two wells are located on Milestone Road, also in Nantucket's Sole Source Aquifer. The wells are screened at a depth of 70 feet below the confining unit.
Wannacomet public water supply wells draw water from a deep aquifer below confining units. A confining unit is a layer of low permeable material (such as clay and fine silt) may help prevent PFAS from moving to deeper aquifer layers. For comparison, most private residential (domestic) wells are screened in the upper Unconfined Aquifer, thus withdrawing groundwater from above the confining unit.
Note that groundwater sample results have been reported by Nantucket Memorial Airport for on-airport shallow monitoring wells and adjacent residential drinking water wells and with private well testing conducted by MassDEP and UMass (see FAQ no.8). This data is not a complete picture of PFAS in the Island's aquifer. The Airport is continuing to advance its investigation through ongoing sampling and source identification activities. The Town with consultant CDM Smith also continues to advance its investigation through on-going sampling program at the WWTP and the landfill. The Water company continues to take samples as mandated by MassDEP.
An aquifer is underground layer of water bearing rock and/or granular materials from which water can be extracted using a well.
A confining unit is relatively dense and contains impermeable materials, such as clay, that may prevent transport of groundwater and pollutants deeper into the subsurface.
Whether you can hook up to public water depends on location and discussions with the Town. If there are existing Town water lines on your street, the process to install a new water service to a property from that existing line may be easier and cheaper. If a property is located in a part of Town without public water lines, it is more difficult. Your location, how close you are to existing water lines, funding, and conditions below the surface may all factor into if you can hook up to public water.
No. There is no specific regulation of PFAS in a Zone II aquifer wellhead protection area (refer to glossary) relative to septic systems. However, the MassDEP Title 5 program and land use controls offers general protection to Zone II aquifer areas. Local Boards of Health and MassDEP are the regulatory authorities for septic systems. The Town of Nantucket’s Septic System Resources website (see call-out box) has helpful resources for you to ensure you are doing your part to protect the Island’s resources, including the Zone II aquifer wellhead protection area.
If homeowners are interested PFAS sampling and testing at their own election, there are laboratories you may contact and request pricing. Here are a few companies that are known to have done PFAS testing on Nantucket. This is not a complete list of all available firms and this list is not to be considered an endorsement for any particular company. Listed alphabetically:
If there are other firms that may be added to the list, please send the information to PFAS@nantucket-ma.gov
No. PFAS sampling results from leachate (liquid coming out of landfills into the ground) or co-compost (leaf/yard waste mixed with municipal solid waste and dewatered sludge (residuals) from the WWTF that are processed through a composter to create biosolids) should not be compared to regulatory or other health-based PFAS standards for soil or groundwater. The risk for each type of media is different, so the standards for one type cannot apply directly to another type. MassDEP is developing screening levels for land application of soil amendments, including biosolids, which would apply to co-compost. FAQs #9 and #10 have more information on the health risk to plants growing in soil with co-compost. Note that co-compost has not been available to the public since August 2019.
Some concentrations of PFAS in domestic wells in the vicinity of landfill has been reported by homeowners and the MassDEP/UMass private well testing performed in 2021.
At the request of MassDEP in 2021, the Town prepared a surface water and ground water sampling plan for the landfill site. The sampling plan was submitted to MassDEP with Form SW-22 in December 2021. The SW-22, related documents and status can be obtained here: https://eeaonline.eea.state.ma.us/EEA/PublicApp/ with "Search All Online Authorizations"
Yes. The Town with CDM Smith are collecting waste stream samples for PFAS testing to better understand the sources and presence of these chemical compounds. The Town is following the requirements of MassDEP along with the recommendations prepared by CDM Smith in the Town-wide Preliminary Assessment and Planning Approach Report.
The Town is posting the testing reports and results on the PFAS webpage after review and verification by CDM Smith.
There are currently no MassDEP or U.S. Environmental Protection Agency (USEPA) guidelines for WWTF or landfill sites at this time. However, both agencies are moving forward to include PFAS in Wastewater National Pollution Discharge Elimination System (NPDES) Permits. For more information check out MassDEP’s website at: https://www.mass.gov/info-details/per-and-polyfluoroalkyl-substances-pfas#pfas-in-wastewater-facilities-with-npdes-permitted-discharge
PFAS are a group of man-made chemicals used since the 1940s. PFAS were used to manufacture commercial products and firefighting foam. Some PFAS are no longer used. The potential source of PFAS present at the Town landfill, such as in waste water treatment residuals and municipal solid waste, are primarily from use of household cleaning products, food packaging, clothing, and beauty products that contained PFAS.
In 2019, Massachusetts Department of Environmental Protection (MassDEP) recognized the need for more information on PFAS characteristics in wastewater treatment residuals. Prior to 2020 on Nantucket, such residuals were mixed with municipal solid waste and leaf/yard waste to be used for compost. Waste Options, the Town Contractor, collected compost samples in 2019 to maintain a proactive approach to environmental quality on the island. Specific PFAS sampling protocols were not established at that time.
The data received could not be readily assessed, as MassDEP has not yet issued criteria to evaluate risk associated with PFAS in wastewater treatment residuals or compost. Further, it is recognized that sampling was not conducted in accordance with current protocols. The Town and its Contractor Waste Options are now performing quarterly monitoring of PFAS in accordance with the recent MassDEP Approval of Suitability (AOS) permit requirement updates. Note that starting in 2019, wastewater residuals and municipal solid waste stopped being used to prepare compost for Town-wide use.
Forty-one (41) private wells were sampled and five (5) had levels that exceeded the MassDEP PFAS drinking water standard MCL of 20 ppt for PFAS6.
Testing results have been posted by MassDEP https://www.mass.gov/info-details/per-and-polyfluoroalkyl-substances-pfas-in-private-well-drinking-water-supplies-faq (scroll down the webpage to “PFAS Testing in Private Wells” for map and results.