Emerging Cmpounds

On August 26, 2020, New York State adopted new drinking water standards for public water systems that set maximum contaminant levels (MCLs) of 10 parts per trillion (ppt) each for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), and 1 part per billion (ppb) for 1,4-dioxane. 

Click below to access the New York State Department of Health’s fact sheet on these new standards.
New York State Department of Health’s fact sheet 

About Drinking Water Standards and MCLs

A maximum contaminant level, or MCL, is the highest level of a contaminant allowed in drinking water delivered by public water systems. They are enforceable regulatory limits. MCLs are set far below levels that cause health effects. According to the New York Department of Health, because MCLs are set at levels with a large margin of protection, an exceedance of an MCL does not mean that water is unsafe for use while the public water system takes actions to reduce the levels.

The US Environmental Protection Agency (EPA) has also established guidance for the presence of PFOA and PFOS in drinking water. The EPA has established a non-enforceable health advisory level of 70 parts per trillion for the sum of PFOA and PFOS. An MCL for 1,4-Dioxane in drinking water has not been established by the EPA.

What Are Emerging Compounds? 

1,4-Dioxane is a synthetic industrial chemical that is present in many goods, including paint strippers, dyes, greases, antifreeze and aircraft deicing fluids, and in some consumer products such as deodorants, shampoos and cosmetics.

PFOA/PFOS are Per- and polyfluoroalkyl substances (PFAS), which are a group of man-made chemicals that can be found in food packaging; commercial household products, including stain- and water-repellent fabrics (ex: Scotchgard), nonstick products (e.g., Teflon), polishes, waxes, paints, and cleaning products; and fire-fighting foams.

Emerging compounds can enter our water resources after being landfilled, spilled, discharged as waste, or by seepage and infiltration into the water table, eventually entering water supplies.


  • In advance of the adoption of these new standards by the State, Liberty tested its entire water supply to determine the presence of these emerging compounds.

    Liberty determined that, of the 55 sites that supply water across Liberty's service areas in Long Island and upstate New York, four sites have detection of emerging compounds above the New York State MCLs. These sites are as follows:

    • Detections of 1,4-Dioxane at the Seamans Neck Well Station in North Wantagh/Levittown at 1.4 ppb. Liberty is pursuing Advanced Oxidation Process (AOP) treatment for 1,4-Dioxane at the Seamans Neck Well Station. Liberty has completed our AOP pilot testing and is working closely with the Nassau County Department of Health on final treatment design. While AOP treatment will take time to fully install, Liberty’s proactive approach has significantly reduced the time needed to install the right treatment system for our customers served by the Seamans Neck Well Station.

    Seamans Neck Road

    • Detections of PFOS at the Glen Head Well in Glen Head at 17 ppt. Liberty is installing Granular Activated Carbon treatment to remove PFOS from water supplied by the Glen Head Well. Liberty has obtained key regulatory approvals and anticipates starting construction of the granular activated carbon treatment this winter. It is important to note that the Glen Head well is a secondary well used during periods of high water demand (typically the summer). The majority of water served to our SA 2: North Shore customers comes from the Sea Cliff Well which does not have detections of emerging compounds. Liberty will limit, to the extent possible, use of the Glen Head well as we construct treatment.

    Glen Head Well

    • Detections of PFOA/PFOS in the Dykeer system that serves The Willows community in Somers. Liberty is pursuing granular activated carbon filtration treatment for this site. 

    Dykeer Operations District

    • Detections of 1,4-Dioxane at Plant #16 in Roosevelt. This plant was taken out of service in October 2019 and is not being used.

    Liberty is pursuing the appropriate treatment where needed. While new treatment will take time to fully install, Liberty’s proactive approach has significantly reduced the time needed to install the right treatment system for our customers.