Water samples collected from public water supply wells located in New Castle County, Delaware were found to contain perfluorinated chemicals (PFCs) including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA).  PFOS and PFOA are organic chemicals used in repellants for stains, water, oil, and grease.  Commercial and consumer products containing or degrading to these compounds were first introduced in the 1950s.  They have been used in a variety of products such as the fabric of upholstered furniture, carpets, nonstick cookware, floor wax, and the lining of microwave popcorn bags.  Certain firefighting foams also contain these chemicals.  

In 2009, EPA issued provisional health advisory levels (HALs) for PFOS and PFOA.  The provisional HAL values were 0.2 micrograms per liter of water (μg/L) for PFOS and 0.4 μg/L for PFOA.  There are no drinking water standards for these chemicals.  From 2013 through 2015, pursuant to the federal Unregulated Contaminant Monitoring Rule 3 (UCMR3), EPA required public water systems that serve more than 10,000 people to sample for a group of 28 unregulated contaminants, including certain PFCs including PFOS and PFOA. 

Samples taken by the Artesian Water Company (Artesian) as part of the federal UCMR3 requirements showed levels of PFOS above EPA’s provisional health advisory level (HAL) in one public water supply well.  The City of New Castle Municipal Services Commission (MSC) voluntarily sampled three of its supply wells in the area.  PFOS and PFOA were detected in the City of New Castle wells above the provisional HALs.  Artesian and the City of New Castle MSC removed the affected wells from service after consultation with the Delaware Division of Public Health (DPH).  Artesian and New Castle MSC are working with the state to determine the potential source(s) of contamination and expect to return the affected wells to service once the appropriate treatment for PFCs is installed.

The Delaware Department of Natural Resources and Environmental Control (DNREC) requested EPA’s assistance in determining whether private drinking water wells and monitoring wells in the vicinity of the New Castle County Airport have been impacted by PFCs. 

EPA is coordinating with DNREC, DPH, the Delaware Air National Guard, the Centers for Disease Control and Prevention (CDC)/Agency for Toxic Substances and Disease Registry (ATSDR), the City of New Castle MSC and Artesian to ensure that public health is protected.

EPA worked to identify private drinking water wells in the area of the New Castle County Airport (NCCA) to determine if they have been impacted by perfluorinated chemicals (PFCs), including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), and to determine if additional actions are needed to protect human health and the environment.

During the reporting period beginning May 1, 2015 through June 22, 2015, the OSC received and reviewed the validated results of the monitoring well sampling conducted on April 29, 2015 at the NCCA.  Low levels of PFCs were detected in all the monitoring wells sampled.  PFOS was detected in MW-17 at a concentration of 0.85 μg/L which exceeded EPA’s provisional health advisory level of 0.2 μg/L for PFOS in drinking water.  None of the other samples collected exceeded EPA's provisional health advisory levels for PFOS or PFOA.  PFOS was detected at a concentration of 0.181 μg/L in MW-1.  During the initial sampling event, conducted in August 2014, PFOS was detected in MW-1 at a concentration of 0.268 μg/L. 

In May 2016, EPA replaced the provisional health advisories discussed above with more conservative levels that accounted for a life-time of exposure to PFOA and PFOS.  EPA established the life-time health advisory levels at 0.070 µg/L which is equivalent to 0.070 parts per billion or 70 parts per trillion.  The new health advisories apply to each individual chemical or, if both PFOA and PFOS are present, the combined concentrations of each chemical.   

In response to the lowering of the health advisory levels,  the OSC requested permission to resample the residential well located near the NCCA.  With the owner's permission, the well was resampled on November 17, 2016.  Two water samples were collected from the well.  PFOA was detected at a concentration of 57.1 nanograms per liter (ng/L) or 57.1 parts per trillion in the first sample and at a concentration of 75.5 ng/L or 75.5 parts per trillion in the second sample.  PFOS was not detected.  The OSC mailed the sampling results to the property owner and requested permission to conduct further investigations.  The OSC made several attempts to reach the owner, however, the owner did not respond.  DNREC has also attempted to contact the owner. 

2.1.2 Response Actions to Date

In 2015, the City of New Castle installed a carbon filtration system and returned the affected public water wells to service.  Artesian had shut down two wells in 2014 and has since returned one well to service after installing a carbon filtration system. 

No EPA response actions were conducted. 

2.1.3 Enforcement Activities, Identity of Potentially Responsible Parties (PRPs)

2.1.4 Progress Metrics