East Basin Road Groundwater Site

The U.S. Environmental Protection Agency (EPA) has added the East Basin Road Groundwater Site in New Castle County to the Superfund National Priorities List (NPL). The site is an approximately seven-square mile area surrounding the city of New Castle’s public wells.

The NPL is EPA’s list of priority sites requiring evaluation for possible remediation from releases of hazardous substances, pollutants or contaminants. The EPA announced its decision to list the East Basin Road Groundwater Site on the NPL and published details in the Federal Register in Spring 2023.

The listing of the East Basin Road Groundwater Site is due to the identification of groundwater plumes containing volatile organic compounds (VOCs) and metals impacting public drinking water supply wells in the City of New Castle and surrounding area. Per- and polyfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have also been found in groundwater and public supply wells.

Public Meetings and Comment Period

The EPA held a pair of public meetings in October of 2022 to allow residents to ask questions and discuss the proposal with EPA staff. There was an in-person meeting on Oct. 4 and a virtual meeting on Oct. 6.

The EPA held a 60-day public comment period, from Sept. 9 to Nov. 8, 2022, and received 19 comments.

Public Drinking Water is Safe

Public drinking water provided by Artesian Water Company (Artesian) and the City of New Castle’s Municipal Services Commission (MSC) is treated to remove contamination, including VOCs and the PFAS compounds, PFOA and PFOS.

The finished drinking water – after treatment – meets all applicable federal and state Safe Drinking Water Act standards, also known as Maximum Contaminant Levels (MCLs), for all other compounds. The finished drinking water does not exceed the proposed State of Delaware MCLs for PFOA and PFOS. Artesian and MSC have the treatment technology in place to reduce other PFAS compounds in finished drinking water.

Find information about the health effects associated with exposure to PFAS on the CDC Website.

The National Priorities List (NPL)

Listing the site on the NPL makes it eligible for remedial action financed under the federal Superfund program. This will allow EPA to use Superfund authority and resources to investigate and remediate the contamination and protect human health and the environment in New Castle.


Groundwater is the main source of drinking water in the New Castle area, which has a population of more than 5,000 people. However, the larger population served by the public wells (including these wells) in the New Castle area may include approximately 215,000 homes and businesses.

Public drinking water in the area is treated to remove several types of contamination, including Volatile Organic Compounds (VOCs) and human-made chemicals used in the manufacture of paints, pharmaceuticals and refrigerants, such as industrial solvents like tetrachloroethene (PCE). Treatment is also underway to address two chemical compounds, perfluorooctanoic acid (PFOA), and perfluorooctane sulfonic acid (PFOS), widely used in grease-resistant food packaging, water-resistant clothing, nonstick cookware and many other everyday products.

Potential sources of contamination near the area’s public drinking water wells include three sites under active investigation by DNREC. These are sites where historical activities may have included the use of compounds which may have contained VOCs, PFOA, and/or PFOS.

  • East Basin Road Groundwater Site (DE-0363)
  • Delaware Air National Guard Base (DE-1003)
  • New Castle County Airport (DE-0357)
  • Duncan Readiness Center and Army Aviation Support Facility (DE-1753)

Additional sources of contamination in groundwater may also be identified in the future as a result of U.S. Environmental Protection Agency (EPA)’s investigation.

Sampling Results

Sampling results for the untreated groundwater samples, from the Expanded Site Inspection in November 2021, indicate PCE was detected at 7.5 micrograms per liter (ug/L), which is above the state MCL of 1 ug/L and the federal MCL of 5 ug/L.

In untreated groundwater from the public wells, the maximum concentration of PFOA was 269 nanograms per liter (ng/L) and PFOS was 3240 ng/L, which are above the interim EPA health advisory levels of 0.004 ng/L and 0.02 ng/L respectively and above the proposed state MCLs of 21 ng/L for PFOA, 14 ng/L for PFOS, or 17 ng/L for combined PFOA and PFOS.

The most recent results for treated drinking water samples show the concentrations continue to meet federal and state drinking water standards, also known as MCLs, for all other compounds. The finished drinking water does not exceed the proposed state MCLs for PFOA and PFOS.