While conducting down gradient sampling for another Superfund site in the area (PCE/TCE Northeast Contamination Site), the PCE Southeast groundwater contaminant plume in York was discovered by the EPA in the fall of 2010. As a result of this discovery, the EPA completed an abbreviated preliminary assessment (APA) for the site in November 2010.
Sampling conducted during the APA identified eight residential drinking wells with concentrations of tetrachloroethylene (PCE) ranging from 9.6 to 32 micrograms per liter (µg/L). Of these wells, one also contained trichloroethylene (TCE) at a concentration of 5.9 µg/L. These levels exceed the EPA's maximum contaminant level (MCL) of 5 µg/L for these hazardous substances.
On April 11, 2011, an Action Memorandum (RV001) was executed by the EPA which approved actions to eliminate, through the provision of a permanent alternate water supply or through the installation of whole-house filtration systems, human exposures to contaminants resulting from the inhalation, dermal contact, and/or ingestion of PCE, and/or other hazardous substances present in the groundwater at the Site.
An Action Memorandum Amendment was signed on March 20, 2014, for a removal project ceiling increase.
In May 2014, the site was listed on the National Priorities List (NPL).
On September 9, 2014, Action Memorandum Amendment 2 was signed to increase the project ceiling and to include the collection of soil samples, groundwater samples, sub-slab soil gas and indoor air samples.
During the week of November 19, 2014, the EPA conducted vapor intrusion sampling in several properties within the downtown area of York, Nebraska, at likely source areas for the contaminant plume of the Site. The sampling was part of an investigation into the source or sources of past releases of PCE at the Site.
During the vapor intrusion sampling event in November 2014, sub-slab soil gas samples were collected from 13 properties. Six of the properties had analytical results above the EPA screening levels for TCE and/or PCE. Five of the properties are businesses, and one is a residence. A release of PCE to groundwater has been documented from an apparent source in the area. Sub-slab soil gas sample results have documented PCE and/or TCE levels above industrial and residential screening levels.
On February 5, 2015 an Action Memorandum RV002 was signed. The purpose of this Action Memorandum was to request funding and document approval of a time critical removal action and a 12-month consistency exemption for the PCE Southeast Contamination Site (Site). This time critical removal action provided for the sampling of groundwater, soil, soil gas, indoor air, and sub slab soil gas to ascertain whether subsurface contamination at, and emanating from, the Site is resulting in vapor intrusion impacts. The action also included the installation of vapor mitigation systems in homes, businesses, day care facilities and/or schools that have been impacted by vapor intrusion from soil and/or groundwater contamination from the Site. Installation of vapor mitigation systems was
driven by indoor air and/or sub-slab soil gas sample results that indicated the presence of contamination at levels that exceeded the U.S. Environmental Protection Agency removal action levels (RALs) or screening levels for PCE and/or TCE. Additionally, the action will included addressing any source areas discovered, which could include soil removal, soil remediation or source removal activities.
The Removal Action has remained opened following the site being listed on the NPL (May 2014) and subsequent Superfund Remediation processes (I.e. Remedial Investigation, Feasibility Study, Proposed Plan, Record of Decision and current Remedial Action) to address additional vapor intrusions that may arise. A new Removal Action - Superfund Technical Assistance Response Team (START) contract was awarded in 2024 to evaluate potential vapor intrusion issues in three new businesses overlying the groundwater contaminant plume and to assess the conditions of the previously installed site vapor mitigation systems (25 systems). An Emergency and Rapid Response Services (ERRS) contract was awarded in 2024 to perform maintenance and repairs on the existing vapor mitigation systems and to install new systems if new business sampling warrants installation.
The Remedial Action (RA) to treat contaminated soil for this site has been underway since March of 2023. In situ thermal remediation is treating contaminated (solvents) soil from two former dry cleaners. The elimination of this soil contamination will prevent further leaching of the dry cleaning solvents in to the groundwater. This Removal Action is scheduled to close out by 9/30/2025.
