The Hormigas Ground Water Plume site sits in Caguas, Puerto Rico, where a plume of volatile organic compounds (VOCs) was found in the groundwater near two former public water supply wells. The affected wells, called Eufracia and Hormigas, served about 5,488 people before being closed in February 2009. The Puerto Rico Aqueduct and Sewer Authority (PRASA) first detected tetrachloroethene (PCE) above federal drinking water standards in the Eufracia well in August 2006. Later sampling by EPA in August 2009 confirmed PCE, trichloroethene (TCE), and cis-1,2-dichloroethene (cis-1,2-DCE) in the groundwater.
EPA placed the site on the National Priorities List (NPL) in March 2011. The NPL is the federal government's roster of contaminated sites that need thorough investigation. A remedial investigation then looked at how far the contamination had spread. Four VOCs were identified as site-related: PCE, TCE, cis-1,2-DCE, and 1,1-dichloroethene. Importantly, no samples exceeded EPA screening criteria, and contamination was not found in three other nearby community and unnamed wells that were tested. Very low concentrations of some VOCs showed up in only a few sampling rounds, all below the screening thresholds.
Because the contamination levels did not pose unacceptable risks, EPA signed a "no action" Record of Decision (ROD) in September 2016 for the entire site. Risk assessments for both human health and ecology supported that conclusion. EPA has confirmed that human exposure is under control, meaning there are no unacceptable pathways for people to contact contamination. Groundwater migration is also under control, and EPA will continue monitoring to confirm the plume stays in its original area. Physical construction of cleanup activities was completed by July 2017, and the site was deleted from the NPL in September 2020, showing that cleanup goals had been met.
Community members who want to review site records can visit the EPA Region 2 Record Center in New York, local offices in Caguas, or the EPA office in Guaynabo, Puerto Rico. Key documents include the 2016 ROD for Operable Unit 1 and the 2020 deletion docket. The EPA's Community Involvement Coordinator and Remedial Project Manager are available to answer questions.
