The Midessa Ground Water Plume site sits in Midland County, Texas, and was added to the National Priorities List in March 2008 after an initial assessment completed in March 2007. Three separate groundwater plumes affect the site. The source or sources of contamination have not been identified. The contaminants are volatile organic compounds, or VOCs, specifically perchloroethylene (PCE), 1,4-dioxane, and carbon tetrachloride.
EPA has divided the site into two operable units, or OUs. OU-01 covers the PCE plume. OU-02 covers the 1,4-dioxane and carbon tetrachloride plumes. For OU-01, a remedial investigation and feasibility study, known as an RI/FS, began in September 2010 and is expected to wrap up between October and December 2027. For OU-02, the RI/FS started in November 2022 and is estimated to finish between August and October 2028. No cleanup decision documents, called Records of Decision, have been issued for either unit yet. Physical construction of the cleanup has not started.
Early work at the site included installing groundwater and soil vapor monitoring wells, as well as test wells for air sparging. EPA is also planning groundwater treatability studies, including a pilot test in Spring 2025. Those results will help shape the final cleanup approach for the site. Both federal and state agencies are involved, with the Texas Commission on Environmental Quality, or TCEQ, participating alongside EPA.
Filtration systems are installed on private wells to prevent people from drinking or touching the contaminated groundwater. EPA assessments indicate human exposure is currently under control. However, contaminated groundwater is still migrating beyond the original area, the cleanup is not finished, and the site has not yet reached its anticipated use.
Community members with questions can contact EPA's Community Involvement Coordinator or the Remedial Project Manager. For state-related questions, contact TCEQ.
