The Lot 46 Valley Gardens Trichloroethylene (TCE) Superfund Site is a TCE-contaminated groundwater plume in Des Moines, Iowa. Investigations led by the Iowa Department of Natural Resources (IDNR) began in 2004, and the site was referred to EPA in 2019 for federal assistance. After monitoring the plume for years and observing its recent migration, EPA plans to propose the site to the National Priorities List in late 2023. Listing the site on the NPL will support long-term cleanup efforts, impede further plume migration, and prevent exposure to site contamination.
The site groundwater contamination plume is southeast of the city of Des Moines Water Works (DMWW) Fleur Drive Treatment Plant infiltration gallery -- the infiltration gallery is a series of underground water collection pipes adjacent to the Raccoon River. Des Moines Water Works draws its water supply from a combination of both local groundwater and the Racoon River. EPA is working with DMWW to sample water from along the infiltration gallery and the site groundwater monitoring well network to ensure that source water is of the highest quality.
Currently, TCE and its degradation products have not been detected in the infiltration gallery at concentrations exceeding safe drinking water standards. Additionally, TCE and its degradation products have not been detected at concentrations exceeding levels of ecological concern in site monitoring wells near the Raccoon River. Monitoring and investigation will continue.
TCE and its degradation products in soil and/or groundwater may emit vapors. Based on current groundwater data, limited soil gas data, and the distribution of TCE and its degradation products in these samples, EPA has not identified a significant risk of exposure to such vapors at this time. However, investigation of vapor sources and pathways is ongoing.