A Certificate of Completion was obtained through the Texas Commission on Environmental Quality (TCEQ) Voluntary Cleanup Program (VCP) for a groundwater contamination site requiring a comprehensive risk-based assessment. The scope included evaluation of soil, groundwater, surface water, sediment, and soil vapor; implementation of chemical and biological groundwater remediation; and restriction of potable groundwater use via a Municipal Setting Designation (MSD).

The Site was previously occupied by an analytical laboratory where chlorinated solvents were used and released into the subsurface through building utility lines. Investigations revealed contamination of groundwater units with chlorinated solvents exceeding federal maximum contaminant levels (MCLs). Given the Site's proximity to surface waters, ecological exposure pathways were also assessed.

Multiple groundwater-bearing units were classified as Class 3 (non-potable) resources. Vapor intrusion risks were ruled out through direct soil vapor sampling. Ecological evaluations eliminated the need for further assessment of groundwater-to-surface water and sediment exposure pathways. However, volatile chemical concentrations in groundwater remained above risk-based thresholds.

A two-part strategy was implemented to address these concerns: (1) modification of cleanup criteria through the MSD to eliminate the ingestion pathway, and (2) reduction of chemical concentrations via subsurface injections using in situ chemical oxidation (ISCO) and biological reductive dechlorination.

Since the City of Webster had no existing MSD ordinance, extensive coordination was required with property owners, nearby public water supply well owners, and surrounding municipalities and districts—including Houston, League City, Friendswood, Nassau Bay, Clear Lake, MUDs, and WCIDs—to secure all necessary resolutions. The MSD was certified by the State of Texas in February 2018, effectively closing the groundwater ingestion pathway. With reduced contaminant concentrations, the site qualified for regulatory closure, and the VCP Certificate of Completion was issued in January 2019.