An underground storage tank was removed from a farmhouse property in Watsonville, California. The tank was used to store gasoline. Gasoline-impacted soil and groundwater were discovered during the tank removal, and investigation commenced. Gasoline components including methyl tertiary butyl ether (MtBE) were identified in soil and groundwater samples. Investigation was completed to discern the magnitude and extent of impact; and a cleanup plan was implemented. Since MtBE-affected groundwater was a primary concern, groundwater extraction with ozone treatment was deployed for cleanup. Groundwater was extracted from the MtBE plume using an array of wells specified through groundwater modeling. Extracted groundwater was treated using ozone, and the treated mixture of groundwater, ozone, and dissolved oxygen was re-injected into a well situated within the core of the MtBE plume. After a period of operation and verification monitoring that included soil and soil gas analyses, the Central Coast Regional Water Quality Control Board closed the site.