Challenge

From 1970 to 2014, a dry cleaner operated in the City of Watsonville and discharged wastewater containing tetrachloroethene (PCE) to the City sewer during its operations. After the dry cleaners closed, the City needed to assess the extent of impacted soil, soil vapor, and groundwater caused by the PCE from the operation. The City was particularly concerned about the location southeast of the former dry-cleaning facility near residential properties and commercial businesses.

Solutions

GLA has provided a range of hydrogologic services for the City, including community outreach, groundwater monitoring and analysis, and preparing a Corrective Action Plan (CAP). The CAP was prepared for the City under Regional Water Board review and approval that summarized numerous prior efforts to characterize groundwater occurrence and flow direction and to address groundwater quality impacts.

GLA promptly began community outreach events to implement corrective actions, including sending notifications through the and door-to-door visits, to request access to residential properties for environmental sampling. In order to evaluate groundwater impacts, we sampled and analyzed data results from several rounds of sampling in area groundwater monitoring wells, collected additional date from soil vapor probes, subslab vapor probes, crawlspace vapor samples, and indoor air and ambient air samples, and developed flow maps to characterize a groundwater divide in the area. Our team evaluated potential commercial and residential human health impacts due to groundwater impacts and resulting indoor air vapor intrusion and designed a plan to implement in-situ chemical reduction and bioaugmentation technologies for groundwater remediation involving numerous groundwater injection points.

Results

GLA’s design and implementation of the unique supplemental reagent injection system has allowed the City to maintain treatment as reagent is consumed and expand the area subjected to treatment. The system has also helped with treating the rebound in groundwater VOC concentrations. Our plan and system have allowed the City to meet all regulatory requirements of the Reginal Water Board, including requirements for vapor monitoring.