Former Electroplating Facility, San Mateo County

Citadel EHS is leading the investigation and remediation of a 3.5-acre former electroplating facility in San Mateo County under the oversight of the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB). Site investigations identified chlorinated volatile organic compounds (VOCs), including trichloroethene (TCE), as well as PFAS impacts associated with historical industrial operations.

As part of a multi-phase investigation, Citadel developed a comprehensive Site Conceptual Model (SCM) to evaluate vapor transport pathways, delineate impacts in soil vapor and groundwater, and assess potential off-site receptors. Indoor air sampling confirmed that vapor intrusion did not pose a risk under existing on-site building conditions; however, elevated VOC concentrations identified along the property boundary indicated a potential vapor intrusion concern at a neighboring residence.

To address site conditions and protect nearby receptors, Citadel implemented a proactive risk management and remediation strategy that included targeted source area excavation, deployment of air purification units, and installation of a soil vapor extraction (SVE) system. Post-treatment monitoring demonstrated greater than 97% reduction in soil vapor concentrations within six months of operation, resulting in the successful mitigation of off-site vapor intrusion concerns. Based on these findings, the SFBRWQCB determined that no further mitigation was required for the off-site property.

Following evaluation of additional remedial alternatives, Citadel developed a phased management approach that combines long-term monitoring, regulatory coordination, and future redevelopment planning. The SFBRWQCB agreed that no further active remediation is required under current land-use conditions, recognizing Citadel's technically defensible and cost-effective approach to risk management and environmental remediation.

Highlights:

• SFBRWQCB Regulatory Oversight
• Delineation of Chlorinated VOCs in Groundwater and Soil Vapor
• PFAS Investigation
• Development of Site Conceptual Model
• Interim Monitoring of Soil Vapor Below Offsite Residence
• Source Excavation and Short-Term SVE to Mitigate Offsite Vapor Migration
• Sea Level Rise Vulnerability Assessment
• Approval for No Further Active Remediation Under Current Land Use Scenario