Terraphase was engaged to take over environmental activities at a long-vacant former gasoline and automotive service station in Northern California that had been stalled in regulatory oversight. The site has multiple underground storage tanks (USTs) and associated piping. The property is now being redeveloped into a low-income apartment complex.

Scope of Services

Terraphase assumed responsibility for regulatory communication with the local oversight agency, conducted additional site characterization, and developed an updated conceptual site model (CSM). A revised remedial strategy was proposed and approved, including the use of a proprietary vapor suppressant and hydroseed to minimize odor impacts to nearby residential areas.

Terraphase managed the public notice process, contractor selection, and on-site remediation activities, including the excavation of approximately 9,700 tons of total petroleum hydrocarbon (TPH) and lead-impacted soil and removal of legacy piping. Following the remediation activities, soil-gas monitoring wells were installed to evaluate vapor intrusion risk. Terraphase also designed and oversaw the installation of a passive vapor intrusion mitigation system (VIMS), as required due to the presence of a regional tetrachloroethylene (PCE) plume, and supported the client in securing city planning and building approvals.

Notable Accomplishments

• Progressed site closure process that was stalled in regulatory oversight and secured regulatory agency approval for a revised remedial plan
• Excavated ~9,700 tons of TPH- and lead-impacted soil
• Designed and implemented a passive VIMS to address vapor intrusion risks
• Minimized community odor impacts with an innovative vapor suppressant and hydroseed application
• Supported the client in obtaining city planning and building department approvals for apartment complex development