A fuel terminal in Spokane, Washington experienced a release of approximately 3,500 gallons of gasoline from a 1.35 million gallon above ground storage tank. The tank was surrounded by an unlined earthen berm, and gasoline infiltrated the soil above a sole-source drinking water aquifer.
Cardno staff mobilized the day of the incident and developed a model of the release extents, implemented safety measures, and directed emergency response efforts. Following the emergency response, additional remediation was conducted. Completed scopes included:
- Direction and oversight of excavation of approximately 1,500 tons of accessible impacted soil within 48 hours of the release
- Soil samples of the excavation extents to gauge progress
- In order to address inaccessible soil impacts located beneath facility piping, a soil vapor extraction remediation system pilot test was completed to assess the effectiveness of this remedial technology
- Full-scale implementation of a soil vapor extraction remediation system, which achieved cleanup goals in less than one year and removed approximately 4,200 pounds of hydrocarbons as vapor
- Collection of soil samples to confirm that cleanup levels were achieved and preparation of a report documenting the cleanup efforts and requesting site closure from the Washington State Department of Ecology’s Voluntary Cleanup Program
Cardno utilized several models including the Hydrocarbon Spill Screening Model, coupled with soil and groundwater sampling data to assess the depth of contaminant infiltration and time required to reach groundwater, successfully demonstrating that the sole-source drinking water aquifer was protected. Subsequent to emergency response and remediation efforts to meet state cleanup levels, the state issued a No Further Action determination for the release. All scopes of work were conducted without a safety incident during frequently challenging winter weather conditions.