An underground pipeline that is used to transfer JP-8 fuel from the Suisun City Interconnect Valve Station to Travis Air Force Base leaked fuel from a high point drain for an undetermined span of time. Fuel was discovered by utility company workers in a utility vault approximately 145 feet east of the intersection of Lawler Ranch Parkway and Highway SR12. An emergency response action was implemented to recover the released fuel and a site assessment was performed in the area to determine the impact of the release to the environment.
Michael Baker Corp. completed a Phase I and a Phase II Investigation, which confirmed soil and groundwater contamination from Total Petroleum Hydrocarbons (TPH) above the San Francisco Region Environmental Screening Levels (ESLs). During the initial response and recovery effort, a vacuum truck was used to remove about 805 gallons of fuel from nearby utility vaults and borings that were placed near the leak area.
The focused site investigation involved collecting additional soil, groundwater and vapor samples south and southwest of the fuel pipeline, around nearby utility lines and in the median of SR 12 to help determine how far the jet fuel traveled from the leak’s point of origin and help identify the most effective way to clean up any contaminated areas. In addition, Conti Federal was tasked with weekly monitoring of the local stormwater drains and utility lines and the eventual conversion of the sampling sites into groundwater monitoring wells or, alternatively, plugging them in accordance with State of California environmental law.
Due to the close proximity to residential property, many stakeholders were involved. Conti Federal collaborated with Travis Air Force Base personnel, subcontractors, Solano County, Suisun City, and 60 residential property owners to ensure requests and modifications were addressed before work commenced. Conti Federal also established a single point of contact individual, on the ground, who launched a proactive community relations effort to inform and address residents’ concerns before the work was started.
The investigation work included sample collection on four residential properties. After the right-of-entry agreements were obtained from the residents, Conti Federal contacted each resident, providing them with a detailed schedule of activities and addressed questions regarding hours of operations, pets, etc. Samples were then collected from the homeowners’ wells where product was found, thereby requiring additional testing and removal.
Interim remedial action implementation took approximately 21 days. It included installation of dewatering wells to approximately 15-feet deep, surface and groundwater management, utility location, soil borings, overburden segregation to separate uncontaminated from contaminated soils, excavation of NAPL-saturated soils, offsite disposal, backfilling, compaction, erosion control, site restoration, and site security.
Despite the small work area and physical constraints on three sides, soil excavation was selected as the best approach to remove the free-phase NAPL within the area where it was known or suspected to exist. The purpose of the excavation was to remove soils with visible free-phase NAPL. The free-phase NAPL was located primarily within the backfill materials of the pipeline and the underground utilities in the area. The vertical extent of the free product extended below the water table, which was approximately 9.6 feet. An additional three feet of material in the vadose was targeted to a depth of 12.6 feet.
Chromium was discovered in the soil, which stopped the landfill from accepting material until testing was completed. Conti Federal then worked with the lab and local regulators to develop an action plan to effectively remove the chromium. After testing and analysis, the material was approved for disposal and Conti Federal proceeded on schedule. Conti Federal excavated and removed over 270 tons of contaminated material from the site, along with 20,000 gallons of contaminated water which was treated offsite. Conti Federal used monitoring wells to find pipe leaks.
Conti Federal performed routine monitoring for vapors and odors in outfall areas and near the site as specified by the Solano County Department of Resource Management (DRM). Tasks included visual inspection for sheen, measurement of volatile jet fuel constituents if needed in AT&T vault, oily water removal from the vault when it reached 20-inches deep, as well as visual inspection for sheen and measurement of volatile jet fuel constituents if needed in storm drains and outfall areas.
“It has been a good experience working with the professionals at Conti.”