Sanpoil Emergency Spill Response

When a tank trailer spilled approximately 2,800 gallons of gasoline into a drainage ditch along a remote stretch of State Highway 21 (SR-21) on the Colville Indian Reservation in northeastern Washington, the gasoline quickly reached groundwater and threatened to migrate to the Sanpoil River on the opposite side of the highway.

Our project client Able Cleanup Technologies responded immediately to contain and remove spilled gasoline on the surface. GeoEngineers was quickly retained to identify and help implement solutions to keep the gasoline from reaching the river. The project team conducted assessment, remediation, and monitoring operations and was able to remove the spilled product from groundwater and keep gasoline from reaching the river, satisfying the requirements and expectations of the local tribal government, Environmental Protection Agency and Bureau of Indian Affairs. The large number of diverse stakeholders necessitated careful project management and clear communication to ensure success.

The project was complicated by a number of factors. State authorities required SR-21 to remain open to traffic during the project. This restricted the team to one narrow lane of the roadway, with the exception of temporary 20-minute closures, and meant extra safety measures to protect staff and members of the public.

The spill location was quite remote (approximately 28 miles from the nearest city with services), and staff had to constantly adapt to changing conditions, hazards from wildfires, traffic, and wildlife. A complete site evacuation during the North Star wildfire temporarily delayed work for three weeks.

Approach

• We worked cooperatively with a large group of contractors, consultants, tribal departments, property owners, regulators, and other governmental entities to develop and implement solutions to keep the gasoline from reaching the river.
• GeoEngineers mobilized a large and diverse project team of more than 80 staff during the project to conduct site characterization, monitoring, and remediation efforts. Early efforts required 24/7 oversight.
• An initial environmental assessment used piezometers, surface water sampling, and groundwater sampling to characterize the extent of contamination at the site.
• GeoEngineers evaluated the subsurface geology and hydrogeology using a variety of tools including a resistivity survey, ground penetrating radar (GPR), advanced groundwater modeling and direct observation from borings and trenches to evaluate how gasoline might spread beneath the site.
• The team designed and installed a temporary pump and treat system using a network of wells to contain and remove gasoline from the subsurface in both the free product and dissolved phases.
• Free product and contaminated groundwater was extracted and transported it off-site for treatment, testing, and temporary storage prior distribution for a variety of uses including fire suppression, irrigation, dust control and eventually, infiltration back into the watershed.
• The team used a soil vapor extraction and air sparging system, coupled with an ISCO injection system, to remove the remaining dissolved-phase gasoline. After full-time work ended, GeoEngineers continued to make weekly site visits to monitor the remediation system and water quality at the site.

Results

The rapid coordinated response to the spill successfully limited the spread of gasoline and prevented adverse environmental impact to the Sanpoil River and its ecosystem. Despite the remote site location and safety challenges, the team removed a majority of the gasoline release from the subsurface in less than three months.