SR21 Gasoline Spill Site

Milepost 136.5, Keller, WA | CHS Tanker Incident

On May 19, 2015, a fuel tanker truck owned by CHS overturned on State Route 21 at Milepost 136.5 near Keller, WA, releasing approximately 2,700 gallons of gasoline and 60 gallons of diesel. The spill occurred near the San Poil River, raising concern for nearby water quality.

The Colville Tribes determined CHS to be the responsible party for the release, which posed a threat to navigable waters of the U.S. Since the time of the incident, the Colville Tribes Environmental Trust Department has worked closely with the U.S. Environmental Protection Agency (EPA) on emergency response and cleanup actions.

Work at the site has included fuel containment, environmental assessments, and long-term planning for remediation. Environmental Trust remains actively involved in both a technical advisory and regulatory role, and will continue oversight until final cleanup is complete.

Remediation Overview

Remedial efforts were phased over several months to address both soil and groundwater impacts, including free product removal and vapor treatment:

May 19 – August 19, 2015

  • Pump and treat of LNAPL (liquid free product)

  • Plume control

  • Soil vapor extraction (SVE)

August 19 – September 11, 2015

  • All systems placed on standby; no active remediation

September 11, 2015 – Spring 2016

  • Winterization of systems

  • Air sparging with enhanced soil vapor extraction

  • In-situ chemical oxidation

Remediation of Vapor Phase Hydrocarbons

  • Soil vapor extraction (SVE)

  • Granular activated carbon (GAC) filtration

  • Effluent testing and monitoring

Treated Groundwater Infiltration Gallery
Tribal Tract No. 101-T1766 via CBC Resolution No. 2015-456

Site Status and Groundwater Monitoring

Since initial cleanup began, groundwater sampling has shown no detectable gasoline or diesel-range hydrocarbons at the site.

To formally close the site, the following groundwater closure criteria must be met:

  • Contaminants of potential concern (COPCs) must remain below CCT HSCA cleanup levels in:

    • Five consecutive samples taken over a period of more than two weeks, and

    • Four consecutive calendar quarters, including both seasonal high and low groundwater conditions

  • No detections of contaminants of concern (COCs) in nearby surface water

The Environmental Trust Department will remain engaged in technical oversight until closure requirements are fully satisfied and final cleanup is certified.