Solid Waste - Colbert Landfill
The Colbert Landfill, a 40-acre municipal solid waste landfill located approximately 15 miles north/northeast of Spokane, operated until 1986, when it became filled to capacity with municipal and commercial waste.
Groundwater in the vicinity of the Landfill was contaminated with chlorinated organic solvents. This contamination has been traced to spent solvents that were disposed of at the landfill. Six solvents were detected in the groundwater near the landfill. These solvents are referred to as the "Constituents of Concern."
In 1980, State and County officials, lead by the County Utilities Department, initiated an investigation into complaints from nearby residents of groundwater contamination in the area. Nearby private wells were sampled. The results of this initial investigation, completed in 1982, indicated that some of these wells were contaminated. In August 1983, the Environmental Protection Agency(EPA) placed that landfill on its National Priorities List(NPL).
Several studies of the landfill were conducted since 1980, including the 1987 Remedial Investigation/Feasibility Study ((RI/FS), prepared by Golder Associates). The purpose of the RI/FS was to determine the nature and extent of contamination caused by the release of chemicals from the landfill and to evaluate potential remedies. The Remedial Investigation determined that the two primary aquifers in the landfill vicinity and a low-productivity aquifer to the east of the landfill were contaminated with one or more of the Constituents of Concern previously mentioned. The FS recommended a "pump and treat" remedy as the most-effective approach to address this groundwater contamination.
The EPA released its Colbert Landfill Record of Decision(ROD) in September of 1987. Based on recommendations in the FS, the ROD provides for a performance-based remedial action consisting of a groundwater pump and treat system. Subsequent to the implementation of the ROD, a Consent Decree for the landfill (1988) was negotiated between the EPA, Ecology, Spokane County, Fairchild Air Force Base and Key Tronic Corporation. By this action, the County agreed to implement the EPA-selected pump and treat remedy in accordance with the Comprehensive Environmental Response Compensation and Liability Act (CERCLA) requirements.
In March 1989, Spokane County entered into an agreement with Landau Associates to provide engineering services for Phase I Remedial Design/Remedial Action (pilot study) and Phase II Remedial Design for the landfill.
Spokane County entered into an agreement with Landau Associates to provide construction management services, and Humphrey Construction and Ershigs for the installation of the Phase II Remedial Action. Phase II construction activities included installation of groundwater monitoring, extraction, treatment, and discharge systems to address contaminated groundwater. Facilities constructed included ten groundwater monitoring wells at six locations, ten groundwater extraction wells, groundwater air stripping and scale control treatment systems, and groundwater conveyance system piping.
In May 1994, the Colbert Treatment Plant came online and since then has been treating approximately 1 million gallons per day.