IWTP Groundwater Monitoring & Ice Mine Rock Fill

Inchelium, WA | Used Oil & Waste Clean Up at Inchelium Wood Treatment Plant

In 2015–2016, the Colville Tribes Environmental Trust Department conducted groundwater monitoring and waste oil removal at the Inchelium Wood Treatment Plant (IWTP) site and the nearby Ice Mine Rock Fill area, located near Inchelium, WA. These actions helped track legacy contamination from former wood-treating operations and ensure site safety.

Background

The IWTP was built in the mid‑1980s on land acquired by Colville Tribal Enterprise Corporation and operated until 2006. It used chromated copper arsenate (CCA) to preserve wood—a process that generated hazardous CCA-contaminated soil, concrete, tanks, ground water and sumps. Inspections by EPA in the mid‑2000s identified violations of federal hazardous waste laws under RCRA, including unpermitted hazardous waste storage and run-off onto surrounding soil.

The site contained chemicals such as chromium, copper, arsenic, and lead at levels significantly above background and tribal cleanup thresholds.