Groundwater Recovery and Treatment for Pentachlorophenol at a Former Mill Site, 1996 Environmental Conference Proceedings

The former mill site is about 0.8 km west of wells that supply drinking water to Independence, Oregon. From approximately 1965 to 1986, lumber was treated as it left the planer shed with Permatox ® , a water-soluble, sodium-based pentachlorophenol (PCP) formula. As a result of long-term use and incidental spills in the planer shed area, PCP migrated downward and contaminated the upper water-bearing zone. The water-soluble nature of the PCP formula allowed it to migrate easily through soil and water; thus, it spread farther and more quickly than oil-based PCP formulas. However, the formula’s solubility could also facilitate groundwater cleanup by means of recovery enhanced by soil flushing or bioremediation. Initial site characterization resulted in the excavation of contaminated soil from the sawmill and planer shed areas. Once groundwater, both on and off site, had been characterized, an interim remedial measures (IRM) plan was designed to recover, hydraulically control, and treat groundwater and reduce PCP concentrations under the planer shed. The interim pump-and-treat system that has been installed is equipped with real-time telemetry so its operations can be checked remotely at any time. The design is flexible and allows for easy modification. Modifications may include soil flushing using treated groundwater, or amending water with nutrients to enhance biodegradation. The IRM plan bypassed the design specification and bid process and allowed site remediation to begin quickly, saving the mill both time and money.