PROJECT: Remedial Design

Portland, Oregon

The McCormick & Baxter site, located on the northeast shore of the Willamette River in north Portland, includes 41 acres of land and 23 acres of sediments beneath the Willamette River. McCormick & Baxter Creosoting Company operated between 1944 and 1991, treating wood products with creosote, pentachlorophenol, and inorganic (arsenic, copper, chromium, and zinc) preservative solutions. Historically, process wastewaters were discharged directly to the Willamette River, and other process wastes were dumped in several areas of the site. Significant concentrations of wood-treating chemicals have been found in soil and groundwater at the site and in river sediments adjacent to the site. The U.S. Environmental Protection Agency (EPA) listed the site on the National Priorities List (NPL) in June 1994 based on information collected by the Oregon Department of Environmental Quality (DEQ) between September 1990 and September 1992. The EPA also designated the DEQ as the lead agency for implementing the selected remedy, while funding for remedial design and construction is being provided by EPA.

GSI staff members led all management and technical elements of the project while working for DEQ. Creosote in the subsurface currently is being passively recovered. Approximately 6,200 gallons have been recovered since 1991. A contingency groundwater remedy was implemented in the summer of 2003, with the construction of a combination steel sheet pile and soil bentonite slurry wall surrounding 18 acres. The purpose of the barrier wall is to prevent migration of creosote to the Willamette River. The sediment remedy, implemented in 2004, primarily consisted of a sand cap placed over 23 acres of contaminated sediment. An oil adsorptive material known as organophyllic clay was used in the creosote seep areas. To protect the cap from erosion, the sand and organophyllic clay were armored with a combination of rock and articulated concrete blocks. The sediment remedy also included the regrading and capping of the riverbank with 2 feet of topsoil. Revegetation of the capped riverbank with native trees and shrubs took place in February 2006 after the soil had been stabilized by the native grasses planted in November 2004. Capping of a 1-acre portion of the contaminated sediments along a high-pressure sewer main was completed in September 2005.

GSI has been retained as the technical consultant and is involved with all phases of this project. Projects currently underway at the site include semi-annual monitoring of interarmoring porewater, subarmoring porewater, and surface water; crayfish sampling; quarterly monitoring of groundwater and the nonaqueous-phase liquid (NAPL) levels; NAPL recovery; and routine operation and maintenance activities. GSI, along with DEQ, is partnering with the University of Texas and Portland State University to determine the significance of ebullition as a potential contaminant pathway, the remaining capacity of the organophyllic clay, and biodegradation occurring within the sediment cap.