The Tacoma Copper Smelter operated for more than 90 years, closing in 1986.
Little information is available from previous studies on the mainland.
All soil sampling occurred in forested areas assumed to represent the least disturbed soils available. Laboratory analyses were performed by OnSite Environmental Inc. of Redmond, Washington. A total of 436 soil samples was analyzed for arsenic, lead, and cadmium. Based on initial results, cadmium analyses were omitted for 98 of the final samples analyzed. Data validation reviews were performed on approximately one-third of the data reported by the laboratory.