The Arsenic Project

For nearly a century, an Asarco, Inc., copper smelter operated in Ruston, Washington. The plant specialized in smelting copper ores that were high in arsenic and lead. For many years the arsenic was rerefined and sold for use in fertilizer, pesticides, and rat poison. For most of that period, the Ruston plant was the sole domestic producer of arsenic.

To reduce impacts on surrounding neighborhoods, by-products from the plant were emitted for wind distribution through a 562-foot tall smokestack. The plant closed in 1986, and the stack was dismantled in 1993. Today the plant and surrounding neighborhoods are undergoing remediation by Asarco, Inc., with oversight from the U.S. Environmental Protection Agency Superfund Program.

Though significant progress is being made on the Superfund site, recent studies have shown that contamination from the plant extends much further than originally believed. The Tacoma-Pierce County Health Department, with grant funding from the Washington Department of Ecology, has partnered with the Washington Department of Ecology to characterize the magnitude, extent, and distribution patterns of contamination in Pierce County.

Data tracking sampled properties were located by either parcel centroid or GPS (if the parcel was large). For mapping purposes, the maximum arsenic and lead result was recorded for each sample site. The resulting map shows the upper limits of concentrations. All data was tracked in a Microsoft Access database. Statistical analysis of arsenic and lead level showed patterns related to the amount of soil disturbance and distance from the smelter. Magnitude and extent of arsenic contamination levels ranged in concentration from 2.9 parts per million (ppm) to 1,050 ppm. Lead concentrations ranged from 8.9 ppm to 6,670 ppm. The state cleanup levels under the Model Toxics Control Act for arsenic and lead are 20 ppm and 250 ppm, respectively. Sample results in Pierce County above the cleanup levels occurred most frequently close to the smelter but extended west to the Gig Harbor Peninsula, east to Browns Point, and as far south as Dupont. The contamination also extends into King, Kitsap, and Thurston counties—nearly 1,000 square miles.

Maps were provided by the Tacoma-Pierce County Health Department with funding from the Washington Department of Ecology.