Publication Summary

The Asarco Tacoma Smelter in Ruston operated from 1890 to 1986. Deposition of smelter emissions containing arsenic and lead have caused soil contamination in areas of King and Pierce counties. A survey of the arsenic concentration in soils of 59 University Place properties was conducted by Ecology during May through June 2000.

The purpose of the survey was to determine typical arsenic concentrations in residential soils in a study area with known elevated background conditions. University Place was chosen for the study because a previous study found elevated background conditions in that city; however, it is believed that other areas are likely to be similarly affected by deposition from the smelter.

The Asarco Tacoma Smelter, located in Ruston, Washington, operated from 1890 to 1986. Deposition of smelter emissions containing arsenic and lead have caused soil contamination in areas of King and Pierce counties. The City of University Place is, at its closest point, three miles south-southwest of the smelter site. A survey of the arsenic concentration in soils of 59 University Place properties was conducted by the Washington State Department of Ecology (Ecology) during May through June 2000.

The purpose of the survey was to determine typical arsenic concentrations in residential soils in a study area with known elevated background conditions. University Place was chosen for the study because a previous study found elevated background conditions in that city; however, it is believed that other areas are likely to be similarly affected by deposition from the smelter.

Soil samples consisting of five subsamples were collected from depths of 0-2", 2-6", and 6-12". Front and back yards were sampled separately. The mean soils arsenic concentration from the properties sampled was 26.4 parts per million (ppm). The highest single sample result was 163 ppm. Eighty percent of the properties had average arsenic concentrations of 40 ppm or lower. Approximately 60% of the properties sampled had higher concentrations than the 20 ppm Model Toxics Control Act (MTCA) cleanup level for arsenic for residential areas.

The age range of the structures on the properties correlated strongly with arsenic concentration. Properties with younger residential structures tended to have arsenic concentrations below the 20 ppm MTCA cleanup level, while properties with older structures had higher concentrations. Front yards tended to have lower arsenic concentrations than back yards. Though not recorded in this study, the extent and timing of landscaping activities such as cutting, filling, working the soil, or adding topsoil may be factors in reducing the influence of aerial deposition of arsenic in University Place soils.