Tacoma-Pierce County Health Department Presents…

The Arsenic

Project

A Brief History

The Tacoma Smelter operated in Ruston, WA from 1890-1986

Specialized in smelting high arsenic ores

Tall stack emissions from the plant contained arsenic, lead and other heavy metals. The purpose of the stack was to disburse

emissions via the wind.

In 1983 the smelter and surrounding area was designated an EPA Superfund Site

Previous Thinking on Contamination

Fugitive emissions were problematic Not a lot of thought about

the extent of low level contamination due to fallout from the plume

Delineation of the superfund area was based on the extent of high levels of contamination due to fugitive emissions

An Evolution in Thought

Several studies unrelated to the Asarco site indicated that the extent of the problem from the plant was much larger than originally thought Maury Island Gravel Pit

Study University Place Water

Tank Study University Place

Residential Sampling

Realizing the Need For a Footprint Study

Ecology realized results from other studies indicated wide-spread contamination over King and Pierce Counties Need for sampling outside

the superfund areaThe Tacoma Smelter Plume Project (TSP) beganIt became the largest Site Hazard Assessment ever conducted in Washington State

Pierce County Footprint

2001- The Tacoma-Pierce County Health Department accepted an SHA grant to conduct the Pierce County Sampling The project became known

as The Arsenic Project

The scale of the project required a change in thinking about Site Hazard Assessments

Goals for the Footprint Study

1. Create a map of the “footprint” of contamination

2. Gather enough information to identify the PLP

New Sampling Methods

Grid Sampling Divided the study

area into 6 zones based on distance and direction from the stack and urbanization

Grid spacing for each zone was dependent on expected variability of sample results

Depth Profiling

New Sampling devices allowed discrete samples from three depths. Allowed a comparison of

contamination between disturbed and undisturbed properties.

Hypothesis that contamination on disturbed properties may be 6”-12” below the surface

Tracer Element Study

Trace elements unique to the smelting processes and ores at the smelter provide a “fingerprint” to identify contamination The ratio of arsenic to antimony, indium, and

bismuth provide credible evidence that the contamination came from the Asarco plant.

Approximately 12% of the samples were sent for tracer analysis

Findings

Low levels of arsenic contaminate soils in much of western Pierce CountyContamination is found at higher levels and farther distances in the downwind directionsUndisturbed properties generally have higher levels of arsenic than disturbed properties In disturbed areas the amount of arsenic in the soil is highly variable and dependent on property history

What We’re Doing With The Results…

Footprint results were used to focus efforts for the Child Use Area Study and outreach and education activities

Ecology is preparing a credible evidence report to identify the PLP.

Future Activities

Complete the CUA

Extend the footprint study

Continue outreach and education activities

Study remedial actions Tilling Bioremediation