Gas Works Parks GW Assessment

Project Summaries


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WA320 - Ground-Water Contamination Assessment at Gas Works Park, Seattle, WA - Completed FY1987

Problem - Gas Works Park, on the north shore of Lake Union in Seattle, Washington, is a municipal park built on the site of an abandoned coal and oil gasification plant. The underlying soils are highly contaminated from past operations of the plant; of most concern is the presence of polynuclear aromatic hydrocarbons (PAH's). Soil samples collected by Environmental Protection Agency (EPA) in 1984 indicate concentrations of total PAH's range from 23,000 to 2,400,000 ug/kg in the park. One of these, benzo (1) pyrene, has been reported to be as high as 10,000 ug/kg, or 1 percent. It is feared that because of the soil contamination, the ground water under the park may be contaminated also, and could be a possible source of contamination to Lake Union.

Objectives -

Describe the geohydrologic setting of Gas Works Park and vicinity;
carry out a qualitative assessment of ground-water contamination by wastes from the gasification plant; and
estimate within broad limits the nature of any contamination that may be moving into Lake Union.

Approach - Review all available data, conduct a literature search, and develop a site safety plan for drilling and data collection. Seismic refraction surveys will be conducted to determine thickness and depth of unconsolidated geologic units and to locate the water table. Soil-gas surveys will also be conducted to determine if volatilization is occurring and, if so, to locate and define plumes. Based on our findings, we will plan and install a network of wells to provide stratigraphy, horizontal- and vertical-head relationships, and water chemistry.