Heglar Kronquist

The nearly four-acre site is 10 miles northeast of downtown Spokane in a rural area. 

The site was a county gravel pit from 1963 to 1969. From 1969 to 1974, Kaiser Aluminum & Chemical Corporation (Kaiser) disposed of aluminum black dross (dross) from its Trentwood facility at the site. Dross is a by-product from processing aluminum. 

Dross disposal activities stopped after elevated levels of chloride and sodium (which come from dross) were detected in water samples collected from a shallow groundwater well and spring near the site.

Past site data showed chemicals of concern related to the aluminum dross include:

• Aluminum
• Ammonia
• Chloride
• Fluoride
• Nitrates and nitrites
• Potassium
• Sodium

Chloride and nitrates were selected as indicators of landfill impacts to groundwater and surface water. Chloride is a good tracer because its related to other contaminants that come from dross and because it does not readily adsorb in groundwater. Nitrate was also selected as an indicator; however, nitrate concentrations can be highly variable at the site, and area-wide sources such as cattle activity and fertilizers may contribute to elevated nitrate concentrations.

Drinking water is not impacted by site-related contaminants.

Kaiser is responsible for cleanup costs.

In 1979, the U.S. Environmental Protection Agency (EPA) conducted water and air sampling to document impacts to groundwater, surface water (springs), and air from the dross. Impacts to groundwater included elevated chloride and sodium concentrations. Elevated ammonia concentrations were measured in air (ammonia is a result of a reaction between dross and water).

In 1979, Kaiser hired a consultant to assess the site, and as a result, conducted the following actions in 1983 and 1984:

• Constructed a 2-foot thick clay cover with a vegetated topsoil surface
• Constructed drainage ditches
• Constructed a fence to restrict access
• Conducted groundwater and surface water monitoring

Based on surface water (springs) collected down gradient from the Site, a 50 percent reduction of chloride concentrations was observed following cover construction; however, chloride concentrations still exceeded water standards.

In 2006, Ecology conducted a Site Hazard Assessment to determine its ranking relative to other contaminated sites in Washington. The Site ranked a 2 on a scale of 1 to 5; 1 represents the highest risk.

Kaiser completed the Remedial Investigation (RI) in 2011, and the Feasibility Study (FS) in 2012. The RI determined the extent of contamination and the FS evaluated cleanup options.

In 2012, Ecology issued the Cleanup Action Plan, identifying the following actions:

• Enhancing the cover to prevent water from infiltrating and spreading the dross contaminants
• Monitoring groundwater 
• Fencing around the landfill property, applying restrictions to limit the use of the property via an environmental covenant recorded as part of the property deed, inspecting and maintaining the cover, signs to warn people about contamination, and financial assurance that the cleanup costs will be covered.

Periodic reviews

Periodic reviews are required when institutional controls are required at a site. Ecology conducts reviews to make sure the controls remain effective and the cleanup still protects human health and the environment. We conduct periodic reviews about every five years.

In 2020, we completed the first periodic review and required no new cleanup actions. However, chloride and nitrate concentrations higher than state standards are still found in some groundwater monitoring wells. Monitoring will continue, and we will assess the cleanup progress in another 5 years.