West Side High School

Schools in the Wenatchee School District were sampled for lead and arsenic contamination as part of Ecology’s Area-Wide Soil Contamination Project.

Area-wide soil contamination is defined as contamination above state cleanup levels that is dispersed over a large geographic area. The soil contamination in this case is a result of central Washington’s orchard industry. Much of the region consists of current or former orchard land, where long-term pesticide application has taken its toll. Lead arsenate, a pesticide commonly used between the years of 1905 and 1947 to control the codling moth, has been identified as the primary source of increased lead and arsenic concentrations.

Due to their chemical structure, lead and arsenic tend to bond with soil particles and often remain at or near ground surface level for decades, creating an exposure pathway through inhalation and/or ingestion.

Although lead and arsenic are naturally occurring elements, elevated concentrations have been proven to have a negative impact on human health. Young children are generally more susceptible than adults, which is why Ecology has focused remediation efforts on schools.

Sampling results from the Wenatchee area showed several schools with soil contamination exceeding state cleanup standards, including Washington Elementary.

After a Site Hazard Assessment, the Site was ranked a “3” on the Hazardous Sites List. The Hazardous Sites List is a statewide list of contaminated properties.  Sites can be ranked from a “1” to “5”.  A rank of “1” is the highest level of environmental concern compared to other sites on the List, and a rank of “5” is the lowest.

During the summer of 2006, Ecology staff managed the cleanups at four schools within the Wenatchee School District. These cleanups used excavation, deep mixing, or a combination of the two, to reduce or eliminate the lead and arsenic contamination.

Generally, soil with arsenic levels above 100 parts per million (ppm) was excavated prior to deep mixing. Then the contaminated soil was disposed of at the Greater Wenatchee Landfill. Once excavation was complete, deep mixing could take place. This involves mixing the contaminated soil with clean soil from beneath the contamination. This is very effective in reducing lead and arsenic concentrations throughout the soil profile.

Once the deep mixing was complete, clean topsoil was imported and new seed or sod was placed down to establish grass. All sites were restored to their original condition. Ecology staff verified through confirmational sampling that the contamination had been either removed or reduced to below state cleanup levels.

Based upon cleanup activities and sampling, Ecology has determined the site is no longer a threat to human health and the environment.  The Site has been removed from the Hazardous Sites List.