Naches Valley Intermediate School

As former orchard land, the site was subjected to historical pesticide applications. In 2005, Ecology staff tested the soil at the site and found lead and arsenic area-wide soil contamination exceeding state cleanup levels.

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.

In 2006, the site was added to Ecology’s Hazardous Sites List with a ranking of “5”. Sites on the Hazardous Sites List are a priority for Ecology, and have completed a Site Hazard Assessment (SHA). A SHA provides information about the environmental risk of the site. Risk is based on the amount of contaminants, how toxic they are, and how easily they can come in contact with people and the environment. Sites are ranked relative to each other on a scale of “1” to “5”; with a rank of “5” being the lowest.

During the summer of 2006, Ecology staff managed a cleanup at the site designed to reduce or eliminate the lead and arsenic contamination. Ecology staff verified through confirmational sampling that the contamination had been either removed or reduced to below state cleanup levels.

Based upon cleanup activities, Ecology has determined the site no longer poses a threat to human health and the environment. The site was removed from the Hazardous Sites List in October 2007.