Prosser Airport Aircraft Applicators

The Prosser Airport Aircraft Applicators site is currently an aircraft hangar and surrounding property has been the location of an aerial pesticide applicator operation since prior to 1966. Investigation revealed areas of stained soil. Soil sampling confirmed contamination from pesticides (e.g., dinoseb, DDT, dieldrin, and others) and petroleum. The site is currently owned by the Port of Benton.

Some cleanup activities have already occurred. More extensive sampling has been completed to determine the extent of the contamination. Excavation of contaminated soils has taken place. Groundwater monitoring wells have been installed.
 
Soil contamination was cleaned up through excavation and offsite disposal as part of an Interim Action in 2007 and 2008. An Interim Action is a partial or short-term cleanup of contamination and is meant to reduce exposure to harmful contaminants while a long-term cleanup plan is worked on. Both soil and groundwater were treated by chemical oxidation. Chemical oxidation is a cleanup option that injects chemicals called oxidizing agents into the contaminated soil and/or groundwater to break down the contaminants. In addition, during the site cleanup actions, soil contaminated with pesticides and herbicides was also removed.

Soil was sampled in 2017 and no contaminants were found above state cleanup standards. Groundwater was sampled between 2007 and 2019, and no contamination was found above state cleanup standards. 

Remaining soil contamination likely remains underneath the structure at the site. The site structure currently prevents access to and cleanup of remaining contaminated soil. In November 2020, an environmental covenant was recorded for the site.

Based on the cleanup actions and recording of the environmental covenant, Ecology issued a no further action letter. In April 2024, the site was updated to reflect a no further action status after a public comment period to remove the site from Ecology's Hazardous Sites List.