Phase II ESA, Remedial Investigation/Feasibility Study, Ecological Risk Assessment
The property was the site of a gravel quarry that operated along the banks of a perennial creek from approximately 1935 until 1945. The pit was gradually filled between 1945 and 1999 with fill of unknown origin as well as gravel-sized asphalt grindings and asphalt batch excesses from the asphalt plant that existed on the site during this period.
Asphalt truck beds were historically sprayed with diesel fuel as a release agent, which led to significant contamination of soil and free product on the groundwater surface near one of the property boundaries. Migration of free product to the adjacent property complicated the site evaluation efforts.
An additional contaminant source was identified where asphalt cold patch was mixed using diesel fuel and asphalt mix. Sediment and surface water was sampled from the adjacent creek, and was found to have been impacted only to a minor degree.
Based on investigations completed by AGI, it was shown that the free-product plume was stable and did not pose a significant threat to human or ecological receptors.
Anderson Geological, Inc. (AGI) worked with Oregon DEQ and the owners of the two impacted properties to develop a remediation strategy. To address potential future exposure to occupational receptors in the former truck-spraying area, an engineering control in the form of an impervious cap (asphalt pavement) was implemented to prevent exposure to contaminated soil and groundwater, as well as preventing surface water infiltration that could mobilize contaminants.
A groundwater restriction was also implemented on both properties that prohibits the installation of water supply wells within 150 feet of the edge of the free product plume.
The site received a No Further Action letter without the need for any active remediation.