15-Mile Creek Bridge, I-84 Freeway, The Dalles, Oregon

Assessment and Removal of Herbicide-Contaminated Soil

Anderson Geological, Inc. (AGI) assisted the Oregon Department of Transportation (ODOT) and Oregon Department of Environmental Quality (DEQ) in the assessment, removal, and disposal of soils contaminated by pesticides during a freeway bridge replacement in near The Dalles Dam. The bridge replacement included the removal of a large quantity of soils from the west end of the bridge where the soils had been contaminated by a pesticide tanker truck accident in 1999.


AGI worked with ODOT and the general contractor to assess the degree and extent of the contaminated soils and profiled the material for disposal as non-hazardous waste. The work involved test pit excavations and direct-push borings through the lahar and loess deposits. AGI provided oversight of the removal and disposal of the impacted soils. The soil removal was complicated by the condition that none of the soils could be allowed to enter the creek, potentially harming fish and other aquatic receptors.

The work was completed successfully with no impacts to the creek.