CDM Smith delivered remedial action construction for the U.S. Environmental Protection Agency (EPA) in northern Louisiana to address creosote contamination.
U.S. EPA
Marion, Louisiana
The Marion Pressure Treating Superfund Site required large-scale remedial action construction to address creosote contamination affecting soil and groundwater at a 22-acre former wood treating facility. Under federal oversight, the project called for construction-based remedies capable of treating subsurface contamination while managing surface waste and protecting nearby environmental features
CDM Smith treated subsurface creosote dense non-aqueous phase liquid (DNAPL) contamination through excavation and onsite consolidation of impacted soils and in-situ stabilization/solidification (ISS) using large-diameter auger mixing.
To remove and isolate contaminated material, the team excavated impacted soils and consolidated surface waste material containing creosote and other contaminants into a controlled onsite waste repository, reducing the risk of further environmental contamination.
To prevent rainfall intrusion and contaminant movement, CDM Smith constructed a multilayer cap over the onsite waste repository, consisting of a clay layer, geosynthetic liner, and vegetated soil cover, providing long-term environmental safety for the community.
The project incorporated comprehensive remedial action construction controls, including stormwater management, waste handling, and site-specific plans for quality, health and safety, and stormwater pollution prevention.
The Marion project received funding from the Bipartisan Infrastructure Law, which enabled the project to proceed under the Superfund program, while reducing the financial burden on the states and community. Our construction, geotechnical engineering, and ISS subcontractor teams collaborated to test and refine the ISS mix to confirm that the ISS mixing approach would achieve the remedial action objectives. The $9.6 million project effectively reduced environmental risks and supported sustainable restoration, delivering lasting value to EPA, the local community, and the surrounding environment. CDM Smith completed remedial action construction at the Marion Pressure Treating Superfund Site in late 2025, successfully addressing creosote contamination across the 22-acre site. In January 2026, team members shared insights on the delivery and outcomes of the project at the Design and Construction Issues at Hazardous Waste Sites Conference, organized by the Society of American Military Engineers.
