Remediation Design for Dioxin Remediation at Bien Hoa Airbase

From 2019 to 2023, Trigon served as the Prime contractor to USAID providing a comprehensive range of technical services required to develop and facilitate approval (by the Government of Vietnam) of a Project Implementation Masterplan, as well as engineering design, construction management implementation support and related project implementation services for dioxin remediation at the Bien Hoa Airbase Area in Vietnam.

Trigon initiated its remediation design process by reviewing a previous Environmental Assessment conducted in late 2014/early 2015. Building upon the findings of this assessment, Trigon conducted a Data Gap Analysis to comprehensively identify areas with dioxin contamination requiring remedial action. This analysis and the associated field investigation results led to the identification of over 68,000 m² at 73 separate sites which required additional site investigation plans to fully delineate dioxin and arsenic contamination. Once the sites were delineated, Trigon’s team developed individual remediation design packages for each site.

Each remediation design package included site topographic surveys, detailed design drawings, treatment designation, material and backfill specifications, and drainage design when applicable. Trigon also designed a 73,000 m² Long-Term Storage Area (LTSA) to landfill excavated sediment and soil which did not require treatment [concentrations of dioxin less than 1200 part per trillion (ppt) Toxic Equivalency (TEQ)]. Key components of the LTSA design included permanent concrete berms, access roads, security features, decontamination areas, and stormwater and process water drainage and storage.

Trigon also designed a 73,000 m² Long-Term Storage Area (LTSA) to hold excavated sediment and soil with concentrations of dioxin less than 1200 parts per trillion (ppt) Toxic Equivalent (TEQ) which did not require treatment.

During the initial excavation of one area in the Southwest Area of the Airbase, Trigon’s site investigation unearthed numerous drums of unknown contents. Subsequently, a ground-pentrating radar survey was conducted which identified additional buried drums in an area correlating to a historical pond. Some of the drums had geophysical signatures associated with liquid contents. Trigon developed a protective plan for the pond area since full characterization and remediation of the pond area was not possible before the start of the rainy season in Vietnam. The plan included a temporary counter-weighted cap comprised of sheet piling, geotextile, and soil to isolate the buried material and protect surface water and groundwater until additional site characterization could be completed.

The proposed remediation design plan recommended the utilization of a thermal conductive heating (TCH) treatment process and the construction of a 42,000 m² TCH treatment facility. The plan received unanimous approval by all stakeholders. Trigon’s design for the TCH facility included plans for a treatment system for contaminated soil, vapor, and wastewater, along with site preparation, facility layout, drainage, and associated infrastructure. Additionally, Trigon prepared the preliminary design for an electrical substation and determined water requirements based on treatment train specifications. To support the TCH treatment facility, Trigon also designed a 40,000 m² pretreatment storage area and a 30,000 m² post-treatment storage area.