A-E Services for Dioxin Remediation at Bien Hoa Airbase Area

Trigon served as the Prime Consultant on this contract to provide A-E and all related technical services to the US Agency for International Development to develop and facilitate approval (by the Government of Vietnam) of a Project Implementation Masterplan and to provide engineering design, construction management implementation support and related project implementation services for dioxin remediation at the Bien Hoa Airport Area in Vietnam – the largest remaining hotspot of dioxin contamination in Vietnam with over 400,000 cubic meters of soil identified as requiring remedial action. Services included compliance with all US and Government of Vietnam regulations for environmental, health & safety, and other aspects of the project. This was one of the most complex and high-profile environmental remediation projects the US Government has undertaken.

Trigon worked closely with USAID, the GVN and other stakeholders to create an Implementation Masterplan for dioxin remediation at the Bien Hoa Airbase Area. The Masterplan described the overall vision for how dioxin remediation will be performed at the sites for the life cycle of the project. It included identification and prioritization of interim measures to address human health or ecological risks and serve as the basis for planning and future remediation and implementation by USAID and GVN of dioxin remediation. To proactively engage the various project stakeholders, a roadmap to Masterplan approval was developed to present concepts, share progress, discuss needs, address concerns and obtain feedback through a series of workshops, leading up to the presentation of the final Masterplan document.

Trigon developed multiple project-wide documents including Site Wide Sampling and Analysis Plan, Site-Wide Health and Safety Plan and Activity Hazard Analysis compliant with USACE EM-385, Site-Wide Quality Assurance Project Plan (UFP-QAPP), Unexploded Ordnance Oversight, and Site-Wide Environmental Monitoring and Mitigation Plan to be followed by all contractors as well as activity-specific addenda for activity-specific investigations. Trigon developed and implemented investigation plans for siting studies for waste storage and treatment facilities. Trigon assimilated data from multiple agency investigations and designed data gap investigations to provide supplemental data required to optimize remedial actions at each area. Trigon’s environmental team conducted the site investigations with reporting to all stakeholders. In addition, Trigon conducted required sampling to establish pre-construction background limits of concentrations of dioxin, arsenic, total suspended solids, dust and other parameters in surface water, groundwater, and air and conducts the monitoring of these media during construction activities.

Trigon also provided detailed engineering designs to implement the approved remediation approach, as well as construction management services overseeing implementation of interim measures packages, procurement support, and post-construction testing.

Trigon subcontracted and oversaw the detailed surveying of over 500 hectares of upland, submerged and intertidal land. The updated detailed maps have been used in design remedial actions, designation of land-use criteria to be applied to areas that may impact down-gradient remedial action areas. The data was used to develop an airbase wide surface water and groundwater hydrology model to further optimize investigations, remedial actions and environmental resiliency as well as support detailed designs regarding modeled flow and storage capacity. Site-wide and activity-level site conceptual models have been developed with respect to these levels. In addition, Trigon developed, has developed threshold levels for the monitoring of construction and operation of site excavation, storage facility construction and operation, and general conditions (haul roads) top ensure there is no impact to workers, the environment or the densely populated areas around the remediation sites. Furthermore, Trigon also developed 95% designs used in solicitation packages for remediation, civil works, and treatment packages.

Environmental resiliency was built into the overall project using threshold and cleanup levels associated with land-use and human health and ecological risk factors. These criteria ensure an area is remediated to levels that support the intended land use (as conservative as aquacultural use) that may not have been achieved with media-based cleanup criteria. An example is Gate 2 Lake that is located outside the airbase boundary and was a public park. The sediments were contaminated with dioxin that was risk to the public. The lake was remediated by dig and haul to land-use standards for unconditional use as opposed to just meeting the project sediment criteria. The lake and surrounding area was turned over to the public in June 2022

Trigon conducted analyses for dioxin (by congener and Toxicity Equivalence), arsenic and other parameters in all media (surface water, groundwater, sediment, soil, and air). NELAP-certified US-based labs were originally used exclusively for analytical services. During COVID shutdowns and limited ability to ship samples to the US, Trigon worked with a Vietnamese lab to develop a QA/QC program and modified methodology to meet data quality objectives specified in the UFP-QAPP. Though sample capacity was limited and samples had to be shipped to the US, the use of a local lab proved to be very valuable to the project and as a capacity building activity within Vietnam.

Since the Bien Hoa Airbase was heavily attacked during the Tet offensive, unexploded ordnance was of high concern throughout the airbase. With prescribed excavation exceeding 4 meters in some local areas, clearance to 5 meters was required. Because US companies are not permitted to conduct UXO clearances on the airbase, Trigon worked with the UXO subcontractor to review and ensure clearances conducted met or exceeded US-required procedures.

All areas were evaluated for archaeological sites such as burial sites. Human remains were discovered during the remedial action in multiple locations. Trigon worked with local governments and religious organizations to conduct public announcements for claims to the remains and ultimately relocate the remains in accordance with local regulations as well as any family religious requirements.