A pond at Robins Air Force Base (AFB) was used to contain runoff from aircraft maintenance hangars in the event of a release of aqueous film forming foam (AFFF), used as part of firefighting or training activities.
The pond, lined with a geosynthetic clay liner, provides containment and retention of AFFF-impacted wastewater prior to discharge to the base's stormwater conveyance system. Constituents of AFFF include per- and polyfluoroalkyl substances (PFAS), a family of thousands of persistent man-made compounds which are rapidly emerging as potential hazards to human health and the environment. For planning related to future pond operations, Geosyntec was selected to investigate the presence of potentially impacted media related to pond operations, the integrity of the pond containment system, and potential compliance concerns with the base's RCRA and NPDES permits.
For a separate task, in response to a concern voiced by the Georgia EPD that 1,4-dioxane may be present in groundwater in excess of the U.S. EPA Regional Screening Level (RSL) for tap water, Geosyntec was asked to assess the potential release and distribution of 1,4-dioxane within previously delineated groundwater plumes associated with the Robins AFB active restoration sites.
Geosyntec's Scope of Services
To avoid compromising the pond liner by coring through it, Geosyntec used direct push technology drilling methods to advance soil borings at a 45-degree angle under the pond liner to collect samples for laboratory analysis for PFOA and PFOS (two of the PFAS compounds of interest). We conducted these activities in accordance with the "Interim Air Force Guidance on Sampling and Response Actions for 1,4-Dioxane at Operational and BRAC Installations." PFOS was detected in a soil sample collected below the pond at an estimated concentration below the US EPA Region 4-recommended residential soil screening criteria. PFOS was also detected in a groundwater sample collected downgradient of the pond at a concentration below the U.S. EPA's Health Advisory level. Based on the investigation results, we provided the Base with recommendations for pond operations and construction improvements, institutional controls, waste disposal options, and long-term monitoring options.
For the 1,4-dioxane investigation, we completed desktop assessments and site-wide and targeted groundwater monitoring events to evaluate if 1,4-dioxane releases had occurred. Based on the Phase 1 sampling results, 1,4-dioxane concentrations in groundwater exceeded the U.S. EPA tap water RSL in samples collected at six sites. We conducted subsequent field efforts at these sites to characterize the vertical and horizontal extent of the 1,4-dioxane groundwater plumes, and our expertise with technical modeling and visualization applications allowed interpolation and visual representation of plume configurations over multiple hydrogeologic zones to refine the understanding of plume delineation.
Due to the complexity and nature of investigations into the presence of emerging contaminants, particularly at low levels where false positives and cross-contamination are significant factors, Geosyntec identified internal experts and subcontractors who had the skill set to provide the technical skills necessary to complete these projects. Consistent favorable feedback from the regulators on the high quality of our work products allowed the base to conduct the projects as planned and without delay-related cost overruns.
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- Location: Robins Air Force Base, Georgia
- Client: Robins Air Force Base
- Project Practice Areas: Contaminated Sites
- Type of Facility: Active military installation
- Services Provided: Site investigations, Multi-media environmental sampling, Regulatory interaction
- Type of Work: Site investigation
- Governing Regulation: Federal and state