Trihydro is completing an Air Force Civil Engineer Center Task Order for architect-engineering services to conduct remedial investigations (RI) for various sites at Eareckson Air Station, a United States Air Force military airport on the Alaskan Aleutian Islands. Situated 1,500 miles southwest of Anchorage and 400 miles from Russia, the Air Station lies at 98 feet above mean sea level on the south side of a 2-mile by 4-mile island.
Trihydro conducted a Phase I RI, which involved site characterization of per-and polyfluoroalkyl substances (PFAS) contamination at four site areas resulting from past aqueous film-forming foam (AFFF) use and development of a conceptual site model (CSM). Trihydro served as the task lead for on-island fieldwork, managing tasks such as:
- Installing and developing groundwater monitoring wells at 13 locations
- Sampling 45 existing groundwater wells
- Collecting 31 surface water/sediment samples to assist in delineating PFAS contamination
- Completing 135 soil borings with select, co-located temporary well groundwater samples to delineate PFAS impacts above the project screening levels in soil and groundwater
- Testing 24 separate PFAS analytes in soil, groundwater, surface water, and sediment
- Performing a synoptic groundwater gauging event of over 100 existing wells and then adding a scope element at no cost to the original contract to re-survey the 100 wells to confirm gauging data would meet the project goals
The project’s extreme remoteness provided early project challenges when a 15-foot Geoprobe 6620 drill rig suffered a head gasket failure. The project team worked quickly to mobilize a repair team and repair parts to the island. Following repairs to the drill rig, the project team worked an accelerated schedule to complete the project on time and within budget with zero safety issues.
The project team also worked proactively with the Air Force and the Alaska Department of Environmental Conservation to bring stakeholders together in the project’s planning phase, which streamlined later-stage regulatory reviews on the Uniform Federal Policy for Quality Assurance Project Plans (UFP-QAPP) and facilitated early conditional approval to execute the first groundwater and surface water sampling event prior to final QAPP approval. Applying a staggered field approach allowed the team to use insights from the data collected in early project stages to field-adjust later-stage sampling locations and minimize data gaps, making for the most efficient use of fixed resources. The Air Force project manager adopted the staggered approach as a Best Management Practice (BMP) for other RIs throughout Alaska.