Formatted Title

Accelerating Site Characterization and Conceptual Site Model Development via TRIAD-Like Stakeholder Engagement Strategies and Technologies

Background/Objectives

The environmental investigation and remediation of PFAS is top priority for the Department of Defense (DoD), with investigations ongoing or planned at over 700 installations nationwide. Remedial Investigations (RIs) are a critical step in the CERCLA process for defining the nature and extent of contamination to facilitate future risk assessment and remedial action (i.e., Feasibility Study).  The evolving nature of PFAS science and regulations, as well as intensified stakeholder (regulatory and public) engagement, may slow progress and significantly extend the performance schedule for completion of RIs. DoD’s time-critical need to improve cost-effective management of their PFAS program and to mitigate ongoing or potential risk to human health and/or the environment cannot be supported by the traditional RI approach and timeline.  Accelerated investigations, paired with innovative stakeholder engagement strategies and technologies and adaptive and high-resolution screening approaches support DoD priorities and interim decision making.    

Approach/Activities

Phase I RIs have been completed or are nearing completion at four Air Force Installations using a TRIAD-like high-resolution site characterization (HRSC) approach to develop stratigraphic flux-based conceptual site models (CSMs).  Multi-media HRSC was performed within and downgradient of over 30 AFFF sources across the four installations. The approach was executed using a TRIAD-like adaptive workflow strategy, whereas the site-specific and base-wide CSMs were refined throughout the RI, interim scoping decisions (ex. step-in or -out sampling locations) were made collaboratively with regulatory and DoD stakeholders in accelerated fashion.  Real-time data review, decision-making, and concurrence on achievement of data quality objectives (DQOs) were facilitated by an online Project Management Dashboard (PMDB) and Digital Conceptual Site Model (dCSM) platform equipped with 3D modelling that synthesized large and complex datasets into comprehensive illustrations and data deliverable summaries. Stratigraphic flux-based CSMs were developed utilizing multiple source-strength leaching evaluations in combination with downgradient groundwater vertical aquifer profiling (VAP) transects to relate leaching “source-strength” from AFFF source areas and map groundwater PFAS mass flux migration pathways within hydrostratigraphic units (to support monitoring infrastructure placement and future remedial design). Data collected under the RIs also supported conducting Phase I Risk Assessments and bench- and field-scale treatability studies.

Results/Lessons Learned

This RI approach has addressed DoD and regulatory priorities associated with source prioritization in terms of mass loading in order to accurately communicate risk and effectively make time-critical remedial action decisions. The RIs have demonstrated that the TRIAD-like HRSC investigation schemes, enhanced by real-time measurement techniques (such as PFAS mobile lab technologies, vertical aquifer profiling), can be executed in an accelerated fashion at sites with various source areas, impacted media types, complex migration pathways, and multiple exposure routes and receptors collaboratively with project stakeholders (DoD, state and federal regulatory agencies).  The approach effectively reduces the need for extraneous mobilizations and interim reporting and review periods to significantly reduce the timeline of an otherwise traditionally slow and rigid RI approach (~3-5 yrs versus 8-10+ yrs).  The robust PFAS datasets have also facilitated identification of potentially uncharacterized source areas and supported the client addressing these and other data gaps in rapid fashion. Additionally, the datasets and restoration infrastructure are poised to bolster development of a framework for parameterization and determination of site-specific screening levels (via pending SERDP/ESTCP proposals).