Background: In September 2020, HGL was retained by Consolidated Nuclear Security, LLC (CNS) to provide optimization services and fate and transport modeling for groundwater remediation efforts, under a 5-year Basic Ordering Agreement (BOA), at the Pantex Plant in Amarillo, TX. Past operations related to the manufacture and maintenance of munitions and weapons resulted in releases of various contaminants of concern (COCs) to groundwater. Priority contaminants include RDX, TNT, and other high explosives; hexavalent chromium; perchlorate; and chlorinated volatile organic compounds. Affected groundwater occurs within a thin, heterogeneous perched unit located 240-300 feet below ground surface, overlying a sole source aquifer. Complexities within the groundwater system include preferential flow paths and diverse historical discharge locations. Under a separate contract, HGL prepared the second 5-Year Review at Pantex including performance evaluation and optimization recommendations for multiple soil and groundwater remedies.
Scope of Services: The optimization project includes using HGL’s Physics-Based Management Optimization (PBMOTM) technology to improve the performance of two large-scale pump-and-treat (P&T) systems consisting of over 80 extraction and injection wells and an off-site combined remedy of in situ bioremediation (ISB) and P&T with 89 amendment injection/extraction wells and 3 pumping wells. Computational optimization is being used to recommend changes to the remedy configuration and operation, including locations and flow rates of individual extractions wells and flow rates for the system. The goal of optimization is to maximize contaminant mass removal, improve hydraulic containment, and identify when part or all of the system becomes ineffective and should be shut down. For the off-site ISB/P&T system, PBMOTM will be used to determine the best locations, system configuration, and operation for the remaining system components. PBMOTM is being used to address recommendations outlined in the 5-Year Review to optimize and improve the efficacy of remedial actions.
Potential Benefits: Groundwater remediation costs represent a significant portion of DOE’s annual environmental budget. The usage of the PBMOTM tool to optimize remedy performance allows a facility, such as Pantex, to efficiently evaluate existing or proposed remediation system configurations and identify the optimal configuration/system operation to achieve restoration goals. PBMOTM develops optimal remedial designs considering multiple objectives including contaminant mass and water volume removal, hydraulic control, cleanup time, and cost. Recommendations are developed for optimal configuration of key elements, including well locations and pumping rates, and operational approaches that lead to timely and cost-effective remedial strategies while still achieving target
cleanup goals. Cloud-based PBMOTM is designed to accommodate thousands of decision variables/constraints and multi-modal objective functions. Stakeholders can have high confidence in PBMOTM-derived solutions because they result from the parallel evaluation of hundreds to thousands of possible remedy scenarios using robust and efficient optimization algorithms in contrast to other numerical optimization techniques and traditional trial-and-error optimization approaches where only a handful of scenarios are subjectively considered and credible optimal results are unlikely to be achieved. The optimization capabilities of HGL’s PBMOTM technology will continue to support environmental management and long-term stewardship of DOE sites and will help DOE achieve site-specific end-state objectives at reduced costs.
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