Work performed:

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• Collection of groundwater, spring, seep, and soil gas samples at quarterly, semiannual, annual, and biennial frequencies

• Groundwater monitoring using low-flow sampling and passive diffusion bag samplers

• Sampling of approximately 135 monitoring wells and 7 springs from 2022 through 2024

• Inspection of inactive landfills and associated monitoring wells

• Maintenance and repair of landfill covers, including erosion repair, backfilling, grading, reseeding, mowing, and placement of filter rock

• Vegetation clearing, access path repair, monitoring well maintenance, lock replacement, bollard replacement, well pad repair, pump and tubing replacement, and well redevelopment

• Management of purge water and investigation-derived waste

• Completed PCB and explosives soil delineation at the Former Weldon Spring Ordnance Works through five field mobilizations between March and August 2025, collecting 144 primary PCB samples and 92 primary explosives composite samples to evaluate residual soil impacts

• Delineated residual PCB impacts across seven historical excavation areas, confirming four areas with PCB concentrations above the 0.23 mg/kg EPA Regional Screening Level and three areas with non-detect PCB results

• Confirmed PCB impacts were limited to shallow soil, with all 5-foot-bgs confirmation samples reported as non-detect

• Characterized the T-13 Excavation Area for explosives using a 6-by-6 sampling grid, with detections of 2,4,6-TNT in 24 samples and 2,4-DNT in four samples; all results were below applicable EPA Regional Screening Levels

• Established surveyed boundaries for impacted PCB areas and the T-13 explosives area to support future site management and environmental notice documentation

• Data validation, database management, ERIS data delivery, and preparation of annual monitoring reports

• Potentiometric surface mapping, contaminant plume mapping, Mann-Kendall trend analysis, MAROS evaluations, and long-term monitoring optimization​

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LATA also performs land use control inspections, evaluates remedy performance, and develops optimization recommendations to improve long-term monitoring efficiency while maintaining data quality objectives and regulatory confidence. At Charles Melvin Price Support Center, LATA prepared an Optimization Plan that resulted in Illinois EPA approval to reduce groundwater sampling frequency to annual sampling.

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Project stakeholders include USACE, U.S. Army Environmental Command, U.S. EPA, and appropriate state regulators, including KDHE, Missouri Department of Natural Resources, and Illinois EPA.

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Sites include:

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• Fort Leavenworth, Kansas

• Fort Leonard Wood, Missouri

• St. Louis Ordnance Plant, Missouri

• Weldon Spring Ordnance Works, Missouri

• Charles Melvin Price Support Center, Illinois

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