Weston conducted an HTRW Assessment, Investigation, Characterization at Mike Monroney Aeronautical Center (MMAC) where chlorinated solvents, including tetrachloroethene (PCE) and trichloroethene (TCE), had historically been used at aircraft and machine maintenance facilities. Significant releases to soil and groundwater beneath MMAC have occurred, resulting in the formation of a chlorinated organics plume in the shallow groundwater, which have potential to contaminate nearby private drinking wells. These releases were first identified during CERCLA-based Site Investigations completed by Weston for the MMAC 26-years ago. Since then, Weston has been the incumbent environmental services consultant for MMAC and the chlorinated organics plume. Our institutional knowledge of site conditions was critical to the design of the phased approach to this RI, which included incrementally evaluating potential data gaps allowing flexibility of scope between the phases and aligned with the Federal Aviation Administration’s available project funding. Phase I included an extensive Soil Vapor Survey with 139 borings advanced and sampled for VOC soil vapor across the 1,100-acre facility. Phase II consisted of a Vapor Intrusion Evaluation consisting of two rounds of seasonal sub-slab and ambient sampling at 11 indoor buildings overlying the plume. The results will be used to evaluate the design Phases 3 and 4 of the RI, which will include installing single and double-cased monitoring wells, downhole geophysics, and aquifer testing and additional soil vapor survey and vapor intrusion work. Results of the Final RI will be used to determine a remedial action to mitigate groundwater contamination at the facility to successfully prevent potential migration to local groundwater production and private residential wells in the adjacent community.
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