A tetrachloroethylene (PCE) plume is present in the groundwater beneath the northern portion of downtown Casper, the extents of which had been assessed throughout nearly 20 years of site characterization and data gathering. However, the exact source(s) of the groundwater impacts had not been identified. RETTEW collaboratively assisted the Wyoming Department of Environmental Quality (WDEQ) with developing a plan to investigate potential sources of PCE in groundwater through extensive historical information review, comprehensive data evaluation, and development of a site conceptual model, all of which we used to design a focused source characterization approach.

RETTEW used state-of-the-science technologies such as discrete depth soil and groundwater sampling to confirm the presence (or absence) of residual source material from potential source locations. The downtown location presented challenges in terms of navigating around traffic, pedestrians, utilities, and a dense population of commercial and residential properties. We overcame these challenges and complexities through close coordination with local traffic authorities, city authorities, and WDEQ. The data RETTEW collected for this investigation significantly refined the extents and connected the PCE plume to an upgradient source that is proposed for remediation. Our efforts and consequential discoveries could result in significant remediation cost reductions through the potential use of targeted remedial strategies for both source and downgradient plume treatment.