Hydrogeology and Chemical Characterization of Hydrocarbon in Domestic Water Wells, Rancho Villa Subdivision, Rogers, Arkansas

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Sherman, Janelle Renee
Earth sciences; Geochemistry; Hydrology
thesis / dissertation description
This project is centered on the Rancho Villa community in Rogers, Arkansas where several residents have had hydrocarbon contamination in their domestic water wells. The goal of this project was to understand the hydrogeology in the study area, characterize the contaminant chemically, and determine the source of the contaminant. The hydrogeology of the area was determined from previous theses. Seventeen samples were taken from the wells in the Rancho Villa community; each sample was analyzed for geochemical parameters and by Gas Chromatography/Mass Spectrometry (GC/MS) for organic compounds analysis. Four of the 17 samples had a visible non-aqueous layer of hydrocarbon on top of the water.Qualitative analyses of the GC chromatograms for the hydrocarbon samples indicate the presence of abundant gasoline and diesel range n-alkanes. Synthetic fuel additives also were detected in the samples. These findings suggest the contamination is from a fuel spill and is not naturally occurring. The carbonate aquifer in the study area is karstified, with anisotropic flow. The contaminant has persisted in the area for the past six years and is localized in the Rancho Villa community. No reported spill sites are near the community, and no possible physical sources have been identified. The study area is located on the up thrown block of a normal fault; stress fractures associated with the normal fault are likely conduits for the contaminant, and allow focused migration of the hydrocarbon. The water samples with visible hydrocarbon had some emulsification, indicative of microbial degradation. The source of the contaminant was not determined; however this study is a foundation for further investigation in the area.