Geophysical and water quality characterization of on-site wastewater plumes
Grant
Overview
abstract
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Non-point sources of pollution such as on-site wastewater systems (OWS) are the most significant contributors to water quality impairment but are the most difficult sources to track and quantify. Innovative approaches are needed to help researchers, resource managers, and policy makers better understand the fate and transport of various contaminants in the subsurface so pollution mitigation efforts can be focused in areas where they will be most effective. Non-intrusive geophysical techniques such as electrical resistivity mapping and ground penetrating radar (GPR) may provide valuable information towards better delineating OWS and other groundwater plumes and thus reduce the number of groundwater monitoring wells needed for groundwater characterization. Two Craven County Public Schools (JW Smith Elementary and West Craven High School), an Environmental Education Center (A Time for Science) and two residential homes/yards will serve as the research sites for assessing the applicability of geophysical tools for delineating wastewater plumes and for assessing the fate and transport of OWS pollutants. The two schools and one home have already been instrumented with groundwater monitoring wells and permission has been granted by the manager of a Time for Science to instrument the site for research. Geo-electrical surveys and groundwater quality analyses will be performed at the sites seasonally (4 times). Survey images will be examined for areas with electrical properties that differ from background conditions, indicating the influence of wastewater on groundwater. Groundwater quality parameters including specific conductance, pH, nitrogen, phosphorus, and indicator microbial concentrations will be analyzed. Groundwater quality within the plume area will be compared to background groundwater quality, OWS effluent and groundwater quality outside the plume area to determine the influence on OWS on groundwater and to evaluate the effectiveness of the geophysical tools in delineating the wastewater plumes. The objectives of this research are to: 1) evaluate the effectiveness of the geophysical tools in delineating OWS contaminant plumes and 2) assess the fate and transport of OWS derived nutrients (nitrogen and phosphorus) and indicator microbial organisms (E. coli, and coliform) from these OWS.
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