Interdisciplinary Geophysical Program to Assess 1,4-Dioxane Impacts in Glacial Deposits and Fractured Bedrock

Monday, December 4, 2017: 1:50 p.m.
Samantha M. Olney , Woodard & Curran Inc., Andover, MA
Mike Apfelbaum , Woodard & Curran, Inc., Andover, MA

A contaminant assessment was recently implemented at a closed landfill following the recent discovery of 1,4-dioxane during post-closure monitoring. Investigation objectives involved a comprehensive program to assess contaminant nature and extent over a broad, variable landscape area, with diverse subsurface aquifer properties. Groundwater flow from beneath the landfill footprint is toward a wetland complex underlain by highly transmissive and heterogenous glacial outwash. Fractured bedrock underlies these deposits with limited fracture interconnectivity and distinct preferential pathways. Based on the diversity and size of the investigation area (~30 acres), the investigation approach included multiple geophysical techniques to locate proposed bedrock boreholes, identify potential water bearing fractures, and determine nature and extent.

Geophysical methods included: (i) review of historic orthophotos that identified two primary lineaments, one east-west trending (corresponding with groundwater flow direction) and one north-south trending (corresponding with the large wetland feature) that intersect within the study area; (ii) an electrical resistivity survey conducted along multiple survey lines within the study area to identify areas of potential leachate migration, identify potentially steeply dipping fluid-filled fractures in bedrock, and support bedrock surface interpolation; and, (iii) drilling and downhole logging of five bedrock boreholes to identify and characterize potential water bearing fractures for subsequent packer isolation sampling.

The results of the resistivity survey were utilized to refine the locations of the bedrock boreholes prior to drilling. The interpolated depth of the bedrock surface, as identified during the resistivity survey, remained consistent with during drilling observations. Borehole logging data was plotted using a series of vertical profiles and great circle projections and identified primarily east-west and north-south trending planar features consistent with the alignment of previously identified air photo lineaments. Combining the suite of geophysical tools resulted in effective subsurface characterization and minimized “overdrilling” of field explorations to achieve investigation objectives.

Samantha M. Olney, Woodard & Curran Inc., Andover, MA
Samantha Olney is a licensed Professional Geologist with experience conducting site and remedial investigations and implementing remedial alternatives. Her experience includes a variety of projects consisting of hydraulic assessments for municipal water treatment systems, operation and maintenance of groundwater treatment systems, and investigation and remediation of sites impacted with petroleum hydrocarbons, chlorinated solvents, and metals in both overburden and bedrock matrices.

Mike Apfelbaum, Woodard & Curran, Inc., Andover, MA
Mike Apfelbaum is a geologist with experience managing site and remedial investigations, feasibility studies, and the implementation of remedial alternatives. He has been involved in a wide range of projects ranging from the management of groundwater recovery and treatments systems to investigation and remediation of sites impacted by chlorinated solvents, petroleum hydrocarbons, and metals. His specialties include investigation and evaluation of fractured bedrock systems, hydrogeology, evaluation of in situ technologies and conducting groundwater contaminant assessments. Apfelbaum is a registered Professional Geologist in New Hampshire.

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