TRC’s innovative solutions to tracking contaminant flows at two geologically complex sites will be featured at the 7th annual technical workshop of the Michigan section of the American Institute of Professional Geologists (AIPG) on June 14.
The theme of the Michigan AIPG Environmental Risk Management Workshop this year is “characterization’s role in remedy selection,” focusing on strategies for data collection and information gathering to make well-informed decisions about remedial solutions to manage site-contaminant risks. TRC teams will be presenting about how they met challenges to identify the most effective risk-management remedies in two complex locations.
Stacy Metz, Mellisa Powers, and Sarah Holmstrom’s “Evaluation of the GSI Pathway and its Effect on Cleanup Level Selection’’ focuses on a former manufacturing facility in southeastern Michigan where chlorinated volatile organic compounds (CVOCs), including industrial cleaners and degreasers, had been released to soil and groundwater. Contaminated groundwater from the site discharges to the downgradient wetland and river through multiple pathways including seeps from a bluff which form channels and flow across the wetland surface and into the river.
With such a complicated hydrogeologic setting and physical access to the wetlands area difficult, Metz’s team developed an increasingly detailed conceptual site model using data from the upland area to focus and minimize work in and near the wetland area. Through comparison of groundwater flux at the downgradient site boundary to the flux under the wetland area, Metz’s team hypothesized that the inconspicuous seeps observed along the embankment could be a significant groundwater discharge pathway. A subsequent tracer dye study determined that more than 98 percent of the groundwater flux to the river was traveling through the small channels across the wetland surface, essentially bypassing the wetland, before discharging to the river. Through the development of a clear and complete conceptual site model TRC helped the client clarify their regulatory obligations and direct their remediation investment to where it would deliver the highest benefit: continued and expanded up-gradient groundwater remediation, rather than a potentially costly (but not yet necessary for regulatory compliance) active remedy at the groundwater/surface water interface in the wetland.
Also being presented is “High Resolution Site Characterization As a Risk Management Tool To Support Remedial Planning – Fenner’s Ditch Venting Oil Well Site, North Muskegon, MI.’’ This project was implemented by a team led by TRC’s Doug Kilmer, P.G., Jim Dexter, and Chris Scieszka as well as the Michigan Department of Environmental Quality’s David Bandlow.
This study involved the venting of groundwater affected by Non-Aqueous Phase Liquid (NAPL) venting into a tributary of Bear Lake and Muskegon Lake, causing oil slicks and sheens emerging on surface water. The source of the NAPL is believed to be an abandoned 1920s oil well that was improperly plugged.
After prior investigations failed to properly identify and quantify the NAPL-affected horizons, potentially underestimating the extent of oil venting to surface water, Kilmer’s team deployed a
Geoprobe Systems® Optical Image Profiler (OIP) to conduct real-time, continuous imaging of the site subsurface along with traditional soil and groundwater sampling. The OIP was deployed on land and in the canal from a barge-mounted drill rig on a pre-defined drilling pattern based on the visual evidence and past investigations, which could also be adjusted based on real-time observations of oil impact. This approach documented a deeper horizon of NAPL greater in lateral extent and apparent volume than had been observed visually or measured in previous investigations.
While these are two very different locations with very different environmental remediations, the common link in these presentations is that innovative TRC solutions are ensuring more accurate characterization of challenging sites. That, in turn, will ensure confident decision making for the most effective, highest-benefit final remedial strategies in both locations.
Stacy Metz, Doug Kilmer, and their teams will be presenting at AIPG’s Michigan Section technical workshop Wednesday afternoon, June 14, at the Ralph A. MacMullan Conference Center in Roscommon County, Michigan. http://mi.aipg.org/workshop.ht...