September 12, 2019

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Geosyntec Staff to Present at the 2019 National Groundwater Association Conference on Fractured Rock and Groundwater

Geosyntec professionals will contribute to the 2019 National Groundwater Association (NGWA) Conference on Fractured Rock and Groundwater at the Hilton Burlington Lake Champlain in Burlington, Vermont on September 23-24, 2019.

David Sherman, P.G. (Pennsylvania) will present "Developing a Robust Conceptual Site Model: A Learning Experience Case Study," and Dariusz Chlebica (Massachusetts) will present "Development of a Conceptual Site Model for Comingled Chlorobenzene Plumes in Weathered Bedrock." In addition, John Persico, P.G. (Massachusetts) is serving as a Program Advisor for the conference.

David is a Senior Geologist with more than 20 years of experience in environmental investigation and remediation. He has managed and planned numerous projects, including hydrogeologic investigations, compliance and performance monitoring programs, vapor intrusion assessments, groundwater modeling, air monitoring, and a number of diverse environmental due diligence and remediation projects. David has expertise with site-wide strategies, hydrogeologic evaluations, remedial characterization, data analysis and interpretation, risk assessments, conceptual site modeling, and site closures.

Dariusz is a Senior Staff Geologist based in Massachusetts with experience in environmental consulting and hydrogeology. Dariusz has performed extensive research on groundwater and bedrock wells, which he has presented at past NGWA conferences and elsewhere.

John is a Senior Consultant who has built a successful remediation practice that includes several large remediation projects. He serves as Operations Manager for the Princeton office, and has extensive experience in client development, complex site remediation, and regulatory compliance.

The 2019 NGWA Conference on Fractured Rock and Groundwater focuses on improved outcomes for groundwater remediation and examines what is needed to construct a sufficiently robust conceptual site model (CSM). New and improved technologies for site characterization and remediation are essential, but innovative technology alone will not solve difficult problems in fractured rock environments.

NGWA is a community of groundwater professionals working together to advance groundwater knowledge and the success of their members through education and outreach, advocacy, cooperation and information exchange, and enhancement of professional practices.

Geosyntec Participation

Developing a Robust Conceptual Site Model: A Learning Experience Case Study
Speaker: David Sherman, Geosyntec Consultants
Time: Sept. 23, 2019 at 1:00 p.m.
A former solvent recycling facility was used for disposal of distillation residues. Following remedial actions in the 1980s and 1990s to remove contaminated source materials, a site characterization was conducted, which indicated perched groundwater zones and high concentrations of chlorinated volatile organic compounds (CVOCs) were present in unconsolidated soil. Perimeter area monitoring wells were installed to evaluate karst bedrock groundwater.

From 2005 to 2015, soil vapor extraction (SVE) was implemented to treat impacted soil and reduce the CVOC concentrations in perimeter area groundwater; however, clean-up goals were not achieved. Following the SVE remedy, additional Site characterization indicated that groundwater is likely not perched, overburden material remains highly impacted, and dense non-aqueous phase liquid (DNAPL) was observed in one SVE well. Groundwater underlying the source has CVOC concentrations that were much higher than the perimeter monitoring wells.

The initial characterization was not detailed and led to a remedy that could not complete cleanup of the site. To develop a robust conceptual site model, the extent of contamination will be further delineated, and the processes that control transport of CVOCs will be evaluated, with an eye towards effective remedy design and implementation.

Development of a Conceptual Site Model for Comingled Chlorobenzene Plumes in Weathered Bedrock
Speaker: Dariusz Chlebica, Geosyntec Consultants
Coauthors: Joseph Jeray, P.E.; Chris Martin, C.G.; and David J. Adilman, P.G., Geosyntec Consultants (Massachusetts)
Time: Sept. 23, 2019 at 1:40 p.m.
The presence of a relatively high hydraulic conductivity (K) weathered bedrock zone at the overburden/bedrock interface created challenges in the development of a Conceptual Site Model (CSM) for the fate and transport of chlorobenzene at a former industrial Site in Southeastern Massachusetts. The CSM formulation required a multi-line of evidence approach including a detailed evaluation of hydraulic gradients and chlorobenzene distribution across multiple units, the use of borehole geophysics to assess vertical gradients prior to bedrock well installation, and characterization of the weathered zone K and thickness across the site. The bedrock chlorobenzene plume appears to discharge to weathered bedrock and shallow overburden in an area with artesian conditions in bedrock. The plume later becomes comingled with the overburden and weathered bedrock plumes beneath an encapsulated lagoon. Downward gradients beneath the lagoon drive groundwater flow into the weathered bedrock in a narrow area where its K is much higher than overburden. Downgradient of this area the plume appears to be confined to the weathered bedrock. A tracer was injected over a 12-hour period into a 100-ft deep bedrock well near the bedrock chlorobenzene source, and tracer concentrations detected in downgradient wells exceeded the background concentrations along the inferred flow path.

More Information

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