Simulation of Borehole Test to Estimate in-situ CVOC Diffusion, Sorption, and Reaction Coefficients

Monday, September 23, 2019: 4:10 p.m.
Paul A. Hsieh , U.S. Geological Survey, Menlo Park, CA
Richelle Allen-King, PhD , Geology, University at Buffalo
Thomas E. Imbrigiotta , New Jersey Water Science Center, U.S. Geological Survey, Lawrenceville, NJ
Daniel J. Goode , Pennsylvania Water Science Center, U.S. Geological Survey, Lawrenceville, NJ

We developed a numerical model and coupled it with parameter estimation software to analyze data from a borehole test to estimate in-situ diffusion coefficients, sorption coefficients, and reactions rates of chlorinated volatile organic compounds (CVOCs) in low-permeability sedimentary rock. The model uses the finite-difference method to solve coupled solute-transport equations governing diffusion, linear sorption, and zero- or first-order sequential degradation of the parent CVOC and its degradation products. Simulation begins at the time when the borehole was drilled, exposing the borehole wall to CVOCs from contaminated fractures. Simulation of CVOC diffusion from the borehole into the rock matrix uses specified concentrations in the borehole as boundary conditions. During the field test, after concentrations of CVOCs in the borehole have been reduced by sparging, the model simulates concentration changes as CVOCs diffuse back out of the matrix and biodegradation occurs in the fully mixed borehole. PEST parameter estimation software identifies the reactive transport coefficients that yield the best match between simulated and measured concentrations in the borehole. Results of modeling borehole tests conducted in mudstone contaminated with trichloroethene showed that sorption limited the penetration of CVOCs into the matrix to just a few centimeters during several decades of contamination.

Paul A. Hsieh, U.S. Geological Survey, Menlo Park, CA
Paul Hsieh, Ph.D., is an emeritus scientist at the U.S. Geological Survey in Menlo Park, California. His research areas includes fluid flow and solute transport in fractured rocks, hydraulic and tracer testing, computer simulation and visualization, groundwater resources in bedrock terrain, poroelasticity analysis of fluid/stress interaction, and subsurface deformation. Among his many distinguished honors, Hsieh served as the NGWREF Darcy Lecturer in 1995 and received NGWA’s John Hem Award in Science & Engineering in 2012.



Richelle Allen-King, PhD, Geology, University at Buffalo
Richelle M. Allen-King is Professor in the Department of Geology at the University at Buffalo, State University of New York. She has three decades of experience with fate and transport of organic contaminants in groundwater.


Thomas E. Imbrigiotta, New Jersey Water Science Center, U.S. Geological Survey, Lawrenceville, NJ
Thomas Imbrigiotta is a Hydrologist with the U.S. Geological Survey. His research interests involve tracking changes in groundwater geochemistry in fractured rock chlorinated solvent plumes during remediation, determining sorption and diffusion coefficients of contaminants from the primary porosity of fractured rock, and developing groundwater passive diffusion samplers.


Daniel J. Goode, Pennsylvania Water Science Center, U.S. Geological Survey, Lawrenceville, NJ
Dan Goode is a Research Hydrologist with the U.S. Geological Survey.