Wednesday, April 2, 2008 : 10:00 a.m.

Using Simple Groundwater Modeling as a Tool for Conceptual Site Model Development and Testing: An Example from the Hanford Site, Washington

Craig C. Arola, Vista Engineering Technologies, LLC, Matthew J. Tonkin, S.S. Papadopulos & Associates, Inc. and David S. Miller, Fluor Government Group

Organic solvents (primarily carbon tetrachloride) were used in plutonium finishing operations at the Hanford Site in the 1950s, 1960s, and 1970s.  Disposal of these solvents resulted in a large (~ 4 square mile) groundwater plume of carbon tetrachloride at the site. The shape of the existing plume at the water table could not be easily explained based on the location of the three primary carbon tetrachloride source areas and knowledge of current groundwater flow conditions.  This resulted in multiple potential conceptual site models (CSMs).  However, groundwater modeling using relatively simple analytical methods and based on rigorous data compilation and transparent methods of analysis revealed that the shape of the existing groundwater plume was the result of historical local variations in groundwater flow direction caused by liquid waste disposal from other nearby sites, thereby eliminating several potential CSMs.  Further, the modeling indicated that additional sources of carbon tetrachloride do not appear to be necessary to produce the current plume shape.  This finding was confirmed by significant field investigations within the vadose zone above the plume, which did not identify any sources other than the three primary source areas. In addition, calibration of these models to historic conditions also provided independent estimates of important hydraulic parameters (e.g. transmissivity and storage) at a scale appropriate to assist in evaluation of potential remedies as part of an RI/FS process.

Craig C. Arola, Vista Engineering Technologies, LLC Mr. Arola is a Senior Environmental Scientist with Vista Engineering Technologies, LLC in Kennewick, Washington. He has a B.A. in Environmental Sciences from the University of Virginia and an M.S. in Geology from the University of Wisconsin-Madison. Mr. Arola has worked on numerous environmental contamination projects throughout the United States during the past 12 years. Mr. Arola's expertise includes environmental modeling, geologic and environmental characterization, and environmental data analysis.

Matthew J. Tonkin, S.S. Papadopulos & Associates, Inc. Mr. Tonkin is an Associate with S.S. Papadopulos & Associates, Inc. in Bethesda, Maryland. Mr. Tonkin has a B.S. in Applied Geology and an M.S. in Hydrogeology from Birmingham University (England). Mr. Tonkin's expertise is in data synthesis to resolve environmental issues, including managing data collection, developing and managing databases, applying models, and presenting information to support decision making.

David S. Miller, Fluor Government Group Dr. Miller is leading strategic integration for the Soil and Groundwater Remediation Project group at Fluor in Richland, Washington. Dr. Miller has a Ph.D. in Geoenvironmental Engineering from The Johns Hopkins University. Dr. Miller is a registered Professional Engineer and Professional Geologist. Dr. Miller’s technical expertise includes contaminant fate and transport, real-time characterization, treatment technologies and project management.


2008 Ground Water Summit