Scott Bair

Ohio State University

The animation of TCE movement from the 5 known sources of contamination at the Woburn Wells G & H Superfund Site is created in both plan view and cross section view. The animation can be viewed by students to help visualize several concepts in an introductory hydrogeology course. It shows how the transient path of a contaminant plume is affected by changes in the pumping rates and schedules of wells; how when the wells are turned off, the plumes flow upward and back to discharge points along the Aberjona River; the impact of partially penetrating pumping wells on flow paths, travel times, and the depth of TCE occurrence in the aquifer; how the Aberjona River does not act as a barrier to groundwater flow from TCE sources on the opposite side of the river as wells G and H; and how different geologic materials transmit TCE at different rates.

The animation was created in TecPlot by Martin van Oort, an M.S. student at Ohio State, and can be viewed in the Windows Media Player, QuickTime Video, and Real Player. It is based on a calibrated, transient groundwater flow model constructed using MODFLOW and a transient solute transport model constructed using MT3D by Maura Metheny for her Ph.D. research at Ohio State.

Municipal wells G and H operated periodically from October 1964 to May 1979. A well operated by the Riley Tannery, which was later bought by Beatrice Foods, was used from before 1960 to after 1986.

Students should have learned the general concepts of flow toward wells, the effects of partial well penetration of flow paths, induced infiltration, the effects of heterogeneity on flow paths and travel times, and why certain organic solutes travel at rates less than groundwater.

I use this animation at the end of my course after students have been exposed to almost all of the concepts to be presented. It is a unifying visualization that shows how many of the processes and concepts presented in the course can seen influencing a poignant real-world problem. The TCE animation is a great follow-up to the animation showing induced infiltration from the Aberjona River to wells G and H, which could be shown earlier in the course.

My goals in having students view the TCE animation are to have students become aware that (1) most flow systems are transient in character, (2) differences in the porosity, thickness, and hydraulic conductivity of geologic materials can significantly impact the arrival times and concentrations of contaminants in a well, (3) the TCE produced by the municipal wells is mixed with water from other parts of the flow system that may or may not be contaminated, (4) partially penetrating screens on pumping wells produce non-textbook flow paths, and (5) once contaminated with TCE, aquifers can take to years and years and years to degrade and flush contaminants.

Because changes in hydraulic heads are not shown in the animation, students are forced to visualize what the equipotential maps and pathlines would look like as the municipal wells turn on and off and pump at greater and lesser rates. Students also have to visually integrate the effects of the partially penetrating river, the partially penetrating wells, and the differences in timing and initial concentrations of TCE at the 5 sources area. Because changes in hydraulic heads are not shown in the animation, students are forced to visualize what an equipotential map and flow paths would look like when river water is induced into an aquifer. This animation enables students to visualize many of the time / space issues presented in the course and promotes an overall synthesis of fundamental principals.

The jury in the actual trial, as described in 'A Civil Action,' found W.R. Grace liable of contaminating wells G and H in September 1974, and found Beatrice Foods (Riley Tannery) not liable of contaminating the wells. After viewing the animation, ask your students what geologic, hydrologic, and contaminant transport concepts the six-person jury would have had to understand all the science underlying the animation. Discuss with your students that jurors are 'passive learners' who usually do not get to take notes and must rely on their collective memory to sort out conflicting testimony, cannot talk about the testimony until after the trial ends, and cannot use referenecs books or the web to sort out the good from the less good testimony. Ask your class how that learner style compares to learning in a college course.

Read some of the testimony presented in 'A Civil Action' and ask students, after viewing the TCE animation, how the testimony differs from what is portrayed on the animation and why there are differences.

To prepare to view the TCE animation, students could view the 'A Civil Action' movie and the instructor could read to them excerpts from the trial testimony and images from Woburn, wells G and H, geologic materials, geologic cross sections, the trial participants, and the federal courtroom in Boston (available as a attachment to this activity and at a website listed below). The discussion in Bair (2001) about scientists in the courtroom, the specific (excerpted) testimony presented by the three expert witnesses in the 'A Civil Action' trial, a chart summarizing the differences in their testimony, and the views of a federal judge on the goal of science versus the goal of a civil trial may also be worthwhile reading by the class prior to the assignment.

The instructor could also show students the large plates included in the USGS report by Myette and others (1987) that display potentiometric data and contours before and after the famous aquifer test performed in December 1985 and January 1986, just before the trial, and discuss the ramifications of having only two sets of water-level measurements to characterize all the changes in the flow system between 1964 and 1979, when wells G and H periodically operated. This makes students consider the substantial differences in making predictions based on a steady-state conceptualization of the flow system or a transient conceptualization.

The instructor could also show the animation of induced infiltration from the Aberjona River to wells G and H that also was created by Martin van Oort (M.S., 2005) and based on the research of Maura Metheny (M.S., 1998; Ph.D., 2004) at Ohio State University. Viewing both animations enables students to see that the water produced by wells G and H is a highly transient mixture derived from many different source areas within the valley.

The article by Bair and Metheny (2002) concerning the remediation activities at the Wells G & H Superfund Site could be used to show how groundwater contamination is cleaned up, why different remediation schemes needed to be used in different hydrogeologic settings, and why cleanup to U.S. EPA standards can take decades.

If the students recognize that the jury did not understand surface water / ground water interaction and how plumes of TCE can migrate under the Aberjona River, how the partial penetration of the screens on the two municipal wells and changes in the pumping rates and schedules of the wells impacted TCE arrival times and concentrations, why lodgement till and outwash transport TCE at different rates, then they have obtained a deeper scientific understanding of the issues than the jury, and perhaps some of the expert witnesses.

See the related activity in this collection, Induced Infiltration Animation: Woburn Wells G & H and the Aberjona River

www.geology.ohio-state.edu/courtroom

Bair, E.S., and M.A. Metheny, 2002. Remediation of the Wells G & H Superfund Site, Woburn, Massachusetts, Ground Water, vol. 40, no 6, p. 657-668.

Bair, E.S., 2001, Models in the Courtroom, Chapter 5, in Model Validation, Perspectives in Hydrological Science, M.G. Anderson and P.D. Bates, eds., John W. Wiley & Sons Ltd., West Sussex, England, 57-76.

Harr, J., 1995, "A Civil Action," Random House, New York, 500 p.

Metheny, M.A., 2004, "Evaluation of Groundwater Flow and Contaminant Transport at the Wells G & H Superfund Site, Woburn, Massachusetts, from 1960 to 1986 and Estimation of TCE and PCE Concentrations Delivered to Woburn Residences," Ph.D. dissertation, Department of Geological Sciences, The Ohio State University, 346 pp.

Metheny, M.A., 1998, "Numerical Simulation of Groundwater Flow and Advective Transport at Woburn, Massachusetts, Based on a Sedimentological Model of Glacial and Glaciofluvial Deposition," M.S. thesis, Department of Geological Sciences, The Ohio State University, 197 pp.

Metheny, M.A., and E.S. Bair, 2001. The Science Behind A Civil Action—The Hydrogeology of the Aberjona River, Wetland and Woburn Wells G and H, West, D.P. and R.H. Bailey, eds., in Guidebook for the Geological Field Trips in New England, 2001 Annual Meeting of the Geological Society of America, p. D1-D25, Boston, Massachusetts.

Metheny, M.A., E.S. Bair, and D.K. Solomon, 2001. Applying variable recharge to a 19-year simulation of groundwater flow in Woburn, Massachusetts and comparing model results to 3H/3He ages, Seo, H.S., E. Poeter, C. Zheng, and O. Poeter, eds., in MODFLOW 2001 and Other Modeling Odysseys—Conference Proceedings, vol. 2, p. 783-789, International Ground Water Modeling Center, Colorado School of Mines, Golden, Colorado.

Myette, C.F., J.C. Olimpio, and D.G. Johnson, 1987, Area of influence and zone of contribution to Superfund-site Wells G and H, Woburn, Massachusetts; U. S. Geological Survey, Water-Resources Investigations Report 87-4100, 21 p.