An On-Campus Well Field for Hydrogeophysics Education and Undergraduate Research

Journal of Geoscience Education, Sep 2006 by Day-Lewis, Frederick D, Gray, Mary Beth, Garfield, Robert L, Day-Lewis, Amy D

ABSTRACT

The emerging subdiscipline of hydrogeophysics is underdeveloped in undergraduate curricula relative to its importance in professional engineering/environmental practice. In 2001, the Bucknell Department of Geology initiated efforts to refocus an undergraduate geophysics course on near-surface geophysical methods for hydrologic, environmental, and engineering problems. In addition to offering students practical experience, treatment of hydrogeophysics provides important pedagogical opportunities. Field-based hydrogeophysics labs challenge students to integrate concepts from other geology courses, as well as from physics, math, and chemistry.

We faced two challenges in revising our geophysics course: (1) access to wells for field exercises on borehole geophysics; and (2) the costs of acquiring and maintaining equipment. We pursued two strategies to solve these problems. First, we established an on-campus well field, which serves as a field laboratory for downhole and cross-hole experiments. Second, we incorporated field demonstrations and lectures by professional geoscientists, including alumni, into our courses. By adding field exercises to our syllabi and promoting undergraduate research, we are building a cutting-edge dataset that includes televiewer and standard wellbore logging, cross-hole tomography, and hydraulic-test data. Student-led analysis or these data has already provided valuable insights into the control of fractures on aquifer properties, and these observations are being combined with outcrop studies to place our results in a more regional context.

INTRODUCTION

Hydrogeophysics is an important, emerging geoscientific subdiscipline. Within this field, applications of near-surface geophysical methods to studies of subsurface fluid flow and mass transport have dominated, yet downhole and cross-borehole techniques are finding increasing popularity in environmental, waer-resource, and geotechnical investigations. At many schools, including Bucknell, these areas represent some of the most promising employment prospects for our graduating geology majors; therefore, focusing undergraduate geophysics education on hydrogeophysics proides students with practical experience relevant to their professional development. Moreover, treatment of hydrogeophysics-and specifically borehole and cross-hole methods-provides several important pedaogical benefits. First, borehole geophysics field exercises can be incorporated not just into geophysics classes, but into many other courses as well, particularly hydrogeology and engineering geology. Coordinating borehole logging with hydraulic experiments (slug and pumping tests), outcrop studies, and surface geological mapping reinforces the crossover between geoscientific subdisciplines, exposing students to the sort of integrated approach now commonly applied to aquifer and petroleum-reservoir characterization. Second, consideration of borehole logs facilitates interpretation of surface geological and geophysical data, giving students more confidence in both the methods and the students' own ability to analyze data and develop reliable interpretations. Third, borehole logging's relevance to geotechnical problems attracts engineering students, which fosters valuable interactions between future geologists and engineers who commonly work together in solving environmental and water-resource problems.

This change in our curriculum came about in 2001 when the Bucknell Department of Geology reassessed our approach to teaching undergraduate geophysics in light or emerging trends in employment opportunities for, and interest among, our students. The primary result was that we chose to focus our undergraduate geophysics course on near-surface methods for hydrologic, environmental, and engineering problems. In developing our revised course, which includes borehole and cross-hole methods, we encountered two major challenges-access to wells and access to equipment. We addressed the first through development or an on-campus well field and the second partially through acquisition of new instrumentation under a National Science Foundation Course, Curriculum and Laboratory Improvement (CCLI) grant (Integrating Applied Geophysics into a Student-Centered Undergraduate Curriculum). Although Bucknell has acquired an impressive toolbox for a small undergraduate program, the purchase of a full complement of borehole probes is impractical for us; hence we sought other means to offer field-based active learning experiences in certain borehole and cross-hole methods. To this end, we have relied on visits by practicing geoscientists, whose lectures and field demonstrations are integrated directly into the classroom and field experiments that are the backbone of the course. Our experience shows that students both enjoy and value interacting in the field with the visitors, especially when they are Bucknell alumni.

INSTALLATION OF THE BUCKNELL HYDROGEOPHYSICS WELL FIELD

Previous to our work, Bucknell's hydrogeology courses included field experiments at an off-campus field of shallow PVC wells penetrating unconsolidated fluvial deposits at a commercial quarry. For geophysical experiments, these wells were too shallow, and the PVC casings and screens, which extended over the entire lengths of the wells, precluded the use of many downhole and cross-hole methods. In addition, the shallow wells could not support extended pumping for aquifer tests, a critical component of hydrologic field methods. Our vision for longterm and multi-stage student research and course projects required continued, easy access to uncased wells in competent rock. Thus we sought to develop an on-campus bedrock well field. Our plan for the well field was based, in part, on models at the University of Massachusetts, Amherst (personal communication, Prof. Laurie Brown), and the work of Rahn and Davis (1996) and Fletcher (1994).