CASE STUDY PROJECT INVESTIGATING TCE GROUNDWATER CONTAMINATION IN A GLACIAL OUTWASH AQUIFER IN WESTERN MICHIGAN

Groundwater contamination of a sand and gravel unconfined aquifer from a leaking TCE underground storage tank in western Michigan is used as a case study that requires undergraduate hydrogeology students to apply skills learned throughout the semester. Students characterize the subsurface geology, direction of groundwater flow, and the distribution of groundwater contaminants at the Delphi Corporation facility in Wyoming, Michigan. The case study uses data on the site obtained from environmental consulting reports at the local library that include information from over 94 wells and 20 different water level measurement periods, with groundwater analyzed for volatile organic compounds on 4 occasions.

Newspaper articles of the Delphi groundwater contamination are used to introduce students to the project and highlight its importance and relevance. The large dataset allows students to individually be assigned a geologic cross-section, water table map, and contaminant plume map to construct. Then, students examine all the different cross-sections and maps produced and are assigned several site analysis questions that require them to synthesize information. They must assess the geology from different perspectives, observe changes in groundwater flow directions seasonally, and monitor the distribution of different chemicals in the subsurface over time. In particular, the case study is a great illustration of how the groundwater flow direction controls the shape and distribution of contaminant plumes and how the subsurface geology can impact groundwater flow as irregular bedrock topography and local bedrock ridges influence hydraulic gradients in the area. The distribution of TCE and its breakdown products, 1,2–DCE and vinyl chloride in groundwater illustrate the impact of chemical processes like degradation on contaminant transport.

Students appreciate the practical experience the project provides that, as I remind them, “somebody got paid to do”. This case study is part of the On the Cutting Edge Peer Reviewed Teaching Activities collection that includes such supporting material as assignments, newspaper articles, lithologic logs, well construction diagrams, water level records, chemical analyses, and select introductory portions of the consulting reports.