Groundwater Case StudyThe following map shows the characteristics of a hypothetical rural...

Groundwater Case Study

The following map shows the characteristics of a hypothetical rural area about a 30-minute drive from a nearby city. The area has two homes that are over 50 years old (near B and C) and a housing development with expensive houses that were built in the southwest corner of the area 3 years ago. A stream flows through the area and is used for recreation (for example, fishing, boating, swimming). Most of the land is used for grazing or is wooded.

All homes are supplied by water from wells (B, C, or D) that are drilled into a sand and gravel aquifer that underlies the whole area. In addition, the county maintains a monitoring well (A) to track aquifer levels and water quality, but nobody uses well A as a source for drinking water. Multiple wells at D serve all the homes in the housing development. The elevations of the land around each well and at the landfill are indicated on the map.

Residents have just learned that the most recent analysis of water from monitor well A revealed unusually high levels of trichloroethylene (TCE). TCE is widely used as a solvent to remove oil and grease from metal surfaces prior to processes such as painting or machining. Drinking water with TCE may cause nausea, liver and kidney damage, and impaired fetal development. The local water board is suspicious that the TCE was added to the well by a disgruntled employee who was fired a couple of months earlier. However, a review of the industrial history of the area revealed that 40 years ago, a machine plant occupied now-overgrown ground about 1,800 meters (5,900 feet) west of well A. No records from the plant were preserved, so no information on whether it used TCE is available. Further, the landfill is licensed to accept industrial wastes from a variety of companies, some of which may have used TCE.

The county paid for analyses of wells B, C, and D that revealed no contamination at this time. The county water board has recommended that residents continue to use water from the wells for the immediate future. They have hired a geologic consultant to evaluate the risk to future drinking water supplies in wells B, C, and D. The county has made funds available to drill five additional test wells to sample the groundwater. Residents are preparing for a meeting with the geologic consultant to discuss where the wells should be drilled to better constrain the source of TCE.

From what you know about groundwater and the hydrologic cycle, answer the questions that follow:

1. What are the main scientific issues in this scenario?

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2. What are the main social issues in this scenario?

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3. Where should the additional wells be drilled? Justify your answer.