2010 Oral Presentation Scenario
PROTECTION OF GROUNDWATER THROUGH URBAN, AGRICULTURAL, AND ENVIRONMENTAL PLANNING
A small town in north central Minnesota has discovered that nitrate levels in two of the town’s four municipal wells have nitrate levels that are elevated above the state drinking water quality standard of 10 mg/liter. In addition to the municipal wells, there are several businesses and a mobile home park that have shown increasing nitrate levels although those wells have not yet exceeded the drinking water standard.
The soils in the area are primarily glacial outwash sands with high infiltration rates. The depth to groundwater is generally greater than six feet, but there is a substantial surficial aquifer that allows most wells, including the municipal wells in question, residential wells and some irrigation wells to deliver adequate water at depths of 50 to 90 feet. Confining layers of glacial till and clay deposits are present at depths ranging from 250 to 400 feet. It is somewhat unclear whether the confining layers are continuous or have areas of groundwater interaction. Several kettle block lakes are nearby, connected by a river that eventually drains to the Mississippi River. The main stem river has several tributaries that support populations of brown trout, although those populations are mainly maintained through stocking.
Economic vitality of the community is maintained by a diverse mix of industries. The town is a regional tourism and fishing destination area centered on the lakes and trout streams. Retail sales and businesses that support the tourism and seasonal residential industries and agricultural production (mainly corn, potatoes and sunflowers, along with some livestock) are also important components of the area economy. One of the major industrial employers in town processes those locally grown potatoes into food products that are sold nationwide. Washing and processing the potatoes uses large quantities of water, drawn from confined aquifers at depths ranging from 200-300 feet. This industry employs over 600 full and part-time employees and several hundred more on a seasonal basis during harvest.
Monitoring conducted over the last several years has indicated that nitrate levels have been rising slowly but steadily causing the Department of Health to require that water quality monitoring be conducted on a quarterly basis rather than the standard annual testing regimen.
There is a variety of land use within the well capture zone including substantial acreage devoted to irrigated agriculture, residential housing, some light industry, a large cemetery and the municipal airport. A mix of hardwood and deciduous forest, wetlands and pastures make up the balance of the land cover within the well capture zone and surrounding the town.
The city council has initiated informal discussions with local well drillers to help them determine a course of action. The well drillers have informed the council that they have drilled wells nearby which ranged from 170 to 500 feet deep. These wells generally produce adequate water supply, but have very different concentrations of minerals such as iron and manganese. While generally non-toxic, these minerals can affect the taste of the water and contribute to aesthetic problems such as staining clothes and water fixtures in the home. It may be necessary to treat the water from these deeper wells to remove iron and manganese.
You and your team have been hired by the City Council to provide them with a set of alternative solutions to the nitrate pollution problem. Your presentation will be given at the beginning of a special public meeting of the Council to discuss the issue.
To prepare for your presentation, you will need to decide what the alternatives are, if you can solve the problem at the source; if you opt for treatment, what costs are involved, and what is the long-term maintenance.
Some of the topics your presentation should address:
• Given the land cover and land use in the area, can you draw any conclusions about potential contributors to the high nitrate levels?
• What options may exist for mitigating the nitrate contribution from those potential contributors?
• What options may exist for treating the existing water supply to remove nitrates?
• What would be involved with drilling a new municipal well?
• What treatment options may be necessary to remove excess minerals from a new, deeper well?
• What may be the long-term effects on the other shallow municipal wells of growth in city population and industrial capacity?
• What are the potential effects of increasing or decreasing groundwater withdrawals on the nearby lakes and trout streams?
• How does the city council’s decision potentially affect the other businesses and residences that use the surficial aquifer?
• What potential effect could the alternatives have on the city government, city residents, farmers, major industrial employer, and the residents outside the municipal well supply system?
• Will any of the alternatives affect aquatics, forestry, soils, or wildlife?
• How do you balance the cost between the benefitting parties and those who may have caused the problem?
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