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Groundwater Threats
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The following information was adapted from "Watershed Resource Papers" developed for the Dowagiac River Watershed Project by Langworthy, Strader, LeBlanc, & Associates, Inc.
Any substance that is placed or injected in the ground has the potential to affect groundwater quality. Businesses such as dry cleaners, photographers and hair salons serve as examples of potentially hazardous land uses due to the types of chemicals they routinely use. If these businesses operate on individual well and septic service, the chance of groundwater contamination, through an accidental spill or mishandling, is especially high. Other businesses normally considered environmentally sound, such as golf courses, can actually threaten groundwater. These businesses often use relatively large amounts of lawn chemicals and can cause temporary "drawdowns" of the water table, affecting nearby uses. Directly applying these chemicals to the ground presents an uninterrupted opportunity for groundwater contamination. Such groundwater contamination could cost a community millions of dollars to remedy or destroy a primary water source. A recent report by the Geophysics Study Committee of the Commission on Physical Sciences, Mathematics, and Resources (National Research Council) stated:
"Groundwater contamination may be localized or spread over a large area, depending on the nature and source of the pollutant and on the nature of the groundwater system. A problem of growing concern is the cumulative impact of contamination of a regional aquifer from nonpoint sources (i.e., those that lack a well defined single point of origin), such as those created by intensive use of fertilizers, herbicides, and pesticides. In addition, small point sources, such as numerous domestic septic tanks or small accidental spills from both agricultural and industrial sources, threaten the quality of regional aquifers."
The State of Michigan Comprehensive Groundwater Protection Program, published by the Michigan Department of Environmental Quality reports that:
"(A)bout half of all Michigan residents depend on groundwater as their primary source of fresh drinking water - either through public water supply systems or private drinking water wells. For many communities, groundwater is the only possible source of fresh water for drinking. Cleanup of groundwater contamination sites is expensive and slow, and often creates hardships for the persons affected."
Previous examinations of areas of groundwater vulnerability within the Dowagiac River Watershed have revealed that nearly the entire watershed may be classified as vulnerable. This is reflected in great part by the fact that the Dowagiac River itself is heavily dependent on groundwater flows.
The following describes some of the more prevalent threats to groundwater.
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Septic Systems
Point Sources
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Septic Systems
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Because septic systems are underground, they are often ignored, even by people who use them. But with septic systems, "out of sight" should not mean "out of mind." Groundwater protection will become increasingly important as population densities in areas not served by public utilities continue to increase. In a watershed, contaminated groundwater has a potentially devastating effect. As a result, maintaining appropriate densities of development and proper disposal of sanitary sewer wastes are critical factors in ensuring the adequacy and quality of domestic water sources.
Not all sites are suitable for septic systems. Of primary concern is the soil at the site. Soils that are too coarse or too fine can limit the effectiveness of the treatment system. A shallow, seasonally high water table or bedrock can also cause problems. Some of these problems can be overcome by altering the design of the septic system.
Where they are properly sited, such as in sparsely populated areas and in soils with good drainage above the water table, septic tanks generally pose little or no hazard. However, even where septic systems are well drained, they may eventually pollute the groundwater. An improperly sited, designed, installed or operated septic system can pollute drinking and surface water. In such situations, sewage may contaminate wells in the area or move to the land surface, or both.
A problem of growing concern is the cumulative impact of contamination of a regional aquifer from nonpoint sources, including septic systems, among others. For example, the Environmental Protection Agency in 1980 found that about a third of all septic tank installations were not operating properly and that the consequent pollution both above and below ground is substantial. Their conclusion was that the solution to groundwater contamination from septic systems, beyond better engineered on-site facilities or improved maintenance, may lie in better land-use control and in effective regulations for septic tank installation. (U.S. Environmental Protection Agency, 1980, Groundwater Protection)
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Point Sources
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Some sources of potential groundwater contamination are somewhat easier to identify. They include industrial operations which may use hazardous chemicals, landfills, gasoline filling stations, and other direct sources of contaminates. For the most part, these sources are heavily regulated by the state or federal government. These include regulations affecting landfill, hazardous wastes, underground storage tanks (removal and construction), and brownfield regulations. (Brownfields are previously contaminated sites that, under certain conditions, may be utilized for particular land uses.)
Other, larger sites, may also be considered point sources. Where there are larger, contiguous areas having a combination of poor soils unsuitable for septic systems, a high water table, an increasing amount of rural development, and a large number of intensive livestock operations, these areas can threaten the quality of the groundwater supplies.
Examples of places which may increase concerns relative to groundwater reservoirs include:
- Existing sites identified by Act 307 or the Michigan Public Acts of 1982, as amended (The Michigan Environmental Response Act) and Michigan Department of Environmental Quality identified LUST (Leaking Underground Storage Tanks) sites;
- Existing licensed landfills (active or inactive);
- Industrially used or zoned sites;
- Existing residential development that equals or exceeds a gross density (total acres divided by number of dwelling units) of one unit for every one and one-half (1.5) acres; or
- Existing agricultural development totaling more than five hundred (500) acres.
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This page last updated on 9/3/2003.
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