The Keweenaw Bay Indian Community (KBIC) in Baraga County uses ground water for most domestic, commercial, and industrial supplies. An industrial park within KBIC could adversely affect some ground-water supplies should contaminants be spilled at the park. Additional development of the park is being planned. Information on water supply potential and aquifer vulnerability to contamination is needed to make sound decisions about future activities at the industrial park.
Unconsolidated glacial deposits overlie bedrock within the Keweenaw Bay Indian Community. Usable amounts of ground water are withdrawn from the glacial deposits only in isolated areas. Principal aquifers are the Jacobsville Sandstone and the Michigamme Slate. Aquifer test and water level data from these principal aquifers indicate that they are confined and hydraulically connected throughout most of KBIC.
Ground water generally flows toward Keweenaw and Huron Bays and the Silver River. Between the industrial park and Keweenaw Bay, ground water flows to the southeast, toward the Bay. Along this flow path in the bedrock, glacial deposits are generally thicker than 25 meters, and contain thick lenses of clay and clay mixed with sand. The average depth to ground water along this flow path is greater than 25 meters, indicating unconfined conditions. Near the shore of Keweenaw and Huron Bays, however, and at isolated areas throughout KBIC, water levels in wells are above land surface.
Analyses of water samples collected in 1991 and 1997 indicate that the quality of ground water and surface water is suitable for most domestic, commercial, and industrial uses. However, U.S. Environmental Protection Agency secondary maximum contaminant limits for dissolved iron and manganese were exceeded in 4 and 5 wells, respectively, which may make the water from these wells unsuitable for some uses. Concentrations of lead in water from one well was above the maximum contaminant limit.
Concentrations of tritium in ground water downgradient from the industrial park indicate that at least some recharge to the Jacobsville Sandstone has taken place within the last 45 years. Where clay lenses greater than 1 meter thick overlie the glacial aquifer or the Jacobsville Sandstone, however, recharge may take longer than 45 years.
A contaminant spill at the industrial park would likely move laterally, toward Keweenaw Bay, in the glacial aquifer. Some infiltration does occur through the glacial aquifer to the bedrock aquifers. No information is available concerning the rate of movement of water within this aquifer, so it is not possible to determine the rate at which a spill would move either vertically or laterally within the glacial aquifer toward either Keweenaw Bay or the Jacobsville Sandstone.
Increased pumping from the existing well at the industrial park, or the development of additional wells, could potentially lower water levels in the Jacobsville Sandstone in the area of the park. Sufficient lowering of water levels could create unconfined conditions in the Jacobsville Sandstone, thereby increasing the susceptability of the aquifer to contamination.
Sweat, M.J. and Rheaume, S.J., 1998, Water Resources of the Keweenaw Bay Indian Community, Baraga County, Michigan: Water-Resources Investigations Report 98-4060.
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