Evaluation of Ground-Water Age and Chemistry Relations in Aquifer Systems in Lake, Porter, and LaPorte Counties of Indiana

Surveyexpensive monitoring techniques can be employed when the knowledge of vulnerability based on the combination of geologic sensitivity and the presence of contaminants indicates that deep water predates activities at the land surface. Project AreaThe project area encompasses much of the Lake Michigan and Kankakee River water management basins in Lake, Porter, and La Porte Counties in northwestern Indiana, one of the major urban areas in Indiana.* The project focuses on the water quality within the postglacial and glacial unconsolidated and Silurian-Mississippian bedrock aquifer systems in this three-county area.Approximately 86 percent of the drinking water used in the Kankakee River Basin and the Lake Michigan Region, which include these counties, is either surface water from Lake Michigan or ground water from public well fields (Beaty and Clendenon, 1990; Beaty and others, 1994).The remainder of the drinking water is from domestic water wells.The landscape and many of the ground-water and environmental concerns of the Lake Michigan rim counties of Indiana relate to the unconsolidated surficial and manmade materials ranging in thickness from 50 to more than 200 feet and that cap the bedrock surface.Distinctive terrain-associated depositional sequences of the Lake Michigan, Lake Border/Wheeler, Valparaiso, and Kankakee physiographic areas comprise this landscape.These sequences reflect the depositional environments of the latest glacial margins and glacial lakes and, finally, of early Lake Michigan.* Project information can be viewed in either a Geographic Information System (GIS) format using Environmental Systems Research Institute's (ESRI) ArcView or a Portable Document Format (PDF) using Adobe Acrobat Reader.If ArcView 3.2 software is available on the computer, one can view the GIS formatted project file (nw_water APR File).To view the ArcView data, click on the CD-ROM Contents button on the main menu of the graphical user interface, open the GISData_NAD83 Folder, and then click on the ArcView project file (nw_water APR File).Adobe Acrobat Reader software must be on the computer to view the PDF files.A copy of Adobe Acrobat Reader 5.0 is available on the CD-ROM for downloading.To view the PDF formatted information, click on the appropriate button on the main menu of the user interface on the CD-ROM, for example, Maps, and then open a PDF document, for example, Well Locations and Identifications. OFS01-21The Antrim Shale ranges in thickness from 60 feet in northwestern Indiana to more than 220 feet in Lagrange and Steuben Counties in the northeastern part of the state.The gray calcareous shale in the lower part of the Antrim thickens from 0 feet in western La Porte County to more than 50 feet in Elkhart County (Hasenmueller and Bassett, 1981).In the core from the North American Exploration, Inc., Arthur W. Alt (INLP-2) well located immediately west of the town of La Crosse in southern La Porte County, the Antrim Shale was found at a depth of 80 feet and was 70 feet thick.The Antrim is composed of brownish-black pyritic shale with scattered medium bluish-gray bioturbated shale zones from a depth of 80 to 151 feet.In Lake County, the Upper Devonian shale units are locally used as sources of water for domestic and farm supplies (Rosenshein and Hunn, 1968a).The Ellsworth Shale is Devonian and Mississippian and overlies the Antrim Shale.The Ellsworth consists of two parts: a lower part of interbedded brownish-black and greenish-gray shale that grades upward and perhaps laterally into an upper part composed of greenish-gray shale (Lineback, 1970).The greenish-gray shale is the dominant lithology.The greenish-gray shale of the Ellsworth is present at the bedrock surface in the easternmost part of central Lake County and thickens to more than 70 feet in northeasternmost La Porte County (Lineback, 1970).None of the bedrock project wells are completed in the Ellsworth. Water Chemistry Environmental Protection Agency Drinking Water StandardsWater samples from all public and private water supply wells sampled meet U.S. Environmental Protection Agency (EPA) primary drinking water standards for arsenic, fluoride, and nitrate.One monitoring well contains 4.1 mg/L fluoride, which exceeds the EPA standard of 4.0 mg/L.(Click on the Maps button on the graphic user interface or access the ArcView view or layout entitled "EPA Primary Drinking Water Standard" for additional information.)Information about current drinking water standards can be found at the EPA Web site (http://www.epa.gov/safewater/mcl.html).Water samples from monitoring wells 13026, 13014, and 13017 in Lake and Porter Counties exceed the EPA secondary standard for chloride in drinking water of 250 mg/L.Samples from 50 wells exceed the EPA secondary standard of 0.3 mg/L for iron.Samples from eight wells, which include monitoring, landfill monitoring, and municipal wells, exceed the secondary standard of 250 mg/L for sulfate.Of the 84 water samples tested, 79 percent contained more than 180 mg/L calcium carbonate (CaCO 3 ) and are designated as very hard water.(Click on the Maps button on the graphic user interface or access the ArcView view or layout entitled "EPA Secondary Drinking Water Standard" for additional information.)The total dissolved solids (TDS) ranged from 130 to 2210 mg/L, and 38 percent of the water samples tested exceed the EPA secondary drinking water standard of 500 mg/L.Tritium, Deuterium, and 18 O in Ground Water factor 1 scores.Project wells completed in the Antrim Shale (13011) and in the Antrim Shale/unconsolidated materials (13014) have high scores for factor 1. Unconsolidated DepositsThe unconsolidated sediments overlying the bedrock have been divided into geologic units that define their spatial distribution in the area.A variety of well types were sampled in the unconsolidated materials: ground-water monitoring wells, landfill monitoring wells, domestic water supply wells, and municipal water supply wells.The water chemistry appears to vary more as a function of geologic unit than type of well sampled.This observation is based on the number of ground-water monitoring wells sampled from a range of geologic units.Supply wells occurred primarily in one unit and had the least chemical variability.The wells in the unconsolidated units that overly the Wabash Formation and Muscatatuck Group in northern Lake County are commonly characterized by lighter δ 18 O values and δ 2 H values, suggesting that upwelling older waters from the bedrock units are mixing with the younger waters of the unconsolidated units.For additional information on the aquifers and ground-water flow paths in the shallow aquifers in the northern part of Lake, Porter, and La Porte Counties, see Shedlock and others (1988; 1994). OFS01-21 19 Summary• Ground-water samples were collected and analyzed from 84 wells in both unconsolidated and bedrock aquifers in Lake, Porter, and La Porte Counties.The wells were monitoring, landfill monitoring, municipal, and private wells and ranged in depth from 25 to 215 feet.• Aquifers in unconsolidated materials within the southern Lake Michigan rim region lie within depositional-sequence-defined sediment packages composed of (oldest to youngest) the Valparaiso, Wheeler, Lake Border, and Lake Michigan sequences.• Bedrock units that immediately underlie the glacial deposits in Lake, Porter, and La Porte Counties include the Wabash Formation (Silurian), Muscatatuck Group (Devonian), the Antrim Shale (Devonian), and the Ellsworth Shale (Devonian and Mississippian).• Factors that influence the chemistry of the water in bedrock aquifers are (1) the depth to bedrock, (2) the character of the bedrock unit, (3) the character of the unconsolidated Pleistocene units capping the bedrock wells, and (4) the direction of the flow system.• The chemistry of the water in bedrock wells is of two types: calcium-bicarbonate-rich younger waters and sodium--bicarbonate--chloride-rich older waters.In northern Lake County, sodium--bicarbonate--chloride-rich older waters characterize the bedrock wells.Table 5. Correlation matrix for each variable of factors 1, 2, and 3 Bicarbonate Chloride Nitrate Sulfate Fluoride Calcium Magnesium Sodium Iron Manganese Strontium Barium Silicon Bicarbonate 1.000 -.

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