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

IfArcView 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 1 3 0 7 3 1 3 0 7 4 1 3 0 7 5 1 3 0 7

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