hydrology and geochemistry of a slag-affected … · 2013. 10. 2. · by e. randall bayless,...

HYDROLOGY AND GEOCHEMISTRYOF A SLAG-AFFECTED AQUIFERAND CHEMICAL CHARACTERISTICSOF SLAG-AFFECTED GROUND WATER,NORTHWESTERN INDIANA ANDNORTHEASTERN ILLINOIS

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 97-4198

Prepared in cooperation with the

INDIANA DEPARTMENT OF ENVIRONMENTAL MANAGEMENT,OFFICE OF SOLID AND HAZARDOUS WASTE

U.S Department of the Interior

U.S. Geological Survey

Hydrology and Geochemistry of aSlag-Affected Aquifer andChemical Characteristics of Slag-AffectedGround Water, Northwestern Indianaand Northeastern Illinois

By E. RANDALL BAYLESS, THEODORE K. GREEMAN,and COLIN C. HARVEY

Prepared in cooperation with the

INDIANA DEPARTMENT OF ENVIRONMENTAL MANAGEMENT,OFFICE OF SOLID AND HAZARDOUS WASTE


Water-Resources Investigations Report 97-4198

Indianapolis, Indiana

1998

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary


Thomas J. Casadevall, Acting Director

The use of trade, product, or firm names is for descriptive purposes only and does not implyendorsement by the U.S. Government.

For additional information, write to: Copies of this report can be purchased from:District Chief U.S. Geological SurveyU.S. Geological Survey Branch of Information ServicesWater Resources Division Box 252865957 Lakeside Boulevard Denver, CO 80225-0286Indianapolis, IN 46278-1996

Contents iii

CONTENTS

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Description of the Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Methods of Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Well Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Water-Sample Collection and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Solid-Phase Sampling and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Mineral-Saturation Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Mass-Balance Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Statistical-Summary Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Hydrology and Geochemistry of a Slag-Affected Aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Hydrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Ground-Water and Surface-Water Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Solid-Phase Geochemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Mineral-Saturation Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

Mass-Balance Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Chemical Characteristics of Slag-Affected Ground Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Supplemental Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

iv Hydrology and Geochemistry of Slag-Affected Aquifer

CONTENTS—Continued

FIGURES

1–3. Maps showing:

1. Location of study area and Bairstow Landfill in northwestern Indiana and northeastern Illinois . . 6

2. Location of Bairstow Landfill, Hammond, Indiana, and vicinity with superimposed surface

elevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3. Ground-water and surface-water levels near Bairstow Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4–11. Figures showing:

4. Hydrogeologic section A–A’ through Bairstow Landfill, showing geology, well positions,

and water levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

5. Solid-phase sample sites at Bairstow Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6. Distribution of pH, specific conductance, and alkalinity in wells at Bairstow Landfill . . . . . . . . . . 17

7. Distribution of calcium, silica, and chloride in wells at Bairstow Landfill . . . . . . . . . . . . . . . . . . . 19

8. Stacked X-ray diffractograms for samples from sites BH-32 and BH-33 at Bairstow

Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

9. Stacked X-ray diffractograms for samples from site BH-34 at Bairstow Landfill . . . . . . . . . . . . . . 24

10. Plot of saturation index by pH and total dissolved solids for all wells at Bairstow Landfill . . . . . . 26

11. Mass exchanges between aqueous and solid phases along a ground-water flowpath at

Bairstow Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

TABLES

1. Sample-preservation requirements for ground-water samples collected at Bairstow Landfill,

Hammond, Ind., August 1996. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2. Results of analyses of ground water and surface water from Bairstow Landfill, August 1996 . . . . . . . . 40

3. Geochemical analyses of solid-phase samples from Bairstow Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . 46

4. Mineral-saturation indices calculated for water samples from Bairstow Landfill . . . . . . . . . . . . . . . . . . 51

5. Geochemical mixing models and mass-transfer estimates along ground-water flowpaths at

Bairstow Landfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

6. Statistical summary of ground-water-quality data from Bairstow Landfill and from the

Grand Calumet aquifer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

Contents v

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

Temperature in degrees Celsius (°C) can be converted to degrees Fahrenheit (°F) as follows:

°F=1.8x°C + 32

Sea Level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929—a geodetic datumderived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called“Sea Level Datum of 1929.”

Abbreviations for water-quality units used in this report: Chemical concentrations and water temperature aregiven in metric units. Volumes of sample are given in liters (L) and milliliters (mL). Chemical concentrations aregiven in milligrams per liter (mg/L), milligrams per kilogram (mg/kg), or micrograms per liter (µg/L). Milligrams perliter is a unit expressing the concentration of chemical constituents in solution as weight (milligrams) of soluteper unit volume (liter) of water. One thousand micrograms per liter is equivalent to one milligram per liter. Forconcentrations less than 7,000 mg/L, the value expressed in milligrams per liter is the same as for concentrations inparts per million (ppm). Mass transfers are expressed in millimoles of mineral per kilogram of H2O. One mole of asubstance has mass equal to the atomic weight of that substance.

Specific conductance of water is expressed in microsiemens per centimeter at 25 degrees Celsius (µS/cm). This unitis equivalent to micromhos per centimeter at 25 degrees Celsius (µmho/cm), formerly used by the U.S. GeologicalSurvey.

Redox potential of water is expressed in millivolts (mv).

Multiply By To obtain

inch (in.) 25.40 millimeter

inch (in.) 25,400 micrometer (µm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer

square mile (mi2) 2.590 square kilometer

pound per cubic foot (lb/ft3) 16.02 kilogram per cubic meter

ton 909.0 kilogram (kg)

ounce 28.3 gram (g)

acre 2.470 hectare

cubic yard (cu yard) .764 cubic meter

Abstract 1

Hydrology and Geochemistry of aSlag-Affected Aquifer and Chemical Characteristicsof Slag-Affected Ground Water,Northwestern Indiana and Northeastern Illinois

By E. Randall Bayless1, Theodore K. Greeman1, and Colin C. Harvey2

Abstract

Slag is a by-product of steel manu-facturing and a ubiquitous fill materialin northwestern Indiana. Ground waterassociated with slag deposits generally ischaracterized by high pH and elevated con-centrations of many inorganic water-qualityconstituents. The U.S. Geological Survey, incooperation with the Indiana Department ofEnvironmental Management, conducted astudy in northwestern Indiana from June 1995to September 1996 to improve understandingof the effects of slag deposits on the waterquality of a glacial-outwash aquifer.

The Bairstow Landfill, a slag-fill depositoverlying the Calumet aquifer near Hammond,Indiana, was studied to represent conditionsin slag-deposit settings that are common innorthwestern Indiana. Ground water from10 observation wells, located in four nests atthe site, and surface water from the adjacentLake George were analyzed for values offield-measured parameters and concentrationsof major ions, nutrients, trace elements, andbulk properties. Solid-phase samples of slagand aquifer sediment collected during drillingwere examined with X-ray diffraction andgeochemical digestion and analysis.

Concentrations of calcium, potassium,sodium, and sulfate were highest in wellsscreened partly or fully in slag. Potassiumconcentrations in ground water ranged from2.9 to 120 milligrams per liter (mg/L), werehighest in water from slag deposits, anddecreased with depth. The highest concentra-tions for aluminum, barium, molybdenum,nickel, and selenium were in water fromthe slag. Silica concentrations were highestin wells screened directly beneath theslag–aquifer interface, and magnesium con-centrations were highest in intermediate anddeep aquifer wells. Silica concentrations inshallow and intermediate aquifer wells rangedfrom 27 to 41 mg/L and were about 10 timesgreater than those in water from slag deposits.The highest concentrations for chromium,lead, and zinc were in ground water fromimmediately below the slag–aquifer interface.

The solid-phase analyses indicated thatcalcite, dolomite, and quartz generally werepresent throughout the slag–aquifer system;barian celestite, cristobalite, manganese-bearing calcite, and minrecordite were presentin fewer samples. Trace elements that areliberated from the slag may be incorporatedas impurities during precipitation of majorminerals, sorbed onto clays and other grain-

1U.S. Geological Survey.2Indiana University, Bloomington, Indiana.

2 Hydrology and Geochemistry of Slag-Affected Aquifer

size fractions not analyzed as part of this study,or present in low-abundance minerals thatwere not detected by the X-ray analysis.

Mass-balance and speciation programswere used to identify geochemical processesthat may be occurring as water infiltratesthrough the slag, flows into the aquifer,and discharges into Lake George. Thegeochemical models indicate that precipi-tation of calcite may be occurring whereslag-affected water enters the aquifer. Modelsalso indicate that dolomite precipitation andclay-mineral dissolution may be occurring atthe slag–aquifer interface; however, dolomiteprecipitation is generally believed to requiregeologically long time periods. Silica may bedissolving where slag-affected ground waterenters the aquifer and may be precipitatingwhere slag-affected ground water dischargesto the lakebed of Lake George.

In addition to the site-specific study,a statistical analysis of regional water qualitywas done to compare ground water in wellsaffected and unaffected by slag. When com-pared to wells in background locations inthe Calumet aquifer, wells screened in slagacross northwestern Indiana and northeasternIllinois generally had relatively higher pH andspecific-conductance values and relativelyhigher concentrations of alkalinity, dissolvedsolids, suspended solids, total organic carbon,calcium, potassium, sodium, chloride, alumi-num, barium, and possibly magnesium,sulfate, chromium, cobalt, copper, cyanide,manganese, mercury, nickel, and vanadium.When compared to wells in slag and wellsin background locations, ground waterfrom immediately beneath or immediatelydowngradient from slag had relatively highconcentrations of arsenic and silica. Water-quality characteristics in ground water atthe Bairstow Landfill were similar to water-quality characteristics in slag-contact andslag-affected wells throughout northwesternIndiana.

INTRODUCTION

Slag deposits have been used to reclaimformer wetlands and to fill low-lying areas thatcover more than 20 mi2 of the Calumet aquiferin northwestern Indiana. Drainage from slagdeposits has been suspected to have some un-desirable chemical properties and to be associatedwith vegetative stress (Kay and others, 1996b;Doss, 1996; Roadcap and Kelly, 1993). A betterunderstanding of the quality of slag-affectedground water would improve the ability of envi-ronmental managers to distinguish slag-relatedeffects on water quality from effects of othersources. The U.S. Geological Survey, in coopera-tion with the Indiana Department of EnvironmentalManagement (IDEM), conducted a study fromJune 1995 to September 1996 to improve under-standing of the effects of mixed steel-productionslag on the water-quality and mineralogy of theCalumet aquifer (a glacial-outwash aquifer innorthwestern Indiana and northeastern Illinois).

Background

Slag originates as a semi-liquid, non-metallicproduct that is separated from molten iron duringthe initial reduction of raw iron ore. Blast-furnaceslags volumetrically comprise most of the slagproduced. Blast-furnace slags generally are 95 per-cent silicates and aluminosilicates of calcium andmagnesium; the remaining 5 percent are composedof iron, manganese, and sulphur compounds, andother iron-ore impurities like phosphorous (Lank-ford and others, 1985, p. 333–334).

Steel-making slag is another type of slagderived from the production of steel. Lime, usedto remove acid oxides from steel, largely is incor-porated into the steel-making slag. Steel-makingslags typically are comprised of calcium silicates,calcium-iron compounds, and minor quantities ofcalcium oxide and magnesium oxide.

Background 3

The physical properties of slag vary. Suchproperties as degree of crystallization, vesicularity,density, and particle size are determined largelyby the method used to cool the molten material(Lankford and others, 1985). Slag is removedfrom the furnaces at about 1,480°C and may becooled slowly in the open air, moderately fastwith controlled sprays of water, or quickly bywater immersion. Slag densities range from 50to 156 lb/ft3, depending on the vesicularity(Lankford and others, 1985).

Steel and slag production along the ChicagoRiver began in the late 1830’s. In the 1880’s,the steel industry moved near the Calumet Riverin south Chicago. Slag was hauled to Indianaand used as lakeshore protection from erosionwherever the railroads followed the Lake Michiganbeach. In 1903, a cement plant was built near GaryStation (later to become Gary, Ind.) to use the slaggenerated by the south Chicago steel industry forthe manufacture of portland cement (Rooney andCarr, 1975, p. 25). In 1906, the steel industryexpanded into Indiana, and slag production quicklyoutpaced the demands of cement manufacturers.During 1945 to 1950, the Gary, Ind., blast furnacesproduced 1,000,000 tons of slag annually (Hurley,1995, p. 20). Slag disposal in swampy, low-lyingland at the southern end of Lake Michigan becamecommonplace to accommodate the oversupply.

In northern Lake County, Ind., more than20 mi2 of the Calumet aquifer is covered with slagand a smaller area is covered by “fill” (Kay andothers, 1996b, pl. 2). Slag also is mixed withash, construction debris, dredging spoils, industrialwastes, municipal wastes, sand, and sludges tocreate “fill.” The thickness of most slag and filldeposits in northwestern Indiana is less than20 ft but may be as much 70 ft adjacent to LakeMichigan (Kay and others, 1996b). As of 1979,about 10.3 mi2 of manmade land had been addedto the State of Indiana by filling along the LakeMichigan shoreline (Indiana Department ofNatural Resources, 1979, p. 3).

Several studies that describe slag effects onground- and surface-water quality have been donein parts of northwestern Indiana. Doss (1996)investigated the effects of drainage from a disposalarea where tar decanter, coal-tar bottom sludges,and slag were disposed adjacent to the MillerWoods wetland. Examination of ground andsurface water indicated that drainage from thelandfill produced elevated values of pH andspecific conductance and elevated concentrationsof most water-quality constituents, includingcalcium, magnesium, potassium, sodium, chloride,and sulfate. Chemical analysis of a single sampleof solid slag with X-ray fluorescence indicatedthe presence of calcium, magnesium, potassium,sulfur, phosphorous, aluminum, iron, manganese,silica, and titanium. The Doss slag sample wasporous, indicating a large surface area availablefor chemical interaction.

Fenelon and Watson (1993) examined waterquality in 35 wells from six land-use areas in theCalumet aquifer and overlying slag and fill depos-its. Water from the monitoring wells screened inslag had the highest values of specific conductance(2,310–5,460µS/cm) and pH (9.7–11.0) (Fenelonand Watson, 1993, p. 45). The median concentra-tions of most metals and arsenic in ground waterfrom steel-making land-use areas, however, wereless than the concentrations found in other areassuch as industrial land-use areas.

Roadcap and Kelly (1994) sampled 21observation wells surrounding Wolf Lake andLake Calumet, Ill., approximately 1 and 4 mi,respectively, west of the site examined in thisstudy. Potentiometric data from that study indi-cated that ground water flowed from the lakes,which were affected by slag filling, into the other-wise unaffected aquifer system. Water quality atbackground sites was pH 7.7 to 8.8; iron 377 to1,270 mg/L; silica 3.77 to 8.34 mg/L; and totalorganic carbon, 6.4 to 12 mg/L (Roadcap andKelly, 1994, p. C-7). Background water-qualitydata were used as input to the speciation modelEQ3 (Wolery, 1979). Results indicated that back-ground water was supersaturated with respect to


calcite (CaCO3) and dolomite (CaMg(CO3)2);supersaturated with respect to aluminosilicateminerals, goethite (a-FeO.OH), hematite (Fe2O3),and magnesite (MgCO3); undersaturated withrespect to amorphous ferric hydroxide (FeOH3)and iron-sulfide minerals; and nearly saturatedwith siderite.

Water from wells with pH values greater than11.0 had elevated concentrations of aluminumand depleted concentrations of magnesium, iron,manganese, and silica relative to the backgroundsamples (Roadcap and Kelly, 1994). Calculationsusing EQ3 indicated that the high pH ground waterwas undersaturated with respect to feldspars, gibb-site (Al(OH)3), and kaolinite (Al4(Si4O10)(OH)8).Precipitation of brucite (Mg(OH)2), high-magne-sian calcite (Ca,Mg(CO3)), iron and manganesecarbonate, and oxyhydroxide minerals was thoughtto explain the relatively low concentrations ofmagnesium, iron, and manganese in ground water.

Calcium concentrations also were elevatedin water from wells with pH values greater than11.0, relative to background wells (Roadcapand Kelly, 1994). The minerals anorthite(CaAl2Si2O8), dicalcium silicate (Ca2SiO4),melilite ((Ca,Na)2[(Mg,Fe

+2,AlSi)3O7]), merwin-ite (Ca3Mg(Si2O8)), monticellite (CaMg(SiO4)),rankinite (Ca3(SiO7)), spinel (MgAl2O4), andwollastonite (Ca(SiO3))—all thought to beconstituents of slag (Lee, 1974; Loomba andPandey, 1993)—were below saturation in allsamples. Ground water was supersaturated withrespect to barite (BaSO4), chromite (Fe

+2Cr2O4),eskolaite (Cr2O3), ilmenite (FeTiO3), rhodo-chrosite (MnO3), rutile (TiO2), strontianite(SrCO3), and witherite (BaCO3).

Purpose and Scope

The purpose of this report is to describe theresults of a site investigation examining geochemi-cal processes in a glacial aquifer that is receivingdrainage from an overlying slag deposit. Ground-water-quality data from this and a previous study

of northwestern Indiana and northeastern Illinoisalso were used in a statistical evaluation ofregional data to evaluate whether slag-affectedwater can be distinguished from background water.

The Bairstow H. Company site (BairstowLandfill), in Hammond, Ind., was instrumentedwith 10 observation wells and samples werecollected for mineralogic, geochemical, andwater-quality analyses. Geochemical models wereconstructed on the basis of data from the BairstowLandfill to examine the potential processes respon-sible for water-quality changes where slag drainageenters a glacial aquifer. The generalized results ofthe site-specific investigation are expected to applyto numerous settings throughout the region wherevariable thicknesses of slag overlay glacial out-wash and other sand aquifers.

A total of 137 ground-water-quality analysesfrom this study and a previous investigation ofthe Calumet aquifer in northwestern Indiana andnortheastern Illinois were statistically summarized.The summary was intended to characterize therange and the variability in ground-water quality innorthwestern Indiana and to examine distinguish-ing characteristics of water from wells screened inslag deposits (“slag-contact wells”), wells screenedin an aquifer immediately beneath or downgradientfrom slag (“slag-affected wells”), and wells up-gradient or at sufficient distance to be unaffectedby slag drainage (“background wells”).

Acknowledgments

The USGS thanks the Robertsdale Foun-dation, Calumet College, and the Board ofCommissioners of Lake County, Ind., for allowingthe installation of observation wells at the BairstowLandfill. The USGS also thanks the Standard OilCompany (Amoco) for coordinating and sharingfluid levels collected on Amoco property. MichalUmbanhowar-Zidek assisted with X-ray diffractionanalyses at Indiana University, Bloomington, Ind.

Methods of Investigation 5

DESCRIPTION OF THE STUDY AREA

The study area is in the Calumet LacustrinePlain physiographic unit (Schneider, 1966, p. 50).The area was scoured smooth by glacial ice fromthe Lake Michigan lobe during the Pleistoceneepoch. Reoccurring several times over the lastmillion years, glacial ice followed a preferredroute from Canada to the Chicago area, followingthe soft bedrocks that underlie the region. As thelast glacier retreated, an ablation till known as theWheeler Sequence (Brown and Thompson, 1995)was deposited onto older tills, leaving a combinedthickness of about 55 ft of till overlying the bed-rock. Meltwater from the glacier formed LakeChicago (ancestral Lake Michigan) that stoodat an elevation of about 640 ft (Fullerton, 1980,p1. 2). Sediments deposited from Lake Chicagoaccumulated to form the relatively thin Lake Bor-der sequence. Southerly lake currents carried largevolumes of fine glacial sand into this area. Muchof the sand was reworked into numerous, distinct,low dune-beach ridges.

The Calumet aquifer is comprised of thosewind- and water-transported fine sand and silt.The Calumet aquifer is a surficial deposit that is18 to 20 ft thick throughout the study area. A thinsequence of fine-grained lacustrine sedimentunderlies the sand; parts of the lacustrine sedimentmay be included in the Lake Border sequence.Thickness of the fine sand aquifer and underlyinglacustrine sediment averages 20 ft (Hartke andothers, 1975, p. 25). A Wheeler sequence tillunderlies the lacustrine sediment.

The climate of northwestern Indiana iscontinental and is characterized by hot, humidsummers and cold winters. The study area receivesan average of about 37 in. of precipitation and29 in. of snowfall annually (National Oceanicand Atmospheric Administration, 1992).

The Bairstow Landfill was selected for asite-specific investigation as part of this study.The Bairstow Landfill is about 1 mi south ofLake Michigan (fig. 1), on the northeast cornerof 129th Street and Calumet Avenue in Hammond,Ind. (fig. 2). Lake George is immediately north of

the Bairstow Landfill, and a wetlands (Lost Marsh)borders the landfill’s east side (fig. 2). CalumetCollege and a residential area are north and eastof Lake George. Amoco maintains a petroleum-storage facility south of the Bairstow Landfill and1,000 ft east of the Lost Marsh.

The wastes deposited at the Bairstow Landfillare described as various steel-production slags,fly ash and bottom ash from power plants, drumsof oily sludge, and road-construction debris (Ecol-ogy and Environment, Inc., 1993). In 1980, aU.S. Environmental Protection Agency (USEPA)inspector noted about 100 drums of grease and oilymaterials lying on or near the Lake George shore-line. By 1987, the drums and 2.5 million cu yardsof contaminated soil had been removed from thesite (Ecology and Environment, Inc., 1993, p. 1).Metals concentrations in the laboratory leachingstudies of 1993 soil samples were invalidated byquality-control data; PCB was detected in theLost Marsh sediment. Air photos from 1951, 1965,and 1986 showed the progressive filling of LakeGeorge that produced the Bairstow Landfill.

The surface area of the Bairstow Landfill is100 acres. The landfill has a maximum relief ofabout 45 ft (fig. 2). The depth of slag at the site is5 to 45 ft, including four slag piles of blast-furnaceand open-hearth-furnace slag. Roy F. Weston, Inc.,(1995) estimated that about 1,500,000 cu yards ofslag exist on the site; about 4,000,000 cu yardswere originally deposited, but 2,500,000 cu yardswere removed later for construction projects.

METHODS OF INVESTIGATION

The investigation consisted of two efforts:(1) a site-specific study to collect data to generateand verify geochemical models for ground-waterquality influenced by slag drainage and (2) a statis-tical analysis of regional data to evaluate whetherslag-affected water quality can be distinguishedfrom ambient or background water quality. Themethods used for each study are described in thissection of the report.

Figure 1. Location of study area and Bairstow Landfill in northwestern Indiana and northeastern Illinois.

0 1 2 3 4 5

0 1 2 3 4 5

41°40'

41°35'

87°30' 87°15'

Base from U.S. Geological Survey digital data 1:24,000, 1991Albers Equal Area projectionStandard parallels 29°30' and 45°30', Central meridian -86°

Calumet

94

90

80 94

65 90

Indi

ana

Illin

ois

Lake Michigan

Calumet

WolfLake

Lake George

Gary Harbor

HarborBuffington

HarborIndiana

Harbor

Lake

River

Grand

Calumet

Little

Calumet

Calum

et

Calum

et

River

River

Wh i t i ng

Ind

ian

a

Harbo

r Can

al

East Chicago

H a m m o n d

G a r y

MillerWoods

Por

ter

Cou

nty

Lake

Cou

nty

Area shown in figure

I l l ino is Indiana

Lake

Cou

nty

Coo

k C

ount

y

S t o n yI s l a n d

Bairstow Landfill

MILES

KILOMETERS

Methods of Investigation 7


The Bairstow Landfill was selected for site-specific study because (1) well drillers’ recordsfor an on-site observation well indicated that thestratigraphy was typical of northwestern Indiana;(2) analytical data for the on-site observation wellindicated that water quality was being affected byslag drainage; (3) the hydraulic gradient in thelandfill area was known from the USGS records forthe northwestern Indiana data network; (4) surfacematerial and material at depth on exposed slopesappeared to be common blast-furnace slag; and(5) active mineral deposition was occurring alongthe southern shoreline of Lake George, apparentlywhere ground water was discharging from thelandfill. The Bairstow Landfill was selected torepresent slag–aquifer systems that are commonthroughout northwestern Indiana; however,the variability of slag-fill chemistry may makethe results of this study less applicable to otherlocations in northwestern Indiana.

Well Installation

A south-to-north flowline was selected forinstrumentation and sampling at Bairstow Landfillalong the ground-water-flow direction interpretedfrom water levels of wells in the USGS network(see line A-A’ on fig. 3). The flowline began at theexisting well BH-31, ended at Lake George, andwas approximately perpendicular to the southernshoreline of Lake George.

The observation-well transect included10 wells at four sites (figs. 3 and 4). Observationwell BH-31 was installed during a previous inves-tigation near the highest accessible elevation atthe landfill. The 15-ft screened interval crosses theslag–aquifer interface. Nested observation wellswere installed July 16 and 17, 1996, at sitesBH-32 and BH-33 at about 510 and 800 ft north ofBH-31, respectively. Wells at BH-32 are screenedin slag (BH-32SL), in the aquifer just beneaththe slag (BH-32S), in the middle of the aquifer(BH-32I), and at the base of the aquifer (BH-32D).Observation wells at BH-33 are installed in the

slag (BH-33SL), across the slag–aquifer interface(BH-33S), and in the middle of the aquifer(BH-33I). The naming convention for these wellsused “SL,” “S,” “I,” and “D” to indicate “slag,”“shallow,” “intermediate,” and “deep,” respec-tively. The S, I, and D wells also are collectivelyreferred to as “aquifer wells” throughout the report.

Wells at BH-32 and BH-33 were installedusing the hollow-stem auger method. Wellsat BH-32 and BH-33 were constructed from2-in.-inner-diameter polyvinyl chloride (PVC)flush-joint casing and 5-ft-long PVC screens with0.010-slot size. Wells were installed with a 6.75-in.hollow-stem auger. The annular space was back-filled with sand to 2 ft above the screen, bentoniteto within 3 ft of land surface, and concrete to thesurface.

Two observation wells were installed inthe lakebed immediately north of the southernshore of Lake George on July 12, 1996. BH-34SSand BH-34ND are 1,200 ft north of BH-31 andabout 5 and 20 ft north of the mean water line,respectively. BH-34SS is screened 2 to 3 ft belowthe lakebed and at least partially in slag, andBH-34ND is screened about 4.5 to 6.5 ft belowthe lakebed. Wells BH-34SS and BH-34ND werehand driven with a 36-kg post driver and con-structed from 2-in.-diameter stainless-steel pipewith 1-ft stainless-steel screens having 0.010-sizedslots. Lakebed wells are designated “ND” and“SS” to indicate “north-deep” and “south-shallow,”respectively.

Water-Sample Collection and Analysis

Ground-water samples were collectedAugust 13 through 15, 1996, from the 10 BairstowLandfill observation wells. An additional samplewas collected from Lake George, 2 ft below watersurface, near well BH-34ND. Two additional sam-ples were collected from well BH-32S to examinethe reproducibility of sampling methodology andanalytical precision.

Water-Sample Collection and Analysis 9

587

586585

584

583584

583

584

585

582581

LAKE GEORGEELEVATION 583.1

WOLF LAKEELEVATION 583.1

Figure 3. Ground-water and surface-water levels near Bairstow Landfill, Hammond, Indiana.

EXPLANATION

Amoco ground-water observation wells

U.S. Geological Survey observation-well site and identification number

Surface-water location

Aerial photomap by U.S. Geological Surveyfrom aerial photograph taken September 25, 1990

0 286 572

0 940 1880 FEET

METERS

87°29'47"87°30'20"

41°40'

41°39'29"

A

A'

587POTENTIOMETRIC CONTOUR--Shows altitude at which water level would have stood in tightly cased wells, (August 13-15, 1996). Dashed where approximately located.Contour interval 1 foot. Datum is sea level

Area shown in figure 1

I l l ino is Indiana

CalumetCollege

Amocotank farm

BH-34

BH-33

BH-32

BH-31

BairstowLandfill

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

��

yyyyyyyyyyyyyyyyyy

zzz

zzz

zzz

zzz

zzz

zzz

zzz

zzz

zzz

{{{{{{{{{{{{{{{{{{

|||

|||

|||

|||

|||

|||

|||

|||

|||

��

��

��yyyyyyyyyyyyyyyyyyyy

zzzzzzzzzzzzzzzzzzzz{{{{{{{{{{{{{{{{{{

||||||||||||||||||

Figure 4. Hydrogeologic section A-A' through Bairstow Landfill, Hammond, Ind., showing geology, well positions, and water levels.

560

550

570

580

590

600

VERTICAL SCALE GREATLY EXAGGERATEDDATUM IS SEA LEVEL

Well

BH

-31

Well

BH

-34S

SW

ell

BH

-34N

D

SLAG

EXPLANATION

Potentiometric surface based on water levels in shallow wells at each site

Water level at well-screened intervals

Well identification and number

FEET

� � � � � � � � �� y��yz��{| �| ��y{ �z�y��y{��{|�{ �� z| �| �y��z|�|�{ ��{|��{| �y��{|�|�| ��yz �y��yz��{|�� z| �y

Well

site

B

H-3

2

Well

site

B

H-3

3

A'A

CALUMET AQUIFER

Lake George

0 150

45 90

300

0

FEET

METERS NORTH

WHEELER SEQUENCE LACUSTRINE CLAY

��{|

BH-34SS

BH-34ND

BH-33I

BH-33S

BH-33SL

BH-32I

BH-32I

BH-32S

BH-32SL

BH-31

BH-32D

583.16 583.21

583.16

583.16

583.16583.17

583.17

582.8

583.17

583.16

583.42

�y�y

Solid-Phase Sampling and Analysis 11

Samples for water-quality analysis werecollected by use of a peristaltic pump equippedwith Tygon tubing. Sampling preparation includedremoval of three times the standing volume ofwater in the well; on-site measurements of pH,specific conductance, redox potential, water tem-perature, and dissolved oxygen were monitoredwith a multiparameter probe and a stainless-steelflow-through chamber. On-site measurementswere recorded and samples collected after on-sitemeasurements had stabilized. Samples were pre-served according to the guidelines specified bythe USGS National Water-Quality Laboratory andare described in table 1. Measurements of redoxpotential are reported as a field measurement rela-tive to the calomel electrode. All samples wereanalyzed by the USGS National Water-QualityLaboratory for concentrations of inorganic com-pounds similar to those examined by Duwelius andothers (1996); the analytical methods are describedin Wershaw and others (1987) and Fishman andFriedman (1989). An incremental titration to deter-mine carbonate alkalinity was done at the site.

Decontamination of the pump, hoses, andflow-through chamber was done between eachsampling. Decontamination consisted of pumpingan Alconox-water mixture through the flow-through chamber, pump, and hoses, followed bytap water and deionized water. The pump andhose exteriors were rinsed between wells withdeionized water.

Solid-Phase Sampling and Analysis

Solid-phase samples were collected duringinstallation of all wells, except BH-31. Hand-driven split-spoon samples were collected inliners at BH-34 sites and immediately sealed withbeeswax. Split-spoon sampling was not capable ofcapturing slag or sand at sites BH-32 and BH-33.Samples at sites BH-32 and BH-33 were takenfrom auger cuttings and from the auger bit as it wasretracted from the screened interval. Auger cuttingsand bit samples were preserved in zip-lock freezerbags and refrigerated until solid-phase analysis inAugust and September 1996.

The geochemistry and mineralogy of solidsamples were determined at the Indiana UniversityDepartment of Geological Sciences. Analysesincluded (1) a determination of solid chemistryfrom sample digestion and major and minor ele-ment quantification using neutron activation orion chromatography and plasma spectroscopy,and (2) a description of bulk mineralogy basedon X-ray diffraction.

Sixteen solid-phase samples were analyzedfor geochemistry and mineralogy. The sampledistribution included two slag samples, one sam-ple from the slag–sand interface, three sandsamples below the sand–slag interface, one sampleof the Lake Border lacustrine deposit subdividedinto three grain-size fractions (125µm-, 125–45µm-, and

Table 1. Sample-preservation requirements for ground-water samples collected at Bairstow Landfill, Hammond, Ind.,August 1996

[ml, milliliter; µm, micrometer;°C, degrees centigrade;

Solid-Phase Sampling and Analysis 13��

��

��

��

yyyyyyyyyyyyyyyyyy

zzzzzzzzzzzzzzzzzz

{{{{{{{{{{{{{{{{{{

||||||||||||||||||

��

��

��

��

yyyyyyyyyyyyyyyyyyyy

zzzzzzzzzzzzzzzzzzzz

{{{{{{{{{{{{{{{{{{

||||||||||||||||||

��

��

��

��

��yz{|

��y{��y{��y{

��yz{|

��y{��y{��y{��y{


The

Mass-Balance Calculations 15

indices do not indicate whether an undersaturatedmineral that is not present in the solid phase hasbeen removed by dissolution or whether it wasnever present.

Mass-Balance Calculations

The computer program NETPATH (Plummerand others, 1994) was used to generate mass-balance models along a ground-water flowpathat Bairstow Landfill. The mass-balance modelswere used to indicate the relative proportions ofprecipitating and dissolving minerals that couldaccount for the observed differences in waterquality between wells in the Bairstow Landfill.

NETPATH generates models based onminerals specified by the user to be important inthe geochemical system. The specified minerals areadded to or removed from the ground-water systemin the computation to account for the differencesin the concentrations of water-quality constituentsbetween two wells. In addition to mineral precipi-tation and dissolution, NETPATH can calculateproportions of mixed ground-water componentsthat can combine with the mineral precipitation anddissolution to account for changes in constituentconcentrations. The number of models generatedby NETPATH is based on the number of water-quality constituents, solid phases, and otherprocesses selected by the user to potentially ex-plain the changes in water quality.

Statistical-Summary Calculations

Data from this study (8 sites) and fromDuwelius and others (1996; 129 wells sampledin June 1993) were used to characterize the rangeand variability of constituent concentrations inslag-affected ground water of northwestern Indianaand northeastern Illinois. Ground-water samplescollected for both studies were analyzed for thesame water-quality constituents and properties.The statistical summary was intended to identifywater-quality constituents and properties that maybe indicators to distinguish water from slag-contactwells, slag-affected wells, or background wells.

A geographical information system (GIS)was used to superimpose locations of the 137ground-water-sample sites on digital maps describ-ing (1) locations of known fill deposits (Kay andothers, 1996b), (2) ground-water levels (Duweliusand others, 1996), (3) well depths, (4) stratigraphy,and (5) fill thicknesses (Kay and others, 1996a).Results of this study identified 3 subsets of wellsthat may represent common settings in northwest-ern Indiana, including 21 slag-contact wells, 25slag-affected wells, and 11 background wells.Eighty observation wells were removed from thedata set because water quality at those sites couldbe influenced by multiple factors, such as proxim-ity to a domestic-waste landfill, in addition to slagdrainage.

The 57 classified sites and their associ-ated water-quality data were then summarizedaccording to the following statistical properties:the total number of measurements in the dataset; the median (middle) data value; the minimumand maximum values from the data set; and thefirst and third quartile (Q1 and Q3). The first quar-tile and third quartile values are the data at which25 percent and 75 percent of the data in the distri-bution are less than or equal to those values in ahierarchial ordering of the data.

HYDROLOGY AND GEOCHEMISTRYOF A SLAG-AFFECTED AQUIFER

The Bairstow Landfill overlays the Calumetaquifer (Roy F. Weston, Inc., 1995). Slag thicknessranges from 0 to 7 m, being thinnest at LakeGeorge and thickening toward the center of thelandfill. The Calumet aquifer is fine- to coarse-grained sand with some gravel and is approxi-mately 18 ft thick at the site. The thicknesses ofthe Lake Border sequence lacustrine sediment andWheeler sequence till at the site are unknown.The Wheeler sequence is regionally underlain bybedrock shale and limestone.


Hydrology

A potentiometric-surface map (Greeman,1995) was constructed from quarterly measure-ments of water levels in a regional network of76 monitoring wells. That map indicates regionalground-water flow in the Calumet aquifer near thesite is generally toward Lake Michigan (Greeman,1995); ground-water flow near the Bairstow Land-fill is usually toward Lake George (fig. 3).

The ground-water flowpaths, based on waterlevels in the Bairstow wells, indicate that rechargemoves down through the slag pile and uppermostsands into the intermediate-depth sands. Groundwater also moves up from the deeper sands toconverge at the intermediate-depth sands, whereground water gains a strong horizontal componentof flow toward Lake George. Ecology and Envi-ronment, Inc., (1993) noted an unidentified whiteleachate material entering Lake George from thenorthwestern corner of the Bairstow Landfill, sug-gesting ground-water discharges to Lake George.

Ground-water flow at the site is affectedby Lake George, the wetlands bordering the eastside of the site, and by induced drawdown on theproperty of the Amoco petroleum-tank farm.Drawdown of the water table is induced at theAmoco site to inhibit off-site migration of non-aqueous-phase liquids (fig. 3). The possibilityexists for ground-water-flow direction at the studysite occasionally to be reversed to north-to-southin response to local drawdowns produced by theAmoco barrier wells or elevated water levels inLake George; as a result of the data collected bythis study, however, conclusions cannot be madeabout occurrences of flow reversals.

Ground-Water and Surface-WaterChemistry

At the Bairstow Landfill, alkalinity, dissolvedsolids, pH, and specific conductance varied simi-larly with respect to depth or stratigraphic positionand were distinctly highest in the water fromthe slag wells (BH-31, BH-32SL, BH-33SL, andBH-34SS) (fig. 6; table 2, back of report).

Alkalinity values ranged from 626 to 903 mg/L asCaCO3 in the water from the slag wells and 420to 590 mg/L as CaCO3 in all other wells. Alkalin-ity was 160 mg/L as CaCO3 in the sample fromLake George. Dissolved-solids concentrationsin water from the slag wells ranged from 848 to1,240 mg/L. The dissolved-solids concentrationwas 864 mg/L at BH-33S but was less in all othersamples, ranging from 506 to 680 mg/L in waterfrom the other wells; it was 433 mg/L in the sam-ple from Lake George. Values of pH ranged from11.9 to 12.3 in the water from the four slag wellsand from 7.4 to 9.9 in all other wells. The pH ofthe sample from Lake George was 8.5. Valuesof specific conductance ranged from 844 to4,640µS/cm in ground-water; specific conduc-tance was 733µS/cm in the sample from LakeGeorge. Specific conductance ranged from 3,180to 4,640µS/cm in the slag wells and from 844 to1,300µS/cm in all other wells. Values of alkalinity,dissolved solids, pH, and specific conductancewere lowest in ground water at BH-32I andBH-32D and were consistently higher in aquiferwells at BH-33 than at BH-32.

Concentrations of dissolved oxygen inground water ranged from 0.1 to 0.4 mg/L,except at BH-34ND where the concentration was1.6 mg/L. The concentration of dissolved oxygenin the sample from Lake George was 6.5 mg/L.Concentrations of dissolved oxygen were highestin the shallowest well at each site, ranging from0.2 to 0.4 mg/L.

Redox potentials in ground water rangedfrom –127 to +53 millivolts (mv). The redoxpotential in the sample from Lake George was+294 mv. Redox potentials ranged –26 to +53 mvin BH-32I, BH-32D, BH33I, and BH-34ND.Redox potentials ranged from –127 to –64 mvin all other wells.

Ground-water temperatures ranged from14.5 to 23.5°C. Temperatures at BH-33 werehigher than at BH-32. BH-34ND had a higher tem-perature than BH-34SS, suggesting that BH-34NDmay be more strongly influenced by Lake George.The water temperature in the sample from LakeGeorge was 28.5°C.

Ground-Water and Surface-Water Chemistry 17��

��

��

��



{{{{{{{{{{{{{{{{{{

||||||||||||||||||

��

��

��

��

yyyyyyyyyyyyyyyyyyyyyyyyyyy

zzzzzzzzzzzzzzzzzz

{{{{{{{{{{{{{{{{{{{{{{{{

||||||||||||||||

��

��

��

��

��yz��yz{|

��{|��yz{|��yz{|

��yz{|��z|��yz{|��yz{|

��z|��z|


As with the general water-quality properties,the distribution of the major ions and silica atBairstow Landfill showed distinct patterns relatedchiefly to depth or stratigraphic position (fig. 7).Major ions (including calcium, magnesium, potas-sium, sodium, bicarbonate alkalinity, chloride,fluoride, sulfate, and ammonium) generally com-pose most of the dissolved mass in these watersamples. Concentrations of calcium, potassium,and sulfate were highest in wells screened (at leastpartly) in slag; silica was highest in wells screenedbelow the slag–aquifer interface; and magnesiumwas highest in intermediate and deep wells. Therelative abundances of the carbonate speciesH2CO3–HCO3

-–CO32- are pH dependent, with

H2CO3 most abundant to pH 6.4, HCO3- greatest in

the interval pH 6.4 to 10.33, and CO32- greatest

above pH 10.33 at 25°C (Drever, 1982). Chlorideconcentrations showed no discernible patterns ofdistribution.

Concentrations of calcium ranged from 210to 270 mg/L in water from the slag wells and11 to 88 mg/L in all other wells (table 2, at backof report). The calcium concentration in the samplefrom Lake George was 23 mg/L. Between theslag and shallow aquifer wells at sites BH-32 andBH-33, the calcium concentrations decreased by219 and 259 mg/L, respectively (fig. 7), indicatingpotential mass transfer lost from solution by min-eral precipitation.

Concentrations of potassium in ground waterranged from 81 to 120 mg/L in water from the slagwells and 2.9 to 92 mg/L in water from all otherwells (table 2). The potassium concentration inthe sample from Lake George was 46 mg/L. At thenested-well sites (BH-32 and BH-33), the potas-sium concentrations were highest in water fromslag wells and decreased with depth. As with manygeneral water-quality parameters, concentrations ofpotassium in aquifer wells at BH-33 were higherthan at BH-32.

Concentrations of sulfate ranged from 91to 220 mg/L in water from the slag wells, 6.7 to67 mg/L in water from the aquifer wells at BH-32and BH-33, and were 110 mg/L in the samplefrom Lake George and the BH-34 wells.

Concentrations of silica ranged from 3.1to 3.9 mg/L in water from the slag wells. Silicaconcentrations in water from shallow and inter-mediate aquifer wells were greater by abouttenfold over the slag wells, ranging from 27 to41 mg/L. The silica concentration in the samplefrom Lake George was 2.9 mg/L and was highestin BH-34ND at 74 mg/L (fig. 6).

Concentrations of sodium ranged from 34 to220 mg/L. Concentrations less than 60 mg/L werelimited to water from wells BH-31, BH-32I, andBH-32D.

Concentrations of magnesium were lessthan the method reporting limit at three of the fourslag wells and 0.01 mg/L at BH-32SL. Magnesiumconcentrations in wells BH32I and BH32D were27 and 41 mg/L, respectively, and ranged from0.12 to 4.4 mg/L in other wells screened in theaquifer. The magnesium concentration was7.2 mg/L in the sample from Lake George.

Trace elements generally compose a smallfraction of the total dissolved mass in groundwater. Trace-element concentrations measured inthis study included aluminum, antimony, arsenic,barium, beryllium, cadmium, chromium, cobalt,copper, iron, lead, manganese, molybdenum,nickel, selenium, silver, uranium, and zinc.

Aluminum, barium, molybdenum, nickel,and selenium generally were present in greaterconcentrations in water from the four slag wellsthan from the slag–aquifer interface or in deeperparts of the aquifer. Aluminum concentrations inwater ranged from 180 to 820µg/L in the slagwells and ranged from 6 to 160µg/L in all otherwells. Barium concentrations in water ranged from180 to 410µg/L in the slag wells and from 24 to200µg/L in all other wells. Barium concentrationswere elevated slightly in water from wells BH-32Iand BH-32D, compared to shallow aquifer wells.Molybdenum concentrations ranged from 58 to200µg/L in water from the four slag wells andfrom 2 to 160 mg/L in all other wells. The molyb-denum concentration in water from well BH-34ND(160µg/L) may be related to elevated concentra-tions in the sample from Lake George (120µg/L).

Ground-Water and Surface-Water Chemistry 19��

��

��

��



{{{{{{{{{{{{{{{{{{

||||||||||||||||||

��

��

��

��

yyyyyyyyyyyyyyyyyy

zzzzzzzzzzzzzzzzzz

{{{{{{{{{{{{{{{{{{

||||||||||||||||||

��

��

yyyyy

{{{{

��

��

��

��

��yz{|��y{

��yz{|��yz{|��y{��yz{|��y{

��yz{|��y{�y��yz{|��y{


Nickel concentrations in water ranged from 9 to13 µg/L in slag wells and from 2 to 6µg/L in allother wells. Selenium concentrations in waterranged from 2 to 4µg/L in slag wells and werebelow reporting limits (

Solid-Phase Geochemistry 21

ranged from 13.0 to 20.0 mg/L in BH32S, BH-33S,and BH-33I and ranged 2.60 to 3.90 mg/L in allother wells and 0.90 mg/L in the sample fromLake George. Orthophosphate concentrationsranged from 0.11 to 0.47 mg/L in the shallowand intermediate-depth aquifer wells at BH-32 andBH-33; concentrations ranged from


By comparison, two sediment samplescollected during 1995 from the southeastern cornerof Lake George contained concentrations of anti-mony, arsenic, chromium, cobalt, iron, lead,manganese, nickel, vanadium, and zinc morethan three times background levels (Roy F.Weston, Inc., 1995). Sediment from the south-western corner of Lake George had no elevatedconstituent concentrations relative to backgroundsamples (Roy F. Weston, Inc., 1995). One sedimentsample from the Lost Marsh had concentrationsof arsenic, cadmium, cobalt, copper, iron, lead,nickel, selenium, thallium, vanadium, and zinc atconcentrations more than three times greater thanbackground (Roy F. Weston, Inc., 1995).

All elemental concentrations in aquifer sam-ples from Bairstow Landfill were elevated relativeto the sample of native sand unaffected by slagdrainage. The sample of dune sand, which mayhave origins that are similar to the lacustrineCalumet aquifer sand, probably has undergoneconsiderable reworking by sedimentary processesand has been exposed to surficial conditions thatmay have altered its geochemistry.

Figure 8 shows the X-ray diffractogramsfor five solid-phase samples, stacked accordingto depth, at BH-32 and BH-33. The intensities ofthe various X-ray peaks were assumed to indicatechanging proportions of the minerals present.The stacked diffractograms indicate that quartz(SiO2) is present at most depths but is most abun-dant in slag and least abundant in the Lake Borderlacustrine sediment. The primary peak for calcite(CaCO3), 2θ = 29.37°, indicates that quartz ispresent at all depths but is most abundant at theslag–aquifer interface. Dolomite (CaMg(CO3)2),primary peak at 2θ = 30.94°, is similarly presentat all depths and is most abundant in slag, leastabundant at the slag–aquifer interface, and ispresent in substantial quantities in the sand imme-diately below the slag–aquifer interface.

Cristobalite (low temperature SiO2), bariancelestite (Ba0.25Sr0.75SO4), and minrecordite(CaZn(CO3)2) are less abundant in all solid-phasesamples than quartz, calcite, and dolomite. The

primary diffractogram peak of low-temperaturecristobalite (2θ = 21.94°) indicates that smallamounts of this mineral are in the slag samples andthat it is less abundant in deeper samples. Theprimary and secondary diffractogram peaks forbarian celestite overlap with the primary quartzand calcite peaks, making barian celestite difficultto distinguish. The identification of barian celestitewas based on a prominent lower order peak atslightly more than 2θ = 44.5° but, because otherlower-order peaks for celestite are not in the dif-fractogram for sample 32A, this identification isconsidered tentative.

The primary peak for minrecordite(CaZn(CO3)2) overlaps the primary dolomite peakand cannot be identified in the solid-phase samples.The secondary and tertiary peaks, however, areclearly identified at about 2θ = 50.75° and 51.25°.Minrecordite may be present at all depths, but itis most abundant near the slag–sand interface.

Clay minerals can be an important geochemi-cal consideration because of their cation-exchangecapabilities. Clay minerals are not present in sig-nificant quantity in any solid-phase sample fromthe study site. Primary diffractogram peaks forclays generally occur at 2θ < 20°; peak intensitiesin this region were subdued. It is possible thatX-ray examination of a finer grain-size fractionwould allow clay minerals to be identified. Clayminerals are considered to be allochthonous miner-als and their presence nonindicative of secondarymineralization processes.

Figure 9 shows stacked diffractograms for aset of four solid-phase samples taken over approxi-mately a 3-ft lakebed interval at BH-34SS. Thissequence may be useful in describing geochemicalchanges occurring as ground water discharges intoLake George. Similar to the core samples at BH-32and BH-33, quartz, dolomite, and calcite are themost abundant minerals in the lakebed samples.The stacked X-ray diffractograms may indicatethat quartz abundance increases with depth, butcalcite and dolomite abundances decrease withdepth.

Solid-P

hase Geochem

istry 23 10 20 30 40 50

32C

32B

32A

33C

33B

Rel

ativ

e In

tens

ity (

Cou

nts)

2-Theta

Figure 8. Stacked X-ray diffractograms for samples from sites BH-32 and BH-33 at Bairstow Landfill.

EXPLANATION

Q QuartzM MinrecorditeC CalciteD DolomiteCr Cristobalite

500

Cou

nts

Solid-P

hase Geochem

istry 23

Q

Q

Q

Q

Q

QC

C

C

CD

Q

M C

D

D

D

D

M

M

M

Q

C

Cr

10 20 30 40 5002-Theta

34E

34A

34B

34C

34D

Figure 9. Stacked X-ray diffractograms for samples from site BH-34 at Bairstow Landfill.

Rel

ativ

e In

tens

ity (

Cou

nts)

500

Cou

nts

EXPLANATION

C CalciteQ QuartzD DolomiteM Minrecordite

Q

Q

Q

QC

CC

DMD

D

D

D

C

Q

M

24 Hyd

rolo

gy an

d G

eoch

emistry o

f Slag

-Affected

Aq

uifer

Mineral-Saturation Simulations 25

Cristobalite may be present in the two middle-depth samples but only as a minor constituent.Minrecordite abundance increases with depth andis almost nonexistent in the shallowest lakebedsample.

A rock sample encrusted with a whitishprecipitate from the southern shoreline of LakeGeorge also was examined by X-ray diffraction.The mineralogy of the precipitate consisted pre-dominantly of calcite, with minor quantities ofquartz and dolomite and lesser quantities of bariancelestite, manganese-bearing calcite, and min-recordite.

Mineral-Saturation Simulations

Constituents used in the WATEQFP calcu-lations are identified in table 2 (back of report)and the calculated saturation indices are shownin table 4 (back of report). Saturation indices for183 minerals were calculated; the minerals auto-matically were selected from the WATEQFP database if the chemical components necessary to buildthe mineral had positive concentrations in thewater-quality sample. For some water-quality-datasets, the saturation indices of some minerals werenot calculated because concentrations of the neces-sary chemical constituents were less than reportinglimits. Minerals with no calculated saturation indexgreater than 10-5 are omitted from table 4.

Calculated saturation indices show that manyminerals are undersaturated in all water samples;these minerals are not thermodynamically favoredto precipitate in the Bairstow Landfill ground-water system and may dissolve if present. Of108 minerals shown in table 4 (back of report),49 were undersaturated in all samples. Eleven of108 minerals were supersaturated in all samples,and 46 minerals were supersaturated in some sam-ples (table 4). Of the 46 minerals that occasionallyare supersaturated, most indicate a tendency toprecipitate in the Calumet aquifer and at siteBH-34ND. Minerals were less frequently super-saturated in the four slag wells and in the samplefrom Lake George.

The saturation states of minerals commonlyidentified in X-ray diffractograms for solid phasesamples from Bairstow Landfill (including calcite,dolomite, quartz, and less commonly cristobalite)indicate a dependency on solution pH (fig. 10). Thesaturation indices of calcite and dolomite increasewith pH, but the saturation indices of quartz andcristobalite become negative at high pH.

Calcite is supersaturated at all well points.Low pH precipitation that has been observed innorthwestern Indiana (Willoughby, 1995, p. 14and p. 30) may react with near-surface slag andmay be responsible for the tremendous quantitiesof dissolved calcium and carbonate present inslag. As ground water percolates into the aquifer,calcium and carbonate concentrations are loweredby dilution and (or) calcite precipitation; as aresult, the calcite saturation indices are lowered.

Calcite is undersaturated at the LakeGeorge sample point; the constituents requiredto form calcite are depleted in lake water bydilution and (or) mineral precipitation at theground-water/surface-water interface. Activemineral precipitation was observed along thelakeshore of Lake George, and X-ray diffractionanalysis indicates that calcite is the primary phase.

Dolomite is saturated at all sample points,except at well BH-32I. The solution pH was lowestfor all wells at BH-32I; dolomite-forming constitu-ents were not particularly low at this well site.Dolomite saturation indices were not calculated formonitoring wells with magnesium concentrationsless than the method reporting limit, includingwells BH-31, BH-33SL, and BH-34SS. Dolomite,however, was observed in X-ray diffraction analy-ses of slag samples, indicating that dolomite ispresent but may be insoluble in slag. Dolomiteprecipitation is generally believed to require geo-logically long time periods.

Cristobalite and quartz were supersaturatedat all sample points, except the four slag wells.Silica is generally soluble at pH values in excess of9.9 (Krauskopf, 1979), and the four slag wells hadpH values greater than 11.9. The pH of all other

7 137 8 9 10 11 12

pH

-4

4

-4

-2

0

2

SA

TU

RA

TIO

N IN

DE

X

Plot of saturation index by pH and total dissolved solids for all wells at Bairstow Landfill.

Calcite

Cristobalite

Dolomite

Quartz

EXPLANATION

Figure 10.

Mass-Balance Simulations 27

sample points was less than 9.9. The pH data andcalculated mineral-saturation indices imply thatsilica forms would be dissolving in slag and pre-cipitating in the shallow aquifer.

Several trace carbonate minerals, notablyrhodochrosite (MnCO3) and siderite (FeCO3), alsowere undersaturated in the slag but were slightlyundersaturated to slightly supersaturated in aquiferwells below the slag. These minerals were notpresent in quantities sufficient to be detected by theX-ray diffraction analyses but may be precipitationcontrols on manganese and iron concentrations inwater.

The ability of WATEQFP to calculate accu-rately the tendency for a mineral to precipitate ordissolve is constrained by several factors, includ-ing the precision of water-quality analyses, theaccuracy of the thermodynamic data base, andthe kinetics of mineral formation. The water-quality input data must (1) include concentrationsfor chemical constituents that are significantcomponents of most minerals in the system and(2) be analytically accurate.

The accuracy of water-quality analysescommonly is assessed by calculating chargebalances. The charge balances for the Bairstowsamples ranged from +4.97 to –15.4 percent andhad median value –4.31 percent. The most extremeimbalances were measured in the four slag wells,with magnitudes of +4.97, –15.9, –10.4 and–15.4 percent. Doss (1996) similarly identifiedrelatively large errors in slag-affected ground-water-quality analyses. The charge balances forwells screened in the Calumet aquifer and in thesample from Lake George ranged from –1.41 to–6.50 and had a median value of –3.66.

Generally, charge balances in water analysesthat are greater than 5 percent or are less than–5 percent are considered to be missing an impor-tant constituent or to be the result of inaccuratelaboratory analyses or inappropriate field methods.Replicate analyses done as part of this study indi-cate that the field and laboratory methods producedconstituent concentrations and water-quality char-acteristics that were nearly identical; however, thepossibility of a consistent error in methods is not

eliminated. Potential sources of error in the resultsof analyses of samples from Bairstow Landfillanalyses may include, but are not limited to, meth-ods used to determine carbonate alkalinity, changesin water quality between sampling and analysis,and complexing of cations by organic constituentsand colloids (Hem, 1989). The extreme and uniquewater-quality conditions at the Bairstow Landfill,particularly at the four slag wells, may make thesesamples unstable at land surface and require non-standard methods of preservation and analysis.

In addition to the errors introduced by sam-pling, preservation, and analysis, saturation indicescalculated by WATEQPF may be affected by in-accuracies in the thermodynamic data base (Balland Nordstrom, 1991). Thermodynamic data gen-erally are more reliable for common rock-formingminerals with simple mineral structure but maycontain significant errors for more complex andrare minerals.

Mass-Balance Simulations

The observation-well transect at the BairstowLandfill intentionally was aligned parallel to thedirection of ground-water flow so that mass bal-ances of dissolved constituents could be calculated.The main flow components simulated by the cal-culations included (1) horizontal flow conditionsalong the south-to-north ground-water flowpathtoward Lake George, (2) flow of recharge downthrough the slag pile and uppermost sands intothe intermediate-depth sands, and (3) ground-waterflow up from the deeper sands to converge withshallow ground-water flow at the intermediate-depth sands. When reviewing results of themass-balance calculations, the alternate, occa-sional possibility of flow reversals also needsto be considered relative to the apparent precisionof the results.

The solid phases included in the mass-balance models were limited to the mineralsdetected in significant quantities in the X-raydiffraction analyses—calcite, dolomite, and quartz(expressed as SiO2 in NETPATH). The mineralsminrecordite, cristobalite, and barian celestite were


not part of the NETPATH data base and, becausethey were only detected infrequently and in rela-tively small abundances in X-ray diffractograms,they were not added to the NETPATH data base.Other phases that exist in the NETPATH database were not considered in the Bairstow Landfillmodels because (1) they were not identified in theX-ray diffraction analyses, and (2) the relativelyminute abundances of other minerals probablydisqualifies them from having a major impact onthe geochemical system.

Calcium, magnesium, and silica concentra-tions were used as constraints for the mass-balancemodels. Chloride was used as a fourth constraintof mixing proportions calculated for models whereground water from two wells combined to form thewater quality observed at a third well. In all mod-els, the situation’s number of constraints equalledthe degrees of freedom to obtain a unique solution.

The non-mixing mass-balance models indi-cated that slag drainage into the Calumet aquifermay precipitate calcite near the slag–aquifer inter-face (fig. 11). The simulated masses of calciteprecipitated from solution, 4.92 and 5.69 milli-moles per kilogram of water, as ground watermoves from BH-31 to BH-32S and from BH-32SLto BH-33S. These mass transfers were largerelative to others calculated for this model. Themass-balance models also indicated that calcitemay be precipitating as ground water moves fromthe deeper aquifer (BH-32D) to the intermediate-depth aquifer (BH-33I) and as ground water flowshorizontally, such as from BH-32I to BH-33I.The possibility that changes in concentrations ofcalcium and carbonate can be attributed to dilutionof slag-contact ground water with less stronglyaffected ground water is addressed by the mixingmass-balance models. The calcite-rich precipitateobserved along the Lake George shoreline con-firms that some calcite precipitation is occurring;the mass transfer between BH-34SS and LakeGeorge is 5.74 millimoles per kilogram of water.

The non-mixing mass-balance calculationsindicate that dolomite is neither precipitating nordissolving in significant quantities; mass transfersrange from –1.56 to +1.13 millimoles per kilogramof water. The models indicate that dolomite disso-lution may be occurring where ground water isflowing from slag into the shallow aquifer orinto Lake George. The mass-balance models alsoindicate that dolomite may be precipitating whereground water flows from the shallow aquifer(BH-32S) and deeper aquifer (BH-32D) to theintermediate-depth aquifer (BH-33I); however,laboratory studies have shown that dolomiteformation occurs by calcite replacement wheremagnesium/calcium is greater than 100 and thatthe process is relatively slow (Ehlers and Blatt,1980).

The mass-balance model indicates that silica,present as quartz and cristobalite in slag and asquartz in the aquifer, may be dissolving from theaquifer matrix where ground water flows fromthe slag into the shallow aquifer. Dissolution ofsilicate minerals where slag drainage enters theaquifer ranges from 0.40 to 0.46 millimoles perkilogram of water, approximately 10 times lessthan the transfer rate for calcite. The transfer rateactually may be lower than the model calculatedvalues because silica concentrations in BH-32Dindicate that a significant silica concentration maynaturally be present in the Calumet aquifer; there-fore the silica concentration in the aquifer is notentirely the result of quartz and cristobalite disso-lution. The low concentrations of dissolved silicain the slag-contact wells, despite the abundanceof quartz and cristobalite in X-ray diffractogramsand pH values in excess of 12, imply that quartzdissolution may be kinetically inhibited.

Mass-balance calculations indicate that silicamay precipitate where ground water dischargesfrom the aquifer into Lake George; the mass trans-fer for ground water flowing from BH-34ND to theLake George sample point is –1.18 millimoles ofsilica per kilogram of water. A more likely processto account for the change in silica concentrations

Mass-Balance Simulations 29

��

��

��

��



{{{{{{{{{{{{{{{{{{

||||||||||||||||||

��

��

��

��

yyyyyyyyyyyyyyyyyy

zzzzzzzzzzzzzzzzzz

{{{{{{{{{{{{{{{{{{

||||||||||||||||||

��

��

��

��

Dire

ctio

n of

gro

und-

wat

er fl

ow

Pot

entio

met

ric s

urfa

ce

EX

PLA

NA

TIO

N

��y{��z|

��z|

��z|

�z

��yz{|��y{

�|��y{


across the ground-water/surface-water interface isdilution and dispersion of silica in the more dilutewater of Lake George. Some combination of thetwo processes also may explain the observations.

Mass-balance models also were developedto evaluate the importance of ground-water mixingrelative to concomitant mineral precipitation anddissolution to explain the observed changes inground-water quality along the Bairstow Landfillflowpath. For example, the water quality atBH-32S alternately may be produced by mixingground water from BH-31 and BH-32SL or byprecipitating or dissolving calcite, dolomite, andsilica.

Concentrations of chloride were used as amodel constraint to determine the mixing propor-tions. Chloride is recognized as a conservative ion,and changes in concentration are likely attributableto ground-water mixing. Besides chloride, all otherconstraints (calcium, magnesium, and silica) andphases (calcite, dolomite, and SiO2) remained thesame as those used in the previously describednon-mixing models.

The results of mixing mass-balance modelsare expressed as equations that relate mixing pro-portions of the two initial well chemistries toproduce the water quality at the final downgradientwell. Ground-water flowpaths determined fromwater-level data were used to select four potentialmixing situations at the study site. Results of thesemodels are presented in table 5.

Mixing model 1 explores the possibility thatground-water quality at well BH-32S is a resultof combining water from BH-31 and BH-32SL(table 5). The calculations indicate that approxi-mately 97 parts BH-31 ground water and 3 partsBH-32SL water plus calcite precipitation of4.94 millimoles per kilogram of water and dis-solution of dolomite and SiO2 at 0.180 and0.407 millimoles per kilogram of water, respec-tively, would yield the ground water observed atwell BH-32S. These mass transfers are similar tothe previously calculated two-component flowsystem from BH-31 to BH-32S.

Mixing model 2 investigated the possibilitythat ground-water quality at well BH-32I is a resultof mixing ground water from BH-31, BH-32S,and BH-32D; these flowpaths are indicated bywater-level data. Model results indicate the waterquality at BH-32I can be simulated by mixingabout 11 parts of water from BH-31, 38 partsof water from BH-32S, and 51 parts of waterfrom BH-32D, with a net dissolution of 0.186and 0.304 millimoles per kilograms of water ofdolomite and SiO2, respectively.

Mixing model 3 attempted to explain theground-water quality at well BH-33S by mixingwater from wells BH-32S, BH-33SL, and BH-33I.A model could not be calculated based on thewater-quality information measured in these wells.The high chloride concentration measured in waterfrom well BH-33S was a limiting factor in calcu-lating a satisfactory model. None of the initialground-water compositions contained sufficientchloride to define the high chloride concentrationsin BH-33S ground water.

Mixing model 4 derived the water qualityfrom well BH-33I by mixing water from wellsBH-32S, BH-32I, and BH-33S. Ground-waterlevels did not indicate flow from BH-32I toBH-33I, but horizontal flow of water with proper-ties similar to BH-32I toward BH-33I maycommonly occur. Results indicated that waterquality at well BH-33I could be simulated bymixing about 1 part water from BH-32I with 99parts water from BH-33S, dissolving 0.033 and0.085 millimoles per kilogram of water ofcalcite and SiO2, respectively, and precipitating0.151 millimoles dolomite per kilogram of water.Calculations indicate that ground water at BH-33Idid not require a contribution from well BH-32S.Water-level data did not indicate a significant com-ponent of flow from BH-33S to BH-33I, but themixing model indicates that this may be the mostcommon situation. Measurements of water levelswere taken only on one occasion and may not rep-resent all details of the prevalent flow regime.

Mass-B

alance Sim

ulations 31

Table 5. Geochemical mixing models and mass-transfer estimates along ground-water flowpaths at Bairstow Landfill, Hammond, Ind.[mmol/kg, millimoles per kilogram of water; SiO2, quartz or cristobalite; --, not used or calculated]

1Negative mass transfer indicates mineral precipitation from the dissolved solids in the mixed waters. Positive mass transfer indicates mineral dissolution contributing dissolved solids to the mixed waters.

Mixingmodel Initial Well 1 Initial Well 2 Initial Well 3 Final Well

Simulatedvolume ofwater frominitial well 1in final well

(percent)


(percent)


(percent)

Simulatedmass

transferof calcite(mmol/kg)

Simulatedmass

transferof dolomite(mmol/kg)

Simulatedmass transfer

of SiO 2(mmol/kg)

1 BH-31 BH-32SL -- BH-32S 96.6 3.36 -- -4.941 0.180 0.407

2 BH-31 BH-32S BH-32D BH-32I 11.1 38.0 50.8 .000 .186 .304

3 BH-32S BH-33SL BH-33I BH-33S no models -- -- -- -- --

4 BH-32S BH-32I BH-33S BH-33I 0.000 1.07 98.9 -.033 .151 -.085


No mixing combination could account forthe chloride concentration in BH-33S because thevalue in that well exceeded the concentration inboth wells immediately upgradient. Similarly,an appropriate mixing model could not be foundby combining ground water at BH-34ND andBH-34SS to derive the water quality in the samplefrom Lake George because the chloride in thelake is higher than in both ground-water samples.Lake George likely has a source of chloride, suchas from road-deicer-affected runoff, in addition toground-water discharge.

Several situations can lead to inaccuraciesin mass-balance models, including:

1) selection of water-quality data fromobservation wells that are not alongthe same ground-water flowpath,

2) analytical mass-balance errors,

3) hydrodynamic dispersion in the aquifer,

4) departure from steady-state conditions,

5) significant and unaccounted recharge(dilution) or evaporation during theperiod that the ground water flows fromthe initial to final observation well, and

6) unknown or unquantified ion exchangeand mineral impurities.

CHEMICAL CHARACTERISTICS OFSLAG-AFFECTED GROUND WATER

The statistical summary of the water-qualitydata identified properties and constituents that havebeen influenced by ground-water interaction withslag. Table 6 (back of report) presents calculatedvalues of the total number of measurements in thedata set, the median (middle) data value, the mini-mum and maximum values from the data set, andthe first and third quartile (Q1 and Q3) that are thedata values at the 25th and 75th positions of a hier-archical ordering of the data.

The statistical summary indicates that water-quality properties that generally are elevated inwater from slag-contact wells include alkalinity,pH, and specific conductance. Alkalinity generallyis elevated in water from slag-contact wells, rela-tive to other ground-water settings, but not allslag-contact wells have high alkalinity values.Alkalinity values range from 24.9 to 884 mg/L inwater from slag-contact wells, with a median of279 mg/L. Almost all of the highest alkalinityvalues are from slag-contact wells; however,the highest alkalinity value in the data set wasmeasured at a hazardous-waste-disposal site.The most consistently observed effect of slag onground water is elevated pH. The pH values ob-served in water from 21 slag-contact wells rangedfrom 6.60 to 12.3, with median of 8.70. Waterfrom slag-affected wells also has higher pHvalues, ranging from 6.9 to 9.90 than values inbackground water that ranged from 6.0 to 7.70.Specific conductance values, a bulk measure ofdissolved solids, also are highest in water fromslag-contact wells.

Numerous chemical elements can be elevatedin slag-contact wells. Major ions with higherconcentrations in water from slag-contact wellsinclude calcium, potassium, sodium, chloride,and occasionally magnesium and sulfate. Themedian calcium concentration is more than threetimes greater in water from slag-contact wells thanfrom background wells. The median potassiumconcentration in water from slag-contact wells(25.1 mg/L) was more than 20 times greater thanfrom background wells. Potassium concentrationsin water from slag-contact wells range from 3.12 to170 mg/L. More than 75 percent of water samplesfrom background wells contained less potassiumthan the lowest measured concentration in allslag-contact samples. The median sodium concen-tration in water from slag-contact wells is eighttimes greater than in background ground water,and the median chloride concentration in slag-contact wells (69 mg/L) is more than five timesthat of water from background wells. Magnesium

Conclusions 33

concentrations in slag-contact ground water varythe most, ranging from 0.010 to 211 mg/L, butthe median value is about 5.0 mg/L less than themedian concentration of water from slag-affectedwells (22.8 mg/L). The median sulfate concentra-tion in slag-contact wells is 190 mg/L, compared to72 and 27.3 mg/L in slag-affected and backgroundwells, respectively, but the highest measured valueoccurred in a slag-affected well.

Trace elements having higher concentrationsin water from slag-contact wells include aluminumand barium and less frequently chromium, cobalt,copper, cyanide, manganese, mercury, nickel, andvanadium. The median aluminum concentration inslag-contact ground water is 49.7µg/L comparedto 23.5 and 23.5µg/L for water from slag-affectedand background wells, respectively. The medianbarium concentration in slag-contact ground wateris 128µg/L compared to 58.0 and 31.1µg/L forslag-affected and background ground water,respectively. Chromium, cobalt, copper, cyanide,manganese, nickel, and vanadium in slag-contactground water have median concentrations that areabout the same as slag-affected and backgroundground water. The range of chromium, cobalt,copper, cyanide, manganese, nickel, and vanadiumconcentrations in slag-contact ground water, how-ever, is more variable than in slag-affected orbackground ground water; usually the maximumconcentration is several times higher in waterfrom slag-contact wells. For example, the medianconcentration of cyanide, a trace species, for allground water is 10.0µg/L (the minimum reportinglimit) but the maximum concentrations for slag-contact, slag-affected, and background groundwater are 212, 31.4, and 10.0µg/L, respectively.Some trace elements or species like cyanide arenot present in solid slag and may indicate possibledisposal with industrial waste.

Total organic carbon (TOC) and suspended-solids concentrations also are high in slag-contactground water relative to slag-affected andbackground ground water. Concentrations ofTOC in slag-contact samples range from 3.70 to209 mg/L, with median value 15.1 mg/L, com-pared to concentrations of TOC in background

ground water that range from


(1) Concentrations of calcium, potassium,sodium, and sulfate were highest in water fromwells screened partially or fully in slag. Potassiumconcentrations in ground water ranged from 2.9 to120 mg/L, were highest in water from slag depos-its, and decreased with depth. Silica concentrationswere highest in wells screened directly beneath theslag–aquifer interface, and magnesium concentra-tions were highest in intermediate and deep aquiferwells. Silica concentrations in shallow and inter-mediate aquifer wells ranged from 27 to 41 mg/Land were about 10 times greater than those in waterfrom slag deposits. The highest concentrations foraluminum, barium, molybdenum, nickel, and sele-nium were in the slag. The highest concentrationsfor chromium, lead, and zinc were in ground waterfrom immediately below the slag–aquifer interface.Nitrite in ground-water from slag and ammoniumin ground water from below the slag were the mostabundant nutrients.

(2) Concentrations of several major ionsand trace elements in water relate to pH valuesand bicarbonate concentrations and their effect onmineral-water interactions. For example, the sam-ples with the largest concentrations in water ofcalcium, potassium, sodium, sulfate, aluminum,barium, molybdenum, nickel, and selenium, alsohave pH values ranging from 11.9 to 12.3 and arefrom slag wells. By comparison, water from wellswith larger concentrations of silica and smallerconcentrations of calcium also have smaller pHvalues. Water with the largest concentrations ofchromium, lead, and zinc also generally havepH values that range from 9.0 to 9.9. Bicarbonateconcentrations, as represented by alkalinity, aresubstantially greater in water from slag wells.Larger alkalinity values favor greater partial pres-sures of carbon dioxide and the dissolution ofpotassium and sodium aluminosilicate minerals(Stumm and Morgan, 1981, p. 545),

hydrology and geochemistry of a slag-affected … · 2013. 10. 2. · by e. randall bayless,...

Documents