Prepared in cooperation with the U.S. Army Corps of Engineers

Geochemistry and Microbiology of Groundwater 

and Solids from Extraction and Monitoring 

Wells and Their Relation to Well Efficiency at a 

Federally Operated Confined Disposal Facility, 

East Chicago, Indiana

Scientific Investigations Report 2018–5073

U.S. Department of the Interior

U.S. Geological Survey
Cover. Photograph of groundwater-quality sampling equipment at well EW–14A. Photograph taken on October 8, 2014, 

by Patrick C. Mills, U.S. Geological Survey (retired).
Geochemistry and Microbiology 

of Groundwater and Solids from 

Extraction and Monitoring Wells and 

Their Relation to Well Efficiency at a 

Federally Operated Confined Disposal 

Facility, East Chicago, Indiana

By E. Randall Bayless, Travis R. Cole, David C. Lampe, Rebecca E. Travis, 

Marjorie S. Schulz, and Paul M. Buszka

Prepared in cooperation with the U.S. Army Corps of Engineers

Scientific Investigations Report 2018–5073

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

RYAN K. ZINKE, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2018

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

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Suggested citation:

Bayless, E.R., Cole, T.R., Lampe, D.C., Travis, R.E., Schulz, M.S, and Buszka, P.M., 2018, Geochemistry and microbiology of groundwater and solids from extraction and monitoring wells and their relation to well efficiency at a Federally 

operated confined disposal facility, East Chicago, Indiana: U.S. Geological Survey Scientific Investigations Report 

2018–5073, 134 p., https://doi.org/10.3133/sir20185073.

ISSN 2328-0328 (online)
iii

Acknowledgments

The authors and the U.S. Geological Survey (USGS) gratefully recognize the contributions of 

many persons to this study. Ben O’Neil and Le Thai of the U.S. Army Corps of Engineers provided background information and well construction diagrams for the confined disposal facility 

(CDF) gradient control system, project supervision, and reviews of this report. Scott Peterson of 

O’Brien & Gere provided groundwater levels, information describing pump failures, and assisted 

with accessing wells at the site. 

Patrick C. Mills, USGS, assisted with sample collection. Sara Peek, USGS, analyzed solids from 

CDF wells for carbon and sulfur isotopes. Kate Campbell, USGS, provided semi-quantitative 

X-ray diffraction analysis of solids collected from CDF wells. John Fitzpatrick, USGS, provided 

inductively coupled plasma mass spectrometry analyses of chemically digested solids from CDF 

wells. James Landmeyer, USGS, provided a chromatograph to determine the presence of hydrocarbons in a scraping taken from a pump at the CDF.

v

Contents

Acknowledgments........................................................................................................................................iii

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

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

Site History.............................................................................................................................................2

Review of Well and Pump Biofouling ......................................................................................6

Purpose and Scope ..............................................................................................................................9

Description of the Study Area ............................................................................................................9

Hydrogeologic Setting .......................................................................................................................10

Methods of Investigation............................................................................................................................13

Well Selection ....................................................................................................................................13

Water-Sample Collection and Laboratory Analysis......................................................................14

Dissolved Gas Samples and Quality Assurance ...........................................................................20

Microbiological Sample Collection and Laboratory Analysis .....................................................21

Solid-Phase Sample Collection and Laboratory Analysis............................................................21

Computed Equilibrium Mineral-Saturation Indices.......................................................................24

Quality-Assurance Procedures........................................................................................................26

Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring 

Wells.................................................................................................................................................26

Groundwater Levels ...........................................................................................................................27

Quality-Assurance Data.....................................................................................................................32

Water Chemistry .................................................................................................................................32

Dissolved Gases..................................................................................................................................46

Microbiological Activity ....................................................................................................................59

Heterotrophic Aerobic Bacteria..............................................................................................59

Slime-Forming Bacteria............................................................................................................59

Iron-Related Bacteria ...............................................................................................................59

Sulfate-Reducing Bacteria.......................................................................................................67

X-Ray Diffraction Analyses ...............................................................................................................72

Scanning Electron Microscopy........................................................................................................72

Inductively Coupled Plasma Mass Spectrometry Analyses........................................................72

Carbon and Sulfur Isotope Analyses...............................................................................................72

Equilibrium Mineral-Saturation Indices..........................................................................................78

Petroleum Hydrocarbons ..................................................................................................................84

Relation of Geochemical and Microbiologic Characteristics to Well Efficiency .............................84

Summary and Conclusions.........................................................................................................................89

Limitations.....................................................................................................................................................92

References Cited..........................................................................................................................................93

Appendix 1. Driller’s Records for Wells at the Confined Disposal Facility used by this Study ......97

Appendix 2. X-Ray Diffractograms of Solids Collected on Filter with 0.45-Micron Pore Size during 

Water-Quality Sampling or from Suspended Sediment in Groundwater Samples Collected 

at the Confined Disposal Facility ...............................................................................................106

Appendix 3. Scanning Electron Micrographs of Solid Samples Collected on Filter with 

0.45-Micron Pore Size during Water-Quality Sampling or from Suspended Sediment in 

Groundwater Samples Collected at the Confined Disposal Facility ....................................115
vi

Figures

1. Map showing location of the confined disposal facility at East Chicago, Indiana............3

2. Map showing locations of monitoring and extraction wells at the confined disposal

facility .............................................................................................................................................4

3. Map showing estimated thickness of light, nonaqueous phase liquids on

groundwater near the confined disposal facility and Indiana Harbor Canal, East

Chicago, Indiana ...........................................................................................................................5

4. Photograph showing solid material adhered to a pump removed from extraction

well EW–4B on May 8, 2014 ........................................................................................................6

5. Graph showing pump replacement frequency data for October 2014 through

September 2015.............................................................................................................................7

6. Schematic diagram showing redox environments near a borehole. Diagram

modified from Vance (1998).........................................................................................................8

7. Graphs showing, A, dates of water-quality sample collection and precipitation and

B, precipitation record at Gary Airport for January 1, 2014, through December 31,

2014 ...............................................................................................................................................16

8. Schematic diagram of the borehole and pump-hydrant system in extraction wells

at the confined disposal facility ...............................................................................................18

9. Photographs showing sampling instruments used to collect water-quality samples

at the confined disposal facility. A, enclosed sampling chamber, manifold,

flow-through cell, water-quality sonde, and sampling lines attached to well

hydrant; B, close-up view of flow-through cell; and C, close-up view of sampling

manifold........................................................................................................................................19

10. Photographs showing microbiological activity reaction tests for A, sterile buffer

water on day 1; B, monitoring well MW–11A positive reactivity on day 2; and 

C, monitoring well MW–4A positive reactivity on day 4.......................................................22

11. Hydrograph for U.S. Geological Survey monitoring well Lake 13.......................................27

12. Groundwater hydrographs for extraction and monitoring wells at the confined

disposal facility during January 1, 2014, through December 31, 2014. A, EW–4B;

B, EW–11B; C, EW–14A; D, MW–4A; E, MW–11A; and F, MW–14A...................................28

13. Groundwater hydrographs for extraction and monitoring wells at the confined

disposal facility during September 1, 2014, through November 30, 2014. A, EW–4B;

B, EW–11B; C, EW–14A; D, MW–4A; E, MW–11A; and F, MW–14A...................................30

14. Distribution of dissolved oxygen concentrations in groundwater samples collected

onsite from selected wells at the confined disposal facility ...............................................42

15. Distribution of the oxidation-reduction potential in groundwater samples from

selected wells at the confined disposal facility ....................................................................43

16. Distribution of sulfide concentrations in groundwater samples from selected wells

at the confined disposal facility ...............................................................................................44

17. Distribution of sulfate concentrations in groundwater samples from selected wells

at the confined disposal facility ...............................................................................................45

18. Distribution of iron concentrations in groundwater samples from selected wells at

the confined disposal facility....................................................................................................46

19. Eh-pH phase diagram showing iron stability fields and data from the confined

disposal facility ...........................................................................................................................47

20. Bar charts showing concentrations of major ions through time during four pumping

regimes—regime 1, September 9–11, 2014 (normal operating conditions); regime

2, October 7–9, 2014 (after pump was not operating for at least 8 hours); regime 3,

October 20–23, 2014 (after pumping had resumed for 7 days); and regime 4,

November 3–6, 2014 (after pumping had resumed for 14 days)..........................................48
vii

21. Bar charts showing populations of heterotrophic, slime-forming, iron-related, and

sulfate-reducing bacteria subtypes through time during four pumping regimes,

including normal operating conditions (September 9–11, 2014), after pump was not

operating for at least 8 hours (October 7–9, 2014), after pumping had resumed for 7

days (October 20–23, 2014), and after pumping had resumed for 14 days (November

3–6, 2014)......................................................................................................................................60

22. Scanning electron microscopy (SEM) images of solid-phase samples from

extraction wells EW–4D and EW–20D at the confined disposal facility showing

euhedral sulfur and calcite, amorphous material, and biofilms .........................................74

23. Plot of sulfur isotopic composition with weight percent sulfur in samples collected

at the confined disposal facility ...............................................................................................79

24. Plot of sulfur and carbon isotopic composition in samples collected at the

combined disposal facility.........................................................................................................79

25. Mineral-saturation indices computed for groundwater samples collected on four

occasions at the confined disposal facility............................................................................84

26. Mineral-saturation indices computed for hypothetical mixtures of groundwater

from wells D40 and EW–4B at the confined disposal facility..............................................86

27. Chromatograph scan of scrapings collected from the pump in well EW–4B on

November 3, 2016........................................................................................................................87

28. Diagram showing the redox environment for groundwater in six wells at the

confined disposal facility. .........................................................................................................88

Tables

1. Hydrocarbons measured in groundwater samples collected June 19, 2014, at the

confined disposal facility...........................................................................................................11

2. Number and type of analyses on groundwater and solids collected from wells at

the confined disposal facility....................................................................................................13

3. Characteristics of extraction and monitoring wells used for this study ...........................15

4. Tested pumping regimes at the confined disposal facility ..................................................17

5. General and subtypes of bacteria measured in groundwater samples............................21

6. Example input file for the PHREEQC program for groundwater chemistry measured

in extraction well EW–4B on September 11, 2014.................................................................25

7. Water-quality data for groundwater samples collected at the confined disposal

facility ...........................................................................................................................................33

8. Bacterial quality-assurance in groundwater samples from wells at the confined

disposal facility ...........................................................................................................................41

9. Redox category and process as computed for groundwater samples .............................53

10. Laboratory measured concentrations of dissolved gases in environmental and

replicate samples of groundwater from the confined disposal facility,

quality-assurance statistics, and hypothetical concentrations of dissolved gas in

equilibrium with the atmosphere .............................................................................................54

11. Heterotrophic aerobic bacteria activity and population in groundwater samples

from wells at the confined disposal facility............................................................................65

12. Slime-forming bacteria activity and population in groundwater from wells at the

confined disposal facility...........................................................................................................66

13. Iron-related bacteria activity and population in groundwater from wells at the

confined disposal facility...........................................................................................................68
viii

14. Sulfate-reducing bacteria activity and population in groundwater from wells at the

confined disposal facility...........................................................................................................70

15. Summary of X-ray diffraction analysis of solids collected as pump scrapings from

wells at the confined disposal facility.....................................................................................72

16. Estimated quantitative mineralogy from X-ray diffraction analysis of solids

collected as pump scrapings from wells at the confined disposal facility.......................73

17. Summary of scanning electron microscopy/energy dispersive spectroscopy and

scanning electron microscopy/backscatter electrons observations made on solids

collected as pump scrapings from wells at the confined disposal facility.......................75

18. Inductively coupled plasma mass spectroscopy analyses of samples collected as

pump scrapings and on filter with 0.45-micron pore size during groundwater

sample collection at the confined disposal facility...............................................................76

19. Carbon and sulfur isotope composition for solid samples collected as pump

scrapings from wells at the confined disposal facility.........................................................78

20. Mineral saturation indices computed using PHREEQC and groundwater quality

data collected at the confined disposal facility from September 9 to November 6,

2014 ...............................................................................................................................................80

21. Mineral-saturation indices computed using PHREEQC and mixtures of groundwater

from D40 (June 14, 1993) and EW–4B (October 9, 2014).......................................................85

22. Summary of potential issues affecting pump efficiency at the confined disposal

facility with synopsis of impacts, mitigation strategies, and criteria for evaluating

improvements from mitigation as developed from literature sources and

observations from this investigation .......................................................................................90
ix

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.4047 hectare (ha)

acre 0.4047 square hectometer (hm2)

acre 0.004047 square kilometer (km2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L)

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

Mass

ounce, avoirdupois (oz) 28.35 gram (g)

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

°F = (1.8 × °C) + 32.

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

°C = (°F – 32) / 1.8.

Datums

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29) or North American Vertical Datum of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.
x

Supplemental Information

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25 °C). 

Concentrations of chemical constituents in water are given in milligrams per liter (mg/L) and 

micrograms per liter (μg/ L). Chemical concentrations and water temperature are given in

metric units. 

A milligram per liter is a unit expressing the concentration of chemical constituents in solution 

as weight (milligrams) of solute per unit volume (liter) of water. For water with dissolved-solids 

concentrations less than 7,000 mg/L, the numerical value for milligrams per liter is the same as 

for concentrations in parts per million.

A concentration of 1,000 μg/L is equivalent to 1 mg/L. For water with dissolved-solids 

concentrations less than 7,000 mg/L, the numerical value for micrograms per liter is the 

same as for concentrations in parts per billion.

The mole ratio of two substances expresses the amount of chemical constituents in solution 

as the weight of a chemical substance, in milligrams (10-3 g), in a liter of water, divided by the 

atomic weight of one atom or molecule of its composition elements, in grams (one mole), divided 

by the amount of a second substance, also expressed in moles. 

One mole is equivalent to 1,000 millimoles.

One atmosphere (atm) of pressure is equivalent to 760 millimeters of mercury.

δ (delta), as used in this report, refers to the stable isotope ratio δx = [(Rx/RSTD)-1] x 1,000, where 

Rx and RSTD are the 13C/12C and 34S/32S values of the sample and reference standard. The value of 

δ is generally expressed in parts per thousand (o/oo, or per mil).
xi

Abbreviations

atm atmosphere

BSE backscatter electrons

CDF confined disposal facility

CFU/mL colony forming units per milliliter

EDS energy dispersive spectroscopy

MRL minimum reporting limit

NAVD 88 North American Vertical Datum of 1988

NBS National Bureau of Standards

NWQL National Water Quality Laboratory

NTU nephelometric turbidity units

RPD relative percent difference

SEM scanning electron microscopy

USACE U.S. Army Corps of Engineers

USGS U.S. Geological Survey

XRD X-ray diffraction

Geochemistry and Microbiology of Groundwater and 

Solids from Extraction and Monitoring Wells and Their 

Relation to Well Efficiency at a Federally Operated 

Confined Disposal Facility, East Chicago, Indiana

By E. Randall Bayless, Travis R. Cole, David C. Lampe, Rebecca E. Travis, Marjorie S. Schulz, and 

Paul M. Buszka

Abstract

In cooperation with the U.S. Army Corps of Engineers, 

Chicago District, the U.S. Geological Survey investigated the 

processes affecting water quality, geochemistry, and microbiology in representative extraction and monitoring wells at 

a confined disposal facility (CDF) in East Chicago, Indiana. 

The CDF is a 140-acre Federally-managed facility that was 

the former location of an oil refinery and is now used for the 

long-term disposal and storage of dredge material from the 

Indiana Harbor and Indiana Harbor Canal. Residual petroleum hydrocarbons and leachate from the CDF are contained 

within the facility by use of a groundwater cutoff wall. The 

wall consists of a soil-bentonite slurry and a gradient control 

system made up of an automated network of 96 extraction 

wells, 42 monitoring wells, and 2 ultrasonic sensors that maintain an inward hydraulic gradient at the site. The pumps in 

the extraction wells require vigilant maintenance and must be 

replaced when unable to withdraw water at a rate sufficient to 

maintain the required inward gradient. The wells are screened 

in the Calumet aquifer, a coarse-grained sand and gravel unit 

that extends approximately 35 feet below the land surface 

and is not utilized for drinking-water supply at the CDF or in 

the surrounding area. This study was initiated to identify the 

cause of decreased pump discharges and to identify potential 

mitigation strategies.

For this study, the U.S. Geological Survey collected 

groundwater and solids from monitoring and extraction wells. 

Groundwater samples were collected during June 2014 for 

precautionary health screening and on four occasions during September 2014 through November 2014. Groundwater 

samples collected from two extraction wells during June 2014 

were analyzed for concentrations of anthropogenic organic 

constituents. During September through November 2014, 

groundwater samples were collected from one additional 

extraction well, and samples from three monitoring wells 

were analyzed for concentrations of inorganic and organic 

constituents, dissolved gases, and bacterial abundance and 

diversity. Solid samples were collected during April 2014, 

during September 2014 through November 2014, and during November 2016. Solid samples were collected from the 

exterior of extraction-well pumps and as flocculent from water 

samples. Solid samples were collected from 10 wells, including 1 extraction well and 3 monitoring wells sampled for water 

quality. Solid samples were analyzed for mineralogy, solidphase habit, geochemistry, and organic composition. 

The following is a list of observations that were made 

during this study: (1) the water quality is substantially variable 

among the six well locations sampled as part of this study—

lower (more negative) redox values and higher concentrations of many constituents (including calcium, magnesium, 

sodium, and sulfate) and properties (including dissolved 

solids, hardness, and turbidity) were detected in sampled wells 

located near the extraction wells with the highest frequency 

of failure; (2) water-level drawdown is variable between 

extraction wells—wells with the greatest drawdown may pull 

deeper groundwater into the borehole; (3) dissolved gas results 

indicate reducing oxidation-reduction processes in the aquifer 

material that can feasibly contribute iron, carbon dioxide, and 

other byproducts from hydrocarbon degradation to precipitates and solids that accumulate on and impair pump operation; (4) crystalline and amorphous solid-phase minerals are 

precipitating in the borehole; (5) several types of bacteria are 

present in water pumped from extraction wells and are likely 

responsible for bonding mineral and microbiologic matter to 

the pump (and other well components); and (6) bacteria may 

create microenvironments that facilitate precipitation of solids 

or inhibit dissolution of unstable minerals once the bacteria 

adhere to biofilm attached to the pump. Results of the study 

indicate that bacteria may be accumulating and entrapping 

solid material on the exterior of pumps. This accumulation 

reduces heat transfer and water discharge from the pump and 

may lead to decreased efficiency or mechanical failure. Observations could not be made on the well screen, gravel pack, or 

surrounding geologic formation; therefore, mitigating measures in the borehole may not solve well-productivity issues.
2 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Remedies for the pump fouling problems were derived 

from the review and interpretation of data collected during 

this study and from information documented in other sources 

about groundwater well fouling. Potential remedies to problems associated with pump fouling at the CDF may include 

the following: (1) reducing attractiveness of the extraction 

wells for microbiological growth by modifying the chemical 

or physical environment of the well, (2) modifying the pump 

exterior to decrease microbiological adherence, (3) changing 

the pumping regime to control the chemistry of water entering 

the well from the surrounding aquifer material, (4) modifying the pumps to be less physically and thermally attractive, 

and (5) removing hydrocarbons from groundwater and the 

aquifer material surrounding the wells or adding surfactants 

to make them more mobile. Pilot scale testing may be necessary to identify the most effective treatment or combination 

of treatments.

Introduction

The U.S. Geological Survey (USGS), in cooperation 

with the U.S. Army Corps of Engineers (USACE), led a study 

during June 2014 through November 2014 to specifically 

identify the hydrologic, chemical, and microbiologic processes 

affecting declining pump efficiency and frequent pump failure 

at a confined disposal facility (CDF) in East Chicago, Ind. 

(fig. 1). A decline in groundwater pump efficiency through 

time is common and can be attributed to biofouling (Sterrett, 

2007). To better understand the causes behind declining pump 

efficiency, data were collected to describe the geochemistry 

and microbiology of groundwater and solids collected from 

extraction and monitoring wells at the CDF.

Site History

 The efficiency of groundwater-extraction wells used to 

maintain an inward hydraulic gradient at the CDF site near 

East Chicago, Ind., is of necessary operational concern for 

the site operator, the USACE, Chicago District. The inward 

hydraulic gradient is maintained by use of a network of monitoring and extraction wells (fig. 2). 

The site was formerly the home of oil-refining operations. 

In 1981, the property owner filed for bankruptcy; therefore, all 

aboveground materials and structures related to refinery operations were removed, and the site was covered with a layer of 

clean soil. Groundwater monitoring began in 1991 following 

the detection of hydrocarbon contamination, and a groundwater-recovery system was installed in 1992 along the southern 

boundary of the CDF property on the north side of the Lake 

George Branch (fig. 1). Organic compounds have been identified in soil and water samples since monitoring began and 

were observed during installation of the extraction and monitoring wells that currently regulate water levels at the CDF 

(Cohen and others, 2002) (fig. 3). Hydrocarbon seepage along 

the south margin of the property and into the Lake George 

Branch also was described in Cohen and others (2002). The 

location of hydrocarbons at the site differs through time.

The Lake George Branch is a segment of the Indiana 

Harbor Canal (fig. 1). The Lake George Branch and Indiana 

Harbor Canal are connected to Lake Michigan (fig. 1) and 

water levels in the Indiana Harbor Canal vary continually in 

response to water levels in Lake Michigan and discharges 

from the Grand Calumet River (fig. 1), another tributary of the 

Indiana Harbor Canal. The gradient-control system at the CDF 

automatically responds to changing water levels in groundwater adjacent to the Indiana Harbor Canal.

The study area is underlain by the Calumet aquifer and 

wells at the CDF are completed in that geologic unit. The 

Calumet aquifer is a coarse-grained sand and gravel unit that 

extends approximately 35 feet (ft) below the land surface. The 

Calumet aquifer is not utilized for drinking-water supply at the 

CDF or in the surrounding area and for purposes of this study, 

is referred to as “aquifer material”.

Maintenance of inward, horizontal hydraulic gradients on 

all sides of the CDF is a critical operating feature of the site 

that enables isolation and control of residual hydrocarbons 

and leachate from the dredged sediment as well as control of 

existing site issues. The 22 nests of 4 extraction wells were 

installed in the permeable aquifer material, surficial sand and 

gravel deposits inside a groundwater cutoff wall. The groundwater cutoff wall consists of an impermeable bentonite slurry 

that extends from land surface to at least 3 ft below the interface between the fine-grained deposit and the surficial aquifer 

material. An additional eight extraction wells were added to 

three well nests along the southern perimeter of the CDF in 

2015. Two monitoring wells are collocated with each nest of 

extraction wells. One monitoring well is located inside the 

slurry wall, and one monitoring well is outside the slurry wall. 

Pumps within the extraction wells are periodically activated 

to maintain an inward gradient between the monitoring wells. 

Extraction wells are about 30 ft with 5-ft screens at their base 

to limit the possibility for drawdown to reach the well screen. 

The wells were screened below occasional residual petroleum 

contamination from prior site activities. 

A strong hydraulic connection between wells and aquifer 

materials surrounding the well screen is necessary to allow 

accurate monitoring of water levels in the subsurface and to 

maintain withdrawal rates required to establish the inward 

gradient. A poor connection between the well and the surrounding materials can increase drawdown in the extraction 

well and delay water-level responses outside the well to 

changes in water levels inside the well. During 2012, fouling 

became evident in some extraction wells at the CDF by the 

accumulation of a black gelatinous matter that formed on the 

pump intakes. Pump efficiency progressively decreased and 

eventually required pump replacement (fig. 4). Fouling of the 

well screen, gravel pack surrounding the screen, and adjacent aquifer material was possible but was not observed nor 

indicated by withdrawal rates when new pumps were installed. 
Introduction 3

Indiana Harbor Canal

Lake George Branch

Grand Calumet

River

LAKE MICHIGAN

Whiting

Hammond

Gary

East Chicago

41° 37'

41° 39'

41° 41'

87° 30' 87° 28' 87° 26' 87° 24'

90

12

912

912

41

D40

Lake 13

INDIANA

Study area EXPLANATION

Municipal boundary

Confined disposal facility

D40 U.S. Geological Survey monitoring 

well and identifier

0.5 1 2 MILES

0 0.5 1 2 KILOMETERS

0 Base from U.S. Geological Survey digital data 1983, 1:100,000

Universal Transverse Mercator projection, Zone 16

Standard parallel 0° (Equator), Central meridian 87° W

North American Datum of 1983

Figure 1. Location of the confined disposal facility at East Chicago, Indiana.
4 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Well 

nest 14 Well 

nest 4

Lake George Branch of Indiana Harbor Canal

87° 29’ 20” 87° 29’ 10” 87° 29’ 87° 28’ 50”

41° 39’ 20”

41° 39’ 10”

41° 39’

41° 38’ 50”

EW–4A

EW–4B

EW–4C

EW–4D

MW–4A

MW–4B

EW–11D

EW–11C

EW–11B

EW–11A

MW–11A

MW–11B

EW–14D

EW–14C

EW–14B

EW–14A

MW–14B

MW–14A

Well 

nest 11

0

0 50 100 200 METERS

250 500 1,000 FEET

EW–4C

MW–4B

WS

EXPLANATION

Extraction well and site identifier

Monitoring well and site identifier

Base from Indiana Office of Information Technology,

Indiana University

State Plane Indiana West Projection

North American Vertical Datum of 1988

WS Weather station

Extraction well with petroleum contamination—

As identified from borehole log

INDIANA 912 CLINE AVENUE

NORFOLK SOUTHERN RAILROAD

INDIANAPOLIS BOULEVARD

EW–1D

EW–6C

EW–6B

EW–6A

EW–5D

EW–5B

EW–5A

EW–10D

EW–12C

EW–15C

EW–16A

EW–16B

EW–17C

EW–17D

EW–18B

EW–20D EW–18B

Figure 2. Locations of monitoring and extraction wells at the confined disposal facility.
Introduction 5

Well 

nest 14 Well 

nest 4

41° 39' 20"

41° 39' 10"

41° 39'

41° 38' 50"

EW–4A

EW–4B

EW–4C

EW–4D

EW–11D

EW–11C

EW–11B

EW–11A

EW–14D

EW–14C

EW–14B

EW–14A

Well 

nest 11

Lake George Branch of Indiana Harbor Canal

INDIANAPOLIS BOULEVARD

NORFOLK SOUTHERN RAILROAD

INDIANA 912 CLINE AVENUE

87° 29' 20" 87° 29' 10" 87° 29' 87° 28' 50"

MW–4A

MW–4B

MW–14B

MW–14A

MW–11A

MW–11B

EXPLANATION

Extraction well and site identifier

Monitoring well and site identifier

EW–4C

MW–4B

Thickness of light, nonaqueous phase liquids—

Modified from Cohen and others (2002).

Less than 0.1 foot

0.1 to 0.5 foot

Greater than 0.5 to 1.0 foot

Greater than 1.0 foot

Location of Amoco Corporation monitoring well—

As reported by Cohen and others (2002)

Location of other monitoring well—

As reported by Cohen and others (2002)

Base from Indiana Office of Information Technology,

Indiana University

State Plane Indiana West Projection

North American Vertical Datum of 1988

0

0 50 100 200 METERS

250 500 1,000 FEET

Figure 3. Estimated thickness of light, nonaqueous phase liquids on groundwater near the confined disposal 

facility and Indiana Harbor Canal, East Chicago, Indiana (modified from Cohen and others, 2002). Data represented 

on the figure were collected before 1998.
6 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Of the affected extraction wells, fouling was more frequently 

evident in some wells than in other wells (fig. 5). 

Assessing changes in water-level recovery and waterwithdrawal characteristics of extraction and monitoring wells 

and determining the physical, chemical, and microbiological causes of decreased well yield are a necessary part of 

well-efficiency evaluation at the CDF. In 2014, the USGS, in 

cooperation with the USACE, led an investigation to identify 

the source of the unknown material causing the pump fouling 

and to describe the subsurface conditions that may control the 

presence or absence of the material on the CDF property. The 

first phase of the investigation used (1) single-well aquifer 

tests of extraction wells to characterize water-level drawdown 

and recovery characteristics relative to the volume of water 

produced during a normal cycle of operation and (2) singlewell slug tests of monitoring wells to measure monitoring well 

characteristics. The tests were done at three sets of extraction 

and monitoring wells and were repeated 6 months later to 

measure changes in well properties through time. The results 

of that investigation were documented in Lampe and Unthank 

(2016) and applied to the data interpretation for this study.

A second phase of the investigation described in this 

report analyzed for possible chemical, microbiological, and 

geochemical processes in the borehole that could explain 

pump fouling. Groundwater samples were collected in the 

same three sets of paired wells on four occasions, and solidphase samples were collected from four of those wells and six 

additional wells. Paired well sets included an extraction well 

and a nearby monitoring well. Water samples were collected 

during four pumping regimes to determine if the pumping 

schedule affected the water chemistry. The four pumping 

regimes were as follows: (1) normal pumping intensity and 

duration, (2) no pumping for 8–16 hours before sample collection, (3) 2 weeks after resuming normal pumping conditions, 

and (4) 4 weeks after resuming normal pumping conditions. 

Samples were analyzed for bulk water properties, inorganic 

aqueous constituents, and dissolved gases. Discrete solidphase samples were analyzed for chemical composition, carbon and sulfur isotopes, mineralogy, solid-phase morphology, 

and bacterial activity.

The information developed from this study addresses 

aspects of the USGS water science goals and objectives to 

clarify the linkage between human water use (engineered 

hydrology) and the water cycle (natural hydrology) (Evenson 

and others, 2012). The USACE and its partners benefit by having an improved understanding of the causes of pump fouling 

at the CDF and actions that might be undertaken to inhibit 

those processes. 

The USGS, in cooperation with Federal and State partners, has published numerous reports on the groundwater, 

surface-water, and water-quality conditions in northwestern 

Indiana. The interaction of surface-water and groundwater 

levels near the Grand Calumet River and Indiana Harbor 

Canal were analyzed by Fenelon and Watson (1993) and 

Greeman (1995). The distribution of hydraulic conductivity in 

the Calumet aquifer and streambed sediments was analyzed 

by Kay and others (1996) and Duwelius and others (1996). 

The hydrology and geochemistry of slag affected aquifers 

and groundwater in northwestern Indiana were analyzed by 

Bayless and others (1998). Isotopic analyses were used to 

identify sources of groundwater, groundwater flowpaths and 

rates, to assess aquifer vulnerability in the Calumet aquifer in 

northwestern Indiana (Kay and others, 2002). These studies 

provided information and data to describe conditions in the 

area surrounding the CDF. 

Review of Well and Pump Biofouling 

Well fouling is a common issue. In about 80 percent 

of well-fouling occurrences, the well is fouled because of 

microbiological processes (Vance, 1998; Sterrett, 2007; 

Hackett, 1987). The symptoms of a fouled well screen often 

include increased drawdown during pumping, prolonged 

recovery following pumping, and poorer water quality relative 

to background conditions. The most notable degradation of 

water quality includes elevated iron or manganese concentrations and larger bacteria populations relative to background or 

Figure 4. Solid material adhered to a pump removed from 

extraction well EW–4B on May 8, 2014.
Introduction 7

Sept. 18, 2014 Nov. 7, 2014 Dec. 27, 2014 Feb. 15, 2015 Apr. 6, 2015 May 26, 2015 July 15, 2015 Sept. 3, 2015

Wells

Pump replacement date

EXPLANATION

EW–20D

EW–18D

EW–18B

EW–17D

EW–17C

EW–16B

EW–16A

EW–15C

EW–14D

EW–12C

EW–10D

EW–6C

EW–6B

EW–6A

EW–5D

EW–5B

EW–5A

EW–4D

EW–4C

EW–4B

EW–1D

Figure 5. Pump replacement frequency data for October 2014 through September 2015.

nonpumped conditions (Vance, 1998). Biofouling is the term 

generally applied to the process of accumulating biofilms on 

well screens that become a nuisance (Characklis and Cooksey, 

1983; Cullimore, 1999). Nuisance biofilms can impede the 

flow of heat across the surface of the pump, increase the fluid 

frictional resistance at the surface, and increase the rate of 

corrosion of the surface resulting in equipment stress and inefficiency (Characklis and Cooksey, 1983). 

Biofilms are bacterial products that adhere to well components. More specifically, biofilms are a complex mixture 

of active microbial cells, extracellular polymeric substances, 

polysaccharides, and other matter that attaches to submerged 

surfaces. Commonly, extracellular polymeric substances 

extend from the cells and form a tangled mass of fibers (Characklis and Cooksey, 1983). These stringy fibers are primarily 

composed of polysaccharides but may also contain glycoproteins, proteins, and nucleic acids (Characklis and Cooksey, 

1983). Polysaccharides are long chains of sugars created by 

the bonding of many monosaccharide molecules. Polysaccharides possess high molecular weight and act as carbohydrate 

storage for active cells. Extracellular polymeric substances 

may also serve the microbial cells by providing cohesive 

forces, adsorbing nutrients, binding particulates, and providing protection from rapid environmental changes including 

biocides (Smith, 1992). The active bacteria cells represent a 

minor component of the total biomass (Vance, 1998). Biofilms 

can be beneficial to the environment by removing organic and 

inorganic substances from stream water and are the basis for 

trickle filters in wastewater treatment systems. 

Mechanisms of biofouling that result in impaired wells 

include the following: (1) the physical presence of extracellular slimes that are excreted by the bacteria and aid attachment to surfaces within the borehole and surrounding geologic 

materials, (2) the accumulation of entrained solids and precipitated minerals within those slime layers; some minerals are 

scavenged from the ambient fluid by extracellular chemicals 

that are excreted by bacteria for that specific purpose, (3) the 

occlusion by gases that are generated by active bacteria, and 

(4) the corrosion of well components by hydrogen sulfide or 

organic acids that are generated by the microbiological activity 

(Vance, 1998). Biofouling can be complex and can be caused 

by a variety of bacteria (Vance, 1998). Black slime is the 

result of sulfur-reducing bacteria that cause precipitation of 

black sulfides, whereas white or clear slimes have not accumulated any precipitated minerals (Vance, 1998). Gray slime 

has accumulated some solids but is not totally dominated by 

sulfur-reducing bacteria (Vance, 1998). Orange, red, pink, or 

brown slimes are present where conditions are significantly 
8 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

or borderline aerobic; the coloration in these slimes is from 

the accumulation of precipitated iron or manganese oxides or 

hydroxides (Vance, 1998). 

Redox conditions affect the formation of biofilms. A 

schematic diagram (fig. 6) conceptually shows how metastable redox domains may form in concentric halos around 

a pump located at the center of a borehole (Vance, 1998). 

The maximum level of microbiological activity commonly 

occurs where redox values range from -50 to +150 millivolts 

(Vance, 1998). 

Other factors affecting biofilm formation are surface 

roughness and borehole turbulence. Well components with 

rough surfaces create more opportunities for microbial cell 

attachment and provide greater shelter from shear forces during pumping (Characklis and Cooksey, 1983). Studies additionally indicate that film density increases with increasing 

borehole turbulence (Characklis and Cooksey, 1983). 

The following four broad treatment approaches for 

improving the functionality of biofouled wells were suggested 

by Vance (1998): (1) mechanical agitation of the borehole by 

surging, water jetting, scrubbing, or air sparging the borehole; 

(2) acidification to solubilize minerals and the polysaccharide portion of the bacteria; (3) flushing to remove soluble 

debris dislodged by the mechanical agitation; (4) introduction 

USGS “modified”

Borehole

–50 mV 

0 mV

+50 mV

+100 mV

+150 mV

Zone 

of maximum growth

mV Millivolt

EXPLANATION

Figure 6. Schematic diagram showing redox environments near a borehole. Diagram modified from Vance (1998).
Introduction 9

of bactericides to suppress bacteria populations. The most 

common acids used in well improvement operations include 

hydrochloric acid, sulfamic acid, and hydroxyacetic acid. 

Some acids and well additives may destroy well components, 

and the selection and concentration of acid should be intentionally selected (Vance, 1998). 

A USGS investigation of well fouling in Suffolk County, 

New York (not shown), identified biofouling as the primary 

cause of reduced well yields (Brown and others, 1999). The 

investigation determined that multiple bacteria were present 

in biofilms. The bacteria included biofilms of aerobic bacteria that encapsulated thicker biofilms of anaerobic bacteria, 

which were primarily responsible for producing the biofilms. 

Fouling was not limited to the pump but also included the well 

screen and surrounding aquifer material. The investigation in 

Suffolk County determined that much of the pump encrusting 

material consisted of extracellular bacteria filaments, and the 

remaining material primarily consisted of amorphous ferric 

hydroxide with lesser amounts of goethite, hematite, other 

iron oxides, and silica. Groundwater samples from biofouled 

wells generally contained median concentrations of total and 

dissolved iron and manganese, total phosphate, and dissolved 

sulfate that were higher than those measured in background 

wells. Lower median concentrations of dissolved oxygen and 

alkalinity and lower pH were also observed in biofouled wells 

(Brown and others, 1999). Bacterial growth was determined to 

be the result of introducing oxygen into an anaerobic aquifer 

through creation of the well and creating redox gradients that 

were favorable for growth.

Rorabaugh (1953) defined “well efficiency” as the ratio 

of the theoretical computed drawdown induced by pumping, 

assuming no turbulence, to the actual drawdown in the well. 

Walton (1959) defined “well efficiency” as the ratio of the 

theoretical specific capacity to the actual specific capacity of 

the well. During well pumping, the water level in the well is 

expected to decline by an amount that is related to the decline 

in water level in the aquifer material surrounding the well. If 

the drawdown in the well declines disproportionately to the 

decline in the aquifer material, the well efficiency is less than 

100 percent. Well efficiency may be affected by non-optimal 

screen placement relative to the vertical position of the aquifer, 

screen type, screen length, open area of the screen, hydraulic 

conductivity of the gravel pack, and incomplete development of the well. A decline in well efficiency may result from 

encrustation and bacterial clogging of the well screen, gravel 

pack, and aquifer material adjacent to the well screen, or other 

factors that create resistance to flow from the aquifer material 

into the borehole (Bierschenk, 1963).

Well efficiency was investigated at six monitoring wells 

and at three extraction wells on the CDF property during 

an earlier phase of this study (Lampe and Unthank, 2016). 

Single-well aquifer tests were completed once in AugustSeptember 2014 and again in March-May 2015 to evaluate 

changes in well efficiency through time. Air-slug test results 

for monitoring wells indicate that with each test in a given 

well, the hydraulic connection between the well and the 

aquifer was increased by the surging of water through the well 

screen. Hydraulic conductivity results from a monitoring well 

located approximately 0.25 mile south of the CDF are substantially higher than hydraulic conductivity results from wells 

on the CDF property. The higher values indicate that (1) the 

offsite well was completed in a part of the aquifer with higher 

hydraulic conductivity or (2) a process may be affecting the 

connectivity of the wells on the CDF property to the Calumet 

aquifer. Between the tests completed in 2014 and again in 

2015, the well and aquifer properties determined from the step 

drawdown and recovery aquifer tests from three extraction 

wells on the CDF property remained relatively similar (Lampe 

and Unthank, 2016). Derived hydraulic conductivity values 

were relatively similar in EW–4B and EW–14A; values for 

EW–11C were substantially lower. Specific-capacity estimates 

derived from the single-well aquifer tests in the tested extraction wells were compared to well development data that were 

collected in 2008 to evaluate change in well efficiency since 

well installation. Specific-capacity estimates for EW–4B, 

EW–11C, and EW–14A are substantially lower than those 

calculated from initial well development data. 

Purpose and Scope

The purpose of this report is to describe (1) the results of 

groundwater, solids, and microbiological analyses for samples 

collected at the site, (2) the physiochemical processes that 

may be active near each well, and (3) the potential applications of those findings to mitigate pump fouling in CDF 

extraction wells. 

This report describes results of water-quality, geochemistry, and microbiological sample collection at the CDF, which 

encompasses 1.87 square miles in East Chicago, Ind. Groundwater samples were collected from three extraction wells and 

three monitoring wells located along the perimeter of the CDF, 

representing three different hydrogeologic and geochemical 

settings (well nests 4, 11, and 14). Additional data used in this 

analysis included historic water-quality measurements from 

two offsite wells and solid samples collected from five other 

wells at the CDF. 

Description of the Study Area

Urban development in the late 1800s and early 1900s 

brought about notable changes in the area surrounding the 

CDF. Changes included the draining of marshes in low-lying 

areas and the digging of the Indiana Harbor Canal to connect 

the Grand Calumet River to Lake Michigan, causing a change 

in direction of flow to the river (Moore and Trusty, 1977). 

Slag, a byproduct of the steel making industry, was used 

extensively as fill material in depressions and marshy areas in 

the region (Kay and others, 1996) and in limited quantities at 

the CDF. 

The CDF property is in East Chicago, Ind., and is 

approximately 1.5 miles south of Lake Michigan. The CDF 
10 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

site is approximately 140 acres and is bounded by Indianapolis 

Boulevard to the east, Indiana 912 (Cline Avenue) to the north, 

Norfolk Southern Railroad to the west, and the Lake George 

Branch of the Indiana Harbor Canal, to the south (fig. 2).

Beginning in 1918, the CDF property was the location of a petroleum refinery with peak production of about 

140,000 barrels of refinery products per day. Products included 

gasoline, fuel oil, kerosene, lubricating oils, grease, asphalt, 

propane, liquefied petroleum gas, phenols, paraffin wax, and, 

for a brief period during the 1940s, insecticides (Geraghty & 

Miller Environmental Services, 1993). In 1981, the property 

owner filed for bankruptcy; therefore, all aboveground materials and structures related to refinery operations were removed 

and the site was covered with a 3-ft thick layer of compacted 

clay (U.S. Army Corps of Engineers, 2000). Groundwater 

monitoring began in 1991 following the detection of hydrocarbon contamination, and a groundwater recovery system 

was installed in 1992 along the southern boundary of the CDF 

property on the north side of the Lake George Branch. Other 

groups of inorganic and organic compounds have been identified in soil and water samples collected before 1998 (Cohen 

and others, 2002).

The USACE took possession of the property and began 

construction of the CDF in 2002 as the final repository of 

dredging wastes, including those from the Indiana Harbor and 

Indiana Harbor Canal. Railroad tracks and buried infrastructure were removed where they conflicted with the installation 

of the groundwater cutoff wall and well arrays. A steel sheetpile groundwater cutoff wall and slurry-barrier groundwater 

cutoff wall seal the border with the Indiana Harbor Canal on 

the south side. The slurry-barrier and sheet-pile groundwater 

cutoff walls were installed to connect with a lower confining 

unit, a silty clay to clay deposit. This groundwater cutoff wall 

system was intended to meet the permeability requirements 

of 2.83 x 10-4 foot per day (1.0 x 10-7 centimeter per second) 

for the CDF perimeter (U.S. Army Corps of Engineers, 2000). 

Inside the groundwater cutoff wall and outside on the landward sides of the site, aquifer materials are capped with a 3-ft 

thick layer of compacted clay. The intention of capping the 

site was to use a relatively impermeable material that would 

inhibit the infiltration of precipitation and force water to move 

laterally as overland flow into the ponds where dredge spoils 

would be deposited.

Within the groundwater cutoff wall, a gradient control 

system was installed to maintain an inward groundwater 

gradient at the site. The gradient control system, at the time 

of the study, consisted of 22 nests. Each nest consisted of four 

extraction wells installed within the groundwater cutoff wall 

and a pair of monitoring wells, one well inside and one well 

outside of the wall. Extraction and monitoring wells were 

installed during 2008. Eight additional extraction wells were 

added to three well nests along the southern perimeter of the 

CDF in 2015. Monitoring wells along the southern perimeter 

of the CDF use the water levels of the Lake George Branch as 

the exterior reference for water altitude. An automated system 

uses continuous water-level data collected from the monitoring 

wells and the Lake George Branch to control the operation 

of the extraction wells within each nest. When the difference 

in water level between the inner and outer monitoring wells 

reaches a threshold, pumps in the extraction wells are activated to lower the water table. Lowering the water level in 

the extraction wells effectively increases the gradient inward 

toward the CDF across the groundwater cutoff wall. Groundwater from the extraction wells is pumped from the aquifer 

inside of the groundwater cutoff wall into the water-collection 

system. The groundwater then discharges into the unlined 

disposal cells in the center of the CDF before treatment by the 

onsite wastewater treatment plant and offsite discharge. The 

monitoring and extraction wells are approximately 30 ft with 

5-ft screens at their base to limit drawdown from reaching 

the well screen and to be screened below residual petroleum 

contamination. Pumps are not installed within the monitoring 

wells on the CDF property, and these wells were not routinely 

pumped or redeveloped. The detection of hydrocarbons during 

extraction well installation was noted on well-drillers’ records. 

Anecdotal observations indicated that the distribution of petroleum hydrocarbons varies spatially with time. Hydrocarbons 

were measured in two groundwater samples collected on June 

19, 2014, to determine the level of personal protective equipment required by the staff for this study (table 1). 

Beginning in 2012, specific extraction wells at the CDF 

site began to show evidence of fouling. A precipitate formed 

on the intake of some of the extraction-well pumps causing 

them to overheat and become inoperable, ultimately requiring 

site personnel to pull the equipment from the well and replace 

each inoperable pump. Of the affected extraction wells, 

fouling was more frequently evident in some wells than in 

other wells. 

Hydrogeologic Setting

The CDF is in Lake County in northwestern Indiana and 

is in the Calumet Lacustrine Plain physiographic province 

(Schneider, 1966). The province is made up of several distinct 

dune-beach complexes formed in the Pleistocene and Holocene Epochs when Lake Michigan was at higher levels than it 

is today (2017) (Leverett and Taylor, 1915; Bretz, 1951; Hansel and others, 1985). The dune; beach; and lacustrine silts, 

sands, and gravels that were deposited form a thin but laterally 

extensive surficial aquifer (referred to herein as the Calumet 

aquifer). In the area of the CDF, the Calumet aquifer extends 

approximately 35 ft below the land surface based on driller’s 

well logs from the extraction wells installed on site (U.S. 

Army Corps of Engineers, written commun., 2014). Glacial till 

and lacustrine clay immediately underlie the Calumet aquifer. 

The thickness of the clay unit ranges from 50 to 140 ft in the 

area surrounding the CDF and forms a confining unit between 

the Calumet aquifer and the underlying carbonate bedrock 

aquifer (Fenelon and Watson, 1993). 
Introduction 11

Hydrocarbons measured in groundwater samples collected June 19, 2014, at the confined disposal facility. Table 1.

[All groundwater samples were analyzed for unfiltered, recoverable compounds in micrograms per liter; --, no data; <, less than; E, estimated]

Station 

name

1,2-Dibromoethene 1,2-Dichloro- ethane 1,2-Dichloro- propane 1,3-Dichloro- propene 1,4-Dichloro- benzene 2,4,5-Trichloro- phenol 2,4,6-Trichloro- phenol 2,4-Dichloro- phenol 2,4-Dimethyl- phenol 2-Methyl-4,6- dinitrophenol

EW–4B -- -- -- -- <2.20 -- <4.98 <3.60 <8.0 --

EW–14A -- -- -- -- <2.20 -- <3.40 <3.60 44.3 --

Station 

name

4-Chloro3-methylphenol 4-Chloroaniline 4-Nitrophenol Aldrin alpha-Endo- sulfan alpha-HCH beta-Endosul- fan beta-HCH Bromomethane Carbon disul- fide

EW–4B <5.40 -- <5.34 <0.013 <0.012 -- -- -- -- --

EW–14A <5.40 -- <5.20 <0.013 <0.012 -- -- -- -- --

Station 

name

Chlordane 

(technical)

cis-1,3-Dichloropropene cis-Chlordane delta-HCH Dieldrin Endosulfan sulfate Endrin alde- hyde Endrin ketone Endrin gamma-Chlor- dane

EW–4B <0.1 -- -- -- <0.008 -- -- -- <0.012 --

EW–14A <0.1 -- -- -- <0.008 -- -- -- <0.012 --

Station 

name

Heptachlor 

epoxide Heptachlor Hexachloro- benzene Lindane Mirex o-Cresol p,p’-DDD p,p’-DDE p,p’-DDT p,p’-Methoxy- chlor

EW–4B <0.009 <0.008 <3.00 <0.014 <0.0060 -- <0.016 <0.014 <0.010 <0.002

EW–14A 1.17 <0.008 <3.00 0.007 <0.0060 -- <0.016 <0.014 <0.010 <0.002

Station 

name p-Cresol Pentachloro- phenol Toxaphene trans-1,3-Di- chloropropene Aroclor 1016 Aroclor 1232 Aroclor 1242 Aroclor 1248 Aroclor 1254 Aroclor 1260

EW–4B -- -- <1 -- -- -- -- -- -- --

EW–14A -- -- <1 -- -- -- -- -- -- --

Station 

name

PCBs 1,1,1-Trichloro- ethane 1,1,2,2-Tetra- chloroethane 1,1,2-Trichloro- ethane 1,1-Dichloro- ethane 1,1-Dichloro- ethene 1,2,4-Trichloro- benzene 1,2-Dichloro- benzene 1,2-Dichloro- ethene (cis & trans) 1,2-Diphenylhy- drazine

EW–4B <0.1 -- -- -- -- -- <2.60 <2.0 -- <3.00

EW–14A 1.4 -- -- -- -- -- <2.60 <2.0 -- <3.00

Station 

name

1,3-Dichlorobenzene 2,4-Dinitrophe- nol 2,4-Dinitrotolu- ene 2,6-Dinitrotolu- ene 2-Chloroethyl vinyl ether 2-Chloronaph- thalene 2-Chlorophenol 2-Methylnaph- thalene 2-Nitroaniline 2-Nitrophenol

EW–4B <2.20 -- <5.60 <4.0 -- <2.40 <2.60 -- -- <5.3

EW–14A <2.20 -- <5.60 <4.0 -- <2.40 <2.90 -- -- <4.0

Station 

name

3,3’-Dichlorobenzidine 3-Nitroaniline 4-Bromophenyl phenyl ether 4-Chlorophenyl phenyl ether 4-Nitroaniline 9H-Fluorene Acenaphthene Acenaph- thylene Acetone Anthracene

EW–4B <4.20 -- <2.40 <3.40 -- E1.46 <2.80 <3.00 -- <3.80

EW–14A <4.20 -- <2.40 <3.40 -- E0.47 E0.46 <3.00 -- <3.80

Station 

name

Benzene Benzo[a] anthracene Benzo[a]pyrene Benzo[b]fluor- anthene Benzo[ghi] perylene Benzo[k]fluor- anthene Benzyl n-butyl phthalate Bis(2-chloroe- thoxy)methane Bis(2-chloro- ethyl) ether Bis(2-chlo- roisopropyl) ether

EW–4B 16.7 E0.18 E0.13 E0.08 E0.07 <3.00 <18 <2.40 <3.00 <1.40

EW–14A 2,780 <2.60 <3.20 <3.00 <3.80 <3.00 <18 <2.40 <3.00 <2.00
12 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana Hydrocarbons measured in groundwater samples collected June 19, 2014, at the confined disposal facility.—Continued Table 1. [All groundwater samples were analyzed for unfiltered, recoverable compounds in micrograms per liter; --, no data; <, less than; E, estimated] Station name Bis(2-ethylhex- yl) phthalate Bromodichloro- methane Chlorobenzene Chloroethane Chloromethane Chrysene Dibenzo[a,h] anthracene Dibenzofuran Dibromochloro- methane Dichlorodifluo- romethane EW–4B E1.7 -- -- -- -- E0.12 <4.20 -- -- -- EW–14A <72 -- -- -- -- <3.20 <4.20 -- -- -- Station name Dichlorometh- ane Diethyl phthal- ate Dimethyl phthalate Di-n-butyl phthalate Di-n-octyl phthalate Ethyl methyl ketone Ethylbenzene Fluoranthene Hexachlorobu- tadiene Hexachlorocy- clopentadiene EW–4B -- <6.20 <3.60 <28.0 <6.0 -- <0.309 E0.21 <2.40 <5.00 EW–14A -- <6.20 <3.60 <28.0 <6.0 -- 17.8 <3.00 <2.40 <5.00 Station name Hexachloroeth- ane Indeno[1,2,3-cd] pyrene Isobutyl methyl ketone Isophorone Methyl tert- butyl ether m-Xylene plus p-xylene Naphthalene n-Butyl methyl ketone Nitrobenzene N-Nitrosodi- methylamine EW–4B <2.40 <3.80 -- <2.60 5.13 2.46 <2.20 -- <3 <3.20 EW–14A <2.40 <3.80 -- <2.60 <10.0 225 <2.20 -- <3 <3.20 Station name N-Nitrosodi-n- propylamine N-Nitrosodi- phenylamine o-Xylene Phenanthrene Phenol Phenolic com- pounds Pyrene Styrene Tetrachloroeth- ene Tetrachloro- methane EW–4B <4.0 <4.80 0.456 E2.22 <2.80 -- E0.84 -- -- -- EW–14A <4.0 <4.80 37.8 E0.32 35.7 -- <3.60 -- -- -- Station name Toluene trans-1,2-Di- chloroethene Tribromometh- ane Trichloroethene Trichlorofluoro- methane Trichlorometh- ane Trihalometh- anes Vinyl chloride Xylene (all isomers) EW–4B 0.26 -- -- -- -- -- -- -- -- EW–14A 25.1 -- -- -- -- -- -- -- --
Methods of Investigation 13

Methods of Investigation

The methods selected for this investigation were intended to characterize the microbiology, aqueous chemistry, 

geochemistry, and mineralogy in select wells at the CDF. This 

section describes the different methods used to sample each 

well type and to prevent cross contamination of wells. Uncommonly high concentrations of solids in the samples required 

modifications of some standard procedures.

Well Selection 

Groundwater and microbiological properties were measured in water from six wells at three locations (table 2). The 

three locations contained the same wells tested for hydrologic 

properties by Lampe and Unthank (2016); these well clusters 

were previously observed to have different rates of pump 

fouling. The historic water-quality data from two offsite wells 

were added to the dataset to represent background waterquality conditions; new samples were not collected from those 

wells. Ten wells were sampled for solid-phase properties, and 

four of those wells were within nests of wells sampled for 

water-quality and microbiological properties; however, none 

of the wells sampled for solid phases were sampled for waterquality and microbiological properties (table 2). The well 

nests sampled for groundwater and microbiological properties 

included extraction well EW–4B and monitoring well MW–

4A (well nest 4), on the west side of the property; EW–11B 

and MW–11A (well nest 11) on the north side; and EW–14A 

and MW–14A (well nest 14) on the east side. Monitoring 

wells tested as part of this investigation were located within 

the perimeter of the CDF slurry wall.

Well nest 4 had high levels of fouling, well nest 14 was 

experiencing well fouling to a lesser extent than well nest 4, 

and well nest 11 was experiencing little to no well fouling. 

The extraction wells are equipped with pumps that need to 

be serviced or replaced whenever fouling causes a significant decline in productivity. The extraction wells are also 

equipped with transducers for measuring groundwater levels. 

The monitoring wells are located near the extraction wells and 

may provide some indication of conditions in the subsurface 

that are not geochemically perturbed by pumping. Monitoring 

wells are equipped with transducers for measuring groundwaTable 2. Number and type of analyses on groundwater and solids collected from wells at the confined disposal facility.

[Scanning electron microscopy analyses by the U.S. Geological Survey (USGS) Rock Kinetics Laboratory, Menlo Park, California; semi-quantitative X-ray 

diffraction analyses by the Biogeochemistry and Mineralogy of Redox-Active Environmental Systems Lab, Boulder, Colorado; inductively coupled plasma 

chromatography by the USGS Metal and Metalloid Isotope Research Laboratory, Menlo Park, Calif.; carbon and sulfur isotope analyses by the USGS Stable 

Isotopes Laboratory; semi-quantitative chromatography for hydrocarbon evaluation by the USGS South Atlantic Water Science Center Studies Unit, Columbia, South Carolina; dissolved gas analyses by the USGS Dissolved Gas Laboratory, Reston, Virginia; bacteria type and approximate population by the USGS 

Ohio-Kentucky-Indiana Water Science Center, Indianapolis, Indiana; and water-quality analyses by the USGS National Water Quality Laboratory, Arvada, 

Colo. Number does not include quality-assurance samples. --, no sample]

Well name

Analyses on solid-phase samples Analyses on aqueous-phase samples

Scanning 

electron 

microscopy

X-ray 

diffraction

Inductively 

coupled plasma 

chromatography

Carbon and 

sulfur isotopes

Petroleum 

hydrocarbons 

scan

Dissolved 

gases

Bacteria Water quality

EW–4B -- -- 2 -- 1 5 16 1,26

EW–4C 1 1 1 1 -- -- -- --

EW–4D 6 1 1 1 -- -- -- --

EW–6C 1 -- 1 1 -- -- -- --

EW–11B -- -- -- -- -- 4 16 4

EW–11D 1 1 1 1 -- -- -- --

EW–14A -- -- -- -- -- 4 16 15

EW–20D 2 3 3 3 -- -- -- --

MW–4A -- -- 2 -- -- 5 16 25

MW–4B-1 8 2 2 1 -- -- -- --

MW–4B-2 -- -- -- 1 -- -- -- --

MW–11A -- -- 2 -- -- 4 16 4

MW–14A -- -- 2 -- -- 4 16 4

1

The sample count at this well includes the precautionary health screening samples collected June 19, 2014.

2

The sample count at this well includes a second sample collected November 5–6, 2014.
14 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

ter levels and are not regularly developed. Water-level data in 

wells at the CDF were provided to the USGS for the purposes 

of this study by a contractor of the USACE and are not publicly available.

Wells were installed at the CDF using the hollow-stem 

auger method during June and July 2008 (U.S. Army Corps 

of Engineers, 2008a). Monitoring wells were constructed with 

2-inch inner diameter fiberglass reinforced epoxy riser and 

5-ft long, 0.010-slot screens (table 3). The annulus surrounding the screens was filled with #5 sand and with bentonite 

pellets above the screen. Extraction wells were constructed 

with 6-inch inner diameter fiberglass-reinforced epoxy riser 

and completed with a 5-ft Johnson Type 316 stainless steel 

0.010-slot screen. The annular space surrounding the extraction well screens was filled with #7 sand and with bentonite 

pellets above the screen. Drillers’ records at the site describe 

the generalized geology as clay, overlain by 30 ft of sand 

with occasional gravel stringers, overlain by 3 ft of clay-rich 

fill (appendix 1). Wells were instrumented with submersible, 

impeller-driven pumps constructed from stainless steel and 

rubber parts.

Water-Sample Collection and Laboratory 

Analysis

Groundwater samples were collected during September 

10, 2014, through November 6, 2014, from the six CDF wells 

(fig. 7A). Historic water-quality data from two offsite wells 

representing background conditions were retrieved from the 

USGS National Water Information System (NWIS) to use in 

comparisons (U.S. Geological Survey, 2016b).

The weather during water-sample collection included 

multiple rain events (fig. 7B). At the nearby Gary Airport, 

three events exceeded 1 inch of rainfall in 24 hours. With the 

exception of a notable rainfall event during September 2014, 

the rain fell at least a few days before sampling. 

Groundwater sampling was done during a variety of 

established pumping conditions to represent the full range of 

conditions that might occur in wells at the site (table 4). Four 

sets of samples were collected. The first set of samples was 

collected during normal pumping conditions with the pumps 

running almost continuously or for an extended period. The 

second set of samples was collected after the pumps in the 

extraction wells had been off for 8–16 hours and water levels 

had mostly recovered. The third set of samples was collected 2 weeks after the resumption of pumping. The fourth 

set of samples was collected 4 weeks after the resumption 

of pumping. 

Extraction wells and monitoring wells were sampled using different pumps. Samples were collected from the extraction wells using the submersible, stainless-steel pumps that are 

installed in the wells for gradient control. The pump intakes 

are 1 ft above the top of the well screen. Water from the pump 

is routed to a hydrant through a series of smaller diameter 

stainless steel, copper, and bronze pipes (fig. 8). Samples 

were collected from the monitoring wells using a submersible pump constructed from plastic and stainless steel. The 

pump was lowered to the bottom of the well and then pulled 

up and secured to locate the pump intake 14–20 inches above 

the top of the well screen. Each monitoring well had its own 

dedicated pump. 

Before each sampling event, all lengths of the polyethylene tubing, submersible pumps, and sampling equipment 

were cleaned by pumping at least 5 gallons of each of the 

following and in the order of (1) a mixture of 1-part laboratory grade detergent to 50 parts tap water, (2) tap water, and 

(3) sterile deionized water. All the polyethylene tubing used 

for water flow from hydrants and plastic pumps was new 

before sample collection and disposed of after each well was 

sampled. The water-quality sonde and sonde flow-through 

cell were fed through a separate line connected to the flow 

manifold (figs. 9A–9C). A valve allowed for the redirection 

of flow from the flow-through cell to the sampling line. The 

same cleaned polyethylene tubing used for sampling was connected from the flow manifold to the flow-through cell. The 

sondes and flow-through chambers were not cleaned with the 

same decontamination procedures as the rest of the equipment 

because the sondes and chambers were not in contact with the 

flow manifold or used for sample water collection. 

Water was pumped through the polyethylene tubing and 

into USGS standard flow manifolds constructed of stainless 

steel fittings, polytetrafluoroethylene tubing, and polytetrafluoroethylene valves. Additional polyethylene tubing was 

used to connect the manifold to a flow-through chamber that 

supported the multiparameter sonde, the discharge line, and 

the sample-collection line. Initial health-screening samples 

collected before the start of the project indicated benzene 

levels as high as 2.78 milligrams per liter (mg/L) and other 

petroleum by-products at lesser concentrations (table 1). As 

a consequence, each well had dedicated sampling equipment. 

Per the USGS National Field Manual for the Collection of Water-Quality Data section 3.3.10.B, pump tubing was replaced 

rather than cleaned when concentrations of volatile organic 

compounds exceeded 700 micrograms per liter (U.S. Geological Survey, variously dated). Some items, such as the stainless 

steel fittings and the USGS flow manifold, were used for the 

monitoring and extraction wells in the same cluster because 

the materials in the fittings and manifold have relatively high 

resistance to chemical absorption and are readily cleaned with 

the proper decontamination procedures.

Wells were pumped at a rate of 0.12–0.35 gallons per 

minute during sample collection. Onsite measurements of 

pH, specific conductance, redox potential, water temperature, 

dissolved oxygen, and turbidity were made with a YSI 600XL 

sonde and were recorded. Redox values measured with a silver 

chloride reference electrode using 3.5 molar potassium chloride were converted to redox (standard hydrogen electrode) 

values by an addition of 231 millivolts to the measured value. 

The general redox category and dominant redox process for 

each water sample collected at the CDF was estimated using 

methods described in Jurgens and others (2009). Assignment 
Methods of Investigation 15

Table 3. Characteristics of extraction and monitoring wells used for this study.[USGS, U.S. Geological Survey; NAVD 88, North American Vertical Datum of 1988; na, not applicable]

USGS site 

identification 

number

Well name

Total well 

depth,

in feet

Casing inside 

diameter, 

in inches

Screen 

length, 

in feet

Land surface 

elevation, 

in feet above 

NAVD 88

Top of sand 

pack,

in feet above 

NAVD 88

Top of screen 

elevation,

in feet above 

NAVD 88

Bottom of 

screen 

elevation, 

in feet above 

NAVD 88

Bottom of 

borehole, 

in feet above 

NAVD 88

Pump altitude, 

in feet above 

NAVD 88

413907087291801 EW–4B 28.1 6 5.0 591.0 586.0 567.9 562.9 559.0 568.9413908087291901 MW–4A 27.5 2 5.0 590.5 571.0 568.0 563.0 562.5 na413921087290103 EW–11B 29.2 6 5.0 592.2 587.2 568.0 563.0 560.0 569.0413921087290101 MW–11A 27.3 2 5.0 590.3 571.0 568.0 563.0 562.5 na413911087285201 EW–14A 27.4 6 5.0 590.4 586.6 568.0 563.0 561.6 569.0413909087285301 MW–14A 24.5 2 5.0 587.5 571.3 568.0 563.0 562.5 na413941087292600 D21 20.0 2 5.5 584.4 na 569.9 564.4 561.4 na413835087245101 D40 6.9 2 4.0 584.2 na 581.3 577.3 575.2 na
16 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana Precipitation, in inches Precipitation, in inches

0

1.0

2.0

3.0

Sept. 1, 2014

Sept. 15, 2014

Oct. 1, 2014

Oct. 15, 2014

Nov. 1, 2014

Nov. 15, 2014

Nov. 30, 2014

Area shown in B

A

B

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

3.5

2.5

1.5

0.5

Jan. 1, 2014

Feb. 1, 2014

Mar. 1, 2014

Apr. 1, 2014

May 1, 2014

June 1, 2014

July 1, 2014

Aug. 1, 2014

Sept. 1, 2014

Oct. 1, 2014

Nov. 1, 2014

Dec. 1, 2014

Jan. 1, 2015

EW−4B

EXPLANATION

MW−4A

EW−11B

MW−11A

EW−14A

MW−14A

Sampling date —Indicated 

by colored bar

Precipitation

Figure 7. A, dates of water-quality sample collection and precipitation and B, precipitation record at Gary Airport for 

January 1, 2014, through December 31, 2014.

of redox category and the dominant redox process were made 

using concentrations of dissolved oxygen, manganese, ferrous iron, sulfate, sulfide, hydrogen sulfide, and dihydrogen 

sulfide. Data were insufficient to estimate redox condition for 

offsite wells.

Samples were collected after the well was purged and 

onsite measurements had stabilized. Stability was determined 

by multiple sonde readings of temperature, specific conductance, pH, and dissolved oxygen until little to no changes were 

observed after a specified amount of water was purged from 

the wells per the USGS National Field Manual for the Collection of Water-Quality Data section 4.2.3 (U.S. Geological 

Survey, variously dated). Only one well volume was purged 

before sampling the extraction wells because those wells are 

almost always continuously pumped. During October 7–9, 

2014, at least two well volumes were purged from the extraction wells because the pumps had not been discharging since 

they were shut off a day before. A minimum of three well 

volumes were purged from each monitoring well before sampling per the USGS National Field Manual for the Collection 

of Water-Quality Data section 4.2.3 (U.S. Geological Survey, 

variously dated).

Samples could not be filtered at the site using normal 

procedures because the filters clogged and prohibited discharge of water. All samples were collected unfiltered and sent 

to the USGS National Water-Quality Laboratory (NWQL) 

for filtration and analysis. Except for filtration, samples were 

collected and preserved for water-quality analysis according 

to guidelines specified by the USGS NWQL and the USGS 

National Field Manual for the Collection of Water-Quality 

Data (U.S. Geological Survey, variously dated). Photometric 

measurements of dissolved oxygen were done because the 

membrane of the oxygen sensor on the multiparameter probe 

was quickly fouled by water during sampling and values could 

not be reliably used for data interpretation. The clean hands/

dirty hands method, as described in the USGS National Field 
Methods of Investigation 17

Table 4. Tested pumping regimes at the confined disposal facility.[Before, pumping regime began at least 1 month before sample collection date; After, pumping regime ended after November 4, 2014]

Well 

name

Pumping 

regime Pumping conditions

Beginning of

pumping regime End of pumping regime Water-quality sample collection time and date

Time Date Time Date Time Date

EW–4B 1 Normal pumping intensity and duration Before Before 1500 October 8, 2014 1410 September 11, 2014EW–11B 1 Normal pumping intensity and duration Before Before 1300 October 6, 2014 0930 September 9, 2014EW–14A 1 Normal pumping intensity and duration Before Before 1400 October 7, 2014 1110 September 11, 2014EW–4B 2 No pumping for 8–16 hours before sample collection 1500 October 8, 2014 1145 October 9, 2014 1410 October 9, 2014EW–11B 2 No pumping for 8–16 hours before sample collection 1300 October 6, 2014 1115 October 7, 2014 1245 October 7, 2014EW–14A 2 No pumping for 8–16 hours before sample collection 1400 October 7, 2014 1130 October 8, 2014 1340 October 8, 2014EW–4B 3 Normal pumping for minimum 2 weeks 1145 October 9, 2014 After After 1353 October 22, 2014EW–11B 3 Normal pumping for minimum 2 weeks 1115 October 7, 2014 After After 0925 October 21, 2014EW–14A 3 Normal pumping for minimum 2 weeks 1130 October 8, 2014 After After 1235 October 21, 2014EW–4B 4 Normal pumping for minimum 4 weeks 1145 October 9, 2014 After After 1230 November 5, 2014EW–11B 4 Normal pumping for minimum 4 weeks 1115 October 7, 2014 After After 0930 November 4, 2014EW–14A 4 Normal pumping for minimum 4 weeks 1130 October 8, 2014 After After 1300 November 4, 2014
18 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Pitless adapter

1.25-inch steel discharge line

Submersible pump

Stainless steel wire-wrapped screen

Pressure transducer

1-inch fiberglass tube

for transducer cable

Subgrade well cap

0.75-inch bronze hydrant

1.25-inch copper discharge line

Land surface

6-inch plastic casing

Figure 8. Schematic diagram of the borehole and pump-hydrant system in extraction wells at the confined disposal facility.

Manual for the Collection of Water-Quality Data section 4.0.2, 

was used inside an enclosed sampling chamber (U.S. Geological Survey, variously dated). Onsite quantification of ferrous iron, sulfide, turbidity, and dissolved oxygen were done 

using onsite photometric methods (Hach method 8146 [Hach, 

2015a], Hack method 8131 [Hach, 2015b], Hack portable turbidimeter 2100P [Hach, 2015c], and CHEMetrics Instrumental 

Kit K–7503[CHEMetrics, 2016]). The analytical results for 

all environmental samples were placed in the NWIS database 

(U.S. Geological Survey, 2016b).

Field sampling equipment was cleaned after each well 

was sampled. The polyethylene tubing was discarded after 

each sampling. Different cleaning procedures were used for 

different pieces of equipment. The flow manifold, which consisted of polytetrafluoroethylene valves and tubing and stainless steel fittings, was cleaned with a four-step process. The 
Methods of Investigation 19

A

B C

Water-quality sonde

Flow-through cell

Sampling line

Sampling manifold

Sampling chamber

Figure 9. Sampling instruments used to collect water-quality samples at the confined disposal facility. A, enclosed sampling 

chamber, manifold, flow-through cell, water-quality sonde, and sampling lines attached to well hydrant; B, close-up view of 

flow-through cell; and C, close-up view of sampling manifold.

stainless steel fittings that were removable were cleaned with a 

six-step process. The submersible plastic pumps were cleaned 

with a seven-step process. The sonde and flow-through cell 

were cleaned with three steps to keep the instruments clean of 

residue and to reduce odor.

The flow manifold and permanently attached stainless 

steel fittings were cleaned with a brush and fluid consisting of 

1-part laboratory grade detergent to 50-parts tap water. The 

manifold pieces were then rinsed thoroughly with tap water, 

methanol, and with sterile deionized water.

The pump and removable stainless steel fittings were 

cleaned with the same four steps as the flow manifold but were 

additionally disinfected for bacteria contamination by submergence in alcohol reagent (ethanol 88 to 91 percent), methanol 

(4.0 to 5.0 volume/volume percent), and isopropyl alcohol (4.5 

to 5.5 percent) and by a rinse with sodium thiosulfate. 
20 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

The submersible pumps were also submerged in the 

alcohol reagent and sodium thiosulfate and were allowed to 

continually circulate fluid for 10 minutes while rinsing the 

outsides of the pumps with the discharge from the pumps. The 

sodium thiosulfate was used to remove the residuals remaining from disinfection with the alcohol reagent. Lastly, sterile 

deionized water was used to rinse all the equipment to remove 

the sodium thiosulfate. The flow-through cells were cleaned 

with the same laboratory grade detergent and tap water mixture, rinsed with tap water, rinsed with methanol, and rinsed 

again with tap water.

Dissolved Gas Samples and Quality Assurance 

Dissolved gas samples were collected in septum vials that 

were bottom filled until overflowing. While still bottom filling, 

the vials were immersed in a volume of groundwater sample 

and capped underwater to retain gases in the vial. Samples 

were collected in sequence as an environmental sample and 

as a replicate sample, with the replicate sample results used to 

compute quality-assurance statistics. Samples were shipped 

on ice to the USGS Dissolved Gas Laboratory, Reston, Va. 

Samples were analyzed by gas chromatography paired with a 

thermal conductivity detector for concentrations of oxygen, 

nitrogen, and argon and paired with a flame ionization detector 

for analyses of carbon dioxide and methane (U.S. Geological 

Survey, 2016a; Busenberg and others, 1998). Analyses of dissolved gases were also periodically checked at the Dissolved 

Gas Laboratory by analyzing standard samples prepared at 

known temperatures in equilibrium with air. 

Field quality assurance for dissolved gas samples collected for this project included analysis of quality-assurance 

samples and data to understand reproducibility of sampling 

and analysis methods for the dissolved gases. Results from 

replicate samples were used to understand overall variability of sampling and analysis processes used for this project. 

Replicate samples were collected in immediate succession to 

the environmental sample from the same source, using identical handling and analysis methods. Variation between environmental and replicate samples that should be identical in 

composition was quantified by computing the relative percent 

difference (RPD) of concentrations of each analyte in each 

sample type (U.S. Army Corps of Engineers, 2008b).

RPD = |(SR-ES)/((SR+ES)/2)| × 100 (1)

where

RPD is the relative percent difference,

SR is the concentration in the replicate sample, 

and

ES is the concentration in the environmental 

sample.

If the RPD of a dissolved gas analysis was within 

10 percent, the sample result met the precision objectives of 

this study. If the RPD was greater than 10 percent, the sample 

result was reported, but the concentration for that analysis 

was flagged with the letter “Q” in data tables to indicate that 

the concentration is an estimate. This RPD precision objective exceeds that permitted for many environmental analyses 

(50 percent; U.S. Army Corps of Engineers, 2008b).

Environmental samples for dissolved gases were also 

evaluated by comparing argon concentrations in environmental samples with hypothetical argon concentrations in equilibrium with air at a range of average monthly air temperatures 

for the region. Argon was used for this comparison because 

argon is a noble gas and is not subject to oxidation-reduction 

related changes to its concentration, as were the other gases 

(oxygen, nitrogen, carbon dioxide, and methane) analyzed by 

this study. Dissolved gas solubility in groundwater depends 

on the average recharge temperature of infiltrating water as it 

enters the water table and on other properties, which include 

salinity, the vapor pressure of water at the water table, and 

barometric pressure. Concentrations of argon may be expected 

to be in equilibrium with the atmosphere at the prevailing surface pressure and with temperature in water infiltrating below 

the water table (Heaton and Vogel, 1981). Hypothetical argon 

concentrations in water in equilibrium with air were computed 

using a formulation of Henry’s law (Ed Busenberg, written 

commun., August 2016).

The Henry’s law equation used to compute argon concentrations in water in equilibrium with air was 

C = (KH (argon) x mf (argon) x (BP – VP) x 39.9480 

milligrams of argon per millimole (2)

where

C is concentration of argon in milligrams per liter,

KH (argon) is the Henry’s law coefficient for argon,

mf (argon) is 0.0934 is the mole fraction of argon in 

dry air (reported in Weiss, 1970),

P (barometric pressure, in atmosphere [atm]) is 

e [Water table altitude (feet above NGVD29) x 0.3048 (meters per foot) 

/8,300 (meters per atm)], 

e is 2.71828183, 

VP (vapor pressure of water, in atm) is e(24.4543-

67.4509(100/T)-4.8489 x ln (T/100)-0.000544 x S),

ln is logarithm (natural),

T is water temperature in degrees Kelvin, 

computed as T = T degrees Celsius + 

273.15, and

S is water salinity in parts per thousand.

The altitude used to compute the hypothetical argon 

concentration in equilibrium with water was assumed 578 ft 

above the National Geodetic Vertical Datum of 1929. The 

land surface altitude for the three sampled monitoring wells 

ranged from 587.5 to 590.3 ft above the National Geodetic 

Vertical Datum of 1929 and the depth to the water table 

during sampling in monitoring wells sampled for this study 

was about 11 ft below land surface. Normal monthly mean 

temperatures during 1981–2010 ranged from -4.1 degrees 
Methods of Investigation 21

Celsius (°C) in January to 22.7 °C in July at a weather station 

about 20.6 miles east of the site at Indiana Dunes National 

Lakeshore (Arguez and others, 2010). Because infiltrating precipitation would not be common in months with subfreezing 

average temperature, a minimum monthly average temperature 

of 3 °C in March was used to compute argon concentrations 

for the comparison. The salinity used for the computation was 

assumed to be 2,000 mg/L, an intermediate value among those 

measured in groundwater from these sites.

The Henry’s law coefficient for argon was computed 

using the following conventions and data, as modified from 

Weiss (1970): 

KH (argon) = exp {A1 + A2 (T/100) + A3 ln (T/100) + S [B1 + 

B2 (T/100) + B3 (T/100)2]}/22.414 (3)

using the following constants for argon (also from Weiss, 

1970): 

where 

A1 is -55.6578, 

A2 is 82.0262, 

A3 is 22.5929,

B1 is -0.036267, 

B2 is 0.016241, 

B3 is -0.0020114, and

22.414 is the volume of 1 millimole of gas at

 1 atm pressure and 25 °C.

Microbiological Sample Collection and 

Laboratory Analysis

Samples to assess microbiological activity were collected from the six wells immediately following collection of 

the water-quality sample. The four general types of bacteria 

measured in groundwater samples included heterotrophic 

aerobic bacteria, slime-forming bacteria, iron-related bacteria, 

and sulfate-reducing bacteria. Populations of more specific 

bacteria that comprised these general types were determined 

if the analytical techniques allowed (table 5). No historical 

microbiological data were available for groundwater from the 

two offsite wells.

Microbiological samples required equipment disinfection 

before sample collection. After all other water-quality samples 

were collected, the polyethylene sampling line that connected 

the pump to the manifold was cut to create a new samplecollection point, therefore, eliminating the need to disinfect 

the manifold between wells. The new sample-collection point 

for microbiological samples was the polyethylene tubing that 

was directly connected to either the permanent hydrants of the 

extraction wells or the removable submersible pumps used for 

sampling the monitoring wells.

Microbiological samples were analyzed for activity of 

four types of bacteria using the Hach Biological Activity 

Reaction Tests (BARTs)(Droycon Bioconcepts, Inc., 2004) 

(figs. 10A–10C). Microbiological activity was measured by 

visual assessment of the sample water matrix. The water 

samples were inspected daily to provide a description for their 

appearance and then were compared to sterile buffer water. 

Visual changes depended on the sample type (environmental 

or quality assurance) and the population of bacteria present 

in the sample. The largest bacteria populations corresponded 

to samples with rapid (1–2 days) visual change. Smaller or 

nonexistent populations corresponded to relatively slow (more 

than 5 days) visual changes. Numerical populations were 

assigned based on the rapidity of the culture response to the 

sample water and utilized a standard table supplied with the 

test kit. The bacteria subtype was deduced from the color of 

water and solids in the sample tube.

Solid-Phase Sample Collection and Laboratory 

Analysis

Solid samples were collected as suspended solids in water 

and as scrapings from extraction-well pumps. Scrapings were 

collected when pumps were removed for cleaning or replacement. As a result, scrapings and aqueous samples were not 

collected simultaneously. The wells where scrapings were collected were EW–4C, EW–4D, EW–6C, EW–11D, EW–20D, 

and MW–4B. The scrapings were collected between September 11, 2014, and November 6, 2014. Some wells sampled for 

water quality were not sampled for solids because the pumps 

did not have accumulations of solids or the pumps had been 

cleaned or replaced during the preceding weeks. Samples of 

Table 5. General and subtypes of bacteria measured in groundwater samples.

[SRB, sulfate-reducing bacteria; na, not applicable]

Heterotrophic 

aerobic bacteria Slime-forming bacteria Iron-related bacteria Sulfate-reducing bacteria

No subtypes Slime forming Iron-related bacteria Aerobic SRB consortium

na Pseudomonads and enterics Enteric Anaerobic

na Dense slime Anaerobic Dense anaerobic SRB consortium

na na Pseudomonads and enterics na
22 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

A

B

C

Figure 10. Microbiological 

activity reaction tests for A, 

sterile buffer water on day 1; 

B, monitoring well MW–11A 

positive reactivity on day 2; and C, 

monitoring well MW–4A positive 

reactivity on day 4.
Methods of Investigation 23

solids were scraped from pumps immediately after the pump 

was removed from the extraction well. Samples were sealed 

in 20-milliliter vials and shipped for analysis. Samples were 

scraped from pumps in some wells that were not sampled for 

water-quality analyses but were in the same well cluster and 

considered potentially useful for improved understanding of 

processes occurring at the CDF. 

An additional scraping was collected from EW–4B 

on November 3, 2016. That sample was collected using 

identical methods to earlier scraping samples. The sample 

collected from EW–4B was submitted to the USGS laboratory in South Carolina and scanned for the presence of 

petroleum hydrocarbons.

Suspended solids were also collected from wells MW–

14A, MW–11A, EW–4B, and MW–4A during November 

3–6, 2014. Samples were collected with the pumps used for 

water-quality sample collection. About 10 gallons of water 

were collected in two plastic containers. The suspended solids 

were allowed to settle to the bottom of the containers for 

30–60 minutes (most supernatant liquid was decanted) and the 

sample was sealed and shipped to the USGS laboratory. 

Samples of solids were analyzed to determine mineralogy, mineral habit, and solid chemistry. Amorphous solids and 

biofilms were also identified. Analytical methods included 

scanning electron microscopy (SEM)/energy dispersive 

spectroscopy (EDS) to describe crystal habit and dominant 

chemical constituents, SEM/backscatter electrons (BSE) to 

characterize sample homogeneity, qualitative and quantitative 

X-ray diffraction (XRD) to determine mineralogy, inductively 

coupled plasma mass spectrometry on chemically digested 

samples to determine the chemical composition, and carbon 

and sulfur isotopes of chemically digested samples to provide 

information about the formative processes. Sample splits were 

analyzed by using SEM, XRD, and geochemical digestion for 

solid chemistry and isotopy. 

Solid-phase samples were analyzed at USGS laboratories 

in Menlo Park, Calif., and Boulder, Colo., and followed the 

documented procedures established for each lab. One solid 

split from each scraping was analyzed by SEM. The SEM split 

was attached to aluminum pins with carbon tape while wet 

and allowed to dry for several days. Prior to analysis, samples 

were plasma coated with gold to reduce potential electriccharge buildup that might occur during SEM analysis (Goldstein and others, 2007). A Tescan VEGA–3 SEM was used to 

image the samples. The magnification of samples ranged from 

22,000 to 40,000 times actual size. 

In conjunction with the SEM analysis, EDS analysis was 

done to provide qualitative information about the elemental 

composition of materials occurring in the SEM samples. EDS 

analyses were done with an Oxford X–Max Silicon Drift Detector (50 millimeter). About 20 EDS analyses were done on 

the mostly homogeneous samples. As many as 100 analyses 

were done on samples displaying some structural variability. 

The chemical elements detected by EDS in CDF samples 

included carbon, iron, sulfur, aluminum, silicon, magnesium, 

potassium, and sodium. One sample (EW–4B November 5, 

2014) also included trace amounts of zinc.

Qualitative and quantitative XRD analyses were done on 

eight samples of pump scrapings collected from five wells; 

the wells were EW–4C, EW–4D, EW–11D, EW–20D, and 

MW–4B. Scraping samples for XRD analyses were collected 

from wells during pump replacement. The wells were different 

wells than from where water-quality samples were collected. 

Although the observations from XRD analyses were generally 

informative, the observations could not be directly compared 

to water-quality data to ascertain agreement between the various observations.

Samples were prepared for XRD using a modified method based on Eberl (2003). An homogenized sample of 1 gram 

was mixed with 20 percent corundum and ground in a McCrone micronizing mill with 4-milliliter ethanol for 5 minutes, 

generating particle sizes on the order of 10–30 micrometers 

(mm). After drying at 60 °C, the mixture was transferred to a 

plastic scintillation vial with three acrylic balls (approximately 

1 centimeter in diameter) along with 200–800 microliters Vertrel solution (DuPont) and shaken for 10 minutes. The powder 

was passed through a 250-mm sieve to break up larger aggregates and loaded onto an XRD sample holder. Qualitative 

samples were prepared by sieving the sample to less than 250 

mm and packing directly into an XRD sample holder. Samples 

were analyzed using a Siemens D500 X-ray diffractometer 

from 5 to 65 degrees two theta using copper-potassium (alpha) 

X-ray radiation, with a step size of 0.02 degrees and a dwell 

time of 2 seconds per step. Quantitative mineralogy was 

calculated using the USGS software, RockJock (Eberl, 2003), 

which fits XRD intensities of individual mineral standards to 

the measured diffraction pattern. The raw X-ray diffraction 

data used in this study are available through a data release at 

https://doi.org/10.5066/F7PK0FBJ (Christian, 2018).

Inductively coupled plasma mass spectroscopy was used 

to measure the concentration of cations in chemically digested 

samples of pump scrapings and flocculent. Samples for analysis were collected from 10 wells, including EW–4B, EW–4C, 

EW–4D, MW–4A, MW–4B, EW–6C, EW–11D, MW–11A, 

MW–14A, and EW–20D. Chemical digestion consisted of 

mixing solids from the pump scrapings and flocculent with 6 

Normal hydrochloric acid and concentrated nitric acid, then 

evaporated to dryness; this process was repeated three times. 

The residue following the third repetition of the chemical 

digestion lastly was mixed with 10 milliliters of 1 Normal 

nitric acid to form the final solution analyzed by inductively 

coupled plasma mass spectrometry. Analytes included aluminum, arsenic, barium, boron, cadmium, calcium, cesium, 

chromium, cobalt, copper, iron, lead, lithium, magnesium, 

manganese, molybdenum, nickel, rubidium, sodium, strontium, phosphorous, potassium, silicon, titanium, uranium, 

vanadium, and zinc. 

Seventeen samples of solids collected from CDF wells 

were analyzed by inductively coupled plasma mass spectrometry. Approximately 10 milligrams of powdered sample was 
24 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

weighed into 15-milliliter polytetrafluoroethylene digestion 

beakers. Deionized water (1 milliliter) was added to each beaker followed by dropwise addition of 6 Normal hydrochloric 

acid. Effervescence in three samples determined the speed of 

acid addition. When effervescence ended, additional acid was 

added totaling 3 milliliters of 6 normal hydrochloric acid and 

1 milliliter of concentrated nitric acid. Beakers were capped 

tightly and allowed to reflux on a 100 oC hotplate for 24 hours. 

Most of the samples were not completely dissolved after the 

24-hour period. Samples were taken to dryness and were 

subsequently subjected to the same acid digestion procedure 

for a total of three cycles. The sample digestions reached various degrees of completion as noted. The insoluble residues 

appeared to be carbon or organic flock but may have also 

included some refractory mineral phases. The samples were 

dissolved in 1 normal nitric acid, filtered through membranes 

with 0.45-mm pore size, and diluted appropriately for analysis. Analyses were made using a Perkin-Elmer Nexion 300Q 

inductively coupled plasma mass spectrometer. Calibration 

curves were produced using commercially available multielement standards. Concentrations are reported as micrograms 

per gram relative to the original sample weight because the 

insoluble fraction weight was unknown. Errors were less than 

5 percent as determined by multiple inter-run analyses of a 

quality-control standard. 

Carbon and sulfur isotopic composition was analyzed 

in splits from samples of pump scrapings to provide information about processes contributing to the formation of the 

solids. Homogenized sample material was weighed into tin 

capsules along with vanadium pentoxide, an aid to combustion. Samples were analyzed for carbon and sulfur content and 

isotopic composition by continuous flow isotope ratio mass 

spectrometry using a Vario ISOTOPE Cube (Elementar) elemental analyzer coupled to a GV Instruments (now Elementar) 

IsoPrime. Internal standards were used for quantifying carbon 

and sulfur content and isotopic composition. These standards 

were calibrated against the National Bureau of Standards 

(NBS) samples appropriate to each element (NBS 18, NBS 19, 

and NBS 22 for carbon; NBS 127 and SO–6 for sulfur). The 

standards were selected to bracket the expected natural sample 

isotopic composition and were run in a range of sizes based 

on expected sample concentrations. Carbon isotopic composition was reported in parts per thousand (‰) relative to Vienna 

Peedee belemnite; sulfur isotopic composition was reported 

in parts per thousand relative to the standard Vienna Canyon 

Diablo Troilite. The 1-sigma standard deviations for standard 

materials are plus or minus 0.4‰ for carbon and plus or minus 

0.6‰ for sulfur. 

The matrix of the CDF samples was an unusual composition that caused some analytical difficulties for sulfur analysis. 

The matrix material affected sulfur combustion and produced 

a considerable tail in the chromatograph. A similar effect on 

carbon combustion was not observed. Carryover from one 

sample to the next that might be anticipated from the tailing phenomenon was eliminated by running a blank sample 

between the CDF samples. During sample analysis, the sulfur 

pulse was trapped, released, and analyzed as is normal; the 

subsequent blank sample effectively flushed the remaining sulfur through the system. Blank samples that contained enough 

carryover sulfur were analyzed, and the analyses determined 

that d34S ({[(34S/32S)sample/(34S/32S)standard]-1}*1000‰) values 

agreed with the sample values within 3‰, indicating limited 

fractionation. The sulfur carryover implies the d34S values 

represent a lower bound. 

Computed Equilibrium Mineral-Saturation 

Indices

Mineral-saturation indices were computed using the 

analyses of groundwater samples collected from wells at the 

CDF to determine if chemical constituents were present in 

sufficient concentrations to abiotically precipitate the minerals 

identified in SEM and X-ray analyses. If mineral precipitation 

was favored, then an engineered solution to mineral encrustation might include changing the water-quality conditions in the 

borehole. If the groundwater from CDF wells, however, was 

determined to be undersaturated with respect to the minerals 

identified in SEM and X-ray analyses, then the conclusion 

might be that either (1) the minerals formed during a different water-quality condition than existed when samples were 

collected and perhaps during pump cycling, (2) the minerals formed in microenvironments possessing different water 

chemistry than existed throughout most of the borehole and 

perhaps hosted by the biofilms (Droycon Bioconcepts, Inc., 

2006), or (3) the minerals were pulled through the well screen 

and into the borehole by pumping. 

Mineral-saturation indices are theoretical computations 

that indicate the thermodynamic tendency of a crystalline mineral to dissolve or precipitate based on water-quality conditions and constituent concentrations in a solution (Hem, 1989). 

The mineral-saturation index is computed as the ratio of the 

ion activity product to the theoretical or empirically estimated 

equilibrium solubility product (Ksp):

SI = log(IAP/Ksp) (4)

where 

SI is the saturation index,

IAP is the ion activity product, and

Ksp is the solubility product constant.

The ion activity product is related to the mathematical 

product of the concentrations of constituents required to form 

the mineral of interest. The solubility product is the theoretical ion activity product at which mineral precipitation begins. 

Computed saturation indices greater than zero indicate supersaturation with respect to a certain mineral and a geochemical tendency for the mineral to precipitate from the solution. 

Computed saturation indices less than zero indicate undersaturation with respect to a certain mineral and a tendency for 

the mineral to not form or dissolve if it is already present. A 
Methods of Investigation 25

saturation index at or near zero indicates that the mineral and 

surrounding solution are in geochemical equilibrium. 

The computer program PHREEQC (Parkhurst and Appelo, 2013) was used to compute mineral-saturation indices 

for groundwater samples collected from wells at the CDF. 

The computer program PHREEQCI (Charlton and Parkhurst, 

2002) was used as the graphical user interface to enter and format data for PHREEQC and to execute the program. Input to 

the PHREEQC computations included the water-quality conditions and concentrations of most chemical elements measured 

in groundwater samples from the CDF wells (table 6). Iodide 

and dissolved organic carbon were not included in the input 

dataset because the concentrations of those elements were 

relatively small and were not measured in all samples. The sulfide-sulfate redox couple was used to represent the Eh for the 

solution in the PHREEQC models for this study to alleviate 

concerns about direct-measurement stability. Sulfide and sulfate were measured in most samples and sulfate was generally 

the dominant anion. The PHREEQC program contains a large 

database of mineral solubility products; minerals for saturation 

index computations were automatically selected by PHREEQC if the necessary chemical constituents of the mineral 

were present in the input dataset. An archive of the PHREEQC 

modeling used in this study is available through a data release 

at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018).

The ability of PHREEQC to calculate accurately the 

tendency for a mineral to precipitate or dissolve is constrained 

by several factors, including the precision of water-quality 

analyses, the accuracy of the thermodynamic database, and 

the kinetics of mineral formation. The water-quality input data 

must (1) include concentrations for chemical constituents that 

are present in the most abundant minerals in the system and 

(2) be analytically accurate. The accuracy of water-quality 

analyses commonly is assessed by calculating the charge balance of a solution. Poor charge balances may indicate the absence of analytical data for a water-quality constituent having 

non-trivial concentrations. The charge balances for groundwater samples could not be directly computed because titrations 

of carbon species could not be done accurately on unstable 

groundwater samples collected at the CDF. For the saturation 

index computations, PHREEQC computed concentrations of 

carbon species from measured concentrations of dissolved 

inorganic carbon.

Quality-assurance samples analyzed as part of this study 

Table 6. Example input file for the PHREEQC program for groundwater chemistry measured in extraction well EW–4B on 

September 11, 2014.

[°C, degrees Celsius; Eh, redox potential; pE, negative base 10 logarithm of the electron activity; mg/L, milligrams per liter; mg/kgw, milligrams per kilogram 

of water; μg/L, micrograms per liter; μg/kgm, micrograms per kilogram of water]

Measured constituent or property, reported units of measure Representation in 

PHREEQC input file

Concentration or 

value in PHREEQC

Units of measure 

in PHREEQC

Temperature, degrees Celsius temp 16.3 °C

pH, water, unfiltered, onsite, standard units pH 6.8 standard

Eh (standard hydrogen electrode), millivolts pE -5.417 unitless

Carbon, inorganic, water, filtered, as carbon, mg/L C (+4) 180 mg/kgw

Calcium, water, filtered, mg/L Ca 276 mg/kgw

Chloride, water, filtered, mg/L Cl 14.5 mg/kgw

Fluoride, water, filtered, mg/L F 0.86 mg/kgw

Iron, water, filtered, μg/L Fe (+2) 5,800 μg/kgm

Potassium, water, filtered, mg/L K 11.5 mg/kgw

Magnesium, water, filtered, mg/L Mg 217 mg/kgw

Manganese, water, filtered, μg/L Mn (+2) 375 μg/kgm

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), 

water, filtered, analytically determined, mg/L

N (-3) 6.16 mg/kgw

Sodium, water, filtered, mg/L Na 50.2 mg/kgw

Dissolved oxygen, spectrophotometric, mg/L O (0) 0.44 mg/kgw

Orthophosphate, water, filtered, mg/L as phosphorus P 0.583 mg/kgw

Sulfate, water, filtered, mg/L S (+6) 906 mg/kgw

Silica, water, filtered, mg/L as silica Si 47.4 mg/kgw
26 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

indicate that the field and laboratory analyses produced constituent concentrations and water-quality characteristics that 

were nearly identical; however, the possibility of a consistent 

error in sampling methodology is possible. Other potential 

sources of error in the CDF analyses include, but are not limited to, changes in water quality between sampling and analysis 

and complexing of cations by organic constituents and colloids 

(Hem, 1989). Field observations reported that some purge 

water during well equilibration rapidly changed from clear to 

black and from transparent to opaque. The extreme and unique 

water-quality conditions at the CDF made these samples 

unstable at land surface and required nonstandard methods of 

preservation and analysis. The kinetics of the precipitation or 

dissolution reaction may explain the difference between the 

theoretically indicated reaction and the observed mineralogy. 

The kinetics of mineral formation describes the rate of reaction as the solid-aqueous system tries to reach thermodynamic 

equilibrium. For example, a mineral that is not observed but is 

theoretically predicted to be supersaturated may not be present because the kinetics of formation are limiting the rate of 

mineral precipitation. 

Disagreement between mineral occurrence and the 

computed saturation index also may be attributed to collection 

of a sample that represents conditions at the time of groundwater collection that are different from the conditions when 

the mineral precipitated in the well. Generally, groundwater 

conditions are assumed to be fairly stable through time, partly 

as a result of the low velocity and thorough mixing in the 

subsurface. Pump cycling at the CDF, however, might negate 

the assumption of geochemical equilibrium in the extraction 

wells where rapid mixing of water with potentially dissimilar 

chemistries is possible. The kinetics of mineral dissolution or 

bacterial encapsulation of microenvironments that are dissimilar from groundwater in most of the borehole may explain the 

presence of a mineral that is theoretically undersaturated with 

respect to that mineral

This study compared computed saturation indices to 

minerals identified in SEM and X-ray analyses of solids collected at the CDF. Solids were not collected from the same 

wells where groundwater samples were collected and this may 

limit definitive correlation between water chemistry and the 

existence of minerals and amorphous compounds. The solids 

were collected, however, from wells in the same well cluster and were generally close to the wells where groundwater 

was sampled.

Quality-Assurance Procedures

Water samples were collected to characterize the quality 

of the sampling procedure. These quality-assurance samples 

included a combination of equipment blanks and replicate 

samples. In total, 10 quality-assurance samples were collected, 

and 26 environmental samples were collected. Analytical procedures for the laboratories were not assessed by this protocol 

but are published independently by individual laboratories.

Quality-assurance samples were collected at the CDF 

during environmental sample collection to evaluate the 

sampling, cleaning, preservation, and shipping procedures. 

Replicate samples were collected to evaluate consistency of 

the sample collection, preservation, and shipping method. 

Equipment blanks were collected to evaluate the selection 

and implementation of procedures used to clean the equipment used for sample collection. In addition to internal quality 

control programs used by the NWQL, the quality of analytical 

data produced by the NWQL is independently monitored by 

the USGS Branch of Quality Systems (https://bqs.usgs.gov/). 

The analytical results for quality assurance samples were 

placed in the NWIS database (U.S. Geological Survey, 2016b).

Equipment blanks were collected by running sterile 

buffer water through the pump and tubing immediately after 

cleaning the sampling equipment. The sampling procedure, 

containers, preservation, shipping, and laboratory analysis 

were identical to the handling of the environmental samples. 

The analytical results for these samples were used to characterize the validity of the adapted cleaning/decontamination 

procedure. Six equipment blanks were collected, including 

one sample during every sampling event at well MW–4A and 

one sample during a single sampling event at wells MW–11A 

and MW–14A. 

Replicate samples were collected immediately following 

collection of the environmental sample without interruption of 

the flow of water from the well. The sampling procedure, containers, preservation, shipping, and laboratory analysis were 

identical to the handling of the environmental samples. The 

analytical results for these samples were used to characterize 

the homogeneity of groundwater chemistry in the borehole, 

the impact of shipping and handling, and the consistency of 

laboratory analyses. 

Multiple samples were collected from an extraction 

well on all four sampling occasions. Replicate samples were 

collected from three different extraction wells to determine if 

variations in site chemistry would affect the analytical results. 

Replicate samples were collected from EW–4B on September 

11, 2014, and November 5, 2014; from EW–11B on October 

7, 2014; and from EW–14A on October 21, 2014. 

A second environmental sample was collected from 

EW–4B and MW–4A on November 5 and 6, 2014, respectively; however, because those samples were collected more 

than 30 minutes after the first sample, the second samples 

were not considered quality-assurance replicate samples.

Geochemistry and Microbiology 

of Groundwater and Solids from 

Extraction and Monitoring Wells

The data collected at the CDF were evaluated by comparing data from (1) monitoring and extraction wells, (2) sites 

with and without pump reliability issues, (3) CDF and 
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 27

background wells, and (4) different pumping regimes (sampling events 1–4). These comparisons allowed observations 

that may be used to develop strategies to reduce pump fouling. 

Groundwater Levels

Hydrographs of groundwater levels were investigated 

to provide information about the relation among hydrogeologic condition, climate, and pumping stresses at the site. A 

nearby monitoring well that is not on CDF property and might 

represent conditions unaffected by anthropogenic activities, USGS well Lake 13 (USGS site identification number 

413559087270301), was also investigated. The hydrograph for 

USGS well Lake 13 for January 1, 2014, through December 

1, 2014, shows a trend of (1) lower groundwater levels during 

late summer and autumn that correlate to enhanced evapotranspiration and (2) higher groundwater levels during winter 

and spring that correlate to periods of relatively low evapotranspiration (fig. 11). Groundwater levels at Lake 13 varied 

from slightly above land surface to about 2.8 ft below land 

surface during the period displayed. During the period when 

water samples were collected at the CDF, the depth to water in 

Lake 13 ranged from 0.98 to 2.37 ft below land surface (U.S. 

Geological Survey, 2016b).

The hydrograph for representative extraction wells was 

strongly affected by pumping in the wells (figs. 12A–12C). 

Groundwater levels in EW–4B during January 1, 2014, 

through December 31, 2014, varied by more than 20 ft and 

ranged from 568.33 to 588.73 ft above North American Vertical Datum of 1988 (NAVD 88) (22.67 to 2.27 ft below land 

surface) (fig. 12A). In comparison, groundwater levels in the 

nonpumped well, MW–4A, varied by 5.8 ft and ranged from 

579.19 to 584.99 ft above NAVD 88 (fig. 12D). Water levels 

in MW–4A were slightly higher in spring and lower during autumn (fig. 12D). During water-quality sampling, the 

groundwater levels in EW–4B ranged from 568.41 to 577.43 

ft (fig. 13A) and in MW–4A ranged from 579.87 to 584.78 ft 

above NAVD 88 (fig. 13D).

Groundwater levels in EW–11B during January 1, 2014, 

through December 31, 2014, varied by more than 13 ft and 

ranged from 570.17 to 583.97 ft above NAVD 88 (22.03 to 

8.23 ft below land surface) (fig. 12B). In comparison, groundwater levels in the nonpumped well, MW–11A, varied by 

6.45 ft and ranged from 579.02 to 585.47 ft above NAVD 88 

(fig. 12E). Water levels in MW–11A were slightly higher in 

spring and lower during autumn (fig. 12E). During waterquality sampling, groundwater levels in EW–11B ranged 

from 570.42 to 580.24 ft above NAVD 88 (fig. 13B) and in 

MW–11A, groundwater levels ranged from 579.86 to 581.42 ft 

above NAVD 88 (fig. 13E). Groundwater levels in MW–11A 

were about 10 ft above groundwater levels in EW–11B during 

water-quality sampling.

Groundwater levels in EW–14A during January 1, 2014, 

through December 31, 2014, varied by almost 26 ft and ranged 

from 567.15 to 593.02 ft above NAVD 88 (23.25 to -0.47 ft 

below land surface) (fig. 12C). In comparison, groundwater 

levels in the nonpumped well, MW–14A, varied by 10.8 ft and 

ranged from 580.32 to 591.15 ft above NAVD 88 (fig. 12F). 

Land surface

Water-level altitude, in feet above NAVD 88

592.5

592.0

591.5

591.0

590.5

590.0

589.5

589.0

Feb. 20, 2014

Apr. 11, 2014

May 31, 2014

July 20, 2014

Sept. 8, 2014

Nov. 28, 2014

Dec. 17, 2014

Jan. 1, 2014

Depth below land surface, in feet

(Land surface elevation is 591.64)

0.5

1.5

2.5

0.0

1.0

2.0

–0.5

Period of groundwater 

sample collection

Groundwater hydrograph in 

monitoring well Lake 13

EXPLANATION

Figure 11. Hydrograph for U.S. Geological Survey monitoring well Lake 13.
28 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Land surface

Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88

C. Extraction well EW–14A

B. Extraction well EW–11B

A. Extraction well EW–4B

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

EXPLANATION

Feb. 20, 2014

Apr. 11, 2014

May 31, 2014

July 20, 2014

Sept. 8, 2014

Nov. 28, 2014

Dec. 17, 2014

Jan. 1, 2014

Feb. 20, 2014

Apr. 11, 2014

May 31, 2014

July 20, 2014

Sept. 8, 2014

Nov. 28, 2014

Dec. 17, 2014

Jan. 1, 2014

Feb. 20, 2014

Apr. 11, 2014

May 31, 2014

July 20, 2014

Sept. 8, 2014

Nov. 28, 2014

Dec. 17, 2014

Jan. 1, 2014

Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

3.0

3.0

 3.0

Period of groundwater 

sample collection

Groundwater hydrographs in 

extraction wells at the 

confined disposal facility

Figure 12. Groundwater hydrographs for extraction and monitoring wells at the confined disposal facility during January 1, 2014, 

through December 31, 2014. A, EW–4B; B, EW–11B; C, EW–14A; D, MW–4A; E, MW–11A; and F, MW–14A.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 29

Land surface

Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88

F. Monitoring well MW–14A

E. Monitoring well MW–11A

D. Monitoring well MW–4A

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

EXPLANATION

Feb. 20, 2014

Apr. 11, 2014

May 31, 2014

July 20, 2014

Sept. 8, 2014

Nov. 28, 2014

Dec. 17, 2014

Jan. 1, 2014

Feb. 20, 2014

Apr. 11, 2014

May 31, 2014

July 20, 2014

Sept. 8, 2014

Nov. 28, 2014

Dec. 17, 2014

Jan. 1, 2014

Feb. 20, 2014

Apr. 11, 2014

May 31, 2014

July 20, 2014

Sept. 8, 2014

Nov. 28, 2014

Dec. 17, 2014

Jan. 1, 2014

Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

3.0

Depth below land surface, in feet Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

3.0

0.5

1.5

2.5

0.0

1.0

2.0

–0.5

Period of groundwater 

sample collection

Groundwater hydrographs in 

monitoring wells at the 

confined disposal facility

Figure 12. Groundwater hydrographs for extraction and monitoring wells at the confined disposal facility during January 1, 2014, 

through December 31, 2014. A, EW–4B; B, EW–11B; C, EW–14A; D, MW–4A; E, MW–11A; and F, MW–14A.—Continued
30 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88

Sept. 1, 2014

Sept. 11, 2014

Oct. 1, 2014

Oct. 11, 2014

Oct. 21, 2014

Oct. 31, 2014

Nov. 10, 2014

Nov. 20, 2014

C. Extraction well EW–14B

B. Extraction well EW–11B

A. Extraction well EW–4B

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

Sept. 21, 2014

Nov. 30, 2014

(1) (2) (3) (4)

(1) (2) (3) (4)

(1) (2) (3) (4)

Sept. 1, 2014

Sept. 11, 2014

Sept. 21, 2014

Oct. 1, 2014

Oct. 11, 2014

Oct. 21, 2014

Oct. 31, 2014

Nov. 10, 2014

Nov. 20, 2014

Nov. 30, 2014

Sept. 1, 2014

Sept. 11, 2014

Sept. 21, 2014

Oct. 1, 2014

Oct. 11, 2014

Oct. 21, 2014

Oct. 31, 2014

Nov. 10, 2014

Nov. 20, 2014

Nov. 30, 2014

Depth below land surface, in feet Depth below land surface, in feet Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

3.0

0.5

1.5

2.5

0.0

1.0

2.0

3.0

0.5

1.5

2.5

0.0

1.0

2.0

 3.0

Approximate dates of 

groundwater sampling 

events 1 through 4

Groundwater hydrographs in 

extraction wells at the

confined disposal facility 

EXPLANATION 

(1) Land surface

Figure 13. Groundwater hydrographs for extraction and monitoring wells at the confined disposal facility during September 1, 2014, 

through November 30, 2014. A, EW–4B; B, EW–11B; C, EW–14A; D, MW–4A; E, MW–11A; and F, MW–14A.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 31

Land surface

Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88 Water-level altitude, in feet above NAVD 88

F. Monitoring well MW–14A

E. Monitoring well MW–11A

D. Monitoring well MW–4A

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

595

585

590

580

575

570

565

560

(1) (2) (3) (4)

(1) (2) (3) (4)

(1) (2) (3) (4)

(1)

Sept. 1, 2014

Sept. 11, 2014

Sept. 21, 2014

Oct. 1, 2014

Oct. 11, 2014

Oct. 21, 2014

Oct. 31, 2014

Nov. 10, 2014

Nov. 20, 2014

Nov. 30, 2014

Sept. 1, 2014

Sept. 11, 2014

Sept. 21, 2014

Oct. 1, 2014

Oct. 11, 2014

Oct. 21, 2014

Oct. 31, 2014

Nov. 10, 2014

Nov. 20, 2014

Nov. 30, 2014

Sept. 1, 2014

Sept. 11, 2014

Oct. 1, 2014

Sept. 21, 2014

Oct. 11, 2014

Oct. 21, 2014

Oct. 31, 2014

Nov. 10, 2014

Nov. 20, 2014

Nov. 30, 2014

Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

3.0

Depth below land surface, in feet Depth below land surface, in feet

0.5

1.5

2.5

0.0

1.0

2.0

–0.5

0.5

1.5

2.5

0.0

1.0

2.0

3.0

Approximate dates of 

groundwater sampling 

events 1 through 4

Groundwater hydrographs in 

monitoring wells at the 

confined disposal facility

EXPLANATION

Figure 13. Groundwater hydrographs for extraction and monitoring wells at the confined disposal facility during September 1, 2014, 

through November 30, 2014. A, EW–4B; B, EW–11B; C, EW–14A; D, MW–4A; E, MW–11A; and F, MW–14A.—Continued
32 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Water levels in MW–14A were slightly higher in spring and 

lower during autumn (fig. 12F). During water-quality sampling, groundwater levels in EW–14A ranged from 568.78 

to 581.35 ft (fig. 13C) and in MW–14A, groundwater levels 

ranged from 581.57 to 585.87 ft above NAVD 88 (fig. 13F). 

Groundwater levels in MW–14A were about 10 ft above 

groundwater levels in EW–14A during water-quality sampling.

Quality-Assurance Data

Measured concentrations of aqueous constituents exceeding the minimum reporting limit (MRL) were detected in 

17 of 75 analyses (excluding pH and dissolved solids) from 

equipment blanks collected at well MW–4A (table 7; Christian, 2018). Ammonia exceeded the MRL in three samples; 

calcium, magnesium, and organic carbon exceeded the MRL 

in two samples; and manganese, silica, sulfate, and orthophosphate exceeded the MRL in one sample. Most exceedances 

were small in comparison to the MRL, but organic carbon and 

sulfate detections were notable. Organic carbon, inorganic carbon, and ammonia exceeded the MRL in the equipment blank 

collected October 7, 2014, at well MW–11A. Only the concentration of organic carbon in the equipment blank was greater 

than 1 percent (2.6 percent) of the concentration measured 

in the environmental sample. Calcium, magnesium, sulfate, 

inorganic carbon, iron, organic carbon, and ammonia exceeded 

the MRL in an equipment blank collected on October 22, 

2014, at well MW–14A. The constituent concentrations in the 

equipment blank were less than 1 percent of the concentrations 

measured in the environmental sample from well MW–14A, 

except the concentration of organic carbon was 15 percent of 

that measured in the environmental sample. 

The detected constituent concentrations in the replicate 

and environmental samples were nearly identical with few 

exceptions. In 2 of the 4 sets of replicate samples, the concentrations of orthophosphate were about twice as high in the 

environmental sample as in the replicate sample; although 

the concentrations were all less than 1 mg/L. On September 11, 2014, the concentration of nitrate plus nitrite at well 

EW–4B was greater than twice as high in the replicate sample 

as in the environmental sample; again, the concentrations were 

near the MRL. A replicate sample was collected on October 

7, 2014, from EW–11B about 3 minutes after the environmental sample was collected. The concentrations of most 

constituents were similar in the replicate and environmental 

samples. Exceptions were that iodide was approximately 

twice as high in the replicate sample as in the environmental 

sample, and orthophosphate was about twice as high in the 

environmental sample as in the replicate sample. A replicate 

sample was collected on October 21, 2014, from EW–14A 

about 3 minutes after the environmental sample was collected. 

No appreciable differences in constituent concentrations were 

observed (table 7).

Quality-assurance data results from the analyses made 

on samples of sterile blank water are listed in tables 7 and 8. 

Equipment blanks indicated limited amounts of inorganic, 

organic, and bacteria carryover; however, these quantities 

were small in comparison to the magnitudes detected in the 

environmental samples. In general, results of the qualityassurance data indicated that analyses made on environmental 

samples should generally be reproducible.

Water Chemistry

Similarities and differences in groundwater chemistry 

were observed at the six locations (three well nests) during the 

four sampling regimes. The data were also compared to the 

groundwater chemistry in two wells (D21 and D40) that are 

near to the CDF but not located on the site (referred to herein 

as ‘offsite’ wells) (table 7; fig. 1). The D21 and D40 wells 

may represent water quality that has not been as significantly 

impacted by human activities as the CDF wells. The waterquality data for D21 and D40 are for samples collected during 

1986–93. Tools used to aid the comparisons included modified 

boxplots, phase diagrams, x-y plots, and scatter plots. Statistical methods were not used to quantitatively evaluate whether 

chemical constituents or property values were higher or lower 

based on a threshold of statistical significance; rather, the 

following discussions use only relative differences to characterize differences in water chemistry between sites. Modified 

boxplots were used to show the relative differences in constituent concentrations and parameter values for the four samples 

at the CDF wells. The terminology ‘modified boxplot’ is used 

to emphasize that the number of values used to construct the 

diagrams was smaller than the number that is normally used 

to construct boxplots. Samples collected for quality-assurance 

purposes were not included in the following description of 

environmental samples. The second samples collected in 

November at EW4B and MW4A also were not included in 

the analysis.

The depth to water varied considerably between the wells 

during sample collection. The lowest water levels ranged 

from 10.5 to 22.5 ft below land surface, with the lowest water 

levels in EW–4B (22.5 ft; 568.5 ft above the vertical datum) 

and EW–14A (22.3 ft; 568.1 ft above the vertical datum). The 

highest water levels ranged from 9.5 to 11.4 ft below land 

surface. During the study period, water levels fluctuated from 

0.7 to 2.4 ft in monitoring wells, compared to 9.7 to 12.3 ft 

in extraction wells. The depths to water in offsite wells when 

those wells were sampled, albeit from a different time period, 

were 0.5 and 2.5 ft. 

Dissolved oxygen ranged from 0.18 to 1.64 mg/L 

(median 0.18 mg/L) in the CDF well waters (hereafter, “well 

waters” is presented as “wells”), compared to 0.0 to 1.6 mg/L 

(median 0.4 mg/L) in the offsite wells. In extraction wells, 

dissolved oxygen ranged from 0.18 to 0.44 mg/L and median 

concentration was 0.19 mg/L in all three wells (fig. 14). In 

monitoring wells, dissolved oxygen ranged from 0.18 to 

1.64 mg/L and median concentrations ranged from 0.18 to 

0.53 mg/L (fig. 14; table 7).
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 33

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

D21 D21 D21 D21

Date sampled

July 22, 1987 May 3, 1988 August 4, 1988 June 15, 1993

Time sampled

1600 1645 1015 1635

Sample type

EnvironmentalEnvironmentalEnvironmentalEnvironmental

Dissolved solids dried at 180 degrees Celsius, water, filtered, milligrams per liter 830 -- -- 641

pH, water, unfiltered, laboratory, standard units 7.5 -- -- --

pH, water, unfiltered, onsite, standard units 7.4 7.7 7.4 --

Specific conductance, water, unfiltered, laboratory, microsiemens per centimeter 

at 25 degrees Celsius

983 -- -- --

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter at 

25 degrees Celsius

1,330 1,200 1,360 --

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), millivolts -- -- -- -120

Eh (standard hydrogen electrode), millivolts1 -- -- -- 111

pE -- -- -- 1.95

Dissolved oxygen, water, unfiltered, onsite, milligrams per liter 0.00 0.40 0.60 0.10

Temperature, in degrees Celsius 19.0 12.3 19.5 13.3

Turbidity, water, unfiltered, broad band light source (400–680 nanometers), 

detectors at multiple angles including 90 plus -30 degrees, ratiometric correction, NTRU

-- -- -- --

Hardness, water, milligrams per liter as calcium carbonate 580 -- -- --

Calcium, water, filtered, milligrams per liter 160 -- -- 120

Magnesium, water, filtered, milligrams per liter 43 -- -- 33

Sodium, water, filtered, milligrams per liter 54 -- -- 40

Potassium, water, filtered, milligrams per liter 15 -- -- 8.5

Sulfate, water, filtered, milligrams per liter 210 -- -- E 187

Chloride, water, filtered, milligrams per liter 78 -- -- E 59.7

Fluoride, water, filtered, milligrams per liter 1.6 -- -- --

Iodide, water, filtered, milligrams per liter -- -- -- --

Carbon, inorganic, water, filtered, as carbon, milligrams per liter -- -- -- --

Sulfide, spectrophotometric, milligrams per liter -- -- -- --

Iron, water, filtered, micrograms per liter 1,600 -- -- --

Ferrous iron, spectrophotometric, milligrams per liter -- -- -- --

Manganese, water, filtered, micrograms per liter 250 -- -- --

Silica, water, filtered, milligrams per liter as silica 38 -- -- E 36

Organic carbon, water, filtered, milligrams per liter -- -- -- --

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), water, 

filtered, analytically determined, milligrams per liter

-- -- -- --

Ammonia, water, filtered, milligrams per liter as nitrogen 8.5 -- -- --

Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen -- -- -- --

Nitrite, water, filtered, milligrams per liter as nitrogen -- -- -- --

Orthophosphate, water, filtered, milligrams per liter as phosphorus 0.12 -- -- --

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
34 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.—Continued

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

D40 D40 D40 D40 D40

Date sampled

August 

28, 1986

July 16, 

1987

May 10, 

1988

August 

2, 1988

June 14, 

1993

Time sampled

950 1318 1000 1845 1705

Sample type

EnvironmentalEnvironmentalEnvironmentalEnvironmentalEnvironmental

Dissolved solids dried at 180 degrees Celsius, water, filtered, milligrams per liter -- 350 -- -- 433

pH, water, unfiltered, laboratory, standard units -- 7.3 -- -- --

pH, water, unfiltered, onsite, standard units 7.1 7.1 7.3 6.9 6.2

Specific conductance, water, unfiltered, laboratory, microsiemens per centimeter at 

25 degrees Celsius

-- 541 -- -- --

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter at 

25 degrees Celsius

1,550 550 1,720 2,070 --

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), millivolts -- -- -- -- -85

Eh (standard hydrogen electrode), millivolts1 -- -- -- -- 146

pE -- -- -- -- 2.58

Dissolved oxygen, water, unfiltered, onsite, milligrams per liter 1.60 0.80 0.40 0.90 0.30

Temperature, in degrees Celsius 16.9 18.1 8.7 19.0 12.1

Turbidity, water, unfiltered, broad band light source (400–680 nanometers), detectors 

at multiple angles including 90 plus -30 degrees, ratiometric correction, NTRU

-- -- -- -- --

Hardness, water, milligrams per liter as calcium carbonate -- 240 -- -- --

Calcium, water, filtered, milligrams per liter -- 77 -- -- 100

Magnesium, water, filtered, milligrams per liter -- 12 -- -- 27

Sodium, water, filtered, milligrams per liter -- 25 -- -- 33

Potassium, water, filtered, milligrams per liter -- 1.5 -- -- 1.2

Sulfate, water, filtered, milligrams per liter -- 49 -- -- E 5.5

Chloride, water, filtered, milligrams per liter -- 11.0 -- -- 29.5

Fluoride, water, filtered, milligrams per liter -- 1 -- -- --

Iodide, water, filtered, milligrams per liter -- -- -- -- --

Carbon, inorganic, water, filtered, as carbon, milligrams per liter -- -- -- -- --

Sulfide, spectrophotometric, milligrams per liter -- -- -- -- --

Iron, water, filtered, micrograms per liter -- 2,800 -- -- --

Ferrous iron, spectrophotometric, milligrams per liter -- -- -- -- --

Manganese, water, filtered, micrograms per liter -- 690 -- -- --

Silica, water, filtered, milligrams per liter as silica -- 24.0 -- -- E 16.9

Organic carbon, water, filtered, milligrams per liter -- -- -- -- --

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), water, filtered, analytically determined, milligrams per liter-- -- -- -- --

Ammonia, water, filtered, milligrams per liter as nitrogen -- 0.87 -- -- --

Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen -- -- -- -- --

Nitrite, water, filtered, milligrams per liter as nitrogen -- -- -- -- --

Orthophosphate, water, filtered, milligrams per liter as phosphorus -- 0.26 -- -- --

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen 

electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 35

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.—Continued

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

MW–4A MW–4A MW–4A MW–4A MW–4A MW–4A MW–4A MW–4A

Date sampled

September 5, 

2014

September 11, 

2014

October 

23, 2014

November 

6, 2014

September 

10, 2014

October 9, 

2014

October 

23, 2014

November 

6, 2014

Time sampled

858 915 1300 1335 1600 915 935 848

Sample type

Equipment 

blank

Equipment 

blank

Equipment 

-manifold 

blank

Equipment 

-pump 

blank

EnvironmentalEnvironmentalEnvironmentalEnvironmental

Dissolved solids dried at 180 degrees Celsius, water, 

filtered, milligrams per liter

<20 <20 <20 <20 2,420 3,450 2,820 3,730

pH, water, unfiltered, laboratory, standard units 6.3 E 6.3 E 6.0 E 6.2 6.8 6.7 6.7 6.7

pH, water, unfiltered, onsite, standard units -- -- -- -- 6.5 6.5 6.6 6.4

Specific conductance, water, unfiltered, laboratory, microsiemens per centimeter at 25 degrees Celsius<5 <5 <5 <5 2,570 3,400 2,890 3,670

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter at 25 degrees Celsius-- -- -- -- 2,410 3,200 2,740 4,160

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), millivolts-- -- -- -- -116 -201 -186 -255

Eh (standard hydrogen electrode), millivolts1 -- -- -- -- 115 30 45 -24

pE -- -- -- -- 2.02 0.53 0.79 -0.42

Dissolved oxygen, water, unfiltered, onsite, milligrams 

per liter

-- -- -- -- 0.87 0.18 0.18 1.10

Temperature, in degrees Celsius -- -- -- -- 14.2 12.6 12.4 12.2

Turbidity, water, unfiltered, broad band light source (400–

680 nanometers), detectors at multiple angles including 

90 plus -30 degrees, ratiometric correction, NTRU

-- -- -- -- 26 2.4 8.5 60

Hardness, water, milligrams per liter as calcium carbonate -- -- -- -- 1,660 2,360 1,910 2,630

Calcium, water, filtered, milligrams per liter 0.035 <0.022 <0.022 0.028 372 468 466 541

Magnesium, water, filtered, milligrams per liter <0.011 <0.011 0.026 0.022 178 288 181 311

Sodium, water, filtered, milligrams per liter <0.06 <0.06 <0.06 <0.06 30.9 45.4 39.8 49.4

Potassium, water, filtered, milligrams per liter <0.030 <0.004 <0.030 <0.030 25.9 27.6 30.8 27.5

Sulfate, water, filtered, milligrams per liter <0.02 <0.02 <0.02 0.163 1,300 2,050 1,230 1,730

Chloride, water, filtered, milligrams per liter <0.02 <0.02 <0.02 <0.02 11.0 11.2 13.9 14.5

Fluoride, water, filtered, milligrams per liter <0.01 <0.01 <0.01 <0.01 0.54 0.49 0.51 0.51

Iodide, water, filtered, milligrams per liter <0.001 -- <0.001 <0.001 0.009 0.013 0.008 0.016

Carbon, inorganic, water, filtered, as carbon, milligrams 

per liter

E 0.4 E 0.3 E 0.5 E 0.3 150 190 140 210

Sulfide, spectrophotometric, milligrams per liter -- -- -- -- 0.481 0.427 0.456 >0.660

Iron, water, filtered, micrograms per liter <4.0 <4.0 <4.0 <4.0 14,100 11,500 11,100 8,980

Ferrous iron, spectrophotometric, milligrams per liter -- -- -- -- >3.30 >3.30 >3.30 3.14

Manganese, water, filtered, micrograms per liter 0.211 <0.2 <0.2 <0.2 855 1,040 1,440 1,980

Silica, water, filtered, milligrams per liter as silica <0.018 <0.018 0.076 <0.018 49.1 55.4 49.3 59.0

Organic carbon, water, filtered, milligrams per liter 15.3 <0.23 <0.23 48.1 29.4 40.0 30.9 48.1

Total nitrogen (nitrate plus nitrite plus ammonia plus 

organic nitrogen), water, filtered, analytically determined, milligrams per liter

<0.05 <0.05 <0.05 <0.05 3.45 3.92 3.14 5.78

Ammonia, water, filtered, milligrams per liter as nitrogen 0.011 0.029 0.013 <0.010 2.28 3.07 1.92 4.12

Nitrate plus nitrite, water, filtered, milligrams per liter as 

nitrogen

<0.040 <0.040 <0.040 <0.040 <0.040 <0.200 <0.040 <0.040

Nitrite, water, filtered, milligrams per liter as nitrogen <0.001 <0.001 <0.001 <0.001 0.001 0.003 <0.001 <0.010

Orthophosphate, water, filtered, milligrams per liter as 

phosphorus

<0.004 <0.030 0.007 <0.004 0.069 0.099 0.027 0.077

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
36 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.—Continued

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

EW–4B EW–4B EW–4B EW–4B EW–4B EW–4B

Date sampled

September 

11, 2014

November 5, 

2014

September 

11, 2014

October 9, 

2014

October 22, 

2014

November 

5, 2014

Time sampled

1413 1348 1410 1410 1353 1230

Sample type

Replicate Replicate Environmental

EnvironmentalEnvironmentalEnvironmental

Dissolved solids dried at 180 degrees Celsius, water, filtered, 

milligrams per liter

2,120 1,950 2,100 2,420 2,020 1,960

pH, water, unfiltered, laboratory, standard units 7.0 7.1 7.0 7.1 7.2 7.2

pH, water, unfiltered, onsite, standard units -- -- 6.8 6.9 6.8 6.8

Specific conductance, water, unfiltered, laboratory, microsiemens per 

centimeter at 25 degrees Celsius

2,470 2,320 2,480 2,670 2,320 2,310

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter at 25 degrees Celsius-- -- 2,430 2,390 2,280 2,210

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), 

millivolts

-- -- -311 -345 -359 -328

Eh (standard hydrogen electrode), millivolts1 -- -- -80 -114 -128 -97

pE -- -- -1.39 -1.98 -2.23 -1.70

Dissolved oxygen, water, unfiltered, onsite, milligrams per liter -- -- 0.44 0.18 0.20 0.18

Temperature, in degrees Celsius -- -- 16.3 16.6 16.3 15.3

Turbidity, water, unfiltered, broad band light source (400–680 nanometers), detectors at multiple angles including 90 plus -30 degrees, 

ratiometric correction, NTRU

-- -- 39 5.2 36 28

Hardness, water, milligrams per liter as calcium carbonate -- -- 1,580 1,700 1,430 1,420

Calcium, water, filtered, milligrams per liter 273 237 276 271 245 276

Magnesium, water, filtered, milligrams per liter 218 188 217 249 198 177

Sodium, water, filtered, milligrams per liter 50.1 52.0 50.2 58.2 52.3 48.0

Potassium, water, filtered, milligrams per liter 11.3 11.1 11.5 12.5 12.1 11.9

Sulfate, water, filtered, milligrams per liter 881 860 906 857 806 871

Chloride, water, filtered, milligrams per liter 14.3 15.8 14.5 12.4 15.1 16.4

Fluoride, water, filtered, milligrams per liter 0.825 1.02 0.86 0.75 0.96 0.93

Iodide, water, filtered, milligrams per liter 0.014 -- 0.031 0.022 0.042 0.031

Carbon, inorganic, water, filtered, as carbon, milligrams per liter 180 170 180 190 180 180

Sulfide, spectrophotometric, milligrams per liter -- -- 0.660 0.481 >0.660 0.496

Iron, water, filtered, micrograms per liter 5,450 4,870 5,800 7,560 5,060 6,500

Ferrous iron, spectrophotometric, milligrams per liter -- -- 2.93 3.14 >3.30 3.25

Manganese, water, filtered, micrograms per liter 378 426 375 409 396 321

Silica, water, filtered, milligrams per liter as silica 47.6 49.8 47.4 52.1 46.6 46.7

Organic carbon, water, filtered, milligrams per liter 48.1 47.2 45.8 47.9 46.8 45.8

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), 

water, filtered, analytically determined, milligrams per liter

6.87 7.88 6.89 7.66 6.82 6.87

Ammonia, water, filtered, milligrams per liter as nitrogen 6.16 6.57 6.16 6.31 6.42 6.07

Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen 0.078 <0.040 <0.040 <0.200 <0.040 <0.040

Nitrite, water, filtered, milligrams per liter as nitrogen <0.002 <0.010 <0.005 <0.002 <0.001 <0.010

Orthophosphate, water, filtered, milligrams per liter as phosphorus 0.265 0.165 0.583 0.627 0.171 0.158

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 37

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.—Continued

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

MW–11A MW–11A MW–11A MW–11A MW–11A

Date sampled

October 7, 

2014

September 9, 

2014

October 7, 

2014

October 20, 

2014

November 3, 

2014

Time sampled

1445 1225 920 1310 1230

Sample type

Equipment 

blank

EnvironmentalEnvironmentalEnvironmentalEnvironmental

Dissolved solids dried at 180 degrees Celsius, water, filtered, milligrams 

per liter

<20 823 903 912 767

pH, water, unfiltered, laboratory, standard units E6.3 6.6 6.8 6.9 6.8

pH, water, unfiltered, onsite, standard units -- 6.5 6.6 6.6 6.5

Specific conductance, water, unfiltered, laboratory, microsiemens per centimeter at 25 degrees Celsius<5 1,240 1,290 1,350 1,250

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter 

at 25 degrees Celsius

 -- 2,180 1,220 1,340 1,240

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), 

millivolts

 -- -240 -211 -135 -155

Eh (standard hydrogen electrode), millivolts1 -- -9 20 96 76

pE -- -0.16 0.35 1.69 1.34

Dissolved oxygen, water, unfiltered, onsite, milligrams per liter -- 0.49 0.18 0.18 0.18

Temperature, in degrees Celsius -- 13.2 12.7 13.4 13.1

Turbidity, water, unfiltered, broad band light source (400–680 nanometers), 

detectors at multiple angles including 90 plus -30 degrees, ratiometric 

correction, NTRU

 -- 3.7 10 12 7.1

Hardness, water, milligrams per liter as calcium carbonate -- 607 652 731 641

Calcium, water, filtered, milligrams per liter <0.022 174 184 210 184

Magnesium, water, filtered, milligrams per liter <0.011 41.7 46.5 50.4 44.4

Sodium, water, filtered, milligrams per liter <0.06 22.8 26.4 26.5 25.7

Potassium, water, filtered, milligrams per liter <0.03 10.0 13.6 18.8 9.77

Sulfate, water, filtered, milligrams per liter <0.02 11.0 44.3 84.6 3.95

Chloride, water, filtered, milligrams per liter <0.02 34.7 34.3 33.4 35.1

Fluoride, water, filtered, milligrams per liter <0.01 0.54 0.43 0.48 0.51

Iodide, water, filtered, milligrams per liter <0.001 -- 0.056 0.049 0.040

Carbon, inorganic, water, filtered, as carbon, milligrams per liter E0.3 220 240 220 220

Sulfide, spectrophotometric, milligrams per liter -- 0.147 0.224 0.162 0.109

Iron, water, filtered, micrograms per liter <4.0 45,900 40,500 34,500 47,400

Ferrous iron, spectrophotometric, milligrams per liter -- >3.30 >3.30 >3.30 >3.30

Manganese, water, filtered, micrograms per liter <0.2 747 761 814 732

Silica, water, filtered, milligrams per liter as silica <0.018 35.3 38.3 38.5 38.0

Organic carbon, water, filtered, milligrams per liter 1.01 43.7 38.6 34.8 39.8

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), 

water, filtered, analytically determined, milligrams per liter

<0.05 8.11 8.09 6.96 8.62

Ammonia, water, filtered, milligrams per liter as nitrogen 0.026 6.50 6.75 5.35 7.21

Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen <0.04 <0.040 <0.040 <0.040 <0.200

Nitrite, water, filtered, milligrams per liter as nitrogen <0.001 0.011 0.018 0.008 <0.010

Orthophosphate, water, filtered, milligrams per liter as phosphorus <0.004 E0.176 0.197 0.091 0.143

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen 

electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
38 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.—Continued

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

EW–11B EW–11B EW–11B EW–11B EW–11B

Date sampled

October 7, 

2014

September 

9, 2014

October 7, 

2014

October 21, 

2014

November 

4, 2014

Time sampled

1248 930 1245 925 930

Sample type

Replicate Environmental

EnvironmentalEnvironmentalEnvironmental

Dissolved solids dried at 180 degrees Celsius, water, filtered, milligrams per liter 869 821 849 917 792

pH, water, unfiltered, laboratory, standard units 6.8 7.0 6.8 6.8 6.8

pH, water, unfiltered, onsite, standard units -- 6.5 6.6 6.6 6.6

Specific conductance, water, unfiltered, laboratory, microsiemens per centimeter at 

25 degrees Celsius

1,260 1,140 1,260 1,340 1,240

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter at 

25 degrees Celsius

 -- 1,040 1,300 1,330 1,200

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), millivolts -- -150 -122 -82 -113

Eh (standard hydrogen electrode), millivolts1 -- 81 109 149 118

pE -- 1.42 1.92 2.62 2.08

Dissolved oxygen, water, unfiltered, onsite, milligrams per liter -- 0.20 0.20 0.18 0.18

Temperature, in degrees Celsius -- 15.2 14.8 13.3 13.5

Turbidity, water, unfiltered, broad band light source (400–680 nanometers), detectors 

at multiple angles including 90 plus -30 degrees, ratiometric correction, NTRU

 -- 4.3 8.3 4.0 3.6

Hardness, water, milligrams per liter as calcium carbonate -- 581 622 682 612

Calcium, water, filtered, milligrams per liter 170 158 170 188 166

Magnesium, water, filtered, milligrams per liter 47.7 45.5 47.9 51.3 48.4

Sodium, water, filtered, milligrams per liter 34.6 29.0 32.7 30.7 31.8

Potassium, water, filtered, milligrams per liter 11.5 7.15 11.7 13.3 8.31

Sulfate, water, filtered, milligrams per liter 47.9 2.48 46.3 105 6.79

Chloride, water, filtered, milligrams per liter 37.5 39.9 37.5 36.9 39.1

Fluoride, water, filtered, milligrams per liter 0.618 0.60 0.58 0.72 0.73

Iodide, water, filtered, milligrams per liter 0.041 -- 0.020 0.041 0.086

Carbon, inorganic, water, filtered, as carbon, milligrams per liter 230 220 230 200 210

Sulfide, spectrophotometric, milligrams per liter -- 0.069 0.098 0.144 0.104

Iron, water, filtered, micrograms per liter 37,900 39,500 37,500 35,800 37,500

Ferrous iron, spectrophotometric, milligrams per liter -- >3.30 >3.30 >3.30 >3.30

Manganese, water, filtered, micrograms per liter 713 717 704 775 752

Silica, water, filtered, milligrams per liter as silica 34.3 32.7 33.8 33.6 33.5

Organic carbon, water, filtered, milligrams per liter 44.1 47.0 44.7 42.5 46.5

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), water, filtered, 

analytically determined, milligrams per liter

8.49 7.92 8.73 7.96 7.84

Ammonia, water, filtered, milligrams per liter as nitrogen 6.3 6.28 6.31 6.15 6.55

Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen <0.04 <0.040 <0.040 <0.200 <0.200

Nitrite, water, filtered, milligrams per liter as nitrogen 0.013 0.011 0.018 <0.002 <0.010

Orthophosphate, water, filtered, milligrams per liter as phosphorus 0.135 E0.067 0.268 0.073 0.279

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen 

electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 39

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.—Continued

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

EW–14A EW–14A EW–14A EW–14A EW–14A

Date sampled

October 21, 

2014

September 

11, 2014

October 8, 

2014

October 21, 

2014

November 4, 

2014

Time sampled

1238 1110 1340 1235 1300

Sample type

Replicate Environmental

EnvironmentalEnvironmentalEnvironmental

Dissolved solids dried at 180 degrees Celsius, water, filtered, milligrams 

per liter

783 733 779 779 793

pH, water, unfiltered, laboratory, standard units 7.1 7.1 7.2 7.4 7.1

pH, water, unfiltered, onsite, standard units -- 6.9 7.0 7.0 6.9

Specific conductance, water, unfiltered, laboratory, microsiemens per centimeter at 25 degrees Celsius1,290 1,320 1,300 1,270 1,270

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter 

at 25 degrees Celsius

 -- 1,290 1,270 1,260 1,170

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), 

millivolts

 -- -95 -147 -112 -121

Eh (standard hydrogen electrode), millivolts1 -- 136 84 119 110

pE -- 2.40 1.48 2.10 1.93

Dissolved oxygen, water, unfiltered, onsite, milligrams per liter -- 0.33 0.20 0.18 0.18

Temperature, in degrees Celsius -- 14.7 15.9 13.6 13.8

Turbidity, water, unfiltered, broad band light source (400–680 nanometers), 

detectors at multiple angles including 90 plus -30 degrees, ratiometric 

correction, NTRU

 -- 3.8 14 5.8 8.0

Hardness, water, milligrams per liter as calcium carbonate -- 636 612 615 601

Calcium, water, filtered, milligrams per liter 154 157 150 151 151

Magnesium, water, filtered, milligrams per liter 57.1 59.4 57.5 57.5 54.6

Sodium, water, filtered, milligrams per liter 52.1 54.7 55.6 54.1 51.2

Potassium, water, filtered, milligrams per liter 11.2 10.7 12.3 11.2 11.0

Sulfate, water, filtered, milligrams per liter 12.6 16.2 15.6 11.7 12.3

Chloride, water, filtered, milligrams per liter 40.1 40.9 38.0 39.3 39.7

Fluoride, water, filtered, milligrams per liter 0.97 0.90 1.12 1.13 1.14

Iodide, water, filtered, milligrams per liter 0.028 0.043 0.075 0.036 0.069

Carbon, inorganic, water, filtered, as carbon, milligrams per liter 180 190 190 180 180

Sulfide, spectrophotometric, milligrams per liter -- 0.057 0.132 0.148 0.174

Iron, water, filtered, micrograms per liter 8,200 8,660 10,500 8,180 7,620

Ferrous iron, spectrophotometric, milligrams per liter -- >3.30 >3.30 >3.30 >3.30

Manganese, water, filtered, micrograms per liter 323 305 337 319 304

Silica, water, filtered, milligrams per liter as silica 40.9 37.9 40.4 41.1 39.1

Organic carbon, water, filtered, milligrams per liter 33.3 33.5 37.1 34.3 35.4

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), 

water, filtered, analytically determined, milligrams per liter

8.52 7.41 9.70 8.65 9.17

Ammonia, water, filtered, milligrams per liter as nitrogen 6.91 6.02 6.14 6.89 6.85

Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen <0.2 <0.040 <0.040 <0.200 <0.080

Nitrite, water, filtered, milligrams per liter as nitrogen <0.010 0.001 0.003 <0.002 <0.010

Orthophosphate, water, filtered, milligrams per liter as phosphorus 0.214 0.229 0.303 0.233 0.218

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen 

electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
40 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 7. Water-quality data for groundwater samples collected at the confined disposal facility.—Continued

[The water-quality data used in this study are available through a data release at https://doi.org/10.5066/F7PK0FBJ (Christian, 2018) and were placed in the 

U.S. Geological Survey’s National Water Information System (U.S. Geological Survey, 2016b). <, less than minimum reporting limit; E, estimated; --, no data; 

Eh, redox potential; pE, negative base 10 logarithm of the electron activity; NTRU, nephelometric turbidity ratio units; >, greater than maximum reporting limit]

Water-quality constituent

Well name

MW–14A MW–14A MW–14A MW–14A MW–14A

Date sampled

October 22, 

2014

September 10, 

2014

October 8, 

2014

October 22, 

2014

November 5, 

2014

Time sampled

1700 1235 925 955 905

Sample type

Equipment 

blank

Environmental 

sample

Environmental 

sample

Environmental 

sample

Environmental 

sample

Dissolved solids dried at 180 degrees Celsius, water, filtered, milligrams 

per liter

<20 1,310 1,060 1,450 986

pH, water, unfiltered, laboratory, standard units E6.3 7.3 7.3 7.2 7.7

pH, water, unfiltered, onsite, standard units -- 6.8 7.0 6.9 6.9

Specific conductance, water, unfiltered, laboratory, microsiemens per 

centimeter at 25 degrees Celsius

<5 1,670 1,520 1,820 1,450

Specific conductance, water, unfiltered, onsite, microsiemens per centimeter at 25 degrees Celsius-- 1,740 1,520 1,810 1,470

Redox potential (silver/silver chloride [Ag/AgCl] reference electrode), 

millivolts

-- -126 -160 -140 -220

Eh (standard hydrogen electrode), millivolts1 -- 105 71 91 11

pE -- 1.84 1.24 1.60 0.19

Dissolved oxygen, water, unfiltered, onsite, milligrams per liter -- 1.64 0.18 0.20 0.18

Temperature, in degrees Celsius -- 15.3 13.2 13.1 13.1

Turbidity, water, unfiltered, broad band light source (400–680 nanometers), detectors at multiple angles including 90 plus -30 degrees, 

ratiometric correction, NTRU

-- 6.0 4.9 4.0 5.5

Hardness, water, milligrams per liter as calcium carbonate -- 975 805 1,040 739

Calcium, water, filtered, milligrams per liter 0.044 284 220 296 197

Magnesium, water, filtered, milligrams per liter 0.012 64.6 62.4 72.8 60.1

Sodium, water, filtered, milligrams per liter <0.06 28.5 48.0 28.2 41.8

Potassium, water, filtered, milligrams per liter <0.03 27.8 24 24 18.4

Sulfate, water, filtered, milligrams per liter 0.037 510 233 649 198

Chloride, water, filtered, milligrams per liter <0.02 17.3 23.4 21 27.8

Fluoride, water, filtered, milligrams per liter <0.01 0.96 1.09 0.99 1.15

Iodide, water, filtered, milligrams per liter <0.001 0.013 0.019 0.007 0.019

Carbon, inorganic, water, filtered, as carbon, milligrams per liter E0.3 130 170 110 160

Sulfide, spectrophotometric, milligrams per liter -- 0.308 0.294 0.348 0.384

Iron, water, filtered, micrograms per liter 5.53 3,100 2,110 3,270 2,410

Ferrous iron, spectrophotometric, milligrams per liter -- 1.48 1.50 2.45 1.50

Manganese, water, filtered, micrograms per liter <0.2 568 512 803 525

Silica, water, filtered, milligrams per liter as silica <0.018 28.0 39.3 26.1 38.5

Organic carbon, water, filtered, milligrams per liter 2.53 17.2 24.5 16.8 25.2

Total nitrogen (nitrate plus nitrite plus ammonia plus organic nitrogen), 

water, filtered, analytically determined, milligrams per liter

<0.25 4.43 4.93 2.36 4.57

Ammonia, water, filtered, milligrams per liter as nitrogen 0.0126 3.02 3.99 1.45 3.37

Nitrate plus nitrite, water, filtered, milligrams per liter as nitrogen <0.04 <0.040 <0.040 <0.040 <0.040

Nitrite, water, filtered, milligrams per liter as nitrogen <0.001 0.004 0.003 0.005 <0.010

Orthophosphate, water, filtered, milligrams per liter as phosphorus <0.004 0.109 0.137 0.07 <0.040

1

Onsite redox values measured with a silver choride reference electrode using 3.5 moles of potassium chloride were converted to Eh (standard hydrogen 

electrode) values by addition of 231 millivolts as described in the manufacturer’s user manual.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 41

Table 8. Bacterial quality-assurance in groundwater samples from wells at the confined disposal facility.

[CFU/mL, colony forming units per milliliter; HAB, Heterotrophic Aerobic Bacteria; --, no data were collected because the test showed no bacterial reaction 

with media; SLYM, slime-forming bacteria; IRB, iron-related bacteria; SRB, sulfate-reducing bacteria; CDF, confined disposal facility]

Well name 

(sample type)

Bacteria 

type

Date

collected

Observation 

date

Days

after 

test 

start

Bacteria

aggressiveness Observation Bacteriadetermination

Approximate 

bacteria 

population 

(CFU/mL)

Lab

(sterile buffer 

water)

HAB 11/4/2014 None -- -- No reaction -- --

SLYM 11/4/2014 None -- -- No reaction -- --

IRB 11/4/2014 None -- -- No reaction -- --

SRB 11/4/2014 None -- -- No reaction -- --

Lab

(sterile deionized 

water)

HAB 11/4/2014 None -- -- No reaction -- --

SLYM 11/4/2014 None -- -- No reaction -- --

IRB 11/4/2014 None -- -- No reaction -- --

SRB 11/4/2014 None -- -- No reaction -- --

Lab

(CDF tap water)

HAB 11/4/2014 None -- -- No reaction -- --

SLYM 11/4/2014 None -- -- No reaction -- --

IRB 11/4/2014 None -- -- No reaction -- --

SRB 11/4/2014 None -- -- No reaction -- --

MW–4A

(pump blank

using sterile

buffer water)

HAB 11/6/2014 11/8/2014 2 Aggressive Bleaching from 

bottom

Aerobic 575,000

SLYM 11/6/2014 11/12/2014 6 Moderate Cloudy growth Slime forming 500

IRB 11/6/2014 11/10/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

11/11/2014 5 Moderate Foam at top Anaerobic 2,200

SRB 11/6/2014 11/12/2014 6 Moderate Cloudy Anaerobic 1,400

MW–4A

(pump blank

using sterile

deionized water)

HAB 11/6/2014 11/8/2014 2 Aggressive Bleaching from 

bottom

Aerobic 575,000

SLYM 11/6/2014 11/12/2014 6 Moderate Cloudy growth Slime forming 500

IRB 11/6/2014 11/10/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

11/11/2014 5 Moderate Foam at top Anaerobic 2,200

SRB 11/6/2014 11/12/2014 6 Moderate Cloudy Anaerobic 1,400

MW–4A

(pump blank 

using CDF tap 

water)

HAB 11/6/2014 None -- -- No reaction -- --

SLYM 11/6/2014 None -- -- No reaction -- --

IRB 11/6/2014 None -- -- No reaction -- --

SRB 11/6/2014 None -- -- No reaction -- --

MW–4A

(Indiana deionized water pump 

blank)

HAB 11/6/2014 11/8/2014 2 Aggressive Bleaching from 

bottom

Aerobic 575,000

SLYM 11/6/2014 11/11/2014 5 Moderate Cloudy plates Slime forming 2,500

11/12/2014 6 Moderate Cloudy growth Slime forming 500

IRB 11/6/2014 11/10/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

11/10/2014 4 Aggressive Foam at top Anaerobic 9,000

SRB 11/6/2014 11/14/2014 8 Moderate Cloudy Anaerobic 75
42 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW−4B MW−4A EW−11B MW−11A EW−14A MW−14A

0.0

0.5

1.0

1.5

Dissolved oxygen, in milligrams per liter

Well name

(4)

(4)

(4)

(4)

(4)

(4)

EXPLANATION

(4)

Median

75th percentile

25th percentile

Highest value

Lowest value

Schematic boxplot

Number of values

2.0

Figure 14. Distribution of dissolved oxygen concentrations in groundwater samples collected onsite from selected wells at the 

confined disposal facility.

The pH values ranged from 6.4 to 7.0 standard units 

(median 6.7 standard units) in CDF wells, compared to 6.2 to 

7.7 (median 7.2 standard units) in offsite wells. The median 

and range of pH values were nearly the same in monitoring 

and extraction wells at the CDF. The pH value was generally 

higher in EW–14A and MW–14A than in wells at the other 

sites. The median pH values in EW–14A and MW–14A were 

6.95 and 6.9 standard units, respectively, compared to 6.8 

and 6.5standard units in EW–4B and MW–4A, respectively, 

and to 6.6 and 6.55 standard units in EW–11B and MW–11A, 

respectively (table 7). 

Specific conductance, turbidity, dissolved solids, and 

hardness values were notably higher in EW–4B and MW–4A 

than in other wells, whereas redox values were generally lower 

in EW–4B and MW–4A. Specific conductance values ranged 

from 1,040 to 4,160 microsiemens per centimeter at 25 °C in 

CDF wells, compared with 550 to 2,070 microsiemens per 

centimeter at 25 °C in two offsite wells. The median specific 

conductance values were 2,335 and 2,970 microsiemens per 

centimeter at 25 °C in EW–4B and MW–4A, respectively, 

compared to a range in medians from 1,250 to 1,630 microsiemens per centimeter at 25 °C in other CDF wells (table 7). 

Turbidity values in CDF wells ranged from 2.4 to 

60 nephelometric turbidity ratio units (NTRU). Median values 

ranged from 4.2 to 32 NTRU in CDF wells. Median turbidity values were 32 and 17 NTRU in EW–4B and MW–4A, 

respectively, compared to a range from 4.2 to 8.6 NTRU in 

all other CDF wells. Dissolved-solids values ranged from 733 

to 3,720 mg/L in CDF wells. Median values were 2,060 and 

3,135 mg/L in EW–4B and MW–4A, respectively, compared 

to a range from 779 to 1,185 mg/L in all other CDF wells. 

Historical turbidity or dissolved-solids data were not available 

for the offsite wells (table 7).

Hardness values ranged from 581 to 2,630 mg/L in CDF 

wells, compared to 240 to 580 mg/L in offsite wells (one 

sample at each well). Median hardness values were 1,505 and 

2,135 mg/L in EW–4B and MW–4A, respectively, compared 

to a range from 614 to 890 mg/L in other CDF wells (table 7). 

Redox values ranged from -359 to -82 millivolts in 

CDF wells (fig. 15) compared to historical values of -85 and 

-120 millivolts for one sample at each of the two offsite wells. 

The median redox value was -336 millivolts in EW–4B, compared to a range in medians from -117 to -194 millivolts in all 

other CDF wells. In summary, (1) the specific conductance, 

turbidity, dissolved-solids, and hardness values were notably 
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 43

EW−4B MW−4A EW−11B MW−11A EW−14A MW−14A

−400

−350

−300

−250

−200

−150

−100

−50

Oxidation-reduction potential, in millivolts

(silver/silver chloride [Ag/AgCl] reference electrode)

Well name

(4)

(4)

(4)

(4)

(4)

(4)

EXPLANATION

(4)

Median

75th percentile

25th percentile

Highest value

Lowest value

Schematic boxplot

Number of values

Figure 15. Distribution of the oxidation-reduction potential in groundwater samples from selected wells at the confined 

disposal facility.

higher in EW–4B and MW–4A than in other wells and (2) the 

redox values were generally lower in EW–4B and MW–4A 

than in other wells (table 7). 

Field test kits were used to measure ferrous iron concentrations in CDF wells. Concentrations ranged from 

1.48 mg/L to the upper reporting limit (3.30 mg/L). Median 

concentrations ranged from 1.50 to greater than 3.30 mg/L 

in CDF wells. The lowest median ferrous iron concentration 

was measured in MW–14A, and the median concentrations 

exceeded 3.10 mg/L in other CDF wells. Sulfide concentrations, measured with field test kits, ranged from 0.057 to 

greater than 0.660 mg/L. Median sulfide concentrations were 

highest in EW–4B (0.58 mg/L) and MW–4A (0.47 mg/L) and 

lowest in EW–11B (0.10 mg/L) and MW–11A (0.15 mg/L) 

(fig. 16; table 7). Historical ferrous iron or sulfide data were 

not available for the offsite wells.

Major cations analyzed included calcium, magnesium, 

sodium, and potassium. The calcium concentrations ranged 

from 150 to 541 mg/L in CDF wells, compared to 77 to 

160 mg/L in offsite wells. The highest and most variable calcium concentrations were in MW–4A. Median calcium concentrations were 274 and 467 mg/L in EW–4B and MW–4A, 

respectively, compared to a range from 151 to 252 mg/L in 

all other CDF wells. In all cases, concentrations were higher 

in monitoring wells than in corresponding extraction wells. 

Magnesium concentrations ranged from 41.7 to 311 mg/L 

in CDF wells, compared to 12 to 43 mg/L in offsite wells. 

Magnesium concentrations ranged from 41.7 to 72.8 mg/L 

in the #11 and #14 well clusters, compared to a range from 

177 to 311 mg/L in the #4 well cluster. Sodium concentrations ranged from 22.8 to 58.2 mg/L in CDF wells, compared 

to 25 to 54 mg/L in offsite wells. Potassium concentrations 

ranged from 7.15 to 30.8 mg/L in CDF wells, compared to 

1.2 to 15 mg/L in offsite wells. Median potassium concentrations were 27.5 and 24.0 mg/L in MW–4A and MW–14A, 

respectively, compared to a range of median concentrations 

from 10.0 to 12.0 mg/L in all other CDF wells. In summary, 

(1) calcium, magnesium, and potassium concentrations were 

higher in CDF wells than in offsite wells; and (2) calcium 

and magnesium concentrations were higher in EW–4B and 

MW–4A than in other wells (table 7). 

Major anions analyzed for this study included sulfate, 

chloride, and fluoride. Alkalinity was not analyzed for this 

study; therefore, carbonate and bicarbonate concentrations 

could not be estimated. Sulfate concentrations ranged from 

2.48 to 2,050 mg/L in CDF wells, compared to 5.5 (estimated) 

to 210 mg/L in two offsite wells. The median sulfate concentrations were 864 and 1,520 mg/L in EW–4B and MW–4A, 

respectively, whereas median concentrations ranged from 

13.9 to 371 mg/L in all other CDF wells (fig. 17). Chloride 
44 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW−4B MW−4A EW−11B MW−11A EW−14A MW−14A

0.0

0.2

0.4

0.6

0.8

1.0

Sulfide, in milligrams per liter

Well name

(4) (4)

(4)

(4)

(4)

(4)

EXPLANATION

(4)

Median

75th percentile

25th percentile

Highest value

Lowest value

Schematic boxplot

Number of values

Maximum reporting limit

Figure 16. Distribution of sulfide concentrations in groundwater samples from selected wells at the confined disposal facility.

concentrations ranged from 11.0 to 40.9 mg/L in CDF wells, 

compared to 11.0 to 78.0 mg/L in offsite wells. Median chloride concentrations were 14.8 and 12.5 mg/L in EW–4B and 

MW–4A, respectively, whereas median concentrations ranged 

from 22.2 to 39.5 mg/L in all other CDF wells. Fluoride concentrations ranged from 0.43 to 1.15 mg/L in CDF wells, compared to 1.0 and 1.6 mg/L in two offsite wells (one sample at 

each well). In summary, (1) sulfate concentrations were higher 

in CDF wells than in offsite wells, (2) chloride and fluoride 

concentrations were comparable in CDF and offsite wells, and 

(3) sulfate concentrations were notably higher in EW–4B and 

MW–4A than in all other wells (table 7).

Trace elements analyzed for this study included total dissolved iron, manganese, iodide, and silica. Iron concentrations 

ranged from 2,110 to 47,400 mg/L in CDF wells, compared to 

1,600 to 2,800 mg/L in offsite wells (one sample at each well). 

Median iron concentrations were 37,500 and 43,200 mg/L in 

EW–11B and MW–11A, respectively, but ranged from 2,760 

to 11,300 mg/L in all other CDF wells (fig. 18). Most iron 

likely occurs as ferrous iron (fig. 19). Manganese concentrations ranged from 304 to 1,980 mg/L in CDF wells and were 

250 and 690 mg/L in two offsite wells (one sample at each 

well). The median manganese concentrations in CDF wells 

ranged from 312 to 1,240 mg/L. Iodide concentrations ranged 

from 0.007 to 0.086 mg/L in CDF wells; iodide was not 

analyzed for in offsite wells. Silica concentrations ranged from 

26.1 to 59.0 mg/L in CDF wells and ranged from 16.9 (estimated) to 38 mg/L in two offsite wells. In general, (1) total 

dissolved-iron concentrations were highest in wells with the 

lowest rate of pump fouling, and (2) manganese, iodide, and 

silica concentrations provided little diagnostic value (table 7).

The highest and lowest results for water-quality characteristics and the constituent concentrations were quantified 

for the four pumping regimes that existed during (and immediately before) sample collection (fig. 20). The water-quality 

data indicate that 45 and 55 percent of the highest values and 

concentrations at EW–14A and EW–4B, respectively, were 

detected during pumping regime 2. The nutrients ammonia, 

total nitrogen, and orthophosphate were highest in EW–4B 

and EW–14A during regime 2; nitrate and nitrite were mostly 

non-detects. The data indicate that 40 to 55 percent of the values and concentrations in EW–11B, MW–11A, and MW–14A 

were highest during pumping regime 3. Most cations and some 

onsite parameters were highest in these wells during pumping 

regime 3. The highest results for water-quality characteristics 

and constituent concentrations were measured in 62 percent of 

the samples from well MW–4A during pumping regime 4. The 

highest redox values were measured in all wells during pumping regimes 1 and 3.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 45

EW−4B MW−4A EW−11B MW−11A EW−14A MW−14A

0

500

1,000

1,500

2,000

Sulfate, in milligrams per liter

Well name

(4)

(4)

(4) (4) (4)

(4)

EXPLANATION

(4)

Median

75th percentile

25th percentile

Highest value

Lowest value

Schematic boxplot

Number of values

2,500

Minimum reporting limit

Figure 17. Distribution of sulfate concentrations in groundwater samples from selected wells at the confined disposal facility.

Nutrients analyzed for this study included ammonia, 

nitrate plus nitrite, nitrite, and orthophosphate. Ammonia 

concentrations (as equivalents of nitrogen) ranged from 1.45 

to 7.21 mg/L in CDF wells, and concentrations were 0.87 

and 8.5 mg/L in two offsite wells (one sample in each well). 

Median ammonia concentrations were 6.24 and 2.68 mg/L in 

EW–4B and MW–4A, respectively; 6.30 and 6.63 mg/L in 

EW–11B and MW–11A, respectively; and 6.50 and 3.20 mg/L 

in EW–14A and MW–14A, respectively. Measurements of 

nitrate plus nitrite (as equivalents of nitrogen) were less than 

the MRL in all CDF and was not analyzed at the offsite wells. 

For some wells, a lower MRL was used to analyze for nitrite 

than was used to analyze for nitrate plus nitrite (as equivalents 

of nitrogen). Nitrite concentrations ranged from less than 

0.001 to 0.018 mg/L, with the highest concentration measured 

in wells EW–11B and MW–11A. The difference between 

total nitrogen concentrations and the sum of the reported 

nitrogenous analytes can be attributed to the presence of other 

unanalyzed nitrogen-containing compounds such as organic 

nitrogen. Orthophosphate concentrations in CDF wells ranged 

from less than 0.04 to 0.627 mg/L, compared to 0.12 and 

0.26 mg/L in two offsite wells (one sample in each well). The 

median orthophosphate concentrations in extraction wells was 

generally greater than the median concentrations in monitoring 

wells. In summary, (1) ammonia concentrations were higher 

in extraction wells EW–4B and EW–14A than in their corresponding monitoring wells, (2) nitrite concentrations were 

higher in EW–11B and MW–11A than other CDF wells, and 

(3) orthophosphate concentrations were higher in extraction 

wells than in monitoring wells.

The redox category identified for most water samples 

was anoxic or mixed (anoxic or oxic-anoxic) (table 9). The 

dominant redox processes included ferric iron (Fe3+), ferric 

iron – sulfate (Fe3+-SO42-) and oxygen – ferric iron (O2

-Fe3+) 

reduction. These processes correspond to the following respective electron acceptor half reactions: 

Fe(OH)3(s) + 3H+ + e- => Fe2+ + 3H2O, (5)

FeOOH(s) + 3H+ + e- => Fe2+ + 2H2O; (6)

Fe3+ and (or) SO 2-

4 individual element half reactions; and

O2 + 4H+ + 4e- => 2H2O. (7)
46 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW−4B MW−4A EW−11B MW−11A EW−14A MW−14A

0

10,000

20,000

30,000

40,000

50,000

Iron, in micrograms per liter

Well name

(4)

(4)

(4)

(4)

(4)

(4)

EXPLANATION

(4)

Median

75th percentile

25th percentile

Highest value

Lowest value

Schematic boxplot

Number of values

Figure 18. Distribution of iron concentrations in groundwater samples from selected wells at the confined disposal facility.

where

Fe(OH)3

(s) is iron hydroxide (solid),

H+ is hydrogen,

e- is an electron,

Fe2+ is ferrous iron,

H2O is water,

FeOOH(s) is iron oxyhydroxide (solid),

Fe3+ is ferric iron, and

SO4

2- is sulfate.

The redox categories for EW–11B, MW–11A, and EW–

14A wells were anoxic Fe3+ reduction. Samples from the other 

wells had variable redox categories and processes.

Dissolved Gases

Dissolved gas concentrations in groundwater samples 

from extraction and monitoring wells were also used to indicate oxidation-reduction conditions. Extraction wells at the 

site have been subjected to recurring drawdown of groundwater levels during operation of the gradient control system. 

Water from extraction wells was considered in the dissolved 

gas sampling to represent possible mixing of water affected 

by recent infiltration nearer the water table. Monitoring wells, 

in comparison, were not regularly pumped during system 

operation. Groundwater from monitoring wells was considered 

in these samples to represent dissolved gas concentrations in 

the aquifer.

Sampling and analysis methods for dissolved gas concentrations were reproducible between most environmental 

and replicate samples analyzed for methane, carbon dioxide, 

nitrogen, and argon; as indicated by RPD statistics for paired 

samples that were less than 10 percent (table 10). Counts of 

samples with reproducible concentrations between paired 

environmental and replicate samples were 26 paired samples 

analyzed for methane, 22 of 26 paired samples analyzed 

for carbon dioxide, 23 of 26 paired samples analyzed for 

argon, and 24 of 26 paired samples analyzed for nitrogen 

(table 10). Analyses of dissolved oxygen were the least 

reproducible in these samples, with 16 of 26 paired environmental and replicate samples having RPD statistics less than 

10 percent (table 10). 

Dissolved gases were identified as having estimated 

concentrations in environmental water samples when the RPD 

statistic was greater than 10 percent when compared with the 

replicate sample (table 10). Samples with estimated concentrations of dissolved gases were used for interpretations in this 

report because of their overall similarity in magnitude with 

samples collected from the same well or other wells at the 

CDF. Dissolved oxygen analyses had the greatest frequency 

of estimated concentrations, possibly because of the small 

dissolved oxygen concentrations (0.0 to 0.19 mg/L) in all 

water samples (table 10). Leakage of air during laboratory 
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 47

pE

pH, in standard units

0 2 4 6 8 10 12 14

-14.0

-10.5

21.0

17.5

14.0

10.5

7.0

3.5

0

-3.5

-7.0

Fe+2

Fe+3

Fe(ΟH)3

Fe(OH)2

25 °C, 1 atm

PH2 = 1 atm

PΟ2

 = 1 atm

EXPLANATION

MW–14A

EW–14A

MW–11A

EW–11B

MW–4A

EW–4B

Fe+3 Ferric iron

PO2 Partial pressure of oxygen gas

atm Atmosphere

Fe+2 Ferrous iron

Fe(OH) 3

 Iron(3+) hydroxide

PH2 Partial pressure of hydrogen gas

Fe(OH)2

 Iron(2+) hydroxide

°C Degrees Celsius

pE Negative base 10 logarithm of the electron activity

Figure 19. Eh-pH phase diagram showing iron stability fields and 

data from the confined disposal facility.

analysis into the replicate sample from well MW–4A collected on October 9, 2014, was interpreted as the source of the 

large RPD statistic difference between paired samples. This 

interpretation was based on the relative enrichment of oxygen, 

argon, and nitrogen in the replicate sample. Carbon dioxide, 

oxygen, argon, and nitrogen concentrations in the paired 

environmental sample from well MW–4A on October 9, 2014, 

were identified as estimated concentrations but were used for 

interpretations in this report because of their overall similarity 

in magnitude with samples collected from other wells at the 

site. Carbon dioxide concentrations in samples from EW–4B 

on September 11, 2014; EW–11B on October 21, 2014; 

and MW–14A on October 22, 2014, were also identified as 

estimated concentrations because of RPD statistic differences 

greater than 10 percent (table 10).

Dissolved argon concentrations in groundwater were 

depleted relative to hypothetical concentrations in equilibrium 

with the atmosphere at temperature and altitude conditions 

similar to those at the site in all samples except from MW–

14A on October 22, 2014 (table 10). Argon concentrations in 

environmental samples ranged from 0.06 mg/L in a sample 

from MW–11A to 0.57 mg/L in a sample from MW–14A. In 

comparison, hypothetical argon concentrations in water in 

equilibrium with the atmosphere at temperature and altitude 

conditions similar to those at the site ranged from 0.51 mg/L, 

for an average monthly July temperature of about 23 °C, to 

0.79 mg/L, for an average monthly March temperature of 

about 3 °C (table 10). These monthly average temperatures 

were from a weather station at a site about 20.5 miles east of 

the CDF site (Arguez and others, 2010). The only groundwater samples with argon concentrations in the range that was 

similar to the hypothetical air-water equilibrium included two 

of the four samples from monitoring well MW–14A. All other 

groundwater samples had smaller argon concentrations than 

this range and were interpreted as having lost argon and other 

gases because of physical outgassing. 

The depletion of argon concentrations in groundwater 

at the CDF is consistent with a pattern of argon loss from 

groundwater and unsaturated zone gas described in another 

study that is related to processes that biotransform and degrade 

residual hydrocarbons in the aquifer and that generate methane 

and carbon dioxide. The depletion of argon in groundwater is 

similar to a pattern described in a study of a crude oil release 

near Bemidji, Minnesota. (Amos and others, 2005). In that 

study, oxygen was consumed and methane and carbon dioxide 

were generated by microbial transformations in anoxic zones 

above and below the water table. Generation of methane and 

carbon dioxide can cause other dissolved gases, including 

argon, to be stripped from groundwater into the unsaturated 

zone and from the unsaturated zone toward the atmosphere 

(Amos and others, 2005; Ng and others, 2015). Feasible pathways for argon and other dissolved gas loss from groundwater 

at the CDF site include fluxes toward the atmosphere through 

the unsaturated zone, at air-water interfaces in extraction 

wells, and through gas leakage into subsurface plumbing. 

Residual hydrocarbons were visually identified in unconsolidated deposits logged in subsurface borings previously 

installed at the CDF site. In addition, groundwater sampling 

for this study identified concentrations of organic carbon in 

groundwater that were considerably greater than the median 

concentration of 7.1 mg/L in groundwater from the Calumet 

aquifer (Duwelius and others, 1996), a possible indication of 

residues in groundwater from hydrocarbon degradation. The 

large methane and carbon dioxide concentrations in dissolved 

gas results from extraction and monitoring wells at the CDF 
48 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Not 

quantified

0

1,000

2,000

3,000

4,000

5,000

0

1,000

1,500

2,000

2,500

3,500

3,000

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

500

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

Dissolved solids,

in milligrams per liter

Hardness,

in milligrams per liter

0

100

200

300

400

500

0

200

300

400

500

700

600

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

100

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

07/22/198707/16/1987

07/22/198707/16/1987

Magnesium,

in milligrams per liter

Calcium,

in milligrams per liter

0

10

15

20

25

35

30

5

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

07/22/198707/16/1987

Potassium,

in milligrams per liter

0

20

30

40

50

70

60

10

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

07/22/198707/16/1987

Sodium,

in milligrams per liter

D21 D40

07/22/198707/16/1987

Figure 20. Concentrations of major ions through time during four pumping regimes—regime 1, September 9–11, 2014 (normal 

operating conditions); regime 2, October 7–9, 2014 (after pump was not operating for at least 8 hours); regime 3, October 20–23, 2014 

(after pumping had resumed for 7 days); and regime 4, November 3–6, 2014 (after pumping had resumed for 14 days).
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 49

Not 

quantified

0

500

1,000

1,500

2,000

2,500

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

07/22/198707/16/1987

Sulfate,

in milligrams per liter

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

07/22/198707/16/1987

07/22/198707/16/1987

Fluoride,

in milligrams per liter

Chloride,

in milligrams per liter

1

Pumpingregime

2 3 4 1

Pumpingregime

2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

Iodide,

in milligrams per liter

0

20

30

40

60

90

80

50

70

10

0

0.4

0.6

0.8

1.2

1.8

1.6

1

1.4

0.2

0

0.03

0.02

0.04

0.05

0.07

0.1

0.09

0.06

0.08

0.01

Figure 20. Concentrations of major ions through time during four pumping regimes—regime 1, September 9–11, 2014 (normal 

operating conditions); regime 2, October 7–9, 2014 (after pump was not operating for at least 8 hours); regime 3, October 20–23, 2014 

(after pumping had resumed for 7 days); and regime 4, November 3–6, 2014 (after pumping had resumed for 14 days).—Continued
50 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0

2

4

6

8

10

12

14

16

18

20

0

1

2

3

4

5

6

7

8

9

Not 

quantified

Not 

quantified

Values less than the

method reporting limit

EXPLANATION

07/22/1987

07/16/1987

07/22/1987

07/16/1987

1 2 3 4 1 2 3 4 1 2 3 1 2 3 4 1 2 3 4 1 2 3 4

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

4

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

0

2

4

6

8

10

12

Total nitrogen,

in milligrams per liter

Ammonia,

in milligrams per liter

PumpingregimePumpingregimePumpingregimePumpingregimePumpingregimePumpingregime

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

Orthophosphate,

in milligrams per liter

Nitrite as nitrogen,

in milligrams per liter (x 0.001)

PumpingregimePumpingregimePumpingregimePumpingregimePumpingregimePumpingregime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

PumpingregimePumpingregimePumpingregimePumpingregimePumpingregimePumpingregime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

PumpingregimePumpingregimePumpingregimePumpingregimePumpingregimePumpingregime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

D21 D40

Figure 20. Concentrations of major ions through time during four pumping regimes—regime 1, September 9–11, 2014 (normal 

operating conditions); regime 2, October 7–9, 2014 (after pump was not operating for at least 8 hours); regime 3, October 20–23, 2014 

(after pumping had resumed for 7 days); and regime 4, November 3–6, 2014 (after pumping had resumed for 14 days).—Continued
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 51

0

1

2

3

4

5

6

7

8

9

0

5

10

15

20

25

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

Specific conductance,

in microsiemens per centimeter

07/22/1987

05/03/1988

08/04/1988

06/15/1993

08/28/1986

07/16/1987

05/10/1988

08/02/1988

06/14/1993

Turbidity,

in nephelometric turbidity units

0

10

20

30

40

50

60

70

Not 

quantified

-400

-350

-300

-250

-200

-150

-100

-50

0

Redox potential, in millivolts

(silver/silver chloride 

[Ag/AgCl] reference electrode)

07/22/198705/03/198808/04/198806/15/199308/28/198607/16/198705/10/198808/02/198806/14/1993

07/22/198705/03/198808/04/198806/15/199308/28/198607/16/198705/10/198808/02/198806/14/1993

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

pH,

in standard units

Water temperature,

in degrees Celsius

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

07/22/198707/16/1987

Dissolved oxygen,

in milligrams per liter

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

05/03/198808/04/198806/15/199308/28/198605/10/198808/02/198806/14/1993

0

2

4

6

8

10

12

14

16

07/22/1987

05/03/1988

08/04/1988

06/15/1993

08/28/1986

07/16/1987

05/10/1988

08/02/1988

06/14/1993

D21 D40

Figure 20. Concentrations of major ions through time during four pumping regimes—regime 1, September 9–11, 2014 (normal 

operating conditions); regime 2, October 7–9, 2014 (after pump was not operating for at least 8 hours); regime 3, October 20–23, 2014 

(after pumping had resumed for 7 days); and regime 4, November 3–6, 2014 (after pumping had resumed for 14 days).—Continued
52 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

0

10,000

20,000

30,000

40,000

50,000

0

500

1,000

1,500

2,000

2,500

0

10

20

30

40

50

60

Iron,

in micrograms per liter

07/22/198705/03/198808/04/198806/15/199308/28/198607/16/198705/10/198808/02/198806/14/1993

07/22/198705/03/198808/04/198806/15/199308/28/198607/16/198705/10/198808/02/198806/14/1993

Not 

quantified

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

1

Pumpingregime

2 3 4 4 1

Pumpingregime

2 3 4 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 Pumping regime Pumping regime Pumping regime Pumping regime

D21 D40

MW–

11A

EW–

14A

MW–

EW–4B MW–4A 14A

EW–

11B

Organic carbon,

in milligrams per liter

Manganese,

in micrograms per liter

Figure 20. Concentrations of major ions through time during 

four pumping regimes—regime 1, September 9–11, 2014 

(normal operating conditions); regime 2, October 7–9, 2014 

(after pump was not operating for at least 8 hours); regime 3, 

October 20–23, 2014 (after pumping had resumed for 7 days); 

and regime 4, November 3–6, 2014 (after pumping had resumed 

for 14 days).—Continued

(table 10) are consistent with their production in the subsurface by anaerobic biotransformation of hydrocarbon compounds (Amos and others, 2005). Carbon dioxide is generated from aerobic hydrocarbon oxidation and as a product of 

hydrocarbon degradation and methane oxidation by anaerobic, 

microbially mediated ferric iron reduction (Baedecker and 

others, 1993). 

Groundwater samples analyzed for dissolved gases from 

the extraction and monitoring wells were substantially anoxic. 

Dissolved oxygen concentrations in water from the extraction 

wells ranged from less than 0.001 in EW–11B to 0.096 mg/L 

in EW–14A. Field measured dissolved oxygen concentrations 

(table 7) were nearly always greater than laboratory analyzed 

dissolved oxygen values (table 10), except for two samples 

from MW–14A in October and November 2014. This difference most likely indicates that some dissolved oxygen was 

consumed in laboratory analyzed samples after collection.

Methane concentrations in groundwater samples from 

extraction wells sampled by this study at the CDF ranged from 

24.1 to 36.2 mg/L and from monitoring wells ranged from 

5.4 to 36.6 (table 10). Methane concentrations in groundwater from the CDF samples were similar to or greater than 

those reported for an anoxic plume of groundwater (about 

10–20 mg/L) in 1998, 2002, and 2003 beneath a crude oil 

spill at Bemidji, Minn. (Cozzarelli and others, 1999; Amos 

and others, 2005). Carbon dioxide concentrations in groundwater samples from extraction wells sampled by this study 

at the CDF ranged from 77 mg/L to an estimated concentration of 260 mg/L and from monitoring wells ranged from 

an estimated concentration of 52 to 330 mg/L (table 10). 

Groundwater with the largest carbon dioxide concentrations 

(155–330 mg/L) also had relatively lower field measured pH 

values (6.4–6.6) than did water with carbon dioxide concentrations of less than about 140 mg/L (pH of 6.8–7.0; tables 7 and 

10). In comparison, Baedecker and others (1993) described a 

dissolved carbon dioxide concentration of about 218 mg/L and 

a methane concentration of about 21.8 mg/L in anoxic groundwater beneath a crude oil spill in 1987, and Amos and others 

(2005) reported dissolved carbon dioxide concentrations of 

about 100 mg/L in the same groundwater plume in about 2002.

The mole ratios of methane to carbon dioxide were 

relatively larger in extraction wells EW–4B and EW–14A than 

in corresponding monitoring wells MW–4A and MW–14A 

(September 9, 2014, and October 21, 2014, samples; table 10). 

Water samples from extraction well EW–11B and monitoring 

wells MW–4A, MW–11A, and MW–14A (October 8, 2014, 
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 53

Table 9. Redox category and process as computed for groundwater samples.[USACE, U.S. Army Corps of Engineers; CDF, confined disposal facility; E, east; Fe(III), ferric iron; SO4, sulfate; O2, oxygen]

Well name Sample collection date General redox category Redox process

USACE CDF extraction well EW–4B, near E Chicago, Indiana September 11, 2014 Mixed (anoxic) Fe(III)–SO4USACE CDF extraction well EW–4B, near E Chicago, Indiana October 9, 2014 Anoxic Fe(III)USACE CDF extraction well EW–4B, near E Chicago, Indiana October 22, 2014 Mixed (anoxic) Fe(III)–SO4USACE CDF extraction well EW–4B, near E Chicago, Indiana November 5, 2014 Anoxic Fe(III)USACE CDF extraction well EW–4B, near E Chicago, Indiana November 5, 2014 Mixed (anoxic) Fe(III)–SO4USACE CDF monitoring well MW–4A, near E Chicago, Indiana September 10, 2014 Mixed (oxic-anoxic)

O2–Fe(III)

USACE CDF monitoring well MW–4A, near E Chicago, Indiana October 9, 2014 Anoxic Fe(III)USACE CDF monitoring well MW–4A, near E Chicago, Indiana October 23, 2014 Anoxic Fe(III)USACE CDF monitoring well MW–4A, near E Chicago, Indiana November 6, 2014 Mixed (oxic-anoxic)

O2–Fe(III)

USACE CDF monitoring well MW–4A, near E Chicago, Indiana November 6, 2014 Mixed (oxic-anoxic)

O2–Fe(III)

USACE CDF extraction well EW–11B, near E Chicago, Indiana September 9, 2014 Anoxic Fe(III)USACE CDF extraction well EW–11B, near E Chicago, Indiana October 7, 2014 Anoxic Fe(III)USACE CDF extraction well EW–11B, near E Chicago, Indiana October 21, 2014 Anoxic Fe(III)USACE CDF extraction well EW–11B, near E Chicago, Indiana November 4, 2014 Anoxic Fe(III)USACE CDF monitoring well MW–11A, near E Chicago, Indiana September 9, 2014 Anoxic Fe(III)USACE CDF monitoring well MW–11A, near E Chicago, Indiana October 7, 2014 Anoxic Fe(III)USACE CDF monitoring well MW–11A, near E Chicago, Indiana October 20, 2014 Anoxic Fe(III)USACE CDF monitoring well MW–11A, near E Chicago, Indiana November 3, 2014 Anoxic Fe(III)USACE CDF extraction well EW–14A, near E Chicago, Indiana September 11, 2014 Anoxic Fe(III)USACE CDF extraction well EW–14A, near E Chicago, Indiana October 8, 2014 Anoxic Fe(III)USACE CDF extraction well EW–14A, near E Chicago, Indiana October 21, 2014 Anoxic Fe(III)USACE CDF extraction well EW–14A, near E Chicago, Indiana November 4, 2014 Anoxic Fe(III)USACE CDF monitoring well MW–14A, near E Chicago, Indiana September 10, 2014 Mixed (oxic-anoxic)

O2–Fe(III)

USACE CDF monitoring well MW–14A, near E Chicago, Indiana October 8, 2014 Mixed (anoxic) Fe(III)–SO4USACE CDF monitoring well MW–14A, near E Chicago, Indiana October 22, 2014 Mixed (anoxic) Fe(III)–SO4USACE CDF monitoring well MW–14A, near E Chicago, Indiana November 5, 2014 Mixed (anoxic) Fe(III)–SO4
54 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana , quality-assurance disposal facility Laboratory measured concentrations of dissolved gases in environmental and replicate samples of groundwater from the confined Table 10. statistics, and hypothetical concentrations of dissolved gas in equilibrium with the atmosphere. [Blue colors indicate extraction well samples and orange colors indicate monitoring well samples. Darker-blue and darker-orange colors are for lines with data from environmental samples used to interpret , month/day/year; hhmm, hours and minutes; °C, -blue and lighter-orange colors are for replicate samples used for quality assurance. USGS, U.S. Geological Survey; mm/dd/yy groundwater conditions. Lighter degrees Celsius; mg/L, milligrams per liter; Q, estimated concentration; --, not computed; RPD, relative percent difference; na, not applicable] Well name USGS station identifier Date sampled (mm/dd/yy) Time sampled (hhmm) Field tem- perature at collection (°C) Sample or computation type Methane (mg/L) Carbon dioxide (mg/L) Oxygen (mg/L) Nitrogen (mg/L) Argon (mg/L) Methane/ carbon dioxide mole ratio Comments EW–4B 413907087291801 09/11/2014 1410 16.32 Environmental 27.8 Q 139 0.030 3.4 0.18 -- Argon depletion from outgassing Replicate 27.4 85 0.031 3.7 0.18 0.88 Argon depletion from outgassing RPD 1.4 48 3.3 8.5 0 -- na EW–4B 413907087291801 10/09/2014 1410 16.59 Environmental 27.0 101 Q 0.030 3.5 0.18 0.73 Argon depletion from outgassing Replicate 27.1 104 0.027 3.5 0.18 0.71 Argon depletion from outgassing RPD 0.4 2.9 11 0 0 -- na EW–4B 413907087291801 10/22/2014 1353 16.28 Environmental 28.8 93 0.029 3.3 0.17 0.85 Argon depletion from outgassing Replicate 28.6 94 0.031 3.6 0.17 0.83 Argon depletion from outgassing RPD 0.7 1.1 6.7 8.7 0 -- na EW–4B 413907087291801 11/05/2014 1230 14.26 Environmental 27.5 90 0.034 3.8 0.19 0.84 Argon depletion from outgassing Replicate 27.4 88 0.034 4.0 0.19 0.85 Argon depletion from outgassing RPD 0.4 2.2 0.0 5.1 0 -- na EW–4B 413907087291801 11/05/2014 1345 15.27 Environmental 28.0 96 Q 0.029 3.2 Q 0.17 0.80 Argon depletion from outgassing Replicate 28.6 99 0.026 3.3 0.11 0.79 Argon depletion from outgassing RPD 2.1 3.1 11 3.1 45 -- na MW–4A 413908087291901 09/10/2014 1600 14.24 Environmental 9.5 155 Q 0.13 9.5 0.37 0.17 Argon depletion from outgassing Replicate 9.8 158 0.092 9.4 0.37 0.17 Argon depletion from outgassing

RPD 3.1 1.9 34 1.1 0 -- na
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 55

, quality-assurance Laboratory measured concentrations of dissolved gases in environmental and replicate samples of groundwater from the confined disposal facility Table 10.

statistics, and hypothetical concentrations of dissolved gas in equilibrium with the atmosphere.—Continued

[Blue colors indicate extraction well samples and orange colors indicate monitoring well samples. Darker-blue and darker-orange colors are for lines with data from environmental samples used to interpret 

, month/day/year; hhmm, hours and minutes; °C, -blue and lighter-orange colors are for replicate samples used for quality assurance. USGS, U.S. Geological Survey; mm/dd/yy groundwater conditions. Lighter

degrees Celsius; mg/L, milligrams per liter; Q, estimated concentration; --, not computed; RPD, relative percent difference; na, not applicable]

Well 

name

USGS station 

identifier

Date 

sampled 

(mm/dd/yy)

Time 

sampled 

(hhmm)

Field temperature at 

collection 

(°C)

Sample or 

computation 

type

Methane 

(mg/L)

Carbon 

dioxide 

(mg/L)

Oxygen 

(mg/L)

Nitrogen 

(mg/L)

Argon 

(mg/L)

Methane/ 

carbon 

dioxide mole 

ratio

Comments

MW–4A 413908087291901 10/09/2014 0915 12.57 Environmental 14.8 Q 203 Q 0.064 Q 6.1 Q 0.27 -- Argon depletion 

from outgassing

Replicate 13.5 240 8.22 47 1.1 0.15 Leak on preparation of sample 

for analysis 

RPD 9.2 17 197 154 121 -- na

MW–4A 413908087291901 10/23/2014 0935 12.43 Environmental 12.3 219 Q 0.088 8.4 0.35 0.15 Argon depletion 

from outgassing

Replicate 12.5 221 0.076 8.3 0.35 0.16 Argon depletion 

from outgassing

RPD 1.6 0.9 15 1.2 0 -- na

MW–4A 413908087291901 11/06/2014 0848 11.85 Environmental 13.9 224 Q 0.070 7.0 0.32 0.17 Argon depletion 

from outgassing

Replicate 14.7 233 0.063 6.6 0.29 0.17 Argon depletion 

from outgassing

RPD 5.6 3.9 11 5.9 9.8 -- na

MW–4A 413908087291901 11/06/2014 0940 12.24 Environmental 16.6 330 Q 0.048 4.5 0.22 0.14 Argon depletion 

from outgassing

Replicate 16.8 327 0.043 4.8 0.23 0.14 Argon depletion 

from outgassing

RPD 1.2 0.9 11 6.5 4.4 -- na

EW–11B 413921087290103 09/08/2014 1400 15.22 Environmental 36.2 214 < 0.001 1.2 0.09 0.46 Argon depletion 

from outgassing

Replicate 35.0 201 < 0.001 1.3 0.09 0.48 Argon depletion 

from outgassing

RPD 3.4 6.3 -- 8.0 0 -- na

EW–11B 413921087290103 10/07/2014 1245 14.83 Environmental 31.9 192 < 0.001 1.5 0.10 0.46 Argon depletion 

from outgassing

Replicate 33.8 204 < 0.001 1.6 0.11 0.45 Argon depletion 

from outgassing

RPD 5.8 6.1 -- 6.5 9.5 -- na
56 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana , quality-assurance Laboratory measured concentrations of dissolved gases in environmental and replicate samples of groundwater from the confined disposal facility Table 10. statistics, and hypothetical concentrations of dissolved gas in equilibrium with the atmosphere.—Continued [Blue colors indicate extraction well samples and orange colors indicate monitoring well samples. Darker-blue and darker-orange colors are for lines with data from environmental samples used to interpret , month/day/year; hhmm, hours and minutes; °C, -blue and lighter-orange colors are for replicate samples used for quality assurance. USGS, U.S. Geological Survey; mm/dd/yy groundwater conditions. Lighter degrees Celsius; mg/L, milligrams per liter; Q, estimated concentration; --, not computed; RPD, relative percent difference; na, not applicable] Well name USGS station identifier Date sampled (mm/dd/yy) Time sampled (hhmm) Field tem- perature at collection (°C) Sample or computation type Methane (mg/L) Carbon dioxide (mg/L) Oxygen (mg/L) Nitrogen (mg/L) Argon (mg/L) Methane/ carbon dioxide mole ratio Comments EW–11B 413921087290103 10/21/2014 0925 13.32 Environmental 31.6 Q 260 0.012 1.4 0.12 0.33 Argon depletion from outgassing Replicate 31.7 197 0.012 1.4 0.11 0.44 Argon depletion from outgassing RPD 0.3 28 0 0 8.7 -- na EW–11B 413921087290103 11/04/2014 0930 13.46 Environmental 32.8 207 Q 0.011 1.3 0.10 0.43 Argon depletion from outgassing Replicate 32.4 212 0.015 1.3 0.10 0.42 Argon depletion from outgassing RPD 1.2 2.4 31 0 0 -- na MW–11A 413921087290101 09/09/2014 1225 13.22 Environmental 35.9 230 < 0.001 Q 1.0 Q 0.07 0.43 Argon depletion from outgassing Replicate 35.9 238 < 0.001 0.9 0.06 0.41 Argon depletion from outgassing RPD 0.0 3.4 -- 11 15 -- na MW–11A 413921087290101 10/07/2014 0920 12.68 Environmental 36.6 230 < 0.001 1.1 0.07 0.44 Argon depletion from outgassing Replicate 37.5 232 < 0.001 1.0 0.07 0.44 Argon depletion from outgassing RPD 2.4 0.9 -- 9.5 0 -- na MW–11A 413921087290101 10/20/2014 1310 13.44 Environmental 35.6 225 < 0.001 1.7 0.10 0.43 Argon depletion from outgassing Replicate 36.1 231 < 0.001 1.7 0.10 0.43 Argon depletion from outgassing RPD 1.4 2.6 -- 0 0 -- na MW–11A 413921087290101 11/03/2014 1230 13.08 Environmental 35.2 241 < 0.001 0.9 0.06 0.40 Argon depletion from outgassing Replicate 35.5 242 < 0.001 0.9 0.06 0.40 Argon depletion from outgassing

RPD 0.8 0.4 -- 0 0 -- na
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 57

, quality-assurance Laboratory measured concentrations of dissolved gases in environmental and replicate samples of groundwater from the confined disposal facility Table 10.

statistics, and hypothetical concentrations of dissolved gas in equilibrium with the atmosphere.—Continued

[Blue colors indicate extraction well samples and orange colors indicate monitoring well samples. Darker-blue and darker-orange colors are for lines with data from environmental samples used to interpret 

, month/day/year; hhmm, hours and minutes; °C, -blue and lighter-orange colors are for replicate samples used for quality assurance. USGS, U.S. Geological Survey; mm/dd/yy groundwater conditions. Lighter

degrees Celsius; mg/L, milligrams per liter; Q, estimated concentration; --, not computed; RPD, relative percent difference; na, not applicable]

Well 

name

USGS station 

identifier

Date 

sampled 

(mm/dd/yy)

Time 

sampled 

(hhmm)

Field temperature at 

collection 

(°C)

Sample or 

computation 

type

Methane 

(mg/L)

Carbon 

dioxide 

(mg/L)

Oxygen 

(mg/L)

Nitrogen 

(mg/L)

Argon 

(mg/L)

Methane/ 

carbon 

dioxide mole 

ratio

Comments

EW–14A 413911087285201 09/11/2014 1110 14.66 Environmental 24.1 81 Q 0.087 9.0 0.46 0.82 Argon depletion 

from outgassing

Replicate 23.4 79 0.11 9.0 0.45 0.81 Argon depletion 

from outgassing

RPD 2.9 2.5 23 0 2.2 -- na

EW–14A 413911087285201 10/08/2014 1340 15.92 Environmental 25.7 77 Q 0.091 8.2 0.44 0.92 Argon depletion 

from outgassing

Replicate 25.7 79 0.11 8.5 0.45 0.89 Argon depletion 

from outgassing

RPD 0.0 2.6 19 3.6 2.2 -- na

EW–14A 413911087285201 10/21/2014 1235 13.62 Environmental 25.2 83 0.096 8.7 0.45 0.83 Argon depletion 

from outgassing

Replicate 25.4 82 0.094 8.8 0.45 0.85 Argon depletion 

from outgassing

RPD 0.8 1.2 2.1 1.1 0 -- na

EW–14A 413911087285201 11/04/2014 1300 13.80 Environmental 25.7 82 0.086 9.1 0.46 0.86 Argon depletion 

from outgassing

Replicate 25.8 84 0.086 8.8 0.45 0.84 Argon depletion 

from outgassing

RPD 0.4 2.4 0 3.4 2.2 -- na

MW–14A 413909087285301 09/10/2014 1235 15.27 Environmental 5.4 61 0.18 13.7 0.51 0.24 Argon depletion 

from outgassing

Replicate 5.4 60 0.17 13.9 0.52 0.25 Argon depletion 

from outgassing

RPD 0.0 1.7 5.7 1.4 1.9 -- na

MW–14A 413909087285301 10/08/2014 0925 13.17 Environmental 19.3 65 0.069 8.8 0.38 0.81 Argon depletion 

from outgassing

Replicate 18.3 66 0.075 8.9 0.38 0.76 Argon depletion 

from outgassing

RPD 5.3 1.5 8.3 1.1 0 -- na
58 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana , quality-assurance Laboratory measured concentrations of dissolved gases in environmental and replicate samples of groundwater from the confined disposal facility Table 10. statistics, and hypothetical concentrations of dissolved gas in equilibrium with the atmosphere.—Continued [Blue colors indicate extraction well samples and orange colors indicate monitoring well samples. Darker-blue and darker-orange colors are for lines with data from environmental samples used to interpret , month/day/year; hhmm, hours and minutes; °C, -blue and lighter-orange colors are for replicate samples used for quality assurance. USGS, U.S. Geological Survey; mm/dd/yy groundwater conditions. Lighter degrees Celsius; mg/L, milligrams per liter; Q, estimated concentration; --, not computed; RPD, relative percent difference; na, not applicable] Well name USGS station identifier Date sampled (mm/dd/yy) Time sampled (hhmm) Field tem- perature at collection (°C) Sample or computation type Methane (mg/L) Carbon dioxide (mg/L) Oxygen (mg/L) Nitrogen (mg/L) Argon (mg/L) Methane/ carbon dioxide mole ratio Comments MW–14A 413909087285301 10/22/2014 0955 13.10 Environmental 6.2 Q 52 0.19 14.6 0.57 0.33 None Replicate 6.7 84 0.18 14.2 0.56 0.22 None RPD 7.8 47 5.4 2.8 1.8 -- na MW–14A 413909087285301 11/05/2014 0905 13.08 Environmental 18.1 65 0.078 8.4 0.38 0.76 Argon depletion from outgassing Replicate 19.9 69 0.080 8.7 0.39 0.79 Argon depletion from outgassing RPD 9.5 6.0 2.5 3.5 2.6 -- na Hypothetical dissolved gas concentrations in equilibrium with the atmosphere at temperature, altitude, and dissolved solids conditions similar to those at the site. Average monthly March temperature of about 3 °C (1981–2010 normals), water table altitude of 578 feet above the National Geodetic Vertical Datum of 1929 and dissolved solids concentration of 2,000 mg/L 0.000 1.1 13.0 20.6 0.79 0.000 Computed concentrations Average monthly July temperature of about 23 °C (1981–2010 normals) and water table altitude of 578 feet above the National Geodetic Vertical Datum of 1929 and dissolved solids concentration of 2,000 mg/L 0.000 0.6 8.3 13.6 0.51 0.000 Computed concentrations
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 59

and October 21, 2104, samples) had relatively smaller ratios of 

methane to carbon dioxide and in all but two cases, had lower 

pH values (tables 7 and 10). The larger ratios of methane 

to carbon dioxide in samples from extraction wells EW–4B 

and EW–14A may indicate the effect of relatively larger 

drawdowns on dissolved gas composition than in samples 

from nearby monitoring wells. Extraction wells produce a 

relatively larger fraction of groundwater from closer to the 

water table than the monitoring wells. Hydrocarbon residues 

were described in core samples of aquifer material at or near 

the water table in borings near EW–4B and in EW–14A 

(U.S. Army Corps of Engineers, 2008a). The water table was 

described in Amos and others (2005) as the zone where hydrocarbon oxidation and methanogens would be most active. 

Methane to carbon dioxide ratios also could be increased by 

precipitation of carbonate minerals in the aquifer.

The lack of dissolved oxygen in groundwater at the site 

is consistent with consumptive loss of dissolved oxygen by 

oxidation-reduction processes. Groundwater samples analyzed 

for dissolved gases from the extraction and monitoring wells 

were substantially anoxic. Dissolved oxygen concentrations 

in water from extraction wells ranged from less than 0.001 in 

EW–11B to 0.096 mg/L in EW–14A. 

Dissolved gas results from groundwater samples at the 

CDF indicate oxidation-reduction processes in the aquifer 

that can feasibly contribute dissolved iron and other products 

from hydrocarbon degradation to groundwater produced by 

extraction wells and to precipitates and solids that accumulate 

on and impair pump operation. The large concentrations of 

carbon dioxide and methane, the depleted argon concentrations relative to atmospheric values and the relatively large 

concentrations of dissolved iron in groundwater samples from 

the field site are consistent with an iron-reduction mediated hydrocarbon oxidation model that was described for a 

different crude oil plume by Baedecker and others (1993). 

Dissolution of ferric iron minerals from the aquifer matrix 

was considered to be the most likely source of iron reacted 

in the hydrocarbon degradation model proposed by Ng and 

others (2015) and Baedecker and others (1993). Simulations 

in that model also postulated that the aquifer was an open 

system from which carbon dioxide and methane outgassed 

from the water table and through the unsaturated zone to the 

atmosphere. The geochemical model of Ng and others (2015) 

also postulated the release of soluble ferrous iron and carbon 

dioxide into groundwater and further proposed that available 

iron in solution could also decrease through precipitation of 

ferrous carbonate minerals, such as siderite. Other studies have 

indicated that the solubility of ferrous iron released through 

reduction of ferric iron precipitates can be enhanced by forming complexes with organic substances (Jobin and Ghosh, 

1972; Rose and Waite, 2003; Munter and others, 2005) such as 

those indicated by total organic carbon present in groundwater 

analyzed by this study (table 7). The abundant methane, carbon dioxide, and iron concentrations in groundwater samples 

and iron and carbonate minerals in solids are also consistent 

with a model of microbial mediated oxidation of hydrocarbon 

residues through reduction of iron in aquifer minerals.

Microbiological Activity 

Microbiological activity reaction tests indicated that bacteria were present in all samples (figs. 21A–21K). Additionally, 

most bacteria are capable of producing slime-like growths 

(Droycon Bioconcepts, Inc., 2006). As a result, identification 

of bacteria present in the individual CDF wells was not indicative of a particular type responsible for biofouling. Concentrations of bacteria subtypes varied between wells and the four 

pumping regimes investigated by this study. Historical microbiological activity data were not available for offsite wells. 

Heterotrophic Aerobic Bacteria

Populations of heterotrophic aerobic bacteria were measurable in all samples and indicated no preference for certain 

well sites (table 11, fig. 21A). Populations of heterotrophic 

aerobic bacteria in groundwater collected during the first two 

pumping regimes were about an order of magnitude higher 

than most samples collected thereafter. The observed reaction 

patterns indicated that aerobic bacteria were dominant with 

some facultative anaerobes present (Droycon Bioconcepts, 

Inc., 2004). Given the anoxic or mixed anoxic conditions at 

the site, the presence of heterotrophic aerobic bacteria may 

be due to atmospheric or equipment exposure. The equipment blanks using sterile buffer water also tested positive for 

heterotrophic aerobic bacteria.

Slime-Forming Bacteria

The populations of three subtypes of slime-forming 

bacteria were measured, including slime-forming bacteria, 

pseudomonad and enteric bacteria, and dense slime bacteria (table 12). Concentrations of slime-forming bacteria in 

groundwater ranged from 500 to 1,750,000 CFU/mL and were 

detected in all samples (table 12, fig. 21B). Slime-forming bacteria tend to be aerobic but can be present at redox interfaces 

(Droycon Bioconcepts, Inc., 2004). 

Pseudomonad and enteric bacteria populations were 

measured with slime-forming bacteria and were detected in 

groundwater from four of the six wells (MW–4A, EW–11B, 

MW–11A, and EW–14A). Populations ranged from 500 to 

440,000 CFU/mL (table 12, fig. 21C). Dense slime bacteria 

were detected in only three wells (MW–4A, EW–14A, and 

MW–11A). The populations of dense slime bacteria were as 

great as 440,000 CFU/mL (table 12, fig. 21D). 

Iron-Related Bacteria

The populations of four subtypes of iron-related bacteria were measured, including iron-related bacteria, enteric 
60 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

1

10

100

1,000

10,000

100,000

1,000,000

EW–4B

MW–4A

EW–11B

MW–11A

EW–14A

MW–14A

Well name

Colony forming units per milliliter (cfu/mL)

EXPLANATION

A. Heterotrophic aerobic bacteria

10

100

1,000

10,000

100,000

1,000,000

10,000,000

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

EW–4B

MW–4A

EW–11B

MW–11A

EW–14A

MW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

MW–4A

EW–11B

MW–11A

EW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

B. Slime-forming bacteria 

C. Slime-forming bacteria—pseudomonad and enteric bacteria subtypes 

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

Figure 21. Populations of 

heterotrophic, slime-forming, ironrelated, and sulfate-reducing bacteria 

subtypes through time during four 

pumping regimes, including normal 

operating conditions (September 9–11, 

2014), after pump was not operating 

for at least 8 hours (October 7–9, 

2014), after pumping had resumed for 

7 days (October 20–23, 2014), and after 

pumping had resumed for 14 days 

(November 3–6, 2014).
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 61

E. Iron-related bacteria 

F. Iron-related bacteria—enteric subtype 

Colony forming units per milliliter (cfu/mL) Colony forming units per milliliter (cfu/mL)

D. Slime-forming bacteria—dense slime bacteria subtype 

MW–4A

MW–11A

EW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

1

10

100

1,000

10,000

100,000

1,000,000

EW–4B

MW–4A

MW–11A

MW–14A

Well name

EXPLANATION

EW–4B

MW–4A

EW–11B

MW–11A

EW–14A

MW–14A

Well name

EXPLANATION

1

10

100

1,000

1

10

100

1,000

10,000

100,000

1,000,000

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

Figure 21. Populations of 

heterotrophic, slime-forming, ironrelated, and sulfate-reducing bacteria 

subtypes through time during four 

pumping regimes, including normal 

operating conditions (September 9–11, 

2014), after pump was not operating 

for at least 8 hours (October 7–9, 

2014), after pumping had resumed for 

7 days (October 20–23, 2014), and after 

pumping had resumed for 14 days 

(November 3–6, 2014).—Continued
62 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW–4B

MW–4A

EW–11B

MW–11A

EW–14A

MW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

G. Iron-related bacteria—anaerobic subtype

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

1

10

100

1,000

10,000

100,000

1,000,000

EW–4B

MW–4A

EW–11B

MW–11A

EW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

H. Iron-related bacteria—pseudomonads and enterics subtype

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

1

10

100

1,000

Figure 21. Populations of 

heterotrophic, slime-forming, ironrelated, and sulfate-reducing bacteria 

subtypes through time during four 

pumping regimes, including normal 

operating conditions (September 9–11, 

2014), after pump was not operating 

for at least 8 hours (October 7–9, 

2014), after pumping had resumed for 

7 days (October 20–23, 2014), and after 

pumping had resumed for 14 days 

(November 3–6, 2014).—Continued
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 63

EW–4B

MW–4A

EW–11B

MW–11A

EW–14A

MW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

J. Sulfate-reducing bacteria—aerobic sulfate-reducing bacteria consortium

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

I. Iron-related bacteria—pseudomonad subtypes 

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

1

10

100

1,000

10,000

MW–4A

EW–14A

1

10

100

1,000

10,000

100,000

1,000,000

10,000,000

Figure 21. Populations of 

heterotrophic, slime-forming, ironrelated, and sulfate-reducing bacteria 

subtypes through time during four 

pumping regimes, including normal 

operating conditions (September 9–11, 

2014), after pump was not operating 

for at least 8 hours (October 7–9, 

2014), after pumping had resumed for 

7 days (October 20–23, 2014), and after 

pumping had resumed for 14 days 

(November 3–6, 2014).—Continued
64 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW–4B

MW–4A

EW–11B

MW–11A

EW–14A

MW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

L. Sulfate-reducing bacteria—dense anaerobic sulfate-reducing bacteria consortium

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

EW–4B

MW–4A

EW–11B

MW–11A

MW–14A

Well name

EXPLANATION

Colony forming units per milliliter (cfu/mL)

K. Sulfate-reducing bacteria—anaerobic sulfate-reducing bacteria consortium 

Pumping 

regime 1

(September 9−11, 2014)

Pumping

regime 2

(October 7−9, 2014)

Pumping

regime 3

(October 20−23, 2014)

Pumping 

regime 4

(November 3−6, 2014)

1

10

100

1,000

10,000

100,000

1,000,000

1

10

100

1,000

10,000

100,000

1,000,000 Figure 21. Populations of 

heterotrophic, slime-forming, ironrelated, and sulfate-reducing bacteria 

subtypes through time during four 

pumping regimes, including normal 

operating conditions (September 9–11, 

2014), after pump was not operating 

for at least 8 hours (October 7–9, 

2014), after pumping had resumed for 

7 days (October 20–23, 2014), and after 

pumping had resumed for 14 days 

(November 3–6, 2014).—Continued
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 65

Table 11. Heterotrophic aerobic bacteria activity and population in groundwater samples from wells at the confined disposal facility.

[CFU/mL, colony forming units per milliliter]

Well name Date sampled Date observed

Days 

after test 

start

Bacteria

aggressiveness Observation Bacteriadetermination

Approximate 

bacteria

population 

(CFU/mL)

EW–4B

9/11/2014 9/12/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/9/2014 10/10/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/22/2014 10/24/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

11/5/2014 11/7/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

MW–4A

9/10/2014 9/11/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/9/2014 10/10/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/23/2014 10/24/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

11/6/2014 11/8/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

EW–11B

9/8/2014 9/10/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/7/2014 10/8/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/21/2014 10/23/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

11/4/2014 11/6/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

MW–11A

9/9/2014 9/10/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/7/2014 10/8/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/20/2014 10/22/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

11/3/2014 11/5/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

EW–14A

9/11/2014 9/12/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/8/2014 10/9/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/21/2014 10/23/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

11/4/2014 11/6/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

MW–14A

9/10/2014 9/11/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/8/2014 10/9/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

10/22/2014 10/24/2014 2 Aggressive Bleaching from bottom Aerobic 575,000

11/5/2014 11/6/2014 1 Aggressive Bleaching from bottom Aerobic 5,400,000

bacteria, anaerobic bacteria, and pseudomonad and enteric 

bacteria (table 13, figs. 21E–21H). These iron-related bacteria included iron-reducing and iron-oxidizing bacteria. 

Iron-related bacteria populations ranged from 8 to 500 CFU/

mL and were measured in EW–4B, MW–4A, MW–11A, and 

MW–14A (table 13, fig. 21E). 

The populations of enteric bacteria ranged from 9,000 to 

140,000 CFU/mL (table 13, fig. 21F). Enteric bacteria were 

present in groundwater from all wells and did not indicate 

preference for well or pumping regime. The populations of 

anaerobic bacteria ranged from 2,200 to 140,000 CFU/mL 

(table 13, fig. 21G). The population of pseudomonads and 

enterics bacteria measured by the iron-related bacteria test 

ranged from less than the minimum measurable quantity to 

500 CFU/mL. These bacteria were detected in groundwater 

from all wells except for MW–14A and did not indicate relation to any of the tested pumping regimes (table 13, fig. 21H).

As with the sulfate-reducing bacteria, iron-related bacteria accumulate on surfaces and the system must be disrupted 

by an action, such as a change in pumping rate, to dislodge 

them. The iron-related bacteria prefer oxygenated conditions, 

but research indicates that the bacteria can use the iron in oxidative and reductive states (Droycon Bioconcepts, Inc., 2004). 

The method used in this study detects both forms of ironrelated bacteria. The analytical method used indicated that the 

iron-related bacteria were the anaerobic variety. 
66 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 12. Slime-forming bacteria activity and population in groundwater from wells at the confined disposal facility.

[CFU/mL, colony forming units per milliliter]

Well name Date 

sampled

Date 

observed

Days 

after 

test 

start

Bacteria

aggressiveness Observation Bacteria determination

Approximate 

bacteria 

population

(CFU/mL)

EW–4B

9/11/2014 9/12/2014 1 Aggressive Cloudy growth Slime forming 1,750,000

10/9/2014 10/10/2014 1 Aggressive Cloudy growth Slime forming 1,750,000

10/22/2014 10/26/2014 4 Moderate Cloudy growth Slime forming 13,000

11/5/2014 11/7/2014 2 Aggressive Cloudy growth Slime forming 440,000

MW–4A

9/10/2014 9/11/2014 1 Aggressive Cloudy growth Slime forming 1,750,000

10/9/2014 10/11/2014 2 Aggressive Cloudy growth Slime forming 440,000

10/14/2014 5 Moderate Blackened liquid Pseudomonads and enterics 2,500

10/23/2014 10/26/2014 3 Aggressive Cloudy growth Slime forming 67,000

10/29/2014 6 Moderate Blackened liquid Pseudomonads and enterics 500

11/6/2014 11/8/2014 2 Aggressive Cloudy growth Slime forming 440,000

11/9/2014 3 Aggressive Blackened liquid Pseudomonads and enterics 67,000

11/9/2014 3 Aggressive Dense slime Dense slime 67,000

EW–11B

9/8/2014 9/9/2014 1 Aggressive Cloudy growth Slime forming 1,750,000

9/12/2014 4 Moderate Blackened liquid Pseudomonads and enterics 13,000

10/7/2014 10/9/2014 2 Aggressive Cloudy growth Slime forming 440,000

10/9/2014 2 Aggressive Blackened liquid Pseudomonads and enterics 440,000

10/21/2014 10/23/2014 2 Aggressive Cloudy growth Slime forming 440,000

10/23/2014 2 Aggressive Blackened liquid Pseudomonads and enterics 440,000

11/4/2014 11/6/2014 2 Aggressive Cloudy growth Slime forming 440,000

11/7/2014 3 Aggressive Blackened liquid Pseudomonads and enterics 67,000

MW–11A

9/9/2014 9/11/2014 2 Aggressive Blackened liquid Pseudomonads and enterics 440,000

9/15/2014 5 Moderate Slime ring Dense slime 2,500

10/7/2014 10/8/2014 1 Aggressive Cloudy growth Slime forming 1,750,000

10/9/2014 2 Aggressive Blackened liquid Pseudomonads and enterics 440,000

10/9/2014 2 Aggressive Dense slime Dense slime 440,000

10/20/2012 10/23/2014 3 Aggressive Cloudy growth Slime forming 67,000

10/23/2014 3 Aggressive Blackened liquid Pseudomonads and enterics 67,000

11/3/2014 11/5/2014 2 Aggressive Blackened liquid Pseudomonads and enterics 440,000

11/5/2014 2 Aggressive Cloudy growth Slime forming 440,000
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 67

Table 12. Slime-forming bacteria activity and population in groundwater from wells at the confined disposal facility.—Continued

[CFU/mL, colony forming units per milliliter]

Well name Date 

sampled

Date 

observed

Days 

after 

test 

start

Bacteria

aggressiveness Observation Bacteria determination

Approximate 

bacteria 

population

(CFU/mL)

EW–14A

9/11/2014 9/12/2014 1 Aggressive Cloudy growth Slime forming 1,750,000

9/15/2014 4 Moderate Blackened liquid Pseudomonads and enterics 13,000

9/17/2014 6 Moderate Slime ring Dense slime 500

10/8/2014 10/10/2014 2 Aggressive Cloudy growth Slime forming 440,000

10/11/2014 3 Aggressive Blackened liquid Pseudomonads and enterics 67,000

10/14/2014 6 Moderate Slime ring Dense slime 500

10/21/2014 10/23/2014 2 Aggressive Blackened liquid Pseudomonads and enterics 440,000

10/24/2014 3 Aggressive Cloudy growth Slime forming 67,000

11/4/2014 11/6/2014 2 Aggressive Blackened liquid Pseudomonads and enterics 440,000

11/6/2014 2 Aggressive Cloudy growth Slime forming 440,000

MW–14A

9/10/2014 9/11/2014 1 Aggressive Cloudy growth Slime forming 1,750,000

10/8/2014 10/10/2014 2 Aggressive Cloudy growth Slime forming 440,000

10/22/2014 10/26/2014 4 Moderate Cloudy growth Slime forming 13,000

11/5/2014 11/7/2014 2 Aggressive Cloudy growth Slime forming 440,000

Sulfate-Reducing Bacteria

The populations of three subtypes of sulfate-reducing 

bacteria were measured, including aerobic sulfate-reducing 

bacteria consortium, anaerobic sulfate-reducing bacteria 

consortium, and dense anaerobic sulfate-reducing bacteria 

consortium (table 14, figs. 21I–21K). The aerobic sulfatereducing bacteria consortiums were detected in every sample. 

Populations of aerobic sulfate-reducing bacteria consortium 

ranged from 27,000 to 2,200,000 CFU/mL (table 14, fig. 21I). 

Populations were generally greater from mid-September 

through mid-October and may indicate that pumping regime 2 

favors higher concentrations of sulfate-reducing bacteria.

Anaerobic bacteria were detected once in five of the six 

wells sampled. The detections were in mid-September through 

mid-October. Populations ranged from 1,400 to 115,000 CFU/

mL (table 14, fig. 21J). The number of positive detections for 

anaerobic bacteria was relatively limited but may indicate 

a preference for certain seasonal hydrogeologic settings for 

pumping regimes 1 and 2. The dense anaerobic sulfate-reducing bacteria consortium was detectable in all groundwater 

samples. Populations of the dense anaerobic sulfate-reducing 

bacteria consortium ranged from 1,400 to 115,000 CFU/mL 

(table 14, fig. 21K). Well EW–14A had the largest populations 

of dense anaerobic sulfate-reducing bacteria consortium in all 

samples during every pumping regime (table 14, fig. 21K). A 

seasonal preference was not indicated by these data. Sulfatereducing bacteria are anaerobic and tend to grow deep within 

biofilms and microbial communities in the well (Droycon 

Bioconcepts, Inc., 2004). The biofilms are often attached to 

well components, as opposed to floating in the water; therefore, as a result, biofilms must be disturbed and dispersed into 

the water column before they can be accurately measured in a 

groundwater sample. Visual observation groundwater samples 

in the BARTs containers indicated that the anaerobic bacteria 

were dominated by Desulfovibrio. This reaction pattern was 

indicated in all samples. Additionally, these results correspond 

to the ferric iron – sulfate (Fe3+ -SO4

2-) reducing environment 

and lower iron-sulfate (Fe/S) ratios computed during redox 

analysis in water from MW–14A and EW–14A. 

The largest and smallest populations of the 11 measured 

bacterial communities were determined for the 4 pumping 

regimes that existed during (and immediately before) sample 

collection (fig. 21A–K). The largest and smallest populations 

were not always unique maxima or minima because they 

occasionally occurred during more than one pumping regime. 

For example, the populations of heterotrophic aerobic bacteria 

in water from EW–4B on September 11, 2014 and October 9, 

2014 were assigned a population of 5,400,000 CFU/ml based 

on visual observation of the BART container, and that was the 

maximum population observed among the four samples collected from EW–4B. In some cases, therefore, the maximum 

or minimum population may have occurred during multiple 

pumping regimes. 

The results indicated that the maximum populations of 

the 11 bacteria communities occurred during pumping regime 
68 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 13. Iron-related bacteria activity and population in groundwater from wells at the confined disposal facility.

[CFU/mL, colony forming units per milliliter]

Well name Date 

collected

Observation 

date

Days 

after 

test 

start

Bacteria 

aggressiveness Observation Bacteria determination

Approximate 

bacteria

population

(CFU/mL)

EW–4B

9/11/2014 9/15/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

9/15/2014 4 Aggressive Foam at top Anaerobic 9,000

9/19/2014 8 Moderate Solution black Pseudomonads and enterics 25

10/9/2014 10/12/2014 3 Aggressive Foam at top Anaerobic 35,000

10/12/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

10/18/2014 9 Not aggressive Black throughout Pseudomonads and enterics 8

10/22/2014 10/26/2014 4 Aggressive Foam at top Anaerobic 9,000

10/26/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

11/5/2014 11/8/2014 3 Aggressive Foam at top Anaerobic 35,000

11/8/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

11/13/2014 8 Moderate Brown gel at bottom Iron-related bacteria 25

MW–4A

9/10/2014 9/14/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

9/15/2014 5 Moderate Foam at top Anaerobic 2,200

9/19/2014 9 Not aggressive Green throughout Pseudomonads and enterics 8

10/9/2014 10/10/2014 3 Aggressive Foam at top Anaerobic 35,000

10/10/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

10/17/2014 8 Moderate Brown gel at bottom Iron-related bacteria 25

10/23/2014 10/26/2014 3 Aggressive Foam at top Anaerobic 35,000

10/26/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

11/6/2014 11/8/2014 2 Aggressive Orange at top Enteric (red cloudy) 140,000

11/9/2014 3 Aggressive Foam at top Anaerobic 35,000

11/12/2014 6 Moderate Brown gel at bottom Iron-related bacteria 500

11/13/2014 7 Moderate Black throughout Pseudomonads and enterics 150

EW–11B

9/8/2014 9/10/2014 2 Aggressive Orange at top Enteric (red cloudy) 140,000

9/12/2014 4 Aggressive Foam at top Anaerobic 9,000

10/7/2014 10/10/2014 3 Aggressive Foam at top Anaerobic 35,000

10/10/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

10/21/2014 10/23/2014 2 Aggressive Orange at top Enteric (red cloudy) 140,000

10/24/2014 3 Aggressive Foam at top Anaerobic 35,000

11/4/2014 11/8/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

11/9/2014 5 Moderate Foam at top Anaerobic 2,200

11/12/2014 8 Moderate Black throughout Pseudomonads and enterics 25
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 69

Table 13. Iron-related bacteria activity and population in groundwater from wells at the confined disposal facility.—Continued

[CFU/mL, colony forming units per milliliter]

Well name Date 

collected

Observation 

date

Days 

after 

test 

start

Bacteria 

aggressiveness Observation Bacteria determination

Approximate 

bacteria

population

(CFU/mL)

MW–11A

9/9/2014 9/12/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

9/13/2014 4 Aggressive Foam at top Anaerobic 9,000

9/16/2014 7 Moderate Solution black at top Pseudomonads and enterics 150

10/7/2014 10/10/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

10/10/2014 3 Aggressive Foam at top Anaerobic 35,000

10/14/2014 7 Moderate Black throughout Pseudomonads and enterics 150

10/20/2014 10/22/2014 2 Aggressive Orange at top Enteric (red cloudy) 140,000

10/24/2014 4 Aggressive Foam at top Anaerobic 9,000

10/29/2014 9 Not aggressive Brown gel at bottom Iron-related bacteria 8

11/3/2014 11/5/2014 2 Aggressive Orange at top Enteric (red cloudy) 140,000

11/6/2014 3 Aggressive Foam at top Anaerobic 35,000

EW–14A

9/11/2014 9/14/2014 3 Aggressive Foam at top Anaerobic 35,000

9/15/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

9/15/2014 4 Aggressive Green at bottom Pseudomonads 9,000

9/17/2014 6 Moderate Solution black Pseudomonads and enterics 500

10/8/2014 10/11/2014 3 Aggressive Foam at top Anaerobic 35,000

10/11/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

10/15/214 7 Moderate Black throughout Pseudomonads and enterics 150

10/21/2014 10/24/2014 3 Aggressive Foam at top Anaerobic 35,000

10/24/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

11/4/2014 11/6/2014 2 Aggressive Orange at top Enteric (red cloudy) 140,000

11/7/2014 3 Aggressive Foam at top Anaerobic 35,000

11/9/2014 5 Moderate Green throughout Pseudomonads and enterics 2,200

11/10/2014 6 Moderate Black throughout Pseudomonads and enterics 500

MW–14A

9/10/2014 9/13/2014 3 Aggressive Foam at top Anaerobic 35,000

9/14/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

10/8/2014 10/11/2014 3 Aggressive Foam at top Anaerobic 35,000

10/11/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

10/17/2014 9 Not aggressive Brown gel at bottom Iron-related bacteria 8

10/22/2014 10/26/2014 4 Aggressive Foam at top Anaerobic 9,000

10/26/2014 4 Aggressive Orange at top Enteric (red cloudy) 9,000

11/5/2014 11/6/2014 2 Aggressive Foam at top Anaerobic 140,000

11/7/2014 3 Aggressive Orange at top Enteric (red cloudy) 35,000

11/12/2014 7 Moderate Brown gel at bottom Iron-related bacteria 150
70 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 14. Sulfate-reducing bacteria activity and population in groundwater from wells at the confined disposal facility.

[CFU/mL, colony forming units per milliliter; SRB, sulfate-reducing bacteria]

Well name Date 

collected

Observation 

date

Days 

after 

test 

start

Bacteria 

aggressiveness Observation Bacteria determination

Approximate 

bacteria 

population

(CFU/mL)

EW–4B

9/11/2014 9/13/2014 2 Aggressive Slight black on ball only Aerobic SRB consortium 500,000

9/15/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

10/9/2014 10/10/2014 1 Aggressive Slight black on ball only Aerobic SRB consortium 2,200,000

10/12/2014 3 Aggressive Black in base Dense anaerobic SRB 

consortium

115,000

10/13/2014 4 Aggressive Cloudy Anaerobic 27,000

10/22/2014 10/24/2014 2 Aggressive Slight black on ball only Aerobic SRB consortium 500,000

10/26/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

11/5/2014 11/8/2014 3 Aggressive Slight black on ball only Aerobic SRB consortium 115,000

11/9/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

MW–4A

9/10/2014 9/13/2014 3 Aggressive Black on ball Aerobic SRB consortium 115,000

9/14/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

10/9/2014 10/12/2014 3 Aggressive Black on ball Aerobic SRB consortium 115,000

10/14/2014 5 Aggressive Black in base Dense anaerobic SRB 

consortium

6,000

10/15/2014 6 Moderate Cloudy Anaerobic 1,400

10/23/2014 10/27/2014 4 Aggressive Black on ball Aerobic SRB consortium 27,000

10/28/2014 5 Aggressive Black in base Dense anaerobic SRB 

consortium

6,000

11/6/2014 11/9/2014 3 Aggressive Black on ball Aerobic SRB consortium 115,000

11/10/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

EW–11B

9/8/2014 9/10/2014 2 Aggressive Slight black on ball only Aerobic SRB consortium 500,000

9/12/2014 4 Aggressive Black in base and cloudy Dense anaerobic SRB 

consortium

27,000

10/7/2014 10/9/2014 2 Aggressive Black on ball Aerobic SRB consortium 500,000

10/11/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

10/12/2014 5 Aggressive Cloudy Anaerobic 6,000

10/21/2014 10/24/2014 3 Aggressive Black on ball Aerobic SRB consortium 115,000

10/26/2014 5 Aggressive Black in base Dense anaerobic SRB 

consortium

6,000

11/4/2014 11/8/2014 4 Aggressive Black on ball Aerobic SRB consortium 27,000

11/10/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 71

Table 14. Sulfate-reducing bacteria activity and population in groundwater from wells at the confined disposal facility.—Continued

[CFU/mL, colony forming units per milliliter; SRB, sulfate-reducing bacteria]

Well name Date 

collected

Observation 

date

Days 

after 

test 

start

Bacteria 

aggressiveness Observation Bacteria determination

Approximate 

bacteria 

population

(CFU/mL)

MW–11A

9/9/2014 9/11/2014 2 Aggressive Black on ball Aerobic SRB consortium 500,000

9/12/2014 3 Aggressive Cloudy Anaerobic 115,000

9/13/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

10/7/2014 10/9/2014 2 Aggressive Black on ball Aerobic SRB consortium 500,000

10/10/2014 3 Aggressive Black in base Dense anaerobic SRB 

consortium

115,000

10/20/2014 10/23/2014 3 Aggressive Black on ball Aerobic SRB consortium 115,000

10/26/2014 6 Moderate Black in base Dense anaerobic SRB 

consortium

1,400

11/3/2014 11/5/2014 2 Aggressive Black on ball Aerobic SRB consortium 500,000

11/9/2014 6 Moderate Black in base Dense anaerobic SRB 

consortium

1,400

EW–14A

9/11/2014 9/13/2014 2 Aggressive Black on ball Aerobic SRB consortium 500,000

9/14/2014 3 Aggressive Black in base Dense anaerobic SRB 

consortium

115,000

10/8/2014 10/10/2014 2 Aggressive Black on ball Aerobic SRB consortium 500,000

10/11/2014 3 Aggressive Black in base Dense anaerobic SRB 

consortium

115,000

10/21/2014 10/24/2014 3 Aggressive Black on ball Aerobic SRB consortium 115,000

10/24/2014 3 Aggressive Black in base Dense anaerobic SRB 

consortium

115,000

11/4/2014 11/6/2014 2 Aggressive Black on ball Aerobic SRB consortium 500,000

11/7/2014 3 Aggressive Black in base Dense anaerobic SRB 

consortium

115,000

MW–14A

9/10/2014 9/12/2014 2 Aggressive Slight black on ball only Aerobic SRB consortium 500,000

9/15/2014 5 Aggressive Black in base Dense anaerobic SRB 

consortium

6,000

10/8/2014 10/10/2014 2 Aggressive Slight black on ball only Aerobic SRB consortium 500,000

10/11/2014 3 Aggressive Cloudy Anaerobic 115,000

10/12/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000

10/22/2014 10/26/2014 4 Aggressive Slight black on ball only Aerobic SRB consortium 27,000

10/27/2014 5 Aggressive Black in base Dense anaerobic SRB 

consortium

6,000

11/5/2014 11/8/2014 3 Aggressive Slight black on ball only Aerobic SRB consortium 115,000

11/9/2014 4 Aggressive Black in base Dense anaerobic SRB 

consortium

27,000
72 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

1 in EW–14A, during pumping regime 2 in wells EW–4B, 

EW–11B, and MW–11A, and during pumping regime 4 in 

wells MW–4A. The maximum populations in MW–14A 

occurred during pumping regimes 2 and 4; five communities 

were greatest during each of the two pumping regimes. The 

results indicated that the minimum populations occurred during pumping regimes 1 and 3 in water from MW–4A, during 

pumping regime 3 at EW–4B, MW–11A, EW–14A, and MW–

14A, and during pumping regime 4 in EW–11B.

X-Ray Diffraction Analyses

Qualitative X-ray analysis indicated a preponderance of 

amorphous phases, calcite, and sulfur, with lesser quantities 

of dolomite and quartz (table 15; appendix 2). XRD traces for 

samples from wells EW–4C, MW–4B, and EW–11D indicated 

substantial quantities of amorphous material. XRD traces for 

samples from EW–4C, EW–4D, and MW–4B indicated mineralogic sulfur, whereas samples from EW–11D and EW–20D 

did not.

Quantitative analysis of the X-ray data also identified the 

presence of ferrihydrite, goethite, and organic carbon phases in 

Table 15. Summary of X-ray diffraction analysis of solids 

collected as pump scrapings from wells at the confined 

disposal facility.

Well 

name Date sampled Time sampled Description

EW–4C October 23, 2014 1130 Crystalline sulfur plus 

amorphous phase(s)

EW–4D September 11, 2014 1310 Sulfur; dolomite

EW–11D September 19, 2014 0830 Amorphous material 

with a trace of calcite

EW–20D September 19, 2014 0900 Calcite with possible 

trace quartz

EW–20D October 23, 2014 1100 Nearly pure calcite

EW–20D October 23, 2014 1100 Nearly pure calcite

MW–4B October 9, 2014 1525 Crystalline sulfur plus 

amorphous phase(s)

MW–4B October 9, 2014 1520 Crystalline sulfur plus 

amorphous phase(s)

some samples. Scraping and flocculent samples from EW–4C, 

EW–4D, and MW–4B contained notably larger quantities of 

sulfur (21–28 percent by mass), ferrihydrite (34–47 percent), 

and organic carbon (25–38 percent) than were observed in 

samples from the other wells (table 16). The sample from 

EW–11D almost entirely comprised of ferrihydrite (40 percent) and organic carbon (55 percent) with no sulfur. Scraping 

samples from EW–20D almost entirely comprised of calcite (86–97 percent) with lesser quantities of organic carbon and ferrihydrite. 

Scanning Electron Microscopy

Most minerals identified with SEM detected euhedral 

crystal habit, indicating that precipitation had fallen near or at 

the site of sample collection. Particularly conspicuous were 

calcite and sulfur, which were present in rhombic and prismatic habits, respectively (fig. 22; appendix 3). Data results 

for solids from EW–20D indicated euhedral calcite crystals. 

Results indicating sulfur crystals included samples from 

EW–4D and MW–4B (table 17). In some images, such as one 

from MW–4B, the sulfur crystals were surrounded by material believed to be biofilm. Other results indicating biofilm 

included samples from EW–4D and EW–20D (table 17). 

Biofilms appeared as hazy, mossy, or cloudy zones.

Vacuoles were identified in scraping samples from 

EW–4D and MW–4D. Vacuoles are membrane-filled sacs in 

plants and fungi. The primarily intact calcified vacuoles likely 

indicate groundwater transport of some mineralogic material 

from the nearby geologic deposits into the borehole. 

The SEM/EDS and SEM/BSE analyses were done on 

solid-phase samples from EW–4D, EW–11D, and MW–4B. 

All samples contained carbon, iron, and sulfur. A sample from 

MW–4B also contained calcium. The sample from EW–11D 

additionally contained phosphorous and silicon.

Inductively Coupled Plasma Mass Spectrometry 

Analyses

In most samples, the weight percent of iron exceeded all 

other analyzed cations; calcium and magnesium were the second and third most abundant elements, respectively (table 18). 

Exceptions to this observation were samples from EW–20D 

and MW–4A where calcium was more abundant than iron (by 

weight), and from MW–11A where proportions of aluminum, 

calcium, iron, and magnesium were nearly equal.

Carbon and Sulfur Isotope Analyses

Eleven measurements of carbon and sulfur isotopes were 

made on pump scrapings and flocculent in groundwater from 

wells EW–4C, EW–4D, EW–6C, EW–11D, EW–20D, and 

MW–4B (table 19). The weight percent of carbon in samples 

ranged from 7.5 to 29.0. Carbon isotope values ranged from 

-36.1 to -12.3‰ d13C. These values are mostly in the range 

expected for subsurface dissolved inorganic carbon (-5 to 

-25‰) that would be produced by weathering of carbonate 

and silicate minerals in the geologic deposits (Kendall and 

others, 1995). Carbon isotope values lighter than -30‰ may 

be attributable to root respiration and oxidation of natural 

organic matter, as well as residual petroleum, natural gas, or 

bacterial methane.

The weight percent of sulfur in samples ranged from 0.1 

to 16.3. Sulfur isotope values ranged from -31.1 to +6.9‰ 

d34S. The values measured in scrapings from EW–20D (+4.7 

to +6.9‰) were notably heavier than values measured in 
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 73

Table 16. Estimated quantitative mineralogy from X-ray diffraction analysis of solids collected as pump scrapings from wells at the confined disposal facility.[Values are reported in units of normalized weight percent, computed as (mineral percent of sample multiplied by specific gravity of mineral) divided by total mass of the sample]

Mineral

Well name/sample collection date and time

EW–4C EW–4D EW–11D EW–20D EW–20D EW–20D MW–4B MW–4B

October 23, 2014 September 11, 2014 September 19, 2014 September 19, 2014 October 23, 2014 October 23, 2014 October 9, 2014 October 9, 2014

 1130 1310 0830 0900 1100 1100 1525 1520

Quartz 1 3 1 0 0 1 1 0Calcite 5 0 2 91 86 97 1 2Dolomite 0 2 1 0 0 0 0 0Sulfur 23 21 0 0 0 0 27 28Organic carbon phases 25 38 55 8 8 3 36 33Ferrihydrite 47 34 40 0 5 0 36 37Goethite (synthetic) 0 1 0 0 0 0 0 0Total 100 100 100 100 100 100 100 100
74 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

The areas circled in red are S crystals. Presumably the spherical object is a whole

vacuole. The area labeled “A” is likely carbon biofilm.

A

This sample is a homogeneous matrix energy dispersive spectroscopy analysis that indicates calcium and carbon;

likely calcium carbonate. Taking images was problematic because the sample was not well grounded. The crystals

were held together by a biofilm; the cracking was because of drying as seen in this image.

Figure 22. Scanning electron microscopy (SEM) 

images of solid-phase samples from extraction 

wells EW–4D and EW–20D at the confined 

disposal facility showing euhedral sulfur and 

calcite, amorphous material, and biofilms.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 75

Table 17. Summary of scanning electron microscopy/energy dispersive spectroscopy and scanning electron microscopy/backscatter electrons observations made on solids collected as pump scrapings from wells at the confined disposal facility.[SEM, scanning electron microscopy; EDS, energy dispersive spectroscopy; BSE, backscatter electrons; C, carbon; Ca, calcium; Fe, iron; Mg, magnesium; --, no observation; S, sulfur; O, oxygen; Al, aluminum; Si, silicon; P, phosphorus; >, greater than; CaCO3, calcium carbonate]

Well name Date sampled SEM/EDS observations SEM/BSE observations Additional comments

EW–4C image 1 October 23, 2014 Matrix contains C, Ca, Fe, and Mg 

in spots

 -- --

EW–4D image 1 September 11, 2014 Fe, C, S More Fe than S BiofilmEW–4D image 2 September 11, 2014 -- -- Relative abundances for various mins. Biofilm shows no C

EW–4D image 3 September 11, 2014 C, O, S present in most; Al, Ca, Fe, 

Si in some

 -- Nine spectral analyses

EW–4D image 4 September 11, 2014 -- C, Fe, S Mineralized biostructures and vacuole; S crystals, C biofilmEW–4D image 5 September 11, 2014 -- C, Fe, S; except sulfur crystals on 

broken vacuole plate

 --

EW–4D image 6 September 11, 2014 -- S crystals, sperical vacuole, C biofilm --EW–6C image 1 November 6, 2014 C, Ca, Fe, P, S, and Si in matrix; 

Fe>Ca>P>Si>C in platy structures

 --

EW–11D image 1 September 19, 2014 C, Ca, Fe, P, Si, and S in spots Uniform in composition BiofilmEW–20D image 1 October 23, 2014 C, Ca, likely CaCO3 matrix -- Crystals bound together by biofilmEW–20D image 2 October 23, 2014 -- Euhedral CaCO3 precipitate --MW–4B image 1 October 9, 2014 -- Matrix is C, Ca, Fe, S; crystals are S 

with C

 --

MW–4B image 2 October 9, 2014 -- Hollow vacuoles --MW–4B image 3 October 9, 2014 -- S crystals with interesting morphology --MW–4B image 4 October 9, 2014 -- Large S crystals --MW–4B image 5 October 9, 2014 -- Cluster euhedral sulfur crystals --MW–4B image 6 October 9, 2014 C, Ca, Fe, S matrix with minor Mg 

and Si

String has high C, Fe, S with trace 

Ca and Mg

Biofilm

MW–4B image 7 October 9, 2014 -- -- --MW–4B image 8 October 9, 2014 -- Sulfur crystals surrounded by biofilm; 

vacuole and matrix C, Fe and S with minor Ca and Mg
76 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana Table 18. Inductively coupled plasma mass spectroscopy analyses of samples collected as pump scrapings and on filter with 0.45-micron pore size during groundwater sample collection at the confined disposal facility. [mg/g, micrograms of analyte per gram of digested solid material] Well name Digestion completion Alumi- num (mg/g) Boron (mg/g) Calcium (mg/g) Lithium (mg/g) Magne- sium (mg/g) So- dium (mg/g) Phos- phorous (mg/g) Potas- sium (mg/g) Silicon (mg/g) Titanium (mg/g) Vana- dium (mg/g) Chro- mium (mg/g) Manga- nese (mg/g) Iron (mg/g) EW–4B sample 1 Almost 7,800 19 23,000 9.7 11,000 480 740 1,800 1,900 180 31 29 240 140,000 EW–4B sample 2 Almost 9,900 24 25,000 12 11,000 870 3,700 2,400 3,100 220 63 51 270 87,000 EW–4C Incomplete 280 2.3 17,000 0.31 2,100 140 93 190 190 10 1.8 4.6 22 300,000 EW–4D Incomplete 530 2.0 9,000 0.72 3,400 110 270 210 140 21 5.9 14 25 210,000 EW–6C Almost 360 38 25,000 2.2 2,600 440 7,800 530 1,400 41 21 620 270 230,000 EW–11D Incomplete 320 9.1 24,000 0.53 1,300 130 16,000 270 1,100 66 15 4.9 130 140,000 EW–20D sample 1 Complete 340 3.6 380,000 2.1 3,200 220 1,000 190 310 5.2 1.3 4.7 430 10,000 EW–20D sample 2 Complete 680 11 350,000 1.6 4,300 270 1,800 210 2,000 9.7 2.7 2.4 620 20,000 EW–20D sample 3 Complete 690 7.4 340,000 1.5 4,400 260 1,800 200 1,600 10 2.8 3.1 640 21,000 MW–4A sample 1 Incomplete 13,000 21 59,000 18 30,000 230 890 3,500 1,600 200 32 35 390 31,000 MW–4A sample 2 Incomplete 13,000 28 56,000 17 29,000 350 1,100 3,400 2,000 210 32 34 520 32,000 MW–4B sample 1 Incomplete 35 0.94 12,000 0.16 3,100 200 73 150 100 2.6 1.7 3.6 13.0 260,000 MW–4B sample 2 Incomplete 16 1.8 9,000 0.20 3,000 200 95 110 83 2.3 1.8 0.53 9.1 180,000 MW–11A sample 1 Incomplete 21,000 14 27,000 25 19,000 210 530 4,300 3,200 68 30 27 300 33,000 MW–11A sample 2 Incomplete 21,000 13 31,000 24 18,000 220 700 4,400 2,700 82 31 25 390 50,000 MW–14A sample 1 Incomplete 13,000 48 31,000 18 11,000 1,400 4,900 5,100 2,400 160 44 48 5400 75,000 MW–14A sample 2 Incomplete 13,000 39 28,000 20 9,500 1,800 3,400 5,300 2,200 170 37 53 280 63,000
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 77

Table 18. Inductively coupled plasma mass spectroscopy analyses of samples collected as pump scrapings and on filter with 0.45-micron pore size during groundwater sample collection at the confined disposal facility.—Continued[mg/g, micrograms of analyte per gram of digested solid material]

Well name Digestion completion Cobalt (mg/g) Nickel (mg/g) Copper (mg/g) Zinc (mg/g) Arsenic (mg/g) Ribidium (mg/g) Strontium (mg/g) Molyb- denum (mg/g) Cadmium (mg/g) Cesium (mg/g) Barium (mg/g) Lead (mg/g) Uranium (mg/g)

EW–4B sample 1 Almost 8.6 5,500 2,200 31,000 170 18.0 33 3.0 3.8 1.0 76 330 0.40EW–4B sample 2 Almost 12 6,000 2,900 43,000 180 22.0 43 4.4 4.8 1.1 149 430 0.47EW–4C Incomplete 1.1 8.4 3,800 130 62 5.3 20 1.1 0.10 2.3 6.0 320 0.11EW–4D Incomplete 3.9 17 67 110 13 1.0 9.1 1.1 0.09 0.06 11 4.0 0.06EW–6C Almost 9.9 700 38 104 380 0.70 160 91 0.26 0.03 840 8.8 0.16EW–11D Incomplete 1.6 4.7 13 43 20 0.82 140 1.3 0.03 0.06 350 1.8 0.12EW–20D sample 1 Complete 0.74 22 3.1 1.9 0.41 0.21 1,100 1.1 0.01 0.01 310 0.60 0.01EW–20D sample 2 Complete 0.65 9.1 1.8 7.0 1.4 0.41 840 0.54 0.01 0.01 390 0.31 0.00EW–20D sample 3 Complete 0.64 9.5 20 9.5 1.3 0.40 830 0.60 0.01 0.02 370 2.0 0.00MW–4A sample 1 Incomplete 10 36 100 820 28 23.0 44 11 1.9 1.3 110 180 2.6MW–4A sample 2 Incomplete 7.6 28 97 730 43 22.0 50 5.3 1.7 1.3 140 180 1.6MW–4B sample 1 Incomplete 1.0 11 42 29 10 0.64 27 0.77 0.04 0.04 15 4.8 0.02MW–4B sample 2 Incomplete 0.52 2.4 8.4 7.4 2.6 0.52 19 0.44 0.02 0.05 12 1.5 0.01MW–11A sample 1 Incomplete 13 30 42 470 31 26.0 37 9.7 0.70 1.6 72 56 4.3MW–11A sample 2 Incomplete 12 29 42 440 35 25.0 50 7.8 0.74 1.7 140 53 4.1MW–14A sample 1 Incomplete 23 44 182 760 130 23.0 96 24 1.6 1.5 250 53 2.1MW–14A sample 2 Incomplete 22 62 260 1,300 90 25.0 61 57 2.3 1.6 110 66 4.1
78 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 19. Carbon and sulfur isotope composition for solid samples collected as pump scrapings from wells at the confined disposal 

facility.

[mg, milligrams; ‰, parts per thousand; %, percent]

Well name Date U.S. Geological 

Survey sample name

Approximate 

sample 

weight 

(mg)

Weight

percent 

carbon in

the sample

δ13C1

(‰)

Weight

percent 

sulfur in

the sample

δ34S2,3

(‰)

EW–4C October 23, 2014 Sample C 2 7.5 -26.1 8.7 -30.4

EW–4C (replicate) October 23, 2014 Sample C replicate 2 7.9 -25.3 16.3 -31.1

EW–4D September 11, 2014 Sample D 2 19.2 -29.0 15.3 -10.4

EW–6C November 6, 2014 Sample B 2 15.6 -36.1 2.5 -15.7

EW–11D September 19, 2014 Sample A 2 8.0 -32.4 2.1 -8.4

EW–20D September 19, 2014 Sample G 40 11.8 -12.3 0.1 6.2

EW–20D October 23, 2014 Sample H 40 12.3 -19.4 0.1 6.9

EW–20D October 23, 2014 Sample I 40 12.4 -19.9 0.2 4.7

MW–4B-1 October 9, 2014 Sample F 2 15.9 -29.1 9.6 -25.5

MW–4B-2 October 9, 2014 Sample E 2 28.6 -30.3 9.4 -23.2

MW–4B-2 (replicate) October 9, 2014 Sample E replicate 2 29.0 -30.2 5.7 -24.1

1

d13C = { [(13C/12C)sample/(13C/12C)standard]-1}*1,000‰; where (13C/12C) is the ratio of carbon isotope 13C to carbon isotope 12C in the sample or the standard, 

and ‰ is the unit parts per thousand.

2

d34S = { [(34S/32S)sample/(34S/32S)standard]-1}*1,000‰; where (34S/32S) is the ratio of sulfur isotope 34S to sulfur isotope 32S in the sample or the standard, and ‰ 

is the unit parts per thousand.

3

Despite taking steps to enhance combustion, sample matrix effects resulted in high sulfur carryover, whereas carbon chromatography was unaffected. 

The Vario Isotope Cube (Elementar) elemental analyzer setup traps sulfur for a specified length of time, then releases it by heating the sulfur trap. This setup 

allows us to measure isotopic values on sharp peaks even in the case of slow-eluting samples such as these. A blank was run after each sample to mitigate the 

effects of sulfur carryover on subsequent samples.

 In cases where evaluation was possible, sulfur carryover δ34S values agreed with sample δ34S values to within 3‰, suggesting fractionation was limited. 

However, sulfur carryover implies that %S values represent a lower bound, and that interpretation of δ34S values should be limited to large variations.

samples from other wells. The isotopically lighter values were 

measured in EW–4C (-31.1 and -30.4‰) and MW–4B (-25.5 

to -23.2‰) and midrange (-8.4 to -15.7‰) values were measured in scrapings from EW–4D, EW–6C, and EW–11D. 

The relatively heavier values of sulfur isotopes for EW–

20D are the most similar to values that would be expected 

in waters equilibrated with natural waters. Alternatively, the 

sulfur isotope values may be indicating that precipitation is a 

strong influence and that microbiological processes are not as 

active in this area of the CDF. Lighter sulfur isotope values are 

likely a result of microbiologically mediated fractionation and 

are consistent with the rapid well fouling and frequent pump 

replacement in the EW4 wells. A plot of d34S with weight 

percent of sulfur in the sample shows a potential relation that 

indicates lighter isotopes with increasing weight percent sulfur 

(fig. 23). This observation is consistent with elevated aqueous 

sulfur concentrations and sulfide mineral formation by bacterial reduction of aqueous sulfate or, alternatively, the degradation of sulfur present in crude oil.

The sulfur isotope values are notably different among 

EW–4C, EW–4D, and MW–4B. The EW–4D sample was collected about 1 month earlier than the other samples and may 

represent values during a different hydrologic period or pumping regime. Alternatively, EW–4D is located further to the 

north and may be affected by other hydrogeologic or biogeochemical constraints. A sandier subsurface, for example, which 

transmits more groundwater, might support more aerobic conditions that would be a less favorable setting for sulfur-reducing bacteria. The pump in EW–4C was replaced seven times 

during water year 2014, compared to two times in EW–4D. 

A plot of sulfur and carbon isotopic composition, excluding the EW–20D wells, may show an inverse correlation 

between the two isotopic ratios (fig. 24). A possible explanation for the observation would be that increased bacterial 

activity in the more organic-rich settings is removing dissolved inorganic carbon by degassing; the result is isotopically heavier carbon being enriched in settings where higher 

microbiological activity is creating isotopically lighter sulfur. 

Equilibrium Mineral-Saturation Indices

The computed saturation indices for groundwater 

samples from EW–4B and MW–4A indicated that most miner-
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 79

-35

-30

-25

-20

-15

-10

-5

0

5

10

0 5 10 15 20

Weight percent sulfur

δ34S, in per mil

δ34S = {[(

34

S/

32

S)sample/(

34

S/

32

S)standard]-1}*1,000‰;

where (34S/32S) is the ratio of sulfur isotope 34S to

sulfur isotope 32S in the sample or the standard,

and ‰ is the unit parts per thousand 

Figure 23. Plot of sulfur isotopic composition with weight percent 

sulfur in samples collected at the confined disposal facility.

δ34S = {[(

34

S/

32

S)sample/(

34

S/

32

S)standard]-1}*1,000‰;

where (34S/32S) is the ratio of sulfur isotope 34S to

sulfur isotope 32S in the sample or the standard,

and ‰ is the unit parts per thousand. 

δ13C = δ13C = {[(13C/12C)sample/(13C/12C)standard]-1}*1,000‰;

where (13C/12C) is the ratio of carbon isotope 13C to carbon

isotope 12C in the sample or the standard, and ‰ is the

unit parts per thousand.

-35

-30

-25

-20

-15

-10

-5

0

5

10

-40 -30 -20 -10 0

EW–11D

EW–20D

MW–4B

EW–4C

EW–6C

EW–4D

δ13C, in per mil

EXPLANATION

δ34S, in per mil

Figure 24. Plot of sulfur and carbon isotopic composition in 

samples collected at the combined disposal facility.

als identified with SEM and X-ray analysis on solids from 

EW–4D and MW–4B, including calcite, dolomite, and quartz, 

were supersaturated (table 20; Christian, 2018). These results 

indicated that those minerals could theoretically precipitate 

abiotically from groundwater in the borehole. Goethite and 

hematite, iron-bearing minerals, were also supersaturated in 

most of the groundwater samples from EW–4B and MW–4A. 

Sulfur was identified in solid samples from EW–4D and MW–

4B but was undersaturated in all groundwater samples from 

EW–4B and MW–4A; this result may indicate that bioslimes 

are creating microenvironments in the well where the water 

chemistry facilitates precipitation of elemental sulfur. 

The computed saturation indices for groundwater samples 

from EW–11B and MW–11A indicated that most groundwater samples were slightly undersaturated or supersaturated 

with respect to calcite and dolomite; calcite was identified in 

the solids from EW–11D. The saturation indices for calcite 

ranged from -0.11 to 0.10 with a mean value of 0.01. Goethite, 

hematite, and quartz were supersaturated in all samples from 

EW–11B and MW–11A. Amorphous solids, often iron-rich 

compounds, were identified in the solids from EW–11D but 

goethite was not. Sulfur was undersaturated in all groundwater 

samples from EW–11B and MW–11A.

The computed saturation indices for groundwater samples 

from EW–14A and MW–14A indicated that most groundwater 

samples were supersaturated with respect to calcite, dolomite, 

goethite, hematite, and quartz. Solids were not collected from 

this well cluster for SEM or X-ray analysis, but these data 

indicate that mineral precipitation is favored in these wells. 

Sulfur was undersaturated in all groundwater samples from 

EW–14A and MW–14A.

Mineral-saturation indices computed for groundwater 

samples from the six CDF wells varied somewhat consistently 

through time (fig. 25). To determine if the variations were 

related to weather or other hydrologic variables or if the variations could be attributed to the differences among the four 

pumping regimes is not possible; however, the variations were 

observed in monitoring wells and the extraction wells. The 

computed saturation indices were generally highest in groundwater collected during the second sampling event (October 

9–11, 2014). That event, with no pumping for several hours 

before sample collection, might represent a period of increased 

groundwater residence and equilibration with minerals in the 

surrounding aquifer materials. The second sampling event 

also may indicate a period of increased isolation from oxygen, 

hence, lower redox and greater solubility of some chemical 

constituents. This result may indicate that continuous pumping 

at lower discharge rates may be preferable to cycling between 

no pumping and pumping at higher discharge rates.
80 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 20. Mineral saturation indices computed using PHREEQC and groundwater quality data collected at the confined disposal 

facility from September 9 to November 6, 2014.

[Simulations used the sulfide-sulfate redox couple (and measured concentrations of sulfide and sulfate) to compute redox potential (Eh) and speciated the concentration of dissolved inorganic carbon to achieve electroneutrality. Other redox sensitive species, such as iron and manganese, were entered as total dissolved 

concentrations and speciated using the specified redox couple and other related data. Supersaturated phases are shaded in gray. pE, negative base 10 logarithm of 

the electron activity; g, gas; a, amorphous; ppt, freshly precipitated and possibly amorphous; d, disordered; na, not applicable]

September 9–11, 2014

EW–4B MW–4A EW–11B MW–11A EW–14A MW–14A

Redox couple S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6)

Computed pE -3.19 -2.49 -2.74 -2.65 -3.10 -2.90

Computed Eh (volts) -0.183 -0.143 -0.156 -0.151 -0.177 -0.166

Mineral name Mineral formula Saturation index

Anhydrite CaSO4 -0.93 -0.69 -3.44 -2.78 -2.65 -1.02

Aragonite CaCO3 0.13 -0.33 -0.26 -0.24 0.15 0.08

Calcite CaCO3 0.28 -0.18 -0.11 -0.08 0.30 0.23

Chalcedony SiO2 0.56 0.60 0.41 0.47 0.48 0.34

Chrysotile Mg3

Si2O5(OH)4 -6.16 -8.53 -9.94 -10.27 -7.17 -8.11

Carbon dioxide1 CO2 (g) -0.98 -0.92 -0.68 -0.68 -1.06 -1.10

Dolomite CaMg(CO3

)2 0.68 -0.49 -0.54 -0.61 0.39 0.04

Iron(III) hydroxide Fe(OH)3

 (a) -7.45 -5.32 -5.02 -4.93 -4.88 -5.42

Mackinawite FeS (ppt) 0.96 0.71 0.41 0.75 0.31 0.44

Fluorite CaF2 -0.89 -1.13 -1.12 -1.14 -0.79 -0.58

Goethite FeOOH -1.88 0.18 0.51 0.52 0.63 0.12

Gypsum CaSO4

.2H2O -0.53 -0.26 -3.03 -2.34 -2.24 -0.62

Hydrogen H2 (g) -7.25 -8.03 -7.55 -7.72 -7.63 -7.82

Water H2

O (g) -1.73 -1.79 -1.76 -1.82 -1.78 -1.76

Hydrogen sulfide H2

S (g) -2.00 -4.04 -4.86 -4.57 -5.07 -4.30

Halite NaCl -7.78 -8.12 -7.53 -7.70 -7.25 -7.93

Hausmannite Mn3

O4 -32.49 -32.83 -33.07 -33.41 -31.97 -31.39

Hematite Fe2

O3 -1.79 2.31 2.98 3.00 3.22 2.20

Hydroxyapatite Ca5

(PO4)3OH -0.18 -4.31 -4.99 -3.77 -1.14 -1.81

Jarosite-K KFe3

(SO4)2(OH)6 -28.22 -20.43 -2.15 -23.62 -24.19 -22.14

Mackinawite FeS 1.70 1.45 1.14 1.49 1.04 1.17

Manganite MnOOH -13.89 -13.68 -13.93 -13.84 -13.51 -13.33

Melanterite FeSO4

.7H2O -6.74 -4.15 -6.24 -5.51 -6.11 -5.12

Ammonia NH3 (g) -8.17 -9.02 -8.48 -8.57 -8.13 -8.51

Oxygen O2 (g) -2.03 -1.76 -2.39 -2.02 -2.17 -1.47

Pyrite FeS2 12.98 11.53 9.90 10.76 9.68 10.75

Pyrochroite Mn(OH)2 -7.36 -7.54 -7.55 -7.54 -7.17 -7.09

Pyrolusite MnO2

.H2O -27.75 -27.51 -27.84 -28.00 -27.46 -27.08

Quartz SiO2 1.01 1.06 0.87 0.93 0.94 0.80

Rhodochrosite MnCO3 -0.22 -0.37 -0.13 -0.13 -0.12 -0.08

Sepiolite Mg2

Si3O7.5OH.3H2O -3.06 -4.49 -5.79 -5.83 -33.80 -4.69

Sepiolite Mg2

Si3O7.5OH.3H2O (d) -5.72 -7.10 -8.42 -8.41 -6.42 -7.32

Siderite FeCO3 -1.26 0.56 1.33 1.36 1.06 0.38

Quartz/chalcedony SiO2

 (a) -0.31 -0.28 -0.47 -0.42 -0.40 -0.53

Sulfur S -0.83 -2.11 -3.39 -2.96 -3.54 -2.56

Sylvite KCl -7.95 -7.72 -7.66 -7.56 -7.47 -7.46

Talc Mg3

Si4O10(OH)2 -1.46 -3.79 -5.57 -5.81 -2.66 -3.87

Vivianite Fe3

(PO4)2.8H2O -6.21 -1.84 -0.21 0.74 0.10 -2.21

1

For a gas, SI = log10(fugacity). Fugacity = pressure * phi/1 atm. For ideal gases, phi = 1.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 81

Table 20. Mineral saturation indices computed using PHREEQC and groundwater quality data collected at the confined disposal 

facility from September 9 to November 6, 2014.—Continued

[Simulations used the sulfide-sulfate redox couple (and measured concentrations of sulfide and sulfate) to compute redox potential (Eh) and speciated the concentration of dissolved inorganic carbon to achieve electroneutrality. Other redox sensitive species, such as iron and manganese, were entered as total dissolved 

concentrations and speciated using the specified redox couple and other related data. Supersaturated phases are shaded in gray. pE, negative base 10 logarithm of 

the electron activity; g, gas; a, amorphous; ppt, freshly precipitated and possibly amorphous; d, disordered; na, not applicable]

October 9–11, 2014

EW–4B MW–4A EW–11B MW–11A EW–14A MW–14A

Redox couple S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6)

Computed pE -3.05 -2.44 -2.71 -2.71 -3.33 -3.13

Computed Eh (volts) -0.176 -0.138 -0.155 -0.153 -0.191 -0.178

Mineral name Mineral formula Saturation index

Anhydrite CaSO4 -0.98 -0.52 -2.16 -2.17 -2.67 -1.43

Aragonite CaCO3 0.34 -0.39 -0.14 -0.12 0.24 0.30

Calcite CaCO3 0.49 -0.24 0.01 0.03 0.39 0.45

Methane CH4

 (g) na na na na na na

Chalcedony SiO2 0.59 0.67 0.43 0.51 0.49 0.51

Chrysotile Mg3

Si2O5(OH)4 -5.28 -8.18 -9.34 -9.56 -6.39 -6.81

Carbon dioxide1 CO2 (g) -0.96 -1.01 -0.78 -0.78 -1.16 -1.19

Dolomite CaMg(CO3

)2 1.18 -0.52 -0.32 -0.37 0.59 0.54

Iron(III) hydroxide Fe(OH)3

 (a) -4.99 -5.42 -4.74 -4.77 -4.66 -5.29

Mackinawite FeS (ppt) 1.01 0.53 0.69 1.02 0.90 0.53

Fluorite CaF2 -1.05 -1.21 -1.12 -1.32 -0.63 -0.50

Goethite FeOOH 0.60 0.01 0.78 0.67 0.90 0.17

Gypsum CaSO4

.2H2O -0.59 -0.08 -1.75 -1.73 -2.27 -1.00

Hydrogen H2 (g) -7.72 -8.15 -7.81 -7.80 -7.45 -7.76

Water H2

O (g) -1.73 -1.84 -1.78 -1.83 -1.74 -1.82

Hydrogen sulfide H2

S (g) -4.18 -4.10 -4.75 -4.43 -4.77 -4.42

Halite NaCl -7.79 -7.96 -7.51 -7.64 -7.26 -7.80

Hausmannite Mn3

O4 -31.40 -32.98 -32.39 -32.87 -31.12 -31.03

Hematite Fe2

O3 3.16 1.97 3.51 3.28 3.77 2.28

Hydroxyapatite Ca5

(PO4)3OH 0.31 -3.91 -2.55 -3.01 -0.23 -0.95

Jarosite-K KFe3

(SO4)2(OH)6 -21.15 -20.56 -21.90 -22.14 -23.68 -23.22

Mackinawite FeS 1.74 1.26 1.42 1.75 1.64 1.26

Manganite MnOOH -13.47 -13.57 -13.63 -13.60 -13.36 -13.04

Melanterite FeSO4.7H2O -4.76 -4.10 -5.01 -4.97 -6.06 -5.59

Ammonia NH3 (g) -8.04 -9.01 -8.40 -8.49 -7.95 -8.30

Oxygen O2 (g) -2.42 -2.45 -2.39 -2.46 -2.38 -2.45

Pyrite FeS2 11.31 11.45 10.55 11.26 10.36 10.72

Pyrochroite Mn(OH)2 -7.17 -7.49 -7.37 -7.35 -6.93 -6.76

Pyrolusite MnO2

.H2O -27.05 -27.62 -27.47 -27.81 -27.19 -27.18

Quartz SiO2 1.05 1.14 0.89 0.98 0.95 0.98

Rhodochrosite MnCO3 -0.01 -0.42 -0.05 -0.04 0.03 0.13

Sepiolite Mg2

Si3O7.5OH.3H2O -2.42 -4.07 -5.34 -5.27 -3.31 -3.45

Sepiolite Mg2

Si3O7.5OH.3H2O (d) -5.09 -6.63 -7.96 -7.83 -5.96 -6.03

Siderite FeCO3 0.99 0.34 1.39 1.40 1.26 0.48

Quartz/chalcedony SiO2

 (a) -0.27 -0.21 -0.45 -0.38 -0.38 -0.37

Sulfur S -2.53 -2.07 -3.03 -2.74 -3.40 -2.77

Sylvite KCl -7.99 -7.70 -7.47 -7.44 -7.43 -7.61

Talc Mg3

Si4O10(OH)2 -0.50 -3.31 -4.93 -5.02 -1.84 -2.25

Vivianite Fe3

(PO4)2.8H2O 0.14 -1.99 1.21 0.96 0.90 -2.00

1

For a gas, SI = log10(fugacity). Fugacity = pressure * phi/1 atm. For ideal gases, phi = 1.
82 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 20. Mineral saturation indices computed using PHREEQC and groundwater quality data collected at the confined disposal 

facility from September 9 to November 6, 2014.—Continued

[Simulations used the sulfide-sulfate redox couple (and measured concentrations of sulfide and sulfate) to compute redox potential (Eh) and speciated the concentration of dissolved inorganic carbon to achieve electroneutrality. Other redox sensitive species, such as iron and manganese, were entered as total dissolved 

concentrations and speciated using the specified redox couple and other related data. Supersaturated phases are shaded in gray. pE, negative base 10 logarithm of 

the electron activity; g, gas; a, amorphous; ppt, freshly precipitated and possibly amorphous; d, disordered; na, not applicable]

October 22–23, 2014

EW–4B MW–4A EW–11B MW–11A EW–14A MW–14A

Redox couple S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6)

Computed pE -3.03 -2.58 -2.65 -2.69 -3.26 -2.96

Computed Eh (volts) -0.174 -0.147 -0.151 -0.153 -0.186 -0.168

Mineral name Mineral formula Saturation index

Anhydrite CaSO4 -1.00 -0.66 -1.80 -1.86 -2.81 -0.94

Aragonite CaCO3 0.20 0.08 -0.14 -0.05 0.21 0.06

Calcite CaCO3 0.35 0.23 0.01 0.10 0.37 0.22

Methane CH4

 (g) na na na na na na

Chalcedony SiO2 0.55 0.62 0.44 0.50 0.53 0.34

Chrysotile Mg3

Si2O5(OH)4 -5.65 -8.16 -9.50 -9.40 -6.68 -7.75

Carbon dioxide1 CO2 (g) -1.08 -0.79 -0.80 -0.75 -1.17 -1.30

Dolomite CaMg(CO3

)2 0.83 0.22 -0.36 -0.24 0.50 0.00

Iron(III) hydroxide Fe(OH)3

 (a) na -5.32 -4.75 -4.82 na -5.19

Mackinawite FeS (ppt) 0.75 0.64 0.80 0.95 0.83 0.59

Fluorite CaF2 -0.82 -1.07 -0.89 -1.20 -0.58 -0.52

Goethite FeOOH na 0.10 0.71 0.64 na 0.26

Gypsum CaSO4

.2H2O -0.60 -0.22 -1.37 -1.38 -2.38 -0.51

Hydrogen H2 (g) -7.77 -8.07 -7.91 -7.84 -7.50 -7.90

Water H2

O (g) -1.73 -1.84 -1.82 -1.81 -1.81 -1.82

Hydrogen sulfide H2

S (g) -4.32 -4.13 -4.60 -4.42 -4.72 -4.38

Halite NaCl -7.74 -7.91 -7.55 -7.66 -7.27 -7.85

Hausmannite Mn3

O4 -31.30 -32.21 -32.57 -32.61 -31.74 -30.80

Hematite Fe2

O3 na 2.15 3.37 3.24 na 2.47

Hydroxyapatite Ca5

(PO4)3OH -1.43 -4.72 -4.24 -3.74 -0.74 -2.06

Jarosite-K KFe3

(SO4)2(OH)6 na -20.91 -21.30 -21.56 na -21.82

Mackinawite FeS 1.48 1.38 1.54 1.68 1.57 1.32

Manganite MnOOH -13.40 -13.31 -13.54 -13.57 -13.35 -12.93

Melanterite FeSO4.7H2O -4.87 -4.35 -4.66 -4.80 -6.25 -4.95

Ammonia NH3 (g) -8.05 -9.10 -8.50 -8.55 -8.03 -8.86

Oxygen O2 (g) -2.42 -2.46 -2.45 -2.45 -2.45 -2.41

Pyrite FeS2 10.97 11.45 10.97 11.21 10.45 10.97

Pyrochroite Mn(OH)2 -7.13 -7.19 -7.34 -7.34 -6.95 -6.72

Pyrolusite MnO2

.H2O -27.01 -27.44 -27.58 -27.64 -27.56 -27.02

Quartz SiO2 1.01 1.09 0.91 0.97 0.99 0.80

Rhodochrosite MnCO3 -0.09 0.11 -0.04 0.00 -0.03 0.06

Sepiolite Mg2

Si3O7.5OH.3H2O -2.74 -4.13 -5.36 -5.20 -3.35 -4.36

Sepiolite Mg2

Si3O7.5OH.3H2O (d) -5.40 -6.68 -7.94 -7.78 -5.94 -6.93

Siderite FeCO3 0.75 0.70 1.33 1.34 1.11 0.39

Quartz/chalcedony SiO2

 (a) -0.32 -0.26 -0.44 -0.38 -0.35 -0.55

Sulfur S -2.62 -2.18 -2.79 -2.69 -3.33 -2.59

Sylvite KCl -7.91 -7.54 -7.42 -7.32 -7.46 -7.43

Talc Mg3

Si4O10(OH)2 -0.98 -3.38 -5.08 -4.86 -2.08 -3.54

Vivianite Fe3

(PO4)2.8H2O -1.27 -2.93 -0.03 0.05 0.33 -2.25

1

For a gas, SI = log10(fugacity). Fugacity = pressure * phi/1 atm. For ideal gases, phi = 1.
Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells 83

Table 20. Mineral saturation indices computed using PHREEQC and groundwater quality data collected at the confined disposal 

facility from September 9 to November 6, 2014.—Continued

[Simulations used the sulfide-sulfate redox couple (and measured concentrations of sulfide and sulfate) to compute redox potential (Eh) and speciated the concentration of dissolved inorganic carbon to achieve electroneutrality. Other redox sensitive species, such as iron and manganese, were entered as total dissolved 

concentrations and speciated using the specified redox couple and other related data. Supersaturated phases are shaded in gray. pE, negative base 10 logarithm of 

the electron activity; g, gas; a, amorphous; ppt, freshly precipitated and possibly amorphous; d, disordered; na, not applicable]

November 5–6, 2014

EW–4B MW–4A EW–11B MW–11A EW–14A MW–14A

Redox couple S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6) S(-2)/S(6)

Computed pE -2.91 -2.30 -2.79 -2.69 -3.16 -3.03

Computed Eh (volts) -0.166 -0.131 -0.159 -0.153 -0.179 -0.173

Mineral name Mineral formula Saturation index

Anhydrite CaSO4 -0.99 -0.51 -3.01 -3.21 -2.78 -1.52

Aragonite CaCO3 0.01 0.12 -0.15 -0.19 0.11 0.11

Calcite CaCO3 0.16 0.28 0.00 -0.04 0.26 0.26

Methane CH4

 (g) nd nd nd nd nd nd

Chalcedony SiO2 0.59 0.74 0.44 0.50 0.50 0.50

Chrysotile Mg3

Si2O5(OH)4 -6.37 -8.25 -9.49 -10.16 -7.35 -7.44

Carbon dioxide1 CO2 (g) -1.04 -0.37 -0.77 -0.65 -1.08 -1.16

Dolomite CaMg(CO3

)2 0.44 0.58 -0.34 -0.52 0.27 0.17

Iron(III) hydroxide Fe(OH)3

 (a) -5.26 -5.56 -4.85 -4.98 -5.00 -5.39

Mackinawite FeS (ppt) 0.78 0.28 0.70 0.63 0.73 0.58

Fluorite CaF2 -0.76 -1.24 -0.91 -1.17 -0.57 -0.48

Goethite FeOOH 0.27 -0.14 0.61 0.47 0.47 0.06

Gypsum CaSO4

.2H2O -0.58 -0.06 -2.58 -2.78 -2.35 -1.08

Hydrogen H2 (g) -7.82 -8.22 -7.65 -7.64 -7.52 -7.76

Water H2

O (g) -1.76 -1.85 -1.81 -1.82 -1.80 -1.82

Hydrogen sulfide H2

S (g) -4.11 -4.19 -4.73 -4.69 -4.60 -4.26

Halite NaCl -7.73 -7.79 -7.50 -7.64 -7.29 -7.71

Hausmannite Mn3

O4 -31.94 -34.20 -32.81 -33.59 -32.28 -31.49

Hematite Fe2

O3 2.51 1.66 3.18 2.90 2.90 2.06

Hydroxyapatite Ca5

(PO4)3OH -1.31 -6.35 -2.63 -3.97 -1.30 -4.10

Jarosite-K KFe3

(SO4)2(OH)6 -21.73 -21.02 -24.16 -24.68 -24.83 -23.47

Mackinawite FeS 1.52 1.01 1.43 1.36 1.46 1.31

Manganite MnOOH -13.52 -13.93 -13.68 -13.90 -13.55 -13.18

Melanterite FeSO4.7H2O -4.79 -4.13 -5.82 -5.97 -6.25 -5.55

Ammonia NH3 (g) -8.17 -9.00 -8.45 -8.54 -8.12 -8.47

Oxygen O2 (g) -2.43 -1.67 -2.45 -2.45 -2.45 -2.45

Pyrite FeS2 11.28 11.19 10.45 10.43 10.48 10.93

Pyrochroite Mn(OH)2 -7.27 -7.88 -7.35 -7.57 -7.15 -6.91

Pyrolusite MnO2

.H2O -27.27 -28.02 -27.83 -28.12 -27.71 -27.35

Quartz SiO2 1.05 1.21 0.91 0.97 0.97 0.97

Rhodochrosite MnCO3 -0.20 -0.18 -0.03 -0.13 -0.14 0.02

Sepiolite Mg2

Si3O7.5OH.3H2O -3.11 -3.99 -5.36 -5.69 -3.85 -3.87

Sepiolite Mg2

Si3O7.5OH.3H2O (d) -5.74 -6.53 -7.95 -8.27 -6.44 -6.45

Siderite FeCO3 0.60 0.81 1.38 1.39 0.99 0.41

Quartz/chalcedony SiO2

 (a) -0.28 -0.14 -0.44 -0.38 -0.38 -0.38

Sulfur S -2.38 -2.09 -3.19 -3.16 -3.19 -2.61

Sylvite KCl -7.90 -7.77 -7.59 -7.57 -7.47 -7.40

Talc Mg3

Si4O10(OH)2 -1.62 -3.25 -5.07 -5.63 -2.80 -2.90

Vivianite Fe3

(PO4)2.8H2O -0.95 -3.70 1.21 0.54 -0.06 -3.65

1

For a gas, SI = log10(fugacity). Fugacity = pressure * phi/1 atm. For ideal gases, phi = 1.
84 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EXPLANATION

Number of supersaturated minerals

 in groundwater sample

0

2

4

6

8

10

12

14

EW-4B

MW-4A

EW-11B

MW-11A

EW-14A

MW-14A

Pumping regime

1 2 3 4

Figure 25. Mineral-saturation indices computed for 

groundwater samples collected on four occasions at the 

confined disposal facility.

Mineral-saturation indices were used to explore the effect 

of overpumping and inducing shallow, oxygenated water into 

the well screen on mineral precipitation (table 21). Shallow groundwater was not sampled at the CDF; therefore, a 

water-quality analysis from a monitoring well approximately 

0.25 mile south of the CDF, D40, was used as a substitute. The 

D40 analysis provides a potential example of shallow groundwater in the area of the CDF; however, the area immediately 

surrounding D40 has not been anthropogenically affected to 

the extent that the area of CDF has been affected. For example, the assumption is that oil is present at the air-water 

interface over most of the CDF (Cohen and others, 2002) and 

oil has not been present at well D40.

Mineral-saturation indices were computed for multiple 

hypothetical mixtures of groundwater from EW–4B, collected 

on October 9, 2014, and groundwater from D40, collected 

on June 14, 1993. A range of mixtures that included zero to 

100 percent groundwater from D40 and EW–4B were analyzed. The analyses indicated that adding larger proportions of 

groundwater from D40 to groundwater from EW–4B resulted 

in fewer saturation indices that were supersaturated (fig. 26). 

Larger proportions of groundwater from D40 resulted in lower 

saturation indices for calcite and dolomite. The minerals hematite, goethite, quartz, and chalcedony remained supersaturated, but the saturation indices decreased with larger proportions of groundwater from D40. 

Petroleum Hydrocarbons

Although a prestudy scan of scrapings from well EW–4B 

indicated that petroleum hydrocarbons were not present, the 

preponderance of historical data motivated the collection of 

a second sample during November 2016. The second sample 

was scanned for the presence of petroleum hydrocarbons at the 

USGS laboratory in the South Atlantic Water Science Center 

Studies Unit. The chromatograph of that sample indicated the 

presence of longer-chain organics similar to those present in 

gasoline (fig. 27). 

Relation of Geochemical and 

Microbiologic Characteristics to Well 

Efficiency 

The measurements, analyses, and observations made on 

groundwater samples collected from wells at the CDF provided multiple lines of evidence that may be used to identify 

traits of wells that require frequent pump replacement. These 

traits include highly variable depth to groundwater in the well, 

higher concentrations of inorganic constituents, lower redox 

values, in place precipitation of minerals formed in aerobic 

and anaerobic conditions, and aggressive bacterial activity. 

The presence of petroleum hydrocarbons may be another trait 

but the occurrence of those compounds was only qualitatively 

identified on one occasion in a well with a historically high 

rate of pump failure. Disrupting one or more of those traits 

might reduce the frequency of pump replacement.

The depth to water was notably more variable in two 

wells than the other wells. Water-level data for the EW–4B 

and EW–14A wells indicated that during some pumping 

regimes, including those measured during sampling, the water 

level nearly reached the depth of the screen. This reaction of 

groundwater levels to pumping likely indicates that the aquifer 

material near these wells has a reduced hydraulic conductivity compared to other wells. The effect of relatively higher 

drawdown and decreased well efficiency in these wells may 

create a periodic cone of depression that brings water from 

nearer the land surface into contact with water from nearer the 

base of the aquifer. Water nearer land surface likely is more 

oxygenated and, therefore, has different chemical and redox 

properties and potentially contains light nonaqueous phase 

liquid hydrocarbons. Relatively higher pumping rates in these 

wells may also induce additional flow from deeper parts of the 

aquifer that likely contain water with higher concentrations of 

inorganic constituents and lower redox potential and water that 

may contain dense nonaqueous phase liquid. Mixing water 

with different chemical properties from near land surface and 

near the base of the aquifer may encourage mineral precipitation in the borehole. More frequent pump cycling for shorter 

duration might reduce drawdown in the well while maintaining the required inward gradient. Additional wells using 

reduced pumping rates might be required to maintain the 

inward gradient.

Location of the well screens near the base of the aquifer 

likely induces flow of water from near the base of the aquifer 
Relation of Geochemical and Microbiologic Characteristics to Well Efficiency 85

Table 21. Mineral-saturation indices computed using PHREEQC and mixtures of groundwater from D40 (June 14, 1993) and EW–4B 

(October 9, 2014).

[Simulations used the sulfide-sulfate redox couple (and measured concentrations of sulfide and sulfate) to compute redox potential (Eh) and speciated the concentration of dissolved inorganic carbon to achieve electroneutrality. Other redox sensitive species, such as iron and manganese, were entered as total dissolved 

concentrations and speciated using the specified redox couple and other related data. Supersaturated phases are shaded in gray. g, gas; --, no data; a, amorphous; 

ppt, freshly precipitated and possibly amorphous; d, disordered]

Mineral name

D40/EW–4B1 100/0 75/25 50/50 25/75 0/100

Mineral formula Mineral

saturation index

Mineral

saturation index

Mineral

saturation index

Mineral

saturation index

Mineral

saturation index

Anhydrite CaSO4 -3.20 -1.61 -1.31 -1.12 -0.98

Aragonite CaCO3 -0.95 -0.59 -0.28 0.02 0.34

Calcite CaCO3 -0.80 -0.44 -0.12 0.17 0.49

Methane CH4 (g) -38.28 -4.94 -4.59 -4.31 --

Chalcedony SiO2 0.16 0.33 0.44 0.53 0.59

Chrysotile Mg3Si2O5(OH)4 -13.27 -10.56 -8.69 -7.04 -5.28

Carbon dioxide2 CO2 (g) -0.59 -0.65 -0.72 -0.82 -0.96

Dolomite CaMg(CO3)2 -2.00 -0.94 -0.18 0.49 1.18

Iron(III)

hydroxide Fe(OH)3

 (a) -1.57 -5.56 -5.55 -5.31 -4.99

Mackinawite FeS (ppt) -- 0.63 1.13 1.45 1.01

Fluorite CaF2 -- -2.21 -1.62 -1.29 -1.05

Goethite FeOOH 3.84 -0.10 0.06 0.24 0.60

Gypsum CaSO4.2H2O -2.76 -1.18 -0.89 0.71 -0.59

Hydrogen H2 (g) -16.34 -7.95 -7.8 -7.67 -7.72

Water H2O (g) -1.85 -1.82 -1.79 -1.76 -1.73

Hydrogen sulfide H2S (g) -- -3.94 -3.62 -3.47 -4.18

Halite NaCl -7.58 -7.60 -7.64 -7.7 -7.79

Hausmannite Mn3O4 -26.24 -33.81 -33.14 -32.44 -31.40

Hematite Fe2O3 9.63 1.74 2.08 2.43 3.16

Hydroxyapatite Ca5(PO4)3OH -- -5.21 -3.06 -1.35 0.31

Jarosite-K KFe3(SO4)2(OH)6 -14.08 -22.92 -22.25 -21.87 -21.15

Mackinawite FeS -- 1.36 1.86 2.18 1.74

Manganite MnOOH -- -13.93 -13.84 -13.73 -13.47

Melanterite FeSO4.7H2O -6.04 -4.70 -4.63 -4.69 -4.76

Nitrogen N2 (g) -- -1.51 -1.16 -0.92 --

Ammonia NH3 (g) -9.93 -9.39 -9.02 -8.74 -8.04

Oxygen O2 (g) -2.24 -71.51 -71.39 -71.25 -2.42

Pyrite FeS2 -- 11.49 12.13 12.43 11.31

Pyrochroite Mn(OH)2 -7.93 -7.76 -7.58 -7.41 -7.17

Pyrolusite MnO2.H2O -19.96 -27.98 -27.76 -27.52 -27.05

Quartz SiO2 0.63 0.79 0.91 0.99 1.05
86 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 21. Mineral-saturation indices computed using PHREEQC and mixtures of groundwater from D40 (June 14, 1993) and EW–4B 

(October 9, 2014).—Continued

[Simulations used the sulfide-sulfate redox couple (and measured concentrations of sulfide and sulfate) to compute redox potential (Eh) and speciated the concentration of dissolved inorganic carbon to achieve electroneutrality. Other redox sensitive species, such as iron and manganese, were entered as total dissolved 

concentrations and speciated using the specified redox couple and other related data. Supersaturated phases are shaded in gray. g, gas; --, no data; a, amorphous; 

ppt, freshly precipitated and possibly amorphous; d, disordered]

Mineral name

D40/EW–4B1 100/0 75/25 50/50 25/75 0/100

Mineral formula Mineral

saturation index

Mineral

saturation index

Mineral

saturation index

Mineral

saturation index

Mineral

saturation index

Rhodochrosite MnCO3 -0.44 -0.32 -0.21 -0.11 -0.01

Sepiolite Mg2Si3O7.5OH.3H2O -8.30 -6.25 -4.86 -3.66 -2.42

Sepiolite Mg2Si3O7.5OH.3H2O (d) -10.84 -8.83 -7.47 -6.3 -5.09

Siderite FeCO3 0.52 0.65 0.76 0.85 0.99

Quartz/

chalcedony SiO2

 (a) -0.73 -0.55 -0.43 -0.35 -0.27

Sulfur S -- -2.10 -1.91 -1.89 -2.53

Sylvite KCl -8.52 -8.10 -7.98 -7.95 -7.99

Talc Mg3Si4O10(OH)2 -9.43 -6.37 -4.26 -2.42 -0.50

Vivianite Fe3(PO4)2.8H2O -- -1.17 -0.53 -0.2 0.14

1

Ratio of the percent D40 in mixture to the percent EW–4B in mixture.

2

For a gas, SI = log10(fugacity). Fugacity = pressure * phi/1 atm. For ideal gases, phi = 1.

-8

-6

-4

-2

0

2

4

6

0 20 40 60 80 100

Percentage of mixture that is from well D40

Calcite

Dolomite

Fe(OH)

3

, iron (3+)

trihydroxide (amorphous)

Goethite, hydroxy(oxo)iron

Quartz

Sulfur

EXPLANATION

Mineral-saturation index

Figure 26. Mineral-saturation indices computed for hypothetical 

mixtures of groundwater from wells D40 and EW–4B at the 

confined disposal facility.

material as well. Water from the base of the aquifer material 

receives less mixing with dilute infiltrating precipitation and 

has longer residence in the subsurface than groundwater from 

nearer land surface, and as a result is likely characterized by 

lower redox values and higher concentrations of dissolved 

organic carbon and inorganic constituents. If present, dense 

nonaqueous phase liquid hydrocarbons would likely be present 

near the base of the aquifer. Wells with shallower well screens 

might reduce potential for introduction of dense nonaqueous 

phase liquids into the borehole.

The concentrations of some bulk properties and inorganic 

constituents were notably higher in EW–4B and MW–4A 

than were observed in the other four wells investigated by this 

study. Elevated results included specific conductance, total 

dissolved solids, turbidity, hardness, calcium, ferrous iron, dissolved carbon dioxide, and sulfide. The EW–4B and MW–4A 

wells also had the lowest redox values. Although water-quality 

may be changing in EW–4B in response to pumping and 

drawdown, the water in the monitoring well (MW–4A) also 

contains relatively elevated values and concentrations. Dissolved gas results indicated oxidation-reduction processes in 

the aquifer that can feasibly contribute iron, carbon dioxide, 

and other constituents derived from hydrocarbon degradation 

to precipitates and solids that accumulate on and impair pump 

operation. These characteristics indicate that the hydrogeologic setting, before petroleum hydrocarbon contamination, 

and ambient water quality in the area surrounding these 

wells are partly responsible for the poorer than average water 

quality. These variables may not be easily addressed using 
Relation of Geochemical and Microbiologic Characteristics to Well Efficiency 87

Figure 27. Chromatograph scan of scrapings collected from the pump in well EW–4B on November 3, 2016.

engineering controls; however, physical and biochemical techniques do exist to alter the inorganic chemistry and to enhance 

the rate of hydrocarbon degradation and removal. These 

methods might include injection of surfactants to reduce the 

viscosity and enhance the transport of hydrocarbon residues, 

injection of microbiological nutrients or oxidants to enhance 

hydrocarbon degradation, use of pump and treat systems, and 

manipulating redox conditions to reduce mineral precipitation 

in the borehole. An assessment of hydrocarbon distribution at 

the site might be useful for understanding the extent and concentrations of those compounds and their potential contribution to the well-fouling issue.

The redox conditions in groundwater in the CDF wells 

are in a theoretical plot of Eh with pH (25 °C and 1 bar pressure) that indicates oxidizing, reducing, and transitional water 

chemistry environments (fig. 28). Data from this study plotted 

on a stability diagram from Krauskopf and Bird (1995). The 

plot indicates that water samples from EW–4B and MW–4A 
88 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

-800

-600

-400

-200

0

200

400

600

800

1,000

1,200

0 2 4 6 8 10 12 14

pH, in standard units

Eh, in millivolts

25 °C, 1 bar

PO2 = 1 bar

OXIDIZING ENVIRONMENTS

TRANSITIONAL

REDUCING ENVIRONMENTS

PH2 = 1 bar

sulfide-sulfate boundary

EXPLANATION

EW–4B and MW–4A

EW–11B and MW–11A

EW–14A and MW–14A

organic carbon-carbonate boundary

Source of boundaries shown: Phase diagram after Krauskopf, K.B., and Bird, D.K., 1995,

Introduction to Geochemistry, 3rd edition, McGraw Hill, p. 227.

ENVIRONMENTS

°C Degrees Celsius 

PO2 Partial pressure of oxygen

PH2 Partial pressure of hydrogen

Eh Redox potential

Figure 28. Diagram showing the redox environment for 

groundwater in six wells at the confined disposal facility. 

are in a transitional environment that is nearest to the theoretical boundary between reducing and oxidizing environments as 

well as the sulfide-sulfate boundary and the organic carboncarbonate boundary. Groundwater samples for the other four 

wells are in the domain of transitional environments but nearer 

to dominantly oxidizing conditions. The inferences from this 

plot correlate with solid-phase observations of euhedral sulfur 

crystals in EW–4D and MW–4B. Altering the redox condition in the well might be possible by providing an alternative electron acceptor, such as oxygen, by using a bubbling 

mechanism. Complicating this potential mitigation strategy, 

however, might be (1) competition with active microbiological communities and (2) formation of oxidized minerals that 

would contribute to additional pump clogging. Microbiological communities have sufficient populations and activity to 

consume more oxygen than can be provided; at the same time, 

significant oxygenation may eliminate borehole environments 

that bacteria now comfortably inhabit by changing the redox 

halo surrounding the pump or physically dislodging bacteria 

from the pump. Oxidation of the abundant metals that appear 

to exist in the ambient water in this area of the CDF, however, 

may negatively affect the pump infrastructure and well by 

forming solid, encrusting, oxidation products.

Multiple analyses indicated the relative activity of 

microbiologic communities. Although all wells had measurable communities of multiple bacteria types, additional tests, 

which included bacterial activity, XRD, SEM, dissolved gas, 

and isotopic quantification, indicated elevated activity in wells 

with biofouling issues relative to wells with infrequent or no 

pump-replacement history.

Aggressive bacterial activity was identified in wells 

requiring frequent pump replacement. Effects of biofouling by 

slime growth on pump infrastructure are exacerbated by the 

accumulation of mineral matter on bacterial polysaccharides. 

The XRD analyses identified notable quantities of crystalline 

sulfur and calcite. Black coloration, similar to that observed at 

the CDF, of slime-forming bacteria by the entrapment of sulfur 

and calcite crystals is commonly observed (Droycon Bioconcepts, Inc., 2004). Slime-forming bacteria thrive near redox 

fronts. Although heterotrophic aerobic bacteria, iron-reducing 

bacteria, and sulfate bacteria were present in measurable 

populations in groundwater at the CDF, the bacteria generally 

prefer redox conditions that are less variable. 

Sulfur precipitates under relatively restricted redox 

conditions; however, microenvironments may exist within the 

borehole or within accumulations of slime. These observations 

agree with Brown and others (1999) that anaerobic bacteria 

survive in aerobic conditions or at a redox interface if the 

bacteria are encapsulated within layers of slime that are more 

tolerant of aerobic conditions. Some of the earliest described 

bacteria were large organisms with inclusions of visible sulfur 

crystals and a large aqueous vacuole (Salman and others, 

2013). SEM observations on CDF samples reported the presence of calcified vacuoles. Physical or chemical disturbance 

(and prevention) of slime-forming bacteria in the borehole 

may be required to prevent pump failure.

Brown and others (1999) determined that biofouling 

also was occurring in the aquifer material surrounding the 

well screen. Aquifer tests at the CDF by Lampe and Unthank 

(2016) determined that the hydraulic conductivity of the skin 

surrounding the well was 7–60 percent (median 19 percent) 

less than the hydraulic conductivity of the surrounding geologic deposits. This observation seems consistent with the possibility that biofouling occurred in the materials immediately 

adjacent to the well screen. Resumption of relatively high well 

discharges following pump replacement at the CDF, however, 

indicates that the primary cause of well inefficiency and eventual pump replacement is likely due to factors occurring within 
Summary and Conclusions 89

the borehole. Occasional redevelopment of the wells might 

help to alleviate reduced pump discharges. 

The impact of changing the pumping regime on water 

chemistry was difficult to discern. The water-quality data 

indicated that most of the highest concentrations and parameter values were detected in groundwater from wells requiring 

the most frequent pump replacement (EW–4B and EW–14A) 

when the pumps had been off for 8–16 hours before sample 

collection. Nutrients, which may be required for bacterial 

growth, were among those elevated constituents. These results 

contrast with observations made on other CDF wells where 

the highest concentrations and parameter values were detected after pumping had resumed for 2 weeks or more. The 

largest populations of slime-forming and sulfate-reducing 

bacteria were measured during the initial sampling and when 

the pumps had been off for 8–16 hours. The smallest populations of those bacteria were measured 1 week after pumping 

had resumed. 

The historic observation of light nonaqueous phase 

liquid, the qualitative detection in one pump scraping from 

well EW–4B, and results of dissolved gas analysis indicate 

that the presence of petroleum hydrocarbons may be a factor 

that adversely affects extraction-well efficiency. Petroleum 

hydrocarbons, especially dense nonaqueous phase liquid, 

may clog the aquifer material, well components, and pump 

infrastructure. Microbiologic processing of hydrocarbons in 

the aquifer material may influence dissolved concentrations of 

some inorganic constituents and mineral precipitation. Surfactants can be used to reduce hydrocarbon viscosity and increase 

compound mobility. Oxidation, pump and treat systems, and 

enhanced natural attenuation may be used to reduce concentrations of hydrocarbons in the aquifer material.

Summary and Conclusions

The U.S. Geological Survey, in cooperation with the 

U.S. Army Corps of Engineers, led a study during June 2014 

through November 2014 to specifically identify the hydrologic, chemical, and microbiologic processes affecting declining pump efficiency and frequent pump failure at a confined 

disposal facility (CDF), for dredge material from the Indiana 

Harbor and Indiana Harbor Canal, in East Chicago, Indiana. 

Pumping efficiency in extraction wells in required at 

the CDF to maintain inward, horizontal gradients at the site. 

Maintenance of gradients on all sides of the CDF enables isolation and control of residual hydrocarbons and leachate from 

the dredged sediment as well as control of existing site issues. 

The gradients are maintained by 96 extraction wells installed 

during 2008 in the permeable, surficial deposits of the CDF 

inside a groundwater cutoff wall. The groundwater cutoff wall 

consists of an impermeable bentonite slurry that extends from 

land surface to at least 3 feet below the interface between the 

surficial sand deposits and an underlying fine-grained deposit. 

Two monitoring wells are in each nest of extraction wells and 

are used to indicate a need for pumps in extraction wells to 

begin and stop pumping.

During 2012, fouling became evident in some extraction 

wells at the CDF. Fouling was indicated by the accumulation of a black gelatinous matter that formed on the intake of 

the extraction-well pumps. In some wells, pump efficiency 

progressively decreased and eventually required pump 

replacement (fig. 4). Of the affected extraction wells, fouling was more frequently evident in some wells than in other 

wells (fig. 5).

The investigation described in this report analyzed 

for possible chemical, microbiological, and geochemical 

processes in the borehole that could explain pump fouling. 

Groundwater samples were collected in the same 3 sets of 

paired wells on 4 occasions, and solid-phase samples were 

collected from 4 of those wells and 11 additional wells. Paired 

well sets included an extraction well and a nearby monitoring well. Water samples were collected during four pumping 

regimes to determine if the pumping schedule affected the 

water chemistry. The four pumping regimes were as follows: 

(1) normal pumping intensity and duration, (2) no pumping for 

8–16 hours before sample collection, (3) 2 weeks after resuming normal pumping conditions, and (4) 4 weeks after resuming normal pumping conditions. Water samples were analyzed 

for bulk water properties, inorganic aqueous constituents, and 

dissolved gases. Discrete solid-phase samples were analyzed 

for chemical composition, carbon and sulfur isotopes, mineralogy, solid-phase morphology, and bacterial activity.

The results of this study indicate that several factors may 

be contributing to high rates of pump failure in some extraction wells at the CDF. These factors occur at wells that require 

frequent pump replacement but do not occur, or occur to a 

lesser extent, at wells that do not require frequent replacement. 

The factors affecting pump efficiency or failure may include 

one or more of the following: (1) extraction rates that likely 

induce flow from the base of the permeable materials where 

dense nonaqueous phase liquid hydrocarbons may exist with 

relatively higher concentrations of dissolved constituents and 

lower redox values than exist at shallower depths; (2) substantial drawdown during pumping that likely brings oxygen, 

oxygenated water, and water of notably different chemistry, which may include light nonaqueous phase liquid, into 

contact with water being induced from the base of the permeable deposits; (3) mineral solids precipitating in or near the 

borehole; (4) measurable populations of aggressive bacterial 

communities that include slime-forming organisms capable 

of encapsulating pump infrastructure and attaching solids; 

and (5) some parts of the geologic deposits at the CDF have 

relatively lower permeability. Some of these factors might be 

addressed through various potential mitigation steps.

The following is a list of mitigation strategies that 

address the potential factors causing well fouling at the CDF 

and indicators of mitigation success. The information is summarized in table 22. The application and effectiveness of some 

of these methods have been reported in the literature but other 

methods might be tested in pilot or laboratory studies.
90 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Table 22. Summary of potential issues affecting pump efficiency at the confined disposal facility with synopsis of impacts, mitigation 

strategies, and criteria for evaluating improvements from mitigation as developed from literature sources and observations from this 

investigation.

Issue Impact on extraction wells Mitigation strategy Evaluation criteria

Legacy hydrocarbons exist 

across the site. Extraction 

wells induce flow of hydrocarbons toward the well screen 

and pump. Hydrocarbons 

may be lighter or heavier than 

water and exist near the water 

table or near the base of the 

formation.

Hydrocarbon residues accumulate on pumps and infrastructure and possibly in the 

gravel pack and surrounding 

formation.

Alter pumping routine to cause 

less drawdown. Consider 

pumping longer periods at 

lower rates. Additional extraction wells might be needed. 

Consider use of medium-depth 

wells to avoid dense nonaqueous phase liquids. Natural 

attenuation, pump and treat 

systems, or air sparging may 

be used to reduce amounts of 

hydrocarbons on site.

Monitor hydrocarbon distribution 

across the site in three dimensions. Use specific capacity or 

recovery tests to monitor changes in well efficiency. Monitor 

the pump replacement rate.

Hydrocarbons accumulate in the 

well and pump infrastructure.

Hydrocarbon accumulations 

clog well screens, pumps, 

and infrastructure causing pump inefficiency and 

failure.

Add a constant drip of surfactant 

that has low-foaming properties in low concentrations to 

increase solubility and mobility of hydrocarbons.

Inspect pumps for accumulation of 

hydrocarbons in the well and on 

the pumps. Use specific capacity 

or recovery tests to evaluate the 

efficiency of the extraction well. 

Monitor the pump replacement 

rate.

Extraction causes water levels 

in the well and surrounding 

formation to drop near to the 

depth of the well screen and 

brings water with different 

water chemistry into the pump.

Minerals and amorphous 

compounds precipitate in the 

well and adhere to bacteria 

on pumps and infrastructure.

Install packers into problematic 

wells to eliminate borehole 

drawdown. Consider pumping 

longer periods at lower rates 

to reduce drawdown in the 

aquifer near the well.

Monitor bacteria and mineral 

accumulation on pumps and in 

the wells. Occasional X-ray and 

scanning electron microscopy 

may indicate mitigation impact 

on mineral precipitation. Use 

specific capacity or recovery 

tests to evaluate the efficiency 

of the extraction well. Monitor 

the pump replacement rate.

Bacteria accumulate in the gravel 

pack, on the well screen, on 

the pump, and on the pump 

infrastructure. Bacteria accumulate solids that harden 

accumulations on the pump.

Bacteria and solid accumulations reduce flow causing 

pump inefficiency and 

failure.

Add a constant drip of a biocide 

in a low concentration to inhibit bacterial accumulations. 

Agitate the borehole by surging, jetting, or air sparging to 

dislodge and mobilize bacteria. 

Periodically redevelop the well 

to clear the well screen.

Inspect pumps for accumulations 

and types of bacteria while 

employing mitigation strategies. Use specific capacity or 

recovery tests to evaluate the 

efficiency of the extraction well. 

Monitor the pump replacement 

rate.

Bacteria are attracted to and 

adhere to the pump partly 

because of the pump texture, 

vibration, and temperature.

Bacteria and solid accumulations reduce flow causing 

pump inefficiency and 

failure.

Modify the thermal properties of 

the pump, modify the exterior 

of the pump, or apply a replacement physical shield.

Monitor accumulation of bacteria 

on pumps while employing different pump modifications.
Summary and Conclusions 91

1. Pump rate, duration, frequency.—Changing the pumping regimes to reduce the range of groundwater-level 

fluctuation and thereby (perhaps) minimize the aeration 

of water and contact with water in quasi-equilibrium 

with shallow sediments, to maximize the depth of water 

standing in the well (while maintaining the required 

gradient), and to minimize the volume of dewatered 

porous media near the extraction wells may change the 

chemistry and microbiology of the borehole. Using a 

borehole packer to isolate the pump from water and 

oxygen standing in the borehole might be considered in 

combination with changing the pumping regime. This 

manipulation of the pumping regimes would of course 

need to be evaluated while maintaining the required 

inward gradient. Continuous water-quality monitoring 

through several pumping cycles could be done to determine the effect of various pumping programs on water 

quality. Discrete inorganic and organic analyte samples 

also should be collected. 

2. Isolating the well site from water of certain water quality.—The groundwater quality in some areas of the CDF 

may contain elements that create issues for the pump 

systems by either providing energy sources for the 

bacteria or by containing constituents that are harmful 

(for example, hydrocarbons) or facilitate precipitation of 

minerals. The need to maintain a uniform inward gradient may reduce the flexibility of relocating extraction 

wells away from areas with problematic water quality. 

Raising the screen in problematic wells might reduce the 

influx of dense nonaqueous phase liquid. Natural attenuation, in place treatment, or pump and treat systems 

might be considered to reduce concentrations of some 

organic constituents. The success of natural attenuation 

at oxidizing hydrocarbons might be evaluated with soilgas or groundwater isotope measurements or borehole 

concentrations of hydrocarbons analyses, or both.

3. Depth of well screens.—Raising well screens to depths 

that do not induce flow from the base of the permeable 

deposits (which contain water with high total dissolved 

solids, low redox, and perhaps dense nonaqueous phase 

liquids) might decrease constituent concentrations and 

reduce mineral precipitation in the borehole and might 

reduce the introduction of dense nonaqueous phase 

liquids into the borehole. This approach would require 

modification of pumping regimes because some wells 

nearly go dry using the current regimes with pumps 

located at the bottom of the well. Continuous monitoring of onsite parameters, which include redox, dissolved 

oxygen, and specific conductance and discrete sampling 

for concentrations of hydrocarbons before and after 

pump relocation, could be used to indicate if this strategy has benefits.

4. Biocides.—The introduction of biocides may be a viable 

option to eliminate slime-producing bacteria buildup in 

the borehole. Drawbacks to chemical ameliorates are 

that they require constant capital investment or maintenance, may damage the pump infrastructure or well components, or may cause water-quality degradation. Waterquality degradation may not be a concern at the CDF, 

and slow degradation of well components may be more 

cost efficient to address than frequent pump replacement 

as a result of biofouling. Consideration might be given to 

regular addition of bactericides to problematic wells or 

a constant-drip system that would maintain a more constant concentration than occasional chemical shocking. 

Regular measurements of bacterial populations might be 

used to evaluate the effectiveness of biocides and guide 

the frequency and concentration of well additives.

5. Chemical Manipulation.—As an alternative or in addition to using biocides, manipulation of redox conditions 

in the well might be used to eliminate redox fronts that 

favor bacterial growth. 

A. Increasing the persistence of iron-organic complexes 

by limiting the in-well oxidation of reduced iron 

could limit formation of precipitates such as those 

described as accumulating on some extraction-well 

pumps at the CDF. Analytical results from this study 

indicate an association of elevated dissolved-iron 

concentrations, reduced conditions in groundwater, 

and presence of organic carbon in groundwater that 

indicate the possible enhancement of ferrous iron 

solubility through iron-organic complexes. These 

complexes are short lived in the presence of dissolved oxygen and ferric iron (Munter and others, 

2005); the dissociation can decrease iron solubility 

in produced water. Maintaining chemically reduced 

conditions should benefit this issue and could be 

monitored with continuous water-quality data.

B. Use of surfactants with low foaming properties 

to maintain or increase the mobility of hydrocarbons might be done with a constant drip system in 

problematic wells. The success of this treatment 

could be qualitatively evaluated by inspection of 

pump scrapings and camera logging the well screen 

and infrastructure.

6. Thermal properties of pump.—Some bacteria are 

attracted to heat and grow faster at higher temperatures. Increased pump insulation might decrease the 

pumps attractiveness as a bacterial anchor point. Pump 

modifications could be done in collaboration with the 

pump manufacturer, and laboratory tests could be done 

to determine the temperature dependence of bacterial 

attraction.

7. Turbulence properties of pump.—Bacteria populations 

may increase with increasing borehole turbulence to a 

point. Adding turbulence to the borehole or pump to the 

point where bacteria become dislodged from the pump is 
92 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

desirable. Pump modifications could be done in collaboration with the pump manufacturer, and laboratory tests 

could be done to determine the threshold of turbulence 

separating biological attraction and discomfort.

8. Texture of pump exterior.—The current pump texture is 

smooth stainless steel. An outer spray coat of polytetrafluoroethylene or other material could be tested for 

effectiveness at discouraging bacterial adhesion (Banerjee and others, 2011). N-acetyl-L-cysteine (also known 

as N-acetylcysteine) may be used to reduce and prevent 

biofilm formation on stainless steel surfaces (Olausson 

and others, 2003). N-acetyl-L-cysteine decreased bacterial adhesion and detached bacteria adhering to stainlesssteel surfaces. N-acetyl-L-cysteine inhibited growth of 

some bacteria and reduced the production of extracellular polymeric substances. Active research in the resistance of bacterial adhesion is also examining the use of 

polyethylene glycol and oligoethylene glycol (Banerjee 

and others, 2011). Visual inspection of bacterial accumulation to evaluate the effectiveness of these technologies 

could be done in the laboratory or borehole, or both.

9. Physical pump protection.—A physical barrier that 

encapsulates the pump and provides an alternative 

substrate for bacterial adhesion may not cost much for 

materials but may require routine replacement; the latter 

requires expensive manpower. 

None of these remedies in singular or combination are 

guaranteed to reduce or eliminate the pump fouling. A few 

of the remedies have indicated some efficacy in applications 

described in the literature. The CDF water quality, hydrogeochemical setting, and pumping regime likely are unique; therefore, pilot scale testing or trial and error evaluations might be 

required. Examination of the well screen and gravel pack also 

might be considered to determine if screen slots and formation 

pore spaces are being occluded by bacterial or mineralogical accumulations. If the screen slots and pore spaces have 

been filled, then remedies proposed may have little impact on 

well productivity. 

Limitations

The data and interpretations for this study were limited in 

the following ways: 

1. Only three well pairs were sampled for water quality. 

Those wells were selected to represent the range of site 

conditions that result in frequent and infrequent pump 

replacement. However, conditions that were not sampled 

may also cause frequent pump failure at the CDF and 

potential mitigating solutions may not be applicable to 

wells at those sites. Examination of more wells might 

be required to further generalize the results reported in 

this document.

2. Precipitation and evapotranspiration were not entirely 

constant during the investigation; therefore, the influence of precipitation and evapotranspiration on conditions observed in the wells could not be fully evaluated. 

For example, the decline in concentrations of some 

constituents that were detected in the weeks following pump inactivity in some wells could be related to 

the lack of pumping or might be related to rain events 

during the time of pump inactivity. A repeat of the 

pumping regime tests during a shorter, more-constant 

weather period might be required to explain the lower 

constituent concentrations.

3. Solid-phase samples were collected as pumps were being 

serviced; however, the samples were not necessarily 

from the same wells as those sampled for water quality 

and bacterial activity. As a result, direct comparisons 

between aqueous, microbiological, and solid phases are 

inferential. Sets of water-quality and solid-phase samples 

from identical wells would be required to directly corroborate some of the suppositions made in this report. 

For example, supersaturated conditions in one well 

were correlated with the presence of minerals identified with X-ray diffraction in a nearby well but without 

identifying the presence of the minerals in the same 

well that produced the groundwater; the conclusion is 

only inferential.

4. Equipment blanks identified small quantities of constituent carryover from imperfect equipment cleaning. These 

concentrations were miniscule in comparison to the 

concentrations detected in environmental samples but 

should be recognized.

5. Groundwater samples for chemical analysis were only 

collected from the screened interval of the extraction 

wells. As a result, proposed mitigation strategies that 

assume increasing concentrations of water-quality constituents and decreasing redox with greater depth in the 

aquifer are based on observations at other sites and may 

not apply to the CDF. Sampling from multiple depths 

in the permeable aquifer material would be needed to 

confirm assumed water-quality stratification.

6. Proposed mitigation strategies are based on disrupting 

bacterial and geochemical processes that were observed 

in wells that require frequent pump replacement but that 

are not observed in wells without frequent pump replacement, strategies that have been applied to other sites, 

or strategies evaluated in the literature using theoretical 

or microcosm studies. To fully evaluate if the strategies 

apply to the CDF, the strategies would need pilot scale 

testing or trial and error evaluations.
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Appendix 1. Driller’s Records for Wells at the 

Confined Disposal Facility used by this Study

Well records do not have an accompanying Extraction Well Construction Report as indicated in 

the REMARKS section.
98 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 
Appendix 1 99
100 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 
Appendix 1 101
102 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 
Appendix 1 103
104 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 
Appendix 1 105
106 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

Appendix 2. X-Ray Diffractograms of Solids 

Collected on Filter with 0.45-Micron Pore 

Size during Water-Quality Sampling or from 

Suspended Sediment in Groundwater Samples 

Collected at the Confined Disposal Facility
Appendix 2 107 10 20 30 40 50 60 Two-Theta (deg) 0

50

100150

200

250

300

350

400

450

) ts (Coun ty Intensi

Sulfur - S

EW–4C Trace 1

Crystalline sulfur plus amorphous phase(s)
108 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Dol Dol Dol Dol Dol Dol Dol Dol Dol Dol Dol Dol Dol Dol Dol

10 20 30 40 50 60

Two-Theta (deg)

0

50

350300250200150100

Intensity(Counts)

Sulfur - S

Dolomite - MgCa(CO3)2

EW–4D Trace 1
Appendix 2 109 10 20 30 40 50 60 Two-Theta (deg) 0

50

200150100

Intensity(Counts)

Calcite - CaCO3

EW–11D Trace 1

Amorphous material with a trace of (?) calcite
110 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

10 20 30 40 50 60

Two-Theta (deg)

0

750500250

Intensity(Counts)

Calcite - CaCO3

Quartz - SiO2

EW–20D Trace 1

Expanded scale to show trace phase

Calcite with possible trace quartz
Appendix 2 111 10 20 30 40 50 60 Two-Theta (deg) 0

500

2500200015001000

Intensity(Counts)

Calcite - CaCO3

EW–20D Trace 2

nearly pure calcite
112 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

10 20 30 40 50 60

Two-Theta (deg)

0

500

2500200015001000

Intensity(Counts)

Calcite - CaCO3

EW–20D Trace 3

nearly pure calcite
Appendix 2 113

Sul

Sul

Sul

Sul

Sul

Sul

Sul Sul Sul Sul

Sul Sul Sul Sul

Sul Sul Sul Sul Sul Sul Sul Sul Sul

Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul

10 20 30 40 50 60

Two-Theta (deg)

0

50

450400350300250200150100

Intensity(Counts)

Sulfur - S

MW–4B Trace 1

crystalline sulfur plus amorphous phase(s)
114 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul Sul

10 20 30 40 50 60

Two-Theta (deg)

0

50

350300250200150100

Intensity(Counts)

Sulfur - S

MW–4B Trace 2

Crystalline sulfur plus amorphous phase(s)
Appendix 3 115

Appendix 3. Scanning Electron Micrographs 

of Solid Samples Collected on Filter with 

0.45-Micron Pore Size during Water-Quality 

Sampling or from Suspended Sediment 

in Groundwater Samples Collected at the 

Confined Disposal Facility
116 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW4C 10-23-14 C

EW4C 10-23-14EDS analyses of the sample matrix reveals Fe, S, Ca, and C and in some spots Mg.Flat piece Fe and S with C.
Appendix 3 117

EW4D 09-11-14 D

The EDS analyses of this sample all have Fe,

S, and C. The gray areas that look “foggy” arelikely biofilm. The BSE image areas that are

brighter have more Fe relative to S.
118 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW4D 09-11-14 D

See next page for analyses.
Appendix 3 119

Spectrum C Al Si S Ca Fe O Total

Spectrum 1 5.74 31.63 62.63 100

Spectrum 2 7.98 28.34 63.68 100Spectrum 3 15.16 3.97 26.86 54.02 100

Spectrum 4 17.07 5.4 18.64 58.89 100

Spectrum 5 6.49 17.2 16.3 7.96 52.05 100Spectrum 6 6.35 30.73 62.92 100Spectrum 7 14.95 4.91 25.61 54.53 100

Spectrum 8 10.75 24.28 64.97 100Spectrum 9 20.01 0.69 1.64 4.19 1.43 7.31 64.73 100

Here is an image with spectra analysis pointsindicated. These data are not quantitative. The 

results can be used to say something about 

concentrations relative to each point, but the results cannot be used as quantitativeconcentrations of elements.

EW4D 09-11-14 D
120 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW4D 09-11-

Presumably

14 D

the spherical

o

bject “V” is a whole vacuole. There are mineralized biostructures

extending off the vacuole; enlarged on the right. EDS indicate Fe, S, and C.

V 
Appendix 3 121

EW4D 09-11-14 D

The EDS analyses of this sample all have Fe, S, and C; 

except the sulfur crystals (on a broken vacuole plate).
122 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana The areas circled in red are S crystals. Presumably the spherical object is a whole vacuole. The area labeled “A” is likely carbon biofilm.

A
Appendix 3 123 EW6C 11-6-14 B

EW6C 11-6-14 This sample has a relatively homogeneous matrix with tubular feature as imaged here. EDS

analysis of the matrix is Fe, Ca, P, Si, and C. The platy structures are Fe > Ca > P > Si > C.
124 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

EW11D 9-19-14 A 

EW11D 9-19-14 This sample is relatively homogeneous as imaged here. EDS analysis reveals Fe, Ca,

P, Si,

and 

C and in some spots S.

The gray shadows (stars) covering and surrounding the “mineral” phase is the biofilm material (carbon).

The panels with 2 images show the SE (secondary electron) image and the BSE (backscattered electron image). In the backscatter image phases with higher mean atomic number will be lighter in color. Here the BSE shows us that the sample is uniform in composition. 
Appendix 3 125

This sample is in a homogeneous matrix as demonstrated by the uniform gray color in the right image (back-scatter electrons). Energy Dispersive X-Ray Spectroscopy (EDS) analyses (not shown) indicate the sample is Ca and C. From the crystal structure the sample is likely calcite, CaCO3. The crystalline material is held together by an amorphous matrix or biofilm as indicated by 

desiccation cracks. The bright area in the left image (secondary electron image) shows that the sample was not well grounded.

EW20D 10-23-14 I 
126 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana EW20D 10-23-14 I

Enlargement of t

he CaC

O3 precipitate.
Appendix 3 127 MW4B 10-9-14 E

These images are representative of most

of this sample. The matrix is

S, Fe,

Ca,

and C.

The crystals are S

with C.
128 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

MW4B 10-9-14 E

Another common occurrence in this sample are hollow vacuoles.
Appendix 3 129

The area circled in red below is imaged here. The buff colored precipitate appeared as the

sample dried on the SEM stub. These are crystals of sulfur, the frilled upper edge of the 

crystals is due to evaporative precipitation. 

MW4B 10-9-14 E
130 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana MW4B 10-9-14 E Morphology of the large sulfur crystals is very interesting.
Appendix 3 131 MW4B 10-9-14 E

A cluster of sulfur crystals.
132 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

This sample had strings of biofilm, one crosses the left image above. The string was high 

C with S, Fe, and traces of Ca and Mg. 

Matrix EDS analyses detected Fe, S, Ca, and C with minor Mg and Si.
Appendix 3 133
134 Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana 

S

S

The sulfur crystals (S) are surrounded by biofilm. 

Vacuole a

n

d matrix Fe,

S, and 

C with minor Ca and Mg.
For additional information contact:

Director, Ohio-Kentucky-Indiana Water Science Center

U.S. Geological Survey

5957 Lakeside Boulevard

Indianapolis, IN 46278-1996

Publishing support provided by the 

Madison and Pembroke Publishing Service Centers
Bayless and others—Geochemistry and Microbiology of Groundwater and Solids from Extraction and Monitoring Wells, East Chicago, Indiana —SIR 2018–5073

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20185073