Prepared in cooperation with the Indiana Department of Natural Resources, 

Division of Reclamation

Hydrogeology and Simulation of Groundwater Flow 

at the Green Valley Reclaimed Coal Refuse Site 

near Terre Haute, Indiana

Scientific Investigations Report 2011–5116

U.S. Department of the Interior

U.S. Geological Survey

Hydrogeology and Simulation of 

Groundwater Flow at the Green Valley 

Reclaimed Coal Refuse Site near 

Terre Haute, Indiana

By E. Randall Bayless, Leslie D. Arihood, and Kathleen K. Fowler

Prepared in cooperation with the Indiana Department of Natural Resources, 

Division of Reclamation

Scientific Investigations Report 2011–5116

U.S. Department of the Interior

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

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Bayless, E.R., Arihood, L.D., and Fowler, K.K., 2011, Hydrogeology and simulation of groundwater flow at the Green 

Valley reclaimed coal refuse site near Terre Haute, Indiana: U.S. Geological Survey Scientific Investigations Report 

2011-5116, 70 p.
iii

Contents

Acknowledgment...........................................................................................................................................v

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

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Previous Investigations........................................................................................................................2

Hydrologic Setting ................................................................................................................................4

Methods of Investigation..............................................................................................................................6

Hydrogeology of the Green Valley Reclaimed Coal Refuse Site..........................................................11

Simulated Groundwater Flow ....................................................................................................................28

Simplifying Assumptions....................................................................................................................28

Model Design.......................................................................................................................................30

Model Calibration................................................................................................................................32

Selection and Sensitivity Analysis of Model Parameters...................................................33

Observations and Observation Weights ................................................................................36

Changes in the Design of the Model During Calibration.....................................................38

Calibration Results.....................................................................................................................38

Calibrated Parameter Values..........................................................................................38

Analysis of the Residuals ................................................................................................39

Model Budget....................................................................................................................46

Simulated Water Levels...................................................................................................47

Simulated Flow Paths.......................................................................................................48

Model Limitations and Qualifications..............................................................................................49

Summary and Conclusions.........................................................................................................................52

References Cited..........................................................................................................................................53

Appendixes 1–4............................................................................................................................................55

Appendix 1............................................................................................................................................56

Appendix 2............................................................................................................................................59

Appendix 3............................................................................................................................................64

Appendix 4............................................................................................................................................67

Figures

1. Location of the Green Valley mine site, near Terre Haute, relative to underground 

and surface coal mines in southwestern Indiana...................................................................3

2. Hydrogeologic section showing the variation in thickness of deposits in the 

Green Valley mine site, Indiana..................................................................................................5

3. Areal extents of gob and mixed gob and tailings deposits in the coal refuse at the 

Green Valley mine site, Indiana..................................................................................................6

4. Location of monitoring wells, weather station, and V-notch weir at the 

Green Valley mine site, Indiana..................................................................................................7
iv

5. Precipitation at the Green Valley mine site, Indiana ............................................................11

6. Air temperature measured at the weather station at the Green Valley mine site, 

Indiana, October 1, 2008, through September 30, 2009.........................................................12

7.Water-level hydrographs for monthly measurements at 11 wells at the 

Green Valley mine site, Indiana................................................................................................13

8.Water-level hydrographs for monthly measurements at nine wells at the 

Green Valley mine site, Indiana................................................................................................14

9. Groundwater levels at the Green Valley mine site, Indiana, indicating a vertical 

gradient from the coal refuse (well GV8A) into the underlying till (well GV8C)................15

10. Continuous water levels in selected wells at the Green Valley mine site, Indiana.........16

11. Groundwater flow directions and rates for measurements made at the Green Valley 

mine site, Indiana, June–July 2008..........................................................................................18

12. Discrete seep-discharge and streamflow measurements at the Green Valley mine 

site, Indiana, 2008–9 ...................................................................................................................22

13. Potentiometric-surface map for August–September 2009 used to (1) show the 

configuration of the water table at the Green Valley mine site, Indiana, and 

(2) estimate hydraulic conductivities from flowmeter data.................................................23

14.Transects used for surface survey of apparent subsurface electrical conductivity 

at the Green Valley mine site, Indiana, December 2008.......................................................25

15. Seep discharges and streamflows at the Green Valley mine site, Indiana ......................26

16. Discharge from seep 1 at the Green Valley mine site, Indiana...........................................27

17. Layering design for the model of the Green Valley mine site, Indiana ..............................29

18. Model grid discretization and river, drain, and constant-head cells used in the 

simulation of groundwater flow at the Green Valley mine site, Indiana ...........................30

19. Relation between land-surface altitude and groundwater-level altitude at 

water-well sites in and near the Green Valley mine site, Indiana......................................32

20. Location of sites used to provide observations of streamflow flux (gain/loss) and 

groundwater levels at the Green Valley mine site, Indiana.................................................37

21. Location of drain cells in simulation used to discharge groundwater that reaches 

land surface at the Green Valley mine site, Indiana.............................................................39

22. Graphical analysis of the steady-state model fit for the area of coal refuse at the 

Green Valley mine site, Indiana................................................................................................42

23. Graphical analysis of the transient model fit for the area of coal refuse at the 

Green Valley mine site, Indiana................................................................................................42

24. Distribution of positive and negative unweighted water-level residuals for the 

steady-state calibration of the model for the Green Valley mine site, Indiana................44

25. Simulated and observed hydrographs from the transient calibration of the model 

for the Green Valley mine site, Indiana...................................................................................45

26. Model-simulated water levels for the coal refuse (model layer 1) of the model, 

Green Valley mine site, Indiana................................................................................................47

27. Model-simulated water levels for the middle of the till (model layer 3) of the 

model, Green Valley mine site, Indiana...................................................................................48

28. Simulated flow paths from points of recharge in the area of coal refuse 

(model layer 1) to points of discharge areas, Green Valley mine site, Indiana................50
v

29. Simulated flow paths projected from points of recharge to row 34 near the center 

of the coal refuse to points of discharge, Green Valley mine site, Indiana ......................51

Tables

1. Selected characteristics for observation wells at the Green Valley 

mine site, Indiana..........................................................................................................................9

2. Selected characteristics for surface-water discharge measurement sites at the 

Green Valley mine site, Indiana................................................................................................10

3. Horizontal flowmeter data for the Green Valley mine site, Indiana, June–July 2008......17

4. Horizontal flowmeter data for the Green Valley mine site, Indiana, 

August–September 2009............................................................................................................20

5. Hydraulic conductivities computed from flowmeter-measured velocities, 

hydraulic gradients computed from measured groundwater elevations, and an 

assumed correction factor (a=5.0) for borehole acceleration, Green Valley 

mine site, Indiana........................................................................................................................24

6. Discrete seep-discharge and streamflow measurements at the Green Valley mine 

site, Indiana, 2008–9 ...................................................................................................................26

7. Horizontal hydraulic conductivities computed from slug-test data collected at the 

Green Valley mine site, Indiana, August–September 2009..................................................28

8. Description of geologic materials and model layers used to represent the 

hydrogeologic system at the Green Valley mine site, Indiana............................................28

9. Model parameters used in the steady-state model of the Green Valley mine site, 

Indiana (June 2009), their initial values, and indication of whether a parameter 

value was estimated ..................................................................................................................33

10. Model parameters used in the transient model of the Green Valley mine site, 

Indiana (June 2009), their initial values, and indication of whether a parameter 

value was estimated ..................................................................................................................34

11. Calibrated parameter values obtained for the groundwater model of the 

Green Valley mine site, Indiana................................................................................................40

12. Unweighted streamflow flux residuals for the steady-state calibration of June 2008 

for the model of the Green Valley mine site, Indiana............................................................43

13. Unweighted streamflow flux residuals for the transient calibration from June 2008 

to June 2009 from the model of the Green Valley mine site, Indiana.................................43

14. Statistical summary for the residuals from the steady-state calibration of the 

model for the Green Valley mine site, Indiana.......................................................................43

15. Statistical summary for the residuals from the transient calibration of the model 

for the Green Valley mine site, Indiana...................................................................................44

16. Simulated steady-state water budget for layer 1 of the model (the coal refuse), 

Green Valley mine site, Indiana, June 2009............................................................................46

17. Simulated steady-state water budget for the model of the Green Valley mine site, 

Indiana, June 2009......................................................................................................................46

18. Percentage of flow paths discharging to the major discharge areas and travel time 

statistics for the flow paths, Green Valley mine site, Indiana.............................................50
vi

Conversion Factors

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) 

Mass

ton 0.001 kilogram (kg)

Volume

cubic foot (ft3) 28.32 cubic decimeter (dm3) 

cubic foot (ft3) 0.02832 cubic meter (m3) 

cubic yard (yd3) 0.7646 cubic meter (m3) 

Flow rate

foot per minute (ft/min) 0.3048 meter per minute (m/min)

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

cubic foot per second (ft3/s) 0.02832 cubic meter per second 

(m3/s)

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

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Hydraulic conductivity

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

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

°C=(°F-32)/1.8

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

(NGVD 29) and the 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.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius 

(μS/cm at 25 °C).

Electromagnetic conductivity is given in millisiemens per meter (mS/cm at 25°C).
vii

Other abbreviations or acronyms used in this report:

Acronym or 

abbreviation Full name of acronym or abbreviation

Cl Chloride

Fe Iron

H Hydrogen

Mo Month

O Oxygen

SO4 Sulfate

PVC Polyvinyl chloride

USGS U.S. Geological Survey 

Acknowledgment

The authors are grateful to Mr. Charles Lee, property owner, for access to the site.

Hydrogeology and Simulation of Groundwater Flow at 

the Green Valley Reclaimed Coal Refuse Site near 

Terre Haute, Indiana

By E. Randall Bayless, Leslie D. Arihood, and Kathleen K. Fowler

Abstract 

The Green Valley reclaimed coal refuse site, near Terre 

Haute, Ind., was mined for coal from 1948 to 1963. Subsurface coal was cleaned and sorted at land surface, and waste 

material was deposited over the native glacial till. Approximately 2.7 million cubic yards of waste was deposited over 

159 acres (92.3 hectares) in tailings ponds and gob piles. During 1993, the Indiana Department of Natural Resources, Division of Reclamation, improved the site by grading gob piles, 

filling tailings ponds, and covering the refuse with a layer of 

glacial drift. During 2008, the Division of Reclamation and 

U.S. Geological Survey initiated a cooperative investigation 

to characterize the hydrogeology of the site and construct a 

calibrated groundwater flow model that could be used to simulate the results of future remedial actions. In support of the 

modeling, a data-collection network was installed at the Green 

Valley site to measure weather components, geophysical properties, groundwater levels, and stream and seep flow.

Results of the investigation indicate that (1) there is negligible overland flow from the site, (2) the prevailing groundwater-flow direction is from northeast to southwest, with 

a much smaller drainage to the northeast, (3) there is not a 

direct hydraulic connection between the refuse and West Little 

Sugar Creek, (4) about 24 percent of the groundwater recharge 

emerges through seeps, and water from the seeps evaporates 

or eventually flows to West Little Sugar Creek and the Green 

Valley Mine Pond, and (5) about 72 percent of groundwater 

recharge moves vertically downward from the coal refuse into 

the till and follows long, slow flow paths to eventual discharge 

points. 

Introduction

The Green Valley reclaimed coal refuse site (Green Valley site) includes approximately 159 acres of reclaimed gob 

(coarse coal refuse) and tailings (fine coal refuse) (Melchiorre, 

Dale, and others, 2005). The site was actively mined from 

1948 to 1963 (Melchiorre, Dale, and others, 2005). Subsurface 

mining of Springfield Coal Member of the Petersburg Formation and Seelyville Coal Member of the Staunton Formation 

produced about 14 million tons of coal (Melchiorre, Dale, 

and others, 2005). The 2.7 million cubic yards of coarse coal 

refuse was deposited on the land surface, near the main shaft. 

The thickness of gob ranged up to 55 ft (Eggert and others, 

1981; Melchiorre, Dale, and others, 2005). In the years after 

site abandonment, three studies documented the degradation 

of adjacent and downstream groundwater and surface-water 

resources as a result of acidic mine drainage and sedimentation (Caserotti and Marland, 1974; Eggert and others, 1981; 

Geosciences Research Associates, Inc., 1985). 

In an effort to reduce water-quality degradation and the 

deposition of eroded refuse in adjacent waterways, the Indiana 

Department of Natural Resources, Division of Reclamation, 

made improvements to the Green Valley site during 1993. The 

gob piles were regraded, and tailings ponds were filled with 

gob. A thin layer of agricultural lime (less than 1 ft thick) was 

spread over the refuse surface, and the site was capped with 

an approximate 3 ft thickness of sandy till that was excavated 

from the property immediately east of the site (Mark Stacy, 

Indiana Department of Natural Resources, oral commun., 

2009). A berm of sandy till was installed around the top of the 

largest, centrally located gob pile to limit overland flow. The 

surface of the capped refuse was plowed to create a corrugated 

surface to capture precipitation and limit overland flow. Acidophilic trees and grasses were sown into the cap material to 

stabilize the surface. Channels were installed around the base 

of the refuse piles and lined with cobble-sized dolostone riprap 

to chemically neutralize and control the conveyance of runoff 

and seep discharges. 

Post-reclamation studies determined that acid mine 

drainage was still emanating from groundwater seeps at the 

Green Valley site and impairing water quality in adjacent 

waterways (Brake and others, 2001; Amt and others, 2003; 

Unger and others, 2003; Melchiorre, Dale, and others, 2005; 

Gibson, 2006). During 2008, the Indiana Department of 

Natural Resources, Division of Reclamation, and the U.S. 

Geological Survey (USGS) began a cooperative investigation 
2 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

to characterize the hydrogeology of the Green Valley site. The 

characterization was accomplished by collecting and analyzing 

field data, describing the hydrogeology, and using a calibrated 

computer model to simulate groundwater flow through and 

beneath the coal refuse deposit. One aspect of the mission 

of the USGS is to protect and enhance our Nation’s water 

resources for human health, aquatic health, and environmental 

quality. This investigation supported the USGS mission by 

characterizing the hydrology of a site that may be adversely 

impacting water quality, and using data analyses and groundwater models to explore potential ways to improve the quality 

of water emanating from the site.

Purpose and Scope

This report describes the hydrogeology and hydrologic 

budget of the reclaimed coal refuse and the adjacent geologic 

deposits at the Green Valley site (study area in fig. 1). The 

analysis presents the basic field data, including continuous 

and periodic groundwater levels, continuous and periodic 

seep measurements, weather data, and surface and borehole 

geophysical surveys. The analysis also includes information 

describing the construction and calibration of a groundwater flow model, steady-state and time-dependent (transient) 

simulations done with the model, and descriptions of the 

simulated water table, groundwater-flow paths, and hydrologic 

budget. The groundwater-flow model was used to simulate the 

movement of acid mine drainage through the coal refuse and 

underlying till. 

Field data were collected for this investigation from May 

2008 through December 2009. The data-collection network 

was distributed across the entire site and monitored hydrologic 

conditions in the coal refuse and underlying glacial till. The 

network consisted of 26 monitoring wells, 5 seep discharges, 

2 streamflow sites, and a weather station. Borehole geophysical logs (including gamma, electromagnetic induction, and 

horizontal flowmeter) were measured in one or more wells at 

most well sites. A surface electromagnetic induction survey 

was done around the perimeter of the site and across the center 

of the refuse. Slug tests were done in four wells to obtain data 

to compute hydraulic properties. 

Previous Investigations

The Green Valley site and nearby waterways have been 

the subject of various scientific investigations, both before 

and after reclamation. Geosciences Research Associates, Inc. 

(1985) assessed the site prior to reclamation and documented 

the mining history, geologic setting, and hydrogeology. Refuse 

at the site is the result of operations between 1948 and 1963. 

The Springfield Coal Member was mined from approximately 

313 ft below land surface until 1952. The Seelyville Coal 

Member was mined from approximately 503 ft below land 

surface until 1963. Room and pillar mining technique was 

used. The Springfield Coal Member extent was 380 acres, and 

the Seelyville Coal Member extent was 3,390 acres (Geosciences Research Associates, Inc., 1985). 

Eggert and others (1981) described the geology and water 

quality of the Green Valley site after mining operations ceased 

but before reclamation; the analysis was done while assessing 

energy resources in the remaining coal refuse. Water-quality 

samples were collected from the reach of West Little Sugar 

Creek that borders the Green Valley site (upstream and downstream from the site), a tailings pond, a stream that drained the 

site, and a well located on one of the coal refuse piles (Eggert 

and others, 1981, p. 144). The quality of West Little Sugar 

Creek surface-water samples downstream from the Green Valley site was noticeably different from that of samples collected 

upstream, including a fivefold increase in dissolved solids. 

Caserotti and Marland (1974) similarly documented the effects 

of effluent from the Green Valley site on West Little Sugar 

Creek. 

Brake and others (2001), Amt and others (2003), Unger 

and others (2003), and Gibson (2006) examined water quality 

in West Little Sugar Creek after reclamation and concluded 

that water quality in West Little Sugar Creek was not improving and might be getting worse with time. Gibson (2006) 

concluded that water quality in the creek was directly related 

to streamflow. Brake and others (2001) and Amt and others 

(2003) indicated that impairment of water quality and ecological communities in West Little Sugar Creek was the result of 

elevated concentrations (above background concentrations) 

of chemical constituents in seep effluent that discharged to 

the creek. Concentrations of most major and trace elements 

decreased with increasing distance from the confluences of 

West Little Sugar Creek and seep channels on the Green Valley site.

Unger and others (2003), Melchiorre, Dale, and others 

(2005), and Melchiorre, Mills, and others (2005), studied the 

water quality and mineralogy associated with the seeps. Unger 

and others (2003) compared constituent concentrations in 

seeps at the Green Valley site with concentrations in unaffected surface water from nearby waterways and determined 

that the seeps contained much higher concentrations of various 

trace elements relative to the other samples. Melchiorre, Mills, 

and others (2005) documented the occurrence of a relatively 

rare mineral, xitieshanite [Fe3+(SO4

)Cl.6H2O], at the Green 

Valley site. The mineral precipitated at a location where seep 

water flowed over limestone riprap and glacial till.

Melchiorre, Dale, and others (2005) examined water 

chemistry and oxygen stable isotopes in samples of groundwater, surface water, and precipitation collected on-site between 

September 2000 and January 2002 to describe hydraulic properties of the coal refuse at the Green Valley site. Melchiorre, 

Dale, and others (2005) collected samples from four wells 

(GV1, GV2, GV3, and GV4); wells GV1, GV2 and GV3 are 

screened in glacial drift and located around the periphery of 

the refuse deposit, whereas GV4 is screened in the coal refuse. 

The specific conductance of water samples from four wells on 

the site responded almost immediately to rainfall, but a 30-day 

lag preceded noticeable dilution in water emanating from 
Introduction 3

10 20 30 40 50 MILES

0 10 20 30 40 50 KILOMETERS

0

South Bend

Mishawaka

, 

Fort Wayne

Kokomo

Lafayette Muncie

Indianapolis

T

EXPLANATION

Major urban areas

Underground mines

Surface mines

38 ̊

39 ̊

40 ̊

41 ̊

88 ̊ 87 ̊ 86 ̊ 85 ̊

Goshen

West

Lafayette

Clarksville

Study 

area

East Chicago, Gary

Hammond, Whiting, 

Hobart, Portage

Elkhart

Anderson

Bloomington

erre Haute

Evansville

New Albany

Jeffersonville

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

Universal Transverse Mercator projection, Zone 16

North American Datum 1983

Mining areas obtained from Indiana

Geological Survey, 2003

Figure 1. Location of the Green Valley mine site, near Terre Haute, relative to underground and surface coal mines in 

southwestern Indiana.
4 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

the seeps. Oxygen isotope data indicated that precipitation 

recharged groundwater flowed to wells GV1, GV2, and GV3 

in less than 8 days and GV4 in about 27 days. Changes in 

isotope values data collected at three seeps, including S3 and 

S4 from this investigation (and a third site that did not seep 

during this investigation) lagged precipitation inputs by 60, 90, 

and 105 days, respectively. Hydraulic conductivities computed 

from these data ranged from 1.05 to 7.37 ft/d in the glacial 

drift and from 7.37 to 16.44 ft/d in the gob. Melchiorre, Dale, 

and others (2005) concluded that multiple sources of recharge 

were required to produce their observations; they hypothesized 

that one source of water was infiltrating precipitation and that 

a second source was water expelled from pre-mining karst-like 

features.

Jennifer Bellamy (Indiana State University, written commun., 2007) examined the effect of the Green Valley site on 

water and sediment chemistry in adjacent John A. Scott Lake 

and the Green Valley Mine Pond. John A. Scott Lake was created by the excavation of till that was used to cap the refuse. 

On the basis of chemical analyses of water and sediment, 

Jennifer Bellamy (Indiana State University, written commun., 

2007) concluded that bank sediments in John A. Scott Lake 

were not contaminated by mine drainage from the Green Valley site. Seep effluent from the northeastern part of the Green 

Valley site into the headwaters of Green Valley Mine Pond, 

however, resulted in elevated concentrations of minor and 

major elements in the vicinity of the channel mouth.

Hydrologic Setting

The study area is in the Central Wabash Valley physiographic area of the Central Tipton Till Plain region of western 

Indiana, near the southern limit of Wisconsin glacial deposits 

(Gray, 2000). Surface topography ranges from nearly flat to 

gently rolling. Surficial deposits in the surrounding area and 

beneath the coal refuse deposit are composed of glacial drift. 

The glacial drift is till that was deposited during the Wisconsin glacial episode, underlain in most places by till deposited 

during the Illinois glacial episode; the latter appears at land 

surface only where the former has been severely eroded 

(Schneider, 1966). The till is generally sandy, with interbedded 

silty and sandy-till stringers. Streams near the site are underlain with a nominal thickness of relatively younger alluvium 

than is found at distance from the streams. The thickness of till 

varied beneath the study area. A test boring done as part of this 

investigation at site GV8, near the center of the refuse deposit, 

determined that the thickness of glacial drift was about 50 ft. 

A boring by Geosciences Research Associates, Inc. (1985), as 

part of an earlier investigation, struck shale at 45 ft below the 

natural land surface. A hydrogeologic cross section through 

the study area, based on well-record information from this 

investigation and from the Indiana Department of Natural 

Resources (2002), indicates that the till thickness is varied 

(fig. 2). 

At the Green Valley site, the glacial till is overlain by 

coal-mining refuse. The refuse deposits consist of gob, tailings, and mining-related rubbish. Gob, created by beneficiation of coal at land surface, was described by Geosciences 

Research Associates, Inc. (1985), as “rock, mineral and coal 

fragments that are wastes from the tipple or preparation plant.” 

Tailings include “accumulations of fine gravel, sand, silt and 

clay size fragments or particles of coal and other materials 

that are washed out of the coal in the wash or preparation 

plant” (Geosciences Research Associates, Inc., 1985). Additional wastes deposited at the site may include debris from the 

mine roof, underclay, and refuse from the tipple and mining 

equipment. Underclay is a layer of clay beneath a coal bed. A 

railway grade that formerly crossed the site from northwest 

to southeast was determined to be composed of soil, gravel, 

and coal with occasional concrete piers, culverts, and wooden 

trestles. 

Geometry of the deposits is uncertain, but maps constructed prior to reclamation showed the general distribution of gob and tailings (Geosciences Research Associates, 

Inc., 1985; fig. 3). The land-surface area of the two gob piles 

was approximately 42 acres. During reclamation, the elevation and slope of gob piles was reduced by moving material 

from higher elevations into the lower lying areas. Well-driller 

records generated as part of this investigation indicate that 

thickness of the coal refuse ranges from zero, at the margins 

of the site, to as much as 69 ft at GV9 near the center of the 

Green Valley refuse deposit; the exceptional thickness at GV9 

is attributed to the well site’s being positioned over a depression in the underlying till. 

John A. Scott Lake was created immediately east of the 

Green Valley site by the excavation of glacial till used to cap 

the coal refuse. John A. Scott Lake is connected by a short 

channel to the Green Valley Mine Pond. The level of the pond 

is maintained by use of an engineered overflow and, as a 

result, little variability (less than 0.5 ft) in lake or pond-surface 

water levels was observed during this investigation. Depth of 

John A. Scott Lake is approximately 45 ft.

The study area is in the Wabash River drainage basin. 

The Green Valley site drains to West Little Sugar Creek to 

the west and the Green Valley Mine Pond to the east. West 

Little Sugar Creek merges with Sugar Creek, which flows 

into the Wabash River approximately 11 mi downstream from 

the Green Valley site. The drainage area of West Little Sugar 

Creek above the Green Valley site is approximately 6.2 mi2

(http://water.usgs.gov/osw/streamstats/indiana.html; accessed 

February 2, 2010). 

West-central Indiana, including the study area, has a 

continental climate. Temperatures in the study area generally range from an average low of about 18°F in January to 

an average high about 87°F in July (Midwestern Regional 

Climatic Center, 2010a), and the average annual temperature 

is 54°F (Clark, 1980).Rainfall is fairly evenly distributed 

throughout the year but is typically highest from March to 
Introduction 5

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

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

Universal Transverse Mercator projection, Zone 16 

North American Datum 1983

EXPLANATION

87°31'30'' 87°31' 87°30'30''

39°31'

39°30'30''

Location at which altitudes of 

grids representing refuse, till, and 

bedrock surfaces were determined 

for hydrogeologic section

500

520

540

560

580

600

620

640

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

Approximate extent of coal refuse

COAL REFUSE

TILL

BEDROCK

West Little Sugar Creek

Green Valley

Mine Pond

West Little Sugar Creek

Green

Valley

Mine

Pond

A A'

A

A'

VERTICAL SCALE GREATLY EXAGGERATED

John A.

Scott Lake

0

0

 FEET

 600 METERS

500 1,000 1,500 2,000

150 300 450

Elevation above NGVD 29, in feet

Distance along section, in feet

Figure 2. Hydrogeologic section showing the variation in thickness of deposits in the Green Valley mine site, Indiana.
6 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

August (averages ranging from 3.68 to 4.46 in./mo) and lowest in September to February (averages ranging from 2.13 

to 3.39 in./mo); annual precipitation averages about 42 in. 

(Midwestern Regional Climatic Center, 2010b). The statewide 

annual average evapotranspiration is about 69 percent of the 

net precipitation, and recharge averages 12 in. (Clark, 1980). 

Methods of Investigation

A data-collection network was installed at the Green Valley site to measure weather components, geophysical properties, groundwater levels, seep discharge, and streamflow. The 

installations consisted of a weather station, monitoring wells, a 

weir, and controlled outfalls. Measurements collected from the 

data network were used to characterize the site hydrology, create input data and flow and head constraints for the groundwater-flow model, and provide verification data for the simulated 

water budget. All data were collected, preserved, and reported 

according to methods that meet the standards of the USGS. 

A weather station (Vaisala Model WXT520) was installed 

at the Green Valley site to collect data that would be used to 

understand relations between weather and site hydrology. 

A tipping-bucket rain gage was installed approximately 20 

ft from the weather station. The weather instruments were 

installed in an open, grassy area near the highest elevation 

at the site and approximately midway between well sites 

GV4, GV8, and GV9 (fig. 4). Measured weather variables 

were wind speed, wind direction, humidity, temperature, and 

EXPLANATION

Area of gob deposits

Area of gob and

tailings mixture

Green

Valley

Mine

Pond

39 ̊31'

39 ̊30'30''

87 ̊31'30'' 87 ̊31' 87 ̊30'30''

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

0

John A.

Scott Lake

West Little Sugar Creek

Base from U.S. Geological Survey digital data, 1983, 1:100,00

Universal Transverse Mercator projection, Zone 16

North American Datum 1983

Figure 3. Areal extents of gob and mixed gob and tailings deposits in the coal refuse at the Green Valley mine site, Indiana.
Methods of Investigation 7

precipitation. Precipitation was measured with an impact 

sensor and a tipping-bucket gage. Measurements were totaled 

every 60 minutes and radio-transmitted from the weather 

station to the USGS Indiana Water Science Center office in 

Indianapolis every 3 hours. The weather data were archived in 

the USGS National Water Information System (U.S. Geological Survey, 2010).

Twenty-two monitoring wells were installed at 16 sites, 

including 2 wells installed at 4 sites and 3 wells installed at 

one site, during June–August 2008. At each of the 16 sites, 

a 4-in.-inside-diameter polyvinylchloride (PVC) casing was 

installed and completed with a 0.010-in. slotted well screen. A 

filter pack of No. 4 sand was used to fill the annular space to 

700 1,400 FEET

0 175 350 METERS

0

600

6 20

6 0 5

6 35

6 30

6 1 0

610

6 2 5 6 2 5

6 0 5 55 5

5 65

6 05

6 0 0

56 0

5 9 5

6 0

5

5

90

5 5

5

0

4 0

5 4

5

6 00

6 00

5 55

58 0

550 560

550

565

585

580

575 570

600 595

575 585

610

630625

615

585

590

595

605

610

615

590

610

620 615

615

605

87 ̊31'30'' 87 ̊31'15'' 87 ̊31' 87 ̊30'45''

39 ̊30'45''

39 ̊30'30''

Approximate extent of coal refuse

Well site with continuous water-level 

data collection and well number

Well site with intermittent water-level 

data collection and well number

Weather station

V-notch weir at measurement site for seep 1 

GV13

GV18

550 LAND-SURFACE ELEVATION CONTOUR —

Contour interval 5 feet. Datum is North American

Vertical Datum of 1988 

John A.

Scott Lake

Green Valley Mine Pond

West Little Sugar Creek

Measured section of seep

2 Seep number and measurement site

3A

4

2

Stream

3B

West Little

Sugar Creek

upstream

West Little

Sugar Creek

downstream

GV1

GV2

GV3

GV4

GV7A,B

GV8A,B,C

GV9A,B

GV10

GV11A,B

GV12A,B

GV13

GV14

GV15

GV16

GV17

GV18

GV19 GV20

GV21

GV22

EXPLANATION

545

550

545

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

Universal Transverse Mercator projection, Zone 16

North American Datum 1983

Figure 4. Location of monitoring wells, weather station, and V-notch weir at the Green Valley mine site, Indiana.
8 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

1 ft above the screen. The remaining annular space was sealed 

with bentonite chips to within 2 ft of land surface. A concrete 

plug and steel well-protector were used to finish the well. 

Second and third wells at clustered-well sites were constructed 

from 2-in.-inside-diameter PVC casing and slotted screens. 

The 2-in. wells were finished in the same fashion as the 4-in. 

wells. The 4-in. well screens had six columns of slots, and 

the 2-in. well screens had four columns of slots. Wells were 

installed by using hollow-stem drilling methods and developed by pumping for a minimum of 1 hour. The latitudes, 

longitudes, and elevations of measuring points of wells were 

surveyed by the IDNR using a global positioning system. An 

IDNR investigation during 2000 installed four additional 2-in. 

wells that were included in the data-collection network. Those 

wells were constructed with methods and materials similar to 

those used during this investigation; however, the bentonite 

was tremied (rather than poured) into the annular space, and 

the wells were not completed with a concrete plug and steel 

well-protector. In total, the groundwater monitoring network 

has 26 wells at 20 sites (table 1, figure 4).

Twenty-one of the well screens installed during 2008 

extended from 0 to 3 ft below the refuse-till interface to about 

5 ft below land surface. Screen lengths ranged from 5 to 30 ft. 

The purpose for long well screens was to accommodate borehole flowmeter measurements. Well GV8C was fully cased 

except for the bottom 5 ft; this well was screened across the 

shallowest sandy horizon found in the till beneath the refusetill interface. The total depths of wells ranged from 14 to 74 ft 

below land-surface datum. Wells were developed by pumping for a period of 1 hour. Wells GV1–3 were cased entirely 

through till and screened across sandier zones that were 

penetrated. All other wells were screened mostly or entirely in 

coal refuse.

The depth to water was measured in all wells with an 

electric tape approximately once per month, provided that sites 

were accessible; during some visits the well-protectors were 

frozen shut or the water in the well was frozen (Appendix 1). 

Pressure transducers were installed in nine wells and used to 

measure the water-level elevation at 60-minute increments 

from November 2008 through December 2009. Vented transducers were installed in wells GV8C, GV9A, GV11A, and 

GV18 (In-Situ model Level Troll 500) and in wells GV7A, 

GV8A, GV12A, GV14, and GV22 (Global Water model 

WL16). Accuracy of the transducer measurements of water 

levels was approximately ±0.01 ft. Transducer measurements 

of water levels were adjusted for mechanical drift by linearly 

averaging the difference between the transducer and electricaltape measurements over the period between electrical-tape 

measurements. Tape-down measurements of groundwater 

levels were not made during September–December 2009; 

transducer measurements of water levels during this period 

were not corrected for mechanical drift. Well-construction 

records, location, elevation, and water-level measurements for 

all wells were preserved in the USGS Ground-Water SiteInventory (GWSI) system. 

Borehole and surface geophysical measurements were 

used to acquire additional information about the hydrogeology 

at the site. Borehole geophysical measurements were made in 

the well network at the Green Valley site to gather information about the stratigraphy, water quality, and groundwater 

flow. Surface measurements of electromagnetic induction 

were made on transects inside and outside of the property 

boundaries and across the center of the coal refuse. Borehole 

geophysical measurements consisted of continuous logs of 

natural-gamma activity and electromagnetic induction, and 

discrete measurements of groundwater velocity and direction. 

Natural-gamma activity was measured through the entire well 

profile in one well at all 20 well sites (Appendix 2). Electromagnetic induction was measured through the entire well profile in 1 well at 11 sites (Appendix 3). Groundwater flow (rate 

and direction) measurements were attempted at one or more 

discrete depths in all 26 wells. Natural-gamma measurements 

are stable in time, so they were completed as time allowed 

throughout the course of the investigation. Electromagnetic 

induction values can change through time, and those logs were 

measured during May–June 2008. Flowmeter measurements 

can vary with time and depth, so those measurements were 

made during June–July 2008 and August–September 2009. 

Natural-gamma activity is a measureable quantity created 

by the spontaneous emission of alpha particles during the 

radioactive decay of elemental potassium that occurs naturally 

in some rock and clay minerals (Keys, 1990). At the Green 

Valley site, the highest gamma values likely indicate clay 

minerals in the till used to cover the coal refuse, till beneath 

the refuse deposit, and non-coal rock fragments that were a 

byproduct of the mining operation and were disposed of and 

intermingled with the coal refuse. Electromagnetic induction 

measures the capacity of the geologic materials and groundwater in the vicinity of a well to conduct electricity (Keys, 1990). 

Geologic materials that increase electromagnetic conductivity include clay minerals and iron-bearing minerals. Electrically conductive rubbish that includes metals and that was 

buried with the coal refuse would also increase the measured 

conductivity. Acid mine drainage, documented at the Green 

Valley site in various studies, is highly conductive relative to 

groundwater unaffected by mining activity. A comparison of 

natural-gamma activity and electromagnetic induction logs can 

be done to identify subsurface intervals where groundwater 

and pore fluids have relatively high electrical conductivity as 

compared to other fluids.

Gamma and electromagnetic induction measurements 

were made by means of a Mt. Sopris MGX logging system 

fitted with a Mt. Sopris Model 2PGA-1000 gamma tool and 

a Mt. Sopris Model 2PIA-1000 electromagnetic induction 

tool. Factory-set parameters were used instead of site-specific 

calibration of the electromagnetic induction tool. Wells were 

logged for natural-gamma activity and electromagnetic induction at a rate of 10–15 ft/min. All data were archived according 

to USGS standards.
Table 1. Selected characteristics for observation wells at the Green Valley mine site, Indiana. [PVC, polyvinylchloride; N100GLCIAL, glacial till; 111GOB, coal gob; C, confined; U, unconfined]

Local well 

identifier1

Top of well 

screen below 

land surface (feet)

Bottom of well 

screen below 

land surface (feet)

Wellscreen 

material 

Geologic unit Aquifer type Land-surface altitude2 Begin date for measuring-point use Measuring-po

altitude3

GV1 3.35 8.35 PVC N100GLCIAL C 593.02 06/19/2008 595.50GV2 4.47 19.47 PVC N100GLCIAL C 609.60 06/02/2008 612.84GV3 11.71 21.71 PVC N100GLCIAL C 601.00 05/22/2008 604.19GV4 28.23 38.23 PVC 111GOB U 628.50 05/22/2008 630.27GV7A 5.22 30.22 PVC 111GOB U 624.39 06/20/2008 624.39GV7B 4.97 29.97 PVC 111GOB U 624.13 10/15/2008 626.12GV8A 14.78 44.78 PVC 111GOB U 629.47 06/25/2008 629.47GV8B 15.11 45.11 PVC 111GOB U 629.66 10/15/2008 631.52GV8C 69.35 74.35 PVC N100GLCIAL C 629.96 09/04/2008 632.24GV9A 16.69 66.69 PVC 111GOB U 632.80 06/25/2008 632.80GV9B 16.67 66.67 PVC 111GOB U 632.98 10/15/2008 635.51GV10 4.50 14.50 PVC 111GOB U 597.09 06/26/2008 597.09GV11A 9.69 29.69 PVC 111GOB U 626.48 06/27/2008 626.48GV11B 10.18 30.18 PVC 111GOB U 626.49 10/15/2008 628.86GV12A 9.86 19.86 PVC 111GOB U 607.38 06/27/2008 607.38GV12B 10.21 20.21 PVC 111GOB U 607.34 10/15/2008 609.41GV13 8.97 33.97 PVC 111GOB U 619.98 06/26/2008 619.98GV14 9.44 24.44 PVC 111GOB U 618.14 06/26/2008 618.14GV15 4.56 19.56 PVC 111GOB U 616.38 09/04/2008 616.34GV16 4.66 19.66 PVC 111GOB U 613.67 09/04/2008 613.67GV17 4.84 19.84 PVC 111GOB U 615.71 09/04/2008 615.68GV18 9.75 24.75 PVC 111GOB U 601.13 09/04/2008 601.11GV19 8.88 23.88 PVC 111GOB U 619.10 09/04/2008 619.10GV20 5.00 20.00 PVC 111GOB U 598.86 09/04/2008 598.95GV21 15.12 40.12 PVC 111GOB U 615.83 09/04/2008 615.83GV22 4.60 14.60 PVC 111GOB U 572.29 09/04/2008 572.24

1 Sites are shown on figure 4.2 Horizontal datum is referenced to North American Datum of 1983.3 Vertical datum is referenced to North America Datum 1988.
10 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

The surface geophysical survey of electromagnetic conductivity was done January 26, 2009, to identify areas where 

acid mine drainage could be flowing offsite in groundwater. 

The electromagnetic survey measured the apparent subsurface electrical conductivity (normalized to 25 degrees Celsius), which is affected by a combination of factors including 

geologic material, anthropogenic influences, and the electrical 

conductivity of groundwater. A Geophex GEM-2 instrument 

was used to simultaneously measure conductivity at six settings, corresponding to different depths of penetration; the 

approximate maximum depth of penetration was 30–65 ft.

Flowmeter measurements in wells were made at 11 sites 

(11 wells) during relatively wet conditions (from June 2 to 

July 1, 2008) and at 18 well sites (24 wells) during relatively 

dry conditions (from August 25 to September 2, 2009). Wells 

at GV13 and GV19 were dry during the 2009 measurement 

period. Flowmeter measurements were attempted at multiple 

depths during 2008 and 2009. Flowmeter measurements made 

during 2008 were used to provide groundwater-flow direction 

information that could be used to locate additional well sites in 

the Green Valley data-collection network. Flowmeter measurements during 2008 and 2009 indicated patterns of groundwater 

flow near the wells during relatively wet and dry conditions 

and were used to estimate the hydraulic conductivity of the 

gob and till. 

Two borehole flow meter instruments were applied at 

the Green Valley site. The Kerfoot Technologies, Inc., Model 

200 GEOFLO instrument monitors the transport of a heated 

parcel of water to measure groundwater-flow rate and direction (Bayless and others, 2011). An AquaVISION Colloidal 

Borescope measures groundwater-flow rate and direction by 

digitally tracking optically observed colloids that are transported throughout the well screen (Bayless and others, 2011). 

In most cases, the technology that was used at a well site 

during the 2008 measurements was used again during the 2009 

measurements.

Streamflow and seep discharge was measured at seven 

sites (table 2) on two to eight occasions between October 2008 

and July 2009. Lack of flow or inaccessibility prevented measurements during some site visits. November measurements 

could not be made in West Little Sugar Creek because of an 

equipment malfunction, and January measurements could not 

be made because ice in the stream was too thick

An acoustic Doppler velocimeter (ADV; SonTek 

Flowtracker) was used to make streamflow measurements at 

sites immediately upstream and downstream of the reach of 

West Sugar Creek that marks the southwestern boundary of the 

Green Valley site. The velocimeter uses acoustic reflections 

from entrained sediment to measure flow. The equal-widthincrement method was used to measure flow through sections 

oriented perpendicular to the flow direction. Conditions in 

West Little Sugar Creek were less than ideal for applying the 

midsection method to measure streamflow because of irregularities in the streambed profile, narrow stream channels, 

shallow water depths, and nonuniform velocities (Rantz and 

others, 1982).

Flow from all seeps except seep 1 was computed by using 

timed-volume measurements. Temporary dams with outflow 

pipes were installed at seep 3A and seep 4. Natural dams and 

outfalls were present at seep 2 and seep 3B. The seep 2 drainage area includes water collected from an engineered channel 

that extends from West Little Sugar Creek uphill to the vicinity of well site GV15. The discharge from seep 2 was measured immediately above the confluence of the seep channel 

with West Little Sugar Creek. The discharge at seep 3A was 

measured near the site where groundwater emerges at land surface on the western side of the refuse deposit. The seep 3B site 

is in the same channel as seep 3A but further downstream and 

immediately above the confluence of the seep channel with 

West Little Sugar Creek. The discharge at seep 3B includes 

water from the seep channel and water from a private farm 

and woodland. The seep 4 drainage area includes engineered 

Table 2. Selected characteristics for surface-water discharge measurement sites at the Green Valley mine 

site, Indiana.

 [USGS, U.S. Geological Survey; °, degrees; ′ minutes; ′′, seconds] 

Local site identifier2 USGS station 

identifier Latitude1 Longitude1 Flow-measurement method 

Seep 1 393047087304701 39°30′39′′ 87°30′47′′ Weir.

Seep 2 393035087312801 39°30′35′′ 87°31′28′′ Pool overflow.

Seep 3A 393035087311401 39°30′35′′ 87°31′14′′ Pipe discharge, dye tracing.

Seep 3B 393027087312101 39°30′27′′ 87°31′21′′ Pool overflow.

Seep 4 393031087310401 39°30′31′′ 87°31′04′′ Pipe discharge.

West Little Sugar Creek, 

upstream

393036087312801 39°30′36′′ 87°31′28′′ Acoustic Doppler 

velocimeter.

West Little Sugar Creek, 

downstream

393025087311901 39°30′25′′ 87°31′19′′ Acoustic Doppler 

velocimeter.

1

 Horizontal datum is referenced to North American Datum of 1983.

2

 Sites are shown on figure 4.
Hydrogeology of the Green Valley Reclaimed Coal Refuse Site 11

channels that extend east to the property boundary, northeast 

to near well site GV15, and north to near well site GV18. Seep 

4 discharges to West Little Sugar Creek approximately 0.20 mi 

southwest from the southwesternmost corner of the Green Valley site. Seep 1 discharge was measured with a V-notch weir. 

Stage behind the weir was continuously recorded with a pressure transducer. The flow rate of water at seep 1 was computed 

from the recorded data. Seep 1 discharges to a small channel 

that flows into the Green Valley Mine Pond.

Aquifer and slug tests were done at the Green Valley site 

to provide data to compute hydraulic properties of the coal 

refuse. Two-well aquifer tests were attempted at five sites, and 

single-well slug tests were done at four sites. Tests were done 

in wells screened in thin sand lenses within the till and wells 

screened in the coal refuse. Slug tests were done in well GV2 

on July 12, 2009, and in wells GV7A, GV11A, and GV12A 

between August 27 and September 2, 2009 (Appendix 4). 

Rising- and falling-head tests were done by introducing 

and removing a weighted section of PVC pipe to a position 

immediately above and below the water table, respectively. 

Groundwater levels were monitored during the test with a 

pressure transducer that was positioned 

below the water table. Slug-test data 

were analyzed with the Bouwer and 

Rice (1976; Bouwer, 1989), Hvorslev 

(1951), and KGS (Hyder and others, 

1994) methods by using AQTESOLV 

software (Hydrosolve, 2002). The 

analyses with the Bouwer and Rice 

method were generally insensitive to 

whether a confined or unconfined aquifer model was used, so the unconfined 

model was used for all slug tests. A 

set of simplifying assumptions was 

used in the analysis of slug tests. The 

vertical anisotropy used in the computations was assumed to be 0.2 for 

all slug-test analyses; testing indicated 

that the results were generally insensitive to this parameter. The tested interval at each well screen was assumed to 

be homogenous and have infinite areal 

extent. The potentiometric surface for 

each test was assumed to be initially 

horizontal. 

Hydrogeology of the Green Valley 

Reclaimed Coal Refuse Site

The precipitation measured with the impact sensor during water year 2009 (October 1, 2008 through September 30, 

2009) at the Green Valley site, totaled 47.17 in. and was higher 

than the average annual precipitation reported for a long-term 

weather station at Terre Haute, Ind. Precipitation measurements m ade with the impact sensor and the tipping-bucket rain 

gages showed strong linear correlation (fig. 5A). The tippingbucket rain gage was not heated and, as a result, could not 

measure solid precipitation and frequently froze in an arrested 

position during cold weather. Conversely, the impact sensor measured precipitation year round. For these reasons, the 

impact-device measured precipitation data were considered 

to be the precipitation record for the period of this investigation (fig. 5B). Air temperature for the period of investigation 

ranged from 0.2 to 91.50°F (median 52.7°F), and relative 

humidity ranged from 18.5 to 100 percent, with a median of 

Figure 5. Precipitation at the Green 

Valley mine site, Indiana. A, Amounts 

of precipitation measured using an 

impact sensor (Vaisala) showing 

relation to amounts measured using a 

tipping bucket gage (measurements 

during periods when the tipping bucket 

gage was frozen are not included). B, 

Precipitation measured for water year 

2009 by use of the impact sensor. 

0

1.0

1.5

2.0

y = 0.914x

R2 = 0.885

0

0.5

1.0

2.0

0 0.5 1.0 1.5 2.0 2.5

0.5

Precipitation measured with a tipping-bucket rain gage, in inches

Precipitation measured with a 

Vaisala impact sensor, in inches Precipitation measured with a 

Vaisala impact sensor, in inches

1.5

A. Precipitation measurement correlation

B. Precipitation during 2008-09

OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP

2008 2009
12 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

76 percent (fig. 6). Assuming evapotranspiration was 69 percent of the total precipitation, as proposed by Clark (1980), an 

evapotranspiration amount of approximately 32.5 in. might be 

expected for the Green Valley site during water year 2009.

Groundwater levels were annually cyclical. At most 

sites, groundwater levels were highest during April to July 

and lowest during September to December (figs. 7 and 8). 

Groundwater levels in wells at four well sites—GV4, GV8, 

GV9, and GV18—were distinctly different throughout the 

year, being highest from June through September and lowest 

around March. The thickness of the unsaturated zone in wells 

GV4, GV8, GV9, and GV18 averaged about 9.0 to 50.62 ft 

during water year 2009 (median: 32.03 ft) compared to 11.10 

to 39.35 in the other wells screened in gob (median: 14.04 ft), 

and may indicate a relation between water-level variability and 

unsaturated-zone thickness. These data represent the hydrologic conditions present during water year 2009 and may vary 

from year to year. 

0

10

20

30

40

50

60

70

80

90

100

OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP

2008 2009

Temperature, in degrees Fahrenheit

Figure 6. Air temperature measured at the weather station at the Green Valley 

mine site, Indiana, October 1, 2008, through September 30, 2009.
Hydrogeology of the Green Valley Reclaimed Coal Refuse Site 13

600

602

604

606

608

610

612

614

600

602

604

606

608

610

612

614

590

592

594

596

598

600

602

604

JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL

2008 2009

GV15

GV7A

GV17

GV11A

GV14

GV16

GV2

GV12A

GV19

GV18

GV3

WATER-LEVEL ALTITUDE, IN FEET ABOVE NAVD 88

EXPLANATION

Water-level measurement

GV12A Label for well hydrograph of well GV12A

Figure 7. Water-level hydrographs for monthly measurements at 11 wells at the Green Valley mine site, Indiana. 
14 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

590

592

594

596

598

600

602

604

578

580

582

584

586

588

590

592

594

560

562

564

566

568

570

572

574

Missing record

Missing record

GV8A

GV4

GV8C

GV10

GV1

GV9A

GV20

GV21

GV22

JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY JUN JUL

2008 2009

WATER-LEVEL ALTITUDE, IN FEET ABOVE NAVD 88

Missing record

EXPLANATION

Water-level measurement

GV22 Label for well hydrograph of well GV22

Figure 8. Water-level hydrographs for monthly measurements at nine wells at the Green Valley mine site, Indiana.
Hydrogeology of the Green Valley Reclaimed Coal Refuse Site 15

Groundwater levels in well GV8A in the gob were consistently higher than in the underlying till (GV8C), indicating 

that the hydraulic gradient is from the coal refuse into the 

underlying till (fig. 9). A specific conductance of 4,300 μS/cm 

of water from well GV8C on August 31, 2009, was higher 

than would be expected for groundwater unaffected by mine 

drainage. This conductance may indicate that water from the 

overlying coal refuse is moving into the underlying till, as suggested by the hydraulic gradient. The distance is 24 ft from the 

well screen at GV8C to the interface between the coal refuse 

and the till. A poor annular seal around the well or inadequate 

well development could also explain the elevated specific 

conductance of the water in the well. A specific conductance 

measurement (20,400 μS/cm) was made in water from well 

GV7A, screened in gob, on June 29, 2009. In the till, historical values of specific conductance were measured in water 

from two wells about 0.75 mi northeast of the Green Valley 

site (790 μS/cm, in well 392854087303199, sampled July 18, 

1979; and 540 μS/cm, in well 393109087300899, sampled 

August 13, 1979; U.S. Geological Survey, National Water 

Information System, 2010). Assuming that these data represent 

current background water-quality conditions in the till, the 

higher specific conductance values under the Green Valley site 

in well GV8C likely indicate that the hydraulic gradients were 

from the gob into the till. 

Continuous groundwater-level data showed similar 

patterns to the monthly measurements but provided additional detail about water-table fluctuations during the periods 

between monthly measurements (fig. 10). Some wells, such as 

GV8A, GV9A, GV11A, and GV18, showed less water-level 

variability than other wells. Water-level fluctuations in well 

GV8C, screened in the underlying till, were the most subdued 

from all of the measured wells. Groundwater-level fluctuations 

during the study period ranged from 0.55 ft at GV10 to 7.54 ft 

at GV2. The median fluctuation (minimum to maximum) for 

all 26 wells was 1.98 ft. In general, water-level fluctuations 

ranged from approximately 2 ft or less near the center of 

the refuse deposit and from about 2 to about 7 ft around the 

margins of the refuse deposit. The observed spatial pattern in 

annual water-level variability may be related to thickness of 

the unsaturated zone, proximity of wells to seep zones, thickness of the glacial drift cap over the refuse, the presence of 

preferential flow paths, or a combination of these factors.

EXPLANATION

596.5

597.5

598.5

599.5

600.5

Water-level altitude, in feet above NAVD 88

JUN JUL AUG SEP OCT NOV DEC

2008

JAN FEB MAR APR MAY JUN JUL AUG SEP

2009

597.0

598.0

599.0

600.0

WELL GV8A Continuous groundwater level measurement

WELL GV8 Continuous groundwater level measurement

Discrete groundwater level measurement

Discrete groundwater level measurement

WELL GV8A

WELL GV8C

Figure 9. Groundwater levels at the Green Valley mine site, Indiana, indicating a vertical 

gradient from the coal refuse (well GV8A) into the underlying till (well GV8C).
16 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

604

605

606

607

608

609

610

611

GV7A

595

596

597

598

599

600

601

602

GV8A

593

594

595

596

597

598

599

600

GV8C

599

600

601

602

603

604

605

606

GV11A

581

582

583

584

585

586

587

588

GV9A

595

596

597

598

599

600

601

602

GV12A

601.5

602.5

603.5

604.5

605.5

606.5

607.5

608.5

GV14

590

591

592

593

594

595

596

597

GV18

O N D J F M A M J J A S

O N D J F M A M J J A S

561

562

563

564

565

566

567

568

GV22

2008 2009

2008 2009

Water-level altitude, in feet above NGVD 88

Figure 10. Continuous water levels in selected wells at the Green Valley mine site, Indiana. 
Hydrogeology of the Green Valley Reclaimed Coal Refuse Site 17

In general, distinct depth-related differences in borehole measurements of natural-gamma activity indicate that 

stratigraphic layering with homogeneous hydraulic properties 

was not observed (Appendix 1). Some logs indicated higher 

gamma activity near land surface that probably was caused by 

the presence of the till cap. Wells GV2 and GV3, completed 

entirely in glacial deposits, also showed relatively high gamma 

activity and may indicate a change from clay-rich to sandier 

till (lower gamma activity) with depth. Many gamma logs 

appeared to indicate a trend toward decreasing gamma activity 

with depth; this may be an indication of historic coal-processing techniques or changing source-rock composition. Some 

wells, including GV4A, GV8C, GV9A, GV11A, GV12A, and 

GV14, contained a 7- to 12-ft-thick interval near the refusetill interface with gamma measurements less than 50 counts 

per second (cps). This interval may represent a common and 

perhaps hydrologically connected layer of refuse, however, 

detailed well-driller records and cores were not collected 

during installation, and a precise interpretation of the gamma 

logs, in this case, is not possible. 

Electromagnetic conductivity varied spatially and with 

depth at the Green Valley site. At wells screened entirely in till 

(GV1–3), electromagnetic conductivity values generally were 

less than 150 mS/m (Appendix 2). Near-surface values at GV1 

were slightly higher than 150 mS/cm2

 and probably indicate 

the infiltration of higher conductivity seep water near the 

well. The electromagnetic conductivity of the till cap overlying the coal refuse also was generally less than 150 mS/cm2

. 

The electromagnetic conductivity of coal refuse ranged from 

150 mS/cm2 to greater than 700 mS/cm2 and, generally, most 

wells spanned intervals that exceeded 400 mS/cm2. Near water 

from some wells, such as GV4 and GV9, higher conductivity 

appeared to be related to intervals with low gamma activity. 

For groundwater from most wells, the highest conductivity 

appeared to be measured in deeper intervals of the wells. 

Flowmeter measurements made from June 2 to July 1, 

2008, indicated that groundwater flow directions through wells 

near engineered ditches at the Green Valley site were affected 

by those structures (table 3; fig. 11). Examples of this observation include measurements made at GV1, GV2, GV3, GV10, 

Table 3. Horizontal flowmeter data for the Green Valley mine site, Indiana, June–July 2008. 

[bmp, below measurement point; Geologic material, the deposits juxtaposed from the flowmeter measurement interval; CBFM, colloidal borescope flow meter; 

ft/d, feet per day; NA, not applicable to the measurement; parentheses, a relatively stable subset of the complete dataset was sampled and analyzed for vector 

properties and is presented in the table; KVA, Kerfoot Technologies, Inc., Model 200 GEOFLO; all times are in Eastern Standard Time]

Local well 

identifier1 Date/time Depth 

(bmp)

Measurement 

Elevation 

(above vertical 

datum)

Geologic 

material in 

measured 

interval 

Data 

points 

collected 

by CBFM

Duration 

of CBFM 

trace

Vector 

velocity2

(ft/d)

Vector 

direction 

of flow (in 

compass 

degrees)

Comments

GV1 6/19/2008

3:40 pm

8.98 586.50 Till NA NA 11.7 332.6

GV2 6/2/2008 

5:40 pm

21.00 591.84 Till NA NA 12.9 132.2

GV3 6/5/2008 

7:42 pm

16.80 587.39 Till (462) (16) (33.3) (252) 

GV4 6/12/2008 

2:03 pm

36.00 594.27 Coal refuse NA NA 3.8 304

GV7A 6/20/2008 31.90 594.93 Coal refuse 530 26:30 8.4 249

GV8A 6/25/2008 36.42 595.49 Coal refuse NA NA 4.7 223.4

GV9A 7/1/2008 52.71 582.80 Coal refuse NA NA 10.8 258.3

GV10 6/26/2008 11.50 588.09 Till NA NA 4.5 115.7

GV11A 6/27/2008 29.50 599.48 Coal refuse NA NA NA NA Swirling flow with 

CBFM. Near zero 

velocity with KVA. 

GV12A 6/30/2008 15.00 594.88 Coal refuse NA NA 10 151

GV14 6/30/2008 16.50 604.14 Coal refuse NA NA 12.0 281.4

GV14 6/30/2008 16.50 604.14 Coal refuse NA NA 12.0 281.4

1

 Sites are shown on figure 4.

2

 Flowmeter velocity measurements have not been corrected for borehole acceleration; formation velocities may be less by a factor from 0.1 to 1.0 times the 

measured borehole velocity.
GV10 GV4 GV2 GV1 GV3 GV9 A GV12 A GV7 A GV14 GV8 A BETWEEN 1 AND 5 FEET PER DAY BETWEEN 5 AND 10 FEET PER DAY BETWEEN 10 AND 15 FEET PER DAY EXPLANATION 0 150 300 450 600 FEET Aerial photo from Indiana Department of Natural Resources, 2007 87°31’30” 87°31’00” 

39°30’45” 39°30’30” 

John Lake West Little Sugar Creek HORIZONTAL GROUNDWATER-FLOW DIRECTION AND VELOCITY, JUNE-JULY 2008, IN FEET PER DAY DRAINAGE DITCHES Figure 11. Groundwater flow directions and rates for measurements made at the Green Valley mine site, Indiana, June–July 2008.
Hydrogeology of the Green Valley Reclaimed Coal Refuse Site 19

GV12, and GV14. Measurements of groundwater flow direction through wells located nearer the center of the refuse pile 

(GV7, GV8, and GV9), however, were similar to the prevailing hydraulic gradient from northeast to southwest. 

In most cases, one interval within each well was determined to have a relatively stable flow direction with a velocity 

that was notably higher than at the other depths tested. These 

data indicate that zones of higher hydraulic conductivity 

are present in the refuse where groundwater-flow rates are 

relatively faster than other zones in the refuse. The flowmetermeasured velocities, therefore, should be considered in that 

context and are likely higher than the average groundwater 

velocity throughout the entire screened interval. Fast flow 

rates through zones of higher hydraulic conductivity have been 

observed in other studies where horizontal borehole flowmeters were applied (Kearl, 1997).

Flowmeter velocity measurements indicate the apparent 

groundwater-flow rate at the depth where the measurement 

was made. Precise velocity determinations require an adjustment that must be measured in the laboratory. Correction 

factors for wells that are screened in materials with relatively 

low hydraulic conductivity, such as the coal refuse at this site, 

may range from 1 to 10 (Kearl, 1997; Wu and others, 2008) 

but more commonly range from 1.8 to 4.0 (Drost and others, 

1968). Correction factors for the two flowmeter technologies 

should not be expected to be the same. Laboratory determination of correction factors was beyond the scope of this investigation and, as a result, the velocities reported in tables 2 and 3 

have not been corrected.

Interpretation of the flowmeter vectors measured during 

2009 is problematic. Despite attempts to measure groundwater-flow vectors at the same depth and with the same technology as used during 2008, the results were notably different. 

Measured groundwater velocities during August–September 

2009 (table 4) were slower and probably indicate the difference in the hydrologic conditions of the site during late 

summer, compared to the early-summer conditions during 

2008 (table 3). In some wells, measurements were made at 

two depths. Groundwater-flow directions through wells GV3, 

GV12, GV15, GV17, and GV18 continued to indicate flow 

towards natural and engineered discharge areas (fig. 12). Flow 

in wells near the center of the coal refuse, including GV4, 

GV8, GV9, and GV11, was in a more northwesterly direction during the late-summer measurements. Wells screened all 

or partly in till and located around the periphery of the site, 

including GV1, GV2, GV10, GV21, and GV22, showed no 

consistent trend in flow direction.

Velocities measured with flowmeters and hydraulic 

gradients estimated from water-level altitudes were used to 

compute the hydraulic conductivity of the till and refuse. 

Hydraulic conductivities computed from flowmeter data can 

be higher than those computed from slug-test data because 

a slug test evaluates the hydraulic response of the entire 

screened interval, whereas flowmeter measurements were normally made in zones where the highest groundwater velocities 

were observed. Hydraulic conductivities were computed from 

a rearranged form of Darcy’s Law: Kxy=v/(ΔH/|Δxy|) where 

Kxy is the horizontal conductivity, v is the Darcy groundwater 

velocity, ΔH is the change in hydraulic head between two 

points x and y along the groundwater-flow vector, and Δxy is 

the absolute value of the distance between x and y. 

For these computations, x was the well where the flowmeter measurement was made, and y was an upgradient or 

downgradient water-table contour along a projection of the 

flowmeter-measured vector. A potentiometric surface based on 

water-level measurements made during the August–September 

(2009) flowmeter measurements was used (fig. 13). A correction factor of 5.0 borehole acceleration was applied; a correction factor of 5.0 is probably appropriate where the well is 

screened in deposits of relatively low permeability. Some data 

were not used in this analysis. For example, (1) if the flowmeter-measured vector indicated flow from lower to higher watertable altitudes or parallel to the potentiometric contours or, (2) 

if there were no potentiometric contours because of positioning near water-surface saddles, surface water or refuse-deposit 

boundaries, then the data were considered poorly suited for 

calculating hydraulic conductivity and were not used. Hydraulic conductivities computed from the 2009 flowmeter data 

ranged from 15.7 to 68.0 ft/d in nine wells screened entirely in 

coal refuse, with a mean value of 47.4 ft/d (table 5). Hydraulic 

conductivities in three wells screened in till ranged from 44.4 

to 83.3 ft/d, with a mean value of 60.6 ft/d; this mean may be 

biased high by the flowmeter velocity measured in GV3 that 

gamma logs indicate was measured in a sandy zone within the 

till.

Little variation in surface-measured electromagnetic 

conductivity was observed between measurements made at the 

various frequencies (penetration depths); therefore, results for 

only one frequency (3,930 mS/m) are depicted (fig. 14). The 

conductivity in transects measured beyond the boundaries of 

the site were generally less than 100 mS/m. On the basis of 

this information, conductivities above 100 mS/m were used to 

indicate areas where coal refuse or acid mine drainage might 

be present in the near subsurface. Areas at the Green Valley site with conductivity exceeding 150 mS/m were (1) an 

underground pipeline on the northern property boundary, (2) 

the coal refuse pile, (3) the seep 3 and seep 4 channels, (3) the 

southeastern boundary of the site, and (4) the foundation of 

a former building in the southeast corner of the site (fig. 14). 

The survey provided no indication of acidic discharge either 

to West Little Sugar Creek along the western boundary of the 

site or to the lakeshore beyond the eastern boundary of the site 

during December 2008. 
Table 4. Horizontal flowmeter data for the Green Valley mine site, Indiana, August–September 2009.—Continued [bmp, below measurement point; Geologic material, the deposits juxtaposed from the flowmeter measurement interval; Center of screen slot, incremented at 90 degrees for 2-in6-inch wells; CBFM, colloidal borescope flowmeter; ft/d, feet per day; NA, not applicable to the measurement; parentheses, a relatively stable subset of the complete dataset wvector properties and is presented in the table; all times are in Eastern Standard Time] Local well identifier1 Date/ time Depth (bmp) Measurement elevation (above vertical datum) Geological material in measured interval Center of screen slot (in compass degrees) Data points collected by CBFM Duration of CBFM trace (minutes) Vector velocity2 (ft/d) Vector direction of flow (in compass degrees) GV1 8/26/2009 5:08 pm 9.0 586.50 Till NA NA NA 2.8 124.9 GV2 8/25/2009 3:15 pm 21.0 591.84 Till 180 NA NA 2.0 15.3 GV3 8/27/2009 11:36 am 16.8 587.39 Till 240 (294) (8) (11.0) (257.3) StGV4 9/01/2009 3:25 pm 32.0 598.27 Coal refuse 135 NA NA 4.6 280.3 GV4 9/01/2009 4:48 pm 36.0 594.27 Coal refuse 135 NA NA 12.6 9.2 GV7A 8/26/2009 11:47 am 31.9 594.93 Coal refuse 300 115 39 2.3 296.7 MGV7B 8/26/2009 1:11 pm NA NA Coal refuse NA NA NA NA NA ToGV8A 8/26/2009 12:36 pm 36.40 595.49 Coal refuse 270 NA NA 1.6 240.0 GV8B 8/26/2009 10:49 am 35.84 595.68 Coal refuse 120 NA NA 5.0 44.4 GV8C 8/26/2009 2:51 pm NA NA Coal refuse NA NA NA NA NA WGV9A 8/31/2009 2:32 pm 52.71 582.80 Coal refuse 90 NA NA 7.9 13.4 GV9B 8/31/2009 3:23 pm 52.47 582.84 Coal refuse 300 NA NA 2.5 305.7 GV10 9/02/2009 10:45 am 11.5 588.09 Till 0 NA NA 2.7 272.5 GV11A 9/01/2009 12:48 pm 29.50 599.48 Coal refuse 30 NA NA 6.2 268.2 GV11B 9/01/2009 11:11 am 29.37 599.49 Coal refuse 315 NA NA 1.5 236.1 GV12A 9/01/2009 11:37 am 15.0 594.88 Coal refuse NA 758 31 3.39 129.50 M
Table 4. Horizontal flowmeter data for the Green Valley mine site, Indiana, August–September 2009.—Continued [bmp, below measurement point; Geologic material, the deposits juxtaposed from the flowmeter measurement interval; Center of screen slot, incremented at 90 degrees for 2-in6-inch wells; CBFM, colloidal borescope flowmeter; ft/d, feet per day; NA, not applicable to the measurement; parentheses, a relatively stable subset of the complete dataset wvector properties and is presented in the table; all times are in Eastern Standard Time]

Local well 

identifier1

Date/

time

Depth 

(bmp)

Measurement 

elevation 

(above vertical 

datum)

Geological 

material in 

measured 

interval 

Center of 

screen slot 

(in compass 

degrees)

Data points 

collected by 

CBFM

Duration of 

CBFM trace 

(minutes)

Vector 

velocity2

(ft/d)

Vector 

direction 

of flow 

(in compass 

degrees)

GV12B 9/01/2009 

12:45 am

14.50 594.91 Coal refuse 100 (538) (17) (7.16) (261.15) St

GV14 8/27/2009 

3:10 pm

19.0 601.64 Coal refuse 315 NA NA 6.1 150.3 

GV15 8/26/2009 

2:35 pm

13.0 605.97 Coal refuse 225 (123) (4) (21.20) (89.00) St

GV15 8/26/2009 

4:40 pm

17.0 601.97 Coal refuse 225 (359) (12) (7.95) (230.99) St

GV16 8/27/2009 

2:16 pm

16.0 600.22 Coal refuse 0 (92) (4) (8.51) (217.75) St

GV17 8/27/2009 

12:05 pm

13.5 604.70 Coal refuse 60 NA NA 9.7 114.3 

GV18 9/01/2009 

3:01 pm

12.0 591.44 Coal refuse 160 (250) (9) (6.99) (245.8) St

GV18 9/01/2009 

4:55 pm

25.31 578.13 Till 160 262 28 7.67 198.3 St

GV20 8/25/2009 

1:14 pm

16.5 584.92 Coal refuse 60 (153) (11) (5.92) (67.01) St

GV21 8/31/2009 

12:56 pm

41.5 578.33 Till 315 (165) (6) (6.63) (82.40) St

GV22 8/31/2009 

2:40 pm

13.0 561.85 Till 300 (257) (9) (5.43) (182.05) St

1 Sites are shown on figure 4.2 Flowmeter velocity measurements have not been corrected for borehole acceleration; actual velocities may be less by a factor of 0.1 to 1.0 times the measured borehole velo
GV22 GV21 GV10 GV18 GV4 GV2 GV14 GV1 GV16 GV3 GV17 GV9 A,B GV8 A,B GV11 A,B BETWEEN 1 AND 5 FEET PER DAY BETWEEN 5 AND 10 FEET PER DAY BETWEEN 10 AND 25 FEET PER DAY EXPLANATION HORIZONTAL GROUNDWATER-FLOW DIRECTION AND VELOCITY, AUGUST-SEPTEMBER 2009, IN FEET PER DAY 0 150 300 450 600 FEET Aerial photo from Indiana Department of Natural Resources, 2007 87°31’30” 87°31’00” 

39°30’45” 39°30’30” 

John Lake West Little Sugar Creek DRAINAGE DITCHES GV12 A,B GV15 GV20 Figure 12. Discrete seep-discharge and streamflow measurements at the Green Valley mine site, Indiana, 2008–9.
BETWEEN 1 AND 5 FEET PER DAY

BETWEEN 5 AND 10 FEET PER DAY

BETWEEN 10 AND 25 FEET PER DAY

EXPLANATION

HORIZONTAL GROUNDWATER-FLOW DIRECTION AND VELOCITY, AUGUST-SEPTEMBER 2009. 

582

OBSERVATION WELL--WITH WATER LEVEL IN FEET ABOVE NGVD88

S3A GROUNDWATER SEEP-IDENTIFIER--CENTERED 

OVER SITE

87 ̊31'30'' 87 ̊31'00'' 

39 ̊30'45''

39 ̊30'30''

0 300 600 FEET

0 100 200 METERS

WATER-LEVEL CONTOUR--APPROXIMATE ALTITUDE OF THE WATER LEVEL IN THE COAL REFUSE OR TILL. CONTOUR IN FEET ABOVE NAVD88. CENTERED OVER SITE

606

602

598

594

590

586

582

S4

S3A

GV19

GV10

GV20

GV21 GV18 GV12

GV3

GV17

GV16

GV4

GV11

GV14

GV1

GV2

GV15

GV8

GV7

(591.85)

(604.14)

(598.53)

(598.65)

(607.76)

(599.51)

(585.30)

(593.75)

(603.10)

(598.54)

(604.52)

(607.70)

(602.25)

(605.52)

(594.83)

(598.02) (588.01)

(580.42)

GV9

GV13

(586.34)

GV22

(563.68)

John Lake

West Little Sugar Creek

GV13

(586.34)

S3A

Aerial photo from Indiana Department of Natural Resources, 2007

Figure 13. Potentiometric-surface map for August–September 2009 used to (1) show the configuration of the water table at the Green Valley mine sithydraulic conductivities from flowmeter data.
Table 5. Hydraulic conductivities computed from flowmeter-measured velocities, hydraulic gradients computed from measured groundwater elevaassumed correction factor (a=5.0) for borehole acceleration, Green Valley mine site, Indiana. [ft, feet; d, day; v, velocity; *, according to Geosciences Research Associates (1985); —, not enough data or poorly suited for use in the calculations] Local well identifier1 Upgradient water- level elevation (ft above vertical datum) Downgradient water-level elevation (ft above vertical datum) Distance between upgradient and downgradient water levels (ft) Hydraulic gradient (ft/ft) Flowmeter measured velocity (ft/d) Corrected velocity for an assumed correction factor= 5.0 (ft/d) Estimated hydraulic conductivity = v/gradient (ft/d

GV1 595.00 591.85 250 0.0126 2.80 0.56 44.4 

GV2 — — — — — — — GV3 598.53 598.00 20 .0265 11.04 2.21 83.3 

GV4 602.00 598.65 210 .0159 3.90 .78 49.0 

GV7A 607.76 606.00 190 .0093 2.25 .45 48.3 

GV8A 599.51 598.00 135 .0112 1.60 .32 28.5 

GV9A 590.00 585.30 150 .0313 7.90 1.58 50.4 

GV10 594.00 593.75 25 .0100 2.70 .54 54.0 

GV11B 603.10 602.00 110 .0100 6.20 1.24 68.0 

GV12B 598.54 594.00 105 .0432 3.39 .68 15.7 

GV14 — — — — — — — 

GV15 607.70 605.00 65 .0415 12.09 2.42 58.3 

GV16 — — — — — — — 

GV17 605.52 602.00 100 .0352 9.70 1.94 55.1 

GV18 598.00 594.83 110 .0288 7.67 1.53 53.1 

GV20 — — — — — — — 

GV21 — — — — — — — 

1 Sites are shown on figure 4.
0-50 

50-100 

100-150 

150-200 

Seep 3channel

Seep 4channel

Pipeline

Tipplefoundation

Coal refuse

JOHN LAKE

John Lake

EXPLANATION

SURFACE-MEASURED ELECTROMAGNETICINDUCTION, IN MILLISIEMENS PER METER (January 26, 2009).

West Little Sugar Creek

Aerial photo from Indiana Department of Natural Resources, 2007

0 300 600 FEET0 100 200 METERS

87 ̊31'30'' 

39 ̊30'45''39 ̊30'30''

87 ̊31'

Figure 14. Transects used for surface survey of apparent subsurface electrical conductivity at the Green Valley mine site, Indiana, December 2008.
26 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

In general, the upstream and downstream streamflow 

measurements made on West Little Sugar Creek rarely differed by an amount that exceeded the expected measurement 

error (Sauer and Meyer, 1992). This difference indicates that 

the combined contributions of base flow, runoff, and seep 

discharges to the creek are a relatively small percentage of the 

total flow in West Little Sugar Creek. Visual inspection reveals 

that a limited amount of mine drainage reaches the stream and 

Table 6. Discrete seep-discharge and streamflow measurements at the Green Valley mine site, Indiana, 2008–9.

[ft3/s, cubic feet per second; mm/dd/yyyy, month/day/year; —, not measured or determined]

Local site Flow (ft3

/s)

identifier1

10/09/2009 11/05/2008 12/16/2008 01/20/2009 03/04/2009 04/16/2009 06/05/2009 07/13/2009

Seep 1, continuous data

Seep 2 — — 0 — 0.0032 0.0046 0 0

Seep 3A — 0.0056 — — .0119 .0050 0.0084 0.0064

Seep 3B — — — — .0150 .0198 .0155 —

Seep 4 — — — — — .0371 .0183 .0107

West Little Sugar Creek, 0.0343 — 2.66 — 4.06 9.356 2.45 —

upstream

West Little Sugar Creek, .0703 — 3.12 — 6.47 9.425 2.59 —

downstream

1

 Sites are shown on figure 4.

causes mineral precipitation that colors the streambed and 

lithifies bed sediments along the eastern streambank. Discrete 

seep-discharge measurements at the Green Valley site ranged 

from 0.00 to 0.0371 ft3/s (table 6; fig. 15). Continuous stage 

recordings at seep 1 provided data to compute the annual 

discharge of 427,000 ft3/yr at seep 1 for the period November 

6, 2008, to November 5, 2009 (fig. 16).

Seep 2

Seep 3A

Seep 3B

Seep 4

West Little Sugar Creek, 

 Upstream

West Little Sugar Creek, 

 Downstream

EXPLANATION

Discharge, in cubic feet per second

0.001

0.01

0.1

1

10

JUN JUL AUG SEP OCT NOV DEC

2008

JAN FEB MAR APR MAY JUN JUL AUG SEP

2009

Figure 15. Seep discharges and 

streamflows at the Green Valley 

mine site, Indiana.
Hydrogeology of the Green Valley Reclaimed Coal Refuse Site 27

Two-well aquifer tests were largely unsuccessful. Aquifer 

tests were attempted in wells at sites GV7, GV8, GV9, GV11, 

and GV12 between June 20 and July 2, 2009. At site GV7, 

well GV7A was pumped at a rate of about 0.5 gal/min, and 

it went dry (12.5 ft drawdown) after 37 minutes; drawdown 

in the adjacent well GV7B was 0.181 ft when GV7A went 

dry. At site GV8, pumping of well GV8A at approximately 

3 gal/min for 130 minutes created approximately 0.45 ft of 

drawdown in the adjacent well GV8B. At site GV9, high 

concentrations of particulates in the water repeatedly caused 

the pumps to jam and prematurely ended the tests. At site 

GV11, pumping of well GV11A at a rate of about 0.4 gal/min 

for 69 minutes created 0.06 ft of drawdown in the adjacent 

well GV11B. At GV12, well GV12A was pumped at a rate of 

about 0.3 gal/min for 125 minutes, and approximately 0.10 ft 

drawdown resulted in the adjacent well GV12B. At sites GV8, 

GV11, and GV12, two-well aquifer test data yielded abnormal 

time-drawdown curves that could not be reliably analyzed 

with AQTESOLV software (Hydrosolve, 2002). In summary, 

results of the two-well aquifer tests indicated that the coal 

refuse may have a hydraulic conductivity that is too low to be 

measured by a two-well aquifer test and that slug testing might 

be a more appropriate technique. 

Slug tests provided useful data at wells GV2, GV7A, 

GV11A, and GV12A. Water levels from rising-head tests 

in wells GV7A and GV11A and from a falling-head test in 

well GV12A were analyzed (table 7). The falling-head tests 

indicated oscillating water levels in wells GV7A and GV11A 

and, as a result, those data were not used to compute hydraulic 

properties. The hydraulic conductivity computed for the till 

at well GV2 was 0.10 ft/d; in the coal refuse at wells GV7A, 

GV11A, and GV12A, hydraulic conductivity ranged from 

0.03 to 0.83 ft/d (table 7). Results were approximately the 

same regardless of the method used to analyze the data in this 

investigation. 

The hydraulic conductivities computed from slug-test 

data were notably lower than the values estimated by other 

methods for the coal refuse at the Green Valley site. Melchiorre, Dale, and others (2005) estimated hydraulic conductivity 

of till at 1.11 to 7.37 ft/d and of the gob at 7.37 to 16.4 ft/d. 

Hydraulic conductivities estimated from flowmeter data 

ranged from 44.4 to 83.3 ft/d in till and from 15.7 to 68.0 ft/d 

in coal refuse. Hydraulic conductivities estimated from tracer 

and flowmeter data commonly indicate relatively high values 

because they generally are a measure of flow through preferential-flow zones or features, in comparison to methods that 

consider the entire screened interval (Kearl, 1997).

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

Discharge, in cubic feet per second

NOV DEC JAN FEB MAR APR JUN

2008

JUL AUG SEP OCT NOV

2009

MAY

Figure 16. Discharge from seep 1 at the Green Valley mine site, Indiana.
28 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

Table 7. Horizontal hydraulic conductivities computed from slug-test data collected at the Green 

Valley mine site, Indiana, August–September 2009.

[ft/d, feet per day; —, no computation made]

Local 

well 

identifier1

Geologic 

material

Horizontal hydraulic conductivity (ft/d)

Bouwer and Rice 

method (unconfined 

aquifer model)

Hvorslev method 

(unconfined 

aquifer model)

Kansas 

Geological Survey 

(unconfined 

aquifer model) 

GV2 Glacial till — — 0.10

GV7A Coal refuse 0.23 0.36 —

GV11A Coal refuse .49 .83 —

GV12A Coal refuse .03 .04 —

1

Sites are shown on figure 4.

Table 8. Description of geologic materials and model layers used to represent the hydrogeologic 

system at the Green Valley mine site, Indiana.

Descriptions of geologic materials

Hydrogeologic framework

Model layer Aquifer system equivalent (Grove, 2009)

Gob, plus gob and tailings mixture Layer 1 None.

Till Layer 2 Dissected Till Residuum/Till Veneer 

(DTR) aquifer system and the Central 

Wabash Valley/Wabash Lowland Till 

(CWV) aquifer subsystem.

Layer 3

Layer 4

Shale No-flow boundary McLeansboro Group Aquifer aquifer 

system.

Simulated Groundwater Flow

A computer-based groundwater model was developed to 

gain a more complete understanding of the groundwater-flow 

system in and near the coal refuse and to improve understanding of how remediation-related changes to the site hydrology could affect flow of groundwater and seepage to surface 

water. The improved understanding of the flow system may 

lead to specific remediation scenarios that otherwise would 

have not been considered. Because remediation scenarios may 

incorporate transient actions, such as intermittent pumping, a 

transient model was constructed and calibrated in addition to a 

steady-state model. This section describes the computer model 

chosen for the analysis, the conceptual hydrogeologic framework used to guide model construction, the calibration of the 

model to observations and simulated results, the sensitivity of 

simulation results to model input, and the model limitations 

and qualifications. The numerical model was calibrated so that 

the simulated water levels and flows were a reasonable representation of measured water levels and flows, The calibration 

was also done so that the residuals, the differences between 

measured and simulated water levels and flows, were normally 

distributed and spatially and temporally unbiased. The model 

will provide a platform to assess new data as they are collected 

and to examine possible remediation scenarios.

The model used for this investigation is based on the 

three-dimensional, finite-difference computer code of Harbaugh and others (2000) called MODFLOW-2000. An 

iterative procedure is used in the model simulation to solve a 

finite-difference version of the continuity equation for steady 

flow in an anisotropic, heterogeneous, multilayer groundwaterflow system. The automated parameter-estimation process 

incorporated into MODFLOW-2000 is used to determine 

model-parameter values (Hill and others, 2000).

Simplifying Assumptions

A set of simplifying assumptions was used in the 

construction of the groundwater model. The choice of 

assumptions was influenced by the data available to define the 

different components of the groundwater-flow system. The 

framework of geologic materials and model layering used 

for the steady-state and transient groundwater-flow models is 

summarized in table 8 and illustrated in figure 17. 
Simulated Groundwater Flow 29

500

520

540

560

580

600

620

640

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000

COAL

REFUSE

MIDDLE 

TILL

BEDROCK

Distance along section, in feet

Elevation above NGVD 29, in feet

West Little Sugar Creek

Green ValleyMine Pond

VERTICAL SCALE GREATLY EXAGGERATED

Model Layer 1

Model Layer 2

Model Layer 3

Model Layer 4

(not modeled)

0

0

 FEET

 600 METERS

500 1,000 1,500 2,000

150 300 450

A A'

UPPER 

TILL

LOWER 

TILL

Figure 17. Layering design for the model of the Green Valley mine site, Indiana. (Trace of section is shown in fig. 2).

The following assumptions pertain to the geometry, hydraulic properties, and other characteristics of the 

groundwater-flow system underlying the area modeled in this 

investigation: 

• The deposits in the coal refuse are represented by a 

single model layer, and the till deposits are represented 

by three layers that evenly divide the overall thickness 

of the till. Three layers were chosen for the till so that 

simulated water levels for the middle of the three layers would coincide with water levels from an observation well screened in the middle of the till.

• The hydraulic properties of the coal refuse represented 

by model layer 1 are defined by two zones within the 

layer. The first zone represents an area of coal gob 

deposits. The second zone represents areas where coal 

tailings were mixed with the gob.

• The hydraulic properties of the till are uniform 

throughout the three layers. The study area is near the 

approximate boundary of two till aquifer systems the 

Dissected Till Residuum/Till Veneer aquifer system 

and the Central Wabash Valley/Wabash Lowland 

Till aquifer subsystem (Grove, 2009). The Dissected 

Till Residuum/Till Veneer aquifer system contains 

few sand lenses within the till; however, the Central 

Wabash Valley/Wabash Lowland Till aquifer subsystem can contain some intertill lenses of sand and gravel 

that are generally less than 5 ft thick. 

• The shale bedrock beneath the till is considered a 

no-flow boundary. The shale bedrock under the site 

is a low permeability part of the Pennsylvanian age 

Patoka Formation of the McLeansboro Group (Cable 

and others, 1971, plates 1 and 2). Five borings drilled 

into bedrock within about 1.5 miles of the Green 

Valley mine site encountered from about 16 to 37 ft 

of non-water-bearing shale (Indiana Department of 

Natural Resources, 2002). Most of the McLeansboro 

Group is composed of fine-grained geologic materials 

that limit the movement of groundwater (Grove, 2009). 

Based on the local drilling record, and the dry conditions encountered, the shale bedrock unit is considered 

to have a significantly lower horizontal and vertical 
30 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

hydraulic conductivity relative to that of the local till 

and coal refuse. The shale bedrock is therefore considered a no-flow boundary at the base of the model.

• The thickness of all simulated streambeds is 1 ft. The 

calibrated value of streambed vertical hydraulic conductivity is based on a 1-ft streambed thickness.

beyond West Little Sugar Creek to the west and the Green 

Valley Mine Pond to the east (fig. 18). The grid was composed 

of 28,032 blocks over four layers that ranged in size from 50 

ft by 50 ft in the central part of the modeled area to 720 ft by 

350 ft at the corners. The finer grid size was generally in the 

area of the coal refuse so that more detailed simulations could 

be made for the area of greatest interest.

River and drain cells (Harbaugh and others, 2000) were 

used in the model to represent local streams. A total of 338 

river cells were used to simulate the Green Valley Mine Pond, 

including the attached borrow area pond (John A. Scott Lake). 

River cells essentially act as large streams that can supply 

substantial water to the groundwater-flow system when the 

Model Design

The computer model is based on a 1.6- by 1.1-mi rectangular, block-centered grid network that extends about 500 ft 

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

Universal Transverse Mercator projection, Zone 16 

North American Datum of 1983

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

0

EXPLANATION

Constant-head cells

Drain cells

River cells

 87°31’30”

 39°31’

39°30’30”

 87°31’ 87°30’30”

Green

Valley

Mine

Pond

John A.

Scott Lake

Figure 18. Model grid discretization and river, drain, and constant-head cells used in the simulation of groundwater flow at the Green Valley 

mine site, Indiana.
Simulated Groundwater Flow 31

water table declines below the bottom of the stream. A total of 

620 cells were used to simulate all streams. Drain cells receive 

groundwater discharge but do not recharge the groundwater 

system, as can river cells. Drain cells represent streams that 

cease to flow when the water table declines below the bottom 

of the stream. All streams, including West Little Sugar Creek, 

were designated as drain cells because observations during the 

investigation indicated they can go dry (no flow).

Thicknesses of model layers were based on data from 

several sources. Total thickness of the till was calculated by 

subtracting a grid of bedrock-surface altitude from a grid of 

land-surface altitude. The grid of bedrock-surface altitude 

was estimated from 104 point values of bedrock-surface 

altitude obtained from water-well driller logs furnished by the 

Indiana Department of Natural Resources (2002). A bedrocksurface-altitude grid was generated by using the point values 

of bedrock altitude as input to the inverse-distance-weighting 

(IDW) surface-interpolation method available in Arc Info 

software (Environmental Systems Research Institute, 2003). 

The grid of land-surface altitude was calculated by using 10-ft 

land-surface contours (U.S. Geological Survey, 2008) as input 

to the TOPOGRID command in Arc Info. Thickness of the 

coal refuse deposits was calculated by subtracting a grid of 

land-surface altitude for the coal refuse from the grid of landsurface altitude for the till. The grid of land-surface altitude 

for the coal refuse was obtained by using 2-ft contours from 

the Indiana Department of Natural Resources, Division of 

Reclamation, as input to the TOPOGRID command. 

Boundary conditions in the groundwater-flow model were 

selected so that the type and location of the boundary would 

have a minimal effect on simulated conditions in the center of 

the model. Model boundaries were defined just beyond West 

Little Sugar Creek and the Green Valley Mine Pond to incorporate their potential effects as hydrologic boundaries. Constant-head boundaries were placed on all four sides of model 

layers 2 through 4. Constant-head cells, however, were not 

used where a river or drain cell was at the edge of the model. 

Generally, constant-head cells are useful to simulate the flow 

of water across the edge of the model (in or out of the model) 

and to help stabilize the iterative solution process in the 

computer code of the model. A no-flow boundary was defined 

around layer 1 (the coal refuse) to represent the thinning out to 

zero thickness of the coal refuse deposits. A no-flow boundary also was assumed below the bottom layer of the model to 

simulate the low-permeability shale at the base of the glacial 

sediments. A variable-flux boundary was used at the top of the 

model to represent recharge from precipitation. Recharge was 

applied to the uppermost active model layer, which is layer 1 

in the area of the coal refuse and layer 2 (the top layer of till) 

outside of the coal refuse. A single recharge rate was used for 

the till, and two recharge rates were used for the coal refuse. 

Areas where the two recharge rates were used for the coal 

refuse correspond to the areas of gob and of a gob and tailings 

mixture (Indiana Geological Survey, 2003; fig. 3). Details on 

estimating the initial values of recharge rates are given later in 

this report in the section describing model parameters.

Initial water-level values for model simulations were 

required for the coal refuse deposits and the till. Initial water 

levels in the coal refuse deposits were assumed to be 10 ft 

higher than the bottom of the coal refuse deposits (also the top 

of till), which is approximately the average saturated thickness 

measured in the coal refuse deposits by this investigation. Initial water levels for the till were estimated from computerized 

well-log records of water levels. The estimation of reasonable 

initial water levels in the till was important for the assignment 

of constant-head values around the model boundaries. Water 

levels from water-well-driller logs submitted to the Indiana 

Department of Natural Resources (2002) were used to obtain 

groundwater levels in the till. Because only 62 water levels 

were available in or near the study area, a water-level surface 

for the model layers of till (layers 2–4) could not be estimated 

directly from the well-log water-level data. Instead, a relation 

was determined between the available water-level data and 

land-surface altitude. The correspondence between land-surface altitude and groundwater altitude has long been recognized (Desbarats and others, 2002, p. 26), and equations have 

been used to establish a relation between the two variables 

(Kuniansky and others, 2009, p. 99). Of the equations tested, 

the most appropriate equation to establish the land-surface/

water-level relation in the study area is a polynomial equation 

of the following form:

wl = 722.1839 – 1.6874 * ls + 0.0024 * ls2, (1)

where 

wl is the groundwater-level altitude, in feet above 

land-surface datum, and 

ls is land-surface altitude, in feet above landsurface datum. 

The resulting polynomial curve follows the data points 

more closely than the other curves; the relation between the 

curve and the data points is shown in fig. 19. The coefficient 

of determination (0.95) indicates a high degree of correlation 

between the two variables of land surface and water level. The 

correspondence between the polynomial equation and the data 

is greatest above 600 ft, which includes the coal refuse and 

upland around the refuse. The equation was used to process 

digital data with 10-ft land-surface contours (U.S. Geological 

Survey, 2008) to generate a continuous surface of initial waterlevels values from which average values for each model cell 

were assigned.

Initial water levels generated from the previous process 

introduced a small but acceptable error to model analysis. The 

water levels from well-driller logs and land-surface altitudes 

from 10-ft land-surface contours are based on the National 

Geodetic Vertical Datum of 1929, whereas the water levels 

used to calibrate the model are based on the North American 

Vertical Datum of 1988. In the study area, NGVD 29 altitudes 

are 0.32 ft higher than NAVD 88 altitudes. The difference is 

considered insignificant relative to the error associated with 

the polynomial equation and error associated with subsequent 

model calibration. 
32 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

450 500 550 600 650

450

500

550

600

650

EXPLANATION

Relation line between land-surface altitude

and ground-water altitude in the till

Plotting position for a land-surface

and water-level data pair

Y = 722.1839 - 1.6874 * X + 0.0024 * X2

Water-level elevation above National Geodetic Vertical Datum of 1929, in feet

Land-surface elevation above National Geodetic Vertical Datum of 1929, in feet

Figure 19. Relation between land-surface altitude and groundwater-level altitude at water-well sites in and near the Green 

Valley mine site, Indiana.

Model Calibration

Model calibration is the process of adjusting the model 

input variables, also called parameters, to produce the closest 

match between simulated and measured streamflow and water 

levels in the model layers. During calibration, parameters 

representing hydraulic properties over specified areas were 

adjusted by automatic parameter-estimation techniques to 

match measured water levels in wells and measured streamflow. MODFLOW-2000 includes a parameter-estimation feature (Hill and others, 2000) that uses a nonlinear least-squares 

regression method to calculate unbiased estimates of hydraulic 

properties and to evaluate model fit. The parameters estimated 

in the calibration process represent the hydraulic properties distributed as constant values over model areas or over 

extended linear features, such as rivers, and therefore are not 

intended to represent specific values of field tests at individual 

points. 

The automated parameter-estimation process involves 

several components. In the process, parameters are selected to 

represent the major features of the flow system, and sensitivity 

analysis is done to determine whether unique parameter values 
Simulated Groundwater Flow 33

for model features can be estimated. The process includes 

assigning weights to calibration data (observations) to reflect 

their accuracy. The numerical difference between measured 

and observed values is called a residual, and the procedure 

minimizes the sum of squared weighted residuals, called the 

objective function (Hill, 1998, p. 4). The final component is an 

evaluation of model fit to the observations and a representation 

of the groundwater-flow system as simulated with the model.

Selection and Sensitivity Analysis of Model 

Parameters

In the model, grid cells that were assumed to have similar 

hydrologic properties were grouped together as a parameter 

zone and assigned a parameter value that can be adjusted 

during the calibration process. The steady-state and transient 

model calibrations required a set of parameters. The steadystate simulation required 16 different parameters, 6 of which 

were estimated automatically by the model, and the transient 

simulation required 41 parameters, 7 of which were estimated 

automatically. The names of the parameters and the model 

component that the parameter represents for both calibrations 

are listed in tables 9 and 10.

Although the initial values for horizontal hydraulic conductivity of the till and coal refuse differ somewhat from the 

final calibrated values, the initial and final values are similar 

to those obtained by this investigation from slug tests. For 

example, the initial hydraulic conductivity value of 0.5 ft/d for 

till in the steady-state simulation was only slightly higher than 

the hydraulic conductivity estimate of 0.1 ft/d for till from the 

slug test of well GV2. The initial hydraulic conductivity value 

Table 9. Model parameters used in the steady-state model of the Green Valley mine site, 

Indiana (June 2009), their initial values, and indication of whether a parameter value was 

estimated.

[ft/d, foot per day; in/yr, inch per year]

Parameter 

name Model component represented Initial parameter value

Parameter 

estimated

k.tail Horizontal hydraulic conductivity of the gob and 

tailings mixture

0.3 ft/d Yes.

k,gob Horizontal hydraulic conductivity of the gob 15.0 ft/d Yes.

k.till Horizontal hydraulic conductivity of the till 0.50 ft/d Yes.

kv.tail Vertical hydraulic conductivity of the gob and tailings mixture0.01 ft/d No.

kv.gob Vertical hydraulic conductivity of the gob 3.0 ft/d No.

kv.till Vertical hydraulic conductivity of the till 0.001 ft/d Yes.

stream Hydraulic conductivity of the streambed for small 

streams in the till

1.0 ft/d No.

seep Hydraulic conductivity of the streambed for small 

streams in the coal refuse and upstream of a flowmeasurement point

1.0 ft/d No.

ds.gob Hydraulic conductivity of the streambed for small 

streams in the coal refuse and downstream of a 

flow-measurement point

1.0 ft/d No.

river Hydraulic conductivity of the streambed for West 

Little Sugar Creek

1.0 ft/d No.

lake Hydraulic conductivity of the lakebed for Green 

Valley Mine Pond 

1.0 ft/d No.

ground Hydraulic conductivity controlling seepage of water 

from the soil to the land surface west of the coal 

refuse

1.0 ft/d No.

rech.tail Recharge rate to the areas of gob and tailings 

mixture

2.6 in/yr Yes.

rech.gob Recharge rate to the areas of gob 4.3 in/yr Yes.

rech.till Recharge rate to the till 2.6 in/yr No.

rech.lake Recharge rate to the area beneath Green Valley 

Mine Pond

0.0 in/yr No.
34 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

Table 10. Model parameters used in the transient model of the Green Valley mine site, Indiana (June 2009), their initial values, and 

indication of whether a parameter value was estimated.

[ft/d, foot per day; in/yr, inch per year; ft-1, 1/feet]

Parameter 

name Model component represented Initial parameter value

Parameter 

estimated

k.tail Horizontal hydraulic conductivity of the tailings and gob mixture 0.75 ft/d Yes.

k,gob Horizontal hydraulic conductivity of the gob 0.032 ft/d Yes.

k.till Horizontal hydraulic conductivity of the till 0.43 ft/d Yes.

kv.tail Vertical hydraulic conductivity of the gob and tailings mixture 0.01 ft/d No.

kv.gob Vertical hydraulic conductivity of the gob 3.0 ft/d No.

kv.till Vertical hydraulic conductivity of the till 0.0019 ft/d No.

Stream Hydraulic conductivity of the streambed for small streams in the till 1.0 ft/d No.

Seep Hydraulic conductivity of the streambed for small streams in the coal refuse and upstream of a 

flow-measurement point

1.0 ft/d No.

ds.gob Hydraulic conductivity of the streambed for small streams in the coal refuse and downstream of 

a flow-measurement point

1.0 ft/d No.

River Hydraulic conductivity of the streambed for West Little Sugar Creek 1.0 ft/d No.

Lake Hydraulic conductivity of the lake bed for Green Valley Mine Pond 1.0 ft/d No.

ground Hydraulic conductivity controlling seepage of water from the soil to the land surface west of the 

coal refuse

1.0 ft/d No.

rech.lake Recharge rate to the area beneath Green Valley Mine Pond 0.0 in/yr No.

till.jun08 Recharge rate to the till during the month of June 2008 5.64 in/yr No.

till.jul08 Recharge rate to the till during the month of July 2008 3.72 in/yr No.

till.aug08 Recharge rate to the till during the month of August 2008 1.20 in/yr No.

till.sep08 Recharge rate to the till during the month of September 2008 0.48 in/yr No.

till.oct08 Recharge rate to the till during the month of October 2008 0.36 in/yr No.

till.nov08 Recharge rate to the till during the month of November 2008 0.60 in/yr No.

till.dec08 Recharge rate to the till during the month of December2008 3.12 in/yr No.

till.jan09 Recharge rate to the till during the month of January 2009 3.48 in/yr No.

till.feb09 Recharge rate to the till during the month of February 2009 4.20 in/yr No.

till.mar09 Recharge rate to the till during the month of March 2009 3.60 in/yr No.

till.apr09 Recharge rate to the till during the month of April 2009 6.84 in/yr No.

till.may09 Recharge rate to the till during the month of May 2009 7.32 in/yr No.

till.jun09 Recharge rate to the till during the month of June 2009 4.56 in/yr No.

mnd.jun08 Recharge rate to the tailings and gob mixture during the month of June 2008 6.43 in/yr No.

mnd.jul08 Recharge rate to the tailings and gob mixture during the month of July 2008 4.24 in/yr No.

mnd.aug08 Recharge rate to the tailings and gob mixture during the month of August 2008 1.36 in/yr No.

mnd.sep08 Recharge rate to the tailings and gob mixture during the month of September 2008 0.55 in/yr No.

mnd.oct08 Recharge rate to the tailings and gob mixture during the month of October 2008 0.41 in/yr No.

mnd.nov08 Recharge rate to the tailings and gob mixture during the month of November 2008 0.68 in/yr No.

mnd.dec08 Recharge rate to the tailings and gob mixture during the month of December 2008 3.56 in/yr Yes.

mnd.jan09 Recharge rate to the tailings and gob mixture during the month of January 2009 3.97 in/yr Yes.

mnd.feb09 Recharge rate to the tailings and gob mixture during the month of February 2009 4.79 in/yr Yes.

mnd.mar09 Recharge rate to the tailings and gob mixture during the month of March 2009 4.10 in/yr No.

mnd.apr09 Recharge rate to the tailings and gob mixture during the month of April 2009 7.80 in/yr Yes.

mnd.may09 Recharge rate to the tailings and gob mixture during the month of May 2009 8.34 in/yr Yes.

mnd.jun09 Recharge rate to the tailings and gob mixture during the month of June 2009 5.20 in/yr No.

sy.gob Specific yield of the coal refuse 0.06 Yes.

ss.till Specific storage of the till 0.00017 ft-1 Yes.
Simulated Groundwater Flow 35

of 0.3 ft/d used for the gob and tailings mixture was within 

the range of hydraulic conductivity values (0.03 to 0.83 ft/d) 

computed for tests in wells GV7A, GV11A, and GV12A in 

the coal refuse. To reduce the number of parameters to be 

estimated in the transient calibration (a total of 41 parameters), 

the horizontal and vertical hydraulic conductivities of the till 

and coal refuse estimated from the steady-state calibration 

were used in the transient calibration and not re-estimated (see 

the table 10).

A relatively large hydraulic conductivity value of 15 ft/d 

was used as the initial value for the gob in the steady-state 

simulation to represent the possibility of more conductive 

deposits of coal refuse in the reclaimed area. That value was 

near the higher part of the range of hydraulic conductivity 

(7.37 to 16.4 ft/day) estimated for gob deposits by Melchiorre 

and others (2005). The final calibrated hydraulic conductivity 

of gob in the steady-state model of 0.032 ft/d was similar to 

the smallest values for gob plus tailings that were derived from 

slug testing. The larger estimates of hydraulic conductivity by 

Melchiorre and others (2005) may have represented relatively 

rapid transport of precipitation-affected water through a partially fractured saturated surface soil to seeps and not the bulk 

permeability of the coal refuse.

The degree of detail used to represent the flow system in 

the model parameters is limited not only by the sensitivity of 

model parameters but also by the availability and distribution 

of observation data (water levels and streamflow flux). For 

example, only one model parameter represented the horizontal hydraulic conductivity of the till because few observation 

water levels were located in the till. In contrast, two parameters represented the horizontal hydraulic conductivities in 

the much smaller area of the model containing coal refuse 

because of the abundance of observation water levels in the 

coal refuse. Multiple stream parameter zones were created to 

provide the opportunity to vary streambed hydraulic conductivity areally in the model, but the response of the model to 

all streambed parameters was found to be insensitive (tables 9 

and 10). All but the recharge parameters from the steady-state 

simulation in table 9 are repeated for the transient state simulation in table 10. The additional parameters in the transient 

simulation (table 10) are the recharge parameters for each 

month of the 13-month simulation and the storage parameters 

for the till and coal refuse.

The decision to estimate a specific parameter was based 

on the sensitivity of simulated water levels and flows to 

changes in model parameters. Sensitivities of various parameters were calculated by using the sensitivity equation method 

(Hill and others, 2000, p. 67). Composite scaled sensitivities 

(CSS) were calculated for each parameter. CSS aid in determining whether there is adequate information in the calibration data to estimate a particular parameter. CSS less than 

about 0.01 times the largest CSS of all the parameters indicate that the nonlinear regression method may not be able to 

estimate that parameter (Hill, 1998, p. 38). The recharge rate 

to the till could be estimated in the steady-state simulation, but 

not in the transient. The few water-level observations in the till 

and the small change in till water level from month to month 

may have limited the model’s ability to estimate till recharge. 

The only recharge parameters that could be estimated for the 

transient simulation were for the coal refuse during months of 

high recharge, which caused large changes in water levels. 

Initial values of recharge rate to the till were estimated 

by using a base-flow separation technique (Rutledge, 1998). 

The study area is not within a gaged drainage basin; therefore, 

a gaged basin with similar geologic deposits (the North Fork 

Embarras River near Oblong, Illinois) was used to compute 

monthly recharge estimates as initial estimates of recharge to 

till in the study area. The 68-year streamflow record (1941–

2009) from the USGS gage on the North Fork Embarras River 

near Oblong, Illinois (station number 03346000; U.S. Geological Survey, 2010), was used for the recharge estimate. The 

drainage basin for the gage encompasses 318 mi2 and lies 20 

mi west of the study area. Loamy till deposits are present in 

both the Embarras River drainage basin and in the study area. 

The base flow is calculated from the total flow record and is 

then reported monthly, yearly, and as a long-term average. The 

base flows are assumed equivalent to groundwater recharge 

and, therefore, are used as estimates for recharge in model 

simulations. 

The monthly estimates of recharge to the till also were 

used to calculate a recharge rate to the areas of gob and 

tailings mixture in the coal refuse. The initial estimates for 

recharge rate to the areas of gob and tailings mixture for the 

transient simulation were based on a ratio of recharge rates 

obtained from the steady-state calibration. The ratio was 

calculated by dividing the steady-state calibrated recharge rate 

to the area of tailings by the steady-state calibrated recharge 

rate to the till. The initial estimates for transient recharge 

rate to the areas of gob and tailings mixture were calculated 

by multiplying the ratio by the initial estimates of monthly 

recharge to the till. The estimates are based on the assumption 

that the steady-state ratio of recharge to the two areas of gob 

and tailings mixture divided by the rate of recharge to the till 

is constant through the period of transient simulation.

The calculation described in the previous paragraph provided an estimate for transient recharge rate to the areas of gob 

and tailings mixture, but not to the area of gob. To obtain an 

estimate for transient recharge rate to the area of gob, the ratio 

between recharge rate to the gob and recharge to the area of 

gob and tailings determined from the steady-state calibration 

was used. The value of the ratio was calculated by dividing 

the calibrated steady-state recharge rate for the area of gob by 

the steady-state rate for the areas of gob and tailings mixture. 

The ratio between the two recharge rates was assumed to 

be the same in the transient simulation as in the steady-state 

simulation. The recharge rate to the area of gob was calculated 

by multiplying the ratio by the estimated recharge rate to the 

areas of gob and tailings mixture. 

Estimating a recharge rate to the areas of gob and tailings 

mixture and then using a ratio to estimate the recharge rate to 

the area of gob reduced the number of estimated recharge rates 

for the coal refuse from two to one. The number of recharge 
36 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

parameters was reduced to decrease the overall number of estimated parameters. The transient calibration required a large 

increase in parameters to represent the system; specifically, 

13 monthly recharge parameters for the till and 13 for the coal 

refuse. Increasing the number of parameters to be estimated 

decreases the capacity of the parameter-estimation process to 

solve for unique values of the parameters from a limited number of water-level and streamflow-flux observations.

The initial estimates for the storage parameters used in 

the transient calibration were based on literature values and 

on texture observations. The specific storage estimate for the 

till (0.00017 ft-1) was assumed to be the same as an average, 

calculated by Shaver (1998, p. 552), of 107 till samples. The 

specific yield for the coal refuse was assumed to be the same 

as the average of 11 values for silt till reported by Morris and 

Johnson (1967). The specific yield of silt till (0.06) was chosen 

to estimate the specific yield of the coal refuse because of the 

similarity in textures of the two deposits (both silt-sized material). Because of lack of data, no attempt was made to distinguish a difference in storage properties between the gob and 

the gob and tailings mixture.

Storage for the top layer of till was represented by a 

specific storage parameter and not a specific yield parameter. 

When a specific yield parameter was estimated, the value calculated by parameter estimation was extremely low (0.0098). 

Although the observed water levels were from the top layer of 

till, the observed data usually were measuring a depth within 

the till that indicated that the material near the well screen 

behaved as though it was confined. Therefore, a specific storage term was used for the top layer of till, and the calibrated 

value for specific storage mostly represents the confined part 

of the layer. Available data were insufficient to justify a thin 

model layer along the top of the till for which a specific yield 

would actually apply.

The steady-state calibration of the numerical model was 

accomplished using water levels measured during the period 

of highest water levels in June 2009. During periods of annual 

high or low groundwater levels, storage processes are inactive 

and the steady-state equation can be applied to calibrate the 

model. The model, when calibrated using high water levels, 

such as during long-term wet conditions, will reflect the higher 

recharge needed to maintain that condition (Anderson and 

Evans, 2007, p.505). Groundwater levels in the Green Valley 

wells were almost at their highest level during June 2009 but 

were not in phase with each other throughout other parts of 

the year. In addition, most seeps and West Little Sugar Creek 

were flowing during June 2009; this set of discharge measurements was available to compare with simulated seep and 

surface-water flows computed by the calibrated groundwater 

model. The recharge values obtained by calibrating to the high 

groundwater level condition enabled the model to provide 

simulation results more useful to evaluate the water budget 

under conditions when higher volumes of groundwater flow 

and seepage were generated from the coal refuse.

The initial water levels for the transient simulation were 

obtained from the steady-state calibration for June 2009. 

Water levels for June 2009 were generally close to their values 

observed in June 2008, when the transient simulation begins. 

Matching measured water levels throughout the year during 

the transient calibration provided an opportunity to calibrate 

the model to all water-level conditions, including average 

conditions.

Observations and Observation Weights

The observations used for model calibration consisted of 

152 water-level observations from 18 wells and 19 streamflow 

measurements from 4 stream locations, all made from June 

2008 to June 2009. The locations of the observation points are 

shown in figure 20. Four of the wells are screened in the upper 

part of the till, and one (GV8C) is located in the center of the 

coal refuse and screened in the middle of the till. Observations 

from well GV8A, in the coal refuse, and adjacent well GV8C, 

in the till, were used to estimate the vertical hydraulic conductivity of the till.

The purpose of weighting the observations used in model 

calibration is twofold. First, weighting reduces the effect of 

observations that are known to be less accurate and increases 

the effect of observations that are known to be more accurate. 

Second, weighting produces weighted residuals (a measure 

of the difference between the observation and its simulated 

equivalent) that have the same units, whether the residual is 

for water level or streamflow flux (gain/loss observations). 

Having water-level and streamflow flux residuals in the 

same units allows both residuals to be included in the sum 

of squared errors to be minimized in model estimates of the 

parameters. Weights on observation data account for measurement error associated with the accuracy of the sampling 

device, method of determining land surface, effects of recent 

pumping, unknown screened intervals of wells, and other 

sources of uncertainty. In theory, weighted observations used 

in the regression procedure can be calculated from estimates 

of the variance of measurement error (Hill, 1998, p. 45–47). 

The weights are proportional to 1 divided by the variance of 

the measurement errors for the observation. To estimate these 

variances, MODFLOW-2000 reads statistics on measurement 

error (supplied by the user) from which the variances of the 

observation errors and the weights are calculated. The standard deviation of the measurement error was used to estimate 

the weights for water-level observations, and the coefficient of 

variation was used to estimate the error for the streamflow-flux 

observations. The calculations of the statistics are described in 

Hill (1998, p. 46–47).

Weights for the water-level observations were based on 

the assumption that 95 percent of the measurements were 

within the measurement error, which was considered to be 

0.03 ft. Statistical theory for normally distributed populations 
Simulated Groundwater Flow 37

1

2

3

4

GV1

GV2

GV3

GV4

GV7A

GV8A

GV8C

GV9A

GV10

GV11A

GV12A

GV14

GV15

GV16

GV17

GV18

GV20

GV21

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

Universal Transverse Mercator projection, Zone 16

North American Datum of 1983

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

0

EXPLANATION

39°30’30”

87°31’30” 87°31’ 87°30’30”

39°31’

1

GV1

Green

Valley

Mine

Pond

John A.

Scott Lake

West Little Sugar Creek

Measured seep reach 

Seep measurement site and number

Groundwater-level observation site 

and number

Figure 20. Location of sites used to provide observations of streamflow flux (gain/loss) and groundwater levels at the Green Valley 

mine site, Indiana.

states that for the 95-percent confidence interval, the measurement error should be 1.96 times the standard deviation of the 

measurement error (Cooley and Naff, 1990, p. 44). The standard deviation of the measurement error is, therefore, equal to 

0.0153 (0.03 divided by 1.96); the standard deviation of the 

measurement error is used as an input to MODFLOW-2000 

for calculating water-level weights.

Weights for streamflow observations were calculated by 

taking the inverse of the product of streamflow and the coefficient of variation associated with the difference in streamflows 

between two points on the stream. The coefficient of variation is calculated by finding the standard deviation of both the 

upstream and downstream streamflow errors, then squaring 

each standard deviation to obtain variances for each streamflow error. The variance of the gain or loss is then calculated 

by adding the two variance values associated with each 

measurement. The coefficient of variation is determined by 

dividing the square root of the summed variances of the gain 

or loss (a standard deviation) by the gain or loss in the stream 

segment (Hill, 1998, p. 47). 
38 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

Changes in the Design of the Model During 

Calibration

Groundwater in the coal refuse appeared to be under 

water-table conditions, but attempts at water-table simulations resulted in unstable solutions, as evidenced by excessive 

iterations. The large number of iterations was caused by model 

cells changing from active to inactive. To improve the stability of model solutions, all layers were simulated as confined. 

The confined thickness of layer 1 was set to approximate the 

saturated thickness within the coal refuse so that the transmissivity for a confined layer 1 approached that for a water-table 

layer. A confined steady-state simulation for June 2009 was 

achieved, and the simulated water levels for layer 1 were used 

to define the top of layer 1. This approximation of the actual 

water-table surface likely would not impair the estimation 

of representative model-parameter values for the coal refuse 

because estimated parameter values were insensitive to the 

change in layer 1 thickness. Parameter estimation simulations 

using land surface as the top of layer 1 resulted in horizontal 

hydraulic conductivities that were similar to those obtained 

using the approximate water-table surface as the top of layer 

1. For example, horizontal hydraulic conductivities in the coal 

refuse estimated by both conceptual models were near 0.1 ft/d. 

An additional parameter was added during calibration. 

The steady-state model was simulating water levels to be 

above land surface just west of the coal refuse. Also, during 

field visits to the study site, USGS personnel noted that the 

land surface just west of the coal refuse was occasionally bare 

and covered with orange stains, apparently from groundwater with high iron concentrations seeping out from the soil. 

To simulate this process, an area of drain cells with altitudes 

equal to land-surface altitude was added to the model from 

the western edge of the coal refuse to the first gully west of 

the refuse (fig. 21). These drain cells allowed groundwater 

to discharge from the model if the water surface rose above 

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

Universal Transverse Mercator projection, Zone 16 

North American Datum of 1983 

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

0

Approximate boundary of coal refuse

EXPLANATION

Area of drain nodes used

to discharge groundwater

that rises to land surface Centerline of

gully Green

Valley

Mine

Pond

John A.

Scott Lake

West Little Sugar Creek

87°31’30”

39°31’

39°30’30”

87°31’ 87°30’30”

Figure 21. Location of drain cells in simulation used to discharge groundwater that reaches land surface at the Green Valley mine 

site, Indiana.
Simulated Groundwater Flow 39

the land surface, as well as allowed groundwater to discharge 

to the gully. No discharge results where groundwater level is 

below the land surface. Although simulated water levels are 

not allowed to be higher than actual, the simulated flux rate to 

land surface may or may not be similar to the actual rate. Any 

error in the flux rate should not affect overall model results 

because the area of observed land-surface seepage is small 

relative to the entire model area. 

Other adjustments and approximations to actual hydrogeologic conditions were made during calibration. The 

estimated water levels from the June 2009 simulation were 

below the bottom of layer 1 in some areas; therefore, cells 

for these areas were simulated as no flow. The thickness of 

the till was not adjusted to its saturated thickness because (1) 

the unsaturated part of the till is a small percentage (about 

5 percent) of the overall till thickness and (2) the till is outside 

the area of primary interest, which is the coal refuse. Use of a 

single recharge rate to the coal refuse and horizontal hydraulic conductivity of the coal refuse was separately tested, but 

the agreement between simulated and observed water levels 

worsened. Two recharge rates and corresponding horizontal 

and vertical hydraulic conductivities were maintained for all 

simulations. 

Calibration Results

This section includes the calibrated values for model 

parameters, indications of how well the model simulates 

observed water levels and streamflow with the calibrated 

parameters, and a description of the groundwater-flow system 

as simulated by the model. The flow system is described by a 

presentation of the simulated model budget, water-level contours, and groundwater-flow paths.

Calibrated Parameter Values

The calibrated parameter values are listed in table 11. The 

calibrated parameter values are listed only for the transient 

simulation because that list includes the steady-state parameter 

values. Calibrated parameter values for the steady-state simulation are the same as listed in table 11.

Some observations on the calibrated values are listed 

below:

1. The horizontal hydraulic conductivities and recharge rates 

for the coal refuse are similar to those for the till. The 

similarity implies that the coal refuse is low in permeability and does not transmit large amounts of groundwater. 

The low volume of water flowing through the coal refuse 

limits the production of acid mine drainage. 

2. Aquifer-test and model-calibration estimates of horizontal 

hydraulic conductivity are similar. The calibrated value 

for horizontal hydraulic conductivity of the gob and 

tailings mixture is 0.75 ft/d, and the value derived from 

the slug test at GV11A (in an area of gob and tailings) is 

0.83 ft/d based on the Hvorslev analysis (1951). The calibrated value for horizontal hydraulic conductivity of the 

gob is 0.03 ft/d, and the value derived from the slug test 

at GV12A (located in an area of gob) is 0.04 ft/d based 

on the Hvorslev analysis (1951). The gob and tailings 

mixture might be expected to be fine-grained material that 

would have a lower horizontal hydraulic conductivity than 

that for the gob, but areas of the gob and tailings mixture 

have been described as a mixture of coarse- and finegrained material. A feasibility investigation by Geosciences Research Associates (1985, p. 8) described tailings 

as a mixture of fine gravel, sand, silt, clay, and particles of 

coal. The sand- and gravel-sized particles within the gob 

and tailings mixture apparently create a zone of higher 

horizontal hydraulic conductivity than is present in the 

gob.

3. The calibrated value of specific storage for the till is high 

compared to values given by Shaver (1998, p. 552). As 

explained in the section on the choice of model parameters, the calibrated value for specific storage was higher 

than expected for till. The observed water levels within 

the till were to some degree affected by release of water 

from gravity drainage. As a result, the calibrated specific storage is higher to reflect that release of water. 

The approximation of two parameters (specific storage 

and specific yield) by one parameter is not expected to 

substantially affect model simulations. The approximation applies to till and not to the coal refuse, the model 

component of interest.
40 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

Table 11. Calibrated parameter values obtained for the groundwater model of the Green Valley mine site, Indiana.

[

ft/d, feet per day; in/yr, inches per year; ft-1, per foot]

Parameter 

name Model component

Calibrated 

parameter 

value

k.tail Horizontal hydraulic conductivity of the gob and tailings mixture 0.75 ft/d

k,gob Horizontal hydraulic conductivity of the gob 0.03 ft/d

k.till Horizontal hydraulic conductivity of the till 0.43 ft/d

kv.tail Vertical hydraulic conductivity of the gob and tailings mixture 0.07 ft/d

kv.gob Vertical hydraulic conductivity of the gob 0.003 ft/d

kv.till Vertical hydraulic conductivity of the till 0.0019 ft/d

Stream Hydraulic conductivity of the streambed for small streams in the till 1.0 ft/d

Seep Hydraulic conductivity of the streambed for small streams in the coal refuse and upstream of a flow-measurement point1.0 ft/d

ds.gob Hydraulic conductivity of the streambed for small streams in the coal refuse and downstream of a flowmeasurement point1.0 ft/d

River Hydraulic conductivity of the streambed for West Little Sugar Creek 1.0 ft/d

Lake Hydraulic conductivity of the lakebed for Green Valley Mine Pond 1.0 ft/d

ground Hydraulic conductivity controlling seepage of water from the soil to the land surface west of the coal refuse 1.0 ft/d

rech.lake Recharge rate to the area beneath Green Valley Mine Pond 0.0 in/yr

till.jun08 Recharge rate to the till during the month of June 2008 4.45 in/yr

till.jul08 Recharge rate to the till during the month of July 2008 3.72 in/yr

till.aug08 Recharge rate to the till during the month of August 2008 1.20 in/yr

till.sep08 Recharge rate to the till during the month of September 2008 0.48 in/yr

till.oct08 Recharge rate to the till during the month of October 2008 0.36 in/yr

till.nov08 Recharge rate to the till during the month of November 2008 0.60 in/yr

till.dec08 Recharge rate to the till during the month of December 2008 3.12 in/yr

till.jan09 Recharge rate to the till during the month of January 2009 3.48 in/yr

till.feb09 Recharge rate to the till during the month of February 2009 4.20 in/yr

till.mar09 Recharge rate to the till during the month of March 2009 3.60 in/yr

till.apr09 Recharge rate to the till during the month of April 2009 6.84 in/yr

till.may09 Recharge rate to the till during the month of May 2009 7.32 in/yr

till.jun09 Recharge rate to the till during the month of June 2009 4.56 in/yr

mnd.jun08 Recharge rate to the tailings and gob mixture during the month of June 2008 3.14 in/yr

mnd.jul08 Recharge rate to the tailings and gob mixture during the month of July 2008 4.24 in/yr

mnd.aug08 Recharge rate to the tailings and gob mixture during the month of August 2008 1.37 in/yr

mnd.sep08 Recharge rate to the tailings and gob mixture during the month of September 2008 0.55 in/yr

mnd.oct08 Recharge rate to the tailings and gob mixture during the month of October 2008 0.41 in/yr

mnd.nov08 Recharge rate to the tailings and gob mixture during the month of November 2008 2.00 in/yr

mns.dec08 Recharge rate to the tailings and gob mixture during the month of December 2008 2.53 in/yr

mnd.jan09 Recharge rate to the tailings and gob mixture during the month of January 2009 4.54 in/yr

mnd.feb09 Recharge rate to the tailings and gob mixture during the month of February 2009 3.89 in/yr

mnd.mar09 Recharge rate to the tailings and gob mixture during the month of March 2009 2.50 in/yr

mnd.apr09 Recharge rate to the tailings and gob mixture during the month of April 2009 10.3 in/yr

mnd.may09 Recharge rate to the tailings and gob mixture during the month of May 2009 5.86 in/yr

mnd.jun09 Recharge rate to the tailings and gob mixture during the month of June 2009 3.50 in/yr

sy.gob Specific yield of the coal refuse 0.013

ss.till Specific storage of the till 0.00197ft-1
Simulated Groundwater Flow 41

Analysis of the Residuals

The degree of fit between field-measured and model-simulated values is an indication of how well the model represents 

the actual groundwater-flow system. Model fit can be assessed 

by means of multiple indicators, including plots of measured 

water levels in relation to simulated water levels, the correlation coefficient between those values, and water-level residuals. Residuals can be analyzed in terms of their distribution 

and degree of bias.

Ideally, simulated values should be close to measured 

values such that when weighted observations are plotted 

against weighted simulated values, the residual values fall 

close to a line with slope equal to 1 and intercept of zero. The 

plot of weighted measured water levels in relation to weighted 

simulated water levels for the steady-state calibration is shown 

in figure 22A, and a similar plot for the transient calibration 

is shown in figure 23A. The correlation coefficient between 

weighted observations and weighted simulated equivalents 

reflects how well the values follow the 1:1 line. A correlation 

coefficient greater than 0.90 is desirable (Hill, 1998, p. 22) 

and the model calibration resulted in a value of 0.99996 

and 0.99993 for the steady-state and transient calibrations, 

respectively. 

Valid parameter estimation is expected to result in normally distributed weighted residuals. The weighted residuals 

are plotted according to their position in an assumed normal 

distribution. The plotting positions for the steady-state calibration are shown in figure 22B. The plotting positions for the 

transient calibration are shown in figure 23B. If the residuals 

are normally distributed, then the residuals should plot along 

a straight line. The statistic that measures the linearity of the 

plot and the independence of one residual to another is called 

the correlation between ordered weighted residuals and normal 

order statistics. This correlation coefficient should be near 1; 

the value associated with the residuals from the model calibration is 0.98 for both the steady-state and transient calibrations 

and is sufficiently close to 1 that the residuals approximate a 

normal distribution. 

Weighted residuals and their weighted simulated values 

for the steady-state and transient calibrations were used to 

evaluate positive or model bias (figs. 22C and 23C). Ideally, 

the weighted residuals should be evenly distributed around 

a mean of zero and not biased positively or negatively. Also, 

the size of the weighted residuals should not be related to the 

magnitude of the weighted simulated values; for example, 

large residuals (relative to the mean residual) associated with 

lower simulated values. These requirements were generally 

satisfied in both model calibrations.

The residual plots do not show the residuals associated with measured streamflow. The plotting position for 

the streamflow flux residuals are near the origin of the axis, 

whereas the water-level residuals are far from the origin. The 

relative plotting positions reflect the difference in magnitude 

of the sum of squared residuals for each type of observation. 

For the steady-state calibration, the sum of squared streamflow 

28,500 29,000 29,500 30,000 30,500

28,500

29,000

29,500

30,000

30,500

WEIGHTED OBSERVED WATER LEVEL,

IN FEET ABOVE NAVD 88

Weighted water-level value

Weighted residual

NORMAL PROBABILITY PLOTTING POSITION

28,500 29,000 29,500 30,000 30,500

-300

-200

-100

0

100

200

300

WEIGHTED SIMULATED WATER LEVEL,

IN FEET ABOVE NAVD 88

A

B

C

Weighted residual

-3 -2 -1

-300

-200

-100

0

100

200

300

1:1 slope

0 1 2 3

WEIGHTED SIMULATED WATER

LEVEL ABOVE NAVD 88, IN FEET

WEIGHTED RESIDUAL VALUE

 ABOVE NAVD 88, IN FEET

WEIGHTED RESIDUAL VALUE

 ABOVE NAVD 88, IN FEET

Figure 22. Graphical analysis of the steady-state model fit for 

the area of coal refuse at the Green Valley mine site, Indiana. 

A, Weighted simulated and weighted observed water levels. 

B, Normal probability plot of weighted residuals. C, Weighted 

residuals and weighted simulated water levels.
42 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

flux residuals is 0.16, and the sum of squared water-level 

residuals is 267,840. Plotting all residuals on the same graph 

would result in the water-level residuals plotting so close 

together that details of the distribution of the water-level 

residuals would be obscured. To display the more important 

error associated with the simulated water levels, the axes on 

the residual plots were chosen to show only the water-level 

residuals. The streamflow flux residual data for the steadystate and transient calibrations are presented in tables 12 and 

13, respectively. The streamflow flux residuals do not generate 

substantial model error because they plotted near the 1:1 line 

in figures 22A and 23A and near the zero line in figures 22C

and 23C.

Although the streamflow flux residuals do not generate 

substantial model error as compared to water-level residuals, 

the flux residuals are sometimes a significant percentage of the 

measured flow. An elaboration on this error is given in the text 

associated with tables 14 and 15, which present basic statistical measures for all residuals. Residuals also can be analyzed 

by their areal distribution and magnitude. The map of waterlevel residuals for all model layers from the steady-state calibration shows a random distribution of positive and negative 

residuals over the model area (fig. 24), which is characteristic 

of an adequately calibrated model (Anderson and Woessner, 1992, p. 242). Positive residuals indicate that the model 

overpredicts a water level. A map of water-level residuals from 

the transient calibration is not shown because the patterns, 

signs, and magnitudes of residuals are similar to those for the 

steady-state calibration. The difference between simulated 

and observed water levels for the transient simulation can be 

observed in a set of simulated and observed hydrographs.

The degree to which simulated water levels represent 

the fluctuations in observed water levels can be seen in figure 

25. The simulated fluctuations are affected by the calibrated 

values for recharge rates, storage properties, and hydraulic 

conductivity. The hydrographs in figure 25, which are representative examples of all the hydrographs, show observed and 

simulated water-level fluctuation in the till (at well GV10), 

in the areas of gob and tailings mixture (at wells GV14 and 

17), and in the area of gob (at wells GV21, GV4, and GV7A). 

Typically, simulated water levels that were above or below 

the observed value in the steady-state calibration remained the 

same throughout the transient simulation. Although the simulated water levels differ moderately from the observed values, 

the range of fluctuation in the simulated water level is usually 

about the same as that for the observed water levels. The rise 

in observed water levels at well GV4 begins later than the rise 

in the simulated water levels. The reason for the delayed rise 

is unknown, but it is not considered to be caused by a longer 

time for recharge to travel from the land surface to the water 

table at site 4 compared to other sites. A delayed rise also 

occurs at site 18, but only 8 ft of unsaturated coal refuse lies 

above the water table at that site. Also, all observed water levels attain their highest level in or near June, indicating timing 

of the recharge process is similar for all sites. The agreement 

between simulated and observed hydrographs is considered 

Figure 23. Graphical analysis of the transient model fit for 

the area of coal refuse at the Green Valley mine site, Indiana. 

A, Weighted simulated and weighted observed water levels. 

B, Normal probability plot of weighted residuals. C, Weighted 

residuals and weighted simulated water levels.

NORMAL PROBABILITY PLOTTING POSITION

28,500 29,000 29,500 30,000 30,500

28,500

29,000

29,500

30,000

30,500

-3 -2 -1 0

-300

-200

-100

0

100

200

300

28,500 29,000 29,500 30,000 30,500

-300

-200

-100

0

100

200

300

1:1 slope

Weighted water-level value

Weighted residual

Weighted residual

A

B

C

1 2 3

WEIGHTED SIMULATED WATER LEVEL,

IN FEET ABOVE NAVD 88

WEIGHTED OBSERVED WATER LEVEL,

IN FEET ABOVE NAVD 88

WEIGHTED RESIDUAL VALUE,

IN FEET ABOVE NAVD 88

WEIGHTED RESIDUAL VALUE,

IN FEET ABOVE NAVD 88

WEIGHTED SIMULATED WATER LEVEL,

IN FEET ABOVE NAVD 88
Simulated Groundwater Flow 43

Table 12. Unweighted streamflow flux residuals for the steady-state calibration of June 

2008 for the model of the Green Valley mine site, Indiana.

[(ft3/s), cubic feet per second]

Seep-measurement 

site1

Observed flow 

(ft3/s) 

Simulated flow 

(ft3/s)

Unweighted 

streamflow flux residual 

(simulated–observed) (ft3/s) 

1 0.000 0.0034 0.0034

2 .0000 .0006 .0006

3 .0102 .0002 -.0100

4 .0183 .0067 -.0116

1

 Site locations shown in figure 20

Table 13. Unweighted streamflow flux residuals for the transient calibration from June 2008 to June 2009 from the 

model of the Green Valley mine site, Indiana.

[(ft3/s), cubic feet per second]

Seep-measurement 

site1

Measurement 

date 

Observed flow 

(ft3/s) 

Simulated flow 

(ft3/s) 

Unweighted streamflow 

flux residual 

(simulated–observed) 

(ft3/s)

1 November 2008 0.0000 0.0020 0.0020

2 November 2008 .0000 .0001 .0001

3 November 2008 .0056 .0001 -.0055

1 December 2008 .0000 .0020 .0020

2 December 2008 .0000 .0001 .0001

3 December 2008 .0000 .0001 .0001

3 January 2009 .0119 .0002 -.0117

1 March 2009 .0063 .0023 -.0040

2 March 2009 .0032 .0001 -.0031

3 March 2009 .0050 .0001 -.0049

4 March 2009 .0186 .0040 -.0146

1 April 2009 .0047 .0027 -.0020

2 April 2009 .0046 .0003 -.0043

3 April 2009 .0084 .0002 -.0082

4 April 2009 .0371 .0067 -.0304

1 June 2009 .0000 .0032 .0032

2 June 2009 .0000 .0003 .0003

3 June 2009 .0102 .0002 -.0100

4 June 2009 .0183 .0059 -.0124

1

 Site locations shown in figure 20

Table 14. Statistical summary for the residuals from the steady-state calibration of the model for the Green Valley mine 

site, Indiana.

[ft, feet; ft3/s, cubic feet per second]

Type of residual Minimum 

residual

Mean 

residual

Maximum 

residual 

Standard 

deviation of 

the residuals 

Mean 

absolute 

error 

Percent mean 

absolute error 

(percent) 

Median 

error

Bias

Water level (ft) -4.34 -0.39 3.78 2.48 2.15 7.6 -0.22 -0.39

Streamflow (ft3/s) -0.011 -0.004 0.003 0.007 0.006 33.3 0.004 -0.004
44 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

Table 15. Statistical summary for the residuals from the transient calibration of the model for the Green Valley mine site, 

Indiana.

[ft, feet; ft3/s, cubic feet per second]

Type of 

residual

Minimum 

residual 

Mean 

residual

Maximum 

residual

Standard 

deviation of 

the residuals 

Mean 

absolute 

error 

Percent mean 

absolute error 

(percent) 

Median 

error

Bias

Water level 

(ft)

-4.52 -0.20 4.70 2.38 2.10 7.0 -0.50 -0.20

Streamflow 

(ft3

/s)

-0.03 -0.006 0.003 0.008 0.006 16.2 -0.004 -0.006

700 1,400 FEET

0 175 350 METERS

0

0.85

-0.78

1.35

3.73

4.33

-2.25

1.08

-1.13

2.36

-3.79

-0.39

-1.91

2.62

-1.24

-2.85

3.49

-1.62

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

Universal Transverse Mercator projection, Zone 16 

North American Datum of 1983 

EXPLANATION

Approximate extent of coal refuse

Location of a well for layer 1 

of the model (coal refuse) and the 

water-level residual for the well site 

Location of a well for layer 2 

of the model (upper till) and the 

water-level residual for the well site

Location of the well for layer 3 

of the model (middle till) and the 

water-level residual for the well site 

-0.39

-1.62

2.62

West Little Sugar Creek

John A.

Scott 

Lake

Green Valley Mine Pond

39°30’30”

39°30’45”

87°31’30” 87°31’15” 87°31’ 87°30’45”

Figure 24. Distribution of positive and negative unweighted water-level residuals for the steady-state calibration of the 

model for the Green Valley mine site, Indiana..
Simulated Groundwater Flow 45

600

601

602

603

604

605

606

607

608

609

610

0 50 100 150 200 250 300 350 400

Well GV14

570

572

574

576

578

580

582

584

586

588

590

0 50 100 150 200 250 300 350 400

Well GV21

590

591

592

593

594

595

596

597

598

599

600

0 50 100 150 200 250 300 350 400

Well GV10

590

591

592

593

594

595

596

597

598

599

600

0 50 100 150 200 250 300 350 400

Well GV4

590

592

594

596

598

600

602

604

606

608

610

0 50 100 150 200 250 300 350 400

600

601

602

603

604

605

606

607

608

609

610

0 50 100 150 200 250 300 350 400

Well GV7A

EXPLANATION

Simulated water level corresponding

to observed water level

Observed water level

WATER-LEVEL SURFACE ALTITUDE

ABOVE NAVD 88, IN FEET

WATER-LEVEL SURFACE ALTITUDE

ABOVE NAVD 88, IN FEET

WATER-LEVEL SURFACE ALTITUDE

ABOVE NAVD 88, IN FEET

WATER-LEVEL SURFACE ALTITUDE

ABOVE NAVD 88, IN FEET

WATER-LEVEL SURFACE ALTITUDE

ABOVE NAVD 88, IN FEET

WATER-LEVEL SURFACE ALTITUDE

ABOVE NAVD 88, IN FEET

DAYS INTO SIMULATION DAYS INTO SIMULATION

DAYS INTO SIMULATION DAYS INTO SIMULATION

DAYS INTO SIMULATION DAYS INTO SIMULATION

Well GV17

Figure 25. Simulated and observed hydrographs from the transient calibration of the model for the Green Valley mine site, 

Indiana (well locations shown in fig. 20).
46 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

acceptable, especially considering that only one specific yield 

parameter was used to simulate all deposits in the coal refuse. 

Using one specific yield for the area containing the gob and 

tailings mixture and another for the area for the gob only was 

not considered because of the lack of field data to help define 

these parameters.

Finally, the residuals were examined by basic statistical 

measures, such as mean absolute error and bias (tables 14–15). 

The statistics for the steady-state and transient calibrations are 

similar, indicating a similar level of accuracy in the two calibrations. Percent mean absolute error is calculated by dividing 

the mean absolute error by the range in observation values 

in the study area; the calculation provides a measure of the 

accuracy of the simulation. For example, a 1-ft mean absolute 

error may appear to be representing an accurate simulation 

unless the range in observations is 2 ft, in which case, the 

percent error would be 50 percent. The percent mean absolute 

errors for the streamflow flux residuals from the steady-state 

and transient calibrations are high (33 and 16 percent, respectively), but they may be a reflection of the small absolute 

values of flux. When the absolute values are small, a small 

error in model-simulated flux can still show a large percent 

mean absolute error. The high values for percent mean absolute errors for the streamflow flux residuals can also indicate a 

limitation of the model to simulate all flow to the seeps. A field 

observation during August 2008 near seep 3 indicated the existence of a preferential flow path to that seep. Preferential flow 

paths can serve as alternative flow path to the seeps in addition 

to normal porous media flow. Additional field data would be 

needed to confirm and characterize preferential flow paths 

elsewhere. The bias data are calculated as the sum of residuals 

divided by the number of observations so that bias represents 

the average amount that the model overpredicts or underpredicts water levels and fluxes. The negative bias (underprediction) for streamflow flux of 0.004 ft3

/s is 12 percent of the 

total flow from the gob (table 16), indicating that the error in 

simulated flow to the seeps is relatively small compared to the 

overall flow out of the gob (model layer 1).

Model Budget

Some insights into the groundwater-flow system can be 

gained by analyzing the simulated groundwater-flow budget. 

Understanding the magnitude and direction of flow can aid 

in developing remediation strategies. The calibrated, steadystate water budget is listed in table 17. The simulated transient 

water budgets are similar to the steady-state budget in terms 

of flow rates except that the transient budgets include flow in 

and out of storage. The only flow component in the transient 

budget that varies noticeably from the steady-state budget 

is recharge. Recharge rates vary throughout the year from 

0.0320 to 0.0636 ft3/s; flows in and out of storage compensate 

for the recharge-rate variation. For the steady-state budget in 

Table 17, most of the inflow (83 percent) is from precipitation 

Table 16. Simulated steady-state water budget for layer 1 of the model (the coal refuse), Green Valley 

mine site, Indiana, June 2009.

[ft3/s, cubic feet per second]

Source of Inflow to model Inflow rate 

(ft3

/s) Outflow from layer 1 Outflow rate (ft3/s)

Recharge 0.0302 Flow to seeps 0.00915

Flow from the till to the coal refuse 0.00222 Flow from the coal refuse to the till 0.0233

Total inflow 0.0324 Total outflow 0.0325

Table 17. Simulated steady-state water budget in June 2009 for the model of the Green Valley mine 

site, Indiana.

[ft3/s, cubic feet per second]

Inflow to model Inflow rate 

(ft3

/s) Outflow from model

Outflow rate

(ft3

/s)

Constant-head boundaries 0.0776 Constant-head boundaries 0.142

Drains 0.290

Leakage from Green Valley 

Mine Pond

0.00430 Leakage into Green Valley 

Mine Pond

0.0558

Recharge

Total inflow

0.406

0.488 Total outflow 0.488
Simulated Groundwater Flow 47

recharge, and most of the outflow (71 percent) is to the drains 

(the seeps in the coal refuse, water seeping to the land surface, 

and local streams) and the Green Valley Mine Pond.

The flow budget is further examined by presenting the 

budget flow rates between layer 1, the coal refuse, and layer 2, 

the top layer of till (table 16). Most of the discharge outflow 

from the coal refuse (72 percent) is downward leakage into 

the till and is not out of the seeps. The seeps are fed mostly by 

precipitation recharge occurring over the coal refuse; however, 

a large amount of seepage (24 percent) comes from the till. If 

the seeps were not present, water from the till currently flowing out to the seeps would discharge as flow elsewhere, such 

as vertically downward deeper into the till.

Simulated Water Levels

The directions of groundwater flow in the model are 

illustrated by contours that depict water-level-altitude data 

and from which direction of flow can be inferred. Waterlevel contours from the steady-state calibration for the coal 

refuse (layer 1) are shown in figure 26 and for the middle of 

the till (layer 3) are shown in figure 27. Contours from the 

transient calibration are similar to those for the steady-state 

ones because of the small fluctuation in water levels over the 

year. A mostly southwesterly groundwater-flow direction can 

be seen in each contour map; a downward flow direction can 

be seen by observing generally higher water levels in the coal 

700 1,400 FEET

0 175 350 METERS

0

545

5 4 5

5 5 0

5 5 5

5

6 0

6 0 5

6 0 0

5 9 5

5 9 0

5 8

5

5

8 0

5

7

5

5 7 0

5 6 5

5 9 5

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

Universal Transverse Mercator projection, Zone 16 

North American Datum of 1983 

EXPLANATION

Approximate extent of coal refuse

Simulated water-level contour.

Interval 5 feet. Datum is NAVD 88

535

540

545

Area where layer 1 is dry

John A.

Scott Lake

 Little Sugar Creek

Green Valley Mine Pond

87°31’30”

39°30’45”

39°30’30”

87°31’15” 87°31’ 87°30’45”

Figure 26. Model-simulated water levels for the coal refuse (model layer 1) of the model, Green Valley mine 

site, Indiana.
48 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

0

580 610 590

5 8 0

6 0 0

5 9 0

5 4 0

560

6 0 0

5 4 0

560 570

5 6 0

550

560

5 9 0

5 3 0

5 8 0

5 7 0

5

6

0

5 5 0

5 4 0

5

4 0

5 5 0

5 6 0 5

7

0

5 8 0

5 8 0

5 7 0

5 6 0

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

Universal Transverse Mercator projection, Zone 16 

North American Datum of 1983 

EXPLANATION

Approximate extent of coal refuse

Simulated water-level contour.

Interval 10 feet. Datum is NAVD 88

Approximate location of

groundwater divide

Direction of groundwater flow

Green

Valley Mine

Pond John A.

Scott Lake

87°31’30”

39°30’45”

39°30’30”

87°31’ 87°30’30”

Figure 27. Model-simulated water levels for the middle of the till (model layer 3) of the model, Green Valley mine 

site, Indiana.

refuse (fig. 26) and lower ones in the till (fig. 27). The horizontal flow direction is towards West Little Sugar Creek. There is 

an approximate 5-ft vertical downward gradient between the 

coal refuse and the middle of the till. The water levels in the 

coal refuse and till also indicate some discharge to the seeps, 

but the area contributing that water is immediately adjacent 

to the seep channels. An approximate groundwater divide is 

shown on figure 27 and indicates that groundwater in a small 

area of the coal refuse flows to the northeast, toward Green 

Valley Mine Pond and John A. Scott Lake.

Simulated Flow Paths

Groundwater-flow paths provide useful information about 

the source, distribution, and discharge flow of ground water in 

the model area. Both steady-state and transient simulations can 

be used to generate flow-path information, but the steady-state 

simulation for June 2009 is used here. Calculations for steadystate simulations are easier to compute, and the flow-path 

information (the location of the path and the path endpoint) is 

essentially the same as for a transient simulation. Flow paths 

can be shown for any area in the model, but a useful set of 

groundwater flow paths for illustration is the paths taken by 

water discharging from the coal refuse. Those paths will also 

show the ultimate discharge for acidic water emanating from 

the coal refuse. Evenly distributed points of recharge (the 

small black dots) over the area of coal refuse are shown in 

figure 28. The ultimate discharge endpoints for these recharge 

points are shown as red dots, and the red dots cluster at four 

major discharge areas: West Little Sugar Creek, Green Valley 

Mine Pond, the downstream part of seep 4, and downgradient streams. Data on how many of the flow paths end in each 

major discharge area and on travel time to those discharge 

areas are given in table 18. The discharge area receiving the 
Simulated Groundwater Flow 49

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

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

Universal Transverse Mercator projection, Zone 16 

North American Datum of 1983

EXPLANATION

Point of recharge

Point of discharge

Approximate extent of coal refuse

Green

Valley

Mine

Pond West Little Sugar Creek

87°31’30” 87°31’ 87°30’30”

39°31’

39°30’30”

Figure 28. Simulated flow paths from points of recharge in the area of coal refuse (model layer 1) to points of 

discharge areas, Green Valley mine site, Indiana.

Table 18. Percentage of flow paths discharging to the major discharge areas and travel time statistics 

for the flow paths, Green Valley mine site, Indiana.

Discharge ouflow area 

of the model

Percentage of flow 

paths flowing to 

area (percent)

Minimum 

traveltime 

(years)

Mean 

traveltime 

(years)

Maximum 

traveltime 

(years)

Maximum 

traveltime 

(years)

West Little Sugar Creek 24 5 152 835 150

Green Valley Mine Pond 9 20 140 827 155

Seep 4 32 0 84 423 83

Streams downgradient from 7 20 231 1,101 242

coal refuse
50 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

most flow paths is the downstream part of seep 4 (32 percent), 

followed by West Little Sugar Creek (24 percent). Average 

travel time along the flow paths is long (from 84 to 152 years), 

allowing substantial time for acidic water to interact with the 

low-permeability sediments and undergo chemical changes. 

Travel times are shorter if the recharge points are close to the 

major discharge area, and can be zero—like at the downstream 

part of seep 4. In that case, the recharge point is placed on the 

seep, resulting in no travel time to the discharge point. Travel 

times can be shorter than those in table 18 if continuous fractures or extensive zones of sand and gravel are present in the 

till, creating high-permeability zones. The longest travel times 

are associated with the red discharge points along the bottom 

center of figure 28 because those discharge points are farthest 

from the coal refuse. The flow paths discharging to the bottom 

center of the figure represent paths in the model that would 

eventually discharge flow to streams further south of the modeled area.

To show the vertical characteristics of the flow paths, a 

cross-sectional view of flow paths through the coal refuse is 

shown in (fig. 29). Various recharge points over the center of 

the coal refuse were selected (part A of fig. 29), and the associated flow paths are shown (part B of fig. 29). Fewer recharge 

points were chosen for figure 29 compared to figure 28 for 

clarity; if all of the flow paths associated with the recharge 

points in figure 28 were shown, then the high density of flow 

lines would reduce the ability to observe vertical flow patterns. 

The flow paths in figure 29 show groundwater from the coal 

refuse flowing vertically downward into the till, then eventually horizontally to West Little Sugar Creek and the Green 

Valley Mine Pond. The almost completely downward vertical 

flow in the coal refuse would indicate that a remediation technique using flow barriers to channel subsurface flow would 

probably be ineffective. The flow paths are shown along the 

cross section row 34 of the model (see fig. 29A for location) 

to help explain flow patterns. None of the flow paths flow 

entirely along row 34 of the model; instead, the flow paths 

are projected onto the cross section for the purposes of this 

figure. Because groundwater is not flowing exactly along row 

34, the flow paths do not appear to discharge into West Little 

Sugar Creek and the lakes, but they actually do at another row 

position. The projected flow paths show the general pattern 

of flow against model features. For example, most flow paths 

discharge end at West Little Sugar Creek but some discharge 

to the Green Valley Mine Pond. The vertical component to 

the flow paths in the coal refuse and till contributes to the 

decades-long travel times within these units.

Model Limitations and Qualifications

Predictive simulations by the groundwater model should 

be evaluated and qualified on the basis of model reliability 

(Anderson and Woessner, 1992, p. 284). The reliability of the 

calibration is dependent upon the assumptions used in construction of the model. The simplifying assumptions used in 

the development of this model were previously discussed, but 

included hydraulic uniformity within model layers and noflow into or out of the shale bedrock. Although these assumptions were in some ways tested and described within this 

report, more data may be required to fully evaluate these and 

other assumptions. The following factors should be considered 

when evaluating this model and predictive simulations that 

this model may produce: 

1. The model is best used to simulate groundwater flow 

in the area of the coal refuse because almost all of 

the observations used to calibrate the model are from 

the area of coal refuse. The positions and times of 

simulated groundwater-flow paths outside the area 

of coal refuse are considered to be less accurate than 

those in or near the refuse. 

2. Sand-and-gravel lenses and fractures in the till were 

not modeled specifically. The existence of fractures 

and sand-and-gravel lenses can shorten groundwater travel times considerably. The error in predicted 

travel times is unknown but is probably related 

to the abundance of these features. Notations of 

sand-and-gravel lenses were not abundant in the few 

well-driller logs available to this investigation, and 

therefore, the travel time errors are expected to be 

small. 

3. Direct measures of recharge rates to the simulated 

deposits were not possible. Estimates of recharge 

from model calibration were influenced by a 

base-flow separation technique and by measurements of flow in the seeps. The base-flow separation technique determined recharge rates to the till, 

and ratios of steady-state recharge rates in the till 

to those in the coal refuse were used to estimate 

monthly recharge rates to the refuse. Actual ratios 

are not known, but the recharge estimates should 

be adequate because of two observations. First, the 

calibrated horizontal hydraulic conductivities are 

similar to the values derived from the aquifer tests. 

If the calibrated horizontal hydraulic conductivities 

are near actual values, then recharge rates must be 

near actual values. If recharge rates are too high and 

horizontal hydraulic conductivities are near actual 

values, simulated water levels would be biased high, 

which is not the case. Second, the estimated ratios of 

recharge rate in the till to that in the coal refuse did 

not create areal bias in water-level residuals. Positive 

and negative residuals are evenly distributed in both 

the area of gob and in the area of the gob and tailings 

mixture.

4. The model was constructed using two hydraulic conductivity zones within the coal refuse. The boundary 

of those zones may be incorrect and the presence 

of additional zones is possible. Regardless of the 
Simulated Groundwater Flow 51

700 1,400 FEET

0 175 350 METERS

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

Universal Transverse Mercator projection, Zone 16 

North American Datum of 1983 

Vertical groundwater flow path

A. Location of starting positions for groundwater flow lines.

B. Vertical flow paths from starting positions to discharge 

points projected onto the model cross section for row 34.

EXPLANATION

Approximate extent of coal refuse

Starting position (recharge point)

of groundwater-flow path

Coal refuse recharge area

West Little 

Sugar Creek

discharge area

Green Valley 

Mine Pond

discharge area

Row 34 of model grid (fig. 18)

700 1,400 2,100 2,800 FEET

0 175 350 525 700 METERS

0

Green Valley Mine Pond

John A.

Scott Lake

 LITTLE SUGAR CREEK

87°31’30” 87°31’15” 87°31’ 87°31’45”

39°30’45”

39°30’30”

WEST EAST

Figure 29. Simulated flow paths projected from points of recharge to row 34 near the center of the coal refuse to 

points of discharge, Green Valley mine site, Indiana.
52 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

inaccuracies in zone boundaries, the actual hydraulic 

conductivity of the coal refuse in any zone is low, 

and the calibrated hydraulic conductivities should 

be similar to actual ones. As such, any simulation is 

expected to adequately reflect the system response.

5. The shale bedrock was assumed to be a no-flow 

boundary. If the shale was actually capable of transporting water, then the travel time to the discharge 

points would increase. The increased travel times 

would further increase the potential for chemical 

changes in the effluent from the coal refuse.

Summary and Conclusions

A four-layer, finite-difference computer model of the area 

near the Green Valley reclaimed coal refuse site was constructed to simulate groundwater flow in the coal refuse and in 

the till beneath and near the refuse. The coal refuse is represented by one model layer, and the till deposits are represented 

by three layers that evenly divide the overall thickness of the 

till. The hydraulic properties of the till are uniform throughout 

the three till layers. 

The hydraulic properties of the coal refuse are defined 

by two zones; the first zone is the area of coal gob, and the 

second is areas where coal tailings were mixed with the gob. 

Thickness of the till was determined by creating surfaces for 

the top of bedrock (based on water-well log data) and for land 

surface (based on 10-ft land-surface contours), then subtracting the two surfaces. The thickness of the coal refuse was 

determined by creating a surface for the top of the coal refuse 

(based on 2-ft contours) and subtracting the land surface 

from the surface of the coal refuse. Model calibration consisted of 152 water-level measurements from 18 wells and 19 

streamflow measurements from four stream sections over 13 

months. The calibrated horizontal hydraulic conductivities for 

the area of gob and the area of gob and tailings are low, 0.75 

and 0.03 ft/d, respectively. The transient simulation with the 

calibrated model estimated water levels within an average of 

2.10 ft of actual values.

Some geophysical measurements indicated that groundwater flow directions were affected by engineered ditches. 

Horizontal flowmeter measurements in 2008 indicated that 

groundwater flow directions through wells near engineered 

ditches were affected by those structures. Flowmeter measured 

directions through wells nearer to the center of the refuse 

followed the prevailing hydraulic gradient from northeast to 

southwest. Results of a surface electromagnetic induction 

survey indicated that higher conductivity values coincided 

with engineered ditches—a possible indication of conductive 

acidic drainage. Some geophysical measurements indicated 

that groundwater flow directions were affected by engineered 

ditches. Horizontal flowmeter measurements in 2008 indicated 

that groundwater flow directions through wells near engineered ditches were affected by those structures. Flowmeter 

measured directions through wells nearer to the center of the 

refuse followed the prevailing hydraulic gradient from northeast to southwest. Results of a surface electromagnetic induction survey indicated that higher conductivity values coincided 

with engineered ditches—a possible indication of conductive 

acidic drainage, and with subsurface utilities or foundations of 

former on-site buildings. 

The calibrated model provided information about 

groundwater-flow rates, sources, directions, and travel times. 

The most reliable predictions are in the area of the coal refuse 

because almost all of the observations used to calibrate the 

model are from the area of coal refuse. Most of the discharge 

from the coal refuse (72 percent) is downward leakage into 

the till and not to the seeps. The seeps are fed mostly by 

precipitation recharge that infiltrates the coal refuse; however, 

a significant amount of seep discharge (24 percent) originates 

as flow from the till. Contours from the two layers in the area 

of coal refuse and groundwater flow paths indicate a mostly 

southwesterly and downward groundwater-flow direction. The 

horizontal flow direction through most of the coal refuse is 

towards West Little Sugar Creek. An approximate 5-ft vertical 

downward gradient is present between the coal refuse and the 

middle of the till. The water-level contours in the coal refuse 

and till also indicate some discharge to the seeps, but the area 

contributing that water is immediately adjacent to the seep 

channels. A groundwater divide trends northwest to southeast 

across the northeast corner of the coal refuse, and groundwater 

in that area flows to the northeast towards the Green Valley 

Mine Pond. Recharge to the coal refuse ultimately discharges 

to four major areas: West Little Sugar Creek, Green Valley Mine Pond, the downstream part of seep 4, and streams 

downgradient of the model area. Average travel time to these 

discharge areas ranges from about 80 to 150 years. A typical 

flow path from the coal refuse is vertically downward in the 

coal refuse, then more horizontal in the till deposits.

Model simulations provided insights into the flow system 

useful in guiding on-site reclamation, as well as reclamation 

at other sites. Results of the model simulations indicated that 

most of the discharge from the coal refuse (72 percent) is 

downward leakage into the till and not to the seeps. Twentyfour percent of the simulated flow is discharged from the till 

and to the seeps. Very little of the seep discharge comes from 

the coal refuse.
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Wu, Y.-S., C.-H. Lee and J.-L Yu, 2008, Effects of hydraulic 

variables and well construction on horizontal borehole 

flowmeter measurements. Groundwater Monitoring and 

Remediation, v. 28, no. 1, Winter 2008, p, 65–74.
Appendixes 1–4 55

Appendixes 1–4

Appendix 1: Measured groundwater levels ..................................................................................56

Appendix 2: Borehole geophysical logs of natural-gamma radiation............................................59

Appendix 3: Borehole geophysical logs of electromagnetic induction..........................................64

Appendix 4: Plots of aquifer-test data with fitted analytical-solution lines..................................67
Table A1. Groundwater levels measured at the Green Valley mine site, near Terre Haute, Indiana, 2008–9. [mm/dd/yyyy, month/day/year;—, not measured or determined; groundwater levels reported as altitudes in feet above National Geodetic Vertical Datum of 1988] Date measured (mm/dd/yyyy) Local well identifier1 GV1 GV2 GV3 GV4 GV7A GV7B GV8A GV8B GV8C GV9A 05/22/2008 — — 599.53 598.65 — — — — — — 06/02/2008 — 607.00 — — — — — — — — 06/05/2008 — — — 598.71 — — — — — — 06/12/2008 — — — 599.23 — — — — — — 06/19/2008 592.21 — — — — — — — — — 06/20/2008 — — — — 608.76 — — — — — 06/25/2008 — — — — — — 599.88 — — 583.506/26/2009 — — — — — — — — — — 06/27/2009 — — — — — — — — — — 09/04/2008 590.86 602.39 597.83 598.92 607.90 — 599.70 — 597.71 585.410/09/2008 591.79 601.89 597.14 598.65 607.31 — 599.41 — 597.51 585.011/05/2008 591.52 601.91 597.19 598.47 607.13 — 599.25 — 597.27 584.812/16/2008 592.93 603.01 598.24 598.01 606.83 — 598.97 — 597.04 584.301/20/2009 — 606.81 598.24 597.70 607.18 607.37 598.80 — 596.88 584.003/03/2009 592.91 608.94 598.57 597.42 607.29 607.38 598.76 598.62 596.80 583.904/15/2009 593.04 609.43 599.64 597.50 607.63 607.7 598.82 598.65 597.03 584.206/04/2009 593.03 607.61 599.71 598.49 608.41 608.65 599.61 599.48 597.59 585.507/14/2009 592.62 — 599.41 598.64 608.27 608.58 599.61 599.48 597.66 585.508/25/2009 — 604.14 — — — 608.09 — — — — 08/26/2009 591.85 — — — 607.73 — 599.53 599.41 597.31 — 08/27/2009 — — 598.53 — 607.76 — — — — — 08/31/2009 — — — — — — 599.51 — — 585.309/01/2009 — — — 598.65 — — — — — — 09/02/2009 — — — — — — — — — — 
Table A1. Groundwater levels measured at the Green Valley mine site, near Terre Haute, Indiana, 2008–9—Continued.[mm/dd/yyyy, month/day/year; —, not measured or determined; groundwater levels reported as altitudes in feet above National Geodetic Vertical Datum of 1988

Date 

measured 

(mm/dd/yyyy)

Local well identifier1

GV1 GV2 GV3 GV4 GV7A GV7B GV8A GV8B GV8C GV9A 

05/22/2008 — — — — — — — — — — 06/02/2008 — — — — — — — — — — 06/05/2008 — — — — — — — — — — 06/12/2008 — — — — — — — — — — 06/19/2008 — — — — — — — — — — 06/20/2008 — — — — — — — — — — 06/25/2008 — — — — — — — — — — 06/26/2008 594.01 — — — — 586.38 605.18 — — — 06/27/2008 603.40 — — 599.05 — — — — — — 09/04/2008 593.64 602.51 — 598.30 — 586.39 603.45 606.81 601.78 605.010/09/2008 593.54 602.10 — 597.74 — 586.33 602.63 606.29 601.06 604.211/05/2008 593.53 602.04 — 597.64 — — 602.36 606.27 600.86 603.712/16/2008 593.78 601.60 — 597.40 — 586.28 602.20 607.66 600.49 603.201/20/2009 593.82 601.84 601.86 598.10 597.54 586.21 603.58 609.18 600.93 604.103/03/2009 593.79 601.96 601.99 598.30 598.08 586.28 604.35 609.47 601.32 604.504/15/2009 594.02 602.75 602.76 598.87 598.70 586.40 606.25 610.31 602.69 605.806/04/2009 594.08 603.37 603.33 599.67 599.42 586.80 606.82 609.69 603.29 607.507/14/2009 594.00 602.90 602.88 599.19 598.88 586.34 607.11 609.07 602.91 606.608/25/2009 — — — — — — — — — — 08/26/2009 — — — — — 586.39 — 607.70 — — 08/27/2009 — — — — — — 604.52 — 602.25 605.508/31/2009 — — — — — — — — — — 09/01/2009 — 603.10 602.36 598.54 598.46 — — — — — 09/02/2009 593.75 — — — — — — — — — 
Table A1. Groundwater levels measured at the Green Valley mine site, near Terre Haute, Indiana, 2008–9.—Continued. [mm/dd/yyyy, month/day/year;—, not measured or determined; groundwater levels reported as altitudes in feet above National Geodetic Vertical Datum of 1988] Date measured (mm/dd/yyyy) Local well identifier1 GV19 GV20 GV21 GV22 05/22/2008 — — — — 06/02/2008 — — — — 06/05/2008 — — — — 06/12/2008 — — — — 06/19/2008 — — — — 06/20/2008 — — — — 06/25/2008 — — — — 06/26/2008 — — — — 06/27/2008 — — — — 09/04/2008 595.44 587.5 580.35 563.20 10/09/2008 595.43 586.87 580.01 562.85 11/05/2008 595.46 586.57 579.81 562.30 12/16/2008 595.43 586.94 579.64 562.84 01/20/2009 595.43 588.31 582.2 563.83 03/03/2009 595.43 588.75 580.54 564.07 04/15/2009 596.18 589.19 581.13 565.62 06/04/2009 595.21 — 581.58 565.90 07/14/2009 598.02 589.09 581.07 565.03 08/25/2009 — 588.01 — — 08/26/2009 — — — — 08/27/2009 — — — — 08/31/2009 — — 580.42 563.68 09/01/2009 — — — — 09/02/2009 — — — — 1Sites are shown on figure 4.
01020304050607080 GV1 GV2 GV3 GV4 0 60 120 180 01020304050607080 01020304050607080 01020304050607080 0 60 120 180 0 60 120 180 0 60 120 

EXPLANATION Natural gamma activity (raw data) Natural gamma activity (smoothed)

DEPTH, IN FEET BELOW LAND SURFACE

NATURAL GAMMA ACTIVITY, IN COUNTS PER SECOND

[393046087304801] [393047087310501] [393035087305601] [393039087310

Figure A2–1. Borehole geophysical logs of natural-gamma radiation for wells GV1, GV2, GV3 and GV4. U.S. Geological Survey well identifier in brackabove each plot.
01020304050607080 GV7A GV8C GV9A GV1

DEPTH, IN FEET BELOW LAND SURFACE

NATURAL GAMMA ACTIVITY, IN COUNTS PER SECOND

0

1020304050607080

0

1020304050607080

0

1020304050607080 0 60 120 180 0 60 120 180 0 60 120 180 0 60 

EXPLANATION

Natural gammaactivity (raw data)Natural gammaactivity (smoothed)

[393045087305901] [393042087310303] [393039087311001] [39304408

Figure A2–2. Borehole geophysical logs of natural-gamma radiation for wells GV7A, GV8C, GV9A, and GV10. U.S. Geological Survey well identifier in above each plot.
0

1020304050607080

GV11A GV12A GV13 GV1

DEPTH, IN FEET BELOW LAND SURFACE

NATURAL GAMMA ACTIVITY, IN COUNTS PER SECOND

0 60 120 180 0 60 120 180 0 60 120 180 0 60 

EXPLANATION

Natural gammaactivity (raw data)Natural gammaactivity (smoothed)

0

1020304050607080

0

1020304050607080

0

1020304050607080

[393040087305501] [393036087305901] [393035087310901] [3930430

Figure A2–3. Borehole geophysical logs of natural-gamma radiation for wells GV11A, GV12A, GV13, and GV14. U.S. Geological Survey well identifier above each plot. 
01020304050607080 GV15 GV16 GV17 GV1

DEPTH, IN FEET BELOW LAND SURFACE

NATURAL GAMMA ACTIVITY, IN COUNTS PER SECOND

0 60 120 180 0 60 120 180 0 60 120 180 0 60 

0

1020304050607080

0

1020304050607080

0

1020304050607080

EXPLANATION

Natural gammaactivity (raw data)Natural gammaactivity (smoothed)

[393046087310101] [393038087305001] [393032087305201] [39303608

Figure A2–4. Borehole geophysical logs of natural-gamma radiation for wells GV15, GV16, GV17 and GV18. U.S. Geological Survey well identifier in above each plot.
0

1020304050607080

GV19 GV20 GV21 GV22

0 60 120 180 0 60 120 180 0 60 120 180 0 60 120 

0

1020304050607080

0

1020304050607080

0

1020304050607080

EXPLANATION

Natural gammaactivity (raw data)Natural gammaactivity (smoothed)

DEPTH, IN FEET BELOW LAND SURFACE

NATURAL GAMMA ACTIVITY, IN COUNTS PER SECOND

[393042087310701] [393042087311201] [393038087311501] [393039087311901

Figure A2–5. Borehole geophysical logs of natural-gamma radiation for wells GV19, GV20, GV21 and GV22. U.S. Geological Survey well identifier in brackets above each plot. 
10203040506070800 GV1 10203040506070800 10203040506070800 10203040506070800 GV2 GV3 GV

0 200 400 600 800 0 200 400 600 800 0 200 400 600 800 0 200 40

ELECTRICAL CONDUCTIVITY, IN MILLISIEMENS PER METER

DEPTH, IN FEET BELOW LAND SURFACE

[393046087304801] [393047087310501] [393035087305601] [39303908

Figure A3–1. Borehole geophysical logs of electromagnetic induction for wells GV1, GV2, GV3 and GV4. U.S. Geological Survey well identifier in braceach plot. 
GV7A

1020304050607080

0

0 200 400 600 800

ELECTRICAL CONDUCTIVITY, IN MILLISIEMENS PER METER

DEPTH, IN FEET BELOW LAND SURFACE

GV8A GV9A GV10

0 200 400 600 800 0 200 400 600 800 0 200 400 600 

1020304050607080

0

1020304050607080

0

1020304050607080

0

[393045087305901] [393042087310303] [393039087311001] [393044087310

Figure A3–2. Borehole geophysical logs of electromagnetic induction for wells GV7A, GV8A, GV9A, and GV10. U.S. Geological Survey well identifier brackets above each plot.
ELECTRICAL CONDUCTIVITY, IN MILLISIEMENS PER METER0 200 400 600 800 01020304050607080 GV14

DEPTH, IN FEET BELOW LAND SURFACE

GV11A GV12A

0 200 400 600 800 0 200 400 600 800

0

1020304050607080

0

1020304050607080

[393040087305501] [393036087305901] [393043087305201]

Figure A3–3. Borehole geophysical logs of electromagnetic induction for wells GV11A, GV12A, and GV14. U.S. Geological Survey well identifier in brackets above each plot.
Appendix 4: Plots of aquifer-test data with fitted analytical-solution lines 67

Appendix 4: Plots of aquifer-test data with fitted analytical-solution lines

Appendix 4. Plots of aquifer-test data with fitted analytical-solution lines Water-level displacement. in feet

Figure 4–1. Time-displacement graph and the solution for the KGS method for well GV2 at the Green Valley site, 

near Terre Haute, Indiana (K = 0.10 feet per day). Well GV2 is screened in till.

Observation in well GV2

Aquifer model used for 

analysis: Unconfined 

Solution used for analysis: KGS model

Parameters from analysis:

Hydraulic conductivity (horizontal) = 0.1047 ft/day

Specific storage = 0.0003092 ft

Ratio of vertical to horizontal hydraulic conductivity = 0.2

-1

10.

1.

0.1

0.01

0 600 1,200 1,800 2,400 3,000

Time, in seconds

Figure A4–1. ime-displacement graph and the solution for the KGS method for well GV2 at the Green Valley site, 

near Terre Haute, Indiana (K = 0.10 feet per day). Well GV2 is screened in till.
68 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

Observation in well GV7A

Aquifer model used for 

analysis: Unconfined 

Solution used for analysis: Bouwer-Rice model

Parameters from analysis:

Hydraulic conductivity (horizontal) = 0.2315 feet/day

Y-axis intercept of solution= 0.2136 feet

Figure 4–2. Time-displacement graph and the solution for the Bouwer and Rice method for well GV7A at the 

Green Valley site, near Terre Haute, Indiana (K = 0.23 feet per day). Well GV7A is predominantly screened in coal gob. Water-level displacement, in feet

1.

0.1

0.01

0 1,500 3,000 4,500 6,000 7,500

Time, in seconds

Figure A4–2. Time-displacement graph and the solution for the Bouwer and Rice method for well GV7A at the Green Valley site, 

near Terre Haute, Indiana (K = 0.23 feet per day). Well GV7A is predominantly screened in coal gob.
Appendix 4: Plots of aquifer-test data with fitted analytical-solution lines 69

Figure 4–3. Time-displacement graph and the solution for the Bouwer and Rice method for well GV11A 

at the Green Valley site, near Terre Haute, Indiana (K = 0.49 feet per day).

Observation in well GV11A

Aquifer model used for 

analysis: Unconfined 

Solution used for analysis: Bouwer-Rice model

Parameters from analysis:

Hydraulic conductivity (horizontal) = 0.4892 feet/day

Y-axis intercept of solution= 0.3341 feet

0 2,000 4,000 6,000 8,000 10,000

Time, in seconds

Water-level displacement, in feet

1.

0.1

0.01

Figure A4–3. Time-displacement graph and the solution for the Bouwer and Rice method for well GV11A 

at the Green Valley site, near Terre Haute, Indiana (K = 0.49 feet per day).
70 Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site, near Terre Haute, Indiana

Figure 4–4. Time-displacement graph and the solution for the Bouwer and Rice method for well GV12A at the 

Green Valley site, near Terre Haute, Indiana (K = 0.03 feet per day). Well GV12A is predominantly screened in coal gob.

0 800 1,600 2,400 3,200 4,000

Time, in seconds

Water-level displacement, in feet

1.

0.1

0.5

0.4

0.3

0.2

0.6

0.7

0.8

0.9

Observation in well GV12A

Aquifer model used for 

analysis: Unconfined 

Solution used for analysis: Bouwer-Rice model

Parameters from analysis:

Hydraulic conductivity (horizontal) = 0.02852 feet/day

Y-axis intercept of solution= 0.3098 feet

Figure A4–4. Time-displacement graph and the solution for the Bouwer and Rice method for well GV12A at the Green Valley 

site, near Terre Haute, Indiana (K = 0.03 feet per day). Well GV12A is predominantly screened in coal gob.

Bayless and others— Hydrogeology and Simulation of Groundwater Flow at the Green Valley Reclaimed Coal Refuse Site near Terre Haute, Indiana—SIR 2011–5116