U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the 

U.S. Air Force, Arnold Air Force Base

Hydrogeology and Simulation of Ground-Water Flow at 

Arnold Air Force Base, Coffee and Franklin Counties, 

Tennessee—2002 Update

J4

Scientific Investigations Report 2006–5157
Cover.  Map showing backward particle tracking from dewatering facilities at the Main Test Area at Arnold Air Force Base.

(Aerial photograph courtesy of the U.S. Air Force, Arnold Air Force Base.)
Hydrogeology and Simulation of Ground-Water Flow at 

Arnold Air Force Base, Coffee and Franklin Counties, 

Tennessee—2002 Update

By Connor J. Haugh

Prepared in cooperation with the

U.S. Air Force, Arnold Air Force Base

Scientific Investigations Report 2006–5157

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark Myers, Director

U.S. Geological Survey, Reston, Virginia: 2006

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Suggested citation:

Haugh, C.J., 2006, Hydrogeology and simulation of ground-water flow at Arnold Air Force Base, Coffee and Franklin 

Counties, Tennessee—2002 update: U.S. Geological Survey Scientific Investigations Report 2006–5157, 70 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................1

Previous Studies ...................................................................................................................................4

Description of Study Area ...................................................................................................................4

Geology............................................................................................................................................................4

Hydrogeology..................................................................................................................................................5

Aquifers ..................................................................................................................................................5

Ground-Water Withdrawals.....................................................................................................11

Ground- and Surface-Water Interactions .............................................................................11

Flow Boundaries ........................................................................................................................13

Recharge.....................................................................................................................................13

Ground-Water Flow...................................................................................................................18

Water Levels...............................................................................................................................18

Simulation of Ground-Water Flow.............................................................................................................22

Previous Ground-Water Flow Model...............................................................................................22

Conceptual Model...............................................................................................................................22

Model Assumptions............................................................................................................................23

Model Boundaries ..............................................................................................................................23

Model Construction............................................................................................................................23

Model Calibration................................................................................................................................28

Sensitivity Analysis.............................................................................................................................35

Advective Flow Particle Tracking..............................................................................................................35

Pre-Ground-Water Withdrawal Wells Particle Tracking .............................................................36

Ground-Water Withdrawal Wells Particle Tracking.....................................................................37

Dewatering Facilities Particle Tracking..........................................................................................38

Model Limitations................................................................................................................................38

Summary........................................................................................................................................................46

Selected References...................................................................................................................................47

Appendix. Comparison of measured and simulated water-level altitudes for the

Arnold Air Force Base area ground-water flow model........................................................51
iv

Figures

1–2. Maps showing—

    1.  Location of study area at Arnold Air Force Base,

Coffee and Franklin Counties, Tennessee .........................................................................2

    2.  Location of Solid Waste Management Units and ground-water contaminant

plumes at Arnold Air Force Base........................................................................................3

3.  Chart showing stratigraphy, lithology, and hydrogeologic units in the

Arnold Air Force Base area ........................................................................................................4

4–7. Maps showing—

    4.  Altitude of the top of the Chattanooga Shale in the Arnold Air Force Base area ......6

    5.  Altitude of the top of the bedrock surface in the Arnold Air Force Base area...........7

    6.  Thickness of bedrock above the Chattanooga Shale in the

Arnold Air Force Base area .................................................................................................8

    7.  Location of wells with hydraulic-conductivity measurements at

Arnold Air Force Base ..........................................................................................................9

8.  Graph showing ranges of hydraulic conductivity from wells and

fracture zones at Arnold Air Force Base ................................................................................10

9–11. Maps showing—

 9. Location of ground-water withdrawal wells and dewatering facilities

in the Arnold Air Force Base area ....................................................................................12

    10. Location of springs in the Arnold Air Force Base area.................................................14

    11. Regional flow boundaries for the Arnold Air Force Base area....................................15

12. Graphs showing precipitation and estimated recharge for the

Arnold Air Force Base area, from 1960 to 2005......................................................................16

13–14. Maps showing—

    13. Altitude of the potentiometric surface of the Manchester aquifer

in the Arnold Air Force Base area, October 2002...........................................................19

    14. Location of selected wells with continuous water-level data

in the Arnold Air Force Base area ....................................................................................20

15–16. Graphs showing—

    15. Water levels in selected wells in the Arnold Air Force Base area

from 2001 to 2006 .................................................................................................................21

    16. Water levels in wells 353, 359, 201, 551, 305, 464, and Sinking Pond

from 2001 to 2006 .................................................................................................................22

17.  Model grid and cell types for the ground-water flow model of the

Arnold Air Force Base area ......................................................................................................24

18–25. Maps showing—

    18. Distribution of simulated recharge zones for the ground-water flow model

of the Arnold Air Force Base area....................................................................................26

    19. Hydraulic-conductivity zones for model layer 2 of the

Arnold Air Force Base area ...............................................................................................27

    20. Hydraulic-conductivity zones for model layer 3 of the

Arnold Air Force Base area ...............................................................................................29

    21. Vertical anisotropy zones for model layer 1 of the

Arnold Air Force Base area ...............................................................................................30
Figures—continued

    22. Simulated steady-state water levels for layer 1 of the

Arnold Air Force Base area ground-water flow model.................................................31

    23. Simulated steady-state water levels for layer 2 of the

Arnold Air Force Base area ground-water flow model.................................................32

    24. Simulated steady-state water levels for layer 3 of the

Arnold Air Force Base area ground-water flow model.................................................33

    25. Simulated steady-state water levels for layer 4 of the

Arnold Air Force Base area ground-water flow model.................................................34

  26. Graph showing simulated and observed water levels and distribution of residuals

for the Arnold Air Force Base area ground-water flow model ...........................................35

27. Boxplot showing distribution of residuals by layer for the Arnold Air Force Base

area ground-water flow model.................................................................................................35

28. Diagram showing distribution of water-budget components among the layers

of the digital flow model for the Arnold Air Force Base area..............................................37

29. Graph showing composite-scaled sensitivities for model parameters.............................38

30–36. Maps showing—

    30. Forward particle tracking from SWMU 1&2, SWMU 5, SWMU 8,

and SWMU 10 at Arnold Air Force Base with no ground-water

withdrawal wells pumping.................................................................................................39

    31. Forward particle tracking from SWMU 10 at Arnold Air Force Base under

an alternative calibration of the flow model ...................................................................40

    32. Forward particle tracking from SWMU 1&2, SWMU 5, SWMU 8,

and SWMU 10 at Arnold Air Force Base with ground-water

withdrawal wells pumping.................................................................................................41

    33. Forward particle tracking from SWMU 1&2 at Arnold Air Force Base

with the airfield road ground-water withdrawal wells pumping.................................42

    34. Forward particle tracking from the Main Test Area (SWMU 74) at

Arnold Air Force Base with all dewatering facilities turned on ..................................43

    35. Forward particle tracking from the Main Test Area (SWMU 74) at

Arnold Air Force Base with all dewatering facilities turned off..................................44

    36. Backward particle tracking from dewatering facilities at the

Main Test Area at Arnold Air Force Base........................................................................45

Tables

1. Sites used to calculate total flow per square mile in the

Arnold Air Force Base model area ..........................................................................................11

2. Estimated annual water budget for the Arnold Air Force Base area

from 1960 to 2005.........................................................................................................................17

3. Recharge and hydraulic-conductivity parameters defined in the

Arnold Air Force Base area ground-water flow model........................................................25

4. Comparison of simulated and measured flows for the

Arnold Air Force Base area ground-water flow model........................................................28

5. Correlation coefficients between estimated parameters of the

Arnold Air Force Base area ground-water flow model........................................................36
vi

Conversion Factors

Multiply By To obtain

Length

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)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2)

Flow rate

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)

cubic foot per second per square

mile [(ft3/s)/mi2]

0.01093 cubic meter per second per square

kilometer [(m3/s)/km2]

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)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

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).

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.
Hydrogeology and Simulation of Ground-Water Flow at 

Arnold Air Force Base, Coffee and Franklin Counties, 

Tennessee—2002 Update

By Connor J. Haugh

Abstract

Arnold Air Force Base (AAFB) occupies about

40,000 acres in the eastern part of the Highland Rim physiographic region in Coffee and Franklin Counties, Tennessee.

The area is characterized by fractured carbonate rock terrane

that complicates evaluation of ground-water flow. Numerous site-specific ground-water contamination investigations

have been conducted at designated Solid Waste Management

Units (SWMUs) at AAFB. Several synthetic volatile organic

compounds (VOCs), primarily chlorinated solvents, have been

identified in the ground water at AAFB. Two ground-water

contaminant plumes that originate at AAFB, the “SWMU 8

plume” and the “northwest plume,” have been shown to extend

to regional discharge points outside the AAFB boundary. In

2002, the U.S. Geological Survey (USGS), in cooperation

with the U.S. Air Force, AAFB, began an investigation to

further refine the understanding of the regional ground-water

system in the AAFB area and to update the previous computer

ground-water flow model incorporating new data and information collected since 1992.

The updated ground-water flow model incorporates

revised structure maps of the top-of-rock surface and the top

of the Chattanooga Shale and the preferential regional flow

paths identified by investigations conducted since 1992. The

preferential regional flow paths play an important role in

ground-water movement and contaminant transport in the

AAFB area. The model is calibrated to steady-state conditions

defined by detailed water-level and streamflow data collected

in 2002. Particle-tracking simulations were used with the

model to simulate ground-water flow paths and travel times

from selected sites at AAFB. The flow paths indicated by the

particle-tracking simulations agree reasonably well with maps

of interpreted contaminant plumes.

Currently (2005), ground-water withdrawal wells are

operating at SWMU 1&2, SWMU 5, SWMU 8, and SWMU 10,

and dewatering occurs at many facilities at the Main Test Area

(MTA). Particle-tracking results show that no particles leave

these SWMUs while the ground-water withdrawal wells are

pumping. Three particle-tracking simulations were run to

analyze the effects of dewatering facilities on flow paths at the

MTA. These simulations indicate that the dewatering facilities

have a substantial effect on flow paths from the MTA and are

effective in containing most of the ground water in this area.

Introduction

Arnold Air Force Base (AAFB) occupies about

40,000 acres in Coffee and Franklin Counties, Tennessee

(fig. 1). The primary mission of AAFB is to support the development of aerospace systems. The mission is accomplished

in part through test facilities at Arnold Engineering Development Center (AEDC), which occupies about 4,000 acres in the

center of AAFB.

Numerous site-specific ground-water contamination

investigations have been conducted at designated Solid Waste

Management Units (SWMUs) at AAFB (fig. 2). Several

synthetic volatile organic compounds (VOCs), primarily chlorinated solvents, have been identified in the ground

water at AAFB. In 1992, the U.S. Geological Survey (USGS)

completed a study of the hydrogeology of the AAFB area.

This study included defining the regional ground-water flow

system and simulating the flow system using a computer

model (Haugh and Mahoney, 1994). Since then (1992), two

ground-water contaminant plumes that originate at AAFB,

the “SWMU 8 plume” and the “northwest plume,” have been

shown to extend to regional discharge points outside the

AAFB boundary (fig. 2) (CH2M Hill, 1999, 2001). In 2002,

the USGS, in cooperation with the U.S. Air Force, AAFB,

began an investigation to further refine the understanding of

the regional ground-water system in the AAFB area and to

update the previous computer ground-water flow model by

incorporating new data and information collected since 1992.

Purpose and Scope

Revisions to maps and interpretation of the hydrogeology of the AAFB area that appeared in previously published

reports prepared by the USGS are provided in this report.

Information from the previous reports is updated for use

in the construction and calibration of an updated regional

ground-water flow model. This report documents the updated
Figure 1.  Location of study area at Arnold Air Force Base, Coffee and Franklin Counties, Tennessee.

Tullahoma

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

Manchester

EXPLANATION

ARNOLD ENGINEERING DEVELOPMENT CENTER

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

BOUNDARY OF ARNOLD AIR FORCE BASE

HIGHLAND RIM ESCARPMENT

SURFACE-WATER DRAINAGE DIVIDE

Woods Reservoir

Estill

Springs

0 2 4 MILES

0 2 4 KILOMETERS

41

24

55

Alt 41

Crumpton Cr

The Barrens

Spring Cr

Bradley Cr

FRANKLIN CO

COFFEE CO

Sinking Pond

Normandy

Lake

Duck River Basin

Elk River Basin

Tims Ford Lake

J4 test

 cell

Coastal Plain

Highland

Rim Central

Basin Cumberland

Plateau

Valley and Ridge

Blue Ridge

Sequatchie Valley

TENNESSEE

Study area

   Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 2.  Location of Solid Waste Management Units (SWMUs) and ground-water contaminant plumes at

Arnold Air Force Base.

Tullahoma

EXPLANATION

PLUME

SWMU SITE

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 KILOMETERS

0 2 4 MILES

35O30'

86O15' 85O56'

35O15'

Estill

Springs

Manchester

Northwest plume

SWMU 5

SWMU 10

SWMU 74

SWMU 1&2

SWMU 8

SWMU 8 plume

41

24

Alt 41

Big Spring at

Rutledge Falls

ARNOLD ENGINEERING DEVELOPMENT CENTER

Introduction 
regional flow model and presents a description and the results

of advective-flow particle-tracking simulations that were

used to evaluate ground-water flow directions and to estimate

time-of-travel from selected locations at AAFB. The updated

ground-water flow model will provide a tool to help manage

the ground-water resources in the AAFB area.

Previous Studies

Haugh and Mahoney (1994) summarized important studies

published prior to 1990. Since then, studies of interest include:

site-specific ground-water contamination studies that

investigate the “SWMU 8” plume (CH2M Hill, 1999;

ATA, 2004), the “northwest plume” (CH2M Hill, 2001),

and the SWMU 10 site (COLOG, 2002; CH2M Hill,

written commun.);

water-quality data and local potentiometric surface maps

(Aycock and Haugh, 2001; Williams and Aycock, 2001;

Williams, 2003);

a detailed study of the effect of the J4 rocket motor test

cell on the local hydrogeology (Haugh, 1996a, 1996b);

studies about the Sinking Pond area (Wolfe, 1996; Wolfe

and League, 1996; and Wolfe and others, 2004);

study of stream base flows (Robinson and Haugh,

2004); and

1.

2.

3.

4.

5.

regional potentiometric surface maps (Mahoney and Robinson, 1993; CH2M Hill, 2001; Robinson and others, 2005).

Description of Study Area

AAFB lies on the eastern Highland Rim physiographic

region of Tennessee (Miller, 1974) and ranges from poorly

drained, flat uplands to valley-dissected, sloping escarpments.

A major surface-water divide separating the Duck and Elk

River drainages bisects AAFB extending from the southwest

to the northeast (fig. 1). Land-surface elevations range from

1,120 feet (ft) above NGVD 29 in the northeastern corner

of the study area at the crest of the drainage divide to about

890 ft above NGVD 29 at the southern tip of the study area

near Tims Ford Lake.

Geology

The AAFB area is located in a fractured carbon­ate terrane

covered by regolith derived from the in-situ weathering of carbonate rocks of Mississippian age. The stratigraphy underlying

the AAFB area consists predominantly of impure carbonate

rocks and some shales (fig. 3). From oldest to youngest, the

strata are Devonian and Mississippian Chattanooga Shale and

Mississippian Fort Payne Formation, Warsaw Limestone, and

6.

Stratigraphy Thickness, 

in feet Lithology Hydrogeologic unit AAFB unit designation

Model 

layer Remarks

Regolith derived

from in-situ

weathering of

the St. Louis

Limestone, Warsaw Limestone,

or Fort Payne

Formation

10–100

Clay, silt, and

sand with some

chert and rock

fragments.

Highland

Rim

aquifer

system

Shallow

aquifer

Shallow

aquifer 1

Low-producing wells,

shallow groundwater circulation,

low dissolved solids,

and bicarbonate

dominant anion.

Rock fragments,

chert gravel,

and rubble with

some clay.

Manchester

aquifer, upper part

Intermediate

aquifer 2 Good-producing wells,

rapid ground-water

circulation, low

dissolved solids, and

bicarbonate dominant anion.

Fort Payne

Formation 20–240

Fractured and

dissolutioned cherty

limestone and

siltstone.

Manchester

aquifer,

lower part

Deep aquifer

3

Dark gray

siltstone;

dense, cherty

limestone; and

bedded chert. 

Few fractures.

Fort Payne

aquifer 4

Low well yield, slow

ground-water

circulation, high

dissolved solids, and

high sulfates.

Chattanooga Shale 20–30

Dark grayish

black, carbonaceous shale.

Chattanooga

confining

unit

Chattanooga

confining

unit

--

Confining unit. Base of

fresh groundwater flow system.

Figure 3. Stratigraphy, lithology, and hydrogeologic units in the Arnold Air Force Base (AAFB) area (modified from Haugh and

Mahoney, 1994).

 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
St. Louis Limestone. Both the Chattanooga Shale and the Fort

Payne Formation crop out in the northwest section of the study

area along the escarpment of the Highland Rim. Since the

1992 regional study (Haugh and Mahoney, 1994) many new

wells and geophysical studies have yielded additional data

about the structure of the top of the Chattanooga Shale and

the top of the bedrock surface. Maps of both of these surfaces

have been reinterpreted and updated jointly by the USGS and

AEDC (figs. 4 and 5).

The Chattanooga Shale ranges from 20 to 30 ft thick in

the study area and is dark grayish black, fissile, and carbonaceous. The Chattanooga Shale surface shows an anticline that

crests under AEDC and is nearly coincident with the regional

drainage divide (fig. 4). The Chattanooga Shale is an important marker bed throughout parts of the eastern United States

because it is a widespread unit with consistent characteristics.

The Chattanooga Shale is overlain by the Fort Payne Formation. In the AAFB area, the Fort Payne Formation as rock

ranges from less than 20 to 240 ft thick (fig. 6) and consists

of dark gray siltstone and cherty limestone with thin beds of

crinoidal limestone and minor amounts of shale. Weathering

of the Fort Payne Formation has occurred to irregular depths,

and may be structurally controlled in some areas. Several

troughs are evident in the bedrock surface. The most prominent trough is northwest of AEDC in the Crumpton Creek

Basin where the top-of-bedrock elevation drops from 980 ft

to 920 ft along a 2-mile-long linear feature (fig. 5). Fracturing

is evident within the Fort Payne Formation with the largest

fractures generally near the bedrock/regolith contact where

they have been enlarged through dissolution. These dissolution

enlarged openings typically are a couple of inches in height;

however, solution enlarged cavities as much as 6 ft in height

have been observed in the Fort Payne Formation at AAFB

(Haugh and others, 1992). Cavities are more common in the

northern part of the study area where the unweathered section

of bedrock is the thickest (Haugh and others, 1992; COLOG,

2002). Most cavities contain mud, gravel, chert, and rock

fragments. Fractures appear to be less common in the lower

part of the unit with the exception of the contact with the Chattanooga Shale where water­-bearing fractures have been noted

(COLOG, 2002).

Regolith derived from weathering of carbonate rocks

of Mississippian age (including in ascending order, the Fort

Payne Formation, Warsaw Limestone, and/or St. Louis Limestone) is 10 to 100 ft thick in the AAFB area. Regolith thickness tends to decrease in the northern half of the study area.

The Warsaw and St. Louis Limestones have been weathered

almost completely to chert, silt, sand, gravel, and clay. Typically, the regolith grades upward from gravel-size chert rubble

at the top of bed­rock to clay-size chert particles with silt, sand,

and clay at land surface (Burchett, 1977). A more thorough

description of the geology and hydrogeologic framework

of the AAFB and surrounding area is presented in previous

reports by Haugh and Mahoney (1994) and Haugh (1996a).

Hydrogeology

The Highland Rim aquifer system is the ground-water

system of interest in the study area (Brahana and Bradley,

1986a, 1986b). The Highland Rim aquifer system can be

divided into several different zones or aquifers (fig. 3). Hydrogeologic investigations by AEDC have typically designated

the aquifers as shallow, inter­mediate, and deep (CH2M Hill,

2001). The 1992 regional ground-water study (Haugh and

Mahoney, 1994) divided the system into three aquifers: the

shallow, Manchester, and Fort Payne aquifers (fig. 3). The

aquifers differ from one another in degree of weathering,

amount of chert, and type of weathering product. The aquifers are not separated by confining units of substantial lateral

extent; therefore, water is able to flow between these zones

at most locations. The Chattanooga Shale is the base of the

Highland Rim aquifer system.

Aquifers

Hydraulic-conductivity data are available from slug or

aquifer tests conducted at 187 wells in the Highland Rim

aquifer system (figs. 7 and 8) (ATA, 2004; Battelle Columbus

Division, 1988, 1989a, 1989b; Battelle Denver Operations,

1989; Benham Group, 1989a, 1989b; CH2M Hill, 1999, 2001;

Dames and Moore, 1975; Engineering Science, 1984; Oak

Ridge National Laboratory, 1989a, 1989b; Post, Buckley,

Schuh and Jernigan, Inc., 1989a, 1989b, 1989c, 1989d, 1989e;

Science Applications International Corporation, 1990; U.S.

Army Corp of Engineers, Mobile District, 1988a, 1988b; and

Woodward-Clyde Consultants, 1990). If a well had more than

one reported hydraulic-conductivity value, an average value

was calculated for the well. Values of hydraulic conductivity from well tests range from 0.09 to 450 feet per day (ft/d)

(fig. 8). Additionally, hydraulic-conductivity measurements are

available for 88 discrete fracture zones in 10 wells to the north

and northeast of AEDC where the bedrock thickens (COLOG,

2002). Values of hydraulic conductivity from discrete fracture

zones range from 0.08 to 3,980 ft/d (fig. 8).

The shal­low aquifer, as designated by the USGS and

AEDC, is described as consisting of alluvium, residual silt,

clay, sand, and clay-size chert particles of the upper part of

the regolith (Haugh and Mahoney, 1994). Ground water in the

shallow aquifer occurs under water-table conditions and may

be perched in some locations. Based on 54 well tests, hydraulic conductivity within the shallow aquifer ranges from 0.09 to

40 ft/d with a median value of 1.5 ft/d (fig. 8). The thickness

of the shallow aquifer ranges from 0 to 100 ft with an average

of about 30 ft.

The Manchester aquifer, the primary source of drinking water in the area, consists of chert gravels at the base of

the regolith and solution open­ings in the upper part of the

bedrock (Burchett and Hollyday, 1974). The upper part of the

Hydrogeology 
Figure 4.  Altitude of the top of the Chattanooga Shale in the Arnold Air Force Base area.

Tullahoma

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Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 MILES

0 2 4 KILOMETERS

EXPLANATION

ARNOLD ENGINEERING DEVELOPMENT CENTER

STRUCTURE CONTOUR—Shows altitude of the

 top of the Chattanooga Shale. Contour interval

 20 feet. Hachures indicate depression. Datum

 is NGVD 29

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

WELL OR OUTCROP USED AS CONTROL

35O30'

86O15' 85O56'

35O15'

Estill

Springs

Manchester

880

41

24

Alt 41

 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 5.  Altitude of the top of the bedrock surface in the Arnold Air Force Base area.

Tullahoma

980

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880

960

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1040

1060

1000

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1000

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980

1040

940

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O55'

35O15'

0 2 4 MILES

0 2 4 KILOMETERS

Estill

Springs

Manchester

EXPLANATION

ARNOLD ENGINEERING DEVELOPMENT CENTER

TOP OF ROCK CONTOUR—Shows altitude of the top

 of the bedrock surface. Contour interval 20 feet.

 Hachures indicate depression. Datum is NGVD 29

HYDROLOGIC BOUNDARY—Delineation of regional

 ground-water flow system underlying Arnold Air

 Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

WELL USED AS CONTROL

900

41

24

Alt 41

Crumpton

Creek

Hydrogeology 
Figure 6.  Thickness of bedrock above the Chattanooga Shale in the Arnold Air Force Base area.

Tullahoma

60

40

80

100

120

140

20

160

180

200

220

240

120

120

120

60

40

20

60

120

140

20

120

20

40

60

20

160

180

80

120

40

20

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100

20

40

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100

80

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40

ARNOLD ENGINEERING DEVELOPMENT CENTER

41

24

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

EXPLANATION

LINE OF EQUAL THICKNESS OF BEDROCK—

 Contour interval 20 feet

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

35O30'

86O15' 85O56'

35O15'

Manchester

Estill

Springs

0 2 4 MILES

0 2 4 KILOMETERS

20

Alt 41

BOUNDARY OF ARNOLD AIR FORCE BASE

 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 7.  Location of wells with hydraulic-conductivity measurements at Arnold Air Force Base.

Tullahoma

EXPLANATION

SWMU SITE

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

WELL—Shows location of well with hydraulic-

 conductivity measurement

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 KILOMETERS

0 2 4 MILES

35O30'

86O15' 85O56'

35O15'

Estill

Springs

Manchester

SWMU 5

SWMU 10

SWMU 74

SWMU 1&2

SWMU 8

41

24

Alt 41

ARNOLD ENGINEERING DEVELOPMENT CENTER

Hydrogeology 
Manchester aquifer, consisting of chert gravels at the base

of the regolith, is designated as the intermediate aquifer by

AEDC. The lower part of the Manchester aquifer, consisting of

solution openings in the top of bedrock, is included in the deep

aquifer as designated by AEDC and is sometimes referred to

as the upper part of the deep aquifer (fig. 3). Ground water in

the Manchester aquifer occurs under confined conditions in

areas where fine-grained materials in the shallow aquifer serve

as a leaky confining unit. Based on 108 well tests, hydraulic

conductivity within the upper part of the Manchester aquifer

ranges from 0.22 to 450 ft/d with a median value of 8.7 ft/d

(fig. 8). The upper part of the Manchester aquifer is typically

about 10 ft thick. The lower part of the Manchester aquifer is

typically 1 to 30 ft thick in the southern half of the study area

0.01

0.1

1

10

100

1,000

10,000

HYDRAULIC CONDUCTIVITY, IN FEET PER DAY

Shallow aquifer well test (model layer 1)

Upper part of Manchester aquifer

well test (model layer 2)

Lower part of Manchester aquifer and Fort Payne

aquifer well test (model layers 3 and 4)

Lower part of Manchester aquifer

fracture zone test (model layer 3)

Fort Payne aquifer fracture

zone test (model layer 4)

NUMBER OF DATA POINTS

EXTREME VALUE

75th PERCENTILE

MEDIAN

25th PERCENTILE

54 108 25 59 29

EXPLANATION

and 40 to 170 ft thick in the northeastern part of the study

area. Well tests for hydraulic conductivity for the lower part

of the Manchester aquifer are discussed with the Fort Payne

aquifer because many of the wells tested screen both the lower

part of the Manchester aquifer and the Fort Payne aquifer.

Hydraulic conductivity for 59 fracture zones in the lower part

of the Manchester aquifer ranges from 0.08 to 3,980 ft/d with

a median of 32 ft/d (fig. 8).

The Fort Payne aquifer is included in the deep aquifer

as designated by AEDC and is sometimes referred to as the

lower part of the deep aquifer (fig. 3). The Fort Payne aquifer

consists of dense limestone in the lower part of the bedrock

where fractures and solution openings are less developed.

Fractures appear to be less common in the Fort Payne aquifer

with the exception of the contact with the Chattanooga Shale

where water-bearing fractures have been observed (COLOG,

2002). The Fort Payne aquifer typically is 1 to 15 ft thick in

the southern half of the study area and 20 to 85 ft thick in the

northeastern part of the study area. Hydraulic conductivity for

29 fracture zones in the Fort Payne aquifer ranges from 0.05 to

882 ft/d with a median of 0.9 ft/d (fig. 8). Hydraulic conductivity from well tests in 25 wells screened in both the lower

part of the Manchester aquifer and the Fort Payne aquifer,

ranges from 0.02 to 23 ft/d with a median value of 1.1 ft/d

(fig. 8). The base of the Fort Payne aquifer is the Chattanooga

Shale (Haugh and Mahoney, 1994; Haugh, 1996a).

Well yields in the AAFB area range from less than

1 gallon per minute (gal/min) to more than 500 gal/min

(Burchett, 1977; Haugh and Mahoney, 1994). This variability

in well yields results from heterogeneities within the aquifers

and can be observed over distances as short as 100 ft (Haugh,

1996a). In the lower part of the Manchester aquifer, wells

that intercept a fracture or fracture zone produce more water

than those that do not intercept fracture zones. Similarly, in

the upper part of the Manchester aquifer, wells screened in

a chert-gravel zone produce more water than those screened

outside of a gravel zone. The presence of these high permeability features within the aquifer creates a system that is heterogeneous and anisotropic on a local scale (Haugh, 1996a).

Since the 1992 regional study, several important pathways in

the regional flow system have been identified. These pathways

appear to be preferential regional flow zones of high permeability within the Manchester aquifer that share the following

characteristics: a depression or trough in the bedrock surface,

a trough in the ground-water surface, low gradients in the

ground-water surface, and a large spring or group of springs at

the downgradient end. The most studied of these pathways is

in the Crumpton Creek Basin where surface-geophysical, geologic, water-quality, and water-level data have been analyzed

to document the flow path of the “northwest plume,” which

discharges to Big Spring at Rutledge Falls (fig. 2) (CH2M

Hill, 2001; Williams, 2003).

No measured values for vertical hydraulic conductivity exist in the study area, but in most settings, the vertical

hydraulic conductivity is smaller than the horizontal hydraulic

conductivity (Heath, 1989). Vertical anisotropy in settings

Figure 8.  Ranges of hydraulic conductivity from wells and

fracture zones at Arnold Air Force Base.

10 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
similar to the study area typically ranges from 100:1 to 2:1

(Freeze and Cherry, 1979). Horizontal layering can increase

the vertical anisotropy, but vertical fractures can decrease vertical anisotropy (Freeze and Cherry, 1979). Vertical hydraulic

gradients at well clusters generally are small indicating small

vertical anisotropy over most of the study area. In some local

areas, water levels in the shallow aquifer appear to be perched,

creating large vertical hydraulic gradients between the shallow

and Manchester aquifers. In these areas, the vertical anisotropy in the shallow aquifer may be greater than in the rest

of the study area. Also, geophysical logging and hydraulic

testing of bedrock wells indicate that in most wells tested,

fractures in the upper and lower parts of the bedrock are not

interconnected (COLOG, 2002). This indicates greater vertical anisotropy in the Fort Payne aquifer compared with the

Manchester aquifer.

Ground-Water Withdrawals

Ground water is withdrawn at numerous locations at

AAFB for two primary reasons: ground-water withdrawal

associated with ground-water contamination and dewatering

activities around below-grade testing facilities. Ground-water

withdrawal wells are currently operating at SWMU 1&2,

SWMU 5, SWMU 8, and SMWU 10 (figs. 2 and 9). Pumping

rates from the withdrawal wells range from less than 1 gal/min

to about 27 gal/min. Dewatering activities also occur at more

than 20 facilities at AEDC (fig. 9). Dewatering at these facilities typically occurs through a gravity drain system whereby

water flows to a sump and then is pumped to the surface. The

deepest and most important of the dewatering systems is at the

J4 test cell, which extends approximately 250 ft below land

surface and dewaters at an average rate of about 105 gal/min

(Haugh, 1996a, 1996b). The other dewatering facilities range

in depth from about 5 to 80 ft below land surface with estimated average ground-water flow rates ranging between less

than 1 and 40 gal/min (CH2M Hill, written commun., 2005).

Ground- and Surface-Water Interactions

Ground water naturally discharges at streams and springs

in the study area. Flow was measured at 109 stream and spring

sites in and nearby the study area during high and low baseflow conditions in 2002 (Robinson and Haugh, 2004). Most

of the ground-water discharge occurs in the lower reaches of

streams within the study area and to streams and springs that

form the boundaries of the study area (Robinson and Haugh,

2004, figs. 3 and 4). Values of flow per square mile for all

sites measured by Robinson and Haugh (2004, table 8) were

0.55 cubic foot per second per square mile [(ft3/s)/mi2] during

high base-flow conditions and 0.37 (ft3/s)/mi2 during low baseflow conditions. Analyzing only those sites that have most of

Table 1. Sites used to calculate total flow per square mile in the Arnold Air Force Base model area.

[Data from Robinson and Haugh, 2004; mi2, square mile; ft3/s, cubic foot per second; (ft3/s)/mi2, cubic foot per second per square mile]

Basin Station 

number

Basin area 

(mi2)

June 2002 October 2002

Stream discharge, 

instantaneous (ft3/s)

Flow per square 

mile [(ft3/s)/mi2]

Stream discharge, 

instantaneous (ft3/s)

Flow per square 

mile [(ft3/s)/mi2]

Bradley Creek 03578502 45.49 34.5 0.76 13 0.29

Possum Branch 03578515 1.90 0.32 0.17 0.19 0.10

Brumalow Creek 03578700 4.13 1.36 0.33 0.28 0.07

Brumalow Creek 03578716 1.06 0 0 0 0

Hardaway Branch 03578725 0.75 0 0 0 0

Rowland Creek 03578988 1.02 0 0 0 0

Spring Creek 03579040 9.29 10.4 1.12 8.32 0.90

Spring Creek 03579050 0.28 0.36 1.29 0.16 0.57

Taylor Creek 03579502 2.92 5.42 1.86 0.71 0.24

Dry Creek 035795035 4.75 7.09 1.49 7.45 1.57

Rock Creek 03579680 36.5 19.0 0.52 13.5 0.37

Cat Creek 03596023 1.24 0.36 0.29 0.41 0.33

Bates Spring Branch 03596025 1.30 0.59 0.45 0.48 0.37

Crumpton Creek 03596120 27.04 12.7 0.47 7.62 0.28

Ovoca Lake 03596201 3.68 1.43 0.39 1.13 0.31

Bobo Creek 03596298 8.32 1.19 0.14 1.21 0.15

Machine Falls Branch 03596298 1.43 0.61 0.43 0.41 0.29

Bobo Creek (Short Spring) 03596300 0 9.22 0 5.16 0

All sites 151.2 104 0.69 59.9 0.40

Hydrogeology 11
Figure 9.  Location of ground-water withdrawal wells and dewatering facilities in the Arnold Air Force Base area.

Tullahoma

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

Manchester

EXPLANATION

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

DEWATERING FACILITY

GROUND-WATER EXTRACTION WELL

Woods Reservoir

Estill

Springs

0 2 4 MILES

0 2 4 KILOMETERS

24

41

Alt 41

SWMU 5

wells

SWMU 1&2

wells

Airfield Road

wells SWMU 10

wells

SWMU 8

wells

J4 test

 cell

ARNOLD ENGINEERING DEVELOPMENT CENTER

12 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
their drainage areas within the study area results in average

flow values of 0.69 (ft3/s)/mi2 in high base-flow conditions and

0.40 (ft3/s)/mi2 during low base-flow conditions (table 1).

An aerial thermography study conducted in 2000 identified 481 potential springs in and around the AAFB area (JAVA

Corporation, 2000; CH2M Hill, 2001); 114 of these potential springs were field verified (fig. 10) (CH2M Hill, written

commun, 2002). Most of these springs are located near the

boundaries of the study area (fig. 10).

Flow Boundaries

A ground-water divide, approximately coinciding with

the Duck River-Elk River surface-water divide, underlies

AAFB and extends from southwest to northeast. Ground water

flows from the divide area to the discharge areas, which are

the major streams, springs, lakes, and reservoirs around the

base. The regional discharge areas define the lateral extent of

the ground-water flow system at AAFB. The boundaries of the

flow system for this study are the same as defined by the 1992

regional study (Haugh and Mahoney, 1994). Moving counterclockwise from the northeastern corner of the study area

(fig. 11), the lateral boundaries of the system are:

Roan Buck Branch, from the head to the confluence with

Wolf Creek;

Wolf Creek, from the confluence with Roan Buck Branch

to the confluence with Little Duck River;

Little Duck River, from the confluence with Wolf Creek

to the Chattanooga Shale outcrop at Little Falls;

the Highland Rim escarpment from the Little Falls in the

Little Duck River to Ovoca Falls on Carroll Creek;

Carroll Creek, from the Chattanooga Shale outcrop at

Ovoca Falls to the head;

an imaginary flow line from the head of Carroll Creek

to the Duck River-Elk River drainage divide, normal to

the divide;

another imaginary flow line from the Duck River-Elk

River drainage divide, normal to the divide to the head of

an unnamed creek;

the unnamed creek, from the head to the confluence with

North Fork Rock Creek;

North Fork Rock Creek, from the confluence with the

unnamed creek to the confluence with Rock Creek;

Rock Creek, from the confluence with North Fork Rock

Creek to the mouth at Tims Ford Lake;

Tims Ford Lake, from the mouth of Rock Creek to the

mouth of the Elk River;

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

Elk River, from the mouth at Tims Ford Lake to

Woods Reservoir;

Woods Reservoir, from the outlet point to the Elk River to

the mouth of Bradley Creek;

Bradley Creek, from the mouth at Woods Reservoir to the

confluence with Blue Spring Creek;

Blue Spring Creek, from the confluence with Bradley

Creek to the head;

an imaginary flow line from the head of Blue Spring

Creek to the Duck River-Elk River drainage divide, normal to the divide; and

a final imaginary flow line from the Duck River-Elk River

drainage divide, normal to the divide to the head of Roan

Buck Branch.

Water levels of Woods Reservoir and Tims Ford Lake

remain relatively constant throughout the year (Flohr and others, 2003). At the northwestern boundary, numerous seeps and

springs drain the ground-water system where the Chattanooga

Shale crops out along the Highland Rim escarpment.

Recharge

In the study area, recharge occurs from direct infiltration

of precipitation throughout the study area. The 1992 regional

ground-water model (Haugh and Mahoney, 1994) used two

recharge zones with recharge rates of 10 inches per year

(in/yr) along the regional drainage divide and 6 in/yr throughout the remaining area. These rates were based on a regional

study by Hoos (1990) in which recharge rates for drainage

basins across Tennessee were estimated using a hydrographseparation technique. Hoos (1990) reported annual recharge

rates during years of average streamflow for drainage basins in

the Highland Rim Physiographic Province of Tennessee ranging from 4.9 to 9.8 inches (in.).

To improve estimates of recharge, the current study also

used a water-budget method to estimate ground-water recharge

and to examine the variations in recharge annually. A simple

water budget, assuming ground-water withdrawals are insignificant, can be described by the following equations:

If PR = ET + SM + SF

and SF = DR + GWD

and assuming GWD = GWR,

then PR = ET + SM + DR + GWR

where

PR is the mean precipitation,

ET is the mean evapotranspiration,

SM is soil moisture storage,

SF is the mean streamflow,

DR is mean direct runoff,

GWD is mean ground-water discharge, and

GWR is mean ground-water recharge.

12.

13.

14.

15.

16.

17.

Hydrogeology 13
Figure 10.  Location of springs in the Arnold Air Force Base area.

Tullahoma

EXPLANATION

ARNOLD ENGINEERING DEVELOPMENT CENTER

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

BOUNDARY OF ARNOLD AIR FORCE BASE

GROUND-WATER DIVIDE—Thinner line represents

 subdivide

HIGHLAND RIM ESCARPMENT

GROUND-WATER TROUGH—Arrow indicates ground-

 water flow direction

FIELD-VERIFIED SPRING

POTENTIAL SPRING FROM THERMOGRAPHY

 SURVEY (JAVA Corporation, 2000)

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

0 2 4 MILES

0 2 4 KILOMETERS

Manchester

Estill

Springs

Bobo Cr

Short Spring

Big Spring at

Rutledge Falls

Crumpton Cr

Sinking Pond

Spring Cr

Dry Cr

Bradley Cr

41

24

Alt 41

14  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 11.  Regional flow boundaries for the Arnold Air Force Base area.

Tullahoma

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

EXPLANATION

ARNOLD ENGINEERING DEVELOPMENT CENTER

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water-flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

SURFACE-WATER DRAINAGE DIVIDE

Estill

Springs

Manchester

Woods Reservoir

Duck

River

Bradley

Creek

55

Alt 41

Normandy

Lake

Ovoca

Falls

Unnamed Carroll Cr

N Fork

Rock Cr

Rock Cr

Elk River

Rowland Cr

Spring Cr

Crumpton Cr

Little Falls

Roan Buck Br

Sinking

Pond

Brumalow

Cr

BradleyCr

Tims Ford Lake

Blue Spring Cr

Wolf Cr

0 2 4 KILOMETERS

0 2 4 MILES

41

24

Taylor Cr

Dry Cr

Bobo Cr

Bates Spring Br

Cat Cr

Duck River Basin

Elk River Basin

Little Duck River

Hydrogeology 15
Using monthly mean precipitation and temperature data

archived by the National Climatic Data Center (NCDC) for

Tullahoma, Tennessee (NCDC station 409155), a Thornwaite water-budget method was used for this investigation to

estimate the amount of precipitation that is lost to evapotranspiration in the study area (McCabe and others, 1985). If the

evapotranspiration demand is greater than precipitation, then

soil moisture storage is used to make up the deficit. If precipitation is greater than evapotranspiration, the surplus water first

replenishes soil moisture storage then supports streamflow

either by direct runoff or by recharging the ground-water system, which then discharges, supplying base flow to streams.

Total streamflow is proportioned into direct runoff and

ground-water discharge using a stream base-flow index, which

estimates the portion of mean annual streamflow attributed

to base flow. A national study by Wolock (2003a) estimates a

base-flow index for the AAFB study area of 32 to 34 percent.

The base-flow index at individual streamgages within the

AAFB study area ranged from 22.4 to 40.9 percent (Wolock,

2003b). Using monthly mean precipitation and temperature

data from Tullahoma and assuming a baseflow index of 30 percent, an annual water

budget for the study area was estimated

for the period from 1960 to 2005 (table 2,

fig. 12). The average annual recharge from

this method is 8.1 in/yr with a median of

8.4 in/yr. Annual estimates ranged from

1.3 in. for 1981 to 13.0 in. for 1994.

Wolfe and others (2004) in a study

of the Sinking Pond Basin on AAFB

developed a hydrologic model based on

a water-balance approach. Sinking Pond

is a seasonally ponded karst depression

located in The Barrens along the regional

drainage divide (fig. 1). During much of

the year, Sinking Pond is filled with water

and provides a constant rate of recharge to

the ground-water system. For the period

1990–2002, the Sinking Pond hydrologic

model produces an average basin recharge

rate of 9.09 in/yr and an average pond

recharge rate of 110 in/yr (W.J. Wolfe,

U.S. Geological Survey, written commun., 2004). The basin recharge rate

represents rainfall that occurs in the basin

and infiltrates through the soil to recharge

the ground water. The Sinking Pond

Basin average recharge rate of 9.09 in/yr

compares favorably with the 1992 regional

ground-water model rate of 10 in/yr for

areas along the drainage divide. The pond

recharge rate represents water that drains

through the bottom of the pond to recharge

the ground water and is a concentrated

source of recharge that is unique to

Sinking Pond.

The distribution of recharge throughout the study area

was further investigated by conducting a detailed stream baseflow study in 2002 (Robinson and Haugh, 2004). Stream

base flows were measured in June and October 2002 at

109 sites. The average flow per square mile for all sites

that have most of their drainage area within the modeled

area was 0.69 (ft3/s)/mi2 in June 2002 and 0.40 (ft3/s)/mi2

in October 2002 (table 1). Expressing these flows in typical recharge units of inches per year would result in 9.2 and

5.4 in/yr, respectively. Data presented by Robinson and Haugh

(2004) show that a group of drainage basins located in the

southwestern part of the study area have higher base flows

(two times or more) compared to other basins throughout the

study area. These basins include Spring Creek, Dry Creek

(near Estill Springs), and Taylor Creek with average flows of

1.35 (ft3/s)/mi2 or 18.3 in/yr in June 2002 and 0.96 (ft3/s)/mi2

or 13.1 in/yr in October 2002. The higher base flows imply

conditions in these basins allow for greater recharge rates

compared to other basins in the study area. A visual inspection

of a stream discharge hydrograph for three sites in the study

Figure 12.  Precipitation and estimated recharge for the Arnold Air Force Base

area, from 1960 to 2005. 1960 1962 1964 1966 1968 1970 1972

1974197619781980198219841986198819901992199419961998200020022004

0

0

10

20

20

15

10

5

30

40

50

60

70

80

90

PRECIPITATION, IN INCHES PER YEAR

Average

RECHARGE, IN INCHES PER YEAR

Average

16  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Table 2. Estimated annual water budget for the Arnold Air Force Base area from 1960 to 2005.

[All values are in inches per year]

Year Precipitation Evapotranspiration Streamflow Direct runoff Recharge Soil moisture

storage

1960 44.1 30.7 13.4 9.4 4.0 0.0

1961 57.8 30.8 27.0 18.9 8.1 0.0

1962 61.2 31.1 30.1 21.1 9.0 0.0

1963 47.8 31.6 18.5 13.0 5.6 –2.3

1964 65.4 33.2 29.8 20.9 9.0 2.3

1965 45.1 33.0 14.3 10.0 4.3 –2.2

1966 49.1 31.3 15.5 10.9 4.7 2.2

1967 58.8 31.1 27.6 19.3 8.3 0.0

1968 45.0 29.4 19.3 13.5 5.8 –3.7

1969 58.1 30.7 23.7 16.6 7.1 3.7

1970 50.7 32.3 18.4 12.9 5.5 0.0

1971 56.3 33.1 23.2 16.2 7.0 0.0

1972 67.6 32.1 35.5 24.9 10.7 0.0

1973 76.8 34.0 42.8 30.0 12.8 0.0

1974 65.5 32.6 32.9 23.0 9.9 0.0

1975 66.1 31.7 34.4 24.1 10.3 0.0

1976 50.5 29.9 20.6 14.4 6.2 0.0

1977 62.4 33.5 28.9 20.3 8.7 0.0

1978 50.5 32.9 17.7 12.4 5.3 0.0

1979 67.4 31.5 35.9 25.1 10.8 0.0

1980 46.3 31.1 21.4 15.0 6.4 –6.2

1981 42.4 31.8 4.4 3.1 1.3 6.2

1982 62.2 32.1 30.1 21.1 9.0 0.0

1983 61.4 29.7 31.7 22.2 9.5 0.0

1984 55.5 31.3 24.2 16.9 7.3 0.0

1985 42.1 32.7 9.9 6.9 3.0 –0.5

1986 53.7 33.4 19.7 13.8 5.9 0.5

1987 44.7 32.3 12.4 8.7 3.7 0.0

1988 47.9 29.2 18.6 13.0 5.6 0.0

1989 73.6 31.7 41.9 29.3 12.6 0.0

1990 72.9 33.1 39.8 27.9 11.9 0.0

1991 64.5 31.9 32.6 22.8 9.8 0.0

1992 55.8 29.0 26.8 18.8 8.0 0.0

1993 51.8 29.4 22.3 15.6 6.7 0.0

1994 74.6 31.4 43.3 30.3 13.0 0.0

1995 62.0 31.9 30.1 21.1 9.0 0.0

1996 65.6 29.9 35.7 25.0 10.7 0.0

1997 70.2 29.3 41.0 28.7 12.3 0.0

1998 75.2 34.8 40.4 28.3 12.1 0.0

1999 56.3 31.2 29.1 20.3 8.7 –3.9

2000 58.3 31.2 23.2 16.3 7.0 3.9

2001 60.9 31.3 29.6 20.7 8.9 0.0

2002 58.8 30.9 27.9 19.5 8.4 0.0

2003 72.4 31.9 40.5 28.3 12.1 0.0

2004 72.9 32.9 40.0 28.0 12.0 0.0

2005 39.2 30.7 11.1 7.8 3.3 –2.61

Average 58.4 32.7 26.9 18.8 8.1 –0.1

Hydrogeology 17
area show that Spring Creek has fewer peaks and higher base

flows than the other sites, Little Duck River and Crumpton

Creek (Robinson and Haugh, 2004, fig. 2). This further supports the concept that in the Spring Creek Basin more recharge

occurs, which results in less runoff and higher base flows.

Based on this information, the AAFB study area can be

divided into four areas with different recharge rates. The four

areas are: The Barrens area along the regional drainage divide;

the Spring Creek, Dry Creek (at Estill Springs), and Taylor

Creek Basins in the southwestern part of the study area; Sinking Pond; and the rest of the study area.

Ground-Water Flow

Regional potentiometric surface maps of the Manchester aquifer for May and October 2002 (Robinson and others,

2005) show that the topography and surface drainage patterns

influence ground-water flow in the AAFB area (fig. 13). The

AEDC facility is on the regional ground-water divide, which

runs southwest to northeast and generally coincides with the

Duck River-Elk River surface-water divide. A broad saddle

in the main ground-water divide separates a ground-water

high southwest of AEDC from a larger, broader ground-water

high north of AEDC. Ground water generally flows from the

regional ground-water divide area toward the northwest or

toward the south or southeast, and discharges to the principal

streams and reservoirs (Mahoney and Robinson, 1993; Haugh

and Mahoney, 1994; Robinson and others, 2005).

Several troughs are present in the potentiometric surface.

The most prominent trough trends northwest to southeast in

the Crumpton Creek Basin (fig. 13) (Robinson and others,

2005, figs. 2 and 4). This trough parallels the main axis of

Crumpton Creek, but generally is not coincident with Crumpton Creek, but is aligned with a trough in the bedrock surface

(fig. 5). During seasonal water-level lows in October 2002,

this trough extended upgradient and toward the northeast to

the Sinking Pond area (fig. 13) (Robinson and others, 2005,

fig. 4). At the downgradient end of this trough is Big Spring at

Rutledge Falls which has a steady discharge of about 3.3 ft3/s

(Williams and Farmer, 2003). Similar troughs in the potentiometric surface exist in the Bradley Creek Basin and discharge

to several springs along the lower reach of Bradley Creek,

in the Spring Creek Basin and discharge to several springs

along the lower reach of Spring Creek, in the Dry Creek

Basin and discharge to Estill Springs, and in the Bobo Creek

Basin and discharge to Short Springs (fig. 13) (Robinson

and others, 2005, figs. 2 and 4; Robinson and Haugh, 2004,

tables 3 and 5). These troughs in the potentiometric surface

are believed to be associated with zones of high permeability within the aquifer that are important regional flow paths

(Haugh, 1996a; CH2M Hill, 1999, 2001; ACS, 2002).

Water Levels

Natural seasonal fluctua­tions of the water table are

related to seasonal changes in precipitation and evapotranspiration and, thus, to changes in ground-water recharge. Groundwater lev­els normally are highest during the spring months

fol­lowing the winter period of high precipitation and low

evapotranspiration. Water levels recede during the summer in

response to diminishing precipitation and higher evapotranspiration and are lowest in the fall. Hydrographs of wells at

AAFB exhibit these characteristic seasonal variations (figs. 14,

15, and 16) (Haugh and others, 1992, figs. 4–6; Haugh and

Mahoney, 1994, figs. 15–22; Haugh, 1996a, figs. 14–16; and

Robinson and others, 2005, fig. 5). Seasonal water-level fluctuations range from about 5 ft to greater than 25 ft. In general,

water-level fluctuations are 10 to 15 ft (AEDC-135, -146,

-185, -305, -551). The smallest water-level fluctuations occur

near the regional discharge areas (AEDC-189, figs. 14 and 15).

The largest water-level fluctuations occur in the northern half

of the study area (AEDC-177, -353, -359, -488, figs. 14, 15,

and 16).

The larger seasonal water-level fluctuations in the

northern half of the study area result in seasonal water-level

gradient reversals locally between the area just north of the

retention pond (as represented by wells AEDC-551 and -305)

and the area around Sinking Pond (as represented by wells

AEDC-359, -201, and 353) (figs. 14 and 16). This gradient

change coincides with the draining and filling of Sinking Pond

(fig. 16). The seasonal change in water-level gradients in this

area may explain the broad spreading observed in the “northwest plume” in the area north of the retention pond (fig. 2).

This gradient change existed for about 4 months during

average rainfall years of 2001 and 2002, 6 months during the

lower than average rainfall year of 2005, and less than 1 month

during the higher than average rainfall year of 2004 (figs. 12

and 16). Regionally, ground water throughout this area (as

represented by wells AEDC-551, -305, -201, -359, and -353)

flows toward the ground-water trough of the Crumpton Creek

Basin (as represented by well AEDC-464) (figs. 14 and 16).

Natural vertical hydraulic gradients between aquifers are

typically small (less than 3 ft). Large natural vertical gradients

(greater than 5 ft) have been noted locally between the shallow

and Manchester aquifers where ground water in the shallow

aquifer appears to be perched, and between the lower part of

the Manchester aquifer and the Fort Payne aquifer at a few

well clusters in the northern part of the study area where the

bedrock is thick (greater than 100 ft).

18  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 13.  Altitude of the potentiometric surface of the Manchester aquifer in the Arnold Air Force Base area,

October 2002. (Robinson and others, 2005.)

Tullahoma

960

920

980

1020

1000

940

1040

1060

1080

1100

960

960 980

1000

1020

1040

1020

960

1000

940

960

1060

960

1000

980

940

1020

1020

980

1020

1040

1000

960

980

940

1060

1080

1040

1000 1000

960

1020

980

1040

980

960

1000

1040

1040

960

980

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

Manchester

EXPLANATION

ARNOLD ENGINEERING DEVELOPMENT CENTER

POTENTIOMETRIC-SURFACE CONTOUR—Shows

 altitude at which water level would have stood in

 tightly cased wells. Dashed where approximately

 located. Hachures indicate depression. Contour

 interval 20 feet. Datum is NGVD 29

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

BOUNDARY OF ARNOLD AIR FORCE BASE

GROUND-WATER DIVIDE—Thinner line represents

 subdivide

HIGHLAND RIM ESCARPMENT

GROUND-WATER TROUGH—Arrow indicates ground-

 water flow direction

WELL OR SPRING IN WHICH WATER-LEVEL

 MEASUREMENT WAS USED AS CONTROL

Woods Reservoir

Estill

Springs

0 2 4 MILES

0 2 4 KILOMETERS

41

24

55

Alt 41

Crumpton Cr

Spring Cr

Bradley Cr

940

Sinking Pond

Hydrogeology 19
Figure 14.  Location of selected wells with continuous water-level data in the Arnold Air Force Base area.

41

24

Alt 41

Tullahoma 189

146

698

305

551

473 464 488

201

353

185 359

177

135

EXPLANATION

ARNOLD ENGINEERING DEVELOPMENT CENTER

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

SURFACE-WATER DRAINAGE DIVIDE

WELL—Shows location and number of well

 with continuous water-level data

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

0 2 4 MILES

0 2 4 KILOMETERS

Manchester

Estill

Springs

Crumpton Cr

Sinking Pond

Spring Cr

Bradley Cr

146

BOUNDARY OF ARNOLD AIR FORCE BASE

20 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 15.  Water levels in selected wells in the Arnold Air Force Base area from 2001

to 2006.

1,010

1,020

1,030

1,040

1,050

1,060

1,070

1,080

1,090

1,010

1,000

990

980

970

1,020

1,030

1,040

1,050

1,060

1,070

1,080

1,090

W

A

TER LEVEL AL

TITUDE, IN FEE

T

AEDC-135

AEDC-189

AEDC-464

AEDC-488

AEDC-201

AEDC-185

AEDC-177

AEDC-698

AEDC-146 AEDC-551

AEDC-177

AEDC-473

AEDC-305

2001 2002 2003 2004 2005 2006

Hydrogeology 21
Simulation of Ground-Water Flow

The physical system described in the hydrogeology section of this report provides the framework for development of

a ground-water flow model for AAFB. The resulting model

provides a useful tool to test the understanding and concepts of the ground-water flow system. Although a model is

necessarily a simplification of the physical system, the model

should be consistent with all known hydrogeologic observations. The ground-water flow model code used in this study,

MODFLOW-2000 (Harbaugh and others, 2000), uses finitedifference techniques to solve the ground-water flow equation

for three-dimensional, steady or nonsteady flow in anisotropic,

heterogeneous media. The model simulations presented in this

report represent steady-state, average annual conditions.

Previous Ground-Water Flow Model

The 1992 ground-water flow model (Haugh and

Mahoney, 1994) provides the foundation for the current

updated flow model. The previous flow model was constructed

using MODFLOW88 (McDonald and Harbaugh, 1988) and

had 106 columns and 95 rows. Three layers, each of which

varied in thickness but had a uniform value of hydraulic conductivity, represented the shallow, Manchester, and Fort Payne

aquifers. Recharge was divided into two zones. The model was

calibrated using manual methods to minimize the difference

between simulated and observed water levels in 158 wells and

streamflows at 7 sites. The updated 2002 model, described

in this report, retains the same flow boundaries and basic

concepts as the previous model, but is a more detailed representation of the flow system.

Conceptual Model

The Highland Rim aquifer system was divided into four

layers to simulate ground-water flow (fig. 3). The layers were

defined on the basis of differences in physical characteristics

that affect hydrologic properties. Model layers are: layer 1

corresponds to the shallow aquifer, layer 2 corresponds to the

upper part of the Manchester aquifer, layer 3 corresponds to

the lower part of the Manchester aquifer, and layer 4 corresponds to the Fort Payne aquifer. Layers 2 and 3 are interconnected and support most of the regional ground-water flow

as indicated by hydraulic-conductivity and geochemical data

(Haugh and Mahoney, 1994). Layer 4, because of its lower

hydraulic conductivity, supports much less of the regional

ground-water flow. Geochemical and potentiometric data

indicate that the Chattanooga Shale is an effective underlying

confining unit for the Highland Rim aquifer system; therefore,

the Chattanooga Shale is the base of the model (Haugh and

Mahoney, 1994).

The streams draining the area are assumed to be hydraulically connected to layer 1 through leaky streambeds. Recharge

by direct infiltration of precipitation occurs across the study

area and is greater in The Barrens area north of AEDC and

in the Spring, Taylor, and Dry Creek Basins. The system

receives no subsurface recharge from outside the hydrologic

boundaries. Ground-water discharge occurs as flow to streams,

springs, Woods Reservoir, Tims Ford Lake, wells, and dewatering facilities.

Figure 16.  Water levels in wells 353, 359, 201, 551, 305, 464, and Sinking Pond from 2001

to 2006.

1,010

1,020

1,030

1,040

1,050

1,060

1,070

1,080

2001 2002 2003 2004 2005 2006

W

A

TER LEVEL AL

TITUDE, IN FEE

T

Sinking

Pond

AEDC-551

AEDC-353

AEDC-359

AEDC-359

AEDC-201

AEDC-305 Pond

dry

AEDC-464

22 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Model Assumptions

The following assumptions were made in the development of the flow model of the hydrologic system in the Arnold

Air Force Base area.

Fracture and dissolution zones are extensive enough in

both aerial and vertical distribution that the hydrogeologic

units can be simulated as porous media.

Over most of the model area, fracture and dissolution

openings are small enough that flow is laminar.

The upper model boundary is assumed to be the watertable surface.

The lower model boundary is assumed to be a no-flow

boundary corresponding to the Chattanooga Shale.

The hydraulic properties of hydrogeologic units are

homogeneous within a block of the finite-difference grid.

Flow within a layer is horizontal; flow between layers

is vertical.

The model grid is aligned with primary axes of fracture

traces and any anisotropy is uniform within a layer.

The ground-water system is a closed system.

Use of steady-state, annual average conditions is representative of long-term flow conditions for simulation of

advective transport with particle tracking.

Model Boundaries

The boundaries of the model correspond to natural

boundaries wherever possible and are the same as defined by

the 1992 regional study (Haugh and Mahoney, 1994) (fig. 11).

Most of the lateral boundaries are streams and are simulated as

head-dependent flow boundaries (river nodes) in layer 1 and

as no-flow boundaries in layers 2, 3, and 4. The western and

northern boundaries that are parts of the drainage divide are

simulated as no-flow boundaries in all layers. Along the southern boundary, Woods Reservoir is simulated as a constanthead boundary in layers 1 and 2. Tims Ford Lake, being

more deeply incised than Woods Reservoir, is simulated as a

constant-head boundary in layers 3 and 4. Layers 1 and 2 crop

out above the shoreline of Tims Ford Lake, therefore, water in

layers 1 and 2 must drain vertically to layers 3 or 4 to discharge to Tims Ford Lake. The northwestern boundary, where

all four layers crop out along the Highland Rim escarpment,

is simulated as head-dependent flow (drain nodes) in layers 3

and 4. In these areas, water in layers 1 and 2 must drain vertically to layers 3 or 4 to discharge from the model. Vertically,

the upper boundary of the model is the water table. The lower

boundary of the model is the Chattanooga Shale, which serves

as a no-flow boundary.

1.

2.

3.

4.

5.

6.

7.

8.

9.

Model Construction

The model grid is approximately a 12- by 17-mile

rectangle consisting of variably sized grid cells (fig. 17). The

grid consists of 150 columns and 132 rows. About 142 square

miles (mi2) of the model grid is active. The smallest grid cells,

located near the J4 test cell, are about 160 by 160 ft, and the

largest grid cells, located near the model boundaries, are about

1,300 by 1,300 ft. The grid is oriented N. 55o E., N. 35o W. so

that flow between model cells is parallel to the primary axes of

fracture traces (Haugh and Mahoney, 1994, figs. 7 and 8).

Model parameters (Harbaugh and others, 2000) were

defined for recharge and hydraulic-conductivity zones and

vertical and horizontal anisotropy (table 3). Recharge to the

model is from direct infiltration of precipitation. Based on

the information in the recharge section of this report, the

model was divided into four recharge zones representing the

following areas: The Barrens area along the regional drainage divide (RCH_divide); the Spring Creek, Dry Creek (at

Estill Springs), and Taylor Creek Basins (RCH_spcr); Sinking

Pond (RCH_sp); and the rest of the study area (RCH_base)

(fig. 18). The recharge rates for all zones were adjusted during

model calibration using ranges estimated from previous work

(described in the recharge section of this report) (table 3).

Recharge rates input to the model are net recharge rates; therefore, evapotranspiration of ground water, typically less than

2 in/yr (Rutledge and Mesko, 1996), is not explicitly included

in the model.

Hydraulic-conductivity zones were determined by

integrating information from several data sets. The spatial

distribution of the hydraulic-conductivity data set is highly

biased to the SWMU sites, so the distribution of values is not

adequate to define regional conductivity zones (fig. 7). Also,

the hydraulic-conductivity values represent point measurements and are highly variable at a small local scale. Which of

the point values are most appropriate to use in a model zone

is dependent on how the local heterogeneities are connected

on a regional scale. Therefore, the shapes of the hydraulicconductivity zones within the model layer are based more

on geology, lithology, top-of-rock surface, potentiometric

data, locations of important springs and discharge points,

conceptual models of the flow system, and trial and error

during model calibration than the distribution of the hydraulicconductivity data. The hydraulic-conductivity data set is used

to define a reasonable range of values for each layer (fig. 8).

Layer 1 consists of a uniform hydraulic-conductivity

value defined by hydraulic-conductivity parameter (HK_1).

Layer 2 consists of six hydraulic-conductivity zones (fig. 19).

The HK_3 zone covers most of the model area where data

indicate hydraulic conductivity is near the average of the unit.

Three of the zones (HK_5, HK_7, and HK_9) cover areas

where data indicate hydraulic conductivity is higher than

the average of the unit based on the following characteristics: a depression or trough in the bedrock surface, a trough

in the ground-water surface, low gradients in the groundwater surface, and a large spring or group of springs at the

Simulation of Ground-Water Flow 23
Figure 17.  Model grid and cell types for the ground-water flow model of the Arnold Air Force Base area.

0 2 4 MILES

0 2 4 KILOMETERS

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

24

41

EXPLANATION

CONSTANT HEAD

ACTIVE

RIVER

DRAIN

INACTIVE

CELL TYPE

BOUNDARY OF ARNOLD

 AIR FORCE BASE

24  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Table 3. Recharge and hydraulic-conductivity parameters defined in the Arnold Air Force Base area ground-water flow model.

Model parameter Description Initial estimates Calibrated value

RCH_base Recharge rate from direct infiltration of precipitation for

most of the study area.

5 to 8 inches per year 4.2 inches per year

RCH_divide Recharge rate from direct infiltration of precipitation in

The Barrens area of the divide.

7 to 10 inches per year 7.8 inches per year

RCH_spcr Recharge rate from direct infiltration of precipitation for

Spring, Taylor, and Dry Creek drainage areas.

13 to 18 inches per year 17.7 inches per year

RCH_sp Recharge rate from water that drains through the bottom of

Sinking Pond.

110 inches per year 110 inches per year

HK_1 Hydraulic conductivity for all of layers 1 and 4 and a small

part of layers 2 and 3.

0.3 to 6 feet per day 1.5 feet per day

HK_2 Hydraulic conductivity for parts of layers 2 and 3 where

data suggest hydraulic conductivity is lower than average

of the layer.

0.08 to 4 feet per day 0.2 foot per day

HK_3 Hydraulic conductivity for most of layers 2 and 3. 1 to 390 feet per day 21 feet per day

HK_4 Hydraulic conductivity for part of layer 3 near the

J4 test cell.

500 to 1,000 feet per day 1,000 feet per day

HK_5 Hydraulic conductivity for parts of layers 2 and 3 where

data suggest hydraulic conductivity is higher than

average of the layer.

20 to 2,000 feet per day 1,900 feet per day

HK_7 Hydraulic conductivity for layers 2 and 3 in the area of the

Crumpton Creek ground-water trough.

500 to 5,000 feet per day 6,500 feet per day

HK_9 Hydraulic conductivity for layers 2 and 3 in the areas of the

Spring Creek and Short Springs ground-water troughs.

500 to 5,000 feet per day 5,900 feet per day

VANI_1 Ratio of horizontal to vertical hydraulic conductivity for

most of layer 1.

10:1 to 100:1 21:1

VANI_1a Ratio of horizontal to vertical hydraulic conductivity for

part of layer 1 where water-level data show vertical gradient greater than 5 feet.

100:1 to 1,000:1 440:1

VANI_2 Ratio of horizontal to vertical hydraulic conductivity in

layer 2.

10:1 10:1

VANI_3 Ratio of horizontal to vertical hydraulic conductivity in

layer 3.

10:1 10:1

VANI_4 Ratio of horizontal to vertical hydraulic conductivity in

layer 4.

1,000:1 1,000:1

Horizontal anisotropy

(layers 1 and 2)

Ratio of hydraulic conductivity along column to hydraulic

conductivity along row.

1:1 1:1

Horizontal anisotropy

(layers 3 and 4)

Ratio of hydraulic conductivity along column to hydraulic

conductivity along row.

1:1 to 2:1 1.5:1

Simulation of Ground-Water Flow 25
Figure 18.  Distribution of simulated recharge zones for the ground-water flow model of the Arnold Air Force Base area.

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

0 2 4 MILES

0 2 4 KILOMETERS

24

41

RECHARGE ZONE

RCH_BASE—Recharge rate from direct

 infiltration of precipitation for most of

 the study area

RCH_DIVIDE—Recharge rate from direct

 infiltration of precipitation in The Barrens

 area of the divide

RCH_SPCR—Recharge rate from direct

 infiltration of precipitation for Spring,

 Taylor, and Dry Creek drainage areas

RCH_SP—Recharge rate from water that

 drains through the bottom of Sinking Pond

EXPLANATION

The Barrens

Spring Cr

Sinking Pond

Taylor Cr

Dry Cr

26  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 19.  Hydraulic-conductivity zones for model layer 2 of the Arnold Air Force Base area.
downgradient end of the zone. The other zones (HK_1 and

HK_2) are present where data indicate hydraulic conductivity is lower than the average of the unit. Layer 3 consists of

seven hydraulic-conductivity zones (fig. 20). The distribution of hydraulic-conductivity zones in layer 3 is identical to

layer 2 with the exception of an additional zone (HK_4) near

the J4 test cell. The HK_4 zone is present where fractures

create higher permeability as indicated by elongated waterlevel depressions around the J4 test cell (Haugh, 1996a).

Layer 4 consists of a uniform hydraulic-conductivity value

defined by parameter (HK_1). Horizontal anisotropy is not

simulated within layers 1 and 2, which represent the regolith,

but is simulated as a uniform value within layers 3 and 4,

which represent the bedrock. Vertical anisotropy is assumed

to be uniform within each layer except layer 1 where vertical

anisotropy is divided into two zones. In layer 1, a second zone

(VANI_1a) is present where water-level data indicate the difference in water levels is greater than 5 ft between the shallow

aquifer and upper part of the Manchester aquifer (fig. 21).

Stream reaches with perennial flow were simulated as

river nodes in layer 1 (fig. 17). Stream reaches that were dry

under both high and low base-flow conditions measured in

2002 were not simulated (Robinson and Haugh, 2004). The

remaining stream reaches, which had flow under high baseflow conditions but were dry under low base-flow conditions,

were simulated as drain nodes in layer 1. Large regional

springs were simulated as drain nodes. Woods Reservoir and

Tims Ford Lake were simulated by constant-head cells using

water-level altitudes of 960 and 888 ft, respectively (Flohr and

others, 2003).

Model Calibration

The process of adjusting the model input variables to

produce the best match between simulated and observed water

levels and flows is referred to as calibration. The digital model

developed for this study was calibrated to steady-state conditions as defined by averaging water-level and flow measurements from the spring and fall 2002 (Robinson and Haugh,

2004; Robinson and others, 2005). Precipitation during 2002

was near average, so these data should be representative of

average annual conditions (table 2). The model was calibrated

using a combination of parameter estimation and manual

methods to minimize the difference between simulated and

observed water levels, streamflows, and spring flows. Initial

calibration was done by fixing recharge to initial estimates and

using parameter estimation procedures to estimate the hydraulic conductivity. Additional parameter estimation calibrations

were then used to further refine the recharge parameters.

Final calibration runs estimated the recharge and hydraulicconductivity parameters together. Vertical anisotropy parameters for layers 2, 3, and 4 (VANI_2, VANI_3, and VANI_4)

were fixed during the calibration process because low sensitivities made them difficult to estimate.

Overall, simulated water levels agree reasonably well

with observed water levels (appendix; figs. 22, 23, 24, 25,

26, and 27). Water-level data at 615 wells were available for

comparison to simulated conditions (appendix). The root mean

square error (RMSE) was calculated to compare simulated and

measured water levels. The RMSE, in feet, is calculated by

2

1

/

N m c

i i

i

RMSE h h N =

æ ö = - ç ÷

ç ÷

ç ÷÷ è

å ø ,

where:

	 N is the number of observations;

hi

m is the measured water level, in feet; and

hi

c

is the simulated water level, in feet.

The RMSE for water levels is 9.8 ft. The average residual

or difference between measured and simulated water levels

is –0.47 ft. Seventy percent of the simulated water levels

are within 10 ft of observed water levels, and 95 percent are

within 20 ft. The range of residuals is similar in each layer.

The residuals show a small positive bias in layer 1 and a small

negative bias in layers 3 and 4 (fig. 27, appendix). The residuals show no significant spatial patterns (figs. 22, 23, 24, and

25). Simulated discharge fluxes to springs and streams are

within ranges of base flow measured in spring and fall 2002

(table 4).

Table 4. Comparison of simulated and measured flows for the Arnold Air Force Base area ground-water flow model.

Model-simulated streamflow, 

in cubic feet per second

Range of measured stream base flow from June 

and October 2002 (Robinson and Haugh, 2004), 

in cubic feet per second

Crumpton and Wiley Creeks 7.1 4.3 – 9.4

Big Spring at Rutledge Falls 3.3 3.1 – 3.5

Little Duck River 7.1 6.6 – 7.4

Bradley Creek 11.4 6.5 – 17.2

Spring Creek 10.3 8.5 – 10.8

Taylor and Dry Creeks 9.9 8.2 – 11.6

Rock Creek 5.3 6.7 – 9.5

J4 0.22 0.2 – 0.26

28  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 20.  Hydraulic-conductivity zones for model layer 3 of the Arnold Air Force Base area.

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

0 2 4 MILES

0 2 4 KILOMETERS

24

41

HYDRAULIC CONDUCTIVITY ZONE

HK_1—Hydraulic conductivity for all of layers

 1 and 4 and a small part of layers 2 and 3

HK_2—Hydraulic conductivity for parts of layers 2 and 3

 where data suggest hydraulic conductivity is lower

 than average of the layer

HK_3—Hydraulic conductivity for most of layers

 2 and 3

HK_4—Hydraulic conductivity for part of layer 3

 near the J4 test cell

HK_5—Hydraulic conductivity for parts of layers 2 and 3

 where data suggest hydraulic conductivity is higher

 than average of the layer

HK_7—Hydraulic conductivity for layers 2 and 3 in

 the area of the Crumpton Creek ground-water

 trough

HK_9—Hydraulic conductivity for layers 2 and 3 in

 the areas of Spring Creek and Short Springs

 ground-water trough

EXPLANATION

Spring Cr

Crumpton Cr

Short Spring

Simulation of Ground-Water Flow 29
Figure 21.  Vertical anisotropy zones for model layer 1 of the Arnold Air Force Base area.

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 MILES

0 2 4 KILOMETERS

35O30'

86O15' 85O56'

35O15'

Alt 41

24

41

VERTICAL ANISOTROPY

VANI_1—Ratio of horizontal to vertical hydraulic

 conductivity for most of layer 1

VANI_1A—Ratio of horizontal to vertical

 conductivity for part of layer 1 where

 water-level data show vertical gradient

 greater than 5 feet

BOUNDARY OF ARNOLD AIR

 FORCE BASE

EXPLANATION

30 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 22.  Simulated steady-state water levels for layer 1 of the Arnold Air Force Base area ground-water flow model.

Tullahoma

970

990

1010

1000

980

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Manchester

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

EXPLANATION

POTENTIOMETRIC CONTOUR—Shows simulated 

 altitude of water level. Hachures indicate depression.

 Contour interval 10 feet. Datum is NGVD 29

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

RESIDUAL, IN FEET

LESS THAN –20

–20 to –10

–10 to 10

10 to 20

GREATER THAN 20

35O30'

86O15' 85O56'

35O15'

Estill

Springs

0 2 4 MILES

0 2 4 KILOMETERS

24

41

Alt 41

900

Simulation of Ground-Water Flow  31
Figure 23.  Simulated steady-state water levels for layer 2 of the Arnold Air Force Base area ground-water flow model.

Tullahoma

1010

990

970

980

1000

1020

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960

920

950

1030

1050

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1060

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1070

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1030

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Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 MILES

0 2 4 KILOMETERS

EXPLANATION

POTENTIOMETRIC CONTOUR—Shows simulated 

 altitude of water level. Hachures indicate depression.

 Contour interval 10 feet. Datum is NGVD 29

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

RESIDUAL, IN FEET

LESS THAN –20

–20 TO –10

–10 TO 10

10 TO 20

GREATER THAN 20

35O30'

86O15' 85O56'

35O15'

Estill

Springs

Manchester

24

41

Alt 41

900

32 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 24.  Simulated steady-state water levels for layer 3 of the Arnold Air Force Base area ground-water flow model.

Tullahoma

970

1010

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990

1000

1020

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1030

1050

950

940

960

920

910

900

1060

1070

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1100

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1000

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1020

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1030

1050

1040

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Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 MILES

0 2 4 KILOMETERS

EXPLANATION

POTENTIOMETRIC CONTOUR—Shows simulated 

 altitude of water level. Hachures indicate depression.

 Contour interval 10 feet. Datum is NGVD 29

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

RESIDUAL, IN FEET

LESS THAN –20

–20 TO –10

–10 TO 10

10 TO 20

GREATER THAN 20

35O30'

86O15' 85O56'

35O15'

Estill

Springs

Manchester

24

41

Alt 41

900

Simulation of Ground-Water Flow  33
Figure 25.  Simulated steady-state water levels for layer 4 of the Arnold Air Force Base area ground-water flow model.

Tullahoma

990

1010

1000

1030

940

930

1020

1040

950

920

1050

960

910

900

1060

1070

1080

1090

1100

1060

1070

1020

980

1000

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1060

990

1000

970

970

1050

970

1040

1020

1010

1010

1060

970

990

980

1010

970

1000

1020

950

1050

1010

990

1020

1050

1030

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 MILES

0 2 4 KILOMETERS

EXPLANATION

POTENTIOMETRIC CONTOUR—Shows simulated 

 altitude of water level. Hachures indicate depression.

 Contour interval 10 feet. Datum is NGVD 29

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

HIGHLAND RIM ESCARPMENT

BOUNDARY OF ARNOLD AIR FORCE BASE

RESIDUAL, IN FEET

LESS THAN –20

–20 TO –10

–10 TO 10

10 TO 20

GREATER THAN 20

35O30'

86O15' 85O56'

35O15'

Estill

Springs

Manchester

24

41

Alt 41

900

34  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
The final values of hydraulic-conductivity parameters

generally were within the range of initial estimates with the

exception of parameters HK_7 and HK_9 where the calibrated

values were slightly higher than the upper range of the initial

estimates (table 3). The calibrated recharge rates generally

were within the range of initial estimates. The calibrated

recharge rates correspond to an average recharge rate over the

entire model area of 7.6 in/yr.

Some of the estimated parameters for the calibrated flow

model show high correlation coefficients (table 5). When

parameters are correlated, the parameter-­estimation process

may not have enough information to estimate parameters individually and may estimate only the ratio or sums of parameters

(Hill, 1998). To determine if the parameters were uniquely

estimated, the parameter estimation was run from several

different sets of starting parameter values. In each case, the

regression converged to the same final values, indicating that

the final values probably were estimated individually.

Components of the steady-state water budget of the

simulated system are shown in figure 28. The primary source

of water to the ground-water system is recharge (79.4 ft3/s)

to layer 1. Most of the water (70.0 ft3/s) discharges from the

ground-water system as seepage to rivers and drains. The

remaining amount discharges to constant-head cells at Woods

Reservoir and Tims Ford Lake (8.87 ft3/s) or ground-water

withdrawal wells and dewatering facilities (0.55 ft3/s). Of the

water entering layer 1, approximately 92 percent reaches layers 2 and 3, whereas only 5 percent reaches layer 4.

Sensitivity Analysis

Composite-scaled sensitivities were calculated for the

calibrated model using the sensitivity process in MODFLOW-2000 for all the hydraulic-conductivity and recharge

parameters (fig. 29) (Hill and others, 2000). Composite-scaled

sensitivities can be used to compare the importance of different parameters to the calculation of model-simulated water

levels and flows (Hill, 1998). Parameters with larger composite sensitivities have greater importance and greater influence

on the model solution than parameters with smaller composite

sensitivities. The most sensitive model parameter is RCH_

divide, the recharge rate in The Barrens area. The next most

sensitive parameter is HK_3. Three of the four most sensitive

parameters were for recharge. The model is least sensitive to

the parameters VANI_4, VANI_3, HK_4, and VANI_2.

Advective Flow Particle Tracking

A particle-tracking program, MODPATH (Pollock, 1994),

used results from the flow model to depict ground-water flow

paths under several different conditions to assess the effects of

ground-water withdrawal wells and dewatering facilities. The

only changes made to the model for the particle-tracking simulations were adding or removing ground-water withdrawals as

All 1 2 3 4

615 98 307 146 64

–40

–30

–20

–10

0

10

20

30

40

RESIDUALS, IN FEET

LAYERS

25th PERCENTILE

MEDIAN

75th PERCENTILE

EXTREME VALUE

EXPLANATION

900 1,000 1,100 1,200

OBSERVED WATER-LEVEL ALTITUDE, IN FEET

900

1,000

1,100

1,200

SIMULATED WATER-LEVEL ALTITUDE , IN FEET

–40 –30 –20 –10 0 10 20 30 40

WATER-LEVEL RESIDUALS, IN FEET

0

25

50

75

100

125

150

NUMBER OF

OCCURRENCES

Figure 26.  Simulated and observed water levels and

distribution of residuals for the Arnold Air Force Base

area ground-water flow model.

Figure 27.  Distribution of residuals by layer for the

Arnold Air Force Base area ground-water flow model.

Advective Flow Particle Tracking  35

All 1 2 3 4

615 98 307 146 64

–40

–30

–20

–10

0

10

20

30

40

RESIDUALS, IN FEET

LAYERS

25th PERCENTILE

MEDIAN

75th PERCENTILE

EXTREME VALUE

EXPLANATION
needed. In each simulation, particles were evenly distributed

within each model cell in the appropriate starting locations.

MODPATH is based on advective transport only and cannot

be used to compute solute concentrations in ground water. In

order to determine time-of-travel for the particles, porosities

of 0.10 for layer 1, 0.20 for layers 2 and 3, and 0.05 for layer 4

were used. These porosity values are consistent with typical

values for the lithologies of the layers (Freeze and Cherry,

1979; Heath, 1989).

Pre-Ground-Water Withdrawal Wells 

Particle Tracking

Particle-tracking analysis was done first under conditions before any ground-water withdrawal wells at SWMUs

were operational. For these simulations, all dewatering at test

facilities were active. Particles were tracked forward from

four sites: SWMU 1&2, SWMU 5, SWMU 8, and SWMU 10

(fig. 30). These path lines should represent the historic flow

paths from these sites. The flow paths indicated by the particle-tracking simulations agree reasonably well with maps of

interpreted contaminant plumes (fig. 2).

From SWMU 1&2, most of the particles (70 percent)

move to the northwest under the retention pond, then move

west under the air field, then follow a prominent trough in the

ground-water surface to discharge to Big Spring at Rutledge

Falls. The estimate of travel times for ground water leaving SWMU 1&2 to reach the discharge point at Rutledge

Falls ranges from 16 to 362 years with a mean travel time of

46 years and a median travel time of 43 years. Some of the

particles (30 percent) from SWMU 1&2 curl around to the

northeast to discharge to the J4 test cell. The estimate of travel

times for ground water from SWMU 1&2 that is captured by

dewatering operations at J4 ranges from 4 to 17 years with

a mean travel time of 8 years and a median travel time of

7 years.

Pathlines from SWMU 5 show that particles generally

move west and northwest to discharge to Cat Creek, Bates

Spring Branch, or seeps and springs along the Highland Rim

escarpment. The estimate of travel times for ground water

from SWMU 5 to discharge locations ranges from 11 to

45 years with a mean travel time of 21 years and a median

travel time of 20 years.

Pathlines from SWMU 8 show that particles move to

the southeast to discharge along Spring Creek. The estimate

of travel times for ground water from SWMU 8 to discharge

locations along Spring Creek ranges from 1 to 8 years with

a mean travel time of 3 years and a median travel time of

2 years.

Pathlines from SWMU 10 show that particles move to the

northeast before turning south to discharge to springs along

the lower reach of Bradley Creek. The estimate of travel times

for ground water from SWMU 10 to discharge locations along

Bradley Creek ranges from 33 to 244 years with a mean travel

time of 78 years and a median travel time of 40 years.

Pathlines from SWMU 10 are sensitive to the extent

of hydraulic-conductivity zone HK_5 in the Bradley Creek

Basin. Under an alternate calibration of the flow model

with a slight modification of the HK_5 zone, particles from

SWMU 10 diverged to show two flow paths that both discharged to springs along the lower reach of Bradley Creek

(fig. 31). Based on a detailed review of local water levels and

water-quality data, these alternate flowpaths are believed to be

less likely than the first scenario presented here, but may occur

periodically or seasonally. SWMU 10 is located in an area

near the regional divide where the horizontal ground-water

gradients are flat and may vary locally in response to individual recharge events. Also, seasonal water levels vary over

a greater range to the north of SWMU 10 when compared to

areas south of SWMU 10. The flat gradient and greater range

in water levels cause some additional uncertainty in modeling

flow paths from SWMU 10.

Table 5. Correlation coefficients between estimated parameters of the Arnold Air Force Base area ground-water flow model.

[See table 3 for parameter descriptions]

Estimated

parameters

Correlation coefficients

HK_1 RCH_divide VANI_1 HK_3 RCH_base RCH_spcr HK_9 HK_2 HK_7 HK_5 VANI_1a

HK_1 1.00

RCH_divide 0.75 1.00

VANI_1 0.03 –0.28 1.00

HK_3 0.57 0.89 –0.28 1.00

RCH_base 0.57 0.83 –0.47 0.90 1.00

RCH_spcr 0.75 0.93 –0.21 0.92 0.81 1.00

HK_9 0.58 0.58 0.23 0.58 0.43 0.73 1.00

HK_2 –0.28 0.12 –0.18 0.18 0.15 0.07 –0.02 1.00

HK_7 0.41 0.41 0.54 0.48 0.37 0.45 0.56 0.02 1.00

HK_5 0.28 0.34 0.00 0.01 0.07 0.14 0.06 0.02 –0.09 1.00

VANI_1a 0.24 0.02 0.09 –0.05 0.01 –0.04 0.02 –0.21 0.03 0.06 1.00

36  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Ground-Water Withdrawal Wells 

Particle Tracking

Currently (2005), ground-water withdrawal wells

are operating at SWMU 1&2, SWMU 5, SWMU 8, and

SWMU 10. Particle-tracking results from these SWMUs under

conditions with the ground-water withdrawal wells pumping

show that no particles leave the SWMUs (fig. 32).

In 2005, five new ground-water withdrawal wells

along the airfield road were scheduled to begin pumping.

To analyze the effect of these new wells on the flowpaths

from SWMU 1&2, a particle-tracking simulation was performed with the existing ground-water withdrawal wells at

SWMU 1&2 turned off and the new wells along the airfield

road turned on. The airfield road ground-water withdrawal

wells and the J4 test cell capture about 89 percent of the

particles from SWMU 1&2, with about 11 percent of the

particles discharging near Rutledge Falls (fig. 33). To estimate

the travel time of ground water from the area near the airfield

road ground-water withdrawal wells to Big Spring at Rutledge

Falls, a simulation was performed starting particles just downgradient of the capture area of the airfield road withdrawal

wells. The estimate of travel time from the airfield road withdrawal wells area to Big Spring at Rutledge Falls ranges from

1 to 5 years with a mean travel time of 2 years and a median

travel time of 2 years. This mean travel time of 2 years from

the airfield road area to Big Spring at Rutledge Falls, compared with the mean travel time of 46 years from SWMU 1&2

to Big Spring at Rutledge Falls implies that the airfield road

withdrawal wells should substantially reduce the time required

to observe a change in contaminant discharge from the “northwest plume” at Big Spring at Rutledge Falls.

Constant head inflow: 0.06

Constant head outflow: 0.14

Constant head inflow: 0.95

Constant head outflow: 4.28

Constant head inflow: 0

Constant head outflow: 5.4

Constant head inflow: 0

Constant head outflow: 0.06

0.15 – Discharge to wells and

 dewatering

4.07 – Seepage to drains

0.18 – Discharge to wells and

 dewatering

5.01 – Seepage to drains

0.22 – Discharge to wells and

 dewatering

1.48 – Seepage to drains

0.004 – Discharge to wells and

 dewatering

Layer 1

Areal recharge

79.4

Seepage to rivers

and drains 

59.3

Layer 2

Layer 3

Layer 4

Leakage

Leakage

Leakage

73.4 53.6

73.0 60.8

3.78 2.23

4.07 RATE OF FLOW, IN CUBIC FEET PER SECOND

 DIRECTION OF FLOW

EXPLANATION

Figure 28.  Distribution of water-budget components among the layers of the digital flow model

for the Arnold Air Force Base area.

Advective Flow Particle Tracking  37
Dewatering Facilities Particle Tracking

Three particle-tracking simulations were run to analyze

the effects of dewatering facilities on flow paths in the Main

Test Area (MTA). In the first simulation, particles were placed

in the MTA (in a rectangular area bounded by Third and Fifth

Streets and Avenues C and E) and tracked forward under

conditions with all dewatering facilities turned on (fig. 34). In

the second simulation, particles were placed in the MTA and

tracked forward under conditions with all dewatering facilities turned off (fig. 35). In the third simulation, particles were

placed at the location of the dewatering facilities and tracked

backwards to their recharge locations (fig. 36). These simulations illustrate that the dewatering facilities have a substantial

effect on flow paths that were simulated from the MTA and are

effective in containing most of the ground water in this area.

Model Limitations

Models, by their very nature, are simplifi­cations of the

natural system. Factors that affect how well a model represents

the natural system include the model scale; inaccuracies in

estimat­ing hydraulic properties; inaccurate or poorly defined

boundary conditions; and the accuracy of pumping, waterlevel, and streamflow data. The model presented in this report

is consistent with the conceptual model and hydrologic data of

the area. The model uses a variably spaced grid so the model

resolution is greatest near SWMUs, ground-water withdrawal

wells, and dewatering facilities. The model will not provide

accurate predictions on a scale smaller than the grid resolution.

The hydraulic-conductivity zones used in the model represent large-scale variations in hydraulic properties; the actual

spatial variations of hydraulic properties of the aquifer system

occur on a much smaller scale and are poorly defined. Additionally, the aquifer system, being karst in nature, has a wide

range of measured hydraulic conductivity. Finally, evidence

indicates that the aquifer system behaves anisotropically, but

no measured values of the degree of anisotropy exist.

The model is calibrated to average annual conditions

during 2002 and may not represent flow during seasonal

extremes. Seasonal potentiometric maps (Robinson and others,

2005) and continuous water-level data (fig. 16) indicate some

local seasonal shifts in flow directions in the upper part of the

Crumpton Creek Basin. Similarly, ground-water gradients near

the divide north of SWMU 10 may change seasonally.

The particle-tracking program, MODPATH, is based on

advective transport of “water” particles and does not consider

additional processes such as sorption, dispersion, and diffusion

that would affect the travel times of a ground-water contaminant. Travel times also are directly related to assumptions

about aquifer porosity. Since no measured values of porosity

exist for the study area, the simulations use a uniform value

of porosity for each layer as estimated from typical values for

the lithologies of the layers. If porosity estimates are too high,

travel times would be underestimated. If porosity estimates are

too low, travel times would be overestimated.

RCH_divide

HK_3

RCH_spcr

RCH_base

HK_1

HK_5HK_7

RCH_sp

Vani_L1

HK_9HK_2

Vani_1a

Vani_4Vani_3

HK_4

Vani_2

PARAMETERS (see table 3)

0

20

40

60

80

100

120

140

COMPOSITE-SCALED SENSITIVITY

Figure 29.  Composite-scaled sensitivities for

model parameters.

38  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 30.  Forward particle tracking from SWMU 1&2, SWMU 5, SWMU 8, and SWMU 10 at Arnold Air Force Base

with no ground-water withdrawal wells pumping.

Tullahoma

Manchester

Estill

Springs

EXPLANATION

SWMU SITE

HYDROLOGIC BOUNDARY---Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

PARTICLE-TRACKING FLOW LINE

HIGHLAND RIM ESCARPMENT

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 KILOMETERS

0 2 4 MILES

35O30'

86O15' 85O56'

35O15'

24

41

Alt 41

SWMU 5

SWMU 1&2 SWMU 74

SWMU 10

SWMU 8

Spring Cr

J4 test

cell

Big Spring at

Rutledge Falls

Bates

Spring Cr

Cat Cr

Bradley Cr

Air Field

BOUNDARY OF ARNOLD AIR FORCE BASE

Advective Flow Particle Tracking  39
Figure 31.  Forward particle tracking from SWMU 10 at Arnold Air Force Base under an alternative calibration of the

flow model.

Tullahoma

Manchester

EXPLANATION

SWMU SITE

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

PARTICLE-TRACKING FLOW LINE

HIGHLAND RIM ESCARPMENT

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O30'

86O15' 85O56'

35O15'

Estill

Springs

0 2 4 KILOMETERS

0 2 4 MILES

SWMU 5

SWMU 1&2 SWMU 74

SWMU 10

SWMU 8

J4 test

cell

Big Spring at

Rutledge Falls

Bates

Spring Cr

Cat Cr

Bradley Cr

Air Field

24

41

Alt 41

BOUNDARY OF ARNOLD AIR FORCE BASE

40 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 32.  Forward particle tracking from SWMU 1&2, SWMU 5, SWMU 8, and SWMU 10 at Arnold Air Force Base

with ground-water withdrawal wells pumping.

Tullahoma

Estill

Springs

Manchester

EXPLANATION

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

SWMU SITE

PARTICLE-TRACKING FLOW LINE

GROUND-WATER EXTRACTION WELL

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 KILOMETERS

0 2 4 MILES

35O30'

86O15' 85O56'

35O15'

24

41

Alt 41

SWMU 5

SWMU 1&2 SWMU 74

SWMU 10

SWMU 8

J4 test

cell

BOUNDARY OF ARNOLD AIR FORCE BASE

J4

Advective Flow Particle Tracking  41
Figure 33.  Forward particle tracking from SWMU 1&2 at Arnold Air Force Base with the airfield road ground-water

withdrawal wells pumping.

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O22' 20''

35O23' 50''

86O05' 10'' 85O03'

EXPLANATION

SWMU SITE

PARTICLE-TRACKING FLOW LINE WITH

 AIRFIELD ROAD TREATMENT 

 SYSTEM PUMPING 

PARTICLE-TRACKING FLOW LINE WITHOUT

 AIRFIELD ROAD TREATMENT SYSTEM

 PUMPING

GROUND-WATER EXTRACTION WELL

SWMU 1&2

Air Field

About 3 miles to

Rutledge Falls

J4 test

cell

0 1,000 2,000 3,000 FEET

0 250 500 METERS

Area enlarged

 above

Location map

42 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Figure 34.  Forward particle tracking from the Main Test Area (SWMU 74) at Arnold Air Force Base with all dewatering

facilities turned on.

Tullahoma

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 KILOMETERS

0 2 4 MILES

35O30'

86O15' 85O56'

35O15'

Manchester

Estill

Springs

24

41

Alt 41

SWMU 5

SWMU 1&2

SWMU 74

SWMU 10

SWMU 8

EXPLANATION

SWMU SITE

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

PARTICLE-TRACKING FLOW LINE

GROUND-WATER EXTRACTION WELL

DEWATERING FACILITY

BOUNDARY OF ARNOLD AIR FORCE BASE

Advective Flow Particle Tracking  43
Figure 35.  Forward particle tracking from the Main Test Area (SWMU 74) at Arnold Air Force Base with all dewatering

facilities turned off.

Tullahoma

Manchester

Estill

Springs

EXPLANATION

SWMU SITE

HYDROLOGIC BOUNDARY—Delineation of

 regional ground-water flow system underlying

 Arnold Air Force Base

PARTICLE-TRACKING FLOW LINE

Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

0 2 4 KILOMETERS

0 2 4 MILES

35O30'

86O15' 85O56'

35O15'

24

41

Alt 41

SWMU 5

SWMU 1&2 SWMU 74

SWMU 10

SWMU 8

BOUNDARY OF ARNOLD AIR FORCE BASE

44  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Base from U.S. Geological Survey topographic quadrangles,

1:24,000 Lambert Conformal Conic Projection, Standard

parallels 35o15'N and 36o25'N, central meridian 86oW and

USGS digital data, 1:100,000

35O22' 20''

35O23' 25''

86O03' 50'' 85O02' 05''

EXPLANATION

FLOW-PATH LINE—Colors delineate

 flow paths associated with individual

 dewatering facilities

DEWATERING FACILITY

0 250 500 METERS

0 1,000 2,000 3,000 FEET

J4 test

cell

Area enlarged

 above

Location map

Figure 36.  Backward particle tracking from dewatering facilities at the Main Test Area at Arnold Air Force Base.

Advective Flow Particle Tracking  45
Summary

Arnold Air Force Base (AAFB) occupies about

40,000 acres in Coffee and Franklin Counties, Tennessee. The

primary mission of AAFB is to support the development of

aerospace systems. Numerous site-specific ground-water contamination investigations have been conducted at designated

Solid Waste Management Units (SWMUs) at AAFB. Several

synthetic volatile organic compounds (VOCs), primarily chlorinated solvents, have been identified in the ground water at

AAFB. Two ground-water contaminant plumes that originate

at AAFB, the “SWMU 8 plume” and the “northwest plume,”

have been shown to extend to regional discharge points outside

the AAFB boundary.

The ground-water system at AAFB can be divided into

several different zones or aquifers. The Manchester aquifer,

the primary source of drinking water in the area, consists of

chert gravels at the base of the regolith and solution openings in the upper part of the bedrock. A ground-water divide,

approximately coinciding with the Duck River-Elk River

surface-water divide, underlies AAFB and extends from

southwest to northeast. Ground water flows from the divide

area to the discharge areas, which are the major streams,

springs, lakes, and reservoirs around the base. Several troughs

are present in the potentiometric surface. The most prominent

trough trends northwest to southeast in the Crumpton Creek

Basin. The troughs in the potentiometric surface are believed

to be associated with zones of high permeability within the

aquifer that are important regional flow paths. These pathways

share the following characteristics: a depression or trough in

the bedrock surface, a trough in the ground-water surface, low

gradients in the ground-water surface, and a large spring or

group of springs at the downgradient end.

In the study area, recharge occurs from direct infiltration

of precipitation throughout the study area. Based on waterbudget and stream base-flow data, the AAFB study area can be

divided into four areas with different recharge rates. The areas

are: The Barrens area along the regional drainage divide; the

Spring Creek, Dry Creek (at Estill Springs), and Taylor Creek

Basins in the southwestern part of the study area; Sinking

Pond; and the rest of the study area.

Ground water is withdrawn at numerous locations at

AAFB for two primary reasons: ground-water withdrawal

wells associated with ground-water contamination and dewatering activities around below-grade testing facilities. Groundwater withdrawal wells currently (2005) are operating at

SWMU 1&2, SWMU 5, SWMU 8, and SMWU 10. Dewatering activities also occur at more than 20 facilities at AEDC.

The previous ground-water flow model (1992) was

updated to incorporate new data and concepts about the

ground-water flow system. For the computer flow model, the

Highland Rim aquifer system was divided into four layers

to simulate ground-water flow. The layers were defined on

the basis of differences in physical characteristics that affect

hydrologic properties. Model layer 1 corresponds to the

shallow aquifer. Model layer 2 corresponds to the upper part

of the Manchester aquifer. Model layer 3 corresponds to the

lower part of the Manchester aquifer. Model layer 4 corresponds to the Fort Payne aquifer.

Model parameters (Harbaugh and others, 2000) were

defined for recharge and hydraulic-conductivity zones. The

digital model developed for this study was calibrated to

steady-state conditions as defined by averaging measurements

from spring and fall 2002. Overall, simulated water levels

agree reasonably well with observed water levels. Water-level

data at 615 wells were available for comparison to simulated

conditions. The root mean square error for measured compared

to simulated water levels was 9.8 feet. The average head difference between measured and simulated heads is –0.47 feet.

The model has seven hydraulic-conductivity parameters with

calibrated values that range from 0.2 to 6,500 feet per day.

The model has four recharge parameters with calibrated rates

of 4.2, 7.8, 17.7, and 110 inches per year (the high value

represents focused recharge at Sinking Pond). The calibrated

recharge rates correspond to an average recharge rate over the

entire model area of 7.6 inches per year.

Particle-tracking flow paths were analyzed from selected

SWMUs. From SWMU 1&2, most of the particles (70 percent) move to the northwest under the retention pond, then

move west under the air field, then follow a prominent trough

in the ground-water surface to discharge to Big Spring at

Rutledge Falls. Pathlines from SWMU 5 show that particles

generally move west and northwest to discharge to Cat Creek,

Bates Spring Branch, or seeps and springs along the Highland

Rim escarpment. Pathlines from SWMU 8 show that particles

move to the southeast to discharge along Spring Creek. Pathlines from SWMU 10 show that particles move to the northeast before turning south to discharge to springs along the

lower reach of Bradley Creek. Under an alternate calibration

of the flow model, particles from SWMU 10 diverged to show

two flow paths that both discharged to springs along the lower

reach of Bradley Creek. Based on a detailed review of local

water levels and water-quality data, this alternate scenario is

believed to be less likely than the first one presented here, but

may occur periodically or seasonally.

Currently (2005), ground-water withdrawal wells

are operating at SWMU 1&2, SWMU 5, SWMU 8, and

SWMU 10. Particle-tracking results from these SWMUs,

under conditions with the ground-water withdrawal wells

pumping, show that no particles leave the SWMUs. In 2005,

five new ground-water withdrawal wells along the airfield

road were scheduled to begin pumping to capture groundwater contamination that has already migrated beyond the

SWMU 1&2 boundaries. The airfield road ground-water

withdrawal wells and the J4 test cell capture about 89 percent

of the particles from SWMU 1&2. About 11 percent of the

particles under this simulation discharge near Rutledge Falls.

Three particle-tracking simulations were run to analyze the effects of dewatering facilities on flow paths in the

Main Test Area (MTA). These simulations illustrate that the

dewatering facilities have a substantial effect on flow paths

46  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
from the MTA and are effective in containing most of the

ground water in this area.

The updated ground-water flow model is consistent with

all current data on the ground-water system at AAFB. The

model should provide a reliable tool to assist AAFB in managing the ground-water resources at the base.

Selected References

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Aycock, R.A., and Haugh, C.J., 2001, Ground-water hydrology and water-quality data for wells, springs, and surfacewater sites in the Bradley-Brumalow Creeks area near

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Contract no. F40650–88–C0014, 6 sections, 1 appendix.

Brahana, J.V., and Bradley, M.W., 1986a, Preliminary delineation and description of the regional aquifers of Tennessee—

The Highland Rim aquifer system: U.S. Geological Survey

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Brahana, J.V., and Bradley, M.W., 1986b, Preliminary delineation and description of the regional aquifers of Tennessee—

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Programs, v. 6, no. 4, p. 338.

CH2M HILL, 1999, Resource conservation and recovery act

facility investigation supplement for solid waste management unit 8 at Arnold Air Force Base: Oak Ridge, Tenn.,

CH2M HILL.

CH2M HILL, 2001, Resource conservation and recovery act

facility investigation supplement for solid waste management unit 74 at Arnold Air Force Base: Oak Ridge, Tenn.,

CH2M HILL.

COLOG, 2002, HydroPhysical and geophysical logging

results for solid waste management unit 10 at Arnold Air

Force Base, Manchester, Tennessee: Golden, Colorado,

COLOG.

Dames and Moore, 1975, Groundwater investigation and

foundation study Aerospace-Jet Propulsion Systems Test

Facility (ASTF): Technical report, unnumbered document,

September 11, 1975, 40 p.

Engineering Science, 1984, Installation restoration program,

Phase I: Records search, Arnold Engineering Development

Center (AEDC), Tennessee: Atlanta, Georgia, Engineering

Science, consultant engineer unnumbered document,

October 1984, 6 sections.

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Flohr, D.F., Garrett, J.W., Hamilton, J.T., and Phillips, T.D.,

2003, Water resources data—Tennessee, water year 2002:

U.S. Geological Survey Water-Data Report TN-02-1, 418 p.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood Cliffs, Prentice Hall, 604 p.

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald,

M.G., 2000, MODFLOW-2000, the U.S. Geological Survey

modular ground-water model—user guide to modularization

concepts and the ground-water flow process: U.S. Geological Survey Open-File Report 00-92, 121 p.

Haugh, C.J., 1996a, Hydrogeology of the area near the J4 test

cell, Arnold Air Force Base, Tennessee: U.S. Geological

Survey Water-Resources Investigations Report 96-4182,

43 p.

Haugh, C.J., 1996b, Well-construction, water-level, and waterquality data for ground-water monitoring wells for the J4

hydrogeologic study, Arnold Air Force Base, Tennessee:

U.S. Geological Survey Open-File Report 95-763, 81 p.

Haugh, C.J., and Mahoney, E.N., 1994, Hydrogeology and

simulation of ground-water flow at Arnold Air Force Base,

Coffee and Franklin Counties, Tennessee: U.S. Geological

Survey Water-Resources Investigations Report 93-4207,

69 p.

Haugh, C.J., Mahoney, E.N., and Robinson, J.A., 1992, Wellconstruction, water-level, geophysical, and water-quality

data for ground-water monitoring wells for Arnold Air

Force Base, Tennessee: U.S. Geological Survey Open-File

Report 92-135, 88 p.

Heath, R.C., 1989, Basic ground-water hydrology: U.S. Geological Survey Water-Supply Paper 2220, 84 p.

Hill, M.C., 1998, Methods and guidelines for effective model

calibration: with application to UCODE, a computer code

for universal inverse modeling, and MODFLOWP, a computer code for inverse modeling with MODFLOW: U.S.

Geological Survey Water-Resources Investigations Report

98-4005, 90 p.

Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, E.R.,

2000, MODFLOW-2000, the U.S. Geological Survey modular ground-water model—user guide to the observation,

sensitivity, and parameter-estimation processes and three

post-processing programs: U.S. Geological Survey OpenFile Report 00-184, 209 p.

Hoos, A.B., 1990, Recharge rates and aquifer hydraulic

characteristics for selected drainage basins in Middle and

East Tennessee: U.S. Geological Survey Water-Resources

Investigations Report 90-4015, 34 p.

JAVA Corporation, 2000, Aerial thermography surveying—

identification of potential springs phases II and III: Huntsville, Alabama, JAVA Corporation.

Mahoney, E.N., and Robinson, J.A., 1993, Altitude of the

potentiometric surface in the Manchester aquifer at Arnold

Air Force Base, May 1991, Coffee and Franklin Counties,

Tennessee: U.S. Geological Survey Water-Resources Investigations Report 93-4059, 1 sheet, scale 1:97,000.

McCabe, G.J., McLaughlin, J.D., and Muller, R.A., 1985,

Thornwaite continuous monthly water budget: Louisiana

Office of State Climatology, Climate Paper 85-1, 19 p.

McDonald, M.G., and Harbaugh, A.W., 1988, A modular

three-dimensional finite-difference ground-water flow

model: U.S. Geological Survey Techniques of WaterResources Investigations, book 6, chap. A1, 576 p. (586 p.)

Miller, R.A., 1974, The geologic history of Tennessee: Tennessee Division of Geology Bulletin 74, 63 p.

National Oceanic and Atmospheric Administration, 1960–

2004, Climatological data annual summary, Tennessee:

Asheville, N.C., National Climate Data Center, published annually.

Oak Ridge National Laboratory, 1989a, U.S. Air Force installation restoration program, phase IV, remedial design for

site 10, Arnold Engineering Development Center, Tullahoma, Tennessee, Task 2.7, Baseline analytical report:

Oak Ridge National Laboratory, Tennessee, Hazardous

Waste Remedial Actions Program, August 1989, 6 sections,

5 appendices.

Oak Ridge National Laboratory, 1989b, U.S. Air Force installation restoration program, draft risk assessment for site 10,

Arnold Engineering Development Center, Arnold Air Force

Base, Tennessee: Hazardous Waste Remedial Actions Program unnumbered document, second draft, December 1989,

103 p.

Pollock, D.W., 1994, User’s guide for MODPATH/MODPATH-PLOT, version 3: A particle tracking postprocessing package for MODFLOW, the U.S. Geological Survey finite-difference ground-water-flow model:

U.S. Geological Survey Open-File Report 94-464, 249 p.

Post, Buckley, Schuh and Jernigan, Inc., 1989a, Installation

restoration program, Phase IV-A, Site 1 remedial action

plan, v. 1, Arnold Air Force Base, Tennessee: Nashville,

Tenn., Consultant engineer report, 6 sections, 3 appendices.

Post, Buckley, Schuh and Jernigan, Inc., 1989b, Installation

restoration program, Phase IV-A, Site 1 remedial action

plan, v. 2, Arnold Air Force Base, Tennessee: Nashville,

Tenn., Consulting engineer report, 7 sections.

Post, Buckley, Schuh and Jernigan, Inc., 1989c, Installation

restoration program, Phase IV-A, Site 1 remedial action

plan, v. 3 (support documentation), Arnold Air Force Base,

Tennessee: Nashville, Tenn., Consultant engineer report,

10 appendices.

48  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Post, Buckley, Schuh and Jernigan, Inc., 1989d, Installation

restoration program, Phase IV-A, Site 1, environmental

assessment, Arnold Air Force Base, Tennessee: Nashville,

Tenn., Consulting engineer report, 4 sections.

Post, Buckley, Schuh and Jernigan, Inc., 1989e, Draft work

management plan for groundwater extraction investigation

for site 1, Arnold Engineering Development Center: Nashville, Tenn., Consulting engineer report, 6 sections.

Robinson, J.A., and Haugh, C.J., 2004, Base-flow data in the

Arnold Air Force Base area, Tennessee, June and October

2002: U.S. Geological Survey Open-File Report 2004-1318,

26 p.

Robinson, J.A., Hileman, G.E., and Haugh, C.J., 2005,

Potentiometric surface of the Manchester Aquifer, Arnold

Air Force Base, Tennessee, 2002: U.S. Geological Survey

Scientific Investigations Map 2005-2882, 1 plate.

Rutledge, A.T., and Mesko, T.O., 1996, Estimated hydrologic

characteristics of shallow aquifer systems in the Valley and

Ridge, the Blue Ridge, and the Piedmont Physiographic

Provinces based on analysis of streamflow recession and

base flow: U.S. Geological Survey Professional Paper

1422-B, 58 p.

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study, stage 2, technical report draft, Arnold Air Force Base,

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4543, task order no. 6, 3 v., 5 sections, 11 appendices.

U.S. Army Corps of Engineers, Mobile District, 1988a, Final

foundation report, FY-89 PCD ANZY870198 Large Rocket

Test Facility (J-6), Arnold Engineering Development Center, Air Force Systems Command, Arnold Air Force Station,

Tennessee: U.S. Army Corps of Engineers, 94 p., 19 plates.

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foundation report, FY-89 PCD ANZY870198 Large Rocket

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data for wells in the Crumpton Creek area near Arnold Air

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U.S. Geological Survey Water-Resources Investigations

Report 03-4175, 28 p.

Williams, S.D., and Aycock, R.A., 2001, Ground-water

levels and water-quality data for wells in the Spring

Creek area near Arnold Air Force Base, Tennessee,

April and May 2000: U.S. Geological Survey Open-File

Report 01-150, 16 p.

Williams, S.D., and Farmer, J.J., 2003, Volatile organic compound data from three karst springs in Middle Tennessee,

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summary of the Manchester quadrangle, Tennessee: Tennessee Division of Geology, MRS 86-NE, scale 1:24,000.

Wolfe, W.J., 1996, Hydrology and tree-distribution patterns of

karst wetlands at Arnold Engineering Development Center,

Tennessee: U.S. Geological Survey Water-Resources Investigations Report 96-4277, 46 p.

Wolfe, W.J., Evans, J.P., McCarthy, Sarah, Gain, W.S., and

Bryan, B.A., 2004, Tree-regeneration and mortality patterns

and hydrologic change in a forested karst wetland—Sinking

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Wolfe, W.J., and League, D.E., 1996, Water-surface elevations

of wetlands and nearby wells at Arnold Air Force Base, near

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Report 95-753, 19 p.

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Tullahoma, Tennessee: Consulting engineer report, September 28, 1990, 7 sections, 7 appendices.

Selected References  49

Appendix

Appendix  51

Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-1 1076.41 1072.43 1074.42 1071.11 3.31

MW-2 1070.48 1066.47 1068.47 1067.20 1.27

MW-9 1084.39 1083.62 1084.01 1079.76 4.25

MW-10 1085.05 1081.04 1083.05 1079.65 3.40

MW-22 1067.08 1055.05 1061.07 1065.05 –3.98

MW-24 1075.00 1063.50 1069.25 1065.75 3.50

MW-25 1064.01 1055.51 1059.76 1066.05 –6.29

MW-27 1073.14 1064.58 1068.86 1063.75 5.12

MW-28 1073.18 1067.89 1070.54 1063.79 6.75

MW-29 1069.25 1049.64 1059.44 1063.17 –3.73

MW-30 1062.89 1060.11 1061.50 1067.85 –6.35

MW-31 1035.59 1033.39 1034.49 1057.69 –23.20

MW-32 1065.00 1055.13 1060.07 1065.00 –4.93

MW-64 1040.28 1037.13 1038.70 1059.06 –20.36

MW-72 1060.69 1055.12 1057.91 1051.86 6.05

MW-75 1057.71 1052.15 1054.93 1047.84 7.09

MW-76 1036.52 1024.87 1030.69 1030.32 0.37

MW-78 1045.30 1034.55 1039.93 1033.48 6.45

MW-80 1032.53 1023.67 1028.10 1031.66 –3.56

MW-81 1064.59 1067.11 1065.85 1067.88 –2.03

MW-82 1078.65 1078.09 1078.37 1075.74 2.63

MW-83 1084.68 1081.70 1083.19 1073.38 9.81

MW-84 1081.23 1079.95 1080.59 1072.35 8.24

MW-85 1084.28 1083.60 1083.94 1072.10 11.84

MW-86 1097.50 1087.99 1092.74 1087.65 5.09

MW-91 1047.51 1043.25 1045.38 1065.44 –20.06

MW-92 1061.63 1054.43 1058.03 1065.51 –7.48

MW-93 1067.78 1060.81 1064.30 1066.34 –2.04

MW-96 1071.27 1065.20 1068.23 1066.00 2.24

MW-97 1067.98 1060.51 1064.24 1066.01 –1.77

MW-98 1059.48 1049.41 1054.44 1058.99 –4.55

MW-99 1055.84 1046.19 1051.02 1061.50 –10.48

MW-102 1074.09 1064.96 1069.53 1064.14 5.39

MW-103 1077.54 1066.24 1071.89 1064.71 7.18

Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.

Appendix  53
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-104 1076.27 1065.28 1070.78 1064.73 6.05

MW-105 1071.87 1059.69 1065.78 1064.10 1.68

MW-106 1075.91 1067.27 1071.59 1064.98 6.61

MW-107 1078.76 1067.85 1073.31 1065.48 7.83

MW-108 1077.44 1067.55 1072.49 1064.86 7.63

MW-109 1074.44 1064.15 1069.30 1064.87 4.43

MW-110 1058.24 1047.47 1052.86 1064.22 –11.36

MW-111 1072.17 1063.93 1068.05 1063.60 4.45

MW-112 1072.69 1064.03 1068.36 1063.62 4.74

MW-113 1069.86 1058.89 1064.38 1062.98 1.40

MW-114 1071.87 1063.25 1067.56 1062.90 4.66

MW-116 1072.69 1063.08 1067.89 1063.82 4.08

MW-117 1073.50 1064.30 1068.90 1063.94 4.96

MW-118 1069.02 1058.26 1063.64 1064.60 –0.96

MW-119 1069.24 1057.74 1063.49 1062.86 0.63

MW-120 1072.16 1060.95 1066.56 1064.88 1.68

MW-121 1073.59 1064.78 1069.18 1063.47 5.71

MW-122 1069.88 1060.28 1065.08 1063.11 1.97

MW-132 1065.80 1056.30 1061.05 1061.12 –0.07

MW-134 1033.24 1021.98 1027.61 1030.42 –2.81

MW-135 1031.14 1020.18 1025.66 1030.47 –4.81

MW-137 1038.76 1032.14 1035.45 1036.53 –1.08

MW-138 1052.38 1037.04 1044.71 1039.38 5.33

MW-139 1056.90 1050.08 1053.49 1042.32 11.17

MW-140 1050.11 1036.52 1043.32 1042.08 1.24

MW-141 1050.14 1036.52 1043.33 1042.14 1.19

MW-143 1062.43 1057.00 1059.71 1047.85 11.87

MW-144 1058.08 1051.35 1054.71 1048.02 6.69

MW-145 1055.07 1055.21 1055.14 1048.48 6.66

MW-146 1049.30 1044.46 1046.88 1034.29 12.59

MW-147 1044.56 1039.33 1041.94 1033.57 8.37

MW-148 1038.27 1032.65 1035.46 1037.76 –2.30

MW-149 1023.77 1019.31 1021.54 1036.78 –15.24

MW-150 1022.72 1018.04 1020.38 1014.41 5.97

54  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-151 1036.66 1027.81 1032.23 1030.03 2.20

MW-152 1022.64 1017.89 1020.27 1017.23 3.04

MW-153 1021.79 1016.75 1019.27 1016.53 2.74

MW-154 1046.68 1043.68 1045.18 1066.39 –21.21

MW-155 1063.82 1060.34 1062.08 1061.88 0.20

MW-156 1079.06 1077.25 1078.16 1075.95 2.21

MW-157 1063.33 1060.09 1061.71 1075.25 –13.54

MW-158 1079.63 1077.33 1078.48 1072.95 5.53

MW-159 1077.85 1074.50 1076.18 1072.38 3.81

MW-160 1079.12 1077.71 1078.42 1072.16 6.26

MW-161 1079.02 1077.61 1078.32 1072.36 5.96

MW-162 1079.65 1078.03 1078.84 1072.46 6.38

MW-163 1077.87 1075.84 1076.86 1072.22 4.64

MW-164 1086.90 1081.91 1084.41 1087.12 –2.71

MW-165 1087.90 1082.94 1085.42 1085.94 –0.52

MW-171 1072.73 1060.57 1066.65 1069.05 –2.40

MW-173 972.02 969.03 970.53 984.59 –14.07

MW-174 968.59 964.60 966.60 986.76 –20.16

MW-177 1078.74 1055.38 1067.06 1049.40 17.66

MW-179 1046.76 1035.78 1041.27 1042.36 –1.09

MW-181 1005.89 997.29 1001.59 1008.90 –7.30

MW-182 1006.05 996.67 1001.36 1008.67 –7.31

MW-183 1007.70 997.91 1002.80 1008.92 –6.12

MW-185 1071.02 1060.92 1065.97 1082.98 –17.01

MW-186 1095.99 1080.52 1088.26 1087.97 0.29

MW-188 972.94 971.14 972.04 977.43 –5.39

MW-189 973.72 971.05 972.39 973.57 –1.19

MW-190 948.06 942.08 945.07 952.43 –7.36

MW-191 949.34 935.25 942.30 952.72 –10.43

MW-194 1005.29 998.34 1001.82 1011.60 –9.78

MW-195 1018.98 1007.40 1013.19 1006.94 6.25

MW-196 1045.66 1045.36 1045.51 1051.66 –6.14

MW-197 1055.62 1040.37 1047.99 1051.79 –3.80

MW-198 1045.33 1029.96 1037.65 1041.94 –4.29

Appendix  55
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-199 1045.48 1030.67 1038.08 1042.41 –4.33

MW-200 1064.23 1045.14 1054.68 1053.88 0.80

MW-201 1064.31 1045.14 1054.72 1054.03 0.69

MW-202 963.51 960.33 961.92 975.12 –13.20

MW-203 963.65 959.81 961.73 975.25 –13.52

MW-213 1050.94 1029.26 1040.10 1037.78 2.32

MW-214 996.28 986.48 991.38 994.24 –2.86

MW-215 1068.87 1047.94 1058.41 1058.60 –0.19

MW-216 1031.98 1014.21 1023.10 1017.20 5.90

MW-217 1046.17 1043.88 1045.03 1061.69 –16.66

MW-218 1078.02 1067.18 1072.60 1061.76 10.84

MW-219 1051.87 1035.59 1043.73 1040.38 3.35

MW-221 1016.00 1007.54 1011.77 995.11 16.66

MW-222 989.61 981.05 985.33 1002.99 –17.66

MW-223 1000.97 992.75 996.86 1011.38 –14.52

MW-224 1064.00 1057.05 1060.53 1036.65 23.88

MW-225 1001.35 998.24 999.80 991.51 8.29

MW-226 1027.11 1020.00 1023.55 1017.11 6.44

MW-227 1027.12 1016.07 1021.60 1009.77 11.83

MW-228 966.98 964.14 965.56 988.52 –22.96

MW-230 1015.57 1010.16 1012.87 1012.36 0.51

MW-231 1027.31 1011.86 1019.59 1036.62 –17.03

MW-232 1031.08 1025.82 1028.45 1040.97 –12.52

MW-236 953.08 946.45 949.77 953.93 –4.17

MW-238 1033.45 1025.71 1029.58 1033.66 –4.08

MW-241 1033.30 1025.45 1029.38 1033.23 –3.85

MW-243 1034.52 1026.95 1030.73 1033.83 –3.10

MW-244 1034.70 1026.29 1030.49 1033.80 –3.31

MW-245 1031.02 1022.90 1026.96 1031.24 –4.28

MW-247 1022.55 1015.78 1019.17 1028.69 –9.52

MW-248 1007.43 1008.89 1008.16 1028.72 –20.56

MW-249 1050.29 1036.78 1043.54 1042.26 1.28

MW-250 1050.51 1036.92 1043.71 1042.28 1.43

MW-251 1050.50 1036.91 1043.70 1042.23 1.47

56  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-252 1052.87 1041.02 1046.94 1042.54 4.40

MW-253 1050.52 1036.90 1043.71 1042.21 1.50

MW-258 1030.01 1022.59 1026.30 1033.75 –7.45

MW-259 1028.07 1027.27 1027.67 1033.90 –6.23

MW-260 1034.51 1027.41 1030.96 1033.88 –2.92

MW-261 1033.83 1025.22 1029.53 1033.79 –4.26

MW-262 1039.88 1038.75 1039.32 1033.96 5.36

MW-263 1042.20 1042.22 1042.21 1034.48 7.73

MW-269 1047.34 1043.00 1045.17 1060.52 –15.35

MW-270 1066.06 1059.70 1062.88 1062.49 0.39

MW-271 1071.90 1064.78 1068.34 1063.62 4.72

MW-272 1045.24 1038.78 1042.01 1056.92 –14.91

MW-273 1033.04 1026.97 1030.01 1057.59 –27.58

MW-274 1054.29 1046.95 1050.62 1057.56 –6.94

MW-275 1072.37 1062.90 1067.64 1061.81 5.83

MW-276 1079.92 1075.73 1077.83 1071.72 6.11

MW-278 1064.56 1058.26 1061.41 1065.59 –4.18

MW-279 1059.21 1054.22 1056.71 1067.28 –10.57

MW-280 1070.71 1065.89 1068.30 1070.31 –2.01

MW-282 1055.94 1049.24 1052.59 1061.09 –8.50

MW-283 1066.78 1059.27 1063.03 1061.12 1.91

MW-284 1075.16 1068.32 1071.74 1061.80 9.94

MW-285 1068.59 1057.18 1062.89 1063.79 –0.90

MW-286 1072.98 1062.26 1067.62 1063.91 3.71

MW-287 1077.94 1067.93 1072.93 1064.63 8.30

MW-288 1072.18 1058.59 1065.39 1068.25 –2.86

MW-289 1072.29 1058.52 1065.41 1068.30 –2.89

MW-290 1075.25 1066.37 1070.81 1069.07 1.74

MW-291 1064.95 1036.94 1050.94 1069.64 –18.70

MW-292 1072.44 1058.94 1065.69 1070.47 –4.78

MW-293 1074.17 1064.48 1069.33 1070.45 –1.12

MW-299 1058.21 1049.99 1054.10 1066.18 –12.08

MW-300 1057.38 1048.78 1053.08 1066.08 –13.00

MW-301 1056.43 1046.83 1051.63 1055.45 –3.82

Appendix  57
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-302 1055.79 1046.49 1051.14 1054.75 –3.61

MW-303 1062.86 1053.35 1058.11 1055.83 2.28

MW-304 1058.33 1048.82 1053.58 1059.53 –5.95

MW-305 1058.32 1048.78 1053.55 1059.49 –5.94

MW-306 1065.59 1060.17 1062.88 1060.30 2.58

MW-307 1063.46 1059.99 1061.72 1063.76 –2.04

MW-308 1064.78 1059.24 1062.01 1066.47 –4.46

MW-310 1070.50 1067.06 1068.78 1067.61 1.17

MW-311 1074.72 1068.83 1071.78 1064.86 6.92

MW-312 1034.20 1025.74 1029.97 1027.67 2.30

MW-314 1050.78 1048.05 1049.42 1063.39 –13.97

MW-315 1055.01 1047.73 1051.37 1065.99 –14.62

MW-316 1054.21 1050.64 1052.43 1065.78 –13.35

MW-317 1059.47 1051.82 1055.65 1067.55 –11.90

MW-319 1044.28 1043.98 1044.13 1062.13 –18.00

MW-321 1066.26 1061.31 1063.79 1068.27 –4.48

MW-322 1069.31 1051.90 1060.61 1068.27 –7.66

MW-324 1082.96 1079.78 1081.37 1071.86 9.51

MW-325 1084.93 1082.45 1083.69 1073.98 9.71

MW-327 1085.08 1082.05 1083.57 1076.65 6.92

MW-330 1071.94 1059.68 1065.81 1065.26 0.55

MW-331 1072.27 1060.97 1066.62 1065.26 1.36

MW-332 1073.91 1060.49 1067.20 1064.06 3.14

MW-333 1070.62 1059.30 1064.96 1063.16 1.80

MW-334 1070.86 1059.14 1065.00 1063.54 1.46

MW-335 1070.23 1058.52 1064.38 1063.56 0.82

MW-336 1079.95 1065.57 1072.76 1065.80 6.96

MW-342 1019.84 1010.33 1015.09 1003.79 11.30

MW-343 1062.11 1046.21 1054.16 1031.79 22.37

MW-344 1032.68 1024.37 1028.53 1031.74 –3.21

MW-345 1022.94 1015.61 1019.28 1028.37 –9.09

MW-347 1046.71 1046.41 1046.56 1033.91 12.65

MW-353 1068.06 1040.76 1054.41 1048.20 6.21

MW-354 1066.47 1045.45 1055.96 1048.23 7.73

58  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-355 1064.60 1037.40 1051.00 1049.44 1.56

MW-356 1066.15 1040.57 1053.36 1055.82 –2.46

MW-357 1055.44 1046.08 1050.76 1052.15 –1.39

MW-358 1070.86 1047.45 1059.16 1057.60 1.56

MW-359 1066.67 1040.22 1053.44 1057.60 –4.16

MW-364 1069.53 1061.17 1065.35 1066.43 –1.08

MW-365 1062.41 1055.44 1058.93 1065.78 –6.85

MW-366 1061.46 1054.11 1057.79 1065.72 –7.92

MW-367 1064.97 1058.11 1061.54 1066.04 –4.50

MW-368 1069.79 1059.91 1064.85 1062.30 2.55

MW-369 1069.15 1054.54 1061.85 1062.50 –0.65

MW-370 1069.12 1057.94 1063.53 1063.77 –0.24

MW-371 1037.71 1030.25 1033.98 1035.99 –2.01

MW-372 1043.03 1043.79 1043.41 1036.08 7.33

MW-373 1033.70 1024.51 1029.11 1032.55 –3.44

MW-374 1029.79 1020.14 1024.96 1032.40 –7.44

MW-375 1033.42 1023.35 1028.39 1030.64 –2.25

MW-381 1063.69 1058.04 1060.87 1054.81 6.06

MW-382 1060.42 1054.92 1057.67 1041.51 16.17

MW-384 1059.38 1057.47 1058.43 1052.45 5.98

MW-387 1037.34 1031.98 1034.66 1028.44 6.22

MW-388 1021.38 1016.93 1019.16 1005.57 13.59

MW-389 1023.78 1019.17 1021.48 1027.79 –6.31

MW-390 1004.60 1000.77 1002.68 994.38 8.30

MW-391 996.64 994.73 995.69 995.31 0.37

MW-392 1022.16 1017.16 1019.66 1002.42 17.24

MW-393 1023.15 1017.95 1020.55 1001.11 19.44

MW-395 970.43 964.63 967.53 973.66 –6.13

MW-397 950.70 943.88 947.29 953.90 –6.61

MW-398 971.78 968.06 969.92 962.79 7.13

MW-403 1072.07 1059.23 1065.65 1068.74 –3.09

MW-404 1071.05 1059.38 1065.21 1070.12 –4.91

MW-411 1071.13 1056.74 1063.93 1068.07 –4.14

MW-412 1069.41 1051.75 1060.58 1067.41 –6.83

Appendix  59
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-413 1069.23 1051.34 1060.29 1068.35 –8.06

MW-419 1072.25 1058.51 1065.38 1067.93 –2.55

MW-420 1069.61 1052.73 1061.17 1067.19 –6.02

MW-421 1068.99 1050.92 1059.95 1068.15 –8.20

MW-422 1080.07 1079.29 1079.68 1075.16 4.52

MW-428 1054.51 1031.16 1042.84 1046.19 –3.35

MW-429 947.73 941.13 944.43 951.94 –7.51

MW-430 953.13 945.56 949.35 954.60 –5.25

MW-431 949.92 943.13 946.53 953.94 –7.42

MW-432 962.60 958.36 960.48 953.81 6.67

MW-435 943.90 937.98 940.94 954.83 –13.89

MW-436 944.07 938.13 941.10 954.73 –13.63

MW-437 949.31 942.55 945.93 952.99 –7.06

MW-438 946.64 939.71 943.18 950.64 –7.46

MW-439 957.98 952.96 955.47 960.78 –5.31

MW-440 953.18 948.58 950.88 951.73 –0.85

MW-441 1022.03 1017.69 1019.86 1010.79 9.07

MW-442 948.56 942.01 945.29 952.21 –6.93

MW-443 959.39 947.06 953.23 957.39 –4.17

MW-444 961.99 948.30 955.15 957.53 –2.38

MW-445 947.98 941.39 944.69 951.10 –6.42

MW-446 941.41 939.81 940.61 951.09 –10.48

MW-447 948.04 939.85 943.95 951.10 –7.15

MW-448 948.08 941.33 944.71 951.10 –6.40

MW-449 937.12 937.65 937.39 951.11 –13.72

MW-450 1042.78 1025.97 1034.38 1017.36 17.02

MW-451 1045.05 1026.19 1035.62 1033.94 1.68

MW-452 1069.24 1050.81 1060.03 1067.10 –7.07

MW-453 1058.48 1048.76 1053.62 1056.62 –3.00

MW-454 1074.15 1059.17 1066.66 1065.90 0.76

MW-455 1069.26 1051.06 1060.16 1065.92 –5.76

MW-456 1045.35 1043.68 1044.52 1062.17 –17.65

MW-457 1057.88 1048.32 1053.10 1060.79 –7.69

MW-458 1059.77 1051.90 1055.84 1063.91 –8.07

60 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-460 1056.36 1046.91 1051.64 1051.46 0.18

MW-461 1039.57 1021.40 1030.48 1018.09 12.39

MW-462 1000.90 990.19 995.55 1008.12 –12.58

MW-463 1058.21 1036.54 1047.38 1032.72 14.66

MW-464 1026.83 1010.56 1018.70 1017.75 0.95

MW-467 1006.28 994.77 1000.53 1019.16 –18.63

MW-468 1001.99 991.97 996.98 998.42 –1.44

MW-469 1001.97 991.46 996.72 998.42 –1.70

MW-470 1071.16 1068.14 1069.65 1072.19 –2.54

MW-471 1046.91 1026.71 1036.81 1025.90 10.91

MW-472 1012.50 998.78 1005.64 1015.35 –9.71

MW-473 1067.98 1048.52 1058.25 1056.51 1.74

MW-474 1001.95 991.39 996.67 998.45 –1.78

MW-475 1078.16 1059.44 1068.80 1066.62 2.18

MW-476 1080.04 1075.99 1078.02 1072.43 5.59

MW-481 1058.13 1047.86 1052.99 1057.23 –4.24

MW-487 1088.17 1078.89 1083.53 1074.92 8.61

MW-488 1053.69 1028.56 1041.13 1040.58 0.55

MW-490 937.77 935.86 936.82 947.43 –10.61

MW-491 937.44 935.37 936.41 947.52 –11.12

MW-492 936.47 935.69 936.08 947.43 –11.35

MW-494 1059.99 1049.13 1054.56 1058.13 –3.57

MW-495 1022.12 1017.20 1019.66 1008.62 11.04

MW-496 1022.23 1017.25 1019.74 1011.89 7.85

MW-497 1022.12 1017.88 1020.00 1018.55 1.45

MW-498 1082.55 1080.14 1081.35 1073.34 8.01

MW-499 1008.06 997.96 1003.01 996.56 6.45

MW-501 1057.43 1037.86 1047.65 1034.16 13.49

MW-502 1062.92 1043.14 1053.03 1040.83 12.20

MW-503 1007.68 998.21 1002.95 997.01 5.94

MW-504 1057.40 1047.08 1052.24 1044.92 7.32

MW-505 1055.86 1046.68 1051.27 1044.86 6.41

MW-506 1057.45 1037.81 1047.63 1034.17 13.46

MW-507 1057.44 1037.82 1047.63 1034.29 13.34

Appendix  61
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-508 1057.42 1037.82 1047.62 1034.32 13.30

MW-509 1057.41 1037.80 1047.61 1034.32 13.29

MW-510 1057.45 1037.66 1047.56 1034.80 12.76

MW-518 1069.14 1050.67 1059.91 1067.13 –7.22

MW-519 1069.16 1050.63 1059.90 1067.15 –7.25

MW-520 1069.16 1050.64 1059.90 1067.16 –7.26

MW-524 1001.59 991.07 996.33 998.31 –1.98

MW-525 1002.24 991.86 997.05 998.66 –1.61

MW-551 1057.58 1047.67 1052.63 1056.66 –4.03

MW-553 1033.93 1025.83 1029.88 1032.81 –2.93

MW-555 1035.47 1027.21 1031.34 1033.85 –2.51

MW-557 1036.64 1028.93 1032.79 1034.44 –1.65

MW-559 1000.11 990.88 995.50 994.50 1.00

MW-560 1016.85 1008.33 1012.59 1000.07 12.52

MW-561 1017.41 1007.79 1012.60 999.53 13.07

MW-562 996.53 987.01 991.77 996.27 –4.50

MW-563 997.66 989.90 993.78 996.22 –2.44

MW-564 1040.85 1033.06 1036.95 1037.78 –0.83

MW-567 1039.34 1031.71 1035.53 1036.76 –1.23

MW-569 1043.22 1034.73 1038.97 1039.56 –0.59

MW-570 1043.18 1035.45 1039.32 1039.77 –0.45

MW-571 1048.65 1036.89 1042.77 1041.78 0.99

MW-572 1049.36 1038.21 1043.79 1042.05 1.74

MW-573 1036.66 1029.62 1033.14 1035.41 –2.27

MW-574 1034.55 1026.18 1030.37 1033.65 –3.28

MW-575 1032.66 1022.81 1027.73 1032.83 –5.10

MW-576 1036.49 1035.53 1036.01 1032.93 3.08

MW-577 947.98 941.32 944.65 951.06 –6.41

MW-578 1034.97 1027.44 1031.20 1034.38 –3.18

MW-580 937.52 933.32 935.42 946.98 –11.56

MW-581 941.46 935.39 938.43 947.36 –8.94

MW-582 937.51 936.33 936.92 947.36 –10.44

MW-583 953.87 946.54 950.21 957.34 –7.13

MW-584 972.99 969.52 971.26 975.15 –3.90

62 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-585 972.06 968.36 970.21 972.07 –1.86

MW-586 1023.68 1018.36 1021.02 1016.72 4.30

MW-588 959.74 955.20 957.47 963.42 –5.95

MW-589 1071.41 1061.48 1066.44 1066.77 –0.33

MW-591 1085.86 1082.81 1084.34 1078.57 5.77

MW-592 1084.55 1082.55 1083.55 1077.98 5.57

MW-594 1079.86 1078.82 1079.34 1072.65 6.69

MW-596 1080.31 1078.96 1079.64 1072.91 6.73

MW-597 1048.79 1046.85 1047.82 1061.62 –13.80

MW-598 1069.13 1057.74 1063.43 1063.25 0.18

MW-599 1056.31 1048.90 1052.61 1066.93 –14.32

MW-600 1056.47 1048.99 1052.73 1066.96 –14.23

MW-601 1006.29 996.41 1001.35 985.52 15.83

MW-602 1007.21 998.66 1002.93 985.41 17.52

MW-603 972.17 971.46 971.82 982.76 –10.94

MW-604 974.99 968.98 971.99 982.37 –10.39

MW-605 974.15 971.11 972.63 983.21 –10.58

MW-606 971.45 966.10 968.78 983.14 –14.37

MW-607 998.40 992.99 995.70 994.92 0.77

MW-608 982.08 975.29 978.69 989.31 –10.62

MW-609 1008.27 1007.01 1007.64 996.12 11.52

MW-610 1000.98 999.99 1000.49 996.14 4.35

MW-611 1026.44 1021.78 1024.11 1009.05 15.06

MW-612 979.38 973.83 976.61 988.30 –11.70

MW-613 995.22 990.08 992.65 983.80 8.85

MW-614 1022.55 1008.91 1015.73 997.56 18.17

MW-615 1044.04 1014.59 1029.32 1031.62 –2.30

MW-616 1051.73 1032.91 1042.32 1039.21 3.11

MW-617 1051.78 1034.34 1043.06 1041.17 1.89

MW-618 1086.51 1082.37 1084.44 1084.45 –0.01

MW-619 1086.10 1082.62 1084.36 1083.59 0.77

MW-620 1009.38 1000.06 1004.72 1028.54 –23.82

MW-621 987.78 982.80 985.29 979.08 6.21

MW-622 1031.27 1020.82 1026.05 1030.22 –4.17

Appendix  63
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-623 1077.69 1076.26 1076.97 1072.54 4.43

MW-624 1079.28 1077.51 1078.40 1072.83 5.57

MW-625 1086.04 1082.06 1084.05 1080.61 3.44

MW-626 1085.32 1082.08 1083.70 1078.84 4.86

MW-628 1043.50 1035.03 1039.27 1040.05 –0.78

MW-629 1044.05 1036.08 1040.07 1040.27 –0.20

MW-630 1043.97 1036.62 1040.30 1040.27 0.03

MW-632 1039.35 1032.01 1035.68 1035.73 –0.05

MW-633 1040.24 1037.05 1038.65 1035.86 2.80

MW-635 1061.49 1055.98 1058.73 1067.22 –8.49

MW-636 1052.59 1035.59 1044.09 1041.41 2.68

MW-642 1085.31 1082.20 1083.76 1077.33 6.43

MW-643LD 1051.03 1048.87 1049.95 1059.56 –9.61

MW-643UD 1058.42 1049.97 1054.19 1059.65 –5.46

MW-644LD 1045.45 1039.31 1042.38 1059.31 –16.93

MW-644UD 1057.91 1048.69 1053.30 1059.39 –6.09

MW-645LD 1044.88 1048.11 1046.49 1059.85 –13.36

MW-645UD 1058.45 1048.17 1053.31 1059.85 –6.54

MW-646LD 1043.47 1038.07 1040.77 1060.11 –19.34

MW-646UD 1056.72 1048.51 1052.62 1060.11 –7.49

MW-647 1030.76 1013.56 1022.16 1017.52 4.64

MW-648 1053.31 1028.57 1040.94 1040.59 0.35

MW-649 1054.88 1031.15 1043.02 1046.12 –3.10

MW-650 1050.47 1030.23 1040.35 1045.90 –5.55

MW-651 1070.22 1055.10 1062.66 1062.31 0.35

MW-652 1070.31 1055.16 1062.73 1062.53 0.20

MW-653 1057.72 1038.13 1047.93 1061.51 –13.58

MW-654 1069.01 1050.37 1059.69 1061.52 –1.83

MW-655 1052.75 1036.38 1044.57 1045.82 –1.25

MW-656 1059.46 1056.44 3.02

MW-656LD 1069.02 1049.73 1058.92 1056.46 2.46

MW-657 1069.15 1050.05 1059.60 1065.11 –5.51

MW-658 1069.10 1050.00 1059.55 1065.13 –5.58

MW-659 1030.59 1026.23 1028.41 1015.98 12.43

64  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-559A 1000.18 990.37 995.28 994.50 0.78

MW-660 1062.50 1053.98 1058.24 1065.94 –7.70

MW-661 1065.25 1051.63 1058.44 1061.47 –3.03

MW-662 1062.33 1055.95 1059.14 1064.52 –5.38

MW-665 1069.10 1050.16 1059.63 1064.56 –4.93

MW-666 1070.81 1066.19 1068.50 1067.38 1.12

MW-667 1070.77 1066.16 1068.46 1067.40 1.06

MW-668 1070.87 1068.35 1069.61 1068.03 1.58

MW-669 1073.22 1064.70 1068.96 1065.77 3.19

MW-670 1075.25 1066.43 1070.84 1066.73 4.11

MW-671 1076.11 1069.13 1072.62 1064.13 8.49

MW-672 1071.74 1065.74 1068.74 1066.91 1.83

MW-674 1071.85 1062.90 1067.38 1065.07 2.31

MW-675 1071.47 1062.52 1066.99 1065.05 1.94

MW-676 1071.63 1062.19 1066.91 1065.84 1.07

MW-677 1050.55 1030.61 1040.58 1051.89 –11.31

MW-678 1050.54 1030.61 1040.58 1051.89 –11.31

MW-679 1074.03 1071.11 1072.57 1074.31 –1.74

MW-680 1073.43 1070.64 1072.04 1074.59 –2.55

MW-681 1091.57 1081.26 1086.42 1087.87 –1.45

MW-682 1092.01 1081.75 1086.88 1087.77 –0.89

MW-683 1090.22 1078.93 1084.58 1086.94 –2.36

MW-684 1087.58 1077.39 1082.48 1086.74 –4.26

MW-685 1084.64 1076.66 1080.65 1092.47 –11.82

MW-686 1084.81 1076.87 1080.84 1092.43 –11.59

MW-687 1077.76 1070.29 1074.03 1086.17 –12.14

MW-688 1078.10 1070.47 1074.29 1086.86 –12.57

MW-689 1085.06 1078.39 1081.72 1086.78 –5.06

MW-690 1077.79 1070.33 1074.06 1086.61 –12.55

MW-691 1081.87 1076.24 1079.06 1086.70 –7.64

MW-698 1039.29 1021.87 1030.58 1034.61 –4.03

MW-699 1045.88 1039.55 1042.71 1035.10 7.61

MW-700 1014.36 1001.18 1007.77 1009.97 –2.20

MW-701 1006.86 994.94 1000.90 1011.10 –10.20

Appendix  65
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

MW-702 1056.77 1051.17 1053.97 1048.51 5.46

19_LF2_MW_01 969.37 965.38 967.38 966.53 0.84

19_LF2_MW_04 1005.85 986.10 995.98 977.70 18.27

19_LF2_MW_06 1000.79 990.07 995.43 982.53 12.90

JAR-002 1106.30 1092.21 1099.26 1091.69 7.57

JAR-003 1084.85 1081.82 1083.34 1082.57 0.77

PZ_22_1a 1006.08 997.78 1001.93 993.56 8.37

PZ_22_2 1005.22 995.59 1000.41 991.76 8.65

PZ_22_3 1003.61 994.74 999.18 993.55 5.62

PZ-BKG-1 1061.16 1039.64 1050.40 1044.31 6.09

SSB7-PZ 1061.07 1045.55 1053.31 1041.13 12.18

UTSI-3 982.31 975.82 979.07 964.15 14.92

UTSI-5 982.39 977.04 979.72 963.52 16.20

UTSI-6 983.48 979.58 981.53 963.75 17.78

A-002 992.09 986.19 989.14 989.54 –0.40

A-003 1011.28 1002.32 1006.80 989.95 16.85

A-010 1065.36 1056.33 1060.85 1044.49 16.36

A-013 972.97 962.74 967.86 987.09 –19.24

A-016 961.71 959.30 960.51 960.65 –0.14

A-021 970.29 967.48 968.89 969.56 –0.68

A-030 1017.64 1007.71 1012.68 1003.83 8.85

A-031 1039.58 1025.74 1032.66 1010.39 22.28

A-034 1040.90 1038.07 1039.48 1044.59 –5.11

B-001 1024.62 1018.18 1021.40 999.85 21.55

B-002 1023.60 991.91 1007.76 1006.42 1.34

B-005 1043.00 1026.04 1034.52 1018.03 16.49

B-006 1028.14 1019.30 1023.72 1028.50 –4.78

B-011 999.66 991.18 995.42 993.28 2.14

B-014 1031.50 1020.35 1025.93 1015.00 10.93

B-015 992.96 988.18 990.57 994.35 –3.78

B-018 1021.38 1015.11 1018.25 1007.33 10.93

B-019 965.20 962.41 963.81 980.66 –16.85

B-022 1012.49 988.50 1000.50 1005.41 –4.91

B-023 1011.91 1006.71 1009.31 1014.14 –4.83

66  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

B-031 1034.23 1022.10 1028.17 1007.52 20.65

B-034 1090.59 1073.30 1081.94 1056.05 25.89

B-038 1044.95 1036.80 1040.88 1025.32 15.56

B-039 964.00 961.43 962.72 975.44 –12.73

C-001 1010.92 1000.28 1005.60 985.22 20.38

C-002 1021.10 1015.39 1018.25 1002.18 16.07

C-003 1024.85 1015.46 1020.16 1019.15 1.01

C-009 1016.80 1006.05 1011.43 997.67 13.76

C-012 1047.90 1036.66 1042.28 1013.37 28.91

C-015 986.55 981.21 983.88 983.44 0.44

C-016 991.84 984.53 988.19 982.30 5.89

C-023 1030.55 1019.69 1025.12 1005.84 19.28

C-025 1023.62 1011.58 1017.60 1011.51 6.10

C-026 1056.46 1042.42 1049.44 1032.83 16.61

C-028 1072.40 1055.66 1064.03 1046.54 17.49

C-029 1062.47 1045.96 1054.21 1048.19 6.02

C-039 1049.73 1035.17 1042.45 1037.00 5.45

D-002 975.64 965.68 970.66 978.20 –7.54

D-008 972.39 967.09 969.74 975.27 –5.53

D-009 972.18 967.42 969.80 974.28 –4.48

D-011 958.96 956.84 957.90 968.10 –10.20

D-012 965.19 962.30 963.75 970.37 –6.63

D-013 968.62 963.85 966.24 968.17 –1.93

D-014 962.30 960.37 961.34 971.07 –9.74

D-016 970.45 962.31 966.38 970.37 –3.99

D-018 983.34 962.40 972.87 971.83 1.04

D-027 1010.80 1001.40 1006.10 997.78 8.32

D-030 971.69 964.72 968.21 977.55 –9.35

DW38 951.13 949.26 950.20 964.51 –14.31

E-001 1107.46 1099.75 1103.61 1122.38 –18.77

E-002 1106.55 1097.86 1108.20 1097.77 10.43

E-003 1051.74 1047.66 1049.70 1067.93 –18.23

E-004 1057.68 1051.70 1054.69 1065.39 –10.70

E-005 1048.53 1043.28 1045.91 1054.79 –8.88

Appendix  67
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

E-006 1058.03 1047.55 1052.79 1058.49 –5.69

E-007 1025.34 1024.05 1024.69 1028.04 –3.35

E-008 1050.51 1045.50 1048.01 1045.99 2.02

E-009 1095.05 1088.86 1091.95 1078.24 13.71

E-010 1103.16 1091.86 1097.51 1099.23 –1.72

E-011 1050.79 1037.40 1044.10 1051.86 –7.76

E-012 1066.70 1058.02 1062.36 1058.74 3.63

E-013 1057.80 1045.58 1051.69 1064.65 –12.96

E-014 1061.51 1050.62 1056.07 1059.95 –3.88

E-015 1055.45 1046.27 1050.86 1060.27 –9.41

E-016 1050.58 1046.30 1048.44 1046.45 1.99

E-017 1091.35 1078.88 1085.12 1062.09 23.03

E-018 1078.65 1068.10 1073.38 1065.28 8.10

E-020 1064.70 1037.71 1051.20 1052.22 –1.02

E-021 1054.17 1042.94 1048.56 1052.12 –3.56

E-022 1063.82 1051.30 1057.56 1065.01 –7.45

F-001 998.30 993.75 996.03 990.35 5.68

F-002 1017.30 1015.90 1016.60 1023.15 –6.55

F-004 1041.41 1032.40 1036.91 1013.62 23.29

F-005 1020.50 1009.90 1015.20 1001.06 14.14

F-007 1020.00 1014.30 1017.15 1016.39 0.76

F-008 1043.00 1037.75 1040.38 1035.08 5.30

F-009 1051.20 1037.90 1044.55 1044.73 –0.18

F-010 1043.44 1036.76 1040.10 1034.44 5.66

F-011 1032.20 1016.20 1024.20 1007.42 16.78

F-012 1022.40 1021.20 1021.80 1010.27 11.53

F-013 1011.90 1007.70 1009.80 990.53 19.27

F-015 1002.10 999.00 1000.55 990.12 10.43

F-018 1009.50 1006.00 1007.75 1003.74 4.01

F-019 1025.50 1016.70 1021.10 1020.14 0.96

F-020 1043.90 1042.10 1043.00 1042.91 0.09

F-021 1024.60 1019.20 1021.90 1029.60 –7.70

F-022 1052.10 1039.10 1045.60 1043.86 1.74

F-023 1043.10 1035.10 1039.10 1033.08 6.02

F-024 1039.60 1030.85 1035.22 1028.52 6.70

68  Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

F-025 1015.80 1004.50 1010.15 997.45 12.70

F-027 998.60 984.50 991.55 973.59 17.96

F-028 1003.50 994.10 998.80 981.16 17.64

F-029 1048.00 1033.30 1040.65 1025.38 15.27

F-030 1003.00 996.20 999.60 984.66 14.94

F-031 976.50 973.20 974.85 976.30 –1.45

F-032 950.70 948.30 949.50 956.37 –6.87

F-033 984.90 981.80 983.35 985.92 –2.57

F-034 938.20 937.50 937.85 954.68 –16.83

F-035 1009.10 997.00 1003.05 1002.40 0.65

F-036 1023.90 1010.60 1017.25 1018.90 –1.65

F-037 1026.00 1013.80 1019.90 982.69 37.21

F-038 1007.50 1001.00 1004.25 984.28 19.97

F-040 996.10 991.40 993.75 975.67 18.08

F-041 1002.40 989.20 995.80 995.23 0.57

F-042 1013.60 1013.50 1013.55 993.09 20.46

F-043 942.90 939.10 941.00 956.78 –15.78

F-044 931.10 928.10 929.60 951.81 –22.21

F-046 1038.40 1029.20 1033.80 1035.34 –1.54

F-047 1030.20 1006.90 1018.55 1024.39 –5.84

F-048 952.30 951.10 951.70 957.59 –5.89

F-049 957.00 954.60 955.80 940.78 15.02

F-050 954.70 953.10 953.90 961.93 –8.03

F-051 956.90 954.20 955.55 965.74 –10.19

F-052 941.50 940.00 940.75 948.49 –7.74

F-053 932.00 929.60 930.80 962.55 –31.75

F-059 1016.90 1007.30 1012.10 1029.02 –16.92

F-060 1021.10 1016.50 1018.80 1007.10 11.70

R-002 972.06 965.14 968.60 977.57 –8.97

R-003 973.93 967.40 970.67 977.92 –7.26

R-006 972.11 966.62 969.37 985.02 –15.66

R-007 997.18 990.21 993.70 987.06 6.63

R-016 966.66 958.36 962.51 980.44 –17.93

R-018 996.81 991.30 994.06 991.83 2.23

R-021 960.34 953.90 957.12 980.93 –23.81

Appendix  69
Appendix. Comparison of measured and simulated water-level altitudes for the Arnold Air Force Base area

ground-water flow model.—Continued

Well

Water-level elevation, in feet

May 2002 October 2002 Average Simulated Residual

R-024 999.10 992.19 995.65 999.28 –3.64

R-026 1003.95 998.26 1001.11 992.64 8.47

R-027 974.50 967.76 971.13 982.05 –10.92

R-028 972.03 965.50 968.77 982.63 –13.86

R-031 964.86 959.99 962.43 978.57 –16.14

R-033 961.98 956.93 959.46 980.11 –20.65

R-034 972.73 966.25 969.49 980.75 –11.26

R-035 995.08 988.41 991.75 1002.21 –10.47

R-040 994.25 987.65 990.95 998.49 –7.54

R-047 1016.34 1006.20 1011.27 994.05 17.22

R-048 974.38 971.36 972.87 985.39 –12.52

R-050 979.65 975.78 977.72 982.65 –4.93

R-062 1015.82 1009.31 1012.57 1002.61 9.96

R-065 998.17 987.29 992.73 993.08 –0.35

R-068 1025.67 1017.56 1021.62 1007.90 13.72

R-100 979.63 974.00 976.82 984.83 –8.02

R-101 983.47 976.47 979.97 979.53 0.44

R-102 966.61 962.25 964.43 967.48 –3.05

R-103 997.17 991.62 994.40 986.79 7.60

R-104 1034.49 1015.57 1025.03 1014.78 10.25

R-105 994.71 985.47 990.09 984.59 5.50

S-001 950.60 938.94 944.77 956.56 –11.79

S-009 949.36 943.11 946.24 959.87 –13.64

S-017 940.46 931.08 935.77 958.23 –22.46

S-019 951.04 943.28 947.16 964.36 –17.20

S-022 941.55 933.46 937.51 955.08 –17.58

S-027 938.74 927.85 933.30 956.56 –23.27

S-029 960.97 941.55 951.26 959.57 –8.31

S-030 1046.10 1028.95 1037.53 1025.18 12.35

S-031 1034.55 1030.31 1032.43 1021.75 10.68

S-032 1007.13 1004.22 1005.68 995.34 10.34

S-033 973.38 972.53 972.96 976.24 –3.29

S-034 1008.22 1004.81 1006.52 1012.49 –5.97

SH17 955.34 958.25 956.80 978.59 –21.80

SJO35 941.10 941.03 941.07 963.29 –22.22

70 Hydrogeology and Simulation of Ground-Water Flow at Arnold Air Force Base ... 2002 Update