U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Characterization of Hydraulic Conductivity of the 

Alluvium and Basin Fill, Pinal Creek Basin 

near Globe, Arizona

TOXIC SUBSTANCES HYDROLOGY PROGRAM

By Cory E. Angeroth

Tucson, Arizona

2002

Water-Resources Investigations Report 02—4205
For additional information write to:

District Chief

U.S. Geological Survey

Water Resources Division

520 N. Park Avenue, Suite 221

Tucson, AZ 85719–5035

Copies of this report can be purchased from:

U.S. Geological Survey

Information Services

Box 25286

Federal Center

Denver, CO 80225–0046

The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute 

endorsement by the U.S. Geological Survey.

Information about U.S. Geological Survey programs in Arizona is available online at http://az.water.usgs.gov.

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director
Contents iii

CONTENTS

Page

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

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

Purpose and scope....................................................................................................................................... 1

Previous investigations................................................................................................................................ 3

Site description............................................................................................................................................ 3

Slug tests .............................................................................................................................................................. 5

Procedure..................................................................................................................................................... 5

Analytical methods...................................................................................................................................... 6

Results and distribution of hydraulic conductivity .............................................................................................. 11

Summary .............................................................................................................................................................. 14

References cited ................................................................................................................................................... 14

FIGURES

1. Map showing location of study area, Pinal Creek Basin, Arizona....................................................... 2

2. Diagram showing Generalized monitor-well construction................................................................... 5

3. Diagram of equipment used in pneumatic slug tests ............................................................................ 6

4. Graphs showing Composite plot of type curves and drawdown data from pnuematic slug tests for: 

A. Straight-line method and data from second test at well 502......................................................... 8

B. Oscillatory type-curve matching method and data from second test at well 51........................... 8

5. Graph showing line of section approximating the principal ground-water flow line from 

Kiser Basin to Inspiration Dam along the channels of Miami Wash and Pinal Creek. 

A Distribution of hydraulic conductivity ......................................................................................... 12 

B. Distribution of pH......................................................................................................................... 12

6. Graph showing relation between pH and hydraulic conductivity in ground water in the 

alluvium and in ground water in the basin fill...................................................................................... 13

TABLES

1. Well-construction data.......................................................................................................................... 4

2. Slug-test results .................................................................................................................................... 9

3. Ground-water pH.................................................................................................................................. 13
iv Contents

CONVERSION FACTORS AND DATUMS

Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times foot of aquifer thickness 

[(ft3d)/ft2]ft. In this report, the mathematically reduced form, foot squared per day (ft2/d), is used for convenience.

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

°F=(1.8°C)+32

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29)—a geodetic datum 

derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level

Datum of 1929; horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27). Altitude, as 

used in this report, refers to distance above or below NGVD 29

Multiply By To obtain

centimeter (cm) 0.3937 inch

millimeter (mm) 0.03937 inch

meter (m) 3.281 foot 

kilometer (km) 0.6214 mile 

meter (m) 1.094 yard 

square meter (m2) 10.76 square foot 

square centimeter (cm2) 0.1550 square inch 

pounds per square inch (psi) 6,895 pascal

meter per day (m/d) 3.281 foot per day 

meter squared per day (m2/d) 10.76 foot squared per day 
Introduction 1

Characterization of Hydraulic Conductivity of the Alluvium 

and Basin Fill, Pinal Creek Basin near Globe, Arizona

By Cory E. Angeroth

Abstract 

Acidic waters containing elevated concentrations of dissolved metals have contaminated the regional 

aquifer in the Pinal Creek Basin, which is in Gila County, Arizona, about 100 kilometers east of Phoenix. 

The aquifer is made up of two geologic units: unconsolidated stream alluvium and consolidated basin fill. 

To better understand how contaminants are transported through these units, a better understanding of the 

distribution of hydraulic conductivity and processes that affect it within the aquifer is needed.

Slug tests were done in September 1997 and October 1998 on 9 wells finished in the basin fill and 

14 wells finished in the stream alluvium. Data from the tests were analyzed by using either the Bouwer 

and Rice (1976) method, or by using an extension to the method developed by Springer and Gellhar 

(1991). Both methods are applicable for unconfined aquifers and partially penetrating wells. The results 

of the analyses show wide variability within and between the two geologic units. Hydraulic conductivity 

estimates ranged from 0.5 to 250 meters per day for the basin fill and from 3 to 200 meters per day for the 

stream alluvium. Results of the slug tests also show a correlation coefficient of 0.83 between the hydraulic 

conductivity and the pH of the ground water. The areas of highest hydraulic conductivity coincide with 

the areas of lowest pH, and the areas of lowest hydraulic conductivity coincide with the areas of highest 

pH, suggesting that the acidic water is increasing the hydraulic conductivity of the aquifer by dissolution 

of carbonate minerals.

INTRODUCTION

The principal aquifer in the Pinal Creek Basin near 

Globe, Arizona, is contaminated with acidic waters that 

contain elevated concentrations of dissolved metals 

(Neaville and Brown, 1993) and has been studied by 

the U.S. Geological Survey (USGS) since 1984. To 

better understand how ground water and dissolved 

contaminants in the ground water are transported 

through the aquifer, better information on the 

distribution of hydraulic conductivity in the aquifer is 

needed. 

Purpose and Scope

The purpose of this study, as part of the larger 

research study, was to determine the distribution of 

hydraulic conductivity and the processes affecting it 

along the alluvial channel from Kiser Basin to the 

outlet of Pinal Creek at Inspiration Dam (fig. 1). The 

primary objectives were to collect and analyze slug-test 

data from as many USGS wells as possible and create a 

cross-section of hydraulic-conductivity distribution 

along the axis of the valley on the basis of test results. 
2 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona

Miami Globe

PINAL

MOUNTAINS

Old Dominion

 mine

Inspiration Dam

Solitude

Tailings

Pond

GLOBE

HILLS

Webster

Lake (dry)

Nugget

Wash

Pinal

Creek

Mia

mi Wash

Pinal

Cr eek

Base from U.S. Geological Survey,

1 :24,000; Globe, 1945, Rockingstraw

Mtn., 1986, Salt River Peak, 1986,

and Inspiration, 1945

Tailings

Mine 

Mine 

PHOENIX

A R I Z O N A

Globe

Study area

Salt Ri ev r

Gila

Ri ev r

Mine Kiser Basin 

R

ussell G

ulch

BASIN BOU NDARY

AQ

U

FI ER

B

O

U NDARY

55'

110°45'

110°55'

 33°35'

 30'

 33°20'

 25'

0 1 2 3 MILES

0 1 2 3 KILOMETERS

 Webster Gulch

(buried) 

Sa

R

lt

iver

700

300

100

50

400

500 540

560

EXPLANATION

WELL GROUP—Number 

 is site identifier

100

Figure 1. Location of study area, Pinal Creek Basin, Arizona.
Introduction 3

This report presents the magnitudes and distribution of 

hydraulic conductivity developed from aquifer testing 

and discusses some of the chemical processes that may 

be affecting them.

Previous Investigations

The USGS, private consulting firms, and other 

government agencies have extensively studied the 

hydrogeology of the Pinal Creek Basin. The presence 

of contaminated ground water has long been 

recognized in the basin, but was not studied until 1979 

(Envirologic Systems, Inc., 1983). Since that time, 

many studies have been completed.

Ransome (1903) and Peterson (1962) produced 

reports that emphasize the mineral resources in the 

area. Hazen and Turner (1946) documented initial 

hydrologic studies of the area, reported water-level and 

well-inventory information, and provided a description 

of the hydrogeologic system. The basin was selected as 

a research site for the USGS Toxic Substances 

Hydrology Program in 1984. Since that time, the 

research study has produced reports and journal articles 

that document the controls on contaminant migration. 

A complete bibliography is available online at 

http://toxics.usgs.gov/bib/bib-pinal.html (accessed 

December 4, 2001). Also under this program, Neaville 

and Brown (1993) produced a report on the 

hydrogeology and hydrologic system that presents 

findings on the hydraulic conductivity and storage 

properties of the alluvial aquifer in the Pinal Creek 

Basin. Pool and Eychaner (1995) used gravity methods 

to determine storage properties of the stream alluvium 

in the basin.

Mining companies, consulting firms, and local 

government agencies have produced reports 

documenting, primarily, the hydrogeology of the 

contaminated area of the creek. Several of these (Hydro 

Geo Chem, 1989a, b; C.G. Taylor, environmental 

engineer, Magma Copper Corporation, written 

commun., 1987) presented hydraulic conductivity and 

storage property values for the basin fill and stream 

alluvium.

Site Description

Pinal Creek Basin is in Gila County, Arizona, 

about 100 km east of Phoenix (fig. 1). Nearly 

18,000 people inhabit the basin (U.S. Bureau of 

Census, 1991), most residing in the communities of 

Globe and Miami. Copper mining began in 1874 and is 

still the predominant industry in the basin. Vegetation 

in the basin is typical of the transition zone between the 

mountains of central Arizona and the hot, arid desert 

region of the southwestern part of the State (Peterson, 

1962, p. 4; Hazen and Turner, 1946, p. 5). Climate in 

the basin generally is arid and mild but varies 

considerably with elevation and season.

The geology of the basin is typical of many in the 

Basin and Range province as reported by Wilson and 

Moore (1959). Basin structure is dominated by northnorthwestward- and north-northeastward-trending 

normal faults that created structural troughs that were 

subsequently filled with alluvium (Neaville and Brown, 

1993). These alluvial deposits constitute the regional 

aquifer in the basin.

The aquifer is made up of two geologic units. 

Unconsolidated stream alluvium containing about 

0.3 percent carbonate is incised in consolidated to 

semiconsolidated basin fill, which contains about 

1.5 percent carbonate (Eychaner, 1989) that occurs 

mostly as a coating on grains and as cement between 

grains. Igneous and metamorphic bedrock bounds the 

aquifer laterally and at depth. The thickness of the 

aquifer varies from about 1,300 m near the Solitude 

Tailings pond to zero at the lateral boundaries. Stream 

alluvium overlying the basin fill ranges in thickness 

from about 35 m near the confluence of Miami Wash 

and Pinal Creek to 5 m at Inspiration Dam.

Activities related to large-scale copper mining have 

contaminated the regional aquifer and perennial 

streamflow with metal-rich, low-pH waters. The most 

acidic ground water currently has a pH of between 

about 3.6 to 5.0 and is partially neutralized by reactions 

with carbonate minerals as it moves through the 

aquifer. Neutralized contaminated water in the aquifer 

has a pH of about 6, and neutralized contaminated 

water in perennial streamflow has a pH of about 8. 

Contaminated ground-water is underlain by 

uncontaminated ground water which has a pH near 7. 

Carbonate minerals are present in the basin fill and the 

neutralized zone of the contamination plume, whereas 

in the acidic portion of the plume most, if not all, of the 

carbonate minerals have been dissolved (Brown and 

others, 1999, p. 143).

The USGS has installed 34 monitoring wells at 

11 sites within the basin (fig. 1). Each site has 

1 to 6 wells screened at different depths (table 1).
4 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona

Table 1. Well-construction data

Well Date completed Drilling method

Hole depth 

(m)

Well depth 

(m)

Depth to water at 

time of slug test

(m)

Screened interval 

(m) Geologic unit

 51 10–11–1984 Rotary, bentonite 33.5 33.4 16.6 32.4–33.3 Basin fill

 52 10–12–1984 Rotary, bentonite 20.1 19.8 16.6 18.8–19.7 Alluvium

 53 10–12–1984 Rotary, bentonite 28.0 27.8 16.6 26.8–27.7 Basin fill

101 10–10–1984 Rotary, bentonite 36.3 36.1 16.9 35.1–36.0 Basin fill

103 10–11–1984 Rotary, bentonite 19.2 25.3 15.1 18.1–19.0 Alluvium

105 05–22–1986 Rotary, bentonite 49.1 48.8 15.1 47.2–48.1 Basin fill

301 10–07–1984 Rotary, bentonite 59.4 59.1 12.6 58.1–59.0 Basin fill

302 10–08–1984 Rotary, bentonite 36.0 35.8 12.5 34.8–35.7 Alluvium

304 05–24–1986 Rotary, bentonite 48.8 30.3 14.7 28.7–29.6 Alluvium

401 10–09–1984 Rotary, bentonite 34.4 34.2 13.2 33.2–34.1 Basin fill

402 10–10–1984 Rotary, bentonite 21.0 20.9 13.2 19.8–20.7 Alluvium

403 10–10–1984 Rotary, bentonite 13.1 13.0 10.7 12.0–12.9 Alluvium

404 09–04–1986 Cable tool 55.5 55.3 10.7 53.7–54.6 Basin fill

501 05–22–1986 Rotary, bentonite 17.1 17.0 3.5 15.4–16.3 Alluvium

502 05–22–1986 Rotary, bentonite 38.1 38.0 3.5 36.5–37.4 Basin fill

503 05–22–1986 Rotary, bentonite 73.2 25.3 3.6 23.4–24.1 Alluvium

504 07–24–1986 Cable tool 69.5 69.2 2.2 67.6–68.6 Basin fill

505 12–17–1988 Hollow-stem auger 22.2 21.6 3.5 15.5–21.6 Alluvium

541 02–22–1997 Hollow-stem auger 24.7 12.6 5.8 11.1–12.6 Alluvium

542 02–22–1997 Hollow-stem auger 20.9 19.8 5.9 18.3–19.7 Alluvium

561 02–23–1997 Hollow-stem auger 17.1 15.3 5.1 13.8–15.3 Alluvium

701 05–11–1990 Hollow-stem auger 8.5 4.7 1.8 3.8–4.7 Alluvium

702 05–11–1990 Hollow-stem auger 8.1 7.3 1.9 6.4–7.3 Alluvium
Slug Tests 5

Most of the wells were constructed using 10.2-cm 

diameter polyvinyl chloride (PVC) well casing and 

0.9-m long PVC screens made from 1,470 factory-cut 

slots 3.6 cm long by 0.64 mm wide. Most of the 

boreholes were constructed using normal-circulation 

rotary drilling with bentonite mud, the other holes were 

drilled with an auger or cable tool. Because of different 

drilling methods, the boreholes have diameters that 

range from 15 cm to 25 cm. Every borehole annulus 

was filled with washed pea gravel to 0.5 m above the 

top of the screen. A layer of bentonite was placed from 

about 0.5 to 1.5 m above the screen. The hole was then 

backfilled with drill cuttings and a concrete seal was 

placed at the surface (fig. 2). The wells were developed 

by jetting air into the well screen under high pressure to 

agitate the gravel pack and formation and to airlift 

water and fine sediments from the well (Eychaner and 

others, 1989).

SLUG TESTS

Twenty-three of the wells were pneumatically slug 

tested to determine the range in hydraulic conductivity 

for the aquifer material. Tests were not done at 11 wells 

because the wells were dry, improperly constructed, or 

damaged. For conditions at Pinal Creek, pneumatic 

slug testing has several advantages over other more 

conventional methods. The most important advantage 

is that this method most closely approximates an 

instantaneous slug of water, which is critical for wells 

in which the water levels recover quickly (water levels 

in several wells fully recovered in less than 

10 seconds). Also, the conventional method of adding 

or removing a column of water could alter the aquifer 

chemistry, which is the primary focus of research at 

this site. Last, with this method only a submersed 

pressure transducer is in contact with the contaminated 

water, reducing the amount of decontamination needed 

between sites (fig. 3; Greene and Shapiro, 1995).

Procedure

The equipment and procedures used in this study 

are described in Greene and Shapiro (1995) and will be 

summarized here. The equipment needed includes a 

wellhead apparatus, pressure source, and pressure 

monitoring equipment (fig. 3). The wellhead apparatus 

is an air-tight enclosure that attaches to the well casing. 

The apparatus includes a release valve and standard 

fittings for the pressure source and monitoring 

equipment. A compressed-air tank was used to apply 

pressures to the wells of between 1.5 and 5.6 psi, which 

equate to an initial displacement of the water level 

between 1.09 and 3.95 m. A two-stage regulator was 

used to control the pressure accurately within the 

casing. For the tests done in 1997, two factorycalibrated 15-psi relative-pressure transducers were 

used: one to measure air pressure within the casing and 

a second, generally submerged 3 m below the water 

surface, to measure the water pressure. For the tests 

done in 1998, two lab-calibrated, 10-psi relativepressure transducers were used with the same set up as 

described above. A datalogger was used to record and 

store the data. Transducers and logging equipment 

capable of acquiring data several times per second 

provided the resolution needed for analysis of rapidly 

changing water levels. 

Water table

Concrete seal

Bentonite

Backfill

Washed

pea gravel

Well

casing

Figure 2. Generalized monitor-well construction.
6 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona

After the equipment was in place, the transducers 

were activated and the static condition was recorded for 

a short time to ensure that the water level had recovered 

from the installation of the transducer. To start each 

slug test, the release valve was closed and the casing 

was pressurized and maintained at a constant air 

pressure. When the readings from the submerged 

transducer stabilized, the release valve was opened 

quickly, and the pressurization source was isolated. 

Recovery was deemed complete when the readings 

from the submerged transducer stabilized at the pre-test 

value. For most wells, the procedure was then repeated 

two more times with the last test using an initial 

displacement similar to that of the first test, as 

recommended by Butler and others (1996). A logging 

rate of eight times per second was used in wells in 

which water levels recovered in less than 1 minute, and 

a logging rate of once per second was used when more 

than 1 minute was required for water-levels to recover 

completely.

Analytical Methods

Analysis of the slug test data was done by using the 

Bouwer and Rice method (1976), or by using an 

extension to the method developed by Springer and 

Water table

Perforated

interval

Submersible pressure transducer

Nonsubmersible pressure transducer

Compressed-air tank

Quick-release valve

Well casing

Access for manual

water-level

measurements

Pressure

regulator

Modified from Greene and Shapiro, 1995

Datalogger Laptop

computer

Figure 3. Diagram of equipment used in pneumatic slug tests.
Slug Tests 7

Gelhar (1991). The methods are applicable to response 

data from wells that fully or partially penetrate an 

unconfined aquifer. Two key assumptions of the 

methods are that (1) the effect of elastic storage 

mechanisms can be ignored, and (2) the position of the 

water table does not change during the course of the 

test (Butler, 1997).

The analytical solution by Bouwer and Rice (1976) 

can be written as:

, (1)

where

An important feature of this solution is that the plot of 

the logarithm of normalized head versus time is a 

straight line. The Bouwer and Rice (1976) method 

involves calculating the slope of the straight line fit to 

the response data and using that value to estimate the 

hydraulic conductivity of the formation. The method, 

as outlined in Butler (1997, p. 107), essentially consists 

of five steps:

1. The logarithm of the normalized response data is 

plotted versus the time since the test began.

2. A straight line is fit to the data plot either by visual 

inspection or an automated regression routine.

3. The slope of the fitted line is calculated. If the time 

lag, T0 (time at which a normalized head of 0.368, 

the natural logarithm of which is -1, is obtained), 

is used in this calculation, the slope, when written 

in terms of the natural logarithm, becomes -1/T0.

4. Values for the anisotropy ratio and the effective 

radius parameter are estimated for the particular 

well-formation configuration, these values are 

incorporated into the empirical parameter as 

described by Butler (1997). Unless information 

exists to the contrary, the anisotropy ratio is 

assumed equal to one.

5. The radial component of hydraulic conductivity is 

estimated with an expression obtained by 

rearranging equation 1 and rewriting it in terms of 

the slope calculated using T0:

, (2)

where

An example of the use of this method using the 

results from the second test at well 502 (fig. 4 a) is

shown below. Using the line fitted to the recovery data 

through the point, well-construction information, 

and an estimate of 2.5341 for the empirical parameter, 

produces a hydraulic conductivity (using equation 2) 

of:

m/s = 13.2 m/day.

This method is efficient but has been shown by 

Kipp (1985) to be invalid for high permeability 

formations. In these types of formations, the waterlevel response is at times oscillatory. These oscillations 

are caused by the inertia of the quickly recovering 

water column. The solution described by Bouwer and 

Rice (1976) does not account for inertia and is not valid 

for this type of response. 

H(t) = head in the well at time t, [L];

H0 = initial head displacement, [L];

Kr = radial component of hydraulic 

conductivity, [L/T];

b = screen length [L];

t = time, [T];

rc = radius of well casing, [L];

= empirical parameter estimated as 

described in Bouwer and Rice (1976) 

and Butler (1997) [dimensionless].

H t( )

H0

ln ---------- 2Krbt

rc

2 Re

rw∗ --------     ln

= –------------------------

Re

rw∗ --------     ln

T0 = time at which normalized head of 

0.368 is obtained.

1Value determined by using equations 6.4a through 6.5c in Butler (1997).

Kr

rc

2 Re rw ln[ ] ⁄ ∗

2bT0

= ---------------------------------

T0

Kr

( ) 0.05m 2( ) 2.534

2 0.9m ( )( ) 23.1s = -----------------------------------------

Kr 1.5 10–4 = ×
8 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona

1.0

0.01

LOG NORMALIZED HEAD, DIMENSIONLESS

0.1

80

TIME, IN SECONDS

0 10 20

1.0

– 0.2

NORMALIZED HEAD, DIMENSIONLESS

0.4

0.2

0

16

TIME, IN SECONDS

0

0.8

0.6

A.

B.

30

T0=23.1 seconds

Response data

Model fit of response data

(Bouwer and Rice, 1976)

40 50 60 70

2 4 6 8 10 12 14 18 20

(Springer and

Gellhar, 1991)

Model fit of response data

Response data

Figure 4. Composite plot of type curves and drawdown data from pnuematic slug tests for: A, Straight-line method and data 

from second test at well 502. B, Oscillatory type-curve matching method and data from second test at well 51.

Springer and Gelhar (1991) extended the Bouwer 

and Rice (1976) method to account for inertial effects. 

Their extension has been incorporated into a spreadsheet solution (Butler and Garnett, 2000) for analysis of 

highly permeable formations. The spreadsheet generates type curves, which are then superimposed on a plot 

of the response data. A dimensionless damping parameter, Cd, and a value that adjusts the dimensionless times 

(termed the modulation factor) are adjusted through 

trial and error until a close match between the type 

curve and response data exists. The spreadsheet calculates the hydraulic conductivity based on the Cd value, 

modulation-factor value, and well-construction information. For example, the type curve that produces the 

best match for the second test at well 51 occurs when 

the Cd value equals 1.5 and the modulation factor is set 

to 1.45 (fig. 4b). This produces a hydraulic conductivity estimate of 140 m/d. For this study, the spreadsheet 

method was used first, and if the Cd value required to 

approach a match became greater than about 5, as suggested by Kipp (1985), then the straight-line method 

was used.
Slug Tests 9

 The matches of the models and data are shown in 

the appendix of this report. The straight-line method 

was used to solve for hydraulic conductivity at 12 of 

the 23 wells tested; the spreadsheet method was used 

for the remaining 11 wells. The range of hydraulic 

conductivity estimates determined by using the 

straight-line method was 33 to 0.5 m/d. The range from 

the spreadsheet method was 250 to 28 m/d. Generally, 

the results of analysis of repeated tests were in close 

agreement and are adequate for producing estimates. 

In some cases the solution is good over only a portion 

of the data. In these cases the straight-line solutions 

were fit through the T0 point and the oscillatory 

solutions were fit through the first trough in the 

oscillatory response.

An inverse relation exists between the size of the 

slug, H0, and the K value (table 2). This relation is 

typical for highly permeable formations and commonly 

is seen as a result of non-Darcian flow losses (Butler 

and others, 1996). When doing slug tests, it is best to 

use a small slug size (H0) because the K value 

determined from using the smaller H0 probably is 

closer to the actual value.

Table 2. Slug-test results

Well_test number Test date

Initial head 

displacement (H0), 

in meters

Damping 

parameter 

(Cd) Analysis type

Hydraulic 

conductivity value, 

in meters per day

Hydraulic conductivity 

value used for 

contouring, 

in meters per day

51_2 10–07–1998 2.080 1.50 Spreadsheet 140

51_3 10–07–1998 1.355 1.36 Spreadsheet 170 170

51_4 10–07–1998 2.182 1.50 Spreadsheet 140

52_1 10–07–1998 1.974 1.95 Spreadsheet 180

52_2 10–07–1998 1.334 1.85 Spreadsheet 200 200

52_3 10–07–1998 2.049 1.95 Spreadsheet 180

53_1 10–07–1998 2.197 1.40 Spreadsheet 210

53_2 10–07–1998 1.279 1.15 Spreadsheet 250 250

53_3 10–07–1998 2.191 1.40 Spreadsheet 210

101_1 10–09–1998 1.982 2.20 Spreadsheet 83

101_2 10–09–1998 1.254 1.98 Spreadsheet 92 90

101_3 10–09–1998 1.942 2.20 Spreadsheet 83

103 09–04–1997 1.760 1.70 Spreadsheet 130 130

105 09–04–1997 1.751 >10 Straight line .8 .8

301 10–09–1998 1.417 >10 Straight line .5 .5

302 09–03–1997 3.950 >10 Straight line 30 30

304_1 10–09–1998 1.878 1.30 Spreadsheet 170

304_2 10–09–1998 1.282 1.18 Spreadsheet 190 190
10 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona

304_3 10–09–1998 1.899 1.30 Spreadsheet 170

401_1 10–08–1998 1.976 >10 Straight line 9.5

401_2 10–08–1998 1.524 >10 Straight line 10 10

401_3 10–08–1998 2.028 >10 Straight line 9.3

402_1 10–08–1998 2.039 2.70 Spreadsheet 84

402_2 10–08–1998 1.420 2.40 Spreadsheet 100 100

402_3 10–08–1998 2.070 2.70 Spreadsheet 92

403 09–05–1997 1.266 4.20 Spreadsheet 110 110

404 09–04–1997 2.780 >10 Straight line 1.2 1.2

501_1 10–08–1998 1.756 >10 Straight line 27

501_2 10–08–1998 1.093 >10 Straight line 32 32

501_3 10–08–1998 1.772 >10 Straight line 18

502_1 10–08–1998 1.825 >10 Straight line 12

502_2 10–08–1998 1.140 >10 Straight line 13 13

502_3 10–08–1998 1.922 >10 Straight line 13

503_1 10–08–1998 1.922 >10 Straight line 11

503_2 10–08–1998 1.284 >10 Straight line 14 14

503_3 10–08–1998 1.959 >10 Straight line 11

504 10–08–1998 1.856 >10 Straight line 7.1 7

505_1 10–08–1998 1.832 >10 Straight line 7.0

505_2 10–08–1998 1.287 >10 Straight line 10 10

505_3 10–08–1998 1.829 >10 Straight line 7.4

541_1 10–08–1998 1.479 1.60 Spreadsheet 42

541_2 10–08–1998 1.091 1.55 Spreadsheet 41 41

541_3 10–08–1998 1.597 1.65 Spreadsheet 42

542_1 10–08–1998 1.845 1.65 Spreadsheet 37

542_2 10–08–1998 1.318 1.45 Spreadsheet 36 36

542_3 10–08–1998 1.711 2.00 Spreadsheet 37

Table 2. Slug-test results—Continued

Well_test number Test date

Initial head 

displacement (H0), 

in meters

Damping 

parameter 

(Cd) Analysis type

Hydraulic 

conductivity value, 

in meters per day

Hydraulic conductivity 

value used for 

contouring, 

in meters per day
Results and Distribution of Hydraulic Conductivity 11

RESULTS AND DISTRIBUTION OF HYDRAULIC 

CONDUCTIVITY

Nine of the wells used in the study are screened 

over short intervals in the upper part of the basin fill. 

Analyses of the data from these wells produced 

hydraulic conductivity estimates that ranged from 

0.5 m/d at well 301 to 250 m/d at well 53 (table 2). 

An analysis of aquifer properties in alluvial basins 

throughout the Southwest produced a hydraulic 

conductivity range of 0.3 to 30 m/d for basin fill 

(Anderson and others, 1992), which is significantly 

lower than some values measured in this study. Slug 

tests done in 14 wells screened in the unconsolidated 

stream alluvium produced hydraulic conductivity 

values that ranged from 3 m/d at the 700 group wells to 

200 m/d at well 52 (table 2).

On the basis of particle sizes at or near the screened 

interval, all wells are finished in zones that contain 

more than 89 percent sand and gravel, except for 

well 501, which is finished in a zone that contains 

33 percent sand and gravel. Although some studies 

show a relation between particle size and hydraulic 

conductivity, the small variation in particle size at this 

site does not suggest a large range in hydraulic 

conductivity. Perhaps the hydraulic conductivity is 

determined not by particle size but by the amount of 

cementation and variations in bedding and deposition 

in the downstream direction as illustrated by the low 

values for the 700 group wells.

The vertical and horizontal distribution of 

hydraulic conductivity along the axis of the valley was 

contoured (fig. 5a) using the slug-test results. The 

pattern of the distribution of hydraulic conductivity is 

similar to that of the distribution of ground-water pH 

(fig. 5b, table 3), with the higher hydraulic 

conductivity units associated with the lower pH areas. 

Statistical analysis of the relation of hydraulic 

conductivity to the hydrogen-ion concentration, which 

is the inverse log of the negative pH, in water from the 

wells produced a correlation coefficient of 0.83 (fig. 6). 

The largest values of hydraulic conductivity were in the 

acidic part of the contaminant plume and likely reflect 

changes to the aquifer caused by contaminated groundwater flow. Chemical analyses of aquifer sediments has 

indicated that in the acidic core of the plume, all the 

carbonate minerals, coatings, and cement were 

completely consumed by neutralization reactions 

(Brown and others, 1999). Loss of this carbonate 

evidently resulted in an increase in the hydraulic 

conductivity of the aquifer in the areas of lowest pH. 

Because the percentage of carbonates in the alluvium is 

about one-fifth that in the basin fill, 0.3 compared to 

1.5, the effects of acidic contamination produced a 

larger range of hydraulic conductivity in the basin fill 

than in the alluvium. 

561_1 10–08–1998 1.837 2.00 Spreadsheet 35

561_2 10–08–1998 1.223 1.60 Spreadsheet 34 34

561_3 10–08–1998 1.940 2.00 Spreadsheet 28

701 09–02–1997 1.423 >10 Straight line 3.3

701_1 10–07–1998 1.698 >10 Straight line 2.8

701_2 10–07–1998 1.171 >10 Straight line 3.1 3

702 09–01–1997 3.669 >10 Straight line 3.1 3

Table 2. Slug-test results—Continued

Well_test number Test date

Initial head 

displacement (H0), 

in meters

Damping 

parameter 

(Cd) Analysis type

Hydraulic 

conductivity value, 

in meters per day

Hydraulic conductivity 

value used for 

contouring, 

in meters per day
12 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona

1,000

980

50

100

300

400

400

500

700

560

540

960

940

920

900

880

860

840

820

6 8 10 12 14 16

DISTANCE, IN KILOMETERS

VERTICAL SCALE GREATLY EXAGGERATED

EXPLANATION

SITE IDENTIFIER

LINE OF EQUAL pH AND pH VALUE

POINT OF KNOWN pH 

18 20 22 24

ALTITUDE, IN METERS ABOVE SEA LEVEL

Water table (1998)

5

6

6

7

7

7

1,000

South North

Pinal Creek

980

50

100

Alluvium

Consolidat

basin fill

ed

300

400

400

Kiser Basin

InspirationDam

500

700

560

540

960

940

920

900

880

860

840

820

EXPLANATION

ALTITUDE, IN METERS ABOVE SEA LEVEL

Water table (1998)

Miami Wash

SITE IDENTIFIER

LINE OF EQUAL ESTIMATED HYDRAULIC

 CONDUCTIVITY— Interval 50 and 40

 meters per day

POINT OF ESTIMATED HYDRAULIC

 CONDUCTIVITY 

50

2

50

1

10

10

10

0

50

50

250

200

Alluviu

Consolidat

m

ed

basin fill

4

B. pH

A. Hydraulic conductivity

Figure 5. Graph showing line of section approximating the principal ground-water flow line from Kiser Basin to Inspiration Dam 

along the channels of Miami Wash and Pinal Creek. A, Distribution of hydraulic conductivity. B, Distribution of pH.
Results and Distribution of Hydraulic Conductivity 13

Table 3. Ground-water pH

Well pH (standard units) Date Well pH (standard units) Date

 51 4.0 11–06–1998 404 7.6 06–08–1998

 52 3.9 11–05–1998 501 5.5 11–03–1998

 53 3.9 11–06–1998 502 7.3 11–03–1998

101 4.0 11–06–1998 503 5.3 11–03–1998

103 3.9 11–06–1998 504 7.6 06–09–1998

105 6.2 11–07–1997 505 5.8 05–02–2001

301 6.3 11–05–1998 541 4.4 11–04–1998

302 4.0 11–05–1998 542 4.4 11–04–1998

304 4.1 11–05–1998 561 4.6 11–04–1998

401 4.4 11–05–1998 701 6.9 11–02–1998

402 4.3 11–05–1998 702 7.0 11–02–1998

403 4.5 11–06–1997 HYDRAULIC CONDUCTIVITY, IN METERS PER DAY

pH

1,000

8 7 6 5 4 3

ALLUVIUM

BASIN FILL 

100

10

1

0.1

Figure 6. Relation between pH and hydraulic conductivity in ground water in the alluvium and in ground water in the basin fill.
14 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona

SUMMARY

The Pinal Creek Basin has been contaminated by 

acidic waters containing elevated concentrations of 

dissolved metals. To better understand how the 

contaminants are transported through the regional 

aquifer, the distribution of hydraulic conductivity and 

the chemical processes affecting the hydraulic 

conductivity need to be better understood.

Pneumatic slug tests were done in 23 wells that are 

screened over small intervals. The data from the slug 

tests were analyzed by using the Bouwer and Rice 

(1976) method, or by using an extension of the method 

developed by Springer and Gelhar (1991). Both 

methods are applicable for unconfined aquifers and 

fully or partially penetrating wells, conditions that 

apply in the Pinal Creek Basin. The tests provide point 

values of hydraulic conductivity at various depths and 

locations along Pinal Creek. Results of the slug tests 

indicate that hydraulic conductivity ranges from 200 to 

3 m/d in the alluvium and ranges from 250 to 0.5 m/d 

in the basin fill.

In the unconsolidated stream alluvium and in the 

basin fill, the distribution of hydraulic conductivity is 

similar to the distribution of pH. Generally, for both 

geologic units, the lower the pH of the ground water, 

the higher the hydraulic conductivity. This increase is 

likely caused by the dissolution of aquifer material by 

low pH water, thereby causing an increase in the 

hydraulic conductivity. The hydrogen ion concentration 

and hydraulic conductivity have a correlation 

coefficient of 0.83.

REFERENCES CITED

Anderson, T.W., Freethey, G.W., and Tucci, Patrick, 1992, 

Geohydrology and water resources of alluvial basins in 

south-central Arizona and parts of adjacent states: U.S. 

Geological Survey Professional Paper 1406-B, 67 p.

Bouwer, Herman, and Rice, R.C., 1976, A slug test for 

determining hydraulic conductivity of unconfined 

aquifers with completely or partially penetrating wells: 

Water Resources Research, v. 12, no. 3, p. 423–428.

Brown, J.G., Glynn, P.D., and Bassett, R.L., 1999, 

Geochemistry and reactive transport of metal 

contaminants in ground water, Pinal Creek Basin, 

Arizona, in Morganwalp, D.W., and Buxton, H.T., eds., 

U.S. Geological Survey Toxic Substances Hydrology 

Program—Proceedings of the Technical Meeting, 

Charleston, South Carolina, March 8–12, 1999, Volume 

1 of 3—Contamination from hard rock mining: U.S. 

Geological Survey Water-Resources Investigations 

Report 99—4018A, p. 141–154.

Butler, J.J., Jr., 1997, The design, performance, and analysis 

of slug tests: Boca Raton, Florida, Lewis Publishers, 

272 p.

Butler, J.J., Jr., and Garnett, E.J., 2000, Simple procedures 

for analysis of slug tests in formations of high hydraulic 

conductivity using spreadsheet and scientific graphics 

software: Kansas Geological Survey Open-File Report 

2000—40, 20 p.

Butler, J.J., Jr., McElwee, C.D., and Liu, Wenzhi, 1996, 

Improving the quality of parameter estimates obtained 

from slug tests: Ground Water, v. 34, no. 3, 

p. 480–490.

Envirologic Systems, Inc., 1983, Mining activities and water 

quality report: Florence, Arizona, Central Arizona 

Association of Governments, Mineral Extraction Task 

Force Report METF-7, 142 p.

Eychaner, J.H., 1989, Movement of inorganic contaminants 

in acidic water near Globe, Arizona, in Mallard, G.E., 

and Ragone, S.E., eds., U.S. Geological Survey Toxic 

Substances Hydrology Program—Proceedings of the 

technical meeting, Phoenix, Arizona, September 26–30, 

1988: U.S. Geological Survey Water-Resources 

Investigations Report 88—4220, p. 567–575.

Eychaner, J.H., Rehmann, M.R., and Brown, J.G., 1989, 

Chemical, geologic, and hydrologic data from the study 

of acidic contamination in the Miami Wash-Pinal Creek 

area, Arizona, water years 1984–87: U.S. Geological 

Survey Open-File Report 89—410, 105 p.

Greene, E.A., and Shapiro, A.M., 1995, Methods of 

conducting air-pressurized slug tests and computation 

of type curves for estimating transmissivity and 

storativity: U.S. Geological Survey Open-File Report 

95—424, 48 p.

Hazen, G.E., and Turner, S.F., 1946, Geology and groundwater resources of the upper Pinal Creek area, Arizona: 

U.S. Geological Survey Open-File Report, 55 p.

Hydro Geo Chem, 1989a, Results and interpretation of 

aquifer test in Kiser basin near Miami, Arizona: 

Claypool, Arizona, Cyprus Miami Mining Corporation 

report, 60 p.

________1989b, Results and interpretation of step 

drawdown tests along Pinal Creek near Miami, 

Arizona: Claypool, Arizona, Cyprus Miami Mining 

Corporation report, 27 p.
References Cited 15

Kipp, Kenneth, Jr., 1985, Type curve analysis of inertial 

effects in the response of a well to a slug test: Water 

Resources Research, v. 21, no. 9, p. 1397–1408.

Neaville, C.C., and Brown, J.G., 1994, Hydrogeology and 

hydrologic system of Pinal Creek Basin, Gila County, 

Arizona: U.S. Geological Survey Water-Resources 

Investigations Report 93—4212, 32 p.

Peterson, N.P., 1962, Geology and ore deposits of the GlobeMiami District, Arizona: U.S. Geological Survey 

Professional Paper 342, 151 p.

Pool, D.R., and Eychaner, J.H., 1995, Measurements of 

aquifer storage-change and specific yield using gravity 

surveys: Ground Water, v. 33, no. 3, p. 425–432.

Ransome, L.F., 1903, Geology of the Globe copper district, 

Arizona: U.S. Geological Survey Professional Paper 12, 

168 p.

Springer, R.K., and Gelhar, L.W., 1991, Characterization of 

large-scale aquifer heterogeneity in glacial outwash by 

analysis of slug tests with oscillatory responses, Cape 

Cod, Massachusetts, in Mallard, G.E., and Aronson, 

D.A., eds., U.S. Geological Survey Toxic Substances 

Hydrology Program—Proceedings of the Technical 

Meeting, Monterey, California, March 11–15, 1991: 

U.S. Geological Survey Water-Resources Investigations 

Report 91—4034, p. 36–40.

U.S. Bureau of the Census, 1991, Summary population and 

housing characteristics—Arizona: U.S. Department of 

Commerce, Bureau of the Census, 1990 Census of 

Population and Housing Report CPH-1-4, 5 p.

Wilson, E.D., and Moore R.T., 1959, Structure of the Basin 

and Range province in Arizona, in Heindl, L.A., ed., 

Southern Arizona guidebook II: Tucson, Arizona 

Geological Society, p. 89–97.
APPENDIX
Appendix 17
18 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona
Appendix 19
20 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona
Appendix 21
22 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona
Appendix 23
24 Characterization of Hydraulic Conductivity of the Alluvium and Basin Fill, Pinal Creek Basin near Globe, Arizona
Appendix 25