Prepared in cooperation with the

Arkansas Department of Environmental Quality

POSSIBLE EXTENT AND DEPTH OF SALT 

CONTAMINATION IN GROUND WATER USING 

GEOPHYSICAL TECHNIQUES, RED RIVER ALUMINUM 

SITE, STAMPS, ARKANSAS, APRIL 2003

Water-Resources Investigations Report 03-4292

U.S. Department of the Interior

U.S. Geological Survey
Cover: 

A. Looking east from 125 meters along resistivity line 1 at the Red River Aluminum site; B. Looking 

southwest from 50 meters along resistivity line 3 at the Red River Aluminum site; C. Resistivity switching 

unit; D. Electrode and cable in use during a two-dimensional, direct-current resistivity survey.

A

B

C

D
POSSIBLE EXTENT AND DEPTH OF SALT 

CONTAMINATION IN GROUND WATER USING 

GEOPHYSICAL TECHNIQUES, RED RIVER ALUMINUM 

SITE, STAMPS, ARKANSAS, APRIL 2003

By Gregory P. Stanton, Wade Kress, Christopher M. Hobza, and John B. 

Czarnecki

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 03-4292

Prepared in cooperation with the

Arkansas Department of Environmental Quality

Little Rock, Arkansas

2003
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information Copies of this report can be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey, WRD Branch of Information Services

401 Hardin Road Box 25286

Little Rock, Arkansas 72211 Denver Federal Center

Denver, Colorado 80225

Any use of industry, firm, trade, and brand names is for identification or location purposes only, and does 

not constitute endorsement by the U.S. Government, nor impute responsibility for any present or potential 

effects on the natural resources.
Contents iii

CONTENTS

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

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

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

Previous Investigations.............................................................................................................................. 4

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

Methodology and Approach............................................................................................................................... 5

Two-Dimensional Direct-Current Resistivity ........................................................................................... 5

Borehole Geophysical Log Evaluation ..................................................................................................... 9

Two-Dimensional Finite Difference Modeling of Resistivity Data .......................................................... 9

Analysis and Results of Surface Geophysical Investigations...........................................................................10

Resistivity Line 1 .................................................................................................................................... 10

Resistivity Line 2 .................................................................................................................................... 11

Resistivity Line 3 .................................................................................................................................... 13

Resistivity Line 4 .................................................................................................................................... 13

Resistivity Line 5 .................................................................................................................................... 17

Summary and Conclusions...............................................................................................................................19

References........................................................................................................................................................20

Supplemental Data ...........................................................................................................................................21

ILLUSTRATIONS

Figure 1. Map showing location of study area................................................................................................ 2

2. Color infrared image showing two-dimensional direct resistivity lines, terrace-deposit monitor

wells, and the Sparta well in the study area of the Red River Aluminum site ......................... 3

3. Aerial photograph showing water-level altitudes within the shallow ground-water system...........7

4. Aerial photograph showing water-level altitudes within the deep ground-water system................ 8

5. Inverted resistivity section of two-dimensional, direct-current resistivity line 1 field data ..........11

6. Inverted resistivity section of two-dimensional, direct-current resistivity line 2 field data ..........12

7a. Inverted resistivity section of modeled resistivity line 2...............................................................14

7b. Model grid of resistivity line 2......................................................................................................15

8. Inverted resistivity section of two-dimensional, direct-current resistivity line 3 field data ..........16

9. Inverted resistivity section of two-dimensional, direct-current resistivity line 4 field data ..........16

10. Inverted resistivity section of two-dimensional, direct-current resistivity line 5 field data..........17

11a. Inverted resistivity section of modeled resistivity line 5...............................................................18

11b. Model grid of resistivity line 5......................................................................................................18

12a. Geophysical log of monitor well 1D.............................................................................................22

12b. Geophysical log of monitor well 2D.............................................................................................23

12c. Geophysical log of monitor well 3D.............................................................................................24

12d. Geophysical log of monitor well 5D.............................................................................................24

12e. Geophysical log of monitor well 6D.............................................................................................25

12f. Geophysical log of monitor well 7D .............................................................................................26

12g. Geophysical log of monitor well 8D.............................................................................................27

12h. Geophysical log of monitor well 9D.............................................................................................28

TABLES

Table 1. Water-level measuring point locations, well-construction data, and water levels.............................6
iv Contents

In this report, vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 (NGVD of 

1929). Horizontal coordinate information is referenced to North American Datum of 1927 (NAD 27).

CONVERSION FACTORS, ABBREVIATIONS, AND VERTICAL DATUM

Multiply By To obtain

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)
Abstract 1

POSSIBLE EXTENT AND DEPTH OF SALT 

CONTAMINATION IN GROUND WATER USING 

GEOPHYSICAL TECHNIQUES, RED RIVER 

ALUMINUM SITE, STAMPS, ARKANSAS, APRIL 2003

By Gregory P. Stanton, Wade Kress, Christopher M. Hobza, and John B. Czarnecki

ABSTRACT

A surface-geophysical investigation of the 

Red River Aluminum site at Stamps, Arkansas, 

was conducted in cooperation with the Arkansas 

Department of Environmental Quality to determine the possible extent and depth of saltwater 

contamination. Water-level measurements indicate 

the distance to water level below land surface 

ranges from about 1.2 to 3.9 feet (0.37 to 1.19 

meters) in shallow monitor wells and about 10.5 to 

17.1 feet (3.20 to 5.21 meters) in deeper monitoring wells. The two-dimensional, direct-current 

resistivity method identified resistivities less than 

5 ohm-meters which indicated possible areas of 

salt contamination occurring in near-surface or 

deep subsurface ground water along four resistivity lines within the site. One line located east of the 

site yielded data that demonstrated no effect of salt 

contamination. Sections from two of the five data 

sets were modeled. The input model grids were 

created on the basis of the known geology and the 

results and interpretations of borehole geophysical 

data. The clay-rich Cook Mountain Formation is 

modeled as 25 ohm-meters and extends from 21 

meters (68.9 feet) below land surface to the bottom 

of the model (about 52 meters (170.6 feet)). The 

models were used to refine interpretation of the 

resistivity data and to determine extent of saltwater 

contamination and depth to the Cook Mountain 

Formation. 

Data from the resistivity lines indicate both 

near-surface and subsurface saltwater contamination. The near-surface contamination appears as 

low resistivity (less than 5 ohm-meters) on four of 

the five resistivity lines, extending up to 775 

meters (2,542.8 feet) horizontally in a line that 

traverses the entire site south to north. Model resistivity data indicate that the total depth of saltwater 

contamination is about 18 meters (59 feet) below 

land surface. Data from four resistivity lines identified areas containing low resistivity anomalies 

interpreted as possible salt contamination. A fifth 

line located just east of the site showed no saltwater contamination. 

INTRODUCTION

The Red River Aluminum site located at Stamps, 

Arkansas (fig. 1), once contained exposed waste piles 

of salt and metal byproducts (referred to as salt cake) 

from the smelting of aluminum. The salt cake was subjected to rainfall, resulting in dissolution of the salts 

and metals (RMT, Inc., 2000). Surface-water brines 

from the piles flowed into canals and ponds (fig. 2). 

Surface-water runoff (from the over 50 inches (128.2 

centimeters) of precipitation per year (Freiwald, 1985) 

occurs radially from a topographic high occurring 

onsite until it is intercepted by man-made or natural 

drainages. 

Red River Aluminum was identified for removal 

action under the Comprehensive Environmental 

Response and Liability Act (CERCLA) and Superfund 

Amendments and Reauthorization Act (SARA) of 

1986. On November 6, 2000, the U.S. Environmental 

Protection Agency (USEPA) Region 6 Response and 

Prevention Branch tasked the Superfund Technical 

Assessment Team (START) contractors to provide 

oversight, sampling, and managerial tasks during 

removal activities at Red River Aluminum under the 

direction of USEPA. Several thousand cubic yards of 

waste were leveled and shaped into a cell that is about
2 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 1. Location of study area.

ARKANSAS

Stamps

3692000

3691000

451000 452000

EASTING, IN METERS

NORTHING, IN METERS

Base Map 1:24,000 USGS Lewisville 7.5 minute topographic quadrangle

Coordinate System: UTM Zone 15

Bodcau

Creek

STUDY

AREA

0

0

0.5 Mile

0.5 Kilometer

0.25

0.25

Red

River

Aluminum

677 feet (206 meters) long by 349 feet (106 meters) 

wide. The waste cell was capped with about 63,000 

cubic yards (82,341 cubic meters) of clay. USEPA completed site work on October 10, 2001 (Weston, 2001).

The site formerly was used as a sawmill until its 

sale to Red River Aluminum in March 1987 (Weston, 

2001). Most of the sawmill water was obtained from 

water mains connected to the city of Stamps water system. One onsite well completed within the Sparta aquifer also supplied water for the sawmill. Two ponds 

(ponds 1 and 2, fig. 2) constructed onsite were used to 

collect and reuse runoff that occurred as water was 

sprinkled on logs stacked on concrete pads located 

between the two ponds. 

In 1987, Red River Aluminum Company occupied the site and began extracting and recovering aluminum as a primary aluminum smelter. The site entered 

into bankruptcy and ceased operations as a primary aluminum smelter in 1988. After reorganization, the facility reopened as a secondary-tertiary smelter utilizing 

dross (the material that forms on the surface of molten 

aluminum during the primary smelting process) as its 

primary feedstock (Weston, 2001). Aluminum was separated from these drosses using natural-gas rotary kilns. 

Halite (NaCl) and sylvite (KCl) salts were added to 

each batch of dross as flux agents. Molten aluminum 

was separated from the overlying flux agents by gravity. 

The remaining salt cake was gathered into piles 

between the two ponds (Woodward-Clyde Consultants, 

1992). Several thousand cubic yards of saltcake was 

stored onsite during plant operation. The two ponds 

subsequently have been drained, and filled with local 

clay (Weston, 2001) as a part of waste cell construction.
Introduction 3

Figure 2. Two-dimensional direct-resistivity lines, terrace-deposit monitor wells, and the Sparta well in the study area of the 

Red River Aluminum site. Color infrared image recorded in 2000 does not show waste cell constructed in 2001.

451500 451700 451900 452100 452300 452500 452700

3691100

3691300

3691500

3691700

3691900

3692100

Line 4

Line 3

Line 1 Line 5

Line 2

Sparta

Well

6S, 6M, 6D

5D, 5M, 5D

3S, 3D

4S

9S, 9D

2S, 2D

1S, 1M, 1D

7S, 7M, 7D

Pond1

Pond2

Site of Present

Waste Cell

Sewage

Disposal

Facility

0 0.1 0.2 0.05 Miles

0 0.2 0.05 Kilometers 0.1

EXPLANATION

Survey lines

Sparta well

Monitor well or well nest

and name (MW-, table 1)

EASTING, IN METERS

NORTHING, IN METERS

US Hwy 82

Tatum Branch

8S, 8M, 8D

RR Tracks

L

owe

St.

1st St.

2nd St.

3rd St.

Worth

e

n

St. Ellis St.

9S

Approximate site boundary

Base map USGS Digital Orthophoto Quarter Quadrangle in color infrared - 2000

Coordinate system: UTM Zone 15, NAD 1927

Extent of figures 3 and 4
4 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

A 3,164 feet (964.3 meters) deep injection well 

was constructed onsite in 1992. A permit was issued 

from Arkansas Department of Environmental Quality 

(ADEQ) for disposal of soluble salts from the salt cake, 

but it is unknown to what extent the well was used for 

that purpose. Red River Aluminum Company abandoned the site in 1998 and site remediation was begun 

by the USEPA in 2000.

Czarnecki and others (2001) documented the 

presence of brine within the shallow ground-water system based on specific conductance of ground water as 

high as 196,200 microsiemens per centimeter at 25 

degrees centigrade (μS/cm). Specific conductance and 

hydraulic head decrease with distance from the saltcake piles indicating the potential for dissolved salts to 

move radially outward from the source. Primary transport of saline water occurs horizontally within the shallow flow system based on specific-conductance data 

from water samples and from borehole geophysical 

logging data. However, some vertical transport of saline 

water has occurred based on elevated specific conductance in water from wells 38 to 64 feet (11.58 to 19.51 

meters) deep. From November 2001 until December 

2002, specific conductance of samples from each monitoring well was measured on site (John Czarnecki, 

U.S. Geological Survey, written commun. 2003). These 

data indicate that very little change has occurred in specific conductance of the ground water sampled at the 

Red River Aluminum site since the study by Czarnecki 

and others (2001) but information is needed on the 

extent and depth of salt contamination. Ground-water 

contamination is particularly a concern with regard to 

the regionally important Sparta aquifer, part of whose 

recharge is derived from the site. This situation is of 

great concern to the local citizens and the city of 

Stamps, Arkansas, as well as State and Federal agencies. The Cook Mountain Formation is a confining unit 

that overlies Sparta aquifer at the site, and information 

about the depth to the top of the Cook Mountain Formation is relevant for assessments of possible contamination. To address these needs, the U.S. Geological 

Survey (USGS) in cooperation with the ADEQ, conducted a two-dimensional, direct-current (2D-DC) 

resistivity survey of the Red River Aluminum site.

Purpose and Scope

This report describes the results of a surface geophysical investigation of near-surface and deep ground 

water in the vicinity of the Red River Aluminum site 

conducted in April, 2003 to determine the possible 

extent and depth of salt contamination in ground water. 

Five 2D-DC resistivity lines were surveyed. The purpose of this report is to document 1) 2D-DC resistivity 

data collected in the vicinity of the Red River Aluminum site, and 2) modeled interpretations of two lines of 

the 2D-DC resistivity data using local known geology 

and results and interpretations of borehole geophysical 

data. The depth of the Cook Mountain Formation was 

determined from the modeled interpretations of 

driller’s and borehole geophysical logs. Geophysical 

logs from Czarnecki and others (2001) necessary for 

interpretations of the surface geophysical data also are 

included. 

The study area (which includes the property previously owned by the Red River Aluminum Company, 

referred to as the Red River Aluminum site, and a portion of a residential area) is east of Bodcau Creek, 

mostly south of Tatum Branch of Bodcau Creek, north 

of the former St. Louis-Southwestern Railroad (now 

owned by Union Pacific Railroad), and west of the city 

of Stamps (fig.1). The areas adjacent to the Red River 

Aluminum site are mostly forested with the exception 

of the area east of the site, which is residential. An inactive wastewater treatment (sewage disposal) facility is 

located directly northwest of the site. The topographic 

relief of the study area is about 20 feet (6.1 meters). Part 

of the study area lies at a local topographic high point, 

and the waste cell is located at this topographic high. 

Previous Investigations

Four reports describe the regional setting and 

hydrogeologic characteristics of the study area. Ludwig 

(1972) described the regional hydrogeologic setting in 

his reconnaissance of the water resources of the area. 

Woodward-Clyde Consultants (1992) characterized the 

lithology and hydrology of five shallow (15 feet (4.6 

meters) deep) borings on the site, and provided slug-test 

data for two monitor wells. RMT Inc. (2000) analyzed 

water samples from surface and ground water, and 

added an additional monitor well (3D) to a depth of 45 

feet (13.7 meters) below land surface. The RMT investigation showed that the shallow wells drilled by Woodward-Clyde Consultants terminated in a shallow 

perched-water body, and that the deeper monitor well, 

3D, was completed in the first saturated sand zone. The 

results from this investigation showed elevated salt concentrations in ground- and surface-water samples. 

Czarnecki and others (2001) documented (1) ground-
Hydrogeology 5

water flow direction in the vicinity of the Red River 

Aluminum site and (2) measured values of pH, temperature, and specific conductance in water samples taken 

from monitor wells, ponds, and Tatum Branch. Czarnecki and others (2001) concluded that no evidence of 

perched water was observed onsite. All wells constructed onsite yielded water with time, even the moderate-depth wells constructed in clay units; albeit, some 

wells yielded very little water. Water levels in two of 

the moderate-depth wells were still recovering weeks 

after construction.

HYDROGEOLOGY

Based on a driller’s log for a 351-foot (106.0-

meter) deep well (Sparta Well, fig. 2) drilled onsite for 

the sawmill operator and logs for numerous shallower 

wells drilled subsequently, the upper 190 feet of sediments beneath the site consist of interbedded sands, 

silts, clays, and gravels associated with stream terrace 

deposits of Quaternary age. Based on the stratigraphic 

section of Ludwig (1972), the Sparta Sand of Tertiary 

age is interpreted from the log of the 351-foot (106.0 

meter) deep well to occur at depths between 190 to 288 

feet (57.9 to 87.8 meters) below land surface, and is 

overlain by a clay unit 68 to 190 feet (21.0 to 57.9 

meters) below land surface. Water-quality samples 

from this well indicate no saltwater contamination was 

present in the Sparta aquifer at this location (C. McWilliams, Arkansas Department of Environmental Quality, 

written comun., 2001).

A detailed investigation of the driller’s log from 

onsite monitor wells revealed that from land surface to 

a depth of about 10 to 20 feet (3.0 to 6.1 meters), sediments consist of sandy clays, gravels, and minor silts 

(Czarnecki and others, 2001). This is underlain by a 

dense, sometimes brittle clay unit between 20 to 30 feet 

(6.1 to 9.1 meters) thick, which is underlain by unconsolidated fine sand with a thickness of at least 20 feet 

(6.1 meters). These shallow units exhibit very little 

contrast in conductivity/resistivity (except in areas 

affected by brine) and are depicted in the 2D-DC resistivity models for this report as a generalized, homogeneous layer for simplification purposes of modeling.

Water levels were measured in all available monitor wells onsite and are listed in table 1. Well names 

include “MW-” followed by a number and letter designating the relative depth of the well - D, deep; M, moderate; and S, shallow. Well locations and names are 

shown in figure 2. Water-level measurements collected 

in April 2003 indicate the depth to water level below 

land surface ranges from about 1.2 to 3.9 feet (0.37 to 

1.19 meters) in shallow monitor wells and about 10.5 to 

17.1 feet (3.2 to 5.21 meters) in deeper monitoring 

wells. Water-level data indicate that flow occurs radially away from the waste cell in the shallow groundwater system (fig. 3) and to the soutwest in the deep 

ground-water system (fig. 4). 

METHODOLOGY AND APPROACH

Surface-geophysical methods offer quick, inexpensive, and non-invasive means that help to characterize subsurface geology (Powers and others, 1999). 

Surface geophysics provides information on the subsurface features, such as sediment thickness, depth to 

bedrock, and presence of conductive fluids (Powers 

and others, 1999). The 2D-DC resistivity method was 

used to identify the areal extent and depth of the saltwater contamination and determine the depths of subsurface strata. Five 2D-DC resistivity lines were collected in April 2003 (fig. 2). Borehole geophysical 

induction-conductivity logs collected in 2001 (Czarnecki and others, 2001) and other nearby logs were 

used to correlate lithologies with 2D-DC resistivity 

data collected in this investigation. Three layer, finitedifference models of two resistivity lines were created 

to aid the interpretation of the 2D-DC resistivity lines. 

The models were constructed using borehole geophysical data collected onsite and from nearby wells and 

known local geology. 

Two-Dimensional Direct-Current 

Resistivity 

Two-dimensional direct-current (2D-DC) resistivity measures the electrical resistivity of the subsurface. Electrical resistivity is determined by the 

resistivity of the sediment, which is related to the quantity and quality of the contained water (Haeni and others, 1993). In general, coarse-grained sediments are 

more resistive compared to fine-grained sediments. 

The presence of dissolved solids such as halite (NaCl) 

and sylvite (KCl) can reduce the resistivity of ground 

water (Loke, 2002). 

2D-DC resistivity uses two electrodes to induce 

current into the ground and the voltage difference is 

measured between two potential electrodes. An apparent resistivity is obtained after dividing the measured 

voltage by the induced current and applying a geometric correction. Field data and model data were inverted 

using RES2DINV version 3.51 (Loke, 2003) to create
Stamps, Arkansas, April 2003

6 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, Table 1. Water-level measuring point locations, well-construction data, and water levels [UTM, Universal Transverse Mercator, North American Datum 1927; NGVD, National Vertical Datum of 1929; MW, monitoring well; D, deep; M, moderate; S, sha

Well or site name UTM easting (meters) UTM northing (meters) Well depth (feet) Midpoint altitude of screen (feet above NGVD of 1929) Measuring point altitude (feet above NGVD of 1929) Borehole diameters (inches) Casing diameter (inches) Screen length (feet) Depth to water below measuring point on 4/25/03 (feet) Depth to water below land surface (feet) 

MW-1D 452152.53 3691363.30 59 207 262.90 7.50 2 5.0 18.65 17.05 MW-1M 452150.68 3691365.72 26 239 263.15 7.50 2 2.5 9.61 7.91 MW-1S 452151.24 3691370.91 13 256 263.05 10.25 4 10.0 5.54 3.04 MW-2D 452115.58 3691186.21 54 209 259.85 7.50 2 5.0 16.91 15.72 MW-2S 452135.27 3691166.60 14 252 260.45 10.25 4 10.0 2.81 1.21 MW-3D 452310.25 3691128.40 45 224 264.50 6.00 2 10.0 17.59 14.19 MW-3S 452333.23 3691146.61 13 255 262.95 10.25 4 10.0 6.15 3.95 MW-4S 452336.00 3691266.99 8 256 261.40 10.25 4 5.0 3.80 1.70 MW-5D 452291.74 3691027.67 43 218 258.40 8.25 2 5.0 11.74 10.53 MW-5M 452290.51 3691028.57 21 238 258.45 7.50 2 2.5 5.32 4.01 MW-5S 452288.98 3691029.16 11 249 258.70 7.50 2 2.5 5.32 3.66 MW-6D 452105.12 3691042.28 49 212 257.65 7.50 2 5.0 14.38 13.13 MW-6M 452106.95 3691042.00 22 237 257.35 7.50 2 2.5 4.28 3.38 MW-6S 452109.38 3691042.32 11 248 258.10 7.50 2 2.5 4.83 3.41 MW-7D 452064.52 3691575.12 60 202 259.35 7.50 2 5.0 13.61 12.11 MW-7M 452061.12 3691579.35 22 238 258.55 7.50 2 2.5 7.92 6.84 MW-7S 452066.01 3691578.79 11 249 258.85 7.50 2 2.5 6.51 5.44 MW-8D 451842.88 3691154.57 64 196 257.95 7.50 2 5.0 17.03 16.00 MW-8M 451843.21 3691151.83 20 242 259.95 8.25 2 2.5 4.88 1.88 MW-8S 451843.84 3691149.10 11 248 257.95 7.50 2 2.5 4.85 3.75 MW-9D 452349.04 3691396.62 38 225 260.50 7.50 2 5.0 14.68 13.48 MW-9S 452349.03 3691398.45 12 249 259.20 7.50 2 2.5 8.75 8.25 Sparta Well 452029.03 3691218.57 286 -16 259.35 N/A 6 20.0 31.88 30.44 
Methodology and Approach 7

Figure 3. Water-level altitudes within the shallow ground-water system. Base aerial photograph was taken January 19, 1994, 

and does not depict actual site conditions today. 

451800 452000 452200

3691000

3691200

3691400

3691600

0 0.1 0.2 0.05 Miles

0 0.1 0.2 0.05 Kilometers

EASTING, IN METERS

NORTHING, IN METERS

2

51

252

253

253

254

254

255

255

256

257

253

EXPLANATION

WATER TABLE CONTOUR -- Shows altitude of water table, April 25,

2003. Contour interval, 1 foot. Datum is National Geodetic Vertical

Datum of 1929

WELL LOCATION -- Number is water-level altitude, in feet above

National Geodetic Vertical Datum of 1929

DIRECTION OF GROUND-WATER FLOW

Base map USGS Digital Orthophoto Quarter Quadrangle - 1994

Coordinate system: UTM Zone 15, NAD 1927

253.1 257.6

253.3

252.3

250.4

256.8

253.4

257.5

257.6

253.1
8 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 4. Water-level altitudes within the deep ground-water system. Base aerial photograph was taken January 19, 1994, and 

does not depict actual site conditions today. 

451800 452000 452200

3691000

3691200

3691400

3691600

0 0.1 0.2 0.05 Miles

0 0.1 0.2 0.05 Kilometers

EASTING, IN METERS

NORTHING, IN METERS

EXPLANATION

WATER TABLE CONTOUR -- Shows altitude of water table, April 25,

2003. Contour interval, 1 foot. Datum is National Geodetic Vertical

Datum of 1929

WELL LOCATION -- Number is water-level altitude, in feet above

National Geodetic Vertical Datum of 1929

DIRECTION OF GROUND-WATER FLOW

Base map USGS Digital Orthophoto Quarter Quadrangle - 1994

Coordinate system: UTM Zone 15, NAD 1927

240.9

242.9

243.3

245.7

245.8

246.9

246.7

244.5

240.9

242

245

242

243

244

246

2

4

7
Methodology and Approach 9

inverted datasets. Inverted datasets provide a much 

closer approximation of the true resistivity of the subsurface (Loke, 2002).

2D-DC resistivity data collection was once a 

repetitive process of setting up electrodes at the appropriate spacing, measuring the resistivity at that point, 

and moving the electrodes to the next spacing to measure the next data point and so on. Recent advances in 

microcomputers and resistivity equipment allow the 

user to set up numerous electrodes in succession along 

a multi-conductor cable, enter the desired array into the 

microcomputer/switching unit, and allow the switching 

unit to collect data facilitating more rapid data collection. The data at the Red River Aluminum site were 

collected using an IRIS Syscal R1 Plus Resistivity 

Meter. The switching unit used 72 electrodes at a 5-

meter spacing to achieve the desired depth of investigation. Resistivity lines were lengthened using the rollalong technique. After collecting an initial resistivity 

section of data, 18 electrodes were moved and switched 

on ahead of the resistivity line. A partial resistivity section of data then is collected using the 18 electrodes 

that were moved. This process is continued until all 

data along the desired line length are collected. A Wenner-Schlumberger array (Loke, 2002 and 2003) was 

used in the data collection, inversion, and modeling of 

the resistivity data. Advantages of the Wenner-Schlumberger array over other arrays are better horizontal coverage in areas of limited open space and greater depth 

of penetration. 

Borehole Geophysical Log Evaluation

Geophysical logs of the boreholes are presented 

in the Supplemental Data section at the end of this 

report. Natural gamma logs indicate the presence or 

absence of clays. Low electrical resistivity is an excellent indicator of the presence of brines resulting from 

leaching of the salt cake. Increased dissolved solids in 

saltwater decrease the resistivity (increase the conductivity) response on the induction logs. The logs presented in the Supplemental Data section also include a 

general lithologic description based on cuttings collected during auger drilling from Czarnecki and others 

(2001). Locations of the wells are included in figure 2. 

The cuttings were sometimes collected at sporadic 

intervals and could not be correlated with precise well 

depths because of field conditions and limitations of 

the auger drilling technique; therefore lithologic 

descriptions from Czarnecki and others (2001) in the 

supplemental data section data section may not correlate with the more detailed log responses. 

Two-Dimensional Finite-Difference 

Modeling of Resistivity Data

The 2D-DC field datasets were inverted to provide a closer approximation of the true resistivity of the 

subsurface (Loke, 2002) and interpretations were 

made; however, those interpretations can be tested with 

a two-dimensional (2D) finite-difference model of the 

resistivity line which comprises a rectangular grid representing the subsurface. A separate model was developed for each resistivity line using RES2DMOD 

(Loke, 2003), which divided the subsurface into rectangular blocks according to the resistivity array represented. For the Wenner-Schumberger arrays used in 

data collection, the thickness of the first row of blocks 

was set to 0.25 times the electrode spacing (5 meters 

(16.4 feet)). The thickness of each deeper subsequent 

row of blocks was increased by 10 percent. Each rectangular block was assigned a resistivity value as model 

input. 

The 2D model inputs are based on known geology, interpretations from the inverted 2D-DC field 

datasets, borehole geophysical logs from wells onsite 

and near the site, and the driller’s logs from the onsite 

Sparta well. The model grid length is equal to the resistivity line it represents. Each model consisted of three 

layers of local geology, which are: dry terrace deposits 

and saturated terrace deposits in the two uppermost layers, and the clay-rich Cook Mountain Formation in the 

lower layer. The top of the Cook Mountain Formation 

as determined from driller’s logs and borehole geophysical logs is about 21 meters (68.9 feet) below land 

surface. The bottom of the model equals the depth of 

investigation for the Wenner-Schlumberger array at the 

5-meter spacing which is about 52 meters (170 feet) 

below land surface (Loke, 2003). The bottom of the 

Cook Mountain Formation (as determined from logs), 

which is the top of the underlying Sparta Sand, is about 

58 meters (190 feet) below surface and is consequently 

below the bottom of the model grid. The inverted field 

datasets indicated areas of low resistivity that were 

anomalous to the local geology and interpreted as areas 

of saltwater contamination. These areas of low resistivity were input to the model as needed to represent the 

saltwater contamination. Several iterations of model 

simulations were produced, each after adjustments 

were made to the resistivity values in the model to rep-
10 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

resent non-homogeneity in the local geology and areas 

of contamination. A model solution was reached when 

the resistivity section from the field data approximately 

matched the inverted modeled resistivity section. The 

resulting model grid serves as a non-unique interpretation of the subsurface geology and saltwater contamination (if present) along the resistivity line. 

ANALYSIS AND RESULTS OF SURFACE 

GEOPHYSICAL INVESTIGATIONS

The apparent resistivity values collected in the 

field were inverted. Results from data collected along 

the five 2D-DC resistivity lines are presented as inversion resistivity sections along the lines. The resistivity 

sections (figs. 5 - 11) show the inverted resistivity data 

as contoured resistivity in gradational colors. Low 

resistivity areas in blue, darkening with lower resistivity, denote possible areas of salt contamination. The 

clay layer of the Cook Mountain Formation is difficult 

to distinguish from shallow silty clay terrace deposits 

on the inverted resistivity section of two-dimensional, 

direct-current resistivity field data because of the low 

contrast in the resistivity of the upper 21 meters (68.9 

feet). Each line is described in detail with analysis of 

the resistivity sections in the following report sections. 

Lines that intersect each other are annotated as such on 

the resistivity sections. In this situation, the resistivity 

values on the corresponding sections may not correlate 

at the point of intersection because of the different orientations of the individual resistivity lines and thus the 

different locations of electrodes. 

The purpose of the modeling process is to determine the resistivity of the rectangular blocks that will 

produce an apparent resistivity section that agrees with 

the actual field measurements (Loke, 2003). A model 

solution is reached after numerous iterations, each with 

a modified model, when the resistivity section from the 

field data and the inverted synthetic resistivity section 

from the model data approximately match (Degnan and 

others, 2001). The model solutions are non-unique; 

however, with inclusion of known information to the 

model, the solutions represent a likely generalized 

interpretation of the subsurface. The modeled interpretation of resistivity lines 2 and 5 can be applied to those 

that were not modeled. Model cross sections of the subsurface resistivity distribution were created for lines 2 

and 5 only and were simulated using RES2DMOD 

(Loke, 2003). The input model grids (figs. 7b and 11b) 

were created on the basis of the known geology and the 

results and interpretations of the inverted field data and 

the borehole geophysical data. Modeled lines (2 and 5) 

are described in more detail based on finite-difference 

model input.

For this investigation, 2D-DC resistivity lines 

and resistivity modeling were used as a reconnaissance 

method, to detect anomalies within the subsurface of 

the Red River Aluminum site. Possible salt contamination and depths of subsurface strata can be substantiated by drilling methods and ground-water quality data 

collection. 

All wells showed decreased resistivity (increased 

conductivity) response that indicated some level of 

saltwater contamination (see Supplemental Data section). Wells 1D, 2D, 3D, and 9D show decreased resistivity in a shallow zone indicating saltwater 

contamination less than 5 meters (16.4 feet) below land 

surface. Wells 2D, 5D, 6D, 7D, and 8D show a deeper 

zone of decreased resistivity indicating saltwater contamination greater than 5 meters (16.4 feet) below land 

surface. 

Resistivity Line 1

Resistivity line 1, which traverses the central 

portion of the Red River Aluminum site in a west-east 

trend, passing just north of the waste cell near wells 1D 

and 9D (figs. 2 and 5), indicates low resistivity fluid 

near the surface and in the deep subsurface adjacent to 

the waste cell. A zone of low resistivity less than 5 

ohm-meters is evident near the surface from 25 to 275 

meters (82.0 to 902.3 feet) along resistivity line 1 (fig. 

5), which indicates a shallow lens of high conductivity 

fluid just below the surface. This zone of low resistivity 

underlies a zone of greater resistivity (50 to 200 ohmmeters) at 25 to 75 meters (82.0 to 246.1 feet) along the 

line, which corresponds to a grassy field with gravelly 

topsoil. The zone of low resistivity appearing on the 

inverted resistivity section at an altitude of about 50 to 

60 meters (164.1 to 196.9 feet) at a distance of about 

210 to 250 meters (689 to 820.3 feet) along the line 

appears to be related to the area of the waste cell that 

was pond 1 (fig. 2). This zone of contamination is possibly associated with leakage through a zone of large 

hydraulic conductivity such as a gravel layer.
Analysis and Results of Surface Geophysical Investigations 11

Figure 5. Inverted resistivity section of two-dimensional, direct-current resistivity line 1 field data.

EXPLANATION

Resistivity, in ohm-meters

WEST EAST

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

DISTANCE, IN METERS

30

40

50

60

70

80

90

100

5 11 23 49 106 228 489 1049

ALTITUDE, IN METERS ABOVE NGVD OF 1929

WOODS

GRASSY

FIELD

ROAD

LINE 2

WELL 1D

LINE 3 ADJACENT TO

WASTE CELL

WELL 9D

LINE 4

Resistivity Line 2

Resistivity line 2 traverses the Red River Aluminum site in a south-north trend, beginning at the railroad tracks, between a building and the waste cell and 

follows a main gravel road passing just west of wells 

6D, 2D and 1D and east of well 7D (figs. 2 and 6). This 

line was modeled with a finite-difference grid model to 

aid in interpretation of the inverted field data. The input 

model cross section (fig. 7a) was created on the basis of 

the known geology and the results and interpretations 

of borehole geophysical data. The clay-rich layer of the 

Cook Mountain Formation is difficult to distinguish 

from shallow silty clay terrace deposits on the inverted 

resistivity section of 2D-DC resistivity line 2 field data 

because of the low contrast in resistivity (fig. 6). The 

depths to the top of the Cook Mountain Formation and 

Sparta Sand were determined only by examining borehole geophysical logs of nearby deep wells and confirmed through the 2D modeling process. Terrace 

deposits were modeled as the uppermost layer with a 

resistivity of 50 ohm-meters in uncontaminated sediments and extend to about 21 meters (68.9 feet) below 

land surface. The clay-rich Cook Mountain Formation 

is modeled as 25 ohm-meters and extends from 21 

meters (68.9 feet) below land surface to the bottom of 

the model. Model data were inverted to represent the 

field-data inversion resistivity section in figure 6. A low 

resistivity zone extends from 0 to 775 meters (0 to 

2,542.8 feet) on the resistivity section and is explained 

in detail below in the model discussion.
12 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 6. Inverted resistivity section of two-dimensional, direct-current resistivity line 2 field data.

Resistivity, in ohm-meters

EXPLANATION

5 11 23 49 106 228 489 1049

DISTANCE, IN METERS

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 7

2030405060708090

ALTITUDE, IN METERS ABOVE NGVD OF 1929 SOUTH 

WELL 6D SAND & GRAVEL

WELL 2D

EDGE OF

WASTE

CELL

CONCRETE SLAB

ADJACENT

TO WASTE

CELL

LINES1&3

WELL 1D SALT SOIL WOODS

OFFICE

WELL 7D

WOODS
Analysis and Results of Surface Geophysical Investigations 13

Modeled inversion results (fig. 7a) indicate nearsurface saltwater contamination on the resistivity section from 0 to 775 meters (0 to 2,542.8 feet) and extensive deep subsurface saltwater contamination from 

about 140 to 410 meters (459.3 to 1,345.2 feet). The 

extensive deep subsurface contamination was modeled 

to a depth of about 18 meters (59.1 feet) below land surface (fig. 7b), which is above the top of the Cook 

Mountain Formation, the overlying confining unit of 

the Sparta aquifer. The inverted resistivity section of 

field data (fig. 6) shows a large deep zone of low resistivity from about 150 to 275 meters (492.2 to 902.3 

feet). This deep zone of low resistivity on the inverted 

resistivity section was emulated on the modeled inversion resistivity section even though saltwater contamination was modeled to only 18 meters (59.1 feet) below 

land surface in the model grid (figs. 7a and 7b). This 

indicated a non-unique model solution of saltwater 

contained in the terrace deposits that did not extend into 

the Cook Mountain Formation or Sparta Sand. Anomalies appearing as high resistivity zones near the surface at about 200 and 250 meters (656.2 to 820.1 feet) 

on the inverted resistivity section (fig. 6) correspond 

with the edges of a concrete slab and could be caused 

by runoff of low conductance precipitation from the 

concrete slab. The shallow, high resistivity anomaly at 

550 to 600 meters (1,805 to 1,969 feet) could be caused 

by fill dirt used during construction of the office building and truck scale in this area. The high resistivity 

anomaly from 775 to 880 meters (2,542.8 to 2,887.3 

feet) probably is associated with the infiltration of relatively high resistivity water from Tatum Branch and 

associated uncontaminated water in stream sediment 

deposits. 

Resistivity Line 3

Resistivity line 3 trends southwest to northeast 

from the bottom woodlands of Bodcau Creek near well 

8D to northeast of well 1D as shown in figure 2. The 

line 3 inverted resistivity section (fig. 8) indicates several near-surface zones of salt contamination. Areas 

underlying woods and grassy fields with high soilmoisture content appear as near-surface zones of 

reduced resistivity from 0 to 300 meters (0 to 984.3 

feet) in the resistivity section. A possible small zone of 

salt contamination appears as a low resistivity zone 

(less than 5 ohm-meters) at an altitude of about 70 

meters (229.7 feet) and about 70 meters (229.7 feet) on 

the resistivity section, which underlies a concrete tank 

on the surface. A more extensive zone of salt contamination appears near the surface from about 300 to 500 

meters (984.3 to 1,641 feet) on the resistivity section as 

less than 5 ohm-meters resistivity. This near-surface 

zone of contamination is possibly associated with leakage through a zone of large hydraulic conductivity such 

as a gravel layer. The low resistivity zone appearing at 

depth near 400 meters (1,312.4 feet) on the resistivity 

section and at an altitude of about 30 to 60 meters (98.4 

to 196.9 feet) is probably an artifact of the inversion 

process as a result of low resistivity shadowing from 

near surface. It is uncertain what the depth of contamination is in this specific area, although the modeled 

resistivity data from line 2 indicates it is probably less 

than 18 meters (59.1 feet) below land surface. 

Resistivity Line 4

Resistivity line 4 extends along the east boundary of the Red River Aluminum site directly west of 

concrete slabs that were formerly occupied by houses 

on Lowe Street in the city of Stamps, Arkansas (fig. 2), 

and indicates a shallow zone of salt contamination 

adjacent to the Red River Aluminum site on the east 

boundary in the area of the former salt cake pile (fig. 9). 

The houses were removed in 2002 and the associated 

properties became part of the Red River Aluminum 

site. Monitor wells 3D and 9D are west of the line at 

about 90 meters (295.3 feet) and 350 meters (1,148.4 

feet), respectively, on the inverted resistivity section 

(fig. 9). A low resistivity zone (less than 5 ohm-meters) 

appears between about 100 and 315 meters (328.1 to 

1,034 feet) on the resistivity section (fig. 9) at an altitude of 70 to 78 meters (229.7 to 255.9 feet), 0 to 8 

meters (0 to 26.2 feet) from land surface. This low 

resistivity zone is probably associated with infiltration 

of precipitation through the salt cake material, which 

was once stored adjacent to the line 4 location, but was 

moved to the waste cell further west of line 4 (fig. 2) in 

2001. A near-surface high resistivity anomaly appears 

from about 115 to 210 meters (377.3 to 689 feet) on the 

resistivity section and is probably caused by a thin layer 

of organic material in the grassy areas that were once 

backyards of the former house locations on Lowe 

Street. 
14 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 7a. Inversion resistivity section of modeled resistivity line 2.

0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 7

DISTANCE, IN METERS

605040302010

Resistivity, in ohm-meters

EXPLANATION

5 11 23 49 106 228 489 1049

0

DEPTH BELOW LAND SURFACE, IN METERSSOUTH 
Analysis and Results of Surface Geophysical Investigations 15 Figure 7b. Model grid of resistivity line 2. 0.5 1.5 5.0 10 25 50 75 100 250 300 350 500 750 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 

DISTANCE, IN METERS 605040

302010

0

Resistivity, in ohm-meters

DEPTH BELOW LAND SURFACE, IN METERS EXPLANATION SOUTH 
16 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 8. Inverted resistivity section of two-dimensional, direct-current resistivity line 3 field data.

Figure 9. Inverted resistivity section of two-dimensional, direct-current resistivity line 4 field data.

EXPLANATION

Resistivity, in ohm-meters

0 50 100 150 200 250 300 350 400 450 500

DISTANCE, IN METERS

20

30

40

50

60

70

80

90

5 11 23 49 106 228 489 1049

ALTITUDE, IN METERS ABOVE NGVD OF 1929

SOUTHWEST NORTHEAST

WOODS

CONCRETE

TANK

RAVINE WOODS

FIELD FIELD

MOIST

WOODS

SOIL FIELD

ROAD

LINE 2

WELL 1D

LINE1

NEAR

WASTE

CELL

SEWER

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

DISTANCE, IN METERS

10

20

30

40

50

60

70

80

90

5 11 23 49 106 228 489 1049

EXPLANATION

Resistivity, in ohm-meters

ALTITUDE, IN METERS ABOVE NGVD OF 1929

SOUTH NORTH WELL 3D

ADJACENT TO FORMER SALT

CAKE PILE

LINE 1

WELL 9D
Analysis and Results of Surface Geophysical Investigations 17

Resistivity Line 5

Resistivity line 5 traces along the side of 

Worthen Street in Stamps, Arkansas, in a south-north 

trend, beginning at Ellis Street, to the end of Worthen 

Street (figs. 2 and 10). The line was constructed in the 

east ditch adjacent to the asphalt surface of Worthen 

Street and crossed the asphalt surfaces of 1st Street, 2nd

Street, and 3rd Street (figs. 2 and 10). This line was 

modeled with a finite-difference grid model to aid in 

interpretation of the inverted field data (figs. 11a and 

11b). The input model grid (fig. 11b) was created on the 

basis of the known geology and the results and interpretations of borehole geophysical data. Although no well 

data adjacent to the line were available, well data from 

nearby wells onsite were used. Terrace deposits were 

modeled as the two uppermost layers with a resistivity 

of 50 ohm-meters in uncontaminated sediments and 

extended to about 21 meters (68.9 feet) below land surface. The clay-rich Cook Mountain Formation is modeled as 25 ohm-meters and extends from 21 meters 

(68.9 feet) below land surface to the bottom of the 

model. Model data were inverted to represent the inversion section resistivity of field data in figure 10, and 

results shown in figure 11a.

Modeled inversion results (fig. 11a) indicate a 

near-surface high resistivity zone (greater than 500 

ohm-meters) from 30 to 210 meters (98.4 to 689 feet) 

on the inversion resistivity section. This zone of high 

resistivity probably is caused by dry gravel material 

present in this area. The terrace deposits present in the 

north part of the model appear as a lower resistivity 

media possibly caused by higher clay content. This 

model produced a non-unique solution showing no saltwater contamination in the terrace deposits, the Cook 

Mountain Formation, or Sparta Sand beneath Worthen 

Street. 

Figure 10. Inverted resistivity section of two-dimensional, direct-current resistivity line 5 field data.

EXPLANATION

Resistivity, in ohm-meters

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

DISTANCE, IN METERS

10

20

30

40

50

60

70

80

90

5 11 23 49 106 228 489 1049

ALTITUDE, IN METERS ABOVE NGVD OF 1929

SOUTH NORTH

GRASSY DITCH 1st STREET

GRASSY-GRAVEL

DITCH 2nd STREET

DRIVEWAY

GRASSY DITCH

WATER MAIN

3rd STREET

GRASSY DITCH
18 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 11a. Inversion resistivity section of modeled resistivity line 5.

Figure 11b. Model grid of resistivity line 5.

SOUTH NORTH

EXPLANATION

Resistivity, in ohm-meters

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

DISTANCE, IN METERS

80

70

60

50

40

30

20

10

0

5 11 23 49 106 228 489 1049

DEPTH BELOW LAND SURFACE, IN METERS

EXPLANATION

Resistivity, in ohm-meters

0 25 50 75 100 125 150 175 200 225 250 275 300 325 350

DISTANCE, IN METERS

60

DEPTH BELOW LAND SURFACE, IN METERS 50

40

30

20

10

0

SOUTH NORTH

25 50 750
Summary and Conclusions 19

SUMMARY AND CONCLUSIONS

The Red River Aluminum site at Stamps, Arkansas, once contained exposed waste piles of salt and 

metal byproducts (referred to as salt cake) from the 

smelting of aluminum. The salt cake was subjected to 

rainfall, resulting in dissolution and transport of the 

salts and metals. Brines from the piles flowed into 

canals and ponds and overland flow moved radially 

away from a topographic high occurring onsite until it 

was intercepted by man-made or natural drainages. The 

presence of brine within the shallow ground-water system has been documented based on specific conductance of ground water as high as 196,200 μS/cm at 25 

degrees Celsius. Water-level measurements indicate 

the depth to water below land surface ranges from 

about 1.2 to 3.9 feet (0.37 to 1.19 meters) in shallow 

monitor wells and about 10.5 to 17.1 feet (3.2 to 5.2 

meters) in deep monitoring wells.

A surface-geophysical investigation of the Red 

River Aluminum site was conducted to determine the 

areal extent and depth of contamination and the depth 

to the Cook Mountain Formation. The two-dimensional, direct-current resistivity method identified 

resistivities less than 5 ohm-meters in the subsurface 

along four resistivity lines within the site. Data with 

resistivity values of 5 ohm-meters or less were considered to be anomalies and were interpreted as possible 

areas of salt contamination. Data from the resistivity 

lines indicate both near-surface and deeper subsurface 

salt contamination. One line located east of the site 

yielded data that indicated no salt contamination. Sections from two of the five data sets were modeled using 

a three-layer, finite-difference resistivity model. The 

input model grids were constructed on the basis of the 

known geology and the results and interpretations of 

borehole geophysical data. The clay-rich Cook Mountain Formation is modeled as 25 ohm-meters and 

extends from 21 meters (68.9 feet) below land surface 

to the bottom of the model (about 52 meters (170.6 

feet)). The models were used to aid in the interpretation 

of the resistivity data. 

Data from resistivity line 1, trending west to east 

across the site, identified an area of possible salt contamination near the surface approximately 250 meters 

(820.1 feet) in length. Low resistivity values approximately 40 meters (131.2 feet) in length range at an altitude of 50 to 60 meters (154 to 196.9 feet) and 

correspond to the waste cell.

Resistivity line 2, trending south to north across 

the site, indicated an area of possible salt contamination near the surface approximately 775 meters 

(2,542.8 feet) in length and deep subsurface area of low 

resistivity values approximately 270 meters (885.9 

feet) in length adjacent to the waste cell. A three-layer 

resistivity model was developed for line 2. Model resistivity data indicate that the total depth of salt contamination in the area adjacent to the waste cell is about 18 

meters (59.1 feet) below land surface. The model resistivity data input simulated the depths of the Cook 

Mountain Formation. 

Resistivity line 3, trending southwest to northeast, detected two low resistivity anomalies. The dominant anomaly occurs near land surface and is 

approximately 200 meters (656.2 feet) in length. This 

near-surface zone of contamination possibly is associated with transport of saltwater through a zone of large 

hydraulic conductivity such as a gravel layer. A small 

anomaly occurs at the southwestern end of the line and 

corresponds to a concrete tank on the surface. 

Resistivity line 4 extends along the east boundary of the site. One anomaly was identified to be 

approximately 215 meters (about 705 feet) in length 

and ranges from 0 to 10 meters (0 to 32.8 feet) from 

land surface. This low resistivity zone probably is associated with infiltration of precipitation through the salt 

cake material, which was stored adjacent to the line 4 

location. 

Unlike the other resistivity lines, line 5 was 

located off the Red River Aluminum site to the east. 

Data from the inverted resistivity sections and the resistivity model indicate no saltwater contamination. 

Resistivity modeling simulated the depth to the Cook 

Mountain Formation in the inversion model. 
20 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

REFERENCES

Czarnecki, J.B., Stanton, G.P., and Freiwald, D.A., 2001, 

Hydrogeology and physical characteristics of water 

samples at the Red River Aluminum Site, Stamps, 

Arkansas, April 2001: U.S. Geological Survey OpenFile Report 01-201, 30 p.

Degnan, J.R., Moore, R.B., and Mack, T.J., 2001, Geophysical investigations of well fields in characterize fractured-bedrock aquifers in southern New Hampshire: 

U.S. Geological Survey Water-Resources Investigations Report 01-4183, 54 p.

Freiwald, D.A., 1985, Average annual precipitation and runoff for Arkansas, 1951-80: U.S. Geological Survey 

Water-Resources Investigations Report 84-4363, 1 

plate.

Haeni, F.P., Lane, J.W., Jr., and Lieblich, D.A., 1993, Use of 

surface-geophysical and borehole radar methods to 

detect fractures in crystalline rocks, Mirror Lake Area, 

Grafton County, New Hampshire, in Hydrogeology of 

Hard Rocks, International Association of Hydrologists, 

XXIVth Congress, Oslo, Norway, June 1993, Proceedings: Oslo, Norway, International Association of 

Hydrologists, 11 p.

Loke, M.H., 2002, Rapid 2D resistivity forward modeling 

using the finite-difference and finite element methods: 

M.H. Loke, 28 p.

——— 2003, Rapid 2D resistivity and IP inversion using the 

least-squares method: Geoelectrical Imaging 2-D and 

3-D - Geotomo Software, 123 p. 

Ludwig, A.H., 1972, Water resources of Hempstead, Lafayette, Little River, Miller, and Nevada Counties, Arkansas: U.S. Geological Survey Water-Supply Paper 1998, 

41 p.

Powers, C.J., Wilson, Joanna, Haeni, F.P., and Johnson, 

C.D., 1999, Surface-geophysical characterization of the 

University of Connecticut landfill, Storrs, Connecticut: 

U.S. Geological Survey Water-Resources Investigations Report 99-4211, 34 p.

RMT Inc., 2000, Red River Aluminum site supplemental 

investigation and feasibility study, Stamps, Arkansas: 

51 p.

Woodward-Clyde Consultants, 1992, Untitled consultant’s 

report to Red River Aluminum, Inc. #89B164C: 41 p.

Weston, Roy F., Inc., 2001, Removal report for Red River 

Aluminum, Stamps, Lafayette County, Arkansas for 

USEPA Region 6: Document control no. 

12632.2001.0297, 2206 p.
Supplemental Data 21

SUPPLEMENTAL DATA
22 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 12a. Geophysical log of monitor well 1D.

0 150 (Counts/Second) 0 20 (Ohm-Meters) 0 1500 (Millimhos/Meter)

-10

-20

-30

-40

-50

-60

Well Name: MW-1D

Location: Stamps RRA

Reference: Ground Surface

NATURAL GAMMA RESISTIVITY CONDUCTIVITY LITHOLOGIC DESCRIPTION

BROWN SAND

WITH GRAVEL

BROWN SAND

WITH FINE GRAVEL

SANDY GRAY

CLAY

TAN SAND

AND CLAY

SANDY

BROWN CLAY

BROWN SILTY SAND

SANDY GRAY

CLAY

(From Czarnecki and others, 2001)

Feet
Supplemental Data 23

Figure 12b. Geophysical log of monitor well 2D.

0 150 0 20 0 1500

-10

-20

-30

-40

-50

-60

(Counts/Second) (Ohm-Meters) (Millimhos/Meter)

Well Name: MW-2D

Location: Stamps RRA

Reference: Ground Surface

Feet NATURAL GAMMA RESISTIVITY CONDUCTIVITY LITHOLOGIC DESCRIPTION

ORANGE RED CLAY WITH SOME GRAVEL

SANDY GRAY CLAY

GRAY PLASTIC WET CLAY

BROWN PLASTIC CLAY

ORANGE-BROWN CLAY

ORANGE-BROWN WET SILTY SAND

(From Czarnecki and others, 2001)
24 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 12c. Geophysical log of monitor well 3D.

Figure 12d. Geophysical log of monitor well 5D.

0 150 0 20 (Ohm-Meters)

20 220

0 1500

0

-10

-20

-30

-40

(Counts/Second) (Millimhos/Meter)

(Ohm-Meters)

Well Name: MW-3D

Location: Stamps RRA

Reference: Ground Surface

Feet NATURAL GAMMA RESISTIVITY CONDUCTIVITY LITHOLOGIC DESCRIPTION

SAND

SANDY

CLAY

SILTY CLAY

CLAY

SAND

CLAYEY SAND

SAND

(From Czarnecki and others, 2001)

RESISTIVITYx10

0

-10

-20

-30

-40

Well Name: MW-5D

Location: Stamps RRA

Reference: Ground Surface

Feet NATURAL GAMMA

0 150

RESISTIVITY

0 20

CONDUCTIVITY

0 1500

LITHOLOGIC DESCRIPTION

REDDISH BROWN CLAYEY SAND

DARK BROWN CLAY

GRAY PLASTIC CLAY

GREENISH GREY CLAY

GRAYISH BROWN CLAY

BROWN CLAY

ORANGISH BROWN PLASTIC CLAY

CHOCOLATE BROWN WET PLASTIC CLAY

BROWN WET SAND

(Counts/Second) (From Czarnecki and others, 2001) (Ohm-Meters) (Millimhos/Meter)
Supplemental Data 25

Figure 12e. Geophysical log of monitor well 6D.

0 150 0 20 0 1500

0

-10

-20

-30

-40

-50

(Counts/Second) (Ohm-Meters) (Millimhos/Meter)

Well Name: MW-6D

Location: Stamps RRA

Reference: Ground Surface

Feet NATURAL GAMMA RESISTIVITY CONDUCTIVITY LITHOLOGIC DESCRIPTION

ORANGE SANDY CLAY

ORANGE CLAY

BROWN CLAY

ORANGE CLAY

ORANGISH BROWN CLAY

FRACTURED CLAY

SANDY CLAY

BROWNISH GREY SAND

(From Czarnecki and others, 2001)
26 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 12f. Geophysical log of monitor well 7D.

0 150 0 20 0 1500 0

-10

-20

-30

-40

-50

-60

(Counts/Second) (Ohm-Meters) (Millimhos/Meter) (From Czarnecki and others, 2001)

Well Name: MW-7D

Location: Stamps RRA

Reference: Ground Surface

Feet NATURAL GAMMA RESISTIVITY CONDUCTIVITY LITHOLOGIC DESCRIPTION

FILL DIRT

GREY SANDY CLAY

GREY SANDY CLAY WITH PLASTIC PIECES

ORANGE CLAY

ORANGE/GREY STREAKING CLAY

ORANGE CLAY

ORANGE BRITTLE CLAY

LIGHT BROWN CLAYEY SAND

SLIGHTLY SANDY TAN CLAY
Supplemental Data 27

Figure 12g. Geophysical log of monitor well 8D.

0 150 0 20 0 1500 0

-10

-20

-30

-40

-50

-60

(Counts/Second) (Ohm-Meters) (Millimhos/Meter)

Well Name: MW-8D

Location: Stamps RRA

Reference: Ground Surface

Feet NATURAL GAMMA RESISTIVTY CONDUCTIVITY LITHOLOGIC DESCRIPTION

RED OXIDIZED CLAYEY SAND

GREY SANDY CLAY

GREY PLASTIC CLAY

HARD GREY CLAY

GREY CLAY WITH SOME SAND

BROWN CLAY

BRITTLE BROWN CLAY

WET BROWN CLAY

GREY SANDY CLAY

(From Czarnecki and others, 2001)
28 Possible extent and depth of salt contamination in ground water using geophysical techniques, Red River Aluminum site, 

Stamps, Arkansas, April 2003

Figure 12h. Geophysical log of monitor well 9D.

0 150 0 20 0 1500

0

-10

-20

-30

-40

-50

(Counts/Second) (Ohm-Meters) (Millimhos/Meter)

Well Name: MW-9D

Location: Stamps RRA

Reference: Ground Surface

Feet NATURAL GAMMA RESISTIVITY CONDUCTIVITY LITHOLOGIC DESCRIPTION

DARK BROWN SANDY

CLAY

GREY/BROWN SANDY

CLAY

ORANGE BRITTLE CLAY

WET SAND

ORANGE WET SAND

(From Czarnecki and others, 2001)
Stanton, G.P., Kress, Wade, Hobza C.M., and Czarnecki, J.B.—POSSIBLE EXTENT AND DEPTH OF SALT CONTAMINATION IN GROUND 

WATER USING GEOPHYSICAL TECHNIQUES, RED RIVER ALUMINUM SITE, STAMPS, ARKANSAS, APRIL 2003

U.S. Geological Survey Water-Resources Investigations Report 03-4292