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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

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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.


TABLE OF CONTENTS

ILLUSTRATIONS
Figure
  1. Map showing location of study area.
  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. Aerial photograph showing water-level altitudes within the shallow ground-water system.
  4. Aerial photograph showing water-level altitudes within the deep ground-water system.
  5. Inverted resistivity section of two-dimensional, direct-current resistivity line 1 field data.
  6. Inverted resistivity section of two-dimensional, direct-current resistivity line 2 field data.
  7. Inverted resistivity section of modeled resistivity line 2.
  8. Model grid of resistivity line .
  9. Inverted resistivity section of two-dimensional, direct-current resistivity line 3 field data.
  10. Inverted resistivity section of two-dimensional, direct-current resistivity line 4 field data.
  11. Inverted resistivity section of two-dimensional, direct-current resistivity line 5 field data.
  12. Inverted resistivity section of modeled resistivity line.
  13. Model grid of resistivity line 5
    1. Geophysical log of monitor well 1D
    2. Geophysical log of monitor well 2D
    3. Geophysical log of monitor well 3D
    4. Geophysical log of monitor well 5D
    5. Geophysical log of monitor well 6D
    6. Geophysical log of monitor well 7D
    7. Geophysical log of monitor well 8D
    8. Geophysical log of monitor well 9D
TABLES
  1. Water-level measuring point locations, well-construction data, and water levels.

U.S. Department of the Interior, U.S. Geological Survey
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Last modified: Thursday, September 01 2005, 05:07:35 PM
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