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Nebraska Water Science Center

Two-Dimensional Direct-Current Resistivity Survey to Supplement Borehole Data in Ground-Water Models of the Former Blaine Naval Ammunition Depot, Hastings, Nebraska, September 2003

By Wade H. Kress, Lyndsay B. Ball, Andrew P. Teeple, and Michael J. Turco

U.S. Geological Survey
Data Series 172—ONLINE ONLY

In cooperation with the U.S. Army Corps of Engineers, Kansas City District


Abstract

The former Blaine Naval Ammunition Depot located immediately southeast of Hastings, Nebraska, was an ammunition facility during World War II and the Korean Conflict. Waste-management practices during operation and decommissioning of the former Depot resulted in soil and ground-water contamination. Ground-water models have been used by the U.S. Army Corps of Engineers to provide information on the fate and transport of contaminants on the former Depot site. During September 2003, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, Kansas City District, conducted a pilot study to collect two-dimensional direct-current resistivity data on the site along six profiles near existing monitoring wells. The inversion results of field data from five of the six two-dimensional direct-current resistivity profiles display distinct electrical stratigraphy consistent with three resistivity units (low resistivity, high resistivity, and low resistivity). These three resistivity units correlate with rock-stratigraphic or hydrogeologic units described prior to this study. To interpret the resistivity profiles, additional data extending through the lower confining unit into the underlying Niobrara Formation could be used with the existing data to construct forward models for data analysis and interpretation.

Table of Contents

Abstract

Introduction

Purpose and Scope

Hydrogeology

Methodology and Approach

Borehole Geophysical Data

Direct-Current Resistivity Data

Inverse Modeling of Resistivity Data

Two-Dimensional Direct-Current Resistivity Survey Results

Summary

References Cited

Appendix 1—Geologist Logs and Borehole Geophysical Resistivity Logs

Appendix 2—Inversion Results of Two-Dimensional Direct-Current Resistivity

Figures

1.   Map showing approximate boundary of the former Blaine Naval Ammunition Depot site
2.   Schematic diagram showing rock stratigraphy, hydrogeologic units, monitoring well construction, ground-water-model layers, and electrical units
3.   Maps showing two-dimensional direct-current resistivity profiles and monitoring well locations of the former NAD site at:
    (a) Study area 1
    (b) Study area 2
4.   Photographs showing collection of (a) borehole geophysical log at monitoring well 113BB3, and (b) positional data at monitoring well 113BB3
5.   Photographs showing setup of two-dimensional direct-current resistivity equipment, (a) multicore cable connected to electrode, (b) resistivity meter connected to multicore cables (orange cables connected in back of unit), (c) one of 11 sets of multicore cableswith 10-meter electrode spacing, and (d) speed bump used to protect cables where profile extends over roads
6.   Diagrams showing geologist log superimposed on inversion results (true resistivity) of two-dimensional direct-current resistivity profile for:
    (a) Section plot 1
    (b) Section plot 2
    (c) Section plot 3
    (d) Section plot 4
    (e) Section plot 5
    (f) Section plot 6
7.   Diagrams showing geologist log and borehole geophysical resistivity log for monitoring well:
    (a) MW9BB
    (b) MW19BB4
    (c) MW20C
    (d) MW105BB
    (e) MW113BB3
    (f) MW155B
    (g) MW170B
    (h) MW175B
8.   Diagrams showing inversion results of two-dimensional direct-current resistivity for:
    (a) Profile 1
    (b) Profile 2
    (c) Profile 3
    (d) Profile 4
    (e) Profile 5
    (f) Profile 6

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