Nevada Water Science Center


Aquifer Tests

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Phil Gardner
Groundwater Specialist
Phone: (775) 887-7664
Email:pgardner@usgs.gov

 

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Nevada Water Science Center
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Carson City, NV 89701

 

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Hawthorne Army Depot

Primary Investigator: Kip Allander

Well Data

USGS Site ID
Local Name Altitude Uppermost
Opening
Lowermost
Opening
Primary Aquifer Hydraulic
Conductivity
(ft/d)
383457118403801 HAAD Well 12 3988.94 12.5 22.5 ALLUVIAL FILL 4
383507118401701 HAAD Well 14 3990.85 12 22 ALLUVIAL FILL 2
383514118400801 HAAD Well 16 3993.69 15.5 25.5 ALLUVIAL FILL 40
383518118400501 HAAD Well 17 3994.84 14 24 ALLUVIAL FILL 20
383523118400201 HAAD Well 18 3996.26 14.5 24.5 ALLUVIAL FILL 5
383532118395701 HAAD Well 20 3996.06 15 25 ALLUVIAL FILL 10

Aquifer Test

All Aquifer Test Files (zip)

Hawthorne Army Depot

Slug Tests (pdf)

Introduction

Walker Lake has been declining at a rate of about 1.6 feet per year since 1917 resulting in total dissolved solids concentrations increasing to the point where the lakes fishery and ecosystem health are being threatened. Uncertainties in the water budget in the Lower Walker River Basin led the U.S. Geological Survey in cooperation with the U.S. Bureau of Reclamation to undertake a study to revise the water budget of Walker Lake. The study was initiated in 2004 and a revised water budget is scheduled to be published in 2009.

Developing a better understanding of the ground-water system in the Lower Walker River Basin is a critical component of this study. To understand how ground-water interacts with Walker Lake it is necessary to understand ground-water levels and aquifer properties in the alluvial aquifers adjacent to Walker Lake. It is planned to conduct a series of aquifer tests in the alluvial aquifers of the Lower Walker River Basin. Planned tests are 1) slug tests of monitor wells installed as part of this study, 2) analysis of historic slug test data (1979) on monitor wells installed at the Hawthorne Army Ammunition Depot, 3) a multiple well aquifer test on the Walker River Indian Reservation, and 4) a single well aquifer test on the Double Springs flowing well. This paper documents the methods, data, analysis, and results of historic slug tests done on monitor wells at the Hawthorne Army Ammunition Depot in 1979.

Slug tests were performed on 7 monitor wells at the Hawthorne Army Ammunition Depot (HAAD) in April of 1979 (Figure 1). These tests were originally done to estimate aquifer properties for a contaminant transport problem on the HAAD (Van Denburgh and others, 1996). Although these historic tests were never fully documented, an excellent paper record was left allowing for this analysis and documentation to proceed with relative ease.

 

Location of wells tested at the Hawthorne Army Ammunition Depot in 1979. Box indicates approximate area of figure 2
Figure 1. Location of wells tested at the Hawthorne Army Ammunition Depot in 1979. Box indicates approximate area of figure 2.

 

Site

Installation, construction properties, and lithologies of the wells tested on HAAD in 1979 were documented in drillers’ notes and from two files located in the USGS Nevada Water Science Center archive records. These notes and files have been scanned and are included as part of this document (appendix A). Driller reports from the Nevada State Engineers office for these wells appear not to be available. All wells were 3-inch inside-diameter galvanized steel monitoring wells installed by the USGS as part of a contaminant transport study on the HAAD in late 1978. The wells were installed on a curved line 5,000 to 6,000 feet south of and parallel to the southern shoreline of Walker Lake (in 1978) and perpendicular to the movement of the contaminant plume (Figure 2). The spacing between the wells tested was about 500 feet to 1000 feet. All of the wells were completed at a similar depth of between 32 and 37 feet below land surface. Each of the wells had a 10 foot screen interval that centered between 15 and 20 feet. Due to the wells being installed using the cable-tool percussion technique, the well screens were all packed with adjacent native material, or whenever possible, with commercial sand and gravel. The borehole was then sealed with clay-sized sediment and capped with cement. Aquifer material adjacent to the well screens was generally fine to coarse sands interbedded with thin layers of clay and occasional gravel.

 

Relative locations of wells slug tested and general direction of ground-water movement at the Hawthorne Army Ammunition Depot (1979)
Figure2. Relative locations of wells slug tested and general direction of ground-water movement at the Hawthorne Army Ammunition Depot (1979).

 

Procedures

Documentation of the field procedures used to slug test the wells were discovered in two files and a set of field notes located in the Nevada Water Science Center Archives and were scanned and are in Appendix B. From these documents it is apparent that some type of pressure transducer with datalogger was used to measure water levels after being displaced by rapid removal of a submerged float. The submerged float was a 2.0 inch diameter pvc pipe that was 7.97 feet long. The measured displacement of this slug device was 2.9 feet in a 3 inch surrogate well. The computed theoretical displacement for a 2-inch outside diameter, 7.97 foot long device inside of a 3 inch inside diameter cylinder was 3.54 feet. However, it is believed that this slug device was only partially submerged and the displacement documented in the historic notes is probably more accurate than the computed theoretical displacement. Each well was slugged 3 to 4 times except well 13, which only had a single test performed.

The data was originally analyzed by hand using a method by Cooper and others (1967). The details of this original analysis are in November 1993 archive file by Rita Carman (Appendix B). The results from this analysis were summarized in the December, 1993 archive file by Van Denburgh (Appendix B) but never published except for the average value which was referenced as a written communication from R.L. Carman in Van Denburgh, 1996. Results from this historic analysis are included in Table 1 as a comparison with the revised results.

The original logged water-level field data was printed on rolled receipt type paper and was located in the Nevada Water Science Center Archive records. These original field records were scanned into bitmap image documents on the computer. An example of the scanned image is presented in appendix C. A character recognition program was used on the scanned image and reviewed for accuracy and all necessary corrections were made.

All historic slug test data were reanalyzed using a spreadsheet developed by Halford and Kuniansky, 2002. The primary method used by this spreadsheet was the High-K Bower and Rice Model which Butler and others, 2003, modified from Bower and Rice, 1976 (KGS method). Field data and all relevant well construction data were entered into the spreadsheets, and the data was then compiled in a summary table (Table 1).

 

Table 1. Site information and hydraulic conductivity results from 7 wells at the Hawthorne Army Ammunition Depot.
Site information and hydraulic conductivity results from 7 wells at the Hawthorne Army Ammunition Depot

Hydraulic Property Estimates

Reanalysis of the data resulted in hydraulic conductivity values that ranged between 2 and 40 feet/day (median of 5 feet/day) (Table 1). Original estimates of hydraulic conductivity averaged 3 times results from this analysis (Table 1). Differences are attributed to interpreting with KGS solution rather than Cooper and others (1967).

Information on the aquifer material surrounding the screened intervals of the wells were obtained from the well installation notes in appendix A, which provided general descriptions of the lithology. All of the sites, except for well 14, generally listed various grades of sand thinly interbedded with clay layers as the aquifer material at the depth of the well screens. For the purposes of assigning a single aquifer material to the spreadsheet, medium sand was chosen for all of these wells (Table 1). The hydraulic conductivities for this aquifer material ranged from 2 to 41 feet/day, which is within the extreme maximum and minimum ranges for medium sand (Bouwer, 1978; Domenico and Schwartz , 1990) and is probably realistic of the actual variability of material that exists at these sites. The historic analysis had hydraulic conductivities ranging between 2 and 100 feet/day at these sites, which is still within the extreme range for medium sand (Bouwer, 1978; Domenico and Schwartz , 1990).

 

 

 

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