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Open-File Report 2014–1255

Prepared in cooperation with the City of Tallahassee

Depth-Dependent Groundwater Quality Sampling at City of Tallahassee Test Well 32, Leon County, Florida, 2013

By W. Scott McBride and Michael A. Wacker

Thumbnail of and link to report PDF (809 KB)Abstract

Public-supply wells sometimes produce water of less than desirable quality because contaminants can migrate to the open interval of wells through preferential pathways. If these pathways can be identified, zones that produce poor quality water can be excluded during the well-construction process. The U.S. Geological Survey has developed geophysical testing methods that can be used to delineate zones of high permeability in test wells. Once the highly permeable zones are identified, water-quality data can be collected from each zone to identify whether any of the zones produce water of poor quality. The zones producing poor quality water can then be cased off in the final well design so that they do not contribute flow to the production well, reducing subsequent water-treatment costs.

A test well was drilled by the City of Tallahassee to assess the suitability of the site for the installation of a new well for public water supply. The test well is in Leon County in north-central Florida. The U.S. Geological Survey delineated high-permeability zones in the Upper Floridan aquifer, using borehole-geophysical data collected from the open interval of the test well. A composite water sample was collected from the open interval during high-flow conditions, and three discrete water samples were collected from specified depth intervals within the test well during low-flow conditions. Water-quality, source tracer, and age-dating results indicate that the open interval of the test well produces water of consistently high quality throughout its length. The cavernous nature of the open interval makes it likely that the highly permeable zones are interconnected in the aquifer by secondary porosity features.

First posted January 26, 2014

  • Appendix 1 PDF (3.39 MB)
    Comparison of borehole image, geophysical, water quality, flowmeter, and sonic logs showing evidence of three productive intervals in the City of Tallahassee test well 32 at Leon County, Florida, December 2013. Only the data collected in the open interval of the test well are displayed at 1 to 96 scale.
  • Appendix 2 PDF (16.2 MB)
    Comparison of borehole image, geophysical, water quality, flowmeter, and sonic logs showing evidence of three productive intervals in the City of Tallahassee test well 32 at Leon County, Florida, December 2013. The full geophysical log is displayed at 1 to 12 scale.

For additional information, contact:
Director, Caribbean-Florida Water Science Center
U.S. Geological Survey
4446 Pet Lane, Suite 108
Lutz, FL 33559
http://fl.water.usgs.gov

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Suggested citation:

McBride, W.S., and Wacker, M.A., 2015, Depth-dependent groundwater quality sampling at City of Tallahassee test well 32, Leon County, Florida, 2013: U.S. Geological Survey Open-File Report 2014–1255, 13 p. and 2 appendixes, https://dx.doi.org/10.3133/ofr20141255.

ISSN 2331–1258 (online)



Contents

Abstract

Introduction

Methods of Study

Results

Summary and Conclusions

References Cited

Appendix 1. Comparison of borehole image, geophysical, water quality, flowmeter, and sonic logs showing evidence of three productive intervals in the City of Tallahassee test well 32 at Leon County, Florida, December 2013. Only the data collected in the open interval of the test well are displayed at 1 to 96 scale

Appendix 2. Comparison of borehole image, geophysical, water quality, flowmeter, and sonic logs showing evidence of three productive intervals in the City of Tallahassee test well 32 at Leon County, Florida, December 2013. The full geophysical log is displayed at 1 to 12 scale


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