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Scientific-Investigations Report 2011–5188

Groundwater Conditions and Studies in the Augusta–Richmond County Area, Georgia, 2008–2009

Prepared in cooperation with the City of Augusta, Georgia

Gerard J. Gonthier, Stephen J. Lawrence, Michael F. Peck, and O. Gary Holloway

ABSTRACT

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Groundwater studies and monitoring efforts conducted during 2008–2009, as part of the U.S. Geological Survey (USGS) Cooperative Water Program with the City of Augusta in Richmond County, Georgia, provided data for the effective management of local water resources. During 2008–2009 the USGS completed: (1) installation of three monitoring wells and the collection of lithologic and geophysical logging data to determine the extent of hydrogeologic units, (2) collection of continuous groundwater-level data from wells near Well Fields 2 and 3, (3) collection of synoptic groundwater-level measurements and construction of potentiometric-surface maps in Richmond County to establish flow gradients and groundwater-flow directions in the Dublin and Midville aquifer systems, (4) completion of a 24-hour aquifer test to determine hydraulic characteristics of the lower Dublin aquifer, and upper and lower Midville aquifers in Well Field 2, and (5) collection of groundwater samples from selected wells in Well Field 2 for laboratory analysis of volatile organic compounds and groundwater tracers to assess groundwater quality and estimate the time of groundwater recharge.

Potentiometric-surface maps of the Dublin and Midville aquifer systems for 2008–2009 indicate that the general groundwater flow direction within Richmond County is eastward toward the Savannah River, with the exception of the area around Well Field 2, where pumping interrupts the eastward flow of water toward the Savannah River and causes flow lines to bend toward the center of pumping.

Results from a 24-hour aquifer test conducted in 2009 within the upper and lower Midville aquifers at Well Field 2 indicated a transmissivity and storativity for the upper and lower Midville aquifers, combined, of 4,000 feet-squared per day and 2x10-4, respectively. The upper and lower Midville aquifers and the middle lower Midville confining unit, which is 85-feet thick in this area, yielded horizontal hydraulic conductivity and specific storage values of about 45 feet per day and 2x10-6 ft-1, respectively. Results from the 24-hour aquifer test also indicate a low horizontal hydraulic conductivity for the lower Dublin aquifer of less than 1 foot per day.

Of the 35 volatile organic compounds (VOCs) analyzed in 23 groundwater samples during 2008–2009, only six were detected above laboratory reporting limits in samples from eight wells. No concentration in groundwater samples collected during 2008–2009 exceeded drinking water standards. Trichloroethene had the maximum VOC concentration (1.9 micrograms per liter) collected from a water sample during 2008–2009. Water-quality sampling of several wells near Well Field 2 indicate that, while in operation, the northernmost production well might have diverted groundwater, containing low levels of trichloroethene from at least two other production wells. Analysis of sulfur hexafluoride data indicate the average year of recharge ranges between 1981and 1984 for water samples from five wells open to the upper and lower Midville aquifers, and 1991 for a water sample from one shallow well open to the lower Dublin aquifer. All of these ages suggest a short flow path and nearby source of contamination. The actual source of low levels of VOCs at Well Field 2 remains unknown.

Three newly installed monitoring wells indicate that hydrogeologic units beneath Well Fields 2 and 3 are composed of sand and clay layers. Hydrogeologic units, encountered at Well Field 2, in order of increasing depth are the lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer. West of Well Field 3, hydrogeologic units, in order of increasing depth are the Upper Three Runs aquifer, Gordon confining unit, Gordon aquifer, lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer.

First posted November 14, 2011

For additional information contact:
Director, Georgia Water Science Center
U.S. Geological Survey
3039 Amwiler Rd.
Suite 130
Atlanta, GA 30360-2824
http://ga.water.usgs.gov/

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Suggested citation:

Gonthier, G.J., Lawrence, S.J., Peck, M.F., and Holloway, O.G., 2011, Groundwater conditions and studies in the Augusta–Richmond County area, Georgia, 2008–2009: U.S. Geological Survey Scientific Investigations Report 2011–5188, 45 p.



Contents

Abstract

Introduction

City of Augusta Cooperative Water Program

Purpose and Scope

Description of Study Area

Physiography and Drainage

Land Use

Hydrogeology

Previous Studies

Well Numbering System

Methods of Analysis and Sources of Data

Groundwater-Use Data

Precipitation Data

Groundwater Levels

Well Construction and Geophysical Logging

Water-Quality Sampling and Analysis

Aquifer Testing and Analysis

Groundwater Conditions

Monitoring Network

Factors Affecting Groundwater Levels

Precipitation

Groundwater Pumpage

Potentiometric Surface

Groundwater Quality

Groundwater-Study Activities

Hydrogeologic Framework Characterization Near Well Fields 2 and 3

Well Field 2

Well Field 3

Hydraulic Properties of the Local Aquifers

Potential Source Areas for Volatile Organic Compounds at Well Field 2

Summary

References Cited

Appendix 1. Estimating Drawdown for Wells in Response to Aquifer-Test Pumping in Well 30AA06 in Well Field 2 near Augusta, Georgia, October 21–23, 2009

Appendix 2. Simulated and Measured Drawdown During the 24-Hour Aquifer Test at Pumped Well 30AA06 in Well Field 2 Near Augusta, Georgia, October 21–23, 2009


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