Introduction

The U.S. Geological Survey (USGS)—in cooperation with the Troup County Board of Commissioners—conducted a well inventory 

to provide information to help evaluate ground-water resources for Troup County, Georgia. In addition, borehole geophysical logs 

were collected in selected wells to provide a better understanding of the subsurface geologic and water-bearing characteristics in 

specific areas of interest. This investigation provides information to help guide future ground-water development and water-management 

decisions for Troup County while enhancing understanding of the hydrogeology of fractured rocks in the Piedmont physiographic 

province. This report presents well data compiled from USGS files and from site visits to wells during November and December 2007. 

Data were entered into the USGS National Water Information System (NWIS) and made available on the Web at http://waterdata.usgs.

gov/ga/nwis/inventory.

Previous studies of ground-water resources have been conducted in the vicinity, but did not include Troup County. The ground-water 

resources of Heard and Coweta Counties, located north and northeast, respectively, of Troup County were part of a larger study by 

Cressler and others (1983) that encompassed the Greater Atlanta Region. That study evaluated the quantity and quality of ground 

water in the Atlanta region and described the methods that could be used for locating high-yielding wells in the Piedmont Province. 

The geology underlying the Atlanta area is similar to that underlying Troup County. Clarke and Peck (1990) conducted a similar 

investigation that included Meriwether and Coweta Counties, located to the east and northeast of Troup County. 

Well Identification System

All of the wells located during this study were assigned a well number according to a system based on the index of USGS 71⁄2-minute 

topographic maps of Georgia. Each map in Georgia has been assigned a three- to four-digit number and letter designation (for example, 

04X) beginning at the southwestern corner of the State. Numbers increase sequentially eastward and letters advance alphabetically 

northward. Quadrangles in the northern part of the State are designated by double letters: AA follows Z, and so forth. The letters “I,” 

“O,” “II,” and “OO” are not used. Wells inventoried in each quadrangle are numbered consecutively, beginning with 001. Thus, the 

fourth well inventoried in the 04X quadrangle is designated 04X004. In the USGS NWIS database, this information is stored in the 

“Station Name” field (http://waterdata.usgs.gov/ga/nwis/gw).

Acknowledgments

The authors of this report wish to thank all of the private well owners, municipalities, and well drillers who provided information and 

assistance in obtaining access to the wells. In particular, the authors would like to thank Dixie Well Boring, Inc., LaGrange, Georgia; 

Phil Adams, U.S. Army Corps of Engineers, West Point, Georgia; and Michael Boatman, Geosciences Department, University of 

West Georgia, Carrollton, for his assistance with the well inventory.

Description of the Study Area

Troup County encompasses about 414 square miles in west-central Georgia and lies entirely within the Greenville Slope District, 

Southern Piedmont Section of the Piedmont Province (Clark and Zisa, 1976). Topographic relief across the county ranges in elevation 

from 539 to 948 feet (ft). The Chattahoochee River flows across the county to the southwest and is impounded near West Point, 

Georgia, to form the 25,900-acre West Point Lake (http://www.georgialakeinfo.com/westpointe/info.shtml, accessed August 6, 2008). 

During 2006, about 63,000 people resided in Troup County, which is an increase of 7.6 percent from 2000 (http://quickfacts.census.gov/

qfd/states/13/13285.html, accessed on August 6, 2008).

Total water use in Troup County for 2000 was 12.68 million gallon per day (Mgal/d), 

of which 12 Mgal/d was from surface-water sources—the Chattahoochee River—and 

0.68 Mgal/d from ground-water sources (Fanning, 2003). The major uses of ground 

water were for domestic and commercial needs (0.63 Mgal/d) and public supply 

(0.03 Mgal/d). 

In Troup County, ground water is obtained from shallow bored wells completed 

in the regolith and from deeper drilled wells completed in the fractured crystalline 

bedrock. In the Piedmont Province, the crystalline-bedrock aquifer is composed of 

highly deformed metamorphic and igneous rocks and ranges in thickness from about 

10 to 10,000 ft (Cressler and others, 1983). Primary permeability in the crystalline 

rocks is low; however, there are areas of secondary permeability where high-yielding 

wells are present (Williams and others, 2005). Ground water is transmitted through 

the regolith and secondary openings in the bedrock, such as along foliation, fractures, 

veins, joints, and contacts between different rock units that have undergone some 

degree of weathering (Cressler and others, 1983). The geologic map shown in this report (Lawton and Marsalis, 1976) indicates most 

of the county is underlain by three rock units: (1) hornblende gneiss/amphibolite, (2) mica schist/gneiss/amphibolite, and (3) granite 

gneiss/granite. Each of these rock units is composed of different rock types with varying hydrologic properties. More detailed geologic 

mapping would be required to identify specific rock types with potential for high-yielding wells.

Well Inventory

Well-construction, water-level, lithologic, and yield data provide important background information to evaluate the hydrogeology of a 

particular area; these data can be used in conjunction with geophysical-log and detailed geologic-mapping data to better understand the 

relation between well yield and geology. For this study, well-construction, yield, and location data were compiled from existing well 

records and then field verified by USGS personnel during a well inventory. 

Prior to this study, data pertaining to the geology and ground-water resources of Troup County were limited, so an extensive field 

inventory of wells was conducted to obtain additional information. Well data were obtained from local well drillers and from the 

USGS NWIS database, and a preliminary location map was constructed. Wells were selected for field inventory to provide a good areal 

distribution and to fill voids in areas of sparse coverage. Data collected and verified in the field included owner name, total well depth, 

casing depth and diameter, open or screened intervals, driller, latitude and longitude, use of water, year drilled, land-surface elevation, 

static and pumping water levels, and estimated yield. Well owners were asked about any problems with the quality of the water or 

effects from recent droughts, such as having to lower the pump because of water-level decline. Collected data were entered into the 

NWIS system and are now available on the Web at http://waterdata.usgs.gov/ga/nwis/. During this study, 132 wells were added to 

the database, which already included 80 wells in Troup County.

Results of the well inventory indicate that well yields vary greatly across the county ranging from 0.5 to more than 150 gallons per 

minute (gal/min). Of the wells inventoried, 97 had estimated yields from 0.5 to 25 gal/min, 13 wells from 26 to 50 gal/min, 14 wells 

from 51 to 100 gal/min, and 1 well had an estimated yield of 150 gal/min. There would seem to be potential for development of 

high-yielding wells because 28 of the wells had yields of 26 gal/min or greater. The majority of the existing wells in the county 

were probably located out of convenience in relation to an existing home or business. A combination of detailed geologic mapping, 

well inventory, and geophysical logging may increase the probability of drilling a high-yielding well (Cressler and others, 1983; 

Williams and others, 2005).

Geophysical-Log Data Collection

Geophysical logging was performed in two wells identified during the well inventory. Well 05Y011 had a reported yield of 10 gal/min, 

whereas well 07X009 had a reported yield of 40 gal/min. Geophysical logging tools measure properties of the rock units, water quality, 

and help to identify the water-bearing zones or fractures in the well (Williams and Peck, 2007). The caliper tool records the borehole 

diameter and is used to identify fractures and detect changes in borehole diameter that may be related to changes in rock type or well 

construction. Natural gamma logs measure gamma radiation emitted by the rock units and can detect the presence of radioactive zones, 

which may degrade water quality. Electric logs (long- and short-normal and lateral resistivity) measure the apparent resistivity of the 

rock units and can be used to identify water-bearing zones (typically areas of low resistivity). Fluid logs measure the fluid resistivity 

and temperature of the water in the well, which may indicate water-producing zones due to changes in resistivity (water quality) and 

temperature (indication of flow into or out of the borehole). Flowmeter logging measures the direction and volume of vertical flow in 

the well and can be used to identify fractures where water is entering or exiting the well (Williams and Peck, 2007). High-resolution, 

oriented color digital images of the borehole were obtained using an optical televiewer tool. Data acquired by this tool can help to 

identify rock units and fractures and determine their orientation, which can then be correlated to surface geologic mapping.

Data from geophysical logs collected in wells 05Y011 and 07X009 showed that water-bearing zones are present along contacts 

between lithologic units, where abundant moderate- to high-angle joints occur, and along subhorizontal fractures. Also apparent 

from the geophysical logs are the relatively low yields associated with rock units with few fractures.

The caliper and optical televiewer logs from well 05Y011 indicate only one major fracture in the well at 337 ft. Although flowmeter 

logs were not run in this well because of the reported low yield, most of the water (10 gal/min) likely is coming from this zone. 

Overall, this well has few fractures in the borehole, as shown on the electric logs as areas of high resistivity.

The geophysical and flowmeter logs from well 07X009 indicate two water-bearing zones in the well that contribute a total reported 

yield of 40 gal/min. Overall, this well has abundant moderately-to-steeply-dipping fractures in the borehole, areas of low resistivity on 

the electric logs, which increase the movement of water through the crystalline rock to the main water-producing fractures. The two 

water-bearing zones were identified by flowmeter logging and optical televiewer and are evident on the caliper log at 100 and 230 ft. 

These zones occur as partings along foliation at contacts between different rock types. The white lines on the optical log at 100 ft are 

sections where the tool did not record any data. Data obtained from logs indicate that about 85 percent of the water is coming from the 

zone at 230 ft and 15 percent of the water is coming from the zone at 100 ft. The flowmeter did not show any flow from the zone near 

the fracture at 106 ft. 

Selected References 

Chapman, M.J., Crawford, T.J., and Tharpe, W.T., 1999, Geology and ground-water resources of the Lawrenceville area, Georgia: 

U.S. Geological Survey Water-Resources Investigations Report 98–4233, 46 p. 

Clark, W.Z., Jr., and Zisa, A.C., 1976, Physiographic map of Georgia: Georgia Geologic Survey, scale 1:2,000,000.

Clarke, J.S., and Peck, M.F., 1990, Ground-water resources of the South Metropolitan Atlanta Region, Georgia: Georgia Geologic 

Information Circular 88, 56 p.

Cressler, C.W., Thurmond, C.J., and Hester, W.G., 1983, Ground water in the Greater Atlanta Region, Georgia: Georgia Geologic Survey 

Information Circular 63, 144 p.

Fanning, J.L., 2003, Water use in Georgia by county for 2000 and water-use trends for 1980–2000: Georgia Geologic Survey Information 

Circular 106, 176 p, available online at http://ga.water.usgs.gov/pubs/other/ggs-ic106/

Lawton, D.E., and Marsalis, W.E., comps., 1976, Geologic map of Georgia: Atlanta, Georgia Geological Survey, scale 1:500,000.

Williams, L.J., Kath, R.L., Crawford, T.J., and Chapman, M.J., 2005, Influence of geologic setting on ground-water availability in the 

Lawrenceville area, Gwinnett County, Georgia: U.S. Geological Survey Scientific Investigations Report 2005–5136, 43 p, Web-only 

publication available at http://pubs.usgs.gov/sir/2005/5136/

Williams, L.J., and Peck, M.F., 2007, Borehole geophysical logging of water-supply wells in the Piedmont, Blue Ridge, and Valley and Ridge, 

Georgia: U.S. Geological Survey Fact Sheet 2007–3048, 4 p, Web-only publication available at http://pubs.usgs.gov/fs/2007/3048/

Well 07X009

Well 05Y011

West

Point

Lake

85

185

85

als

a

a

bg

bg

bg

bg

bg/a

gg/gr

gg/gr

gg/gr

gg/gr

gru

gru

gru

gru

ggu

ggu

ggu

ggu

ggu

ms

q

ms

my/umy

hg/a

hg/a

hg/a

hg/a

hg/a

hg/a

q

q

q

q

q

q/ms

um

um

um

bg/ms/a

bg/ms/a

bg/ms/a

bg/ms/a

ms/g/a

ms/g/a

ms/g/a ms/g/a

ms/g/a ms/g/a

ms/g/a

ms/g/a

ms/g/a

gg/gr

04X005

06Z023

06Z020

06Z019 06Z014

06Z016

06Z015

06Z002 06Z008

06Z018

06Z007 05Z024

05Z029

05Z021

06Z001 05Z007

05Z009

05Z022

05Z023

06Z022

05Z028

05Z032 05Z027

06Z012

06Z004 05Z017 05Z025

06Z010

06Z013

05Z018

05Z019

06Z021

06Z003 05Z026

05Z030

05Z008

06Z011

05Z031

04Z024

04Z025

05Z033

04Z027

04Z028

05Z020

04Z026 05Z035

05Z034 05Y018

06Y034

05Y011

05Y006

05Y016 06Y032 06Y020

05Y015 04Y029

04Y030 04Y001

05Y022

05Y021

06Y016

05Y019

05Y005 06Y031

06Y017 06Y007

06Y029 06Y040 06Y014

04Y031

07Y006

04Y032

06Y015

06Y027

06Y013

04Y035

06Y021

06Y023 06Y033 04Y038

06Y008

04Y003

04Y005

04Y004

04Y002

06Y024 04Y037

04Y009

04Y033 06Y026

05Y002

05Y013

06Y010 06Y039 06Y030 07Y007 04Y012

06Y038

04Y019 04Y006

04Y008

04Y013 06Y011 05Y024 04Y015

05Y001

04Y039 04Y024 04Y034 04Y014

04Y018

06Y035

04Y022

06Y018

04Y020

04Y021

05Y004 04Y023

04Y016

06Y037 04Y017 04Y011 04Y010

04Y007 06Y022

04Y036 04X025

06X016 04X016 04X009

04X017 04X008

04X034

04X035 04X039

06X017 04X020

04X011 04X001

06X013

06X008

05X017 06X024

05X021

06X023

06X029

06X005

06X015 06X001

06X012

04X010

06X006

04X037 04X024

06X020

04X014

05X009

06X003

05X011

05X006

04X029

05X018 05X013

04X036 05X012

04X015 04X007 04X040

04X006

04X013

04X012 04X033

06X002 04X019

04X027

05X019

04X021

06X021

05X008

06X022

04X028

04X023

04X018 04X022

04X026 06X009

06X004

04X004 04X002 05X007

04X003

06X010 06X026

07X009

06X027

05X020

05X016

06X025

06X019 06X018

05W007 06X007

06Y009 LaGrange

Lanett

Huguley

Hogansville

West

Point

Grantville

Valley

Corinth

Pine

Mountain

Rock

Mills

Yellowjacket

Beech Creek

06Z024

05Y023

06Y025

04Y025

06Y036

06X028

04X030 04X038

05Y020

05Y017

06Y028

06Z017

Harris County

Troup County

Meriwether County

Troup County

Heard County

Coweta County

Troup County

Heard County

Troup County

ALABAMA

ALABAMA

Chattahoochee River

Chattahoochee River

Creek

Base modified from U.S. Geological Survey 1:100,000-scale digital data

Geology modified from Lawton and Marsalis, 1976; digitized 1991

Horizontal datum for wells is North American Datum 1983

0 1 2 3 4 MILES

0 2 4 KILOMETERS

05Y003

04Y027

85°10' 85°0' 84°50

33°10'

33°0'

Aluminous schist

Amphibolite

Biotite gneiss

Biotite gneiss/amphibolite

Biotite gneiss/mica schist/amphibolite

Granite gneiss/granite

Granite, undifferentiated

Granitic gneiss, undifferentiated

Hornblende gneiss/amphibolite

Mica schist

Mica schist/gneiss/amphibolite

Mylonite and ultramylonite

Quartzite

Quartzite/mica schist

Ultramafic rocks, undifferentiated

EXPLANATION

Well type—Number in 

 parentheses is number 

 of wells of each type

No yield data available (55)

0.5 to 25 (97)

26 to 50 (13)

51 to 100 (14)

101 to 150 (1)

Reported well yield in drilled 

 wells, in gallons per minute—

 Number in parentheses is

 number of wells in each range

Rock type

Bored (37)

Drilled (180)

bg/ms/a

my/umy

als

a

bg

bg/a

gg/gr

gru

ggu

hg/a

ms

ms/g/a

q

q/ms

um

100

150

50

200

250

0

DEPTH, IN FEET BELOW LAND SURFACE

7.5 9.5 0 100 200 300 0 100 200 300 0 1,000 2,000 3,000 4,000 5,000

106.0

108.0

110.0

99.5

100.5

101.5

102.5

226.0

228.0

230.0

232.0

Gamma, in APIU

(American Petroleum Institute Units)

Fluid

resistivity

(ohm-m)

Normal resistivity, 16 inch

(ohm-m)

Normal resistivity, 64 inch

(ohm-m)

Lateral resistivity

(ohm-m)

OPTICAL TELEVIEWER IMAGES

Oriented to magnetic north

(two-dimensional projection

of borehole wall)

Water level

N E S W N

N E S W N

N E S W N

a

b 

c

a

b 

c

Small water-bearing parting plane

 showing oxidation and weathering 

 along foliation

Water-bearing parting plane 

 developed at a contact between 

 darker and lighter rock

Cross-cutting open joint

Features

Waterbearing

zone

Waterbearing

zone

Caliper,

in inches

Casing

100

150

50

0

200

250

300

350

400

450

500

180.0

182.0

184.0

186.0

336.0

338.0

340.0

Caliper,

in inches

7.5

Water level

Waterbearing

zone

9.5 0 100 200 300 0 100 200 300 0 1,000 2,000 3,000 4,000 5,000

Gamma, in APIU

(American Petroleum Institute Units)

Fluid

resistivity

(ohm-m)

Normal resistivity, 16 inch

(ohm-m)

Normal resistivity, 64 inch

(ohm-m)

Lateral resistivity

(ohm-m)

N E S W N

N E S W N

a

b 

c

a

b 

c

Cross-cutting vein

Trace of low-angle foliation

Cross-cutting open joint

Features

DEPTH, IN FEET BELOW LAND SURFACE

OPTICAL TELEVIEWER IMAGES

Oriented to magnetic north

(two-dimensional projection

of borehole wall)

Casing

Ground water

0.68 Mgal/d

Surface water

12 Mgal/d Ground water

Total water use

Public supply

0.03 Mgal/d

Other

0.02 Mgal/d

Domestic and

commercial

0.63 Mgal/d

Atlanta

Coastal Plain

Piedmont

Valley

and

Ridge

Fall Line

 Troup County 

study area

Cumberland Blue Ridge

Plateau 

Chattahoochee

Yellowjacket Creek

Beech Creek

River

West Point

Lake

Shaded relief of Troup County

Data from U.S. Geological Survey 

30-meter digital elevation models

Physiographic provinces modified

from Clarke and Zisa, 1976

Physiographic provinces

of Georgia

Greenville

Slope

District

Well Inventory and Geophysical Logging of Selected Wells in Troup County, Georgia, 2007–2008

By 

Michael F. Peck, David C. Leeth, and Michael D. Hamrick

2008

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY Prepared in cooperation with

Troup County Board of Commissioners

Scientific Investigations Map 3058

Well Inventory and Geophysical Logging of Selected Wells in Troup County, Georgia, 2007–2008—SHEET 1 OF 1

Peck, M.F., Leeth, D.C., and Hamrick, M.D., 2008, Well Inventory and Geophysical Logging of Selected Wells in Troup County, Georgia, 2007–2008