U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3112

January 2010

Drilling a Deep Geologic Test Well at

Fort Pulaski National Monument, Georgia

Printed on recycled paper

The U.S. Geological Survey (USGS), in cooperation 

with the National Park Service (NPS), is drilling a deep 

geologic test well at Fort Pulaski National Monument, 

Georgia. The test well is located near the picnic grounds, 

and the operation is scheduled to run between mid-February and mid-April 2010. When completed, the well will be 

about 1,500 feet deep. The purpose of this test well is to 

gain knowledge about the regional-scale Floridan aquifer, 

an important source of groundwater in the Savannah area 

(fig. 1). Also, cores obtained during drilling will enable 

geologists to study the last 60 million years of Earth history in this area.

Why Is the Drilling at Fort Pulaski?

The USGS has undertaken a five-year study of the 

geology of the greater Savannah region. This endeavor 

combines mapping of the surface geology with detailed 

study of the subsurface geology. The Fort Pulaski site 

was chosen to complete a series of test wells in Georgia 

that parallel the Savannah River from the Savannah River 

Nuclear Site to the Atlantic Coast. The data gathered from 

these wells will be combined with published information 

from the South Carolina side of the river to enable us to 

model the subsurface geology across the State line.

Why Are We Doing This Study?

Groundwater is a vital natural resource in the southeastern Atlantic Coastal Plain. The Floridan aquifer, one 

of the most productive aquifers in the world, is a regionalscale source of groundwater that has been used locally for 

more than 100 years. Recently, heavy use of this resource 

has caused some wells along the coast to experience 

saltwater intrusion, rendering them unsuitable for drinking water (fig. 2). As water use increases in response to 

growing municipal, industrial, and agricultural demand, 

State and local governments will face difficult decisions 

about future use of the Floridan aquifer. A primary goal 

of the USGS is to make information on the aquifer available to decisionmakers. Defining the internal character and 

boundary of the aquifer in the subsurface requires detailed 

knowledge of the rock types, their ages, and their physical 

characteristics. This information will help water resource 

specialists to model groundwater flow and to correlate subsurface characteristics across State and local boundaries. 

The results from the test well at Fort Pulaski will be added 

to the larger database that describes the Floridan aquifer.

What Exactly Are We Doing? 

 The test well is obtained using a technology called 

wireline core drilling (fig. 3). A hollow drill stem (pipe) 

Figure 1.  Extent of the Floridan aquifer. In the Savannah, Ga., area,

the Floridan is about 400 feet thick and the top is about 200 feet

below the surface.

MISS. ALABAMA

GEORGIA

FLORIDA

SOUTH

CAROLINA

Atlantic Ocean

Gulf of Mexico

Savannah Fort

Pulaski
Figure 2.  Floridan aquifer

groundwater flow models. A, Before

the 1880s; B, As of 2005. Modified

from Falls and others, 2005.

NE

 Area of freshwater recharge

from the surficial aquifer to

the Upper Floridan aquifer

Area of freshwater discharge

from the Upper Floridan aquifer

toward the saline water

of the surficial aquifer

SW

Sea level

NOT TO SCALE Predevelopment (before 1880s)

upper confining unit

surficial aquifer

Land surface

Atlantic Ocean Upper Floridan aquifer

Lower Floridan aquifer 

lower semiconfining unit

middle semiconfining unit

c.f.

Area of freshwater recharge

from the surficial aquifer to

the Upper Floridan aquifer

Area of saline water recharge

from the ocean and surficial aquifer

toward the Upper Floridan aquifer

 Upper Floridan aquifer

SW NE

Sea level

NOT TO SCALE

upper confining unit

surficial aquifer

Land surface

lower semiconfining unit

Atlantic Ocean

Lower Floridan aquifer 

Present Day (2005)

middle 

 semiconfining unit

c.f.

Water-supply wells for

Chatham County

EXPLANATION

Fresh groundwater

Very saline groundwater

Moderately saline 

groundwater 

Seawater

Potentiometric surface of

the Upper Floridan aquifer

General direction of

groundwater flow

Trace of cross section on 

it 

NE

SW

GEORGIA

SOUTH

CAROLINA

NE

 Area of freshwater recharge

from the surficial aquifer to

the Upper Floridan aquifer

Area of freshwater discharge

from the Upper Floridan aquifer

toward the saline water

of the surficial aquifer

SW

Sea level

NOT TO SCALE Predevelopment (before 1880s)

upper confining unit

surficial aquifer

Land surface

Atlantic Ocean Upper Floridan aquifer

Lower Floridan aquifer 

lower semiconfining unit

middle semiconfining unit

c.f.

Area of freshwater recharge

from the surficial aquifer to

the Upper Floridan aquifer

Area of saline water recharge

from the ocean and surficial aquifer

toward the Upper Floridan aquifer

 Upper Floridan aquifer

SW NE

Sea level

NOT TO SCALE

upper confining unit

surficial aquifer

Land surface

lower semiconfining unit

Atlantic Ocean

Lower Floridan aquifer 

Present Day (2005)

middle 

 semiconfining unit

c.f.

Water-supply wells for

Chatham County

EXPLANATION

Fresh groundwater

Very saline groundwater

Moderately saline 

groundwater 

Seawater

Confining unit

Potentiometric surface of

the Upper Floridan aquifer

General direction of

groundwater flow

Trace of cross section on 

inset map

NE

SW

GEORGIA

SOUTH

CAROLINA

FLORIDA

NE

 Area of freshwater recharge

from the surficial aquifer to

the Upper Floridan aquifer

Area of freshwater discharge

from the Upper Floridan aquifer

toward the saline water

of the surficial aquifer

SW

Sea level

NOT TO SCALE Predevelopment (before 1880s)

upper confining unit

surficial aquifer

Land surface

Atlantic Ocean Upper Floridan aquifer

Lower Floridan aquifer 

lower semiconfining unit

middle semiconfining unit

c.f.

Area of freshwater recharge

from the surficial aquifer to

the Upper Floridan aquifer

Area of saline water recharge

from the ocean and surficial aquifer

toward the Upper Floridan aquifer

 Upper Floridan aquifer

SW NE

Sea level

NOT TO SCALE

upper confining unit

surficial aquifer

Land surface

lower semiconfining unit

Atlantic Ocean

Lower Floridan aquifer 

Present Day (2005)

middle 

 semiconfining unit

c.f.

Water-supply wells for

Chatham County

EXPLANATION

Fresh groundwater

Very saline groundwater

Moderately saline 

groundwater 

Seawater

Confining unit

Potentiometric surface of

the Upper Floridan aquifer

General direction of

groundwater flow

Trace of cross section on 

inset map

[c.f., channel fill (permeable)]

NE

SW

GEORGIA

SOUTH

CAROLINA

FLORIDA
closed off. We will transport the collected core and samples back to USGS laboratories for completion of testing 

and descriptions. Paleontologists at the USGS will examine the core for microfossils that help explain the geologic 

history (fig. 5).

What Will Be the Final Products of This Study?

Following analysis of all the information gathered 

from the Fort Pulaski test well, the USGS will publish a 

set of reports and make them available to the public. These 

reports will include technical descriptions of the entire 

1,500-foot corehole as well as assessments of fossil content, chemical characteristics, and ages of the sediments. 

This information will be correlated with data from other 

test wells in the Floridan aquifer. Information gathered 

from the groundwater monitoring instrument will be available as those data are accumulated.

is carefully drilled through the soil into the underlying 

variably indurated sands, silts, clays, and limy sediments, 

which are collected in an inner core barrel in 10-foot sections. These sections are pulled back to the surface and 

the collected core is boxed for study (an example of boxed 

core is shown in figure 4). On site, the freshly cored sediments are described and sampled for laboratory analysis. 

The inner barrel is then put back down the hole to drill 

and collect the next 10-foot section. The Fort Pulaski test 

well will take about two months to drill. After the hole is 

completed, we will conduct a variety of tests in the open 

hole. These are referred to as “downhole geophysics” and 

involve lowering several instruments on cables in order to 

measure physical properties of the sand, silt, clay, and limy 

sediment layers such as electrical resistance and natural 

radiation. Finally, we will place a small groundwater monitoring instrument at a specific level in the hole and connect 

it to a surface graph. The hole then will be permanently 

Figure 3.  U.S. Geological Survey drill rig and crew conducting

wireline core drilling on the Atlantic Coastal Plain.

Figure 4.  Section of poorly indurated limestone core recovered

from a well drilled into the Floridan aquifer, Pineora, Ga. Box

contains core from 473.4 to 481.2 feet down. This well was

completed in April 2009 and is part of our USGS project work.

Photograph by Colleen Durand, USGS.
For additional information, please contact:

Randy Wester, Park Superintendent

Fort Pulaski National Monument

National Park Service

P.O. Box 30757

Savannah, GA 31410-0757

Telephone: (912) 786–5787

E-mail: Randy_Wester@nps.gov

Arthur P. Schultz, Project Chief

U.S. Geological Survey

926A National Center

Reston, VA 20192 

Telephone: (703) 648–6501

E-mail: aschultz@usgs.gov

Edward H. Martin, Director

Georgia Water Science Center

U.S. Geological Survey

3039 Amwiler Road, Suite 130

Atlanta, GA 30360-2824

Telephone: (770) 903–9100

E-mail: ehmartin@usgs.gov

Who Will Benefit From This Information?

1. Federal, State, and local water management agencies. 

2. Environmental and geological consultants.

3. State and local academic institutions.

4. The general public.

Figure 5.  Photomicrographs of microfossils from the Atlantic

Coastal Plain. A, Dinoflagellate; B, Calcareous nannofossil.

50μm

Cordosphaeridium

cantharellus

B A

7μm

Pemma sp.

B

Reference Cited

Falls, W.F., Ransom, Camille, Landmeyer, J.E., Reuber, E.J., 

and Edwards, L.E., 2005, Hydrogeology, water quality, 

and saltwater intrusion in the Upper Floridan aquifer in 

the offshore area near Hilton Head Island, South Carolina, 

and Tybee Island, Georgia, 1999–2002: U.S. Geological 

Survey Scientific Investigations Report 2005–5134, 48 p. 

(available only online at http://pubs.er.usgs.gov/usgspubs/sir/

sir20055134).

By Arthur P. Schultz and Ellen L. Seefelt

How Is the Drilling Funded? 

Funding for the Fort Pulaski test well comes from 

the USGS National Cooperative Geologic Mapping Program. This program is funded by Congress through the 

Department of the Interior and includes components that 

fund Federal, State, and academic research. Additional 

support comes from the USGS Georgia Water Science 

Center and the National Park Service. Funding covers 

all costs associated with drilling, salaries for science 

staff, and final publication of the results.