In cooperation with the Brunswick-Glynn County Joint Water and Sewer Commission

Saltwater Intrusion in the Floridan Aquifer System 

Near Downtown Brunswick, Georgia, 1957–2015

Introduction

The Floridan aquifer system (FAS) consists of the Upper 

Floridan aquifer (UFA), an intervening confining unit of highly 

variable properties, and the Lower Floridan aquifer (LFA). 

The UFA and LFA are primarily composed of Paleocene- to 

Oligocene-age carbonate rocks that include, locally, Upper 

Cretaceous rocks (Miller, 1986; Krause and Randolph, 1989). 

The FAS extends from coastal areas in southeastern South Carolina and continues southward and westward across the coastal 

plain of Georgia and Alabama, and underlies all of Florida. The 

thickness of the FAS varies from less than 100 feet (ft) in aquifer 

outcrop areas of South Carolina to about 1,700 ft near the city 

of Brunswick, Georgia (Williams and Kuniansky, 2015). 

Locally, in southeastern Georgia and the Brunswick– Glynn 

County area, the UFA consists of an upper water-bearing zone 

(UWBZ) and a lower water-bearing zone (LWBZ), as identified 

by Wait and Gregg (1973), with aquifer test data indicating 

the upper zone has higher productivity than the lower zone. 

Near the city of Brunswick, the LFA is composed of two 

permeable zones: an early middle Eocene-age upper permeable 

zone (UPZ) and a highly permeable lower zone of limestone 

(LPZ) of Paleocene and Late Cretaceous age that includes a 

deeply buried, cavernous, saline water-bearing unit known as 

the Fernandina permeable zone (Krause and Randolph, 1989). 

Maslia and Prowell (1990) inferred the presence of major 

northeast–southwest trending faults through the downtown 

Brunswick area based on structural analysis of geophysical 

data, northeastward elongation of the potentiometric surface of 

the UFA, and breaches in the local confining unit that influence 

the area of chloride contamination. Pronounced horizontal and 

vertical hydraulic head gradients, caused by pumping in the 

UFA, allow saline water from the FPZ to migrate upward into 

the UFA through this system of faults and conduits.

 Saltwater was first detected in the FAS in wells completed 

in the UFA near the southern part of the city of Brunswick in late 

1957 (Wait, 1965). By the 1970s, a plume of groundwater with 

high chloride concentrations had migrated northward toward 

two major industrial pumping centers, and since 1965, chloride 

concentrations have steadily increased in the northern part of 

the city (fig. 1). In 1978, data obtained from a 2,720-ft-deep test 

well (33H188; fig. 2) drilled south of the city showed water with 

a chloride concentration of 33,000 milligrams per liter (mg/L), 

suggesting the saltwater source was located below the UFA in 

the Fernandina permeable zone (FPZ) of the LFA (Jones and 

others, 2002).

All U.S. Geological Survey (USGS) data collected for this 

study, including groundwater levels in wells and water-chemistry 

data, are available in the USGS National Water Information 

System (U.S. Geological Survey, 2016). 

U.S. Department of the Interior

U.S. Geological Survey

South side of Jekyll Island, Georgia. 

Photograph by Alan M. Cressler, USGS.

Open-File Report 2017–1010

February 2017
October 2014

Bay Street

source area

Reynolds Street

source area Brunswick

1957–1962 January 1970–January 1971 March–June 1980

June 2000 October 2015

Figure 1. Chloride concentration in the upper water-bearing zone of the Upper Floridan aquifer in Brunswick, Georgia.

Chloride concentration, in milligrams per liter

EXPLANATION

GEORGIA

Map

area

GLYNN

COUNTY

Brunswick

<250

250 to 750

750 to 1,250

1,250 to 1,750

1,750 to 2,250

>2,250

Brunswick Cellulose

 Well Field

Pinova

Well Field

N

Figure 1. Chloride concentration in the upper water-bearing zone of the Upper Floridan aquifer in Brunswick, Georgia.

2
NAVARRO ROCKS

PALEOCENE ROCKS

TAYLOR ROCKS

Upper

confining

unit

Upper

Floridan

aquifer

Middle

composite

unit

Surficial aquifer

system

Lower

confining unit

Lower

Floridan

aquifer

0 10 20 30 40 MILES

0 10 20 30 40 KILOMETERS

OCALA LIMESTONE EARLY EOCENE ROCKS

SUWANNEE LIMESTONE

UNDIFFERENTIATED 

Gulf

Trough

Recharge area Discharge area

Glauconitic 

silt and sand

? ?

Floridan aquifer system

Sand, clay

FLORIDAN AQUIFER SYSTEM BASE OF 

TOP OF FLORIDAN AQUIFER SYSTEM

Fernandina

permeable zone CRETACEOUS

FORMATIONS

F

NORTHWEST

NGVD 29

–500

–1,000

–2,000

500

–1,500

–2,500

FEET

F'

SOUTHEAST 35H068

Clay

?

?

Brunswick

MIDDLE EOCENE ROCKS

UNDIFFERENTIATED 

UWBZ

LWBZ

UPZ

LPZ

UWBZ - Upper water-bearing zone

LWBZ - Lower water-bearing zone

UPZ - Upper permeable zone

LPZ - Lower permeable zone

ALABAMA GEORGIA

FLORIDA

SOUTH

CAROLINA

35H068

F

F' 33H188

34H495

Southeastern Coastal Plain aquifer system

Fernandina Beach

Jacksonville

MIOCENE OR YOUNGER SEDIMENTS

LATE EOCENE ROCKS UNDIFFERENTIATED 

34H428

Figure 2. Generalized hydrogeologic cross section F-F’ and groundwater-flow directions 

(modified from Williams and Kuniansky, 2015).

Southeastern Coastal Plain aquifer system

Colors used to differentiate

Surficial aquifer system

Aquifer

Upper confining unit of

Floridan aquifer system

Confining unit

Leaky

dolostone

VERTICAL SCALE GREATLY EXAGGERATED

EXPLANATION

Well—Permit number or

 other unique identifier.

Formation contact

Hydrogeologic boundary

Approximate 10,000 mg/L

 total dissolved solids

 concentration

35H068

Floridan aquifer system

Aquifer

Upper

Floridan

Lower

Floridan

Property

Semi- Confining

confining

Groundwater-flow direction

Figure 2. Generalized hydrogeologic cross section F–F' and groundwater-flow directions 

(modified from Williams and Kuniansky, 2015).

3
Groundwater Levels, Groundwater Pumping, and 

Flow in the Floridan Aquifer System

Prior to development of the UFA in the late 1800s, groundwater levels in the Brunswick area were estimated to be as high 

as 55 ft above land surface [65 ft above the North American 

Vertical Datum of 1988 (NAVD 88)] and groundwater flow was 

in an easterly direction toward the coast (Johnston and others, 

1980). Since that time, the UFA has become a major source 

of water supply for industrial and municipal use along coastal 

Georgia, including Glynn County and the city of Brunswick. 

In Glynn County, large withdrawals began in the early 1940s, 

mostly by industry, and increased by 11.6 million gallons per 

day (Mgal/d) between 1950 and 1960 to a reported total of 

55.3 Mgal/d during 1960 (Cherry and others, 2011). Groundwater use peaked in the early 1980s with reported average annual 

pumping rates of 58.8 and 19.5 Mgal/d at Brunswick Cellulose 

Inc. and Pinova Inc. (formerly Hercules Inc.), respectively, and 

an average annual pumping rate of 9.8 Mgal/d (fig. 3) for public 

supply (Krause and Randolph, 1989; Jones, 2001). 

A steady increase in pumping since predevelopment caused 

groundwater-level declines in the UFA ranging from 20 ft in 

southernmost Glynn County to as much as 80 ft near pumping 

centers in northern Brunswick. This increase altered the natural 

groundwater-flow direction from eastward toward the coast to 

north and northeast toward the center of pumping in Brunswick 

(Jones, 2001). Groundwater use near the city of Brunswick has 

steadily declined since 1990. Water conservation measures in 

effect during late 2011 at the Brunswick Cellulose well field 

reduced pumping from about 35 Mgal/d to 23.3 Mgal/d during 

2015 (S. Swan, Brunswick–Glynn County Joint Water and Sewer 

Commission, written commun., August 2015). A similar decline 

in groundwater use occurred at the Pinova well field, with a 

reduction in pumping from about 6 Mgal/d in 2010 to 4.2 Mgal/d 

during 2015. Pumping for public supply in Brunswick–Glynn 

County also decreased slightly from 9.8 Mgal/d during 1980 

to 9.3 Mgal/d in 2015. Groundwater use from the UFA for 

public supply in Brunswick–Glynn County declined despite an 

increase in population from 54,980 persons in 1980 to 83,579 

in July 2015 (U.S. Census Bureau, 2015). 

Water levels in the UWBZ of the UFA (well 34H328; 

fig. 3) are primarily influenced by changes in pumping. The 

early part of the record from 1939 to 1948 indicates that water 

levels were about 40 ft above NAVD 88. Over the following 

30 years, as pumping increased, water levels declined by more 

than 30 ft, and a cone of depression formed near the industrial 

well fields in the northern part of Brunswick. This period was 

followed by a recovery in water levels in the early 1980s, when 

industrial groundwater users reduced pumping by 23.5 Mgal/d. 

Since the mid-1980s, water levels in well 34H328 have ranged 

between 8.5 and 14.3 ft above NAVD 88. During the peak of 

groundwater use in the early 1980s, the water levels in the 

UFA were near sea level (NAVD 88) in the northern part of 

the Brunswick area and about 15 ft below NAVD 88 near the 

industrial well fields (Johnston and others, 1980).

During October 2015, water levels from continuous 

recorders and synoptic water-level measurements were collected 

from 50 wells completed in the UWBZ of the UFA. The 

potentiometric surface map (fig. 4) constructed using these 

water-level data indicates the general direction of groundwater 

flow is from the southwest in neighboring Camden and 

Brantley Counties towards the northeast across Glynn County 

and into McIntosh County. The water-level contours indicate 

that a portion of groundwater flow is captured and directed 

toward pumping centers in northern Brunswick. This captured 

flow is evident from the 15- and 10-ft contours that surround 

the pumping centers, indicating groundwater flow toward 

downtown Brunswick from the southwest, the southeast, and 

Figure 3. Major groundwater pumpage from the Upper Floridan aquifer in the Brunswick–Glynn County

area, Georgia, 1940–2015 and water levels in well 34H328, 1939–2013 (see fig. 2 for well location). 

0

10

20

30

40

50

60

70

Pumpage, in million gallons per day

Brunswick Cellulose Inc.

Pinova Inc.

Public supply

1940 1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015

Water level above NAVD 88, in feet

0

10

20

30

40

50

Water levels in well 34H328 (Upper Floridan aquifer)

Figure 3. Major groundwater pumpage from the Upper Floridan aquifer in the Brunswick–Glynn County area, 

Georgia, 1940–2015 and water levels in well 34H328, 1939–2013 (see fig. 2 for well location).

4
MCINTOSH

WAYNE

BRANTLEY

CAMDEN

GLYNN

Brunswick

Chloride plume outline

25.0

11.7

15.7

12.8

34.6 33.8 27.4 35.1

34.3

28.8

26.3

39.8

25.9 34.6

34.7

15.8

13.4

7.1

1.9

15.9

12.6

35.2

18.5

14.2

Image from National Agriculture Imagery Program 2010 east digital ortho quarter quad tiles, available via

https://www.fsa.usda.gov/programs-and-services/aerial-photography/imagery-programs/naip-imagery/index

5

15

20

25

30

35

10

10

15

20

9.89 Well and water level—In feet 

 above NAVD 88 

General direction of groundwater flow

EXPLANATION

Potentiometric contour—Shows

 altitude at which water level

 would have stood in tightly cased

 wells, October 2015. Hachures

 indicate depression. Contour

 interval 5 feet. Datum is NAVD 88 

10

10 KILOMETERS

5 10 MILES

5

0

0

N

Figure 4. Potentiometric surface of the Upper Floridan aquifer, Brunswick–Glynn County, Georgia, October 19–22, 2015.

the north. The map of downtown Brunswick (inset, fig. 4) 

shows the 10-ft contour covering the northwest part of the city 

near the Brunswick Cellulose well field, which is an indication 

of the continued presence of a cone of depression caused by 

pumping. However, when compared to previous contour maps, 

the October 2015 potentiometric contours near the Brunswick 

Cellulose well field indicate that water levels have increased 

since the peak of pumping during 1980. 

5
Chloride Concentrations in the 

Upper Floridan Aquifer

The area of chloride contamination in the UWBZ of the 

UFA near the city of Brunswick during October 2015 was 

mapped using groundwater samples collected from 33 wells. 

The chloride concentration in an approximate 2-square-mile 

area near the city of Brunswick was greater than the 250-mg/L 

State and Federal secondary maximum contaminant level 

(SMCL) (Georgia Environmental Protection Division, 1997; 

U.S. Environmental Protection Agency, 2000) and exceeded 

2,250 mg/L in part of the area (fig. 1). The extent of chloride 

concentrations shown on the October 2014 and 2015 maps 

is similar to the extent shown on the map published for 2000 

(Hamrick and Cherry, 2015), with areas of highest chloride 

concentration found in the northern part of the city, as well 

as near the Bay Street source area in the southern part of the 

city (fig. 1). The potentiometric surface map (fig. 4) of the 

UWBZ of the UFA near downtown Brunswick indicates that 

the groundwater-flow direction is northwest from the Reynolds Street source area (fig. 1) toward the Brunswick Cellulose 

well field. The long-term changes in chloride concentration 

are consistent with the primary groundwater-flow direction, 

which controls the lateral movement of chloride from the 

Bay Street source area (fig. 1) toward the north and then from 

the Reynolds Street source area toward the industrial well 

fields. Low horizontal hydraulic head gradients in the UWBZ 

of the UFA toward the Pinova well field, or another source 

of chloride contamination, possibly allow an area of elevated 

chloride concentrations to extend to the northeast from the 

Reynolds Street source area.

A comparison of results from separate groundwater 

samples collected during October 2014 and October 2015, in 

12 wells open to the UWBZ of the UFA, indicates a maximum 

increase in chloride concentration of 8.8 mg/L and a maximum 

decrease of 390 mg/L (fig. 5A). The outline of the chloride 

plume is shown in figure 5A for the UWBZ of the UFA. The 

maximum decrease in chloride concentrations was reported 

in well 34H393 (390 mg/L), located within the Bay Street 

source area. Increases in chloride concentrations were limited 

to 8.8 mg/L in well 34H344, located south of the Pinova 

well field. Chloride concentrations in the northern part of the 

chloride plume, near the Reynolds Street source area, decreased 

in wells 33H130 (310 mg/L), 34H424 (320 mg/L), and 33H133 

(230 mg/L). The mean decrease in chloride concentration for 

12 wells over the 1-year period was 145 mg/L. 

A comparison of results from separate groundwater 

samples collected during October 2014 and October 2015, in 

six wells open to the LWBZ of the UFA, indicates a maximum 

increase in chloride concentration of 70 mg/L and a maximum 

decrease of 320 mg/L (fig. 5C). Near the Reynolds Street 

source area, within the central part of the chloride plume, 

decreases in chloride concentration ranged from 320 mg/L 

(well 34H402) to 20 mg/L (well 34H354). Decreases in 

chloride concentration were also evident near the industrial 

well fields, with an 80-mg/L decrease in well 34H334 south 

of Pinova and a 250-mg/L decrease in well 33H154, which 

is located east of the Brunswick Cellulose plant. The mean 

decrease in chloride concentration for the six wells was 

124 mg/L. 

Due to increasing chloride levels in well 34H134, modifications were made to the well to reduce water inflow from 

the deeper part of the aquifer. The bottom of the well, between 

the depths of 942 ft and 724 ft, was sealed with concrete grout, 

thereby eliminating water production from a 218-ft zone that 

yields higher chloride water. Subsequently, a water sample 

collected by the USGS in October 2015 from the modified well 

34H560 showed a decrease of 26 mg/L in the chloride concentration (fig. 5A) since the plugging of the lower zone, which 

indicates a slight reduction in the upward migration of chloride 

into the open interval of the well. Chloride concentrations have 

increased in well 34H134/34H560 from near background levels 

(20 to 30 mg/L) during June 2000 (32.0 mg/L) to 96 mg/L 

for the sample collected during October 2015 (fig. 5B). This 

increase in chloride suggests either a lateral movement of 

chloride in the UWBZ from the plume or the continued upward 

migration of chloride from lower depths. In late 2009, well 

34H134/34H560 was equipped to monitor daily changes in 

specific conductance. Specific conductance is a surrogate for 

chloride concentration and is used to monitor the potential 

movement of saltwater into the freshwater zones of the UFA 

(Cherry and others, 2011).

Decreases in the chloride concentration in several wells 

open to the UPZ in the LFA suggest reduced upward flow 

from the LFA into the UWBZ and LWBZ of the UFA. The 

groundwater sample collected in October 2015 at well 34H391, 

which taps the UPZ of the LFA, had a chloride concentration of 

2,430 mg/L, indicating a decrease of 540 mg/L when compared 

with the sample taken in October 2014. Results from water 

samples collected from LFA well 34H399, which is open to a 

slightly deeper interval of the UPZ than well 34H391, indicated a 

chloride concentration of 5,530 mg/L during October 2015 and a 

decrease of 130 mg/L over a 1-year period. Well 33H188, which 

is open to the deeper FPZ of the LFA, had a chloride concentration of 11,500 mg/L during July 2013. Results from a discrete 

groundwater sample collected from well 34H495 (location shown 

in fig. 2), at a depth of 2,720 ft (lower portion of FPZ) during 

August 2000, had a chloride concentration of 26,000 mg/L, 

which is higher than the 19,000-mg/L chloride concentration of 

modern seawater (Hem, 1989; Falls and others, 2005).

A comparison of results from separate groundwater 

samples collected during June 2000 and October 2015, 

in 12 wells open to the UWBZ of the UFA, indicates a 

maximum increase in chloride concentration of 550 mg/L and 

a maximum decrease of 678 mg/L (fig. 5B). The maximum 

increase in chloride concentration was reported in well 33H133 

(550 mg/L), east of the Brunswick Cellulose plant. Well 

34H424 had a chloride increase of 230 mg/L, which coincides 

with one of the two areas with the greatest chloride concentrations north of the Reynolds Street source area. The maximum 

decrease of 678 mg/L (well 34H469) was also located in the 

northern part of the chloride plume and may be the result of 

preferential flow paths and changes in local hydraulic head 

gradient caused by nearby pumping. Well 34H393, located 

within the Bay Street source area, had a decrease in its chloride 

concentration of 90 mg/L. North of well 34H393, chloride 

concentrations decreased in wells 34H112 (230 mg/L), 34H125 

(317 mg/L), and 34H434 (190 mg/L). The mean decrease in 

chloride concentrations for 12 wells over the 16-year period 

(June 2000–October 2015) was 54 mg/L.

6
Turtle River

East River

Oglethorpe Bay

34H393 Bay Street

source

area

34H125

34H112

34H434

34H355

34H344

34H424

34H469

33H133

33H130

34H134/34H560

–50 to 0.0

0.001 to 50

Change in cloride concen-

 tration from 2014 to 2015,

 in milligrams per liter

EXPLANATION

8.8

–27

8.8

33H133 Well identifier

Reynolds Street

 source area

Brunswick

Cellulose

well field

 Pinova

well field

Outline of chloride plume

in UWBZ of UFA

–90 –50.01 to –250

–390 –250.01 to –390

–310

–230

–58

–320

–140

–52

–90

–110

–27

A. Upper water-bearing zone (UWBZ) of Upper Floridan aquifer

 (UFA) 2014 to 2015

–26

17

25 

4TH STREET

4TH AVE

NEWCASTLE STREET

341

N

Brunswick

–390

34H401

133

33H133

34H469

33H130

34H424

34H344

34H355

34H434

34H125

34H112

34H393

34H134/34H560

–50 to 0.0

0.001 to 50

50.01 to 250

Change in cloride concen-

 tration from 2000 to 2015,

 in milligrams per liter

EXPLANATION

133

10

–2.3

51

250.01 to 550 550

10

33H133 Well identifier

–50.01 to –250

–250.01 to –500

–190

–678

–317

–500.01 to –678

–230

–317

550

–190

–170 –678

230

–90

B. UWBZ of UFA 2000 to 2015

64

34H401

–20

70

33H154

(LWBZ)

34H403

(LWBZ)

–141

33H206

(LFA)

–540

34H391

(LFA)

34H399

(LFA)

33H127

(LWBZ)

34H334

(LWBZ) 34H402 (LWBZ)

34H354

(LWBZ)

–250

–50 to 0.0

0.001 to 50

50.01 to 250

Change in cloride concen-

 tration from 2014 to 2015,

 in milligrams per liter

EXPLANATION

70

20

–20

–80

–320

33H154 Well identifier

–5

–130 –50.01 to –250

–250.01 to –540 –320

–130

C. Lower water-bearing zone (LWBZ) of UFA and Lower Floridan

 aquifer LFA) 2014 to 2015

34H403

(LWBZ)

33H206

(LFA)

–17034H391

(LFA)

34H399

(LFA)

34H354

(LWBZ)

34H334

(LWBZ)

33H127

(LWBZ)

33H154

(LWBZ)

–50 to 0.0

0.001 to 50

50.01 to 250

Change in cloride concen-

 tration from 2000 to 2015,

 in milligrams per liter

EXPLANATION

120

6.0

–2.3

250.01 to 450 260

33H154 Well identifier

–50.01 to –250

–250.01 to –500

–170

–1,770

–290

–500.01 to –1,770

129

–150

180

450

260

120

214

–1,770

D. LWBZ of UFA and LFA 2000 to 2015

34H402

(LWBZ)

Figure 5. Change in chloride concentration in the Upper and Lower Floridan aquifers in the Brunswick area, Georgia. Figure 5. Change in chloride concentration in the Upper and Lower Floridan aquifers in the Brunswick area, Georgia.

7
A comparison of results from separate groundwater 

samples collected during June 2000 and October 2015, in six 

wells open to the LWBZ of the UFA, indicates general increases 

in chloride concentration ranging from 120 mg/L (well 34H403) 

to 450 mg/L (34H354; fig. 5D). The mean increase in chloride 

concentration in four wells (33H127, 34H402, 34H354, and 

34H334) located near the Reynolds Street source area was 

255 mg/L. The mean increase in chloride concentration for six 

wells open to the LWBZ of the UFA was 172 mg/L. Increases in 

the chloride concentration in well 34H334 (180 mg/L) suggest 

the lateral movement of chloride in the LWBZ of the UFA 

outside the current inferred boundary of the chloride plume in 

the UWBZ of the UFA. The only decrease in chloride concentration in the LWBZ of the UFA over the 16-year period was 

the 150-mg/L decrease reported in well 33H154.

A comparison of results from separate groundwater 

samples collected during June 2000 and October 2015, in 

three wells open to the UPZ of the LFA, indicates an increase 

in the chloride concentration in well 33H206 of 214 mg/L 

and decreases of 1,770 mg/L in well 34H399 and 170 mg/L 

in well 34H391. These results suggest a continued vertical 

migration of chloride from the FPZ of the LFA into the UFA 

near the Brunswick Cellulose well field. These results also 

suggest a change in the vertical hydraulic head gradient near the 

Bay Street source area that has reduced chloride concentrations 

in wells 34H391 and 34H399. The chloride distribution within 

the LWBZ of the UFA and UPZ of the LFA are difficult to map 

because fewer wells are open to these zones.

Additional groundwater samples were collected from seven 

production wells at Brunswick Cellulose to assess the vertical 

movement of chloride near the Brunswick Cellulose well 

field (fig. 6). The seven active production wells tap different 

water-bearing zones of the UFA, with three wells open to the 

UWBZ of the UFA and four wells open to both the UWBZ 

and LWBZ of the UFA. The chloride concentrations in the 

three production wells open to the UWBZ of the UFA ranged 

from 18.5 to 75 mg/L and are located outside of the chloride 

plume area. The chloride concentrations in the four production 

wells open to the UWBZ and LWBZ of the UFA ranged from 

176 to 1,000 mg/L. In three of these four production wells, 

chloride concentrations exceeded the SMCL of 250 mg/L, 

indicating a deterioration of water quality with depth and 

suggesting greater rates of lateral movement of chloride within 

the LWBZ. 

Additional groundwater samples were collected from two 

production wells at the Pinova well field to assess the lateral 

movement of chloride in the UWBZ of the UFA near the well 

field. Numerous production wells at Pinova were originally 

constructed in the UWBZ and LWBZ, but open intervals 

tapping the LWBZ were plugged during the mid-1960s to 

improve water quality in the well field (Cherry and others, 

2011). Results from the samples collected during October 

2015 indicate a sharp transition in chloride concentration from 

near background levels of 16.9 mg/L in well 34H450, which 

is located outside the chloride plume area, to 533 mg/L in 

well 34H413, which is located near the center of the facility 

(fig. 6). These two wells are located approximately 1,360 ft 

apart. The USGS well-cluster site located south of the Pinova 

well field has a well open to the UWBZ and another well 

open to the LWBZ of the UFA. Chloride concentrations from 

samples collected during October 2015 show chloride levels 

above background (70 mg/L) in well 34H344, which is open to 

the UWBZ, and elevated chloride levels (1,180 mg/L) in well 

34H334, which is open to the LWBZ of the UFA.

Water Chemistry of the Upper Floridan Aquifer

Water samples were collected and analyzed for major ions 

from seven production wells tapping the UWBZ of the UFA and 

from six production wells tapping both the UWBZ and LWBZ 

of the UFA. The results of the analyses indicate that groundwater 

chemistry changes with depth in the UFA and approaches the 

composition of modern seawater in the FPZ of the LFA. Previous 

analyses performed by Falls and others (2005) show the isotopic 

composition of groundwater in the FPZ of the LFA to be fossil 

seawater trapped in the formation. The groundwater chemistry 

of the chloride plume in the UFA near downtown Brunswick 

indicates it is a mixture of about 10 to 20 percent of FPZ fossil 

seawater and 80 to 90 percent freshwater from the UFA.

A trilinear plot was used to classify the water type of the 

UWBZ and the LWBZ of the UFA based on major cation and 

anion compositions (Piper, 1944). The major ion compositions 

were plotted as a percentage of total milliequivalents per liter 

for the major cations and anions for 13 groundwater samples 

(fig. 7). The major ion compositions of groundwater from 

several depth intervals within the FPZ of the LFA and modern 

seawater are included to show potential sources (Hem, 1989; 

Falls and others, 2005). The trilinear plot indicates groundwater 

from the UWBZ of the UFA is a mix of cations, with calcium 

(Ca2+) plus magnesium (Mg2+) ranging from 74 to 85 percent, 

and the remaining 15 to 26 percent from sodium (Na+). 

Potassium (K+) is considered a minor component, with concentrations ranging from 1.7 to 2.2 mg/L. The anion composition 

is a mix of sulfate (SO4

2–) plus chloride (Cl–

) ranging from 

54 to 71 percent, with the remaining 29 to 46 percent composed 

of bicarbonate (HCO3

–

). 

The most noticeable change, with the introduction of 

groundwater from the LWBZ of the UFA, is the increase of 

the anion chloride and the cation sodium, which is a major 

component of trapped fossil seawater from the FPZ of the 

LFA. The trilinear plot indicates mixed groundwater from 

wells open to the UWBZ and LWBZ of the UFA is composed 

of 33 to 61 percent sodium and 39 to 67 percent calcium plus 

magnesium. The anion composition is dominated by sulfate 

plus chloride ranging from 71 to 95 percent and 5 to 29 percent 

bicarbonate. The trilinear plot shows groundwater transitions, 

along with increased depth, from a calcium-magnesiumchloride-sulfate type to a chloride type. The groundwater 

chemistry of two samples collected from deep well 34H495 

and a sample from modern seawater were used as endmembers 

or potential sources. The composition of modern seawater is 

78 percent sodium, 22 percent calcium plus magnesium, and 

99 percent sulfate plus chloride, with chloride and sulfate 

concentrations of 19,000 and 2,700 mg/L, respectively (Hem, 

1989). Sprinkle (1989) attributed the major sources of dissolved 

constituents (common ions) in the FAS to the dissolution 

of calcite (CaCO3 ), dolomite (CaMg(CO3 )2 ), and gypsum 

(CaSO4

•2H2O) and the solubility of calcite (HCO3

–

). Chloride 

and sodium increase where freshwater and saltwater mix. 

8
Figure 6. Chloride concentration in the upper water-bearing zone (UWBZ) of the Upper Floridan (UFA) aquifer during 

October 2015 and chloride concentration at select production wells open to the UWBZ of the UFA and UWBZ and lower 

water-bearing zone (LWBZ) of the UFA in the Brunswick area.

9

 Bay Street

 contaminated

 area

Pinova

well field

Brunswick

Brunswick

Cellulose

well field

2015 chloride concentration in the 

 upper water-bearing zone (UWBZ)

 of the Upper Floridan aquifer (UFA),

 in milligrams per liter (mg/L) 

EXPLANATION

Chloride sampling point,

 in mg/L, UWBZ of UFA 

0 to 250

251 to 750

751 to 1,250

1,251 to 1,750

1,751 to 2,250

2,251 to 2,880

46

70/1,180

Chloride sampling point,

 in mg/L, UWBZ & LWBZ

 of UFA 

1,000

USGS well-cluster site,

 chloride sampling point,

 in mg/L, open interval in

 UWBZ of UFA/open interval

 in LWBZ of UFA

 

Image from National Agriculture Imagery Program 2010 east digital ortho quarter quad tiles, available via

https://www.fsa.usda.gov/programs-and-services/aerial-photography/imagery-programs/naip-imagery/index

347

1,000

818

176

75

46

18.5

96

31

533

16.9

70/1,180

19.1

Figure 6. Chloride concentration in the upper water-bearing zone (UWBZ) of the Upper Floridan (UFA) aquifer during

October 2015 and chloride concentration at select production wells open to the UWBZ of the UFA and UWBZ and 

lower water-bearing zone (LWBZ) of the UFA in the Brunswick area.

0 0.5 1 MILE

0 0.5 1 KILOMETER

Area of

enlarged

map 

GLYNN

COUNTY

Reynolds Street

 contaminated 

 area

N
References Cited

Cherry, G.S., Peck, M.F., Painter, J.A., and Stayton, W.L., 2011, Groundwater 

conditions in the Brunswick–Glynn County area, Georgia, 2009: 

U.S. Geological Survey Scientific Investigations Report 2011–5087, 

58 p. [Also available at http://pubs.usgs.gov/sir/2011/5087/.]

Falls, W.F., Harrelson, L.G., Conlon, K.J., and Petkewich, M.D., 2005, 

Hydrogeology, water quality, and water-supply potential of the Lower 

Floridan aquifer, coastal Georgia, 1999–2002: U.S. Geological Survey 

Scientific Investigations Report 2005–5124, 89 p., 1 pl. [Also available at 

http://pubs.usgs.gov/sir/2005/5124/.]

Georgia Environmental Protection Division, 1997, Secondary Maximum 

Contaminant Levels for drinking water—Environmental Rule 391-3-5-19, 

revised October 1997: Official Code of Georgia Annotated Statutes, 

Statute 12-5-170 (Georgia Safe Drinking Water Act), variously paged.

Hamrick, M.D., and Cherry, G.S., 2015, Monitoring saltwater contamination in

the Upper Floridan aquifer, Brunswick, Georgia, in McDowell, R.J., Pruitt, C.A.,

Bahn, R.A., eds., Proceedings of the 2015 Georgia Water Resources Conference, held April 28–29, 2015: The University of Georgia, Athens.

Hem, J.D., 1989, Study and interpretation of the chemical characteristics of 

natural water (3d ed.): U.S. Geological Survey Water-Supply Paper 2254, 

263 p. [Also available at https://pubs.er.usgs.gov/publication/wsp2254.]

Johnston, R.H., Krause, R.E., Mayer, F.W., Ryder, P.D., Tibals, C.H., and 

Hunn, J.D., 1980, Estimated potentiometric surface for the Tertiary 

limestone aquifer system, Southeastern United States, prior to development: 

U.S. Geological Survey Open-File Report 80–406, 1 map sheet. [Also 

available at https://pubs.er.usgs.gov/publication/ofr80406.]

Jones, L.E., 2001, Saltwater contamination in the Upper Floridan aquifer at 

Brunswick, Georgia, 1999–2000, in Hatcher, K.J., ed., Proceedings of the 

2001 Georgia Water Resources Conference, March 26–27, 2001: Athens, 

Ga., University of Georgia, Institute of Ecology, p. 644– 647. [Also available 

at https://smartech.gatech.edu/handle/1853/44296.]

Jones, L.E., Prowell, D.C., and Maslia, M.L., 2002, Hydrogeology and water 

quality (1978) of the Floridan aquifer system at U.S. Geological Survey Test 

Well 26, on Colonels Island, near Brunswick, Georgia: U.S. Geological 

Survey Water-Resources Investigations Report 02– 4020, 44 p. [Also available at http://pubs.usgs.gov/wri/2002/wri02-4020/.]

Krause, R.E., and Randolph, R.B., 1989, Hydrology of the Floridan aquifer system in southeast Georgia and adjacent parts of Florida and South Carolina: 

U.S. Geological Survey Professional Paper 1403–D, 65 p., 18 pl.

Maslia, M.L., and Prowell, D.C., 1990, Effects of faults on fluid flow and chloride

contamination in a carbonate aquifer system: Journal of Hydrology, v. 115,

nos. 1– 4, p. 1– 49. [Also available at http://pubs.er.usgs.gov/publication/70016336.]

Miller, J.A., 1986, Hydrogeologic framework of the Floridan aquifer system in 

Florida and in parts of Georgia, Alabama, and South Carolina: U.S. Geological

Survey Professional Paper 1403–B, 91 p., 33 pl. [Also available at

http://pubs.er.usgs.gov/publication/pp1403B.]

Piper, A.M., 1944, A graphic procedure in the geochemical interpretation of

water analyses: American Geophysical Union Transactions, v. 25, p. 914–923.

[Also available at http://dx.doi.org/10.1029/tr025i006p00914.]

Sprinkle, C.L., 1989, Geochemistry of the Floridan aquifer system in Florida 

and parts of Georgia, South Carolina, and Alabama: U.S. Geological Survey 

Professional Paper 1403-I, 105 p. [Also available at https://pubs.er.usgs.gov/

publication/pp1403I.]

U.S. Census Bureau, 2015, State & county quickfacts—Glynn County, Georgia: 

U.S Census Bureau Web site, accessed May 11, 2016, at http://www.census.gov/

quickfacts/table/PST045215/13127,00.

U.S. Environmental Protection Agency, 2000 (revised), Maximum Contaminant 

Levels (Part 143, National Secondary Drinking-Water Regulations):

U.S. Code of Federal Regulations, Title 40, parts 100–149. [Also available 

at https://www.epa.gov/sites/production/files/2015-11/documents/howeparegulates_cfr-2003-title40-vol20-part143.pdf.]

U.S. Environmental Protection Agency, 2003, Contaminant Candidate List 

(CCL) and Regulatory Determination, accessed May 11, 2016, at 

https://www.epa.gov/ccl/regulatory-determination-1-support-documents-sodium.

U.S. Geological Survey, 2016, National Water Information System—Web interface, accessed September 28, 2016, at http://dx.doi.org/10.5066/F7P55KJN.

Wait, R.L., 1965, Geology and occurrence of fresh and brackish water in Glynn 

County, Georgia: U.S. Geological Survey Water-Supply Paper 1613–E, 94 p. 

[Also available at http://pubs.er.usgs.gov/publication/wsp1613E.]

Wait, R.L., and Gregg, D.O., 1973, Hydrology and chloride contamination of 

the principal artesian aquifer in Glynn County: Georgia Department of 

Natural Resources Hydrologic Report, 93 p.

Williams, L.J., and Kuniansky, E.L., 2015, Revised hydrogeologic framework 

of the Floridan aquifer system in Florida and parts of Georgia, Alabama, and 

South Carolina (ver. 1.1, March 2016): U.S. Geological Survey Professional

Paper 1807, 140 p., 23 pls. [Also available at http://dx.doi.org/10.3133/pp1807.]

Suggested citation: Cherry, G.S., and Peck, M.F., 2017, Saltwater intrusion in the Floridan 

aquifer system near downtown Brunswick, Georgia, 1957–2015: U.S. Geological Survey 

Open-File Report 2017–2010, 10 p., https://doi.org/10.3133/ofr20171010.

10

transition

Calcium (Ca)

100 80 60 40 20 0 0 20 40 60 80 100

Chloride (Cl)

Sulfate (SO4

) Calcium plus magnesium

Carbonate plus bicarbonate

Magnesium (Mg)

Sulfate plus chloride

Sodium (Na) plus potasium (K)

PERCENT OF TOTAL MILLIEQUIVALENTS PER LITER

CATIONS ANIONS

Magnesium

 type

Calcium

 type

Sodium

 type or

potassium

 type

Sulfate

 type

Bicarbonate

 type

Chloride

 type

HCO3

 + CO3

 type

Na + K type

Ca + Mg type

Cl + SO4 type

Mixed

 zone

Mixed

 zone

EXPLANATION

Groundwater samples from

 Upper Floridan aquifer

Upper water-bearing zone

Upper and lower water-bearing zones

Groundwater samples from

 Fernandina permeable zone 

 of Lower Floridan aquifer

Brunswick, 34H495 (depth of sample: 

 2,084 feet)

1

1

2 Brunswick, 34H495 (depth of sample: 

 2,720 feet)

2

Modern seawater (Hem, 1989)

1

2

1

2

Na(K) HCO3 type

Ca(Mg) HCO3

 type

Na (K) Cl (SO4

) type

Ca(Mg) Cl(SO4) type

Figure 7. Major cation and anion compositions of water samples from the upper and lower water-bearing zones of the Upper Floridan

aquifer, the Fernandina permeable zone of the Lower Floridan aquifer, and modern seawater sample (Hem, 1989; Falls and others, 2005). 

CATION/ANION

CROSSPLOT

Figure 7. Major cation and anion 

compositions of water samples from 

the upper and lower water-bearing 

zones of the Upper Floridan aquifer, 

the Fernandina permeable zone 

of the Lower Floridan aquifer, and 

modern seawater sample (Hem, 

1989; Falls and others, 2005).

ISSN 2327-6932 (online)