Six aquifer
systems underlie the ACE Basin. They encompass rocks of the Late
Cretaceous-age Cape Fear, Middendorf, and Black Creek formations, the
Tertiary-age Black Mingo Formation, Santee and Ocala limestones, Cooper
Formation, and a veneer of Quaternary-age deposits mainly associated with
barrier-island formation. Review the Geologic Time Scale
for geologic ages. Each aquifer system has unique and diagnostic
combinations of lithology, hydraulics, and water chemistry, and the aquifer
systems are separated by confining units 18 to 76 meters (60 to 250 feet)
thick. The six aquifer systems also share the characteristic condition of
localized saltwater intrusion. Ground water supplies almost all water demand.
The public water supply systems for Edisto Beach and Walterboro are the largest
users. Private domestic wells are used elsewhere and account for most of the
water pumped.
Information provided in this summary is derived principally from the
publications listed at the end of the section. Files of the South Carolina
Department of Natural Resources (SCDNR) Land, Water, and Conservation Division
provided supplemental information on well depths and yields, aquifer
hydraulics, and water chemistry. (See
hydrologic sections and selected wells
)
There are no reports devoted specifically to the hydrogeology of the ACE Basin, but a number of ground-water study areas include, overlap, or lie near the basin, and they provide insight into local conditions. Siple (1965 and 1967) summarized saltwater encroachment along the South Carolina coast and presented geologic sections, an Eocene-limestone structure map, and a chloride-distribution map, all of which included the ACE Basin. The ACE Framework Study (South Carolina Water Resources Commission 1972) was a planning study that summarized geologic, water-resource, and climate conditions in the basin and surrounding counties. Ground-water conditions in the South Carolina Low Country were investigated by Hayes (1979), and his geologic sections, structure maps, and water-level maps extend into the basin. Potential contamination sites and lithologic and background water-quality data for shallow aquifers of the lower coastal plain were described in a nine-volume report (Glowacz et al. 1980). A Trident-area ground-water study included a geologic section; and structure, water-level, and water-quality data for the Santee Limestone at Edisto Island and Edisto Beach (Park 1985) . A hydrologic framework of the South Carolina coastal plain was presented by Aucott et al. (1987), and their extensive atlas defines six principal aquifer systems with hydrologic sections and depth-to-aquifer maps that encompass the ACE Basin. Potentiometric-data for the basin are included in water-level atlases for the Floridian aquifer (Crouch et al. 1987; DNR file data), the Black Creek aquifer (Hockensmith 1998), and the Middendorf aquifer (Hockensmith and Waters 1998). Pre-development water level maps for the South Carolina coastal plain were published by Aucott and Speiran (1984) and Aucott (1988). Aucott and Speiran (1985) and Stringfield and Campbell (1993) published isodecline maps and potentiometric maps for 1982 and 1989, respectively.
Useful reports on areas near the ACE Basin include Hassen (1985), Speiran (1985), Dale (1995), and Hockensmith (1997). Hassen presented detailed water-level and water-quality data for the Floridian aquifer in northeastern Beaufort County, and he mapped ground-water movement from Ladies and St. Helena islands into the St. Helena Sound estuary, Speiran (1985), Dale (1995), and Hockensmith (1997) made water-table aquifer studies and constructed ground-water flow models for parts of Wadmalaw and Hilton Head Islands. The reports included information on geology, ground-water behavior, and chemical quality that are representative of the shallow aquifer in much of the ACE Basin.
The SCDNR Hydrology Section, using recent hydro-stratigraphic nomenclature proposed by Aadland et al. (1995) and core-drilling data, is revising its definitions for coastal plain aquifers. Until the reclassification process is completed, the hydrogeologic framework defined by Aucott et al. (1987) is being used for regional projects such as potentiometric mapping (Hockensmith 1997; Hockensmith and Waters 1998), and it is used for this report.
Six aquifer
systems and three principal confining beds have been defined in
the lower coastal plain (Aucott et al. 1987). The
principal aquifer systems
, in ascending order, are as follows:
- Cape Fear Aquifer System
- Middendorf Aquifer System
- Black Creek Aquifer System
- Tertiary Sand Aquifer System
- Floridian Aquifer System
- Shallow Aquifer System
Cape Fear Aquifer
System
The Cape Fear aquifer
system was described as typically consisting of sand,
silt, and gravel separated by thick silt and clay layers (Aucott et al.
1987). The appendix of McLean (1960) includes a lithologic description of
cuttings from a -1,052-m (-3,450-ft) well at Parris Island, 19 kilometers (12
miles) south of the basin. The rock correlating to the Cape Fear aquifer
system, below about -820 m (-2,700 ft) mean sea level (msl), is described as
marine and non-marine, Woodbinian, light gray, fine-to-coarse, micaceous or
argillaceous
quartz sand and sandstone; and multicolored, gray, purple, tan,
yellow, greenish, and red, micaceous silty to sandy clay and shale. Cuttings
and sidewall-core descriptions from the interval at a Hilton Head Island test
well are similar. The surface of the Cape
Fear aquifer
dips southward from -610 to -850 m (-2,000 to -2,800ft) along
the basin axis, and its base rests on pre-Cretaceous
basement rock at depths of
-700 to -1,040 m (-2,300 to -3,400 ft).
Pilot holes at Fripp, Parris, and Hilton Head islands penetrated the Cape Fear, and about 30 m (100 ft) of screen is set in the aquifer at the Hilton Head Island test well. Poor sorting, the prevalence of silt and clay, and interbeded clay within the sand units limit the transmissivity of screened intervals to less than 186 m2/day (2,000 ft2/day) in spite of the section's thickness. Transmissivity estimates based on aquifer tests range from 288 to 400 m2/day (3,100 to 4,300 ft2/day) for 58 m (190 ft) of screen open to the Middendorf and Cape Fear systems (Anonymous 1993). Sidewall cores in the thin sand and gravel layers had hydraulic conductivities of 3 to 10 m/day (10 to 20 ft/day) in the upper half of the system and 1 to 3 m/day (3 to 10 ft/day) in the lower half (DNR file data; Anonymous 1993). Cape Fear wells can be expected to produce more than 1,900 L/min (500 gpm), owing to the depth available for drawdown.
Chemical analyses of water samples from -844 m (2,786 ft) and -862 m (2,831
ft) were reported at two Parris Island wells (Siple 1960). The water chemistry
is typical of Cretaceous aquifers along the South Carolina coast: soft,
moderately basic, sodium bicarbonate type water with total dissolved-solids
concentrations of about 1,000 mg/L (milligrams per liter) and fluoride
concentrations of 4.0 to 5.0 mg/L. Dissolved iron concentrations are less than
100 mg/L and chloride concentrations are about 60 mg/L. U. S. Geological Survey
(USGS ) analyses of samples squeezed from sidewall cores at Hilton Head
reported chloride concentrations of about 1,500 mg/L near the top of the Cape
Fear (-965 m or -3,164 ft) and 260 mg/L at the base (-1,108 m or -3,634 ft).
The ground-water temperature is about 110°F near the base of the
system at Hilton Head. Review the
analyses of Cape Fear aquifer water samples
.
Middendorf Aquifer
System
The Middendorf aquifer
system, at Parris Island, consists of gray, commonly
calcareous, micaceous, glauconitic clay and siltstone and beds of poorly
sorted, fine- to moderately-coarse grained, micaceous, argillaceous
sand and
soft sandstone (McLean 1960). The section appears predominantly marginal
marine with continental facies
toward its base. The corresponding hydrologic
section at Kiawah Island exhibits similar characteristics, and a DNR-file
faunal summary (author unknown) describes the interval as marginal marine to
inner neritic
at the top and continental(?) near the bottom; fauna
in the
interval are Santonian. The top of the Middendorf system dips southward from
about -460 m (-1,500 ft) msl near Walterboro to -700 m (-2,300 ft) msl at Fripp
Island (See Middendorf Aquifer
). Its base is separated from the top of the Cape Fear system
by a 18- to 21-m (60- to 70-ft) section of clay and silt.
The Middendorf system is tapped by wells at Walterboro and at Kiawah, Seabrook, Fripp, Parris, and Hilton Head islands. A transmissivity of 325 m²/day (3,500 ft²/day) and a specific capacity of 23 L/min/m (1.7 gpm/ft) was calculated at Kiawah Island well 20FF-v1 (Aucott and Newcome, 1986). They reported specific capacities of 220 to 290 L/min/m (16 and 22 gpm/ft) for two 488 to 537-m (1,600 to 1,760-ft) wells having 18 m (60 ft) of screen at Walterboro. Transmissivity at the Walterboro site probably exceeds 558 m²/day (6,000 ft²/day). Tests of sidewall cores taken between -854 and -915 m (-2,800 and -3,000 ft) at Hilton Head measured hydraulic conductivities of 1.4 to 6.4 m/day (4.7 to 6.4 ft/day) (DNR files; Anonymous 1993). The reported well yield at Kiawah Island was 1,600 L/min (430 gpm); 4,500 to 5,300 L/min (1,200 to 1,400 gpm) is reported for Middendorf aquifer wells at Walterboro (Newcome 1989).
Analyses of composite samples from wells at Walterboro and Fripp and Parris islands indicate that the water is soft, basic and high in fluoride, sodium, and bicarbonate. Salinity ranges from fresh in the northwestern part of the basin to brackish along the coast. Total dissolved solids increase coastward from about 200 mg/L to more than 1,000 mg/L. Fluoride concentration increases coastward from less than 1.0 to more than 4.5 mg/L.
Total dissolved solids and chloride concentrations typically increase with depth in coastal, brackish-water aquifers. Discrete-interval samples from Middendorf wells near the eastern ACE Basin do not display this tendency everywhere, however--probably owing to relatively effective bed separation, to differences in hydraulic conductivity, and to variations in the continuity of individual sand beds. Total dissolved solids concentrations of 1,660 to 2,577 mg/L and chloride concentrations of 60 to 464 mg/L were reported at Kiawah Island between -619 and -677 m (-2,030 and -2,220 ft) (Park 1985). The highest concentrations occur at the top of the aquifer and the lowest occur in the middle. Discrete samples at Hilton Head Island show chloride increasing from about 150 to 1,500 mg/L between the middle Middendorf and the upper Cape Fear and decreasing with depth to 260 mg/L about 61 m (200 ft) from the base of the Cape Fear. Ground-water temperature ranges between 80 and 104° F.
Black Creek Aquifer
System
The Black Creek aquifer
system encompasses mainly marginal-marine sediment
generally described from cuttings as gray to blue-gray, fossiliferous,
glauconitic, sandy clay, shale, and silt, and gray fine-grained sand. Electric
logs, a generic term for any electrical measurement made within the borehole of
an uncased well, are used to measure the characteristics of the sediment and
pore water in wells. It typically refers to a log suite consisting of a
spontaneous-potential log, which measures millivoltages generated by the
electrochemical interaction of drilling mud, rock, and pore water, and (1)
electrical resistance measurements between an electrode in the well bore and an
electrode at ground surface; or (2) electrical resistivity measurements, the
electrical resistance of a cubic meter of rock as ohm-meters²/meter (or
ohm-meters), between closely spaced electrode pairs (typically 40 - 160 cm or
16 and 64 inches) within the well bore. In the Black Creek aquifer system,
these logs indicate high-resistance zones of sand and limestone throughout the
lower two-thirds of the system near Walterboro, but thickness diminishes
coastward and is negligible on the basin's southern side. At Kiawah Island, the
Black Creek aquifer system sediments are of an early Maestrichtian-Campanian,
middle neritic
environment (V. V. Vanstrum, written communication). Elevations
on the top of the system are approximately 300 m (1,000 ft) below MSL near
northern edge of the ACE Characterization project area and dip generally
southeastward (See Black Creek Aquifer
).
Few wells are known to be completed in the aquifer system near the ACE Basin. They probably would produce sodium bicarbonate type water with high fluoride concentrations throughout most of the basin. High chloride concentrations are likely to extend farther inland than in the underlying systems, owing to low hydraulic conductivity and consequently poor circulation. Well yields will be impracticably small except in the western extent of the basin because of poor hydraulic characteristics and system depth.
Tertiary Sand Aquifer
System
The Tertiary
sand aquifer
system consists of the permeable part of the Early
Eocene-age and Paleocene-age Black Mingo Formation. The upper Black Mingo
Formation and lower Santee Limestone are hydraulically connected owing to
similar water levels and water chemistry (Park 1985). The upper Black Mingo
Formation is considered to be part of the Floridian aquifer system for lack of
an intervening confining bed (Aucott et al. 1987). The Black Mingo is a
heterogenous, fossiliferous sequence of white to pale-gray limestone, green to
gray argillaceous
sand, carbonate- and silica-cemented sandstone, and dark-gray
to black clay (Park 1985). A sequence of gray, fine-grained sand, sandstone,
and sandy limestone and dark-gray to black clay in the upper 15 m (50 ft) of
the formation constitutes the permeable section in the western two-thirds of
the basin. It thickens and grades into an impure limestone in southeastern
Charleston County. The underlying, low-permeability section of the Black Mingo
Formation and the Peedee Formation are delineated as a confining unit.
Wells open only to the Tertiary sand aquifer system are rare, for the system is tapped by open-hole wells that also obtain water from the overlying Floridian aquifer system. Tertiary sand/Floridian wells are ubiquitous in Charleston, Berkeley, and Dorchester counties (Park 1985), and they are common in the northeastern half of the ACE Basin. The Tertiary sand aquifer yields water to wells more consistently than the Floridian, and drillers use it routinely to assure the success of their wells. Caliper logs show relatively smooth, bit-diameter boreholes through the Floridian section of the well and wider diameter washouts in the sandy section of the Tertiary sand. Sand pumping is seldom a problem in open-hole Floridian/Tertiary sand wells, even where pumping rates exceed 1,000 L/min (300 gpm). At least one well in the basin has a recorded yield of 2,500 L/min (660 gpm); several screened wells near the western reach of the basin have reported yields of 280 to 760 L/min (75 to 200 gpm); and yields adequate for domestic supply are found everywhere in the basin. Specific capacities typically are 55 to 81 L/min/m (4 to 6 gpm per foot of drawdown).
Water in the Tertiary sand aquifer is of the sodium bicarbonate type and grades into the sodium chloride type coastward. The highest known chloride concentration, about 6,000 mg/L, was measured in a well just north of Edisto Beach. Hardness and high iron concentrations rarely cause problems, but fluoride concentrations increase coastward and range from 2.0 to 4.0 mg/L at and southeast of Edisto Island. Dissolved-silica concentrations exceeding 25 mg/L occur in the Black Mingo Formation section of the Tertiary sand aquifer, and the silica is attributed to the presence of silica-cemented sandstone, cristobalite, and clinoptilite (Park 1985). Water temperatures are about 68° F throughout the ACE Basin.
Floridian Aquifer
System
In the ACE Basin, the Floridian aquifer
system is formed by the Santee
Limestone, the Ocala Limestone, and the Cooper Formation. The Santee Limestone
underlies the entire basin and typically is a creamy-white to gray,
fossiliferous, Eocene
limestone. Two members northeast of the basin have been
identified; the lower, biosparitic, Middle Claiborne-age Moultrie and the
upper, biomicritic, late Claiborne Cross (Ward et al. 1979). The Ocala
Limestone consists of a thick, silty to clayey, glauconitic limestone overlain
by a clean, permeable, bioclastic limestone of Jackson (Late Eocene) age. The
upper limestone thins northeastward and is present only along the southwestern
boundary of the ACE Basin. The Cooper Formation was divided into the late
Eocene Harleyville, late Eocene Parkers Ferry, and Oligocene
Ashley Members by
Ward et al. (1979). At their type localities, the members respectively are
described as: compact, phosphatic, calcareous clay and clayey calcarenite;
glauconitic, clayey, fine-grained, fossiliferous limestone; and glauconitic,
calcareous, muddy, fine sand. Elevations on top of the
Floridian aquifer system
(Hayes 1979) begin at about 20 feet above mean sea-level at
the northern end of the ACE Basin and dip generally coastward.
The Floridian aquifer system is composed principally of fine-grained and
impure limestone in which permeability is poorly developed, and wells open to
the Floridian commonly are also completed in the top of the Tertiary
sand
system. Locally, thin water-yielding zones may be associated with geologic
contacts, but such zones are less continuous than the contacts. A relatively
clean, permeable section occurs at about 150 m (500 ft) msl beneath eastern
Edisto Island and produces as much as 1,900 L/min (500 gpm) to wells. Poor
yields from wells of similar depth can occur locally, although yields of at
least 380 L/min (100 gpm) probably can be obtained in most of the basin. Yields
of 380 to 760 L/min (100 to 200 gpm) also can be obtained from wells less than
30 m (100 ft) deep along the southeastern boundary of the basin: they tap the
upper permeable zone of the Ocala Limestone, which thickens southward to more
than 30 m (100 ft) and becomes the most productive aquifer in South Carolina.
Specific capacities through most of the basin probably range from 15 to 80 L/min/m (1 to 6 gpm/ft), but are 135 to 270 L/min/m (10 to 20 gpm/ft) at Edisto Island and in the northwestern reaches of the basin. Aucott and Newcome (1986) reported 230 L/min/m (17 gpm/ft) for a Floridian (and Tertiary sand aquifer) well at Walterboro. Hayes (1979) reported 14 to 54 L/min/m (1 to 4 gpm/ft) and as much as 2,000 L/min (530 gpm) from eight Floridian wells in Colleton County. The hydraulic conductivity of the Ocala upper permeable zone ranges from 15 to 45 m/day (50 to 150 ft/day) on northern Port Royal Island; transmissivity is less than 46 m²/day (500 ft²/day) (Hughes et al. 1989). Similar values of hydraulic conductivities probably occur at geologic contacts within the Santee Limestone section of the Floridian aquifer, but the thickness of the permeable sections is small.
The potentiometric surface of the Floridian aquifer dips southeastward
across the basin. The hydraulic gradient is 0.5 m/km (2.5 ft/mile) across the
northwestern reach of the basin and abruptly diminishes to 0.1 m/km (0.4
ft/mile) across the southeastern three quarters. Comparison of November 1982
(Park 1985) and July 1986 (Crouch et al. 1987)
potentiometric surface maps
show 0.3- to 1.2-m (1- to 4-ft) declines across the eastern
half of the basin--much of the difference is the result of seasonal differences
in ground-water use, but part is the result of increased withdrawals. Water
levels were measured in November 1990, and these suggest that levels in
southern Charleston County are 0.7 to 1.4 m (2.3 to 4.6 ft) lower than
measurements made during November 1982. The levels at Edisto Island declined to
-1.2 to -2.4 m (-4 to -8 ft) below MSL by November 1990 (Dale, pers. comm.).
Floridian aquifer water typically is a hard, calcium bicarbonate type with
low iron concentrations. On the southeastern side of the basin, high iron
concentrations are prevalent in the upper permeable zone. Water at the base of
the system in southern Charleston County is similar to that from the Tertiary
sand aquifer. Chloride concentrations
increase coastward and exceed 500 mg/L at Edisto Beach.
Chloride concentrations there can be expected to increase with time owing to
pumping-induced upconing and saltwater intrusion. Additional
selected chemical analyses
are available for the Floridian aquifer.
Shallow Aquifer
System
The shallow aquifer
system encompasses a thin, laterally and vertically
variable system of Quaternary-age sediment. It includes marine, estuarine, and
fluvial
facies; averages about 15 m (50 ft) in thickness near the coast; and
thins to less than 6 m (20 ft) in the upper reaches. The areal geology as
mapped by McCartan et al. (1990) indicates the extent of
depositional lithofacies
and the approximate time of deposition. They broadly
categorized lithofacies as swamp, fluvial, backbarrier, and beach in accordance
with the environment of deposition.
Holocene fluvial deposits predominate along the major streams of the ACE Basin and were described as "fine gravel at the base of a sequence, through coarse to fine, locally muddy sand...to overbank mud at the top" (McCartan et al. 1990). Aquifers, mainly channel-lag and point-bar deposits, can have relatively high hydraulic conductivities but are laterally discontinuous. Extensive backbarrier and beach facies, whose ages increase landward, occur within stream interfluves. Backbarrier deposits are muddy sand with clay, shell, and sand layers. Little or no yield will be typical of wells completed in backbarrier deposits, although good yields are likely where wells are screened in tidal-inlet and -channel deposits. Beach deposits include barrier island depositional environments ranging from dune to shelf (McCartan et al. 1990) . They encompass the most hydraulically consistent and laterally extensive aquifers owing to the well- to moderately well-sorted sand of dune and beach environments and to their typical history of progradation, (See related sections: Geology, Geomorphology.)
Data on the hydraulic characteristics of the system are scant within the basin, but data from nearby, geologically similar areas have been published in several reports. Smith (1987) reported hydraulic conductivity values for a site on northern Port Royal Island, apparently located over backbarrier deposits. Horizontal and vertical conductivities (K and Kv) of 0.1 to 0.3 m/day (0.3 to 0.9 ft/day) and 6 x 10-5 to 2 x 10-1 m/day (2 x 10-4to 7 x 10-1 ft/day), respectively, were measured through an alternating sequence of fine sand and clay. Shallow-aquifer test results are published for areas underlain by beach facies at Wadmalaw, Hilton Head, and Edisto islands. At Wadmalaw Island where 4-6 m (14-20 ft) of beach sand overlies backbarrier deposits, 18 tests indicated hydraulic conductivities of 1.2 to 6.7 m/day (4 to 22 ft/day) and averaging 2.7 m/day (9 ft/day) (Hockensmith 1997). M. W. Dale and A. D. Park (unpublished data) obtained nearly identical results at two sites on Hilton Head Island: 16 tests indicated hydraulic conductivities of 1.8 to 7.3 m/day (6 to 24 ft/day) and averaging 3.0 m/day (10 ft/day). The K/Kv was about 20. The U. S. Navy Department (1993) and Landmeyer et al. (1996) reported hydraulic conductivities of 2.7 to 5.2 m/day (9 to 17 ft/day) for sandy Holocene deposits on Port Royal Island. Saturated thicknesses of 9 m (30 ft) or more occur in many such areas, and transmissivities of 25 to 45 m2/day (250 to 500 ft2/day) should be common. An average hydraulic conductivity of 5.8 m/day (19 ft/day) and a transmissivity of 56 m2/day (600 ft2/day) was reported for a pumping-test at Edisto Island (Park 1985).
The maximum yield of individual wells is probably about 200 L/min (50 gpm). Public-supply wells 15-17 m (50-55 ft) deep on eastern Edisto Island produced 100 to 180 L/min (25 to 48 gpm): a four-well header system was used at one time and probably pumped 280 to 380 L/min (75 to 100 gpm). Lower yields will be more typical but should be adequate for domestic supply. Domestic irrigation wells having 3 to 6 m (10 to 20 ft) of screen at Hilton Head Island produce 40 to 150 (10 to 40 gpm); 5- to 6-m (15- to 20-ft) observation wells with 1.5 to 3 m (5 to 10 ft) of screen produced 7 to 20 L/min (2 to 5 gpm) there. However, wells screened in backbarrier deposits are likely to produce little water. Yields from fluvial facies will be variable but generally low.
Seasonal fluctuations usually are less than 1.8 m (6 ft), and the range of
fluctuation decreases with increasing proximity to streams. The
hydrograph
shows water-table depths at Edisto Island from October 1989
through September 1991 and reflects the seasonal range typically expected in
the shallow system.
Water chemistry data
is available for the shallow-aquifer, mainly from Glowacz et
al. (1980) and Park (1985). Shallow-aquifer water is soft with low total
dissolved solids and high iron concentrations in most of the basin. The iron is
ubiquitous owing to iron-bearing heavy minerals. Hard, basic water is common in
the lower third to half of the basin where fossil-shell material is present:
soft, slightly-acidic water occurs farther inland where deposits are older and
leaching has removed shell. In beach facies, total dissolved solids, pH, and
hardness increase with depth where water moves from dune sand into
fossiliferous sections of beach and backbarrier facies.
The ACE Basin contains six aquifer systems, and three are used; the Tertiary sand, the Floridian, and the shallow. The Tertiary sand and Floridian aquifer systems are the principal sources of domestic, commercial, and public water supplies, and well yields as great as 1,900 L/min (500 gpm) are reported for most of the basin. The shallow aquifer system is the least consistent with respect to well yield. However, wells drilled in areas underlain by beach facies provide enough water for domestic supply and produce up to 190 L/min (50 gpm) locally. The upper part of the Cape Fear aquifer system and the Middendorf aquifer system should yield more than 3,800 (1,000 gpm) to individual wells screened in both systems. Wells screened in the Middendorf aquifer system should produce 1,900 to 3,800 (500 to 1,000 gpm).
Water quality generally is good in the northwestern half of the basin, where low dissolved-solids concentrations are prevalent. Treatment is likely to be required for hardness in water from the Tertiary sand and Floridian aquifer systems and for dissolved iron in water from the Floridian and shallow systems. Fluoride, sodium, bicarbonate, and chloride increase coastward in all but the shallow system. The shallow aquifer produces water with low dissolved solids concentrations except where it contacts saltwater marshes and streams. Saltwater intrusion occurs in the Floridian aquifer system at Edisto Beach owing to water-level declines. The saltwater wedge is diffuse, hydraulic conductivities and gradients are small, and intrusion consequently is slow.
Author
D. Park, SCDNR Land, Water, and Conservation Division
Aadland, R. K., J. A. Gellici, and P. A. Thayer. 1995. Hydrogeologic framework of west-central South Carolina. South Carolina Department of Natural Resources Water Resources Report 5.
Anonymous. 1993. Well completion report on Cretaceous aquifer test well (BFT-2055), Hilton Head, South Carolina. Report 89-1601. Atlanta Testing and Engineering, Columbia, SC.
Aucott, W. R. 1985. Potentiometric surfaces of the coastal plain aquifers of South Carolina prior to development. U.S. Geological Survey, Water Resources Investigations Report 84-4208. U.S. Geological Survey, Columbia, SC.
Aucott, W. R. 1988. The predevelopment groundwater flow system and hydrologic characteristics of the coastal plain aquifers of South Carolina. U. S. Department of Interior, Geological Survey, Columbia, SC.Aucott, W. R., M. E. Davis, and G. K. Speiran. 1987. Geohydrologic framework of the coastal plain aquifers of South Carolina. U.S. Geological Survey, Water Resources Investigations Report 85-4271. U.S. Geological Survey, Columbia, SC.
Aucott, W. R. and R. Newcome, Jr. 1986. Selected aquifer-test information for the coastal plain aquifers of South Carolina. U.S. Geological Survey, Water Resources Investigations Report 86-4159. U.S. Geological Survey, Columbia, SC.
Aucott, W. R. and G. K. Speiran. 1984. Water-level measurements for the coastal plain aquifers of South Carolina prior to development. U.S. Geological Survey Open-File Report 84-803. U.S. Geological Survey, Columbia, SC.
Aucott, W. R. and G. K. Speiran. 1985. Potentiometric surfaces of November 1982 and declines in the potentiometric surfaces between the period prior to development and November 1982 for the coastal plain aquifers of South Carolina. U.S. Geological Survey Water Resources Investigations Report 84-4215. U.S. Geological Survey, Columbia, SC.
Crouch, M. S., W. B. Hughes, W. R. Logan, and J. K. Meadow. 1987. Potentiometric surface of the Floridian aquifer in South Carolina, July 1986. South Carolina Water Resources Commission Report 157.
Dale, M. W. 1995. Evaluation of the shallow aquifer, Hilton Head Island, South Carolina. South Carolina Department of Natural Resources, Water Resources Division Open-File Report 2. Columbia, SC.
Dale, M. W. [not dated]. pers. comm. South Carolina Department of Natural Resources, Land, Water, and Conservation Division, Columbia, SC.
Glowacz, M. E., C. M. Livingston, C. L. Gorman, and C. R. Clymer. 1980. Economic and environment impact of land disposal of wastes in the shallow aquifers of the lower coastal plain of South Carolina. South Carolina Department of Health and Environmental Control, Ground Water Protection Division, Columbia, SC.
Hassen, J. A. 1985. Ground-water conditions in the Ladies and St. Helena Islands area, South Carolina. South Carolina Water Resources Commission Report 147. Columbia, SC.
Hayes, L. R. 1979. The ground-water resources of Beaufort, Colleton, Hampton, and Jasper Counties, South Carolina. South Carolina Water Resources Commission Report 9. Columbia, SC.
Hockensmith, B. L. 1997. Effects of pond irrigation on the shallow aquifer of Wadmalaw Island, South Carolina. South Carolina Department of Natural Resources, Water Resources Report 17. South Carolina Department of Natural Resources, Water Resources Division, Columbia, SC.
Hockensmith, B. L. 1997. Potentiometric surface of the Black Creek aquifer in South Carolina - November 1995. South Carolina Department of Natural Resources, Water Resources Report 16. South Carolina Department of Natural Resources, Water Resources Division, Columbia, SC.
Hockensmith, B. L. and K. E. Waters. 1998. Potentiometric surface of the Middendorf aquifer in South Carolina - November 1996. South Carolina Department of Natural Resources, Water Resources Report 19. South Carolina Department of Natural Resources, Water Resources Division, Columbia, SC.
Hughes, W. B., M. S. Crouch, and A. D. Park. 1989. Hydrogeology and saltwater contamination in the Floridian aquifer in Beaufort and Jasper Counties, South Carolina. South Carolina Water Resources Commission Report 158. Columbia, SC.
Landmeyer, J. E., F. H. Chapelle, and P. M. Bradley. 1996. Assessment of intrinsic bio-remediation of gasoline contamination in the shallow aquifer, Laurel Bay Exchange, Marine Corps Air Station, Beaufort, South Carolina. Water Resources Investigations Report 96-4026. U.S. Geological Survey, Reston, VA.
McCartan, L., R. E. Weems, and E. M. Lemmon. 1990. Studies related to the Charleston, South Carolina, earthquake of 1889, Neogene and Quaternary lithostratigraphy and biostratigraphy. U.S. Geological Survey Professional Paper 1367 A.
McLean, J. D. 1960. Stratigraphy of the Parris Island area, South Carolina. McLean Paleontological Laboratory Report 4. McLean Paleontological Laboratory, Alexandria, VA.
Newcome, R., Jr. 1989. Ground-water resources of South Carolina's coastal plain - 1998 - an overview. South Carolina Water Resources Commission Report 167. Columbia, SC
Park, A. D. 1985. The ground-water resources of Charleston, Berkeley, and Dorchester Counties, South Carolina. South Carolina Water Resources Commission Report 139.
Siple, G. E. 1960. Geology and ground-water conditions in the Beaufort area, South Carolina. Report to the Department of the Navy. U. S. Geological Survey, Columbia, SC.
Siple, G. E. 1965. Salt-water encroachment of Tertiary limestones along coastal South Carolina: hydrology of fractured rocks. Proceedings of the symposium at Dubrovnik, Yugoslavia. International Association of Scientific Hydrology
Siple, G. E. 1967. Salt-water encroachment in coastal South Carolina. Geologic Notes No. 2(2). South Carolina State Development Board, Division of Geology, Columbia, SC.
Smith, B. S. 1987. Vertical hydraulic conductivity, porosity, and vertical gradient of sediments above the upper Floridian aquifer at a site at the Marine Corps Air Station, Beaufort, South Carolina. Administrative Report for the Department of the Navy, Southern Division Naval Facilities Engineering Command. U. S. Geological Survey, Columbia, SC.
South Carolina Water Resources Commission. 1972. ACE framework study - Ashley-Combahee-Edisto River Basin. South Carolina Water Resources Commission, Columbia, SC.
Speiran, G. K. 1985. Effects of high-rate wastewater spray disposal on the water table aquifer, Hilton Head Island, South Carolina. Water Resources Investigations Report 84-4291. U.S. Geological Survey, Reston, VA.
Stringfield, W. J. and B. G. Campbell. 1993. Potentiometric surfaces of November 1989 and declines in the potentiometric surfaces between November 1982 and November 1989 for the Black Creek and Middendorf aquifers in South Carolina. Water-Resources Investigations Report 92-4000l. U.S. Geological Survey, Reston, VA.
U.S. Department of the Navy, Southern Division Naval Facilities Engineering Command. 1993. Contamination assessment report, Laurel Bay Exchange Service Station, Marine Corps Air Station, Beaufort, South Carolina, Ground-Water Protection Site #A-07-AA-13575. (cited in Landmeyer et al. 1996).
Vanstrum, V. V. [not dated]. pers. comm. South Carolina Department of Natural Resources, Hydrology Section file.
Ward, L. W., B. W. Blackwelder, G. S. Gohn, and R. Z. Poore. 1979. Stratigraphic revision of Eocene, Oligocene, and Lower Miocene formations of South Carolina: Geologic Notes. South Carolina State Development Board, South Carolina Geological Survey 23(1):2-32.