USGS Georgia Water Science Center
This report is available online in pdf format (1 MB): USGS WRIR 98-4246 (
)
David C. Leeth
U.S. Geological Survey Water-Resources Investigations Report 98-4246, 28 pages (Published 1999)
Neogene and Quaternary sediments constitute the surficial aquifer beneath the study area; in descending order from youngest to oldest these include—the Quaternary undifferentiated surficial sand and Satilla Formation; the Pliocene(?) Cypresshead Formation; and the middle Miocene Coosawhatchie Formation. Beneath the surficial aquifer, the upper Brunswick aquifer consists of part of the lower Miocene Marks Head Formation.
The surficial aquifer is divided into three water-bearing zones on the basis of lithologic and geophysical properties of sediments, hydraulic-head differences between zones, and differences in ground-water chemistry. The shallowest zone—the water-table zone—consists of medium to fine sand and clayey sand and is present from land surface to a depth of about 77 feet. Below the water-table zone, the confined upper water-bearing zone consists of medium to very coarse sand and is present from a depth of about 110 to 132 feet. Beneath the upper water-bearing zone, the confined lower water-bearing zone consists of coarse sand and very fine gravel and is present from a depth of about 195 to 237 feet. Hydraulic separation is suggested by differences in water chemistry between the water-table zone and upper water-bearing zone. The sodium chloride type water in the water-table zone differs from the calcium bicarbonate type water in the upper waterbearing zone. Hydraulic separation also is indicated by hydraulic head differences of more than 6.5 feet between the water-table zone and the upper water-bearing zone.
Continuous and synoptic water-level measurements in the water-table zone, from October 1995 to April 1997, indicate the presence of a water-table high beneath and adjacent to the former landfill—the surface of which varies about 5 feet with time because of recharge and discharge. Water-level data from clustered wells also suggest that restriction of vertical ground-water flow begins to occur at an altitude of about 5 to 10 feet below sea level (35 to 40 feet below land surface) in the watertable zone because of the increasing clay content of the Cypresshead Formation.
Abstract
Introduction
Purpose and scope
Description of the study area
Methods of investigation
Previous investigations
Well-numbering system
Acknowledgments
Hydrogeology
Regional geologic setting
Geologic units
Undifferentiated surficial sands and Satilla Formation (Holocene and Pleistocene)
Cypresshead Formation (Pliocene (?))
Coosawhatchie and Marks Head Formations (Miocene)
Coosawhatchie Formation (middle Miocene)
Marks Head Formation (lower Miocene)
Hydrogeologic units
Surficial aquifer
Water-table zone
Upper water-bearing zone
Lower water-bearing zone
Upper Brunswick confining unit
Upper Brunswick aquifer
Ground-water levels and precipitation data
Seasonal fluctuations in water levels
Vertical distribution of hydraulic head
Water table
Estimated ground-water velocities
Ground-water quality
Summary
Selected references
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