Selected abstracts on engineering geology and related subjects

Interlayered sand, silt, and clay of middle Eocene to late Paleocene age in east-central Georgia form the Gordon aquifer system which ranges in thickness from about 20 to 180 ft. Estimated transmissivities range from 620 to 13,000 sq ft/day. During 1980, approximately 24 million gpd (gallons per day) was withdrawn from the Gordon aquifer system, of which about 70% was used for irrigation. Water levels in the aquifer throughout the study area generally showed little change during 1934-68; however, during 1969-81, local declines as great as 33 ft have occurred in areas of increased irrigation or large scale municipal and industrial pumping. The Gordon aquifer system is recharged by precipitation in the outcrop area and in interstream drainage divides in and near the outcrop area, and by leakage through adjacent confining units. Discharge from the aquifer occurs predominantly as flow into streams or as leakage into underlying and overlying units. Water from the Gordon aquifer system is generally a calcium bicarbonate type that ranges from soft to hard, and in most areas has constituent concentrations that are within the Georgia Environmental Protection Division recommended drinking water standards. (Author 's abstract)