Water Supply and Irrigation Papers of the United States Geological Survey . re reaching the deep wells, but in thenorthern part of the State wells equally as deep may be supplied withwater falling as rain only a few hundred yards distant. The conditions governing the water supply of shallow wells arepractically the same in all parts of the State, especially where thewells obtain water from surficial deposits and residual clays. The water from the shallow wells supplying small towns in northGeorgia was usually found to be in fair sanitary condition, but in aikr 114—05 11 156 UNDERGROUND WATERS,
Water Supply and Irrigation Papers of the United States Geological Survey . re reaching the deep wells, but in thenorthern part of the State wells equally as deep may be supplied withwater falling as rain only a few hundred yards distant. The conditions governing the water supply of shallow wells arepractically the same in all parts of the State, especially where thewells obtain water from surficial deposits and residual clays. The water from the shallow wells supplying small towns in northGeorgia was usually found to be in fair sanitary condition, but in aikr 114—05 11 156 UNDERGROUND WATERS, EASTERN UNITED STATES. [no. 114. few instances analyses made in the laboratory of the State geolog-ical survey gave unmistakable evidence of sewage local geologic conditions, which are peculiar to the northernportion of the State, seem to be the cause of this contamination. Theywill be described somewhat in detail. All of the rivers and large streams throughout the crystalline andthe Paleozoic areas traverse valleys of erosion which vary in width. Fig 21.—Areas of flowing wells in Georgia. Flowing wells may be obtained in shaded areas. • from a few hundred yards or less to a mile or more. These valleys,parts of which now lie several feet above the present flood plain of theriver, are often covered to the depth of many feet with alluvialdeposits left by the stream when it flowed at a higher level. Thedeposits usually occur in two layers. The lower layer, which liesdirectly upon the eroded edges of the underlying rocks, consists MCALLIE.] GEORGIA. 157 chiefly of coarse waterworn gravel and rounded stones, the latter oftenattaining a weight of many pounds. The thickness of this layer isvariable and depends somewhat upon the irregular eroded surfaceof the underlying rock, but generally it is from 10 feet to a fewinches. The upper layer, which is usually much thicker than thelower, is made up largely of silt or sandy clays. The two layers areconformable
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