Along the southeast flank of the Flattop Mountain anticline in Washington, Smyth, and Tazewell counties, Virginia from Tumbling Creek, Washington County, northeast to and beyond Tannersville, Tazewell County, the Silurian Tonoloway limestone is intercalated within a succession of otherwise impervious strata. Groundwater circulation is localized within the Tonoloway in which large groundwater conduits have been created by dissolution. The area studied contains sedimentary rocks that range in age from Upper Silurian to Upper Devonian, inclusive. This report describes the lithology and terrain distribution of these formations and discusses their effect on the groundwater circulation in the area. The Tonoloway limestone serves a special function in controlling the infiltration and direction of movement of subsurface waters. The locally reversed hydraulic gradients of groundwater infiltrating the Tonoloway in various portions of the area along Poor Valley between Tumbling Creek and Tannersville are largely determined by streams, tributary to the North Fork of the Holston River, which have eaten headward through Brushy Mountain to become extended subsequent streams draining segments of Poor Valley. Subsurface conditions are favorable for recovering large quantities of groundwater for industrial use from the cavernous Tonoloway during the warm months of the year with subsequent recharge during the colder months when cool groundwater is not needed by nearby industries. Recharge could be substantially increased by installation of infiltration wells which would convey a larger quantity of surface water leaving such remote valleys as Redrock Cove directly into the cavernous Tonoloway. The advantage of infiltration conduits would be to effect some semblance of continuous recharge and thus increase the quantity of water that could be withdrawn during the summer periods when demand for industrial water is particularly great.