Because of the features of karst terrain, the pollution potential in the Valley and Ridge is very high. Streams and surface runoff entering sinkholes or caves contribute to aquifer recharge, providing direct conduits for surface watercarrying contaminants and bypassing filtration through the soil, which can remove some contaminant. The Blue Ridge province is a relatively narrow zone of mountains with the highest elevations in the state. Only between 4 to 25 miles in width, the rocks underlying the area are granite, gneiss, and marble. Steep terrain, thin soil, and weathered rock covering bedrock result in rapid surface runoff and low groundwater recharge.
Bedrock is somewhat impervious, so water is held in joints, fractures, and faults.
In the eastern portion of the Blue Ridge, igneous and metamorphic rocks are most common, and in the west, sedimentary rocks predominate. Groundwater use is limited to domestic rather than public wells, because of limited industrial and residential development in the province. Along the lower slopes, which favor groundwater accumulation, springs are common and serve as private water supplies. Water quality is generally good because the rocks are relatively insoluble, but the iron content may be high in some locations. This is the largest province with some sedimentary rocks, but mainly dominated by hard, crystalline igneous and metamorphic formations or bedrock overlain by saprolite.