The purpose of this study is to use the water-well data to determine if the rock types and geologic structures present in the Blue Ridge have any bearing on the yields of the wells drilled into them, and to present preliminary variography to determine if additional spatial analysis is warranted. The drilling of water wells is a complex socio-economic process having numerous variables. Factors such as initial well yield, depth, elevation, and rock type tell only part of the story. Other pertinent factors include the drilling technology employed, the thickness of overburden or regolith reported as depth to bedrock, and the topographic location of the well site. Over the last decade or so, drilling technology has changed with the introduction of rotary drilling and hydrofracking.
Rotary drills are faster and can drill deeper than the cable tools that had been used previously.
He found that wells in the most productive rock types have average yields twice those of wells in the least productive types. Wells sited in draws and valleys in the most productive rock types average five times more yield than wells on hills and ridges in the least productive types. Along with this variability on yield imposed by topography, rock type may exert an influence on whether a well provides the amount of yield sought. The data set for the water wells of Loudoun County, Virginia, was provided by the Virginia state geologist. Unfortunately, for 12,827 of these wells, the reported yield is zero.