L.J. Drew J.H. Schuenemeyer W.C. Burton David M. Sutphin 2000 Mean yields and the numbers of wells drilled are presented for 35 rock types containing 4,115 wells in the Blue Ridge of Loudoun County, Virginia. Analysis of variance of the well yields shows that Harper's Formation phyllite and Catoctin Formation metabasalt have yields significantly different from those of other rock types. Preliminary variography has identified an anisotropy that roughly parallels the general compressional trend of the Blue Ridge. application/pdf 10.3133/ofr00280 en U.S. Geological Survey, Characteristics of water-well yields in the Blue Ridge of Loudoun County, Virginia reports