Sowers, J.M., 1993, Soil stratigraphic investigations in the Hoover Dam area, in Anderson, L.W., and O'Connell, D.R., Seismotectonic study of the northern portion of the Lower Colorado River, Arizona, California, and Nevada; for Hoover Dam - Boulder Canyon Project, Davis and Parker Dams - Parker-Davis Project, Palo Verde Diversion Dam - Palo Verde Diversion Project, and Headgate Rock Dam - Bureau of Indian Affairs: U.S. Bureau of Reclamation Seismotectonic Report no. 93-4, Appendix C, 18 p.