The Eocene Ballena Gravels supplied the Poway Group alluvial fan whose apex lies southwest of San Vicente Reservoir. The sediments extend east to west from San Vicente to Del Mar, and south to north from Lemon Grove to Rancho Santa Fe. No estimates of the volume of sediments in the Poway fan are available. Through extensive fieldwork and utilization of geologic maps, I determined 91 stratigraphic thicknesses to describe the fan. By establishing thicknesses on an x,y coordinate frame, I have analyzed these data using Dr. David Huntley'sContour program. This program draws contour lines at prescribed intervals and calculates a volume from the data points. The existing outcrop of Poway fan has a volume of about 16.5 km3 •
