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Tracy Airport. At this time, however, Teichert does not anticipate the use of evening illumination. Dozers and scrapers, like cars, can activate headlights for night work. Mining Depth The maximum anticipated depth is ±80 feet. Clay lenses, however, will determine the exact depth. It is probable that certain areas will only be mined to a lesser depth. Given the layered gravel tiers prominent in the Corral Hollow alluvial fan, one must allow for some variability. When the site is reclaimed for agricultural, it will be graded to roughly the same depth to permit convenient farming. Groundwater In response to comments from County Planning Staff and Michael Sandecki of the Division of Mines and Geology, additional data were obtained on groundwater depth. Four test borings were drilled by Kleinfelder, Inc., using a hollow stem drill with depth varying from 50 to 80 feet. Groundwater was not encountered in any of the test borings in Kleinfelder's investigation. John Jones, Water Plant Supervisor for the City of Tracy, has estimated the depth of the groundwater in this area to be ±140 feet. Based on nearby mining sites, groundwater in the area is conservatively estimated to be below 120 feet. At its adjacent excavations, Teichert has not mined into the water table. In the early 1980's, groundwater, whether perched or active, was determined by Teichert to be in excess of 105 feet below grade. Teichert is seeking permission to mine only to a depth of approximately 80 feet, which is well above all estimates of the water table. Using the average estimate of groundwater depth, the attached modified site map depicts a distance of 120 feet below grade. Soil Variety The soils should have been described as Zacharias gravelly clay loam. This descriptor is preferred by the Soil Conservation Service. (Sorrento gravelly clay loam has become an obsolete reference.) 5