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C maximum temperature in July and August is in excess of 90°F, with frequent daily highs over 100°F. Minimum temperatures in January average between 35 and 40°F, with maximum temperatures in the mid -50s. Rainfall is seasonal with 90 percent of the precipitation occurring from October to May. The State of California Department of Water Resources publication, Rain- fall Analysis for Drainage Design. volume 1, Short Duration Precipitation Fre- quency Analysis, October 1986, lists a maximum annual precipitation of 23.11 inches recorded in 1958 at the Stockton Disposal Plant station (37056' lat- itude, 121019' longitude) and a 24-hour, 100 -year precipitation of 3.65 inches. The Stockton Disposal Plant station, located approximately 10 miles southwest of the landfill site is climatologically very similar to the landfill site. Records for 34 years are available for the Stockton Disposal Plant station. According to DWR's publication, the mean annual precipitation is 13.85 inches. An isohyetal map prepared by the San Joaquin County Flood Control and Water Conservation District indicates an average annual precipitation of 15 inches (see Figure 4-6). Evaporation data recorded between 1931 and 1979 for the Lodi evaporation sta- tion listed in the State of California Department of Water Resources Bul- letin 73-79, Evaporation from Water Surfaces in California, November 1979, gives a mean annual Pan A evaporation of 67.95 inches. A minimum mean monthly evaporation of 1.06 inches occurs in December, and a maximum mean monthly evaporation of 11.34 inches occurs in July. Data collected from 1974 to 1976 at the Rancho Seco wind monitoring station (37°54' latitude, 121115' longitude) show winds blowing most frequently from the west (12.8 percent of the time) and west southwest (10.2 percent of the time), with calm periods 43 percent of the time. A wind rose developed from Rancho Seco wind monitoring station records is presented in Figure 4-7. 4.3 GEOLOGY This section presents a summary of the regional and site geology, soil conditions, and seismicity. A detailed evaluation is contained in Appendix A, Geologic and PJ9 9390218A.00W 19 Rev. 0 July 20, 1989