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3-10 Forward Composting Facility SWT Engineering Report of Composting Site Information - August 2019January 2022 z:\projects\allied waste\forward\resource recovery facility\5 yr permit rvw 2019-2020\rcsi 2019\text\sec 3.doc temperature variation can be as high as 30°F. Winters for the most part a ndre mild and humid. Average high temperatures during the winter are in the 50’s, while the average daily low temperature is approximately 45°F. Precipitation. Precipitation at the project site is typical of the Central Valley region. Rainfall is seasonal, with approximately 90 perce nt of the rainfall occurring between November and April. Snowfall is unusual at the site. Figure 7 presents an isohyetal precipitation map for San Joaquin County showing lines of equal precipitation on a countywide basis (San Joaquin County Department of Public Works, 1991). The isohyetal precipitation map divides the whole of San Joaquin County into three rainfall intensity zones. The project site is located in Zone 2 of the three rainfall zones, as illustrated in Figure 7. Mean annual precipitation f or Zone 2 on the San Joaquin County isohyetal precipitation map is approximately 13.5 inches. Specific precipitation intensities are based on precipitation data from the Stockton weather station number B00-8560 located approximately 8 miles northwest of t he site at latitude 38°00', longitude 121 °316', and an elevation of 12 feet National Geodetic Vertical Datum (NGVD) (California Department o f Water Resources, 1981). This precipitation station was selected due to its long and reliable period of record and its proximity to the project site. The precipitation depth-duration-frequency data for the site was obtained from the Stockton Weather Station Number B00-8560 (except where noted): ♦ 100-year, 24-hour storm intensity of 3.578 inches* ♦ 1,000-year, 24-hour st orm intensity of 4.92 inches* ♦ 100-year annual precipitation of 25.42 inches ♦ Annual mean precipitation of 14.2713.31 to 14.35 inches *Source: Non-Water Corrective Action Plan for Forward Landfill, GeoLogic Associates, November 2011 ; Updated November 2017 . From the lat e 1980s to the early 1990s as well as recently, California is experiencing a severe drought. Although the precipitation data available during this period may not represent the statistical minimum precipitation that could occur at the project site, the lik ely minimum precipitation range anticipated during the service life and post -closure period of the landfill can be estimated. Table 9 presents monthly average total precipitation recorded for the Stockton Area, for a period of 62 years, between 1950 and 2012. During this period, the average annual precipitation recorded for the Stockton area was approximately 17.87 inches. Considering the drought conditions experienced during that period, a minimum annual average precipitation of 17.87 inches during the service life and post -closure period of the landfill site was estimated. As shown in Figure 8, the Forward site is located between the North Fork and the South Fork of the South Littlejohn’s Creek. Based on the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Maps (FIRMs) for the San Joaquin Valley, Forward Landfill is located within four FIRM Panels: 0490F; 0495 F; 0630F; and, 0635F. From the FIRM Legend, the majority of the landfill (including the RRF and Composting Facility) is located within “Zone X”, which are areas determined to be outside the 0.2 percent annual chance of being in a floodplain. The area east of Austin Road at the North Fork of South Littlejohn’s Creek is labeled as “Zone AO, (Depth 1)”, which are areas with flood dept hs of one to three