ARCHIVED REPORTS_JULY 2014 FINAL TPR

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1-4 Forward Resource Recovery Facility SWT Engineering Transfer/Processing Report - July 2014 z:\projects\allied waste\forward\resource recovery facility\5 yr permit rvw 2013-14\tpr 2014\text\sec1.doc 1.7.2 Precipitation Precipitation at the project site is typical of the Central Valley region. Rainfall is seasonal, with approximately 90 percent of the rainfall occurring between November and April. Snowfall is unusual at the site. Figure 4 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 shown on Figure 4. Mean annual precipitation for 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 the site at latitude 38°00’, longitude 121°316, and an elevation of 12 feet National Geodetic Vertical Datum (NGVD) (California Department of Water Resources, 1981). This precipitation 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 from the Stockton WBAP Station Number B00-8560 are: ♦ 100-year, 24-hour storm intensity of 3.58 inches* ♦ 1,000-year, 24-hour storm intensity of 4.92 inches* ♦ 100-year annual precipitation of 25.42 inches ♦ Annual mean precipitation of 14.27 inches *Source: Non-Water Corrective Action Plan for Forward Landfill, GeoLogic Associates, November 2011. 1.7.3 Floodplain The Forward Landfill is located between the North Fork and the South Fork of the South Littlejohn’s Creek; the RRF is south of the South Fork of the South Littlejohn’s Creek (see Figure 5). 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; 0495F; 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 depths of one to three feet. This information was factored into the North Fork realignment of the South Littlejohn’s Creek relocation design. For additional information regarding the floodplain, refer to the 2014 RCSI (SWT). The North Fork of South Littlejohn’s Creek was relocated to allow continued development of the Forward Landfill. The 7,600-foot reach of the creek relocation was designed to channel