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5.11:SOILS <br /> • Estimates of soil loss (in tons) were made for the site-specific soil mapping unit <br /> characteristics that were all available within the RUSLE2 database. <br /> • RUSLE2 rainfall erosivity conditions were estimated for the LEC site coordinates using <br /> site-specific rainfall estimates from online National Weather Service data (NOAA <br /> Atlas 2) at online at http://hdsc.nws.noaa.gov/cgi-bin/hdsc/na2.html (verified <br /> May 29,2008). <br /> • A 100-foot slope length was assumed for all soil units. The median of each soil unit slope <br /> class was used for the RUSLE calculations. For this project, an average slope of 1 percent <br /> (i.e.,mid-point of 0 to 2 percent slope class) was assumed for all soil units. <br /> Soil losses are estimated using the following RUSLE2 conditions: <br /> Construction and demolition soil losses were approximated using Management as'bare <br /> ground, smooth surface; Contouring: Rows up and down hill;Diversion/terracing: None; <br /> and Strips and Barriers: None. <br /> Active grading soil losses were approximated using Management as'bare ground,rough <br /> surface' soil conditions; Contouring: Rows up and down hill;Diversion/terracing: None; <br /> and Strips and Barriers: None. <br /> Construction soil losses with implementation of construction BMPs was approximated <br /> using Management as Silt fence; Contouring: Perfect,no row grade;Diversion/terracing: <br /> None;and Strips and Barriers: two silt fences,one at end of RUSLE2 slope. <br /> A'No Project'soil loss estimate was also approximated using Management as'Dense grass <br /> -not harvested; Contouring: Rows up and down hill;Diversion/terracing: None;and Strips <br /> and Barriers: None. <br /> With the implementation of appropriate BMPs that will be required under the National <br /> Pollutant Discharge Elimination System (NPDES) permit, the total project soil loss of <br /> 0.20 ton is considered to be a minimal amount and would not constitute a significant impact. <br /> It should also be recognized that the estimate of accelerated soil loss by water is very <br /> conservative (overestimate of soil loss) because of it assumes only a single BMP (i.e.,silt <br /> fencing),whereas a SWPPP will require multiple soil erosion control measures. <br /> 5.11.2.4.2 Wind Erosion <br /> The potential for wind erosion of surface material was estimated by calculating the total <br /> suspended particulates (TSP) that could be emitted as a result of grading and the wind <br /> erosion of exposed soil. The total site area and grading duration were multiplied by <br /> emission factors to estimate the TSP matter emitted from the site. Fugitive dust from site <br /> grading was calculated using the default particulate matter less than 10 microns in <br /> equivalent diameter (PM1o) emission factor used in URBEMIS2002 and the ratio of fugitive <br /> TSP to PMlo published by the Bay Area Air Quality Management District (BAAQMD,2005). <br /> Fugitive dust resulting from the wind erosion of exposed soil was calculated using the <br /> emission factor in AP-42 (U.S. Environmental Protection Agency [EPA], 1995; also in <br /> Table 11.9-4 in BAAQMD,2005). <br /> Table 5.11-3 summarizes the mitigated TSP predicted to be emitted from the site from <br /> grading and the wind erosion of exposed soil. Without mitigation, the maximum predicted <br /> SACI371322I082330009(LEC_5.11_SOILS.DOC) 5.11-9 <br />