SITE INFORMATION AND CORRESPONDENCE

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5.11:SOILS During construction of the project, dust erosion control measures would be implemented to minimize the wind-blown loss of soil from the site.Water of a quality equal to or better than existing surface runoff would be sprayed on the soil in construction areas to control dust prior to completion of permanent control measures. Sediment barriers slow runoff and trap sediment. Sediment barriers include straw bales, sand bags, straw wattles, and silt fences. They are generally placed below disturbed areas, at the base of exposed slopes, and along streets and property lines below the disturbed area. Sediment barriers are often placed around sensitive areas to prevent contamination by sediment-laden water near areas such as wetlands,creeks, or storm drains. The site will be constructed on relatively level ground;therefore,it is not considered necessary to place barriers around the entire site perimeter. However,some barriers would be placed in locations (such as the southern boundary) where offsite drainage could occur to prevent sediment from impacting the canal or from leaving the other areas of the site. If used, sediment barriers would be properly installed (staked and keyed),then removed or used as mulch after construction. Runoff detention basins, drainage diversions,and other large-scale sediment traps are not considered necessary due to the small site size,level topography, and surrounding paved areas. Any soil stockpiles, including sediment barriers around the base of the stockpiles,would be stabilized and covered. Mitigation measures, such as watering exposed surfaces, are used to reduce PM10 emissions during construction activities. The PM10 reduction efficiencies are taken from the SCAQMD CEQA Handbook (1993) and were used to estimate the effectiveness of the mitigation measures. Table 5.11-4 summarizes the mitigation measures and PMlo reduction efficiencies. Additional fugitive dust mitigation measures are discussed in Section 5.1,Air Quality. TABLE 5.11-4 Mitigation Measures for Fugitive Dust Emissions PM10 Emission Reduction Mitigation Measure Efficiency(%) Water active sites at least twice daily 34-68 Enclose, cover,water twice daily,or apply non-toxic soil binders,according to 30-74 manufacturer's specifications,to exposed piles(i.e., gravel, sand,dirt)with 5 percent or greater silt content Source: SCAQMD CEQA Handbook, Table 11-4 (1993) 5.11.4.2 Permanent Erosion Control Measures Permanent erosion control measures on the site will include graveling,paving, and drainage systems, as well as revegetating to stabilize land surfaces. 5.11.5 Laws, Ordinances, Regulations, and Standards Federal, state,county, and local LORS applicable to soils are discussed below and summarized in Table 5.11-5. SACI371322I082330009(LEC_5.11_SOILS.DOC) 5.11-13