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5.11:SOILS <br /> also result from vehicle traffic along temporary access roads and in the equipment staging <br /> (laydown) and parking areas. Soil compaction increases soil density by reducing soil pore <br /> space. This also reduces the ability of the soil to absorb precipitation and transmit gases for <br /> respiration of plant roots and soil microfauna.Soil compaction can result in increased <br /> runoff, erosion, and sedimentation. The incorporation of BMPs,in accordance with the <br /> SWPPP/DESCP guidelines during construction,will result in less-than-significant impacts <br /> from soil compaction. <br /> Before use of the construction laydown and parking areas,minimal grading is expected <br /> because the site and proposed laydown areas are relatively flat. After grading,runoff from <br /> the site and laydown area would either occur as overland flow or infiltrate the soil and <br /> percolate to groundwater. However,the laydown and parking areas will likely be graveled <br /> to allow for wet season use and further minimize soil erosion potential. Heavy equipment <br /> stored onsite will be placed on dunnage to protect it from ground moisture. Once <br /> construction is completed,the gravel will either be removed from the site or incorporated <br /> into the site paving. <br /> Because the LEC will be constructed in previously developed area,the amount of soil <br /> compaction that will be required to establish permanent road beds and foundation areas for <br /> buildings should be minimal. Because these areas will be paved or otherwise protected after <br /> construction,the overall anticipated effects of compaction during construction are <br /> considered to be less than significant. <br /> Operation of the LEC would not result in impacts to the soil from erosion or compaction. <br /> Routine vehicle traffic during plant operation will be limited to existing roads, all of which <br /> are paved or will be graveled, and standard operational activities should not involve the <br /> disruption of soil. Therefore,impacts to soil from project operations would be less than <br /> significant. <br /> 5.11.2.7 Effects of Emissions on Soil-Vegetation Systems <br /> There is a concern in some areas that emissions from a generating facility,principally oxides <br /> of nitrogen from the combustors or drift from the cooling towers,would have an adverse <br /> effect on soil-vegetation systems in the project vicinity. This is principally a concern where <br /> environments that are highly sensitive to nutrients or salts,such as serpentine habitats, are <br /> downwind of the project. Aerial nitrogen deposition is also known to reduce the activity of <br /> mycorrhizal fungi in the soil. <br /> The proposed LEC project will include a selective catalytic reduction (SCR) system to <br /> control NOx air emissions and a carbon monoxide (CO) catalyst to control carbon monoxide <br /> air emissions (one SCR/CO catalyst per exhaust train). The additional nitrogen from air <br /> emissions from the LEC would be negligible when compared to the fertilizers that are likely <br /> already being applied in cultivated fields. In addition,there are no serpentine habitats in or <br /> surrounding the project area. Therefore and the addition of small amounts of nitrogen to the <br /> area would result in less than significant impacts on soil-vegetation systems. <br /> 5.11.3 Cumulative Effects <br /> A cumulative impact refers to a proposed project's incremental effect together with other <br /> closely related past,present,and reasonably foreseeable future projects whose impacts may <br /> SACI371322I082330009(LEC_5.11_SOILS.DOC) 5.11-11 <br />