SITE INFORMATION AND CORRESPONDENCE

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5.11:SOILS erosion of material from the site is estimated at 2.12 tons over the course of the project construction cycle. This estimate is reduced to approximately 0.76 ton by implementing basic mitigation measures such as water application(see mitigation measures,below). These estimates are conservative because they make use of emission rates for a generalized soil rather than for site-specific soil properties. TABLE 5.11-3 Soil Loss(TSP)from LEC Grading and Wind Erosion Duration Unmitigated Mitigated TSP Emission Source Acreage (months) TSP (tons) (tons) Grading Dust: Project Site 4.4 2 0.151 0.053 Laydown Areas (A through D) 9.8 1 0.108 0.059 Natural Gas Line (4-ft wide trench) 1.21 3 0.382 0.134 Wind Blown Dust: Project Site 4.4 22 0.307 0.107 Laydown Areas (A through D) 0.00 23 0.000 0.000 Natural Gas Line(30-ft corridor) 9.09 3 1.170 0.410 Estimated Total 24 2.118 0.763 Notes:Assumptions for these calculations are found in Appendix 5.11A. 5.11.2.5 Expansive Soils An important characteristic of the proposed LEC project site is the potential for soils with moderate to high shrink-swell potential. As previously explained in subsection 5.11.1.4, despite the fact that map unit 149 on which the project site is located has a low shrink-swell potential in the upper soil layers,there is a possibility that expansive soils may be found in the area. The presence of expansive clays in the soil may affect the suitability of the soil as a bearing surface for foundations and pipelines because expansive clays have the potential to shrink or swell in volume with changing moisture content. Although the WPCF has already been built on another portion of the property,it shouldn't be assumed that the soils will behave similarly. Additionally,up to 15 percent of map units 149 and 169 may be made up of soil components that have properties that different from the dominant soil component. A preliminary onsite geotechnical evaluation was performed for the LEC property that indicated that expansive soils may be present on site (Carlton Engineering,2008) but that the potential for damage to onsite structures was low. It was expected that expansive soils could be mitigated with standard design and construction techniques but that further geotechnical investigations should be completed to support both of these aspects of the project. 5.11.2.6 Compaction during Construction and Operation Construction of the proposed project would result in soil compaction during the construction of foundations and paved roadway and parking areas. Soil compaction would 5.11-10 SAC/371322/082330009(LEC_5.11_SOILS.DOC)