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5.11:SOILS management practices (BMPs)will be implemented during construction,as described in the Stormwater Pollution Prevention Plan(SWPPP) that is required for all construction projects over 1 acre under the general permit covering discharges of stormwater from construction activities. The California Energy Commission(CEC) also requires that project owners develop and implement a drainage,erosion, and sediment control plan (DESCP) to reduce the impact of runoff from a construction site. Therefore,impacts from soil erosion are expected to be less than significant. Monitoring will involve construction site inspections to ensure that the BMPs described in the SWPPP/DESCP are properly implemented and provide an effective combination of erosion and sediment controls. Despite the low potential for soil erosion in the proposed LEC project area, estimates of erosion by water and wind are provided in the following sections. 5.11.2.4.1 Water Erosion An estimate of soil loss during construction by water erosion was developed using the Revised Universal Soil Loss Equation(RUSLE2), and is summarized in Table 5.11-2. Detailed calculations for the soil loss estimates are found in Appendix 5.11A. TABLE 5.11-2 LEC Construction Soil Loss Estimates Using the Revised Universal Soil Loss Equationa Soil Loss Soil Loss Soil Loss Feature Duration (tons)without (tons) (tons/yr) (acreage)b Activity (months) BMPs with BMPs No Project Project Site–(4.4 acres) Grading 2 0.8 0.010 0.0233 Construction 22 4.1 0.113 — Laydown Areas(A through D, Grading 1 0.9 0.011 0.0519 9.8 acres total) Construction 23 0.0 0.00 — Natural Gas Line–(1.25 acre Grading 3 2.50 0.032 0.0482 for trench)and 9.45 acres for construction corridor) Construction 3 1.16 0.032 — Project Soil Loss Estimates 24 9.48 0.20 0.12 a Soil losses(tons/acre/year)are estimated using RUSLE2 software available online [http://fargo.nserl.purdue.edu/rusle2–dataweb/RUSLE2–index.html. b Acreages assume 30-ft corridors for the natural gas construction corridor.Trench for the natural gas pipeline is assumed to be 4-ft wide. The following assumptions,which are also shown in Appendix 5.11A,were used in the model. • The LEC construction site totals 4.4 acres. Active soil grading will occur over a 2-month period. The soil in this area will then be exposed for an additional 22 month construction period, after which the majority of the site will be paved or covered with LEC facilities. It is assumed that around 1/10thof the project site will have bare soil exposure during the construction period. 5.11-8 SAC/371322/082330009(LEC_5.11_SOILS.DOC)