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4 ENVIRONMENTAL ANALYSIS 4.7 GEOLOGY,SOILS,AND SEISMICITY the data used to model the slope stability impact did not represent actual site-specific soils and did not necessarily model slope response of the proposed quarry slopes. Geomatrix conducted their slope stability analyses of the proposed temporary and permanent slopes using the slope stability computer model SLOPE/W. This model solves the general solution of slope stability problems using a two-dimensional,limit equilibrium method. The model calculated the slope response under static and seismic conditions of the proposed 100-foot high,3/4:1(H:V)slope and the permanent 100-foot high,2:1 slope. Geomatrix considered the temporary slope condition with the excavation pit without water and assumed groundwater below �- the level of excavation. Modeling of the permanent slope condition considered a 2:1 (H:V) slope constructed with compacted fill material without intermediate benches. The Geomatrix slope stability analysis also incorporated the consideration that,because a 100-foot deep pit would be excavated, the soil material exposed in the pit bottom and excavation slopes would be in the state of over-consolidation which increases the soil strength effects. The Geomatrix slope stability modeling approach was appropriate considering the limited site-specific soil engineering parameters input data available. Slope Configuration Requirements As presented in the Regulatory Framework section of this chapter,Chapter 9-1415-3 of the San Joaquin County Development Title, Ordinance for Quarry Excavations(Title)require that .. temporary cut slopes not exceed 1:1 (H:V)although temporary slopes at setback lines can be maintained at r/z:l (H:V)if geologic and engineering analysis determine that the slopes will have a minimum factor of safety of 1.5 under static conditions and 1.1 under seismic conditions. Permanent slopes are required by the Title not to exceed 2:1 (H:V)but can be maintained at 1.5:1 (H:V)if slope stability analysis demonstrates that the slope can would have the minimum V, required factor of safety. Permanent 2:1 slopes exceeding 50-feet in height are required by the Title to be terraced with a maximum vertical distance between terraces of 50-feet. Terraces must be 12-feet wide and have appropriate drainage. Results of Slope Stability Analysis The Geomatrix slope stability analysis indicated a static factor of safety of 1.2 for temporary slopes and 1.6 for permanent slopes at the site. The 1.2 static factor of safety determined for the temporary slopes indicate that the slope would likely remain stable in the 3/4:1 (H:V) configuration. The San Joaquin County Quarry Excavation Standards do not specify a required factor of safety for temporary working slopes(see Regulatory Background section of this chapter). However,temporary cut slopes must comply with the Cal OSHA Code of Regulations and/or Federal OSHA Code of Regulations as applicable. The periodic,localized fall of unsupported and loose rock from a slope, often referred to as raveling,is anticipated for temporary slopes during the project,but due to its isolated and localized occurrence,raveling is not considered to have a significant effect on mining activities. The factor of safety for the permanent slope configuration exceeds the minimum factor of safety established by the San Joaquin County Quarry Excavation Standards for surficial and deep seated slope failures. ti RMC Pacific Vernalis Quagv Mining and Reclamation Project 4.7-19 ESA/203015 Administrative Draft EIR Mach 2004