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~ CORNERSTONE 1.:: EARTH GROUP Seismically-induced settlement estimates were generally less than'/< inch. Given the magnitude of potential settlement, in our opinion, the potential impact to the proposed site improvements due to seismically-induced settlement is considered low. 4.5 LATERAL SPREADING Lateral spreading is horizontal/lateral ground movement of relatively flat-lying soil deposits towards a free face such as an excavation, channel, or open body of water; typically lateral spreading is associated with liquefaction of one or more subsurface layers near the bottom of the exposed slope. As failure tends to propagate as block failures, it is difficult to analyze and estimate where the first tension crack will form. Although the potential for liquefaction at the site is considered low, the north end of the site is located approximately 85 to 90 feet from the top edge of an existing approximately 150-foot deep quarry pit. Therefore, a slope stability analysis was performed to further evaluate the stability of the quarry pit slope, as discussed in the following section. 4.6 QUARRY SLOPE STABILITY 4.6.1 Summary of Conditions As discussed, the parcel is located south of the existing quarry pit that is currently referred to as Lake I of the nearby Hanson Aggregates plant. Based on our review of the slope evaluation _ report prepared by Geocon Consultants for Hanson Aggregates, the quarry pit is reportedly to be turned over to the Zone 7 Water Agency for future water storage, recreation and ground water recharge uses. The top of the quarry pit is located approximately 85 to 90 feet north of the site. The quarry pit slope reportedly extends down to approximately Elevation 210 feet (RJA, 2002) and is inclined at roughly 2:1 (horizontal:vertical). The upper portion of the slope is covered with sparse grasses. A horizontal bench is located at approximately Elevation 280 feet and localized steepened areas reportedly exist on the quarry slope. The future water level in the adjacent Lake I reportedly will vary between Elevation 250 and 330 feet, which was used in our analysis to represent "low-water" and "high-water' conditions, respectively. A generalized cross section through the existing quarry slope is shown on Figure 4, which actually extends beyond the limits of recent topographic information provided by RJA (2007). It should be noted that ground surface elevations were based on topographic plans prepared by RJA dated December 12, 2007 and February 28, 2002. The topographic information presented in the 2002 RJA plan extended approximately 275 feet north of the top of the quarry slope. We also reviewed and extrapolated field ground surface measurements reported by Geocon in their report dated October 2007. The 2007 Geocon report recommends that the over-steepened portions of the quarry slope adjacent to the site be flattened to a 2:1 (horizontal:vertical) inclination to reduce long-term erosion and shallow sloughing of exposed surface soils. To achieve this slope inclination, an engineered fill buttress will need to be constructed on the existing lower benches. Ponderosa Active Adult Community Paga 7 132-2-1