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C CORNERSTONE EARTH GROUP by very dense gravel to a depth of 65 feet, the maximum depth explored in Boring GB-4. With the exception of the upper fill layer, the conditions encountered in Boring GB-4 were generally consistent with those encountered in our Boring EB-1. Amore detailed description of the subsurface conditions is presented on the boring logs in Appendix A. 3.2.1 Plasticity/Expansion Potential Based on our review of the near-surface soils and review of Plasticity Index (PI) tests performed during the previous investigations for the Ironwood development, the near surface soils generally exhibit non-plastic to low plasticity behavior. The results of the previous surficial PI tests (Lowney Associates, 2002) indicated Pls ranging from 9 to 10, indicating low expansion potential to wetting and drying cycles. 3.2.2 In-Situ Moisture Contents Laboratory testing indicated that the in-situ moisture contents within the upper 10 feet range from approximately 5 to 8 percent below to 5 percent over the estimated laboratory optimum moisture for the near-surface soils. 3.3 GROUND WATER Ground water was not encountered in any of our borings during drilling; however, the borings were not left open but were immediately backfilled when the boring was completed. Based on our review of previous subsurface data in the area, we anticipate that the high ground water level will likely be greater than 50 feet below current grades. Once the water level in the adjacent Lake I quarry pit has stabilized at Elevation 330 feet, it is possible that ground water could stabilize near the top of the low gravel layer, or approximately 40 to 45 feet below existing site grades (Elevation 310 to 315 feet). Fluctuations in ground water levels occur due to many factors including the following: seasonally water levels can generally fluctuate 2 to 5 feet, underground drainage patterns can cause perched water conditions above steady ground water levels, regionally the average ground water level can fluctuate over long time periods, and other factors. SECTION 4: GEOLOGIC HAZARDS 4.1 FAULT RUPTURE As discussed above several significant faults are located within 25 kilometers of the site. The site is not located within aState-designated Alquist Priolo Earthquake Fault Zone. As shown in Figure 3, no known surface expression of fault traces is thought to cross the site; therefore, fault rupture hazard is not a significant geologic hazard at the site. Ponderosa Active Adult Community Page 5 132-2-1