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524 S Shawnee Dr. <br />Santa Ana CA 92704 <br />Groundwater <br />Groundwater was not encountered within the borings. Groundwater is not expected to be encountered <br />on this site. <br />Liquefaction <br />Potential consequences of liquefaction or secondary liquefaction included hazards generally consist of <br />differential settlement (vertical deformations), lateral movement/lateral spreading (horizontal defor- <br />mations), oscillation, and reduction in foundation soil-bearing capacity (bearing failure). <br />A sloping condition or drainage or stream channel does not exist at the site, therefore, lateral move- <br />ment/lateral spreading, oscillation, etc, due to potential liquefaction are not anticipated to be credible <br />hazards for the proposed new structure. <br />Differential settlement due to liquefaction (and reduction in foundation soil-bearfng capacity) is <br />roughly estimated to be about 1/4 inch (for a horizontal distance of 40 feet). This is only a rough esti- <br />mate. <br />To reduce the potential adverse effects to the new structure due to potential liquefaction induced differ- <br />ential settlement and/or reduction in foundation soil-bearing capacity, a strengthened foundation sys- <br />tem with thicker and stronger reinforcement slabs and deeper and wider and stronger reinforcement <br />footings as compared to a regular foundation system for a residential structure as recommended in this <br />report should be used for the new structure. <br />During our research, and in conversations with other Engineers and Contractors, it was discovered <br />many of the new residences in the area have been designed and constructed with regular, shallow foot- <br />ings with slabs on grade, not with strengthened foundation supports. <br />Our belief is if the area would be liquefied due to a very strong earthquake, the potential for damage to <br />the proposed new structure which will be structurally designed in accordance with new building codes, <br />if any, would be much less severe than the existing on-site structure and existing homes in the vicinity. <br />These homes were built and designed structurally based on old building codes. <br />It should be noted that in accordance with SP117A, a detailed site-specific liquefaction study is <br />not required since the proposed new structure is less than three stories and less than four units. <br />Shrinkage and Subsidence <br />Based on the in-place densities of the natural soil and assuming an average fi ll density of 92 percent <br />relative compaction, calculations indicate that there will be a 5 percent decrease in volume between the <br />cut and fill operations. In addition, it is estimated that there will be 0.15 of a foot of subsidence due to <br />reworking the surface soils. <br />4 <br />524 S Shawnee Dr & <br />Unit# 22/7/2025