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Cirminrlwater Groundwater was encountered within the borings. Groundwater is not expected to within the site. Liquefaction CITY OF SANTA ANA Planning and Building Agency 1602 W Brook St ants Ana CA 92703 Approved FOR PERMIT ISSUANCE Date: red Potential consequences of liquefaction or secondary liquefaction included hazards generally consist of differential settlement (vertical deformations), lateral move ment/lateraI spreading (horizontal deformations), oscillation, and reduction in foundation soil -bearing capacity (bearing failure). A sloping condition or drainage or stream channel does not exist at the site, therefore, lateral movement/lateral spreading, oscillation, etc, due to potential liquefaction are not anticipated to be credible hazards for the proposed new structure. Differential settlement due to liquefaction (and reduction in foundation soil -bearing capacity) is roughly estimated to be about'/o inch (for a horizontal distance of 40 feet). This is only a rough estimate. To reduce the potential adverse effects to the new structure due to potential liquefaction induced differential settlement and/or reduction in foundation soil -bearing capacity, a strengthened foundation system with thicker and stronger reinforcement slabs and deeper and wider and stronger reinforcement footings as compared to a regular foundation system for a residential structure as recommended in this report should be used for the new structure. During our research, and in conversations with other Engineers and Contractors, it was discovered many of the new residences in the area have been designed and constructed with regular, shallow footings with slabs on grade, not with strengthened foundation supports. Our belief is if the area would be liquefied due to a very strong earthquake, the potential for damage to the proposed new structure which will be structurally designed in accordance with new building codes, if any, would be much less severe than the existing on -site structure and existing homes in the vicinity. These homes were built and designed structurally based on old building codes. It should be noted that in accordance with SP117A, a detailed site -specific liquefaction study is not required since the proposed new structure is less than three stories and less than four units. Shrinkage and Subsidence Based on the in -place densities of the natural soil and assuming an average fill density of 92 percent relative compaction, calculations indicate that there will be a 5 percent decrease in volume between the cut and fill operations. In addition, it is estimated that there will be 0.15 of a foot of subsidence due to reworking the surface soils. 2