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Mater Dei High School October 20, 2023 Proposed Dance Studio, Santa Ana, California Project No. 3204.I 3204-I-01R (10/23) 10 During backfill of excavations, the fill should be properly benched into the construction slopes as it is placed in lifts. 4.3.6 Shrinkage and Subsidence Shrinkage is the loss of soil volume caused by compaction of fills to a higher density than before grading. Subsidence is the settlement of in-place subgrade soils caused by loads generated by large earthmoving equipment. For earthwork volume estimating purposes, an average shrinkage value of 10 to 15 percent and subsidence of 0.2 feet may be assumed for the surficial soils. These values are estimates only and exclude losses due to removal of vegetation or debris. Actual shrinkage and subsidence will depend on the types of earthmoving equipment used and should be determined during grading. 4.3.7 Trench/Wall Backfill Utility trench backfill should be mechanically compacted in lifts. Wall backfill, while not anticipated for the project, should consist of the on-site sandy soils or imported sand. Lift thickness should not exceed those values given in the "Compacted Fill" section of this report. Jetting or flooding of backfill materials should not be permitted. A representative of GPI should observe and test trench and wall backfills as they are placed. In backfill areas where mechanical compaction of soil backfill is impractical due to space constraints, sand-cement slurry may be substituted for compacted backfill. The slurry should contain at least one sack of cement per cubic yard and have a maximum slump of 5 inches. Within building areas, the slurry should contain at least two sacks of cement per cubic yard. 4.3.8 Observation and Testing A representative of GPI should observe excavations, subgrade preparation, and fill placement activities. Sufficient in-place field density tests should be performed during fill placement and in-place compaction to evaluate the overall compaction of the soils. Soils that do not meet minimum compaction requirements should be reworked and tested prior to placement of additional fill. 4.4 FOUNDATIONS 4.4.1 Foundation Type Due to the potential settlements induced by liquefaction, we have assumed that the proposed building will be supported on mat foundations or spread footings connected with grade beams. If spread footings connected with grade beams are used for the building, the Structural Engineer should consider the items below to further mitigate potential distress from seismic settlements: •Additional reinforcement in continuous footings; •Slab-on-grade floors of a minimum of 5 inches thick; •Additional reinforcement in the floor slab; 1202 W Edinger Ave10/3/2024