CITY PROJECT - 1821 & 1823 E Chestnut Ave - Plan

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ASSOCIATED SOILS ENGINEERING, INC. Project No.: 7160.23 2860 Walnut Avenue, Signal Hill CA 90755 January 23, 2024 Tel: (562) 426 -7990 * Fax: (562) 426 -1842 Page 12 5.2 Site Grading In minimizing the potential adverse effects associated with the development of excessive total or differential settlement underneath the Building, as well as to ensure uniform bearing competency for the foundations and slabs, preparation of on-site soils is recommended in the following sections. 5.2.1 Undocumented Fill/Disturbed Native Soils: Although not encountered in ASE’s exploratory borings, any undocumented fill soil, if encountered during site grading in the areas of the Building, as well as any native soils disturbed during demolition and clearing operations, should be excavated full depth under the observation and confirmation by the Geotechnical Consultant. Lateral extent of overexcavation beyond the Building perimeters, where possible, should be to a minimum distance equal to the depth of undocumented fill/disturbed soil encountered or four (4) feet, whichever is greater. For other secondary improvements such as free-standing walls or hardscape, the lateral extent of removal should be to a minimum distance equal to the depth of undocumented fill/disturbed soils encountered or eighteen (18) inches, whichever is greater. The exposed excavation bottom should be scarified/reworked to a minimum one (1) foot depth and recompacted to at least 90 percent relative compaction with a minimum moisture content of two (2) percentage points above optimum moisture content, prior to backfilling with approved soils as specified in Section 5.2.6. 5.2.2 Expansive Soils: Laboratory testing result on a near surface site soil sample indicates "Low” soil expansion potential (i.e. Expansion Index, EI = 31 per ASTM D4829-21 Test Method) as defined in Table 1 of ASTM D4829-21 Test Method and Section 1803.5.3 of 2022 CBC. Lightly loaded structural elements such as shallow foundations and slabs could undergo noticeable movements, at time unevenly, in areas underlain by soils with “Low” expansion potential. It should be noted that design provisions such as increased reinforcements, deeper foundations or other measures discussed in this Soils Report may help to alleviate the undesirable effects of “Low” soils expansion on the slabs and structures but may not completely eliminate the problem. It is recommended that the soil expansion potential be re-evaluated through additional testing during or after rough grading operations to verify the design adequacy of footing foundation and lab-on-grade against the re-tested soil expansion potential as heterogeneity within soil mass is not uncommon.