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625 Cypress Avenue <br />Geotechnical Investigation <br /> <br />Project No. W1895-88-01 - 15 - April 23, 2024 <br />7.1.5 Based on these considerations, where new footings are required for support of the proposed <br />improvements, conventional foundations may be used. Foundations should derive support <br />in the undisturbed alluvial soils found at and below a depth of 5 feet. Foundations should be <br />deepened as necessary to penetrate through any unsuitable soils and derive support <br />exclusively in the undisturbed alluvial soils. All foundation excavations must be observed and <br />approved in writing by the Geotechnical Engineer (a representative of Geocon) prior to <br />placement of steel or concrete. Recommendations for the design of a conventional <br />foundation system are provided in Section 7.6. <br />7.1.6 Where new foundations are constructed immediately adjacent to existing foundations, the <br />new foundation should be deepened to match the depth of the existing foundation to <br />prevent a surcharge on the existing foundation. <br />7.1.7 Where a proposed foundation will be deeper than an existing adjacent offsite foundation, <br />the proposed foundation must be designed to resist the surcharge imposed by the existing <br />foundation. The surcharge area may be defined by a 1:1 projection down and away from the <br />bottom of the foundation. <br />7.1.8 All excavations must be observed and approved in writing by the Geotechnical Engineer <br />(a representative of Geocon). <br />7.1.9 Where new concrete slab-on-grade is to be constructed, it is recommended that any soils <br />disturbed during construction activities be properly compacted for slab support. <br />Recommendations for earthwork are provided in the Grading section of this report (see <br />Section 7.4). <br />7.1.10 Where new paving is to be placed, it is recommended that all existing fill and soft alluvial <br />soils be excavated and properly compacted for paving support. The client should be aware <br />that excavation and compaction of all existing fill and soft alluvial soils in the area of new paving <br />is not required; however, paving constructed over existing uncertified fill or unsuitable <br />alluvial soil may experience increased settlement and/or cracking and may therefore have a <br />shorter design life and increased maintenance costs. As a minimum, the upper 12 inches of <br />subgrade soil should be scarified and properly compacted for paving support. Paving <br />recommendations are provided in the Preliminary Pavement Recommendations section of this <br />report (see Section 7.9).