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330 Land Company, LLC Arroyo Lago 9785.004.001 Design-Level Geotechnical Report Page | 18 April 16, 2024 Latest Revision October 31, 2025 5.6 FILL PLACEMENT After subexcavation and recompaction of undocumented fill in cut-to-fill transition material, where applicable, the exposed non-yielding surface of areas to receive fill or to be left at grade should be scarified to a depth of 12 inches, moisture conditioned, and recompacted to provide adequate bonding with the initial lift of fill. The loose lift thickness should not exceed 12 inches or the depth of penetration of the compaction equipment used, whichever is less. The following compaction control requirements should be applied to all fill, including backfill, except for landscape areas. TABLE 5.6-1: Compaction Control Requirements FILL LOCATION MATERIAL TYPE REQUIRED RELATIVE COMPACTION** (%) MINIMUM MOISTURE CONTENT (percentage points above optimum) General Fill Expansive* 87 to 92 4 Low-Expansive* 90 2 Pavement and Flatwork Subgrade* Expansive* 90 4 Low-Expansive* 95 1 Pavement and Flatwork Aggregate Base Class 2 Aggregate Base 95 0 * Expansive: PI greater than 20 Low-Expansive: PI less than 20 ** Relative compaction refers to the in-place dry density of soil expressed as a percentage of the maximum dry density of the same material. 5.7 UNDERGROUND UTILITY BACKFILL The contractor is responsible for conducting trenching and shoring in accordance with Cal/OSHA requirements. Project consultants involved in utility design should specify pipe-bedding materials. Exercise care where utility trenches are located beside foundation areas. Locate utility trenches constructed parallel to foundations entirely above a plane extending down from the lower edge of the footing at an angle of 45 degrees. Provide utility companies and landscape architects with this information. Where utility trenches cross underneath buildings or cross perimeter building foundations, we recommend that a plug be placed within the trench backfill to prevent the normally granular bedding materials from acting as a conduit for water to enter beneath the building . The plug should be constructed using sand-cement slurry (minimum 28-day compressive strength of 500 psi) or relatively impermeable native soil for pipe bedding and backfill. We recommend that the plug extend for a distance of at least 3 feet in each direction from the point where the utility enters the building perimeter. Use well-graded import less than ¾ inch in maximum dimension for pipe zone backfill (i.e., material beneath and immediately surrounding the pipe). Use fine- to medium-grained sand or a well-graded mixture of sand and gravel for pipe zone backfill import material. Avoid using this material within 2 feet of finish grades. In general, avoid using uniformly graded gravel for pipe or trench zone backfill due to the potential for migration of: (1) soil into the relatively large void spaces present in this type of material; and (2) water along trenches backfilled with this type of material. Native soil for trench zone backfills (i.e., material placed between the pipe zone backfill and the ground surface) should be compacted in accordance with recommendations in Section 5.6.