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Project No. JB-20100 4 December 2000 Page 6 important that our representative be present during the demolition, stripping and scarification process to observe whether undesirable materials are encountered. Loose, soft, uncontrolled fill, or disturbed native soils must be removed from all structural areas, beneath adjacent walks and slabs, beneath areas to receive fill, and beneath areas to be paved. Excavations must extend at least 5 feet beyond the structure and slab areas, if practicable. The term uncontrolled fill refers to any existing fill that was not properly placed, inspected or tested by an engineering firm. 5.1.3 Excavations and Utility Trenches As discussed earlier, loose to medium dense sandy silt was encountered at the site. Native soils may be excavated utilizing conventional equipment. Contractors, especially those digging utilities, should satisfy themselves as to the hardness of deposits and equipment required. All applicable safety measures should be enforced during excavation and trenching operations. Utility trenches that parallel the sides of the buildings should be placed so that they do not extend below a line sloped down and away at a slope of 2H:1V (horizontal to vertical) from the bottom outside edge of the perimeter foundations. All trenches should be backfilled with native materials compacted uniformly to the relative compaction specified in the following section. If local building codes require use of sand as the trench backfill, all utility trenches entering the building should be provided with an impervious seal of either cohesive soil or lean concrete where the trench passes under the building perimeter. The impervious plug should extend 4 feet into, and out of, the building perimeter. Jetting of trench backfill is not recommended as it may result in an unsatisfactory degree of compaction. 5.1.4 Fill Placement and Compaction After performing the required excavations and/or prior to foundation excavations, the exposed subgrade soil should be carefully inspected to verify removal of all unsuitable deposits. The exposed subgrade soil should then be scarified to a depth of 12 inches, moisture-conditioned, and compacted to a minimum of 90 percent relative compaction at a minimum of 2 percent over optimum moisture content according to the latest ASTM test methods and procedures. After compacting the subgrade soil, all required fill should be placed in loose lifts a maximum of 8 inches in thickness. J MKorbmacher Engineering, Inc.