04 ATTACHMENT 6 - Laserfiche WebLink

Project No. E9164-04-0 2 - 9 - April 15, 2020 existing excavations or depressions, should be restored with engineered fill in accordance with the recommendations of this report. 6.5.5 After stripping, the exposed subgrade should then be over-excavated to a depth of approximately 1 foot. The exposed bottom should be scarified 8 to 12 inches moisture conditioned to at least 2% above optimum moisture and recompacted to at least 90% relative compaction. 6.5.6 In general, over-excavated materials may be used for new engineered fill, provided they do not contain deleterious matter, organic material, or cementations larger than 6 inches in maximum dimension. Over-excavations and the exposed bottom surfaces and bottom processing should be observed by our representatives. Supplemental recommendations may be provided based on site conditions during grading. 6.5.7 All structural fill and backfill should be placed in layers no thicker than will allow for adequate bonding and compaction (typically 8 to 12 inches). Fill soils should be placed and compacted to at least 90% relative compaction at least 2% above optimum moisture. Fill areas with in-place density tests showing moisture contents less than those recommended may require additional moisture conditioning prior to placing additional fill. 6.6 Shallow Foundation Recommendations 6.6.1 The proposed one- and two--story structures may utilize conventional foundations consisting of continuous strip or isolated spread footings founded in competent native materials or properly compacted fill. Continuous strip footings should be used at the building perimeter; any spread footings for columns should be integral with the perimeter strip. Continuous strip footings may be used for ancillary site structures such as short retaining walls, screen walls, or trash enclosures. The following recommendations assume that soils within 5 feet of finish grade will consist of very low expansive materials (Expansion Index less than 20). 6.6.2 It is recommended that conventional continuous footings have a minimum embedment depth of 18 inches below lowest adjacent pad grade. Interior spread footings should be founded at least 18 inches below lowest adjacent pad grade and be at least 24 inches square. Continuous footings should be at least 12 inches wide. 6.6.3 Footings proportioned as recommended may be designed for an allowable soil bearing pressure of 2,500 pounds per square foot (psf). The allowable bearing pressure is for dead + live loads may be increased by up to one-third for transient loads due to wind or seismic forces. 6.6.4 The allowable passive pressure used to resist lateral movement of the footings may be assumed to be equal to a fluid weighing 300 pounds per cubic foot (pcf). The allowable passive pressure assumes a horizontal surface extending at least 10 feet or 3 times the surface generating the passive pressure, whichever is greater. The allowable coefficient of friction to resist sliding is 0.30 for concrete against soil. Combined passive resistance and friction may be utilized for design provided the frictional resistance is reduced by 50%. Where not protected by flatwork or pavement, the upper 1 foot of soil should be neglected when calculating passive resistance to lateral loads. 6.6.5 Minimum reinforcement for continuous footings should consist of four No. 4 steel reinforcing bars; two placed near the top of the footing and two near the bottom. Isolated column footing reinforcement should be specified by the structural engineer.