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Lutzky Associates Development, LP - Geolechnical Investigation <br />MACTEC Project 4953-03-2631 <br />Sepiember 18, 2003 <br />Bearing Value <br />Isolated or continuous spread footings established on competent soils may be designed to impose a <br />net dead-plus-live load pressure of 2,000 pounds per square foot. The footings should extend <br />about 3 feet below the lowest adjacent grade or floor slab on grade (i f any), whichever is lower. <br />A one-third increase can be used for wind or seismic loads. The recommended bearing values are <br />net values, and the weight of concrete in the footings can be taken as 50 pounds per cubic foot; the <br />weight of soil backfill can be neglected when determining the downward loads. <br />For structural analyses of the structure foundations established either in the properly compacted <br />fill soils or natural soils, a vertical modulus of subgrade reaction of 100 pounds per cubic inch may <br />be used. These values are unit values for use with a 1 -foot-square area. The modulus values <br />should be reduced in accordance with the following equation when used with the larger <br />foundations: <br />B+1-2 <br />KR=K - <br />28 <br />- <br />where K =unit subgrade modulus <br />KR = reduced subgrade modulus <br />B = equivalent foundation width <br />Please note that where adjacent footings are required at different elevations, the higher footing <br />should be located below a 1:1 plane extending upward from the bottom outer edge of the lower <br />footing to avoid imposing significant surcharge loads. In addition, the proposed foundations should <br />be located below a 1:1 (horizontal to vertical) plane extending upward from the bottom outer edges <br />of the adjacent existing building foundations SO that the new foundations do not surcharge the <br />existing foundations. <br />Footings for minor structures (minor retaining walls and free-standing walls) that are structurally <br />separate from the building may be designed to impose a net dead-plus-live load pressure of <br />1,000 pounds per square foot at a depth of 1 96 feet below the lowest adjacent grade. Such footings <br />may be established on properly compacted fill soils or natural soils. <br />20