3105 PINE ST 2018-01-01 MF Import

^ Voth Brothers Construction, Inc. E-1201-1 � October 20, 1960 Page 5 � Foundations ,., The seven-story section of the proposed structure may be � supported at the basement level on conventional continuous and/ �_ or spread footings supported on dense undisturbed till. Exter- ior footings should be bottomed a minimum depth of 18 inches below the lowest adjacent final grade. Basement wall footings extending into dense undisturbed till, may be designed for an ^ allowable bearing pressure of 7.5 kips per square foot, with a minimum width of 24 inches, for dead plus live loads. Individual column footings may also be supported on the dense undisturbed till soils. These footings may be propor- ' � tioned for an allowable bearing pressure of 10 kips per square � foot, provided the footings are at least 4 feet wide. For the single-story section of the facilityr the structure � ' may be supported on continuous and/ur spread footings bearing on � , the near surface medium dense sandy silts and silty sands. Foot- ings extending into these medium dense undisturbed soils may be � � designed for an allowable bearing pressure of 3 ksf, dead plus live loads. Exterior footings should be bottomed a minimum � � depth of 18 inches below the lowest adjacent final grade. In- , terior footings may be at 12 inches below the top of slab. All footings should have a minimum width of 18 inches. i� When considering the effects of wind or seismic loads, a � ' one-third increase over the above bearing pressures may be used. � Use of the comparatively high bearing pressure will require . , that footing excavations be carefully prepared to avoid distur- bance of the subgrade below footings. Excavation equipment can '- loosen the subgrade, especially if cobbles are encountered. Loosened soil in the footing excavations should be removed or re- compacted by hand tamping. Hackfill used to bring overexcava- - tions back to grade should be lean concrete or pea gravel. Normal construction traffic can also disturb the subgrade, especially if the surface is wet from rainfall or from pockets � of perched groundwater that drain into the excavations. Because the till soils at this site have up to 40 percent fines or more, it will not be possible to recompact these materials after they - absorb excess water. Such materials must be removed to expose firm, undisturbed subgrade. To minimize disturbance to the bearing stratum caused by wetting, the excavations should be - continuously drained of all surface water and the final 6 inches of footing excavations completed just prior to pouring concrete. Loose soils in the footing excavations after final excavation � should be removed. Earth Consultants, Inc. �- -