1130 RAINIER AVE Geotech Report 2025-07-28

Everett Housing Authority JN 12080 May 16, 2012 Page 6 the top of the pile during driving. If the piles are installed by alternative methods, such as a vibratory hammer or a hammer that is hard-mounted to the installation machine, numerous load tests to 200 percent of the design capacity would be necessary to substantiate the allowable pile load. The appropriate number of load tests would need to be determined at the time the contractor and installation method are chosen. Although it is difficult to determine the final depths of the piles, we anticipate approximately 10 feet of pile embedment into the competent native soils to achieve the noted capacities. As a minimum, Schedule 40 pipe should be used. Due to the existence of peat soils, which can corrode metal, we recommend the piles be galvanized. Pile caps and grade beams should be used to transmit loads to the piles. Isolated pile caps should include a minimum of two piles to reduce the potential for eccentric loads being applied to the piles. Subsequent sections of pipe can be connected with slip or threaded couplers, or they can be welded together.. If slip couplers are used, they should fit snugly into the pipe sections. This may require that shims be used or that beads of welding flux be applied to the outside of the coupler. Lateral loads due to wind or seismic forces may be resisted by passive earth pressure acting on the vertical, embedded portions of the foundation. For this condition, the foundation must be either. poured directly against relatively level, undisturbed soil or be surrounded by level compacted fill. We recommend using a passive earth pressure of 300 pounds per cubic foot (pcf) for this resistance. If the ground in front of a foundation is loose or sloping, the passive earth pressure given above will not be appropriate. We recommend a safety factor of at least 1.5 for the foundation's resistance to lateral loading, when using the above ultimate passive value. Due to their small diameter, the lateral capacity of vertical pipe piles is relatively small. However, if lateral resistance in addition to passive soil resistance is required, we recommend driving battered piles in the same direction as the applied lateral load. The lateral capacity of a battered pile is equal to one-half of the lateral component of the allowable compressive load. The allowable vertical capacity of battered piles does not need to be reduced if the piles are battered steeper than 1:5 (Horizontal:Vertical). PERMANENT FOUNDATION AND RETAINING WALLS Retaining walls backfilled on only one side should be designed to resist the lateral earth pressures '• imposed by the soil they retain. The following recommended parameters are for walls that restrain level backfill: PARA-NI FITER VALUE Active Earth Pressure* 35 pcf 1 Passive Earth Pressure 300 pcf 1 Soil Unit Weight 130 pcf Where: (I) pcf is pounds per cubic foot, and (ii) active and passive earth pressures are computed using the equivalent fluid pressures. *For a restrained wall that cannot deflect at least 0.002 times its height,a uniform lateral pressure equal to 10 psf times the height of the wall should be added to the above active equivalent fluid pressure. GEOTECH CONSULTANTS,INC.