3702 TULALIP AVE 2016-01-01 MF Import

SERS Public Safc -1-1 Communication Tower PSI Report No. 704-05224-5 Decerc�ber2G, 2000 Page 10 mitigate the potential for concrete component segregation. Once placed, the concrete should be properly vibrated for the fuil depth of the pier in accordance with ACI recommendations. The drilling contractor should be prepared with appropriate and adequate equipment with sufficient size and torque for drilling into the very dense silty sand with gravel stratum. 5.4 Equipment Building Foundation S�rppoK Based on the results of our geotechnical investigation, it is our opinion that!he proposed iightly loaded equipment building can be supported on a conventional shallow foundation designed for a maximum allowable soil bearing pressure of up to 3,000 psf, when founded on the undisturbed, stiff silty lean clay, or on an engineered, granular structural fill placed overlying the stiff silty lean clay stratum. The allowable bearing pressure stated above includes a safety factor of 3 and is intended for dead loads and sustained live loads and can be increased by one-third(or the total of all loads, including short-term wind or seismic loads. Continuous and isolated footings should be at least 18 and 24 inches in width, respectively and extend to a minimum depih of 18 inches beneath the lowesl adjacent exterior grade to provide frost protection. The structure should be constructed at le:•st 10 feet laterally from the top of any slopes, which should be permanently graded no steeper than 2 horizontal: 1 vertical. Allowabie lateral irictional resis!ance between the base of footings and the subgrade can be expressed as the applied vertical load multiplied by a coefficient of friction of 0.30 for the very dense native silty sand with gravel soil. In addition, lateral loads may be resisted by an passive earth pressure based on an equivalent fluid density of 260 pounds per cubic foot (pc� on footings poured"neaP'against in-situ soils or properly backfilled with granular slructural fill, respectively. These recommended values include a factor of safety o(approximately 1.5, which is appropriate due to the amount o(movement required to develop full passive resistance. We estimate that foundations designed and constructed in accordance with the above recommendations will experience to!al settlements yenerally less than 1-inch with differentiai settlements between columns generally less lhan Y-inch. If footings are constructed during wet weather, it may be necessary to protect the founda�ion excavation bottorr�s from disturbance during construction activities. In this regard, we recommend that a 3 to 4-inch thickness of crushed rock be placed at the bottom oF the footing excavations immediately after the excavation is completed. If(notings are constructed during the drier swiimer months, this crushed rock layer should nol be required.