3702 TULALIP AVE 2016-01-01 MF Import

� SERS Public Sa 9-1-1 Communication Tower ' P51 Report No. 704-05224-5 December 2G, 2000 __ Page 9 observation and cleaning of the excavation. Drilled piers shouid be spaced a minimum of four pier diameters apart (measured center to center) in order to be considered as acting independently and not as a group. The piers may be designed using a rr�aximum net allowabie end bearing pressure of 15,000 pounds per square foot (ps� for the first 15 feet of embedment in the very dense stratum, and may be increased 900 psf for each additional foot of embedment. An allowable skin friction value of 165 psf may be used for the first 15 feet oF embedment in the very dense stratum, and may be increased 11 psf for each additional foot of embedment. The increases in end bearing pressure and skin friction for each additionai foot of embedment beyond 15 feet are limited to a total pile length of 208, where 8 equais ttie pile diameter. Uplift ski� friction values equal to two-thirds of the allowable skin friction values may be used for uplift design capacity. The allowable end bearing and skin friction values incorporate factors of safety of 3 and 'J_, respectively. Due to the presence of free groundwater at the site and cohesionless overburden soil�, it may be necessary to case the drilled pier excavaticn, depending upon the pier design depth. Any water and loose materials which accumulate at the bottom of tha pier excavation should be removed prior to concrete piacement. If water is present in the bottom of the excavation, a pump should be used to remove the water. If it is not feasib�e to remove the water in its e�tirety (i.e. the pump cannot keep up with the water seepage) then the concrete should be tremied or pumped. The tremie, or pump, should be piaced at the bottom of the excavation so that the concrete pushes the free water up and out of the excavation. The �;ibrator should not be placed in the fresh concrete until all of the free water is pushed out of the hole. The intent o(this placement method is to prevent the (ree water from mixing with the iresh concrete, which wouid potentially reduce the concrete strength. The pier excavation should be filled with concrete immediately following approval by the geotechnical engineer or his representative. Excavations should in no case be allowed to stand open over night. Cast-in-place piers should fill ihe entire excavation. If casing is used, it should be withdrawn as the concrete is poured, while maintaining the casing bottom at a level below the top of the concrete. The geotechnical engineer or his representative should be present during pier drilling and pier concrete placement operations to monitor subsurface conditions and to observe ihe drilled pier excavation prior to concrete placement. If the concrete is allowed to free-fall, the chute should be positioned such that the falling concrete does not come in contact with ll�e sidewall of the excavation or the steel rein(orcing. Typically, the concrete should not be allowed to free-(all a distance greater than 8 feet. When free-fall distances would be greater than 8 feet, a tremie or concrete pump shouid be used to