1600 W MARINE VIEW DR 2016-01-01 MF Import

1 , 1 1 1 1 July 30, 1997 HWA Project No. 96028 ert►bedded only severel fat into the underlyin8 glacial drift deposit. Coneequanly, if concrete piles are used on this project, we anticipate that use of an impact hunmv combined with jetting may be rcquired to achieve the recomma�ded embedmert deptha without danuging the piles. Ahematively, pn-diilling or tlu use of an H-pile "stingd' attached to the bottom of the pile may be considered in fieu of jetting. HWA is available to provide addiaonal recommendations for these alternatives, if necessary. It should be noted that conducting jetting and pre-drilling under water will create some disturbance and sedimentation. The contractor should use reasonable precaudors to reduce the amount of disturbance created by the pile driving activities, and comply with any regulatory requiremenu goveming such activities. , All pites should be driven using an approved top-impact hammer. We recommaid an impact hemmer with a ma�dmum rated driving energy between 45,000 aod 80,000 foot- , pounds. Selxtion of an appropriate hammer will depend on the pile types �nd stcdona selected for use on the project, the contractor's methods, and other factors. F6ad lads should be udlized to reduce the potemial for the piles being d[iven out of alignme�. ' 1 t 1 , 1 LJ' 1 ' 1 Following selxtion of a pile hammer, cushioq and driving system, HWA should be consulted to provide criteria for final driving raistance, using an appropriate dymmic pile driving analysis. The driving resistance criteria should be detecmined by incorpoRting the contractor-proposed hamma/cushion system into the analysis. All pile driving operadons should be observed by the geotechnical consultant, or his representative expaienced in the design and observation of pile foundation installations. Local variations in subsurface conditions should be anticipated. This is partiwlarly the case since offshore borings were not performed. As a result, actual pile lengths may vary. We therefore recommend the pile driving conuact be structured to allow for adjustmmt for pile payment, based on actual pile lengths installed. Furthermorc, several boulders on the order of 1 to 2 feet in diameter wero observed within utility mnches excavated in the hydraulic fill. These oversize particles could impede pile installation. The contractor should be prepazed to deal with such obstacles during pile installedon. 6.0 UNCERTAINTY AND LIIYIITATIONS We have prepared this report for the PoR of Everett and the Reid Middleton design team for use in the design of a portion of this project. This report should be provided in its entirety to prospective contractors for bidding and estimating purposes; however, the conclusions and interpretations presented in this report should not be constcued as a warranty of the subsurface conditions. Experience has shown that subsurface soil and groundwater conditions can vary significantly over small di�tances. Inconsistent 96028RF.DOC 10 HoNa Wesr B Asaocu�s, Ir�c.