4003 NASSAU PL 2016-01-01 MF Import

� Geotechnical Engineering Rcport Kvemmo Single-Family Residence � 4003 Nassau Piace, Everett September 17, 2002 NGA File No. 356102 t Page 6 is marginally stable in its current condition. Adding the structure loads and new fill will only worsen the tstabiliry of thc existing fill. ' r I � ' We recommend that the stability of the existing fill be improved by constructing a rock butress at the toe of the fill and a cut-off drain along the top of the fill mass to reduce subsurface recharge into the fill. These measures are described in more detail in the Rock Buttras and Cut-Of'f Drain subscetions of this rcport. Supporting the residence and deck on 4-inch diameter pipe piles should be feasib�e from a geotechnical standpoint, afier the recommended site stabili7ation measures have been completed. Pin piles should provide adequate vertical support for the structure, but are not capable of resisting significant lateral forces. Lateral forces should be resisted by battering some or all of the piles and/or designing a suitable grade beam to provide a passive resistance to the lateral loads. iSupporting basement and garage siabs on the existing fill may also result in some settlement and cracking that might require on-going maintenance. [f slab settlement can not be tolerated, the slabs should be designed as structural slabs and should be supported on pin piles. Hawever, if some risk of settlement �_ can be accepted, the slabs could be"floated" on the fill, after some surEicial fill msdnent has been � completed. 71iis is further discussed in the Slabs-on-Gnde subsection ofthis report. The soils likely to be exposed during construction are highly moisture-sensitive and will disturb essily when wet. We recommend that construction tske place during the drier summer months. However, if construction takes place during the wet season, additional expenses and delays could be expected due to the wet conditions. Additional expenses could include the export of on-site soil, the imQoR of clean, granular soil for fill, and the need to place a blanket of rock spalls in paved areas prior to placing structurel fill. Erosion Control Measures The erosion ha7ard for the on-site soils is considered high when stripped of vegetation and will be dependent on how the site is graded and water is allowed to accumulate. Best Management Practices (BMPs) should be used to control erosion. Areas disturbed during construction should be protected from WELSON GEOTECHNICAL ASSOC/ATES, INC. ^ 1��