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I <br /> May 28, 2007 <br /> Proposed Office Building <br /> L&A Job No. 7A053 <br /> Page 7 <br /> Seismic Hazard <br /> The Puget Sound region is in an active seismic zone. The site of generally gentle terrain is <br /> underlain at shallow depth by very-dense fresh till soils of high shear strength. Also, there is a <br /> lack of extensive, static, static groundwater table at shallow depth under the site. Therefore, the <br /> potential for seismic hazards, such as landslides, liquefaction and lateral soil spreading,to occur <br /> on the site should be minimal. The buildings to be constructed on the site, however, should be <br /> designed for seismic forces induced by strong earthquakes. Based on the soil conditions <br /> encountered by the test pits, it is,our opinion that Seismic.Use Group I and Site Class C should <br /> Ibe used in the seismic design of the proposed residences in accordance with the 2003 <br /> International Building Code(IBC). <br /> I <br /> SITE PREPARATION AND GENERAL GRADING <br /> The vegetation within construction limits should be cleared and their roots thoroughly grubbed. <br /> The existing structures on the site to be demolished should also have their foundations <br /> completely removed. Surficial loose topsoil and medium-dense weathered soils should be <br /> stripped within the building pad, parking lot, driveways and in areas where structural fill is to be <br /> I] placed. The exposed surface should be compacted to a non-yielding state with a vibratory roller <br /> compactor and proof-rolled with a fully loaded dump truck or water truck. During construction, <br /> storm runoff and groundwater seepage, if any, should be intercepted with ditches or interceptor <br /> trench drains, as required, to minimize soil erosion and to facilitate site grading work. <br /> Intercepted water should be conveyed into a nearby street-side storm inlet. The storm inlet <br /> should be covered with a filter sock to prevent sediment from entering the storm sewer system. <br /> �. The filter sock should be cleaned frequently to prevent clogging. <br /> The on-site surficial soils contain a high percentage of fines and are sensitive to moisture. A <br /> layer of clean quarry spalls should be placed over excavated areas and areas of frequent traffic,as <br /> required, to protect the subgrade soils from disturbance by construction traffic. Silt fences <br /> LIU & ASSOCIATES, INC. <br /> I <br />