4624 SEAHURST AVE 2018-01-02 MF Import

March 7, 2011 Mr. Paul Thompson/Kolbear. Inc. L&A Job No. 11-001 Page 6 dispersion over vegetated segments. Driveway may be paved with p-r-%ious pavement to allow runoff to disperse into the ground. Seismic Hazard The Puget Sound region is in an active seismic zone. The site is underlain at shallow depth by fresh very -dense fresh glacial till soils of very -high shear strength. Therefore, it is our opinion that the potential for seismic hazards, such as landslides, liquefaction, lat^ral soil spreading, to occur on the site should be minimal if the erosion mitigation, drainage control, site stabilization measures recommended in this report are fully implemented. The proposed residences, however, shou' m be designed for seismic forces induced by strong earthquakes. Based on the soil conditions encountered by the test pits, it is our opinion that Seismic Use Group I and Site Class D should be used in the seismic design of the proposed residences in accordance with the 2009 International Building Code (IBC). CONCLUSION AND RECOMMENDATIONS GENERAI. The site is underlain by fresh, very -dense till and dense advance outwash soils. The proposed new residences may be supported on footing foundations poured on or into these competent soils. Based on the soil data obtained from the test pits excavated on the site. infiltration trenches may be used along the common lot line of Lots I and 2 for these two lots where sand deposit was encountered by test pits, and surface dispersion may be used on Lot 3 for onsite disposal of roof runoff of the new residences. As most of the site is underlain by fresh till of extremely low permeability, pervious pavement should be considered for the new joint -use driveway to disperse runoff into the ground. LIU & ASSOCIATES, INC.