1228 GRAND AVE Geotech Report 2022-10-25

April 7,2008 Mr.Don Levin L&A Job No. 8A037 Page 6 Progressive erosion may result in shallow, skin-type mudflows on the steep slope. To mitigate such hazard, the vegetation cover outside of construction limits should be preserved and maintained, and concentrated stormwater should not be discharged uncontrolled onto the steep slope or anywhere within the site. Storm runoff over impervious surfaces, such as roofs and paved driveway should be captured with underground drain line systems tied to roof downspouts and by catch basins installed in paved driveway. Water collected into these underground drain lines should be tightlined to discharge into a nearby storm sewer. Yard waste and spoil soils should not disposed of onto the steep slope. Exposed unpaved ground resulted from construction activities should be re-vegetated as soon as possible. If the above recommendations are implemented and observed during and after construction,the erosion hazard of the site should be minimal. SEISMIC HAZARD AND DESIGN CONSIDERATIONS The Puget Sound region is in an active seismic zone. The subject site is underlain at shallow depth by dense silty fine sand and hard fine sandy silt soils of high shear strength. There is a lack of continuous,extensive groundwater table at shallow depth under the site. The combination of the above should make it rather unlikely for seismic hazards, such as liquefaction or soil lateral spreading, to occur on the site during strong earthquakes. Therefore,the seismic hazard for the site should be minimal. The proposed new residence should,however, be designed to withstand 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 2003 International Building Code(IBC). LIU & ASSOCIATES, INC.