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JAM-22-9E FRI 14:19 <br />DAVID L. NELSON AND ASSOCIATES. INC. <br />• Consulting EngintednR Geunugv <br />October 10, 1990 <br />project Ito. 9490 <br />page 2 <br />findings of the eubcurface conditions, including soils and hydrologic <br />conditions, and our conclusions and recommendations for developnant and <br />constnsctiai within the site area. In general, we concluded that the <br />evaluated site area should bo canpatable with the proposed residential <br />development. We then presented our rocannendations for development and <br />construction of the proposed residences within the lot areas. <br />The fnformation presented in this letter should be considered as additional <br />and eupplesontal inform3tjon to our original geotechnical evaluation report on <br />the site area. <br />SMITIVH AyTA EVAUWICH <br />%fie subject site area was evaluated for sensitive area evaluation, as <br />reconoeded in the now ordinance. of the potential reasons for classification <br />as nsnlirramentally sensitive (onviroraventally sensitive characteristics), the <br />following could occur on site; unstable soils hazard areas, landslide hazard <br />areas, seismic hazard arean, springs, ground water seepage, and steep slopes <br />associated or in conjunction with one or more of the onvirumuntally sensitive <br />area elensnts. we will discuss these potential elosnants below. <br />seismic Hazard <br />The Puget Saud region is classified as a zone 3 by the Uniform Building Code. <br />Seismic considerations for this type of site include liquefaction potential <br />and attenuation of ground .rations by soft soil deposits. Typically, seismic <br />hazards are highest for thick alluvial (organic and/or normally consolidated) <br />soils. The liquefaction potential is highest for loose sand and silty sand <br />deposits with a high ground water table. The thickness of the sand deposit <br />should be considered, an liquefaction is dependent on the ability of excess <br />pore pressures to dissipate. That is, if the deposit is relatively thin with <br />a short drainage lath, tho pore pressures can dissipate fairly rapidly. <br />We did not encounter any alluvial type soils on site which are typically <br />liquefaction sensitive. We did not find a significant thickness of fill or <br />