1718 ENGLAND AVE 2016-01-01 MF Import

[ Geotechnical L'nginecrine Ev:duation England Avenuc Lot � Jmie 2, 2005 NGA File No.41 ISOS Pagc 4 IHydrologic Conditions Groundwater seepage was not encountercd within any of the explorations. Ho��ever, it is our opinion that ( if low pernieability silt Icnses occur within Ihc sand dcposits a perched groundwater condition could develop on this site during the wetter time of the ycar. Perched water a:curs when surface water I infiltrates through Icss dcnsc, more pcmieablc soils and accumulatcs on top of a relativcly impernicablc material. The more penneablc soils consist of the sand, but low permcability silt or silty sand Icnses may I be present within thc sand deposit, which could perch the infiltrating watcr. Perchcd water does not rcpresent a regional groundwater "table" �vithin thc upper soil horizons. Perchcd water tcnds to vary I spatially and is depcndent upon the amount of rainfall. Wc would cspect the amount of perchcd groundwater to decrease during drier times of the ycar and increase during wettcr periods. ISF,IVSITIVE AREr1 �VALUATION Seismic Hazard IMedium densc to very dcnse sand was cncountercd underlyino the site. Based on the 2003 lntern,uiun:d Building Code Q13C),the site conditions best fit the description for Site Class D. 1-Iazards associated with seismic activity include liquefaction potential and amplification of growid Imotion by soft deposits. Liquefaction is causeJ by a risc in pore pressures in a loose, fine sand deposit bcneath the groundwater table. The medium dcnse to very dense sand inte�pretcd to underlic the siic has ia low potcnlinl (or liyucfaclion or amplificalion of��round motion. ILrosion Ha•r.ard The crosion hazarJ criteri:� used for determination of affected arcas includes soil type, slope gradient. Ivegetation cover, and groundwatec conditions. The erosion sensitivity is rclated to veaetative cover anJ the specific surface soil types, which are rclated to the underlying geologic soil units. The Soil Survev, I Snohomish Counlv Area. �Vashincton, by the Soil Conservation Service (SCS) was reviewed to deterniine the erosion hazard of the on-site soils. The site surface soils were classified using the SCS r classification system as Aldenvood-Everett gravelly sandy loam, 25 to 70 percent slopes. This unit is Ilistcd as having .i high erosion hazard (or areas wherc the soils are exposed. It is our opinion th�t thc � erosion hazard for site soils should bc low to moderate in .ueas �vhere ve�ctation is not diswrbed. � NELSON GEOTECHN/CAL ASSOC/ATES, INC. �I I