2222 EVERETT AVE 2016-01-01 MF Import

i Subsurface Ecpforation, Geo(ogic Na:.nrd, and Evercrt Schooi District Mainlenancc Facrliry Preliminary Geotechnicaf Engincering Repon Everett, Wathington Deslgn Recomniendarioru / II. GEOLOG[C 1{AZARDS AND MITIGATIONS The following discussion of potential geologic hazards is based on die geologic, slope, ground water, and surf'acc water conditions as observed and discusscd herein. The discussion will be lunited to seismic, erosion hazards, and landslide hazards. 5.0 SEISMIC HAZARDS AND RECOMMENUED MIT[GATION Earthquakcs occur in the Puget Lowland with gmat regularity. 1'he vast majority of these events are small and are usually not felt by people. However, large earthquakes do occur as evidenced by the 1949, 7.2 magnitude evcnt, the 1965, 6.5 magnitude event, and the 2001, G.8 magnimde event. The 1949 earthyuakc appears to have been the largest in this area during recorded hisrory. Evaluation of return rates indicares that an earthquake of a magnitudc between 6.0 and 7.0 is likcly within a given 15- to 20-year period. Generally, there are four types o( potential gcologic hazards associatec; with large seismir events: 1) surficial ground rupmre; 2) seismically induced landslides; 3) liquefaction; and �i) ground motion. The potential ti>r cach of these hazards ro adversely impact the proposr�l � project is discussed below. 5.1 Surficial Ground Rupmre Gcnerally, the largest eard�quakes, ��hich have occurred in the Puget Sound area, are suh- crustal events with epicentcrs ranging from 50 to 70 kilometers in depth. For this reason, no surficial faulting or earth rupmre, as a result of deep, seismic activiry has been documented, tu date, in the vicinity of the site. "Thereforc, it is our opinion, based on existing geologic Jata, that the risk of surface rupture impacting the proposed project is low and no mitigations are necessary. 5.2 Seismically Induced Landslides Based on the existing geologic data and thc lack uf existing or proposed slopes at the site, it is our opinion, that the risk of scismically in�uccd landslides is low and no mitigation efforts arc necessary. 53 Liquefaction The encountered stratigraphy at the site has a low potential for liquefaction due to the grain size of the on-sit� soils, its generally medium dense/stiff to very stiff state, and lack of Csignificant shallow ground water. No mitigation efforts are necessary. May !, 2001 ASSOCIATED EARTN SCIENCES, INC. JDC/dn-KEOIOSIA!-D:Iup4IaIJ-01-IY'A Page 5 t.:/