Laserfiche WebLink
� <br />Geotechnical Engineering Study Page 29 <br />00-2267 Three Story Addition - 500 Laurel Street, Everett <br />January 31, 20G1 <br />Slope Condition Minirtaum Factor <br />of Safety <br />Static - Shallow 1.035 <br />Static - Deep 1.769 <br />Dynamic - Shallow 0.86 <br />D namic - Dee 1.O6F <br />With the exception of the apaarent "failure" of the shallow "face" of the bluff slope <br />under dynamic (earthquake) conditions the slope appears to be stable. Under <br />dynamic conditions it appears tF�at a small segment of the biui� slope may be <br />"sloughed off' the bluff. If this does occurthe potential lateral exter�t (back towards <br />the residence) is sufficiently small as to pose no significant threat to the stability or <br />integrity of the residence. These minimum or most "critical" potential failure <br />surfaces are depicted for informational purposes on Plates G and 7, attached. <br />Summary of Stability: Based on the above, and in consideration of the <br />apparently competent nature of the bulk of the underlying soil, it is our professional <br />opinion that the site's westem slope is generally stable in its current configuration. <br />Based on our observations ofthe existing slope and the subsurFace data generated <br />by our exploratory boring it is also our opinion that the primary mode of failure on <br />this slope, should it occur, is "surficial" in nature. That is, a shallow "wedge" or <br />"slab" of soil (usually covered with vegetation) will slough off the steeper and <br />generally more exposed portion of the slope and will slide to the toe. This form of <br />"failure" tends to re-expose the fresh suils to the elements and restarts the erosional <br />and lan�slide cycle. <br />14 is also our opinion that the bulk of this slope should be expected to remain stable <br />under static and cJynamic conditions in its undisturbed post constructicn <br />configura±ion. As can be seen on Plates 6 and i the "large" failure mass which <br />extends back approximately to ?he perimeter of th�e building exhibits a generally <br />acceptable factorofsafety, particularly when considering the relatively conservative <br />soil parameters used in the analysis. Even under earthquake conditions the risk <br />of a slope failure extending back into close proxirnity of the buildirq should be <br />u �� <br />