3505 SHORE AVE 2016-01-01 MF Import

Geotxbnical Enginccring I.etter 3505 Shore Avcnue Deck Addition Evcrett,Washington May 26,2010 NGA Filc No. 827110 Page 5 listal as having a high erosion }�azard for areas whcre the soils are exposed. It is our opinion that the erosion hazard for site soils should be low to moderate in areas where vegetation is not disturbed. LandsIIde Hazard,'Slope Stability The criteria used for evaluation of lendsGde hazards include soil type, slope gradient, and gcoundwater conditions. A steep north-facing slope with a gradirnt of up w approximately 45 degrees(100 pacent) with a height of approximately 100 fcet is located beloa the planned building area. The slope wes well vegetated and we did not observe evidence of recent failures,tension cracks,or seepagc on the slopc. Our exploraGons indicate that t6e core of the steep slope consists Nrimarily of inedium dense to very dense sand. Inclinations of up to 45 degrees an the slope indicate high shength end intemal friction angle within the underlying soils. Relatively shallow failwes as well as sur6cial erosion aro natwal processes and should be expected on these slopes. It is our opinion that while there is potrntial for erosion, soil creep, and shallcw failuros within the loose sur&cial soils on the steep slope; H�e�e is nol a significant potential for dcep-seated slope failure under current site wndiaons. Proper site gtadiug and drainage az recommended in this letter should help maintein r.vrrent stebiliry condilions. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion from a geoYchnical stardpoint t6at the sita is compatible with the plenned construction of a new deck along the north side of the residence. In our opinion the earthwork associated with the planned deck and patio �lab addiUon should be minor and should not have deleterious effects on the adjacent slope if conducted according to the tecommendations presented in this letter. Our explorations indicateA ihat a surficiel layer of loose undocumenied fill extends to depths of 1.0 W 2.0 feet in the area of the planned deck. Beneath the Gll, the explorations encountered medium dense to dense sand soils and sti(f silt in lhe planned development a;rz. We recommend that the new deck footings be extended through any loose soil or undocumrnted fill and be supported on the med:um dense or better native soil. The native soils should provide adequate support for the planned dxk foundarions. NEL50N GEOTECHNICAL ASSOCfATES, INC. �I�� i