5902 EVERGREEN WAY HOUSING HOPE 2018-01-01 MF Import

t Subsurfnce Erp/oratton, Geolagic Ha:ard, and � Noruing llope PJust!/ Prrlimi�wr� Gtotahnica!Engineering Rcpart F.rrrrtt. Rasi:iagron Yroj�ct anJ Site Conditions � The following section pre�ents more detailed subsurface infonnation organized from the u��er (shalluwestl to the lower (derpest) soil tyges. � d.l $tI3l�lf�ph�' f'�tll � �tan-placed fill consisting of loose, moist, gray silry sand widi gravel, trash and woody debris � was identifirci in EP-3, EP-I, EP-6, and EP-7. A relict topsoil horizo❑ was occasionally present beneath the fill. The fill/relict topsoil extended to a maximum depth of 4 feet in EP-3. The fill was likely derived from grading of the residential por�ion of the lot to the west of die proposed building sit�. The stecp, 2H:IV (HorizontaL•Verticall slopes along the w�est site � boundary are [ikely composed of fill �ni! that w:u pushed over the embankment duriug construction of the building pads for the exis[ing strucmres. Abundant cons�*uction debris and � trash wa�s observeci �aithin the shallow s;irficial soils comprising chese slopes. Recessrona! Ourn�ash ( Loose eradin� to mr,ciium dense, red-brown to gray sand with varying silt content and some gravel was eocountered in all ezploration pi[s to depths ranging &om I.5 feet ia EP-1 to � greater than 16 fee[ in EP-3. In general, these sediments were loose oxidized, silty, and contained roots to a maximum depth of 7 feet in EP-3 grading to medium dense, gray, clean to f slightly silty with depth. At an approsimate depth of 13 to 14 feet in thc vicinity of EP-2 and EP-3, [hese sedime�cs became very moist and interbedded with dense silty fine sand. In EP-2, ' this denser ma[erial was interprcted as till. The medium dense outwash is suitable for shallow I spread footing foundations and pavement support, provided our recommendations are followed. Infiltracion may also be feasible withio this sediment ptovided fl�ere is enough site area and sufficient permeable soil depth to constn;ct appropriate infr;dration facilities. Once a 1 target infiltration design concept and area have been established by the design team, we can . further evalua[e soil contiitions as necessary. ( Till � Giacial soils beneath the outwash are interpreted as Vashon till. The till generally consists of I dense to very dense, moist to wet, silty sand with gravel and cobbles. Several thousand ieet of ice consolidated these sediments approximately 14,000 years ago during the last southward � glacial advance into the Puget Sound. This process resulted in a compact soil possessing high strength, low compressibil�.ry, and low permeability charactcristics. Till was encountered at depths ranging from 1.5 to 13 feet beneath the property. [n general, till was encountered at � shallow depths on the east half and south end of the property and below approximately 13 to 14 feet in the nor[hwest corner of the site. The dense to vzry dense till is also suitable for foundation support, but is not suitable for infiltration. IFebrtrary !1, 2002 ASSOClATED F14RTf1 SClENCES, INC. S.7L-N�K£01 if7A:�P�prn'�.:UJI if9�REIWP�µ^.X Page 4 � r S/ � 73