1621 ENGLAND AVE 2016-01-01 MF Import

Pebruary 27, 2009 Sullun Crossing L&A Job No. 9A008 Pagc ? and soil conditions of Uic sitc. According to this publication, the suriiciul soil units at and in thc vicinity oP the subject project sitc are mapped as Csperancc Sand (Q�) deposits undcrlain by Whidbey formntion (Q��.). "I�he geoiogy of the Puget Sound Low�and has becn modilicd by the advance and retreat of several glacicrs in thc past and subscquent deposits and crosion. "I'hc latest glacicr advanced to the Puget Sound Lowland is refcrzed to as i:re Vashon Stadc of lhe rrascr Glaciation, which has occuned during the later sta�;cs of thc Pleis�ocene Lpoch and retreated Gom the region somc 14,500 ycars ago. "I'he Gsperance sand soil unit is composcd oCproglacial Iluvial and lacuslrine deposits laid down by slo�v-moving meltwater strcams from the advancing but distant Vashon �I�cier. It gcncrally consists of light-brown to light-gray, well-sorted, fine-to-mcdium-gr�ined sand. Also included in lhis soil unit are occasional Icnscs of thin silt or coarse sand :md small gravcL In confined situations, tlie rsperance sand deposits arc generally in dcnse to vcry dense state and azc quite stablc. 7'hey, however, can subject rather casily to raimvash erosion and gullying, and may loosen and slough to its anglc of repose �ti�hen exposed on slopes dcvoid of vegetntirni. Thc redeposited sand soils on slopes arc loose a��d have a tendency to creep slowly downhill, while thc underlying undisturbed native sand soils are stable .md can providc good foundation support to struclures. The Whidbcy formation underlying the I:spemnce sand deposits is cotnposcd of non-glacial river Ilood-plain deposits. It wnsists of ligl�t-bro�m to gray, fine-sandy silt to clayey silt with occasional graveL The Whidbey formation deposits are generally very-stii7'to hard as diey hact 6cen ovco-consolidated by Vashon Glacic�. Thcy are of extremely low pernieability and tends to perch sromtwater infiltrating into the more permcable surficial soils. Seepage would emergc out of slopcs wherc the �Vhidhcy 1'ormation is esposcd. When the seepage pressure is high, the LIU & ASSOCIATCS, INC. �S