1212 GRAND AVE 2016-01-01 MF Import

March 31, 2008 Mr. Paul Tessier L&A Job No. 8A027 Page 3 the Puget Sound Lowland is referred to as the Vashon Stade of the Fraser Glaciation, which has occurrcd during the later stagcs of the Pleistocene Epoch and retreated from the region some 14,500 yc:us ago. The Vashon till soil unit is depositcd direcUy by glucial ice during thc most recent glacial period as it advanced over an eroded, irregular surfacc of older formations and sedimcnts. It is a vcry dcnse mixture of unsorted clay, silt, sand, gravel, and scattcred cobbies and boulders, often rcicrred to as "hard pan". The V;�shon till over the top two to four feet is normally weathered to a medium-dense state, and is moderately permcable and compressible. The underlying fresh till is very dense and is practically impervious to stormwatcr infiltration. The Gesh till has the strength of low-grade concrete and can stand in a steep natural or cut slope for a long period. If rcmains undisturbed and well-dr�ined, the fresh till can provide excellent foundation suppoR with IitUe scltlement cxpected. Thc advancc outwash soil unit undcrlying thc Vashon !ill is compused of stratificd sand and gravcl with minor amounts of silt and clay, dcposited by thc mcltwatcr of advuncing glacial icc. Duc to thcir gencrally granular com�msition, the advance outwash deposits are of moderately high pemieability and generally drains fairly well. The advance outwash deposits are glacially overriddcn :uid are generally dcnse to very dense in its natural, undisturbed state,except the top 2 to 4 fect where cxposed on slopes which may be wcathered to a loose to medium-dense slate. "1'hc advancc outwash dcposits can stand in stcep cuts or natural slopes for extended period when undisturbcd. Whcre exposed on slopcs with Ewor vegetation cover and subject to storm runotTor groundwater seepagc, thc advance outwash deposits can be gradually eroded and may slough and redeposit to a flatter inclination. �l'hc underlying fresh advance outwash deposits in their native, LIU & ASSOCIATES, INC. _ , .