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� May 7, 2001 � <br /> Rockery—Pete Peters Residence <br /> L&A]ob No. 1058 <br /> Page 2 <br /> GEOLOGIC SETTING <br /> The Geolo i�Map of the Everett 7.5-Minute OuadranKle. Snohomish County Washington, by <br /> James P. Minazd, published by U. S. Geological Survey in 1985, was referenced for the geologic <br /> i and soil conditions at the your property. According to this publication, the surficial soil units at <br /> and in the vicinity of the site is mapped as Vashon Till (Q� underlain by Advance Outwash <br /> �Qv� <br /> TLe geology of the Puget Sound Lowland has been modified by the advance and retreat of severai <br /> " glaciers in the past and subsequeat deposits and erosions. The latest glacier advanced to the <br /> Puget Sound Lowland is referred to as.the Vashon Stade of the Fraser Glaciation wlrich had <br /> occurred during the later sta�es of the Pieistocene Epoch, and retreated from the region some <br /> 14,500 years ago. <br /> The Vashon Till was deposited direcfly by glacial ice during the most recent glacial period as it <br /> advanced over an eroded, irregulaz surface of older for�tions and sediments. It is a very dense <br /> mixture of unsorted clay, silt, sand, graval, and scattered cobbles and boulders, often referred to <br /> as "hazd pan". The Vashon Till over the top two to three feet is weathered to a medivm dense <br /> state, and is moderately permeable and compressible. The underlying fresh till is very dense and is <br /> practically impervious to stormwater infiltration. The fresh till has �ihe suength of low-grade <br /> concrete and can stand in a steep natural or cut slope for a long period. If remain� undisturbed <br /> and well-drained, the fresh till can provide excellent foundation support with littke settlement <br /> expected. <br /> The Advance Outwash consists of stratified sand and grau�l with minor amounts of silt and clay, <br /> deposited by the meltwater oF advancing glacial ice. Due to its ganulaz composition, the <br /> Advance Outwash is of relatively lvgh permeability and is generally well-drained. The Advauce <br /> Outwash is glaciatly overridden and is general(y dense to very dense in its natural, undisturbed <br /> state. It can stand in steRp cuts or natural slopes when undisturbed. When stripped of vegetation <br /> LIU&ASSOCIATES,INC. Z/ <br />