12728 19TH AVE SE BASE FILE Geotech Report 2025-07-29

I May 28, 2007 Proposed Office Building L&A Job No. 7A053 Page 3 and west. The cul-de-sac end of 127th Place SE stops at the northwest corner of the site. The site is situated on a broad, very-gentle plain, declining northerly to the nearby Silver Lake. According to the plat plan provided to us, the terrain within the site generally slopes down northerly at grades from about 2 to 10 percent across the site. 1 The site is currently occupied a house and detached garage and storage shed over its central south side. The unpaved area immediately around these existing structures are covered with lawn grass, with the remaining areas dotted with scattered mature deciduous and evergreen trees and covered with thick underbrush. GEOLOGIC SETTING The Geologic Map of the Everett 7.5-Minute Quadrabgle, Snohomish County, Washington, by James P. Minard, published in 1985 by U. S. Geological Survey,was referenced for the geologic and soil conditions of the site. According to this publication,the surficial soil unit at and in the vicinity of the subject site is mapped as Vashon Till (Q . The geology of the Puget Sound Lowland has been modified by the advance and retreat of several glaciers in the past and subsequent deposits and erosion. The latest glacier advanced to 111 the Puget Sound Lowland is referred to as the Vashon Stade of the Fraser Glaciation, which has occurred during the later stages of the Pleistocene Epoch and retreated from the region some 14,500 years ago. The Vashon till soil unit is deposited directly by glacial ice during the most recent glacial period as it advanced over an eroded, irregular surface of older formations and sediments. It is a very dense mixture of unsorted clay, silt, sand, gravel, and scattered cobbles and boulders, often referred to as "hard pan". The Vashon till soils over the top two to four feet are normally weathered to a medium-dense state, and is moderately permeable and compressible. The LIU & ASS OCIATES, INC. I