5131 DOGWOOD DR 2016-08-31 - Laserfiche WebLink

August 12, 2015 G-3945 Geotechnical Evaluation & Underpinning Engineering Page 2 5131 Dogwood Drive, Everett Foundation settlement of up to about 1.5 inches has occurred along a portion of the east perimeter foundation wall. The footing of the east foundation wall was measured to be approximately 7.5 inches tall and 14 inches in width. The stem wall above the footing is 6 inches wide and 27.5 inches tall. Geology According to the area geologic maps, the site is mapped as Till (Qvt), described as a very compact non-sorted mixture of sand, silt, clay, gravel cobbles and boulders that was deposited directly by, and compacted by, glacial ice during the Fraser glaciation period that ended some 12,000 years ago. Subsurface Conditions The subsurface soil conditions were investigated with a hand auger boring and by probing with a 1/2-inch steel rod. The boring was located next to the east foundation wall in the middle portion of the wall. Soils next to the foundation had been removed down to approximately the base of the wall footing (the starting depth of the boring). The soils encountered in the boring consisted of loose brown sand mixed with some chunks of dark brown organic silty sand (fill) to a depth of about 2 feet below the footing. Below 2 feet, the soils encountered consisted of brown to oxidized red-brown sand with some gravel. A gravel lense was encountered at 2.2 feet below the footing and the boring was terminated due to gravel refusal. Soils below 2.2 feet were probed with a 1/2-inch diameter extendable probing rod and found to be loose to a depth of 6.0 feet below the bottom of the footing. Soils at 6.0 feet below the footing appeared to be dense based on probing. Based on the soil conditions encountered, the sand encountered at a depth of 2 feet below the footing is likely recessional outwash sand that was deposited in a low area as the glacier receded. The fill was likely placed during the initial site development to create a level building site. 1 Minard J. P., 1985, "Geologic Map of the Everett 7.5-Minute Quadrangle, Snohomish County, Washington," Dept. of the Interior, U.S. Geological Survey, Map MF-1748, Scale 1:24,000. GEO Group Northwest, Inc.