1209 MADRONA AVE 2016-11-17 - Laserfiche WebLink

Geotechnical Engineering Evaluation Packez� Prop�rty Retaining VtTatls and Steep Slope Evaluation Everett, Washington NGA File Ivo. R7�113 March 11, 2013 Page 5 Exptorations: The subsurface conditions within the site were explored on February 1, 2013 with four hand auger exploraTions. The approximate locations of our explorations are shown on the Schematic 5ite Plan in Figure 2. .A geologist from NGA was present during the explorations, ex�nined ihe soils and geoiogic conditions encountered, obtainec� san�pies of the different sail types, and maintained logs of the hand augers. The soils were visually classified in general accordance with the Unified Soil Ctassification System, pi•esented in Figure 4. The logs of our ha�-�d augers are attached io this report and are presented as Figure 5. VJe present a brief summazy of the subsurface condztions in the following paragraph. For detailed descriptions of the subsurface conditions, the hand auger logs should be revieu�ed. !�t the surface af all of the hand augers, ��e encountered approxirnately 0.2 to Q.3 feet of surficial topsoil. Below the topsoil in Hand Augers l, 2, and �, we eneountered approxzr�ately 3.3 to 4.7 feet of inedrum dense to dense, fine to caarse sand with silt, gravel, and organics, and medium stiff sandy silt u°ith arganics that we interpreted as undocumented fill. Underlying the fiil in Hand Augers 1, 2, and 4 and the topsoil in Hand Auber 3, we encountered very stiff to l�ard, Iight brown to dark gray, sandy silt and silt with sand that we interpreted as native Transitional Bed deposits. The hand au�ers were terminated within the native transitionaI bed deposits at depths in the range of 1.0 to 5.5 feet below the existing ground surface. Flydrologic Conditions Uroundwater seepage was encountered in all of our explorations rangin� from 0.8 feet to �.0 feet beiow the existin� gr�und surface. We also observed naturai groundw�ater seepage emitting from the slope along the western property line, mostly from the neighboring property, «�ithin the vieinity of the block waIls. We interpret all af the ground water fonnd on this site to be a permanent perched groundwater condition. Perched water occurs u,hen surface water infilt:rates through less dense, more permeable soils, such as topsoil and the weathered horizon, and accun�ulates an top of a less peimeable soil, such as the derise!hard glacial soils. Perched water typically does not represent a regional groundwater "table" within the upper sail horizons; however, due to the relatively larbe recharge area surrounding this site, it is aur opinion that groundwater on this site is a chronic enndition that wiil persist thraughout the year. This is consistent with the description provided by the property owner. Perched water tends to vary spatially and fVELSON GEOTECHNICAL ASSOCIA7�ES, tNC.