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Geotechnical Evaluation.pdfRECEIVED • Group Northwest, Inc. February 15, 2018 Mr. James Corier 2901 Rucker Ave, #718 Everett, WA 98201 Subject: GEOTECHNICAL EVALUATION Proposed Tree Removal on Slope 8732 - 209'" Place SW Edmonds, WA Mr. Corier, FEB 2 G 2030 DEVELOPMENT SERVICES COLWER Ceolcchnical Engineers. Geologi*4 & Cnvironrncoal Spccialisis G-4619 We understand the a tree is proposed to be cut down at 8732 - 209" Place SW in Edmonds, Washington. The tree is located on a steep slope behind the house and the tree is leaning toward the house. The City of Edmonds has requested a geotechnical evaluation to evaluate whether the tree removal will impact the stability of the slope and whether replacement trees should be planted to improve the stability of the slope. A site visit was conducted by Wade Lassey with GEo Group Northwest, Inc., on February 14, 2018, for this purpose. Site Conditions The site is located on the northwest flank of the upper Shell Creek drainage in a residentially developed area. The subject tree is located on the steep slope on the east side of the home and the home is located at the top of the slope. The height of the slope is estimated at around 50 feet with a gradient of approximately 40 percent. A neighboring home is located at the bottom of the slope on Pioneer Way. The tree to be removed is a tall pine, approximately 17 inches in diameter, located on the upper portion of the slope. The slope is well vegetated with trees and ornamental plants. No visual indicators of slope instability were observed such as past slumps or slides. No soil tension cracks were observed. The slope appeared to be stable. 13705 Bel -Red Road • Bellevue, Washington 98005 Phone 425;'649-8757 - Fax 435f649-8758 February 15, 2018 G-4619 Geotechnical Evaluation Page 2 8732 - 209`h PL SW, Edmonds Geology According to the area geologic maps, the soils at the top of the slope appear to be mapped as Glacial Till (Qvt), described as a compact nonsorted mixture of sand, silt, clay and gravel deposited under glacial ice. Soils on the slope below the house appear to be mapped as Advance Outwash (Qva) deposits, described as m0lostly clean, pebbly sand, with cross and horizontal stratification. The Advance Outwash stratigraphically underlies the Glacial Till. The soils were deposited during the Vashon stade of the Pleistocene Fraser glaciation period that ended some 14,000 years ago. Conclusions and Recommendations Based on our site observations the slope appears to be stable. It is our professional opinion that cutting down of the tree will not negatively impact the stability of the slope. We recommend that the tree stump will be left in place and not be removed. In general, the presence of trees and vegetation on slopes has a stabilizing effect on the upper soil zone. Existing trees and vegetation appear to be relatively dense and well established in the area where the tree is to be cut. It is our opinion that planting replacement trees in the immediate area where the tree is to removed is not needed from a geotechnical perspective. If replacement trees are to be planted, we recommend locating them on the slope east of the southern portion of the house where the existing trees and shrub vegetation is not as dense and the ground surface is covered with ivy. Limitations This report has been prepared for specific application to the proposed tree removal. The findings and recommendations stated herein are based on our field observations, the documents reviewed, our experience and judgement. The recommendations are our professional opinion derived in a Minard J. P., 1993, "Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington," U. S. Dept. Of The Interior, U. S. Geological Survey, Miscellaneous Field Studies Map MF-1541, Scale 1:24,000. GEO Group Northwest, Inc. February 15, 2018 Geotechnical Evaluation 8732 - 209'h PL SW, Edmonds G-4619 Page 3 manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area and within the budget constraint. No warranty is expressed or implied. Please contact us if you have any questions. Sincerely, GEO GROUP NORTHWEST, INC. Wade J. Lassey Engineering Geologist William Chang, P.E. Principal GEO Group Northwest, Inc.