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Kierstein Residence Retaining Wall Everett, Washington Geotechnical Engineering Report evergreen and deciduous trees with a light to moderately dense understory of blackberry brambles and other low-lying native shrubs. Based on discussions with you regarding different potential wall replacement options and your discussions with wall contractors, we understand you have selected the SierraScape retaining wall system. The face of the wire -formed wall elements will be not be vegetated but backfilled with gravel. AESI has prepared this geotechnical engineering report in support of the selected wall type. 1411Il":lgKO -11%lI:QL Our field study included drilling two exploration borings at the top of the slope (top of the upper wall) and advancing two exploration borings near the bottom of the lowermost wall. The two borings at the top of the upper wall were drilled using a small rubber -track hollow stem auger drill. The two borings situated near the bottom of the lowermost wall were drilled using a portable "Acker" drill using hollow stem auger tooling. The locations of the exploration borings are shown on Figure 2 (Site and Exploration Plan). The various types of sediments, as well as the depths where the characteristics of the sediments changed, are indicated on the exploration logs presented in Appendix A. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types. If changes occurred between sample intervals in our explorations, they were interpreted. Our explorations were approximately located in the field by measuring from known site features depicted on the topographic survey. The conclusions and recommendations presented in this letter -report are based, in part, on the explorations completed for this study. The numbers, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may sometimes be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this letter -report and make appropriate changes. Hollow -Stem Auger Borings The exploration borings for this study (EB-1 through EB-4) were completed by advancing a 7-inch, outside -diameter, hollow -stem auger using a drilling company subcontracted by AESI. During the drilling process, samples were generally obtained at 2%- to 5-foot-depth intervals. The borings were continuously observed and logged by an engineering geologist from our firm. The exploration logs presented in Appendix A are based on the field logs, drilling action, and observation of the samples collected. Disturbed but representative samples were obtained by using the Standard Penetration Test (SPT) procedure in accordance with American Society for Testing and Materials (ASTM) D-1586. July 1, 2022 ASSOCIATED EARTH SCIENCES, INC. SASlih - 20180614EO01-002 Page 2