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ENG GEO TECH REPORT• Group Northwest, Inc. July 24, 2017 Mr. Steve Lovell 8312 Talbot Road Edmonds, Washington 98026 ritme0nical Engineers. Geologists & Enviroammw spocialiw G-3384 Subject: GEOTECHNICAL EVALUATION OF TIERED MODULAR BLOCK WALLS 8312 TALBOT ROAD, EDMONDS, WASHINGTON Dear Mr. Lovell. GEO Group Northwest, Inc. has completed its geotechnical inspection and evaluation activities regarding your construction of tiered modular block walls at the above -subject location in Edmonds, Washington. PROJECT DESCRIPTION The subject property is a residential lot on which you have been constructing a series of tiered modular block walls in the upward -sloping rear yard area. We visited the site on June 16, 2017, and met with you to discuss and evaluate the constriction of the walls. We observed that much of the construction has been completed, and that a limited amount of block and backfill placement remained to be done. We also reviewed photographs that you had taken during your construction of the walls. These photographs showed the placement of the blocks, drain pipe and drainage zone behind the blocks, geogrid layers, and backfill placement and compaction. We also reviewed the recommendations in the geotechnical engineering report prepared by Liu & Associates, Inc. dated June 12, 2006, regarding the walls and the on -site project plans for the walls. We observed that the walls had heights of 4 feet or less, and that the horizontal distance between the wall tiers typically was 4 feet. We noted that there is one area where the horizontal spacing 11705 Bea -Red Road, Belk: uc. 14 . ,h ! e!"n SJsi ON Phone 425/649-6757 Fax 425i044-s 58 July 24, 2017 G-3384 Mr. Steve Lovell Page 2 was approximately 3 feet. This area is located between the top two tiers in an area where the walls have a pronounced nearly U-shaped concave -inward curvature, forming a local, narrow promontory. This feature imposes significantly less load than a typical tier or backslope, because of its limited width as measured perpendicular to the face of the walls. During our visit, we reviewed photographs that you had taken during your construction of the walls. These photographs showed the placement of the blocks, drain pipe and drainage zone behind the blocks, geogrid layers, and backfill placement and compaction. We also reviewed the recommendations in the geotechnical engineering report prepared by Liu & Associates, Inc. dated June 12, 2006, regarding the walls and the on -site project plans for the walls. We observed that backfill behind the zone of drain rock consisted of sandy site soils. We probed the exposed fills by using a 0.5"-diameter steel T-bar probing rod. Based on our probing, we found the fills to typically be competent and medium dense in condition, except in a few locations where we were able to probe to depths ranging between 6 and 12 inches. We recommended that these area be moistened and compacted further by using a large plate compactor, and then be checked again. On June 26, 2017, we re -visited the site and met with you to update our observations and evaluation of the backfill that we recommended be further compacted. You informed us that the areas had been moistened and re -compacted using a large plate compactor per our recommendation, and we observed imprints from compaction on the exposed fills. We probed these areas and found them to be competent and medium dense to dense in condition. CONCLUSIONS Based upon our observations, it is our opinion that the tiered modular block walls have been constructed in an adequate manner that is consistent with the recommendations in the Liu & Associates geotechnical report referenced herein, with which we concur, and the plans we reviewed during our visits. It is also our opinion that the walls present minimal risk to the stability of the site and adjacent property. LINUTATIONS Our findings and recommendations stated herein are based on field observations, our experience and judgment. The recommendations are our professional opinion derived in a 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 GEO Group Northwest, Inc. J July 24,2017 G-3384 Mr. Steve Lovell Page 3 constraint. No warranty is expressed or implied. In the event that site conditions not anticipated in this letter are encountered during construction, GEO Group Northwest, Inc. should be notified and the above conclusions and recommendations should be re-evaluated, and revised where appropriate. CLOSING If you have any questions regarding this report, or if we may be of further service, please do not hesitate to contact us. Sincerely, GEO GROUP NORTHWEST, INC. Keith Johnson Project Geologist r ' William Chang. PE V Principal Engineer `'jsed Geo,- KEIT'H A. JOHNSON GEO Group Northwest, Inc.