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REVIEWED ENG RESUB2 BLD2023-1125+Geotechnical_Letter+3.7.2024_1.49.30_PM+4111600NELSON GEOTECHNICAL ASSOCIATES. INC. March 6, 2024 Bryan Navarro VIA Email: bryannavarro@alderwoodlandscaping.com Geotechnical Plan Review Letter —REVISED Olympic View Drive Landscaping 9309 Olympic View Drive Edmonds, Washington NGA File No. 1443123 Dear Bryan: 17311-135' Ave. N.E. Suite A-500 Woodinville, WA 98072 (425)486-1669 www.nelsongeotech.com This letter presents the results of our geotechnical engineering review of your current plans for your proposed landscaping project located at 9309 Olympic View Drive in Edmonds, Washington. INTRODUCTION We previously prepared a report titled, "Geotechnical Engineering Report — Olympic View Drive Landscaping — 9309 Olympic View Drive — Edmonds, Washington," dated July 7, 2023. We understand that the City of Edmonds is requesting a letter from the geotechnical engineer indicating that the proposed landscaping plans are consistent with the recommendations and findings contained within the geotechnical report for the development. PLAN REVIEW As part of the current plan review, the following documents were reviewed: • Current set of plans titled "Kiewicz-Brooks Residence Stormwater Drainage Site Plan" dated November 20, 2023. • NGA report titled "Geotechnical Engineering Report — Olympic View Drive Landscaping — 9309 Olympic View Drive — Edmonds, Washington," dated July 7, 2023. 0 Drainage inspection letter provided by Bodine Construction dated November 1, 2023. Geotechnical Plan Review Letter —REVISED Olympic View Drive Landscaping Edmonds, Washington NGA File No. 1443123 March 6, 2024 Page 2 The plans show the proposed landscaping area to the northwest of the existing residence. The landscaping includes a hot tub slab, paver walkways, rockeries, and a water feature. It also includes a curtain drain running parallel to the top of slope, approximately 20 feet from top of slope. The drain consists of a 4-inch perforated pvc pipe embedded approximately 4 feet below the ground surface and surrounded by drain rock and filter fabric. The drain connects to a catch basin within the northern corner of the property which then extends downslope. We were provided a drainage inspection letter prepared by Bodine Construction. The letter states that the existing drain line that runs down slope from the residence was inspected with a video camera to confirm there was not existing damage or leaks. An associate of Bodine Construction observed the length of the pipe and noted water was flowing at the base of the hillside from the outflow pipe during cleaning. They also noted that no signs of leaks were found within the outflow pipe. In our opinion, this inspection letter provided by Bodine meets our requirements to confirm the drain is undamaged and in working order. The plans also show that the proposed landscaping will not encroach on the 15-foot buffer from top of slope; however, we recommend a barrier such as a silt fence, be installed to mitigate any traffic within the buffer zone. In our report, we recommended instrumentation be installed near the top of slope to monitor slope movement during and after construction of the project. Due to the proximity of the planned improvements to the bluff, and height of the bluff, along with the addition of a working water feature, we highly recommend that the recommendations of slope monitoring stated in our report be followed. We have reviewed other geotechnical aspects of the provided plans and found the plans to be in general compliance with our recommendations, as presented in our previous report. All other recommendations found in our previous report and letters should be followed. CLOSURE We recommend that we be retained to provide monitoring and consultation services during construction to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not earthwork activities comply with plans and specifications. We should be contacted a minimum of one week prior to construction activities to engage our services; we could also attend pre -construction meetings if requested. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Plan Review Letter —REVISED Olympic View Drive Landscaping Edmonds, Washington NGA File No. 1443123 March 6, 2024 Page 3 We appreciate the opportunity to provide service to you on this project. Please contact us if you have any questions regarding this letter or require further information. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. Daniel J. O'Dell, Project Geologist 3.06.2024 Khaled M. Shawish, PE Principal DJO:KMS:dy NELSON GEOTECHNICAL ASSOCIATES, INC.