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REVIEWED ENG RESUB 3-BLD2022-0527+Geotech Report-PIPE ANCHORS+2.6.2024_4.47.33_PM+4043753RESUB Feb 07 2024 CITY OF EDMONUS DEVELOPMENT SERVICES DEPARTMENT 17311-13511 Ave. N.E. Suite A-500 Woodinville, WA 98072 NELSON GEOTECHNICAL (425) 486-1669 ASSOCIATES. INC. www.nelsongeotech.com BLD2022-0527 February 6, 2024 Mr. Robert Gregg Gregg Property and Associates, LLC Via Email: rrgregg@comcast.net Geotechnical Comment Response Letter Westgate Station Commercial Development 9601 Edmonds Way Edmonds, Washington NGA File No. 1156720 Dear Mr. Gregg: This letter presents our geotechnical engineering comment response regarding for the proposed Westgate Station Commercial Development project located at 9601 Edmonds Way in Edmonds, Washington. INTRODUCTION We understand that the proposed development for the property will include the construction of a new commercial building within the central portion of the property along with associated paved parking areas and underground utilities. We previously prepared a geotechnical evaluation for the site dated April 14, 2020 along with a plan review letter dated March 24, 2023. In general, we concluded that the planned site development was feasible from a geotechnical standpoint. We understand that the City of Edmonds has requested additional information regarding the geotechnical aspects of this project in a letter dated December 1, 2023. For our use in preparing this plan review letter, we have been provided with the following documents: • Civil plan set titled "Westgate Station," dated February 7, 2024, prepared by CG Engineering. In the following section, we summarize the City's comments and our responses. Geotechnical Comment Response Letter NGA File No. 1156720 Westgate Station Commercial Development February 6, 2024 Edmonds, Washington Page 2 CITY OF EDMONDS REVIEW COMMENTS AND OUR RESPONSES Sheet C3.1 Grading and Drainage Plan Stormwater Review Comment 12: 12101123 Please provide documentation that the geotechnical engineer has reviewed and approved the pipe anchor design and note that anchors will also be needed for the second pipe conveying runoff from the parcel above. It currently connects to the existing rain garden. 319123 Where 32 LF pipe called out by CB 1, it is noted it will have a slope of 32%. Please add further note that pipe anchors are required and are to be designed by the ge%ivil engineer. Our Response 12: Review of the proposed plans indicates that an existing yard drain and the existing outfall of the stormwater detention vault associated with the neighboring property to the north will be directed to flow through pipes mounted to the surface of a graded slope area within the northern portion of the site. The portions of the pipe that will be on the slope will be supported with galvanized clamps anchored to the slope with 1.5-in diameter, six-foot long metal stakes driven into the ground surface. The pipe anchors will be spaced a maximum of 10 feet on center on the slope. In our opinion, the proposed pipe anchors are feasible from a geotechnical standpoint and should adequately support the sections of pipe located within the northeastern graded slope area. CLOSURE We recommend that NGA 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 contract plans and specifications. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Comment Response Letter Westgate Station Commercial Development Edmonds, Washington NGA File No. 1156720 February 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. Lee S. Bellah, LG Senior Geologist 2.06.2024 Khaled M. Shawish, PE Principal LSB:KMS:dy NELSON GEOTECHNICAL ASSOCIATES, INC.