2320 RAILWAY AVE Geotech Report 2023-02-01

Interwest Construction Co.-Everett Contractor Yard Site Improvements,Everett,WA March 12,2021 Geotechnical Engineering Report P2184-T20 I I I I I I Subgrade Observation and Compaction Testing: Regardless of material or location,all structural fill should be placed over firm, unyielding subgrades prepared in accordance with the Site I Preparation section of this report.The condition of all subgrades should be observed bygeotechnical eP P g personnel before filling or construction begins. Also, fill soil compaction should be verified by means of in-place density tests performed during fill placement so that adequacy of soil compaction efforts may be evaluated as earthwork progresses. Soil Moisture Considerations: The suitability of soils used for structural fill depends primarily on their grain-size distribution and moisture content when they are placed. As the"fines"content(that soil fraction passing the U.S.No.200 Sieve)increases,soils become more sensitive to small changes in moisture content. Soils containing more than about 5 percent fines (by weight) cannot be consistently compacted to a firm,unyielding condition when the moisture content is more than 2 I I I percentage points above or below optimum. For fill placement during wet-weather site work,we I recommend using"clean"fill,which refers to soils that have a fines content of 5percent or less (by weight)based on the soil fraction passing the U.S. No. 4 Sieve. 5.0 RECOMMENDED ADDITIONAL SERVICES Because the future performance and integrity of the structural elements will depend largely on proper site preparation, drainage, fill placement, and construction procedures, monitoring and testing by experienced geotechnical personnel should be considered an integral part of the construction process. Subsequently,we recommend that MGI be retained to provide the following I I post-report services: I .I Review all construction plans and specifications to verify that our design criteria presented in this report have been properly integrated into the design; I . Prepare a letter summarizing all review comments (if required); and 1 • Prepare a post-construction letter summarizing all field observations,inspections,and test results (if required). Migizi Group, Inc. Page 15 of 16 MIGIZI IIitil ,I