3003 W CASINO RD BLDG 45-06 Geotech Report 2025-03-03

Geotechnical Engineering Report Proposed Flight Line Steam Line Project lierracon Boeing Everett Facility • Everett, Washington January 17, 2012 • Terracon Project No.: 81115085 On-Site Soils In general, the existing site soils encountered within anticipated excavation depths primarily consist of silty sand with gravel. These soils are considered acceptable for use as engineered ' fill above the top of the utilidor from a compositional perspective. The on-site soils are not suitable for use as wall backfill due to their high fines content. The on-site soils are considered to have a moderate to high moisture sensitivity relative to compaction due to their high fines content. The use of on-site soils will require strict control of the soil moisture content to achieve adequate compactions. Selective drying of over-optimum moisture soils may be achieved by scarifying or windrowing surficial materials during extended periods of dry weather. Soils which ' are dry of optimum may be moistened through the application of water and thorough blending to facilitate a uniform moisture distribution in the soil prior to compaction. It should be understood ' that the on-site soils are moisture sensitive and adequate compaction may be difficult to achieve, even during favorable weather conditions. Import Material for Utilidor Trench Backfill We recommend that import backfill for the Utilidor, including backfill for cast-in-place and precast utilidor subgrade walls, meet requirements of Section 9-03.14(1), Gravel Borrow, as presented in the Washington State Department of Transportation (WSDOT) Standard Specifications for Road, Bridge, and Municipal Construction. Gravel Borrow may also be used an engineered fill above the utilidor as an alternate to the on-site soils. The use of Gravel Borrow above the utilidor would reduce the risk of wet weather delays. Gravel Borrow can be placed and compacted in a wider variety of weather conditions than the moisture sensitive on- site soils. Import Material below Foundations We recommend that import fill placed below foundation elements meet the requirements of Section 9-03.17, Foundation Material Class A, as presented in the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction. ' Import Material for Foundation/Wall Drains We recommend that import fill placed around foundation drains meet the requirements of Section 9-03.12(4), Gravel Backfill for Drains, as presented in the WSDOT Standard Specifications for Road, Bridge, and Municipal Construction. 4.2.8 Compaction Recommendations Engineered fill should be placed in lifts no greater than 8 inches in loose thickness and compacted to a firm and non-yielding condition. Recommended compaction and moisture content criteria for engineered fill materials, including trench backfill, are as follows: I Responsive ■ Resourceful ■ Reliable 9