8417 EVERGREEN WAY Geotech Report 2022-10-25

Geotechnical Engineering Report-Revised lierracon Proposed CFT Retail ■Everett,Washington February 1, 2018■Terracon Project No. 81185002 Based on the results of our explorations,the existing fill soil is generally in a loose to medium dense condition. After re-working the upper 24 inches of soil in pavement areas and implementing recommended improvements the risk of excessive settlements is low to moderate. Areas of unsuitable or compressible fill may be present within the remaining fill that were not observed in our explorations. 4.7.1 Subgrade Preparation On most project sites, the site grading is accomplished relatively early in the construction phase. Fills are placed and compacted in a uniform manner. However, as construction proceeds, excavations are made into these areas, rainfall and surface water saturates some areas, heavy traffic from concrete trucks and other construction vehicles disturbs the subgrade,and many surface irregularities are filled in with loose soils to temporarily improve trafficability. As a result, the pavement subgrades, initially prepared early in the project, should be carefully evaluated as the time for pavement construction approaches. We recommend that the moisture content and density of the top 24 inches of the subgrade be evaluated and that the pavement subgrades be proofrolled within two days prior to commencement of actual paving operations. Areas not in compliance with the required ranges of moisture or density should be moisture conditioned and recompacted. Particular attention should be paid to high traffic areas that were rutted and disturbed earlier and to areas where backfilled trenches are located. Areas where unsuitable conditions are located should be repaired by removing and replacing the materials with properly compacted structural fill. If a significant precipitation event occurs after the evaluation or if the surface becomes disturbed, the subgrade should be reviewed by qualified personnel immediately prior to paving. The subgrade should be in its finished form at the time of the final review. 4.7.2 Design Considerations We anticipate that traffic loads will be produced primarily by automobile traffic and by occasional delivery and trash-removal trucks. The thickness of pavements subjected to heavy truck traffic should be determined using expected traffic volumes, vehicle types, and vehicle loads and should be in accordance with local, city or county ordinances. Pavement thickness were determined using AASHTO methods based on provided values of maximum ESAL loading of 60,000 (ESAL=equivalent 18-kip single axle load)for standard duty car and parking areas over a 20-year design life. For heavy duty truck traffic areas, we used an assumed traffic loading of 200,000 ESALs for use in our analysis. The minimum pavement sections outlined below were determined based on the laboratory test results and post-construction traffic loading conditions. These pavement sections do not account for heavy construction traffic during development. A partially constructed structural section may be subjected to heavy construction traffic that can result in pavement deterioration and premature failure. Our experience indicates that this pavement construction practice can result in pavements Responsive ® Resourceful is Reliable 17