7500 HARDESON RD Geotech Report 2022-10-25

1 Geotechnical Engineering Report SSGC Hardeson Road Retail Everett,Washington ' SSGC Project No. 18072 September 18,2018 ' Surfacing per Section 9-03.9(3) of the 2016 WSDOT.M-41 manual, with the modification that a maximum of 5 percent by weight shall pass the U.S.No. 200 sieve for these soil types. It should be noted that structural fill placement and compaction is weather-dependent. Delays due ' to inclement weather are common, even when using select granular fill. We recommend site grading and earthwork be scheduled for the drier months of the year. Structural fill should not consist of frozen material. Structural Fill Placement We recommend structural fill is placed in lifts not exceeding about 10 inches in loose measure. It may be necessary to adjust lift thickness based on site and fill conditions during placement and compaction. Finer ' grained soil used as structural fill and/or lighter weight compaction equipment may require significantly thinner lifts to attain required compaction levels. Coarser granular soil with lower fines contents could potentially be placed in thicker lifts if they can be adequately compacted. Structural fill should be compacted to achieve the recommended levels presented in Table 1,Compaction Criteria. Table 1.Compaction Criteria ' Fill Application Compaction Criteria*' Footing areas(below structures and retaining walls) 95 % ' Upper 2 feet in pavement areas,slabs and sidewalks,and utility trenches 95 % Below 2 feet in pavement areas,slabs and sidewalks,and utility trenches 92% Utility trenches or general fill in non-paved or-building areas 90% Per the ASTM D 1557 test method. ' Trench backfill within about 2 feet of utility lines should not be over-compacted to reduce the risk of damage to the line. In some instances the top of the utility line may be within 2 feet of the surface. Backfill in these circumstances should be compacted to a firm and unyielding condition. We recommend fill procedures include maintaining grades that promote drainage and do not allow ponding of water within the fill area. The contractor should protect compacted fill subgrades from disturbance during wet weather. In the event of rain during structural fill placement, the exposed fill surface should be allowed to dry prior to placement of additional fill. Alternatively, the wet soil can be removed. We recommend consideration be given to protecting haul routes and other high traffic areas with free-draining granular fill material (i.e. sand and gravel containing less than 5 percent fines) or quarry spalls to reduce the potential for disturbance to the subgrade during inclement weather. 1 r 5 i