7500 HARDESON RD Geotech Report 2022-10-25

' Geotechnical Engineering Report SSGC Hardeson Road Retail Everett,Washington ' SSGC Project No. 18072 September 18,2018. and replaced with structural fill. The depth of over-excavation should be based on soil conditions at the ' time of construction. A representative of SSGC should be present to assess subgrade conditions during proofrolling. In building footprints and pavements underlain by the fill, we recommend over-excavation and replacement with granular structural fill. Alternatively, finish site grades could be adjusted(lowered) to reduce the amount of replacement structural fill. Grading and Drainage ' Positive drainage should be provided during construction and maintained throughout the life of the development. Allowing surface water into cut or fill areas, utility trenches,and building footprints should be prevented. Structural Fill Materials ' The suitability of soil for use as structural fill will depend on the gradation and moisture content of the soil when it is placed. Soils with higher fines content (soil fraction passing the U.S. No. 200 sieve) will ' become sensitive with higher moisture content. It is often difficult to achieve adequate compaction if soil moisture is outside of optimum ranges for soils that contain more than about 5 percent fines. Site Soils: The observed fill is generally not considered suitable. Although some of the fill was granular in nature (sand and gravel), variable fines, organics, debris and larger cobbles and boulders were present that would require separation of usable and non-usable materials. Native soils observed are considered suitable for use as structural fill provided theycan be 1 moisture conditioned to within optimal ranges and larger cobbles and boulders (greater than 4- inch nominal diameter) are removed (screened). Optimum moisture is considered within about +/-2 percent of the moisture content required to achieve the maximum density per the ASTM D- I 1557 test method. If moisture content is higher or lower than optimum, soils would need to be dried or wetted prior to placement as structural fill. Larger cobbles and boulders can become clustered during earthwork,create voids,and prevent uniform compaction. ' Import Fill Materials: We recommend import structural fill placed during dry weather periods consist of material which meets the specifications for Gravel Borrow as described in Section 9- '1 03.14(1) of the 2016 Washington State Department of Transportation (WSDOT) Specifications for Road, Bridge. and Municipal Construction (Publication M 41-10). Gravel Borrow should be protected from disturbance if exposed to wet conditions after placement. 111 During wet weather, or for backfiIl on wet subgrades, import soil suitable for compaction in wetter conditions should be provided. Imported fill for use in wet conditions should generally conform to specifications for Select Borrow as described in Section 9-03.14(2), or Crushed 4 i