4920 24TH AVE W Geotech Report 2023-06-22

GeoTest Services, Inc. October 8,2021 2405 Hillside Lane, Everett,WA Project No.21-0845 ate` Reuse of On-Site Soil The non-organic,native,glacial soils are suitable for reuse as structural fill when placed at or near optimum moisture content, and if allowed for in the plans and specifications. Soils comprised of Transitional Beds contain high percentages of fines and should be considered moisture sensitive. Reuse of these soils may be considerably more difficult to use at or near perched groundwater elevations and during the wet weather season. If using on-site materials, the Contractor and Owner should be prepared to manage over optimum moisture content soils. The moisture content of the soils may be difficult to control during periods of wet weather. Imported Structural Fill GeoTest recommends that imported structural fill consist of clean, well-graded sandy gravel, gravelly sand, or other approved naturally occurring granular material (pit run) with at least 30 percent retained on the No.4 sieve, or a well-graded crushed rock.Structural fill for dry weather construction may contain up to 10 percent fines (that portion passing the U.S. No. 200 sieve) based on the portion passing the U.S. No. 4 sieve. The use of an imported fill having more than 10 percent fines may be feasible, but the use of these soils should be reviewed by the design team prior to the start of construction. Imported structural fill with less than five percent fines should be used during wet weather conditions. Due to wet site conditions, soil moisture contents could be high enough that it may be difficult to compact even clean imported select granular fill to a firm and unyielding condition. Soils with an over-optimum moisture content should be scarified and dried back to a suitable moisture content during periods of dry weather or removed and replaced with drier structural fill. Keying and Benching Where fill is to be placed on slopes steeper than 5H: 1V,the base of new structural fill should be tied to firm and unyielding native soils by appropriate keying and benching. The purpose of a keyway is to embed the toe of new structural fill into existing slopes. Keyways for hillside fills should be at least 5 feet wide, 2 feet deep, and cut into the native soil. Level benches can then be cut following the contours of the slope. Benches in native soils are typically cut a few feet wider than the equipment being used to cut them. Backfill and Compaction Structural fill should be placed in horizontal lifts. The structural fill must measure 8 to 10 inches in loose thickness and be thoroughly compacted.All structural fill placed under load bearing areas 10