3322 KROMER AVE Geotech Report 2023-05-25

6eoTest Services, Inc.—Revision 1 April 10,2020 Kikuchi Retaining Wall, Everett,Washington Project No. 20-0344 immier 10 percent fines may be feasible, but the use of these soils should generally 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. 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 should be compacted to at least 95 percent of the maximum dry density, as determined using test method ASTM D1557. The top of the compacted structural fill should extend outside all foundations and other structural improvements a minimum distance equal to the thickness of the fill. We recommend that compaction be tested after placement of each lift in the fill pad. 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. Wet Weather Earthwork If construction takes place during wet weather, GeoTest recommends that structural fill consist of imported, clean, well-graded sand or sand and gravel as described above. If fill is to be placed or earthwork is to be performed in wet conditions, the contractor may reduce soil disturbance by: • Limiting the size of areas that are stripped of topsoil and left exposed • Accomplishing earthwork in small sections • Limiting construction traffic over unprotected soil • Sloping excavated surfaces to promote runoff • Limiting the size and type of construction equipment used • Providing gravel 'working mats' over areas of prepared subgrade 15