20 SW EVERETT MALL WAY Geotech Report 2018-01-02 MF Import

Campbell-Fleury Investmer�ts/Mallwest Center W-3103-1 9 April 1986 Page 5 _ removed from other settlement-sensitive areas. This overexcavation is discussed further in Shallow Foundations and Slab-On-6rade sections of this report. The natural soils exposed by fill and organic soil removal will probably consist of a silty sand with some gravel or a clayey silt. We recommend that a representative of our firm observe the exposed surface, so that recommendations for the removal of any soft, loose, or organic areas encountered during fill removal can be made at this time. All areas of unsuitable fill removed should be replaced with - "structural fill" described in Section 4.2. Ideally, all unsuitable fill shouid also be removed from any sidewalk, parking or paved areas. However, if the risk of long-term settlement, warping and cracking can be tolerated, then as a minimum the upper 1 foot of existing fill below pavement subgrade elevation should be removed, and the su•rface compacted to a density of at least 90 percent of the modified Proctor maximum dry density, as determined by ASTM:D 1557 test procedure. The subgrade soils should be free of oryanics, debris and other deleterious material. We re�ommend that the subgrade areas be prerclled � and compacted with a roller or other suitable heavy equipment to a firm and non- yielding condition in order to achieve the minimum of compaction level. Any soft, wet, or significantly organic areas disclosed by the stripping and prerclling should be overexcavated as necesssry and backfilled with structural fill as described subsequently. Much of the site soils are silty and therefore moisture-sensitive. These soils are prone to disturbance when wet. Prerolling and compaction may not be practical during wet site conditions, and may lead to disturbance of the fine-grained subgrade soils. Prerolliny should be assessed at the time of construction. The contractor � should minimize vehicular traffic above prepared subgrades. In very wet conditions, - the use o� a working surface of quarry spalls or sandy gravel may be required to .� protect the subgrade, especially from heavy rubber-tired vehicular traffic. J Additionally, all existing utilities should be removed from within the buildiny area. The existing culvert should be rerouted around the building location and the resu'Iting overexcavation backfilled with "structural fill".