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

f � Campbell-Fleury Investments/Mallwest Center 9 April 1986 W-3103-1 Page 8 _ ray increase. For that reason, the condition of the footing subgrade should be looked at by our staff prior to concrete placement, to see that the condition of the bea�•ing soils are consistent with those assumed during design. 4.4 Structural Floor Due to the presence of the compressible, uncontrolled fill, if this material is not remuved and replaced, we recommend structural suppori of the proposed floor slab • loads. Structural floors could be installed, which would rest upon grade beams spanning between individual piers, or upon continuous footings. This method would __. therefore not require removal of the uncontrolled fill. Two general options with regard to structural floors are presented here. One option would be to pour a structurally reinforced concrete floor slab directly over the onsite soils, of sufficient strength, so as to be only relying upon subsoils to act as a"form" during concrete placement. We would recommend that the floor slab be underlain by at least 4 inches of clean, sand and gravel, crushed rock or pea gravel to provide a capillary break. Additionally, an impervious moTsture barrier should be placed beneath the slab. . - The other option would be to utilize crawl-space-type construction with a raised floor. With this approach, the condition of the onsite fill during construction is not a pro6lem. In the case of a crawl space, the soil beneath the floor system should be covered with Visqueen or similar plastic sheeting to reduce dampness. Also, if a crawl space is included in design, a footing drain will be required. 4.5 Slab-On-Grade Floors Slab-on-grade support of the first floor is recortmended only after total removal -- of the existing loose fill. The subgrade should be prepared in accordance with -- previous Site and Preparation and Structural Fill recommendations presented in Section 4.1 and 4.2. bJe recommend that the floor slab be underlain by a minimum � 4-inch thickness of clean sand and gravel, crushed rock or pea gravel to serve as � a capillary break and working surface. An impervious moisture barrier should also