2320 106TH ST SW Geotech Report 2022-10-25

October 14,2015 Project No.T-6116-2 DISCUSSION AND RECOMMENDATIONS 5.1 General Based on our study, there are no geotechnical considerations that would preclude development of the site, as currently planned. The structure can be supported on conventional spread footings bearing on competent native soils observed below the upper six inches of organic surface soil or on structural fill placed and compacted above these native soils. Floor slabs and pavements can be similarly supported. The native soils encountered at the site contain a significant amount of fines and will be difficult to compact as structural fill when too wet. The ability to use native soil from site excavations as structural fill will depend on its moisture content and the prevailing weather conditions at the time of construction. If grading activities will take place during winter, the owner should be prepared to import clean granular material for use as structural fill and backfill. The following sections provide detailed recommendations regarding the preceding issues and other geotechnical design considerations. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 Site Preparation and Grading lo prepare the site for construction, all vegetation, organic surface soils, and other deleterious material should be ripped and removed from the site. Surface stripping depths of about six to seven inches should be expected to remove the organic surface soils. Organic topsoil will not be suitable for use as structural fill,but may be used for limited depths in nonstructural areas. Once clearing and stripping operations are complete, cut and fill operations can be initiated to establish desired grades. Prior to placing fill, all exposed bearing surfaces should be observed by a representative of Terra Associates to verify soil conditions are as expected and suitable for support of new fill or building and infrastructure elements. Our representative may request a proofroll using heavy rubber-tired equipment to determine if any isolated soft and yielding areas are present. If excessively yielding areas are observed, and they cannot be stabilized in place by compaction, the affected soils should be excavated and removed to firm bearing and grade restored with new structural fill. Beneath embankment fills or roadway subgrade if the depth of excavation to remove unstable soils is excessive, the use of geotextile fabrics, such as Mirafi 500X, or an equivalent fabric,can be used in conjunction with clean granular structural fill. Our experience has shown that, in general, a minimum of 18 inches of a clean, granular structural fill placed and compacted over the geotextile fabric should establish a stable bearing surface. A representative of Terra Associates,Inc. should observe all bearing surfaces prior to fill placement to verify that soil conditions exposed are as expected and suitable for support of additional fill and/or building construction. Page No.6