6101 23RD DR W NORPRO Geotech Report 2025-07-29

June 3,2011 Project No.T-6578 5.0 DISCUSSION AND RECOMMENDATIONS 5.1 General Based on our study, in our opinion, there are no geotechnical considerations that would preclude development of the site as planned. The building can be supported on conventional spread footings bearing on competent native soils below the organic surface soils or on structural fill placed and compacted above competent native soils. Floor slabs and pavements can be similarly supported. Based on the finish floor elevations,we expect that buried organics along the water utility corridor will be removed during excavation for perimeter and interior footings. The native glacial till soils encountered at the site contain a sufficient amount of fines (silt- and clay-sized I particles) such that they will be difficult to compact as structural fill when too wet. Accordingly, the ability to use soils from site excavations as structural fill will depend on their moisture content and the prevailing weather conditions at the time of construction. If grading activities will take place during the winter season, the owner should be prepared to import free-draining granular material for use as structural fill and backfill. In our opinion soil conditions would be suitable for using rockeries to face the near vertical grade breaks planned I along the eastern boundary and the northwest margin of the site. If smaller footprint retaining walls are desired, Terra Associates, Inc.can aid in the design if needed. I Detailed recommendations regarding these issues and other geotechnical design considerations are provided in the following sections of this report. These recommendations should be incorporated into the final design drawings and construction specifications. 5.2 Site Preparation and Grading 1 To prepare the site for construction, all vegetation and organic surface soils should be cleared from below proposed building and pavement areas. Based on conditions observed in the borings, surface stripping depths on the order of 6 to 18 inches should be expected to remove organic fill and topsoil over most the site. Stripped vegetation debris should be removed from the site. Organic soil 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 surfaces should be observed by a representative of Terra Associates to verify that soil conditions exposed are as expected and suitable for fill placement or building construction. Our representative may require the exposed grade be proofrolled with heavy rubber-tired equipment to determine if any isolated soft and yielding areas are present. If excessively yielding areas are observed and cannot be stabilized in place by compaction, the affected soils 11 should be excavated and removed to firm bearing and grade restored with new structural fill. If the depth of excavation to remove unstable soils is excessive, in pavement areas, the use of a geotextile reinforcing/separation fabric, such as Mirafi 500X or equivalent, can be considered to reduce the excavation depth. Our experience has shown that, in general, a minimum of 18 inches of a clean, granular structural fill placed over the geotextile fabric would establish a stable bearing surface. Page No. 6