6307 36TH AVE W Geotech Report 2025-07-29

I August 13,2008 Project No.T-6241 The native near-surface and deeper glacial till soils observed at the site contain a significant amount of fines and will be difficult to compact as structural fill when too wet or too dry. The ability to use these native soils 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 the wet winter months, 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 above issues and other geotechnical design considerations. These recommendations should be incorporated into the final design drawings and ' construction specifications. 5.2 Site Prejaration and Grading To prepare the site for construction, all vegetation, organic surface soils, and other deleterious materials should ' be stripped and removed from the site. Based on conditions observed in our test pits, we expect that surface stripping depths of about six inches will be required to remove organic surficial soils. These organic surficial soils will not be suitable for use as structural fill, but may be used for limited depths in nonstructural areas or for landscaping purposes. Once clearing and grubbing operations are complete, cut and fill operations to establish desired roadway and building grades can be initiated. Prior to placing fill, we recommend proofrolling all exposed surfaces to determine if any isolated soft and yielding areas are present. Proofrolling should also be performed in cut areas which will provide direct support for new construction. ' If excessively yielding areas are observed, they should be cut to firm bearing soil and filled to grade with structural fill. If the depth of excavation to remove unstable soils is excessive, use of geotextile fabric such as Mirafi 500X or equivalent in conjunction with structural fill can be considered in order to limit the depth of removal. A minimum of 18 inches of clean, granular structural fill over the geotextile fabric should establish a stable bearing surface. A representative of Terra Associates, Inc. should examine all bearing surfaces to verify that conditions encountered are as anticipated and are suitable for placement of structural fill or direct support of building and pavement elements. Our study indicates that the native near-surface and deeper glacial till soils contain a significant amount of soil fines (silt and clay size particles). These soils are difficult to compact as structural fill when too wet or too dry. ' Accordingly, the ability to use native soils from site excavations as structural fill will depend on their moisture content and the prevailing weather conditions at the time site grading activities take place. ' Laboratory testing indicates that at the time of our study, in general the soil's moisture content below approximately three to four feet was near optimum. Provided these soils are placed during dry weather conditions, we anticipate they will be suitable for direct use as structural fill. At the time of our study, the moisture content of the near-surface soils was above optimum. In order to use these materials for structural fill, the contractor will need to consider drying by aeration during dry weather conditions or using an additive such as cement or lime to stabilize the soil. Page No. 7