9909 2ND AVE W 2018-08-01 - Laserfiche WebLink

December 13,2006 Project No.T-6001 5.2 Site Preparation 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. Stripping depths ranging from 6 to 12 inches should be expected to remove the topsoil/duff layer, with additional excavation depths likely in some locations(see discussion below). Organic topsoil will not be suitable for use as structural fill; but may be used for limited depths in nonstructural areas. Based on oar observations, we expect that the native soils at the site will generally be suitable for use as structural fill if properly moisture conditioned. As noted above, in some locations, organic soils were found in our test pits to a maximum depth of three feet. We recommend removing the organic soils from below all building and paved areas. Foundations, floor slabs, and pavements can then be supported on exposed competent native soils, or on grades restored with new structural fill. Where structural fill is used to restore building grades, the overexcavation to remove unsuitable existing fill should extend laterally from the footing edge a distance equal to one-half the depth of fill below the footing. Due to its organic content, the organic soils will not be suitable for reuse as structural fill at the site. Once clearing and stripping operations are complete, cot and fill operations can be initiated to establish desired grades. Prior to placing fill, all exposed surfaces should be recompacted using a large, heavy, vibratory roller to compact the upper, organic-free soils and determine if any isolated sofl and yielding areas are present. This subgrade compaction should also be performed in cut areas that will provide direct support for new construction. If excessively yielding areas are observed and cannot be stabilized in place by compaction, the affected soils should be excavated and removed to firm bearing and restored to grade with new structural fill. If the depth of excavation to remove unstable soils is excessive, use of a geotextile reinforcing/separation fabric, such as Mirafi 500X or equivalent can be considered in conjunction with structural fill. Our experience has shown that, in general, a minimum of I8 inches of a clean, granular structural fill over the geotextile fabric should establish a stable bearing surface. The native soils encountered at the site contain a sufficient amount of fines (silt and clay size particles), which will make them difficult to compact as structural fill if they are too wet or too dry. Accordingly, the ability to use these soils from site excavations as structural fill will depend on their moisture content and the prevailing weather conditions when site grading activities take place. The test pits indicate the site soils were several percentage points above optimum moisture content at the time of our field study. Native soils that are too wet to properly compact could be dried by aeration during dry weather conditions, or mixed with an additive such as cement, cement kiln dust (CKD), or lime to stabilize the soil and facilitate compaction. If an additive is used, additional Best Management Practices (BMPs) for its use will need to be incorporated into the Temporary Erosion and Sedimentation Control (TESC)plan for the project. If grading activities are planned during the wet winter months, or if they are initiated during the summer and extend into fall and winter, the owner should be prepared to import wet wear:er structural ii; . For this purpose, we recommend importing a granular soil that meets the following grading requirements: U.S. Sieve Size Percent Passing 6 inches 100 No.4 75 maximum No.200 5 maximum* *Based on the 3/4-inch fraction. Page No. 5