4812 HARBOR LN 2018-01-02 MF Import

December 3,1"ll Project No. T4199 Soils containing organic material will not be suitable for use as structural fill but may be used in non-structural areas or for landscaping purposes. The underlying native soils contain a sufficient percentage of fines (silt and clay size particles) that will make it difficult to compact as structural fill when too wet or too dry, or if placed on a wet subgrade. Accordingly, the ability to use native soils from site excavations as structural fill or backftll will de; end on their moisture content and the prevailing weather conditions at the time site grading activities take place. If grading activities take place during the wet winter months or if it is anticipated that earthwork will extend into fal! and winter, the owner should be prepared to import wet weather structural fill. For this purpose, we recommend importing a granular soil that meets the following grading requirements: U.S. Sieve Size Percent Passing 3 inches 100 No. 4 75 maximum No. 200 5 maximum' 'Based on the 314-inch fraction. Prior to use, Term Associates, Inc. should examine and test all materials imported to the site for use as structural fill. Structural fill should be placed on a firm subgrade of undisturbed native soil in uniform loose layers not exceeding 12 inches. It should then be compacted to a minimum of 95 percent of the soil's maximum dry density, as determined by ASTM Test Designation D-698 (Standard Proctor). The moisture content of the soil at the time of compaction should be within two percent of its optimum, as determined by this same ASTM standard. In non-structural areas or for backfill in utility trenches below a depth of 4 feet, the degree of compaction can be reduced to 90 percent. Slopes and Embankments All permanent cut and fill slopes should be graded with a finished inclination no greater than 2:1. Upon completion of grading, the slope face should be appropriately vegetated or provided with other physical means to guard against erosion. Final grades at the top of the slope must promote surface drainage away from the slope crest. Water must not be allowed to flow in an uncontrolled fashion over the slope face. If it is necessary to direct surface runoff towards the slope, it should be controlled at the top of the slope, piped in a closed conduit installed on the slope face, and taken to an appropriate point of discharge beyond the slope toe. All fill used to construct embankments should meet the structural fill requirements, as described in the Site Preparation and Grading section of this report. Fills placed on slopes with gradients greater than 20 percent should be keyed and benched into competent native slope soils. A typical slope key and L-nch configuration is shown on Figure 3. At minimum, a toe drain installed in the key cut should be constructed. Depending on seepage conditions, drains may also be required along the individual benches excavated on the -lope face. The need for drains along the upper benches will be best determined in the field at the time of construction. Page No. 5