5700 23RD DR W 2018-06-28 - Laserfiche WebLink

November 29,2016 Project No.T-5922-6 Our study indicates that the silty sand soils contains a sufficient percentage of fines (silt and clay size particles) that will make them difficult to compact as structural fill if they are too wet or too dry. Accordingly,the ability to use these silty sand soils from site excavations as structural fill will depend on their moisture content and the prevailing weather conditions when site grading activities take place. Inorganic 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 plan (TESC) for the project. The underlying clean sand should be suitable to reuse as structural fill in most weather conditions. 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 weather structural fill. 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. Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural fill. Structural fill should be placed in uniform loose layers not exceeding 12 inches and compacted to a minimum of 95 percent of the soil's maximum dry density, as determined by American Society for Testing and Materials (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 ASTM standard. In nonstructural areas, the degree of compaction can be reduced to 90 percent. 5.3 Excavations and Slopes Excavations All excavations at the site associated with confined spaces, such as utility trenches or construction of lower building levels must be completed in accordance with local, state, or federal requirements. Based on current Washington Industrial Safety and Health Act(WISHA)regulations, the loose to medium dense fill soils, and any soil`containing groundwater would be categorized as a Type C soil. The dense outwash sands and silty sands would be categorized as a Type B soil. Page No. 6