905 80TH ST SW MTORRES AMERICA 2018-09-18

February 22,2016 Project No. T-7364 Once clearing and grubbing operations are complete, cut and fill operations to establish desired building grades can be initiated. A representative of Terra Associates, Inca 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 representative may request proofrolling exposed surfaces with a heavy rubber-tired vehicle to determine if any isolated soft and yielding areas are present. If unstable 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 inorganic 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. In general, our experience has shown that a minimum of 18 inches of clean, granular structural fill over the geotextile fabric should establish a stable bearing surface. The native soils observed at the site contain a sufficient amount 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 soils from site excavations as structural fill will depend on their moisture content and the prevailing weather conditions when site grading activities take place. 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 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 (TESL)plan for the project Soils that are dry of optimum should be moisture conditioned by controlled addition of water and blending prior to material placement. Due to the fine-grained nature of the site soils, it is our opinion that compaction of properly moisture conditioned fill materials can best be accomplished using a sheep's-foot compactor. 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* I *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. Page No.7