3301 SEAWAY BLVD Geotech Report 2022-10-25

January 13,2016 Project No. T-7342 The native till and siltier outwash soils encountered at the site contain a sufficient amount of soil fines that will make them difficult to compact as structural fill when too wet or too dry. The ability to use these native soil from site excavations as structural fill will depend on its moisture content and the prevailing weather conditions at the time of construction. If wet soils are encountered, the contractor will need to dry the soils by aeration during dry weather conditions or use an additive such as cement or lime to stabilize the soil. If the soil is amended, additional BMPs addressing the potential for elevated pH levels will need to be included in the Storm Water Pollution Prevention Program (SWPPP) prepared with the TESC plan. The cleaner outwash soils observed should be suitable for use as structural fill year round. 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. All structural fill in City of Everett rights of way must conform to City materials and compaction specifications. 5.3 Excavations All excavations at the site associated with confined spaces, such as utility trenches, must be completed in accordance with local, state, and federal requirements. Based on current Washington Industrial Safety and Health Act (WISHA) regulations, loose to medium dense weathered soils and medium dense to dense outwash soils would be classified as Type C soils. The dense to very dense unweathered till soils would be classified as Type A soils. Page No. 9