2000 TOWER ST INDEX HALL 2023-12-29

i&I •E ENGINEERING Pipe Bedding Pipe zone bedding material should consist of crushed, processed, or naturally occurring granular material, free of organic matter and other deleterious material, and should meet the gradation requirements of Gravel Backfill for Pipe Zone Bedding per Section 9-03.12(3) of the 2021 WSDOT Standard Specifications. Trench Backfill and Compaction Trench backfll material should meet the material and compaction requirements as described in Section 4.9 of this report. 4.9 STRUCTURAL FILL The term "structural fill' refers to any materials placed under foundations, slab -on -grade floors, sidewalks, pavements, and other structures. Our comments, conclusions, and recommendations concerning structural fill are presented in the following paragraphs. Materials Typical structural fill materials include gravel, crushed rock, quarry spalls, CDF, LMC, well -graded mixtures of sand and gravel (commonly called "gravel borrow" or "pit -rum"), and miscellaneous mixtures of silt, sand, and gravel. Soils used for structural fill should not contain any organic matter or debris, or any individual particles greater than approximately 6 inches in diameter. Fill Placement Generally, quarry spalls, CDF, and LMC do not require special placement and compaction procedures. In contrast, gravel, crushed rock, soil mixtures, and recycled materials should be placed in horizontal lifts not exceeding 8inches in loose thickness, and each lift should be thoroughly compacted with a mechanical vibratory compactor. Compaction Criteria Using the Modified Proctor test (ASTM D1557) as a standard, we recommend structural fill be used for various on -site applications and compacted to the following minimum densities: MP ENGINEERING, PLLC MPGEOTECH.COM