3003 W CASINO RD BLDG 40-23 Geotech Report 2025-01-22

on various support equipment. We understand that the allowable differential slab deflection within a 4-foot distance is less than 4/10,000 of an inch. We understand the design team has elected to support the HBL positions on a minimum 4-foot-thick structural mat foundation. 5.3.1. Mat Foundation PLAXIS 3D Finite Element Analysis was used to evaluate the modulus of subgrade reaction beneath the proposed 4-foot-thick mat foundation for varying thicknesses of weathered glacial till based on the observed subsurface conditions in the current borings. The results of the PLAXIS 3D modeling indicate that a uniform modulus of subgrade reaction of 475 pci is appropriate for design of the mat foundation for HBL Positions 5 through 7. Additional details of the PLAXIS analyses are provided in Appendix D. 5.4. Earthwork 5.4.1. Site Preparation Site development will require demolition of the existing slab, new foundation construction, and installation of subsurface utilities. The existing soils underlying the concrete slab possess high fines (silt) content such that they are moisture sensitive. Based on the results of laboratory moisture content tests, the soils are near the optimum content required for adequate compaction and should be suitable for re -use at other sites provided they are protected from wet weather. Following excavation, we recommend the exposed subgrade be evaluated by a representative from our firm to assess the adequacy of the subgrade conditions and to confirm subsurface soils are as anticipated. Any disturbed or otherwise unsuitable areas identified should be excavated and replaced with crushed rock or controlled density fill (CDF) as recommended. 5.4.2.Structural Fill We anticipate that minor quantities of structural fill may be required to backfill against foundation elements. Crushed rock or CDF should be utilized for structural backfill. We recommend that GeoEngineers be present to evaluate the exposed subgrade soils in the foundation areas, and during placement of structural fill. We will evaluate the adequacy of the subgrade soils and identify areas needing further work, perform in -place moisture -density tests and advise on any modifications to the procedures that may be appropriate for the prevailing conditions. Each lift of structural fill (if crushed rock is used) should be uniformly compacted to at least 95 percent of the maximum dry density (MDD) as determined in accordance with the ASTM International (ASTM) D 1557 test method. 5.4.2.1. Re -use of On -site Soils The on -site soils are moisture -sensitive and generally have natural moisture contents that are near the anticipated optimum moisture content for compaction. As a result, the on -site soils will likely be suitable for re -use as structural fill at other sites, provided the soils meet project criteria for gradation and are protected from wet weather. 5.4.2.2. Fill Placement and Compaction Criteria Structural fill should be mechanically compacted to a firm, non -yielding condition. Structural fill should be placed in loose lifts approximately 6 to 8 inches thick (small vibratory equipment) or 10 to 12 inches thick (large vibratory equipment). Each lift should be conditioned to the proper moisture content and compacted to the specified density before placing subsequent lifts. Structural fill placed against foundation elements GEOENGINEERS June 15, 2022 Page file NoO 0-29G-02