2514 RAINIER AVE Geotech Report 2022-10-25

a a iec },1., foster wheeler 4.8 PAVEMENT I New asphalt pavement will be constructed for the private vehicle drives, parking areas, bus drive lanes, and possibly widening of entrances. The following comments and recommendations are given for pavement design and construction. Subcirade Preparation: To achieve the planned grades, portions of the bus driveway will need to be cut below existing grades, and other portions may require new structural fill to raise grades. All pavement subgrades should be proof-rolled with a loaded dump truck or heavy compactor to verify the density, but this is especially important for subgrade cut into native soils. Any areas of yielding subgrade disclosed during this proof-rolling operation should be overexcavated and replaced with a suitable structural fill. Soil Design Values: Based on our classifications of on-site soils and our previous laboratory testing performed on similar soils, we estimate that the near-surface soils will provide a California Bearing Ratio (CBR) value of at least 10 percent. If the site soils (sandy silt or silt) are used for structural fill, then the same CBR value is applicable. Traffic Design Values: Traffic volumes for the project were provided by Coughlin Porter Lundeen via email dated October 13, 2017. We understand that average daily traffic will consist of approximately 1,400 vehicles, including cars, light trucks, buses, and other heavy vehicles (fire trucks, garbage trucks, etc.). Heavy vehicles will not typically use the parking areas but will use the drive and parking lanes. A breakdown of specific traffic volumes by type was not provided, therefore we have conservatively assumed that 10 percent of the average daily traffic will consist of buses and other I heavy vehicles. Pavement Sections: A conventional pavement section typically comprises a hot-mix asphalt (HMA) I pavement over a crushed rock base (CRB) course, over a suitable subgrade or subbase that consists of granular structural fill. Based on the estimated design values, the following minimum pavement , sections are recommended for preliminary design: Minimum Thickness , Conventional Passenger Car Heavy Vehicle Pavement Course Only Areas (Bus) Driveways HMA 3 inches 5 inches CRB 4 inches 6.5 inches 1 Amec Foster Wheeler 18 Project No.6-917-18116-0 \\Sea-fs1\WordProc\_Projects\18000s\18116 Everett School District\Geotech Report\Revised\2017_10-19_Everett Middle School Geotech_Sx.docx