11831 AIRPORT RD WHOLE SITE FILE Geotech Report 2022-10-25

by loose to dense native deposits. We recommend the subsurface soil conditions be evaluated by a representative from our firm during installation of the signal poles to confirm soil conditions are as anticipated and to make modifications to the foundation support requirements as necessary. There are eight types of cantilever signal and strain pole standards that are covered in Section J of the WSDOT Standard Plans. Type PPB (pedestrian push bottom pole), PS (pedestrian head standard), Type I/RM (vertical head and ramp meter), Type FB (flashing beacon standard) and Type IV (strain pole standard) are structures that generally consist of a single vertical metal pole member. Type II (mast arm standard), Type III (lighting and mast arm standard) and Type V (lighting and strain pole standard) have a vertical metal pole member with a horizontal mast arm. Lights and/or signals will be suspended from the mast arm. The standard foundations for these structures consist of square or round shafts that vary from 1.5 feet to 3.0 feet for square foundations and 2.0 to 4.0 feet in diameter for round shaft foundations. The standard designs assume a concrete to soil contact. Foundations depths vary from 6 to 15 feet for signal structure Types II, Ill, IV and V. Foundations for mast arm traffic signal poles, designed in accordance with Chapter 1330 of the WSDOT Design Manual and Chapter 17 of the WSDOT GDM, require a lateral-bearing pressure to determine the shaft depth required. The WSDOT design method to estimate lateral-bearing pressures is based on empirical correlations with blow count data and the angle of internal friction of the soil.The lateral-bearing pressure presented in Table 10 below is based on our review of available data in the site vicinity,the WSDOT design guidelines, and our experience. TABLE 10.SIGNAL POLE DESIGN LATERAL AND SOIL BEARING PRESSURES Allowable Soil Bearing Pressure (psf) Allowable Lateral Founded at a Founded at a Bearing Pressure Friction Angle Depth of Depth of 9 or Location (psf) (degrees) 6 feet more feet SR 527 and SR 524 3,500 36 2,500 6,000 SR 527 and 196th Street SW 2,500 32 2,000 2,500 SR 527 and 164th Street SE 3,000 33 2,500 4,000 SR 527 and 153rd Street SE 3,500 34 2,500 8,000 SR 527 and Trillium Boulevard 3,500 34 3,500 4,000 132nd Street SW and Dumas Road' 2,000 28 1,500 2,500 132"Street SE and 16th Avenue SE 2,700 32 2,500 4,000 3 128th Street SW and 3rd Avenue SE 3,500 34 2,500 4,000 128th Street SW and 1-5 on-ramps 2,500 32 2,000 2,500 Airport Road and SR 99 1,500 30 1,500 2,500 GEOENGINEERS� April 14,2017 Page 19 File No.2095-032-00