5228 EAST DR Geotech Report 2022-10-25

COBALT GEOTECHNICAL INVESTIGATION GEOSCIENCES EVERETT,WASHINGTON December 5,2019 The subgrade should be compacted to at least 95 percent of the maximum dry density as determined by ASTM Test Method Di557. In place density tests should be performed to verify proper moisture content and adequate compaction. The recommended flexible and rigid pavement sections are based on design CBR and modulus of subgrade reaction (k)values that are achieved, only following proper subgrade preparation. It should be noted that subgrade soils that have relatively high silt contents will likely be highly sensitive to moisture conditions. The subgrade strength and performance characteristics of a silty subgrade material may be dramatically reduced if this material becomes wet. Based on our knowledge of the proposed project,we expect the traffic to range from light duty(passenger automobiles) to heavy duty (delivery trucks). The following tables show the recommended pavement sections for light duty and heavy duty use. ASPHALTIC CONCRETE(FLEXIBLE)PAVEMENT LIGHT DUTY Asphaltic Concrete Aggregate Base* Compacted Subgrade*** 2.o in. 6.o in. 12.0 in. HEAVY DUTY Asphaltic Concrete Aggregate Base* Compacted Subgrade*** 3.o in. 6.o in. 12.0 in. PORTLAND CEMENT CONCRETE (RIGID)PAVEMENT Min.PCC Depth Aggregate Base* Compacted Subgrade* ** 6.o in. 6.o in. 12.0 in. *95%compaction based on ASTM Test Method D1557 **A proof roll may be performed in lieu of in place density tests The asphaltic concrete depth in the flexible pavement tables should be a surface course type asphalt,such as Washington Department of Transportation (WSDOT) 1/2 inch HMA. The rigid pavement design is based on a Portland Cement Concrete (PCC)mix that has a 28 day compressive strength of 4,000 pounds per square inch (psi). The design is also based on a concrete flexural strength or modulus of rupture of 550 psi. 11 PO Box 82243 Kenmore,WA 98028 cobaltgeoc gmail.coum 206-331-1097