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June 13, 2023 <br />HWA Project No. 2022-188-21 <br />Based on the results of our investigation and our previous experience, we have based the <br />pavement structure design assuming a prepared subgrade (lean clay) design resilient modulus <br />(Mr) of 5 kips per square inch (ksi) <br />We have undertaken the pavement design using the DARWin computer program which is based <br />on the AASHTO Guide for Design of Pavement Structures, 1993. The following parameters, <br />based on recommendations given in the AASHTO Guide, were used in the analysis: <br />■ Initial Serviceability 4.5 <br />■ Terminal Serviceability 3.0 <br />■ Reliability Level 90% <br />■ Overall Standard Deviation 0.5 <br />The recommended pavement layer thickness requirements are summarized on Tables 3 through 6 <br />for the recycling area, tire recycling area, scale and transfer station and the compost area, <br />respectively: <br />Table 3. Recommended Pavement Layer Thickness for Southwest Area <br />Material <br />Description <br />Minimum Pavement Layer Thickness <br />(inches) <br />WSDOT Standard <br />Specification <br />HMA' <br />4.0 <br />9-02.1(4) <br />CSBC2 <br />6.0 <br />9-03.9(3) <br />Select Borrow <br />12.03 <br />9-03.14(2) <br />(1) HMA: Hot Mix Asphalt: Binder Grade PG 641-1-28. HMA shall be placed in 2 lifts. <br />(2 <br />) CSBC: Crushed Surfacing Base Course, compacted as specified. <br />131 Thickness of Select Borrow may be reduced if base of over -excavation and replacement with <br />CSBC is at least 22 inches below the top of new roadway. <br />2022-188-21 KCTS — Final Geotechnical Report 18 HWA GEOSC[ENCES INC. <br />