2400 33RD ST GEOTECHNICAL INVESTIGATION 2018-01-02 MF Import

• Place a geotextile, Mirafi Geolon HP-370 or equivalent over the fill. The geotextile should be polypropylene to resist chemicals, woven, and permeable; and • Place structural fill to the height of final subgrade and compact as specified in the Structural Fill Materials and Compaction Section in the October 2001 report. If the pond is deeper than we understand, the pond can be drained and unsuitable backfill placed to a depth two feet below the level of the final subgrade. The geotextile should then be placed on the fill, and the remaining two feet be backfilled with compacted structural till, as described above. Recommendations for Design of Pavement Section We have compared the recommended pavement thicknesses in the City of Everett Standards for Streets and Related Work with the recommendations in the MPA 2001 report. These are shown in 'rabic 2 below. m..M..e_ir... kf:v A.. hnIt (1rMA) R,.rnmmnnded Pavement Section Source Location Thickness City of Everett Standards _ Packing Areas • 2 inches of HMA • 4 inches of Crushed Surfacing Base Course (CSBC) MPA 2001 Report Parking Areas • 3 inches HMA • 4 inches CSBC MPA 2001 Report i;ntrance Driveways . 4 inches HMA • 8 inches CSBC Pavement sections for the project were designed based on site soil conditions and expected traffic loads. Our evaluation assumed that the pavement sections would be constructed on subgrades prepared as described in the Site Earthwork section of the MPA 2001 report and the Over -excavation and Subgrade Preparation section above. The uppermost 18 inches of soil beneath the pavement section must consist of dense to very dense granular soil, either natural soil or structural fill. We recommend that base course materials conform to WSDOT Crushed Surfacing — Base Course (9-03.9(3)). We recommend that an MPA representative be on site to observe pavement subgrade preparation. We have also reevaluated the pavement design section Subgrade soils for the pavement at the Everett site are anticipated to be fill material. A California Bearing Ratio (CBR) of 15 should be used for the properly compacted in -place fill material. The corresponding values of modulus of Subgrade reaction, for both the CBR values and the density of the soil, would be approximately 225 pounds per cubic inch (pci) for the fill (Reese, 1974). The existing site soils are considered to have moderate frost susceptibility. The Asphalt Concrete (AC) pavement design was based on the methods outlined in Designs and Specifications for Asphalt Concrete Pavements and Bases, published by the Geotechnical and Tunnel Consultants 17270 Woodinville -Redmond Rd, Ste 703 Phone (425) 486-6561 Woodinville, WA 98072 Page 6 Fax (425) 488-2660