1304 80TH ST SW EVERETT SCHOOL DISTRICT 2018-01-02 MF Import

Subsurface Esplomtion and Everett Bus Facility Geotechnical Engineering Report ` Everett, Washington Design Recommendations 1 fill) subgrade compacted to at least 95 percent of the modified Proctor maximum dry density, as determined by ASTM:D-1557. Areas that will be used for buses, fire trucks, garbage trucks, or other heavy vehicles should be designed using a section consisting of 4 inches of Class "B" asphalt above 8 inches of compacted crushed surfacing base course over a 95 percent compacted granular subgrade. We anticipate that Portland cement concrete (PCC) will he used for any new walkways and courtyards. We recommend a concrete sidewalk and courtyard section consisting of 4 inches of PCC surfacing above a minimum of 4 inches of crushed surfacing top course per WSDOT Standard Specification 9-03.9(3) above a subgrade compacted to at least 95 percent of the modified Proctor maximum dry density, as determined by ASTM:D-1557. Areas that will be crossed by delivery trucks, buses, garbage trucks, or other heavy vehicles should be designed using a section consisting of at least 6 inches of PCC above a minimum of 8 inches of compacted crushed surfacing top course above a subgrade compacted to at least 95 percent. After the areas to be paved are stripped and/or excavated to pavement subgrade elevation, the exposed ground should be compacted to at least 95 percent of ASTM:D-1557, or to a firm and unyielding condition, as determined by the geotechnical engineer or his representative. We recommend proof-rolling pavement subgrades that will underlie vehicle traffic with a loaded dump truck to identify any soft or yielding areas. If required, the unsuitable material will be removed to the geotechnical engineer's satisfaction and structural fill may then be placed to achieve desired subbase grades. Upon completion of the compaction and structural rill placement, the pavement section for the design level of services can be constructed. Depending on construction staging and desired performance, the crushed surfacing base course material may be substituted with asphalt treated base(ATB) beneath the final asphalt surfacing. The substitution of ATB should be as follows: 4 inches of crushed rock can be substituted with 3 inches of ATB, and 8 inches of crushed rock may be substituted with 5.5 inches of ATB. ATB should be placed over a properly compacted, native or structural fill subgrade compacted to at least 95 percent of ASTM:D-1557, and a 1.5- to 2-inch thickness of crushed rock to act as a working surface. If ATB is used for construction access and staging areas, some rutting and disturbance of the ATR surface should be expected. The general contractor should remove affected areas and replace them with properly compacted ATB prior to final surfacing. 9.0 VAULT FOUNDATIONS ' Spread footings may be used for vault support when founded on medium dense to dense lodgement till or on new str',,ctui.il fill placed as previously discussed. We recommend that an allowable bearing pressure of 5,000 pounds Per square foot (psl) (including both dead and live loads) be utilized for vault foundation design purposes if it is founded on combinations of the Aw4mber28, 1005 ASSOMTED EIRMSCIEWM,INC. E Md.M360:82-n"t n,uozrm:LrnWr Page 9 1