6605 HARDESON RD BASE FILE 2016-01-01 MF Import

� Intracorp September 21, 1998 E-3592-720 Pape S Utility trench backfill is a primary concern in preventinp settlement elonp utility aliynments, particularly in pavement areas. Therefore, it is fmportant that each aection of utility lina be adequateiy supported in the bedding material. The material should be hand tamped to ensure support is provided around the pipe haunches. Fill shouid be carefully placed and hend tamped to about twelve inches above the crown of the pipe before heeW compaction equipment is brought into use. The remainder of the trench backfill ahould be placed in lifts having a loose thickness of less than twelve inchea. A typical trench backflll aection and compaction requirernents for load supporting and non-load supporting areas ia presented on Plate 5. Pevament Prg� The adequacy of site pavements is related in part to the condition of the underlying subgrade. To provide a properly prepared subgrade for pavements, the subgrade should be treated and prepared as described in the Site Prepaiation and Genera/ Earthwork section of this report. This means at least the top twelve (12) inches of the subgrade should be compacted to 95 percent of the maximum dry density (per ASTM 0-1557-911. It is possible that some localized areas of soft, wet or unstable subgrade may still ex(st after this process. Overexcavation and replacement with structural fill or crushed rock may be needed to stabilize these localized areas. The following pavement section for lightly-loaded areas can be used: • Two inches of asphalt concrete (AC) over four inches of crushed rock base (CRB) material, or • Two inches of AC over th;ee inches of asphalt treated base (ATB) mate�ial, Heavier truck-traffic areas will require thicker sections depending upon site usage, pavement life and site traffic. In our opinion, the following pavement sections can be used for truck- trafficked areas: • Three inches of AC over six inches of CRB, or • Three inches o� AC over four and one-half inches of ATB, All pavement materials should conform to WSDOT specifications. A Cl;:ss B asphalt mix shouid be used. Ereh Comukma. Yw.