Laserfiche WebLink
� <br />.� <br />� <br />GEOTECHNICAL ENGINEERING STUDY <br />Trace and Associates <br />July 19, 2005 <br />E-11880 <br />Page 13 <br />� Fill should be carefully placed and hand tamped to about 12 inches above the crown of <br />tlie pipe before heavy compaction equipment is brought into use. The remainder of the <br />trench backfill should be placed in lifts having a loose thickness of less than 12 inches. <br />� Sugqested Pnvement Sections <br />� The adequacy of site pavements is related in part to the condition of the underlying <br />subgrade. To provide a properly prepared subgrade for pavements, the subgrade should <br />� be treated and prepared as described in the Site Preparafion and General Eartliwork <br />section of this report. This means at least the top 12 inches of the subgrade should be <br />compacted to a minimum of 95 percent of the maximum dry density (per ASTM D- <br />� 1557). It is possible that some localized areas of soft, wet, or unstable subgrade may <br />still exist after this process. Therefore, a greater thickness of structural fill or crushed <br />rock may be needed to stabilize these localized areas. Proofrolling of the pavement <br />� subgrade should be performed with a loaded dump truck prior to paving. ECI should <br />observe the proofrolling and identify areas of unstable subgrade. <br />� <br />� <br />� <br />� <br />� <br />�I <br />� <br />� <br />� <br />The following pavement section for lightly-loaded areas is suggested: <br />• 2 inches of asphalt concrete iAC) over 4 inches of crushed rock base (CRB) <br />material, or <br />• 2 inches of AC over 3 inches of asphalt treated base (ATB) material. <br />If heavy truck-traffic areas are planned, we can provide appropriate pavement sections <br />for these areas. <br />f'avement materials sliould conform to WSDOT specifications. The use of a Class B <br />asphalt mix is suggested. <br />LIMITATIONS <br />Our recommendations and conclusions are based on the observed site materials, <br />selective laboratory testing, engineering analyses, preliminary design information, and <br />our experience and engineering judgment. The conclusions and recommendations are <br />professional opinions derived in a manner consistent with that level of care and skill <br />ordinarily exercised by ottier members of the profession currently practicing under <br />similar conditions in this area. No warranty is expressed or implied. <br />Garth Consullanls, Ina <br />