9909 2ND AVE W 2018-08-01 - Laserfiche WebLink

December 13,2006 Proect No.T-600l Subsurface We recommend installing a continuous drain along the outside lower edge of the perimeter building foundations. The foundation drains should be tightlined to an approved point of controlled discharge independent of the roof drain system. Subsurface drains must be laid with a gradient sufficient to promote positive flow to the point of 111 discharge. All drains should be provided with cleanouts at easily accessible locations. These cleanouts should be serviced at least once every year. 5.9 Utilities Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) or the applicable jurisdiction's specifications. As a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 5.2 of this report. As noted, successful use of on-site soils as fill will require close moisture control. When moisture cannot be controlled to facilitate proper compaction, trench backfill should consist of an imported granular soil that meets the grading requirements presented in Section 5.2 of this report. 5.10 Pavements Driveway and parking pavements within the project site should be constructed on subgrades as described in Section 5.2 of this report. Reprdess of the relative compaction achieved, the subgrade must be firm and unyielding before pavane. Proofroiling the subgrade with heavy construction equipment should be completed to verify this condition. The thickness of the various components of the pavement depends on the subgrade soils and the traffic conditions to which the pavement will be subjected. We expect traffic to mainly consist of light passenger vehicles, with only occasional heavy service vehicles. Based on this information, and assuming a properly prepared and stable subgrade, we recommend the following option for pavement sections: • Two inches of asphalt concrete(AC)over four inches of crushed rock base(CRB) • Two inches of AC over three inches of asphalt-treated base(ATB) All paving materials should conform to the 2006 WSDOT specifications for "Hot Mix Asphalt" (HMA). Crushed rock base course and ATB material should aso conform to the 2006 WSDOT specifications. Long-term pavement performance will depend on surface drainage. A poorly-drained pavement section will be subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their supporting capability. To improve performance, we recommend surface drainage gradients of at least two percent. Some longitudinal and transverse cracking of the pavement surface should be expected over time. Regular maintenance should be planned to seal cracks when they occur. Page No. 9