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RDC EVERETT TRANSFER FACILITY Everett,Washington <br /> Utility trench backfill should consist of structural fill and should be placed in lifts of 12 inches or <br /> less (loose thickness) when using heavy compaction equipment such as a hoe pack so that <br /> adequate compaction can be achieved throughout the lift. Each lift must be compacted prior to <br /> placing the subsequent lift. Prior to compaction, the backfill should be moisture conditioned to <br /> within 3 percent of the optimum moisture content, if necessary. The backfill should be compacted <br /> in accordance with the criteria discussed above. Figure 3 illustrates the recommended trench <br /> compaction criteria under pavement and non-structural areas. <br /> Sedimentation and Erosion Control <br /> In our opinion, the erosion potential of the on-site soils is low. Construction activities including <br /> stripping and grading will expose soils to the erosion effects of wind and water. The amount and <br /> potential impacts of erosion are partly related to the time of year that construction actually occurs. <br /> Wet weather construction will increase the amount and extent of erosion and potential <br /> sedimentation. <br /> Erosion and sedimentation control measures may be implemented by using a combination of <br /> interceptor swales, straw bale barriers, silt fences and straw mulch for temporary erosion <br /> protection of exposed soils. All disturbed areas should be finish graded and seeded as soon as <br /> practicable to reduce the risk of erosion. Erosion and sedimentation control measures should be <br /> installed and maintained in accordance with the requirements of the City of Everett. <br /> Recommended Additional Geotechnical Services <br /> Throughout this report, recommendations are provided where we consider additional geotechnical <br /> services to be appropriate. These additional services are summarized below: <br /> I . Additional explorations may be needed depending on the final development plans at the site. <br /> Additional explorations and geotechnical recommendations can be provided if requested. <br /> ■ GeoEngineers should be consulted as the design progresses and retained to review the project <br /> plans and specifications when complete to confirm that our design recommendations have <br /> been implemented as intended. <br /> ■ During construction, GeoEngineers should observe and evaluate the removal of unsuitable <br /> soils, evaluate the suitability of pavement subgrades and other appurtenant structures, <br /> observe and test structural backfill, and provide a summary letter of our construction <br /> observation services. The purposes of GeoEngineers construction phase services are to <br /> confirm that the subsurface conditions are consistent with those observed in the explorations <br /> and other reasons described in Appendix C, Report Limitations and Guidelines for Use. <br /> 1 <br /> LIMITATIONS <br /> We have prepared this report for the exclusive use of the RDC, Reid Middleton, and other <br /> authorized agents for the proposed Pavement and Stormwater Master Plan for RDC Everett <br /> Transfer Facility in Everett,Washington. <br /> I <br /> Page 10 June 18,2013 GeoEngineers,Inc. <br /> File No.4322-002-00 <br />