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DevCo, Inc. ES-6516 <br />April 1, 2019 Page 12 <br />Final pavement design recommendations, including recommendations for heavy traffic areas, <br />access roads, and frontage improvement areas, can be provided once final traffic loading has <br />been determined. Road standards utilized by the governing jurisdiction may supersede the <br />recommendations provided in this report. The HMA, ATB, and CRIB materials should conform to <br />WSDOT specifications. All soil base material should be compacted to a relative compaction of <br />95 percent, based on the laboratory maximum dry density as determined by ASTM D1557. <br />Utility Support and Trench Backfill <br />In our opinion, on -site soils will generally be suitable for support of utilities. Remedial measures <br />may be necessary in some areas to provide support for utilities, such as overexcavation and <br />replacement with structural fill and/or placement of geotextile fabric. Groundwater seepage may <br />be encountered within utility excavations, and caving of trench walls may occur where <br />groundwater is encountered. Depending on the time of year and conditions encountered, <br />dewatering, as well as temporary trench shoring, may be necessary during utility excavation and <br />installation. <br />Using on -site soils successfully as structural backfill throughout utility trench excavations will <br />depend on the moisture content at the time of placement and compaction. Moisture conditioning <br />of the soils may be necessary at some locations prior to use as structural fill. Each section of the <br />utility lines must be adequately supported in the bedding material. Utility trench backfill should <br />be placed and compacted to the specifications of structural fill as previously detailed in this report, <br />or to the applicable specifications of the responsible jurisdiction or agency. <br />LIMITATIONS <br />The recommendations and conclusions provided in this study are professional opinions <br />consistent with the level of care and skill that is typical of other members in the profession <br />currently practicing under similar conditions in this area. A warranty is neither expressed nor <br />implied. Variations in the soil and groundwater conditions observed at the boring locations may <br />exist and may not become evident until construction. ESNW should reevaluate the conclusions <br />provided in this study if variations are encountered. <br />Additional Services <br />ESNW should have an opportunity to review final project plans with respect to the geotechnical <br />recommendations provided in this report. ESNW should also be retained to provide testing and <br />consultation services during construction. <br />Earth Solutions NW, LLC <br />