Preliminary Geotechnical Engineering Report <br />Project No. 18-4986, 177 Day Island Road, Eugene, Oregon <br />NO " <br />of 5 feet will be sufficient to achieve the recommended replacement. However, the depth of this <br />layer of loose sand may vary across the site and should be evaluated during construction. Since <br />groundwater levels on the site are expected to vary with the level of the slough of the Willamette <br />River adjacent to the site, we recommend that removal of the layer of loose sand be performed in a <br />period when water levels in the adjacent slough are low. <br />This geotechnical engineering report is considered preliminary since plans for development of the <br />site have not yet been provided to GeoPacific for review. The following report sections provide <br />preliminary recommendations for site development and construction in accordance with the current <br />applicable codes and local standards of practice. <br />Site Preparation Recommendations <br />Areas of proposed buildings, new pavement sections, and areas to receive fill should be cleared of <br />vegetation and any organic and inorganic debris. Existing buried structures should be demolished <br />and any cavities structurally backfilled. Inorganic debris and organic materials from clearing should <br />be removed from the site. <br />Existing fill and any organic-rich topsoil should then be stripped from construction areas of the site <br />or where engineered fill is to be placed. The estimated depth necessary for removal of topsoil is <br />approximately 8 to 10 inches - deeper stripping may be necessary to remove large tree roots in <br />isolated areas or disturbed soils. The final depth of soil removal will be determined on the basis of <br />a site inspection after the stripping/ excavation has been performed. Stripped topsoil should <br />preferably be removed from the site. Any remaining topsoil should be stockpiled only in <br />designated areas and stripping operations should be observed and documented by the <br />geotechnical engineer or his representative. <br />Any remaining undocumented fills and subsurface structures (tile drains, basements, driveway and <br />landscaping fill, old utility lines, septic leach fields, etc.) should be removed and the excavations <br />backfilled with engineered fill. <br />The layer of loose sand should be removed from the influence zones of proposed structures or <br />other settlement-sensitive improvements and should be replaced with engineered fill. Removal of <br />undocumented fill soils should extend horizontally to include the influence zone of the proposed <br />structure, extending at a 1 H:1 V line from the edge of the perimeter footing. It will likely be feasible <br />for the layer of loose SAND (SP) to remain in place beneath parking areas, landscape areas, and <br />other improvements not sensitive to static or seismically-induced settlement. <br />Once stripping of a particular area is approved, the area must be ripped or tilled to a depth of 12 <br />inches, moisture conditioned, root-picked, and compacted in-place prior to the placement of <br />engineered fill or crushed aggregate base for pavement. Exposed subgrade soils should be <br />evaluated by the geotechnical engineer. For large areas, this evaluation is normally performed by <br />proof-rolling the exposed subgrade with a fully loaded scraper or dump truck. For smaller areas <br />where access is restricted, the subgrade should be evaluated by probing the soil with a steel <br />probe. Soft/loose soils identified during subgrade preparation should be compacted to a firm and <br />18-4986, 177 Day Island Road GRPT 5 GEOPACIFIC ENGINEERING, INC. <br />Version 1, August 27, 2018 <br />