below the test depth at P-3. The gravel was encountered at ±5.5 feet at TP-6, or <br />±1.5 feet below the infiltration test depth. Consistent with the observed test results, <br />we anticipate significantly higher infiltration rates will be possible if infiltration facilities <br />extend to depths corresponding to the underlying gravel stratum. However, the gravel <br />depth fluctuates across the property and, at some locations, may be close to or below <br />the seasonally high ground water depth. <br />Laboratory Testing <br />Current laboratory testing was limited to index tests (i.e., Atterberg limits, percent <br />fines and water contents) on select samples to help classify the soils according to the <br />Unified Soil Classification System (USCS) and estimate their engineering properties. <br />The results are summarized in Table 2. The results indicate the soils encountered at <br />the foundation level typically consist of low to medium plasticity silt to clayey silt. <br />Table 2. Natural Water Content, Atterberg Limits & Percent Fines <br /> <br />Sample Sample Natural Percent USCS <br />Depth Water Fines <br />Number LL PL Classification <br />PI <br />(feet) Content (%) (%) <br />R,1,00-4ũ2-/18-2432408LG <br />R,3,01-4ũ2-/21-142221/LG <br />R,4,12-/ũ3-/16-6312000LK <br />R,0/,06-4ũ7-/24-/3224782-6LK <br />GEOTECHNICAL CONSIDERATIONS <br />The following provides a general discussion of pertinent geotechnical considerations. <br />More specific recommendations for site development, structural foundation design, <br />and pavements can be provided once the planning and design progress past the <br />conceptual stage. <br />Foundation Soils <br />The soils encountered at the anticipated foundation elevation consist of low to <br />medium plasticity silt to clayey silt. The foundation soils were typically damp to moist <br />and stiff to very stiff at the time of the exploration. The subsurface profile and/or <br />geological conditions are generally consistent with our observations at other nearby <br />locations. <br />The foundation soils are suitable for supporting conventional shallow spread footings <br />with modest bearing pressures similar to other developments in the area. We did not <br />encounter high plasticity clays, deep deposits of peat or organic soils, construction <br />debris, or other deleterious materials that would require significant overexcavation, <br />use of deep foundations, or other extensive mitigation measures. Additional <br />geotechnical explorations should be completed to confirm the subsurface conditions <br />once building locations are identified. <br />River Road Multi-Family Development April 30, 2018 <br />Preliminary Geotechnical Investigation 6. Project 2171066 <br />Eugene, Oregon Evergreen Housing Development Group, LLC <br /> <br />