The Mark at Eugene January 6, 2026 <br />Geotechnical Investigation and Seismic Hazard Study 12 Project No.: 2251077 <br />Eugene, Oregon Landmark Construction, LLC <br />Excavations, Shoring, and Dewatering <br />It is the contractor’s responsibility to provide and maintain stable cut slopes, <br />benching, or shoring as required by the Oregon Occupational Safety and Health <br />Administration (OR-OSHA). Excavations are expected to extend through <br />predominately medium stiff to stiff fine-grained alluvium and/or dense crushed gravel. <br />Portions of the site include backfill associated with previous basements that may <br />require additional considerations for excavations or shoring. Therefore, field <br />confirmation of soil conditions and the appropriate shoring or excavation slopes <br />should be anticipated. <br />The medium stiff to stiff fine-grained alluvium corresponds most closely to OR‐OSHA <br />Type B soil. OR-OSHA recommends maximum allowable temporary cut slopes of <br />1H:1V in Type B soil. The crushed gravel corresponds to and OR-OSHA Type C soil. <br />OR-OSHA recommends maximum allowable temporary cut slopes of 1½H:1V in Type <br />C soil. The actual cut slopes will need to be confirmed based on the actual conditions <br />at the time of construction. <br />We anticipate the static groundwater level will be below the typical planned <br />foundation excavation depths. Demolition excavations at existing basements may <br />require dewatering as part of the work. However, perched water or runoff from <br />adjacent slopes may be encountered if the work is completed during wet weather. <br />RECOMMENDATIONS <br />General Earthwork and Material Recommendations <br />The construction recommendations provided below assume earthwork will occur <br />during dry weather. Depending on the actual time of year construction begins, <br />modifications to the respective recommendations may be required. <br />1. Base Aggregate as defined in this report should consist of ¾- or 1-inch minus, <br />clean (i.e., less than 5% passing the #200 U.S. Sieve), well-graded, crushed <br />gravel or rock. <br />2. Granular Structural Fill should consist of 3- to 4-inch minus, clean, <br />open-graded, crushed quarry rock. <br />3. On-site Granular Structural Fill should consist of on-site concrete with <br />reinforcing steel removed and crushed to 3-inch minus, well-graded granular <br />fill. <br />4. Drain Rock should consist of ¾ to 1½-inch, clean (less than 2% passing the <br />#200 sieve), open-graded, angular, crushed quarry rock. Other gradations <br />may be acceptable, provided the rock is durable and free draining. We should <br />be provided a gradation sheet for this material for approval prior to delivery <br />to the site.