The Mark at Eugene January 6, 2026 <br />Geotechnical Investigation and Seismic Hazard Study 13 Project No.: 2251077 <br />Eugene, Oregon Landmark Construction, LLC <br />5. Subsurface Drainage Geotextile should be a non-woven geotextile with Mean <br />Average Roll Value (MARV) strength properties meeting the requirements of <br />an AASHTO M 288-24 Class 3 geotextile (Subsurface Drainage Geotextile), <br />with a maximum AOS of 0.3 mm (max average roll value) and a permittivity <br />greater than 0.1 sec-1. We should be provided a specification sheet on the <br />selected geotextile for approval prior to delivery to the site. <br />6. Place and compact all imported or on-site granular fill in loose lifts not <br />exceeding 12 inches. Thinner lifts (8 inches or less) will be required where <br />light or hand-operated equipment is used. <br />Compact the Base Aggregate, Granular Structural Fill, On-site Structural Fill <br />and existing gravel fill in deeper excavations (i.e., utility trenches or basement <br />backfill) to a minimum 95% relative compaction. The maximum dry density <br />of ASTM D698 should be used as the standard for estimating the relative <br />compaction. <br />Efficient compaction of granular soils will require a smooth drum, vibratory <br />roller. Walk-behind plate compactors or hoe-mounted compactors may be <br />required in areas of limited access. <br />Field density tests should be performed frequently to confirm adequate <br />compaction of all granular fills. Granular Structural Fill which is too coarse <br />for density testing should be proof-rolled using a loaded ±10-yd3 dump truck <br />or other approved vehicle or method. Any compaction verification with <br />proof-rolling should be evaluated by a FE representative. Areas of pumping <br />or deflection may be reworked, or overexcavated and replaced with <br />compacted Base Aggregate and proof-rolled again. <br />7. Excavations should be shored or sloped in accordance with Oregon OSHA <br />requirements to protect workers. The excavations are expected to extend <br />through medium stiff to stiff fine-grained alluvium or medium dense to dense <br />crushed gravel. The fine-grained alluvium typically corresponds to an <br />OR-OSHA Type B soil. OR-OSHA recommends a maximum temporary cut <br />slope of 1H:1V in Type B soil. The crushed gravel corresponds to an <br />OR-OSHA Type C soil. OR-OSHA recommends a maximum temporary cut <br />slope of 1½H:1V in Type C soil. Suitable cut slopes should be confirmed in <br />the field by a FE representative at the time of construction. <br />8. The groundwater depth should be established prior to beginning excavations <br />by monitoring the piezometer at BH-2 or other installations the contractor <br />may use. We recommend the groundwater levels be monitored over the <br />upcoming winter months prior to construction. <br />All excavations should be pumped to remove any standing water prior to <br />placing fill and constructing new foundations. The existing basement <br />excavation and backfilling are expected to require pumping throughout the <br />backfill work.