The Mark at Eugene January 6, 2026 <br />Geotechnical Investigation and Seismic Hazard Study 10 Project No.: 2251077 <br />Eugene, Oregon Landmark Construction, LLC <br />The analysis was completed assuming the footings will be sized using an allowable <br />bearing pressure of 2,000 psf and the provided maximum foundation loads. We <br />assumed the footings will extend ±1.5 feet below the existing ground surface and <br />bear on a minimum of 12 inches of compacted granular fill extending a minimum of <br />12 inches outside the footing. Our analysis indicates total foundation settlement of <br />up to ¾ inch for the maximum foundation loads. <br />Differential settlement between adjacent footings across the site may be assumed to <br />be up to ½ inch for the maximum foundation loads. This differential settlement is <br />expected to occur over a distance of 30 feet or greater within the building footprint. <br />In an effort to minimize the impacts of differential settlement, we anticipate that <br />excavation and backfill of areas adjacent to previous basements will require deeper <br />excavation during the site preparation work. We recommend that the location of the <br />transition of previous basement areas and proposed foundations be confirmed in the <br />field at the time of construction. <br />Modulus of Subgrade Reaction for Concrete Slab or Mat Foundations <br />We recommend a modulus of subgrade reaction, ks, of 50 kips/ft3 (kcf) for the design <br />of slab-on-grade foundations. This value has been reduced from typical values used <br />for slab-on-grade over granular fill to account for the larger footprint of the post- <br />tensioned slab being used to support the structure. This value assumes the slabs or <br />mats will be supported on compacted Base Aggregate that is at least 18 inches thick <br />and extends a minimum of 12 inches beyond the edges. Reinforcement of the mats <br />or slabs should be designed by the structural consultant to resist cracking or warping <br />due to differential settlement. <br />Sliding Coefficient and Passive Resistance for Footings <br />A sliding coefficient of 0.5 is recommended to analyze the sliding resistance between <br />the base of the concrete footings or mat and the underlying Base Aggregate. <br />Passive resistance of the backfill in front of the mats or buried footings was <br />calculated as an equivalent fluid density equal to γ*Kp, where γ is the unit weight of <br />the backfill and Kp is the passive earth pressure coefficient. We used an angle of <br />internal friction (φ) of 34 degrees and a moist unit weight of 125 pcf for the backfill, <br />assuming the backfill around the footings will consist of compacted Base Aggregate. <br />Based on these values, an equivalent fluid density of 150 pcf is recommended for <br />design. A factor of safety of 3 has been applied to the passive resistance values, <br />since it is unlikely the footings will move laterally enough to fully mobilize the passive <br />resistance.