The Mark at Eugene January 6, 2026 <br />Geotechnical Investigation and Seismic Hazard Study 5 Project No.: 2251077 <br />Eugene, Oregon Landmark Construction, LLC <br />• Residual soil. Residual soil consisting of very stiff to hard clayey silt with <br />varying amounts of sand was encountered in each of the borings underlying <br />the alluvium. Additional residual soil consisting of very dense silty sand with <br />some gravel was encountered in the bottom of BH-4 and the deeper profile of <br />BH-2 underlying the clayey silt and extending to ±81.5 feet, the maximum <br />depth of the explorations. <br />Groundwater <br />The use of mud-rotary drilling methods precluded the measurement of groundwater <br />at the time of drilling. However, a one-inch (I.D.) standpipe piezometer was installed <br />in BH-2 to monitor the groundwater level after drilling. The installation was capped <br />at the ground surface with a locking cap and a flush Morris monument set in <br />concrete. The piezometer was slotted from ±10 to 25 feet. <br />Following the piezometer installation, a groundwater measurement was taken <br />indicating a static water level of ±6 feet. The depth was measured at 6.1 feet in a <br />subsequent measurement on December 30, 2025. The depth is referenced to the <br />surface of the Morris monument. We anticipate the groundwater level fluctuates <br />seasonally and a perched water condition may develop near the ground surface <br />during periods of sustained or heavy rainfall typical in the winter and spring months. <br />SEISMIC ANALYSIS AND EVALUATION <br />We reviewed the potential seismic-geologic hazards at the site including landslides <br />(i.e., slope instability), liquefaction, seismically-induced settlement and subsidence, <br />fault rupture, seiche, and flooding or inundation in general accordance with OSSC <br />Section 1803.6.1. The evaluation of the local seismic hazards was completed by <br />Brooke Running R.G., C.E.G. The results of the evaluation are provided in the Seismic <br />Hazard Study report in Appendix D. The findings indicate there are no seismic hazards <br />that would preclude the development of the project. <br />Site Response Spectrum <br />A design spectral acceleration response spectrum for the site was developed in <br />accordance with the 2022 OSSC, which is based on Section 1613 of the 2021 <br />International Building Code (IBC) and ASCE 7-16. The design maximum considered <br />earthquake ground motion maps in IBC 2021 are based on modified 2014 USGS <br />maps with a 2% probability of exceedance in 50 years (i.e., a ±2,475-year return <br />period) for design spectral accelerations. The modifications include factors to adjust <br />the spectral accelerations to account for directivity and risk. <br />