An 80 m long and 7.4 m wide Structural Plate Corrugated Steel Pipe (SPCSP) culvert is being proposed to accommodate a multi-purpose crossing near the top of an approximately 60 m high future earth fill dam. The proposed culvert crossing will accommodate a two-lane heavy haul road (HHR) with approximately 6.5 m of cover over the crown of the culvert. Total and differential settlements of the culvert will occur as a result of the post-construction consolidation settlement of the dam fill, dead load from the grade raise overtop and the live load conditions varying from heavy haul mining trucks to very large mine shovels. Due to the complexities of the ground and live loading conditions, a three-dimensional soil-structure interaction analysis was carried out to estimate the performance of the proposed culvert. Initially, a stress analysis using Settle3 was conducted to estimate the stress versus depth for the two types of design vehicles including two-way CAT 797F heavy haulers versus a single CAT 7495 HF shovel to determine the worst-case live loading condition. The performance of the culvert under the worst-case shovel loading condition was then evaluated using the numerical software PLAXIS 3D. To support the serviceability limit state design of the culvert, the differential settlements along the longitudinal direction under different construction stages and loading conditions were estimated. Soil improvement options below the culvert were also assessed by reviewing the sensitivity of the improvements on the predicted differential settlement response of the culvert.