The Mactaquac Main Dam is a 56 m high zoned rockfill dam founded on glacial till underlain by an artesian aquifer. A two-dimensional FLAC seismic deformation analysis was completed for the 1-in-10,000-year event after pseudostatic analyses did not meet CDA Dam Safety Guidelines stability criteria. The 2018 FLAC analysis indicated that overtopping and overall slope failure were not expected, although downstream-bench deformation could damage the relief wells. Subsequent survey data and additional historical records indicated that the modelled section represented tender-stage rather than the most likely as-built geometry and provided improved material-strength information. A screening workflow was used to determine whether the revised conditions warranted redevelopment of the dynamic model. Simplified methods were applied to the original dam conditions, and the resulting crest-displacement estimates were compared with the FLAC results to establish a project-specific interpretation of the relative agreement and conservatism of each method. The simplified methods were then applied to the revised geometry and material properties to assess whether the expected crest displacement would change sufficiently to warrant redevelopment of the dynamic model. For the revised conditions, the screening indicated likely crest displacements of about 10 cm, with more conservative estimates not exceeding 25 cm. Within the limitations of the screening, the revised information did not indicate a material change in crest-displacement or overtopping potential. Unless additional shear-wave velocity data, if obtained, indicate a materially different dynamic stiffness profile, redevelopment of the dynamic model was not considered warranted at that time. Although the workflow may be transferable, interpretation of the simplifiedmethod results is project-specific. The screening did not reassess internal dam response or potential relief-well damage.