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Concrete manholes are widely used in sanitary sewer and storm water systems in Canada. However, technical information regarding their structural aspects is limited. The main objective of this paper is to evaluate the effect of main parameters that impact the design of precast concrete manholes. A three-dimensional finite element model for circular precast concrete manholes was developed using Plaxis 3D and was calibrated against the experimental results presented in an earlier paper by the authors. The calibrated numerical model was used to analyze different configurations of concrete manholes and to conduct a parametric study on the parameters that govern its design including: type of native soil around the manhole; trench width ( Tw); water table elevation ( Wt); effect of manhole stage installation; and effect of soil compaction. The critical conditions were identified based on the change in the pressure underneath the centre of the manhole base and the bending moments within the manhole base. It was found that the trench width, stage installation of manhole, and filling soil compaction had marginal effects on the total vertical pressure beneath the centre of the manhole base. The presence of the water table at the top of the manhole resulted in the most critical contact pressure at the manhole base. [ABSTRACT FROM AUTHOR]