Contaminant transport in subsurface is affected by phenomena at different spatial scales, from micrometers to kilometres. Pore-scale modelling is a precise approach to simulation of fundamental flow behaviour, but large-scale simulations require macroscopic inputs. The main objective of this thesis is to highlight the importance of simulation of contaminant transport in the groundwater from the pore scale to large scale. Pore-scale modelling of contaminant transport in groundwater through soil utilizing multiphase flow approach is addressed most frequently to improve understanding of flow and transport phenomena in such settings, and It can be used to obtain macro-scale constitutive equations in order to assign multiphase flow properties in large scale models, While large scale simulation provides useful information which helps contaminated site planners and decisionmakers to find optimum remediation designs. Two different approaches, namely coupled groundwater and contaminant transport model and Theory of Porous media, are developed in order to simulate contaminant transport in large scale. The coupled groundwater and contaminant transport model have been discretized with Meshfree method. Moreover, utilizing Genetic Algorithm (GA) and Particle swarm optimization (PSO) method, the optimum remediation design for two contaminated sites have been found. Utilizing extended Theory of Porous Media (eTPM), a continuum mechanical description for contaminant transport is developed. The main objective of this thesis is the development of a continuum mechanical description for solidification processes. Furthermore, its preparation for numerical treatment and implementation in the framework of the Finite Element Method (FEM) will beexplained in detail.