Tunnels play a pivotal role in the successful execution of infrastructure projects, particularly in hilly terrains like the Himalayas. This article focuses on the stability analysis and design of tunnel supports at various chainages within a tail race tunnel (TRT) of Tehri Pumped Storage Plant (PSP), a significant component of the 2,400 MW Tehri Hydro Power plant situated along the Bhagirathi River in the Indian state of Uttarakhand. The study employs finite element method (FEM) Phase 2 to evaluate the effectiveness of tunnel support design, plastic zone dimensions, and deformation within the TRT. The geological composition in this region primarily comprises phyllitic rock type with a pronounced foliation, and overburden reaching up to 350 m. Ground conditions were examined, and the study confirmed that the rock strata exhibited non-squeezing behaviour based on Q-values assessment. The design recommendations for tunnel support in this study are primarily based on the principles of the New Australian Tunnelling Method (NATM). In certain sections of the TRT tunnel, the recommended quantum of support solutions closely aligns with the actual on-site support system. However, in other sections, the study identified instances of excessive conservatism, leading to over-designed support structures. Furthermore, a disparity in the thickness of shotcrete application between the modelling and actual site conditions resulted in visible cracks on the surface of the shotcrete in some areas. Thus, the study recommended an optimised support system for enhanced stability, highlighting the effectiveness of numerical modelling in improving outcomes.