Ensuring stability to the dam foundation of a hydropower plant involves understanding geological conditions, adhering to quality standards, and implementing regular maintenance. The economic performance of the plant depends on both construction and long-term operational costs. Curtain grouting is an effective method for enhancing dam stability by injecting grout to fill voids and fractures, reducing seepage, and increasing the foundation's strength and impermeability. After drilling holes to the designed depth, grouting was conducted in an upward sequence, with intervals of 3–5 m at the maximum pressure of 10 bars. Employing a stage-wise approach, encompassing primary, secondary, and tertiary stages, this study demonstrates a notable reduction in permeability values and a gradual decrease in grout injection rate across successive stages, indicative of a successful intervention. Through this case study, we underscore the significance of targeted grouting techniques in the Himalayan rock masses. The findings offer valuable insights for future dam construction and infrastructure projects in similar geologic contexts, emphasizing the importance of proactive mitigation strategies in ensuring the safety and longevity of critical infrastructure in the Himalayan rock mass.