The city of Terre Haute, Indiana, faces significant challenges with its combined sewer system (CSS), which frequently results in combined sewer overflows (CSOs) during heavy rainfall events. These overflows lead to the discharge of untreated wastewater into local water bodies, posing environmental and public health risks. This study focuses on the application of the Storm Water Management Model (SWMM) to analyze and propose solutions for the CSO problem in Terre Haute. The SWMM was employed to simulate various hydrologic and hydraulic conditions within the CSS, assessing the impact of different storm events and potential mitigation strategies. Key parameters such as rainfall intensity, sewer capacity, and land use were incorporated into the model to ensure accurate representation of the system’s performance. Over the course of the study, we created a model in SWMM consisting of 9 subcatchments, 42 conduits, 33 junctions, and 11 outfalls for the city of Terre Haute. The simulation results identified critical areas prone to overflow and evaluated the effectiveness of various control measures, including green infrastructure, storage tanks, and sewer separation. The findings suggest that a combination of these measures can significantly reduce CSO occurrences, improving water quality and compliance with environmental regulations. Future work will focus on optimizing the model and aligning the model with the new plans based on city of Terre Haute’s CSO Long-Term Control Plan.