A combined sewer overflow (CSO) occurs when a sewage system designed to handle both stormwater and wastewater becomes overwhelmed, typically during heavy rainfall. In these situations, excess water can lead to the release of untreated sewage into nearby rivers, lakes, or oceans, posing environmental and public health risks. CSOs are a concern in many urban areas where the infrastructure is outdated or insufficient. To manage this issue, cities often implement strategies such as green infrastructure, which includes rain gardens and permeable pavements, to reduce stormwater runoff and improve the overall efficiency of the sewer system.