Charlotte Water's Use of a Risk Management Tool to Effectively Mitigate Sanitary Sewer Overflows

Purpose of Presentation: This presentation will enable the following learning objectives: -Understand the use of a risk assessment tool and its application in infrastructure management. -Understand the factors considered in risk assessment for potential sanitary sewer overflows, such as previous spills, infrastructure conditions and potential impact areas. -Understand the benefits of smart sewer technology and its role in improving wastewater management. Benefits of Presentation: Charlotte Water, the largest water and wastewater utility provider in the Carolinas, received an Administrative Order from the US EPA mandating the reduction of sewer overflows occurring throughout the system. To combat the overflows, Charlotte Water deployed real-time satellite sewer monitoring technology in targeted creek basin hotspots utilizing a unique risk assessment tool which helped identify and prioritize locations where spills were most likely to occur. In order to assess vulnerable regions and spill risks within their collection system, Charlotte Water employed a tool called Smart Nodal Analysis Protocol (SNAP). This GIS-based tool provided a means to maximize the effectiveness of smart sewer monitoring, while reducing risk and minimizing cost. SNAP incorporated Charlotte Water's field historical data with the physical properties of the collection system to identify and prioritize locations for smart sewer monitoring. This analysis allowed Charlotte Water to provide effective tradeoffs between risk reduction and the costs of basin coverage, producing an 'optimized solution' for deployment plans. All study basins were able to achieve Administrative Order compliance with less than 1% of manholes having a unit across the study areas. The SNAP tool incorporated the evaluation of the probability of an event and the potential consequence of that event. Spill probability included elements such as previous spills, intense cleaning areas, aging infrastructure, I&I regions, lift stations, etc. as compared with the evaluation of the consequences of a spill where it could potentially occur such as schools, parks, commercial areas, high density areas, beaches, rivers, lakes, etc. Status of Completion: Charlotte Water has thus far analyzed 8 out of 33 total basins covering 258 of 546 square miles or 47.25% of geographic area. This included approximately 68,201 gravity mains (out of 115,453 total) which covered 59% of gravity mains and about 2,650 miles of pipe (out of 4,430 total miles) or 59.8% miles of pipe. Conclusion: Charlotte Water currently has more than 450 monitoring units installed in targeted watershed basins to monitor trends and protect the collection system. Charlotte Water has seen substantial success with the placement of their smart sewer technology, reducing the number of SSOs by nearly 70% through FY2023. The location of the technology has prevented 33 SSOs in FY2022 and 60 in FY2023, preserving public health, the environment, utility assets and resources.