Embracing the Unknown: Integrating Operational Flexibility in Collections System Master Planning

Utilities across the United States and globally are being faced with the increasing challenge of planning infrastructure investments which will meet their community's needs for the next 25-50+ years when future demand scenarios or needs are becoming harder to predict. Despite unprecedented access to data for guiding plans, managing uncertainty about future conditions and ensuring flexibility have become central to capital improvement and master planning. Considering a wide variety of possible infrastructure investments and potential system demands to ensure a system can appropriately support future growth is a challenging and time-consuming process, even with the power of modern hydraulic computer modeling. To build resilience and operational flexibility into their CIP, Pinellas County Utilities (PCU) partnered with Wade Trim to streamline CIP development and address required updates to the hydraulic system. PCU has two distinct basins within their wastewater collections network, North and South. The collections systems within these basins had different challenges to address to meet their overall CIP objectives, which required potential solutions to be developed for each basin separately. For the South Basin, one major focus was on the rehabilitation of collections pipes to reduce inflow & infiltration (I&I)-related capacity demand. To explore where and how to do this, the PCU team was considering over 135 areas to invest in system improvements involving 5 technologies. The primary issue was uncertainty around the real-world effectiveness of each of those technologies and finding the most cost-effective solution from hundreds of thousands of potential combinations of the 5 technologies. For the North Basin, concern was capacity issues related to undersized sewers and pump stations leading to spills, and oversized sewers which caused low velocity in dry weather. The variability in potential future growth in the area required a potential overhaul of the flow throughout the basin on top of addressing the existing capacity issues. The adjustment in flow within the basin led to 4 very different operational and CIP scenarios, each of which leading to a different set of upgraded pipes and pump station. Using this information, they were able to identify common projects across all the operational scenarios. This offered a high degree of certainty on how they could approach their CIP investments despite the uncertainty of the future capacity needs. Wade Trim and PCU primarily used the Optimization software from Optimatics to sort through hundreds of thousands of potential solutions, balancing tradeoffs between hydraulic performance and costs by using genetic algorithms to narrow in on the highest-performing and most cost-effective solutions. Integrating a hydraulic model into optimization software results in a uniquely robust analysis of the network to efficiently find solutions that best meet a range of criteria, objectives, and constraints. This approach enabled them to systematically and objectively explore different ways they could address the existing deficiencies within their collections system, but through solutions that will meet their future capacity needs. Through the Optimization tool, the interdependence between specific projects and performance outcomes within the two basins were also explored, enabling the systems to be adjusted based on information gathered by previous iterations and runs, called 'Operational Flexibility'. This level of insight underpins clear, objective decision-making by highlighting infrastructure and operations choices which meet performance criteria in multiple scenarios for a resilient CIP. What was identified very quickly using optimization was different projects in the resulting plans which were interchangeable to solve sewer overflow problems. Discussing these resulting projects created the opportunity to choose effective solutions that also aligned with PCU's strategic preferences (e.g. avoiding upstream tanks). The plans developed through optimization also offered substantial cost savings for implementation. Overall, this presentation showcases the analytical framework, optimization strategies and decision-making that drove improvements to the Pinellas County CIP plan, demonstrating the impact that the Optimization tool has on developing solutions. Navigating uncertainty with confidence is the power that comes from leveraging the power of optimization to effectively integrate operational flexibility into infrastructure investment plans. PCU was able to use evolving digital tools to answer complex questions to direct how to invest resources to best address their collection system needs today and well into the future.