Unifying Strategies for Wastewater System Revitalization: Lessons from the City of Copperas Cove

Driven by a commitment to reinvest in its wastewater system and spurred by a surge in development, the City of Copperas Cove embarked on the formulation of a tangible Capital Improvement Plan (CIP). The primary objective was not merely to assess the system based on its condition or capacity individually but to amalgamate these perspectives into a comprehensive CIP. The initiative aimed to develop a project that would scrutinize both the present and future capacity of Copperas Cove's wastewater collection system, concurrently establishing a framework for a condition assessment program. This undertaking involved the installation of 16 flow meters across the collection system, GPS data collection for 75 manholes, and the inspection of approximately 15% of the system, encompassing manhole inspections, smoke testing, and CCTV inspections. The installation of flow meters occurred from September 22nd to December 1st, 2022, during which various rain events were documented to calibrate the hydraulic model. A comprehensive hydraulic model was crafted to assess the capacity requirements of the sewer collection systems. Calibration of the model utilized flow monitoring data from all 16 meters under both dry and wet weather conditions. InfoWorks ICM, employing Wallingford's fixed runoff methodology and the groundwater infiltration model (GIM), was used to calibrate the model's hydrology. This dual-method approach enabled simulation of the City's rapid inflow responses and the slower infiltration of groundwater into the sewer collection system. The calibrated model facilitated a detailed analysis of the system's performance, addressing concerns related to small- and large-diameter pipes, lift stations, and forcemains upstream of future development areas. The Inflow and Infiltration (I/I) analysis from the flow monitoring efforts revealed that quick response inflow posed more significant challenges to the City than infiltration responses. Approximately half of the City experienced excessive inflow, with a quarter nearing the threshold of 10,000 gpd/1,000 lf of inflow. While this typically calls for prioritizing a condition assessment I/I removal program, the City's intention to create prompt action construction packages that factored in capacity needs led to discussions about capacity restrictions when determining condition assessment locations. Crucially, the analysis highlighted that areas where the City faced capacity issues were not necessarily the same areas with the most I/I. This prompted a decision-making process on whether to target I/I location and removal or identify condition issues in areas requiring capacity improvements. The timing of capacity improvement needs was also a factor in determining locations for condition assessment, prioritizing areas with existing capacity concerns related to the current level of service/development. This strategic approach allows for a systematic, comprehensive effort across the City. As part of the project, the City initiated a planned condition assessment program, involving manhole inspections, smoke testing, and CCTV inspections of targeted wastewater gravity mains. The evaluated assets were assessed for structural integrity and sources of inflow/infiltration. The program was designed to identify both public sector and private sector sources during field investigations. While public sector sources will be integrated into the CIP, the City plans to address private sector sources primarily based on the results obtained from smoke testing. While the City remains focused on CIP projects to alleviate capacity constraints for future development, it also intends to address larger inflow areas as funding becomes available, recognizing the impact on overall wastewater treatment capacity.