Alternate: Successful Collaboration between Operations and Engineering by Leveraging Countywide Hydraulic Model to Improve Collection System Performance and Increase Operational Efficiencies

The Gwinnett County Department of Water Resources (GCDWR) recently developed a comprehensive, countywide sanitary sewer model to facilitate a holistic evaluation of the current system operations in support of a viable capital improvement program. The new countywide hydraulic model provides enhanced functionality to understand regional and local system conditions at pump stations, flow diversions, and water reclamation facilities. Operations staff are a critical component of the model development process to accurately simulate field conditions given their first-hand knowledge of the system. An overview of GCDWR collection system service area is shown in Figure 1. Using two case studies, this paper demonstrates that hydraulic modeling provides a mutually beneficial outcome through the collaboration of operations and engineering teams. These studies show that successful collaboration yields a better understanding of operational needs and capacity deficiencies. In addition, these studies illustrate the importance of Supervisory Control and Data Acquisition (SCADA) and a flow monitoring program to accurately simulate the actual system conditions.

Case Study 1: Eastside Conveyance System -- The eastside conveyance system consists of a manifolded force main that conveys flow from three regional pump stations. The force main also contains two booster pump stations with variable frequency drives (VFDs). During large, countywide rainfall events, operations staff reported that the three regional pump stations could not simultaneously operate at firm capacity without forcing the Alcovy River Pump Station (shown in Figure 1) to operate beyond the allowable operating range. The engineering team used SCADA and flow monitoring data to confirm these observations and calibrate the hydraulic model. An example of the model vs. observed pump hydrographs are shown in Figure 2. Subsequent simulations conducted using the calibrated model isolated the issue and facilitated the evaluation of several solutions, which allowed engineering and operations staff to analyze several strategies increasing understanding and enabling collaboration prior to implementation.

Case Study 2: Crooked Creek WRF Service Area -- In the second case study, the operations group collaborated with the engineering team to evaluate the emergency storage needs as well as locations vulnerable to surcharge in the event that the North Chattahoochee Pump Station (shown in Figure 1) goes offline. The Countywide hydraulic model was used to analyze the emergency storage volume requirements, the estimated time to fill the storage volume and the estimated time to reach the high-level alarm at the pump station. This information helped the operations group better understand the response time to implement operational procedures at the upstream flow diversion structures in the event of an emergency. This case study summarizes the hydraulic modeling efforts used to make informed decisions and prepare an emergency plan of action.