Challenges of Model Development & Calibration in the Development of Multiple Basin-Level Models and their Integration into the City’s Sanitary Long-Range Plan: A Case Study of City of Calgary Sanitary District Studies

One of the roles of the Asset Planning group within the City of Calgary Water Resources Business Unit is to assess the performance of its sanitary conveyance systems and if necessary, recommend upgrades both to address current deficiencies in service levels and to provide capacity for future growth.The City of Calgary has a large scale multi-year flow monitoring program and a uniform framework for model development and calibration methodology based on the Hydraulic Modeling Guidance Document (HMGD) (AECOM, 2011).Given the large size of the City, efforts have been focused on the development of multiple basin-level “sanitary district models” for the major catchment areas, which when combined have been used to form the basis for modeling in the overall Sanitary Long Range Plan.Numerous sanitary district studies (SDS) were initiated and tasked with the development of a MikeUrban Basin-level model as described in the City’s Hydraulic Modeling Guidance Document (HMGD). The basin-level model typically includes only pipes 300mm in diameter or larger.This presentation will focus on the challenges faced and results of the development and calibration of multiple basin-level hydraulic models for the City of Calgary’s sanitary sewer collection system. The presentation will focus on the McKenzie, Nose Creek and Southeast Industrial SDS projects. Note: The Southeast Industrial SDS will be complete by June 2016, results are not available at this time.For the McKenzie SDS (1,800 ha; 3 Flow Monitors), one of the key challenges of this project was the calibration and modeling approach used to simulate the performance of the McKenzie Siphon. The hydraulic capacity of the inlet chamber and downstream siphon was a primary focus of the modeling analysis, of which our team ensured the calibration of the model represented actual system performance. Key recommendations of the study were focused on the siphon inlet chamber and improving the capacity of the siphon to accommodate future flows. For the Nose Creek SDS (17,800ha; 15 Flow Monitors), some of the key challenges of this project included the iterative approach for model calibration that was required in integrating inflows from the Inner City/Glenmore Sanitary District Study models (by others), modeling of system improvements in progress (Nose Creek Trunks), as well as the modeling and calibration of numerous siphons and boundary conditions along the 15th Street Siphon and Bonnybrook WWTP.The presentation will discuss the aspects of:MikeUrban model development and structure for SDS and integration into the Sanitary Long Range Plan;Selection of initial model parameters;Dry Weather Flow (DWF) calibration, verification of depths and velocities;WWF Wet Weather Flow (WWF) Calibration using the MikeUrban “Model A” (long duration Infiltration) and “RDI” (short duration inflow and infiltration) modules;Flow calibration iterations and results, verification of depths and velocities; andTypical challenges associated with keeping modeling calibration and recommendations up to date.The results and hydraulic models developed in each of the City’s SDS projects were then incorporated into the development of the skeleton hydraulic model for the Sanitary Long Range Plan. In doing so, there was some degree of work involved inputting and converting these models into a format that was compatible with the skeleton model, particularly in setting up the modeled wet weather events to be consistent from model to model to simulate peak flows in the downstream trunks and to the various WWTPs.