Water Service - Municipal Infrastructure
Lower Mill Creek Systems Analysis
Metropolitan Sewer District of Greater Cincinnati
Updating model of 45,000 acres/22,000 pipes into a version that could simultaneously run in a reasonable timeframe and prodeuce meaningful results for testing alternatives
XCG Consultants, Inc. (XCG) was contracted by MSDGC to perform a review and update of the System Wide Model (SWM) for the Mill Creek WWTP sewershed. The purpose of the project is to update the SWM with features that have been constructed since the last model update in 2008 as well as to further calibrate the model based on recent flow monitoring data. The base model includes over 20,000 pipes & manholes and over 6,000 runoff catchments. The model update included a review of all hydrology parameters and catchment delineation and a review of the hydraulic network. Significant changes to the model include:
- Addition of Real Time Control (RTC) facilities
- Updates to the CSO regulators and site-specific CSO regulator settings;
- Updated and expanded modeling of SSO 700 High Rate Treatment Facility; and
- Adjustments to WWTP inflow pumping to more closely simulate the operation of the WWTP and reflect the hydraulic grade line of the collection system.
Several versions of the SWM were developed to reflect the Mill Creek WWTP sewershed as it existed in December 2007 (baseline), is expected by December 2010 (improvements to date), and is anticipated for December 2011 (scheduled improvements). The purpose of this effort is to demonstrate the impact of the various improvements that MSDGC has made in reducing overflow volumes via the Wet Weather Improvement Plan.
To speed the modeling of alternatives, XCG developed a streamlined consolidated model for each version of the SWM. The consolidations feature a simplified hydraulic network and aggregated catchments to reduce the Typical Year model run times from days to hours.
XCG worked collaboratively with MSDGC and other consulting firms to model green infrastructure utilizing the SWM as part of this project. Specifically, a green modeling methodology was developed to standardize the modeling of green infrastructure alternatives. XCG then applied the methodology to model the green infrastructure alternatives for specific CSO areas including the Lick Run, Ross Run, Bloody Run, West Fork and Ludlow Run sewersheds. The specific sewershed modeling aided in determining the green infrastructure sizing required and estimated the impact on CSO volumes. XCG is further utilizing the updated SWM to perform alternatives analysis within the Mill Creek sewershed. Alternatives considered include grey infrastructure such as: sewer separation, deep tunnel, storage elements, and addition of High Rate Treatment facilities; as well as the addition of the green infrastructure elements.
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