GIS Tool Quantifies the Consequences of Overflow in Cincinnati’s Sewer System
The Metropolitan Sewer District of Greater Cincinnati’s (MSDGC) Watershed Operations Division, with support from CH2M HILL, has been working to develop a Decision Support System tool to evaluate the Triple Bottom Line (TBL) impacts of an overflow at individual locations throughout the city’s sewer system. This GIS-Based Operational Decision Support Tool uses GIS and spreadsheet tools to quantify the Consequences of Overflow (COO) for a set of metrics designed to evaluate impacts to the TBL.
This work consists of a Consequence of Overflow framework which categorizes overflow locations in the MSDGC wastewater system based on the consequence of failure. Facilitated workshops with key personnel were used to determine the criteria, as well as the associated weighting used to determine the failure consequences.
The MSDGC is advancing its capabilities in real-time control to better leverage capacity in the existing collection system and optimize treatment plant operations during wet weather. MSDGC has taken a watershed-based approach in the development of its operational tools that incorporate system-wide data to best manage operable equipment. While targeted real-time control can be effective in mitigating localized or smaller rain events at one location, implementing controls for a broad area or watershed, requires an understanding of the relative impact, or consequence of overflow, at each overflow due to the interconnected nature of the sewer system.
To address this, MSDGC developed the framework, mentioned above, which provides a methodology of ranking each overflow location, in order to provide an important element of the decision support and control system algorithms. This value-based framework incorporates aspects of the MSDGC environmental, social, and economic goals (TBL approach).
The purpose of the GIS-Based Operational Decision Support Tool is to develop a methodology that can be used to inform decision making related to the consequence of overflow from a known overflow point. The tool can be continuously modified for enhanced support, which will aid in evaluating potential overflow control measures. This framework does not include the likelihood or risk of overflow.
The Watershed Operations Division was formed to incorporate wet weather operational control strategies that can minimize the pollutants entering receiving streams. These strategies are intended to leverage the available pipe capacity in the wastewater collection system through advanced analytics and control of operable structures, and provide optimal wet weather controls at the treatment plants.
MSDGC has 212 combined sewer overflows (CSOs), 55 sanitary sewer overflows (SSOs), and 24 pump station overflows (PSOs). Additionally, there are bypass locations within the wastewater treatment plants (WWTPs), and 79 areas with known issues related to basement backups (Water-In-Basement Clusters or WIBCs). Due to the interconnected nature of the sewer system, controls at one overflow location may have impacts on other overflow locations. Each of these overflows has some impact on the environment, the public, and has a cost associated with controlling and reducing events. By incorporating a Decision Support System tool, MSDGC can better manage its Watershed Operations and evaluate the positive and negative consequences on its environmental, social, and financial goals.
Source: CH2MHill Blogs: http://www.ch2mhillblogs.com/water/2014/09/29/gis-tool-quantifies-consequences-overflow-cincinnatis-sewer-system/