A benefit-cost framework for evaluating alternative real time control strategies in Louisville, Kentucky

摘要

The Louisville and Jefferson County Metropolitan Sewer District (MSD) operates and maintainscombined and sanitary sewer systems that serve over 700,000 people in Louisville and itssurrounding areas. The MSD service area encompasses 11 watersheds in the Ohio RiverWatershed spanning approximately 385 square miles. Real Time Control (RTC) has been acritical part of MSD’s control strategy for more than a decade and will continue to be goingforward. At present, MSD employs a Global Optimal Predictive (GOP) RTC system thatcurrently services nine RTC sites distributed throughout the system that utilize in-line storage,off-line storage, and flow diversion to minimize flooding, minimize combined and sanitary seweroverflows, maximize treatment and minimize energy costs. Smart use of RTC technology hasallowed MSD to enhance the sustainability of their sewer systems, by improving the waterquality of surrounding waterways.In December, 2008, MSD submitted their Integrated Overflow Abatement Plan (IOAP), as partof their Amended Consent Decree (ACD) requirements, to the US EPA and KentuckyEnvironmental and Public Protection Cabinet. The IOAP includes provision for the design andconstruction of a number of new facilities that will incorporate an RTC component. As MSDembarks on expansion of their RTC system, they are developing a holistic operating and controlstrategy for MSD’s facilities. Developing this strategy has provided MSD with an opportunity totake a step back, three years into running their RTC system, and evaluate the lessons learned thusfar. In so doing, MSD has been able to identify ways in which their RTC system can beimproved to help them better manage and operate their sewer system. As part of the study MSDalso took time to re-evaluate the RTC strategy currently employed and, at the same time,consider alternative RTC strategies. In order to achieve this, a benefit/cost framework wasdeveloped and applied to determine the most sustainable RTC strategy for their current andfuture facilities. In addition, MSD has developed a set of RTC design standards to be used in thedesign of future RTC facilities and has identified ways to modify their internal organizationalstructure to ensure the sustainability of RTC operation and management.This paper will highlight the lessons learned from MSD’s experience with RTC thus far anddescribe the benefit-cost framework and its application in Louisville. Together, these willdemonstrate how this process has helped enhance the sustainability of the MSD sewer system.