The Louisville and Jefferson County Metropolitan Sewer District (MSD) pioneered the implementation of intelligent control in the United States as part of its Long Term Control Plan (LTCP) in order to reduce combined sewer overflows and improve operation.
Tetra Tech CSO carried out several feasibility studies to evaluate the potential of global, optimal and predictive real time control, known as intelligent control, for the MSD sewer system. Study results showed significant CSO reductions at a relatively low cost by maximizing the storage and conveyance capacities within the existing system. The estimated unit costs ranged from $0.006 to $0.021 per gallon of CSO reduction per year, which was 4 to 10 times lower when compared to other alternatives without using RTC. The MSD has included RTC as a feature of their LTCP and negotiated it into their consent decree with the US EPA.
During Phase 1 of the project, five control sites were implemented, including the use of two storm water retention basins (15.7 MG and 17.2 MG) for CSO control, inline storage and flow diversions. Four new control sites were added during Phase 2 of RTC implementation. The key benefits of Phase 2 came from a new control site equipped with a large inflatable dam and from the inclusion of inflow control in the main wastewater treatment plant under RTC. The RTC system has been in operation since April 2006, with operational results matching study findings. The Tetra Tech CSO team is currently involved in the planning process for the operation optimization of the MSD's collection and treatment facilities. The activities performed by Tetra Tech CSO included:
- Network study and model analysis;
- Definition of control strategies, as well as intervention to minimize CSOs;
- Design and implementation of the RTC system, including civil engineering works, instrumentation, telemetry and SCADA;
- Technical assistance during and post-construction;
- Start-up, commissioning and training;
- Creation of an automated reporting system;
- System performance follow-up and evaluation.
Average % of CSO volume reduction: 64%
% reduction total storage needs: 38%
Capital investment savings: $117M
“Real Time Control (RTC) is the most cost effective way to address the problem of untreated overflow into Beargrass Creek and the Ohio River. This will be a significant improvement to our system.”
– Gordon Garner, Executive Director of the Louisville Metropolitan Sewer District