Chief Minister MK Stalin accorded in-principle approval for the much-awaited project of implementation of a Ring Main System (RMS) to strengthen the city’s drinking water supply network. He also approved the initiation of improvement works to the existing sewerage system under the Nesapakkam Treatment Plant catchment. Both projects will be executed by the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB) department. The total project cost of installing the RMS within the Greater Chennai Corporation areas, including operation and maintenance for 10 years, is estimated at Rs 3,108.55 crore. The project will be funded through a loan from the Asian Development Bank (ADB) and is expected to be completed within four years.
At present, Chennai’s water supply depends on surface water sources, groundwater, and desalination plants. Treated water from eight systems, including five water treatment plants and three desalination plants at Minjur and Nemmeli, is pumped through transmission mains to various Water Distribution Stations (WDSs). A fourth desalination plant with a capacity of 400 MLD is currently under construction at Perur along the East Coast Road. Since these water supply systems function independently, any shutdown or failure of a source affects the respective areas dependent on it, even when surplus water is available in other sources.
To address the issue, the proposed RMS will interconnect all nine water sources, including the upcoming desalination plant, through a closed-loop network consisting of pumping stations, feeder mains, ring mains, and transmission mains. This will enable equitable distribution of drinking water to all WDSs based on overall availability, even during source failures or maintenance shutdowns. Under the project, a 98-km-long Ring Main Comprising Mild Steel (MS) pipelines will be laid around the GCC area.
The system will be continuously monitored using advanced instrumentation and operated through a Programmable Logic Controller (PLC) system with SCADA-based Master Control Centre supervision at the CMWSSB head office. Currently, the CMWSSB supplies about 1,200 MLD of water to a population of 85.7 lakh through 84 Water Distribution Stations. The RMS is designed to distribute water to all 84 WDSs and handle a projected demand of 1,762 MLD by 2057.
Meanwhile, the proposed improvement work to the existing sewerage system under the Nesapakkam STP catchment involves the replacement of inadequate gravity and pumping mains, upgradation of sewage pumping stations, and enhancement of pumping capacity to meet present demand, at an estimated cost of Rs 689.40 crore. The works will be executed in four packages with a contract period of three years, with funding support from ADB. The project is expected to benefit about 1.16 lakh households.
As the sewerage system in Chennai has been in existence for about 40 years and has become inadequate due to rapid urbanisation, the system is currently facing operational challenges due to frequent surcharging, sewage overflows, and bursts in pumping mains, posing health hazards. To address these issues, the CMWSSB has proposed STP-wise improvement of the existing sewerage network in the core city in a phased manner, with the first phase covering the Nesapakkam STP catchment.
