The Tamil Nadu government, through the Tamil Nadu Urban Infrastructure Financial Services (TNUIFSL), has invited private-sector companies to implement underground sewerage projects in Madurai and Nagercoil under the Public-Private Partnership (PPP) model. The combined estimated cost of the two projects is ₹2,527.30 crore (US$262 million), comprising ₹2,337.48 crore for Madurai and ₹189.82 crore for Nagercoil.

TNUIFSL has invited bids from private-sector companies to undertake the two projects, for which it has already prepared Detailed Project Reports (DPRs). The government expects to appoint an advisor to assess the feasibility of implementing the projects under the PPP model and prepare the necessary reports. The selected private company would subsequently conduct a detailed assessment of the projects before taking them forward.

The Madurai project involves the rehabilitation of the existing underground drainage network and the development of new sewage collection infrastructure in areas recently incorporated into the city corporation. The project will also include sewage-treatment facilities and other associated infrastructure to improve the city's wastewater management system.

The Nagercoil project involves developing a new sewage collection network, including around 111 km of pipelines to connect households and approximately 19.93 km of pipelines linking pumping stations. The project is intended to expand and strengthen the city's sewerage infrastructure and improve the collection and treatment of wastewater.

The proposed PPP model has faced opposition from the Communist Party of India (CPI) and Communist Party of India (Marxist) (CPM). The parties have argued that sewerage and drainage are essential public services and should remain under the control of local bodies rather than being operated through private entities. They have also raised concerns that private participation could place greater emphasis on commercial returns rather than public welfare.