Metrowater plans to plug sewage outfalls and strengthen sewer network; work to get under way in January
Cleaner waterways could become a reality in four years’ time if the various projects proposed by Chennai Metrowater are implemented.
With the State government approving works worth ₹1,001 crore, the water agency is set to call for tenders this month.
Though Chennai Rivers Restoration Trust has already taken up eco-restoration projects along Cooum and Adyar rivers at a cost of ₹300 crore, the new projects aim at a comprehensive clean-up of the Cooum and Adyar rivers and Buckingham Canal and its associated drains. Work is expected to begin in January next year.
It may be recalled that a government order was issued recently sanctioning various projects worth ₹2,371 crore proposed by Chennai Metrowater to plug sewage outfalls into the city’s waterways and also strengthen the sewer network, through short-term and long-term strategies.
Two consultants — WAPCOS and NSS Consultants, Hyderabad — have been engaged to prepare detailed project reports to intercept and divert untreated sewage from reaching city waterways, Metrowater officials said.
About 380 sewage outfalls have been identified in the major waterways and their associated drains. There are nearly 217 outfalls on various stretches of the Buckingham Canal and its 21 drains such as Kodungaiyur drain, Captain Cotton Canal, Keelkattalai drain and Adambakkam drain. The remaining were found to be along Cooum and Adyar rivers, officials said.
Inadequacy of system
Inadequacy of the sewage collection system and pumping capacity as well as linking of stormwater drains to the sewer network were some of the challenges faced by the city’s sewer network. Excess sewage is often let into smaller drains. The proposed works are expected to address such issues by intercepting sewage flow and diverting it to the nearest sewage pumping station, officials said.
Modular sewage treatment plants with a capacity to treat even a small volume of 0.3 million litres of sewage a day would be built along the waterways. In places like CIT Nagar, Bharathi Salai, Porur and G.N.Chetty Road, mini sewage pumping stations would be built to prevent raw sewage from entering rivers. Similarly, sewage pumping stations would be built at areas such as Saligramam, Arumbakkam and Greams Road to divert raw sewage.
Old sewer lines
“We have about 3,000 km of sewer pipelines that function as a collection system across the city. Though these were designed for a 30-year life, most of them have functioned for over five decades. The proposed projects would help in improving a minimum 20-30% of the existing collection system,” an official said. The 85 works would include strengthening capacity of sewage pumping stations and enlargement of sewer pipelines and would be completed by December 2022.
Metrowater is also simultaneously preparing estimates for the second phase, wherein shortfalls in the sewer infrastructure would be improved from the collection system to final stage of treatment. “We have asked area engineers to come up with proposals identifying stretches that need to be upgraded. It could be replacement of old pipelines, laying of main lines to handle larger capacity or construction of pumping stations,” said an official.
The second phase of the project would begin within the next one year.