the core problem of the Cooum has been that due to the sand bar, the river mouth near the Napier Bridge gets blocked for most of the time, preventing the river water from draining into the sea. This has, eventually, made the river, in its 18-km-long stretch in the central district, a stinking cesspool
Tests of water samples reveals almost zero dissolved oxygen and substantial presence of faecal coliform bacteria, besides heavy metals such as lead, zinc and cadmium.
A study of the river shows that it is 80 per cent more polluted than treated sewer. Fish were able to survive in the water for only 3 to 5 hours even after samples were diluted. There are traces of heavy metals like copper and pesticides like endosulphan and lindane in it.
Due to its narrowness and about 3,500 illegal hutments along its banks, it has not been recently desilted, which has closed it to river traffic.
Per 2003 enumeration, about 9,000 families live along the river, in addition to 450 shops and commercial buildings.
There are 700-odd points in the river bank where sewage flows straight into the river.
There are 127 identified sewage outfalls into the river, out of which 85 are in use.
Public Works Department sources said government agencies like Chennai Corporation and business units and retail outlets on the banks of the river were responsible for the pollution.
Nearly 30 per cent of the estimated 55 million litres (15,000,000 US gal) of untreated sewage being let into the waterways of Chennai daily, including by Chennai Metropolitan Water Supply and Sewerage Board, gets into the Cooum river.
About 60 per cent of the untreated sewage gets into the Buckingham Canal and the Adyar River takes the rest.
In 2010, about 340 sewage outfalls into the waterways were identified. Of them, more than 130 sewage outfalls were in the Cooum River and a majority of them were between Aminjikarai and Nungambakkam.
In some of the spots in areas such as Maduravoyal, more than 7 tonnes of municipal solid waste is being dumped in the river every day.