CHENNAI: A simple design fix to stormwater drains in the city is expected to help reduce instances of men being lowered into the drains for desilting and also reduce accumulation of silt, according to corporation officials.
The distance between two manholes in stormwater drains is five metres at present. Accumulation of silt in the gap between two manholes has been a challenge for officials to clear manually. This results in the drain being choked with no pathway for carrying rainwater, and in turn, leading to flooding.
“We are now introducing two inset slabs between manholes so we get a two-foot clearing to desilt drains between every five metres of the manholes,” said a senior corporation official. These two cut slabs can be simply lifted to desilt the drains by sitting or standing on top of the drains instead of having to send men down into openings.
For so long, men being sent into stormwater drain manholes to desilt portions of the drain ahead of the monsoon was a common sight. This had drawn considerable criticism since stormwater drains are carriers of sewage. According to corporation estimates, the city has 13 lakh houses, of which only about eight lakh have sewage connections. The carrying capacity of the present sewerage infrastructure, however, is only four lakh, resulting in overflow connections to stormwater drains.
Apart from helping reduce these instances, this will keep silt from accumulating, allowing for better drainage of rainwater, say corporation officials. It may also prevent instances of the top slab of stormwater drains being broken during rains to urgently clear silt during the rain and causing losses to the civic body. “Stormwater drains should be built to last. So, with this design fix, there will be no need to break top slabs. This fix will be introduced in all the new drains and missing link projects that are being taken up now,” said the official.
As for existing drains, desilting is to be carried out all through the year and not in the three months ahead of the monsoon, as was the practice. “While desilting old drains, we will remove the top slab and introduce the slabs in old drains too,” said a corporation official.