Mumbai’s manhole puzzle: Inside the century-long evolution of manhole covers

From iron gratings to cast iron covers

As Bombay expanded in the mid 19th century, concerns over sanitation and the open drain system prompted the municipality to plan an underground sewer network. In 1868, Major Tulloch submitted a report recommending the separation of sewer and storm water drains. A decade later, the city sanctioned its first comprehensive sewerage scheme.

A civic official accompanying the inspection team fell into an open manhole. (Ai-enhanced screen grab)

As the underground network expanded, manholes were built at regular intervals to allow workers to inspect and clean the sewers. These openings were initially covered with iron gratings.

The Report of the Commission on the Drainage and Water Supply of Bombay (1868) records that iron gratings were installed over sewer shafts to ventilate toxic gases. In areas such as Bazaar Gate Street and Elphinstone Circle, the municipality even experimented with charcoal filled wire screens to reduce foul odours.

Dr Madhu Kelkar, who has extensively researched Bombay’s colonial water management system, said the gratings in areas like Kamathipura were gradually removed after residents complained about foul gases. “In places like Kamathipura, the iron gratings installed over manholes in the 1880s had been condemned. As complaints of foul gases poured in, the municipal commissioner ordered for these gratings to be removed.”

By the late 19th century, circular cast iron covers had become the preferred design in the city. In “Oriental Drainage”, sanitary and drainage engineer with the municipal body, C C James wrote that circular covers were easier to remove for inspection and maintenance while providing a tighter seal.

While the earliest covers were imported by the British administration, they began to be manufactured locally by the early 1900s with CC James attributing the procurement of sewerage appliances to local firms like Messrs. Richardson & Cruddas of Bombay, and Messrs. Burn & Co. of Calcutta in his accounts.

In the years that followed, the covers came to be manufactured in the municipal foundry at Byculla.

The theft problem

For decades, cast iron has remained the standard preference of the city’s manhole covers as they can withstand heavy traffic. But its scrap value also made it vulnerable to theft.

According to BMC officials, thefts began surfacing in the early 2000s, particularly in areas such as P D’Mello Road. In several cases, covers were stolen entirely; in others, they cracked while thieves attempted to remove them. “Cast iron has good re sale value in the scrap market. In many cases, the covers would be completely stolen. Even in botched theft cases, the cast iron cover being brittle would end up broken,” an official said.

To curb theft, the BMC in 2008 began replacing cast iron covers with fibre reinforced plastic (FRP) covers in theft prone areas, including Sewri, P D’Mello Road, Dharavi and Malwani.

Initially, the experiment worked.

“We observed that after a while the robbery had dwindled as the anti social elements realised that they did not offer much value in the scrap market. The covers were also good in sustaining traffic load,” a source said.

But the FRP covers brought a different set of problems. Being lighter, they were more likely to get dislodged during heavy rain, particularly in flood prone areas. Officials also found that the material wore out faster. “Unlike a cast iron cover which is upto 100 kg in weight, the FRP covers are much lighter. They would come off during heavy rainfall and therefore, we stopped deploying them in flood prone areas,” a civic official told The Sunday Express.

Express Photo by Sankhadeep Banerjee.

Even the steel handles fitted to the FRP covers eventually became targets for theft.

By 2016, the BMC shifted to ductile iron covers, which retained the strength of cast iron while offering far less resale value in the scrap market.

“The benefit of the ductile iron was that it resembled cast iron but it was significantly lighter and had little to no resale value in the market,” officials from the BMC’s sewerage and storm water drain departments said. The FRP covers were gradually phased out.

After every tragedy, a new experiment

The death of gastroenterologist Dr Deepak Amrapurkar, who was swept into an open manhole during heavy rain in 2017 and whose body was recovered nearly two days later in Worli, brought renewed attention to the dangers posed by missing manhole covers.

In 2019, the civic body introduced hinge based covers that could be opened without being removed completely, along with chain linked covers that were fixed to the frame.

Neither proved effective.

Express Photo by Sankhadeep Banerjee.

“The idea behind hinge-based cover was that it would open upto 120 degree, rather than coming off completely. But due to rain and saline winds, these hinges would rust,” said an official, adding that the metal chains ended up stolen themselves.

The next experiment came in 2024, when the BMC introduced “smart manholes” fitted with sensors designed to trigger alarms and alert a control room if a cover was removed.

Officials said the idea was to ensure civic teams could reach the site before an accident occurred. But technical issues prevented the project from achieving the desired results.

The BMC also shifted its focus to reducing the risk even if a cover went missing. Since 2023, it has been installing metal protective grills beneath manhole covers following directions from the Bombay High Court. The grills are designed to prevent pedestrians from falling into the drains even if the cover is stolen or removed.

The latest experiment

Mumbai today has more than one lakh manhole covers. Of these, 73,437 cover sewer lines while more than 25,500 are installed over storm water drains. Officials said the lower number over storm water drains is because several large suburban drains remain open.

Ahead of this year’s monsoon, Municipal Commissioner Ashwini Bhide directed that protective grills be installed beneath all remaining manholes before the rains.

Following the death of Aslam Isaq Shaikh earlier this month, Bhide also directed that the BMC’s annual inspection of manholes be advanced to January instead of the usual March April pre monsoon exercise.

The civic body is now preparing to pilot what it calls a “manhole railguard” in L ward. Unlike earlier interventions that focused on the cover itself, the proposed railguard is a square shaped protective enclosure that surrounds an open manhole on all four sides while maintenance work is underway, preventing pedestrians from accidentally stepping into the opening.

The BMC is also examining whether protective grills can eventually be integrated into the manhole cover itself.

“In Mumbai, we are always experiencing new and unique challenges. Through trial and error, we are working towards making these covers safe all across,”a senior BMC official told The Sunday Express.