What has been named the Whitechapel fatberg is a rock-solid agglomeration of fat, disposable wipes, diapers, condoms and tampons. It was discovered to the east of the city’s financial district, occupying a sixth of a mile of sewer.

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There is a monster beneath the streets of London, menacing the East End underworld.

What has been named the Whitechapel fatberg is a rock-solid agglomeration of fat, disposable wipes, diapers, condoms and tampons. It was discovered to the east of the city’s financial district, occupying a sixth of a mile of sewer under Whitechapel Road, between one of London’s largest mosques and a pub called the Blind Beggar, where walking tours are taken to reminisce about a notorious gangland murder.

Thames Water, the capital’s utility, said the fatberg weighed as much as 11 of the city’s double-decker buses: more than 140 tons. That was 10 times the size of a similar mass that the company had found beneath Kingston, in South London, in 2013, and declared the biggest example in British history.

To prevent the contents of the sewer from flooding streets and homes nearby, the utility is sending an eight-member team to break up the fatberg with high-powered jet hoses and hand tools. The task is expected to take them three weeks, working seven days a week.

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“It’s a total monster and taking a lot of manpower and machinery to remove,” said Thames Water’s head of waste networks, Matt Rimmer. “It’s basically like trying to break up concrete.”

Such blockages are not unique to London. New York City has spent millions of dollars on problems created by disposable wipes. Even the ones branded as flushable were combining with materials like congealed grease to upend their plumbing. Hawaii, Alaska, Wisconsin and California have struggled with similar problems.

This city’s sewage system, however, presents special challenges. The backbone of the network was built in the 19th century, after a series of cholera outbreaks and the “Great Stink” of 1858, when lawmakers abandoned the Houses of Parliament because of the stench of raw sewage from the nearby River Thames.

That 1,100-mile system, originally designed to serve 4 million people, has been struggling to cope with the waste of about twice that number. Work is underway on a new super sewer.

Joseph Bazalgette, who designed the Victorian network, probably did not account for the disposable diapers and wipes that, in a matter of days, can mate with oil and grease to create fatbergs big enough to block tunnels that are six feet tall.

The sewer under Whitechapel Road is about four feet high and less than three feet wide, and Thames Water engineers found the fatberg there during a routine check. They regularly walk through the system to look for problems. Lee Irving, a spokesman for Thames Water, described the experience of encountering a fatberg as overwhelming, with a smell that mixed rotting meat and pungent toilet.

The utility is trying to prevent fatbergs with publicity campaigns urging residents to dispose of wipes and fat in the garbage can, rather than down the drain. It has said that it clears three blockages from fat, and four or more caused by items like wipes, every hour.

It has also targeted restaurants, encouraging them to use grease traps. “There’s a clear link between our fatberg hot spots and high concentrations of food outlets,” Steve Spencer, then the utility’s head of waste networks, said in February.

Thames Water has tried to put all that congealed fat to use. Some is converted into biodiesel for power generators.

The utility said it was also working with a renewables company, Argent Energy, on turning its waste fat into environmentally friendly fuel. (Maybe some day, fatbergs could power those double-decker buses.)

And there is a chance that a slice of the fatberg will be preserved for generations to come. The Museum of London said on Wednesday that it hoped to acquire a cross-section of the blob for its collection.

“It is important for the Museum of London to display genuine curiosities from past and present,” the director of the museum, Sharon Ament, said in a news release.