Far from prying eyes, in the darkness deep underneath the streets of the London suburb of Kingston-upon-Thames, an unspeakable horror was taking shape.
It went largely unnoticed until residents began reporting increased difficulty in flushing their toilets. When Thames Water went to investigate, they made a gruesome discovery: a festering, double-decker bus-sized lump of solidified grease, frying oil, baby wipes, and other sanitary detritus was blocking 95% of the nearly 8-foot-diameter main sewer pipe.
According to Thames Water spokesperson Simon Evans, the so-called "fatberg" -- which weighed more than 15 tons -- was discovered just in time. "Kingston came very close to being flooded with sewage," he said.
Thames Water waste contracts supervisor Gordon Hailwood, whose team discovered the monstrosity, told the BBC,
"The sewer was almost completely clogged with over 15 tonnes of fat. If we hadn't discovered it in time, raw sewage could have started spurting out of manholes across the whole of Kingston. It was so big it damaged the sewer and repairs will take up to six weeks."
Hailwood and his crew had to spend three weeks in the sewers breaking up the fatberg into manageable chunks with high-pressure water jets. This is by all accounts an unbelievably disgusting task; Evans describes a fatberg as "a heaving, sick-smelling, rotting mass of filth and feces" that "hits the back of your throat." He says, "it's steaming and it unleashes an unimaginable stink."
Fatbergs form when a wet wipe, used condom, tampon, or some other item that's not supposed to be in the sewer gets snagged on the wall of a sewer pipe (usually on the ceiling). Fat from restaurants and household cooking begins to congeal around it. The mass builds up, collecting more fat and nasty sewer debris, and voilà: a full-fledged fatberg is born.
Workers at Thames Water regularly find themselves fighting with fatbergs large and small: the utility dislodges almost 40,000 of them every year, thanks to the millions of liters of cooking oil Londoners pour down the drain. But the Kingston fatberg is believed to be the largest in British history.
The whole episode has turned Hailwood into an unlikely hero. "Hailwood and his team certainly saved Kingston from a terrible fate," Mr. Evans said.