"It's basically like trying to break up concrete", said Rimmer.
A massive 20 to 30 tons will be removed from the fat mass under Whitechapel Road by an eight-man crew, every day.
At 130 tonnes (143.3 tons) and covering 250 metres (820 feet), it's the biggest ever unearthed in Britain.
Sewer workers investigating the 'berg say that over time it has solidified, and is now as hard to remove as concrete.
This latest fatberg blows that one out of the sewer. Then they'll suck up the broken pieces of the fatberg, gather them all in tankers and send them to a recycling site in Stratford, England.
A disgusting, congealed blob of fat, oil, and other unpleasant household waste has been discovered blocking a major sewer line underneath London.
Thames Water engineers have said it will take them three-weeks to clear the mass.
Inspections by CCTV showed that the sewer, which is 47 inches high and 27.6 inches wide is blocked by the fatberg.
Mr Rimmer warned that fatbergs are not inevitable and that London's residents have a role to play in preventing their formation.
Each month, Thames Water spends about £1 million (US$1,328,000) clearing such blockages in London and Thames Valley sewers.
"The sewers are not an abyss for household rubbish and our message to everyone is clear - please bin it - don't block it". It also visited food outlets earlier this year to discuss how they dispose of fat and food waste.
Among the most common causes of drain blockages are make-up and nappy wipes, fat and grease, chewing gum, dental floss, plasters and building debris.
These fatbergs have been a recurring problem with the rise in popularity of self-described "flushable" wipes, which don't disintegrate in water and are therefore not actually flushable.
The utility has introduced a "Bin it - Don't Block It" campaign to discourage its customers from flushing problematic items down the toilet.