Workers in Metro Vancouver have chiselled away about 50 tonnes of so-called 鈥渇atbergs鈥� that have clogged the sewer system and prompted a reminder to residents not to dump grease down the drain.

Dana Zheng, a program manager with the Metro Vancouver regional district, says that while it isn鈥檛 the first time they鈥檝e encountered the problem in the system, this latest discovery of hardened fat is the 鈥渕ost serious鈥� they have seen in recent years.

Zheng says workers at the Lulu Island wastewater treatment plant in Richmond have been running into the giant mounds of fat since the summer, gradually extracting more than 50 tonnes in total, and costing about $1 million so far.

A photo issued by the regional district shows some of the hardened chunks of yellowish and brown fat are large enough to reach a worker鈥檚 thighs.

Zheng says Richmond has been one of the hot spots for fat deposits because of the city鈥檚 flat terrain, giving grease more time to settle and harden inside the pipes.

The regional district is urging residents to dispose of fats properly by placing them in green bins for composing, rather than pouring them down the drain.

The district鈥檚 website says Metro Vancouver municipalities spend about $2.7 million every year to repair damage caused by fats, oils and grease in the sewer systems.