Grease in Sewers

Grease in Sewers – Feb 2011 from Metro Vancouver on Vimeo.

Nasty, hardened grease build-up in our sewers is a $2-million a year problem in Metro Vancouver. New regulations could help.

Orange traffic barriers are the first sign that something is going on under the streets of Metro Vancouver.  Workers are using heavy equipment, as they move slowly from manhole to manhole. But just what are they doing?

The answer is simple enough.  The sewer lines that handle our flushes also get a regular flushing themselves. A hose is fed into a sewer access point, where high pressure water is used to clean the pipe’s walls. A camera goes into the sewer from the upstream end, to follow what’s called the flushing hose on its return journey.  Maintenance workers use video imaging from the camera to look for trouble spots. They know the hot spots and trouble areas. This location is known to be problematic

The camera sends back pictures of the pipe’s interior. Congealed grease has collected in white clumps all along the length of the sewer. Most of it comes from the many restaurants along this stretch of road.

“If you leave it alone there’s the potential for the grease to build up and become a grease blockage,” explains Shant Bedrossian, a civil maintenance planner for Metro Vancouver. “Then when you have a heavy rainstorm you could have the sewer backup and overflow.”

The Marshend pumping station is one of more than 500 facilities operated by Metro Vancouver that pump sewage uphill until gravity can take over and deliver it to the closest treatment plant. Here too, grease is the target, as a Metro Vancouver worker directs a high pressure stream of water along the sides of the station’s wet well.

“If it sits for a while it actually gets to the solidity of almost a concrete,” says Systems Operator Mike Statham. “It just builds up and builds up and builds up, and without regular washing of the wet well that’ll just keep on going and building up and chunks will start breaking off which can lodge in the pumps and just cause all sorts of havoc.”

Commercial kitchens are part of the problem.  But they can also be part of the solution with responsible management of the grease they inevitably produce.

At Troll’s Restaurant, the grease trap is pumped out by a trained professional at least once every three weeks, and much more often in the busy summer months. But not all restaurants are as diligent.  So Metro Vancouver is proposing several changes to the regulations governing the operation and maintenance of kitchen grease traps.

“We’re looking at having people remove grease from the grease trap at least once per month,” explains Metro Vancouver Permitting and Enforcement Officer Riley Sziklai. “Also to have the grease trap fully pumped out four times a year, as well as keep maintenance records on hand for two years for us to view and inspect if necessary.”

Trolls’ general manager Holly Kemp is glad her restaurant can help address the problem.

“If you consider how many restaurants there are out there and how much grease is used in the course of a day, if it’s going directly into our sewer system or into our drainage then we’re going to see problems at the other end.”

In an older restaurant, a grease trap might be located in the floor.  In recent years it’s more likely to be found under a sink.  Regardless, the grease that’s collected can only go to one of Metro Vancouver’s five waste water treatment plants.

At Iona, a special grease collection facility separates out the solids for incineration and uses the remaining grease to help make methane gas, which the plant uses for power.  In this case, grease is actually useful, but elsewhere in the plant it can really gum up the works.

Ultimately it’s taxpayers who are footing the bill for the 2 million dollars Metro Vancouver spends annually to deal with grease in the sewer system.  That’s a cost that could decrease – if these new regulations are put into place.  A win for taxpayer’s wallets, and for the region’s environment.

Want to learn more? This how-to video provides an overview of the rules and procedures implemented in 2012 that restaurants and commercial kitchens must follow in order to meet local regulations.


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