Following reports of a large deposit of concrete, which Thames Water found blocking a sewer in Islington, a second “concreteberg” has been discovered, and removed, by Northern Ireland Water (NI Water).

The blockage, found by cleaning crews, measured 30ft long and weighed half a tonne, equal to an adult tiger shark.

It is estimated that enough concrete has been removed from the Omagh Inner Trunk Sewer to build a small garden wall.

NI Water insists that blockages such as these are often due to human fault and the public has the power to prevent them. This can be done by properly disposing of anything that is not flushable, ensuring fat and oil are not poured down the sink, and not washing any substances into manholes or drainage systems.

The company has invested more than £1.5 billion in water and wastewater infrastructure in the last ten years.

Anthony McGirr, the area’s wastewater manager, said “We are used to tackling fatbergs and other inappropriate items in our sewers but this is a ‘solid’ find.

“Staff came across this concrete block as part of their four-week programme to clean this vital piece of infrastructure which collects sewage from Omagh Town. They couldn’t quite believe what they found and it took hours to break up and finally dislodge, not to mention the cost.

“Rogue discharges like this are found around building sites where the remains of concrete are washed down into the drainage system. This is typical of material getting into our sewers from new building works and developments. Combined with brick bats, stones and inappropriate rags it can be a real pain to get removed and a very expensive piece of maintenance work.”

He added: “This act shows not only lack of respect for our network but also for the people living in the area. NI Water would remind all customers that opening a manhole or washing substances into the drainage system is prohibited. By doing this, you are obstructing a working sewer which is designed to take waste away from homes.

“By obstructing the sewer in this way, it reduces the pipe capacity and the volume of waste it is able to take; this can lead to increased blockages and out of sewer flooding in the street or into a river. Out of sewer flooding is extremely unpleasant and affects the whole community and damages the environment. We have all seen the disgusting effects of an overflowing manhole in the street and no one wants to see or smell it (not even us) but the reality is, it happens regularly at a cost of millions to NI Water each year.”

NI Water also recently found hundreds of potatoes and carrots washed up at a wastewater treatment works in Londonderry.

Water companies are increasingly focused on educating the public on what can and cannot be flushed in their fight against sewer blockages. Earlier this year Water UK created a “fine to flush” symbol to help consumers identify wet wipes which could be safely flushed.

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