A building contractor is thought to have screwed up its piling operations and pumped a sewer full of concrete.

Hackney Gazette: Wenlock Road is closed after concrete was found blocking the sewer. Photo Emma BartholomewWenlock Road is closed after concrete was found blocking the sewer. Photo Emma Bartholomew (Image: Archant)

Thames Water – which is carrying out emergency works after Wenlock Road, Hoxton, flooded with sewage – does not yet know which contractor is responsible for the mistake.

The road is expected to be closed for a month while 65m of piping, lying four metres underground, is replaced,

A Thames Water spokesman said: “Normally blockages are caused by fat, oil and grease building up in the sewer but unfortunately in this case it’s concrete, so we can’t just jet it through.

“It’s in there and it’s set to the pipe, it means we need to remove the pipe and replace it with new ones.”

CCTV investigations identified concrete in two sections of the sewer spanning a length of 40m.

TfL’s website said the situation required “constant tankering to prevent an environmental contamination issue”, and lorries from “Muck and Waste London” are transporting the sewage away from the site.

The spokesman from Thames Water said the priority was to get the repair fixed: “At the moment is we don’t know who’s responsible for the concrete in the pipe, they only started digging it out this week, once they get it out we will start trying to trace it.

She continued: “There are so many contractors in the area, if it was just one it would be straight forward, but we need to examine what’s in the pipe, I don’t know how they mange to work it out but apparently they do have ways and means of tracing it.”

She was unable to provide an estimated cost for the works.