"Partial blockage" caused high E.coli levels at north coast bay

Tuesday 21 May 2024

The suspected cause of the issue which led to high E.coli levels at Grève de Lecq bay has been discovered.

A partial blockage caused some sewage to enter the water system which normally carries the surface water out to sea, according to the Government's infrastructure team.

Islanders were advised to avoid swimming at Grève de Lecq following a high reading of 3,300 parts E.coli per 100ml last week.

This is over six times higher than the E. coli threshold for 'poor' water – which is indicated by a value of 500 cfu/100ml.

Pictured: Poor water is indicated by a value of 500 E. coli (Escherichia coli) per 100ml, and there was a high of 3300 E. coli per 100ml measured at Grève de Lecq.

Follow-up tests later in the week showed 1,800 parts E.coli per 100ml of water in the north coast bay – more than three-and-a-half times the threshold figure of 500 for 'poor' quality water.

E.coli levels had further dropped to 727 cfu/100ml and 709 cfu/100ml in routine samples taken yesterday, although still remain rated 'poor'.

This afternoon, the suspected cause of the problem was identified. 

Infrastructure Minister Andy Jehan explained: “The Infrastructure team have now identified what they believe to have been causing the poor seawater quality at Grève de Lecq, and have taken steps to stop any further discharges into the bay. 

“It appears there was a partial blockage on the incoming sewer to one of the pumping stations, causing some sewage to overtop the foul sewer and enter the surface water system, which normally carries just the surface water out to sea."

He added: “I’d like to thank the team who quickly isolated the station and found the exact location of the problem, to stop further leakage into the environment.”

The Public Health team is still advising against entering the sea at Grève de Lecq and the stream there.