Untreated gases released over Cork suburbs after fault at wastewater station

More than 100 Cork residents have complained of persistent sewage odours, with Uisce Éireann acknowledging that untreated gases were released into the atmosphere in recent weeks

Uisce Éireann said the issue arose at the Ballinure Header Chamber in Mahon, a key part of the sewer network serving the area. Picture: Larry Cummins

Untreated gases have been released into the atmosphere over parts of two Cork suburbs in recent weeks because of a fault at a wastewater transfer station, Uisce Éireann has confirmed.

The utility said the issue arose at the Ballinure Header Chamber in Mahon, a key part of the sewer network serving the area. Residents reported feeling ill as a result of the smells, with the majority saying it is having a direct negative impact on their daily lives.

A spokesperson for the EPA said that Uisce Éireann is solely responsible for the operation of wastewater treatment plants (WWTP) and sewer networks, and that the EPA will “continue to monitor Uisce Éireann's progress in resolving odour issues”.

In communications obtained by the Irish Examiner, Uisce Éireann confirmed that untreated hydrogen sulphide (H2S) emissions were released from the facility in recent weeks, as three of four fan units and three air handling units at the WWTP are “operating below design criteria”.

According to the Health and Safety Authority, H2S is “a colourless, highly flammable, and extremely poisonous gas characterised by the distinct, foul odour of rotten eggs”.

Uisce Éireann said following an investigation and specialist contractor report, “a capital project has been commenced to replace components in the extraction system and is currently at design stage”.

Reduced flows and higher temperatures in recent weeks had contributed to the release of gases at the facility, it said, adding that an underperforming extraction system meant the building had to be ventilated daily on health and safety grounds, allowing gases to escape untreated.

The utility said a new gas detection and monitoring system installed in June had recorded elevated hydrogen sulphide levels on only one occasion, indicating that the odour was not toxic and was consistent with general sewage smells. It has an alarm set at H2S of five parts-per-million

Uisce Éireann also said it had identified a seized ducting damper at the facility. The damper has since been manually opened and a replacement has been ordered.

According to the Centre for Disease Control, exposure to hydrogen sulphide at concentrations below 10 parts per million can cause eye irritation, headaches, and fatigue. People with asthma may also experience breathing difficulties, while nausea and vomiting can occur in some cases.

Uisce Éireann said its wastewater teams are "now progressing a programme of works to address the issue".

Speaking to the Irish Examiner, Labour Party councillor for the Cork City South East ward, Peter Horgan, said it is "quite concerning"  that ambient gases are being released into the community".

“What’s critical now is resolving the issue, and assessing the public health impact," said Mr Horgan. “There should be direct communication to each household, and a dedicated phone line and email set up to deal with concerns from the Mahon and wider Blackrock community.

“Locals have told me that they can’t have friends or family over — there's a feeling that they can’t be present in their own homes, and some people have suffered sicknesses at the same time these gases were released."

Mr Horgan said the issue is impacting on residents' quality of life and raised concerns about the potential long-term health implications for people living in the area.