Raw sewage was flushed for five months into a river that feeds the Glashaboy reservoir, one of Cork's main drinking-water sources serving about 40,000 people, according to a report published 2 September by the Irish Examiner. The utility Uisce Éireann told the paper that drinking-water quality at the Glashaboy water treatment plant was never affected, but the Environmental Protection Agency (EPA) was only told of the incident after the newspaper contacted the company for comment.
Key takeaways
- A 30-apartment development in Glanmire was connected in error to the East Cliff Rd storm drain instead of the adjacent sewage mains, with the connection works approved by Uisce Éireann in March 2026.
- Sewage flowed through an overflow pipe on the Butlerstown bridge into the Butlerstown river, which feeds the Glashaboy reservoir producing about 20 million litres of water per day for roughly 40,000 people in Glanmire, Glounthane, Carrigtwohill, Little Island and Cobh.
- The Glashaboy water treatment plant was forced to cease operations three times in the past month after dry weather exposed dangerous ammonia levels from the sewage.
- Uisce Éireann disconnected the Ashbrook apartments' pipe from the storm drain in the past fortnight, with sewage now removed periodically by private contractors.
- The EPA said it was informed by Uisce Éireann three hours after the Irish Examiner asked for comment.
What happened
According to the Irish Examiner, the incident stems from a connection error at the Ashbrook apartments, a new 30-apartment development in Glanmire. In March 2026 the development was connected to the East Cliff Rd storm drain rather than the adjacent sewage mains, even though the works had been approved by Uisce Éireann. Sewage from the apartments then ran through the storm drain to an overflow pipe on the Butlerstown bridge and into the Butlerstown river.
The Butlerstown river feeds the Glashaboy reservoir, which the Irish Examiner reports produces approximately 20 million litres of water per day and serves Glanmire, Glounthane, Carrigtwohill, Little Island and Cobh, an area with an estimated population of 40,000 people. Normal river levels masked the contamination until recent hot weather lowered flows. In the past month, the Glashaboy water treatment plant was forced to cease operations three times because ammonia levels in the raw water became dangerous. Members of the public walking on the new Glanmire greenway noticed the smell on 13 August and saw toilet paper and human excrement entering the river.
The Ashbrook sewage pipe was disconnected from the storm drain in the past fortnight and the sewage is now being removed periodically by private contractors, the Irish Examiner reports. Uisce Éireann told the paper that drinking water supplied from the Glashaboy water treatment plant remained safe to drink: "At no time was there any impact on the quality of drinking water supplied to customers or any risk to public health," a spokesperson said. The spokesperson added that "as designed, these systems temporarily suspend treatment operations when changes in raw water quality are detected, ensuring the continued protection of drinking water supplies," and that "upon becoming aware of an issue relating to a wastewater connection at a private development which resulted in wastewater entering a local watercourse, corrective works were undertaken, and the matter has since been resolved," according to the Irish Examiner.
The EPA told the Irish Examiner it was informed of the incident by Uisce Éireann last Tuesday afternoon, three hours after the newspaper asked for comment.
Specification read
For an operator sizing a comparable facility, the headline number is 20 million litres per day, equal to 20,000 m³/day, serving about 40,000 people, or roughly 500 litres per person per day across the Glanmire–Cobh catchment, as reported by the Irish Examiner. A surface-water treatment train at this scale typically runs coagulation, flocculation and sedimentation, followed by filtration and disinfection, with continuous online ammonia, turbidity and organic-carbon monitoring on the raw-water feed so the plant can shut down the instant raw-water quality drifts out of specification. The Glanmire event bears directly on that monitoring layer: three emergency plant shutdowns in a single month were triggered by ammonia spikes in the reservoir feed, not by any failure inside the treatment train itself, a reminder that intake protection and source-water quality control are part of the asset, not an add-on.
For a reader scoping procurement, the recognition test is straightforward. If your plant is a surface-water works of roughly 5,000–50,000 m³/day (general industry range, not from the sources) drawing on a river or reservoir that also receives stormwater or cross-connected sewage flows, and you already have continuous ammonia and TOC monitoring with automatic raw-water shut-off logic, the Glanmire case is a near-perfect analogue: the failure here was upstream of treatment, and the engineered response was the monitoring system doing its job. If you do not have that monitoring and shut-off logic, the same incident at your intake could pass contamination straight into the clearwell. See our reference page on water purification process trains and the engineering specs in Drinking Water Treatment Plant Design Criteria: 2026 Engineering Specs, and review the wastewater-side controls on our Municipal and Integrated Sewage Treatment pages.
FAQ
What did Uisce Éireann say about drinking-water quality during the Glanmire incident?
Uisce Éireann told the Irish Examiner that drinking water from the Glashaboy plant was never affected and there was no risk to public health, and that the plant's continuous monitoring and automated shut-off systems suspended operations when raw-water ammonia rose.
How large is the Glashaboy reservoir supply, in buyer units?
The Irish Examiner reports the Glashaboy plant produces about 20 million litres per day, which is 20,000 m³/day, serving an estimated 40,000 people across Glanmire, Glounthane, Carrigtwohill, Little Island and Cobh.
What is a typical lead time for upgrading raw-water ammonia and TOC monitoring with automatic shut-off on a 20,000 m³/day surface-water plant?
For a municipal surface-water works in the 10,000–50,000 m³/day band, procurement, installation and commissioning of online ammonia plus TOC monitoring tied to a raw-water shut-off loop typically runs 6–12 months from order (general industry range, not from the sources); budget envelopes depend on whether existing SCADA tags and analyser shelters can be reused.
What should a buyer check when comparing suppliers for that monitoring upgrade?
Confirm the analyser has a documented ammonia range that covers the trip setpoint your plant will use on reservoir feed, that the shut-off logic is fail-safe on analyser fault, and that the supplier provides a documented I/O list for SCADA integration. Reference the engineering framework in Drinking Water Treatment Plant Design Criteria: 2026 Engineering Specs.
