The Cork Lower Harbour Main Drainage Project consists of: 

  • A new Wastewater Treatment Plant (WwTP)
  • Circa. 15 new pumping stations and the upgrading of 4 existing pumping stations
  • Approximately 30km of new sewers
  • A drilled crossing under the estuary

The raw sewage* from Cobh, Passage West, Glenbrook, Monkstown, Carrigaline, Ringaskiddy and Shanbally will be collected into new pipes and redirected to a new WwTP plant at Shanbally.

The treated wastewater will then be safely discharged into the estuary via an existing pipeline near Dog Nose Point.

*The amount of raw sewage currently discharged is equivalent to 49,000 people, i.e. 49,000 PE (Population Equivalent).

The Cork Lower Harbour Main Drainage Project is required to significantly enhance the water quality in Cork Harbour. Currently, wastewater from Cobh, Carrigaline, Passage West/Monkstown and Ringaskiddy is discharged untreated into the Harbour.

The Cork Lower Harbour Main Drainage Project aims to provide enhanced wastewater treatment through the development of a new wastewater treatment plant at Shanbally County Cork. The Project is important in terms of protecting the environment, facilitating economic development and providing for a growing population. The plant will serve the areas of Cobh, Carrigaline, Crosshaven, Passage West/Monkstown (including Glenbrook) and Ringaskiddy (including Shanbally & Coolmore).

In addition to this, the need for a wastewater treatment plant for Cork Lower Harbour is a requirement under both European and National legislation in order to improve health, integrity of the environment and improve water quality in compliance with the European Union’s Urban Waste Water Treatment Directive. The Cork Lower Harbour Main Drainage Project will ensure that these water quality standards set down by regulatory bodies will be achieved, which will help Ireland to avoid substantial financial penalties.

The Project will also have a positive impact on the local economy and community as improved water quality will increase the amenity value of the Lower Harbour, and act as a platform for social and economic development.

The Project includes built-in resilience in order for the wastewater infrastructure to be able to accommodate the increase in local population.

We all create wastewater in our everyday lives. At home, we access water with ease; we twist the tap, we flush the toilet, we hit the button on the washing machine and we twist the nozzle on the shower. Industry, hospitals, schools and offices also create wastewater.

Wastewater can contain a wide range of contaminants, some of which can be broken down in the environment easily, while others are not so easily degraded.

Untreated wastewater poses a threat to public health and the environment. Treatment is therefore carried out in order to produce an environmentally safe liquid that is suitable for disposal to our aquatic environment, such as rivers and seas.

Proper wastewater treatment systems are essential for sustaining modern living and contributing to development, as householders, businesses, industries, schools and hospitals all rely on a robust wastewater treatment system to maintain their daily activities.

Untreated raw sewage has been discharging directly in to the lower harbour for decades.  Wastewater is collected from homes and businesses across the lower harbour area and undergoes no treatment before being discharged into the sea. This practices is in breach of national and European legislation and means Ireland is currently in contravention of the European Union Urban Wastewater Directive.

Wastewater treatment plants are described in terms of their designed treatment capacity, which is generally expressed as population equivalent (PE).

This is a measurement of total organic biodegradable load, including industrial, institutional, commercial and domestic organic load, on a wastewater treatment plant, converted to the equivalent number of population equivalent (PE). One person is considered to generate 60g of BOD per day (BOD is the 5 day biochemical oxygen demand); and 1PE is defined as being equivalent to 60g of BOD per day.

In the case of the WwTP at the site in Shanbally, the estimated PE for the plant is 65,000 PE in the first phase. The plant will be a modular design with capability to expand to 80,000PE as population growth demands as per the original Planning Application.

A site for the new WwTP has been selected at Shanbally (north of West Carrigaline), utilising the existing IDA outfall discharging to the Harbour at Dognose Bank.

The planning application for the WwTP at Shanbally was given permission by An Bord Pleanála in 2009 subject to conditions.

From 2000 to 2009, the Project Team (Mott Mc Donald Pettit), managed by Cork County Council, undertook an Environmental Impact Assessment (EIA) on the Project. The Environmental Impact Assessment looked at any potential environmental impacts of the Project and associated mitigation measures that may be required.

As part of the EIA process an Environmental Impact Statement (EIS) is produced, and can be viewed here. This stated that the provision for a WwTP at Shanbally will not have significant adverse effects on the environment and would be in accordance with proper planning and development of the area.

The EIS examined nineteen potential sites for wastewater treatment. Nine of these were examined in detail as part of ten options, ranging from one treatment plant (the recommended solution) to four individual treatment plant sites.

In 2009, An Board Pleanála approved the construction of a wastewater treatment plant at Shanbally, Ringaskiddy Co. Cork and the construction of four major pumping stations at West Beach (Cobh), Carrigaloe , Monkstown and Raffeen, together with the modification of Church Road (Carrigaline) pumping station, to result in an overall catchment network of twenty small and five large pumping stations, as well a single outfall off Ringaskiddy which is already in operation. You can view the planning approval here.

From the 1st of January 2014, Irish Water took over responsibility for water and wastewater services in Ireland in partnership with the Local Authorities.

Irish Water recognises the vital importance of the Cork Lower Harbour Main Drainage Project to Cork and to Ireland. Cork County Council will support Irish Water in the continued development of this Project.

The Project Team are still refining the locations of the larger pumping stations, and have undertaken engagement with local communities in order to get feedback on possible location points.

The works for the Project have been split into five contracts:

  • WwTP Contract: This contract will provide the new wastewater treatment plant and connect the flows from Carrigaline and Crosshaven to the plant.
  • Cobh Network Contract: This contract will intercept all of the existing raw sewage outfalls in Cobh and transfer them onwards to the wastewater treatment plant.
  • Estuary Crossing Contract: This contract will transfer flows from Cobh to the network in Passage West/ Monkstown for onward transfer to the wastewater treatment plant.
  • Passage West/ Monkstown Contract: This contract will intercept all of the existing raw sewage outfalls in Passage West/Monkstown and transfer them onwards to the wastewater treatment plant and pumping station.
  • Carrigaline /Ringaskiddy contract: This contract will intercept all of the existing raw sewage outfalls in Ringaskiddy and Coolmore and transfer them onwards to the wastewater treatment plant. In addition, sewerage upgrade works will be carried out in Carrigaline.

One of the most modern wastewater treatment plants in Ireland is the Shanganagh-Bray WwTP in Shankill, Co. Dublin, which opened in January 2013. It was provided through a Design, Build and Operate (DBO) contract by Sisk Dragados Drace (SDD) – see photo.

This plant has a design capacity of 186,000 Population Equivalent (PE), which is almost double that of the WwTP proposed at Shanbally. It is one of the most recent WwTPs in Ireland and occupies a site area of approximately 4 hectares. All units within this WwTP are covered, and strict odour and noise controls exist at the boundary of the site. The area around the Shanganagh plant is landscaped and used by the local community for walking, playing pitches and a community garden.

The Environmental Impact Statement (EIS), approved by An Bord Pleanála, concluded that the project will have a positive impact of the environment, marine life, water quality and economy in the Harbour in general by removing the current raw sewage discharges.

Modelling, completed by University College Cork, of the existing untreated discharges and the future treated discharge at 80,000 PE, is included as part of the EIS. The modelling shows a positive impact in reduction of nitrogen levels and faecal coliform pollution. The positive impact extends, not only to the inner Harbour, but also to Lough Mahon, the North Channel of Cobh and the outer Harbour to Roches Point. Specialist Marine Flora and Fauna surveys and analysis also supports this conclusion.

Modern wastewater treatment plants are designed to minimise the risk of odour emissions. There have been extensive engineering advances in the technology employed to run wastewater treatment plants in recent years. Modern plants are covered and have extensive odour, emissions and noise controls in place, and this will be the case with the Shanbally site.

The following measures are being taken:-

  • Even though many modern wastewater treatment plants are as little as 50 metres from houses, the perimeter of the Shanbally site is at least 250 metres from the nearest existing house.
  • Odour limits at the boundary of the site have been set at 3 odour units on a 98th percentile basis by An Bord Pleanála conditions.

An odour unit is a measurement of the concentration of odour(s) that can be detected. It is measured as 1 ouE, a European Odour Unit. An odour unit of 1 is very weak, and wouldn’t be detectable outside the environment in which it was caused. As odour becomes more concentrated, it then gradually becomes more apparent. A good guidance rule of thumb on concentration is (and this is based on laboratory conditions):

  • 1 ouE m -3 is the point of detection;
  • 5 ouE m-3 is a faint odour; and
  • 10 ouE m-3 is a distinct odour

A 98th Percentile is the value ‘x’ of a year of hourly averaged concentrations means that hourly averaged concentrations will be less than or equal to ‘x’ (in this case 3 odour units) for 98% of the year.

There are no known health risks to the general population posed by the operation of WwTPs. All gases produced during the treatment processes will be treated on site before venting to the atmosphere.

An appropriately constructed and well operated plant and sewer network should have no adverse impact on the area in which it is located.

The Project Team has liaised with local business groups and restrictions will be placed on Contractors to minimize construction impacts on tourism. In practical terms, no work will be permitted in certain areas during the tourist season. The improvement in the water quality will be a major benefit to all water-contact tourism.

All potential impacts resulting from construction works have been assessed during the preparation of the Environmental Impact Statement (EIS and Natura Impact Statement (NIS)) and suitable management measures will be identified to reduce or eliminate any impacts.

The most noticeable impact during the network contracts will be on traffic as temporary lane closures and road closures will be required in order to safely lay sewers in the road. Irish Water, and its Contractors will liaise with the local area staff of the Cork County Council, the Gardaí, local industry, schools, businesses and local residents to minimize the impacts of the works.

Lands will be reinstated ( i.e. returned to their previous state), and Irish Water will ensure that the Contractors comply with this commitment through liaison with the Local Authority.

Furthermore, Irish Water, and its Contractors, will liaise closely with the community before and during construction to ensure a constant flow of information, and to ensure that local considerations are taken into account, such as in developing the traffic management plan, for example.

A new wastewater treatment plant at Shanbally commenced operations in December 2016   treating wastewater from Carrigaline, Crosshaven and Shanbally. Construction is underway   for the sewer network contracts on the southern side of harbour. An Bord Pleanála approved   an amendment to the original grant of planning for Cobh sewer network in March 2017 and   design is being finalised for this part of the project.

If you have any questions or require further information you can contact the project team:


Telephone: 1850 278 278 (LoCall, 9am to 5pm Monday to Friday)

Minicom: 1890 378 378 (for hearing impaired customers with their own minicom equipment)

Cork Lower Harbour Main Drainage Project,
Irish Water,
PO Box 860,
South City Delivery Office,
Cork City.


Current opportunities to consult on this project are outlined here. In addition, the Project team will be holding additional public information events and these will be advertised here.

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