Cork wastewater treatment plant

The Cork wastewater treatment and mud-recycling plant, located at Carrigrenan at the very tip of the verdant Little Island peninsula at the mouth of the Lee River and 15 kilometres east of Cork, was upgraded to serve a population of 250,000. The plant is the final component in the city’s water-sanitation network. VINCI Construction Grands Projets led the civil-engineering mandate that includes 16 hydraulic storage tanks, 10 reinforced-concrete transfer chambers, 7 buildings, 23,000 m3 of concrete, and 3,800 tonnes of steel. The plant was opened in January 2004.

BACKGROUND

In the past few years, the Republic of Ireland has experienced soaring economic growth. Cork is the country’s second-largest city and the economic and cultural hub of the whole of the southwestern region of the island. The Lee River, which runs through the city, received wastewater from various water-management networks. That is why, by the early 1990s, a wastewater treatment and sanitation plant was needed. Following an international call for tenders launched at the end of 1999 by the Cork County Council, a bid was submitted in March 2000 for the design, construction, operation, and maintenance for 20 years of a wastewater-treatment and mud-recycling plant.

TECHNICAL OVERVIEW

The part of the mandate attributed to VINCI Construction Grands Projets encompasses the design and construction of the wastewater-treatment and mud-recycling plant. A conventional gravity mechanism was selected for this project, with the discharge of clean water into the bay at Cork by means of an underwater pipe. For ecological and environmental reasons, all basins were built underground. Particular attention was paid to the architectural design of the buildings and metal storage tanks to ensure that they blend in harmoniously with the local landscape. If we follow the flow of the plant’s operations, the project’s 45 civil-engineering structures include a building that receives wastewater and sewage equipped with a primary treatment system to ensure screening and degreasing of local wastewater, followed by an underground double reinforced-concrete basin for pre-aeration. Primary treatment is carried out in 2 circular reinforced-concrete basins that are 35 metres in diameter. Four circular reinforced-concrete basins, also 35 metres in diameter, can store excess water in the event of storms. Secondary treatment consists of 8 circular reinforced-concrete basins 45 metres long and 35 metres wide (Cyclazur) and a building that provides ventilation. A 800-metre-long polyethylene pipe with an interior diameter of 1,480 millimetres discharges the treated water into the bay at Cork.

Investments made in the water-supply network in Ireland have helped strengthen water-preservation measures, improve water quality, and reduce pollution hazards.

IMPACT

The plant, which is located in a residential zone, amid little cottages, golf courses, and a natural wildlife and aquatic vegetation reserve, was the focus of constant attention and monitoring by the local population. Associations, organised during both the design and construction phases, oversaw landscape architecture and the choice of floral species, monitored wetland ecosystems, dust emissions, and the noise produced by worksite machinery as well as the quantity of leaves on saplings planted on the mounds.

Project participants

Client
Cork City County Council

Project management
Eg. Pettit & Co / Matt Macdonald

Key figures

Implementation dates
September 2001 to January 2004

Earthworks
500,000 m3

Concrete
23,000 m3

Reinforcement
4,000 t