Dublin Bay Project – Contract No.2

T.J. O’Connor & Associates acted as Civil/Structural Consultants for the ABA (Ascon, Black & Veatch, Anglian) Joint Venture to Design, Build and Operate the upgraded Wastewater Treatment Plant in Ringsend which serves the greater Dublin area as part of the overall Dublin Bay Project, catering for 1.64 million P.E. (40% of the country’s population).

We are also part of the Joint Venture acting as Employer’s Representative for the current Ringsend Upgrade Project, set to increasing the Plant capacity to 2.4 million P.E., equating to effluent treatment for 60% of the country’s population.

The design involved the upgrading of the existing treatment plant to cater for a design population of 1.64 million with a full flow to treatment of 11.1m³/s and a peak flow of 22.6m³/s. Some of the physical constraints were that the site was less than 15 hectares which is unusually small for a plant of this capacity and also that part of the plant was built on an old refuse site.

T J O’Connor & Associates were responsible for the civil and structural design which included over 15km of pipeline ranging from 0.1m up to 2.1m diameter, new inlet works and associated building, primary tanks, storm tank refurbishment, sludge building, CHP building, sludge digesters, gas holder, SBR tanks, UV disinfection and associated building, new roofs on existing admin and workshop buildings and numerous other elements and site works.

Some of the unique features of the constrained site included the largest Sequencing Batch Reactors (SBR) ever built. This was the first time a 2 level SBR system has been built in Europe and over 4,000 piles were used in its construction. The plant also contained the largest sludge hydrolysis plant ever built. There was also a requirement to maintain continuous flow of the various existing wastewater streams coming into the old plant whilst demolishing the old plant in a phased manner and building the new structures within the contract time allowed. An example of this was the existing primary treatment tanks which were upgraded and replaced with new primary treatment elements one by one while flow was maintained to adjacent tanks.

Start/End Date:

1994 – March 2004

Contract Value:



Civil & Structural Consulting Engineers

Key Features:

  • Design population of64 million
  • Full flow to treatment of 11.1m³/s
  • Peak flow of 22.6m3/s
  • Constrained site built on old refuse site
  • 15km of pipelines from 0.1m to 2.1m dia
  • Largest Sequencing Batch Reactors (SBR) ever built
  • First 2 level SBR built in Europe
  • Over 4,000 piles used in construction
  • Largest sludge hydrolysis plant ever built
  • Continuous flow of various wastewater streams maintained during construction
  • Design and preparation of Contract Documents under a Design, Build Operate from of Contract

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