Carrigtohill Main Drainage Scheme

T J O’Connor & Associates were engaged by Cork County Council to act as Client’s Representative in connection with upgrading the pipe network throughout Carrigtohill to allow for the level of development anticipated in the Cork Area Strategic Plan and alleviate the overloading of the existing plant.

T.J.O’ Connor & Associates carried out a full range of services as Civil Engineers on this traditional pipe network contract and were responsible for compiling the Preliminary Report for the overall scheme through to contract document preparation, tender stage documentation, construction supervision and final account agreement on the initial construction works already completed.

The pipelaying works included pipe sizes ranging from 225mm to 900mm diameter in addition to a 1,200mm twin tunnelled section in the town centre. Due to extremely poor ground conditions, the 900mm diameter trunk sewer leading to the WWTP was constructed on a piled foundation and pre-cast concrete cradle at depths up to 9 metres adjacent to a tidal estuary. There were a number of pumping stations including a new 10 metre deep pumping station adjacent to the existing WWTP.

The project included for tunnelling the pipelines through the town centre and pipejacking across the N25 motorway. An existing causeway (circa 160 years old) prevents seawater flooding the surrounding area. This causeway contains five discharge culverts. The causeway was assesed structurally and hydraulically and works were carried out to seal the causeway and replace the culvert gates/valves to limit seawater ingress.

A number of separate contracts were undertaken to implement the scheme. These involved the construction of pipelines and ancillary works, pumping stations, the upgrade of the causeway and associated sea defences within and the construction of a large surface water pumping station to alleviate flooding.

Start/End Date:

2002 – 2010 (Phase 1)

Contract Value:



Full Engineering Services on traditional pipe network contract from Preliminary Report to Contract Documents, Tender and Construction Stages and PSDS/PSDP

Key Features:

  • Tunnelling of pipelines though town centre with 1200mm diameter shafts
  • Pipejacking across N25 motorway of 900mm diameter sewer
  • 0 km of sewers ranging in size from 225mm to 900mm diameter
  • Pipes of 1200mm and 900mm diameter installed on piles up to 9 metre depths adjacent to harbour
  • 3 new pumping stations up to 10m deep
  • Upgrading of existing 160-year-old causeway, replacement of sluice gates and installation of storm water pumping station with 4m3/sec discharge capacity
  • Modelling of networks using Hydroworks
  • Flow surveys
  • Part VIII Planning procedures for pumping stations
  • Modelling of Slatty Pond for flow discharge calculations
  • Assessment of existing causeway and tidal effects

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