Project Description

Sligo Main Drainage

The Sligo Main Drainage Project provided for the construction of a new 50,000p.e. Wastewater Treatment Plant(WwTP), Main Pumping Station and Sludge Treatment Centre to serve the City of Sligo and surrounding environs.  The Wastewater Treatment Plant is capable of being expanded to treat a combined domestic and commercial loading of 80,000p.e. at a future date.

The WwTP was procured as Design Build Operate Contract and included for the provision of a 7,300l/s combined Foul and Stormwater Pumping Station and Outfall. The DBO Contract also included the construction of a Sludge Treatment Centre to serve all municipal waste water sludges produced in County Sligo.


The Main Pumping Station captures sewage which previously discharged untreated to Sligo Harbour. The pumps transfer the sewage for full treatment, to the treatment works located some 1km downstream.  The treatment works provides for preliminary, primary and activated sludge treatment supplemented by phosphorous removal and disinfection using ultra-violet lamps.

Sligo is a designated sludge hub centre under the County Sligo Sludge Management Plan and therefore includes a sludge acceptance facility and Sludge Treatment Centre for sludges generated in County Sligo. The sludge arising from the Sligo Wastewater Treatment Plant, together with the imported sludges, receives treatment to reach the standards of a Class A Biosolid suitable for reuse by spreading on agricultural land. Sludge is treated using anaerobic digestion with pre-pasteurisation followed by dewatering to achieve a 25% Dry Solids Class A Biosolid.

An Advanced Civil Works Contract (CN2) for the provision of the new WWTW was completed in December 2002.  The location of the WWTW is in a bunded area in the estuary, which was developed during dredging works, which took place in the Harbour area in the 1980’s. This included repairs to and raising of the bund wall at the proposed site, provision of 130,000m3 stone fill, removal of an existing pumping station, 800mm pipeline rising main and service pipe work and the provision of an access road to the bund site. JOD prepared the Contract Documents and administered this Contract on behalf of Sligo County Council.

Services Provided by Jennings O’Donovan

Jennings O’Donovan provided Consulting Engineering services as a sole trader for the Preliminary Report Stage (i) and as the lead on a JV on Stages (ii) to (v) on this project.  The main consultancy services and technical assistance provided by Jennings O’Donovan included:

  • Inputs to Sligo County Sludge Management Plan.
  • Preparation of an Environmental Impact Statement for the Sligo Wastewater Treatment Plant, Pumping Station and Outfall Pipeline.
  • Organising sewer network studies including manhole, CCTV, flow and load, infiltration, sewer rehabilitation, Hydraulic Modelling and GIS.
  • Risk Assessment of overall project including workshop with Council Staff and allocation of specific risks through the contract documents.
  • Preparation of Pre-Qualification documents and evaluation of submissions from Contractors.
  • Preparation of Contract/Tender Documents.
  • Tender evaluation and recommendation on the most economically advantageous tender for both contracts.
  • Undertaking the role of PSDP.
  • Site inspections, contract administration, checking and financial management.
  • Provision of site supervisory staff.
  • Preparation of the Final Account, as constructed drawings, delivery of the Safety File and O&M Manuals.