Wexford Collection Systems Extension Scheme

Case Studies

Wexford Collection Systems Extension Scheme - Contract No. 1 (Taghmon & Crosstown / Ferrybank)

This Contract was designed to provide for the construction of 3 new pumping stations and Associated rising mains and gravity sewers to connect the area of Crosstown, Ferrybank and the village of Taghmon to the public sewer network in Wexford Town and includes the following works:

  • Construction of a pumping station, control kiosk and ancillary site works at Crosstown/Ferrybank pumping station site.
  • Construction of a pumping station and control kiosk as well as the provision of a ferric sulphate tank and bund and ancillary site works at existing Taghmon wastewater treatment Plant site.
  • Construction of a pumping station and control building as well as the provision of a ferric Sulphate tank and bund and ancillary site works at Keeloges pumping station site.
  • Construction of gravity sewer from Crosstown to Ferrybank PS comprising 817m of 300mm dia gravity sewer.
  • Construction of twin rising mains from Crosstown/Ferrybank PS to Wexford Bridge comprising 639m of 150mm I.D. rising mains.
  • Construction of 160m of 225mm and 274m of 300mm dia gravity sewer from Wexford Bridge to Crosstown Ferrybank PS.
  • Construction of rising main and gravity sewer from Taghmon to Keeloges comprising 6908m of 250mm I.D. rising main and 1502m of 225mm dia gravity sewer.
  • Construction of rising main from Keeloges to Carcur comprising 4294m of 250mm I.D. rising main.
  • Construction of gravity sewer for Ballyhine Housing development comprising 168m of 225mm and 22m of 200mm dia gravity sewer.
  • Construction of 50 No manholes associated with the above pipework.
  • Provision of temporary and permanent road reinstatement as specified in the contract.
  • Ancillary fittings, connections, etc on the above pipelines as well as remedial and rehabilitation works of some existing pipelines and culverts.
  • All ancillary works required.

Further to the above the following major additional works were also constructed:

  • Construction of a 4th Pumping Station and control kiosk as well as the provision of a ferric sulphate tank and bund and ancillary site works at Piercetown.
  • Construction of rising main comprising 3,251m of 250mm I.D. rising from existing Castlebridge Pumping Station to header manhole in Crosstown.
  • Construction of gravity sewer at Tincone Lane (near Crosstown) 511m of 225mm dia gravity sewer.

During the course of this contract there were significant elements of Contractor led proposals, re-design (due to site issues) and construction of works such as:

  1. Construction of 4 nr insitu concrete pumping stations with PERI shuttering system to depths of 6.5 metres in restricted sites including SKYDECK system for insitu concrete roof slabs.
  2. Preparation of pour sequences and temporary works designs for Wall and roof slab pours.
  3. Fixing/erecting of scheduled reinforcement in situ and pre fabricated to bases / walls / columns / beams / roof slabs as required.
  4. Selection of craneage and preparation of lift plans.
  5. Proposal to directional drill 14.5km of 315/250mm rising main allowed local roads to remain open without need for closures, works to progress and reduce disruption to all.
  6. Directional drilling under 3 arch masonry bridge at Castlebridge adjacent foreshore and existing pump station.
  7. Directionally drilling 315mm rising main underneath national primary road (N25) crossing including additional sleeve for future use.
  8. Installation of Siemens flowmeters in pumped rising mains and use of Area Velocity flow measurement from overflows in pump stations during storm events.
  9. Permanent reinstatement to local, regional and national primary routes with surface dressing, HRA and SMA/Clause 912 as required.
  10. Provision of 17nr 350x350 Precast Concrete Piles for Keelogues Pumping Station including increased CAPWAP/Dynamic testing in lieu of static load testing; all of the piles driven indicated a safety factor of 3 for the working load against mobilised capacity.
  11. Temporary works for deep gravity sewers including trench/drag boxes as the ground dictated and sheet piles/frames where boxes could not be used.
  12. Temporary works to Taghmon, Piercetown and Keelogues Pump Stations involving battering of excavation and dewatering of works.
  13. Redesign of pipework bridge/culvert crossings to Cantilever system in road embankments.
  14. Redesign of sewer rising main scour chambers with baur connection.
  15. Construction of Cofferdam for Crosstown Pumping Station to a depth of 7 metres in small site adjacent Wexford Harbour in sands/silts.
  16. Installation of 2nr piezometers to monitor ground water rise and water pore pressure on cofferdam sheet pile walling/2nr hydraulic frames.
  17. 24/7 dewatering plan incorporating slit traps for discharge of ground water in a Special Area of Conservation (SAC).
  18. Directional drilling gravity sewers in Crosstown in order to maintain traffic flow and works in busy arterial route into Wexford town and proceed with works; issues here included regrading of sewer with accurate topographical survey, repositioning of manholes to facilitate access/egress, change in pipe material to HDPE from Class H concrete pipes to insure no reduction in hydraulic capacity, development of open body reamer (450dia) to accurately drill at 4 metres depth in clays/sands/gravels; ongoing monitoring of line and level to ensure sewer was constructed within agreed tolerances and positive grade.
  19. Additional 23nr sewer laterals in Crosstown with internal backdrop connections were possible to offset deep excavation.
  20. Redesign of Control Building foundations to raft type to reduce over dig in soft clays.
  21. Reclassification of soils to general fill material in accordance with series 600 of the NRA Earthworks specification and subsequent use as approved backfill material to pumping stations.
  22. Provision and installation of ducting layouts to accommodate dosing/power/telemetry requirements at 4nr pumping stations.
  23. Permanent reinstatement to pump station site works and access roads including kerbing, storm water drainage and security fencing.
  24. Co ordination, procurement and installation of mechanical and electrical fit out including pumps, macerators, screens, pipe work, penstocks, lever sensors, liaison with ESB and installation of control panels for 4nr Pump Stations.
  25. 25) Development of control philosophy for pumping stations and installation of SCADA which was integrated with existing Wexford Countywide system.

Other Ancillary Works included:

  1. SHR Quality Management Plan implemented to ensure works were constructed to the works requirements/proposals and to the required quality standards.
  2. Traffic Management design and control on local, regional and national roads in rural and urban environments.
  3. Customer liaison carried out on regular basis to inform local residents of traffic management, progress and upcoming works.
  4. Archaeological monitoring.
  5. PAH Testing of subsoils.
  6. Structural and condition surveys of properties/structures on pipeline routes.
  7. Ongoing testing of PE welding and procedures in accordance with WIS 4-32-08 with oversight from external Quality Auditor.
  8. Classification of soils in accordance with series 600 of the NRA specification.
  9. Plate bearing testing (converted to CBR) to confirm compaction reached as required.
  10. Type 2 Pressure testing of PE pipework in accordance with IGN 4-31-02 (March 2011).
  11. Preliminary and final Air test to Class H concrete pipes for gravity sewers.
  12. Hydro-test selected Manholes on Gravity sewers.
  13. Water tight testing of insitu concrete structures.
  14. Connections/working with live sewers as required in Ballyhine, Crosstown, Piercetown and Taghmon.

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Proportion of Contract Undertaken:100% ShareRidge
Tender Entity:Main Contractor
Start Date:October 2012
Completion Date:May 2014*
*Programme Contingency of 209 days granted due to additional works
Contract Value:€5 million
Contracting Authority:Wexford County Council / Irish Water