T J O’Connor & Associates were engaged by Wexford County Council in connection with the provision of a new Waste Water Treatment Plant in New Ross. The WWTP has a capacity of 16,000 PE and treats flow to a secondary standard before discharging to the River Barrow. The treatment works was constructed as a DBO Contract and included the main pumping station, which lifts the sewage to the new WWTP via a 2km long, 600mm diameter sewage rising main. The WWTP provides treatment to a secondary standard with Sequencing Batch Reactors used to provide the required 16,000 PE capacity. The works also included storm water holding tanks, SCADA systems, preliminary treatment works, sludge dewatering, using two centrifuges, and an acceptance plant for importing and dewatering liquid sludges from other (smaller) works in the vicinity of the New Ross plant.
Difficult ground conditions, associated with deep alluvial deposits, were experienced in the construction of the WWTP. A geotextile reinforced 'earth mattress' was constructed over the existing soft alluvial deposits. Settlement of the mattress on the existing soft alluvial deposits was accelerated by the construction of a vertical drainage system comprising 'wick' drains at 1m centres, and surcharge loading. The system used successfully accelerated primary settlements (pore water extrusion) for around 6 months.
The works also included two marine outfall pipes to the Barrow estuary. The first carries treated effluent from the WWTP via a 150m long, 900mm diameter pipe. The other provides for emergency discharge from the main pumping station to the Barrow, below the low water mark, via a 1,050mm diameter pipe. The work was facilitated under a foreshore licence and separate consultations with the New Ross Harbour Commissioners. An ElS was prepared by T J O'Connor & Associates and planning approvals for the main pumping station were obtained through the Part 8 (local authority) procedure based on planning documents prepared by TJOC.
Aug 2007 – Dec 2009
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