A €300 million project is transforming Cork. Barry Roche, Southern Correspondent, reports.
Cork's new €300 million main drainage scheme will be completed in the spring, 15 years after it was first planned.
The project, which will ensure that the city's sewage system complies with the EU Waste Water Directive and the Government's Environment Action Plan, has involved the biggest engineering works in the State.
At its height, up to 450 people were employed on the drainage scheme.
In all, 38 km of interceptor sewers, including new sewer connections to all premises on Cork's central island, were laid, along with some 39 km of rising mains. A total of 1,134 metres of culverts and 10 pumping stations were also constructed.
Before the system was laid, some 13 tonnes of raw, untreated sewage were being discharged into the River Lee every day.
Cork's River Lee divides into two main channels to form the island on which the city-centre was developed.
Historically, sewage has been discharged into the two channels through smaller streams.
Cork City Council had been working for many years to address the problem and in the 1960s and 1970s spent about £20 million laying new interceptor sewers along the north and south quays to catch and collect waste water.
This involved moving the main points of discharge from the north and south sides of the city downstream of the city-centre to Horgan's Quay on the northern side and to Kennedy Quay on the southern side, where it emerged, untreated, to be dispersed by the tide.
According to the project engineer for the scheme, Mr Denis Duggan, approval for the drainage plan was obtained from the Department of the Environment in 1990.
Design work began a year later and Cork consultant engineers E G Pettit & Co reported in 1992 on various options for the drainage scheme.
"Pettit's report recommended that sewage would flow from the city as far as a site east of the Atlantic Pond, where a large pumping station would be constructed, and sewage would be pumped from there to a new treatment plant at Little Island," Mr Duggan explained.
A lengthy period of preparation followed, during which the plan was given approval by Cork City Council.
Planning permission for the treatment plant was obtained from Cork County Council and granted by An Bord Pleanála after an oral hearing.
Tender documents were then drawn up for 22 constituent contracts.
Work on the main contracts began in 1998, when the contractors moved on to the island to begin the difficult task of laying pipes in the busy city-centre.
While the scheme was not designed to deal with surface water, as occurred last October, when a combination of high tides and heavy rainfall led to flooding, it has at least meant that foul water is no longer washed back up on to the streets.
The laying of pipes in the city centre involved close liaison with the ESB, Bord Gáis and other utility companies as well as with Bus Éireann and the Garda Síochána to minimise traffic disruption.
Mr Duggan held regular briefings with traders before work began on the city's streets.
"Meeting groups in advance of work in each area was of great advantage. People appreciate being consulted and hearing what is going to happen prior to the works. It meant people felt more involved and were understanding of our efforts," he said.
While the city centre work was the most disruptive, some of the tougher engineering challenges were less visible, such as the construction of 2.7 km of the main trunk sewer linking Kennedy Quay with the pumping station at Atlantic Pond.
"That work involved 10 months of tunnelling, using a special boring machine which was enlarged to 3.5 metres for the Cork scheme. There were two crews working 24-hour shifts, boring some 8 metres below ground," Mr Duggan said.
"Both Victoria Road and Monaghan Road remained open to traffic and motorists and the general public were unaware that, beneath them, a huge machine, a railway system and 20 men were hard at work."
Equally challenging was the construction of a siphon under the River Lee connecting the outfall at Horgan's Quay on the north side with that at Kennedy Quay on the south side and the subsequent linking up of a third shaft from the city centre at Custom House Quay.
Transporting the sewage from the pumping station at Atlantic Pond back across Lough Mahon and the Lee estuary to the treatment plant at Carrigrenan on Little Island involved the dredging of the harbour bed and the laying of nine twin 450-metre-long pipes.
The first flows into Carrigrenan began in August 2003, with throughput being built up incrementally until the end of 2003, when all of the city and the Tramore valley were linked up and the waste water started discharging via an outfall pipe off Marino Point.
"The plant has been designed on a modular basis to allow expansion as necessary over the next 20 years, but already this year the results have been terrific, with water quality levels in the river being well in excess of EU directives," Mr Duggan said.
"The directive stipulates that biochemical oxygen demand levels should be under 25 parts per 1 million. We are five times below that, with typical results of four to five parts. Water quality in the Lee in the city is now almost the equivalent of what is upstream of the city."
The scheme is due to be officially opened next March.