Council hoping to tackle River Liffey pollution by resurfacing Portobello streets
Dublin City Council (DCC) is hoping to arrest the decline in the River Liffey’s water quality by resurfacing and redesigning primarily residential streets in the suburb of Portobello.
In a new project called the Integrated Mobility, Ecology, and Natural Drainage (Imend) scheme, the authority is set to introduce interventions to slow the flow of rainfall water through the sewer network, thereby reducing the level of pollution making its way into the Liffey.
Headed up by the council’s Protection of Water Bodies Office, the scheme aims to redesign certain elements of the streetscape to slow the flow of rainwater into the overcapacity, aged drainage system.
The area where the interventions will take place is outlined in red
Suggested changes include the introduction of permeable materials to replace existing tarmac and concrete, redesigning junctions to attenuate water better, and replacing hard filtered permeability structures with planting that absorbs rainfall.
“The specific issue here is water quality,” Roy O’Connor, a senior engineer at DCC told councillors last week.
He said that between Dublin’s canals and the North and South Circular Roads, much of the drainage system is combined.
"That means the foul [water] from private property and commercial property all enters the same drainage system as our rain water does,” he said.
When this system is overwhelmed, such as in major rainfall events, the additional waste water and sewage flows directly into the River Liffey via a network of overflow pipes.
Alternative materials are suggested for Portobello junctions
The largest of these pipes passes directly under the Dublin City Council civic offices at Wood Quay, discharging effluent directly into the river.
Sewage and rainfall from the residential areas of Portobello, in large part, feed this outflow at Wood Quay, explaining the council’s choice of location for the project.
"One of the greater challenges in the Dublin city area is the quantity of area that is impermeable, predominantly concrete and tarmacadam,” said Mr O’Connor, adding that upwards of 85pc of the city centre does not absorb rainfall.
"That all contributes towards pollution in our water bodies,” he said.
Existing filtered permeability bollards could be replaced with planted areas
Climate change and the increasing severity of weather events is also making these projects more urgent, he said.
“We’re seeing the wettest summers on record, the warmest months, and that all facilitates more rainfall and more frequent and intense rainfall events.”
DCC said the project is currently in the initiation phase, and a lead consultant to progress designs would be appointed by March.
If it all goes to plan, Mr O’Connor said the council would hope to expand the street redesign to more areas of the city, with interest also expressed by Cork City Council and Uisce Éireann in its findings.
Independent councillor Mannix Flynn welcomed the initiative, saying that the water in the Liffey was “pretty manky”.
"I’m very pleased that the issue in relation to Wood Quay and the sewage that emanates from this pipe under Wood Quay are going to be dealt with, because I’ve often walked by the [River] Liffey, and literally it is like a lavatory,” he said.
The latest water quality report from the Environmental Protection Agency found that barring a few exceptions, our nation’s rivers, including the Liffey, have been in a state of decline for decades.
The main reason for our dwindling water quality is agricultural runoff, however, wastewater pollution remains a significant contributor.