At Merrion Strand, a Complex Set of Problems Lead to the Closure of City Beach for Bathers

Beside the Merrion Gates railway crossing, between Sydney Parade and Booterstown DART station is a laneway leading into Merrion Strand. The entrance is cordoned off with concrete bollards, where a group of teenagers are gathered asking passersby for cigarettes.

The beach, which spans approximately 0.7 kilometres is almost empty, save for one family, listening to music and enjoying a picnic atop a sand dune. Just a few kilometres down is Sandymount Strand which is in full-swing – throngs of people are swimming, sunbathing, and patiently queuing for an ice cream truck.

As of 1 June, Merrion Strand is declassified as a bathing area after the water quality was found to be “poor” for five years running. Under EU law, Dublin City Council was obliged to advise against swimming there.

Overflowing sewers, feeding into urban streams when it rains, are part of a complex set of problems that have led to the closure of the city beach.

Working Flat-Out

Dublin City Council is working together with Dún Laoghaire-Rathdown County Council, Irish Water, and a University College Dublin science project called Acclimatize – to try to get to the bottom of where the pollution is coming from.

“We are working flat-out on getting it sorted,” says Padraig Doyle, a senior engineer in the environment department of Dublin City Council. Doyle says he’s dedicated to tackling pollution on Merrion Strand and the adjoining Sandymount beach.

“We are starting to narrow in on particular areas where we believe there are significant problems,” says Doyle. “All you can do is take a broad-brush approach, try and work out an area where there are problems, then try and narrow it down further.”

Much of the pollution at Merrion Strand is likely coming from the Elm Park and Trimleston streams, which start out in the Dún Laoghaire-Rathdown County Council area and end up in Merrion Strand, says Jenny Deakin, a senior catchment scientist with the Environmental Protection Agency (EPA).

Doyle’s team have taken 250 samples in those streams for testing in recent months, he says. “A lot of work has gone into trying to find the sources of pollution,” he says.

There are various factors at play, he says.

At a national level, an EPA report into pollution incidents on beaches found that in 54 percent of them the cause was urban wastewater.

Overflowing Sewers

Heavy rain can wash dirt from roads into streams, says Doyle.

Rain can also cause the sewers to overflow into the wastewater system which ends up in streams and rivers and then eventually the beaches.

When there is really heavy rain, the combined sewerage system is designed to overflow, says Doyle. “In an extreme rainfall event it is permitted to have some spillage of sewerage into the watercourse – on the basis that it will be very dilute,” he says.

The problem is that some of the time the overflow system is not performing well and in that case, fairly ordinary rainfall might cause the sewerage to overflow into the wastewater.

Doyle and his team have identified one such issue, in Goatstown, a suburb in south Dublin, where he says “sewerage is getting out of the pipe and into the watercourse in small rainfall events and a lot more often than it should be”.

Irish Water is in charge of fixing pipes and agreed to carry out the necessary works at Goatstown, which will likely involve replacing around 100 meters to 300 meters of piping says Doyle.

The works were delayed by Covid-19 says Doyle, but will be completed by next summer.

There are overflow issues in other places too, but they are less severe, says Doyle.

Says a spokesperson for Irish Water: “Since its establishment, Irish Water has been investing heavily in wastewater treatment and sewage infrastructure, which are essential to ensuring the quality of coastal waters.”

Irish Water is surveying the entire pipe network and running simulations to figure out the best designs, says Doyle. That research will take three or four years, he says.

Leaky Pipes

There is some evidence that leaking sewerage pipes might be polluting the streams that run into Merrion Strand too, says Deakin, of the EPA.

Some of the pipes in Dublin are around 100-years-old but replacing the pipe network would be a massive job. “You are into billions there as well as digging up the whole city,” she says.

“It would be logical that there would be a certain amount of leakage,” says Doyle.

Some of that sewerage will be soaked up into the ground, but some of it might end up in the streams, too, he says. But that issue is more difficult to identify than overflows. “You will never see that on the surface,” he says.

Other Issues

Both Dublin City Council and Dún Laoghaire-Rathdown County Council have attempted to tackle another source of pollution going into the streams due to misconnections, says Doyle.

A misconnection happens when a plumber sends a sewerage pipe out into the wastewater system instead of into the sewerage system.

The national analysis carried out by the EPA estimated that misconnections were responsible for approximately 10 percent of pollution incidents on beaches.

Doyle says that Dublin City Council is almost finished surveying the Elm Park and Trimleston streams for misconnections and has identified a number of households as well as two large industrial premises that had misconnections.

From Sandymount beach you can see the Ringsend wastewater treatment works so some people think it must be a factor in the pollution on the beach, says Doyle.

But Irish Water has done hydraulic modelling, looking at how the sewerage behaves once it goes out of the plant, he says. That included placing objects in the water and watching where they go, he says.

Studies by UCD’s Acclimatize project also show that the pollution reduces as you go out from the shore, he says. “All the evidence to date is that because of dispersion patterns in the bay, the stuff coming out of Ringsend is not ending up in Sandymount or Merrion,” he says.

One thing that is certainly contributing to pollution on the beaches though is animal waste, says Doyle.

Merrion Strand is a conservation area and bird droppings contribute to bacteria in the water there, he says.

Doyle is appealing to dog owners to clean up after their pets. “One dog incident can put a lot of bacteria into the water and if that happens shortly before we take our sample, that could be enough to close the beach for a couple of days,” he says.

Green Party Councillor Hazel Chu says that some of the issues with pollution are human-made. “We have people throwing stuff into rivers, and dog fouling. On the one hand it is bureaucratic measures, red tape and organisation but on the other hand, people are not helping the situation,” she says.

According to Chu, Dublin City Council is looking into a rewetting programme for Elm Park as one possible solution to pollution.

What Now?

Last year swimming was not permitted on either of the adjoining beaches, but this year Sandymount was upgraded from “poor” to “sufficient”, meaning that bathing is allowed there again.

Doyle says that improvements in Sandymount are “a good news story”. He says he hopes that Merrion Strand will also be reopened soon too, but it won’t be for “perhaps a couple of years”.