Play facilities are planned for an area in Dodder Valley Park which regularly "overflows with raw sewage", according to a local councillor.
Fianna Fail councillor Deirdre O'Donovan said she is seeking clarification from Irish Water that the issue can be resolved, as a vote by councillors is scheduled to take place today in relation to the development.
"I will be proposing an amendment that the proposed play trail stops at the Firhouse Weir.
"That is where the issues with the raw sewage originate from, and [I will also be proposing] that the council does not proceed with this part of the play trail until we get written confirmation from Irish Water as to what the permanent solution to the issue is and when that will be delivered," she told the Herald.
"I will also be supporting local groups who have pointed out how unsuitable the site at Cherryfield is for the third playspace, at the Spawell end of the Dodder Valley Park."
A group called Save Our Cherryfield Space was set up in response to proposals by South Dublin County Council (SDCC)for three playgrounds and a play trail in the park.
It has no objection to the other elements of the plan, but the contentious part involves putting in the new playground at the Spawell end of the park, east of the M50.
Ms O'Donovan explained the sewage issue has been a serious issue for park users.
"After very heavy rainfall, the drains overflow and you can see raw sewage and used toilet paper flowing through the park, beyond the Firhouse Weir down towards the Spawell end of the park," she said.
"Initially South Dublin County Council said that the €1.2m Ballycullen Flood Alleviation Scheme would solve the problem, but unfortunately this was not the case.
"And when I raised it again in December 2017, SDCC agreed to fence off the worst-affected drain to keep dogs and kids away from the source of the sewage.
"But now they are proposing to introduce play facilities in the park, including a play trail right by the source of the raw sewage.
"SDCC have said that the issue will be resolved before the proposals are put in place, but we are seeking clarification from Irish Water as to what can be done.
"There's a play space planned for another park, Delaford Park, just 500 metres away, so the much-needed facilities will be delivered once that is completed."
Locals, including dog walkers, are also concerned that the works would disturb the area's biodiversity and flora and fauna.
A statement from Irish Water said: "The Dodder Valley Scheme is a strategic sewer and Irish Water are assessing the need for future upgrade requirements to the sewer in terms of dealing with storm water flows. The upgrade is dependent on the delivery of a drainage area plan.
"Following discussions with SDCC we have implemented the Dodder Valley Sewer Drainage Area Plan which is under way in the catchment. It is currently in stage two where the investigative surveys are being procured and implemented.
"It's estimated that it will take a further two years to fully complete.
"Irish Water is committed to ensuring wastewater is safely returned to the environment and the current issues identified will require ongoing clean-ups, post heavy rain."