The construction of 14 steps and a ramp as part of a new entrance to a South Dublin park ended up costing more than €500,000 above the original estimated cost.

The National Transport Authority (NTA) said the ultimate bill of more than €750,000 for the project at Deer Park in Mount Merrion represented “a significant increase over the initial cost estimates” provided by a local authority for the project.

The Irish Times reported in November that the works, which involved the building of 14 steps and a ramp at Deer Park, had cost a total of €753,500 including VAT.

Documents released by the NTA under the Freedom of Information Act show that at one point in 2024, there were indications in a report submitted by Dún Laoghaire Rathdown County Council that the development could cost up to €935,200, including VAT.

The National Transport Authority said this figure set out in a cost report was “a potential estimate” and was not realised.

The park at Mount Merrion is run by Dún Laoghaire-Rathdown County Council, which developed the project, but funding was provided by the NTA.

The State agency said in a subsequent statement that the original construction cost estimate for the project was €200,000 in a grant application form submitted by the local authority in 2023.

The documents stated that at the time, the existing entrance to Deer Park from North Avenue was via steps and that this was not suitable for people with a mobility impairment, cyclists or those with buggies or pushchairs.

The documents also state that it was proposed to construct a ramp and replace existing steps to improve accessibility between the park and the adjacent primary school and local church.

Reports on costs submitted to the NTA by the local authority show financial projections for the steps and the new entrance subsequently began to increase.

The National Transport Authority said that in a report for July 2024, that it received the following month, the council “signalled there were delays due to challenges on site which would lead to additional costs”.

“Following NTA on-site assessment and meetings with the council, the NTA decided to provide additional funding to complete the project.”

The National Transport Authority said this week that the council had told it that the cost increases were due to unforeseen site conditions – tree roots and uncharted high-voltage ESB cables – along with additional measures needed to protect trees.

The NTA said the council had maintained that additional costs were also due to the diversion of utilities and associated delays.

Some elements of the project had to be redesigned to avoid electricity cables “causing demobilisation and re-mobilisation and an increased construction programme”, the agency said.

Details of the cost of the works raised criticism about overspending with public funds when they emerged late last year.

Taoiseach Micheál Martin told the Dáil that the cost involved in the project was “excessive by any yardstick”, while Sinn Féin contended that it represented another example of a waste of public money.

The National Transport Authority told The Irish Times before Christmas that in 2023, the council had applied for “active travel” funding to improve access to Deer Park from North Avenue in Mount Merrion, as the existing steps were unsuitable for those with mobility impairments, cyclists or those using buggies or push chairs.

However, following the controversy about the costs, some locals had contended there were two other entrances to the park in proximity that were accessible to wheelchairs and buggies, albeit with differing gradients.

One entrance is less than 50m away at the corner of Deerpark Road, while the other is a further 100m away next to a row of shops.