The use of a helipad at one of Dublin's largest hospitals, which it is estimated could save nine lives a year, is in doubt after planners raised concerns about its impact on local residents.
The Mater Hospital submitted a fresh application for planning permission for the use of the helicopter landing pad in its car park on Eccles Street.
Although it secured approval three years ago, the Mater has not put the helipad into use and its current permission is due to expire in December.
Dublin City Council has sought further information about the hospital's plans for the use of the helipad amid "significant concerns" about its potential impact on residential properties nearby.
A risk assessment report said the potential for a bird strike on a helicopter using the facility was unacceptable and a bird management policy needed to be put in place.
It also concluded that a safe approach and departure can only be performed in one direction from the helipad.
The local authority said the location of the helipad could also jeopardise plans for the future expansion of the Mater.
Council planners claimed there were a number of anomalies in documentation submitted by the hospital in relation to the number of helicopter trips using the helipad and the timing of its use.
They called for more information, including a noise impact assessment.
The Mater had signalled that it expected there would be an infrequent number of helicopters using the helipad.
The hospital said it had already carried out a survey, which concluded that noise levels from the helipad would not be "appreciably higher than the pre-existing baseline ambient noise level".
The survey said the disturbance from helicopters was likely to be limited to a 15-minute period every 1.5 days.
Without the helipad, patients are likely to be transferred from either Dublin Airport or a helipad at the Army Grounds in the Phoenix Park to the hospital.
The Mater said it had previously investigated having a rooftop helipad on the main hospital building, but it was deemed to be unsuitable.
The hospital's director of estates and facilities, Alan Sharp, said it was "imperative that patient transfer to the hospital for early treatments is as rapid as possible", as the Mater was the national centre for cardiac surgery, heart and lung transplants and spinal injuries.
"At least nine deaths per year are attributed to delays in getting such patients to hospital using road transport," he said.
Three years ago, local residents, as well as a number of councillors, including former lord mayor Nial Ring, unsuccessfully opposed the development of the helipad, primarily on grounds of noise.
The hospital said the helipad would be for "life or death use only". It acknowledged that some lampposts and fencing would need to be removed to facilitate the approach flight path to the helipad.