The company, which wants to build the €160m facility, was responding to claims made last month by the Irish Air Corps and the Department of Defence, which included fears of an effective no-fly zone due to the proximity of a stack to the naval base at Haulbowline and concerns over how the area would be evacuated in the case of a serious incident at the incinerator.
Fiona Patterson, of consultant engineers Arup, said there were already a number of existing industrial facilities in the Cork Lower Harbour, as well as wind turbines and church spires, and that it was assumed that all of these had an effective 500ft flight ‘buffer’.
Commandant David Brown of the Air Corps had argued that any helicopter pilot would have to assume there was a 1,000ft danger area above a chimney stack.
Ms Patterson said the proposed Indaver stack would be located 1km from the southern side of Haulbowline Island and a similar distance from the western side of Spike Island.
“Allowing for the 1,000ft avoidance area, as a worst case scenario based on the Department of Defence submission, from the stack buffer, there is still a distance of approximately 2,280ft between the 1,000ft avoidance area and Haulbowline and Spike islands,” said Ms Patterson.
“The conclusions of this assessment are that the exhaust plume from the Indaver stack will be in compliance with the recommended levels for turbulence, temperature, and oxygen content within 100m of the stack top and thus is within the 500ft radius which is required in order to comply with the physical structure exclusion zone. Thus it is considered that a 1,000ft avoidance zone is unnecessary.”
Ms Patterson said obstruction lighting would be installed as per department requirements and that risk assessment showed there were no scenarios for which the evacuation of Haulbowline would be required.
Dr Edward Porter, of AWN Consulting, used analysis of plume emissions and severe turbulence risk and modelling of plume dilution to argue that risk to helicopters was not as high as had been argued by the department.
He said the maximum risk height, based on a worst-case scenario, was 100m above the stack in cases of elevated temperature, 70m in cases of depleted oxygen, and 50m in cases of severe turbulence.
The Indaver delegation put forward a report by a group called Wind Farm Aviation Consultants Ltd, which states the Irish Aviation Authority had not raised any objection to the proposal and that it did not infringe the IAA’s safeguarding policy.
It argued that the basis for the objections by the department’s and Air Corps around flight paths and dangers from exhaust plumes — an Air Accident Investigation Unit report — had since been superceded by another report which did not specify a 1,000ft avoidance zone.
The Wind Farm Aviation Consultants report instead focuses on a Federal Aviation Authority report, which states that unless a pilot were to directly overfly the chimney, at what could be considered a low level and in contravention of mandated regulation, there would likely be no effect on an aircraft.
In response to Air Corps concerns that the effects of southerly winds on plumes would rule out flight in the area, the report said any flight into a southerly wind would be from the north and remain well clear of any plume at all times and any effects would have well dissipated before the landing site.
“There is nothing within the mandated IAA rules of the air or the Federal Aviation Authority guidance/modelling which would appear to support the Irish Air Corps assertion that any helicopter approaches to the island would be made unsafe as a result of the operation of the chimney,” states the report.
“Airmanship would dictate that, in any event and in common with any other vertical structure around the landing site, helicopters should not overfly the chimney.”
Solicitor Joe Noonan, representing Chase (Cork Harbour Alliance for a Safe Environment), said the Indaver response documents should have been circulated earlier, not almost two weeks after the initial submissions by the Department of Defence.
He claimed it was a “discourtesy” to the department to issue the reports on the morning of the hearing, given that the issues in question involved “the security of the State” and were “of the highest possible significance” in planning terms.
Fred Bradley, principal officer in the department, said it was “unfortunate, to say the least” that the documents had not been made available earlier.
Rory Mulcahy, SC for Indaver, said no discourtesy was intended and any delay was due to the applicant wanting to make the most comprehensive response possible and was due to the bank-holiday weekend.
Chief Inspector Derek Daly said it would have been “preferable, if not desirable” had the information been made available earlier. He said he would allow the department time to form a response, likely to be next week.