STORMONT'S environment minister has refused to disclose whether a potentially dangerous chemical was used in the exploratory oil drill at Woodburn Forest near Carrickfergus.
East Antrim MLA Oliver McMullan asked Michelle McIlveen to confirm whether disinfectant Biocide T was used in the test bore operation and what dangers the chemical posed.
Oil company Infrastrata ceased drilling at the NI Water-owned site a month ago without finding oil.
Its operation was carried out against opposition from environmentalists who had expressed concerns about the impact on nearby reservoirs, which provide drinking water for the south Antrim area and parts of greater Belfast.
NI Water has previously said it has "no concerns" about the quality of drinking water.
The overtime bill for the policing operation at the site came to almost £200,000.
Mr McMullan tabled a written assembly question to the new DUP agriculture, environment and rural affairs minister on June 6.
He asked Ms McIlveen to state whether Biocide T was used at Woodburn and to "detail the dangers to the environment from this chemcial".
But the minister said the information was "confidential" and could not be made public for four years.
However, in response to Mr McMullan's question about the dangers posed by Biocide T, Ms McIlveen added that "all chemicals pose a risk to the environment".
"... Therefore their transport, use, handling, storage and disposal must be carefully managed to prevent linkages or pathways developing between chemical sources and environmental receptors, in which case the risk would be negligible," she said.
Mr McMullan described the minister's response as "far from satisfactory" and said there was an onus on her to tell the public what chemicals were used in the drill operation.
"I believe the minister is duty-bound to release this information so the public know what exactly went on at the Woodburn site," he said.
"Ms McIlveen has herself conceded that all chemicals pose a risk and I believe Biocide T poses a particular risk to human health."
The Sinn Féin MLA claimed the public interest was not being served in relation to the Woodburn drilling operation.
"When we are dealing with publicly-owned land and a public water supply what is needed is complete transparency," he said.
Niall Bakewell from Friends of the Earth claimed the minister's response highlighted the "folly" of NI Water's decision to lease the land to Infratstrata.
"If NI Water did know there would be an embargo on this information then they have clearly placed too much trust in the developer's assurances and if they didn't know, then they have failed the public to which they should be accountable," he said.
According to campaigners opposed to the Woodburn drill operation, documents obtained under freedom of information show Infrastata highlighted the potential dangers of Biocide T.
The documents state that the chemical is harmful if swallowed, toxic by inhalation and poses a risk of serious damage to eyes.
