Duchas is examining the granting of planning permission by Mayo County Council to Enterprise Energy Ireland (EEI) to construct a gas terminal in north Mayo to clean the gas from the Corrib field.
The council granted the permission on August 3rd after receiving further information from EEI on July 13th.
The outfall pipe from the terminal building will flow into a candidate Special Area of Conservation (SAC). SACs are under the remit of Duchas.
In a letter dated July 16th, the council asked Duchas to reply "within 10 days" with any comments on the further information. Duchas failed to reply.
"Duchas is examining the decision of the local authority. The decision has been sent to our archaeologists, wildlife staff and people involved in the Corrib project. We have until September 3rd to make a decision on what action we propose to take," according to a spokesperson.
Duchas may decide to allow the decision to stand, appeal the decision to An Bord Pleanala, appeal the conditions of the planning or seek a judicial review (only on a point of law).
The spokesperson said Duchas provided a service to local authorities in the form of advice on the protection of our heritage.
While the spokesperson said Duchas did not make the submission in time, another source said Duchas believed the planning decision would not be made until mid-September.
The source added that some people within Duchas "are very annoyed" with Mayo County Council over limiting the submission time to 10 days.