You must give notice to the Environment Court and all other parties to that you wish to be a party to the proceedings within 15 working days after the period for lodging a notice of appeal ends (section 274). Your notice needs to be in accordance with Form 33 and contain:
A description of the proceedings in which you have an interest
The grounds on which you are seeking to become a party to the proceedings
Whether you are interested in all or part of the proceedings
The particular issues you are interested in
Whether you support or oppose the proceedings and the reasons for that support or opposition