Retaining wall over a Council stormwater drain

I'm looking to construct a retaining wall over a Council stormwater drain and need the help of a freelancer to get the necessary permits and approvals from the council. The wall needs to be more than 3 meters in length and I was thinking steel beams as the appropriate material. It's essential that the construction is done according to the approved plans and I need assistance to obtain the permits and approvals before the project is commenced.