Auckland Council is pressing ahead with its planned downtown rail tunnel despite the Government remaining unconvinced about the $2.4 billion plan.
Councillors have given the go-ahead to the planning and preparation processing after hearing of serious rail and road congestion ahead.
The councillors have been told the city's rail terminus will reach the maximum number of trains it can handle by early next year.
Auckland Council hopes to use the two-year planning period to persuade the Government that its sums on the economic benefits really do add up.
The Government last week said it was unconvinced by the case for building a tunnel to create a rail loop through the downtown area and wants the council to explore other options.
The council says consultation with local Maori will deal with any issues should the proposed rail tunnel need to be built near a taniwha.
A member of Auckland's Independent Maori Statutory Board has told councillors that the taniwha Horotiu lives near the Town Hall on Queen Street.
The taniwha is a being in Maori mythology that lives in waterways, and the Wai Horotiu was a stream that once drained Queen Street.
Local iwi Ngati Whatua O Orakei chose not to comment on the issue on Wednesday, but a statement from the council said consultation has begun.
The council has not yet determined the route of the proposed downtown rail tunnel.