The studies will now be sent to National Accounts Tribunal (TCU) in preparation for the tendering of the project, which is scheduled for October 18.
The Reais 3.25bn ($US 1.44bn) railway is part of the 11,000km of new lines proposed by the federal government in its Logistics Investment Programme (PIL).
The project will include the construction of 70 major structures, and the line will primarily carry bulk iron-ore, grain, and bauxite traffic, although it may also accommodate other commodities such as petroleum, sugar, corn, ethanol, and soya.
The railway will pass through 11 towns in the states of Maranhão and Pará, with a maximum line speed of 80km/h. The successful bidder must complete construction within four years of signing the contract, and will be responsible for managing and maintaining the infrastructure for a period of 35 years.
Brazil's federal railway engineering and construction company Valec will be responsible for allocating capacity on the new line.