In 1991, the portuguese government created a new office for managing the construction of the planned new crossing of the Tagus River at Lisbon called GATTEL. The office identified three potential corridors for the new road bridge: eastern (Sacavém-Montijo), central (Chelas-Barreiro) and western (Algés-Trafaria).
The non-governmental organization Grupo de Estudos de Ordenamento de Território e Ambiente-GEOTA sent an open letter to the Prime-Minister calling for more detailed information about this project, and defending the option of the central corridor as the most suitable. The Ministries of Planning, Environment, Industry, Employment, Defence and Justice, members of the GATTEL, the municipalities of Almada, Barreiro, Seixal and Moita, environmental NGOs and experts on transport, territory and environmental management, all supported GEOTA's choice.
However, on April 25th the option for the eastern corridor (Sacavém-Montijo) was adopted as the definitive one. In October the bridge location, the associated tender and the concession rules were published by approved Decree. The winning bidder was the Lusoponte consortium. The government applied the new crossing to the Community Cohesion Fund, which then implied an Environmental Impact Assessment (EIA). In June, the final EIA report was delivered to GATTEL , which concluded that some of the consequences of this project would be speculative processes, acculturation and identity loss of the Tagus river south bank. The route of the new bridge was located in a classified area, a Special Protection Area-SPA for birds. The EIA nonetheless characterized in the project as viable.
The EIA public consultation period was open in July. The NGOs GEOTA, Liga para a protecção da Natureza-LPN, Quercus and the Dom Dinis Institute-IDD pointed out several study flaws and questioned the final conclusion of the project's viability. There were public hearings. The European Commission opened an investigation into the application of cohesion funds in the new bridge construction, adding to the World Wide Fund For Nature report, which denounced irregularities in compliance with the EIA. GEOTA filed a complaint against the Portuguese government for breaches of European directives regarding species and habitats conservation. In December, LPN, Quercus and IDD, presented a similar complaint to the European Commissioner for the Environment. The complaints were filed and the Community funding approved.
In January 1995, LPN resent a formal complaint requesting action by the European Commission. In February, the government proposed the creation of a Construction Monitoring Committee-CMC with the participation of environmental organizations, which did not accept this invitation. In March, the Supreme Administrative Court dismissed an application by the LPN for annulment of the executive decision to build the new bridge between Sacavém and Montijo. In the same month, the final contract of the bridge construction was signed, and the name of the bridge was announced as the Vasco da Gama Bridge.
Environmental harms were denounced and one infraction proceeding was initiated to Lusoponte. In July, the Portuguese government and the European Commission signed a memorandum of understanding: Portugal has pledged to strengthen environmental control measures and Brussels to release a quota of the funding.
They required enlargement of the Special Protected Area (SPA) to more 400 hectares and the strengthening of CMC powers, of which the organizations began to participate, becoming responsible for the coordination of all involved entities in the inspection process. On March 29, 1998, the bridge Vasco da Gama was inaugurated. In April, representatives of the central and local government and local NGOs formed an Observatory of Spatial Planning and Environment.