Plans for a tunnel were developed in Andorra during the late 1950s. In 1963, the Envalira Tunnel design tender was awarded to French engineers Semet and Phillip Studies, and subsequent negotiations were conducted for years and the access roads were improved. On June 1, 1999, Spanish companies FCC and NECSO (today ACCIONA) began construction work on the Grau Roig side of the massif; and on August 2, 1999, work began on the Pas de la Casa side.