Hydro-Québec wanted to complete the transmission line in time, which was only possible with an overhead crossing of Saint Lawrence River.
However, due to the negative visual impact of the large towers of the overhead crossing on the local populations of Grondines and Lotbinière, it was decided to build a cable tunnel under the river, although this made the project more expensive.
[1] Building these towers required five months construction time and approximately 40 specially trained workers.
[2] In spring 1989 work on the 3,954 metres (12,972 ft) long cable tunnel started, which took six months of drilling in two 12-hour shifts.
[citation needed] In 1992 the overhead line over the Saint Lawrence River, including the artificial islands and the jetties were dismantled.