 Of the 25 million tons of fill needed to construct the islands, 10-12% was coming from the Montreal Metro's excavations, a public works project that was already under construction before Expo was awarded to Montreal.The remainder of the fill came from quarries on Montreal and the South Shore, however even with that it was insufficient and so bodies of water on both islands were added (lakes and canals) to reduce the amount of fill required.Expo's initial construction period mainly centered on enlarging Saint Helen's Island, creating the artificial island of Île Notre-Dame and lengthening and enlarging the Mackay Pier which became the Cité du Havre.