Because exports from Porthmadog exceeded imports many ships arrived at the port in ballast. In 1862 when the “Rotten Tare” (where South Snowdon Wharf is today), the original dumping ground for ballast, was levelled at 18 feet above low water, a new site had to be found and a sandy site east of the Glaslyn was utilised. An island gradually developed here. In 1868 a wharf was built where the ballast was unloaded. Three brothers, Joseph, John and Evan Lewis, ship’s carpenters and block makers, built the wharf and maintained it. On some old maps it is called Lewis Island.
A small mobile crane transferred the ballast to small trucks which were manhandled along the track to the end of the island. A house was built for the crane operator and his family. According to the book “Immortal Sails” this was the Roberts family. Stones from many parts of the world can be found on Ballast Island.