The existing canal basin and wharves were rapidly becoming inadequate, even in the 1820s, with the increasing size and numbers of the ships seeking to collect cargoes at Cardiff. Ships greater than 300 tons were unable to berth and had to be loaded from lighters. Shipowners addressed a petition to the Marquis of Bute in 1825 calling for the improvement of navigation and by 1828 the Marquis had employed David Stuart as engineer-in-charge of preliminary work on the construction of a dock along the east bank of the Taff Estuary and a Parliamentary Bill was obtained in 1830 for the construction of the Bute West Dock, which was opened on 9 October 1839. The occasion was declared a general holiday and the Mayor and Corporation of Cardiff attended in full ceremonial. The first ship to enter the dock was the Manulus. After the opening of the Dock the shipping of coal from Cardiff increased dramatically and by 1850 had reached over 730,000 tons, with more than half going abroad. It was this huge increase in the transport of coal that was to lead to the rise of the Cardiff tramp steamer trade and the establishment of the many Cardiff shipowning companies which appeared over the ensuing 50 -60 years, as well as the establishment of Cardiff offices of many other ship owners.
The opening of the Bute West Dock, of course, rapidly relegated the old Quay to a backwater.