In order to allow boats to dock without running aground at low tide and to remain afloat, the "Float" was constructed: the Tawe was diverted and a new dock with locks created. Work began in 1852, and the result was New Dock in 1859. Further changes to the docks were proposed, and the town authorities realised the potential grave effect on public health, particular in the riverside St Thomas area. Drinking water came from springs locally but clean water sources were increasingly rare. Cholera broke out in 1832; and again in 1849.