Mulvany qualified through practical experience as an engineer. He learned technical drawing with an architect and joined the Irish Survey Office at the age of 20 years as a surveyor. In 1836 he became an employee of the Board of Public Works in Ireland. Mulvany was successively responsible for planning of waterways and the modernization of the fishing industry, but especially for the purpose of drainage of large areas of agricultural exploitation. During the Great Irish Famine 1845 - 1849 the projects of the Board of Works were simultaneously job creation schemes for the suffering rural population and in 1853, the work was stopped due to high costs, and Mulvany quit the civil service.