Hawksley was also a Gas Engineer and was responsible for building Basford, Eastcroft and Radford Gasworks, as well as numerous other Gasworks in various cities around the country. He was to achieve national fame in 1944, whilst attending a public inquiry into the state of public health in towns. Facing fierce opposition from some of his fellow engineers, Hawksley forcibly argued for social reform, and for the provision of his innovation of a clean constant supply of fresh water to be made available to everyone. He then went on to take his own town’s council and the slum landlords of Nottingham through a Parliamentary enclosure bill; this then allowed common land to be used to replace the squalid back to back slums with much more appropriate housing. Nottingham was the first of more than 30 British towns and several places abroad including Bombay, to benefit from Hawksleys genius.
Hawksley was examined by the Royal Commissioners (1844-1845) for inquiring into the state of large towns and populous districts. He explained how his system of a constant supply of water could be adapted for hosing the streets, for fire-plugs and fire engines, and for public baths and wash-houses. He also advised on the use of sewage as a form of liquid manure and the cultivation of market gardens. He advised the commissioners too on the provision of gas, and on the general organisation of public services. Hawksley clearly grasped the enormity of Nottingham's social problems, which was illustrated by his attitude to enclosure and mortality. Indeed, Hawksley was the first civil engineer to grasp the enormous problems of urban living, in an ever increasing industrial society and in turn, he applied his talent almost exclusively to them.
In 1852, Hawksley left Nottingham for London, setting up his own engineering practice in Westminster, later taking his son Charles into the practice in 1866. He was the first President of the Institution of Gas Engineers and Managers, a position which he held for three years, and he was also President of the Institution of Civil Engineers in 1871, a post which in 1901, his son Charles was also to hold. Between 1869 and 1879 Hawksley acted as a consultant on the construction of Lindley Wood, Swinsty and Fewston Reservoirs on behalf of Leeds Waterworks Company. In 1876 and again in 1877-78 he is credited with the first two uses of pressure grouting in order to control water leakage under an embankment dam. This procedure of rock grouting is now a standard practice in dam construction; it was an invention of great importance.