Establishing large foundries, he was a pioneer in casting structural ironwork, most notably for canal aqueducts and early suspension bridges.
[2][3][4] The partnership with Webster was dissolved, and in 1793 he purchased land at Coleham in Shrewsbury, where he set up a larger foundry with steam-powered equipment.
He built a large foundry at Plas Kynaston, Cefn Mawr, where he made the iron deck for the nearby Pontcysyllte Aqueduct, completed in 1805.
[2][3] The Bonar Bridge in Scotland, an innovative design by Telford with a central span of 150 feet (46 m), was built in 1811–12; The ironwork was cast at Plas Kynaston, and Hazledine supervised its erection.
The tensile strength of the wrought iron chains, made at Upton Forge, was important to these suspension bridges.
[5] Hazledine died in 1840 at his home, Newport House, in Dogpole, Shrewsbury, and was buried at St Chad's Church.
There is a memorial, with a bust of Hazledine by James Heffernan whilst working under Francis Leggatt Chantrey, in the church.