Mike Morris, historic environment project manager, said the site lies in the northern part of a former Roman fortress which includes barrack blocks and accommodation.

BBC: Remains of two Roman roads found in Chester

Project manager Tony Bathmaker said the old bridge had been in place since 1921 in "a pretty hostile environment".

BBC: Shoreham swing bridge nearing completion

Dawn Harrington, project manager, said the work will allow sewers to hold more storm water and would help protect the environment.

BBC: Lancaster ?18m sewer upgrade meeting held