There were a large number of Nowell civil engineers. The information on the Macclesfield Canal link which you may have read is a start, but I should warn you there is a mistake in the ancestry they quote. There is a book about civil engineers in the UK in Google Books which has an entry about the Nowells, but several pages are missing. I found a hard copy of the book and copied these pages which I have somewhere and I can scan them and send them to you if you would like.
The way I traced my Dewsbury stone-mason Nowells (and I am now confident their name was a coincidence; they were not closely related to their namesakes) was to follow the births of their children, through Macclesfield, Widnes, Liverpool, Chorley, and in 1841 Todmorden.