The upgrade work at Rawenstall in the Rossendale Valley, began in January this year and was carried out in five separate phases, requiring temporary road closures and traffic management.
UU admitted that “on occasions the work did generate a barrage of complaints about traffic delays”.
UU project coordinator Brian Jenkins said: “We completely understand carrying out engineering work on this scale has impacted the community and business owners getting on with their daily routine.
“We also realise people may not be able to see the real tangible benefits, but we do hope everyone appreciates the reason why the work has taken place.”
He apologised for the delays caused by the work and added: “We even resorted to tunnelling under sections of roads, rather than open digging, which helped minimise disruption on site.”
During their time on site, UU used its partnership with regeneration charity Groundwork set up a Rossendale Community Fund, to look at opportunities to offer a helping hand.
Throughout the duration of the sewer work 35 local groups applied for grants or services of up to £750.