Guernsey Water says work on the 33 year old facility included replacing pipework, building a new underground chamber and putting in a new control panel to the landward side.
The work saw a contraflow in place along the eastern seafront opposite the Forester's pub for a nearly two months.
This enabled staff to work in safety on the underground facility which is invisible to passers by.
Carl Falla is in charge of major projects like this for Guernsey Water:
“This station is a small but vital part of the island’s critical infrastructure and this investment means we can ensure wastewater is safely returned to sea for decades.
We worked closely with other utilities and Traffic and Highways to minimise disruption and align with their works, and I want to thank everyone for their patience while the work was carried out."
Work to improve visibility for cyclists and walkers crossing the busy main road was carried out at the same time. This includes new drain hole covers around the pumping station, which fit properly and do not bang every time they are cycled over.
Guernsey Water's attention will now turn to upgrades to the sewer network and to its treatment works at St Saviour's and the facility at Moulin Huet.
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