Northumbrian Water and Mott MacDonald Bentley are working on the project at Heworth to create a new pumping station in the long stay car park, which will be complete in January.
This will redirect large volumes of surface water away from the sewer network, increasing capacity and reducing the chances of sewage spilling into the Tyne.
Working in conjunction with Gateshead Council, Northumbrian Water has also introduced additional highway drainage and increased the size of sewers in Sunderland Road, as well as constructing a new relief chamber next to the Swan Pub, reducing the risk of flooding.
During the work, it was necessary to reduce the capacity of the car park, but now 90 bays have been re-opened.
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However, while passengers will be able to catch buses from the station on Friday, December 20, and Saturday, December 21, the Metro service will face a shutdown due to a driver strike.
Project manager Paul Davison said: "It's great that we are able to put these parking bays back in use.
“I'd like to thank Gateshead Council, Nexus and car park users for their patience and cooperation while we completed the construction work and we hope the extra capacity we are freeing up, with 90 more bays back in use, will come in handy for that last-minute shopping."