The University Reservoir at Smithfield has been brought back online after several months of repairs.
The 20-megalitre reservoir was drained late last year due to a significant water leak that was undermining its footings and structural integrity.
Ground penetrating radar also revealed numerous cavities beneath the structure, which had placed extra stress on the reservoir and caused it to tilt and bulge.
As part of an extensive repair program, more than 100 holes were drilled through the reservoir's slab to allow concrete grout to be pressure injected into the subterranean cavities.
This resulted in stabilisation of the foundations, raised the footing to re-level the structure, and allowed Council to address a 13mm bulge of the reservoir's wall.
A specialised coating was also applied to the internal walls to address leakages, before a low-level filling, along with water quality, taste and odour testing was undertaken.
The reservoir has now been filled to 60% capacity and reconnected to the Cairns water supply.
Council is undertaking a staged filling of the reservoir, increasing the volume week-by-week and actively monitoring to ensure the successful full return to service of the storage.
