A further void under the current centre has also been identified and investigated.
A council spokesman said:
The multi-million pound investment project at Ripon Leisure Centre shows our commitment to providing modern, fit-for-purpose leisure facilities for the people of Ripon.
Given the well-known ground conditions in Ripon, we employed qualified and experienced geologists and geo-technic engineers to carry out necessary investigation works and advice on what would be required to provide this much need facility.
A total of 441 grouting sites received 3,043 tonnes of grout which, along with the casting of a reinforced concrete slab, provides the foundation for the new swimming pool building.
The void which is underneath the existing leisure centre is understood to have been present a number of years. This was only discovered as a result of the work to prepare the new swimming pool site.
It is now being investigated and should any remedial work be required then it will be carried out.
We are committed to providing this much needed facility that will encourage a healthier and more active lifestyle for our residents and something they can be proud of.