The project was still in the construction process and it was important for council to honour "confidential agreements".
"The council is a little bit precious about the legal risk while it remains a live project. There may be elements of it that have some legal protection."
It was also in the ratepayers' interest for the details to remain undisclosed, he said.
"There are legal liability risks that the council wishes to preserve.
"The protection is in the ratepayers interest, they are the ones who are exposed if these protections are exposed," Mr ten Hove said.
The commercial relationship with Beca could mean legal privilege, or preserving negotiation positions before completion.
Once the project had been completed it would be over to the council of the day to determine which details were released to the public, he said.
"At the end of the day, both our annual expenditure and our overall project will be able to be reported, there may be individual components that council may be precious about.
"The aggregate amount will come up, its component amounts have legal privilege to them."
The $30 million budget did not include risk contingencies, but the council was operating well within the overall budget.
Mr ten Hove said 70 per cent of the ponds, which acted as reservoirs, had been completed and were performing well.
"Things are moving along pretty well, we're pretty confident that things are moving along pretty well."
The irrigation flood system would be commissioned over the summer and the decommissioning of the old ponds, which would then be reinstated and grassed over, would take place the following summer of 2014/2015.
Ratepayers were "paying for a better urban footprint," Mr ten Hove said.