"It is not an easy process to get everything in place in the short space of time that we've got it in place."
He said Napier City Council should be commended "for pulling out all sorts of stops" to get it to a stage where they could get funding for the project from the Lotteries fund and get started.
"Although we are off the start line thanks to the $13.5m commitment by three vital funding partners, we need more money to complete the project."
Funding has come from the Government via the Infrastructure Reference Group Covid Response and Recovery Fund which contributed $6.4m, $4.1m from Napier City Council and $3m from the New Zealand Lotteries Significant Project Fund.
Waterhouse said the trust will launch a region-wide community fundraising campaign for the $5m shortfall.
The new facility is much needed as the sports it will serve are growing, community demand has increased "significantly" and there have been large national sport events it has missed out on hosting, Waterhouse said.
Hawke's Bay Under 15 Basketball Representatives team captain and Hastings Boys' High School Year 10 student Ezra Eagle said PGA has provided the facilities to help him develop as an athlete.
But due to the growing number of young people playing basketball and the lack of court space, sometimes he gets home from games after 9.30pm and some year levels can only play mini ball every second term due to this and with the centennial hall out of action.
When the new courts are built, more than three games can be played at once and they will be able to get home earlier, he said.
"When construction is complete, more young basketballers can participate and we can see the sport flourish here in Hawke's Bay."
Waterhouse said the extra capacity of the new facility will mean national events can be held at the arena.
"This will have not only a substantial impact on the health of our community, but also be an economic driver with additional sporting events held in Hawke's Bay."
Napier City councillor Keith Price says the need for additional indoor space, due to the growth of indoor sport, has been a long time coming.
"Basketball has a phenomenal growth and is in dire need of more court space so this growth can continue, as are the likes of futsal, netball and volleyball."
The 5900sq m facility behind PGA is set to be completed in July 2022.