The donation, announced at a roof-shout event last week, was made by the Otago Community Trust and is on top of the $2m it donated in 2023.
The amount raised was now "well over $31m", Waitaki Event Centre Trust chairman Kevin Malcolm said.
The trust put on some food and drinks for the tradies and contractors on site as well as inviting "key benefactors" and supporters of the project, he said.
Naming sponsors Network Waitaki, North Otago Rugby and Parafed were among those in attendance.
Later in the afternoon, anyone who donated was also invited to have a look around, no matter the size of their donation.
"Every dollar we get, we believe is equally important," Mr Malcolm said.
He had loved watching the event centre take shape throughout the build.
"The Apollo crew are doing a great job and all the tradies are doing a great job and you can see it when you come by that things are really rattling along."
The project is "on time, on budget and up to spec", Mr Malcolm said.
He could not be happier with how it was progressing.
"I’m past happy, really.
"What we’ve dreamed about is finally happening.
"When your dreams start to be a reality, that’s pretty cool isn’t it?"
When finished, the event centre will house six timber-sprung courts, a multi-purpose room for cricket that could also accommodate other codes such as archery, as well as conference rooms and office space.
Construction is due for completion in February, 2026.
