While the excavation was suspended for a day during the heaviest of the rain, other work was able to continue and no time had been lost, a Council spokesperson said.
"The project is highly weather sensitive at this early stage while the excavations are taking place," said director infrastructure Jon Kingsford. "Once the excavations have been completed and drainage metal placed, the weather risks are reduced significantly."
The council is confident the bulk of the excavation will be completed in the first two-and-a-half weeks.
The entire oval is being excavated to a depth of 450mm (almost half-a-metre) and being used to fill lower-level areas of the coastal reserve alongside State Highway 2 between Napier and Awatoto.
It will be replaced by 150mm of drainage gravel, 260mm of specialist-grade sand from South Wairarapa, and the 40mm turf being grown near Pukekohe, which will arrive in rolls — "like ready lawn" — to be laid in July.
A city council spokesperson said about 10,500 cubic metres is being trucked "off-site", with about 1800 "truck movements" are scheduled, through the Morris St entrance nearest Latham St.
Residents had been informed of the scale of the project, and road management warnings are in place around the entrance to the park, and at the fill site south off SH2.
One season ticket holder said he had been told Taupo's Owen Delany Park — named after a former Hawke's Bay union president who was also Mayor of Taupo — is a preferred option if Napier's venue is still unsuitable for use in early September, but Mr Campbell said that with the number of weeks allocated for the job and the time after completion he doesn't think needing a standby venue "is going to enter the equation."
The company heading the project has worked on major turf construction projects such as the Melbourne Cricket Ground and Wellington's Westpac Stadium.
Mr Campbell said the union will receive regular updates, and the experts are confident the project will be completed in time.
"They've done a lot of this stuff before," he said. "So you've got to go with what they say."