And it's all good so far.

Archaeologists and staff from the Ballarat office of A.S James Geotechnical Engineers spent the weekend drilling, digging, sifting and sampling soil from underneath the stadium property on Creswick Road - and the showgrounds next door.

Workers also dug several bore holes to a depth of 12 metres on Saturday.

Wade Fullerton from A.S. James said while the samples needed detailed lab analysis, much of the land between the showgrounds and oval (the space used by visiting circuses) was a relatively undisturbed layer of clay over siltstone - and thankfully, no high water table.

They didn't exactly hit gold - or any old mineshafts - but small amounts of quartz were found in the samples.

The Creswick Road showgrounds have been council property since at least 1934 and before that, the show was held on a site closer to Lake Wendouree.

Maps from 1861 depict paddocks across the area.

Archaeologists representing local indigenous groups were also on hand to check the level and amount of siltstone, which Mr Fullerton said could sometimes yield aboriginal artefacts.

The testing is the first stage to determine what sort of grandstands, parking and more can go on top.

Eureka Stadium will get a $159 million upgrade ahead of the March 2026 Commonwealth Games in country Victoria to prepare the site for athletics and para-athletics.

It includes the addition of 5000 permanent seats to the stadium.

A.S. James was also the company that tested Ballarat's GovHub site in 2019 - revealing thousands of intact goldrush-era bottles and a giant boulder with a core of hundreds of 10 centimetre crystals known as Natrolite.

Staff said the boulder cracked open during removal and was mistaken for naturally-occurring asbestos.

They said they would have liked the crystals to have been put on display at the government offices but were unsure what had happened to the huge rock.

A.S James is also hoping to work on the former saleyards site at Delacombe, which is expected to be used for a Commonwealth Games village.

The State Government estimates the games will create more than 600 full-time equivalent jobs before they start, another 3900 during the games and an extra 3000 after the closing ceremony.

They believe it will inject $3 billion into the Victorian economy.

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