OBJECTORS to mining exploration in Bacchus Marsh are worried that native grasses will be destroyed if exploration continues.

Concerns for the Parwan grasslands were raised at Mantle Mining's open day on Saturday when almost 100 people were invited to observe the drilling process and its desired achievements.

Access routes to the site were changed at the last minute when V/Line requested that Albys Lane, which runs adjacent to the paddock that Mantle is drilling on, not be used by the public due to safety and environment concerns.

"We couldn't have up to 200 cars accessing the site there. There's endangered grass, and we had safety concerns with cars being close to the railway with trains going up to 160km/h," a V/Line spokesman said.

Moorabool Environment Group spokeswoman Deb Porter said she saw a truck driving over the grasslands, possibly depositing weed seeds which had the potential to proliferate.

Mantle Mining's exploration manager, Callum Lamont, confirmed a Mantle vehicle had driven over the grass patch. "One [truck] did mistakenly come in through the incorrect entry. We've lodged a work plan through Department of Primary Industries which specifies that as our access route. The driller is aware of the location of the grasslands."

Parwan Landcare spokesman Simon Jolly said he had doubts that rare species of grasslands could be successfully revegetated once ripped up.

"It's proven very difficult in the past to revegetate endangered grass ... I am trying to on my property, but it's extremely difficult. They have complex eco-systems, right down to soil crusts, which have a whole community of fungi and bacteria right up to the different grasses themselves, and there are hundreds of species involved."

Dr Jolly said the ramifications of losing the grasslands were huge, with much of Victoria's native species already lost.

"The biggest danger is the strip mining itself as it's horizontal mining. Square kilometres of grass will be lost."

Dr Jolly said although the area affected by exploration was small, any damage to the grass was significant.

Mr Lamont said the concern was premature.

"We don't know if there's a resource that's even developable, so if we did mine, all stakeholders, including grasslands experts, would be consulted and involved in the process on whether we could do it. All the agencies, DSE, Landcare groups, every stakeholder would have an input."