The criticism, levelled by concerned residents and supported by well-known horticulturist John Hawker, turns on month-long roadworks undertaken at Learmonth Street, west of Warrenheip Street at the town's centre.

Along that strip, standing sentinel, are five Avenue of Honour trees, comprising mature silver poplars, oaks and elms, including a heritage-listed Exeter Elm.

The statuesque, heritage-protected Chinese Elm, which previously stood at the entrance to the Avenue of Honour, was destroyed in the recent truck accident at the roundabout.

Compounding that loss, members of the Friends of Buninyong Botanical Gardens were alarmed to discover trenching works carried out within one to two metres around the remaining trees, resulting in what they perceive to be considerable damage to the trees' roots.

"Their roots have been significantly disturbed and severed," said president and chair Roger Permezel, adding that the resulting damage inevitably "posed an existential threat" to the long-term viability of the trees.

It was a sentiment shared by member Richard Patterson, who was particularly concerned at council's apparent failure to preserve the protection ordinarily afforded by the heritage overlay and listing.

"This is a rare, heritage tree," he said, pointing to the Exeter Elm. "Look at how close and deep those trenches are around it - it's root pruning, and it's not necessary; a tree cannot live without its roots."

The road upgrade was undertaken with a view to creating more car parks and green space, as well as a new vehicle exit onto the Midland Highway.

Mr Hawker, a long-term member of the National Trust significant tree committee, whose four-decade long career spans work with both Heritage Victoria and the Melbourne Botanical Gardens, said the roadworks appeared to fall foul of the National Standard for the protection of trees on development sites.

The national standard - which, incidentally, is endorsed by the Australian Council of National Trusts and the Australian Local Government Association, among many others - expressly advises against construction works which encroach on the tree's protection zone by more than 10 per cent, the tree protection zone being the calculated area above and below ground level at a given distance from the trunk to protect the tree.

"For trees to survive, they need an extensive root system," Mr Hawker said. "If you have a trunk diameter of one metre, you've got a tree protection zone of 12 metres radius - so you're looking at a large area to ensure the tree remains alive and viable in the construction zone."

"While you can do work within 10 per cent of that tree protection zone, you wouldn't be doing open trenching or excavating."

"This is not some new, ground-breaking approach," he added. "It's been accepted practice for nearly 20 years."

Under the national standard, the closest any council sanctioned trenching works could have taken place, without compromising the health of the trees, was at least 10 metres away from each tree. The works carried out were conversely in the order of one to two metres away; in some instances, less.

Mr Hawker, who visited the site last week, said he also saw no evidence of any tree protection fencing or other restrictions around the trees - something the national standard strongly recommends.

"Clearly, the intention of having a heritage overlay with tree controls was to protect those avenue trees, and I don't have a lot of confidence the trees will escape any [adverse] impact," he said.

"The damage is extensive and it threatens the viability, health and safety of the trees."

The national standard, likewise, warns that "damage to the root system is a common cause of tree decline and death and is the most common form of damage associated with development sites".

City of Ballarat chief executive Evan King, however, rejected Mr Hawker's assessment.

"We obtained arboriculture and heritage advice as part of the design development," he said. "The tree roots have not been damaged in these works."

"Our excavation works uncovered a large dead root, and the recent truck accident unearthed some other tree roots which weren't damaged."

Though Mr King confirmed council had undertaken tree assessments, it wasn't clear to what extent that expert advice guided the construction works, still less whether a tree management plan was in place.

Council's assurances have also proved cold comfort for the Buninyong community, which is still reeling from the death of the Chinese Elm.

The difference here, however, they say, is that the probable demise of these trees was, on any view, not only avoidable, but served little purpose.

"Here we are standing in a place where they're adding some car spaces that doesn't even require a car park," Mr Patterson said. "We might end up with a nicer road, but at what price?"

"Digging this close to some magnificent trees raises serious questions about the way City of Ballarat is treating its trees - especially its heritage trees."

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