Workers on the once-in-a-century Ballarat Sewer Build project are determined to minimise disruption to businesses and keep traffic moving as tunnelling begins.
The project will double Ballarat's sewer capacity, but will mean installing massive pipes beneath the CBD along Peel Street.
Eventually, the new sewer system will connect Mount Clear in the south to Brown Hill in the north-east, but for now, engineers are focused on getting through the complex CBD part.
Microtunnelling along Peel Street - underneath Little Bridge Street, Curtis Street, and later Mair Street - avoids having to close off the entire street for an open excavation, and should save time as well, according to Central Highlands Water project manager Mick Dwyer.
"We'll do a bore underneath Little Bridge Street and Curtis Street, then install a pipe behind the bore," he explained.
"There's no effect on the east-west traffic, and the bus parks in Little Bridge Street remain as per usual, and it allows the north-bound lane of Peel Street to stay open.
"Once the two pipes are installed on the microtunnels, we'll open-excavate between Little Bridge and Curtis streets so we can once again maintain that traffic flow north-bound but not affect the east-west traffic."
The microtunnelling work is expected to be completed in the next week or so, before the open-excavation work begins.
Mr Dwyer expects between 10 to 30 metres of pipe will then be installed each day, as the worksite moves up and down Peel Street.
The next section, after the Bridge Mall, will be north from Curtis Street past Mair Street, before returning to complete the southern section from Little Bridge Street to Eastwood Street, turning onto Anderson Street.
All businesses will remain open, with pedestrian access and car parking remaining as well, Mr Dwyer said.
"We've been grateful to the traders, we've had some constructive conversations with traders in the area who've come up with some good initiatives on ways we can structure the works to keep minimising the impact," he said.
"It's a good sign that the car parks are full too - the workers are all going to the cafes in this area, we're making sure we're spending some money in the area too.
"Tradies' morning tea is always pretty impressive, but at the Healthy Hub, they're eating a lot healthier than they'd normally eat."
The work has also involved using ground penetrating radar to explore the systems beneath the city, some of which was unmarked on modern maps.
"We've done a lot of preliminary work in locating underground services - being in a CBD area, there are a lot of underground service infrastructures," Mr Dwyer said.
"Everything we've then found, we need to physically find, so we use what we call non-destructive digging with a pressured water and vacuums.
"We found some we weren't aware of as well."
The 6km Ballarat Sewer Build, to be completed in stages, is expected to be finished in the next three to five years.
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