Navy to fill in 'engineering feat'

By CLAIRE TREVETT

The Navy is to fill in tunnels in Devonport dating back to World War II to placate the subsidence fears of some residents.

Project manager Andrew McDonald said about half the length of the 155m-long tunnels, where they extended under private property and Calliope Rd, would be backfilled.

The rest would be used to store fuel in newly built tanks.

The 9m-diameter, 1/2m-thick concrete tunnels were about 15m beneath the ground, he said.

They had not been used since 1993, when the Navy emptied and cleaned them in case fuel leached through the unlined concrete into the ground.

Mr McDonald said inspections showed there had been surprisingly little leakage and there was no risk of subsidence.

North Shore City deputy mayor Dianne Hale said residents approached the Navy in the mid-1990s about concerns the tunnels might affect their property values.

They asked the Navy to fill the tunnels in so they could never collapse.

"It's certainly what they wanted," she said.

"I would hope they are happy, because I imagine it would cost a lot of money to pour concrete down there. It's a huge area they're filling in and it will take them a few concrete sacks to do it, that's for sure."

However, at least one affected landowner, Valerie Grant, says the community is divided on the issue.

Mrs Grant and her husband, architect Kelvin Grant, consider the tunnels an "engineering feat".

"They seem to be of historic importance, a useful asset in times of trouble and the idea of filling them in is ridiculous," Mrs Grant said.

Mr Grant's business, on Summer St and Calliope Rd corner, has a tunnel underneath.

"We've always known about the tunnels and not minded a bit,"Mrs Grant said.

"Filling them in will be hugely expensive and disruptive. It will take months and months and truckloads and truckloads of concrete and that seems bizarre."

Navy museum administrator Brian Burford said the building of the tunnels began in 1943 as part of an upgrade of the Navy base during World War II.

When the war reached the Pacific, Devonport was used for repairs, overhauls and maintenance of Allied ships. Fuel, a potential target for bomb hits, was stored underground for protection.

The tunnels held furnace oil fuel until the 1980s, when ships converted to diesel-power.

Mr McDonald said the tunnels would be filled with about 15,000cu m of a sand and cement slurry which had to be the same strength as the surrounding earth.

The slurry would be pumped in from bore holes drilled in Calliope Rd or through other tunnels leading to the fuel tunnels.

Mr McDonald said there was no risk the process of filling the tunnels would destabilise the ground or cause any problems to buildings above them.

The Navy's future fuel storage and pumping needs would be met by a new facility, which included fuel tanks placed inside the remaining sections of the old tunnels.

Pipelines would take the fuel out to pumps on the wharves.

The new fuel facility would hold about 9 per cent of the 24,000 tonnes the tunnels held.

The project would go out to tender in the next two months.

Construction was expected to take 13 weeks.