A truck containing thousands of litres of sewage is still sitting on the seabed off Sydney’s northern beaches some three weeks after a barge carrying the vehicle capsized.

NSW’s Roads and Maritime Services says salvage operation is unusually complex and efforts had been hampered by adverse weather.

“It’s a significant sized barge, it capsized with a sullage tank on board that was holding approximately 10,000 litres of sullage, and to complicate things even more, it capsized in a protected seagrass bed just off Mackerel Beach,” spokesman Daniel Duemmer told AAP on Wednesday.

Mr Duemmer said violent winds, rain, and choppy waves forced salvagers to sink the barge just hours after it was first raised on Friday afternoon.

It was then brought to the surface a second time after the weekend when the wild weather had passed. It’s now floating at the site.

“It was quite ironic that – at the end of the day – we spent all this time and energy trying to lift and salvage the barge only to have to sink it again to secure it over the weekend,” he said.

The sewage truck remains underwater but Mr Duemmer hopes it will be lifted from the seabed on Thursday and placed on a separate barge.


Crews will then work to bring both the original barge and the truck back to land.

No sewage escaped from the truck but the barge spilled diesel and hydraulic oil, most of which, has been contained and cleaned up, the RMS said.