Leaked correspondence obtained by the ABC shows 11 fuel tanks built to support US military activities in the Indo-Pacific have been unlawfully constructed on Darwin Harbour.

Despite having an initial completion date of September 2023, the tanks are still not operational due to "water intrusion" in their leak detection system.

ABC has obtained correspondence from February 20, 2024 that shows the tanks were constructed without a building permit — a legal requirement under the Northern Territory Building Act.

The tanks' owner-occupier, US-based company Crowley, says it's working with the Northern Territory government to complete the project in compliance with the law.

Crowley said Project Caymus was issued a development permit in November 2021 "to allow the land to be developed for the project". The development permit, which has also been obtained by the ABC, explicitly notes that it "is not an approval to undertake building work".