 In March 1944 the Commonwealth government requisitioned part of the quarry reserve above tanks 3-5 to establish an observation and communications post for the protection of the fuel storage tanks below.After the war the Commonwealth removed the structures associated with the observation post on Mt Islay, but decided to retain the fuel storage tanks for their intended purpose.In the late 1940s and early 1950s the Commonwealth formalised its occupation of the land, gaining title to Lot 346 (tanks 1-2), Lot 348 (fire station and foam tank) and Lot 349 (tanks 3-5) and taking up an easement over the pipeline (Lot 95A) as far south as Little Street.