The third landing, which involved 2ACS, 3ACS, 6ACS, 8ACS and a detachment of 14ACS was the Oboe 2 landing at Balikpapan, used by the Japanese as one of its main sources of aviation fuel. The landing was made east of Klandasan, where the main coastal road allowed access to the two airfields, Mangarr and Seppingang, respectively a distance of 20 and 10 kilometres east, of the landing beach. Although the 2/14th Battalion secured Seppingang on 2nd July, 2ACS and 6ACS did not land at Klandasan until 5th July. However, a bulldozer and two operators had landed from LST 466 on the previous day to undertake work on the beach and to push a track across an anti tank ditch near Seppingang Creek. For the veterans of Tarakan the landing went smoothly. LST 910 was unloaded during the morning and LST 466 beached closer to Seppingang next day. Construction commenced on the airfield on 7th July, with the main task being the backfilling of bomb craters. Work was on the usual ACS three shift 24 hour basis, and the airstrip was ready to accept a Catalina, Beaufighter and 11 Spitfires on 15th July The day before, work commenced on surveying the airfield at Mangarr and 5ACS assumed the task of building a 2,134 metre heavy bomber strip there on 9th August.
The last construction squadron to arrive at Balikpapan was 3ACS, which landed from LSTs 466, 470, 476, and 911 on 19th July. In addition to the bitumen sealing of Seppingang, the construction units were tasked with the maintenance of the Vasey Highway and the construction of facilities for other units, such as 23 Air Stores Park, the clearing of sites for radar stations and, after the war, the development of cricket pitches and other sporting facilities.