A loan of US$195M has been proposed for the project, which is foreseen as a 156MW facility in the Vu Gai-Thu Bon river basin in Quang Nam province, near the border with Loa PDR. The loan amount sought was previously given as US$196.5M.

The project is also to hear on the proposal for a US$2M grant that would be used for livelihood improvements for ethnic minority communities that would be affected by the scheme, which is to have a reservoir of 15.8km2.

The Song Bung 4 project is to have a 110m high RCC dam of 367m crest length. A 3.1km headrace tunnel is to be built to feed the power house before the waters are discharged by tailrace canal to the river, about 5km downstream of the RCC dam. The plant is to be operated as a peak load facility, which could see fluctuations in water level of up to 1.5m near the station.

The total project budget is estimated from feasibility studies at US$254M, an increase on the estimate at the pre-feasibility stage of about US$220M. Following studies commencing in 2005, the scheme is to built by 2011.

The loan proposals for the Song Bung 2 and Song Bung 5 projects, to be built on the same river, are not due for decision by ADB until 2009 and 2010, respectively.