The transaction includes the transfer of the assets, liabilities including employee entitlements, employees and contracts comprising the Open Cut Mining East business to BUMA.
Downer Open Cut East has two contracts with BHP Mitsubishi Alliance at Goonyella Riverside and Blackwater, one with Stanwell Corporations' Meandu mine, and one with Intergen's Commodore mine in Queensland.
A Downer spokesman said existing mine personnel would continue to manage the operations once the acquisition was complete.
The Open Cut East fleet includes hydraulic excavators and shovels from the 100-to 800-tonne class; off-highway dump trucks from 90t to 300t class; ancillary support equipment, including dozers from D9 to D11, graders from 14G to 24M, water carts from 17 kilolitre to 130Kl; and drills capable of 102mm to 311mm holes.
BUMA is the second largest independent coal mining contractor in Indonesia.
It was established as a family business and bought by Delta Dunia in 2009.
It holds about 20% market share by providing coal mining services to some of the largest and longest-running names in the Indonesian coal industry.
On its website, BUMA states it carries out a comprehensive scope of work from overburden removal, coal mining, coal hauling as well as reclamation and land rehabilitation.
"BUMA's operations is supported by close to 12,000 employees and a solid and experienced management team as well as equipped with advanced technologies and more than 2500 units of heavy equipment in various quality brands such as Komatsu, Caterpillar, Hitachi, Volvo, Scania and Mercedes," it states.
"BUMA has two representative offices located in Balikpapan, South Kalimantan and Tanjung Redeb, East Kalimantan."
Downer will receive about $150 million in cash from the transaction, subject to completion adjustments.
BUMA has paid Downer a deposit of $16 million with the remainder of the purchase price payable at completion.
Downer CEO Grant Fenn said the sale of Open Cut Mining East was the final step in Downer's divestment of its mining portfolio of businesses.
Together with the previously announced mining and laundries transactions, total proceeds from Downer's mining divestment program amount to $778 million.
"An important part of our Urban Services strategy was the exit from our capital-intensive mining businesses," Fenn said.
"The sale of Open Cut Mining East is the last step of this process and follows the divestments of Open Cut Mining West, Downer Blasting Services, Underground mining, Otraco, the Snowden consulting business and our share in the RTL Mining and Earthworks joint venture."
Completion of the transaction, which is subject to customary conditions, is expected to occur before the end of 2021.
