Macmahon Holdings' (ASX:MAH) wholly-owned unit, Macmahon Underground, executed an agreement with CTP JV, the manager of the Central Tanami project joint venture, to develop an exploration decline at the Groundrush gold deposit in the Northern Territory, according to a Tuesday Australian bourse filing.

The agreement is valued at around AU$38 million for a scope of work that includes portal and vent establishment.

MGX Resources (ASX:MGX) and Tanami Gold (ASX:TAM) each hold a 50% stake in the joint venture.

The underground decline will initially extend for 3.5 kilometers to a depth of 350 meters, providing underground drilling platforms to facilitate around 33,000 meters of infill drilling.