The new owner of the Ekati diamond mine in N.W.T. is applying to do work it says would extend the life of the mine by 10 to 20 years.
Dominion Diamond Corporation filed the application with the Wek'eezhii Land and Water Board on Wednesday.
It wants to mine two kimberlite pipes it has been exploring 25 kilometres from its main Lac de Gras camp.
Dominion says one of them, the Jay pipe, is the largest known diamond deposit in North America.
Without the expansion, Ekati is scheduled to wind down operations in 2019.
The application to mine the Jay and Cardinal pipes comes about a month after Dominion applied to mine the much smaller Lynx kimberlite pipe.
Dominion bought BHP Billiton's 80 per cent share of the Ekati mine six months ago.