Toronto-based Bunker Hill Mining is advancing the restart of its Bunker Hill silver-lead-zinc mine in Idaho.

"We are moving forward at a rapid pace and remain on course to restart the Bunker Mill mine by the end of 2023," chief executive Sam Ash said.

The mine has been on care and maintenance since 1983. It previously operated between 1887 and 1981.

Bunker Hill is driving a decline from the 5 level, the highest accessible level of the mine, to the 6 level. The company has installed ventilation fans, and an underground haul truck is at work.

Connection to Level 6 will be completed in the September quarter, which will provide rubber tire access from the main operational base to the highest four levels of the mine.

The decline also opens up access to mineralised material, which may allow Bunker Hill to sign toll milling or ore purchase agreements prior to the commissioning of its Pend Oreille mill.

Bunker Hill is currently in negotiations to acquire the mill.

In 2023, Bunker Hill plans to drive an additional decline from the 8 level to the 9 level to connect the five highest levels with the Kellogg Tunnel, which leads to the yard and processing plant.

Bunker Hill has also installed a pilot water treatment plant, which is now operational. The pilot plant uses a Lamella clarifier to separate clean water from metals and other solids.

These two streams will be combined and mixed, and will then be treated at the central treatment plant.

The testing programme will last throughout the spring.

The plant can be operated remotely, Bunker Hill said.

Bunker Hill will publish a prefeasibility study by the end of the June quarter.

The mine has a projected net present value of US$143 million, with a 35% investor rate of return and a 2.6-year payback, according to an updated preliminary economic assessment released November 2021.