The PEA put initial capex at US$42 million for a 10-year mine producing more than 550 million pounds of zinc, 290Mlb of lead and 7 million ounces of silver, at all-in sustaining costs of 65c per payable pound of zinc, net of by-products.
It forecast annual free cash flow of $20 million, an after-tax NPV5 of $100.1 million, IRR of 46.2% and 2.5-year payback, using prices of $1.15/lb zinc, 90c/lb lead and $20/oz silver.
"Our PEA confirms that by maximising the use of existing resources, partnerships and infrastructure, the Bunker Hill mine has the potential to be restarted rapidly as a low-cost, long life, sustainable operation," CEO Sam Ash said.
He said the anticipated cash flow could self-fund ongoing silver exploration for further upside.
The company said the mine would achieve carbon neutrality in the first year of operations and would deposit all waste and tailings underground to maintain a minimal environmental footprint.
The mine had operated for almost 100 years until 1981, when it was closed due to low metal prices, an extended labour strike and capital shortfalls required to meet new environmental standards.
Bunker Hill was holding discussions with the Environmental Protection Agency to reschedule outstanding payments regarding water treatment cost recovery, it said in its MD&A filed in March.
The payments, if all were made, would total $20 million, according to Bunker Hill's purchase agreement.
The company had renegotiated the amended option agreement to purchase the mine from Placer Mining in November, reducing the amount payable by August 2022 to US$3.4 million and $2 million in shares.
Bunker Hill raised about C$8 million in February at 40c per unit.
The funds were to progress the rapid restart programme, for exploration and general corporate and working capital purposes, including a US$2 million payment in line with the renegotiated purchase agreement.
Bunker Hill shares (CSE: BNKR) closed up 7.8% yesterday to C34.5c, at the lower end of a one-year range, valuing it about $54 million (US$43 million).
