The Section 404 permit, governed by the Clean Water Act, is to be issued shortly by the US Army Corp of Engineers (USACE). Development of the road will unlock the economic potential of the region by improving access.

Trilogy is a partner in Ambler Metals together with South32, which will develop the Arctic copper deposit.

"I would like to express my sincere appreciation to the BLM and the USACE for overseeing and managing the long approval process for the Ambler Access Road. The formal permitting of the AMDIAP is a significant event for the Company and for all Alaskans," said Trilogy president and CEO Tony Giardini.

"We welcome the Record of Decision, a key milestone to further progress the Ambler Metals project. We look forward to continuing our partnership with Trilogy to unlock the value of the project's high-quality base and precious metals resources, working together to advance it through the current study phase," said South32 CEO Graham Kerr.

The Ambler road will transect the Rambler District, giving Trilogy access to its Upper Kobuk mineral projects (UKMP) including the Arctic and Bornite deposits.

The road will be built by AIDEA (the Alaska Industrial Development Export Authority) and it is expected to stimulate other mining and exploration activity in the region. AIDEA previously developed the road and port facility for the Red Dog base metals mine.

In June, AIDEA approved a memorandum of understanding (MOU) with Ambler Metals specifying how the parties will jointly establish a plan regarding the permitting, feasibility, engineering and design, construction and operation, financing and closure of the Ambler road. Ambler Metals committed to contribute up to US$35 million to match AIDEA's contribution of $35 million for this.

AIDEA authorised spending up to $500,000 from funds in the Arctic Infrastructure Development Fund for 2020 predevelopment work on the Ambler road. These funds will be matched by Ambler Metals.

The issuance of the Section 404 permit will establish a programme to regulate the discharge of dredged or fill material into waters of the US, including wetlands. This is the key federal permit required for the development of the Ambler road.

Trilogy expects to complete a feasibility study for Arctic in the third quarter, which Giardini expects will figure a higher initial capital expenditure than the $780 million outlined in the 2018 pre-feasibility study.

The February 2018 pre-feasibility study outlined a 10,000 tonnes per day operation to produce more than 159 million pounds of copper, 199Mlb zinc, 33Mlb lead, 30,600 ounces gold and 3.3Moz silver in three different concentrates over a 12-year mine life.

Arctic hosts an indicated resource of 36Mt grading 3.1% copper, 0.7% lead, 4.2% zinc, 0.6 grams per tonne gold and 47.6g/t silver for 2.4Blb copper, 581Mlb lead, 3.4Blb zinc, 728,000oz gold and 55Moz silver. Bornite is estimated to contain an inferred cobalt resource of 182.4Mt grading 0.019% for 77Mlb and an inferred copper resource of 141.9Mt grading 1.74% for 5.5Blb.

Shares in Trilogy Metals jumped 17% on the news to C$3.05, valuing the company at $430 million.