Grande Portage Resources Announces Results of Preliminary Economic Assessment (PEA) Study for the New Amalga Gold Project in SE Alaska

VANCOUVER, BC / ACCESS Newswire / April 15, 2026 / Grande Portage Resources Ltd. (TSXV:GPG)(OTCQB:GPTRF)(FSE:GPB) ("Grande Portage" or the "Company") is pleased to announce positive results from the Preliminary Economic Assessment ("PEA") study of its New Amalga Gold Project ("New Amalga" or the "project"), located approximately 25km north of the city of Juneau in Southeast Alaska, USA.

A National Instrument 43-101 - Standards of Disclosure for Mineral Projects ("NI 43-101") compliant technical report (the "Report") entitled "PRELIMINARY ECONOMIC ASSESSMENT FOR THE NEW AMALGA GOLD PROJECT" with an effective date of February 11, 2026 will be filed on SEDAR+ at www.sedarplus.ca under the Company's profile within 45 days of this news release. All currency amounts are stated in US dollars (US$).

This is the first PEA study that has been conducted for the project. A resource model update was not performed for this study, which utilizes the company's previously-disclosed 2024 resource statement as originally documented in the NI 43-101 report ("TECHNICAL REPORT ON THE HERBERT GOLD PROPERTY") with an effective date of July 17, 2024.

The New Amalga project hosts a near-surface mesothermal gold resource with grade and characteristics enabling the material to be sold without requiring conventional onsite processing or tailings storage facilities. The project site is located near existing transportation infrastructure and the Report outlines a low-footprint, low-initial-capital scenario with a selective underground mine transporting material offsite for processing at third-party facilities. With a robust NPV and IRR, the Company believes the New Amalga Gold Project offers exceptional potential economics as described in the sections below.

ECONOMIC & PRODUCTION HIGHLIGHTS

• The Base Case using a $3,200/oz gold price generates a pre-tax Internal Rate of Return ("IRR") of 69% (after-tax 56%) and a pre-tax net present value ("NPV") at a 5% discount rate of US$979 million (after-tax US$721 million).

• 1.1 year pre-tax payback (1.3 year after-tax) on invested capital at the Base Case gold price.

• Based on price sensitivity analysis at the recent spot gold price of approximately US$5,000/oz, the project returns a pre-tax IRR of 109% (after-tax 91%) and a pre-tax NPV at a 5% discount rate of US$2,128 million (after-tax US$1,557 million) with an after-tax payback period of 0.8 years.

• The PEA production plan incorporates an underground mine with a Base Case production life of 7 years with total production of 1.05 million gold ounces shipped.

• Gold production averages approximately 150,000 ounces shipped per year.

• Average shipped gold grade of 17.6 g/t (after sorting), average mined gold grade of 13.6 g/t (before sorting).

• Pre-Production Capital Cost (CAPEX) of US$254.8M (including US$46.4M contingency).

• Operating Cost (OPEX) of US$272 per production tonne mined including mining, sorting, overland and seaborne transportation, and minesite G&A.

• All-in Sustaining Cost (AISC) of $1,408 per ounce payable, inclusive of operating costs, sustaining capital costs, royalty payments, treatment costs and refining costs.¹

Ian Klassen, President & CEO remarked that "The strong results of the PEA confirm our contention that the project's offsite processing strategy is the optimal development pathway, with high margins, rapid payback, and straightforward engineering combined with a very small environmental footprint. This PEA positions the project well for the future, where detailed design, capital optimization, baseline environmental studies and permitting can advance with confidence."

The following table summarizes the pre-tax and after-tax financial indicators for the New Amalga Gold Project at the base case $3,200/oz gold price.

Table 1: Financial Indicators at $3,200/oz Base Case Gold Price

The following table summarizes the gold price sensitivity of the pre-tax and post-tax economic results.

Table 2: Pre-Tax and Post-Tax Sensitivity to Gold Price

Initial capital expenditures are estimated at US$254.8M as detailed below:

Table 3: Initial (Pre-Production) Capital Expenditures (CAPEX)

The mine operating costs were calculated to average $272.11 per tonne mined as summarized below. Note that some operating costs apply per tonne of production mined, while others apply per tonne shipped, and G&A is an annual fixed cost.

Table 4: Components of Operating Cost (OPEX)

Life-of-Mine sustaining capital totals $269.3M and is summarized in the table below.

Table 5: Sustaining CAPEX

MINERAL RESOURCES

The PEA utilizes the previously-released Mineral Resource Estimate prepared by DRW Geological Consultants Ltd., with an effective date of July 17, 2024. Details of this Mineral Resource Estimate can be found in the PEA Report to be filed on SEDAR+ within 45 days of this release.

Utilizing a base case cut-off of 2.5 gpt, the nine veins on the property host an Indicated Mineral Resource of 4,726,000 tonnes at a grade of 9.47 gpt (1,438,500 ounces of gold and 891,000 ounces of silver at 5.86 gpt) and an Inferred Mineral Resource of 1,813,000 tonnes at a grade of 8.58 gpt (515,700 ounces of gold and 390,600 ounces of silver at 6.70 gpt) using a 181 gpt top cut.

The mineral resource sensitivity to cutoff grade is shown below.

Table 6: Sensitivity Table showing Indicated Mineral Resource by cut-off