Grande Portage Resources Ltd. press release

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

2026-04-15

TSXV - TSX Venture Exchange · Gold · Silver · Canada · Technical Studies

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

Pre-Tax NPV5

$979

M USD

Pre-Tax IRR

69%

After-Tax NPV5

$721

M USD

After-Tax IRR

56%

Avg NSR per Tonne Mined (net of royalty)

$1,042

US$ / metric tonne mined

Operating Cost per Production Tonne Mined

$272

US$ / metric tonne mined

Operating Cost per Gold Ounce Shipped

$630

US$ / ounce shipped

LOM All-in Sustaining Cost (AISC)1

$1,408

US$ / ounce payable

Pre-Production CAPEX per Ounce Payable

$285

US$ / ounce payable

Initial Capital Payback Period (after-tax)

1.3

years

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

Pre-Tax

After-Tax

Au Price ($/oz)

NPV5 ($M)

IRR

NPV5 ($M)

IRR

$1,600

-$42

-1%

-$63

-5%

$1,800

$86

15%

$42

10%

$2,000

$213

26%

$143

20%

$2,200

$341

35%

$241

28%

$2,400

$468

43%

$339

35%

$2,600

$596

50%

$435

41%

$2,800

$724

57%

$532

46%

$3,000

$851

63%

$627

52%

(Base Case) $3,200

$979

69%

$721

56%

$3,400

$1,107

74%

$815

61%

$3,600

$1,234

79%

$909

65%

$3,800

$1,362

84%

$1,002

70%

$4,000

$1,489

88%

$1,095

73%

$4,200

$1,617

93%

$1,188

77%

$4,400

$1,745

97%

$1,280

81%

$4,600

$1,872

101%

$1,373

84%

$4,800

$2,000

105%

$1,465

88%

(Recent Spot Price Case) $5,000

$2,128

109%

$1,557

91%

$5,200

$2,255

112%

$1,650

94%

$5,400

$2,383

116%

$1,742

97%

$5,600

$2,510

119%

$1,835

100%

$5,800

$2,638

123%

$1,927

103%

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

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

Pre-Production CAPEX

Cost $M USD

Eng. & Env. Studies, Definition Drilling, Permitting, Owner's Construction Mgmt. Team

$16.9

Mine Access Road

$9.4

Mine Site Surface Facilities

$73.6

Surface Haulage Equipment & Ore Containers

$9.9

UG Pre-Production Capital Development

$22.0

UG Equipment (Mobile & Fixed)

$47.0

Ore Loading Dock

$12.3

Indirect Costs (10%)

$17.4

Contingency applied to Equipment Purchases (15%)

$8.5

Contingency applied to Construction, UG Dev't, & all other pre-production activities (25%)

$37.9

Total Pre-Production CAPEX

$254.8

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)

Mining & Backfilling OPEX

$114.70

US$ / metric tonne of mined production

Crushing & Ore Sorting OPEX

$7.00

US$ / metric tonne of mined production

Surface Road Haulage to Barge Dock OPEX

$11.16

US$ / metric tonne of shipped production

Barging to Deepwater Port, Storage, and Transloading

$39.67

US$ / metric tonne of shipped production

Bulk Freighter Vessel Transport to Overseas Processor

$95.00

US$ / metric tonne of shipped production

Overhead G&A (staff, environmental, insurance, etc)

$13.7

US $ annually (millions) - fixed cost

LOM Overall Average Operating Cost

$272.11

US$ / metric tonne of mined production

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

Table 5: Sustaining CAPEX

Sustaining CAPEX

Cost $M USD

Sustaining UG Development & Definition Drilling

$172.4

Sustaining Mine Equipment & Rebuilds

$26.9

Indirect Costs (10%)

$19.9

Contingency applied to Equipment Purchases/Rebuilds (15%)

$7.0

Contingency applied to UG Dev't and Drilling (25%)

$43.1

Total Sustaining CAPEX

$269.3

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

Cut-off (g/t)

Tonnes

Grade Au (g/t)

Grade Ag (g/t)

Ounces Au

Ounces Ag

3.0

3,931,000

10.83

6.60

1,368,400

834,600

2.5

4,726,000

9.47

5.86

1,438,500

891,000

2.0

5,654,000

8.28

5.21

1,505,500

946,900

Table 7: Sensitivity Table showing Inferred Mineral Resource by cut-off

Cut-off (g/t)

Tonnes

Grade Au (g/t)

Grade Ag (g/t)

Ounces Au

Ounces Ag

3.0

1,562,000

9.82

7.34

493,300

368,400

2.5

1,813,000

8.58

6.70

515,700

390,600

2.0

2,383,000

7.26

5.59

556,400

428,300

A top cut of 181 gpt gold is applied to all zones

Mineral Resources are not Mineral Reserves and do not have demonstrated economic viability.

Conforms to NI 43-101, Companion Policy 43-101CP, and the CIM Definition Standards for Mineral Resources and Mineral Reserves. Inferred Resources have been estimated from geological evidence and limited sampling and must be treated with a lower level of confidence than Measured and Indicated Resources.

All numbers are rounded. Overall numbers may not be exact due to rounding.

MINE PLAN

The mine plan is conceived as an underground operation with a production rate of 1,150 tpd utilizing a gold cutoff grade of 7.0 g/t. This cutoff criteria is driven by the minimum shipment grade required for offtake payability and is not a conventional marginal-cost-breakeven cutoff. The primary mining method will be longitudinal longhole open stoping supplemented by a much smaller amount of cut-and-fill mining reserved for zones of lower rock mass quality.

The mine will be accessed via a 900m decline initiated from a surface portal. No shaft sinking is necessary. Ventilation and secondary escapeway will be achieved via raisebore to surface. Haulage ramps will be progressively developed to access all mining areas within the various resource veins. Mine development is assumed to be undertaken by a contractor and will incorporate cover drilling and pressure grouting on advance to control potential water inflows. None of the underground workings lie beneath the Herbert Glacier.

As there will be no tailings onsite, stope backfill will consist of cemented rockfill (CRF) batched on surface using development waste rock. Production haul trucks will bring CRF underground on the back-haul.

Mined production output consists of 2,438 kt at a grade of 13.6 g/t (before sorting) over a seven-year production life.

The image below shows a 3-D view of the underground mine when all development and production activities are complete.

Figure 1: 3-D View of Underground Mine Plan

The image below shows a side view of the mining layout with overlying terrain.

Figure 2: Side View of Underground Mine Plan Looking North, Showing Overlying Surface Terrain

INFRASTRUCTURE & LOGISTICS

The project site will be accessed via a new 5.2km access road connecting to Glacier Highway, a paved public highway connecting to the city of Juneau. No personnel housing camp facilities are planned, rather the workforce will be transported by crew bus from Juneau for each shift as the site will be only an approximately 35-minute drive from the Juneau suburbs. The city of Juneau serves as a regional mining hub currently supporting two major underground mines, with a skilled local mining workforce and equipment maintenance facilities.

Figure 3: Project Location Relative to Juneau, Cascade Point and Glacier Highway

The mine site will include surface infrastructure typical of most underground mines such as an administrative office, vehicle maintenance shop, fueling facilities, backfill batch plant, and water treatment plant. Power will be generated onsite using diesel generators, with the potential to tie in to grid power pending the planned future development of a new third-party hydroelectric facility in the region.

Figure 4: Conceptual Surface Infrastructure Layout Utilized for the PEA. Layout may change pending further environmental baseline studies, engineering, environmental review and permitting processes.

Production rock will be crushed to a 100mm topsize and subjected to a sensor-based ore sorting process wherein each particle of rock will be scanned while passing under a sensor array on a conveyor belt. Particles identified as non-mineralized (dilution) will be removed to a reject bin via a puff a compressed air, while the remaining particles will be loaded into a sealed ore container for transport. See the company's April 8, 2025 news release for additional information regarding sensor-based ore sorting of New Amalga material.

Figure 5: Steinert Sensor-Based Ore Sorting Machine

Fig. 6: Removal of Dilution Inside Steinert Ore-Sorting Machine

The ore sorter reject rock along with waste rock from underground development will be staged in the Temporary Backfill Materials Stockpile. This lined stockpile will be progressively drawn down during the mine life to feed the batch plant for making CRF backfill. The stockpile will be completely returned underground before closure.

Fig. 7: "Rotainer" type Ore Container

Ore containers will be loaded onto flat-deck trailers and trucked approximately 32km north via Glacier Highway to a barge dock facility. Conventional single trailers will be utilized (not double/tandem units). While mining operations continue 24/7, haulage operations will be paused on weekends and holidays during warm weather months since most of the private vehicle traffic on this segment of highway is for recreational access to campgrounds, beaches and other wilderness sites.

Once at full production there will be approximately 36 truck cycles per 12-hour shift. This is roughly one truck leaving the site every 20 minutes on average, however trucks may travel in convoys at less-frequent intervals to increase traffic efficiency on the single-lane site access road as well as to reduce perceived frequency of traffic noise.

The barge dock will be built at Cascade Point, a private parcel owned by Goldbelt Inc., an Alaska Native Corporation. See the Company's September 10, 2024 news release for additional information regarding the Company's relationship with Goldbelt and the Cascade Point site. This site is also the location for a planned Alaska Marine Highway System (AMHS) ferry terminal being developed by the Alaska Department of Transportation. While limited amounts of infrastructure (such as the Cascade Point access road) could be shared, the barge dock will be a separate part of the site and is not dependent or contingent upon construction of the ferry terminal; this study assumes that no further development of the site is undertaken as part of the ferry terminal project.

At the barge dock, containers will be unloaded into a small staging yard and then loaded onto barges for transport to deepwater port facilities in British Columbia, where the containers would be emptied and the material loaded onto trans-oceanic bulk vessels for overseas processing. Empty containers would be returned to the minesite on the back-haul for reuse.

Over the life-of-mine plan the shipments of sorted material total 1,859 kt at a grade of 17.6 g/t Au, containing approximately 1,053 koz Au.

OFFTAKE

The Company has received indicative offtake terms for the New Amalga production from a major global metals concentrate trading firm. See the Company's October 20, 2025 news release for additional information. The sorted material will ultimately be sold to a variety of potential overseas processors, primarily base metals smelters. The PEA utilized the indicative term sheet which incorporated variable gold payability based on shipment grade (average approximately 85% over the mine life), treatment charges of $95/tonne, a refining charge of $10/oz Au payable, and a minimum shipment gold grade of 7.0g/t for payability. Silver is present at low grades in the sorted material and is not payable.

PERMITTING, ENVIRONMENTAL PROTECTION & SOCIAL LICENSE

The PEA Report envisions a small-footprint underground mining operation which would transport material offsite for processing by a third party, eliminating the need for an onsite gold recovery plant or tailings storage facility.

In addition to reducing up-front capital cost, this setup provides numerous environmental benefits compared to a conventional onsite-processing configuration:

Eliminates the need to build a gold recovery plant, minimizing developed footprint, power and water requirements.

No use of chemical reagents for gold processing at the site.

Eliminates the need to develop a tailings disposal facility at the site, as no tailings would be generated.

Removes the need for permanent waste rock storage facilities. All waste rock generated from mine development would be returned to the underground workings as backfill, avoiding permanent significant change to the local surface topography.

Dramatically reduces land usage and overall environmental footprint.

Greatly facilitates post-mining closure and reclamation.

In addition to environmental stewardship, the New Amalga Gold Project is also committed to being a good neighbor to the Juneau community by minimizing impacts to the surrounding area while providing extensive economic benefits to the region. Specific examples include:

Strategic siting of surface infrastructure to minimize visual and noise impacts to the Herbert Glacier hiking trail

Pausing haulage operations to the barge dock on weekends and holidays during warm weather months to minimize truck traffic for recreational visitors to the area

Road transport and barge transport in fully-enclosed ore containers instead of as loose/bulk material. This serves to mitigate against airborne dust during product movement and transloading.

Utilizing crew buses for workforce transportation to minimize commuter traffic from Juneau

Creation of an estimated 277 mining-wage direct jobs (not accounting for indirect or induced employment) which will be prioritized for Juneau-area residents aligned with the plan for a non-camp-based commuter workforce

Payment of local property tax, Alaska Corporate Income Tax, and Alaska Mining License Tax which will help support the local community and the broader region.

The Project will be subject to NEPA environmental review with the US Forest Service and will also require a variety of federal, state, and local permits. The Company has been engaging with the relevant agencies at both the state and federal levels to establish alignment and prepare for the upcoming regulatory processes.

TECHNICAL REPORT AND QUALIFIED PERSONS

The Report entitled "PRELIMINARY ECONOMIC ASSESSMENT FOR THE NEW AMALGA GOLD PROJECT" with an effective date of February 11, 2026 and which will be prepared by the following Qualified Persons (as defined under NI 43-101), all of whom are independent of the Company, will be filed by the Company within 45 days of this news release on www.sedarplus.com:

Mr. Jack DiMarchi, CPG, PG (Core Geoscience LLC) - Environmental Studies, Permitting, and Social or Community Impact

Dan Mackie, P.Geo. (SRK Consulting Canada Inc.) - Hydrogeological Factors

Kyle Mehalek, PE (OreLogic LLC) - Property Description and Location, Accessiblity, Climate, Local Resources, Infrastructure and Physiography, Mineral Processing and Metallurgical Testing, Mining Methods, Recovery Methods, Project Infrastructure, Market Studies and Contracts, Economic Analysis

Bruce Murphy, P.Eng. (SRK Consulting Canada Inc.) - Geotechnical Factors

Sterling Watson, P.Eng. (RESPEC Inc.) - Capital and Operating Costs

Dr. Dave Webb, Ph.D., P.Eng., P.Geo., (DRW Geological Consultants Ltd.) - History, Geological Setting and Mineralization, Deposit Types, Exploration, Drilling, Sample Preparation, Analysis and Security, Data Verification, Mineral Resource Estimate

The PEA Report is preliminary in nature; it includes inferred Mineral Resources that are considered too speculative geologically to have the economic considerations applied to them that would enable them to be categorized as Mineral Reserves, and there is no certainty that the PEA will be realized. There is no Mineral Reserve at the New Amalga Gold Project at this time, and therefore no material which would meet the definition of "ore" under NI 43-101. Mineral resources that are not mineral reserves do not have demonstrated economic viability. The word "ore" is therefore used in this news release only in the context of referring to specific equipment, processes or installations, such as "Ore Sorting", "Ore Container", etc.