Grande Portage Resources Announces Results of Preliminary Economic Assessment (PEA) Study for the New Amalga Gold Project in SE Alaska
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Grande Portage Resources Announces Results of Preliminary Economic
Assessment (PEA) Study for the New Amalga Gold Project in SE Alaska
Vancouver, British Columbia — 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).
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• 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%
1 AISC is a non-GAAP measure. Please see below under the heading “Non-GAAP Financial Measures” below.
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$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
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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 o f
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.
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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 u ndertaken 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.
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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
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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
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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 f erry
terminal project.