Grande Portage Resources Initiates Full Scale Geochemical Characterization Program and Backfill Testwork for the New Amalga Gold Project

About this update from Grande Portage Resources Ltd.

VANCOUVER, BC / ACCESS Newswire / April 29, 2026 / Grande Portage Resources Ltd. (TSXV:GPG)(OTCQB:GPTRF)(FSE:GPB) ("Grande Portage" or the "Company") is pleased to announce that it has initiated a formal, comprehensive Geochemical Characterization Program to advance permitting for the New Amalga Gold property in Southeast Alaska, with samples shipped on April 24. Geochemical characterization is a standard environmental study for metals mining projects. This testwork determines whether any of the different types of rock to be produced by the project have the potential to be reactive (acid-generating leading to metals release) over the long term. Previous limited testwork on a small number of New Amalga wallrock samples conducted in 2020-2021 showed favourable results, demonstrating significant net-acid-neutralizing ratios with all samples tested (Table 1). The current program will test a far larger number of samples which are representative of the different rock types in the areas planned to be extracted under the Preliminary Economic Assessment (PEA) mine plan (with an effective date of February 11, 2026). Labwork will be performed by SGS North America with program design and technical oversight provided by Stantec Consulting Services Inc. In the PEA mine plan all development rock and ore sorter rejects produced by the mine are to be returned underground, primarily in the form of cemented rock fill (CRF) backfill, with no waste rock left on surface stockpiles after closure. Accordingly, the testing program will also include the first-ever creation of CRF utilizing New Amalga material. Crushed rock samples will be mixed with cement and cast into cylinders, which will undergo both geochemical testing as well as uniaxial compressive strength (UCS) crush testing. This will assess the strength of the backfill and help determine the cement content required to provide the necessary structural support for mining. Ian Klassen, President and CEO comments: "The initiation of the geochemical program is a significant milestone in the progression of our environmental studies. The results of this program will be key inputs for the Federal NEPA environmental review process as well as State of Alaska mining permits. The backfill testing will also provide critical data to inform future engineering and costing studies. We are pleased that the project continues to gather mom...

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