The Portland Canal Tunnels occurrence is located along the south side of Glacier Creek, 6.5 kilometres northeast of Stewart. A 1.10 kilometre long tunnel was extended eastward into the Portland Canal Fissure Zone, between 1912 and 1914, in an attempt to discover veins at depth within the zone. The crosscut tunnel was started at an elevation of 97 metres above sea level.

The tunnel intersected nine veins in argillite (slate) of the Middle Jurassic Salmon River Formation (Hazelton Group). The Portland Canal Fissure Zone is a zone of faulting and shearing which trends north, dips steeply west and hosts a vein system that extends southward for 6.5 kilometres from the Victoria/Dandy occurrence (104A 067) on the north, through the Dunwell mine across Glacier Creek to the Ben Bolt occurrence (103P 080).

Four of the nine breccia veins discovered in the tunnel are of significance, from west to east these are: Lucky Boy, Melba, Richard and Mosquito (Green) veins. The veins are spaced between 76 and 210 metres apart and strike approximately north and dip west. The Lucky Boy vein strikes at 007 degrees and dips 45 degrees west. The veins vary from 12 (Melba) to 30 metres (Lucky Boy) in width. The veins have been traced along strike for up to 160 metres (Lucky Boy and Melba) and are commonly associated with dikes.

Mineralization consists of pyrite, galena, and minor sphalerite and chalcopyrite and occurs as disseminations, massive stringers and bands up to 0.6 metre wide in a gangue of quartz and minor calcite. A 0.25 metre chip sample across a massive stringer in the Mosquito vein assayed 3.8 grams per tonne gold and 200 grams per tonne silver (Minister of Mines Annual Report 1914, page 160), and locally, up to 2 per cent copper (Minister of Mines Annual Report 1914, page 155). Significant lead and zinc values were also reported.

During 2005 through 2010, Auramex completed programs of prospecting, geological mapping, geochemical sampling and airborne geophysical surveys on the area as the Bear River-Surprise Creek property. During 2017 through 2020, Singer Resources Inc. and American Creek Resources Ltd. completed programs of geochemical sampling, a 13.5 line-kilometre induced polarization survey and a 438.5 line-kilometres airborne magnetic and LiDAR survey on the area as the Dunwell property.