Hard Rock Exploration License | Proposed Amendment for Sentinel Metals (dba Great Plains Mining LLC) – Columbia Gold – LICENSE NO. 00816 | Comment Period Closes April 6, 2026.

The Montana Department of Environmental Quality (DEQ) is seeking public comment on a draft Environmental Assessment (EA) for a proposed exploration project near Lincoln, Montana in Lewis and Clark County. Sentinel Metals, doing business as Great Plains Mining, LLC., has filed an application with DEQ for an Amendment to an Exploration License under the Metal Mine Reclamation Act. The Exploration License Amendment would authorize collection of subsurface geological information through core drilling to characterize mineralization at the Columbia Gold Project area, building on prior exploration conducted in 2016. 

Location: Lewis and Clark County (46.948465°, -112.511792°) 

 

Associated Materials:  

Draft Environmental Assessment 

 
Comment Period Closes: April 6, 2026 @ 11:59 p.m. 
 
Submit Comments To: deqmepa@mt.gov 
 

Field Services and Technology Section  
Mining Bureau  
Montana Department of Environmental Quality  
2401 Colonial Drive  
Helena, MT 59601 

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Tags: MEPA, Public Comment and Hard Rock