Various Sites – Mine Closures
Client: State of Colorado Division on Minerals & Geology
Location: Colorado, United States
Oliver Twist Project – 1999 – closure of approximately 30 inactive mine portals and shafts. Elevations to 12,000’ on flanks of Mosquito Pass. With the exception of the American shaft, the mines in the closure project were closed using standard grouted rock bulkheads, concrete panels, backfill, and corrugated metal pipe and grate door closures.
The project included the underground shaft collar stabilization and polyurethane foam grouting of the American shaft at the London Mine near Alma, Colorado. The purpose was to affect both a safety closure and retard groundwater ingress and provide shaft collar stabilization and closure.
Working at over 11,000’ elevation under a historic headframe structure that could not be disturbed, the MES Mining crew hung from ropes to stabilize or remove rotten shaft cribbing, stripped ladders and landings, installed a bottom form and steel dowels into the shaft ribs, installed a 40-foot thick vertical shaft plug to seal off water ingress at the colluvium/bedrock contact.
Sunshine Project- 1998 – closure of approximately 45 inactive mine portals and shafts. Closures included backfills, bulkheads, installation of precast concrete panels, and installation of bar grating over shafts and adits. Elevations were at 8,500’.
One unique closure was for a large tunnel that had a roof fall impounding water just by the portal. MES designed and constructed a closure utilizing both horizontally and vertically emplaced precast panels, with door access. Three vertical panels were placed onto a horizontally laid panel and dowelled into the sculpted bedrock tunnel brow using grouted rebar dowels. The structure provided lockable access with a pump platform for the local fire department to store and draw emergency water from the mine. MES used subcontractor McCollum’s Excavating to perform a portion of the work scope on this project.
Soda Creek Project – 1997 – closure of approximately 60 inactive mine portals and shafts. Installed remote mountain area mine closures involving concrete panels, welded grates, & grouted rock bulkheads. Elevations were at approximately 8,500’.