MINE RECLAMATION

PROJECT HIGHLIGHT

LEGACY COPPER MINE RECLAMATION
CHELAN, WASHINGTON

  • In-water construction of an island during winter month
  • Site access, bridge, USFS road improvements
  • Quarry and borrow source development and operation
  • Diversion and reconstruction of Railroad Creek
  • Reconstruction/lining of Copper Creek
  • Mill and ancillary structure demolition
  • Tailings regrading and capping
  • Slurry cutoff wall construction
  • Installation of more than 4 miles of seep and groundwater collection trenches and piping

 

This project involved the remediation of a former copper mine on the upper reaches of Lake Chelan. Located deep in the Cascade Mountains, all access to the site is via barge and U.S. Forest Service roads.

 

Construction included the development of quarry and borrow areas, road and infrastructure upgrades, demolition of mine structures, regrading and capping of mine tailings, rerouting and reconstruction of Railroad Creek (a stream adjacent to the tailings), and the relining and reconstruction of Copper Creek (a stream that transects the tailings before its confluence with Railroad Creek). Work also included installation of a slurry cutoff wall; seep and groundwater collection trenches and piping systems to capture and redirect mine drainage and seepage to an on-site wastewater treatment plant; jet grout stabilization of tailings slimes; and final grading and capping of the tailings.

 

The primary goal of the project was to mitigate mine impacts and restore the watershed and riparian habitat above Lake Chelan. The former mining village is a seasonal retreat owned and operated by the Lutheran Church, and has also functioned as a crew camp during each of six construction seasons from 2011 to 2016, providing lodging for up to 21 days per rotation.

 

Great Lakes Environmental & Infrastructure (Great Lakes E&I) performed early actions and preliminary site preparation activities in 2011 in order to improve contractor access to the site, develop borrow sources and other facilities for future work, and construct a project bypass road around Holden Village. This work was designed to accommodate full scale mine reclamation activities and included access road pioneering and USFS road improvements, bridge improvement and replacement, timber removal from select work areas, and SWPPP controls and ecological protection. Access road construction was performed to provide heavy equipment access to key features of work including the slurry wall work pad adjacent to Railroad Creek and the new streambed for the Railroad Creek realignment. USFS 8301 road improvements included widening, safety berm construction, and construction of turnouts along a 10 mile section between the Lucerne Barge Dock and Holden Village to accommodate mobilization and demobilization of heavy equipment and quarry/borrow area crushing and screening equipment to and from the project site.

 

After the 2011 construction season, Great Lakes E&I was awarded two subsequent seasons of work, including the construction of a temporary bypass and relocation of nearly a mile of Railroad Creek in 2012 to 2013. Additional scope elements included construction of a new stream channel and restoration of riparian habitat that would stimulate recovery of the fishery; preliminary shaping and lining of the Copper Creek stream channel; quarry development and operations; borrow area development and operations; slurry wall work pad construction; and demolition of the former mill and ancillary structures.

Remedial work from 2014 to 2016 included the installation of a 3,000 lf cement-bentonite slurry cutoff wall to depths of 90 ft between Railroad Creek and the tailings piles; installation of an HDPE groundwater collection trench inside the wall alignment; jet grout stabilization of slimes in the tailings piles; regrading and capping of two waste rock piles and three tailings piles; final reconstruction of Copper Creek; and the construction of an extensive network of collection trenches and piping required to intercept and redirect seeps and groundwater.