Holden Mine Remediation Project

Project Name: Holden Mine Remediation Project

Project Location: Chelan, WA

Owner: Rio Tinto

GC: Magnus Pacific

Engineer: MWH

Project Start and End Date: 2012 – 2015

CHALLENGE:

Mine clean-up is part of the ongoing Legacy Program at Holden Mine. The site was remotely located in the Cascade Mountain Range; all personnel and materials had to come up Lake Chelan by boat.

SOLUTION:

Griffin was responsible for management of multiple phases of this project from field data gathering to system installations and removals. 200+ deep wells were installed with air rotary over a 3-year period.

· 2012-wellpoint pump test in Railroad Creek Realignment area.

· 2013-installation of 66 deepwells, from 30 to 50 ft. deep, to dry area for 900+ LF of engineered creek bed realignment construction to depths of 12 to 15 ft. below original ground surface.

· 2014-Installation of 20 wells for collection pipe installation under diverted creek bed with multiple pump tests along collection pipe alignment.

· 2015-installation of 133 deepwells, 40 ft. in depth, along 1.25 miles of collection pipe trench extending to 20 ft. in depth.

GRIFFIN DIFFERENCE:

Careful planning was required to minimize the amount of material that had to be brought up lake but to prepare for most eventualities.