2300 Wickdrains
900 Stone Columns

The Upper Pond Dam Remediation project was completed for Vale – formerly Inco – Nickel Mines in Sudbury, Ontario. The project consisted of the installation of a stone columns with wick drains at intermediate points between the stone columns. The solution was designed to increase the soil strength behind the South Dam, so that a large buttress can be installed.

In consideration of the poor existing ground conditions encountered at site, it was required to
carry out ground improvement in order to allow for the installation of the toe berm to increase the
factor of safety of the dam and prevent potential failures.
The wick drains were installed prior to the stone columns to aid in the dispersion of the excess
pore pressures and air introduced to the soil during installation of the stone columns. The stone columns were then advanced between the wick drains.

The soils to be improved consisted of fine, machine-produced silt tailings. Prior to the start of works, the working area surface soils were excavated between two and three feet, filled with crushed stone and roller compacted to support the heavy soil improvement equipment. The depth of improvement was about 4 to 8 m across the area.

Based on Vale’s design, the approximately 35,000 square meter platform was improved using a
wick drain mast mounted to a specially modified excavator and bottom feed vibro densification rig mounted to a modified 110 ton crane.

The vibro and wick drain program was completed on schedule, with all tests achieving the
intended results. Geopac delivered a value engineering solution.