The McMillan Drilling crew used their Geoprobe® 8140LS Rotary Sonic on an environmental project recovering core samples to circa 25-30 mbgl through coarse-grained alluvial deposits (mainly gravels and cobbles). On completion, the boreholes were equipped with 50 NB uPVC monitoring wells for ongoing water sampling and level logging.
The success of their first Geoprobe® 8140LS Rotary Sonic rig and associated tooling led McMillan Drilling to the purchase of a Geoprobe 8140LC just 12 months later. McMillan Drilling, located in New Zealand, had investigated sonic technology for almost ten years before purchasing their 8140LS.
The Geoprobe® 8140LS sonic rig was one of the first proprietary sonic rigs in New Zealand.
According to Iain Haycock, Group Manager for McMillan, the rigs have proven to be very successful over the past 5-6 years. “The success includes us completing a wide range of applications spanning both the geotechnical and environmental markets,” Iain said.
High Sample Recovery Success
“One of the strengths of these rigs is the ability to achieve very high sample recovery in cohesionless, inundated, interbedded sand/gravel/cobble formations where traditional drilling methods struggle,” he explained. “The unique capability of running clear, PVC sample liners as an option, and using a dual tube approach in lieu of ‘bottom out’ or ‘over casing’ techniques, are some of the key points of difference between Geoprobe® and more conventional sonic systems. The dual tube system makes sonic drilling a viable investigation tool for geotechnical investigations where in-situ testing is required.”
McMillan Drilling’s sonic rigs are mainly utilized in the predominantly coarse-grained alluvial soils.However, Iain said they have completed many other projects in a range of soil and rock formations including highly-fractured Greywacke, Basalt and extremely variable volcanic deposits to very soft sensitive organic silts and clays.
The company’s rigs have also found themselves in various environments, both on land and off shore. Iain said the relatively compact footprint of the rigs and the “platform kinematics are such that there are not many sites that cannot be reached by tracking, crane assistance, and even occasionally floating on a barge. The only feature that is missing is a set of wings for the rig to fly!”
McMillan Drilling’s sonic rigs have found projects in various environments, both on land and off shore.
Best Choice for McMillan
The McMillan Drilling team is certain that selecting a Geoprobe® sonic rig was the best choice. Iain recalled numerous discussions with Tom Omli and Greg Johnson trying to understand the capacity and reliability of the sonic oscillator as one of the main areas of concern as a potential customer. “While any sales pitch is probably a bit subjective, based on our experience using the rigs continuously, the capacity and reliability was understated and over delivered. I think this bears good testimony to the integrity of the design, manufacture and the team at Geoprobe®,” he concluded.