Critical Crane Lift (GPR)
An industrial complex in the middle of Alberta’s industrial heartland was expanding. In order to accommodate this expansion, a 65 tonne crane lift was planned to remove a vessel from an existing unit, and replace it with a newer technology. The critical lift was planned for the following shutdown, a few months ahead of time. It had been years since the concrete pad had been installed. Because of the weight and positioning of the lift it was imperative that key information be known regarding the underground stability prior to trusting the concrete pad to handle the weight. A ground failure could cause a serious accident which could result in major injuries or deaths along with millions of dollars in damage and hundreds or thousands of hours of unplanned downtime.
The plant site called Maverick, who suggested the use of GPR to examine the area ahead of time. Specifically, attention would be paid to signatures in the data related to the existence of subsurface saturations, voids or other subsurface movements. Enough data was gathered in a half-day to provide the safety-critical information required by the client. The data was then re-interpreted on a Maverick Inspection Ltd. workstation, using a combination of our experience and sophisticated computerized interpretation methods. A report was generated within one or two business days. The complete results of the inspection were therefore provided to the client’s qualified engineering staff months prior to the critical lift, allowing for ample time to alter lift-plans or correct deficiencies.
During the inspection, Maverick noted some significantly unusual radar signal returns. The unusual returns centered on an open-topped storm sewer catch-basin. The data from the area immediately surrounding the catch-basin showed significant indications of voiding. The area surrounding the likely voiding showed significant water saturation signatures, and the abnormal signal was several meters across. It appeared that some water leakage had caused a significant washout void in this area in the years since the concrete pad and the sewer catch basin had been installed, and in exactly the spot planned for one of the crane outriggers. Had the crane lift proceeded on the assumption that there were no subsurface hazards, then a serious accident would likely have ensued. However, because the client contacted Maverick Inspection Ltd. prior to the lift they were able to provide the appropriate professionals with enough information to determine there was a hazard and engineer a safe solution. After multiple truckloads of fill material, the crane was set up for a safe and successful lift.