A Comparative Analysis Between the Tender Estimate and the Actual Completion Cost of High Voltage Fluid Filled Cable Decommissioning

This research investigates the relationship between a tender-stage cost estimate and the actual cost incurred to complete decommissioning of aging high voltage power cables connected to the transmission network. Such work is essential to preserve health and safety (H&S) of on-going power generation activities. The research adopts a mixed postpositivist and interpretivist epistemological lens to analyse longitudinal cost data accrued via a case study of an underground cable decommissioning project. Quantitative cost data and qualitative feedback from project stakeholders was analysed using summary statistical analysis and content analysis. The data from the comparative analysis then informed the basis of an interview with industry professionals and practitioners with a view to identifying the key drivers of change between tender estimate and actual cost. The interview content was analysed and key themes were extracted. Findings from the case study suggest that the niche nature of fluid-filled cable decommissioning, combined with the diminishing number of experienced practitioners in the field, contributed to the variances seen within the cost data. The interviews conducted indicate that the three key drivers for cost variance between tender and actual cost are: lack of decision around methodology at tender stage, changes in method of delivery and changes to programme and planned durations. The data suggests that many of the variances could have been foreseen and considered within risk allowances or contingencies. This research is the first published work in this area. The content provides rare insight into the electricity transmission sector and specifically the decommissioning of high voltage fluid filled cables and the cost variances that occur between the estimated and actual costs incurred.