Third party damage is the highest risk to the National Transmission gas pipelines. The costs of repairs and disruption are always significant, typically in the range of £30k to £M’s especially if the pipeline has to be shut down whilst the damage is repaired.
Reduced depth of cover and shallow ditch crossing are increasingly being identified e.g. from pipeline walking surveys. Several innovation projects have been and others are being progressed to mitigate against third party damage, e.g. the use of PE slabs and in-line depth of cover assessments and some of these are already in use.
Arising from research for these innovation projects, the ‘overpipe’ net solution, already in use in parts of Europe, was identified. The technology comprises of a high strength yellow geo-fibre net grid that is very visible to excavator operators whilst restricting the dig capabilities of the excavator bucket and minimizing the likelihood of deeper excavation.

Objectives

To trial and demonstrate the suitability of overpipe geo-grid protection. The method can then be used by National Grid in future new build projects, diversions and existing pipelines where a higher than normal risk of third party damage is identified.