200mm gas pipeline, NL0014 Reading Branch, crosses a watercourse, The Cut, just north of the M4 near Maidenhead.
Inspections had revealed that, because of scour partly caused by upstream vegetation and debris, a section of the riverbank had eroded to the point where the pipe’s swan-neck, previously within the bank, had become exposed, putting the pipeline at risk of damage.
Northern Divers were employed through an existing National Framework Contract to undertake the survey, design and repair of the eroded bank in order to maintain protection to the pipeline.
The design comprised a combination of stone-filled gabion baskets forming the bank and protecting the pipeline with 300mm diameter coir rolls up- & down-stream to build-out the bank. The bank was graded with soil and topped with pre-seeded nag matting.
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Exposed swan-neck to gas pipeline.
Because a significant amount of the protection work had to be installed below the water line, only qualified divers were used to undertake the work. All personnel wore diving suits and all required safety equipment was at-hand.
From the first stages of the contract The Environment Agency were consulted on the proposed works and, with the client concerns satisfied, a proposal was agreed upon that met the requirements of all concerned.
During the course of the works, when the gabion baskets had created a working platform adjacent the pipeline, National Grid used the opportunity to repair damage to pipe’s coating.
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Impact damage to exposed gas pipeline.
The main environmental issue was preventing pollution of the adjacent water course.
This was managed through careful planning and the selection of construction materials that would not disperse fines.
Any waste materials and arisings were taken off-site and disposed-of in accordance with the Site Waste Management Plan.
The landowner and the Environment Agency were consulted on the proposed works from the beginning of the scheme and kept informed of progress throughout the construction phase.
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Upstream vegetation and debris partly responsible for bank erosion.
200mm gas pipeline, NL0014 Reading Branch, crosses a watercourse, The Cut, just north of the M4 near Maidenhead.
Inspections had revealed that, because of scour partly caused by upstream vegetation and debris, a section of the riverbank had eroded to the point where the pipe’s swan-neck, previously within the bank, had become exposed, putting the pipeline at risk of damage.
Northern Divers were employed through an existing National Framework Contract to undertake the survey, design and repair of the eroded bank in order to maintain protection to the pipeline.
