Works to a gas pipeline (600mm – Penicuik to Boon) that passes beneath Leader Water, near Lauder in the Scottish Borders.
Inspections had revealed that, due to scour, the top of the pipeline had become exposed and therefore was susceptible to damage.
Also, erosion had undermined a section of the bank close to the pipeline crossing.
Northern Divers were employed through their existing National Framework Contract to undertake the survey, design and repair of the river bank and bed in order to maintain protection to the underlying gas pipeline.
The design for the bank repair comprised excavation of the bank and toe, placement of 0.5-1.0m rock armour with 50mm stone and a Terram reinforcing membrane behind.
The bed repair around the pipe was achieved through use of 50-300mm stone to build-up the bed and cover the pipe to prevent scour and maintain continued protection to the pipeline.
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Bank erosion and scour over pipeline.
Any work that had to be undertaken within or close to the watercourse was only undertaken by fully qualified divers. In such cases, personnel wore diving suits and all required safety equipment was at-hand.
Due to the proximity of the 600mm gas pipeline, The clients permit system was thoroughly adhered-to and a Competent Person was on-site at all times during the works.
Where plant and other site traffic were required to pass over the buried gas pipeline, timber mats were installed to ensure the service wasn’t adversely affected.
The large stone was carefully placed using a hydraulic grab fitted to the excavator. A banksman guided and supervised the placement so as to ensure no damage could be caused to the pipeline.
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Turbulent water causing scour over the pipeline.
The main environmental issue was preventing the pollution of Leader Water. This was managed through careful planning and the selection of construction materials that would not disperse fines downstream.
All mobile plant was altered to run on bio-oil.
All waste materials and arisings were taken off-site and disposed-of in accordance with the Site Waste Management Plan.
The local landowner and the Scottish Environment Protection 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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Timber mats used to protect underlying gas pipeline from site traffic and plant.
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.
