A gas pipeline (600mm - PL1075 - Winwick - Shelvington) that passes close to the north bank of Sankey Brook, just north of Sankey Railway Viaduct, Newton-le-Willows.
Inspections had revealed that, due to erosion, the north bank of the watercourse had partially collapsed, thereby reducing the cover to the pipeline.
All indications were that, through continued erosion, the pipeline would eventually be exposed and therefore be susceptible to damage.
Northern Divers were employed through their existing National Framework Contract to undertake the survey, design and repair of the river bank in order to maintain protection to the adjacent gas pipeline.
The design comprised excavation of the bank and toe, placement of a rip-rap foundation with a 150mm layer of smaller grit stone on top and a row of pre-seeded coir and rock rolls in front. The bank was then built-up with stone in 400mm layers with Geogrid reinforcement between and topped with soil and seeded Salix C350 nag matting.
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Construction of temporary access track using sand and timber mats.
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 high-pressure pipeline, National Grid’s permit system was thoroughly adhered-to and a Competent Person was on-site at all times during the works.
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Re-setting of old pre-cast concrete head wall over existing land drain.
In order to maintain at least 1.0m of cover to the gas pipeline alongside the watercourse, a temporary track of sand and timber mats was constructed for site vehicles and plant to run along.
The main environmental issue was preventing the pollution of Sankey Brook. 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.
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Pre-seeded coir and rock-rolls along toe of bank and build-up of batter using stone with Terram behind.
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 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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Continued build-up of batter using stone in 400mm layers with Geogrid reinforcement between.
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.
