National Grid has employed ACS to carry out a number of excavations on their main gas terminals at St. Fergus in Aberdeenshire and Bacton in East Anglia and a large compressor site in Aberdeen. There have been 8 excavations with in a 9 month period which ranged from 2.5 to 3.5m deep, with the largest being 6.5m long by 4m wide by 3.5m deep.
The works involved the excavation over a live high pressure gas pipeline and adjacent above ground installations in a potentially explosive atmosphere. Detailed shoring designs needed to be obtained and coordinated because as well as large diameter gas pipes, there were various other services in the location. Sheet piles and frames were used to ensure the excavation was shored safely to allow National Grid operatives safe access and egress.
A variety of excavation techniques was also utilised for the excavations including Vacuum, mechanical and hand excavation.
ACS also employed ground penetrating radar survey equipment to establish what others services/ obstructions were in the ground before any excavation works could take place. A drawing was then produced and issued to National Grid to show all obstructions for future works.
ACS supplied supervision and personnel with specific National Grid training to obtain the National Grid permits as well as complying with all National Grid health, Safety and Environmental procedures.