Montrose Depwater Berth - Dredging & Underwater Clearance

Montrose Depwater Berth - Dredging & Underwater Clearance

Contract Value: £916,000
Consulting Engineer: Arch Henderson
Engineer's Representative: Craig Saunders (01382 561141)
Client: Farrans (Construction) Ltd
Client's Representative: John McReynolds
Works Completion Date: July 2011

Scope of the Works:

  • Dredging and disposal at sea of 32,500m3 to provide a berthing pocket at -8m CD for a new Deepwater Berth – the plan area of dredge being approx. 225m long x 40m wide with trimming of side slopes to existing bed levels.
  • Underwater clearance including removal and segregation of approx. 250m3 of concrete and 50T of steel fragments.
  • Clearance along and removal of 112m of sheet piles and 56No H Piles along a section of quay which had collapsed in 2003 and which had been pre-cleared by Farrans to allow installation of the adjacent new quay wall – this comprised final clearance and airlifting within the 3m gap between new quay wall and the collapsed sheet and H Piles which had to be burned off and removed from the seabed at -9m CD (i.e. 1m below final dredge level).
  • Removal of an additional 58No H Piles along the line of the original quay wall which had not been pre-cleared prior to our mobilisation to site. These additional isolated H piles were at irregular centres along the line of the old quay wall and were embedded in clay to a depth of up to 9m – and required the clearance around individual piles using the long reach excavator, followed by underwater water-jetting of clay to expose steelwork and the underwater burning by divers to allow for their successful removal in circa 3 stages to -9m CD. These operations resulted in significant difficulties and hazardous working conditions given the occurrence of banks of clay around each pile which had to be water-jetted by the divers to allow for burning of steelwork. 
  • All the above dredging and underwater clearance works were carried out using floating plant and equipment including a spudleg barge, 95T Long Reach Excavator.



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