Marine works are continuing apace on the second phase of the multi-million pound redevelopment project of Torry Quay in Aberdeen.
Phase 1 was successfully completed a few months ago, including the realignment and widening of the channel in the river Dee, dredging for deep water berths, reinforced quayside areas all designed to improve navigation and cargo handling facilities.
Following extensive design and underwater survey operations, the new river bed profile and the extent of existing obstructions to be removed was identified.
This included the existing sheet piled quay wall, analysis of the original fill material, disused rail lines, redundant crane bases and reinforced concrete piles extending into the bed of the harbour channel.
Main contractor McLaughlin & Harvey is undertaking the work for Aberdeen Harbour Board, one of the harbour’s largest civil engineering schemes in recent years.
Having started the piling operations in early 2011, the widening of the harbour channel and removal of the old steel piles and excavation of backfill followed in late 2011.
Long-reach excavator specialist WM Plant Hire provided a 100t machine with an outreach of 26m to dig down to depths over 14m and load material into barges for transport to the disposal site 3.2km offshore.
For the removal of the sheet piles a 200t crawler crane was used after the material had been cleared from both sides of the pile section. Where old or deteriorated piles were located including steel, timber and concrete sections, specialist hydraulic attachments were fitted to the long-reach excavator.
This custom-built CAT 375 machine, capable of handling up to 4t work tools, used an underwater breaker, a multi-processor with a combi-jaw for steel and concrete and a pile cropping ring to crush the circular concrete piles.
Underwater surveys were made using a multi-beam survey vessel, using computer modelling to produce very detailed imagery of the new underwater profile.
Phase 2 began this March and involves the infilling of the river Dee dock and construction of around 100m of new deep drafted quay walling using steel piles and concrete capping beam.
The works are due for completion towards the middle of 2013.