DEEP DOWN DEMOLITION

With a wealth of experience in marine civil engineering throughout the UK and Ireland, County Down headquartered Ashleigh Contracts have a long-held and well-established reputation of providing high quality projects. These extend from coastal defenses and dredging, to scour protection and underwater demolition. The jobs undertaken require a diverse range of specialist equipment – and that includes the largest in the fleet, a specially modified Hitachi EX1200XXL Triple Boom Long Reach excavator. We recently travelled to the Isle of Arran off the west coast of Scotland to discover some of its amazing capabilities.

Ashleigh Contracts acquired the excavator in 2018 which was originally modified inhouse by Van Leeuwen Sloopwerken in Holland. The undercarriage has been heavily reinforced, lengthened and widened to give it an impressive footprint measuring around eight metres long, with tracks that are seven and a half metres wide. Weighing in at 200 tonnes, it boasts a proven lift capability of 45 tonnes and a maximum outreach of 23m or 25m depending on dipper configuration.

The excavator has been proving its worth over the last couple of years, being utilised on the Aberdeen Harbour Expansion project and the Alexandra Parade Revetment project in Peterhead, undertaking heavy lift duties in the placement of concrete sea defense units. Earlier this summer it was fully utilised to demolish the remains of an old ferry terminal at Brodick on the eastern side of Arran. It was replaced several years ago by Main Contractor George Leslie Ltd for ferry operators Caledonian Maritime Assets Limited with a new, two-storey building including departure lounge, new docking pier and passenger access walkway that, incidentally, won the UK Port Awards ‘Port Infrastructure Project of the Year’ 2018 and was a finalist for the RICS ‘Infrastructure’ award, also in 2018.

Last year, Glasgow based George Leslie Ltd was again appointed by Caledonian Maritime Assets Limited as principal contractor to remove the old pier structure, including the pier deck, support structures and other deck furniture, such as bollards and handrails. George Leslie then subsequently appointed Ashleigh Contracts on a plant hire basis to provide the resources necessary to demolish and remove four circular concrete caissons which sat up to 10m below water level and in places were buried more than 2m below the seabed.

“It was a project that required an extreme demolition machine and was ideal for our Hitachi EX1200XXL,” says Ashleigh Contracts’ Greg Brown. “It was transported from our yard to Larne Port where it was assembled on the quayside and loaded on to a CW-6 55m x 18m spudleg barge supplied by Coastworks who are based on the West coast of Scotland in Fairlie. Once onboard and fully commissioned, the machine was then taken back to Brodick for the underwater demolition project, to be preferably undertaken during summer months.”

The caissons were broken up using a range of attachments including an Atlas Copco HB4200 underwater hydraulic breaker weighing in at 5 tonnes, a 10-tonne Mantovanibenne CR80R concrete pulverisor, a TGS orangepeel grab weighing in at 9 tonnes and a range of buckets. Once the caissons were broken up, the Hitachi EX1200XXL, using the TGS grapple attachment, then brought up the reinforced concrete in chunks which were placed and subsequently further processed on a 30m x11m flat top barge. The material was then taken to Troon where a material handler offloaded it on to tipper trucks bound for a recycling facility; the vast majority of material was recycled into aggregates, while the steel content also went for recycling.

Behind the controls of this modified Hitachi EX1200 triple boom was Keiron Manuel who has nearly two decades of experience in the marine dredging sector. He says the excavator provides him with a comfortable working environment. It was his first time in this particular machine and adds that he found it to offer a stable work platform with plenty of heavy lift capabilities.

Working ‘blind’ under water can present some challenges, of course, but these are taken care of by a state-of-theart James Fisher Prolec PCX Pro 3D GPS system which shows the operator the position and orientation of the excavator’s attachments relative to a target surface in real time.

Indeed, seeing the benefits, Ashleigh Contracts has invested heavily in these GPS machine control systems across its entire long-reach fleet, helping to increase accuracy and efficiency when positioning construction material, such as rock armour, scour protection bedding material and concrete sea defence units, including Accropodes, Core-locs and x-Blocs.

The durable design and real-time progress monitoring feature of the PCX system not only delivers assured performance in harsh environments, but also allows Ashleigh Contracts to capitalise on low tide conditions, thereby maximising productivity during short windows of opportunity.

The company’s extensive specialist fleet features a range of Hitachi and CAT machines. These include a Hitachi ZX750 (25m) Long Reach Excavator, a Hitachi (28.5m) EX1200 Super Long Reach 120-tonne excavator, a CAT390 (17.5m reach), a CAT 395 (21m reach) and a CAT 345LR (19.5m reach). All machines are fitted with the Prolec PCX Pro 3D GPS system and are currently working on a London Gateway project. Here, construction is underway for a new fourth berth at the DP World deep-water port. It is due to be completed next year, lifting London Gateway’s capacity by a third thus giving it more room to handle the world’s largest vessels, more than any other port in the country.

Since it was acquired in 2018, the Hitachi EX1200XXL triple boom has played a major role in other notable contracts. One such job is Aberdeen Harbour’s Expansion Project in Nigg Bay, south of the main Aberdeen Harbour where Ashleigh Contracts constructed a 450m length of the North Breakwater. The work included receiving and stockpiling 110,000 tonne of Rock Armour predominantly sourced from Norway, building the Core of the Breakwater with 300,000 tonne of locally sourced Core Material, constructing the Underlayer Armour protection to the Breakwater and placing 3,000 Accropode Primary Precast Armour Units, each weighing 20 tonnes.

"Modified Hitachi EX1200XXL triple boom excavator offers a stable work platform with plenty of heavy lift capabilities…"