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Subterranean success for 777 Group at Greenwich

18 Aug 11 Demolition and dismantling specialist 777 Group has recently completed a major project in the centre of London using two giant, 140 tonne Hitachi excavators.

The undertaking centred on removing and recycling the subterranean foundations which once supported an uninspiring office block named Peggy Middleton House. With the building already demolished, the subsequent removal of its foundations by 777 Group has ensured that the site, which is currently at the centre of a £400m mixed-use regeneration scheme, will be available for developers on time and in good order.

Despite the immediate area having been earmarked for regeneration since the late 1990s, the recent extension of the Crossrail scheme to Woolwich has provided renewed impetus for the redevelopment scheme which will include building a supermarket, 1000 flats and Greenwich council’s new civic offices on the site where Peggy Middleton House once stood.  With the green light finally given to developers, 777 Group was given just eight weeks to break-out and recycle the building’s foundations; a task which proved more challenging than it sounds according to 777 Group’s Business Development Manager Daryl Pearce, “During our initial examination of the site it was difficult to tell the depth and strength of the building’s concrete foundations. These unknowns, coupled with a time restriction for completing the project, meant we had to deploy our machines and operatives en-masse at the site. Suffice to say, it was a good job we have the in-house capability for such undertakings as the foundations have proved tougher and deeper than first thought”. 

Instrumental in 777 Group’s ability to break-out, crush, back fill and compact the concrete foundations has been its extensive fleet of demolition machinery which includes two heavyweight Hitachi EX1200 excavators. Equipped with mass-excavation arms the EX1200s weigh in at nearly 140 tonnes each. Whilst one machine utilised a 7m3 bucket, the other hosted a brand new Atlas Copco hammer. Reputed to be the largest volume produced hammer in the world, the 10 tonne Atlas Copco HB10000 was used to good effect to break out over 50,000 m3 of reinforced concrete. The attachment housed a 24cm wide pin which can smash against concrete at a rate of 380 times a minute. According to Daryl, the breaker’s performance played a vital role, “The combination of one of our EX1200s coupled with Atlas Copco HB10000 breaker really sped up the demolition process. With the Hitachi’s strong hydraulic power pack supporting the giant hammer, the concrete came free at an impressive rate. Of course, having a second machine which can shift the giant slabs of broken concrete also helped things along”. 

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The number of vehicle movements in and out of the site was significantly less than most operations of this size thanks to an on-site recycling programme. Approximately half of all the concrete arisings generated by the foundation demolition were crushed, backfilled and compacted in-situ in order to facilitate a level change for the base of the new building. The remainder was dispatched to 777 Group’s recycling facility nearby. Some 200 tonnes of rebar was extracted from the concrete foundations and also removed from the site.

With the project completed on time and on budget, 777 Group’s ability to rapidly and safely remove irksome, stubborn structures such as the foundations of an uninspiring office have again been proven thus ensuring the long overdue redevelopment of central Greenwich starts without delay.

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