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Cantillon and Goliath cut a swathe through Thames warehouses

Heayweight equipment and river barges have proved invaluable on a tricky London job. By Kevin Walsh

Client St Martin’s Property Corporation
Demolition ContractorCantillon
Contract Value £5.2 million
Start date August 2008
Completion date March 2009

Bermondsey is home to London’s last original wharf – its historic warehouses have been used to store everything over the years from food and textiles to gold bullion.

Since 2007 property developer St Martins has been looking to turn the former larder into a mixed-use riverside development which will provide over 600 homes, offices and retail units.

London-based demolition contractor Cantillon took on the job of clearing out the 4 acre site, and tasked with demolishing 15 buildings including 11 large warehouses, it needed some serious plant.

Detailing some of the rigs used on site to date, Cantillon’s operations manager Nick Taylor says: “We’ve got two long arms working here plus around six other units available so we can do a fair bit of work. We’ve got a Goliath there with a 130 tonne payload, we’ve also got a 60 tonne machine, and an FH450 long reach rig.”

The Goliath excavator has been on the site since the start and has been fundamental to Cantillon’s progress on the job.

The Liehberr 974 Goliath was originally built in Germany specifically for the demolition of Wembley stadium in 2002, and since then its acquisition has proven vital for Cantillon.

Project manager Andrew Dyson explains: “Being able to use that Goliath crane on site has been underpinning the success of this job. Without it we wouldn’t have been able to do this job in a safe manner and in the time frame we have.”

Need to keep road open Chambers Street is a fairly busy road running near the wharf which has to be kept open to traffic throughout the demolition.

Many of the warehouses face this thoroughfare and so their demolition has to be very carefully controlled.

To enable this Cantillon has been using the Goliath’s 35 m reach to lift a mini-excavator onto the upper floors of these buildings to ensure controlled demolition, with the long reach excavators demolishing the easily accessible rear parts of the building and the mini-excavators slowly taking down the front of the building closer to the road.

Mr Taylor explains: “The concern is the front facades and their proximity to Chambers Street. With long reaches they’re wonderful tools, incredibly powerful but sometimes you can take a bit too much. So doing it with a mini, in just a little bit more controlled and diligent manner, we really do reduce the risk of uncontrolled collapse or potential for debris falling where it shouldn’t.

For example, for one of the panelled structures there, our demolition guys are concerned that some of the last panels could fail catastrophically. So to keep it safe we put a mini-excavator up there, de-panel it, then tackle the frame structure with the long arm. It’s worked really well so far.”

This kind of careful demolition is par for the course on this site, as in the next few weeks the same method will be used on a warehouse on the opposite side of Chambers Street which is literally metres from the rear blocks of a local school.

Mr Taylor clearly appreciates the sensitive nature of the work on this part of the site, admitting: “There will be noise but you can deal with noise better than you can deal with unpredictable falling material.”

Site workers will use acoustic screening to try and minimise disruption to the school, and to ensure compliance with the Considerate Constructors scheme there is also a noise monitoring station located behind the school.

The proximity of the site to the River Thames has given Cantillon the chance to maximise the use of sustainable transport of demolition waste.

Using transport barges with at least a 1000 tonne capacity, all materials from the site will be taken away on the river to be recycled.

Cantillon expects to make just over 100 barge trips to move inert material and other scrap off site, compared to the 6,000 lorry trips that would be necessary had there been no access to the river.

Carbon saving

By current estimates this will mean that the 70 tonnes of carbon that would be generated by road transport will actually be cut by a factor of 10. All that was needed to facilitate this was the placement of a spreader mat on the jetty, which spread the weight of the 450 tonne long reach rigs used to load the barges across the jetty’s support beams.

“Absolutely everything has been barged out of here as opposed to lorries, which is a massive carbon footprint saving” says Mr Taylor.

“By barging the scrap off site we got that down to around seven tonnes which is quite an impressive saving really. We’re doing our bit, hopefully were setting a precedent.”

The firm hopes to get further work at Chambers Wharf when the jetty is demolished and moved back to the original river wall.

This promises to be a challenging job as there will be a large archaeological attendance to work around during the jetty demolition.

Underneath the jetty and across the foreshore area, archaeologists from the Museum of London have discovered several items of significance dating back to the Neolithic period, making any disruption potentially very costly.

The tender for this work is expected to go out in early 2009.

‘IT WAS QUITE EMOTIONAL FOR A WHILE’

For Cantillon’s operations manager Nick Taylor, the biggest challenge faced so far was the excavation of a massive 300 tonne sunken barge in the Thames very near to the jetty.

The barge had been sitting on the bed of the Thames for over 20 years and had accumulated around 450 tonnes of silt and sludge which needed excavation before it could be re-floated.

Mr Taylor explains that as this was the first time Cantillon had done anything like this, nerves on site were more than a little frayed for the three weeks it took to accomplish.

“We were all a bit nervous about it, that’s was the trickiest part of the job really. Just dealing with the unknown and the potential for serious errors while working in a water course with machines, and the environmental aspects of that. All of it was quite emotional for a while.

"In the end, when it actually came to the nuts and bolts of doing the job, the team performed really well and from start to finish, cradle to grave, so we were very pleased in the end.”

Once the silt was flushed from the vessel and all ballast excavated, contractors did spot repairs on the hull and it was re-floated once seaworthy.

With Cantillon’s job done, the barge has now been moved to Kent where it has found a new role as a storage vessel at a sand quarry.

SAFETY BY REMOTE CONTROL

Although most of the buildings on site have laid derelict sine the 1980s, a handful of them have some particularly beautiful reusable elements to them which Cantillon were eager to save.

One in particular was constructed using 23 cm–long, 5 cm-thick maple leg wood flooring, which the contractor was eager to keep and sell on.

However once removed, this made using a typical manned mini-excavator much more risky, so instead Cantillon used a Brokk 330 remote demolition robot.

The frame of the building consists of large cast steel girder sections, so once the strength of the horizontal sections had been proven, a temporary platform was installed using locking pins that would allow the Brokk demolition robot, fitted with a long chisel, access for demolition work. Then it can be controlled remotely by an operator in a cherry picker or elsewhere on the scaffold.

Although this platform could easily accommodate a 6 tonne rig, Cantillon’s operations manager Nick Taylor decided to err on the side of caution, saying: “It costs about £110,000 for a Brokk 330, but at the end of the day it’s just money.

“God forbid there’s a catastrophic failure and the platform and the Brokk goes, but that’s what your insurance is for, if you had a man in a rig up there it doesn’t bear thinking about.”