We’ve made several meaningful and thought-through suggestions in the half-dozen articles, and as many letters to the main bridge protagonists in the last year, from simple widening the pathways to make the bridge more accessible, and to improve public safety, to ways to invisibly fix the 19th century structure for the longer term, in a maintainable 21st century way.  Put simply, we believe the current premise for repairs has set the engineers off on a bit of a wild goose chase.  While much good work has been done, how much is useful under an alternate premise, and at what opportunity cost ?

Bridge anchor (cover removed)

As we pass six months since complete closure, we’ve made it crystal clear that there appears very little, if any, value in repairing the much-debated, though normally invisible, cast iron pedestals shown.  We continue to be dismayed that so much attention is paid to evaluating and repairing these simple yet demonstrably unsuitable bolted-in components (c.f. Mott MacDonald summary and more detailed  Aecom report) when replacement with modern equivalents is an obvious solution.  Not only that, but by including, as we’ve suggested, a built-in lifting or jacking mechanism for the chains in a new design pedestal, future maintenance inspections and bearing replacements (the cause of many of the current problems, and certainly the precipitous closure), would be reduced to perhaps scheduled weekend roadway closures every 5 years or so, at low cost and public impact.  This, without even considering the environmental and financial running costs of the proposed chain heating and monitoring systems that would no longer be needed. 

Surely we can’t be the first to spot such an opportunity for a better and long-lasting engineered solution at lower overall cost – plus the opportunity to cut a whole phase of repair work ? The question is why can we only find passing reference to renewal as an option in the copious Aecom report?  Which is where we return to the issue of the premise, assumed to include retaining the original components.

A false premise

Temporary pedestal support frame

The TfL drawings shown at the public meeting in October, to which we responded, show a temporary support frame for “emergency stabilisation” – already designed – that could be better used during pedestal renewal, using offsite built and tested replacements, instead of a long and expensive (£13.9M + percentage  – say half – we don’t have a detailed cost breakdown) of the permanent stabilisation costs, totalling c.£30M. 

The current proposal for onsite shoring-up would hardly respect the Grade II* listing, Bazalgette’s design, or materials (assuming that’s the rationale), rendering the pedestals unrecognisable as historic components, especially when infilled with [c. 6 tonnes] of steel fibre reinforced concrete as proposed, and would, according to the Aecom report, leave further nascent cast-iron problems, including a possible failure mode where the cast iron collapses onto the unusual prop/concrete/cast iron mix. The cast iron pedestals would instead make fine museum pieces, to accompany Tower Bridge’s stream engine, removed from service when proven equally obsolete over 40 years ago.

Bridge Permanent Stabilisation – pedestal props

Not only would the current approach not address long-term maintainability of the bearings, it would put additional unnecessary load on the weak footings, and in extremis, make the bridge effectively irreparable in future.  The reports list residual issues with pedestal material and casting quality, loadings (“Utilisation Factors”), bearings – their material and design – and the potential pedestal failure mode after all this work and expenditure ! (§4.7)  Our proposal would yield a permanent, invisible, maintainable repair for these parts of the bridge more quickly, potentially allowing reopening for traffic with other repairs being scheduled off-peak, much as TfL does on the tube.

To date, our suggestions appear to have fallen on deaf ears, and the task force has only agreed to fettle the cast iron, and tender for ferries – which in our view are distractions from the job in hand, which could by now be cost-effectively heading towards first stage completion.  True, there would be the roadway and longer term maintenance still to do, but the bridge would be safe and passable at least to pedestrians, cyclists, and river users, with one aspect of long-term repairs in place.