6 questions we still have about London's Garden Bridge

The Garden Bridge: monster or marvel?

London’s proposed Garden Bridge is a bit like the Rorschach inkblot test. To some, it looks like a new piece of public space and infrastructure in central London, littered with delightful greenery. To others, it looks a bit like a suspect waste of money probably motivated by, basically, pure evil.

These different perspectives are possible largely because of the substantial number of unanswered questions still surrounding the plans for the bridge, construction of which is due to begin at the end of 2015. Here are six – plus any answers we’ve been able to unearth so far.  

1. Just how much public money will be spent on it?

Until recently, everyone has been under the impression that the £175m cost of the bridge's construction will split into £60 worth of public investment and £115m of private money. Earlier this month, mayor Boris Johnson assured LBC listeners  that “the maintenance cost will not be borne by the public sector, I’ve made that clear.”

But last week, Architects’ Journal got hold of a letter in which the Greater London Authority appears to agree to underwrite the bridge’s £3.5m maintenance cost. 

We asked the Garden Bridge Trust (GBT) about this, and a spokesperson told us that the GLA had only underwritten the costs because the GBT could promise a “robust business plan” which should cover all maintenance: 

The Garden Bridge Trust fully intends and expects to raise the money required for both the construction of the Garden Bridge and the ongoing maintenance and operations. More than £120m has been pledged so far and we have a clear business plan in place to raise the estimated £3.5m per annum needed to cover the on-going costs.

Answer: Probably only that initial £60m. Probably.

2. Will you have to pay to cross it?

Rumours about the bridge's funding and its closure for private events led some to think passerby would have to pay to cross the bridge. This, however, isn't the case: private events would presumably be ticketed, but anyone crossing during normal hours could do so for free. 

Answer: No. 

3. Does it even count as a bridge?

Back in November, reports emerged that the bridge would not be open to cyclists, would close at night and for private events, and would only be open to groups of eight or more if they let staff know in advance. Also, that picnics (read: joy) would be banned. 

These regulations would hugely negate the usefulness of the bridge as a pedestrian walkway – you wouldn't be able to rely on crossing it whenever you needed to, so it'd be unlikely to form part of anyone's regular journeys. The rules on large groups and eating sandwiches would also make it less of a park or public space. 

On this, the GBT spokesperson said that the regulations on use are still under discussion. On the groups of eight issue, they said: 

Most public spaces have ways of managing large groups to ensure the safety and comfort of visitors. The Trust had to include this in the planning application and put forward an initial figure of more than 8 people... this was a starting point only and we are talking to stakeholders and the local planning authority to confirm our agreed numbers. 

And on the picnics?

The bridge is a place for people to linger and admire new views of the city, but it will also provide an efficient route for commuters... We will ask users to be considerate to others when using the bridge.

So, not massively clear then.

Answer: Yes, if enough of the limitations on its use are taken away. 

4. Is it in the right place?

Even if you do consider a walkway that's shut half the time and closed to cyclists a "bridge", it hasn't been planned for an area that particularly needs one. The proposed site is between Blackfriars Bridge and Waterloo Bridge, to link Temple with the Southbank:

This location only strengthens the impression that this is more tourist attraction than infrastructure project, however. There are already three bridges within 1km of the proposed crossing.

To the east, meanwhile, there's a long stretch of the river which is effectively uncrossable, where a bridge – even a limited one – would have genuinely come in handy. 

Answer: For maximum footfall from West End audiences and Southbank visitors, yes. For actual Londoners, no. 

5. Was Thomas Heatherwick the right designer for the job?

In another exclusive, Architects’ Journal revealed a couple of weeks ago that the bridge's chosen designer, Thomas Heatherwick, was scored more highly for bridge experience by TfL than the other two firms, despite the fact that both have designed far more bridges than him. 

Wilkinson Eyre, one of the firms turned down for the contract, lists 27 bridge projects on its website. Heatherwick, meanwhile, has reportedly only designed one. 

6. Is it a secret Diana memorial?

When Joanna Lumley first dreamt up the idea of a garden bridge back in 1997, she envisioned it as a memorial for the recently deceased Lady Di. We thought it was worth checking whether this was still the case.

According to the GBT spokesman, at least, the project is no longer linked to the people's princess in any way.

Answer: No, thank goodness. She's stuck with that fountain in Hyde Park and Kensington's Diana Memorial Playground. Sorry, Express readers.

 
 
 
 

The mountain in North Wales that tried to stop the UK’s blackout

Elidir Fawr, the mountain in question. Image: Jem Collins.

Last Friday, the UK’s National Grid turned to mush. Not the official term perhaps, but an accurate one after nearly one million people were left without power across the country, with hundreds more stranded at train stations – or even on trains (which isn’t nearly as fun as it might immediately sound). 

Traffic lights stopped working, back-up power failed in hospitals, and business secretary Andrea Leadsom launched an investigation into exactly what happened. So far though, the long and short of it is that a gas-fired power station in Bedfordshire failed just before 5 o’clock, followed just two minutes later by Hornsea offshore wind farm. 

However, amid the resulting chaos and inevitable search to find someone to blame for the outage, a set of mountains (yes, mountains) in North Wales were working extremely hard to keep the lights on.

From the outside, Elidir Fawr, doesn’t scream power generation. Sitting across from the slightly better known Mount Snowdon, it actually seems quite passive. After all, it is a mountain, and the last slate quarry in the area closed in 1969.

At a push, you’d probably guess the buildings at the base of the mountain were something to do with the area’s industrial past, mostly thanks to the blasting scars on its side, as I did when I first walked past last Saturday. 

But, buried deep into Elidir Fawr is the ability to generate an astounding 1,728 megawatts of electricity – enough to power 2.5 million homes, more than the entire population of the Liverpool region. And the plant is capable of running for five hours.

Dubbed by locals at the ‘Electric Mountain’, Dinorwig Power Station, is made up of 16km of underground tunnels (complete with their own traffic light system), in an excavation which could easily house St Paul’s Cathedral.

Instead, it’s home to six reversible pumps/turbines which are capable of reaching full capacity in just 16 seconds. Which is probably best, as Londoners would miss the view.

‘A Back-Up Facility for The National Grid’

And, just as it often is, the Electric Mountain was called into action on Friday. A spokesperson for First Hydro Company, which owns the generators at Dinorwig, and the slightly smaller Ffestiniog, both in Snowdonia, confirmed that last Friday they’d been asked to start generating by the National Grid.

But just how does a mountain help to ease the effects of a blackout? Or as it’s more regularly used, when there’s a surge in demand for electricity – most commonly when we all pop the kettle on at half-time during the World Cup, scientifically known as TV pick-up.

The answer lies in the lakes at both the top and bottom of Elidir Fawr. Marchlyn Mawr, at the top of the mountain, houses an incredible 7 million tonnes of water, which can be fed down through the mountain to the lake at the bottom, Llyn Peris, generating electricity as it goes.


“Pumped storage technology enables dynamic response electricity production – ofering a critical back-up facility during periods of mismatched supply and demand on the national grid system,” First Hydro Company explains.

The tech works essentially the same way as conventional hydro power – or if you want to be retro, a spruced up waterwheel. When the plant releases water from the upper reservoir, as well as having gravity on their side (the lakes are half a kilometre apart vertically) the water shafts become smaller and smaller, further ramping up the pressure. 

This, in turn, spins the turbines which are linked to the generators, with valves regulating the water flow. Unlike traditional UK power stations, which can take hours to get to full capacity, at Dinorwig it’s a matter of 16 seconds from a cold start, or as little as five if the plant is on standby.

And, designed with the UK’s 50hz frequency in mind, the generator is also built to shut off quickly and avoid overloading the network. Despite the immense water pressure, the valves are able to close off the supply within just 20 seconds. 

At night, the same thing simply happens in reverse, as low-cost, surplus energy from the grid is used to pump the water back up to where it came from, ready for another day of hectic TV scheduling. Or blackouts, take your pick.

Completed in 1984, the power station was the product of a decade of work, and the largest civil engineering project commissioned at the time – and it remains one of Europe’s largest manmade caverns. Not that you’d know it from the outside. And really, if we’ve learned anything from this, it’s that looks can be deceiving, and that mountains can actually be really damn good at making electricity. 

Jem Collins is a digital journalist and editor whose work focuses on human rights, rural stories and careers. She’s the founder and editor of Journo Resources, and you can also find her tweeting @Jem_Collins.