The true cost of undergrounding?


Stour Valley Underground contest the validity of National Grids assertion that the cost of putting the proposed power lines underground is 12 - 17 times as much as overground. Here we present evidence of this exaggeration based on National Grids own figures from a project near London.

Querying the Cost of Undergrounding

Monday, 9 November 2009

In our ongoing quest to identify the true cost of undergrounding power lines we have written to Jim Street, NG Project Manager as follows, presenting evidence from their own website of the inflated costings they have published. Naturally, we will be posting the response here when we have it.

Dear Mr Street

Powerline Undergrounding Costs

I am writing to request your response to the following argument and reasoning regarding the possible undergrounding of the proposed power lines from Bramford to Twinstead

As you are no doubt aware, there is a huge amount of support amongst the public and in particular, the parishioners represented by our Parish Council, for the idea of undergrounding any new power lines and so I would like to know your response to the following:-

Information sources:-

In a written reply dated 29thSeptemebr 2009 to a question raised by members of the Groton Pylon Alliance about the details of the costs for the under grounding you say:

The proposed power line would link our existing installations at Bramford and Twinstead. Depending on the chosen route, the length of line would be between 26 and 30 km in length.

The cost to build an overhead line is approximately £1.5M per kilometre and the cost to underground an overhead line is in the region of 12 to 17 times that amount. For this project these costs would be towards the higher end of this range.

From the National Grid web site I read details of your already completed underground cable projects in London, in particular the Case Study of the Elstree – St Johns Wood cable tunnel.

So from information that National Grid have provided:-

I understand that the new Bramford - Twinstead overhead line will cost £1.5m per km 

that equates to 1.5 x 26 = £39m with all its associated over ground activity.

To underground this you say it will be the higher end of 12 to 17 times this

i.e. 39 x 17 = £663m

If we now look at the Elstree – St Johns Wood tunnel Case Study:

The 20 Km tunnel cost £70 or £3.5m per km, to fit the tunnel with 1 x 400 kV circuit cost £45m or £2.25 per Km

Making simple projections based on this:-

the tunnel cost for a 26km tunnel would be 26 x £3.5 = £91m,

the cable cost would be 26 x £2.25m = £58.5

multiplied by two 400kV circuits = £117m.

This gives a total of £210m.

The inescapable conclusion for me is that the true cost would be vastly lower than that suggested by your oft quoted 12-17 times figures (i.e, less than one third of the cost suggested by your underground cost multiplier).

I also reason that if you were to design the tunnel so that it took the EDF 2 x 132kV circuits as well, we believe the cost addition to be comparatively low when set against the huge environmental advantages and NG would save the considerable capital cost of a sub station.

I would further reason that if such a tunneled underground option were adopted:

Most people would back the project.

The environmental effect on the Dedham Vale AONB and Stour Valley Project Area would be minimal, as the tunnel would be under both.

The 132Kv pylons would be removed without the environmental and economic cost of an unsightly GSP

The whole project would provide a smart grid compatible solution and would be eminently upgradable to meet future needs without further consultation and public alarm.