The building site where the HS2 railway dips into a tunnel under the Chilterns is to be turned into a large nature reserve once the construction works have finished.

Approach to the tunnel portals (c) HS2

The site, which was a number of monoculture arable fields sits just inside the M25 motorway and is currently being used to start construction of the two tunnels that run under the Chilterns.

At the moment, it’s a huge building site, and they were always required to restore the landscape afterwards, but rather than returning it to fields, they’re taking an opportunity created by the tunnels themselves to create a nature reserve instead.

The tunnels are digging through a chalk landscape under the Chilterns, and that spoil needs to be removed, but by using it to landscape the local area by the tunnel mouth instead they are both reducing the amount of traffic needed to remove the spoil, but also creating a chalk rich reserve.

Around 3 million cubic metres of chalk from the tunnels, along with soil from the construction site will be piled up into new hills and slopes around the HS2 railway to create a chalk valley landscape.

Above the tunnel portals (c) HS2

Calcareous grasslands, which develop on shallow soils overlying chalk or limestone, are a valuable, scarce and rapidly declining habitat in the UK, with this decline reflected in both the Colne Valley and adjacent Chiltern Hills.

The neighbouring Chilterns Area of Outstanding Natural Beauty is currently thought to support around 700 hectares of chalk grassland, and at 90 hectares, the HS2 site will increase that by nearly 13 percent.

In addition, nearly 65,000 trees and shrubs of 32 species will be planted together with nearly 3.5km of new hedgerows. The loss of hedgerows, mainly in arable farms, has been identified as a factor in the decline of many plant and animal species in the UK.

In total, the new nature reserve will be nearly 130 hectares in size and will include around 4.5km of new footpath, cycling and horse-riding routes.

Looking north (c) HS2

Those who hate HS2 will never stop hating it, but the question at this stage should be less about trying to stop HS2, as that ship has long since sailed, but maximising the various opportunities that it can bring, or if you prefer another way of putting it, minimising the downsides.

This is one site where once there was bland arable fields next to a noisy motorway, but in a decade’s time will be a thriving haven for wildlife.

HS2 site (c) Google Earth

Tunnelling at the Chiltern portal is set to start shortly and should be completed in 2024. Field trials are in preparation ahead of the final seeding, and planting of trees and shrubs in 2025.


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  1. 100andthirty says:

    I really hope they choose trees that are not prone a) to drop their leaves on the track and b) won’t fall on the track

    • Maurice Reed says:

      The trees will be well away from the tracks and OLE.

      I think it’s an excellent scheme šŸ‘

  2. Melvyn says:

    This article does what the Antis dare not do and shows the before and after construction of HS2 and the before shows just a large empty boring field no sign of woodland in fact barely any trees !

    For those who wonder about those long concrete tunnels beyond the tunnel mouths they are required because one side effect of high speed trains is that they can create the equivalent of a sonic boom when leaving tunnels and these overhang tunnels are to prevent this from happening.

    Itā€™s also worth noting how much less land a twin track railway will use compared to motorway with a total of eight lanes !

    So why is Highway Agency not required to do likewise when motorways are built !

  3. John says:

    I love the castle folly type portals that the Victorian railway builders would use for celebrated tunnel entrances. Such a shame that the tunnel portals of today look like large precast concrete drainpipes. Given the huge funding for HS2, it would be nice if the portals could be more interesting architecturally. Same comment applies to the Channel Tunnel portals. At least the nature reserve is a great idea.

  4. ChrisC says:

    ā€˜Interesting architectureā€™ costs money.

    A lot of the niceties have been stripped out to save money on an already expensive project.

    Simple is also better for maintenance,

    • CliveW says:

      It is a shame this was not applied to Crossrail. Whilst northern Councils and Government agencies are scratching around for funds for simple new stations more than the cost of these is squandered on the architectural look of Crossrail. Would Paddington have looked worse without the cloud sculpture roof or Farringdon without it’s intricate diamond ceiling or the wave form of Whitechapel ? No. And we are told we can’t afford simple platforms with a bus shelter to help others seek better opportunities. Then worst of all a meagre pot of money is made available by central Government that doesn’t cover the total cost of the most deserving schemes and then it is open to a scrum to who can jump through even more hoops to get the money !

    • ianVisits says:

      The artwork in the stations was all paid for by local sponsors and the City of London – if you want more art in stations up north, do the same thing we did down south, pay for it locally.

  5. Oliver O'Brien says:

    The site’s quite a bit bigger than in your aerial image above – it includes the fields to the south too, either side of Tilehouse Lane, which is getting rerouted at the moment. The bridge in the third graphic is the new bridge for this road and the path in the foreground is the diverted Old Shire Lane bridleway. You can see it at

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