Proposed view of the Colne Valley Western Slopes site

HS2’s Chiltern tunnel chalk grassland project approved

Approval has been granted for an ambitious HS2 scheme, which will see material excavated from the Chiltern tunnels used to create new chalk grassland, wooded and wetland habitats around the tunnel’s southern entrance.

The Colne Valley Western Slopes project was approved by Three Rivers District Council and Buckinghamshire Council, and will see the creation of 127 hectares of new chalk grassland, woodland, wood pasture and wetland habitats.

Once complete, the project will have transformed what is currently a construction site into one of the largest areas of new chalk grassland in the Chiltern hills.

Chalk grassland is considered a habitat of international conservation importance mainly found on limestone and chalk valleys in the South East of England and the Isle of Wight.

Lime-rich but low in nutrients, the thin soil holds little water and heats up quickly, which creates conditions which encourage a huge variety of smaller herbs and wildflowers to grow. Over 40 species can be found in one square metre of grassland, including some of the UK’s rarest orchids and invertebrates.

Only 700 hectares of chalk grassland exist across the whole of the Chilterns Area of Outstanding Natural Beauty (AONB).

In collaboration with Cranfield University and industry partners, HS2 will see 90 hectares of chalk grassland seeded into reprofiled soil layers, using the nutrient poor subsoils on the site and mixing these soils with chalk from the tunnelling, and recycled concrete and aggregates from construction works.

The ambitious project will also lead to the creation of new areas of woodland, wood pasture and wetlands, including almost 65,000 new trees, shrubs of 32 species and nearly 3.5km of new hedgerows.

Around 4.5km of new footpath, cycling and horse-riding routes will provide public access to large parts of the site, which sits between the Colne Valley Regional Park and the Chilterns AONB.

Welcoming the news, HS2’s Environment Director Peter Miller said: “The Western Valley Slopes project is one of the most important parts of our Green Corridor programme to establish better connected, sustainable and biodiverse landscapes along the route of the new railway and will contribute substantially to HS2’s carbon reduction target.

“It demonstrates HS2’s approach to addressing many of the complex issues surrounding climate change and which are central to protecting our environment, and is a great example of how good design and planning can mitigate the effects of climate change.

“A huge amount of work has gone into the planning for this ambitious project and it’s great that that’s been recognised in the approval.”

The plans were approved by the Three Rivers District Council - which covers more than 99% of the site - and Buckinghamshire Council under Schedule 17 of the HS2 Act 2017.

Cllr Phil Williams, Lead Member for Environmental Services, Climate Change and Sustainability, at Three Rivers District Council, added: “We welcome the plans to transform this site which will significantly enhance local biodiversity as well as providing a great new visitor attraction and amenity for people in Three Rivers and further afield.

"The design has evolved from the original proposals thanks to the work of council officers and engagement with the Colne Valley Regional Park Panel, which includes a range of local groups, working collaboratively to achieve a more distinctive and sensitive outcome in the Colne Valley.”

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