HS2 in Hertfordshire
Britain's new high-speed railway
The Colne Valley viaduct carries the new high-speed railway from Harefield in Hillingdon across the Colne Valley into Buckinghamshire. The route enters the 10-mile Chiltern tunnel at its southern portal, just inside the M25 in Hertfordshire.
This area around the new high-speed railway will also feature over 90 hectares of chalk grassland.
Programme reset
We’re making sure HS2 provides the best value for Britain by carrying out a full review of the programme for the government.
Our CEO Mark Wild is resetting HS2’s cost and schedule. He successfully led Crossrail’s recovery in the wake of major challenges. This led to the successful opening of the Elizabeth line – now the busiest in the UK.
What we're building in Hertfordshire
Chilterns chalk grassland
The western slopes of the valley of River Colne are dedicated habitat creation sites. We’re creating over 90 hectares of chalk grassland alongside new areas of woodland, wood pasture and wetlands, including almost 65,000 trees and shrubs of 32 species and nearly 2 miles (3.5 km) of new hedgerows.
Chiltern tunnel
Chiltern tunnel is the longest tunnel on the HS2 route, stretching 10 miles (16km) beneath the Chiltern Hills.
Chiltern tunnel headhouses
Five headhouses will support the Chiltern tunnel.
A headhouse sits above shafts, which ventilate the tunnels for the railway and provide emergency access.
Chalfont St Peter headhouse
The Chalfont St Peter headhouse design has been improved. The single-storey building is now set back from the road and wrapped in a simple grey zinc roof with dark bronze openings. Taking its inspiration from the style of local barns and other agricultural buildings, it’s designed to blend into the surrounding landscape. The pre-weathered grey zinc roof will age naturally over time, without loss of robustness or quality, while the whole structure will sit on a simple dark blue brick base.
Learn more about the Chalfont St Peter headhouse
Chalfont St Giles headhouse
The Chalfont St Giles headhouse will fit into the surrounding landscape, taking inspiration from the style of local barns and other agricultural buildings. The design uses a simple range of materials inspired by local agricultural and industrial buildings. The building colour and detail blend into the landscape.
Learn more about the Chalfont St Giles headhouse
Amersham headhouse
The Amersham headhouse sits in the middle of a road junction just outside Amersham, Buckinghamshire. The building design has changed based on feedback from Buckinghamshire Council. The weathered steel boundary wall is being replaced with a more traditional stone wall made of flint. Flint occurs naturally within chalk hills like the Chilterns. Flint facades have been a prominent feature of local architecture for hundreds of years.
Learn more about the Amersham headhouse
Little Missenden headhouse
The Little Missenden headhouse is a single-storey building that will sit on top of a 35-metre deep ventilation shaft. The shaft reaches down to the Chiltern tunnel below. The headhouse is set back from the main A413 in Little Missenden.
Learn more about the Little Missenden headhouse
Chesham Road
The Chesham Road headhouse (intervention shaft) is located off the B485 at Hyde End, near Great Missenden. The arrangement of the buildings is based on an agricultural courtyard layout with the overall footprint of the compound kept to a minimum. Pitched roofs wrap around the buildings, creating simple agricultural barn forms.
Current work in the area
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