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CGI of the headhouse and vent shaft at Year 15 following construction
Artist's impression of the Chalfont St Giles at Year 15 following construction.

Chalfont St Giles Headhouse

The Chalfont St Giles Headhouse is one of four structures that will be built to provide ventilation and emergency access to the high-speed rail line’s 10 mile-long Chiltern tunnel. The headhouse provides emergency services access to the Chiltern tunnel beneath, includes ventilation fans to manage the environment in the tunnel, as well as a series of plant rooms.

Headhouse construction

We have been working closely with local stakeholders to review our traffic management strategies during construction and will cut the number of HGV movements by reducing the size of the vent shaft excavation, building a temporary access road to remove HGVs and site traffic from Bottom House Farm Lane, signalising the junction of the A413 with the temporary access road and scheduling all deliveries electronically to prevent congestion near the site.

Excavated material will be reused to landscape and restore the vent shaft site. The area around the site will be landscaped to blend in with the contours of the existing area, while the temporary access road linking the site with the A413 will be removed after construction, and the land restored to its former state.

The excavation of the ventilation shaft is now complete.

Headhouse design

Taking its inspiration from the style of local barns and other agricultural buildings, the headhouse is designed to fit into the surrounding landscape. The building colour and detail has been designed to blend into the landscape, using a simple palette of materials inspired by local agricultural and industrial buildings.

The arrangement of the buildings is based on an agricultural courtyard layout, with the overall footprint of the compound kept to a minimum. The pitched roofs will wrap around the buildings, creating simple agricultural barn forms orientated to reduce their perceived scale.

The landscape will be shaped to maintain the profile of the chalk valley, whilst planting and chalk grasslands will reinforce the rural setting. Native tree and hedgerow species will be planted throughout and the existing woodland vegetation substantially retained to help screen structures.

We will create habitats which contribute to the biodiversity of the site and its surroundings, and our works will also follow strict protocols to protect existing wildlife. Habitats will reflect the locality and include the creation of calcareous grassland, new wetland habitat, integration with connecting habitats to encourage animal foraging and movement and the protection of existing mature vegetation on neighbouring boundaries.

Design engagement

Chalfont St Giles Headhouse and Ventilation Shaft information boards

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Archaeology

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