Artist impression of the Green Park Way Headhouse.

Green Park Way Headhouse

The Green Park Way Headhouse in Ealing is one of four shafts along the Northolt Tunnel route of HS2.

A ventilation shaft, or vent shaft, is the vertical opening that connects the HS2 tunnels, 35 metres below the surface, to the open air. It regulates air quality and temperature in the tunnel and allows smoke to be extracted in the event of a fire. The headhouse is the building on top of the ventilation shaft which contains fire control systems and the ventilation systems for the railway tunnels below.

Headhouse design

Located along the Chiltern line embankment, the Green Park Way ventilation shaft has been thoughtfully designed to integrate seamlessly with its environment. The structure merges with the green corridor—a network of newly created wildlife habitats, woodlands, and community spaces—contributing to a sustainable legacy along the HS2 route.

The landscaping plan includes a green roof and diverse vegetation to help the headhouse blend harmoniously into its natural surroundings.

Slide 1 of 6: Artist impression of the Green Park Way Headhouse - south elevation

Slide 2 of 6: Artist impression of the Green Park Way Headhouse - north elevation

Slide 3 of 6: Artist impression of the Green Park Way Headhouse - east elevation

Slide 4 of 6: Artist impression of the Green Park Way Headhouse - west elevation

Slide 5 of 6: Artist impression of the Green Park Way Headhouse - view from Network Rail

Slide 6 of 6: Artist impression of the Green Park Way Headhouse - view hard standing

TBM reception chamber

Green Park Way will serve as the endpoint for the four tunnel boring machines (TBMs) excavating the Northolt Tunnel. The TBMs will arrive in a specially designed reception chamber, or “can,” filled with foam concrete—an innovative solution developed to counter the site’s high groundwater pressure.

The site’s geological profile transitions from made ground at the surface into layers of London Clay, followed by the Harwich Formation, which contains granular material. This then moves into the Lambeth Group, characterised by clay with sand channels, and finally, the Upnor Formation above the Chalk layer.

The reception chamber allows the TBMs to maintain their pressure during arrival. Sealant is applied to the tunnel lining to prevent water ingress before the chamber is depressurised. Once complete, the TBMs are opened and lifted out of the ground.

All four TBMs working on the Northolt Tunnel will be extracted via the two shafts at Green Park Way, making the site a pivotal part of HS2’s construction journey.