Agenda item

Align is the Main Works Contractor for both the Colne Valley Viaduct and the Chiltern Tunnel for HS2. Duncan Fallon d.fallon@alignjv.com HS2 Engagement Manager Colne Valley (viaduct) and Emma Gaydon HS2 Engagement Manager for Maple Cross to Great Missenden e.gaydon@alignjv.com (Emma’s responsibility included Chiltern Tunnel and vent shaft sites) were welcomed to the meeting. Another email address included hs2enquiries@hs2.org.uk/ communityengagement@alignjv.com.

(Background information - Chesham and Villages Community Board September 2020 – HS2 update)

https://buckinghamshire.moderngov.co.uk/documents/s12536/200930%20CVCB%20HS2%20Update.pdf

South Portal

The main construction compound was at South Portal Chalfont Lane, near West Hyde. From here, one team would launch the tunnels northwards, while another heads towards London on the adjacent Colne Valley Viaduct. The tunnel precast factory and all 2,400 tonnes of structural steelwork at the South Portal site were next to the M25. The factory would allow Align to cast all the tunnel segments on site to avoid putting extras HGVs onto local roads. The South Portal had ANPR and good car parking capacity to take traffic off Chalfont Lane and A412. Security checks were undertaken on site. The impact of the lockdown had meant that more people were travelling by car rather than train. There had been recent road closures for A412. Other works included the creation of new public right of way footway diversion crossing Shire Lane, road crossing for traffic light ducting, installation of diverted cabling, removing trees and vegetation for the access road. The 17 metre high headwall has been completed which the tunnel boring machines would break through.

Government guidance was that construction works should continue during the Covid-19 pandemic but with working practices adapted in line with guidance from Public Health England to maintain the safety of the workers and stop the spread of the virus. These include but were not limited to; the detailed planning of each operation to maintain 2 metre social distancing where possible; if not possible then appropriate Personal Protective Equipment to be provided; staff temperature and health screening every day for signs of Covid-19 by the occupational health specialists; start and finish times staggered to reduce congestion and avoid workers coming into close contact; enhanced cleaning and hygiene regimes; worker travel arrangements assessed and adapted; home/lodging arrangements assessed for risk. An additional third storey had been added to ensure social distancing was maintained in the offices.

Align’s programme shows their construction work at the North Portal (South Heath) scheduled to start in December 2022, with the site being handed over to them. The TBMs were due to arrive at the North Portal in late 2023/early 2024, where they would be ‘de-constructed’. This site was also due to be handed over to the rail systems contractor in early 2025

Vent shaft

The Chalfont St Peter vent shaft headhouse has been built to provide ventilation and emergency access to the high speed rail line 10-mile-long Chiltern tunnel. The headhouse has been designed to fit into the surrounding landscape. The 60 metre ventilation shaft would reach down to the twin tunnels below, with fans and other equipment designed to regulate air quality and temperature in the tunnels, remove smoke in the event of a fire and provide access for emergency services.

Initial site set-up at the Amersham vent shaft has begun and below-ground work at the site was due to start in April 2021. Construction work would continue at the site until 2025, when the site would be handed over to the (yet to be appointed) rail-systems contractor. The Little Missenden (A413) and Great Missenden (Chesham Road) shafts follow-on, with initial site set-up from October 2020 and February 2021 respectively; excavation work would start in May/June 2021 and continue until 2025. Work was expected to be noisy.

Temporary Access Road

A temporary access road has been completed to link the site with the A413 Amersham Road, which would allow construction traffic to avoid the centre of Chalfont St Peter and stop HGVs. A new temporary marshalled lorry holding area has been put in place on the A413 near Gerrards Cross. HGVs would be held in this layby until their approach to the vent shaft site was clear to help reduce congestion and eliminate queueing at the site entrance. The temporary traffic lights on A413 should be removed by the end of the year. CCTV had been installed.

Chiltern Tunnel

Two tunnelling machines (TBM) have been bought and these excavators would bore a 10 mile tunnel through parts of the Chilterns, from the South Portal site. Both machines are 170m long and have been designed for the chalk and flint under the Chilterns. They will run non-stop and were expected to take about three years to excavate the tunnel which would be lined with concrete. The twin bore Chiltern tunnels would be the longest and deepest on HS2 with separate north and southbound tunnels with five ventilation shafts. Concrete pouring has begun at the Chiltern Tunnel site for the Tunnel Boring Machine launch pad. The two TBMs would begin work next Spring to dig the tunnel.

Colne Valley Viaduct

Other work taking place includes a separate precast plant for sections of the Colne Valley Viaduct while a slurry treatment plant, where the chalk from the tunnels, which was pumped out in a slurry mixed with water, dried and then used for landscaping elsewhere on site, was also being built. There was fence installation, vegetation and tree removal and ditch works. A cabin had been installed with a car park.

Community Engagement Calender

• Little Missenden Design Input closes 29 November
• Colne Valley construction webinair – 3^rd and 9^th December
• You said we did – Chalfont St Giles  January 2021, Chesham Valley February 2021, Amersham late February 2021

Investment in community projects

There were opportunities for community projects and residents were asked to put forward ideas which included funding, STEM education activities, reuse of materials and volunteering time. The Business and Local Economy Fund had also been created to support local economies that had been demonstrably disrupted by the construction of phase one of Hs2.

During discussion the following points were made:-

• Flooding at Chesham Lane – Align were working with Transport for Buckinghamshire and this hopefully should soon be resolved. A comment was made that the public right of way was a mud bath and Emma Gaydon informed him that they were taking action on the drainage.
• A Parish Councillor raised concerns about the amount of mud on A412 whilst works were being carried out near Denham Water Ski Club and A413 Shaft area which covered car vehicles. Align were creating two new site entrances and building crossing points for a haul road on the A412 near Denham Water Ski Club on Moorhall Road. This work was in preparation for the creation of a new haul road to support the construction of the Colne Valley Viaduct. In addition she referred to the welfare facilities at the South Portal site – lorries were parking by children’s playground to access the site and were also gauging out road surfacing on A40 and A412. Duncan Fallon reported that he was appalled by the state of the roads and had sent an update to the Parish Clerk. He commented that there were no HGV movements yet and that they would come via M25. They were making enquiries about quarry activities at Denham Farm. Road sweepers had been arranged as it was dangerous for this amount of mud on the road. The Parish Councillor commented that the roads had still not been swept.
• Reference was made to the proposal to build a new service area on the M25 near J16 and 17, near Chalfont St Peter (Warren Farm) and how this would impact on the HS2 works. Duncan Fallon replied that a written response would be sent to the Board Co-ordinator. The Member asked a further question regarding the variance in geographical structure in Chalfont St Peter and Chalfont St Giles which impacted on the water flow and the need to divert the River Misborne. A written response would be provided on this question as well.
• A Member asked whether there were wheel washing facilities on site and was assured that all sites should have this facility. He commented that there were witnesses that vehicles from HS2 sites were fouling the roads, without using the wheel washing facilities and Duncan Fallon and Emma Gaydon agreed to investigate this issue.

The Chairman asked Members to submit any ideas for community funding. Jackie Copcutt introduced herself as Lead Project Officer HS2 for Buckinghamshire Council Jackie.copcutt@buckinghamshire.gov.uk and commented that she worked closely with the Align Team and HS2 contractors.