HS2 Colne Valley mitigation plan released

In the plan, High speed 2: Additional mitigation plan for the Colne Valley, it said the construction of the new line would bring “profound” change to parts of the area, resulting in “substantial” environmental and social impacts.

The Colne Valley Regional Park is the first large countryside area outside of London and covers 111km² from Rickmansworth in the north to Staines and Egham in the south; and from Uxbridge and Heathrow in the east to Chalfont St Peter and Langley in the west.

The independent panel was set up to consider the potential implementation of additional environmental mitigation measures that could be delivered alongside measures already proposed by HS2 Ltd for the area. It comprises a number of local councils, wildlife groups, HS2 Ltd and the Department for Transport (DfT).

Within the park area the high speed line will be raised up on a 3.4km long major viaduct which covers a significant proportion of the park.  

During construction, the plan said land would be required for compounds and stockpiling of materials and diversions for roads, footpaths and bridleways would need to be put in place.

It said landscape impacts would largely lie outside of the valley floor and closer to the boundaries of the park, where it enters and exits the tunnel, owing to construction compounds, feeder stations and land needed to temporarily store excavated material from tunnel construction.

Within the valley floor area, it said trees which had not yet grown to their mature height (20m to 30m) would eventually limit the visual impact of the viaduct. It said it could also seek to create views of countryside, “uninterrupted by HS2 construction works and the final proposed scheme”.

The plan states the ecological disturbance of wildlife populations will “extend to areas beyond the route of the railway line”, where it said noise and air quality was likely to be affected.

Several additional proposals have been made in the report with an anticipated £3M being made available by HS2 Ltd to contribute towards the projects. However, it said further funding would be required from external sources to cover the full cost of the projects.

These proposals include the planting of woodland and wetland in the Broadwater Lake area to compensate for the loss of habitat caused by the construction, however it said noise during construction and subsequent train noise in the operational phase were likely to disturb birds, and this had not been fully mitigated.

It says work on the majority of the 14 additional proposals could start in advance of the construction of the line to ensure mitigation measures were in place before the communities were impacted.

A spokesperson for HS2 said: “We welcome publication of the independent Colne Valley Regional Park Panel’s Additional Mitigation Plan.  

“We committed to establishing the Panel during HS2’s hybrid bill journey because we want to involve local stakeholders in developing a positive legacy for the area. As part of this we pledged £3m to support delivery of the Panel’s environmental proposals and we will now work with the Panel on its proposals.”