News on HS2 in Hillingdon

We have introduced a new and innovative approach to tackling Invasive Non-Native Species (INNS), saving money - an estimated £1.8m in the Colne Valley - time, and carbon output by minimising soil excavation and heavily reducing waste to landfill.

INNS are recognised as a major cause of biodiversity loss in the UK, and are unwelcome intruders in many areas. Non-native plants such as Japanese Knotweed, Himalayan Balsam, Giant Hogweed and Rhododendron are becoming more common to our landscapes, to the detriment of native habitats. Working with AECOM, we have implemented an effective strategy which drastically reduces waste creation, only implementing offsite disposal of soil contaminated with INNS and their seeds if other solutions are not feasible.

Traditionally on infrastructure projects, all soil containing INNS plants, rhizomes and seeds would be removed from site, including excavation of a larger buffer zone, and disposed of according to current legislation for controlled waste. Instead, we are implementing measures focused on biosecurity and ‘surgical’ excavation, avoiding most of the costs and lorry movements associated with waste disposal, while assuring removal of the problem.

Our contractor Fusion JV worked with specialists in AECOM to manage a range of INNS, including the removal of significant areas of Japanese Knotweed in the Colne Valley area. Minimising excavation saves substantial time, cost and carbon footprint by heavily reducing waste to landfill, resulting in cost savings estimated at £1.8m. The site preparation works by Fusion JV for the 3.5km Colne Valley Viaduct involved extensive herbicide treatment followed by 4,700m3 of Japanese Knotweed-infested soil removal, all executed with strict biosecurity protocols within the Mid Colne Valley Site of Special Scientific Interest.

Conventional excavation of the Japanese Knotweed would have required vastly more soil to be removed, including areas adjacent to waterbodies in the Colne Valley, which would have necessitated major temporary works and significantly more waste disposal and imported backfill. Through a more strategic approach involving avoidance, partial removal, selective re-use, and capping instead of simply transporting away soil potentially impacted by INNS material, the excavation requirements were less than 30% of original estimates.

AECOM uses an array of different methodologies focused on biosecurity, including soil protection, fencing and washdown stations, as well as in situ herbicide treatment. Alongside detailed specialist surveys and minimised excavations, this approach reduces environmental impacts and lorry loads of waste that would otherwise be transported away from site to landfill.

If you have a question about HS2 or our works, please contact our HS2 Helpdesk team on 08081 434 434 or email hs2enquiries@hs2.org.uk .