In practice: Network Rail’s Bermondsey Dive Under biodiversity project

The challenge

Located about a mile away from London Bridge on its eastern approach, the Bermondsey Dive Under project is part of the Thameslink Programme in south-east England to upgrade and expand the Thameslink rail network.

The challenge at hand for this project was to untangle tracks to ensure Thameslink lines can cross over Kent lines and run more efficiently. The works involved demolition and reconstruction of the 180-year-old brick arch viaduct to create new infrastructure that allows Southeastern and Southern services to ‘dive under’ the Thameslink lines unimpeded.

Prior to the beginning of construction in 2012, the Bermondsey site had limited botanical diversity and low conservation value. The inherited site contained previous tenant’s debris and soils heavily contaminated with asbestos, hydrocarbons and Japanese knotweed.

The solution

The £50m Bermondsey Dive Under project required a collaborative approach between client, designers and contractors to create a sustainable design that significantly reduced carbon, materials, waste and cost.

Construction work began in 2013. Existing structures were re-used where possible to minimise disruption and reduce waste. Over the course of the project, 21,900 tonnes of contaminated material had to be removed. The extent of this contamination meant only 0.1 hectares of the original 1.5 hectares of vegetation could be retained. Wildflower planting and green walls were installed to offset lost vegetation using techniques easily replicable and scalable.

In total, 765m2 of green walls were installed in locations that would otherwise be void space under arches and access ramps. Meanwhile, 0.63 hectares of wildflower planting on railway embankments created green corridors and stepping stones to the wider area. The wildflower mix was selected for its native species, high distinctiveness and low maintenance parallel to the railway where safety restrictions limit vegetation height.

Network Rail worked with Lewisham and Southwark Council to ensure the scheme enhanced the vegetation condition throughout while complementing the surrounding area. Using a carbon measrement tool provided by construction firm Skanska, Network Rail was able to produce an embodied carbon assessment for the project. A material use and management plan was also drawn up to manage the project’s carbon and materials usage. The project was completed in April 2017. 

The benefits

A remarkable environmental and aesthetical legacy has been left for the local community thanks to this project. The green wall and wildflower areas are visible to the community, providing social value and enhancing natural capital through promoting biodiversity and creating a visually appealing area, in what used to be an industrial waste facility. The project was externally verified to have more than doubled the amount of biodiversity units present in preconstruction, leading to a quantifiable net-positive increase in biodiversity of 113%.

During the project’s construction phase, many site interventions led to further carbon and cost savings. For instance, switching from a generator to mains for the offices saved 133TCO2/a with a less-than-two-year payback period. Ecolite Zero Carbon Lighting saved 89TCO2e, while theuse of an electric van on the site saved 2TCO2e. Meanwhile, eco cabins were used and waterless urinals saved approximately 200,000 litres of water per year.

The project diverted 99.49% of all waste from landfill. Early consideration of reusing demolition material led to the production of the material management plan. This allowed 31,500m3 of material to be reused onsite for the construction of railway embankments, piling mats and fill material drastically reducing the material quantities, transport movements and associated carbon.

At a local level, the project has provided public social space, linking two areas with a pedestrian and cycle route by a series of tunnels. Another social success of the project was the extensive community engagement it has driven. The project maintained regular contact with the local community through delivering notification letters, holding community information sessions and running several open days where local residents had the opportunity to visit the site and meet the project team.

As part of Thameslink’s overarching sustainability strategy and the project community outreach plan, Bermondsey Dive Under also undertook extensive community improvement projects such as upgrading the garden in the Lewington Community Centre, volunteering on a youth charity mobile youth bus and spent a week refurbishing a youth club in a local church.

The project employed 10 previously unemployed Southwark residents to undergo roles such as quantity surveying and plant operating. This represents the great opportunity the project has provided for diversity, inclusion and local employment.

The future

Two new lines for Southeastern traffic will come into service after the August 2017 Bank Holiday and the overall programme of work is expected to be completed by the end of 2018, with the ‘Dive Under’ lines entering into service on 2 January 2018. 

The project is expected to reduce congestion, reduce delays and improve air quality through reduced train idling times. Improving national railways in this manner will ultimately boost the use of public transport and help the country meet its carbon reduction targets.

 George Ogleby