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Biodiversity at Bermondsey

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You can always tell a major construction site. There are acres of bare earth, often rutted and with stones sticking out of it, dirt tracks carved into the landscape by the passage of countless heavy machines, and weeds starting to appear in the more neglected corners.

Finally, after construction is finished, the whole lot gets smoothed off and grass is planted, along with a few trees with those plastic tubes round them for protection, returning the site “back to nature”.

However, it isn’t always like that. One of the major railway construction sites in recent years has been the Bermondsey dive-under, a joint project by Network Rail and partners Skanska and Ramboll to untangle the tracks approaching London Bridge station as part of the Thameslink programme.

This £50 million project began construction in 2012 and was completed for hand over to maintenance in April 2017. At the height of construction, the project employed 45 office staff and 200 site personnel including graduates and operatives from the local area. Rail Engineer covered its construction on several occasions.

Before it was built, train lines to Sussex and Kent criss-crossed over each other at a series of flat junctions, causing delays and limiting the number of trains that could travel per hour. Demolition and reconstruction of the 180-year-old brick arch viaduct created new infrastructure that will allow designated lines for Southeastern trains to Kent and Southern trains to Sussex to ‘dive under’ new Thameslink lines from January 2018, reducing delays and increasing reliability for passengers.

Green walls replace Japanese Knotweed

What may surprise readers is that the construction of the Bermondsey dive-under has increased biodiversity in the urban area of Bermondsey by 113 per cent and has won the team a coveted CEEQUAL ‘Excellent’ award.

Prior to the beginning of construction in 2012, the Bermondsey site had limited botanical diversity and low conservation value. It was scattered with the previous tenant’s debris and the soil was heavily contaminated with asbestos, Japanese Knotweed and hydrocarbons. The extent of this contamination meant only 0.1 hectares of the original 1.5 hectares of vegetation could be retained.

The project removed over 21,900 tonnes of contaminated material and eradicated the Japanese Knotweed. To increase biodiversity, wildflower planting and green walls were installed to offset vegetation lost in the process of removing the contaminated soils.

In total, the project installed 765 square metres of green walls under arches and access ramps, areas that would otherwise be void space, and planted wildflowers on the railway embankments. This created green corridors and stepping-stones to the wider area, leaving a fantastic legacy both environmentally and aesthetically for the local community.

Sustainable project

However, this improvement in biodiversity is only the most visible part of various activities to produce a sustainable design that significantly reduced carbon, materials, waste and cost. For example, the number of piles was reduced from 1,600 to 1,000 decreasing the total by over 175 tonnes and the overall length by 10,000 metres.

Changing the specification for a structural steel bridge from painted steel to weathered steel led to almost halving the total costs over the bridge’s lifetime, through lower initial costs and elimination of maintenance materials.

The Bermondsey dive-under also produced a materials management plan that allowed material from the demolition of the viaduct arches to be reused onsite. This resulted in a total of 31,500m3 of material being reused on site, reducing the costs of fill material and waste removal while also minimising lorry movements through the local community.

Creating wildlife diversity and new green spaces wasn’t the only way in which the project team engaged with the local community. The team also upgraded the garden in the Lewisham Community Centre, refurbished a youth club in a local church and volunteered on the XLP youth charity bus. All of this work resulted in excellent community relations, fewer complaints, positive media coverage on TV and newspapers, and left a positive legacy within the community.

The success of these initiatives resulted in CEEQUAL, the international evidence-based sustainability assessment, rating and awards scheme for civil engineering, awarding the project a Whole Team Award with an ‘Excellent’ rating of 96.6 per cent. The assessors commented that “the project leaves a fantastic legacy both environmentally and aesthetically for the local community”.

It had been a whole-team effort. Skanska project manager Charl de Kock said: “We were able to achieve this excellent CEEQUAL score due to us embedding a sustainable approach from the design stage through to the delivery of the project. This success is testament to the commitment to sustainability from our client, Network Rail, our design partner, Ramboll, and all our other contracting partners and supply chain.”

So next time you see a row of saplings protected by plastic tubes on a recently completed site, remember what can be achieved with a little thought and effort. This article ‘stolen with pride’ from Network Rail and CEEQUAL.

Read more: Under the wires to Swindon



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