Environmental engineering solves Marriott’s Way badger problem

Norfolk County Council has started work to repair an unsafe, closed section of the Marriott’s Way at Whitwell, near Reepham, after the project was given the green light by nature watchdog, Natural England.
 

Part of the badger sett near Whitwell Station. Photo: Michael Pender-Cudlip

 
The £35,000 scheme is needed after a network of tunnels, dug by Norfolk’s biggest badger colony, had left the long-distance trail Marriott’s Way, which runs along the old railway embankment there, liable to collapse at any time.
 
That posed a real danger to the thousands of walkers, cyclists, horses and riders who use the trail every year and forced NCC to close a 300-metre stretch of the popular trail two years ago, for safety reasons.
 
But with strict badger protection rules in place* and any possibility of moving the colony ruled out, engineers had to go back to the drawing board when estimates for plans to solve the problem using traditional methods, such as building bridges over the affected section or creating a permanent new route for the path, showed they could have cost between £200,000 and £500,000.
 
These initial proposals included construction of heavy-duty walkways and bridges along the original line of the path or building a brand new route. Typical costs for these plans included infrastructure design and building, land purchase, drainage works and registering the new route.
 
The approved scheme will now see the path reinforced using a system that is frequently used in a wide range of civil engineering applications, from roads and airfields to construction sites and old landfills, to stabilise ground where it is prone to subsidence.
 
It will involve setting layers of geotextile membrane and aggregate over the path, to create a strong and durable new structure, safe enough to support heavy regular use over the long term, especially by horses and their riders, and protect the badgers beneath.
 
The scheme was designed by civil engineering specialists Naue Geosynthetics based on detailed site investigations undertaken by earth scientists based in NCC’s closed landfill management team, both of whose work includes dealing with unstable land, and after they carried out a series of geophysical surveys that looked into the ground below the path to identify the composition of the substructure of the soil and the precise location and extent of the tunnels.
 
Charles Wright, NCC’s landfill strategy manager, who headed the site investigation and design team for the Marriott’s Way project, said: “This is a good example of a multidisciplinary approach that has resulted in a standard design using well-proven technology for the Marriott’s Way. That helped drive down the cost of providing a durable long-term solution.
 
“It was made possible because we carried out detailed investigations into the ground structure along this stretch of the Marriott’s Way. In this respect we had to work around the strict badger protection rules, which put limits on the investigation methods and the times when setts can be examined, so we initially commissioned Dr Jenni Turner and undergraduate Louise Christopher from the University of East Anglia to run a geophysical survey of the area, which could be carried out on the surface without disturbing the badgers below.
 
“The initial UEA geophysics gave us a good general data about the ground beneath and a comparison of techniques, which we were then able to investigate further with more detailed geophysics and by drilling cores in selected locations away from the badger setts when we were permitted to do so.
 
“All of this gave us an accurate picture of the precise depth, length and location of the tunnels. What it showed was that the badgers have almost entirely tunnelled through a very specific section of the embankment. This is made up of softer sand and gravel which was presumably backfilled between two areas of solid clay when the embankment was originally built.
 
“The tunnelled section had completely undermined the path above, but the clay sections were intact, and it was this that enabled us to commission the ‘bridging’ design from the expert structural engineering company.
 
“They are more used to providing schemes that are suitable for driving lorries and other vehicles over, rather than safely keeping badgers and path users apart, but in terms of strength and durability, the principles are exactly the same.”
 
The work will take about two weeks to complete, subject to the weather, so the trail could be open for Easter. Until then, all the diversions will stay in place for safety reasons.
 
David Brown of Natural England, which approved the scheme, said: “Although this is an engineering solution based on tried and trusted technology, this is a novel approach to the very specific problem at Whitwell.
 
“Mitigation measures have been designed into the scheme to prevent any blockages of the tunnel entrances so that the movement of badgers in and out of the sett will not be inhibited. And given the depth of the tunnels and chambers beneath the surface of the bridleway we’re confident that any disturbance to the badgers during the work will be minimal.”
 
“Once the scheme is finished, it means that people and badgers alike will be able to go about their business as normal along the Marriott’s Way in the very near future.”
 
David Harrison, NCC Cabinet Member for the Environment, said the engineering project was “not only the best solution, but the cheapest on the table, too”.
 
James Joyce, County Councillor for Reepham, said the Marriott’s Way supports many businesses along the route, which make a big contribution to the local economy: “The closure of the path at Whitwell has been painful for many people for a long time, and I’m very pleased that we are now seeing light at the end of this very long tunnel. “
 
The construction project will be aided by Whitwell Station, which will be providing space in its ground to store equipment and materials and by providing a diversion through the station yard while the work is being carried out.
 
Dr Turner, a lecturer in environmental earth sciences at UEA’s School of Environmental Sciences, who guided the geophysical survey, added: “This project also gave one of our undergraduates hands-on experience of collaborating with other agencies and putting her knowledge into practice in order to help solve this challenging real-time environmental problem.”
 
Marriott’s Way is a 26-mile footpath, bridleway and cycle route that follows the routes of two disused railway lines, running between Aylsham and Norwich. The route is named after the chief engineer and manager of the Midland and Great Northern Railway system William Marriott. For more information, visit www.norfolk.gov.uk/trails
 
* Badgers and their setts are protected under the Protection of Badgers Act 1992, which makes it illegal to kill, injure or take badgers or to interfere with a badger sett. Activities affecting badgers or their setts which would otherwise be illegal can be carried out under licence from Natural England, where there is suitable justification and the problem cannot be resolved by alternative means.
 
See our earlier news story:

 

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