Muntons Embankment, Stowmarket

Muntons embankment from aerial view. This was a highly complex project with a large scope including landscaping and arboriculture, fencing and surveying works. 

The project site was situated within Muntons PLC, a maltings facility that sells 210,000 tonnes of malt annually.  The Great Eastern Main Line serving the town of Stowmarket is located on the embankment in front of the factory, north-east of the site.  The River Gipping is located directly adjacent to the site.

This project was completed as part of the CP6 Anglia Civils Framework.  The Anglia Civils Framework is the vehicle for the delivery of works which mitigate the adverse impacts of climate change such as increased flooding which can disrupt rail services and damage infrastructure.  Schemes such as this help to improve weather resilience along Network Rail’s assets.

The Challenges

Muntons embankment undergoing vegetation works. The River Gipping was located directly adjacent to the site, with the site within Flood Zone 3.  Our client had a land access agreement with Muntons PLC which sited our compound within the floodplain.  Following site establishment, the region experienced exceptional rainfall causing flooding on site.

During the design stage a topographic survey was carried out after the devegetation works.  Following topsoil strip, it became apparent that three sections (over the 600m embankment) did not reflect the angle or condition of the rest of the slope.  Due to the condition and angle of the slope we modified the design to allow construction to be carried out safely.

As part of the site was located on the opposite side of the River Gripping from the main site and compound, we required a land access agreement.  Unfortunately, we were met with delays from the landowner and so we managed this by directly contacting the Environment Agency with a request to install a temporary river crossing in the form of a ‘launched’ bridge.

The client instructed that we use quarried rather than recycled product for the fill and gabion media, therefore we had to source products that were acceptable from aesthetic, engineering, and economic perspectives.

Muntons embankment from ground view.In addition to Network Rail’s OHLE system, a set of 132kv transmission lines intersected the site to connect the railway OHLE to the national grid.  This posed various methodology challenges, in particular to the piled king-post wall.  We modified the design, halving the 7m piles and designing a splice detail which ensured we did not enter the proximity zones of the surrounding electrical equipment.

The Solution

We worked collaboratively with the neighbouring farmer to clear the 1.5km flood ditch system on the adjacent flood meadows, improving the landscapes hydraulic capacity and clearing the water from site.

We selected to install a Covamat on the embankment faces as its organic biodegradable nature helps to improve soil conditions.  It incorporates organic fertilisers and dry microorganisms improving the soil microclimate for ideal germination.  Due to the flooding nature of the site, this mat helps to protect the soil surface from future flooding events through the control of runoff and erosion, creating a positive and more resilient environment than was initially present.

Devegetation works required sectional felling activities to be completed.  We opted to use Eco-plugs to kill off the remaining tree stumps as this process was 100% selective and significantly reduced risk to the surrounding environment, with no effect on adjacent trees and vegetation.

For the last month of the on-site works, we implemented new solar-powered generators to power our facilities.  During this time, our diesel consumption decreased by 97% compared to the normal generators we had previously used, equating to a 13 tonne reduction in carbon dioxide.  This success has led to this green technology being introduced on future sites.

The Result

Muntons embankment with new drainage system installed.This multi-discipline scheme showed our capabilities to successfully organise and collaborate with our subcontractors, carrying out the works required to successfully complete the project to the high standards of our client.  On this project we worked closely with the constraints of the landscape, selecting environmentally friendly solutions that created a resilient site in the face of potentially harmful future flooding.

We regraded 600m of flood embankment, installing a seeded erosion blanket, new troughing and a CESS walkway.  Additionally:
•    100m of gabion wall was installed and 50m of piled kingpost with GRP handrails;
•    1.5km of a 3rd party floodplain ditch system were reprofiled and 120m drainage system was installed on the east side of the train track; and
•    we carried out improvement to the three culverts on site - two required extension and one was relined based on 3D laser scan survey.

Sep 2019 - Sep 2020

The scope of the works included:

The scope of the works included:

  • Vegetation management and topsoil strip of the embankment.
  • Cable slew.
  • Track and OHLE stanchion monitoring.
  • Ecological survey and mitigation work, licenced eviction of active badger setts.
  • Relocation of rabbits.
  • Fencing (500m take down and 100m replacement).
  • Temporary works design and install of bailey bridge spanning over main river crossing.
  • Regrade 600m of embankment.
  • 2 culverts dewatered, cleaned, CCTV survey and 3D topographic survey.
  • Full permanent work design for relining of elliptical culvert.
  • Culvert extension.
  • 1.5km of reprofiling of third-party floodplain ditch system.
  • 120m, 1m diameter piped drainage system, including catch pits and new headwalls.

Installation of:

  • Haul road and compound.
  • Seeded erosion control blanket and rabbit mesh.
  • 600m of new troughing.
  • 600m of CESS walkway.
  • 50m of piled kingpost wall, 6m embedment, with GRP handrails fitted.
  • 100m gabion retaining wall.