CASE STUDY:
Civil Engineering

This was one of the most expensive projects ever undertaken by Natural England, and presented a number of key challenges to contractors:

• The narrow waterway link made access for heavy plant extremely difficult
• Timescales were tight because the nesting season had to be respected
• The need to create a sustainable geo-wall with the dredged material at the river bank in order to retain the new fenland area
• Getting the equipment to the site presented a range of logistical difficulties: plant had to be transported by road before being floated to the excavation site
• The project had been designed by a third party but needed to be fulfilled by a water specialist, so it was vital to all project partners that we delivered to specification

As experts in water-based construction and land protection, we were able to deliver a solution that used specialised equipment, dedicated geotextile bags and experienced operators in order to deliver this complex project. We provided:

• Knock down pontoon and eight-tonne long reach excavator for dredging in Hudson Bay
• Two fourteen-tonne long reach excavator mounted on NATO pontoons
• Heavy-duty pumps for redistributing dredged silt and filling geotextile bags
• One fourteen-tonne long reaches mounted on NATO pontoon for dredging Hoveton Great Broad
• Tugs and mud hoppers
• Amphibious excavator for site clearance and further silt distribution

Making a difference

We navigated this equipment through the channel using tree shearers, which caused minimal disruption to the environment and saved considerable time and money over transporting the equipment by land.

Choosing to use pumps to move the dredged material from the water into the geotextile bags allowed us to pump up to 900m3 per day – a non-invasive, faster, more reliable efficient way of working. Most contractors cannot offer this. We deliberately chose to create a bigger geo-wall to make sure that the new land was securely and properly retained. We sourced outsized geotextile bags to help achieve this. This added complexity to the pumping process and to the building process, but ultimately resulted in a robust retaining wall that will last for far longer than a simpler solution.

Nature watch

Our work is carried out around the natural lifecycles of the creatures and plant-life that rely on it for sustenance. We’re always aware of the need to plan and, where necessary, adapt our work to allow for nesting seasons, fish spawning times and other environmental concerns – things that are often not on the radar on a traditional construction project, but will be highlighted by any environmental consultants or lobbying groups involved in the project.

In Hoveton, for example, we dredged the waterways to make them deeper – this is because local swans had eaten all the vegetation from the current riverbed, reducing oxygen levels and threatening other species. By making the waterway deeper, we improved the water quality and the general water habitat.