Client

Network Rail

Value

£350k

Duration

10 weeks

Location

Dumfries & Galloway

THE PROJECT

The culvert carries Garpol Water stream into the Evan Water stream and required strengthening in order to allow continuation of the West Coast Services.

The scheme involved the application of a spray applied concrete system to the natural rock culvert. Due to freeze thaw and natural weathering of the rock, the upstream entrance to the culvert was seen to be in an unstable condition, therefore requiring large volumes of rock to be removed from this area by way of rope access equipment prior to starting the project.

Despite the volatile water levels of Garpol Water, difficult access constraints and the challenges around the COVID-19 pandemic, the scheme was successfully completed on programme and with zero accidents or incidents.

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The scope of the project was to design and implement the following works:

  • Provide a solution to prevent further rock degradation and strengthen the existing culvert.
  • Develop a temporary works access system down a 20m embankment and through the existing 40m long rock culvert.
  • Final design to satisfy strict SEPA conditions surrounding working in water.
  • Access methodology to be developed to accommodate spray applied concrete installation
  • Construction methodology and solution to be developed around fluctuating river levels.

Our project team worked in close collaboration with SEPA and the local fisheries authority to programme within consent restrictions. These restrictions also had a bearing on how the works would be undertaken.

Working closely allowed the works to be completed with no adverse environmental impacts.

This project also allowed for innovative technologies to be used in the form of a cantilevered dam system being installed with floating bypass channels to allow water to continue to flow without the need for pumps. A telemetry system was also installed upstream of the dam to inform all onsite of rising water levels and flooding events, ensuring all on site worked safely.

The project was able to celebrate success and demonstrated best practice within the following areas:

  • Management of complex and dynamic temporary works throughout project.
  • Early sub-contractor involvement allow design to be tailored to client’s requirements including a bespoke rope access system, designed and installed to facilitate future inspections.
  • Overcoming flooding events to ensure a safe and practical working environment on site.
  • Management of unforeseen changes on site to allow project to follow budget and programme and be completed on time.
  • Bespoke design and build complex scaffolding system, comprising of access staircase, working platform split over sever lifts and intermediate sections, all installed to facilitate the difficult and complex surroundings of a natural rock culvert.
  • Engineering solutions to allow watertight sealing of vertical cores with environmental issues.

During the design & delivery stages of our project, we identified and implemented the following value engineering and efficiency ideas:

• Story specialist GI team brought into core culvert soffit to determine rock depth with no issues caused to track level. Backfilling of vertical cores then carried out ALO due to careful planning and specialist sub-contractor involvement.

  • Early specialist rope access contractor involvement allowed design to be tailored to provide system to access culvert for future inspections.
  • Installation of dam system in conjunction with telemetry system and bypass channels allowed works to be completed without the requirement for over pumping, reducing the environmental risks.
  • Reduced the volume of concrete required by analysing the structural impact within the culvert.

80m3 of spray applied concrete

delivered

20t of unstable rock removed

via rope access

70m of fluming

for existing water course

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