Drainage Case Study

In June 2020, an extreme flash flooding event severely damaged several sections of embankment and an adjacent property in the Lochailort area of the Fort William to Mallaig railway line, Scotland. Following emergency repairs by QTS and Story, along with a further extreme rainfall event in August 2020, Network Rail commissioned QTS through their Renewals and Enhancement (R&E) Framework Contract to design and implement a long-term permanent solution to reduce the likelihood of infrastructure damage from future extreme weather events.

Fairhurst were engaged as design consultant partners and carried out a comprehensive catchment area analysis based on visual inspections along with multiple phases of intrusive investigation and topographic survey data undertaken by QTS in-house resources. Early consultation with key stakeholders including SEPA, local estate/landowners and the road authority (due to A380 trunk road downstream from the site) ensured that our proposed solution considered mitigated flood risks for all parties involved.

Lochailort - Image 1 Lochailort - Image 2

In advance of the main works, the construction of a haul road, widening of access routes and creation of a rock pad for the crane were all completed. The crane pad underwent plate bearing tests to certify stability and safety for operations.

All works were self-delivered using QTS resources, including all safety critical staff, except the permanent way removal and reinstatement by our key supply chain partner and peer R&E framework contractor, Story Contracting. To mitigate risk related to ground conditions, Fairhurst were present on site during the disruptive possession to carry out ground condition checks during excavation and provide QA overview during the culvert installation. This approach proved key to the successful delivery of the project as a large boulder was encountered during the excavation, and we were able effectively adjust the formation level to compensate for the large boulder rather than removing it.

All works were completed within the published times and the possession handed back with 5hrs spare. Upon completion of the culvert installation and track reinstatement, track monitoring ensued in line with the track monitoring plan and NR/L2/CIV/177 by QTS in-house surveying team.

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