DYWIDAG Case Study

Drone-Assisted Structural Examination

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Client: DYWIDAG

Service Delivered: Drone-Assisted Structural Examination
Location: North West & Central – Wigan Culvert (River Douglas)
Project: Difficult Access Structural Examination

Background

GeoAccess was commissioned to examine a large culvert carrying the River Douglas beneath multiple railway lines, located 200m east of Wigan North Western Station.

Historically, inspections of this structure were complex, expensive, and high-risk, often involving scaffolding or boat access with pole-mounted cameras. These methods were time-consuming and limited visibility.

To overcome these challenges, GeoAccess deployed a confined space inspection drone, offering a safer, faster, and more cost-effective approach without compromising inspection quality

Method

A two-person rope access qualified flight crew was suspended in cradles at the downstream end of the structure to hand-launch and recover the drone during successive flights.

Across nine drone flights, a detailed visual examination was conducted, with particular focus on difficult-to-access areas such as undersides and recessed structural elements. The operation yielded 70 minutes of high-quality video footage, capturing the full internal profile of the culvert.

Using specialist analysis software, frames were extracted from the footage and annotated with:

Defect type
Dimensions
Severity rating

This streamlined workflow replaced traditional manual image reviews, cutting report preparation from weeks down to days. The approach also ensured no critical defects were overlooked while significantly improving reporting speed and accuracy.

Innovations & Solutions

Drone technology eliminated the need for scaffolding, boats, or pole-cams.
Faster inspections completed within hours rather than days.
Reduced risk to personnel by minimising confined space entry.
Cost-effective solution with lower project overheads.
Software-enabled defect mapping ensured clarity and speed in reporting.

Results & Conclusion

The Wigan Culvert inspection was completed successfully, demonstrating the benefits of drone-based structural examinations:

Time efficiency: inspections and reporting delivered in a fraction of traditional timelines.
Cost savings: no need for scaffolding or specialist marine access.
Enhanced safety: personnel exposure to high-risk environments was minimised.
Comprehensive data: detailed defect logs and severity ratings supported targeted maintenance planning.

By adopting drone technology, GeoAccess provided DYWIDAG with a safer, faster, and more sustainable solution for examining difficult access railway structures, setting a benchmark for future culvert and confined space inspections