Client
Weymouth & Portland Borough Council
Value
£150,000
Sectors & Services
Highway Structures Concrete Repair Anchors/Remedial Ties Structural Strengthening Projects Projects
This project involved major structural repairs to a historic brick-lined tunnel located on the Rodwell Trail in the West Country. The tunnel forms part of a valued heritage asset and recreational route, requiring a sensitive yet technically robust intervention to address long-term water ingress and deterioration of the original brickwork.
Undertaken between May and July 2013, the works were necessary to improve drainage, protect the historic fabric and ensure the tunnel’s continued safe use. The scheme balanced preservation with modern engineering solutions, aligning with best practice in concrete repairs and asset management while respecting the tunnel’s historic character and setting.
Services undertaken
- Installation of Delta 500 drainage membrane
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Fixing of membrane using Delta Quick Seal plug fixings
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Fixing of steel mesh reinforcement with steel dowels
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Installation of 100 mm plastic drainage pipe with weep holes at 1.5 m centres
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Formation of ACO drainage channel within tunnel lining foundation
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Installation of fixed platform scaffold for preparation works
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Use of mobile scaffold platforms for follow-on works
CRL delivered a carefully sequenced repair and lining scheme designed to stabilise the tunnel structure and manage groundwater ingress without compromising the historic brickwork. Preparation works commenced with high-pressure water jetting to clean the existing brick surfaces, removing contaminants and loose material to provide a sound substrate for subsequent systems. Access for these operations was provided by a fixed platform scaffold, ensuring safe and efficient working within the confined tunnel environment. Mobile scaffold platforms were then used for the remainder of the works to maintain flexibility as activities progressed along the tunnel length.
A new Delta drainage membrane system was installed to the prepared brickwork. The Delta 500 membrane was mechanically fixed using Delta Quick Seal plug fixings and carefully dressed into the stone quoins at either end of the tunnel to maintain continuity and respect the original construction. This membrane provided a controlled drainage layer, allowing water to be collected and directed away from the historic structure.
Over the membrane, a sprayed concrete lining was applied to form a durable internal shell. The lining was reinforced with a steel mesh, securely fixed back to the original brick structure using steel dowels to ensure composite action and long-term stability. To further enhance drainage performance, a 100 mm plastic pipe was cast into the tunnel lining, incorporating weep holes at 1.5 m centres. This system feeds into a newly formed ACO drainage channel within the concrete foundation of the lining.
The drainage channel discharges to soakaways at the north end of the tunnel, constructed using perforated downpipes set within 10 mm pea shingle and fully encapsulated with geotextile to the top and sides. Throughout the works, CRL managed site logistics and public safety, installing Heras fencing and diversion signage to temporarily close the Rodwell Trail path. The project demonstrates CRL’s expertise in specialist concrete repairs and structural repairs UK, particularly where heritage structures demand precision, care and durable engineering solutions.
"The re-lining and drainage works to the tunnel were completed to programme and provide a greatly improved access route for the public"
Steve Jones | Southern Regional Director | CRL
The completed works provide long-term protection to the historic tunnel by combining effective drainage management with a robust internal lining system. High-pressure water jetting ensured thorough surface preparation, enabling secure fixing of the drainage membrane and strong bonding of the sprayed concrete lining. The Delta 500 membrane creates a permanent barrier that controls water movement, preventing moisture build-up behind the new lining and protecting the original brickwork from further deterioration.
The integrated drainage pipework, ACO channel and soakaway system ensures water is safely collected and dispersed away from the structure, reducing hydrostatic pressure and future maintenance requirements. Reinforced sprayed concrete, mechanically tied to the existing tunnel, enhances structural resilience and extends the service life of this historic asset. Through a technically sensitive approach, CRL preserved the tunnel’s integrity while delivering a durable, low-maintenance solution aligned with long-term asset management objectives.
