DCL/40 Cherwell Scour Protection

DCL/40 Cherwell Scour Protection

Kaymac was contracted to carry out Scour Protection Works to Structure DCL/40 Cherwell on the DCL Line between Heyford and Didcot.

The project was part of a Network Rail CP5 programme of works to upgrade infrastructure along the LNW route and where possible, enhance structures to higher specifications and standards. Kaymac were contracted by Story Rail to carry out the Scour Protection works to DCL/40 Cherwell.

DCL/40 Cherwell is a twin span underline bridge carrying non-electrified twin track railway across the river Cherwell near to Steeple Aston.

The structure comprises of two 4 brick ring arches with a supporting substructure of a cut water pier masonry abutments and wing walls that was constructed in 1848.

Kaymac mobilised to site and Environmental Protection Measures in the form of sedi-mats and hay bales were set up downstream. A temporary sandbag bund was installed to divert the flow of the water through the North Span, and extended the central pier upstream with bulk sandbags to the Gabion Wall and downstream with bulk sandbags to the embankment to create a bunded area within the South Span. Once the bunded area had been created, small submersible pumps were placed into the impounded water, the South Span was then dewatered and a fish rescue was carried out.

Excavation works were carried out within the South Span down to formation level. Type 1 stone was placed, compacted and reinforcement was installed to design specification. Formwork was erected and concrete was placed in three pours – base, ramps and upstands with a static pump.

Following completion of the scour protection works within the South Span, the temporary sandbag bunds upstream and downstream were moved to divert the flow of water from the North span through the newly surfaced South span. A clean stone ramp was then installed up to the river and a piped causeway was installed in the river to allow access to the North span for the excavator and dumper (both fitted with bio-oils).      

With the Environmental Protection Measures still in place downstream, small pumps were placed into the impounded water area to dewater the North Span and a fish rescue was carried out. Excavation works either side of the barrel invert were carried out down to formation level, Rock Armour was installed and grouted into place, tying into the existing invert as per the design. Upon completion of the works, the temporary works and environmental protection measures were recovered from the watercourse and both spans opened to the river flow.  The site was then left in a clean and tidy condition and all labour, plant & materials demobilised. Despite high rainfall and fast flows Kaymac successfully upgraded the safety of the structure on time and to budget. 

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