Terra Solutions Limited were recently employed to undertake one of the largest diameter culvert rehabilitation schemes in the UK with a 1500mm dimension..
Holywell culvert crosses the A59 near Skipton and comprises a straight run between existing concrete bag headwalls of nominal 1500 mm diameter corrugated steel pipe (CSP) in corroded condition. As part of renovation by lining of the culvert, owners North Yorkshire County Council (NYCC) proposed to extend the culvert at both ends to new stone headwalls to be aligned with the edges of existing concrete inlet and outlet roof slabs. At the upstream end the extension piece was to form a bend to bring the inlet more in line with the existing watercourse.
As Main Contractor for the project, Terra Solutions Ltd were responsible for design as well as installation. The design had to account for the practical implications of the proposed introduction of a bend in the culvert alignment at the upstream end.
Terra engaged Mr. John Gumball of JG Pipeline Consultancy to conduct a report to review both the NYCC culvert extension specification and the supplier submitted CIPP liner designs, and Reline Europe’s Alphaliner 1800H was chosen.
Great care was taken to develop a technique that avoids the use of any materials that would have had a detrimental impact on the watercourse or wider environment. Through collaboration with the EA and NYCC it was agreed that the use of RE’s UV-cured CIPP liner, as opposed to a more traditionally cured liner, would remove the requirement of using chemicals and resins in the curing process.
Due to the flow through the culvert, a robust flow management system was required using a series of 6” and 8” pumps. In order to minimize disruption, it had been agreed with Bolton Abbey that the discharge pipes from the pumps would be run alongside the railway track and discharged into the field. This negated a road closure and reduced risk of spillage. If a closure was required, this would have entailed a 10miles+ traffic diversion causing major inconvenience to the community.
Extensive devegetation was required prior to lining works to facilitate access to the inlet and outlet points of the culvert. For the extensions reinforced plastic was selected due to their light weight characteristics when compared with other alternatives such as steel or concrete. This meant they could be lifted into place using a 14T excavator. It also negated the requirement for welding in confined spaces and live flow conditions.
Local stone was sourced and used for the headwall façade construction. This helped to integrate the works with the surrounding landscape and was locally aesthetically pleasing.
This impressively turn-key, large diameter, culvert remediation was completed ahead of programme, and within budget to the satisfaction of the NYCC, local residents and all stakeholders.