The emergency works at Shade Chapel, Todmorden to install temporary propping to the partially collapsed culvert on Walsden Water has now been completed.
The emergency works were carried out on behalf of the Environmental Agency by BAM Nuttall and Peter Duffy Ltd to stabilise the culvert running beneath Shade Chapel. These temporary works were essential to prevent the risk of collapse of the building, the watercourse becoming blocked and the possible flooding of up to 250 properties in the area. On completion the work would allow access and provide time to assess and develop a permanent solution.
Significant damage to the culvert caused by recent flooding events affected the culvert bed, walls and soffit which were an integral part of the support beams to Shade Chapel. The watercourse ran adjacent to the highway and to enable these works to go ahead traffic management was put in place to provide both site access and to accommodate a significant over pumping operation to divert the river flows.
The over pumping operation consisted of 8 no. 200mm diameter pumps connected to a special manifold, fixed to a 600mm diameter steel delivery pipe.
The unstable nature of the culvert and building created a dangerous and confined environment for the works and temporary propping. The operatives also needed to be prepared to evacuate the works in times of heavy rain should the flows exceed the pumping capacity. Added to this was the need to manage the risk of Covid-19. Comprehensive safe systems of work and controls were developed by the site team to manage the risks for the work to be carried out safely.
As work progressed the initial temporary works design required revisions as the extent of the damage varied, being more significant in areas and requiring bespoke localised design for support. Several areas within the base and sides of the culvert were repaired and infilled to prevent further erosion to the culvert and building foundations.
As a result of completing the temporary works installation, the over pumping arrangement was demobilised, returning Walsden Water back to its original route through the culvert below Shade Chapel.
The work took 14 weeks to complete and make safe. The temporary propping now allows a full assessment of the damage to Shade Chapel to be carried out by the Environmental Agency.