Bailey Street Culvert Repairs for Torfaen County Borough Council

EDS was appointed by Torfaen County Borough Council to inspect Bailey Street culvert, particularly to assess the scale of a known defect where scour of the invert and washout of the abutment was occurring.

Our inspection identified significant scour damage, measuring 10m long by up to 1m deep, to the stone invert of the masonry barrel. One abutment had been undercut over a 5m length, while the opposite abutment had collapsed over a 3m length, with another section showing movement. EDS developed a methodology to repair the damaged areas.

Large void to invert and collapsed abutment and large cracks showing evidence of abutment movement (prior to works).

Large void to abutment and section of collapsed abutment (prior to works).

Methodology:

  • Create access across the playing field with ground protection mats and temporary removal of fencing
  • Install temporary propping of unstable areas with sacrificial Acrow props
  • Install water management measures (bypass pipes and a 6” submersible hydraulic pump), followed by pollution control measures
  • Pump approximately 40m³ of ready-mixed concrete into the invert void to stabilise the invert, fill the abutment undercutting, and prevent further movement
  • Construct a new abutment wall using dense concrete blocks laid flat and staggered to achieve a circular profile, backfilled with pumped grout in a number of lifts. Grout was also used to fill voids behind the downstream abutment wall
  • Apply steel mesh and spray a structural render system to finish the abutment reconstruction, tying into the original circular culvert profile
  • Repoint and reset large masonry stone

Ground protection mats and access in fencing created, large hydraulic pump power pack on site.

Void pumped dry of water, temporary propping and concrete supply lines in place.

The works were carried out over 4.5 weeks and included additional scour remediation upstream of the main repair area. Challenging access via a narrow manhole and chamber was resolved by arranging, with the cooperation of local landowners, temporary access for large plant and equipment across private property at the start and end of the contract. All other access was through the narrow manhole.

All pumped concrete was an RC32/40 mix with an underwater additive (Sika UCS), supplied as a high-slump pump mix with 10 mm aggregate to ensure efficient delivery into the void.

The project was highly commended by the Torfaen County Borough Council project supervisor. Reinstating the large void prevented the potential collapse of the culvert — an event that could have carried significant safety, cost and disruption implications for both residents and the Local Authority.

Temporary works installed to manage water flows.

Initial concrete pour complete and staggered blockwork wall under construction.

Blockwork wall under construction and prepared for spray rendering.

Structural spray rendering in progress and completed repair.