Introduction
DDC was appointed to survey this section of the southbound carriageway which had flooded during recent weather events.
Over five months of nightshifts, the team surveyed, cleaned, cut and repaired the drainage network from end to end, returning the system to full working order, before re-surveying the network and handing an up-to-date record back to National Highways via the GDMS.
The challenge
The original remedial schedule, prepared using historic survey data, identified 48 pipe runs to clean and survey with CCTV, and 55 defects.
Once the team arrived on site, however, a pre-repair survey found that all but five of the pipe runs were blocked, and there were 19 additional defects to address.
Working closely with MJ Church and National Highways through fortnightly reviews, scope changes were recorded and agreed to keep the project on track and under control.
What we delivered
This project was self-delivered under a single subcontract over 50 night shifts using the same multi-skilled crew on every shift. Crew continuity meant no handovers between teams and no risk of data gaps between shifts.
The team carried out tasks concurrently, meaning a length could be surveyed, cleaned, cut and repaired all within a single closure, thus maximising value and minimising disruption.
Our works included:
- CCTV survey and re-survey: pre- and post-works CCTV inspection of the whole network to OS19X, coded to CS551
- Cleansing: high-pressure jetting and combi-unit cleansing with tanker de-watering of chambers
- Root and deposit removal: mechanical (Warthog) and robotic cutting to clear root masses, settled deposits and intruding material
- Structural repair: localised patch repairs across pipe diameters from 150 mm to 450 mm, with full-length relining where a patch could not achieve the repair
- Filter-drain recycling: on-site cleaning, recycling and re-levelling of over 700 m of overburdened filter media across central reserve and verge
- Carriageway sweeping
- Vegetation clearance
Alongside the physical works, we processed all the data in-house and handed National Highways a complete, auditable record of the asset in its repaired state.
This included:
- WinCan defect, remedial and condition reports
- Before-and-after CCTV for every repaired length
- Condition and asset-inventory drawings
- GPR and topographical survey
- An updated GDMS shapefile issued to National Highways’ SEDDMS
- A schedule of the defects needing more extensive works
