Following a successful competitive tender process, Wardell Armstrong, on behalf of Michelmersh Brick appointed McPhillips as the principal contractor to construct the new Hadley Road Attenuation basin.
The attenuation basin was the final phase of construction of a S278 Agreement for carriageway realignment on Hadley Road.
The basin allows storm water from the new carriageway to be held back in times of flood. A downstream Hydro-brake manhole was constructed which restricts storm flows into the local drainage network as times of severe flooding.
Earthworks consisted of excavating approximately 9,300m3 of material to form the attenuation of the basin, together with the haulage and deposition of the basin arising to the agreed deposition area. A 3m wide maintenance track was constructed around the attenuation basin perimeter.
An impermeable membrane with mechanical fixings to the pre-cast concrete and hessian headwalls was fitted to prevent water loss. Erosion control matting was also placed to encourage vegetation growth and to protect the topsoil from premature erosion.
Connection of the existing drainage system into a manhole located within a private property. Reinstatement works to the satisfaction of the resident.
Crossing a new highway with large articulated dump-trucks.
Excavation of the basin while minimising operatives in the area.
Ensuring correct basin profiles were formed as per designed.
Alterations to existing drainage network to facilitate new outfall from the basin.
Lining of the Pond using heavy duty 2mm thick liner and protection membranes.
A meeting was held with the residents to introduce ourselves, explain the proposed works and methodology. We also agreed any reinstatement work that would be necessary. Affected parties were provided with the contact details for a member of our management team should they have further questions or issues. The works were completed as agreed and to the full satisfaction of the residents and client.
A protection mat was formed over the existing Hadley Road. The road was closed to public traffic at the time. The matt consisted of polythene, sand bed and large road plates covered in 400mm of 6F2 to even out levels.
A GPS system was used within the lead excavator. A 3d model of the Basin was created and uploaded to the machine. The driver was then able to excavate the pond profile to within +/- 15mm of design. This also prevented the need for a banksman in the working area.
A specialist in-house drainage team was employed to undertake Hydro-brake manhole construction and drainage connection.
We appointed a specialist approved lining company employed to undertake lining works. The contractor also undertook all necessary testing of the joints to ensure compliance to the specification. A 22t excavator was employed to lift lining rolls due to weight constraints.
The basin was constructed on programme and within budget. The works were completed to the full satisfaction of the client and client’s engineers, Wardell Armstrong. There were no safety incidents or near misses reported.
“We have created balancing ponds before; however, this was an interesting project as it allowed us to fully utilise our GPS controlled machinery, we gained valuable insight for similar projects in future. Because we were ahead of schedule, we were able to reopen the adjacent road a week earlier than planned, which was the result of great work by our team.”
Andrew Dunham, Contracts Director, McPhillips.