Background

The Helliers Lane development in Cheddar required the installation of a new foul pumping arrangement to serve a residential scheme. The works needed to be delivered without delaying the wider construction programme, while accommodating poor ground conditions and a high water table.

Given the site constraints and challenging ground conditions, the project team required a solution that could be installed quickly, reliably and with minimal on site risk.

The challenge

The site presented several critical difficulties:

  • Poor ground conditions with a high groundwater table
  • Restricted working space within an active residential development site
  • A requirement to install pumping infrastructure without holding up building works
  • Programme sensitivity and risk associated with in situ construction

Traditional in situ or brick built solutions carried increased risk of water ingress, prolonged installation time and programme delay.

The solution

Marshalls Off Site Solutions team worked with the contractor to develop a bespoke precast solution, manufactured under controlled factory conditions.

The final solution comprised:

  • A prefitted 2100mm diameter precast pump chamber
  • A bespoke valve chamber measuring 1800mm x 2400mm x 2000mm deep

Both units were delivered to site complete and ready for installation, significantly reducing on site construction activities. Temporary works were established to manage the high water table during excavation, after which the chambers were installed, positioned and backfilled.

The precision of manufacture allowed rapid fitting of mechanical and electrical equipment, reducing installation risk and improving programme certainty.

The outcome

The bespoke precast solution delivered clear programme, quality and constructability benefits.

  • Pump and valve chambers installed and backfilled within 11 working days
  • High integrity, watertight structures despite a high groundwater environment
  • Pump gear installation reduced from an expected four days to just over one day
  • No delays to the wider residential development programme

Symon Wheeler of Brandwell Construction commented:

“The integrity of the design gave the team involved the security that the chambers would not leak, and the accuracy of the manufacture meant pump installation was completed in just over a day.”

He added:

“Facing a similar challenge in the future, I would certainly discuss it with Marshalls Civils & Drainage again.”